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)

Activation of the pituitary gonadotropin-releasing hormone receptor, a member of the seven-transmembrane G protein-coupled receptor (GPCR) family, triggers a cascade of events leading to gonadotropin release and stimulation of the reproductive system. An unusual feature of this receptor, observed in mice, rats, and humans, is the presence of Asn87 in the second putative transmembrane helix at the location of a highly conserved aspartate in the GPCR family and of Asp318 in the putative seventh transmembrane helix where nearly all other GPCRs have asparagine. The possibility that these residues interact was suggested by this reciprocal pattern and by a three-dimensional model of the gonadotropin-releasing hormone receptor and was investigated by site-directed mutagenesis. Replacing Asn87 in the second transmembrane domain by aspartate eliminated detectable ligand binding. A second mutation, generating the double-mutant receptor Asp87Asn318, recreated the arrangement found in other GPCRs and re-established high affinity agonist and antagonist binding. The restoration of binding by a reciprocal mutation indicates that these two specific residues in helices 2 and 7 are adjacent in space and provides an empirical basis to refine the model of the transmembrane helix bundle of the receptor.
Mol Pharmacol 1994 Feb
PMID:A reciprocal mutation supports helix 2 and helix 7 proximity in the gonadotropin-releasing hormone receptor. 811 67

In primary cultures of rat pituitary, GnRH receptor has been reported to up-regulate when exposed to GnRH. The molecular basis of this regulation could, in theory, involve modulation of gene transcription, RNA processing or stability, translation, and/or receptor degradation. The role of altered biosynthesis was investigated in the mouse gonadotrope cell line, alpha T3-1 cells, by studying the homologous up-regulation of GnRH receptor binding, mRNA levels, and mRNA activity. After GnRH exposure, ligand binding was performed on alpha T3-1 cell membranes. To correlate changes in receptor number and measurements of biosynthetic activity, GnRH receptor mRNA levels were quantitated by solution hybridization/RNase protection assay and Northern blot analysis, and the capacity of RNA from treated cells to direct the synthesis of new receptors (mRNA activity) was evaluated using a Xenopus oocyte-based bioassay. GnRH agonist radioligand binding assay results showed that exposure of alpha T3-1 cells to 10(-10) or 10(-8) M GnRH for 20 min induced an approximately 50% increase in the number of GnRH receptors, similar to previously reported results in rat pituitary primary culture. Despite the increase in receptor number, however, cytosolic and total GnRH receptor mRNA levels assayed by solution hybridization/RNase protection assay with GnRH receptor cRNA probes and by Northern blot analysis were not altered. In contrast to the unchanging mRNA levels, the measurements of mRNA activity paralleled the changes observed at the binding level. alpha T3-1 RNA from treated and control cells were injected into Xenopus oocytes, and the GnRH-induced Cl- current was quantified 48 h later by voltage clamp recording of the response to GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1993 Dec
PMID:Homologous up-regulation of the gonadotropin-releasing hormone receptor in alpha T3-1 cells is associated with unchanged receptor messenger RNA (mRNA) levels and altered mRNA activity. 814 68

We have isolated a full length cDNA clone coding for the sheep GnRH receptor (GnRH-R). The amino acid sequence shows greater homology to the human GnRH-R sequence than the two rodent receptors published so far. We have also carried out physiological studies investigating the pattern of expression of the GnRH-R mRNA throughout the estrous cycle. GnRH receptor mRNA and GnRH binding levels were both significantly (P < 0.05) increased over luteal levels up until the time of the preovulatory LH surge, whilst post-surge, a significant (P < 0.05) decline was seen. These changes were related to increased follicle estradiol production in the follicular phase. In contrast, no changes in the abundance of LH beta mRNA were seen throughout the estrous cycle, but the pituitary content of LH significantly (P < 0.05) decreased after the preovulatory LH surge. These results suggest that there is a close relationship between the abundance of GnRH-R mRNA and translation of the GnRH-R in sheep.
Mol Cell Endocrinol 1993 Aug
PMID:Cloning and sequencing of the sheep pituitary gonadotropin-releasing hormone receptor and changes in expression of its mRNA during the estrous cycle. 822 16

A cDNA encoding the human GnRH receptor (GnRHR) has been cloned and functionally expressed in both Xenopus oocytes and COS-1 cells. The 2160 bp cDNA encodes a 328 amino acid protein with a predicted amino acid sequence that is 90% identical to that of the mouse GnRHR (Tsutsumi et al. (1992) Mol. Endocrinol. 6, 1163-1169). Injection of synthetic RNA transcript into oocytes led to the development of a depolarizing response to agonists when assayed by voltage-clamp electrophysiology. Consistent with the expression of a mammalian GnRHR, the response was blocked by GnRH antagonists. Following expression of the human GnRHR in COS-1 cells, agonists and an antagonist displaced [125I]GnRH agonist from membrane isolates with nanomolar range dissociation constants similar to those described for displacement from human pituitary membranes. Transfected COS-1 cells manifested a GnRH-stimulated increase in phosphoinositol turnover, with an EC50 of approximately 3 nM, which was inhibited by GnRH antagonists. Northern blot analysis revealed a single band of approximately 4.7 kb expressed in human pituitary which was not detected in testis. The predicted structure of the human GnRHR is similar to that previously reported for the mouse receptor. Although the mammalian GnRHR is a seven transmembrane domain receptor, it differs from other G-protein coupled receptors in several respects, most notably the lack of a cytoplasmic C-terminal domain. The present study demonstrates that the cDNA isolated encodes the human GnRHR and suggests that several unique features conserved among mammalian GnRHRs may be essential for receptor function and/or regulatory control.
Mol Cell Endocrinol 1993 Feb
PMID:Cloning and characterization of the human GnRH receptor. 838 8

