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Desaulniers AT, White BR. Role of gonadotropin-releasing hormone 2 and its receptor in human reproductive cancers. Front Endocrinol (Lausanne) 2024; 14:1341162. [PMID: 38260130 PMCID: PMC10800933 DOI: 10.3389/fendo.2023.1341162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 12/13/2023] [Indexed: 01/24/2024] Open
Abstract
Gonadotropin-releasing hormone (GnRH1) and its receptor (GnRHR1) drive reproduction by regulating gonadotropins. Another form, GnRH2, and its receptor (GnRHR2), also exist in mammals. In humans, GnRH2 and GnRHR2 genes are present, but coding errors in the GnRHR2 gene are predicted to hinder full-length protein production. Nonetheless, mounting evidence supports the presence of a functional GnRHR2 in humans. GnRH2 and its receptor have been identified throughout the body, including peripheral reproductive tissues like the ovary, uterus, breast, and prostate. In addition, GnRH2 and its receptor have been detected in a wide number of reproductive cancer cells in humans. Notably, GnRH2 analogues have potent anti-proliferative, pro-apoptotic, and/or anti-metastatic effects on various reproductive cancers, including endometrial, breast, placental, ovarian, and prostate. Thus, GnRH2 is an emerging target to treat human reproductive cancers.
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Affiliation(s)
- Amy T. Desaulniers
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Brett R. White
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, United States
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The Association of Polymorphisms in the Gene Encoding Gonadotropin-Releasing Hormone with Serum Testosterone Level during Androgen Deprivation Therapy and Prognosis of Metastatic Prostate Cancer. J Urol 2018; 199:734-740. [DOI: 10.1016/j.juro.2017.09.076] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2017] [Indexed: 02/04/2023]
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Desaulniers AT, Cederberg RA, Lents CA, White BR. Expression and Role of Gonadotropin-Releasing Hormone 2 and Its Receptor in Mammals. Front Endocrinol (Lausanne) 2017; 8:269. [PMID: 29312140 PMCID: PMC5732264 DOI: 10.3389/fendo.2017.00269] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Accepted: 09/26/2017] [Indexed: 11/13/2022] Open
Abstract
Gonadotropin-releasing hormone 1 (GnRH1) and its receptor (GnRHR1) drive mammalian reproduction via regulation of the gonadotropins. Yet, a second form of GnRH (GnRH2) and its receptor (GnRHR2) also exist in mammals. GnRH2 has been completely conserved throughout 500 million years of evolution, signifying high selection pressure and a critical biological role. However, the GnRH2 gene is absent (e.g., rat) or inactivated (e.g., cow and sheep) in some species but retained in others (e.g., human, horse, and pig). Likewise, many species (e.g., human, chimpanzee, cow, and sheep) retain the GnRHR2 gene but lack the appropriate coding sequence to produce a full-length protein due to gene coding errors; although production of GnRHR2 in humans remains controversial. Certain mammals lack the GnRHR2 gene (e.g., mouse) or most exons entirely (e.g., rat). In contrast, old world monkeys, musk shrews, and pigs maintain the coding sequence required to produce a functional GnRHR2. Like GnRHR1, GnRHR2 is a 7-transmembrane, G protein-coupled receptor that interacts with Gαq/11 to mediate cell signaling. However, GnRHR2 retains a cytoplasmic tail and is only 40% homologous to GnRHR1. A role for GnRH2 and its receptor in mammals has been elusive, likely because common laboratory models lack both the ligand and receptor. Uniquely, both GnRH2 and GnRHR2 are ubiquitously expressed; transcript levels are abundant in peripheral tissues and scarcely found in regions of the brain associated with gonadotropin secretion, suggesting a divergent role from GnRH1/GnRHR1. Indeed, GnRH2 and its receptor are not physiological modulators of gonadotropin secretion in mammals. Instead, GnRH2 and GnRHR2 coordinate the interaction between nutritional status and sexual behavior in the female brain. Within peripheral tissues, GnRH2 and its receptor are novel regulators of reproductive organs. GnRH2 and GnRHR2 directly stimulate steroidogenesis within the porcine testis. In the female, GnRH2 and its receptor may help mediate placental function, implantation, and ovarian steroidogenesis. Furthermore, both the GnRH2 and GnRHR2 genes are expressed in human reproductive tumors and represent emerging targets for cancer treatment. Thus, GnRH2 and GnRHR2 have diverse functions in mammals which remain largely unexplored.
