Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF IDENTIFYING TRANSMEMBRANE PROTEIN-INTERACTING
COMPOUNDS
FIELD OF THE INVENTION
This invention relates to methods for screening compounds for their
ability to interact with transmembrane proteins. The invention further relates
to methods for screening transmembrane proteins for their ability to dimerise
or oligomerise into groups of two or more proteins.
lip BACKGROUND OF THE INVENTION
In the description which follows, references are made to certain
literature citations which are listed at the end of the specification.
Transmembrane proteins have been classified in several major classes,
including G protein coupled receptors, transporters, tyrosine kinase
receptors,
cytokine receptors and LDL receptors. G protein coupled receptors (GPCRs)
can be grouped on the basis of structure and sequence homology into several
families. Family 1 (also referred to as family A or the rhodopsin-like family)
is by
far the largest subgroup and contains receptors for small molecules such as
the
catecholamines, dopamine and noradrenaline, peptides such as the opioids,
somatostatin and vasopressin, glycoprotein hormones such as thyrotropin
stimulating hormone and the entire class of odorant molecules (George et al,
2002). Family 2 or family B contains the receptors such as for glucagon,
parathyroid hormone and secretin, These GPCRs are characterised by a long
amino terminus that contains several cysteines, which may form disulphide
bridges. Family 3 or family C contains receptors such as the metabotropic
glutamate, the Ca2 -sensing and the gamma-amino butyric acid (GABA)B
receptors. These receptors are also characterised by a complex amino
terminus. Although all GPCRs share the seven membrane-spanning helices,
the various GPCR families show no sequence homology to one another.
GPCRs are the largest known group of cell-surface mediators of signal
transduction and are present in every cell in the body. GPCR action regulates
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the entire spectrum of physiological functions, such as those involving the
brain,
heart, kidney, lung, immune and endocrine systems. Extensive efforts during
the
past decade has identified a large number of novel GPCRs, including multiple
receptor subtypes for previously known ligands, and numerous receptors for
which the endogenous ligands are as yet unidentified, termed 'orphan'
receptors
or oGPCRs (Lee et al., 2001; Lee et al., 2002; Bailey et al., 2001).
GPCRs have been the successful targets of numerous drugs for diverse
disorders in clinical use today, with an estimated 50% of the current drug
market
targeting these molecules. Among the known GPCRs, ¨335 receptors are
potential drug development targets, of which 195 have known ligands, and the
remaining 140 being oGPCRs, awaiting identification of their ligands. Although
various methodological advances have accelerated the pace of novel receptor
discovery, the pace of ligand and drug discovery lags far behind.
Conventional,
small-scale pharmacological screening assay methods were initially used to
discover the ligands and drugs for many of the GPCRs, but newer assay
procedures are continually being sought.
Since GPCRs form over 80% of cell surface receptors, they represent a
substantial resource and constitute a highly relevant group of protein targets
for
novel drug discovery. Drugs interacting with GPCRs have the potential to be.
highly selective, as the interactions will be confined to the cell surface and
to
tissues bearing the receptors exclusively. The convergence of the discovery of
GPCRs with the realisation that they are important drug targets, has led to
intense pharmaceutical interest in devising better ways to detect and screen
for
compounds interacting with GPCRs. Therefore, creating improved assay
methods is an urgent requirement towards the goal of more rapid drug screening
and discovery. There is a need to optimise the ability to detect an
interaction
between test compounds and the receptors, which is the fundamental initial
step
in the process of drug development.
Improved ligand-identification strategies to accelerate the characterisation
= of all GPCRs will define their physiological functions and realise their
potential in
discovering novel drugs. Even with the identified GPCRs, there is a paucity of
highly selective subtype specific drugs being discovered and pharmaceutical
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houses are experiencing a dearth of promising lead compounds, in spite of the
wealth of drug targets defined. The list of new drug product approvals by the
top
20 pharmaceutical companies has declined considerably over the period 1999-
2001, compared to the preceding three year period (Smith, 2002). Thus there is
a real need to have improved, versatile assay systems, where not just
endogenous ligands, but novel compounds interacting with receptors can be
tested and identified in a quick and efficient manner that is amenable to
automation.
As the signal transduction pathway required to activate an oGPCR cannot
be predicted, an assay system for interacting compounds which is independent
of prior predictions of which effector system (such as adenylyl cyciase, PLC,
cGMP, phosphodiesterase activity) is employed by the receptor is required.
Assigning ligands to GPCRs and oGPCRs is an important task; however the
diversity of both GF;CR ligands and effector systems can limit the utility of
some
existing ligand-identification assays, requiring novel approaches to drug
discovery.
Recently, several methods utilising refined assay systems testing tissue
extracts, large ligand libraries and specific ligands of interest have
successfully
discovered the endogenous ligands for a number of these oGPCRs. Such
methods have been collectively referred to as "Reverse Pharmacology" (Howard
et al., 2001). Various methods have been used to assay induced cell activity
in
response to an agonist compound, including the Fluorescence Imaging Plate
Reader assay (FLIPR, Molecular Devices Corp., Sunnyvale, Calif.) and Barak et
al., (1997), and U.S. Patents Nos. 5,891,646 and 6,110,693 which disclose the
use of a 8-arrestin-green fluorescent fusion protein for imaging arrestin
translocation to the cell surface upon stimulation of a GPCR.
The potential disadvantages of such methods are as follows: 1)
visualisation is not of the receptor; 2) the protein translocation requires
complex
computerised analytical technologies; 3) prior identification of agonist is
necessary to screen for antagonists; and 4) specific G protein coupling is
necessary to generate a signal.
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Mechanisms of ligand binding and signal transduction by GPCRs
traditionally have been modelled on the assumption that monomeric receptors
participate in the process, and a monomeric model for GPCRs has been
generally accepted. Since the mid-1990s, however, numerous reports have
demonstrated oligomerisation of many GPCRs (reviewed by George et at.,
2002), and it is now realised that oligomerisation is an inherent aspect of
GPCR
structure and biology. Also certain receptor subtypes formed hetero-oligomers,
and these receptors have functional characteristics that differ from
homogeneous
receptor populations. At present, studies of GPCR oligomerisation do not make
a distinction between dimers and larger complexes, and the term dimer is used
interchangeably with the terms oligomer and multimer. There are no conclusive
data to indicate how large the oligomers of functional GPCRs are. Importantly,
generation of new properties through hetero-oligomerisation suggested a
mechanism for generating diversity of function among GPCRs.
Homooligomerisation of GPCRs is accepted as a universal occurrence and a
number of GPCRs are known to assemble as heterooligomeric receptor
complexes (George et at., 2002). For example, the GABA-B1 and GABA-B2
receptors are not functional individually and only form a functional receptor
when
co-expressed (White et al., 1998). The assembly of heterooligomer receptor
complexes can result in novel receptor-ligand binding, signalling or
intracellular
trafficking properties. For example, co-transfection of the mu and delta
opioid
receptors resulted in the formation of oligomers with functional properties
that
were distinct from each of the receptors individually (George et al., (2000)
3. The
interaction of mu and delta opioid receptors to form oligomers generated novel
pharmacological and G protein coupling properties. When mu and delta opioid
receptors were co-expressed, the highly selective agonists (DAMGO, DPDPE,
and morphine) had reduced potency and altered rank order, whereas certain
endogenous ligands endomorphin-1 and Leu-enkephalin had enhanced affinity,
suggesting the formation of a novel ligand binding pocket (George et at.,
2000).
In contrast to the individually expressed mu and delta receptors, the
coexpressed
receptors showed pertussis toxin insensitive signal transduction, likely due
to
interaction with a different subtype of G protein. It would therefore be very
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useful, from the point of view of identification of potential drug targets, to
have a
means of determining whether a particular pair of GPCRs are able to form
heterooligomers.
In many reports, heterooligomers have been tentatively identified by the
5 ability to co-immunoprecipitate. When two GPCRs are shown to co-
immunoprecipitate, however, there are two possible interpretations; either the
receptors are directly physically interacting, or both are interacting through
contact with a common third protein (or proteins). An alternative approach to
detecting receptor oligomers has been the development of energy transfer
assays using bioluminescent resonance energy transfer (BRET) or fluorescence
resonance energy transfer (FRET). Although these methods detect energy
transfer between two receptor molecules labelled by fluorophores at
proximities
of less than 100 angstroms, it is unclear whether receptor conformational
changes can be reliably distinguished from de nova oligomerisation.
Transporters are protein pumps that move molecules, ions and other
chemicals in and out of cells and exist in virtually all cells. The
transporters
can be grouped into families on the basis of structure, sequence homology
and the molecules they transport. Separate transporters exist for monoamine
neurotransmitters such as dopamine, serotonin, norepinephrine and GABA,
for amino acids such as glycine, taurine, proline and glutamate, for vesicular
monoamines, acetylcholine and GABA/glycine, for sugars such as glucose
and disaccharides, for organic cations and organic anions, for oligopeptides
and peptides, for fatty acids, bile acids, nucleosides, for water and for
creatine. Pumps that export large molecules such as drugs, toxins and
antibiotics from the cell are exemplified by the P-glycoprotein (multidrug
resistance protein) family. There are also several related transporters the
function of which remains unknown (Masson et al., 1999). These transporters
are membrane proteins consisting of a polypeptide generally with 12
transmembrane domains. The glutamate and aspartate transporters belong
to a separate family whose members have 6 to 10 TM domains and share no
homology to the other transporters (Masson et al., 1999). Both the amino and
carboxyl termini are located on the intracellular side of the membrane.
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A large number of neurological and psychiatric disorders including
depression, Parkinson's disease, schizophrenia, drug addiction, Tourette's
syndrome, and attention deficit disorders are considered to involve the
monoamine transporters. The dopamine transporter (DAT) is the major target
for psychostimulants such as cocaine and methylphenidate. The transporters
have been the successful targets of numerous drugs for diverse disorders in
clinical use today, particularly antidepressant drugs, including fluoxetine,
sertraline and the other related serotonin selective reuptake inhibitors
(SSR1s). Although methodological molecular advances have identified the
known transporters, the pace of ligand and drug discovery lags behind.
Conventional, pharmacological screening assay methods were used to
discover the ligands and drugs for some of the transporters, but newer assay
procedures are urgently being sought. Improved ligand-identification
strategies to accelerate the characterisation of all the transporters will
further
define their physiological functions and realise their potential in
discovering
novel drugs. Even with the identified transporters, there is a paucity of
highly
selective specific drugs being discovered.
The tyrosine kinase receptor family members are characterised by their
structural similarity, with an extracellular ligand binding domain, a single
transmembrane domain and an intracellular domain with tyrosine kinase
activity for signal transduction. There are many subfamilies of receptor
tyrosine kinases, exemplified by the epidermal growth factor (EGF) receptor
(also called HER1 or erbB1), which is one of four members of such a
subfamily, which also includes HER2, HER3 and HER4. The principal EGF-R
ligands are EGF, TGF-a, heparin binding EGF, amphiregulin, betacellulin and
epiregulin (Shawver et al., 2002). Activation of the EGF-R causes the
receptor to dimerise with either another EGF-R monomer or another member
of the HER subfamily. Marked diversity of ligand binding and signalling is
generated by the formation of heterodimers among family members (Yarden
and Sliwkowski, 2001). The EGF-R is widely expressed in a variety of tissues
and mediates important functions such as cell growth and tissue repair.
Overexpression of EGF-R occurs in many types of cancer, such as head and
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neck, lung, laryngeal, esophageal, gastric, pancreatic, colon, renal, bladder,
breast, ovarian, cervical, prostate, thyroid, melanoma and glioma, and
correlates with a poor outcome (Nicholson et al., 2001). Therefore there is
great interest and need for developing drugs targeting the EGF-R and for
methods which assist in identifying such drugs.
Other subfamilies of receptor tyrosine kinases are exemplified by the
receptors for vascular endothelial factor (four members) and fibroblast growth
factor (four members). These have important roles in angiogenesis and also
have significant roles in the uncontrolled proliferation of vessels
characterizing
carcinogenesis (Hanahan and Folkman. 1996).
The cytokine receptors are proteins spanning the membrane with an
extracellular ligand binding domain and an intracellular domain with intrinsic
kinase activity or adapter regions able to interact with intracellular
kinases.
The receptors are divided into subclasses based on their structural
complexity. The 'simple' receptors are those including receptors for growth
hormone, erythropoietin and interleukins, and the 'complex' receptors include
the tumour necrosis factor receptor family, the 4-helical cytokine receptor
family, the insulin/ insulin-like receptor family and granulocyte colony
stimulating receptor (Grotzinger, 2002).
The insulin and insulin-like growth factor (IGF) receptor family controls
metabolism, reproduction and growth (Nakae et al., 2001). There are nine
different insulin-like peptides known and there are three known receptors that
interact with them, IR, IGF-1R and IGF-2R, and an orphan member IR-related
receptor. Each receptor exists as homodimers on the cell surface or
heterodimers. The IR subfamily is also related to the EGF-R family.
IR, produced from a single mRNA, undergoes cleavage and dimerisation
and translocation to the plasma membrane. Each monomer component
contains a single transmembrane domain; the complete receptor comprised
two a and two 13 subunits, linked by disulphide bridges. Thep subunit
contains the single TM and the intracellular region. This receptor is a
tyrosine
kinase that catalyzes the phosphorylation of several intracellular substrates.
The low density lipoprotein (LDL)-receptor family act as cargo
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tranporters, regulating the levels of lipoproteins and proteases (Strickland
et
al., 2002). There are nine recognised members of the family, all of which
share structural similarity, including an extracellular region, a single
transmembrane domain region and a cytoplasmic tail. The LDL receptor
plays a major role in the clearance of lipoproteins, and genetic defects in
the
LDL receptor can result in the accumulation of LDL in the bloodstream.
The first characterised motif shown to be able to direct protein nuclear
importation was exemplified by the amino acid sequence (PKKKRKV) contained
in the SV40 large T antigen protein. The nuclear localisation sequence (NLS)
motifs are recognised by the importin c=-f3 receptor complex, which binds the
NLS
(Gorlich et al., 1996). These are cytosolic proteins, which recognise NLS
containing proteins and transport these proteins to dock at the nuclear pore.
The
entire complex subsequently docks at the nuclear pore complex (Weis et al.,
1998, Schlenstedt et al., 1996), contained at the nuclear envelope. The
nuclear
envelope is a boundary containing pores that mediate the nuclear transport
process (Weis et al., 1998).
There have been very few and rare reports of GPCRs localising in the
nucleus. One such example is the GPCR angiotensin type 1 (ATi) receptor,
which contains an endogenous NLS which serves to direct the GPCR into the
nucleus (Lu et al., 1998), providing evidence that this NLS sequence was
involved in the nuclear targeting of the All receptor. These authors and Chen
et
al., (2000) reported that All receptors increased in the nucleus in response
to
agonist. The nuclear localisation of the parathyroid hormone receptor has been
reported (Watson et al, 2000). However very few of the superfamily of GPCRs
contain an endogenous NLS mediating translocation of the receptor to the
nucleus.
There therefore remains a need for new, more convenient methods for
identifying compounds which interact with transmembrane proteins such as
GPCRs, transporters, etc. There also remains a need for improved, less
ambiguous methods for detecting oligomerisation of transmembrane proteins.
=
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SUMMARY OF THE INVENTION
The inventors have shown that the incorporation of a nuclear localisation
sequence (NLS) into a transmembrane protein (not containing an endogenous
functional NLS) routes the protein from the cell surface into the nucleus of a
cell
in a time-dependent and ligand-independent manner. In order to visualise this
trafficking of transmembrane proteins from the cell surface, they carry a
detectable moiety for visualisation by a variety of means. It has been
demonstrated that membrane proteins from diverse protein families containing a
synthetically incorporated NLS are redistributed under basal conditions from
the
cell surface to and towards the nucleus.
This process can be exploited to identify compounds which interact with
transmembrane proteins by determining whether candidate compounds are able
to modulate this ligand-independent transfer of a transmembrane protein away
from the cell membrane.
It is also now possible, using methods based on this process, to determine
whether protein molecules are able to oligomerise.
In accordance with one embodiment, the invention provides a method
for screening a candidate compound for its ability to interact with at least
one
transmembrane protein comprising:
transfecting a cell with at least one nucleotide sequence encoding a
protein comprising a transmembrane protein containing at least one nuclear
localisation sequence (NLS) and a detectable moiety and permitting
expression of the encoded protein in the cell;
contacting the cell with a candidate compound; and
determining the distribution of the expressed protein in the cell by
detecting the distribution of the detectable moiety in the cell;
wherein detection of an altered distribution of the detectable moiety in
the cell relative to the distribution of the detectable moiety in a control
cell not
contacted with the candidate compound indicates that the compound interacts
with the transmembrane protein.
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In accordance with a further embodiment of this method, the cell is
contacted with a compound known to interact with the at least one
transmembrane protein prior to contacting the cell with the candidate
compound and
5 wherein detection of an altered distribution of the detectable moiety in
the cell relative to the distribution of the detectable moiety in a control
cell
contacted with the compound known to interact with the transmembrane
protein but not contacted with the candidate compound indicates that the
candidate compound interacts with the transmembrane protein.
10 In accordance with a further embodiment, the invention provides a
method for screening a candidate compound for its ability to interact with at
least one transmembrane protein comprising:
transfecting a cell with at least one nucleotide sequence encoding an
NLS-containing transmembrane protein and permitting expression of the
encoded protein in the cell;
contacting the cell with a candidate compound; and
determining the level of NLS-containing transmembrane protein
remaining at the cell membrane by isolating the cell membrane fraction of the
cell, contacting the fraction with a labelled ligand of the transmembrane
protein and determining the level of binding of the ligand to the fraction;
wherein detection of an altered level of the transmembrane protein at
the cell membrane relative to the level at the cell membrane in a control cell
not contacted with the candidate compound indicates that the compound
interacts with the transmembrane protein.
In accordance with a further embodiment, the invention provides an
isolated cell transfected with at least one nucleotide sequence encoding a
protein comprising a transmembrane protein containing at least one NLS and
a detectable moiety.
In accordance with a further embodiment, the invention provides a
method for determining whether a first protein and a second protein are able
to oligomerise comprising:
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transfecting a cell with a first nucleotide sequence encoding a first
protein containing an NLS and a second nucleotide sequence encoding a
second protein comprising a detectable moiety and permitting expression of
the encoded first and second proteins in the cell; and
determining the distribution of the detectable moiety in the cell;
wherein detection of the detectable moiety in or adjacent to the nucleus
of the cell or detection of a reduced level of the detectable moiety at the
cell
surface, relative to a control cell, indicates that the first and second
proteins
interact.
SUMMARY OF THE DRAWINGS
Certain embodiments of the invention are described, reference being
made to the accompanying drawings, wherein;
Figure 1 shows in diagrammatic form the structure of a typical GPCR, the
dopamine D1 receptor, modified to contain an NLS.
Figure 2 shows fluorescence (Relative fluorescence units) at surface of
HEK cells transfected with dopamine D1 receptor-NLS and treated with various
concentrations of butaclamol.
Figure 3 shows cell surface fluorescence of HEK cells transfected with
HA-dopamine D1 receptor-NLS and treated with various concentrations of
SCH23390 alone or with SKF81297 (100 nM).
Figure 4 shows cell surface fluorescence of HEK cells transfected with
HA-dopamine D1 receptor-NLS and treated with 0.5 1.LM SCH23390 alone or
together with various concentrations of SKF81297.