Recently, cloning of the gonadotropin-releasing hormone (GnRH) receptor from the human breast tumor cell line (MCF-7) and from an ovarian tumor, and its expression in various other human tumors, tumor cell lines and reproductive organs have been reported (Kakar et al., Mol. Cell. Endocrinol., 106 (1994) 145-149). In the present studies, we investigated the expression of GnRH and GnRH receptor mRNAs in normal human non-reproductive tissues. Using reverse transcriptase-polymerase chain reaction (RT-PCR) techniques and specific oligonucleotide primers derived from the placental GnRH cDNA sequence, PCR products of the expected size were obtained from human liver, heart, skeletal muscle, kidney, placenta, and pituitary. The authenticity of the PCR products was confirmed by Southern blot analysis with an internal oligonucleotide primer as probe. Similarly, using specific oligonucleotide primers for the GnRH receptor selected from the human pituitary GnRH receptor cDNA sequence, PCR products of the expected size were amplified from human liver, heart, skeletal muscle, kidney, placenta, and pituitary, and these strongly hybridized with the human GnRH receptor cDNA on Southern blot. Cloning and nucleotide sequencing of the PCR products for the GnRH and GnRH receptor from heart revealed identical sequences when compared to the human placental GnRH and pituitary GnRH receptor cDNAs, respectively. These data demonstrate for the first time the existence of GnRH and GnRH receptor mRNAs in normal human non-reproductive tissues and suggest that GnRH and its receptor may play an important role in the regulation of cellular functions in an autocrine or paracrine manner, in addition to regulating the secretion of gonadotropins from the anterior pituitary.
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PMID:Expression of gonadotropin-releasing hormone and gonadotropin-releasing hormone receptor mRNAs in various non-reproductive human tissues. 852 6

The purpose of the present study was to determine if gonadal steroids can alter the amounts of GnRH receptor mRNA in the pyramidal and granule neurons of the hippocampus of female and male rats and if GnRH causes a change in the production of inositol phosphates in hippocampal slices in vitro. The results show that in the ovariectomized rat the amount of GnRH receptor mRNA is increased to 137% in area CA1 and to 147% in area CA3 and in the dentate gyrus when compared to the ovariectomized, estradiol-progesterone treated animal. Similarly, in the orchidectomized male rat the amount of GnRH receptor mRNA is increased to 155% in area CA1, to 146% in area CA3 and to 145% in the dentate gyrus when compared to the intact male rat. There was no significant difference in the relative amounts of GnRH receptor mRNA when gonadectomized male and female rats were compared. Addition of GnRH (100 pM-1 microM) to hippocampal slices in vitro caused a dose-dependent increase in the production of [3H]inositol phosphate which was abolished by co-administration of a GnRH antagonist. The increase in inositol phosphate production was significantly higher at low doses of GnRH (100 pM-1 nM) in estradiol-progesterone treated female and in intact male rats when compared to gonadectomized rats. The results suggest that the amount of GnRH receptor mRNA in the hippocampus is at least in part regulated by gonadal steroids and that the steroid hormones can sensitize the GnRH target neurons to respond more robustly to a GnRH stimulus.
Brain Res Mol Brain Res 1995 Oct
PMID:Regulation of hippocampal gonadotropin releasing hormone (GnRH) receptor mRNA and GnRH-stimulated inositol phosphate production by gonadal steroid hormones. 877 51

Gonadotropin releasing hormone (GnRH) is crucial in regulating the reproductive system of female vertebrates. In the present study we have analyzed the estrogen regulation of the GnRH receptor mRNA at the cellular level in Sprague-Dawley female rats. Northern blot analysis detected 3 species (5.0, 4.5 and 1.4 kb) of GnRH receptor mRNA in pituitary tissues. The GnRH receptor mRNA levels of these 3 species were increased by estrogen. By in situ hybridization we observed a 3.5-fold increase in GnRH receptor mRNA levels after 48 h of estrogen treatment when compared to ovariectomized (OVX) rats, 12 h of estrogen treatment did not change the GnRH mRNA levels. Similar increases in GnRH receptor mRNA levels by estrogen were also found in Wistar-Imamichi female rat pituitary tissue. In situ hybridization analysis identified clusters of anterior pituitary cells that expressed the GnRH receptor mRNA. The estradiol effect depends on increased mRNA levels in these clusters. Moreover, a significant increase in the number of pituitary cells that expressed GnRH receptor was observed after 48 h of estrogen treatment. These findings suggest that the mechanisms for estrogen regulation of GnRH receptor include changing levels of GnRH receptor mRNA in the rat pituitary.
Brain Res Mol Brain Res 1996 Jun
PMID:Estrogen regulation of gonadotropin-releasing hormone receptor messenger RNA in female rat pituitary tissue. 879 12

