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(Received for publication, December 6, 1994) From the
Two isoforms of the dopamine D2 receptor have been
characterized, D2L (long) and D2S (short), generated by alternative
splicing from the same gene. They differ by an in-frame insert of 29
amino acids specific to D2L within the putative third intracytoplasmic
loop of the receptor. We have previously demonstrated (Montmayeur,
J.-P., Guiramand, J., and Borelli, E.(1993) Mol. Endocrinol. 7, 161-170) that D2S and D2L, although presenting very
similar pharmacological profiles, couple differently to the
Dopamine mediates its effect in vivo through the
activation of five different receptors, which show distinct
pharmacological profiles(1) . All dopamine receptors belong to
the large family of seven-transmembrane domain
G-protein( Analysis of the
amino acid composition of the third loop of the known 7TM receptors has
shown the presence of highly charged residues in the N- and C-terminal
regions of the loop. It is known that an alternation of
hydrophobic/hydrophilic amino acids can influence the secondary
structure of proteins inducing an amphipathic An
interesting feature of the D2 receptor is that the D2L-specific insert
is located outside of the regions mentioned above. Furthermore, the
insert interrupts a putative To establish the importance of
this region in determining the D2L coupling characteristics, we
generated amino acid substitution mutations in the 29-amino acid
insert. We took advantage of the observed D2L requirement for Gi Amino acid mutations were generated in the D2L insert in
order to identify the residues playing a role in the coupling to
G-proteins. Charged amino acids were substituted with valine, a
nonpolar amino acid. In addition, proline 264 was substituted with
glycine, and serines 259 and 262 with alanines. These mutant receptors
were analyzed for their ability to bind D2-specific ligands and to
transduce the signal at the cAMP level. We have identified mutants with
an associated increase in the inhibition of cAMP levels. This clearly
demonstrates that the D2L-specific insert determines the selectivity of
coupling of this isoform to G-proteins.
Figure 1:
Construction of the mutant D2L
receptors. A, nucleotide sequence of the mouse D2L receptor
cDNA from nucleotides 715 to 834 and the corresponding amino acid
sequence. The cleavage sites for Bsu36I, BspHI, and SacI used for the construction of the various mutants are
indicated by arrows. The D2L-specific insert is indicated by
the blackdiamonds located beneath the amino acid
sequence. B, sequences of the oligonucleotides used to
construct mutant D2L receptors. The nucleotides that differ from the
wild-type sequence are indicated in boldface. C,
amino acid sequence from positions 239 to 278 of the D2L receptor
compared with the various mutants. The mutagenized amino acids for each
mutant are indicated. The blackdiamonds above the
sequence indicate the 29-amino acid D2L-specific
insert.
To perform [
The K
Figure 2:
Dose-response curves for inhibition of
cAMP formation by DA in D2L-transfected (
Figure 3:
Dose-response curves for inhibition of
cAMP formation by DA in D2L-transfected (
Noticeably, all the D2L mutants present an unaltered
efficacy (I
These data show that the increased potencies observed
in the cAMP tests for the mutant receptors correlate, as expected, with
a gain in the affinity of these receptors for the agonists. They also
indicate that these receptors can interact better, with respect to D2L,
with the G-proteins available in JEG3 cells, in a manner similar to the
D2S isoform. The dopamine D2 receptor represents an interesting paradigm
among the characterized 7TM receptors to understand the
structure/function relationships of these proteins. Two isoforms of
this receptor have been isolated with comparable pharmacological
characteristics and anatomical distribution. This is in spite of the
structural difference located at the level of the third
intracytoplasmic loop. This loop plays a central role in the coupling
of this class of receptors to G-proteins(23, 24) . In
particular, the regions flanking each extremity of the loop, adjacent
to transmembrane domains V and VI, are fundamental to the coupling of
the receptor with
G-proteins(16, 17, 25, 26) . The
insert present in D2L does not affect these regions, while it adds 29
amino acids at a position 31 residues C-terminal from transmembrane
domain V. Nevertheless, both receptors transduce the signal correctly
and are consequently able to interact with G-proteins. Interestingly,
in previous reports, we have demonstrated that the D2L isoform requires
the presence of G Comparison of the dopamine D2 receptor gene in human and
mouse demonstrates that its sequence and splicing events have been
highly conserved through evolution. This might indicate that the
presence of two isoforms and their selective interaction with different
G-proteins represent an essential feature of dopamine D2 receptor
function in vivo. It is tempting to speculate that in
vivo, these receptors might serve different functions by
activating different G-proteins and possibly different transduction
pathways. The simultaneous activation of different G-proteins might be
a cellular mechanism to amplify the cellular response to the
dopaminergic signal. The nucleotide
sequence(s) reported in this paper has been submitted to the
GenBank(TM)/EMBL Data Bank with accession number(s)
X55674[GenBank].