Figure 5 shows the amount of 3H-SCH 23390 bound to the cell membrane
fraction of HEK cells transfected with dopamine D1 receptor-NLS and treated
with butaclamol (A) or control untreated cells (w).
DETAILED DESCRIPTION OF THE INVENTION
The invention provides, in one embodiment, a new and convenient
method for screening candidate compounds for their ability to interact with a
transmembrane protein.
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As used herein, when a candidate compound and a transmembrane
protein "interact", this means that the compound is a ligand of the
transmembrane protein and binds to the protein or is able to modulate the
trafficking of the transmembrane protein away from the cell membrane described
herein.
Identification of compounds which interact with a transmembrane protein
is the first important step in the process of identifying lead compounds for
drug
development.
Working initially with GPCRs, the inventors have found that when a
nucleated eukaryotic cell is transfected with a nucleotide sequence which
encodes a GPCR containing a synthetically incorporated NLS, or a naturally
occurring NLS, and the cell is permitted to express the nucleotide sequence,
the
expressed GPCR travels first to the cell membrane and then is transferred to
the
cell nucleus. This process is independent of ligand activation and takes from
about 6 to about 72 hours, depending on the transmembrane protein involved,
with an average of 24 to 48 hours. This is in contrast to the situation when a
GPCR not containing an NLS is expressed in a cell, when the expressed GPCR
remains predominantly at the cell surface, with small amounts occurring in the
cytoplasm but no detectable amounts in the nucleus.
The inventors have also found that the transfer or trafficking of the
expressed NLS-containing GPCR from the cell membrane to or towards the
nucleus can be modulated by treating the transfected cell with a compound
which
interacts with the GPCR. Screening of candidate compounds for their ability to
interact with a GPCR can therefore be carried out by detecting this modulation
of
transfer of the expressed GPCR from the cell membrane to the nucleus.
The inventors have further found that these observations are widely
applicable to transmembrane proteins generally, and are not limited to GPCRs.
"Transmembrane protein" as used herein means a single chain protein
found in the cell membrane and having at least one domain that spans the cell
membrane.
The inventors have shown that a wide variety of transmembrane proteins
from several families of the GPCR group, from the transporter group, from the
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cytokine receptor group, from the tyrosine kinase group and from the low
density
lipoprotein receptor group, if expressed in a nucleated cell so that they
contain an
NLS group, all show initial accumulation of the expressed protein at the cell
membrane, followed by ligand activation-independent transfer of the expressed
protein away from the cell membrane and into the cell nucleus.
The wide applicability of the methods of the invention is indicated by the
immense variety of transmembrane protein structures represented by the
exemplified transmembrane proteins used in the method; NLS insertion into a
transmembrane protein resulting in translocation of the protein off the cell
surface
and to the nucleus has been shown to be effective with membrane proteins
having one transmembrane (TM) domain, seven TM domains and twelve TM
domains and sharing little or no sequence homology.
It has been found that the method of the invention is widely applicable to
identifying compounds which interact with transmembrane proteins.
Compounds which interact with transmembrane proteins have been found
to modulate their transfer from cell membrane to nucleus in different ways,
including inhibition of the transfer, acceleration of the transfer and
interference
with the modulation produced by other compounds. Any interacting compound is
of interest as a potential drug candidate.
Modulation of the transfer of expressed transmembrane protein is
determined by comparing the distribution of the transmembrane protein within
the
cell in control cells and cells treated with a candidate compound.
In one embodiment, the method provides a convenient tool for screening
candidate compounds for their ability to interact with a GPCR and modulate its
trafficking. Compounds that specifically interact with the GPCR may inhibit or
prevent transfer of the GPCR from the cell surface to the nucleus and may be
antagonists to the GPCR, whereas other compounds can accelerate the transfer
of GPCR to the nucleus, relative to a control cell and may be agonists to the
GPCR.
To allow determination of the distribution of the expressed transmembrane
protein within the cell, with and without exposure to a test compound, the
expressed transmembrane protein must carry a detectable moiety, which can be
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detected in the cell. The detectable moiety may be any moiety which will
remain
. associated with transmembrane protein throughout its expression and
trafficking
within the cell and can be directly or indirectly detected to determine its
distribution within the cell and to determine an altered distribution
resulting from
exposure to a candidate compound.
In a first embodiment, the cell is transfected with a nucleotide sequence
encoding a fusion protein comprising a transmembrane protein containing at
least one NLS linked to a detectable moiety comprising a detectable peptide or
polypeptide. As used herein, a peptide means a sequence of two to 20 amino
acid residues, preferably a sequence of about 5 to about 15 amino acid
residues,
and a polypeptide means a sequence of more than 20 amino acid residues,
including full proteins of any length. The detectable peptide or polypeptide
may
be directly detectable or may be reactable to give a detectable signal. The
detectable peptide may be, for example, an antigenic peptide or epitope which
is
expressed, for example, at the amino terminus of the transmembrane protein.
The distribution of the transmembrane protein within the cell is detected by
detection of the epitope using a detectable antibody specific for the epitope.
A
number of suitable epitope antibody systems are available commercially.
Examples are the HA (Roche Diagnostics), FLAG (Sigma Chemical Co.), c-myc
(Santa Cruz), Histidine hexamer (BD Biosciences Clontech), GST (ABR Affinity
BioReagents), V5 (Abcam) and Xpress (Invitrogen) epitope/antibody systems.
Nucleotide sequences encoding these epitopes can be purchased, as well
as antibodies specific for the epitopes. These antibodies may carry a
detectable
label (e.g. fluorescein isothiocyanate (FITC)) or may themselves be detected
by
use of a second antibody carrying a detectable label, as will be understood by
those of skill in the art. This embodiment of the invention is particularly
adaptable to an automated or semi-automated method, for example by
=
examining antibody-treated plates of cells in an automated plate reader,
allowing
for high through put screening.
The detectable polypeptide may be an optically detectable polypeptide
such as green fluorescent protein (GFP), red fluorescent protein (RFP), yellow
fluorescent protein (YFP) and or cyan fluorescent protein (CFP), or any of the
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modified variants of these proteins, which are commercially available. The
detectable polypeptide may also be an enzyme such as luciferase or 0-
galactosidase, which can be reacted to give a detectable end point such as
light
emission or colour change. Nucleotide sequences encoding such polypeptides
5 are readily available, for example from Clontech, and are linked to the
nucleotide
sequence encoding the NLS-containing transmembrane protein, preferably at the
C-terminal end of that protein.
In a further embodiment, the detectable moiety is an antigenic peptide
comprising a portion of the amino acid sequence of the transmembrane
10 protein itself, preferably a portion of an extracellular region of the
protein. As
described above, the distribution of the transmembrane protein within the
cell is determined using a detectable antibody specific for the epitope.
=
Suitable antibodies are available commercially, e.g. anti-D1 antibody
directed to amino terminal amino acids 9-21 of the human D1 dopamine
15 receptor, or may be prepared by conventional methods.
In a further embodiment, applicable to transmembrane proteins with
known ligands, the cell is transfected with a nucleotide sequence encoding a
transmembrane protein containing at least one NLS. The cells are contacted
with a candidate compound and incubated as described above. The cells are
then harvested and the cell membrane fraction is isolated and contacted with a
detectably labelled ligand of the transmembrane protein, for example a radio-
labelled ligand. Determination of the amount of labelled ligand bound to the
membrane fraction of treated cells, relative to the amount bound to the
membrane fraction of control cells not contacted with the candidate compound,
can be used to quantitate the transmembrane protein remaining at the cell
surface and indicate interaction of the candidate compound with the
transmembrane protein.
Transmembrane protein-encoding nucleotide sequences can be obtained
from public databases such as Genbank
(http://www.ncbi.nlm.nittgov:80/entrez) or from commercial databases.
Suitable constructs may be synthesised by conventional methods, as described
in the examples herein, or obtained commercially.
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"An NLS-containing transmembrane protein" includes a
transmembrane protein which contains an NLS in its wild type sequence and
a transmembrane protein whose amino acid sequence has been modified to
contain an NLS.
Conventional NLSs are short peptide sequences that facilitate nuclear
localisation of the proteins containing them (see for example, Table 1 which
lists NLSs and Jans et al., 2000). There are three major classes of NLSs; two
of these classes consist of basic amino acid residues, the monopartite NLSs,
exemplified by the SV40 large tumor antigen, PKKKRKV, consisting of a
single stretch of basic amino acids, and the bipartite NLSs which 'contain two
stretches of basic amino acids separated by 10 to 22 (sometimes up to
hundreds) amino acids. Other types of NLSs are exemplified by those of the
yeast protein Mata2 NLS where charged/polar residues are contained within
the stretch of non-polar residues, or the protooncogene c-myc NLS, where
proline and aspartic acid residues flanking the basic residues are required
(PAAKRVKLD) for nuclear targeting. All classes of NLS are recognized
specifically by the a-f3-importins.
Any NLS may be employed in the methods of the invention.
Nucleotide sequences encoding a selected NLS may be derived from the
amino acid sequence of the NLS and are synthesised and incorporated into
the nucleotide sequence encoding the transmembrane protein by
conventional methods, as described herein. Many different locations within
any of the intracellular loops or intracellular termini of the transmembrane
protein are suitable for insertion of the NLS. Insertion of the NLS within an
intracellular domain of the protein is preferred. For example, in a GPCR, the
NLS could be placed in any of the intracellular loops or intracellular
carboxyl
tail. In a 12 TM transporter, the NLS could be placed in the intracellular
amino or carboxyl termini or any of the intracellular loops.
When an NLS is inserted into a transmembrane protein for use in the
methods of the invention, the efficacy of the insertion can be screened by
confirming that the NLS-containing transmembrane protein is substantially
translocated from the cell membrane to the cell nucleus within 24 to 48 hours
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and that ligands of the transmembrane protein interfere with the
translocation.
Nucleotide sequences encoding NLS-containing transmembrane
proteins are linked to sequences encoding detectable peptides or
polypeptides by conventional methods.
A nucleotide sequence encoding a selected NLS-containing
transmembrane protein containing or linked to a detectable moiety, is
transfected into a nucleated cell by cloning the sequence into a vector
system containing a suitable promoter, using conventional techniques as
described in the scientific literature, for example in Current Protocols in
Molecular Biology, (1987). Suitable vectors include the pEGF-N1 (Clontech)
which contains the human cytomegalovirus (CMV) promoter, and the vector
pcDNA. =
Any cell may be used which is capable of expressing the transfected
nucleotide sequences and in which an NLS facilitates transfer of a
transmembrane protein away from the cell membrane. Suitable cells include
prokaryotic cells, including bacterial cells, and eukaryotic cells. Suitable
eukaryotic cells include isolated mammalian cells, yeast cells, plant cells,
insect cells, nematode cells and fungal cells. Suitable mammalian cells
include human cell lines, rodent cell lines, hamster cell lines, non-human
primate cell lines.
In one embodiment, the cell is transfected with a number of nucleotide
sequences, each encoding a different NLS-containing transmembrane
protein and a different detectable moiety. Interference with trafficking of
the
transmembrane protein away from the cell membrane by a test compound
can be related to interaction of the compound with a particular
transmembrane protein by the identity of the detectable moiety whose
movement from the cell surface is interrupted.
In a further embodiment, for higher throughput initial screening, the
cell is transfected with a greater number of nucleotide sequences, each
encoding a different NLS-containing transmembrane protein and a
detectable moiety, some of the detectable moieties being common to more
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than one transmembrane protein. If initial screening indicates that a
candidate compound is interacting with one or more of the transmembrane
proteins, the compound is rescreened using a cell expressing fewer
transmembrane proteins, or, only one, until the specific interacting
transmembrane protein is identified.
In cells transfected with more than one transmembrane protein, there
may be oligomerisation between pairs of proteins as discussed herein, and
this may affect the interpretation of the effect of a candidate compound.
Subsequent rescreening of the compound using cells transfected with only
one transmembrane protein allows clarification of the interaction of the
compound with a particular protein.
Alternatively, for multiply transfected cells, transmembrane proteins
may be selected which have been shown not to oligomerise with each other.
Identification of interacting compounds
In one embodiment of the invention, nucleated cells are transfected
with a nucleotide sequence encoding a protein comprising a transmembrane
protein containing an NLS and a detectable moiety and incubated for a
suitable period of time to allow expression of the NLS-transmembrane protein
and commencement of its accumulation at the cell membrane. For GPCRs
and transporters, for example, a time period of about 6 to 24 hours is
suitable.
One of skill in the art can readily determine a suitable incubation time for
other
transmembrane proteins by observation of the accumulation of the protein at
the cell membrane. All of the expressed transmembrane protein need not
have reached the cell membrane when the candidate compound is added.
Test cells are then contacted with a candidate compound which is to be tested
for interaction with the transmembrane protein for a period of time which is
sufficient to allow translocation of a substantial portion of the NLS-
transmembrane protein, preferably at least 20%, more preferably at least.
50%, and still more preferably at least 90%, away from the cell membrane
and into or towards the nucleus in a control cell not treated with compound.
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Depending on the transmembrane protein, this period of time may be
from about 6 hours to about 72 hours; a time period of about 24 to about 48
hours is suitable for most transmembrane proteins examined. One of skill in
the art can readily determine a suitable time by observation of control cells.
Test compounds are initially tested generally at a concentration of
about 1 to 10 micromolar.
Test and control cells are then examined to determine the distribution
of the detectable moiety and thereby the distribution of the NLS-
transmembrane protein. The distribution of the detectable moiety may be
determined by various methods. For example, when the detectable moiety is
an optically detectable protein, the cells may be examined by direct
microscopy and the amount of protein in the nucleus compared between test
and control cells. In another embodiment, the amounts of detectable protein
or peptide remaining in the membrane of control and test cells are compared.
In several microscopic fields (5-10), each containing 30-100 cells, the
location
of the detectable moiety in these cells is determined and counted for each
location. The percentage of cells having cell surface, or nuclear labelling
and
the sum of all the fields is then calculated for the treated and control
cells.
In a further example, when the detectable moiety is an antigenic
epitope, the cells are contacted with a detectable antibody system containing
an antibody specific for the epitope, as described above. For example, a first
antibody specific for the epitope may be used, followed by a fluorescently
labelled second antibody specific for the first antibody, the fluorescent
signal
being quantified by fluorometer.
Where control cells show a substantial portion, preferably at least 50%,
of the transmembrane protein translocated away from the cell membrane and
test cells show retention of the transmembrane protein at the cell membrane,
relative to control cells, this indicates interaction of the test compound
with the
transmembrane protein. In a preferred embodiment, interaction is indicated
when the level of protein at the cell membrane is higher in the test cells by
at
least 10%, preferably by at least 15%, and more preferably by at least 20%.
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The proportion of the detectable moiety remaining at the cell
membrane on exposure to the interacting compound is related to the
concentration and potency of the compound. For example, the use of a
known potent GPCR antagonist in micromolar concentration typically resulted
In a variant of this method, used where the transmembrane protein has
known ligands, an expressed NLS-containing transmembrane protein without
a detectable moiety is used and distribution of the protein in the cell after
treatment with a test compound is determined by isolation of the cell
In a further embodiment of the invention, a similar method is used to
identify compounds which interact with an NLS-transmembrane protein to
promote its translocation away from the cell surface and into or towards the
Test cells are then contacted with a candidate compound, and
individual test and control cells are immediately observed in real time for up
to
4 hours to observe the distribution of the detectable moiety. An increased
accumulation of detectable moiety in the nucleus of test cells compared with
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indicated when test cells show nuclear accumulation increased by at least
5%, preferably by at least 10%, and more preferably by at least 20%.
A further embodiment of the invention is a method for identifying
compounds which, although they do not themselves prevent translocation of
an NLS-containing transmembrane protein away from the cell membrane,
nevertheless can interfere with the interaction of the transmembrane protein
with an interacting compound.
Compounds which have proved negative in the first screening method
described above may be tested by this further method for their ability to
compete with a known interacting compound.
In this method, cells are transfected as described above and incubated
for a suitable period of time to allow expression and accumulation of the
transmembrane protein at the cell surface, for example for about 24 to about
48 hours.
Test cells and control cells are then contacted with a compound known
to interact with the transmembrane protein, either a known ligand or an
interacting compound identified by the method described above, for about 24
to about 48 hours. Test cells are then contacted with a candidate compound
and test cells and control cells are observed after 1 hour, at one or more
time
points, up to 24 hours, to determine distribution of the NLS-transmembrane
protein within the cells as described above. In control cells, the known
interacting compound causes the transmembrane protein to be retained at the
cell membrane. If the candidate compound competes with the interacting
compound, test cells show a reduction of transmembrane protein at the cell
surface and increased translocation of the protein away from the cell surface.
In a preferred embodiment, interaction is indicated when test cells show a
reduction of at least 10%, preferably 15%, and more preferably 20%.
In a further embodiment, a cell which endogenously expresses an
NLS-containing transmembrane protein may be employed, in conjunction with
a first compound which has been demonstrated to interact with the protein
and inhibit its transfer from the cell membrane, thus retaining the protein at
the cell membrane. When such a system is contacted with a candidate
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compound, if that compound interacts with the transmembrane protein and
competes with the first compound, an increased transfer of the protein away
from the cell membrane is observed.
Identifying transmembrane protein interactions with other proteins
A number of transmembrane proteins, including GPCRs, transporters,
tyrosine kinase receptors, the cytokine receptors for insulin, insulin-like
growth
factors, the epidermal growth factor and vascular endothelial growth factor,
are capable of both homo- and heterooligomerisation (see, for example,
review of GPCRs in George et al., 2002). As used herein, "oligomerisation" of
a protein means association of two or more molecules of the protein.
For hypothetical receptors A and B, the cell surface may contain
dinners AA, BB and AB and it is believed that these may represent three
different functional complexes and therefore three different drug targets. It
is
therefore important to identify which transmembrane proteins can interact with
each other or with other proteins by oligomerisation.
In further embodiments, the invention provides methods for
determining whether two transmembrane proteins are capable of
oligomerisation or whether a transmembrane protein and a non-
transmembrane protein are capable of oligomerisation.
In one embodiment, a nucleated cell is co-transfected with a first
nucleotide sequence encoding a first transmembrane protein containing an
NLS and a second nucleotide sequence encoding a second transmembrane
protein lacking an NLS but carrying or linked to a detectable moiety. Creation
of these nucleotide sequences is as described above. After a suitable time
interval to allow for expression of the encoded proteins, accumulation at the
cell membrane and subsequent translocation of the NLS-containing protein
away from the cell membrane to or towards the nucleus, the distribution of the
detectable moiety in the cell is determined, for example by determining an
increase of .detectable moiety in the nucleus or by a decrease of detectable
moiety at the cell surface.
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It has been found that when cells are doubly transfected, and the first
and second transmembrane protein are the same, except that one
transmembrane protein contains an inserted NLS and the other does not,
there is a slowing of the transfer of the NLS-containing transmembrane
protein to the cell nucleus compared with transfer in a cell transfected only
with the NLS-containing protein. The process of protein translocation to the
nucleus now may take about 24 to 48 hours. In this method, therefore, the
cells are incubated for about 24 to 48 hours before examination of the
distribution of protein in the cell.
lo Translocation of the detectable moiety from the cell surface to or
towards the nucleus indicates that the first transmembrane protein has carried
the second transmembrane protein away from the cell surface, indicating
oligomerisation of the first and second proteins. Retention of the detectable
moiety at the cell surface indicates a lack of interaction between the
proteins.
