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Radomsky T, Anderson RC, Millar RP, Newton CL. Restoring function to inactivating G protein-coupled receptor variants in the hypothalamic-pituitary-gonadal axis 1. J Neuroendocrinol 2024:e13418. [PMID: 38852954 DOI: 10.1111/jne.13418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 03/30/2024] [Accepted: 05/15/2024] [Indexed: 06/11/2024]
Abstract
G protein-coupled receptors (GPCRs) are central to the functioning of the hypothalamic-pituitary-gonadal axis (HPG axis) and include the rhodopsin-like GPCR family members, neurokinin 3 receptor, kappa-opioid receptor, kisspeptin 1 receptor, gonadotropin-releasing hormone receptor, and the gonadotropin receptors, luteinizing hormone/choriogonadotropin receptor and follicle-stimulating hormone receptor. Unsurprisingly, inactivating variants of these receptors have been implicated in a spectrum of reproductive phenotypes, including failure to undergo puberty, and infertility. Clinical induction of puberty in patients harbouring such variants is possible, but restoration of fertility is not always a realisable outcome, particularly for those patients suffering from primary hypogonadism. Thus, novel pharmaceuticals and/or a fundamental change in approach to treating these patients are required. The increasing wealth of data describing the effects of coding-region genetic variants on GPCR function has highlighted that the majority appear to be dysfunctional as a result of misfolding of the encoded receptor protein, which, in turn, results in impaired receptor trafficking through the secretory pathway to the cell surface. As such, these intracellularly retained receptors may be amenable to 'rescue' using a pharmacological chaperone (PC)-based approach. PCs are small, cell permeant molecules hypothesised to interact with misfolded intracellularly retained proteins, stabilising their folding and promoting their trafficking through the secretory pathway. In support of the use of this approach as a viable therapeutic option, it has been observed that many rescued variant GPCRs retain at least a degree of functionality when 'rescued' to the cell surface. In this review, we examine the GPCR PC research landscape, focussing on the rescue of inactivating variant GPCRs with important roles in the HPG axis, and describe what is known regarding the mechanisms by which PCs restore trafficking and function. We also discuss some of the merits and obstacles associated with taking this approach forward into a clinical setting.
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Affiliation(s)
- Tarryn Radomsky
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Ross C Anderson
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Department of Physiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Robert P Millar
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Deanery of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Faculty of Health Sciences, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Claire L Newton
- Centre for Neuroendocrinology, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
- Deanery of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
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Casati L, Ciceri S, Maggi R, Bottai D. Physiological and Pharmacological overview of the Gonadotropin Releasing Hormone. Biochem Pharmacol 2023; 212:115553. [PMID: 37075816 DOI: 10.1016/j.bcp.2023.115553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 04/07/2023] [Accepted: 04/10/2023] [Indexed: 04/21/2023]
Abstract
Gonadotropin-releasing Hormone (GnRH) is a decapeptide responsible for the control of the reproductive functions. It shows C- and N-terminal aminoacid modifications and two other distinct isoforms have been so far identified. The biological effects of GnRH are mediated by binding to high-affinity G-protein couple receptors (GnRHR), showing characteristic very short C tail. In mammals, including humans, GnRH-producing neurons originate in the embryonic nasal compartment and during early embryogenesis they undergo rapid migration towards the hypothalamus; the increasing knowledge of such mechanisms improved diagnostic and therapeutic approaches to infertility. The pharmacological use of GnRH, or its synthetic peptide and non-peptide agonists or antagonists, provides a valid tool for reproductive disorders and assisted reproduction technology (ART). The presence of GnRHR in several organs and tissues indicates additional functions of the peptide. The identification of a GnRH/GnRHR system in the human endometrium, ovary, and prostate has extended the functions of the peptide to the physiology and tumor transformation of such tissues. Likely, the activity of a GnRH/GnRHR system at the level of the hippocampus, as well as its decreased expression in mice brain aging, raised interest in its possible involvement in neurogenesis and neuronal functions. In conclusion, GnRH/GnRHR appears to be a fascinating biological system that exerts several possibly integrated pleiotropic actions in the complex control of reproductive functions, tumor growth, neurogenesis, and neuroprotection. This review aims to provide an overview of the physiology of GnRH and the pharmacological applications of its synthetic analogs in the management of reproductive and non-reproductive diseases.
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Affiliation(s)
- Lavinia Casati
- Department of Health Sciences, Università degli Studi di Milano, Milano, Italy
| | - Samuele Ciceri
- Dept. of Pharmaceutical Sciences (DISFARM), Università degli Studi di Milano, Milano Italy
| | - Roberto Maggi
- Dept. of Pharmaceutical Sciences (DISFARM), Università degli Studi di Milano, Milano Italy.
| | - Daniele Bottai
- Dept. of Pharmaceutical Sciences (DISFARM), Università degli Studi di Milano, Milano Italy
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3
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Wu HM, Chang HM, Leung PCK. Gonadotropin-releasing hormone analogs: Mechanisms of action and clinical applications in female reproduction. Front Neuroendocrinol 2021; 60:100876. [PMID: 33045257 DOI: 10.1016/j.yfrne.2020.100876] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/23/2020] [Accepted: 10/04/2020] [Indexed: 12/15/2022]
Abstract
Extra-hypothalamic GnRH and extra-pituitary GnRH receptors exist in multiple human reproductive tissues, including the ovary, endometrium and myometrium. Recently, new analogs (agonists and antagonists) and modes of GnRH have been developed for clinical application during controlled ovarian hyperstimulation for assisted reproductive technology (ART). Additionally, the analogs and upstream regulators of GnRH suppress gonadotropin secretion and regulate the functions of the reproductive axis. GnRH signaling is primarily involved in the direct control of female reproduction. The cellular mechanisms and action of the GnRH/GnRH receptor system have been clinically applied for the treatment of reproductive disorders and have widely been introduced in ART. New GnRH analogs, such as long-acting GnRH analogs and oral nonpeptide GnRH antagonists, are being continuously developed for clinical application. The identification of the upstream regulators of GnRH, such as kisspeptin and neurokinin B, provides promising potential to develop these upstream regulator-related analogs to control the hypothalamus-pituitary-ovarian axis.