Volume 270,
Number 13,
Issue of March 31, 1995 pp. 7354-7358
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS
DISCUSSION
FOOTNOTES
ACKNOWLEDGEMENTS
REFERENCES
-subunit of guanine nucleotide-binding regulatory proteins
(G-proteins). In particular, D2L, but not D2S, requires the presence of
the -subunit of the inhibitory G-protein (Gi2) to elicit
greater inhibition of adenylyl cyclase activity. The insert present in
D2L must therefore confer the specificity of interaction with Gi2.
Thus, we introduced substitution mutations within the D2L insert. These
mutant receptors were expressed in JEG3 cells, a Gi2-deficient
cell line, scoring for those presenting an increased inhibition of
adenylyl cyclase by dopamine. Our analysis identified two mutants,
S259/262A and D249V, with these properties. These results clearly show
that the insert present in D2L plays a critical role in the selectivity
for the G-proteins interacting with the receptor.
)-coupled receptors (7TM receptors).
Interestingly, the receptor with a pharmacology corresponding to the D2
subtype is represented by two isoforms generated by alternative
splicing of the same
gene(2, 3, 4, 5, 6, 7, 8, 9, 10) .
These isoforms, named D2L and D2S, are identical except for an insert
of 29 amino acids present in the putative third intracellular loop of
D2L. The pharmacological profiles of these isoforms are very similar in
transfected cells. Ligand activation of both receptors lowers
intracellular cAMP
levels(2, 3, 4, 5, 6, 7, 8, 9, 10) .
Thus, it appears that both isoforms have very similar functional
properties. However, the D2L insert confers a different specificity for
the coupling to G-proteins. Our previous studies have shown that D2L
and D2S couple differently to G-proteins(11) . Specifically,
D2L requires the presence of the -subunit of the inhibitory
G-protein (Gi2) to inhibit adenylyl cyclase more
potently(12) . Similar results have also been obtained in other
systems(13) . These observations underline the functional
significance of the 29-amino acid insert in the third loop of D2L. In
general, the third intracytoplasmic domain of 7TM receptors appears to
direct the interaction of the receptor with the appropriate G-proteins.
For example, swapping of this region from the - to the
-adrenergic receptor creates a chimeric receptor with
the signal transduction characteristics of an
-adrenergic receptor(14) . Similarly, swapping
experiments performed between the m1- and m2-muscarinic receptors also
demonstrate the importance of this loop in the selective coupling to
specific G-protein/effector systems(15) .-helical structure.
Thus, the N- and C-terminal regions of the third loop are postulated to
adopt such a structure. Moreover, these highly charged regions of the
third loop are strikingly conserved between many different 7TM
receptors. Point mutations or deletions affecting these regions disrupt
the normal signal transduction by these receptors by altering their
binding to
G-proteins(16, 17, 18, 19) .-helical structure present in the D2S
third loop and incorporates a novel stretch of alternating
hydrophobic/hydrophilic residues.2
in JEG3 cells to score for mutants that display a higher potency of
adenylyl cyclase inhibition and, in this respect, that behave similarly
to D2S.
