Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CRH exerts its actions via activation of specific G protein-coupled receptors, which exist in two types, CRH-R1 and CRH-R2, and arise from different genes with multiple spliced variants. RT-PCR amplification of CRH receptor sequences from human myometrium and fetal membranes yielded cDNAs that encode a novel CRH-R type 1 spliced variant. This variant (CRH-R1d) is present in the human pregnant myometrium at term only, which suggests a physiologically important role at the end of human pregnancy and labor. The amino acid sequence of CRH-R1d is identical to the CRH-R1alpha receptor except that it contains an exon deletion resulting in the absence of 14 amino acids in the predicted seventh transmembrane domain. Binding studies in HEK-293 cells stably expressing the CRH-R1d or CRH-R1alpha receptors revealed that the deletion does not change the binding characteristics of the variant receptor. In contrast, studies on the G protein activation demonstrated that CRH-R1d is not well coupled to the four subtypes of G proteins (G(s), G(i), G(o), G(q)) that CRH-R1alpha can activate. These data suggest that although the deleted segment is not important for CRH binding, it plays a crucial role in CRH receptor signal transduction. Second messenger studies of the variant receptor showed that CRH and CRH-like peptides can stimulate the adenylate cyclase system, with reduced sensitivity and potency by 10-fold compared with the CRH-R1alpha. Furthermore, CRH failed to stimulate inositol trisphosphate production. Coexpression studies between the CRH-R1d or CRH-R1alpha showed that this receptor does not play a role as a dominant negative receptor for CRH.
Mol Endocrinol 1999 Dec
PMID:A novel spliced variant of the type 1 corticotropin-releasing hormone receptor with a deletion in the seventh transmembrane domain present in the human pregnant term myometrium and fetal membranes. 1059 91

Glucocorticoids act through the glucocorticoid receptor (GR) to enhance or repress transcription of glucocorticoid responsive genes depending on the promoter context and cellular background. The human GR primary transcript is alternatively spliced resulting in hGR alpha and hGR beta isoforms. Transactivation and transrepression are mediated by hGR alpha and while it has been demonstrated that hGR beta, can act as a dominant negative inhibitor of hGR alpha mediated transactivation, its effects on transrepression are not known. To investigate hGR beta actions, we used GR-deficient COS-7 and HEK-293 cells. When hGR alpha (0.5 microg 10(6) cells(-1)) was transfected into COS-7 cells dexamethasone (150 nM) inhibited TNF alpha (80 U ml(-1)) effects on a NF-kappaB responsive reporter gene by 40%. There was no evidence of a dominant negative effect when hGR beta (1-10 microg) was co-transfected with hGR alpha up to ratios of 10:1. Similarly hGR beta had no effect on hGR alpha inhibition of a phorbol ester stimulated Ap-1-responsive reporter gene in COS-7 or HEK-293 cells. In comparison, an apparent dominant negative effect of hGR beta on hGR alpha-mediated transactivation was found to be attributable to non-specific transcriptional squelching in COS-7 cells. In summary, the potential for hGR beta, to act as a dominant negative inhibitor of hGR alpha-mediated transactivation remains controversial, but our data suggest that hGR beta, was unable to act as a dominant negative inhibitor of either hGR alpha-mediated transrepression or transactivation in these promoter and cell contexts.
Mol Cell Endocrinol 1999 Nov 25
PMID:Interaction of glucocorticoid receptor isoforms with transcription factors AP-1 and NF-kappaB: lack of effect of glucocorticoid receptor beta. 1061 1

The melanocortin receptor MC1 is expressed on melanocytes and is an important control point for melanogenesis and other responses. Alpha-MSH, which is considered to be the major ligand at the human melanocortin (MC)1 receptor (hMC1R), is produced from proopiomelanocortin (POMC) in the pituitary and in the skin by melanocytes and keratinocytes. Other POMC peptides are also produced in the skin and their concentrations exceed those of alpha-MSH by several fold. One of the most abundant is ACTH1-17. We have shown that adrenocorticotrophic hormone (ACTH)1-17 is more potent than alpha-MSH in stimulating melanogenesis in human melanocytes and unlike alpha-MSH produces a biphasic dose response curve. In this study we have examined the ability of ACTH1-17 to function as a ligand at the hMC1R. Competitive binding assays with [125I]Nle4 DPhe7 alpha-MSH as labelled ligand were carried out in HEK 293 cells transfected with the hMC1R. ACTH1-17 showed high affinity for the hMC1R with a Ki value of 0.21 +/- 0.03 nM which was slightly higher than that of 0.13 +/- 0.005 nM for alpha-MSH. ACTH1-17 was, however, more potent than alpha-MSH in increasing cAMP and IP3 production in the transfected cells. Our results demonstrate that ACTH1-17 is a potent agonist at the hMC1R. It is therefore possible that ACTH1-17, which is found in the skin in greater concentrations than alpha-MSH, has an important role in the regulation of human melanocytes and other cell types that express the hMC1R.
Cell Mol Biol (Noisy-le-grand) 1999 Nov
PMID:ACTH1-17 is a more potent agonist at the human MC1 receptor than alpha-MSH. 1064 6