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Affiliation(s)
- Hsien-Ming Wu
- Department of Obstetrics and Gynecology, Chang Gung Memorial Hospital, Linkou Medical Center, Chang Gung University School of Medicine, Taoyuan 333, Taiwan, ROC
| | - Hsun-Ming Chang
- Department of Obstetrics and Gynaecology, BC Children's Hospital Research Institute, University of British Columbia, Vancouver, British Columbia V6H 3V5, Canada
| | - Peter C K Leung
- Department of Obstetrics and Gynaecology, BC Children's Hospital Research Institute, University of British Columbia, Vancouver, British Columbia V6H 3V5, Canada.
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Sharker MR, Sukhan ZP, Kim SC, Lee WK, Kho KH. Molecular Identification, Characterization, and Expression Analysis of a Gonadotropin-Releasing Hormone Receptor (GnRH-R) in Pacific Abalone, Haliotis discus hannai. Molecules 2020; 25:molecules25122733. [PMID: 32545589 PMCID: PMC7355911 DOI: 10.3390/molecules25122733] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/02/2020] [Accepted: 06/11/2020] [Indexed: 12/24/2022] Open
Abstract
A full-length cDNA sequence encoding a GnRH receptor was cloned from the pleuropedal ganglion of the Pacific abalone, Haliotis discus hannai. The cloned sequence is 1499-bp in length encoding a protein of 460 amino acid residues, with a molecular mass of 52.22 kDa and an isoelectric point (pI) of 9.57. The architecture of HdhGnRH-R gene exhibited key features of G protein-coupled receptors (GPCRs), including seven membrane spanning domains, putative N-linked glycosylation motifs, and phosphorylation sites of serine and threonine residues. It shared 63%, 52%, and 30% sequence identities with Octopus vulgaris, Limulus polyphemus, and Mizuhopecten yessoensis GnRH-R II sequences, respectively. Phylogenetic analysis indicated that HdhGnRH-R gene was clustered with GnRH-R II of O. vulgaris and O. bimaculoides. qPCR assay demonstrated that the mRNA expression level of this receptor was significantly higher in the pleuropedal ganglion than that in any other examined tissue. Transcriptional activities of this gene in gonadal tissues were significantly higher in the ripening stage. The mRNA expression of this gene was significantly higher in pleuropedal ganglion, testis, and ovary at higher effective accumulative temperature (1000 °C). In situ hybridization revealed that HdhGnRH-R mRNA was expressed in neurosecretory cells of pleuropedal ganglion. Our results suggest that HdhGnRH-R gene synthesized in the neural ganglia might be involved in the control of gonadal maturation and gametogenesis of H. discus hannai. This is the first report of GnRH-R in H. discus hannai and the results may contribute to further studies of GPCRs evolution or may useful for the development of aquaculture method of this abalone species.
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Affiliation(s)
| | | | | | | | - Kang Hee Kho
- Correspondence: ; Tel.: +82-616-597-168; Fax: +82-616-597-169
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Olberg DE, Bauer N, Andressen KW, Hjørnevik T, Cumming P, Levy FO, Klaveness J, Haraldsen I, Sutcliffe JL. Brain penetrant small molecule 18F-GnRH receptor (GnRH-R) antagonists: Synthesis and preliminary positron emission tomography imaging in rats. Nucl Med Biol 2016; 43:478-89. [DOI: 10.1016/j.nucmedbio.2016.05.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 04/18/2016] [Accepted: 05/06/2016] [Indexed: 10/21/2022]
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Maitra SK, Hasan KN. The Role of Melatonin as a Hormone and an Antioxidant in the Control of Fish Reproduction. Front Endocrinol (Lausanne) 2016; 7:38. [PMID: 27199895 PMCID: PMC4854901 DOI: 10.3389/fendo.2016.00038] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2016] [Accepted: 04/21/2016] [Indexed: 11/13/2022] Open
Abstract
Reproduction in most fish is seasonal or periodic, and the spawning occurs in an appropriate season to ensure maximum survival of the offspring. The sequence of reproductive events in an annual cycle is largely under the control of a species-specific endogenous timing system, which essentially relies on a well-equipped physiological response mechanism to changing environmental cues. The duration of solar light or photoperiod is one of the most predictable environmental signals used by a large number of animals including fish to coordinate their seasonal breeding. In vertebrates, the pineal gland is the major photoneuroendocrine part of the brain that rhythmically synthesizes and releases melatonin (N-acetyl-5-methoxytryptamine) into the circulation in synchronization with the environmental light-dark cycle. Past few decades witnessed an enormous progress in understanding the mechanisms by which melatonin regulates seasonal reproduction in fish and in other vertebrates. Most studies emphasized hormonal actions of melatonin through its high-affinity, pertussis toxin-sensitive G-protein (guanine nucleotide-binding protein)-coupled receptors on the hypothalamus-pituitary-gonad (HPG) axis of fish. However, the discovery that melatonin due to its lipophilic nature can easily cross the plasma membrane of all cells and may act as a potent scavenger of free radicals and stimulant of different antioxidants added a new dimension to the idea explaining mechanisms of melatonin actions in the regulation of ovarian functions. The basic concept on the actions of melatonin as an antioxidant emerged from mammalian studies. Recently, however, some new studies clearly suggested that melatonin, apart from playing the role of a hormone, may also be associated with the reduction in oxidative stress to augment ovarian functions during spawning. This review thus aims to bring together the current knowledge on the role of melatonin as a hormone as well as an antioxidant in the control of fish reproduction and shape the current working hypotheses supported by recent findings obtained in carp or based on knowledge gathered in mammalian and avian species. In essence, this review highlights potential actions of melatonin as a hormone in determining temporal pattern of spawning and as an antioxidant in regulating oocyte maturation at the downstream of HPG axis in fish.
