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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have taken advantage of the sequence conservation in the G protein-coupled receptor superfamily to isolate a fragment of a novel G protein-coupled receptor sequence using polymerase chain reaction (PCR) amplification of human genomic DNA. Screening of human genomic and hippocampal cDNA libraries with this amplified receptor fragment revealed a number of related sequences. Sequence analysis of four genomic clones and one cDNA clone clearly identifies these as related members of the G protein-coupled receptor family, as the deduced amino acid sequence reveals putative transmembrane domains and conserved amino acid residues. Southern blot analysis of restriction digests of human genomic DNA indicates that these receptor subtypes are likely to belong to a family of related genes. One of the proposed receptor sequences indicates the presence of pseudogenes in this family. Based on the homology of these sequences to a family of recently described receptors expressed exclusively in rat olfactory epithelium, it is suggested that these receptors represent a family of human odorant receptors.
Brain Res Mol Brain Res 1992 Mar
PMID:Novel G protein-coupled receptors: a gene family of putative human olfactory receptor sequences. 131 13

The LH/CG receptor is a G protein-coupled receptor present on gonadal cells whose levels are modulated by a number of hormones, growth factors, and second messenger analogs. With the recently cloned cDNA for the LH/CG receptor, it has been shown that changes in the levels of the cognate mRNA are involved, at least in part, in the observed changes in receptor density. In order to study the transcriptional regulation of the LH/CG receptor we have isolated a 2-kilobase region of the 5'-flanking region of the rat LH/CG receptor gene and subcloned nucleotide -1 (relative to the translational initiation codon) to -1370 into a luciferase reporter plasmid. We show here that this region of the LH/CG receptor gene is able to enhance luciferase activity in MA-10 cells, a line of Leydig tumor cells that normally express LH/CG receptors, as opposed to human kidney 293 cells, which do not. Furthermore, the addition of 8-bromo-cAMP to MA-10 cells, under conditions known to decrease LH/CG receptor numbers and receptor mRNA levels, decreases the relative luciferase activity to about 26% of control. This decrease in reporter gene activity is severely blunted in a subclone of MA-10 cells with a cAMP-resistant phenotype. Our studies show, for the first time, that sequence(s) present with 1370 base pairs of the translational start site of the rat LH/CG receptor gene are sufficient for conferring expression of this gene in Leydig cells and for the negative modulation of LH/CG receptor gene transcription by high concentrations of cAMP.
Mol Endocrinol 1992 Mar
PMID:The 5'-flanking region of the rat luteinizing hormone/chorionic gonadotropin receptor gene confers Leydig cell expression and negative regulation of gene transcription by 3',5'-cyclic adenosine monophosphate. 131 38

A cDNA encoding a G protein-coupled receptor of unknown ligand specificity was isolated from a human hippocampal cDNA library by virtue of the high degree of structural homology between members of this receptor family. The cloned receptor DNA was transfected into human embryonic kidney 293 cells. Stably transfected cell lines bound a variety of adenosine agonists and antagonists with affinities characteristic of a brain adenosine A2a receptor. The A2a specific agonist CGS21680 stimulated cAMP production but did not alter intracellular calcium concentrations in transfected 293 cells.
Brain Res Mol Brain Res 1992 Sep
PMID:Molecular characterization of a human brain adenosine A2 receptor. 133 70

Using the sequence conservation in the G protein-coupled receptor superfamily, we have isolated an adenosine A1 receptor cDNA from a human hippocampal cDNA library by homology screening. When expressed in mammalian CHO.K1 cells, the protein encoded by this cDNA binds the A1-specific antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) with high affinity (Kd = 0.56 +/- 0.11 nM) and, functionally, is able to inhibit cAMP production upon receptor activation with the A1-specific agonist N6-cyclopentyladenosine (CPA) (> 80% inhibition at 10(-7) M CPA). The binding and functional characteristics of the expressed cDNA demonstrate that we have isolated a human brain adenosine receptor cDNA of the A1 subtype.
Brain Res Mol Brain Res 1992 Dec
PMID:Molecular cloning and characterisation of a human brain A1 adenosine receptor cDNA. 133 1