When the first and second transmembrane proteins are the same
protein, the method allows the identification of the ability of the protein to
homodimerise. When the first and second transmembrane proteins are
different, the method allows the identification of the ability of two
different
proteins to heterodimerise and permits the determination of the specificity of
interaction between two transmembrane proteins.
The method may be carried out either in the absence of ligand
activation or in the presence of a ligand of either protein.
Using this method, oligomerisation has been demonstrated both within
and between different classes of GPCRs and within and between other
classes of transmembrane proteins.
In addition, interactions have been detected between GPCRs and non-
GPCR transmembrane proteins, for example between the D5 dopamine
receptor and the GABA-A receptor, and between transmembrane proteins
and non-transmembrane proteins.
The invention therefore generally provides a method for detecting
oligomerisation between two proteins by the method described above, where
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a cell is co-transfected with one of the proteins containing an NLS and the
other protein carrying a detectable signal.
Co-transfection of a cell with a first transmembrane protein containing
an NLS and a second.detectably labelled protein, such as a transmembrane
protein from a different group, which has been shown by the method of the
invention to oligomerise with the first protein, provides a cell which can be
used to screen candidate compounds for interaction with either the first or
second protein. A compound which interacts with either protein will influence
oligomerisation or translocation of the oligomerised proteins away from the
cell membrane. Compounds which interact with one member of the protein
pair or with the oligomer to cause retention of the detectable protein at the
cell
surface or to cause accelerated translocation of the detectable protein away
from the cell surface may be identified by this method.
In a further embodiment, a cell which endogenously expresses an
NLS-containing transmembrane protein is transfected with a nucleotide
sequence encoding a second transmembrane protein carrying a detectable
moiety but lacking an NLS. Oligomerisation of the two proteins is indicated by
trafficking of the detectable moiety away from the cell membrane and into or
towards the nucleus.
In a further embodiment, a membrane protein containing an NLS may
be used to identify novel interacting proteins. In this method, an NLS-
containing transmembrane protein is expressed in a cell and is allowed to
translocate to the nucleus. The nuclei are then harvested and assayed for
newly appeared protein bands by Coomassie staining or silver staining and
then identification by mass spectroscopy. The control will be nuclei from
cells
expressing the membrane protein without a NLS.
Use.of FRET for detection of nuclear translocation.
In a further aspect of the invention, involving fluorescence resonance
energy transfer (FRET) (Halley et al., 2002), a nucleated cell is co-
transfected with a first nucleotide sequence encoding a first NLS-containing
transmembrane protein linked to a first optically detectable protein and a
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second nucleotide sequence encoding a second non-NLS-containing
transmembrane protein linked to a second optically detectable protein,
whose fluorescence can be activated by the emission of the first optically
detectable protein when these are in close proximity. For example, the first
5 protein may be linked to GFP and the second any other optically
detectable
moiety that can be activated by the laser activated emission spectrum of
GFP. This second optically detectable moiety, after activation by the GFP,
emits at a different wavelength. Where oligomers are formed between the
two transmembrane proteins, the two labels are in close proximity to each
10 'other and their FRET interaction can be detected. The physical
interaction is
detected by selective fluorescence activation of the donor and detection of
emission by the acceptor, using the FRET method or its variants such as
photobleaching FRET, FRAP or FLIM. Lack of a FRET interaction indicates
lack of oligomerisation.
15 Confocal microscopy with FRET between two fluorescent molecules
may be performed (e.g. the spectral pairs GFP and DsRed2, or CFP and
YFP) to obtain a quantifiable signal indicating translocation to the nucleus.
FRET requires an overlap between the emission and excitation spectra of =
donor and acceptor molecules and a proximity of under 100 angstroms (10-
20 100), making FRET a highly suitable system to assay for specific close
protein-protein interactions in cells. The fluorescent proteins listed above
are excellent spectral partners. A resident fluorophore in the nucleus would
enable FRET to occur when a transmembrane protein tagged with second
fluorophore is translocated to the nucleus. This will facilitate an easy
25 readout,
using a FRET plate reader. This method is useful for detecting =
interactions between two transmembrane proteins or between a
transmembrane protein and another protein and provides a signal readout
more amenable to automation.
This method can also be used in GPCR agonist and antagonist
screening procedures. In the antagonist screening method, a reduction of a
FRET Signal between a GPCR-NLS-GFP trafficked to the nucleus with a
fluorophore in the nucleus of treated cells compared to non treated cells
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would indicate an antagonist effect. In the agonist screening method, the
increase in the FRET signal between a GPCR-NLS-GFP trafficked to the
nucleus with a fluorophore in the nucleus of treated cells compared to non
treated cells would indicate an agonist effect. In a further embodiment, the
doubly transfected cells may be treated with an agonist before examination
for evidence of oligomerisation, since this may be enhanced in the presence
of agonist. In the measurement of receptor:receptor interactions, a GPCR-
NLS-GFP is co-expressed with a second GPCR-DsRED. If these receptors
interact with each other and traffic together to the nucleus a nuclear FRET
signal will be detected. If the receptors do not interact then no FRET signal
will be obtained in the nucleus. FRET may also be measured between two
fluorophore-conjugated antibodies recognising incorporated ot native
epitopes on the GPCRs.
EXAMPLES
The examples are described for the purposes of illustration and are
not intended to limit the scope of the invention.
Methods of chemistry, molecular biology, protein and peptide
biochemistry and immunology referred to but not explicitly described in this
disclosure and examples are reported in the scientific literature and are well
known to those skilled in the art.
Materials and Methods
Green fluorescent protein: a DNA sequence encoding the Aeduoria
victoria green fluorescent protein (Prasher et al., 1992) was obtained from
ClOntech, U.S.A.
Red fluorescent protein: a DNA sequence encoding the red
fluorescent proteins (Matz et al., 1999) pDsRed2 and pDsRed2-nuc were
obtained from Clontech, U.S.A. This construct encodes a protein derived
from Discosoma sp.
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COS cells and HEK cells were obtained from American Type Culture
Collection, Washington, D.C. The cell culture media were prepared by
laboratory services at the University of Toronto.
Antagonist and agonist compounds were obtained from various
commercial sources such as Sigma Chemical Company U.S.A.
Antibodies used for immunodetection of epitope tags were obtained
from the following sources: Anti-HA monoclonal antibody was obtained from
Roche Diagnostics, U.S.A. Anti-FLAG monoclonal antibody was obtained
from Sigma Chemical Company, U.S.A. Anti-c-myc monoclonal antibody
was obtained from Santa Cruz, U.S.A.
Radioligand 3H-SCH 23390 used in the receptor binding assay was
obtained from NEN Perkin Elmer, U.S.A.
Creation of DNA Constructs
Nucleotide sequences encoding GPCR's or transporters were
obtained from the Genbank (http://www.ncbi.nlm.nih.gov:80/entrez) web site,
established by the National Library of Science. A nucleotide sequence
encoding a selected transmembrane protein was attached to a nucleotide
sequence encoding a selected detectable signal protein. The constructs
were cloned into the vector system, pEGFP (Clontech) or the pDsRed2-N1
vector or the vector pcDNA3.
1a. Construction of the human D1 dopamine receptor with a NLS
in the proximal carboxyl tail (helix 8) and fused to GFP (D1-GFP and
D1-NLS-GFP).
Using the PCR method with the following experimental conditions,
DNA encoding the human D1 dopamine receptor in the vector pcDNA3, was
subjected to PCR. The reaction mixture contained water (32 microlitres),
10x Pfu buffer (Stratagene) (5 microlitres), dNTP (2'-deoxynucleoside 5'-
triphosphate, 10mM) (5 microlitres), DMSO (5 microlitres), oligonucleotide
primers (bong) (1 microlitre each), DNA template (10Ong), Pfu enzyme
(5units). Total volume was 50 microlitres. The following PCR conditions
were used, one cycle at 94 C for 2 mins, 30-35 cycles at 94 C for 30 secs,
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55 C for 30 secs, 72 C for 1 min, per cycle, and then one cycle at 72 C for
mins.
Primer set for amplification of the DNA encoding the D1-dopamine
receptor:
5 HD1-P1: 5' GAGGACTCTGAACACCGAATTCGCCGCCATGGACGG
GACTGGGCTGGTG 3'
HD1-P2: 5' GTGTGGCAGGATTCATCTGGGTACCGCGGTTGGGTG
CTGACCGTT 3'
The restriction site EcoR1 was incorporated in the primer HD1-P1,
and restriction site Kpn1 was incorporated into the primer HD1-P2. The
PCR product, which contained no stop codon was unidirectionally subcloned .
into vector pEGFP (from Clontech) at EcoR1 and Kpn1 and inframe with the
start codon of the GFP protein.
The NLS sequence, KKFKR from the human AT1 receptor was
inserted into DNA encoding the base of TM7 (helix 8) of the D1 dopamine
receptor by PCR, replacing the natural sequence coding for DFRKA.
The primer set for the construction of DNA encoding D1-NLS:
HD1-NLSF: 5' CCTAAGAGGGTTGAAAATCT.TTTAAATTTTTTAGCA
TTAAAGGCATAAATG 3' =
HD1-NLSR: 5' GCCTTTAATGCTAAAAAATTTAAAAGATTTTCAACC
CTCTTAGGATGC 3'
Using the DNA encoding D1-GFP as template, PCR with the primers
HD1-P1 and HD1-NLSF resulted in a product of 1000bp (PCR#1). Using
DNA encoding D1-GFP PCR with primers HD1-P2 and HD1-NLSR resulted
in a product of 300bp (PCR#2). A subsequent PCR carried out with HD1-P1
and HD1-P2 primers resulted in a product of 1300 bp using the product from
PCR#1 and the product from PCR#2 as templates. The resulting DNA
encoding D1-NLS was subcloned into vector pEGFP at EcoR1 and Kpn1
restriction sites.
All the additional constructs described below were made using the
same PCR method and experimental conditions as described above for the
D1 dopamine receptor, but with specific primers as described below.
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lb. Constructing the human dopamine D1 receptor containing a
NLS and fused to RFP (Dl-NLS-RFP)
The NLS sequence KKFKR was inserted into the helix 8 segment of
the intracellular carboxyl tail of the human D1 receptor by PCR method as
follows. Using the DNA encoding the human D1 in pcDNA3 vector as
template, the first PCR was carried out with HD1-P1 and HD1-NLSR primers
resulting in a 1kb product. A second PCR was done using HD1-P2 and HD1-
NLSF primers resulting in a 300bp product,. Using PCR#1 and PCR#2
products as templates, the final PCR was done with HD1-P1 and HD1-P2
primers which generated a 1.3kp product.
Dl NLS was subcloned into vector pDsRed (Clontech ) at EcoRI and
Kpnl and fused to RFP.
Primer sequences:
HD1-P1: 5' GAGGACTCTGAACACCGAATTCGCCGCCATGGACGGGACTG
GGCTGGTG 3'
HD1-P2: 5' GTGTGGCAGGATTCATCTGGGTACCGCGGTTGGGTGCTGAC
CGTT 3'
HD1-NLSF: 5' GCCTTTAATGCTAAAAAATTTAAAAGATTTTCAACCCTCTT
AGGATGC 3'
, 20 HD1-NLSR: 5' CCTAAGAGGGTTGAAAATCTTTTAAATTTTTTAGCATTAAA
GGCATAAATG 3'
D1- wildtype: NPIIYAFNADFRKAFSTLL
D1NLS-Helix8: NPIIYAFNAKKFKRFSTLL
lc. Construction of the dopamine D1 receptor with a
hemagglutinin (HA) epitope tag in the amino terminus
The HA-Tag is as follows:
Nucleotide sequence: TACCCTTACGACGTGCCGGATTACGCC
HA amino acid sequence: YPYDVPDYA
The HA epitope tag was inserted into the amino terminal of the human
D1 receptor using D1-pcDNA3 as template with the following primers:
P1HA-BamH:
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5'ggatccactagtaacggccgccagaccaccATGGGATACCCGTACGACGTCCGCGA
CTACGCAAGGACTCTGAACACCTCTGCC 3'
P2-Notl: 5' ggccgccagctgcgagTTCAGGTTGGGTGCTGACCG 3'
The resulting amplified cDNA (1.3 kb) was subcloned into pcDNA3 vector at
5 BamH land Not I.
D1 wildtype: MRTLNTSAMDGTGLVV.
D1-HAtag: MGYPYDVPDYARTLNTSAMDGTGLVV
Id. Construction of the human dopamine DI receptor with a HA
epitope and NLS in the proximal carboxyl tail (helix 8) (D1HA-NLS)
10 Primer set for the PCR amplification of DNA encoding D1-NLS (helix
8), using DNA encoding D1-HA as template. Using DNA D1-HA as template
with primers T7 and HD1-NLSR primers the resulting amplified DNA was
1000bp (PCR#1). Using DNA D1-HA as template with primers Sp6 and HD1-
NLSR primers the resulting DNA was 300bp, (PCR#2). Using primers 17 and
15 Sp6 primers and the product of PCR#1 and PCR# 2 as templates the
resulting DNA was 1300 bp (PCR#3).
HD1-NLSR: 5' CCTAAGAGGGTTGAAAATCTTTTAAATTTTTTAGCA
TTAAAGGCATAAATG 3'
HD1-NLSF: 5' GCCTTTAATGCTAAAAAATTTAAAAGATTTTCAACC
20 CTCTTAGGATGC 3'
The result Dl HA-NLS (helix 8) PCR was blunt-ended into pcDNA3 at
EcorV. The correct orientation clone was sequenced.
Dl-HA wildtype: NPIIYAFNADFRKAFSTLL
25 D1HA-NLS (helix 8): NPIIYAFNAKKFKRFSTLL
le. Construction the dopamine DI receptor with a NLS in
intracellular loop 3, fused to GFP (D1-NLS-1C3-GFP)
Primer set for the construction of Dl-NLS-IC3-EGFP:
D1NLSF-1C3: 5' GGAAAGTTCTTTTAAGAAGAAGTTCAAAAGAGAAAC 3'
30 D1-NLSR-1C3: 5' GTTTCTCTTTTGAACTTCTTCTTAAAAGAACITTCC 3'
Using D1 pcDNA3 template:
PCR#1: HD1-P1 and D1NLSR-1C3 primers
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PCR#2: HD1-P2 and D1NLSF-1C3 primers (500bp)
PCR#3: HD1-P1 and HD1-P2 primers using PCR#1 and PCR#2 as templates
(1.3 kb)
The resulting DNA fragment encoding D1-NLS-1C3 was subcloned into vector
pEGFP at EcoR1 and Kpn1.
D1-wildtype: QPESSFKMSFKRETKVL
D1-NLS-1C3: QPESSFKKKFKRETKVL
The NLS sequence KKFKR was inserted into the IC loop 3 segment
of the D1 receptor replacing the sequence MFSKR, using D1 pcDNA3 as
lo template.
Using the DNA encoding D1 in pcDNA3 as template, PCR was carried
out with the following primers HD1-P1 and D1-NLSR-1C3 resulting in a
product of 800 bp (PCR#1). Using DNA encoding D1 in pcDNA3 with primers
HD1-P2 and HD1-NLSF-1C3 resulted in a product of 500 bp (PCR#2). A
subsequent PCR carried out with HD1-P1 and HD1-P2 primers resulted in a
product of 1300 bp using the product from PCR#1 and the product from
PCR#2 as templates. The resulting construct encoding D1-NLS was
subcloned into vector pEGFP at EcoR1 and Kpn1 restriction sites.
If. Construction of human Di dopamine receptor with a NLS in
intracellular loop 2 fused with GFP (D1-NLS-1C2-GFP)
The primer set for the construction of DNA encoding D1NLS-IC2
D1NLSF-1C2: 5' CCGGTATGAGAAAAAGTTTAAACGCAAGGCAGCCTTC 3'
Dl-NLSR-1C2: 5' GGCTGCCTTGCGTTTAAACTTTTTCTCATACCGGAAAG
G3'
Using DNA encoding D1 dopamine receptor in pcDNA3 as template,
PCR with the primers HD1-P1 and D1NLSR-1C2 (PCR#1), resulted in a
product of 500 bp. Using DNA encoding D1 dopamine receptor in pcDNA3 as
a template with primers HD1-P2 and D1NLSF-IC2 (PCR#2) resulted in a
product of 800 bp. A subsequent PCR carried out with primers HD1-P1 and
HD1-P2 using PCR#1 and PCR#2 as templates resulted in a product of 1300
bp.
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The resulting DNA encoding Dl NLS-1C2 PCR was subcloned into
vector EGFP at EcoR1 and Kpn1.
D1- wildtype: NPFRYERKMTPKAAFILI
D1-NLS-1C2: NPFRYEKKFKRKAAFILI
, 1g.
Construction of the human DI dopamine receptor with a NLS
in intracellular loop 1 fused with GFP (D1-NLS-ICI-GFP)
The primer set for the construction of DNA encoding Dl -NLS-ICI.
Dl-NLSF-IC1: 5' GTGCTGCCGTTAAAAAGTTCAAACGCCTGCGGTCCAAG
G3'
D1-NLSR-ICI: 5' GGACCGCAGGCGTTTGAACTTTTTAACGGCAGCACAG
ACC 3'
Using the DNA encoding D1 dopamine receptor in pcDNA3 as
template, PCR with the primers HD1-P1 and Dl-NLSR-ICI (PCR#1), resulted
in a product of 300 bp. Using DNA encoding D1 dopamine receptor in
pcDNA3 as template PCR with primers HD1-P2 and D1NLSF-IC1 resulted in
a product of 1000 bp (PCR#2). A subsequent PCR carried out with primers
HD1-P1 and HD1-P2 using PCR#1 and PCR#2 as templates resulted in a
product of 1300 bp.
The resulting DNA encoding D1-NLS-ICI was subcloned into vector
pEGFP at EcoR1 and Kpn1.
D1- wildtype: LVCAAVIRFRHLRSKVTN
D1-NLS-ICI: LVCAAVKKFKRLRSKVTN
1h. Construction of human dopamine D1 receptor with an alternate
NLS in the proximal carboxyl tail and fused to GFP (D1-NLS2-GFP)
The PCR method was used to introduce the NLS sequence PKKKRKV in
replacement of the natural sequence ADFRKAF in the D1 receptor.
The DNA encoding the D1 dopamine receptor in pcDNA3 was subjected to
PCR with the primers HD1-P1 and HD1-NLS2R, resulting in a product of 1kb
(PCR#1). Another PCR using D1 in pcDNA3 with primers FID1-P2 and HD1-
.
NLS2F resulted in a product of 300bp (PCR#2). The third PCR using PCR#1
and PCR#2 as templates HD1-P1 and HD1-P2 primers resulted in a product
of 1.3kb, and was subcloned into vector pEGFP at EcoR1 and Kpn1.
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HD1-NLS2F: 5' GCCTTTAATCCTAAAAAAAAAAGAAAGGTTTCAACCCTCT
TAGG 3'
HD1-NLS2R: 5' CCTAAGAGGGTTGAAACCTTTCTTTTTTTTTTAGGATTAA
AGGC 3'
D1-wildtype: NPIIYAFNADFRKAFSTLL
D1-NLS2: NPIIYAFNPKKKRKV STLL
2. Construction the dopamine D2 and D2-NLS dopamine
receptors fused to GFP (D2-GFP and D2-NLS-GFP)
Primer set for amplification of the DNA in pcDNA3 encoding the D2-
dopamine receptor.