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Affiliation(s)
- Amy T. Desaulniers
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Rebecca A. Cederberg
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, United States
| | | | - Brett R. White
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, United States
- *Correspondence: Brett R. White,
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Desaulniers AT, Cederberg RA, Mills GA, Ford JJ, Lents CA, White BR. LH-Independent Testosterone Secretion Is Mediated by the Interaction Between GNRH2 and Its Receptor Within Porcine Testes. Biol Reprod 2015; 93:45. [PMID: 26134865 DOI: 10.1095/biolreprod.115.128082] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 06/17/2015] [Indexed: 11/01/2022] Open
Abstract
Unlike classic gonadotropin-releasing hormone 1 (GNRH1), the second mammalian isoform (GNRH2) is an ineffective stimulant of gonadotropin release. Species that produce GNRH2 may not maintain a functional GNRH2 receptor (GNRHR2) due to coding errors. A full-length GNRHR2 gene has been identified in swine, but its role in reproduction requires further elucidation. Our objective was to examine the role of GNRH2 and GNRHR2 in testicular function of boars. We discovered that GNRH2 levels were higher in the testis than in the anterior pituitary gland or hypothalamus, corresponding to greater GNRHR2 abundance in the testis versus the anterior pituitary gland. Moreover, GNRH2 immunostaining was most prevalent within seminiferous tubules, whereas GNRHR2 was detected in high abundance on Leydig cells. GNRH2 pretreatment of testis explant cultures elicited testosterone secretion similar to that of human chorionic gonadotropin stimulation. Treatment of mature boars with GNRH2 elevated testosterone levels similar to those of GNRH1-treated males, despite minimal GNRH2-induced release of luteinizing hormone (LH). When pretreated with a GNRHR1 antagonist (SB-75), subsequent GNRH2 treatment stimulated low levels of testosterone secretion despite a pattern of LH release similar to that in the previous trial, suggesting that SB-75 inhibited testicular GNRHR2s. Given that pigs lack testicular GNRHR1, these data may indicate that GNRH2 and its receptor are involved in autocrine or paracrine regulation of testosterone secretion. Notably, our data are the first to suggest a biological function of a novel GNRH2-GNRHR2 system in the testes of swine.