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Affiliation(s)
- Saumen Kumar Maitra
- Department of Zoology, Visva-Bharati University, Santiniketan, India
- *Correspondence: Saumen Kumar Maitra,
| | - Kazi Nurul Hasan
- Department of Zoology, Visva-Bharati University, Santiniketan, India
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Molecular cloning, sequencing, and distribution of feline GnRH receptor (GnRHR) and resequencing of canine GnRHR. Theriogenology 2014; 83:266-75. [PMID: 25442384 DOI: 10.1016/j.theriogenology.2014.09.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 09/11/2014] [Accepted: 09/12/2014] [Indexed: 11/20/2022]
Abstract
GnRH receptors play vital roles in mammalian reproduction via regulation of gonadotropin secretion, which is essential for gametogenesis and production of gonadal steroids. GnRH receptors for more than 20 mammalian species have been sequenced, including human, mouse, and dog. This study reports the molecular cloning and sequencing of GnRH receptor (GnRHR) cDNA from the pituitary gland of the domestic cat, an important species in biomedical research. Feline GnRHR cDNA is composed of 981 nucleotides and encodes a 327 amino acid protein. Unlike the majority of mammalian species sequenced so far, but similar to canine GnRHR, feline GnRHR protein lacks asparagine in position three of the extracellular domain of the protein. At the amino acid level, feline GnRHR exhibits 95.1% identity with canine, 93.8% with human, and 88.9% with mouse GnRHR. Comparative sequence analysis of GnRHRs for multiple mammalian species led to resequencing of canine GnRHR, which differed from that previously published by a single base change that translates to a different amino acid in position 193. This single base change was confirmed in dogs of multiple breeds. Reverse transcriptase PCR analysis of GnRHR messenger RNA in different tissues from four normal cats indicated the presence of amplicons of varying lengths, including full-length as well as shortened GnRHR amplicons, pointing to the existence of truncated GnRHR transcripts in the domestic cat. This study is the first insight into molecular composition and expression of feline GnRHR and promotes better understanding of receptor organization, and distribution in various tissues of this species.
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Abstract
Reproductive hormones affect all stages of life from gamete production, fertilization, fetal development and parturition, neonatal development and puberty through to adulthood and senescence. The reproductive hormone cascade has, therefore, been the target for the development of numerous drugs that modulate its activity at many levels. As the central regulator of the cascade, gonadotropin-releasing hormone (GnRH) agonists and antagonists have found extensive applications in treating a wide range of hormone-dependent diseases, such as precocious puberty, prostate cancer, benign prostatic hyperplasia, endometriosis and uterine fibroids, as well as being an essential component of in vitro fertilization protocols. The neuroendocrine peptides that regulate GnRH neurons, kisspeptin and neurokinin B, have also been identified as therapeutic targets, and novel agonists and antagonists are being developed as modulators of the cascade upstream of GnRH. Here, we review the development and applications of analogues of the major neuroendocrine peptide regulators of the reproductive hormone cascade: GnRH, kisspeptin and neurokinin B.
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Affiliation(s)
- Robert P Millar
- Mammal Research Institute, Department of Zoology and Entomology, Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa.
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9
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Biochemistry, molecular biology and cell biology of gonadotropin-releasing hormone antagonists. Curr Opin Obstet Gynecol 2011; 23:238-44. [DOI: 10.1097/gco.0b013e328348a3ce] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Beyer DA, Amari F, Thill M, Schultze-Mosgau A, Al-Hasani S, Diedrich K, Griesinger G. Emerging gonadotropin-releasing hormone agonists. Expert Opin Emerg Drugs 2011; 16:323-40. [PMID: 21244327 DOI: 10.1517/14728214.2010.547472] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Gonadotropin-releasing hormone agonist analogs (GnRHa) are peptides that mimic the action of gonadotropin-releasing hormone (GnRH) and are used to suppress subsequent sex steroid production. Although the analogs are a rather defined group of drugs, there have been developments in the past decades and there is still ample room for improvement. New therapeutic strategies in the use of GnRHs are discussed. AREAS COVERED Major points of discussion include: i) the use of concomitant treatment of early breast cancer in premenopausal estrogen-positive and -negative patients, ii) the use of GnRHa for fertility preservation in young female patients with malignant diseases and iii) the use of GnRH analogs in assisted reproduction. The manuscript provides a better understanding of GnRH agonists as well as an explanation of their major indications, biochemical pathways and concluding therapeutic strategies. Recent results from international meetings and debates are described to explain current controversies. EXPERT OPINION This paper highlights the need for more complex GnRH analogs. In the next few years, there will be longer acting GnRHas that may improve adherence. New therapeutic targets in oncological concepts may go beyond fertility preservation and focus on the antiproliferative effects of GnRH analogs.
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Affiliation(s)
- Daniel Alexander Beyer
- University of Schleswig Holstein, Department of Obstetrics and Gynaecology, Campus Lübeck, Ratzeburger Allee 160, D- 23538 Lübeck, Germany.