Materials
[
H]Spiperone
([H]SPI; benzenering-H; 920 GBq/mmol) and
(-)-N-propyl[H]propylnorapomorphine
([H]NPA; 1900 GBq/mmol) were purchased from
DuPont NEN. (+)-Butaclamol and(-)-isoproterenol
((-)-IPR) were from Research Biochemicals Inc. (Natick, MA);
dopamine (DA) and isobutylmethylxanthine were from Sigma. The cAMP
radioimmunoassay kit was obtained from Immunotech.Construction of Mutant Forms of the D2L Receptor
A
585-base pair HincII fragment of the mouse D2L cDNA (10) containing the 87-base pair D2L-specific sequence was
subcloned into pBluescript SK (Stratagene, La Jolla, CA) with deleted
endogenous SacI and BspHI sites to generate pD2L-HII.
To generate each mutant, pD2L-HII was digested with two restriction
enzymes, and the wild-type fragment was substituted with the
mutagenized fragment. Pairs of complementary oligonucleotides including
the mutations were synthesized corresponding to the sequences between
the two restriction sites (see Fig. 1). After annealing, the
oligonucleotides were ligated into pD2L-HII, generating the different
mutants. The HincII-mutated fragments were then sequenced and
exchanged with that of wild-type D2L. The D2L mutants were verified by
restriction digests and sequencing. The full-length inserts containing
the entire D2L coding region were finally subcloned into the pSG5
eucaryotic expression vector(20) . To generate mutants K251V
and D249V, pD2L-HII was digested with Bsu36I and BspHI at positions 868 and 896 of the full-length mouse D2L
cDNA, respectively(10) . For mutants K3R-V, K5R-V, P264G,
S259/262A, and D271V, pD2L-HII was digested with Bsu36I and SacI at positions 868 and 953, respectively. The sequences of
the oligonucleotides are presented in Fig. 1.
[
JEG3 cells were grown in modified Eagle's medium
(Life Technologies, Inc.) supplemented with 10% fetal calf serum. They
were plated at 1 H]SPI and
[H]NPA Binding of Transiently Transfected JEG3
Cells
10
cells/35-mm well and
transfected with 1.6 µg of total DNA containing 0.4 µg of
specific wild-type or mutated D2 expression vectors using the calcium
phosphate coprecipitation technique. Cells were washed 8 h after
transfection. [H]SPI binding experiments were
performed 18 h later on whole cells as already described(12) . H]NPA binding (21, 22) to transfected JEG3 cell membranes, cells
were first harvested in phosphate-buffered saline and pelleted at 500
g. After homogenization in 10 mM Tris-HCl (pH
7.5) and 5 mM EDTA with 10 strokes of a Dounce homogenizer,
membranes were isolated by centrifugation at 1000 g for 10 min. The supernatant was recovered and centrifuged at
45,000 g for 40 min. The pellet containing the
membranes was resuspended in the same buffer and centrifuged again at
the same speed. The final pellet was resuspended in 50 mM Tris-HCl (pH 7.7) and stored in aliquots at -80 °C.
[H]NPA binding was performed in buffer containing
40 mM Tris-HCl (pH 7.7), 96 mM NaCl, 4 mM KCl, 1.6 mM CaCl, 0.8 mM MgCl, and 0.1% ascorbic acid. Membranes were incubated
in this buffer in the presence of increasing concentrations of
[H]NPA ranging from 0.08 to 5 nM for 30
min at 37 °C. Nonspecific binding was determined in the presence of
1 µM (+)-butaclamol. Incubations were terminated by
rapid filtration at 0-4 °C through Whatman GF/B filters using
a Brandel harvester apparatus, followed by three washes with 2 ml of
ice-cold 50 mM Tris-HCl (pH 7.7). Binding data were analyzed
with the EBDA-LIGAND program (Elsevier-Biosoft) using the one-site
fitting model, allowing the determination of dissociation constant (K
) and maximal binding capacity (B
) values for each experiment.Cyclic AMP Measurements
Cells were cultured and
transfected as described above, with the exception that 0.4 µg of
pKSVTF, a vector expressing the -adrenergic receptor,
was added to each well. 18 hours after transfection, cells were
incubated for 45 min at 37 °C with 2 ml of modified Eagle's
medium supplemented with 25 mM HEPES (pH 7.5). Then, 100
µl of a 10 mM solution of isobutylmethylxanthine was
added, and the cells were further incubated for 20 min at 37 °C.