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Affiliation(s)
- Amy T Desaulniers
- University of Nebraska- Lincoln, Department of Animal Science, Lincoln, Nebraska
| | - Rebecca A Cederberg
- University of Nebraska- Lincoln, Department of Animal Science, Lincoln, Nebraska
| | - Ginger A Mills
- University of Nebraska- Lincoln, Department of Animal Science, Lincoln, Nebraska
| | - J Joe Ford
- US Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, Clay Center, Nebraska
| | - Clay A Lents
- US Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, Clay Center, Nebraska
| | - Brett R White
- University of Nebraska- Lincoln, Department of Animal Science, Lincoln, Nebraska
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Servili A, Lethimonier C, Lareyre JJ, López-Olmeda JF, Sánchez-Vázquez FJ, Kah O, Muñoz-Cueto JA. The Highly conserved gonadotropin-releasing hormone-2 form acts as a melatonin-releasing factor in the pineal of a teleost fish, the european sea bass Dicentrarchus labrax. Endocrinology 2010; 151:2265-75. [PMID: 20215565 DOI: 10.1210/en.2009-1207] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
With the exception of modern mammals, most vertebrate species possess two GnRH genes, GnRH-1 and GnRH-2. In addition, in many teleost fish, there is a third gene called GnRH-3. If the main function of GnRH-1 is unambiguously to stimulate gonadotropin release, the other two GnRH forms still lack clear functions. This is particularly true for the highly conserved GnRH-2 that encodes chicken GnRH-II. This GnRH variant is consistently expressed in neurons of the dorsal synencephalon in most vertebrate groups but still has no clear functions supported by anatomical, pharmacological, and physiological data. In this study performed on a perciform fish, the European sea bass, we show for the first time that the pineal organ receives GnRH-2-immunoreactive fibers originating from the synencephalic GnRH-2 neurons. This was shown through a combination of retrograde tracing and immunohistochemistry, using highly specific antibodies. Supporting the presence of GnRH-2 functional targets, RT-PCR data together with the in situ hybridization studies showed that the sea bass pineal gland strongly expressed a GnRH receptor (dlGnRHR-II-2b) with clear selectivity for GnRH-2 and, to a lesser extent, the dlGnRHR-II-1a subtype. Finally, in vitro and in vivo experiments demonstrate stimulatory effects of GnRH-2 on nocturnal melatonin secretion by the sea bass pineal organ. Altogether, these data provide, for the first time in a vertebrate species, converging evidence supporting a role of GnRH-2 in the modulation of fish pineal functions.
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Affiliation(s)
- Arianna Servili
- Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Puerto Real, Spain
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Kim DK, Yang JS, Maiti K, Hwang JI, Kim K, Seen D, Ahn Y, Lee C, Kang BC, Kwon HB, Cheon J, Seong JY. A Gonadotropin-Releasing Hormone-II Antagonist Induces Autophagy of Prostate Cancer Cells. Cancer Res 2009; 69:923-31. [DOI: 10.1158/0008-5472.can-08-2115] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Cho HJ, Acharjee S, Moon MJ, Oh DY, Vaudry H, Kwon HB, Seong JY. Molecular evolution of neuropeptide receptors with regard to maintaining high affinity to their authentic ligands. Gen Comp Endocrinol 2007; 153:98-107. [PMID: 17286976 DOI: 10.1016/j.ygcen.2006.12.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 11/22/2006] [Accepted: 12/25/2006] [Indexed: 01/04/2023]
Abstract
Recently, we cloned many of the bullfrog neuropeptide G protein-coupled receptors (GPCRs), including receptors for vasotocin (VT), mesotocin, gonadotropin-releasing hormone (GnRH), neurotensin, apelin, and metastin. Bullfrog GPCRs usually have high affinity for bullfrog ligands but relatively low affinity for mammalian ligands. Reciprocally, synthetic agonists and antagonists developed based upon mammalian ligands display lower affinity at bullfrog receptors. Studies using chimeric or domain-swapped receptors indicate that the motifs responsible for differential ligand selectivity usually reside within transmembrane domain 6 (TMD6)-extracellular loop 3 (ECL3)-transmembrane domain 7 (TMD7). Triple mutation of mammalian V1aR (Phe(6.51) to Tyr, Ile(6.53) to Thr, and Pro(7.33) to Thr) increases VT affinity but greatly reduces arginine vasopressin affinity. This binding profile is similar to that of bullfrog VT1R. Changing just three amino acids in the bullfrog GnRH receptor-1 (i.e. Ser-Gln-Ser in the ECL3) to those found in the type-I mammalian GnRH receptor (i.e. Ser-Glu-Pro) reverses GnRH selectivity. In conclusion, specific receptor motifs that govern ligand selectivity can be determined by comparative molecular analyses of GPCRs and their ligands. Such analysis provides clues for understanding how GPCRs maintain high affinity to their authentic ligands.
