GnRH receptor is a seven-transmembrane, G protein-coupled plasma membrane protein. The mouse receptor was originally isolated based on expression cloning in Xenopus oocyte (Tsutsumi et al., 1992 ). Following expression cloning of rat GnRH receptor cDNA by Sealfon et al. (1990), Kakar et al. (1992) isolated a cDNA for the human GnRH receptor. In addition to the pituitary, GnRH receptors have also been found in diverse tissues including gonadal cells and multiple tumor cell lines (Hsueh et al., 1983).
General function
Receptor
Comment
Adipokinetic hormone signaling through the gonadotropin-releasing hormone receptor modulates egg-laying in Caenorhabditis elegans. Lindemans M et al. In mammals, hypothalamic gonadotropin-releasing hormone (GnRH) is a neuropeptide that stimulates the release of gonadotropins from the anterior pituitary. The existence of a putative functional equivalent of this reproduction axis in protostomian invertebrates has been a matter of debate. In this study, the ligand for the GnRH receptor in the nematode Caenorhabditis elegans (Ce-GnRHR) was found using a bioinformatics approach. The peptide and its precursor are reminiscent of both insect adipokinetic hormones and GnRH-preprohormone precursors from tunicates and higher vertebrates. We cloned the AKH-GnRH-like preprohormone and the Ce-GnRHR and expressed the GPCR in HEK293T cells. The GnRHR was activated by the C. elegans AKH-GnRH-like peptide (EC(50) = 150 nM) and by Drosophila AKH and other nematode AKH-GnRHs that we found in EST databases. Analogous to both insect AKH receptor and vertebrate GnRH receptor signaling, Ce-AKH-GnRH activated its receptor through a Galpha(q) protein with Ca(2+) as a second messenger. Gene silencing of Ce-GnRHR, Ce-AKH-GnRH, or both resulted in a delay in the egg-laying process, comparable to a delay in puberty in mammals lacking a normal dose of GnRH peptide or with a mutated GnRH precursor or receptor gene. The present data support the view that the AKH-GnRH signaling system probably arose very early in metazoan evolution and that its role in reproduction might have been developed before the divergence of protostomians and deuterostomians.
Cellular localization
Plasma membrane
Comment
Evidence for different gonadotropin-releasing hormone response sites in rat ovarian and pituitary cells
Mongiat LA, et al 2004 .
The participation of type I GnRH receptor (GnRH-R) on GnRH-II-induced gonadotropin secretion in rat pituitary cells was investigated. Furthermore, we extended the study of GnRH-II action to ovarian cells. The GnRH-II was able to mobilize inositol triphosphate (IP(3)) and to induce LH and FSH release in a dose-dependent manner in pituitary cells and in a GnRH-I-like manner. The GnRH-analog 135-18 (agonist for type II GnRH-R and antagonist for type I GnRH-R) was unable to elicit any cellular response tested in these pituitary cells. The GnRH-II responses were blocked by the type I GnRH-R-antagonists CRX or 135-18, suggesting that these effects were mediated by the type I GnRH-R. In contrast to pituitary cells, GnRH-I, but not GnRH-II, elicited an IP(3) response in superovulated ovarian cells; 135-18 also had no effect. However, GnRH-II as well as GnRH-I presented antiproliferative effects on these cells. Surprisingly, 135-18 had stronger antiproliferative effects than either GnRH peptide. The 135-18 analog, but not GnRH-I or GnRH-II, increased progesterone secretion in superovulated ovarian cells. These results strongly suggest that GnRH-II is able to stimulate rat pituitary cells through the type I GnRH-R, with no evidence for the presence of type II GnRH-R. On the other hand, our results indicate a putative GnRH-R in superovulated ovarian cells with response characteristics that differ from those of the GnRH-R in the pituitary.
Characterization of the Gonadotropin Releasing Hormone Receptor (GnRHR) expression and activity in the Female Mouse Ovary. Torrealday S 2013 et al.