The cells were then stimulated for 45 min at 37 °C with 2 ml of
phosphate-buffered saline containing(-)-IPR (10 µM)
and DA at increasing concentrations. To stop the reaction and to
extract cAMP, the medium was removed, and 500 µl of 65% ethanol was
added. The extracts were lyophilized, and cAMP was measured by
radioimmunoassay using an Immunotech kit as described by the supplier.
The maximal inhibition (I) of
the(-)-IPR-evoked cAMP response as well as the concentration of
DA required to obtain 50% of the maximal inhibition (IC
)
were calculated on each dose-response curve using the EBDA program.
Mutations in the D2L-specific Insert
The
29-amino acid insert characterizing the D2L isoform is located 31
residues C-terminal from the end of the putative fifth domain, as
compared with D2S. The computer-predicted secondary structure of this
region, using the method of Garnier et al.(27) , shows
alternating -helices and -sheets. To establish whether
mutations in the D2L-specific insert may alter the coupling
characteristics of the receptor, we substituted lysines and arginines
for valine. These changes lie within or adjacent to the 29-amino acid
insert, creating mutants K251V, K3R-V, and K5R-V (Fig. 1). In
the mutant P264G, proline 264 was exchanged with glycine. Serines 259
and 262 were mutated to alanine to create the mutant S259/262A.
Finally, aspartates 249 and 271 were replaced by valine in mutants
D249V and D271V, respectively.[
Wild-type D2L and D2S receptors and the D2L
mutants were transiently transfected in JEG3 cells.
[H]SPI Binding Characteristics of
Mutant ReceptorsH]SPI binding on D2L- or D2S-transfected JEG3
cells is saturable, and the Scatchard representation of this binding
fits a one-site model(12) . Analogous results were obtained
with the mutant receptors, indicating that they maintain a conformation
able to sustain ligand binding. Thus, we determined the binding
characteristics (K and B)
of the mutant receptors as compared with the wild-type D2L receptor (Table 1).
of
[H]SPI for the D2L receptor was in agreement with
that observed in vivo(28, 29) . As described
previously(12) , these binding characteristics are not
significantly different from those of the D2S isoform (Table 1).