HD2-P1: 5' GGCCGTGGCTCCACCGAATTCGCCGCCATGGATCCACTGA
ATCTG 3'
HD2-P2: 5' CTGTGCGGGCAGGCAGGGTACCGCGCAGTGGAGGATCTT
CAGG 3'
The restriction site EcoR1 was incorporated into primer HD2-P1, and
the restriction site Kpn1was incorporated into primer HD2-P2. The D2-PCR
product, which contained no stop codon, was unidirectionally subcloned into
vector pEGFP (Clontech) at EcoR1 and Kpn1 and inframe with the start
codon of the GFP protein.
Primer set for the construction of D2-NLS-GFP
HD2-NLSF: 5' CACCACCTTCAACAAAAAATTCAAAAGAGCCTTCCTGAA
GATCC 3'
HD2-NLSR: 5' GGATCTTCAGGAAGGCTCTTTTGAATTTTTTGTTGAAGG
TGGTG 3'
The NLS sequence KKFKR was inserted into the base of TM7
segment of the D2 receptor replacing the sequence 1EFRK, using D2-GFP
DNA construct as template.
Using the DNA encoding D2-GFP as template, PCR was carried out
with the following primers HD2-P1 and HD2-NLSR resulting in a product of
1300bp (PCR#1). Using DNA encoding D2-GFP PCR with primers HD2P2
and HD1-NLSF resulted in a product of 100bp (PCR#2). A subsequent PCR
carried out with HD2-P1 and HD2-P2 primers resulted in a product of
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1400bp using the product from PCR#1 and the product from PCR#2 as
templates. The resulting construct encoding D2-NLS was subcloned into
vector pEGFP at EcoR1 and Kpnl restriction sites.
3. Construction of DNA encoding the D3 and D5 dopamine
receptors fused to GFP (D3-GFP and D5-GFP)
Primer set for amplification of the DNA in pcDNA3 encoding the D3-
dopamine receptor.
HD3-Hind: 5' GGCATCACGCACCTCAAGCTTGCCGCCATGGCATCTCTG
AGTCAGC 3'
HD3-Kpn: 5' GAGTGTTCCCTCTTCTGCGGTACCGCGCAAGACAGGATCT
TGAGG 3'
The restriction site Hind111 was incorporated into primer HD3-Hind,
and the restriction site Kpnl and was incorporated into primer HD3-Kpn. The
D3-PCR product, which contained no stop codon, was unidirectionally
subcloned into vector pEGFP at Hindi!' and Kpnl and inframe with the S start
codon of the GFP protein.
Primer set for amplification of the DNA in pcDNA3 encoding the D5
dopamine receptor.
T7: 5' AATACGACTCACTATAG 3'
HD5-Kpn: 5' CGCCAGTGTGATGGATAATGGTACCGCATGGAATCCATTC
GGGGTG 3'
The restriction site Kpnl and was incorporated into primer HD5-Kpn.
The D5-PCR product, which contained no stop codon, was unidirectionally
subcloned into vector pEGFP at EcoRI and Kpnl and inframe with the start
codon of the GFP protein.
4. Construction of the Histamine1 and Histamine1-NLS
receptors fused to GFP (H1-GFP and 111-NLS-GFP)
Primer set for amplification of the DNA, from human genomic DNA,
encoding the encoding the H1 histamine receptor.
H1-MET: 5' GCGCCAATGAGCCTCCCCAATTCC 3'
H1-STOP: 5' GAGCCTCCCTTAGGAGCGAATATGC 3'
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This H1-PCR product was used as a template for the subsequent
PCR experiment.
Primer set for amplification of the DNA encoding the H1-GFP
construct.
5 H1-PST: 5' CGCCTGCAGGCCGCCATGAGCCTCCCCAATTCCTCC 3'
H1-APA: 5' CCGGTGGATCCCGGGCCCCGGAGCGAATATGCAG 3'
The restriction site Pstl was incorporated into primer H1-PST, and the
restriction site Apal was incorporated into primer H1-APA. This H1-PCR
product, which contained no stop codon, was unidirectionally subcloned into
10 vector pEGFP at Pstl and Apal and inframe with the start codon of the
GFP
protein.
Primer set for amplification of the DNA encoding the H1-NLS-GFP
H1-NLSR: 5' GGGCCCCGGAGCGAATATGCAGAATTCTCTTGAATGTCC
TCTTGAAT _____ I I I I I ATTGCACAAGG 3'
15 The NLS sequence: KKFKR was inserted into the DNA encoding the
TM7 segment of the H1 receptor by the PCR method, using the H1-GFP
template, replacing the sequence ENFKK. PCR with H1-PST and H1-NLSR
primers gave a product of 1500bp. The resulting fragment encoding H1-NLS
was subcloned into vector pEGFP at Pstl and Apal restriction sites.
20 5. Construction the cysteinyl leukotriene receptor 1 and CysLT1-
NLS fused to GFP (CysLT1-GFP and CysLT1-NLS-GFP).
Primer set for amplification of the DNA in pcDNA3 encoding the
CysLT1 receptor.
LT1-Ecorl: 5' AAGAATTCGCCACCATGGATGAAACAGGAAATCTG 3'
25 LT1-Kpnl: 5' GGGTACCGCTACTTTACATATTTCTTCTCC 3'
The restriction site EcoR1 was incorporated into primer LT1-EcoRI
and the restriction site Kpn1was incorporated into primer LT1-Kpnl. The
CysLT1-PCR DNA product, which contained no stop codon, was
unidirectionally subcloned into vector PGFP at EcoR1 and Kpn1 and inframe
30 with the start codon of the GFP protein.
Primer set for amplification of the DNA encoding the CysLT1-NLS -
GFP
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LT1 -NLS F: 5' TTCTTTTCTGGGAAAAAATTTAAGAGAAGGCTGTCTAC 3'
LT1-NLSR: 5' TGTAGACAGCCTTCTCTTAAATTTTTTCCCAGAAAAG 3'
The NLS sequence KKFKR was inserted into the DNA encoding the
TM7 segment of the CysLT1 by PCR, using DNA encoding the CysLT1-GFP
as template, replacing the sequence GNFRK. Using the DNA encoding
CysLT1-GFP as template, PCR with the following primers LT1-EcoRI and
LT1-NLSR resulted in a fragment of 900bp (PCR#1). Using DNA encoding
CysLT1-GFP PCR with primers LT1-Kpnl and LT1-NLSF resulted in a
fragment of 100bp (PCR#2). A subsequent PCR carried out with LT1-EcoRI
and LT1-Kpnl primers resulted in a product of 1000bp using the product from
PCR#1 and the product from PCR#2 as templates. The resulting DNA
encoding CysLT1-NLS was subcloned into vector pEGFP at EcoR1 and
Kpn1 restriction sites.
6. Construction of the cysteinyl leukotriene receptor CysLT2 and
CysLT2-NLS fused to GFP (CysLT2-GFP and CysLT2-NLS-GFP)
Primer set for amplification of the DNA in pcDNA3 encoding the
CysLT2 receptor.
LT2-EcoRI: 5' CTTTTTGTGTCTGTTTCTGAATTCGCCACCATGGAGAGAA
AATTTATG 3'
LT2-Kpnl: 5' GAACAGGTCTCATCTAAGAGGTACCGCTACTCTTGTTTCC
TTTCTC 3'
The restriction site EcoR1 was incorporated into primer LT2-EcoRI,
and the restriction site Kpn1was incorporated into primer LT2-Kpnl. The
CysLT2 Product, which contained no stop codon, was unidirectionally
subcloned into vector pEGFP at EcoR1 and Kpn1 and infrarne with the start
codon of the GFP protein.
Primer set for the amplification of the CysLT2-NLS-GFP
LT2-NLSF: 5' GCTGGGAAAAAATTTAAAAGAAGACTAAAGTCTGCAC 3'
LT2-NLSR: 5' GTCTTCTTTTAAATTTTTTCCCAGCAAAGTAATAGAGC 3'
The NLS sequence KKFKR was inserted into the TM7 segment of the
CysLT2 by PCR method replacing the sequence ENFKD. Using the DNA
encoding CysLT2-EGFP as template, a PCR with the following primers LT2-
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EcoR1 and LT2-NLSR primers resulted in a fragment of 900bp (PCR#1).
Using DNA encoding LT2-Kpnl and LT2-NLSF primers a PCR resulted in a
fragment of 200bp (PCR#2). A subsequent PCR carried out with LT2-EcoR1
and LT2-Kpnl primers using the product of PCR#1 and the product of
PCR#2 as templates resulted in a product of 1100 bp. The resulting DNA
encoding CysLT2-NLS was subcloned into vector pEGFP at EcoR1 and
Kpnl restriction sites.
7. Construction of the M1 muscarinic receptor and the
muscarinic NLS receptor fused to GFP (M1-GFP and Ml-NLS-GFP)
Primer set for amplification of the DNA encoding the muscarinic
receptor (M1) from human genomic DNA.
M1-MET: 5' CCCCACCTAGCCACCATGAACACTTC 3'
M1-STOP: 5' GGGGACTATCAGCATTGGCGGGAGG 3'
Primer set for MR1-EGFP
M1-PST: 5' CCCCACCTGCAGCCACCATGAACACTTCAGCC 3'
M1-BAMH: 5' GGGGAGGATCCGCGCATTGGCGGGAGGGAGTGC 3'
The restriction site Pstl was incorporated into primer M1-PST, and the
restriction site BamHlwas incorporated into primer M1-BAMH. The M1 PCR
product, which contained no stop codon, was unidirectionally subcloned into
vector pEGFP at Pstl and BamHI and inframe with the start codon of the
EGFP protein.
Primer set for M1-NLS EGFP
M1-NLSF: 5''CGCACTCTGCAACAAAAAATTCAAACGCACCTTTCGCC 3'
M1-NLSR: 5' GGCGAAAGGTGCGTTTGAATTTTTTGTTGCAGAGTGCG 3'
The NLS sequence KKFKR was inserted into the TM7 segment of the
M1 by PCR, using the MR1 template, replacing the sequence KAFRD.
Using the DNA encoding MR1 as template, PCR with the following primers
using M1-PST and M1-NLSR resulted in a product of 1200bp (PCR#1).
Using DNA encoding MR1 a PCR with primers reaction using Ml-BAMH and
M1-NLSF primers resulted in a product of 100bp (PCR#2). A subsequent
PCR carried out with M1-PST and M1-BAMH primers resulted in a product of
1300bp using the product from PCR#1 and the product from PCR#2 as
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templates. This fragment encoding MR1-NLS was subcloned into vector
pEGFP at Psti and BamHI restriction sites.
8. Construction of the serotonin (5HT1B) and the serotonin NLS
receptors fused to GFP (5HT1B-GFP and 5HT1B-NLS-GFP)
Primer set for amplification of the DNA encoding the 5HT1B receptor
from the plasmid pcDNA3 encoding the 5HT1B receptor.
5HT1B-E1: 5' GGGGCGAATTCGCCGCCATGGAGGAACCGGGTGC 3'
5HT1B-KPN: 5' GCAAACGGTACCGCACTTGTGCACTTAAAACGTA 3'
The restriction site EcoR1 was incorporated into primer 5HT1B-E1
and the restriction site Kpn1was incorporated into primer 5HT1B-KPN. The
5HT1B -PCR product, which contained no stop codon, was unidirectionally
subcloned into vector pEGFP at EcoR1 and Kpn1 and inframe with the start
codon of the GFP protein.
Primer set for 5HT1B-NLS EGFP
5HT1B-NLSF: 5' ATGTCCAATAAAAAATTTAAAAGAGCATTCCATAAACT
G3'
5HT1B-NLSR: 5' GGAATGCTCTTTTAAATTMTATTGGACATGGTATAG
3'
The NLS sequence: KKFKR was inserted into the TM7 segment of
the 5HT1B by PCR using 5HT1B-EGFP template, replacing the sequence
EDFKQ. Using the DNA encoding 5HT1B-EGFP as template, a PCR with
the following primers with 5HT1B-E1 and HD1-NLSF primers gave a product
of 1100bp (PCR#1). Using DNA encoding 5HT1B-EGFP with 5HT1B-KPN
and HD1-NLSR primers resulted in a product of 100bp (PCR#2). A
subsequent PCR carried out with 5HT1B-E1 and 5HT1B-KPN primers
resulted in a product of 1200bp using the product from PCR#1 and the
product from PCR#2 as templates. The resulting DNA encoding 5HT1B-
NLS was subcloned into vector pEGFP at EcoR1 and Kpn1 restriction sites.
=
=
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9. Construction of the beta2-adrenergic (beta2-AR) and the
beta2-AR-NLS1 receptors fused to GFP (beta2-AR-GFP and beta2AR-
NLS1-GFP)
Primer set for amplification of the DNA encoding the beta2-AR
receptor from pcDNA3.
T7: 5' AATACGACTCACTATAG 3'
Beta2-Kpn: 5' GCCGCCAGTGTGATGGATACTGGTACCGCTAGCAGTGA
GTCATTTGTAC 3'
lo The restriction site Kpn1was incorporated into primer beta2-Kpn. The
beta 2-AR product, which contained no stop codon, was unidirectionally
subcloned into vector pEGFP at EcoR1 and Kpn1 and inframe with the start
codon of the GFP protein.
The NLS sequence KKFKR was inserted into the TM7 segment of the
beta2-AR by PCR using beta2-AR-EGFP template, replacing the sequence
PDFRI. Using the DNA encoding beta2-AR-EGFP as template, a PCR with
the following primers with T7 and B2-NLSR primers resulted in a product of
1100bp (PCR#1). Using DNA encoding beta2-AR-EGFP with beta2-Kpn
and B2-NLSF primers resulted in a product of 300bp (PCR#2). A
zo subsequent PCR carried out with primers T7 and beta2-Kpn resulted in a
product of 1300bp using the product from PCR#1 and the product from
PCR#2 as templates. The resulting DNA encoding beta2-NLS was
subcloned into vector pEGFP at EcoR1 and Kpn1 restriction sites.
10. Construction of the beta 2-adrenergic receptor with an
alternate NLS and fused to GFP (beta2-NLS2-GFP)
Primer set for amplification of the DNA encoding the beta2-NLS2
receptor from pcDNA3.
B2D1 NLSF: 5' CCCCTTATCTACGCCTTTAGCGCAAAGAAGTTCAA
GCGC 3'
B2D1 NLSR: 5' GCGCTTGAACTTCTTTGCGCTAAAGGCGTAGATA
AGGGG 3'
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Using the DNA encoding beta2-AR-GFP as template, a PCR with the
following primers with T7 and B2D1NLSR primers resulted in a product of
1000bp (PCR#1). Using DNA encoding beta2-AR-GFP with beta2-Kpn and
B2D1NLSF primers resulted in a product of 300bp (PCR#2). A subsequent
5 PCR carried out with primers 17 and beta2-Kpn primers using PCR#1 and
PCR#2 as templates resulted in a product of 1300 bp. The resulting DNA
encoding beta2-NLS2 was subcloned into vector pEGFP at EcoR1 and Kpn1
restriction sites.
The NLS sequence AFSAKKFKR was inserted into the TM7 segment
10 of the beta2-AR by PCR using beta2-GFP template, replacing the sequence
CRSPDFRIA.
The resulting DNA encoding beta2-NLS2 was subcloned into vector
pEGFP at EcoR1 and Kpn1 restriction sites.
11. Construction of the beta 2-adrenergic receptor with an
15 alternate NLS and fused to GFP (beta2-NLS3-GFP)
The NLS sequence KKF KR was inserted into another location of the
proximal segment of the carboxyl tail of the beta2-AR. Using the DNA
encoding the beta2AR in pcDNA3 vector as template, PCR was carried out
with T7 and r B2-NLS3R primers resulting a 1000bp product. PCR using
20 primers Beta2-Kpn and B2-NLS3F resulted in a 300bp product. Using PCR#1
and PCR#2 products as templates PCR with T7 and Beta2-Kpn primers
generated a 1300bp product (beta2AR-NLS3) which was subcloned into
vector pEGFP at EcoR1 and Kpn1.
= Primer set for Beta2-NL$3-GFP
25 B2-NLS3F: 5' CTGCCGGAGCAAAAAATTCAAAAGAGCCTTCCAGGAGC
3'
B2-NLS3R: 5' CCTGGAAGGCTCTTTTGAATTTTTTGCTCCGGCAGTAG 3'
WildtypeBeta2: NPLIYCRSPDFIRAFQELL
30 Beta2AR-NLS3: NPLIYCRSKKFKRAFQELL
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12. Construction of the dopamine transporter fused to GFP
(DAT-GFP)
The full length cDNA encoding the human dopamine transporter (hDAT)
was amplified using DAT in pcDNA3 as template by PCR with primer T7 and
primer DT-1 (5' CGTCTCTGCTCCCTGGTACCGCCACCTTGAGCCAGTGG 3').
This PCR product contained no stop codon and was unidirectionally subcloned
into vector pEGFP (from Clontech) at the EcoRl and Kpnl restriction sites and
inframe with the start codon of the GFP protein.
13a. Construction of the human dopamine transporter containing a
NLS and fused to RFP (DAT-NLS-RFP)
The cDNA encoding the human dopamine transporter (hDAT) was
amplified by PCR with 1718 and hDAT-NLSF primers, producing a fragment of
100 bp. The cDNA encoding the human dopamine transporter (hDAT) was also
amplified by PCR with T7 and hDAT-NLSR primers, producing a fragment of1.7
kB. These two PCR fragments were used as templates with T7 and 1718
primers, resulting in a fragment of 1.8 kB.
Primer T7: 5' TAATACGACTCACTATAGGG 3'
Primer 1718: 5' CGTCTCTGCTCCCTGGTACCGCCACCTTGAGCCAGTGG 3'
hDAT-NLSF: 5' CTATGCGGCCAAAAAGTTCAAAAGACTGCCTGGGTCC 3'
hDAT-NLSR: 5' CAGGCAGTCTTTTGAACTTTTTGGCCGCATAGATGGGC 3'
This PCR product was unidirectionally subcloned into vector pRFP at
EcoR1 and Kpnl and inframe with the start codon of the RFP protein.
The resulting PCR fragment encoded the NLS sequence KKFKR after
TM12 as follows:
DAT-wildtype: SSMAMVPIYAAYKFCSLPGSFREK
DAT-NLS: SSMAMVPIYAAKKFKRLPGSFREk
13b. Construction of the human dopamine transporter with a NLS
and fused to GFP (DAT-NLS-GFP)
The NLS sequence KKF KR was inserted into the proximal carboxyl
tail following the transmembrane 12 segment of the human DAT. Using the
DNA encoding the human DAT-cDNA in pcDNA3, as template, the first PCR
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was carried out with T7 and hDAT-NLSR primers resulting a 1.7kb product. A
second PCR was done using 1718 and hDAT-NLSF primers resulting in a
100bp product; then using PCR#1 and PCR#2 products as templates the final
PCR was done with T7 and 1718 primers which generated a 1.8kp product
(DAT-NLS) which was subcloned into vector pEGFP (Clontech ) at EcoR1
and Kpn1 and fused GFP.