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Enright BP, Leach MW, Pelletier G, LaBrie F, McIntyre BS, Losco PE. Effects of an antagonist of neurokinin receptors 1, 2 and 3 on reproductive hormones in male beagle dogs. ACTA ACUST UNITED AC 2010; 89:517-25. [DOI: 10.1002/bdrb.20274] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Conn PM, Janovick JA. Trafficking and quality control of the gonadotropin releasing hormone receptor in health and disease. Mol Cell Endocrinol 2009; 299:137-45. [PMID: 19059461 PMCID: PMC2655134 DOI: 10.1016/j.mce.2008.10.051] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Accepted: 10/27/2008] [Indexed: 01/09/2023]
Abstract
In order to serve as enzymes, receptors and ion channels, proteins require structural precision. This is monitored by a cellular quality control system (QCS) that rejects misfolded proteins and thereby protects the cell against aberrant activity. Misfolding can result in protein molecules that retain intrinsic function, yet become misrouted within the cell; these cease to perform normally and result in disease. A therapeutic opportunity exists to correct misrouting and rescue mutants using "pharmacoperones" (small molecular folding templates, often peptidomimetics, which promote correct folding and rescue) thereby restoring function and potentially curing the underlying disease. Because of its small size, the GnRH (gonadotropin-releasing hormone) receptor (GnRHR) is an excellent model for GPCR (G protein-coupled receptor) and has allowed elucidation of the precise biochemical mechanism of pharmacoperone action necessary for rational design of new therapeutic agents. This review summarizes what has been learned about the structural requirements of the GnRHR that govern its interaction with the QCS and now presents the potential for the rational design of pharmacoperones. Because of the role of protein processing, this approach is likely to be applicable to other GCPCs and other proteins in general.
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Affiliation(s)
- P Michael Conn
- Oregon National Primate Research Center and Departments of Physiology and Pharmacology and Cell Biology and Development, Oregon Health & Science University, United States.
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Janovick JA, Patny A, Mosley R, Goulet MT, Altman MD, Rush TS, Cornea A, Conn PM. Molecular mechanism of action of pharmacoperone rescue of misrouted GPCR mutants: the GnRH receptor. Mol Endocrinol 2009; 23:157-68. [PMID: 19095769 PMCID: PMC2646616 DOI: 10.1210/me.2008-0384] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 12/08/2008] [Indexed: 12/22/2022] Open
Abstract
The human GnRH receptor (hGnRHR), a G protein-coupled receptor, is a useful model for studying pharmacological chaperones (pharmacoperones), drugs that rescue misfolded and misrouted protein mutants and restore them to function. This technique forms the basis of a therapeutic approach of rescuing mutants associated with human disease and restoring them to function. The present study relies on computational modeling, followed by site-directed mutagenesis, assessment of ligand binding, effector activation, and confocal microscopy. Our results show that two different chemical classes of pharmacoperones act to stabilize hGnRHR mutants by bridging residues D(98) and K(121). This ligand-mediated bridge serves as a surrogate for a naturally occurring and highly conserved salt bridge (E(90)-K(121)) that stabilizes the relation between transmembranes 2 and 3, which is required for passage of the receptor through the cellular quality control system and to the plasma membrane. Our model was used to reveal important pharmacophoric features, and then identify a novel chemical ligand, which was able to rescue a D(98) mutant of the hGnRHR that could not be rescued as effectively by previously known pharmacoperones.
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Affiliation(s)
- Jo Ann Janovick
- Oregon National Primate Research Center/Oregon Health Sciences University, Beaverton, Oregon 97006, USA
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Pfleger KDG, Pawson AJ, Millar RP. Changes to gonadotropin-releasing hormone (GnRH) receptor extracellular loops differentially affect GnRH analog binding and activation: evidence for distinct ligand-stabilized receptor conformations. Endocrinology 2008; 149:3118-29. [PMID: 18356273 DOI: 10.1210/en.2008-0002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GnRH and its structural variants bind to GnRH receptors from different species with different affinities and specificities. By investigating chimeric receptors that combine regions of mammalian and nonmammalian GnRH receptors, a greater understanding of how different domains influence ligand binding and receptor activation can be achieved. Using human-catfish and human-chicken chimeric receptors, we demonstrate the importance of extracellular loop conformation for ligand binding and agonist potency, providing further evidence for GnRH and GnRH II stabilization of distinct active receptor conformations. We demonstrate examples of GnRH receptor gain-of-function mutations that apparently improve agonist potency independently of affinity, implicating a role for extracellular loops in stabilizing the inactive receptor conformation. We also show that entire extracellular loop substitution can overcome the detrimental effects of localized mutations, thereby demonstrating the importance of considering the conformation of entire domains when drawing conclusions from point-mutation studies. Finally, we present evidence implicating the configuration of extracellular loops 2 and 3 in combination differentiating GnRH analog binding modes. Because there are two endogenous forms of GnRH ligand but only one functional form of full-length GnRH receptor in humans, understanding how GnRH and GnRH II can elicit distinct functional effects through the same receptor is likely to provide important insights into how these ligands can have differential effects in both physiological and pathological situations.
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Affiliation(s)
- Kevin D G Pfleger
- Medical Research Council Human Reproductive Sciences Unit, Centre for Reproductive Biology, The Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom.