Gonadotropin releasing hormone agonists (GnRHa) are increasingly used for fertility preservation in women undergoing gonadotoxic chemotherapy. However, the protective mechanisms of action for these compounds have not yet been elucidated. In this study, we aimed to determine whether GnRHa have a direct effect on ovarian granulosa cells. Gonadotropin releasing hormone receptor (GnRHR) expression was determined in mouse somatic and gonadal tissues including granulosa/cumulus cells and oocytes using quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry. Granulosa cells were isolated from mouse ovaries primed with pregnant mare serum gonadotropin (PMSG). Response to GnRHa in cultured granulosa cells was assessed by determining the increase of intracellular cAMP and by assessing phosphorylation of downstream mediators of GnRH signaling: ERK and p38. To measure intracellular cAMP in our system, the cells were transfected with a cAMP-responsive luciferase reporter plasmid and stimulated with GnRHa. For all experiments, pituitary tissue and/or the aT3-1 mouse pituitary cell line were used as controls. GnRHR mRNA and protein were detected in mouse ovaries, granulosa/cumulus cells, and oocytes. Following GnRHa stimulation at various time intervals, we were unable to detect a cAMP increase or activation of the ERK or p38 signaling pathway in cultured primary mouse granulosa cells, while activation was detected in the control aT3-1 mouse pituitary cells. In this study, we have not detected activation of the canonical GnRH signaling pathways in mouse ovarian somatic cells. Our findings suggest that the mechanism of action of GnRHa in the ovary is either below the detection level of our experimental design or is different from that in the pituitary. (THIS PAPer MISSED ALL THE LITERAYRE ON EARLIER STUDIES.)
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Gonadotropin releasing hormone antagonists suppress aromatase and anti-M?an hormone expression in human granulosa cells. Winkler N et al. OBJECTIVE: To investigate the effects of a gonadotropin-releasing hormone antagonist (GnRH-ANT) on the expression of anti-M?an Hormone (AMH) and aromatase (via the exon CYP19IIa promoter), in cultured human granulosa cells (hGCs) and the human granulosa cell line (HGL5). DESIGN: Primary cell cultures of hGCs and culture of HGL5 cells. SETTING: Academic center. PATIENT(S): Women undergoing IVF because of male factor, tubal infertility, or donor eggs. INTERVENTION(S): hGCs and HGL5 cells were treated with a GnRH-ANT (1 nM and 1 muM) alone or in combination with cAMP (1 mM). Media was collected and stored at -80 degrees C until assayed. MAIN OUTCOME MEASURE(S): mRNA levels of CYP19 IIa, AMH, steroidogenic factor 1 (SF-1) and liver receptor homologue-1 (LRH-1) were determined by quantitative polymerase chain reaction. ELISA was used to determined estradiol (E(2)) levels in the culture media. Pooled results from triplicate experiments were analyzed using one-way analysis of variance with Student-Newman-Keuls multiple-comparison methods. RESULT(S): The GnRH-ANT decreased the expressions of CYP19 IIa, AMH, SF-1, and LRH-1. cAMP induced aromatase and AMH expression. Cotreatment with cAMP and GnRH-ANT caused a dose-dependent suppression of AMH and CYP19 IIa mRNA. A GnRH agonist (GnRH-A) increased the mRNA expressions of CYP 19 IIa and AMH. The GnRH-ANT decreased E(2) production in cultured hGCs. CONCLUSION(S): GnRH-ANTs, in addition to their central suppressive effects on the pituitary, may have a direct effect on ovarian granulosa cells with inhibition of aromatase and AMH expression. Furthermore, the inhibitory effect could be mediated via suppression of SF-1 and LRH-1, and may play a role in estrogen-mediated ovarian folliculogenesis.
Ovulation induced by a gonadotropin releasing hormone analog in hypophysectomized rats involves prostaglandins
Ekholm C, et al .
A potent analogue of gonadotropin releasing hormone D-Ala6- Des-Gly10-NH2-GnRH ethylamide (GnRHa) caused oocyte maturation and ovulation when injected in the afternoon of proestrus in immature PMSG-treated female rats, hypophysectomized on the morning of proestrus. This action of GnRHa was accompanied by a marked increase in ovarian PGE levels. Furthermore, the pretreatment of the animals with a prostaglandin synthetase inhibitor (indomethacin) completely inhibited this PGE increase and ovulation. These data suggest a role for prostaglandins in GnRHa induced ovulation.
Gonadotropin releasing hormone agonists stimulate meiotic maturation of follicle-enclosed rat oocytes in vitro.
Hillensjo T, et al .