Sequences of the primers:
hDAT-NLSF: 5' CTATGCGGCCAAAAAGTTCAAAAGACTGCCTGGGTCC 3'
hDAT-NLSR: 5' CAGGCAGTCTTTTGAACTTTTTGGCCGCATAGATGGGC
3'
HumanDATwildtype:SSMAMVPIYAAYKFCSLPGSFREK
HumanDAT-NLS: SSMAMVPIYAAKKFKRLPGSFREK
14. Construction of the human serotonin transporter fused to
GFP (SERT-GFP)
The full length human SERT cDNA was isolated by PCR from pcDNA3
containing the SERT cDNA, using the two following primers:
SERT-HIND: 5' GTCATTTACTAAGCTTGCCACCATGGAGACGACGCCCTT
G3'
SERT-KPN: 5' CCTCTCGGTGAGTGGTACCGCCACAGCATTCAAGCGG 3'
This PCR product contained no stop codon and was unidirectionally
subcloned into vector pEGFP (Clontech ) at HindIII.and Kpnl and inframe with
the start codon of the GFP protein,
15. Construction of the human Low Density Lipoprotein Receptor
fused to GFP (LDL-R-GFP)
The full length cDNA encoding LDL was subjected to PCR with LDLR-
HIND and LDLR-KP.N primers:
LDLR-HIND: 5' GGACACTGCCTGGCAAAGCTTGCGAGCATGGGGCCCTG
G3'
LDLR-KPN: 5' GGCGGGACTCCAGGCAGGTACCGCCGCCACGTCATCCT
CC 3'
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This PCR product (2600bp) contained no stop codon and was
unidirectionally subcloned into vector pEGFP (Clontech) at Hind111 and Kpnl
and inframe with the start codon of the GFP protein.
16. Construction of the human Low Density Lipoprotein Receptor
with a NLS and fused to GFP (LDLR-NLS-GFP)
The NLS sequence KKFKR was inserted into DNA encoding the LDL
receptor by PCR, replacing the natural sequence coding for RLKNI.
The primer set for the construction of DNA encoding LDL-NLS:
LDL-NLSF: 5' CTATGGAAGAACTGGAAAAAA'TTTAAAAGAAACAGCATCAA
C3'
LDL-NLSR: 5' CAAAGTTGATGCTGTTTCTITTAAATTTTTTCCAGTTCTTCC
3'
Using the human DNA encoding LDL cDNA in pcDV1 as template,
PCR with the primers LDLR-HIND and LDL-NLSR resulted in a product of
2450 bp (PCR#1). Using DNA encoding LDL as a template with primers
LDLR-KPN and LDL-NLSF resulted in a product of 150 bp (PCR#2). A
subsequent PCR carried out with primers LDLR-HIND and LDLR-KPN using
the product of PCR#1 and PCR#2 as template resulted in a product of 2600
bp.
The resulting PCR contained the NLS sequence KK F KR mutation as
follows:
HumanLDL-Rwildtype: FLLWKNWRLKNINSINFDNP
Human LDL-R: FLLWKNWKKFKRNSINFDNP
This PCR product contained no stop codon and was unidirectionally
subcloned into vector pEGFP (Clontech) at Hindi! and Kpnl and inframe with
the start codon of the GFP protein.
17. Construction of the Epidermal Growth Factor Receptor fused
to GFP (EGFR-GFP)
The full length human EGFR cDNA in Prkf vector was isolated by PCR
with the two following primers:
HER-XHO: 5' GCTCTTCGGGCTCGAGCAGCGATGCGACCCTCCGGGACG
G3'
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HER-KPN: 5' CTATCCTCCGTGGTACCGCTGCTCCAATAAATTCACTGC 3'
This PCR product (3600 bp) contained no stop codon and was
unidirectionally subcloned into vector pEGFP (Clontech) at Xhol and Kpnl and
inframe with the start codon of the GFP protein.
18. Construction of the human serotonin transporter with a NLS
and fused to UP (SERT-NLS-GFP) =
The NLS sequence KKFKR was inserted into DNA encoding the SERT
by PCR, replacing the natural sequence coding for GTFKE.
The primer set for the amplification of the DNA encoding SERT-NLS.
SERT-NLSF: 5' GATCATCACTCCAAAGAAATTTAAAAGACGTATTATT 3'
SERT-NLSR: 5' TAATACGTCTTTTAAATTTCTTTGGAGTGATGATCAACCG
3'
Using the human SERT-cDNA in PcDNA3 as template, PCR with the
primers SERT-HIND and SERT-NLSR resulted in a product of 1800 bp
16 (PCR#1). Using DNA encoding SERT as a template with primers SERT-KPN
and SERT-NLSF resulted in a product of 100 bp (PCR#2). A subsequent
PCR carried out with primers SERT-HIND and SERT-KPN primers using the
product of PCR#1 and PCR#2 as template resulted in a product of 1900 bp.
The resulting PCR product encoded the NLS sequence KKFKR
mutation after TM12 of the SERT as follows:
Human SERT wildtype: RLIITPGTFKERIIKSIT
Human SERT: RLIITPKKFKRRIIKSIT
This PCR product contained no stop codon and was unidirectionally
subcioned into vector pEGFP (Clontech) at Hindu, and Kpnl and inframe with
the start codon of the GFP protein.
19. Construction of the metabotropic glutamate-4-receptor fused
to GFP, with and without NLS (mGluR4-GFP and mGluR4-NLS-GFP)
The DNA encoding mGluR4 was isolated from a rat cDNA using the
primer set
GLUR4-HIND: 5' GGGTCTCTAAGCTTGCCGCCATGTCCGGGAAGGG 3'
GLUR4-ECORI: 5' CCGCGGCCCGGAATTCGGATGGCATGGTTGGTG 3'
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A restriction site HindlIl was incorporated into primer GLUR4-HIND,
and a restriction site EcoRI was incorporated into primer GLUR4-ECORI. The
mGluR4-PCR product, which contained no stop codon, was unidirectionally
subcloned into vector EGFP (Clontech) at Hind Ill and Ecorl and inframe with
5 the start codon of the GFP protein.
The NLS KKFKR was introduced into the DNA encoding the mGluR4
replacing the natural sequence KRKRS.
Primer set for the amplification of the DNA to introduce the NLS into
the Rat rnGluR4-EGFP
10 GLUR4-NLSF: 5' CGTGCCCAAGAAATTCAAGCGCCTCAAAGCCGTGGTC
3'
GLUR4-NLSR: 5' CGGCTTTGAGGCGCTTGAATTTCTTGGGCACGTTCTG
C3'
Using the rat DNA encoding GluR4 as template PCR with the primers
15 GLUR4-HIND and GLUR4-NLSR resulted in a product of 2600 bp (PCR#1).
Using DNA encoding GluR4 with primers GLUR4-ECORI and GLUR4-NLSF
resulted in a product of 160 bp (PCR#2). A subsequent PCR carried out
using the product of PCR#1 and PCR#2 as template, with primers: GLUR4-
HIND and GLUR4-ECORI, resulted in a product of 2760 bp.
20 The
resulting PCR contained the NLS sequence KKF KR mutation as
follows:
RatmGluR4Wildtype: FHPEQNVPKRKRSLKAVVTAAT
Rat mGiuR4: FHPEQNVPKKFKRLKAVVTAAT
This PCR product was unidirectionally subcioned into Vector pEGFP
25 (Clontech) at HindlIl and EcoRI and inframe with the start codon of the
GFP
protein.
20. Construction of the Human Insulin Receptor fused to GFP
(IR-GFP)
The full length IR cDNA in plasmid pRK5 was isolated with the two
30 PCR primers:
HIR-HIND: 5' GGAGACCCCAAGCTTCCGCAGCCATGGGCACCGGGGGCC
3'
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H1R-APA: 5' CCCCGCCACGGGCCCCGGAAGGATTGGACCGAGGCAAGG
3'
The PCR product (4.2kb) contained no stop codon and was unidirectionally
subcloned into vector pEGFP ( Ciontech ) at Hind Ill and Apal and fused to
the GFP protein.
21. Construction of the Human Insulin Receptor with a NLS and
fused to GFP (IR-NLS-GFP)
The NLS sequence KKFKR was introduced into the human insulin
redeptor to replace the sequence LYASS.
Using the human insulin receptor cDNA in pRK5 vector as template,
the first PCR #1 with HIR-HIND and H1R-NLSR primers generated a 2.9 kb
product, the second PCR #2 with HIR-APA and HIR-NLSF primers generated
a 1.3 kb product, and then using the products from PCR#1 and PCR #2 as
templates, the third PCR #3 produced a fragment with HIR-HIND and HIR-
APA primers (4.2 kb). This contained no stop codon and was unidirectionally
subcloned into vector pEGFP at Hind Ill and Apal and thus fused to the GFP
protein.
Primers for H1R-NLS:
HIR-NLSF: 5' CCGCTGGGACCGAAAAAATTTAAGAGAAACCCTGAGTATC
TC 3'
HIR-NLSR: 5' GATACTCAGGGTTTCTCTTAAATTTTTTCGGTCCCAGCGG
CCC 3'
22. Construction of the human Erythropoietin receptor fused to
GFP (EPO-GFP).
Using PCR method and the cDNA in pc3.1 vector encoding the human
Erythropoietin receptor (EPO) as template, the full length cDNA was isolated
with the following primers:
=
T7: 5' TAATACGACTCACTATAGGG 3'
EPO-KPN: 5' GACTGCAGCCTGGTGGTACCGCAGAGCAAGCCACATAGC
TGGGG 3'
This PCR product (1.6kb) contained no stop codon and was unidirectionally
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subcloned into vector pEGFP at Hind Ill and Kpnl and fused to the GFP
protein.
23. Construction of the human Erythropoietin receptor with a NLS
and fused to GFP (EPO-NLS-GFP).
The NLS sequence KKFKR was inserted into the DNA encoding the
EPO receptor by PCR, replacing its natural sequence RRALK.
Using the human EPO-cDNA in pc3.1 as template, the first PCR #1
with T7 and EPO-NLSR primers generated a 900bp product, the second PCR
#2 with EPO-KPN and EPO-NLSF primers generated a 700bp product, and
then using .the products from PCR#1 and PCR #2 as templates, the third PCR
#3 with T7 and EPO-KPN primers produced a 1.6 kb fragment. This PCR
product (1.6kb) contained no stop codon and was unidirectionally subcloned
into vector pEGFP at HindlIl and Kpnl and thus fused to the GFP protein.
Primer sequences:
T7: 5' TAATACGACTCACTATAGGG 3'
EPO-KPN: 5' GACTGCAGCCTGGTGGTACCGCAGAGCAAGCCACATAGC
TGGGG 3'
EPO-NLSF: 5' GCTGCTCTCCCACAAAAAGTTTAAGCGGCAGAAGATCTG
G3'
EPO-NLSR: 5' CCAGATCTTCTGCCGCTTAAACTTTTTGTGGGAGAGCAG
03'
HumanEPOwildtype: TVLALLSHRRALKOKIWPGIP
Human EPO NLS: TVLALLSHKKFKROKIWPGIP
24. Construction of the human epidermal growth factor receptor
fused to GFP (EGFR-GFP)
Using the human epidermal growth factor receptor cDNA in Prk5 vector
as template, the full length cDNA was isolated by PCR with the two following
primers:
= HER-XHO (5' GCTCTTCGGGCTCGAGCAGCGATGCGACCCTCCGGGACG
G 3') and
- HER-KPN (5' CTATCCTCCGTGGTACCGCTGCTCCAATAAATTCACTGC
3')
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This PCR product (3.6kb) contained no stop codon and was unidirectionally
subcloned into vector pEGFP (Clontech ) at Xhol and Kpnl and fused to the
GFP protein.
25. Construction of the human epidermal growth factor receptor
with an NLS and fused to GFP (EGFR-NLS-GFP)
The NLS sequence KKF KR was inserted into the sequence of the
human epidermal growth factor receptor by PCR method as follows. Using the
human EGFR cDNA in Prk5 vector as template, the first PCR was carried out
with HER-XHO and EGF-NLSR primers resulting in a 2.1kb product. A
second PCR was done using HER-KPN and EGF-NLSF primers resulting a
1.5kb product, and then using PCR#1 and PCR#2 products as templates, the
final PCR was done with HER-XHO and HER-KPN primers, which generated
a 3.6kp product (EGFR-NLS) which was subcloned into vector pEGFP
(Clontech) at Xho1 and Kpnl and fused to GFP.
Primer sequences:
EGF-NLSF: 5' CACATCGTTCGGAAGAAGTTTAAGCGGAGGCTGCTGC 3'
EGF-NLSR: 5' CCTGCAGCAGCCTCCGCTTAAACTTCTTCCGAACGATGT
G3'
HumanEGFRwildtype: RRRHIVRKRTLRRLLQERE
Human EGFR-NLS: RRRHIVRKKFKRRLLQERE
26. Construction of the human D1 dopamine receptor containing
2 NLSs and fused to RFP (D1-NLS(Helix 8 and C-tail)-RFP)
A second NLS sequence KKKRK was inserted into the carboxyl tail
segment of the human D1-NLS-Helix 8 by PCR method as follows. Using the
DNA encoding the human D1-NLS-Helix 8 in pDsRed vector as template, the
first PCR was carried out with HD1-P1 and HD1-NLSCR primers resulting in a
1.2kb product, and a second PCR was done using HD1-P2 and HD1-NLSCF
primers resulting in a 100bp product. Then using PCR#1 and PCR#2
products as templates, the final PCR was done with HD1-P1 and HD1-P2
primers which generated a 1.3kp product (D1-NLS-Helix 8 and C-tail) which
was subcloned into pDsRed vector at EcoRI and Kpnl and fused to the DsRed
protein.
=
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Primer sequences:
HD1-P1: 5' GAGGACTCTGAACACCGAATTCGCCGCCATGGACGGGACTG
GGCTGGTG 3'
HD1-P2: 5' GTGTGGCAGGATTCATCTGGGTACCGCGGTTGGGTGCTGAC
CGTT 3'
HD1-NLSCF: 5' CCTCTGAGGACCTGAAAAAGAAGAGAAAGGCTGGCATC
GCC 3'
HD1-NLSCR: 5' GGCGATGCCAGCCTTTCTCTTCTTTTTCAGGTCCTCAGA
GG 3'
D1- wildtype:
NPIIYAFNADFRKAFSTLL ........................ SSEDLKKEEAAGIA
D1-NLS (Helix 8 and C-tail):
NPIIYAFNAKKFKRFSTLL ........................ SSEDLKKKRKAGIA
27. Construction of the Mu opioid receptor fused to GFP (MU-
GFP)
Using the DNA encoding the Mu opioid receptor in pcDNA3 vector as
template, PCR was carried out with the following two primers.
RATMU1: 5' CCTAGTCCGCAGCAGGCCGAATTCGCCACCATGGACAGCA
GCACC 3'
RATMU-2: 5' GATGGTGTGAGACCGGTACCGCGGGCAATGGAGCAGTTT
CTGCC 3'
Restriction site EcoRI was incorporated into primer RATMU-1. Restriction site
Kpnl was incorporated into primer RATMU-2
The PCR product (1.2 kb) which contained no stop codon, was then
unidirectionally subcloned into vector pEGFP (Clontech) at EcoR1 and
Kpn1 and thus fused to GFP.
28. Construction of the Mu opioid receptor containing a NLS and
fused to GFP (Mu-NLS-GFP)
The NLS sequence KKFKR was inserted into the proximal carboxyl
tail segment (helix 8) of the Mu opioid receptor by PCR as follows. Using the
DNA encoding the Rat Mu in pcDNA3 as template, the first PCR was carried
out with RATMU1 and MU-NLSR primers resulting a 1000bp product, another
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second PCR was done using RATMU-2 and MU-NLSF primers resulting a
200bp product. Using PCR#1 and PCR#2 products as templates the final
PCR was done with RATMU1 and RATMU2 primers generated a 1200bp
product (Mu-NLS) which was subcloned into vector pEGFP at EcoRl and
5 Kpn1 and fused to GFP.
Primer sequences:
RATMU-1: 5' CCTAGTCCGCAGCAGGCCGAATTCGCCACCATGGACAGC
AGCACC 3'
RATMU-2: 5' GGATGGTGTGAGACCGGTACCGCGGGCAATGGAGCAGTT '
10 TCTGCC 3
MU-NLSF: 5' GCCTTCCTGGATAAAAAATTCAAGCGATGC 3'
MU-NLSR: 5' GCATCGCTTGAA ______ I I I I I I ATCCAGGAAGGCG 3'
Cell culture and transfection
15 COS-7 monkey kidney cells and HEK293T human embryonic kidney
cells (American Type Culture Collection, Manassa, VA) were maintained as
monolayer cultures at 37 C and 5% CO2 in minimal essential medium
supplemented with 10% fetal bovine serum and antibiotics. For cell
membrane harvesting, 100 mm plates of cells were transiently transfected at
20 70-80% confluency using lipofectamir0eagent (Life Technologies,
Rockville, MD). For confocal microscopy studies, 60 mm plates of cells were
= T
transiently transfected at 10-20% confluency using lipofectaminMe reagent.
Six hours after transfection, the solution was removed and fresh media
added and again replaced with fresh media 24 hours after transfection.
25 Transfection medium was prepared by mixing 120 microlitres medium
without antibiotics and/or fetal bovine serum (FBS) and 15 microlitress
lipofectamine in a 14 ml tube, 2 micrograms DNA construct encoding the
desired fusion protein and 120 microlitres medium were mixed and added to
the 14 ml tube, which was mixed gently and incubated at room temperature
30 for 25 minutes. A further 4 ml of medium was added and mixed. If
multiple
transmembrane proteins are being transfected, the cDNAs are mixed and
transfected together. Growth medium was removed from a plate of cells and
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replaced with the transfection mixture from the 14 ml tube. Cells were
Incubated with the transfection. mixture for 5 - 6 hours, after which the
mixture was removed and replaced with regular growth medium containing
FBS and antibiotics. Cells were incubated with a change of regular growth
medium on the second day.
Treatment with Test Compounds
Protocol for determining retardation of transiocation off cell
surface
Test' compounds were prepared in a stock solution of 1 millimolar
concentration and diluted in growth medium to achieve a final concentration
ranging between 10 nanomolar and 10 microm9lar when added to cell
plates. Fresh compound-containing medium was added to cells at 6 hours,
22 hours, 30 hours and 42 hours after transfection.
Protocol for determining promotion of translocation off cell
surface
Test compounds were prepared in a stock solution of 1 millimolar and
diluted in growth medium at 37 C to achieve a final concentration of 10
micromolar when added to cells. Cell cultures were examined
microscopically to focus on a single cell and to detect the presence of
surface expression of the detectable label protein. Growth medium was
replaced with compound-containing medium and the cells were examined
microscopically in real time 5, 10, 15, 20, 30 and 35 mins. after addition of
compound for changes in distribution of the detectable moiety.
Microscopy
TM
Cells were visualised using the LSM510 Zeiss confocal laser
microscope. GFP was visualised following excitation with the argon laser at
488nm excitation wavelength and the DsRed was visualised following
excitation with the helium neon laser at 543 nm wavelength for excitation.
The confocal images were captured On disk and evaluated. In each
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experiment, multiple fields of cells (n=6-8 with 30-90 cells each) were
counted and evaluated for localisation of the signal on the cell surface, in
the
cytoplasm and in the nucleus.