1. The visual transduction system of the vertebrate retina is a well-studied model for biochemical and molecular studies of signal transduction. The structure and function of rhodopsin, a prototypical G protein-coupled receptor, and transducin or Gt, the photoreceptor G protein, have been particularly well studied. Mechanisms of rhodopsin-Gt interaction are discussed in this review. 2. The visual pigment rhodopsin contains a chromophore, and thus conformational changes leading to activation can be monitored spectroscopically. A model of the conformational changes in the activated receptor is presented based on biophysical and biochemical data. 3. The current information on sites of interaction on receptors and cognate G proteins is summarized. Studies using synthetic peptides from amino acid sequences corresponding to Gt and rhodopsin have provided information on the sites of rhodopsin-Gt interaction. Synthetic peptides from the carboxyl terminal region of alpha t mimic Gt by stabilizing the active conformation of rhodopsin, Metarhodopsin II. 4. The conformation of one such peptide when it is bound to Metarhodopsin II was determined by 2D NMR. The model based on the NMR data was tested using peptide analogs predicted to stabilize or break the structure. These studies yield molecular insight into why toxin-treated and mutant G proteins are uncoupled from receptors.
Cell Mol Neurobiol 1991 Dec
PMID:Molecular interactions between the photoreceptor G protein and rhodopsin. 178 50

We have used the polymerase chain reaction technique to selectively amplify guanine nucleotide-binding regulatory protein (G protein)-coupled receptor cDNA sequences from rat striatal mRNA, using sets of highly degenerate primers derived from transmembrane sequences of previously cloned G protein-coupled receptors. A novel cDNA fragment was identified, which exhibits considerable homology to various members of the G protein-coupled receptor family. This fragment was used to isolate a full-length cDNA from a rat striatal library. A 2.2-kilobase clone was obtained that encodes a protein of 326 amino acids with seven transmembrane domains, as predicted by hydropathy analysis. Stably transfected mouse A9-L cells and Chinese hamster ovary cells that expressed mRNA for this clone were screened with putative receptor ligands. Saturable and specific binding sites for the A1 adenosine antagonist [3H]-1,3-dipropyl-8-cyclopentylxanthine were identified on membranes from transfected cells. The rank order of potency and affinities of various adenosine agonist and antagonist ligands confirmed the identity of this cDNA clone as an A1 adenosine receptor. The high affinity binding of A1 adenosine agonists was shown to be sensitive to the nonhydrolyzable GTP analog guanylyl-5'-imidodiphosphate. In adenylyl cyclase assays, adenosine agonists inhibited forskolin-stimulated cAMP production by greater than 50%, in a pharmacologically specific fashion. Northern blot and in situ hybridization analyses of receptor mRNA in brain tissues revealed two transcripts of 5.6 and 3.1 kilobases, both of which were abundant in cortex, cerebellum, hippocampus, and thalamus, with lower levels in olfactory bulb, striatum, mesencephalon, and retina. These regional distribution data are in good agreement with previous receptor autoradiographic studies involving the A1 adenosine receptor. We conclude that we have cloned a cDNA encoding an A1 adenosine receptor linked to the inhibition of adenylyl cyclase activity.
Mol Pharmacol 1991 Jul
PMID:Cloning and expression of an A1 adenosine receptor from rat brain. 185 34

We examined the functional significance of two residues present in the second (Asp100) and seventh (Asn391) transmembrane domains of the rat cholecystokininB (CCKB) receptor that are highly conserved among the members of the G protein-coupled receptor family. Substitution of Asn for Asp100 by using site-directed mutagenesis did not change the affinity and selectivity for agonists but slightly increased the affinity of three CCKB-selective antagonists of different chemical structures. Cells expressing the mutant receptor exhibited a 50% reduction in CCKB-induced phosphoinositide turnover compared with cells expressing the wild-type receptor, suggesting a critical role for this residue in the coupling of the CCKB receptor to G protein. This latter was shown to be insensitive to pertussis toxin treatment and could therefore belong to the Gq family. Replacement of Asn391 by Asp located in the seventh transmembrane domain did not change agonist binding or phosphoinositide turnover. This suggests that in contrast to the gonadotropin-releasing hormone receptor, there is no direct interaction in the CCKB receptor between Asp100 and Asn391. However, a rhodopsin-based molecular modeling of the CCKB receptor showed a spatial proximity between Asp100 and the carboxyl terminal part of the third intracellular loop, known to interact with G protein. This could explain the reduction in phosphoinositide turnover observed with the Asn100 mutant.
Mol Pharmacol 1995 Nov
PMID:Mutation of Asp100 in the second transmembrane domain of the cholecystokinin B receptor increases antagonist binding and reduces signal transduction. 747 7