Although the principal function of gonadotropin releasing hormone (GnRH) is to stimulate the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH), there is evidence that agonistic analogues of GnRH directly inhibit steroidogenesis in the testis and ovary. On the other hand, Clark et al. have demonstrated that GnRH and two agonists have a marked stimulatory effect on prostaglandin synthesis by granulosa cells isolated from immature rats treated with pregnant mare's serum gonadotropin (PMSG). Stimulation by these compounds was distinct from that by LH in that no changes in cyclic AMP production were detected. Thus it seems important to investigate the effect of these peptides on other aspects of ovarian function, for example oocyte maturation. Mammalian oocytes are arrested in the dictyate stage of the first meiotic prophase, and meiosis (oocyte maturation) normally resumes in preovulatory follicles as a consequence of the surge of LH and FSH. This maturation can also be initiated in vitro by the addition of gonadotropins to isolated preovulatory follicles, and is accompanied by an increase in the production of lactate. We now report that GnRH and two potent agonists stimulate meiosis in vitro in follicle-enclosed oocytes in a dose-dependent and specific manner, and also cause an increase of lactate accumulation during incubation.
Expression regulated by
FoxL2
Comment
Microarray analysis of Foxl2 mediated gene regulation in the mouse ovary derived KK1 granulosa cell line: Over-expression of Foxl2 leads to activation of the gonadotropin releasing hormone receptor gene promoter. Escudero JM et al. ABSTRACT: BACKGROUND: The Foxl2 transcription factor is required for ovarian function during follicular development. The mechanism of Foxl2 regulation of this process has not been elucidated. Our approach to begin to understand Foxl2 function is through the identification of Foxl2 regulated genes in the ovary. METHODS: Transiently transfected KK1 mouse granulosa cells were used to identify genes that are potentially regulated by Foxl2. KK1 cells were transfected in three groups (mock, activated, and repressed) and twenty-four hours later RNA was isolated and submitted for Affymetrix microarray analysis. Genesifter software was used to carry out pairwise analysis of microarray data. One identified target, the gonadotropin releasing hormone receptor (GnRHR) gene, was chosen for further study and validation of Foxl2 responsiveness. Transient transfection analyses were carried out to study the effect of Foxl2 over-expression on GnRHR gene promoter-luciferase fusion activity. Data generated was analyzed with GraphPad Prism software. RESULTS: Microarray analysis identified 489 genes of known function that are potentially regulated by Foxl2 in mouse KK1 granulosa cells. The steroidogenic acute regulatory protein (StAR) gene that has been identified as Foxl2 responsive by others was identified in this study also, thereby supporting the effectiveness of our strategy. The GnRHR gene was chosen for further study because it is known to be expressed in the ovary and the results of previous work has indicated that Foxl2 may regulate GnRHR gene expression. Cellular levels of Foxl2 were increased via transient co-transfection of KK1 cells using a Foxl2 expression vector and a GnRHR promoter-luciferase fusion reporter vector. The results of these analyses indicate that over-expression of Foxl2 resulted in a significant increase in GnRHR promoter activity. Therefore, these transfection data validate the microarray data which suggest that Foxl2 regulates GnRHR and demonstrate that Foxl2 acts as an activator of the GnRHR gene. CONCLUSIONS: Potential Foxl2 regulated ovarian genes have been identified through microarray analysis and comparison of these data to other microarray studies. The Foxl2 responsiveness of the GnRHR gene has been validated and provided evidence of Foxl2 transcriptional activation of the GnRHR gene promoter in the mouse ovary derived KK1 granulosa cell line.
Ovarian localization
Granulosa, Theca, Luteal cells
Comment
The diverse actions of GnRH mediated by its receptors appear to be species-specifc. Although GnRH receptors have been clearly demonstrated in rats, the presence of ovarian GnRH receptors in rodent and several domestic species are uncertain. In humans, conflicting reports have been published (Kakar et al., 1992).