Fluorocytometry
A 96 well plate was coated with poly-L-ornithine (1/10 in PBS) and
incubated for one hour. 50,000 cells were added to each well and
transfected with cDNA encoding the epitope-tagged receptor, using
TM
Lipofectamine -(Invitrogen, U.S.A.). The medium (MEM) was changed every
12 hours and contained test drug at varying concentrations or vehicle. 48
hours later, cells were washed and fixed with 4% paraformaldehyde and
incubated for 30 min on ice. Cells were then incubated with the primary
antibody directed against the epitope and then with the secondary antibody
conjugated to FITC (fluorescein isothiocyanate) and kept shielded from light.
Excess antibody was washed off and the signal detected by reading the
plate in a CytofluoTrM4000 (PerSpective Biosystems, U.S.A.). The FITC was
activated using light at 488 nm for excitation and the signal read at its
emission wavelength 530 nm.
Radioligand Binding
Cells were transfected with DNA encoding D1-NLS and treated with
varying concentrations of antagonist drug or left untreated. After 48 hours,
the cells were washed, harvested, lysed and homogenised by polytron. The
membrane fraction was collected by centrifugation and then layered over 35%
sucrose solution and centrifuged at 30,000 rpm at 4 degrees C for 90 min to
collect the heavy membrane fraction. The supernatant was again centrifuged
at 35,000 rpm at 4 degrees C for 60 min to collect the light membrane
fraction. The membranes were subjected to radioligand binding assay using
[31-1]-SCH23390 with (+)butaclamol 10 micromolar used to define specific
binding. The incubation was at room temperature for 2 hours, followed by
rapid filtration and quantitation by scintillation counting.
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Isolation of Nuclei from Cultured Cells
Wash cells with PBS 3 times, using 10 ml and scrape gently off the
culture dishes. Pool and spin the cells at 500g for 5 min, at 4 degrees C.
Resuspend pelleted cells in lysis buffer (Tris HCI 10 mM, pH 7.4, NaCI 10
mM, MgC12 3 mM) and inhibitor cocktail (0.5% leupeptin,1% soybean
trypsin,1% benzamidine) at a density of 50 million cells per ml. Homogenize
TM
with sterile glass Teflon pestle B (tight,clearance 20-50 mm; Bellco Glass)
using 100 up and down strokes.
Spin at 4 degrees C for 700 g for10 min, then sequentially centrifuge
supernatant at 10 000 g, for 15 min at 4 C (to remove mitochondria) and 120
000g for 60 min, 4 degrees C (to remove plasma membrane).
The nuclear pellet is resuspended in lysis buffer (with inhibitors) and
TM
0.1 % of NP-40, kept on ice 6 min and then centrifuged at 700 g for 10 min at
4 degrees C. The supernatant is discarded and washing process repeated 3
X with 15 ml lysis buffer. Nuclear pellet is resuspended in 2 ml lysis buffer
and
loaded on top of discontinuous sucrose gradient made by successive layering
of 4.5 ml of 2.0 and 1.6 M sucrose containing MgC12 1 mM and spun at 100
000g for 60 min at 4 degrees C. The pellet at the bottom of the tube is
collected and will contain pure nuclei.
Example 1: Dopamine D1 receptor fused to the red fluorescent
protein (D1-RFP) or containing a NLS and fused to the red fluorescent
protein (D1-NLS-RFP)
The sequence of the dopamine D1 receptor, which does not contain
an NLS, was modified to replace the amino acids DFRKA at the base of TM7
domain with the NLS sequence KKFKR (which corresponds to the NLS of
the human ATI receptor), as described in the methods (see Figure 1). DNA
constructs were created encoding the D1 dopamine receptor fusion proteins
D1-RFP and DI -NLS-RFP. COS cells were transfected with DNA encoding
D1-NLS-RFP or D1-RFP (2 micrograms) and incubated for 24 and 48 hours.
The cells were examined by confocal microscopy at 100X magnification.
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Cells were counted manually in 8 to 10 microscopic fields and the
percentage labelling in different subcellular compartments was calculated.
At 24 and 48 hours, cells transfected with D1-RFP showed expression
at the cell surface in the majority of cells, whereas cells transfected with
D1-
NLS-RFP showed little receptor expression at the cell surface, with nuclear
localisation in 60% of the cells at 24 hours, and in 80% of the cells at 48
hours.
Example 2: Dopamine D1 receptor fusion protein containing a NLS
(D1-NLS-RFP) treated with antagonist
lo COS cells were transfected with a construct encoding D1-NLS-RFP
and with wildtype D1 (2 micrograms) for 48 hours. At 6, 22, 30 and 42 hours
after transfection, the cells were treated with the dopamine D1 receptor
antagonist SCH23390 (final concentration 10 micromolar). Also at 6, 22, 30
and 42 hours after transfection, cells were treated with the antagonist
(+)butaclamol (final concentration 10 M). Control cells received no
antagonist treatment.
At 48 hours, the majority of control cells had detectable D1-NLS-RFP
in the nucleus. In contrast, the majority of antagonist-treated cells had
fluorescence only on the cell surface, while 42% had fluorescence both on
the surface and in the nucleus.
Example 3: Dopamine D1 receptor (D1-GFP) co-expressed with D1
receptor containing a NLS (D1-NLS)
HEK cells were transfected with DNA constructs encoding D1-NLS (3
micrograms) and/or D1-GFP (1.5 micrograms), and incubated for 48 hours.
The cells were also transfected with a plasmid encoding DsRed-NUC to
verify the localisation of the nucleus (1 microgram).
Cells were also transfected with. DNA encoding Dl-GFP (2
micrograms), incubated for 48 hours and examined by confocal microscopy.
D1-GFP expressed alone revealed that 90% of the cells
demonstrated cell surface labelling and 10% showed both nuclear and cell
surface labelling. With any DNA encoding a GPCR transfection, up to 10%
of cells may be observed with a nuclear localisation.
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Cells expressing D1-GFP and D1-NLS showed 35% of cells with both
nuclear and cell surface labelling and 70% with receptor expression on cell
surface only. This experiment indicated that DI -GFP co-trafficked with D1-
NLS resulting from oligomerisation of the DI-NLS and DI-GFP.
5 Example 4: Dopamine D1 receptor containing a NLS (D1-NLS-GFP),
was treated with an antagonist in a dose response study
HEK cells were transfected with DNA encoding D1-NLS-GFP (2
micrograms), and DI-WT (6 micrograms) for 48 hours. These cells were
treated 6 hrs after transfection with SCH- 23390 (10 micromolar), or
10 (+)butaclamol (10 micromolar). The medium containing antagonist was
changed at 6, 22, 30 and 42 hours after transfection. Control cells received
no antagonist treatment.
Following SCH-23390 treatment for 48 hours, 58% of the cells had
cell surface expression of Dl-NLS-GFP, less than 10% of the cells had
15 receptor expression in the nucleus and 32% of the cells had receptor
expression on both the cell surface and in the nucleus.
Following (+)butaclamol treatment for 48 hours, 62% of the cells had
cell surface expression of the D1-NLS-GFP receptor, 1'0% had receptor
expression in the nucleus, and 28% of the cells had receptor expression on
20 the cell surface and in the nucleus.
Control cells at 48 hours showed approximately 65% with DI-NLS-
GFP receptor expression in the nucleus, and 35% with receptor expression
in the cytoplasm. No receptor D1-NLS-GFP expression was found on the
cell surface of control cells.
25 Incorporation of an NLS into the receptor sequence caused a very
efficient removal of the D1-NLS-GFP receptor from the cell surface and
localisation in the nucleus.
Similar studies were carried out at various doses of SCH-23390 or
(+)butaclamol. Results are shown in Tables 2 and 3. 32% to 35% of control
30 cells showed receptor in cytoplasm.
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Table 2
% cells
SCH-23390 receptor on , receptor on receptor in
concn surface surface and in nucleus
nucleus
p,M 58% 32% <10%
5 p,M 46% 42% 12%
1 Oil 39% 46% 15%
0.5 p,M 36% 44% 20%
0.2 32% 49% 19%
0.0 p.M 0% 62% - 70%
5 Table 3
% cells
(+)butaclamol receptor on receptor on receptor in
concn. surface surface and in nucleus
nucleus
10 p.M 62% 28% 10%
5 p.M 47% 43% 10%
ljM 41% 43% 16%
0.5 M 40% 41% 19%
0.2 p,M 39% 21% 40%
0.0 ILLIVI 0% 62% - 70%
Incorporation of an NLS into the receptor sequence caused a very
efficient removal of the D1 dopamine receptor from the cell surface and
10 localisation in the nucleus. Treatment with D1 selective antagonists
prevented this receptor translocation in a dose-responsive manner.
Example 4a: Expression of the dopamine D1 receptor with an
inserted NLS (D1-NLS-GFP) and treatment with agonists
HEK cells were transfected with a DNA construct encoding D1-NLS-
GFP (1.5 micrograms), and incubated with the D1 agonist SKF-81297 (10
=
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micromolar) for 48 hours. At 6, 22, 30 and 42 hours after transfection, the
cells
were treated with fresh medium containing SKF-81297 (final concentration 10
micromolar). The cells were examined by confocal microscopy.
HEK cells were transfected with a DNA construct encoding D1-NLS-
GFP (1.5 micrograms of DNA), and incubated with the agonist pergolide (10
micromolar) for 48 hours. At 6, 22, 30 and 42 hours after transfection, the
cells were treated with fresh medium containing SKF-81297 (final
concentration 10 micromolar). The cells were examined by confocal
microscopy.
Control HEK cells were transfected with a DNA construct encoding D1-
NLS-GFP (1.5 micrograms of DNA) and left untreated.
In the untreated cells after 48 hrs, there was no receptor detected at the
cell surface. With cells treated with SKF-81297, 59% of cells had receptor
expression at the cell surface. With cells treated with perglolide there was
receptor surface expression in 59% of the cells. Thus long-term treatment with
agonists prevented the modified D1 receptor from trafficking to the nucleus.
Example 5: Dopamine D1 receptor with an incorporated NLS (D1-
- NLS-RFP) co-expressed with the wild type D1 receptor
COS cells were co-transfected with a DNA construct encoding D1-
NLS-RFP (1 microgram) and a DNA sequence encoding the native
dopamine D1 receptor (D1-WT, 7 microgram) and incubated for 24 or 48
hours.
At 24 hours, D1-NLS-RFP was detected only at the cell surface,
whereas at 48 hours, 80% of cells had Dl-NLS-RFP in the nucleus. The
wild type receptor retarded the movement of the Dl-NLS-RFP to the nucleus
by homo-oligomerisation.
Example 6: D1 dopamine receptor with an incorporated NLS (D1-
NLS-RFP) co-expressed with D1-GFP
COS cells were transfected with a construct encoding D1-NLS-RFP (4
micrograms) and the dopamine D1-GFP (4 micrograms), and incubated for
48 hours. The cells were examined by confocal microscopy.
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Dl-GFP was detected at the cell surface and a yellow fluoresence
was detected in the nuclei, the latter indicating co-localisation of both D1-
NLS-RFP and DI-GFP in the nucleus, confirming oligomerisation of DI-
NLS-RFP and DI-GFP, leading to importation of DI-GFP into the nucleus.
Example 6a: Expression of the D1 dopamine receptor with an NLS
inserted in the third intracellular cytoplasmic loop (D1-1C3-NLS-GFP)
HEK cells were transfected with a DNA construct encoding DI-1C3-NLS-
GFP (2 micrograms), and incubated for 48 hours. Nuclei were visualised with
DsRED-NUC (2 micrograms). The cells were examined by confocal microscopy.
io In cells transfected with D1-1C3-NLS-GFP, the receptor was detected in
the nucleus of 85% of cells. Thus insertion of a NLS into the third
intracellular
loop enabled receptor trafficking to the nucleus.
Example 6b: Expression of the DI dopamine receptor with an NLS
inserted in the first intracellular cytoplasmic loop (D1-1C1-NLS-GFP)
HEK cells were transfected with a DNA construct encoding D1-IC1-
NLS-GFP (2 micrograms), and incubated for 48 hours. Nuclei were visualised
with DsRED-NUC (2 micrograms). The cells were examined by confocal
microscopy.
In cells transfected with D1-1C1-NLS-GFP, the receptor was detected
in the nucleus of 86% of cells. Thus insertion of a NLS into the first
intracellular loop enabled receptor trafficking to the nucleus.
Example 6c: Effect of the antagonist butaclamol or SCH-23390 on the
trafficking of the Dl dopamine receptor with an NLS inserted in the first
cytoplasmic loop (D1-1C1-NLS-GFP)
HEK cells were transfected with a DNA construct encoding D1-1C1-NLS-
GFP (2 micrograms), and treated with either butaclamol (final concentration I
micromolar or SCH-23390 (1 micromolar), for 48 hours. Nuclei were visualised
with DsRED-NUC (2 micrograms). The cells were examined by confocal
microscopy.
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With the butaclamol treated cells, 82% had receptor on the cell surface or
in the cytoplasm. 18% of the cells had receptor in the nucleus. Thus treatment
with butaclamol reduced D1-IC1-NLS-GFP trafficking to the nucleus.
With the SCH-23390 treated cells, 77% of the cells had receptor on the
cells surface or in the cytoplasm. 23% of the cells had receptor in the
nucleus.
Thus treatment with SCH-23390 reduced receptor trafficking to the nucleus.
With the untreated cells 76% had receptor expression in the nucleus
and cytoplasm.
Example 6d: Effect of the antagonist SCH-23390 on the trafficking of
w the D1 dopamine receptor with an NLS inserted in the third cytoplasmic
loop
(D1-IC3-NLS-GFP)
HEK cells were transfected with a DNA construct encoding D1-IC3-NLS-
GFP (2 micrograms), and treated with four different concentrations of SCH-
23390
(10 micromolar, 1 micromolar, 500 nanomolar and 100 nanomolar), for 48 hours.
Nuclei were visualised with DsRED-NUC (2 micrograms). The cells were
examined by confocal microscopy.
86% of the cells transfected with D1-IC3-NLS-GFP had the receptor in the
nucleus, and 0% had receptor on the surface. With the SCH-23390 treated cells,
84% had receptor in the nucleus and 15% of the cells had receptor on the
surface. The insertion of an NLS at this position in the GPCR will translocate
the
receptor to the nucleus efficiently but does not respond to the drug.
Example 6e: Expression of the D1 dopamine receptor with an NLS
inserted in the second intracellular cytoplasmic loop (D1-1C2-NLS-GFP)
HEK cells were transfected with a DNA construct encoding D1-IC2-NLS-
GFP (2 micrograms), and incubated for 48 hours. Nuclei were visualised with
DsRED-NUC (2 micrograms). The cells were examined by confocal microscopy.
In cells transfected with D1-1C2-NLS-GFP, the receptor was detected in
the nucleus of 51% of cells.
Example 6f: Ability of the dopamine D1 receptor to homodimerise,
with staggered transfection
HEK cells were transfected with a DNA construct encoding D1-RFP (2
micrograms) and after 24 hours incubation, the cells were transfected with a
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second DNA construct encoding DI-NLS-GFP (2 micrograms). Control cells were
transfected with the DI -RFP (2 micrograms) construct alone. The cells were
incubated for 48 hours following the second transfection and examined by
confocal
microscopy.
5 90% of the cells transfected with Dl-RFP alone expressed receptor on the
cell surface, and 6% of the cells expressed receptor in the nucleus. In
contrast,
97% of the cells expressing both forms of the receptor expressed both
receptors
(red plus green equals yellow fluorescence) in the nucleus. Thus, the D1
receptor
without the NLS interacted with the DI receptor with the NLS in order to
traffic to
10 the nucleus.
Example 7: Dopamine D5 receptor (D5-GFP)
A construct encoding the dopamine D5 receptor-GFP (D5-GFP) was
prepared and used to transfect COS cells (4 micrograms).
Cells transfected with dopamine D5-GFP, at 48 hours, showed mainly
15 a cytoplasmic localisation of receptor, with cell surface localisation
in only a
few cells and no instances of nuclear localisation.
Example 8: Dopamine DI with an incorporated NLS (D1-NLS) co-
expressed with the D5 dopamine receptor (D5-GFP)
HEK cells were transfected with two DNA constructs, one encoding
20 DI-NLS (7 micrograms) and the other encoding D5-GFP (1.5 micrograms),
and incubated for 48 hours.
Approximately 70% of the cells transfected with DI-NLS and D5-GFP
had cell surface expression of D5-GFP, 20% of the cells had both surface
and cytoplasm, expression of D5-GFP, and 10% had nuclear expression of
25 D5-GFP. There was no nuclear translocation of the D5 dopamine receptor
coexpressed with DI-NLS, indicating that the DI and D5 receptors did not
oligomerise.
Example 9: D1 dopamine receptor containing two NLS motifs (D1-
2NLS-RFP) and treated with antagonist
30 By modifying the construct encoding DI-NLS-RFP, a DNA construct
(D1-2NLS-RFP) was created to introduce a second NLS into the carboxyl tail
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of the dopamine D1 receptor by replacing the KKEEA sequence of the wild
type D1 dopamine receptor with the NLS, KKKRK.
HEK cells were transfected with DNA encoding this construct (D1-
2NLS-RFP), and treated at intervals with the antagonist SCH-23390 (10 M)
as previously described. At 6, 22, 30 and 42 hours after transfection, the
culture medium containing antagonist was replaced. Control cells received
no antagonist.
In both COS and HEK cells transfected with D1-2NLS-RFP, the
receptor was located in the nucleus in 100% of cells after 24 hours,
indicating enhanced nuclear translocation when a second NLS was present.
At 48 hours, 90% of cells not treated with antagonist showed
fluorescence in the nucleus and 0% of cells had fluorescence on the cell
surface. Antagonist-treated cells showed 51% of cells with cell surface label
and 49% with nuclear label.
Incorporation of a second NLS resulted in a more efficient transport of
the receptor to the nucleus, and this event was still retarded by antagonist
treatment.
Example 10: 02 dopamine receptor (D2-GFP)
HEK cells were transfected with DNA constructs encoding D2-GFP (2
micrograms) and DsRed-NUC (1 microgram), and incubated for 48 hours.
Cells were examined by confocal microscopy.
Approximately 90% of the cells expressing D2-GFP had cell surface
expression, and 10% had nuclear or cytoplasm expression. The D2
dopamine receptor, having no endogenous NLS, is predominantly expressed
on the cell surface.
Example 11a: Dopamine D1 receptor with an incorporated NLS (D1-
NLS) and dopamine D2 (D2-GFP)
HEK cells were transfected with DNA constructs encoding Dl-NLS (7
micrograms), and D2-GFP (1.5 micrograms) and incubated for 48 hours.
The cells were also transfected with Ds-Red-NUC to verify the localisation of
the nucleus (1 microgram). The cells were examined by confocal
microscopy.
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In cells transfected with D1-NLS and D2-GFP, 33% of the cells had
D2-GFP expression in the nucleus, indicating transport of both D1-NLS and
D2-GFP to the nucleus, due to oligomerisation between the D1 and 02
receptors. 67% of the cells had D2-GFP receptors on the cell surface only
or on surface and cytoplasm.
Example 11b: Ability of D2 dopamine receptor D2 short (D2S) to
dimerise with dopamine receptor D2 long (D2L)
HEK cells were transfected with DNA constructs encoding D2S-GFP (2
micrograms) and D2L-NLS (2 micrograms) and were incubated for 48 hours.
Nuclei were visualised with DsRED-NUC (2 micrograms). The cells were
examined by confocal microscopy.