Among the different mutants studied, we noticed that mutations
affecting the positively charged residues (i.e. K251V, K3R-V,
and K5R-V) resulted in B values lower than those
for the wild-type D2L receptor (Table 1) for equal amounts of
transfected vectors. This effect becomes more evident as the number of
mutated residues increases (Table 1). Indeed, with the K3R-V
receptor, in which 4 residues (1 lysine and 3 arginines) were
substituted with valine, the B value is about
half that for D2L. For the K5R-V receptor, in which 6 residues (1
lysine and 5 arginines) were mutated, B values
are 40% lower with respect to D2L. In addition, we also observed a
slightly higher affinity of [H]SPI for the K5R-V
mutant receptor than for the wild-type D2L receptor (Table 1). No
significant differences in the [H]SPI binding to
the other mutants have been observed (Table 1).Inhibition of Adenylyl Cyclase by Mutant
Receptors
To test whether the G-protein coupling characteristics
of the mutant receptors were different from those of D2L, we measured
their ability to inhibit the activity of adenylyl cyclase. Transient
cotransfection assays were performed in JEG3 cells in the presence of
the -adrenergic receptor and either the wild-type or
mutant receptors. This way, upon stimulation by the
-agonist IPR, it is possible to calculate the extent
of inhibition of the cAMP level evoked by the wild-type and mutant D2
receptors in the presence of dopamine. The IC value of DA
for D2S receptors is significantly lower than that for the wild-type
D2L receptors, indicating a better efficiency of coupling of D2S
receptors in these cells (Table 1). We have previously shown that
this difference is due to the absence of the -subunit of Gi2 in
JEG3 cells(11, 12) . Conversely, the I values are similar.Mutations Affecting Basic Residues
Mutant K251V
behaved like D2L with respect to the inhibition of adenylyl cyclase,
indicating that this residue is not involved in the determination of
the coupling characteristics of D2L. In contrast, mutants K3R-V and
K5R-V displayed a decreased potency toward adenylyl cyclase inhibition
as compared with the wild-type receptor (Table 1). Considering
that the B obtained by the transfection of these
mutants in JEG3 cells is always half that of D2L, we believe that these
effects are related to a decreased number of receptor sites. The
decrease is not due to a different expression efficiency between the
mutants and wild-type receptors as this was controlled for by Northern
blot analysis of transfected cells (data not shown). We then
compensated for the difference in the number of sites by transfecting
higher amounts of mutant versus D2L expression vector. In this
way, the lower potency of these mutants as compared with that of D2L
was not observable anymore. This suggests that the basic residues
mutated in K3R-V and K5R-V mainly affect the integration of the
receptor into the plasma membrane without directly altering the
coupling properties of D2L.Mutations Affecting the Coupling Properties of
D2L
In contrast to the results obtained by the substitution of
the basic residues in the D2L insert, we found two mutants that
displayed a higher potency in the cAMP tests. Indeed, the IC values for DA of mutants S259/262A and D249V were significantly
lower than that of the D2L receptor ( Fig. 2and Fig. 3and Table 1). The IC of mutant
S259/262A was almost 3-fold lower than the one obtained for the D2L
isoform, which brings the activity of this receptor to the same level
as that of D2S. Interestingly, the IC value for DA of
D249V is even lower than that of S259/262A, which is at least 5-fold
lower than the IC of the D2L receptor and is lower to a
lesser extent than that of D2S. It thus seems that substitution of
serines 259 and 262 and particularly of aspartate 249 creates a D2
receptor similar to or even more potent than the respective wild-type
D2 receptor.
) and
S259/262A-transfected (
) JEG3 cells. Cells were cotransfected with
0.4 µg of plasmid expressing wild-type or mutant D2 receptors and
0.4 µg of a plasmid expressing the -adrenergic
receptor. 18 hours after transfection, the cells were incubated for 20
min with 500 µM isobutylmethylxanthine and then stimulated
for an additional 45 min with 10 µM(-)-IPR and
increasing concentrations of DA ranging from 0.1 nM to 10
µM. After extraction, the cAMP was quantified by
radioimmunoassay. The results are expressed as percentages of the cAMP
concentration. The values of cAMP obtained by stimulation of the
transfected cells with(-)-IPR, in the absence of dopamine, were
taken as 100%. The fittings of the curves were calculated using the
EBDA program. This figure is representative of one experiment performed
at least three times, each in duplicate. In this experiment, we
obtained the following values: IC = 5 nM and I = 64% for D2L and IC = 3 nM and I = 65%
for S259/262A.
) and D249V-transfected
() JEG3 cells. The experiments were performed as described for Fig. 2. These data, expressed as percentages of
the(-)-IPR-evoked cAMP concentration, are representative of one
experiment performed in duplicate and repeated at least three times.
Estimated values corresponding to the experiment presented in this
figure are as follows: IC = 14 nM and I = 71% for D2L and IC = 3 nM and I = 74%
for D249V.