Follicle stages
Antral, Preovulatory, Corpus luteum
Comment
Gonadotropin-Releasing Hormone 1 Directly Affects Corpora Lutea Life-Span in Mediterranean Buffalo (Bubalus bubalis) During Diestrus: Presence and In Vitro Effects on Enzymatic and Hormonal Activities. Zerani M et al. The expression of gonadotropin-releasing hormone (GNRH) receptor (GNRHR) and the direct role of GNRH1 on corpora lutea function were studied in Mediterranean buffalo during diestrus. Immunohistochemistry evidenced at early, mid, and late luteal stages the presence of GNRHR only in large luteal cells and GNRH1 in both small and large luteal cells. Real-time-PCR revealed GNRHR and GNRH1 mRNA at the three luteal stages, with lowest values in late corpora lutea. In vitro corpora lutea progesterone production was greater in mid stages and less in late luteal phases, while prostaglandin (PG) F2a (PGF2a) increased from early to late stages, and PGE2 was greater in the earlier-luteal phase. Cyclooxygenase 1 (prostaglandin-endoperoxide synthase 1, PTGS1) activity did not change during diestrus, while PTGS2 increased from early to late stages, and PGE2-9-ketoreductase (PGE2-9-K) was greater in late corpora lutea. PTGS1 activity was greater than PTGS2 in early corpora lutea and less in late luteal phase. In corpora lutea cultured in vitro, the GNRH1 analog (buserelin) reduced progesterone secretion, and increased PGF2a secretion as well as PTGS2 and PGE2-9-K activities at mid and late stages. PGE2 release and PTGS1 activity were increased by buserelin only in late corpora lutea. These results suggest that GNRH is expressed in all luteal cells of buffalo, whereas GNRHR only in large luteal phase. Additionally, GNRH directly down-regulates corpora lutea progesterone release, with the concomitant increases of PGF2a production and PTGS2 and PGE2-9-K enzymatic activities.
The distribution of GnRH receptors was studied by Seguin et al. (1982) in the adult rat ovary using autoradiography after injection of the stable LHRH agonist 125I-labelled D-Ser(TBU)6,des-Gly-NH2(10)]LHRH ethylamide (Buserelin) and by radioreceptor assay using the same tracer. Radioautographic data show a comparable
distribution of grains over theca interna and externa, granulosa and luteal cells. The data indicate the presence of GnRH receptors in both the interstitial and follicular cells throughout all stages of cellular differentiation.
Immunolocalization of Gonadotropin-Releasing Hormone (GnRH)-I, GnRH-II, and Type-I GnRH Receptor during Follicular Development in the Human Ovary. [Choi JH et al. Context: Gonadotropin releasing hormone (GnRH) and its receptor have been detected, at the mRNA level, in different ovarian cell types, implicating an autocrine role of the GnRH system in the human ovary. However, the expression, at the protein level, of GnRH and its receptor in specific cell types during follicular development has not been documented in humans. Objective: We evaluated the immunohistochemical expression of GnRH-I (the classical form of mammalian GnRH), GnRH-II (the novel isoform) and the type-I GnRH receptor (GnRHR) that is known to bind both forms of GnRH, in ovaries of pre-menopausal women. Main Outcome Measures: Immunohistochemistry, immunofluorescence, immunoblot assay and real-time RT-PCR were performed. Results: GnRH-I, GnRH-II and GnRHR were not immunostained in the follicles from the primordial to the early antral stage. In preovulatory follicles, both forms of GnRH and their common receptor were localized predominantly to the granulosa cell layer, whereas the theca interna layer was weakly positive. In the corpus luteum, significant levels of GnRH-I, GnRH-II as well as GnRHR were observed in granulosa luteal cells, but not in theca luteal cells. Both GnRH isoforms and the type-I GnRHR were localized also to the ovarian surface epithelium (OSE) from which over 85% of ovarian cancer are thought to be derived. Conclusion: The expression of GnRH-I, GnRH-II and GnRHR protein in the human ovary is temporally and spatially specific, and further support the physiological role of an autocrine regulatory system involving GnRH-I, GnRH-II and GnRHR in follicular development and corpus luteal function.
Phenotypes
Mutations
1 mutations
Species: human
Mutation name: None
type: naturally occurring fertility: infertile - non-ovarian defect Comment: In a family with an affected brother and sister, de Roux et al. (1997) demonstrated that the affected individuals were compound heterozygotes for mutations of the GnRHR gene. Layman et al. (1998) also demonstrated compound heterozygosity for 2 missense mutations in the GnRHR gene in each of 4 affected sibs of a family.