We have previously shown a conserved glutamate/dileucine motif ((335)ELRSLL(340)) in the intracellular C terminus of the vasopressin V(2) receptor (V(2) receptor) to be essential for receptor transport from the endoplasmic reticulum (ER) to the Golgi apparatus. The motif may represent a transport signal that is recognized by a component of ER to Golgi vesicles. Alternatively, it may be necessary for transport-competent receptor folding to pass the quality-control system of the ER. To assess these two possibilities, we constructed a receptor fragment that allows transport studies independent of full-length receptor folding. Transmembrane domains II-VII were deleted, thereby fusing the intracellular C terminus to the first cytoplasmic loop. The mutations that impaired transport of the full-length receptor were introduced, and receptor fragments were localized in transiently transfected HEK 293 cells. All mutant receptor fragments were detectable at the plasma membrane, demonstrating that the glutamate/dileucine motif does not function as a small, linear vesicular transport signal. Instead, our data strongly suggest that this motif is required for transport-competent folding of the full-length receptor. To assess the underlying conformational features, a three-dimensional homology model of the V(2) receptor was computed. Our model predicts that the glutamate/dileucine motif contributes to a U-like loop within the intracellular C terminus. Residue Leu(339) may be required for folding back the intracellular C terminus to residue Leu(62) of the first cytoplasmic loop. We characterized the naturally occurring L62P and DeltaL62-R64 mutations in the first cytoplasmic loop and show that they lead to transport-defective full-length V(2) receptors that are retained in the ER, consistent with the structure model.
Mol Pharmacol 2000 Feb
PMID:Molecular and conformational features of a transport-relevant domain in the C-terminal tail of the vasopressin V(2) receptor. 1064 32

Homer proteins bind specifically to the C termini of the metabotropic glutamate receptor mGluR1alpha/a and mGluR5, play a role in their targeting and modulate their synaptic properties. We have discovered that extensive alternative splicing generates a family of 17 Homer proteins. These fall into two distinct groups of 12 "long" Homers, which all have a coiled-coil domain at their C termini, and five "short" Homers, which lack such a domain. All Homers contain the N-terminal sequence responsible for their binding to mGluR1alpha/a receptors and can be co-localised with the recombinantly expressed mGluR1alpha/a protein in HEK-293 cells. The existence of the long and the short variants of each of the Homer-1, Homer-2 and Homer-3 proteins reflects the fundamental principles of Homer functions.
J Mol Biol 2000 Feb 04
PMID:Molecular characterisation of two structurally distinct groups of human homers, generated by extensive alternative splicing. 1065 96

Homer-1c/Vesl-1L is a 48-kDa protein that forms part of a family of conserved Homer-related proteins that interact with the C-termini of the metabotropic glutamate receptors mGluR1alpha and mGluR5. In order to examine the function of Homer-1c, HEK-293 cells have been transfected with mGluR1alpha, Homer-1c, and both proteins together. When cells were transfected with both proteins, biotinylation of cell surface molecules revealed a significant increase in the amount of receptor and Homer-1c associated with the cell surface compared with cells transfected with mGluR1alpha alone. This finding was paralleled by a concomitant increase in the production of inositol after treatment of the doubly transfected cells with agonist. Cell surface immunostaining of mGluR1alpha showed that Homer-1c can induce clustering of the receptor in the plasma membrane of HEK-293 cells and suggested that the surface receptor was associated with Homer-1c in the plasma membrane. The presence of Homer-1c reduced the rate of loss from the cell surface of mGluR1alpha from 5 to 1%/min and increased the extent of dendritic trafficking of the receptor in rat primary cultured neurons. Our results suggest that Homer-1c increases the cell surface expression of the metabotropic glutamate receptor type 1alpha by increasing its retention in the plasma membrane.
Mol Cell Neurosci 2000 Jan
PMID:Homer-1c/Vesl-1L modulates the cell surface targeting of metabotropic glutamate receptor type 1alpha: evidence for an anchoring function. 1066 4

Cranial motor axons navigate along a variety of pathways to their targets in the periphery of the head. Whereas somatic motor axons innervate tongue and eye muscles, visceral motor axons innervate parasympathetic ganglia, and branchiomotor axons innervate the branchial arches. The formation of these diverse pathways must depend upon molecules present in the environment traversed by growing axons. We have analyzed the potential roles of the ephrin ligands and their Eph tyrosine kinase receptors during cranial motor neuron development and axon pathfinding, by investigating expression patterns of these molecules at relevant stages in the chick. We detected expression of EphA3 and EphA4 among trigeminal and facial motor neurons, at times when these neurons are projecting to their muscle targets in the branchial arches. Corresponding ephrin-A ligands for these receptors were found to be expressed in specific regions of the arches during the same period, implicating ephrin-mediated interactions in cranial motor axon pathfinding.
Mol Cell Neurosci 2000 Feb
PMID:Eph receptors and ephrin expression in cranial motor neurons and the branchial arches of the chick embryo. 1067 22