D2S-GFP receptor was visualised in the nuclei of 29% of cells. This
indicated that D2S dimerised with D2L and was transported to the nucleus.
Example 11c: Ability of dopamine receptor D2S to dimerise with
=
dopamine receptor D2L.
HEK cells were transfected with DNA constructs encoding D2S-RFP (2
micrograms) and D2L-NLS-GFP (2 micrograms) and incubated for 48 hours. The
cells were examined by confocal microscopy.
40% of the cells had a yellow colour (red plus green overlay) in the
nucleus, indicating that D2L-NLS dimerised with D2S-RFP and transported it
to the nucleus.
Example 12: D2 dopamine receptor with an incorporated NLS (D2-
NLS-GFP) treated with antagonists
HEK cells were transfected with DNA encoding D2-NLS-GFP and the
cells were treated with the D2 dopamine receptor antagonists, (+)butaclamol
(10 micromolar) or raclopride (10 micromolar). At 6, 22, 30 and 42 hours
after transfection, the cells were treated with the antagonists. Cells were
incubated 48 hrs after drug treatment and examined by confocal microscopy.
In the absence of antagonist, cells expressing D2-NLS-GFP showed
nuclear label in 70% of cells, and cytoplasmic labelling in 20% and
cytoplasmic and surface labelling in 10% of cells. With (+)butaclamol
treatment, nuclear labelling appeared in only 5% of cells, 5% of cells had
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cytoplasmic label and 90% of the cells had cell surface labelling. With
raclopride treatment, 5% of cells showed nuclear labelling, 15% of cells had
cytoplasmic labelling and 80% of cells had cell surface labelling. Both
antagonists of the D2 receptor prevented the translocation of the receptor off
the cell surface and to the nucleus.
Example 13: Beta2-adrenergic receptor-GFP (beta2-AR-GFP)
A DNA construct was created encoding a fusion protein comprising
the human beta2-adrenergic receptor and GFP (beta2-AR-GFP). Cells were
transfected with the DNA construct encoding beta2-AR-GFP (2 micrograms),
and incubated for 24 hours and examined by confocal microscopy.
In cells expressing beta2-AR-GFP, 42% of cells had receptor
expression in cytoplasm only, and 58% of the cells had receptor expres-sion
in the cytoplasm and on the cell surface. No nuclear localisation of the
receptor was observed.
Example 14: Beta2-adrenergic receptor with an incorporated NLS
(beta2-AR-NLS3-GFP)
A DNA construct was created encoding a fusion protein comprising
the human beta2-AR-NLS3-GFP. HEK cells were transfected with DNA
encoding beta2-AR-NLS3-GFP-3 (2 microgram), and Ds-Red-NUC (1
microgram) and the cells were incubated for 48 hours.
45% of the cells transfected with beta2-AR-NLS3-GFP had nuclear
localisation of receptor and 55% of the cells had surface and cytoplasmic
expression. Incorporation of a NLS into the beta2-AR induced receptor
translocation to the nucleus.
Example 15: Beta2-adrenergic receptor with an incorporated NLS
(beta2-AR-NLS3-GFP), treated with antagonist
HEK cells were transfected with DNA encoding beta2-AR-NLS3-GFP-
(1microgram), and Ds-Red-NUC (1 microgram) and incubated for 48
hours. Cells were treated at intervals with atenolol (10 micromolar), an
adrenergic receptor antagonist. At 6, 22, 30 and 42 hours after transfection,
the culture medium containing the antagonist was replaced.
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Control cells received no antagonist. In control cells, 60% had
receptor expression in the nucleus, 21% had receptor expression on the cell
surface, 19% had receptor expression in the cytoplasm.
In antagonist atenolol-treated cells, 70% had receptor expression on
Example 16: Beta2-adrenergic receptor (beta2-AR-GFP)
HEK cells were transfected with DNA constructs encoding the beta2-
AR-GFP (1.5 microgram) and D1 -NLS (3 microgram) for 48 hours.
Approximately 40% of cells showed beta2-AR-GFP receptor
expression in the nucleus, demonstrating that the beta2-AR not containing
Example 17: Beta2-adrenergic receptor (beta2-AR-GFP) and
HEK cells were transfected with DNA constructs encoding beta2-AR-
GFP (1.5 micrograms) and D1-NLS (3 micrograms) and incubated for 48
hours. These cells were treated with the adrenergic antagonist, propranolol
25% of control cells showed beta2-AR-GFP nuclear expression and
75% of cells showed label in cytoplasm and on cell surface.
30 In propranolol-treated cells, beta2-AR-GFP nuclear expression was
10%, and 90% of the cells showed cytoplasmic and surface label. The
formation of a heterooligomer with between beta2-AR-GFP and Dl-NLS
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resulted in the trafficking of the beta2-AR-GFP to the nucleus. This
trafficking was attenuated by the presence of the antagonist to the
adrenergic receptor.
Example 18: Beta2-adrenergic receptor with an incorporated NLS
5 (beta2-AR-NLS3-GFP)
HEK cells were transfected with a DNA construct containing an NLS
encoding beta2-AR-NLS3-GFP (8 micrograms) for 48 hours. The cells were
also transfected Ds-Red-NUC to verify the localisation of the nucleus (1
microgram).
10 80% of cells showed beta2-AR-NLS3-GFP receptor in the nucleus.
The efficiency of the NLS was improved, resulting in a greater localisation of
receptor in the nucleus.
Example 19: Serotonin 1B receptor with an incorporated NLS
(5HT1B-NLS-GFP) and treatment with antagonist
15 HEK cells were transfected with a DNA construct encoding the
serotonin 5HT1B-NLS-GFP (2 micrograms). The cells were transfected with
Ds-red-NUC to verify the localisation of the nucleus (1 microgram). Cells
were treated with methysergide (10 micromolar), a serotonin receptor
antagonist. At 6, 22, 30 and 42 hours after transfection, the culture medium
20 containing antagonist was replaced. Control cells received no
antagonist.
The cells were examined by confocal microscopy.
Control cells, not treated with antagonist, showed 55% with receptor
localised in the nucleus, and 20% with receptor localised on the cell surface.
At 48 hours, methysergide-treated cells showed 25% of the cells had
25 receptor in the nucleus and 62% of the cells had cell surface
localisation.
The serotonin 5HT1B receptor was efficiently translocated from the
cell surface to the nucleus by insertion of the NLS. Treatment with the
serotonin antagonist methysergide prevented the translocation of the
receptor.
30 Example 20: Cysteinyl leukotriene receptor-2 with an incorporated
NLS (CysLT2-NLS-GFP)
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HEK cells were transfected for 48 hours with a DNA construct
encoding CysLT2-NLS-GFP (8 micrograms). The cells were also
transfected with Ds-RED-NUC to verify the localisation of the nucleus (1
microgram). The cells were examined by confocal microscopy.
83% of cells expressing Cys-LT2-NLS-GFP showed receptor
expression in the nucleus and 0% of cells had receptor expression on the
cell surface, indicating Cys-LT2-NLS-GFP receptor localisation in the
nucleus.
Example 21: Cysteinyl leukotriene receptor-2 with an incorporated
NLS (Cys-LT2-NLS-GFP) treated with antagonist
The DNA encoding Cys-LT2-NLS-GFP (3 micrograms) was used to
transfect HEK cells. These cells were treated with the cysteinyl leukotriene
receptor antagonist, montelukast (10 micromolar). At 6, 22, 30 and 42 hours
after transfection the culture medium containing antagonist was replaced.
Control cells received no antagonist. The cells were examined by confocal
microscopy.
In the absence of antagonist, 70% of cells expressing Cys-LT2-NLS-
GFP had localisation of receptor in the nucleus and 30% of cells showed a
cytoplasmic localisation with 0% of cells showing receptor on the cell
surface. For the antagonist-treated cells, only 10% showed nuclear
localisation of the receptor, while 90% showed cell surface expression of
receptor. Thus the cysteinyl leukotriene receptor antagonist montelukast
prevented the transport of the Cys-LT2-NLS-GFP receptor off the cell
surface and into the nucleus.
Example 22: Mu opioid receptor with an incorporated NLS (mu
opioid-NLS-GFP)
HEK cells were transfected for 48 hours with a DNA construct
encoding the mu opioid-NLS-GFP (2 micrograms). The cells were also
transfected with Ds-Red-NUC (1 microgram) to verify the localisation of the
nucleus. The cells were examined by confocal microscopy.
65% of the mu opioid-NLS-GFP transfected cells showed receptor
expression in the nucleus. 15% of the cells showed cell surface localisation
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of receptor and 20% receptor of cells had cytoplasmic labelling. Thus the
insertion of the NLS permitted the mu opioid receptor to traffic to the
nucleus.
Example 23: Mu opioid receptor with an incorporated NLS (mu-NLS-
GFP) treated with antagonists
HEK cells were transfected with a DNA construct encoding the mu,
opioid-NLS-GFP (2 micrograms). The transfected cells were treated with the
mu opioid antagonists, naloxone (10 micromolar) or naltrexone (10
micromolar). At 6, 22, 30 and 42 hours after transfection the culture medium
containing the antagonist was replaced. Control cells received no
antagonist. The cells were examined by confocal microscopy.
When untreated, 62% of cells had Mu-NLS-GFP in the nucleus and
20% of cells had receptor detectable on the cell surface. With naloxone
treatment, 21')/0 of cells had receptor expression in the nucleus and 66% of
cells had receptor on the cell surface. With naltrexone treatment, 22% of
cells had receptor expression in the nucleus and 58% of cells had receptor
on the cell surface. Thus the mu opioid antagonists naloxone and
naltrexone reduced receptor translocation off the cell surface and to the
nucleus.
Example 24: Muscarinic M1 receptor with an incorporated NLS (M1-
NLS-GFP) treated with antagonist
HEK cells were transfected with DNA encoding M1-NLS-GFP (1
microgram), and Ds-Red-NUC (1 microgram) for 48 hours. These cells were
treated with iprotropium bromide (10 micromolar). The medium containing
antagonist was replaced at 6, 22, 30 and 42 hours after transfection. Control
cells received no antagonist treatment. The cells were examined by
confocal microscopy.
Following iprotropium bromide treatment, 72% of the cells had
receptor expression on the cell surface, 17% had receptor expression in the
cytoplasm only, 11% of the cells had receptor expression in the nucleus.
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For control cells, 64% had receptor expression in the nucleus, 23%
had receptor expression on the cell surface and 13% of the cells had
receptor expression in cytoplasm.
Treatment with a muscarinic antagonist prevented the M1-NLS-GFP
from translocating off the cell surface and trafficking to the nucleus.
Example 25: Histamine H1 receptor with an incorporated NLS (H1-
NLS-GFP)
HEK cells were transfected with a DNA construct encoding the
histamine H1-NLS-GFP receptor (2 micrograms), and a construct encoding
Ds-Red-NUC (1 microgram) for and incubated for 48 hours.
Approximately 65% of the cells had receptor expression in the
nucleus, and 35% of the cells had receptor expression on both surface and
cytoplasm. Insertion of the NLS into the H1 histamine receptor resulted in
translocation of the receptor off the surface and to the nucleus.
Example 26: Effect of the antagonist promethazine on the trafficking of
the H1 histamine receptor with an NLS inserted (H1-NLS-GFP)
HEK cells were transfected with H1-NLS-GFP (2 micrograms) and
DsRED- Nuc (2 micrograms) and incubated for 48 hours. The cells were
treated with promethazine (10 micromolar) for 48 hours. Nucleii were
visualised with DsRED- Nuc. The cells were examined by confocal
microscopy.
With the promethazine treated cells 88% of the cells had receptor on
the cell surface, 10% of the cells had receptor in the nucleus. With the
untreated cells 85% had receptor expression in the nucleus and cytoplasm.
Thus treatment with promethazine reduced H1-NLS-GFP trafficking to the
nucleus.
Example 26: Angiotensin AT1 receptor (AT1R)
A DNA construct (All R-RFP) was created encoding a fusion protein
comprising the NLS-containing human angiotensin AT1 receptor and
DsRed2 (RFP).
COS cells were transfected with the DNA construct AT1R-RFP (4
micrograms) and incubated for 48 hours at 37 C.
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Cells were examined by confocal microscopy and the receptor was
found to be located exclusively within the nuclei of the cells, indicating a
basal agonist-independent translocation of the AT1R into the nucleus.
Example 27: Dopamine receptor (D1 -NLS-GFP) treated with agonist
for a short term
HEK cells were transfected with the DNA constructs encoding D1-
NLS-GFP (2 micrograms), and D1-WT (4 micrograms), and the cells
incubated for 24 hours. The cells were treated with the dopamine D1
agonist, SKF 81297 (10 micromolar) for 35 mins. A single group of cells
were visualised by confocal microscopy in real time.
An increased expression of the receptor in the nucleus was
demonstrated, with a maximum increase occurring at 20 minutes, indicating
short term agonist effect.
Example 28: Dopamine transporter with a NLS, fused to GFP and
RFP (DAT-NLS-GFP and DAT-NLS-RFP)
HEK cells were transfected with a DNA construct encoding DAT-GFP (2
micrograms) for 48 hours. Nuclei were visualised with DsRED-nuc (2
micrograms) using confocal microscopy.
At 48 hours, DAT-GFP was detected on the cell surface or in the
cytoplasm in 86% of the cells. In 14% of the cells, the transporter was in the
nucleus.
HEK cells were transfected with a construct encoding DAT-NLS-RFP (2
micrograms) and visualised by confocal microscopy at 48 hours. DAT-NLS-RFP
was detected in the nuclei in 85% of the cells. In 18% of the cells, the
transporter
was either at the surface or in the cytoplasm.
HEK cells were then transfected with DNA encoding DAT-NLS-GFP (2
micrograms) and visualised by confocal microscopy at 48 hours. Nuclei were
visualised with DsRED-nuc (2 micrograms). DAT-NLS-GFP was detected in the
nucleus of 77% of cells.
Example 29: Co-trafficking of DAT-GFP with DAT-NLS-RFP
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HEK cells were transfected with DNA constructs encoding DAT-NLS-RFP
(2 micrograms) and DAT-GFP (2 micrograms), and incubated for 48 hours. The
cells were examined by confocal microscopy.
A yellow fluorescence was detected in the nuclei in 56% of the cells,
5 indicating co-localisation of DAT-NLS-RFP and DAT-GFP in the nucleus,
confirming oligomerisation of DAT-NLS-RFP and DAT-GFP.
Example 30: Effect of cocaine on DAT-NLS-RFP trafficking to the
nucleus
HEK cells were transfected with a DNA construct encoding DAT-NLS-RFP
10 (2 micrograms) and incubated for 48 hours. At 6, 22, 30 and 42 hours
after
transfection, the cells were treated with cocaine or amphetamine (final
concentration 10 micromolar), or left untreated. The cells were examined by
confocal microscopy.
In the non-treated HEK cells, 77% of the cells had DAT-NLS-RFP
15 expression in the nucleus.
Following cocaine treatment, 75% of the cells had cell surface or
cytoplasmic expression of DAT-NLS-RFP, whereas 25% of the cells had
transporter expression in the nucleus and cytoplasm. Treatment with cocaine
reduced the trafficking of the DAT-NLS-RFP to the nucleus.
20 Following amphetamine treatment, 34% of the cells had cell
surface/cytoplasm expression, and 66% of the cells had transporter expression
in
the nucleus/cytoplasm. Treatment with an amphetamine (which does not target
DAT but targets the vesicular rnonoamine transporter, VMAT) had no inhibitory
effect on the trafficking of the DAT-NLS-RFP to the nucleus.
25 Example 31: Expression of the dopamine transporter with a NLS (DAT-
NLS-GFP) and treatment with antagonists
HEK cells were transfected with a DNA construct encoding DAT-NLS-GFP
(2 micrograms) and incubated for 48 hours. At 6, 22, 30 and 42 hours after
transfection, the cells were treated with GBR-12909 (final concentration 1
30 micromolar). The cells were examined by confocal microscopy.
HEK cells were transfected with a construct encoding DAT-NLS-GFP (2
micrograms) and incubated for 48 hours. At 6, 22, 30 and 42 hours after
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transfection cells were treated with mazindol (final concentration 1
micromolar).
The cells were examined by confocal microscopy.
Control HEK cells were transfected with DAT-NLS-GFP incubated for 48
hours and not treated with drug.
In the untreated HEK cells transfected with DAT-NLS-GFP, 77% of the
cells had transporter expression in the nucleus and cytoplasm, 23% in the
cytoplasm only, and 0% on the cell surface.
Following GBR-12909 treatment, 62% of the cells had transporter
expression on the cell surface and in cytoplasm, and 38% of the cells had
transporter expression in the nucleus and cytoplasm. Treatment with GBR-
12909 reduced DAT-NLS-GFP translocation off the cell surface and trafficking
to
the nucleus.
Following mazindol treatment 61% of the cells had cell surface and
cytoplasm expression of transporter, and 39% of the cells had transporter
expression in the nucleus and cytoplasm. Treatment with mazindol reduced the
DAT-NLS-GFP translocation of the cell surface and trafficking to the nucleus.
Example 32: Ability of dopamine transporter to homooligomerise, using
staggered expression of DAT-GFP and DAT-NLS-RFP
HEK cells were transfected with the DNA construct encoding DAT-GFP (2
micrograms) and 24 hrs later with the DNA construct encoding DAT-NLS-RFP (0.5,
1, and 2 micrograms) and incubated for 48 hours. Cells were also transfected
with
DAT-GFP alone as control. The cells were incubated 48 hours after the second
transfection. Total incubation period was 72 hours.
85% of the cells transfected with DAT-GFP alone contained transporter in
the cytoplasm, and 7% in the nucleus. In the staggered experiment (ratio
1:0.5),
97% of the cells had yellow (= red + green) fluorescence in the nucleus. In
the
staggered experiment (ratio 1:1), 94% of the cells had yellow fluorescence in
the
nucleus. In the staggered experiment (ratio 1:2), 94% of the cells had yellow
fluorescence in the nucleus. Therefore the DAT-GFP interacted with and
dimerised with DAT-NLS-RFP in order to traffic to the nucleus.
Example 33: Expression of the metabotropic glutamate-4-receptor
(mGluR4-GFP)
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=
HEK cells were transfected with a DNA construct encoding nriGluR4-GFP
(2 micrograms) and incubated for 48 hours. Nuclei were visualised with DsRED-
NUC (2 micrograms). The cells were examined by confocal microscopy.
89% of the receptors were expressed at the cell surface. Thus the
mGluR4 receptor was largely located at the cell surface.
Example 34: Expression of the metabotropic glutamate-4 receptor
with an inserted NLS (mGluR4-NLS-GFP)
HEK cells were transfected with a DNA construct encoding mGluR4-
NLS-GFP (2 micrograms), and incubated for 48 hours. The cells were also
transfected with Ds-RED-NUC (2 micrograms) to verify the localisation of the
nucleus. The cells were examined by confocal microscopy.
60% of cells expressing mGluR4-NLS-GFP showed expression of
receptor in the nucleus.
Thus the insertion of an NLS into the mGluR4 receptor increased the
nuclear localisation of the receptor.
Example 35: Expression of the muscarinic M1 receptor with or without
NLS incorporation (M1-GFP and M1-NLS-GFP)
HEK cells were transfected with a DNA construct encoding the M1-GFP (2
micrograms) or with a construct encoding the M1-NLS-GFP (2 micrograms) and
incubated for 48 hours. Nuclei were visualised with DsRED-NUC (2
micrograms). The cells were examined by confocal microscopy.