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Affiliation(s)
- Hyun Ju Cho
- Graduate School of Medicine, Korea University, Seoul 136-705, Republic of Korea
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Herédi-Szabó K, Murphy RF, Lovas S. Is lGnRH-III the most potent GnRH analog containing only natural amino acids that specifically inhibits the growth of human breast cancer cells? J Pept Sci 2007; 12:714-20. [PMID: 16967433 DOI: 10.1002/psc.783] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Analogs of the decapeptide, gonadotropin-releasing hormone (GnRH), used in the treatment of hormone-dependent tumors, contain numerous unnatural amino acids, giving rise to many adverse effects. lGnRH-III, a natural isoform of GnRH isolated from the sea lamprey, is a weak agonist of GnRH in the pituitary, but inhibits the growth of human cancer cells in micromolar concentrations. As lGnRH-III is not a natural ligand in humans, it is possible that a more potent peptide, also containing only natural amino acids, can be synthesized. A positional scanning peptide library, focused on the variable region of the GnRH family of peptides, residues 5-8, was synthesized. The synthesized peptides were analyzed in competitive binding experiments and six new analogs were designed on the basis of the results. Their biological activities were evaluated in cell growth experiments. The only natural sequence selected was chicken GnRH-II. The synthetic library did not yield a more potent peptide than lGnRH-III.
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Affiliation(s)
- Krisztina Herédi-Szabó
- Department of Biomedical Sciences, School of Medicine, Creighton University, 2500 California Plaza, Omaha, Nebraska 68178-0405, USA
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Mamputha S, Lu ZL, Roeske RW, Millar RP, Katz AA, Flanagan CA. Conserved amino acid residues that are important for ligand binding in the type I gonadotropin-releasing hormone (GnRH) receptor are required for high potency of GnRH II at the type II GnRH receptor. Mol Endocrinol 2006; 21:281-92. [PMID: 16973761 DOI: 10.1210/me.2006-0150] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GnRH I regulates reproduction. A second form, designated GnRH II, selectively binds type II GnRH receptors. Amino acids of the type I GnRH receptor required for binding of GnRH I (Asp2.61(98), Asn2.65(102), and Lys3.32(121)) are conserved in the type II GnRH receptor, but their roles in receptor function are unknown. We have delineated their functions using mutagenesis, signaling and binding assays, immunoblotting, and computational modeling. Mutating Asp2.61(97) to Glu or Ala, Asn2.65(101) to Ala, or Lys3.32(120) to Gln decreased potency of GnRH II-stimulated inositol phosphate production. Consistent with proposed roles in ligand recognition, mutations eliminated measurable binding of GnRH II, whereas expression of mutant receptors was not decreased. In detailed analysis of how these residues affect ligand-dependent signaling, [Trp2]-GnRH I showed lesser decreases in potency than GnRH I at the Asp2.61(97)Glu mutant. In contrast, [Trp2]-GnRH II showed the same loss of potency as GnRH II at this mutant. This suggests that Asp2.61(97) contributes to recognition of His2 of GnRH I, but not of GnRH II. GnRH II showed a large decrease in potency at the Asn2.65(101)Ala mutant compared with analogs lacking the CO group of Gly10NH2. This suggests that Asn2.65(101) recognizes Gly10NH2 of GnRH II. GnRH agonists showed large decreases in potency at the Lys3.32(120)Gln mutant, but antagonist activity was unaffected. This suggests that Lys3.32(120) recognizes agonists, but not antagonists, as in the type I receptor. These data indicate that roles of conserved residues are similar, but not identical, in the type I and II GnRH receptors.