) of dopamine inhibition of
(-)-IPR-induced cAMP formation, which is comparable to that of
the wild-type D2 receptors. This indicates that the D2L insert does not
directly participate in the recruitment of the G-proteins to the
receptor, in agreement with findings showing that the regions
responsible for such function reside elsewhere in the third loop (16, 17, 18, 19) . However, the
lower IC suggests that the insert is implicated in the
establishment of the interactions of the D2L receptor with specific
G-proteins. Mutants P264G and D271V were not significantly different
from the wild-type receptor in the inhibition of cAMP levels (Table 1).[
The increased potency of S259/262A and D249V observed
in the cAMP tests led us to investigate whether this effect could have
also been at the level of agonist binding to the receptors. Indeed,
[H]NPA Binding of Mutant D2L
ReceptorsH]NPA binding experiments with membranes of
transfected JEG3 cells indicated that these two receptors present
higher affinity for the binding of D2-specific agonists. The K of [H]NPA for the D2L
receptor was 459 ± 65 (n = 9). We then
calculated the ratio between the K of D2L versus the K of D249V, S259/262A, and
D2S. This way, we obtained the following values: 0.54 ± 0.08 (n = 3, p < 0.05) for S259/262A, 0.51
± 0.02 (n = 3, p < 0.05) for D249V,
and finally 0.43 ± 0.08 (n = 3, p <
0.05) for D2S.
i2 for maximum inhibition of adenylyl
cyclase(12) . This indicates that the insert plays a role in
specifying the interaction of D2L with Gi2, although even in its
absence, this receptor is able to interact less efficiently with other
G-protein(s). The results presented in this paper support this
hypothesis. Indeed, none of the amino acid substitutions tested creates
mutant D2L receptors that are unable to inhibit cAMP levels in
transfected cells. In contrast, we show that S259/262A and in
particular D249V display a lower IC ( Fig. 2and Fig. 3and Table 1), demonstrating that these mutants
acquire an increased potency with respect to D2L in inhibiting cAMP
levels. This is of particular interest given that the wild-type D2L
receptor works less efficiently in these cells than in other cell types
due to the lack of the -subunit of Gi2. This indicates that the
mutations generate receptors able to interact more efficiently with
G-proteins other than Gi2. Indeed, mutants S259/262A and D249V
present IC values similar to and even higher than that of
the D2S isoform, respectively (Table 1). We believe that the
29-amino acid insert of D2L generates a structure that confers
interaction selectivity for Gi2. Computer analysis of the sequence
of the D2L insert, using the method of Garnier et
al.(27) , predicts an -helical structure. This type
of structure has been previously shown to be important for
receptor/G-protein
interaction(30, 31, 32, 33) . The
substitution of a negatively charged amino acid, such as aspartate 249,
with a nonpolar amino acid might modify the structure of the
neighboring region of the protein, and in this way, the mutant receptor
may acquire novel G-protein specificities. This could also apply for
mutant S259/262A. Alternatively, serines 259 and 262 might represent
phosphorylation target sites. Phosphorylation is believed to be
involved in mechanisms of G-protein-coupled receptor
desensitization(19, 34) ; therefore, mutant S259/262A
could be more efficient because it is not desensitized as efficiently
as the wild-type receptor. However, by sequence comparison, serines 249
and 262 do not constitute consensus substrates for known kinases. While
consensus phosphorylation sites for 7TM receptor kinases are not well
defined, it seems that acidic residues are required in the proximity of
the target Ser or Thr residues(35) . This is not the case for
either serine 259 or 262. Future experiments will be required to assess
whether these serines are phosphorylation sites for known or still
uncharacterized kinases. In conclusion, our experiments reinforce the
notion of the importance of the D2L-specific insert in determining the
functional properties of this isoform with regard to coupling to
G-proteins.
)i2, -subunit of the inhibitory G-protein;
[H]SPI, [H]spiperone;
[H]NPA,
(-)-N-propyl[H]propylnorapomorphine;
(-)-IPR,(-)-isoproterenol; DA, dopamine.