The present studies were undertaken to examine the role of the cytoplasmic tail of the G protein-coupled receptor for PTH and PTH-related protein (PTHrP) on receptor signaling and expression. The wild type (WT) receptor (585 amino acids) and five truncated receptors whose cytoplasmic tails terminated at residues 507, 494, 474, 466, and 458 were expressed in COS-7 cells. Based on [125I]PTHrP binding, mutants T507, T494, and T466 displayed progressively decreased levels of expression, compared with WT. The tailless mutant T458 was not expressed in a functional form, whereas T474 was expressed at a level similar to WT. Comparable results were obtained when expression levels of WT and mutated PTH/PTHrP receptors were evaluated by Western blotting. Binding affinities were similar for all mutated receptors (IC50 = 1-2 nM). Immunocytochemistry showed that WT and mutated receptors were diffusely distributed, presumably at the cell surface, except for the tailless mutant T458, which displayed striking perinuclear localization. T458 did not display an adenylyl cyclase response to PTH, while the other mutants were similar to WT both with respect to their maximal adenylyl cyclase responses to PTH and to their EC50 values. Cai2+ signaling properties of these mutants were assessed as PTH-stimulated 45Ca efflux from Xenopus oocytes that had been injected with in vitro transcribed PTH/PTHrP receptor cRNAs. The WT and mutated receptors (except for T458) responded to PTH with significant (6- to 27-fold) increases in 45Ca efflux.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1995 Sep
PMID:Mutational analysis of the cytoplasmic tail of the G protein-coupled receptor for parathyroid hormone (PTH) and PTH-related protein: effects on receptor expression and signaling. 749 Nov 16

The neurokinin-1 tachykinin receptor is a member of the G protein-coupled receptor superfamily. An unusual feature of the neurokinin-1 receptor is the presence of glutamic acid (residue 78) in the second putative transmembrane domain, at the location of a highly conserved aspartate residue in the G protein-coupled receptor superfamily. The rat neurokinin-1 receptor cDNA was mutated to lysine, aspartate, and glutamine at this site and functionally expressed in Chinese hamster ovary cells, and clonal cell lines were isolated and characterized. Radioligand binding demonstrated that the Asp78 and Lys78 receptors have substance P binding affinities indistinguishable from those of the wild-type receptor and are expressed at roughly the same number of receptors per cell. The Gln78 receptor variant, on the other hand, exhibited no detectable agonist binding. Although wild-type and Asp78 receptors have essentially the same ability to stimulate inositol phospholipid turnover, cAMP production, and arachidonic acid release, the Lys78 variant is markedly attenuated in its ability to activate any of these pathways. These data indicate that residue 78 plays a role in the coupling of the rat neurokinin-1 receptor to cellular effectors. In addition, both Asp78 and Lys78 receptors show a greater percentage of high affinity binding that is resistant to guanosine-5'-O-(3-thio)triphosphate than does the wild-type receptor, indicating a potential difference in G protein coupling between wild-type and mutated receptors.
Mol Pharmacol 1995 May
PMID:Residue 78 in the second transmembrane domain of the neurokinin-1 receptor is important in coupling high affinity agonist binding to multiple second messenger responses. 753 94

Because cAMP exerts opposite effects on cell proliferation in different cell types, we undertook to study its effect on the mitogen-activated protein kinase (MAPK) pathway in three cell lines (Rat-1, Swiss-3T3, and COS-7) chosen for their different mitogenic responses to cAMP. We measured the effect of cAMP on MAPK, MEK, and Raf-1 activities after stimulation by agonists acting through a tyrosine kinase receptor (epidermal growth factor) or a G protein-coupled receptor (lysophosphatidic acid). In Rat-1 cells we found that cAMP strongly inhibited all three activities (MAPK, MEK, and Raf-1), in good agreement with its effect on cell proliferation in these cells. In Swiss-3T3 and COS-7 cells, on the contrary, cAMP did not inhibit epidermal growth factor- and lysophosphatidic acid-induced stimulation of MAPK and MEK activities, and even stimulated MAPK activity slightly on its own. Again these results are in good agreement with the proliferative effect of cAMP in Swiss-3T3 cells. Raf-1 activity on the hand, was inhibited by cAMP in Swiss-3T3 and COS-7 as it was in Rat-1 cells. This result indicates that signaling pathways in Swiss-3T3 and COS-7 cells can activate MEK and MAPK in a Raf-1-independent and cAMP-insensitive manner. Our results add to growing evidence for the existence of Ras- and/or Raf-1-independent pathways leading to MEK and MAPK activation.
Mol Biol Cell 1995 Aug
PMID:Differential effects on cAMP on the MAP kinase cascade: evidence for a cAMP-insensitive step that can bypass Raf-1. 757 5


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