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Affiliation(s)
- Sipho Mamputha
- Medical Research Council/University of Cape Town Research Group for Receptor Biology, Institute for Infectious Diseases and Molecular Medicine and Division of Medical Biochemistry, Cape Town, South Africa
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Tello JA, Rivier JE, Sherwood NM. Tunicate gonadotropin-releasing hormone (GnRH) peptides selectively activate Ciona intestinalis GnRH receptors and the green monkey type II GnRH receptor. Endocrinology 2005; 146:4061-73. [PMID: 15961566 DOI: 10.1210/en.2004-1558] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In vertebrates, GnRH binds to its receptor and stimulates predominantly G(q/11)-mediated signal transduction in gonadotropes. However, little is known about the GnRH receptor and its signaling pathway in tunicates, a group that arose before the vertebrates. Although tunicates have had duplications of a few genes in the last 600 million years, the early vertebrates had duplications of the full genome. Also unknown is the nature of GnRH signaling in the tunicate, which lacks both a pituitary gland and sex steroids. However, we know that tunicates have GnRH peptides because we previously reported six GnRH peptides encoded within the tunicate genome of Ciona intestinalis. Here we clone and sequence cDNAs for four putative GnRH receptors from C. intestinalis. These are the only invertebrate GnRH receptors found to date. Each Ciona GnRH receptor was expressed in COS-7 cells, incubated with each of the six C. intestinalis GnRHs and assayed for a signaling response. GnRH receptors 1, 2, and 3 responded to Ciona GnRH peptides to stimulate intracellular cAMP accumulation. In contrast, only GnRH receptor 1 activated inositol phosphate turnover in response to one of the Ciona GnRHs. The green monkey type II GnRH receptor cDNA was tested as a comparison and a positive control. In conclusion, the four GnRH receptors encoded within the C. intestinalis genome were all transcribed into messenger RNA, but only three of the Ciona GnRH receptors were biologically active in our assays. The Ciona GnRH receptors almost exclusively activated the cAMP pathway.
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Affiliation(s)
- Javier A Tello
- Department of Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia, Canada V8W 3N5
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Maiti K, Oh DY, Oh DY, Moon JS, Acharjee S, Li JH, Bai DG, Park HS, Lee K, Lee YC, Jung NC, Kim K, Vaudry H, Kwon HB, Seong JY. Differential effects of gonadotropin-releasing hormone (GnRH)-I and GnRH-II on prostate cancer cell signaling and death. J Clin Endocrinol Metab 2005; 90:4287-98. [PMID: 15870130 DOI: 10.1210/jc.2004-1894] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT GnRH is known to directly regulate prostate cancer cell proliferation, but the precise mechanism of action of the peptide is still under investigation. OBJECTIVE This study demonstrates differential effects of GnRH-I and GnRH-II on androgen-independent human prostate cancer cells. RESULTS Both GnRH-I and GnRH-II increased the intracellular Ca(2+) concentration ([Ca(2+)](i)) either through Ca(2+) influx from external Ca(2+) source or via mobilization of Ca(2+) from internal Ca(2+) stores. Interestingly, the [Ca(2+)](i) increase was mediated by activation of the ryanodine receptor but not the inositol trisphosphate receptor. Trptorelix-1, a novel GnRH-II antagonist but not cetrorelix, a classical GnRH-I antagonist, completely inhibited the GnRH-II-induced [Ca(2+)](i) increase. Concurrently at high concentrations, trptorelix-1 and cetrorelix inhibited GnRH-I-induced [Ca(2+)](i) increase, whereas at low concentrations they exerted an agonistic action, inducing Ca(2+) influx. High concentrations of trptorelix-1 but not cetrorelix-induced prostate cancer cell death, probably through an apoptotic process. Using photoaffinity labeling with (125)I-[azidobenzoyl-D-Lys(6)]GnRH-II, we observed that an 80-kDa protein specifically bound to GnRH-II. CONCLUSIONS This study suggests the existence of a novel GnRH-II binding protein, in addition to a conventional GnRH-I receptor, in prostate cancer cells. These data may facilitate the development of innovatory therapeutic drugs for the treatment of prostate cancer.