We thank A. Staub and F. Ruffenach for oligonucleotide
synthesis; Serge Vicaire for the sequencing of mutant receptors; and
J.-H. Baik, R. Picetti, B. Kieffer, and P. Hubert for discussions. We
also acknowledge N. Foulkes and P. Sassone-Corsi for critical reading
of the manuscript.
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
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 N. Ben-Jonathan and R. Hnasko Dopamine as a Prolactin (PRL) Inhibitor Endocr. Rev., December 1, 2001; 22(6): 724 - 763. [Abstract] [Full Text] [PDF]
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M. A. King, S. Bradshaw, A. H. Chang, J. E. Pintar, and G. W. Pasternak Potentiation of Opioid Analgesia in Dopamine2 Receptor Knock-Out Mice: Evidence for a Tonically Active Anti-Opioid System J. Neurosci., October 1, 2001; 21(19): 7788 - 7792. [Abstract] [Full Text] [PDF]
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 J. N. Oak, N. Lavine, and H. H. M. Van Tol Dopamine D4 and D2L Receptor Stimulation of the Mitogen-Activated Protein Kinase Pathway Is Dependent on trans-Activation of the Platelet-Derived Growth Factor Receptor Mol. Pharmacol., July 1, 2001; 60(1): 92 - 103. [Abstract] [Full Text]
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D. A. McCulloch, E. M. Lutz, M. S. Johnson, D. N. Robertson, C. J. MacKenzie, P. J. Holland, and R. Mitchell ADP-Ribosylation Factor-Dependent Phospholipase D Activation by VPAC Receptors and a PAC1 Receptor Splice Variant Mol. Pharmacol., June 1, 2001; 59(6): 1523 - 1532. [Abstract] [Full Text]
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A. Nicot and E. DiCicco-Bloom Regulation of neuroblast mitosis is determined by PACAP receptor isoform expression PNAS, April 10, 2001; 98(8): 4758 - 4763. [Abstract] [Full Text] [PDF]
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D. Prou, W.-J. Gu, S. Le Crom, J.-D. Vincent, J. Salamero, and P. Vernier Intracellular retention of the two isoforms of the D2 dopamine receptor promotes endoplasmic reticulum disruption J. Cell Sci., January 10, 2001; 114(19): 3517 - 3527. [Abstract] [Full Text] [PDF]
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Y. Wang, R. Xu, T. Sasaoka, S. Tonegawa, M.-P. Kung, and E.-B. Sankoorikal Dopamine D2 Long Receptor-Deficient Mice Display Alterations in Striatum-Dependent Functions J. Neurosci., November 15, 2000; 20(22): 8305 - 8314. [Abstract] [Full Text] [PDF]
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 A. M. Hartmann, O. Nayler, F. W. Schwaiger, A. Obermeier, and S. Stamm The Interaction and Colocalization of Sam68 with the Splicing-associated Factor YT521-B in Nuclear Dots Is Regulated by the Src Family Kinase p59fyn Mol. Biol. Cell, November 1, 1999; 10(11): 3909 - 3926. [Abstract] [Full Text]
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Y.-X. Pan, J. Xu, E. Bolan, C. Abbadie, A. Chang, A. Zuckerman, G. Rossi, and G. W. Pasternak Identification and Characterization of Three New Alternatively Spliced {micro}-Opioid Receptor Isoforms Mol. Pharmacol., August 1, 1999; 56(2): 396 - 403. [Abstract] [Full Text]
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J. Y. A. Lehtonen, L. Daviet, C. Nahmias, M. Horiuchi, and V. J. Dzau Analysis of Functional Domains of Angiotensin II Type 2 Receptor Involved in Apoptosis Mol. Endocrinol., July 1, 1999; 13(7): 1051 - 1060. [Abstract] [Full Text]
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 L. Daviet, J. Y. A. Lehtonen, K. Tamura, D. P. Griese, M. Horiuchi, and V. J. Dzau Cloning and Characterization of ATRAP, a Novel Protein That Interacts with the Angiotensin II Type 1 Receptor J. Biol. Chem., June 11, 1999; 274(24): 17058 - 17062. [Abstract] [Full Text] [PDF]