In the GnRH receptor, the NPX2-3Y motif that is present in the seventh transmembrane helix of most G protein-coupled receptors is unusual in containing Asp instead of Asn but retains the highly conserved Tyr residue. The importance of this aromatic residue in the DPLIY sequence of the GnRH receptor function was analyzed by replacing Tyr322 with Ala or Phe residues. The Y322A mutant receptor expressed in COS-7 cells had high agonist binding affinity, but its ability to interact with G protein(s) and to activate inositol phosphate production in response to GnRH was abolished. Although functionally inactive, the Y322A mutant receptor was internalized at about 50% of the rate of the wild type receptor in agonist-treated cells. When Tyr322 was replaced with Phe to preserve its aromatic nature, the Y322F mutant receptor displayed normal G protein activation and inositol phosphate responses to GnRH and was internalized in the same manner as the wild type receptor. These findings demonstrate that the aromatic moiety of the Tyr322 component of the DPLIY motif in the GnRH receptor is a critical determinant of agonist-induced receptor activation and signal transduction.
Mol Endocrinol 1996 Aug
PMID:Dependence of agonist activation on an aromatic moiety in the DPLIY motif of the gonadotropin-releasing hormone receptor. 884 14

The mode of action of GnRH on pituitary gonadotropes involves metabolism of phospholipids, protein kinase-C (PKC) and voltage sensitive Ca2+ channels (VSCC) activation. We have studied the differential role of PKC and VSCC on the coupling of the GnRH receptor with phospholipases-C (PLC), -A2 (PLA2) and -D (PLD) activities in a gonadotrope cell line (alpha T3-1), by measuring the production of inositol phosphates (IPs), arachidonic acid (AA) and phosphatidylethanol (PEt) respectively. We demonstrated that in these cells GnRH stimulated through a specific receptor, IPs formation, a rapid and sustained diacylglycerol generation, consequently AA release and a delayed PEt production in a dose-dependent manner. In contrast to GnRH-induced PLC activity, the PLA2 and PLD stimulation by the neuropeptide involved Ca2+ mobilization via VSCC activation. BAY-K8644 a VSCC agonist significantly potentiated, while the VSCC antagonist nitrendipine markedly inhibited GnRH-induced AA release and PEt production. TPA, a phorbol ester which induced a rapid and important redistribution of PKC, although unable to elicit PLC or PLA2 stimulation, specifically provoked PLD activation in a PKC-dependent but Ca(2+)-independent manner. The PKC stimulation by TPA significantly inhibited the GnRH-stimulated IPs and AA formation, while it potentiated the GnRH-evoked PEt production. This negative feed-back of PKC on GnRH-Induced PLC and PLA2 activities was reversed when PKC was either down regulated after long TPA treatments or inhibited by the PKC inhibitors, staurosporine or GF109203X. The GnRH-induced PEt formation was markedly diminished in PKC depleted cells or after PKC inhibition. Under such conditions, both agonist and antagonist of VSCC became less effective in modulating the remaining GnRH-evoked PEt formation. These results suggest that PKC, in coordination with Ca2+, plays a key role in regulating the cross-talk between the multiple phospholipases implicated in the GnRH signal transduction.
Mol Cell Endocrinol 1996 Aug 30
PMID:Differential involvement of calcium channels and protein kinase-C activity in GnRH-induced phospholipase-C, -A2 and -D activation in a gonadotrope cell line (alpha T3-1). 889 46

Idiopathic neuromuscular disease of the gastrointestinal tract (functional bowel disease) is thought to result from the malfunction of neurons within the enteric nervous system. Gonadotropin-releasing hormone (GnRH) analogs have recently been shown to organize the disordered motility patterns typical in these patients and to produce significant, long-term symptomatic improvement. To determine whether GnRH analogs might bind to an endogenous enteric nervous system GnRH receptor, reverse transcription-polymerase chain reaction (RT-PCR) was performed using cultured neonatal rat enteric neuron RNA and rat GnRH receptor primers. A PCR product of the predicted size was cloned and nucleotide sequence analysis demonstrated that the myenteric plexus PCR product encoded a portion of the GnRH receptor sequence previously identified in rat pituitary. These results suggest that cells in the myenteric plexus express GnRH receptors that may bind exogenously administered GnRH analogs. The expression of GnRH receptors in enteric neurons would provide an explanation for the effectiveness of GnRH analogs in treatment of idiopathic neuromuscular disease of the gastrointestinal tract.
Comp Biochem Physiol B Biochem Mol Biol 1996 Apr
PMID:Presence of gonadotropin-releasing hormone (GnRH) receptor mRNA in rat myenteric plexus cells. 892 50


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