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Betz SF, Zhu YF, Chen C, Struthers RS. Non-Peptide Gonadotropin-Releasing Hormone Receptor Antagonists. J Med Chem 2008; 51:3331-48. [DOI: 10.1021/jm701249f] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stephen F. Betz
- Endocrinology & Metabolism, Neurocrine Biosciences, Inc., 12790 El Camino Real, San Diego, California 92130
| | - Yun-Fei Zhu
- Endocrinology & Metabolism, Neurocrine Biosciences, Inc., 12790 El Camino Real, San Diego, California 92130
| | - Chen Chen
- Endocrinology & Metabolism, Neurocrine Biosciences, Inc., 12790 El Camino Real, San Diego, California 92130
| | - R. Scott Struthers
- Endocrinology & Metabolism, Neurocrine Biosciences, Inc., 12790 El Camino Real, San Diego, California 92130
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Struthers RS, Xie Q, Sullivan SK, Reinhart GJ, Kohout TA, Zhu YF, Chen C, Liu XJ, Ling N, Yang W, Maki RA, Bonneville AK, Chen TK, Bozigian HP. Pharmacological characterization of a novel nonpeptide antagonist of the human gonadotropin-releasing hormone receptor, NBI-42902. Endocrinology 2007; 148:857-67. [PMID: 17095587 DOI: 10.1210/en.2006-1213] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Suppression of the hypothalamic-pituitary-gonadal axis by peptides that act at the GnRH receptor has found widespread use in clinical practice for the management of sex-steroid-dependent diseases (such as prostate cancer and endometriosis) and reproductive disorders. Efforts to develop orally available GnRH receptor antagonists have led to the discovery of a novel, potent nonpeptide antagonist, NBI-42902, that suppresses serum LH concentrations in postmenopausal women after oral administration. Here we report the in vitro and in vivo pharmacological characterization of this compound. NBI-42902 is a potent inhibitor of peptide radioligand binding to the human GnRH receptor (K(i) = 0.56 nm). Tritiated NBI-42902 binds with high affinity (K(d) = 0.19 nm) to a single class of binding sites and can be displaced by a range of peptide and nonpeptide GnRH receptor ligands. In vitro experiments demonstrate that NBI-42902 is a potent functional, competitive antagonist of GnRH stimulated IP accumulation, Ca(2+) flux, and ERK1/2 activation. It did not stimulate histamine release from rat peritoneal mast cells. Finally, it is effective in lowering serum LH in castrated male macaques after oral administration. Overall, these data provide a benchmark of pharmacological characteristics required for a nonpeptide GnRH antagonist to effectively suppress gonadotropins in humans and suggest that NBI-42902 may have clinical utility as an oral agent for suppression of the hypothalamic-pituitary-gonadal axis.
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Affiliation(s)
- R Scott Struthers
- Department of Endocrinology, Neurocrine Biosciences Inc., 12790 El Camino Real, San Diego, California 92130, USA.
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Sullivan SK, Hoare SRJ, Fleck BA, Zhu YF, Heise CE, Struthers RS, Crowe PD. Kinetics of nonpeptide antagonist binding to the human gonadotropin-releasing hormone receptor: Implications for structure–activity relationships and insurmountable antagonism. Biochem Pharmacol 2006; 72:838-49. [PMID: 16930559 DOI: 10.1016/j.bcp.2006.07.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 06/28/2006] [Accepted: 07/17/2006] [Indexed: 11/21/2022]
Abstract
Numerous nonpeptide ligands have been developed for the human gonadotropin-releasing hormone (GnRH) receptor as potential agents for treatment of disorders of the reproductive-endocrine axis. While the equilibrium binding of these ligands has been studied in detail, little is known of the kinetics of their receptor interaction. In this study we evaluated the kinetic structure-activity relationships (SAR) of uracil-series antagonists by measuring their association and dissociation rate constants. These constants were measured directly using a novel radioligand, [3H] NBI 42902, and indirectly for unlabeled ligands. Receptor association and dissociation of [3H] NBI 42902 was monophasic, with an association rate constant of 93+/-10 microM(-1) min(-1) and a dissociation rate constant of 0.16+/-0.02 h(-1) (t(1/2) of 4.3 h). Four unlabeled compounds were tested with varying substituents at the 2-position of the benzyl group at position 1 of the uracil (-F, -SO(CH3), -SO2(CH3) and -CF3). The nature of the substituent did not appreciably affect the association rate constant but varied the dissociation rate constant >50-fold (t(1/2) ranging from 52 min for -SO(CH3) to >43 h for -CF3). This SAR was poorly resolved in standard competition assays due to lack of equilibration. The functional consequences of the varying dissociation rate were investigated by measuring antagonism of GnRH-stimulated [3H] inositol phosphates accumulation. Slowly dissociating ligands displayed insurmountable antagonism (decrease of the GnRH E(max)) while antagonism by more rapidly dissociating ligands was surmountable (without effect on the GnRH E(max)). Therefore, evaluating the receptor binding kinetics of nonpeptide antagonists revealed SAR, not evident in standard competition assays, that defined at least in part the mode of functional antagonism by the ligands. These findings are of importance for the future definition of nonpeptide ligand SAR and for the identification of potentially useful slowly dissociating antagonists for the GnRH receptor.
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Affiliation(s)
- Susan K Sullivan
- Department of Pharmacology and Lead Discovery, Neurocrine Biosciences Inc., 12790 El Camino Real, San Diego, CA 92130, USA
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Kanda A, Takahashi T, Satake H, Minakata H. Molecular and functional characterization of a novel gonadotropin-releasing-hormone receptor isolated from the common octopus (Octopus vulgaris). Biochem J 2006; 395:125-35. [PMID: 16367741 PMCID: PMC1409690 DOI: 10.1042/bj20051615] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GnRH (gonadotropin-releasing hormone) plays a pivotal role in the regulation of reproduction in vertebrates through interaction with a specific receptor. Previously, we isolated a GnRH homologue, oct-GnRH, from the common octopus (Octopus vulgaris). In the present study, we have identified a GnRH receptor (oct-GnRHR) specific for oct-GnRH from Octopus brain. Oct-GnRHR includes domains and motifs typical of vertebrate GnRH receptors. The intron-inserted positions are conserved between oct-GnRHR and the chordate GnRHR genes. The oct-GnRHR expressed in Xenopus (South African clawed frog) oocytes was responsive to oct-GnRH, but not to any other HPLC fractions of the Octopus brain extract. These results show that oct-GnRHR is an authentic receptor for oct-GnRH. Southern blotting of reverse-transcription PCR products revealed that the oct-GnRHR mRNA was widely distributed in the central and peripheral nervous systems and in several peripheral tissues. In situ hybridization showed that oct-GnRHR mRNA was expressed in some regions involved in autonomic functions, feeding, memory and movement. Oct-GnRH was shown to induce steroidogenesis of testosterone, progesterone and 17beta-oestradiol in Octopus ovary and testis, where oct-GnRHR was abundantly expressed. These results suggest that oct-GnRH, like its vertebrate counterparts, acts as a multifunctional neurotransmitter, neuromodulator and hormone-like factor, both in Octopus central nervous system and peripheral tissues, and that both structure and functions of the GnRH family are, at least partially, evolutionarily conserved between octopuses and chordates.