After transfection with M1 -GFP, 67% of the cells had receptor expressed
on the cell surface or in the cytoplasm.
Transfection with M1-NLS-GFP showed 92% of the cells with nuclear
expression of the receptor, indicating that the NLS directed the receptor to
the
nucleus.
Example 36: Expression of the H1 histamine receptor (H1-GFP)
HEK cells were transfected with a DNA construct encoding H1-GFP (1.5
micrograms) and incubated for 48 hours. Nuclei were visualised with DsRED-
NUC (2 micrograms). The cells were examined by confocal microscopy.
97% of the cells expressed receptor at the cell surface. Thus, the
unmodified receptor did not traffic to the nucleus. ,
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Example 37: Expression of the Cysteinyl leukotriene receptor with NLS
inserted (CysLT1-NLS-GFP)
HEK cells were transfected with a DNA construct encoding CysLT1-NLS-
GFP (2 micrograms) and incubated for 48 hours. Nuclei were visualised with
DsRED-NUC (2 micrograms). The cells were examined by confocal microscopy.
With the control untreated cells, 0% of the cells had receptor expression
on the cell surface, and 100% of the cells had nuclear expression, indicating
robust removal of the receptor off the cell surface.
Example 38: Expression of the serotonin transporter fused to GFP
(SERT-GFP)
HEK cells were transfected with a DNA construct encoding SERT-GFP
(2 micrograms) and incubated for 48 hours. 91% of the cells expressed
transporter on the cell surface and cytoplasm.
Example 39: Expression of the serotonin transporter with an inserted
NLS and treatment with fluoxetine (SERT-NLS-GFP)
HEK cells were transfected with DNA encoding SERT-NLS-GFP (2
micrograms of DNA) and treated with fluoxetine (final concentration1
micromolar)
for 48 hours. At 6, 22, 30 and 42 hours after transfection, the cells were
treated
with fluoxetine (final concentration 1 micromolar). The cells were examined by
confocal microscopy.
In the untreated cells expressing SERT-NLS-GFP, 0% of the cells had
transporter expression on the cell surface, 26% had transporter expression in
the cytoplasm, and 60% of the cells had transporter expression in the nucleus
and cytoplasm.
Following fluoxetine treatment, 68% of the cells had SERT-NLS-GFP
transporter expression on the cell surface and cytoplasm, and 27% of the
cells had transporter expression in the nucleus and cytoplasm. Thus
treatment with fluoxetine inhibited the SERT-NLS-GFP from translocating off
the cell surface and trafficking to the nucleus.
Example 40: Evaluation of the ability of two different cell surface
membrane proteins to interact with each other (D2-GFP and DAT-NLS-RFP)
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HEK cells were cotransfected with DNA constructs encoding the D2-GFP (2
micrograms) and DAT-NLS-RFP (2 micrograms) and incubated for 48 hours.
Cells were also transfected separately with D2-GFP and DAT-NLS-RFP alone as
controls. The cells were examined by confocal microscopy.
85% of the cells transfected with DAT-NLS-RFP contained transporter in
the nucleus. 97% of the cells transfected with D2-GFP contained the receptor
on
the cell surface, and 4% of the cells contained receptor in the nucleus. 86%
of the
cotransfected cells contained yellow (red plus green) fluorescence in the
nucleus,
indicating the presence of both D2 and DAT proteins in the nucleus and
confirming dimerisation of the co-expressed proteins.
Example 41: Evaluation of the ability of a membrane protein and a non-
membrane protein, to associate in a complex and interact with each other (D1-
NLS and beta-arrestin1-GFP)
HEK cells were co-transfected with DNA constructs encoding D1-NLS (2
micrograms) and beta-arrestin1-GFP (2 micrograms) and incubated for 48 hours.
Cells were also transfected with beta-arrestin1-GFP alone. The cells were
checked by confocal microscopy.
100% of cells transfected with beta-arrestinl-GFP alone expressed
fluorescent protein in the cytoplasm. Of these cells 15% also had fluorescence
in
the nucleus. 89% of cells co-transfected with both proteins expressed
fluorescent
protein in the nucleus and of these 16% had expression in the cytoplasm. Thus,
the interaction between the GPCR and the non-membrane protein enabled the
trafficking of the non-NLS containing beta-arrestin protein to the nucleus.
Example 42: Expression of the dopamine D1 receptor with an inserted NLS
(HA-D1-NLS) treatment with antagonist and detection with fluorometry
Wells in a multi-well plate were coated with poly-L-ornithine and then plated
with 50,000 cells per well. The cells were transfected with DNA encoding an HA
epitope tagged Dl-NLS receptor and treated with (+)butaclamol (10 nanomolar to
10 micromolar) over 48 hours. Following this, the cells were fixed with
paraformaldehyde, and cell surface receptors were detected with a rat anti-HA
antibody and then a goat anti-rat antibody conjugated to FITC. The fluorescent
signal was detected by fluorometry (Cytofluor). The results are the average of
five
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wells per experimental condition and are shown in Figure 2. There was a dose-
dependent effect of butaclamol to retain receptor on the cell surface,
indicating that
this antagonist reduced receptor trafficking from the cell surface. Thus
fluorometry
can be utilised to detect receptor retained at the cell surface.
5 Example 43: Expression of the dopamine D1 receptor with an inserted NLS
(HA-D1-NLS), and blockade of antagonist dose-response effect by agonist and
detection with fluorometry
Wells in a multi-well plate were coated with poly-L-ornithine and then plated
with 50,000 cells per well. The cells were transfected with DNA encoding an HA
10 epitope tagged D1-NLS receptor and treated with the antagonist SCH 23390
(1
nanomolar to 1 micromolar) with or without the agonist SKF 81297 (1
micromolar)
over 48 hours. Following this, the cells were fixed with paraformaldehyde, and
cell
surface receptors were detected with a rat anti-HA antibody and then a goat
anti-
rat antibody conjugated to FITC. The fluorescent signal was detected by
15 fluorometry (Cytofluor). The results are the average of five wells per
experimental
condition. There was a dose-dependent effect of SCH 23390 to retain receptor
on
the cell surface, indicating that this antagonist reduced receptor trafficking
from the
cell surface. The concomitant addition of agonist reduced the antagonist
effect
(Figure 3). Thus agonist action can be detected by blockade of antagonist
effect
20 and fluorometry can be utilised to quantify the agonist effect.
Example 4313: Expression of the dopamine D1 receptor with an inserted
NLS (HA-D1-NLS), and blockade of antagonist effect by agonist dose-response
=
and detection with fluorometry.
HEK cells were transfected with HA-D1-NLS in a multi-well plate were
25 coated with poly-L-ornithine at a concentration of 50,000 cells per
well. The cells
were treated with the antagonist SCH 23390 (0.5 micromolar) for 48 hrs. The
agonist SKF 81297 (100 nanomolar to 1 micromolar) together with SCH 23390 was
added for the last hour of incubation. Following this, the cells were fixed
with
paraformaldehyde, and cell surface receptors were detected with a rat anti-HA
30 antibody and then a goat anti-rat antibody conjugated to FITC. The
fluorescent
signal was detected by fluorometry (Cytofluor). The results are the average of
five
wells per experimental condition.
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Treatment with SCH 23390 retained HA-D1-NLS on the cell surface (Figure
4, Bar 1 vs. Bar 6). Short-term addition of the agonist resulted in a dose-
dependent blockade=of SCH 23390 effect. Removal of SCH 23390 from the cells
for the last hour of incubation (and in the absence of agonist) resulted in a
33%
loss of HA-D1-NLS receptors from the cell surface (Figure 4, Bar 5 vs. Bar 6),
whereas addition of agonist SKF 81297 100 nanomolar in the continued presence
of SCH 23390 resulted in a 66% loss of receptors from the cell surface (Figure
4,
Bar 4 vs. Bar 6), up to a 78% loss of receptors with addition of SKF 81297 1
micromolar (Figure 4, Bar 2 vs. Bar 6).
The effect of the antagonist SCH 23390 resulted in retention of receptor on
the cell surface, indicating that this antagonist reduced receptor trafficking
from the
cell surface. The concomitant addition of agonist reduced the antagonist
effect and
accelerated the removal of the receptor from the cell surface in a dose-
responsive
manner. Thus interacting compounds can be detected by blockade of the effect
of
is compounds that retain the NLS-containing receptor at the cell surface
and
fluorometry can be utilized to quantify the effect.
Example 44: Expression of the dopamine DI receptor with an inserted (D1-
NLS), treatment with (+)butaclamol 10 micromolar and detection with
radioligand
binding
HEK cells were transfected with DNA encoding D1-NLS and treated with
(+)butaclamol (10 micromolar) or left untreated. After 48 hours, the cells
were
washed, harvested, lysed and homogenised by polytrorri. ihe membrane fraction
was collected by centrifugation and then layered over 35% sucrose solution and
centrifuged at 30,000 rpm at 4 degrees C for 90 min to collect the heavy
membrane
fraction.
The membrane fractions were subjected to radioligand binding assay using
[31-0-SCH23390 with (+)butaclamol (10 micromolar) used to define specific
binding.
The incubation was at room temperature for 2 hours, followed by rapid
filtration and
quantitation by scintillation counting.
Antagonist treatment of D1 -NLS prevented its translocation off the cell
surface and to the nucleus and the receptor retained on the cell surface was
quantified by radioligand binding assay (Figure 5).
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Example 45: Expression of the dopamine D1 receptor with an inserted NLS
(D1-NLS), treatment with (+)butaclamol 500 nanomolar and detection with
radioligand binding
HEK cells were transfected with DNA encoding D1-NLS and treated with
(+)butaclamol 500 nanomolar or left untreated. After 48 hours, the cells were
washed, harvested, lysed and homogenised by polytron. The membrane fraction
was collected by centrifugation and then layered over 35% sucrose solution and
centrifuged at 30,000 rpm at 4 degrees C for 90 min to collect the heavy
membrane
fraction.
lo The membranes were subjected to radioligand binding assay using CHF
SCH23390 with (+)butaclamol 10 micromolar used to define specific binding. The
incubation was at room temperature for 2 hours, followed by rapid filtration
and
quantitation by scintillation counting. Results are shown in Tables 4 and 5.
Table 4: control plasma membrane fraction
Sample Sample Mean NSB SB pmol/mg prot
1 2
2739 3596 3167 1077 2090 1.42
Table 5: Butaclamol treated plasma membrane fraction
Sample1 Sample2 Mean NSB SB pmol/mg prot
16419 15362 15890 471 15419 13.15
NSB: non-specific binding SB: specific binding
Antagonist treatment with (+)butaclamol of Dl-NLS prevented its translocation
to
the nucleus and the receptor retained on the cell surface was quantified by
radioligand binding assay.
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Example 46: Expression of the dopamine D1 receptor with an inserted NLS
(D1-NLS), treatment with (+)butaclamol 100 nanomolar and detection with
radioligand binding
HEK cells were transfected with DNA encoding D1-NLS and treated with
(+)butaclamol 100 nanomolar or left untreated. After 48 hours, the cells were
washed, harvested, lysed and homogenised by polytron. The membrane fraction
=was collected by centrifugation and then layered over 35% sucrose solution
and
centrifuged at 30,000 rpm at 4 degrees C for 90 min to collect the heavy
membrane
fraction.
The membranes were subjected to radioligand binding assay using
[31-]-SCH23390 with (+)butaclamol (10 micromolar) to define specific binding.
The incubation was at room temperature for 2 hours, followed by rapid
filtration and quantitation by scintillation counting.
Antagonist treatment with (+)butaclamol (100 nanomolar) prevented D1-NLS
translocation to the nucleus and the receptor retained on the cell surface was
quantified by radioligand binding assay. In the absence of butaclamol
treatment,
0.03 pmol/mg protein of receptor was detected in the cell surface membranes,
and
with butaclamol treatment, 0.09 pmol/mg protein of receptor was detected in
the
cell surface membranes.
Example 47: Expression of the epidermal growth factor receptor
(tyrosine kinase receptor) EGFR-GFP and EGFR-NLS-GFP.
HEK cells were transfected with DNA encoding EGFR-NLS-GFP (2
micrograms). HEK cells were also transfected with DNA encoding EGFR-GFP
(2 micrograms) and incubated for 24 hours.
EGFR-GFP was expressed on the cell surface in 73% of cells and 12%
; of cells had receptor in the nucleus. EGFR-NLS-GFP was expressed in the
nucleus in 91% of cells and 0% of cells had receptor on the cell surface. The
incorporation of a NLS into the sequence of the EGF receptor induced robust
translocation off the cell surface and into the nucleus.
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Example 48: Expression of the low density lipoprotein receptor (LDL-
GFP)
HEK cells were transfected with DNA encoding the LDL-GFP (2
micrograms) and incubated for 24 hours. The receptor was expressed on the
cell surface in 67% of cells and in the nucleus in 8% of cells.
The LDL receptor is expressed on the cell surface in the majority of
cells with not many cells containing receptor in the nucleus.
Example 49: Expression of the LDL receptor with a NLS (LDL-NLS-
GFP)
HEK cells were transfected with DNA encoding LDL-NLS-GFP (2
micrograms), and DsRED-NUC (2 micrograms), and incubated for 48 hours.
Cells were examined by confocal microscopy.
LDL-NLS-GFP was expressed in the nucleus in 22% of cells, and on
the cell surface in 67%. The incorporation of a NLS into the LDL receptor
induced receptor translocation into the nucleus.
Example 50: Expression of the erythropoietin receptor (cytokine
receptor) EPO-GFP and EPO-NLS-GFP
HEK cells were transfected with DNA encoding EPO-NLS-GFP (2
= micrograms). HEK cells were transfected with EPO-GPF (2 micrograms).
Example 51: Expression of the serotonin transporter with a NLS
(SERT-NLS-GFP) and treatment with sertraline
HEK cells were transfected with DNA encoding SERT-NLS-GFP (2
30 micrograms of DNA) and treated with sertraline (final concentration 500
nanomolar) for 48 hours. At 6, 22, 30 and 42 hours after transfection, the
cells
were treated with sertraline. The cells were examined by confocal microscopy.
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In the untreated cells expressing SERT-NLS-GFP, 0% of the cells had
transporter expression on the cell surface and 75% of the cells had
transporter expression in the nucleus and cytoplasm.
Following sertraline treatment, 69% of the cells had SERT-NLS-GFP
5 transporter expression on the cell surface and cytoplasm, and 21% of the
cells had transporter expression in the nucleus and cytoplasm. Thus
treatment with sertraline inhibited the SERT-NLS-GFP from translocating off
the cell surface and trafficking to the nucleus.
Example 52: Expression of D1 dopamine receptor with an alternate NLS
10 (D1-NLS2-GFP) and treatment with antagonists
HEK cells were transfected with DNA encoding D1-NLS2-GFP (2
micrograms) and treated with (+)butaclamol or SCH 23390 (1 micromolar) for
48 hrs. Nuclei were visualised with DsRed-nuc (2 micrograms). Cells were
examined by confocal microscopy.
15 With
butaclamol treatment, 81% of cells had receptor on the cell surface
or in cytoplasm and 19% of cells had receptor expression in the nucleus. With
SCH 23390 treatment, 78% of cells had receptor on the cell surface or in
cytoplasm and 22% of cells had receptor expression in the nucleus
In the untreated cells, 89% of cells had receptor expression in the
20 nucleus and cytoplasm.
Thus treatment with the dopamine D1 antagonists prevented D1 -NLS2-
GFP receptor translocation off the surface and trafficking to or toward the
nucleus.
The present invention is not limited to the features of the embodiments
25 described herein, but includes all variations and modifications within
the
scope of the claims.
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TABLE 1 EXAMPLES OF NUCLEAR LOCALISATION SEQUENCES
(adapted from Jans et at. 2002)
Protein Nuclear Localisation Sequence (SEQ ID NO)
Human al T-ag PKKKRKV 129
CBP80 RRR-(11 aa)-KRRK 130
DNA helicase Q1 KK-(15 aa)-KKRK 131
BRCA1 KRKRRP, PKKNRLRRK 132, 133
Mitosin KRQR-(20 aa)-KKSKK 134
Myc PAAKRVKLD 135
NF-kB p50 QRKRQK 136
NF-kB p65 HRIEEKRKRTYETFKSI 137
HIV1422 KKKYKLK 138
HIV1423 KSKKKAQ 139
Human a2 T-ag PKKKRKV 129
NF-kB p50 QRKRQK 136
DNA helicase Q1 KK-(15 aa)-KKRK 131
LEF-1 KKKKRKREK 140
EBNA1 LKRPRSPSS 141
HIV-1 IN KRK-(22 aa)-KELQKQITK 142
HIV-1 MA GKKKYKLKH 143
HIV1422 KKKYKLK 144
HIV1423 KS KKKAQ 145
RCP 4.1R EED-(350 aa)-KKKRERLD 146
Human a3 T-ag PKKKRKV 129
DNA helicase Q1 CYFQKKAANMLQQSGSKNTGAKKRK 147
tTS DILRR-(323 aa)-PKQKRK 148
Human a4 T-ag PKKKRKV 129
Mouse al LEE-1 KKKKRKREK 140
Mouse a2 T-agaCK2 site SSDDEATADSQHSTPPKKKRKV 149
Impa-P1) T-ag PKKKRKV 129
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TABLE 1 - cont'd
N1N2 RKKRK-(9 aa)-KAKKSK 150
RB KR-(11 aa)-KKLR 151
Dorsal aPrA site RRPS-(22 aa)-RRKRQK 152
CBP80 RRR-(11 aa)-KRRK 153
DNA helicase Q1 KK-(15 aa)-KKRK 131
LEF-1 KKKKRKREK 140
Mouse a2 T-agaCK2 SSDDEATADSQHSTPPKKKRKV 149
Impa-P1) T-ag PKKKRKV 129
N1N2 RKKRK-(9 aa)-KAKKSK 150
RB KR-(11 aa)-KKLR 151
Dorsal aPrA RRPS-(22 aa)-RRKRQK 152
CBP80 RRR-(11 aa)-KRRK 153
DNA helicase Q1 KK-(15 aa)-KKRK 131
LEF-1 KKKKRKREK 140
Xenopus al T-ag PKKKRKV 129
Nucleoplasmin KR-(10 aa)-KKKL 154
Yeast al T-ag PKKKRKV 129
(SRP1, Kap60) T-agaCK2 SSDDEATADSQHSTPPKKKRKV 149
N1N2 RKKRK-(9 aa)-KAKKSK 150
HIV-1 IN KRK-(22 aa)-KELQKQITK 142
Plant al T-ag PKKKRKV 129
T-agaCK2 SSDDEATADSQHSTPPKKKRKV 149
Opaque-2 RKRK-(7 aa)-RRSRYRK 155
R Protein (Maize) MISEALRKA 156
N1N2 RKKRK-(9 aa)-KAKKSK 150
RAG-1, recombination activating protein 1; RCP, red cell protein; RB,
Retinoblastoma protein; STAT, signal transducer and
activator of transcription (TF); CBP80, Cap-binding protein; LEF, Lymphocyte
enhancer factor; EBNA, Epstein-Barr virus nuclear antigen; IN, HIV-1
integrase; tTG, tissue transglutaminase; ICP, Infected cell protein.