The importance of the amino-terminal domain of the mu opioid receptor (MOR) as a component of the high affinity ligand-binding pocket was evaluated. A deletion mutant lacking 64 amino acids from the amino-terminus of MOR (DeltaN64) was constructed and expressed in HEK 293 cells. The affinities of bremazocine and cyclazocine were similar for the truncated and full-length MORs. Affinities of the mu receptor antagonist, naloxone, and the mu receptor agonist, morphine, were decreased 3.5-fold and 6-fold, respectively, for the truncated receptor relative to the wild-type MOR. Similarly, the affinities of the opioid peptide agonists, DAMGO (Tyr-D-Ala-Gly-MePhe-Gly-ol), beta-endorphin, and DADL (Tyr-D-Ala-Gly-Phe-D-Leu), for the DeltaN64 receptor were decreased from 3- to 8-fold as a result of the deletion. In contrast, the affinities of the alkaloid agonists, methadone and fentanyl, and the peptide agonists, endomorphin 1 and endomorphin 2, for the truncated receptor relative to MOR were reduced dramatically by 20- to 60-fold. MOR is glycosylated when expressed in HEK 293 cells; however, analysis of N-glycosidase F-treated membranes indicated that N-glycan chains within the amino-terminal domain of MOR do not contribute significantly to ligand affinities. These results indicate that amino acid residues within the amino-terminal domain of MOR play a crucial role in the composition of the binding pocket for a select group of agonists.
Brain Res Mol Brain Res 2000 Mar 10
PMID:mu Opioid receptor: role for the amino terminus as a determinant of ligand binding affinity. 1071 16

gamma-Aminobutyric acid(A) receptor gamma-subunits are important for benzodiazepine (BZD) binding and modulation of the gamma-aminobutyric acid-mediated Cl(-) current. Previously, by using gamma2/alpha1 chimeric subunits, we identified two domains of the gamma2-subunit, Lys-41-Trp-82 and Arg-114-Asp-161, that are, in conjunction, necessary and sufficient for high-affinity BZD binding. In this study, we generated additional gamma2/alpha1 chimeric subunits and gamma2 point mutants to identify specific residues within the gamma2 Lys-41-Trp-82 region that contribute to BZD binding. Mutant gamma2 and gamma2/alpha1 chimeric subunits were expressed with wild-type alpha1 and beta2 subunits in HEK 293 cells, and the binding of several BZDs was measured. We present evidence that the gamma2 region Met-57-Ile-62 is important for flunitrazepam binding and that, in particular, gamma2 Met-57 and gamma2 Tyr-58 are essential determinants for conferring high-affinity binding. Furthermore, we identify an additional residue, gamma2 Ala-79, that not only is important for high-affinity binding by flunitrazepam (a strong positive modulator) but also plays a crucial role in the binding of the imidazobenzodiazepines Ro15-1788 (a zero modulator) and Ro15-4513 (a weak negative modulator) in the BZD binding pocket. Results from site-directed mutagenesis of gamma2 Ala-79 suggest that this residue may be part of a microdomain within the BZD binding site that is important for binding imidazobenzodiazepines. This separation of drug-specific microdomains for competitive BZD ligands lends insight into the structural determinants governing the divergent effects of these compounds.
Mol Pharmacol 2000 May
PMID:Identification of benzodiazepine binding site residues in the gamma2 subunit of the gamma-aminobutyric acid(A) receptor. 1077 76

The 5-hydroxytryptamine (5-HT)(3) receptor is a member of the ligand-gated ion channel receptor family with significant homology to the nicotinic acetylcholine, gamma-aminobutyric acid(A), and glycine receptors. In this receptor class, the agonist binding site is formed by parts of the extracellular amino-terminal region. This study examines the effects of altering phenylalanine 107 (F107) of the 5-HT(3AL) subunit, obtained from NG108-15 cells, using site-directed mutagenesis. The wild-type (WT) and mutant receptors were expressed in HEK 293 cells and characterized using both whole-cell patch-clamp and radioligand binding. The tyrosine mutant F107Y exhibits a significantly lower affinity for the agonist 5-HT (K(i) = 203 versus 15.6 nM) and an increase of similar magnitude in the EC(50) value (10.6 versus 1.2 microM) compared with WT. The activation kinetics of the maximal currents generated by 5-HT with this mutant were markedly slower than those of the WT receptor, but application of supramaximal concentrations of the agonist markedly decreased the time to half-peak. The asparagine mutant F107N displayed a significantly higher affinity for 5-HT than the WT receptor (1.62 versus 15.6 nM), which was mirrored in direction and magnitude by changes in the EC(50) value for this agonist (0.2 versus 1.2 microM). In contrast to the WT receptor, the mutant F107N was activated by acetylcholine (EC(50) = 260 microM). The response to acetylcholine was blocked by the 5-HT(3) receptor antagonist renzapride with a similar IC(50) value as that determined against currents generated by 5-HT in the WT receptor. These data suggest that F107 is an important determinant of agonist recognition at the 5-HT(3) receptor.
Mol Pharmacol 2000 Jun
PMID:Importance of phenylalanine 107 in agonist recognition by the 5-hydroxytryptamine(3A) receptor. 1082 97


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