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Affiliation(s)
- Atsuhiro Kanda
- Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
| | - Toshio Takahashi
- Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
| | - Honoo Satake
- Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
| | - Hiroyuki Minakata
- Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
- To whom correspondence should be addressed (email )
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19
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Söderhäll JA, Polymeropoulos EE, Paulini K, Günther E, Kühne R. Antagonist and agonist binding models of the human gonadotropin-releasing hormone receptor. Biochem Biophys Res Commun 2005; 333:568-82. [PMID: 15950933 DOI: 10.1016/j.bbrc.2005.05.142] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2005] [Accepted: 05/07/2005] [Indexed: 10/25/2022]
Abstract
G-protein-coupled receptors (GPCRs) constitute one of the most important classes of drug targets. Since the first high-resolution structure of a GPCR was determined by Palczewski and co-workers [K. Palczewski, T. Kumasaka, T. Hori, C.A. Behnke, H. Motoshima, B.A. Fox, I. Le Trong, D.C. Teller, T. Okada, R.E. Stenkamp, M. Yamamoto, M. Miyano, Crystal structure of rhodopsin: a G-protein-coupled receptor, Science 289 (2000) 739-745], development of in silico models of rhodopsin-like GPCRs could be rationally founded. In this work, we present a model of the human gonadotropin-releasing hormone receptor based on the rhodopsin structure. The transmembrane helices are modeled by homology, while the extra- and intra-cellular loops are modeled in such a way that experimentally determined interactions and microdomains (e.g., hydrophobic cores) are retained. We conclude that specifically tailored models, compared to more automatic approaches, have the benefit that known interactions are easily introduced early in the homology modeling. Furthermore, tailored models, although more tedious to construct, are better suited for drug lead finding and for compound optimization. To test the stability of the receptor, we performed a 1 ns molecular dynamics simulation. Moreover, we docked two agonists (native GnRH and Triptorelin, [dTrp(6)]-GnRH) and two antagonists (Cetrorelix, dNal(1)-dCpa(2)-dPal(3)-Ser(4)-Tyr(5)-dCit(6)-Leu(7)-Arg(8)-Pro(9)-dAla(10)), and the covalently constrained dicyclic decapeptide dicyclo(1,1'-5/4-10)[Ac-Glu(1)(Gly(1)')-dCpa(2)-dTrp(3)-Asp(4)-dbu(5)-dNal(6)-Leu(7)-Arg(8)-Pro(9)-dpr(10)-NH(2)] into the putative receptor binding site. The docked ligand conformations result in ligand-receptor interactions that are generally in good agreement with site-directed mutagenesis and ligand-binding studies presented in the literature. Our results indicate that the binding conformation of the antagonists differs from that of the agonists. This difference can be linked to the activation or inhibition of the receptor.
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MESH Headings
- Binding Sites
- Computer Simulation
- Gonadotropin-Releasing Hormone/analogs & derivatives
- Gonadotropin-Releasing Hormone/chemistry
- Humans
- Models, Chemical
- Models, Molecular
- Protein Binding
- Protein Conformation
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/analysis
- Receptors, G-Protein-Coupled/antagonists & inhibitors
- Receptors, G-Protein-Coupled/chemistry
- Receptors, LHRH/agonists
- Receptors, LHRH/analysis
- Receptors, LHRH/antagonists & inhibitors
- Receptors, LHRH/chemistry
- Sequence Analysis, Protein/methods
- Triptorelin Pamoate/chemistry
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Affiliation(s)
- J Arvid Söderhäll
- Institute for Molecular Pharmacology, Robert-Rössle-Strasse 10, D-13125 Berlin, Germany
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Silver MR, Nucci NV, Root AR, Reed KL, Sower SA. Cloning and characterization of a functional type II gonadotropin-releasing hormone receptor with a lengthy carboxy-terminal tail from an ancestral vertebrate, the sea lamprey. Endocrinology 2005; 146:3351-61. [PMID: 15878963 DOI: 10.1210/en.2005-0305] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A full-length transcript encoding a functional type II GnRH receptor was cloned from the pituitary of the sea lamprey, Petromyzon marinus. The current study is the first to identify a pituitary GnRH receptor transcript in an agnathan, which is the oldest vertebrate lineage. The cloned receptor retains the conserved structural features and amino acid motifs of other known GnRH receptors and notably includes a C-terminal intracellular tail of approximately 120 amino acids, the longest C-terminal tail of any vertebrate GnRH receptor identified to date. The lamprey GnRH receptor was shown to activate the inositol phosphate (IP) signaling system; stimulation with either lamprey GnRH-I or lamprey GnRH-III led to dose-dependent responses in transiently transfected COS7 cells. Furthermore, analyses of serially truncated lamprey GnRH receptor mutants indicate perturbations of the C-terminal tail disrupts IP accumulation, however, the tailless lamprey GnRH receptor was not only functional but was also capable of stimulating IP levels equal to wild type. Expression of the receptor transcript was demonstrated in the pituitary and testes using RT-PCR, whereas in situ hybridization showed expression and localization of the transcript in the proximal pars distalis of the pituitary. The phylogenetic placement and structural and functional features of this GnRH receptor suggest that it is representative of an ancestral GnRH receptor. In addition to having an important role in lamprey reproductive processes, the extensive C-terminal tail of this lamprey GnRH receptor may have great significance for understanding the evolutionary change of this vital structural feature within the GnRH receptor family.