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L. Franzoni, G. Nicastro, T. A. Pertinhez, E. Oliveira, C. R. Nakaie, A. C. M. Paiva, S. Schreier, and A. Spisni Structure of Two Fragments of the Third Cytoplasmic Loop of the Rat Angiotensin II AT1A Receptor. IMPLICATIONS WITH RESPECT TO RECEPTOR ACTIVATION AND G-PROTEIN SELECTION AND COUPLING J. Biol. Chem., January 1, 1999; 274(1): 227 - 235. [Abstract] [Full Text] [PDF]
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 D. Guivarc'h, J.-D. Vincent, and P. Vernier Alternative Splicing of the D2 Dopamine Receptor Messenger Ribonucleic Acid Is Modulated by Activated Sex Steroid Receptors in the MMQ Prolactin Cell Line Endocrinology, October 1, 1998; 139(10): 4213 - 4221. [Abstract] [Full Text] [PDF]
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 C. MISSALE, S. R. NASH, S. W. ROBINSON, M. JABER, and M. G. CARON Dopamine Receptors: From Structure to Function Physiol Rev, January 1, 1998; 78(1): 189 - 225. [Abstract] [Full Text] [PDF]
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T. A. Samad, W. Krezel, P. Chambon, and E. Borrelli Regulation of dopaminergic pathways by retinoids: Activation of the D2 receptor promoter by members of the retinoic acid receptor-retinoid X receptor family PNAS, December 23, 1997; 94(26): 14349 - 14354. [Abstract] [Full Text] [PDF]
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S. Conchon, M.-B. Barrault, S. Miserey, P. Corvol, and E. Clauser The C-terminal Third Intracellular Loop of the Rat AT1A Angiotensin Receptor Plays a Key Role in G Protein Coupling Specificity and Transduction of the Mitogenic Signal J. Biol. Chem., October 10, 1997; 272(41): 25566 - 25572. [Abstract] [Full Text] [PDF]
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K. N. Furuya, J. V. Thottassery, E. G. Schuetz, M. Sharif, and J. D. Schuetz Bromocriptine Transcriptionally Activates the Multidrug Resistance Gene (pgp2/mdr1b) by a Novel Pathway J. Biol. Chem., April 25, 1997; 272(17): 11518 - 11525. [Abstract] [Full Text] [PDF]
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N. Yang, H. Shigeta, H. Shi, and C. T. Teng Estrogen-related Receptor, hERR1, Modulates Estrogen Receptor-mediated Response of Human Lactoferrin Gene Promoter J. Biol. Chem., March 8, 1996; 271(10): 5795 - 5804. [Abstract] [Full Text] [PDF]
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M. Zhang, X. Zhao, H.-C. Chen, K. J. Catt, and L. Hunyady Activation of the AT1 Angiotensin Receptor Is Dependent on Adjacent Apolar Residues in the Carboxyl Terminus of the Third Cytoplasmic Loop J. Biol. Chem., May 19, 2000; 275(21): 15782 - 15788. [Abstract] [Full Text] [PDF]
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T. Koch, S. Schulz, M. Pfeiffer, M. Klutzny, H. Schroder, E. Kahl, and V. Hollt C-terminal Splice Variants of the Mouse {micro}-Opioid Receptor Differ in Morphine-induced Internalization and Receptor Resensitization J. Biol. Chem., August 10, 2001; 276(33): 31408 - 31414. [Abstract] [Full Text] [PDF]
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J. L. Leaney and A. Tinker The role of members of the pertussis toxin-sensitive family of G proteins in coupling receptors to the activation of the G protein-gated inwardly rectifying potassium channel PNAS, May 9, 2000; 97(10): 5651 - 5656. [Abstract] [Full Text] [PDF]
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