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Affiliation(s)
- Kaushik Maiti
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
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Li JH, Choe H, Wang AF, Maiti K, Wang C, Salam A, Chun SY, Lee WK, Kim K, Kwon HB, Seong JY. Extracellular Loop 3 (EL3) and EL3-Proximal Transmembrane Helix 7 of the Mammalian Type I and Type II Gonadotropin-Releasing Hormone (GnRH) Receptors Determine Differential Ligand Selectivity to GnRH-I and GnRH-II. Mol Pharmacol 2005; 67:1099-110. [PMID: 15635044 DOI: 10.1124/mol.104.004887] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mammalian type I and II gonadotropin-releasing hormone (GnRH) receptors (GnRHRs) show differential ligand preference for GnRH-I and GnRH-II, respectively. Using a variety of chimeric receptors based on green monkey GnRHR-2 (gmGnRHR-2), a representative type II GnRHR, and rat GnRHR, a representative type I GnRHR, this study elucidated specific domains responsible for this ligand selectivity. A chimeric gmGnRHR-2 with the extracellular loop 3 (EL3) and EL3-proximal transmembrane helix 7 (TMH7) of rat GnRHR showed a great increase in ligand sensitivity to GnRH-I but not to GnRH-II. Point-mutation studies indicate that four amino acids, Leu/Phe(7.38), Leu/Phe(7.43), Ala/Pro(7.46), and Pro/Cys(7.47) in TMH7 are critical for ligand selectivity as well as receptor conformation. Furthermore, a combinatory mutation (Pro(7.31)-Pro(7.32)-Ser(7.33) motif to Ser-Glu-Pro in EL3 and Leu(7.38), Leu(7.43), Ala(7.46), and Pro(7.47) to those of rat GnRHR) in gmGnRH-2 exhibited an approximately 500-fold increased sensitivity to GnRH-I, indicating that these residues are critical for discriminating GnRH-II from GnRH-I. [Trp(7)]GnRH-I and [Trp(8)]GnRH-I but not [His(5)]GnRH-I exhibit a higher potency in activating wild-type gmGnRHR-2 than native GnRH-I, indicating that amino acids at positions 7 and 8 of GnRHs are more important than position 5 for differential recognition by type I and type II GnRHRs. As a whole, these data suggest a molecular coevolution of ligands and their receptors and facilitate the understanding of the molecular interaction between GnRHs and their cognate receptors.
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Affiliation(s)
- Jian Hua Li
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea
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Abstract
Hypothalamic gonadotropin releasing hormone (GnRH I) and its pituitary receptor are responsible for the CNS regulation of reproduction. However, a second GnRH (GnRH II) is also expressed in humans and a gene that resembles the GnRH II receptor in fish has been identified in humans and monkeys. The amino-acid sequence of this newly identified, seven-transmembrane, G-protein-coupled receptor in monkeys differs from the human GnRH I receptor by having a C-terminal, cytoplasmic tail. GnRH II is approximately 400-fold more potent at GnRH II receptors than GnRH I receptors. GnRH I directly inhibits proliferation of human tumor cells, and GnRH II and its receptor might have a similar role. Limited progress has been made, however, because of difficulty translating the mRNA that encodes the human GnRH II receptor. Nevertheless, such receptors are likely to exist in humans because GnRH II is more inhibitory to tumor cell replication than GnRH I, and GnRH I and GnRH II have reciprocal effects on human decidual stromal cells in culture. The focus of this review is the identity of a possible translatable, functional GnRH II receptor in humans. The two possibilities considered are either that GnRH II receptor mRNA is expressed that encodes either 5 or 7 transmembrane domains or that a GnRH II-responsive complex is formed by the GnRH I receptor and fragments derived from the GnRH II receptor.
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Affiliation(s)
- Jimmy D Neill
- University of Alabama School of Medicine, Department of Physiology and Biophysics, MCLM 816, 1918 University Boulevard, Birmingham, AL 35294-0005, USA.
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