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Affiliation(s)
- Matthew R Silver
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824, USA
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21
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Cheng CK, Leung PCK. Molecular biology of gonadotropin-releasing hormone (GnRH)-I, GnRH-II, and their receptors in humans. Endocr Rev 2005; 26:283-306. [PMID: 15561800 DOI: 10.1210/er.2003-0039] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In human beings, two forms of GnRH, termed GnRH-I and GnRH-II, encoded by separate genes have been identified. Although these hormones share comparable cDNA and genomic structures, their tissue distribution and regulation of gene expression are significantly dissimilar. The actions of GnRH are mediated by the GnRH receptor, which belongs to a member of the rhodopsin-like G protein-coupled receptor superfamily. However, to date, only one conventional GnRH receptor subtype (type I GnRH receptor) uniquely lacking a carboxyl-terminal tail has been found in the human body. Studies on the transcriptional regulation of the human GnRH receptor gene have indicated that tissue-specific gene expression is mediated by differential promoter usage in various cell types. Functionally, there is growing evidence showing that both GnRH-I and GnRH-II are potentially important autocrine and/or paracrine regulators in some extrapituitary compartments. Recent cloning of a second GnRH receptor subtype (type II GnRH receptor) in nonhuman primates revealed that it is structurally and functionally distinct from the mammalian type I receptor. However, the human type II receptor gene homolog carries a frameshift and a premature stop codon, suggesting that a full-length type II receptor does not exist in humans.
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Affiliation(s)
- Chi Keung Cheng
- Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, British Columbia, Canada V6H 3V5
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22
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Reinhart GJ, Xie Q, Liu XJ, Zhu YF, Fan J, Chen C, Struthers RS. Species selectivity of nonpeptide antagonists of the gonadotropin-releasing hormone receptor is determined by residues in extracellular loops II and III and the amino terminus. J Biol Chem 2004; 279:34115-22. [PMID: 15155770 DOI: 10.1074/jbc.m404474200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Efforts to develop orally available gonadotropin-releasing hormone (GnRH) receptor antagonists have led to the discovery of several classes of potent nonpeptide antagonists. Here we investigated molecular interactions of three classes of nonpeptide antagonists with human, rat, and macaque GnRH receptors. Although all are high affinity ligands of the human receptor (K(i) <5 nm), these compounds show reduced affinity for the macaque receptor and bind only weakly (K(i) >1 microm) to the rat receptor. To identify residues responsible for this selectivity, a series of chimeric receptors and mutant receptors was constructed and evaluated for nonpeptide binding. Surprisingly, 4 key residues located in the amino terminus (Met-24) and extracellular loops II (Ser-203, Gln-208) and III (Leu-300) of the GnRH receptor appear to be primarily responsible for species-selective binding. Comparisons of reciprocal mutations suggest that these may not be direct contacts but rather may be involved in organizing extracellular portions of the receptor. These data are novel because most previous reports of residues involved in binding of nonpeptide ligands to peptide-activated G protein-coupled receptors, including the GnRH receptor as well as mono-amine receptors, have identified binding sites in the transmembrane regions.
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Affiliation(s)
- Greg J Reinhart
- Department of Endocrinology, Neurocrine Biosciences Inc., 10555 Science Center Drive, San Diego, CA 92121, USA
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23
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Abstract
GnRH and its analogs are used extensively for the treatment of hormone-dependent diseases and assisted reproductive techniques. They also have potential as novel contraceptives in men and women. A thorough delineation of the molecular mechanisms involved in ligand binding, receptor activation, and intracellular signal transduction is kernel to understanding disease processes and the development of specific interventions. Twenty-three structural variants of GnRH have been identified in protochordates and vertebrates. In many vertebrates, three GnRHs and three cognate receptors have been identified with distinct distributions and functions. In man, the hypothalamic GnRH regulates gonadotropin secretion through the pituitary GnRH type I receptor via activation of G(q). In-depth studies have identified amino acid residues in both the ligand and receptor involved in binding, receptor activation, and translation into intracellular signal transduction. Although the predominant coupling of the type I GnRH receptor in the gonadotrope is through productive G(q) stimulation, signal transduction can occur via other G proteins and potentially by G protein-independent means. The eventual selection of intracellular signaling may be specifically directed by variations in ligand structure. A second form of GnRH, GnRH II, conserved in all higher vertebrates, including man, is present in extrahypothalamic brain and many reproductive tissues. Its cognate receptor has been cloned from various vertebrate species, including New and Old World primates. The human gene homolog of this receptor, however, has a frame-shift and stop codon, and it appears that GnRH II signaling occurs through the type I GnRH receptor. There has been considerable plasticity in the use of different GnRHs, receptors, and signaling pathways for diverse functions. Delineation of the structural elements in GnRH and the receptor, which facilitate differential signaling, will contribute to the development of novel interventive GnRH analogs.
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Affiliation(s)
- Robert P Millar
- Medical Research Council Human Reproductive Sciences Unit, Centre for Reproductive Biology, Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, Scotland, United Kingdom.
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Hara T, Araki H, Kusaka M, Harada M, Cho N, Suzuki N, Furuya S, Fujino M. Suppression of a pituitary-ovarian axis by chronic oral administration of a novel nonpeptide gonadotropin-releasing hormone antagonist, TAK-013, in cynomolgus monkeys. J Clin Endocrinol Metab 2003; 88:1697-704. [PMID: 12679460 DOI: 10.1210/jc.2002-021065] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
TAK-013 is a novel nonpeptide and orally active GnRH antagonist. We first examined the effect of TAK-013 on GnRH-stimulated LH release using primary-cultured pituitary cells of cynomolgus monkeys. TAK-013 suppressed LH release to below basal levels at concentrations higher than 100 nM with the IC(50) value of 36 nM. Next, we examined the effect of chronic oral administration of TAK-013 on serum hormone levels in regularly cycling female cynomolgus monkeys. TAK-013 administered at 90 mg/kg x d (30 mg/kg 3 times daily) for approximately 80 d continued to suppress LH, estradiol, and progesterone, but not FSH. The suppressive effect was reversible, in that normal profiles of sex steroids were observed immediately after discontinuation of the TAK-013 treatment. Interestingly, the suppressive effect of TAK-013 was not observed in marmoset monkeys. In summary, TAK-013 by oral administration suppresses a pituitary-ovarian axis continuously and reversibly in cynomolgus monkeys. Considering that TAK-013 has more potent antagonistic properties for human GnRH receptor than for monkey receptor, our data suggest that TAK-013 would be effective for reproductive disorders such as endometriosis and uterine leiomyoma and useful for assisted reproductive technology procedures.
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Affiliation(s)
- Takahito Hara
- Pharmaceutical Research Division, Takeda Chemical Industries, Ltd., Osaka 532-8686, Japan.
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25
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Elmore CS, Dean DC, DeVita RJ, Melillo DG. Synthesis of two non-peptidyl GnRH receptor antagonists via [14C]carbonylation. J Labelled Comp Radiopharm 2003. [DOI: 10.1002/jlcr.733] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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26
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Beckers T, Bernd M, Kutscher B, Kühne R, Hoffmann S, Reissmann T. Structure-function studies of linear and cyclized peptide antagonists of the GnRH receptor. Biochem Biophys Res Commun 2001; 289:653-63. [PMID: 11726197 DOI: 10.1006/bbrc.2001.5939] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Structurally new analogs of the peptidic GnRH receptor antagonist Cetrorelix as well as conformationally constrained cyclized deca- or pentapeptides were synthesized and selected peptides evaluated comprehensively. To understand how structural variations of the antagonistic peptide effect pharmacodynamic properties, binding affinities and antagonistic potencies toward the human and rat GnRH receptor were determined. Whereas large substituents in position 6 of linear peptides are compatible with high binding affinity (K(D) < 0.5 nM), all cyclized peptides except the cyclo[3-10] analog D-52391 depicted low binding affinity (K(D) > 10 nM). Binding affinity and antagonistic potency in vitro correlated for all peptides and surprisingly no discrimination between human and rat receptor proteins was observed. Since receptor residues W(101) and N(102) are involved in agonist and antagonist binding, equally potent but structurally different antagonists were tested for binding to the respective W(101)A and N(102)A mutants. In contrast to linear decapeptides, residues N(102) and W(101) are not involved in binding of D-23938 and W(101) is the critical residue for D-52391 binding. We conclude that although equally potent, peptidic GnRH receptor antagonists do have distinct interactions within the ligand binding pocket. Finally, selected antagonists were tested for testosterone suppression in male rats. The duration of testosterone suppression below castration levels differed largely from 1 day for Ganirelix to 27 days for D-23487. Systemic availability became evident as the most important parameter for in vivo efficacy.
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Affiliation(s)
- T Beckers
- Department of Cancer Research, ASTA Medica AG, Weismüllerstrasse 45, 60314 Frankfurt/Main, Germany.
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27
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Okubo K, Nagata S, Ko R, Kataoka H, Yoshiura Y, Mitani H, Kondo M, Naruse K, Shima A, Aida K. Identification and characterization of two distinct GnRH receptor subtypes in a teleost, the medaka Oryzias latipes. Endocrinology 2001; 142:4729-39. [PMID: 11606438 DOI: 10.1210/endo.142.11.8475] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We report the identification and characterization of two distinct GnRH receptor (GnRH-R) subtypes, designated GnRH-R1 and GnRH-R2, in a model teleost, the medaka Oryzias latipes. These seven-transmembrane receptors of the medaka contain a cytoplasmic C-terminal tail, which has been found in all other nonmammalian GnRH-Rs cloned to date. The GnRH-R1 gene is composed of three exons separated by two introns, whereas the GnRH-R2 gene has an additional intron and therefore consists of four exons and three introns. The GnRH-R1 and GnRH-R2 genes, both of which exist as single-copy genes in the medaka genome, were mapped to linkage groups 3 and 16, respectively. Inositol phosphate assays using COS-7 cells transfected with GnRH-R1 and GnRH-R2 demonstrated that they had remarkably different ligand sensitivities, although both receptors showed highest preference for chicken-II-type GnRH. Phylogenetic analysis showed the presence of three paralogous lineages for vertebrate GnRH-Rs and indicated that neither GnRH-R1 nor GnRH-R2 is the medaka ortholog to mammalian GnRH-Rs that lack a cytoplasmic tail. This, together with an observation that medaka-type GnRH had low affinity for GnRH-R1 and GnRH-R2, suggests that a third GnRH-R may exist in the medaka.
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Affiliation(s)
- K Okubo
- Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
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Abstract
G protein-coupled receptors (GPCRs) represent the largest family of signal-transducing molecules known. They convey signals for light and many extracellular regulatory molecules. GPCRs have been found to be dysfunctional/dysregulated in a growing number of human diseases and have been estimated to be the targets of more than 30% of the drugs used in clinical medicine today. Thus, understanding how GPCRs function at the molecular level is an important goal of biological research. In order to understand function at this level, it is necessary to delineate the 3D structure of these receptors. Recently, the 3D structure of rhodopsin has been resolved, but in the absence of experimentally determined 3D structures of other GPCRs, a powerful approach is to construct a theoretical model for the receptor and refine it based on experimental results. Computer-generated models for many GPCRs have been constructed. In this article, we will review these studies. We will place the greatest emphasis on an iterative, bi-directional approach in which models are used to generate hypotheses that are tested by experimentation and the experimental findings are, in turn, used to refine the model. The success of this approach is due to the synergistic interaction between theory and experiment.
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Affiliation(s)
- M C Gershengorn
- Division of Molecular Medicine (M.C.G.), Department of Medicine, Weill Medical College and Graduate School of Medical Sciences of Cornell University, New York, New York 10021, USA.
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