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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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2
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Yang X, Lin G, Xia A, Liu J, Zhang S, Zhou P, Wang Y, Zhang J, Zhou Y, Chen P, Wang Y, Zheng T, Li L, Yang S. Discovery of Small Molecule Agonist of Gonadotropin-Releasing Hormone Receptor (GnRH1R). J Chem Inf Model 2022; 62:5009-5022. [DOI: 10.1021/acs.jcim.2c00639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Affiliation(s)
- Xin Yang
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Guifeng Lin
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Anjie Xia
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Jingming Liu
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Shiyu Zhang
- Key Laboratory of Drug Targeting and Drug Delivery System of Ministry of Education, West China School of Pharmacy, Sichuan University, Sichuan 610041, China
| | - Pei Zhou
- Key Laboratory of Drug Targeting and Drug Delivery System of Ministry of Education, West China School of Pharmacy, Sichuan University, Sichuan 610041, China
| | - Yiwei Wang
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Jiahao Zhang
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Yangli Zhou
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Pei Chen
- Key Laboratory of Drug Targeting and Drug Delivery System of Ministry of Education, West China School of Pharmacy, Sichuan University, Sichuan 610041, China
| | - Yifei Wang
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Tao Zheng
- Engineering Research Center of Medical Information Technology, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Linli Li
- Key Laboratory of Drug Targeting and Drug Delivery System of Ministry of Education, West China School of Pharmacy, Sichuan University, Sichuan 610041, China
| | - Shengyong Yang
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
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3
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Arthur DE, Soliman ME, Adeniji SE, Adedirin O, Peter F. QSAR AND MOLECULAR DOCKING STUDY OF GONADOTROPIN-RELEASING HORMONE RECEPTOR INHIBITORS. SCIENTIFIC AFRICAN 2022. [DOI: 10.1016/j.sciaf.2022.e01291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022] Open
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4
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Toufaily C, Fortin J, Alonso CA, Lapointe E, Zhou X, Santiago-Andres Y, Lin YF, Cui Y, Wang Y, Devost D, Roelfsema F, Steyn F, Hanyaloglu AC, Hébert TE, Fiordelisio T, Boerboom D, Bernard DJ. Addition of a carboxy terminal tail to the normally tailless gonadotropin-releasing hormone receptor impairs fertility in female mice. eLife 2021; 10:72937. [PMID: 34939930 PMCID: PMC8741216 DOI: 10.7554/elife.72937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 12/06/2021] [Indexed: 11/13/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) is the primary neuropeptide controlling reproduction in vertebrates. GnRH stimulates follicle-stimulating hormone (FSH) and luteinizing hormone (LH) synthesis via a G-protein-coupled receptor, GnRHR, in the pituitary gland. In mammals, GnRHR lacks a C-terminal cytosolic tail (Ctail) and does not exhibit homologous desensitization. This might be an evolutionary adaptation that enables LH surge generation and ovulation. To test this idea, we fused the chicken GnRHR Ctail to the endogenous murine GnRHR in a transgenic model. The LH surge was blunted, but not blocked in these mice. In contrast, they showed reductions in FSH production, ovarian follicle development, and fertility. Addition of the Ctail altered the nature of agonist-induced calcium signaling required for normal FSH production. The loss of the GnRHR Ctail during mammalian evolution is unlikely to have conferred a selective advantage by enabling the LH surge. The adaptive significance of this specialization remains to be determined.
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Affiliation(s)
- Chirine Toufaily
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Jérôme Fortin
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Carlos Ai Alonso
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Evelyne Lapointe
- Département de biomédecine vétérinaire, Universite de Montreal, Ste-Hyacinthe, Canada
| | - Xiang Zhou
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Yorgui Santiago-Andres
- Departamento de Ecología y Recursos Naturales, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Yeu-Farn Lin
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Yiming Cui
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Ying Wang
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Dominic Devost
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Ferdinand Roelfsema
- Department of Internal Medicine, Leiden University Medical Center, Leiden, Netherlands
| | - Frederik Steyn
- School of Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - Aylin C Hanyaloglu
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, United Kingdom
| | - Terence E Hébert
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Tatiana Fiordelisio
- 3epartamento de Ecología y Recursos Naturales, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Derek Boerboom
- Département de biomédecine vétérinaire, Universite de Montreal, Ste-Hyacinthe, Canada
| | - Daniel J Bernard
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
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5
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Panknin O, Wagenfeld A, Bone W, Bender E, Nowak-Reppel K, Fernández-Montalván AE, Nubbemeyer R, Bäurle S, Ring S, Schmees N, Prien O, Schäfer M, Friedrich C, Zollner TM, Steinmeyer A, Mueller T, Langer G. Discovery and Characterization of BAY 1214784, an Orally Available Spiroindoline Derivative Acting as a Potent and Selective Antagonist of the Human Gonadotropin-Releasing Hormone Receptor as Proven in a First-In-Human Study in Postmenopausal Women. J Med Chem 2020; 63:11854-11881. [PMID: 32960053 DOI: 10.1021/acs.jmedchem.0c01076] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The growth of uterine fibroids is sex hormone-dependent and commonly associated with highly incapacitating symptoms. Most treatment options consist of the control of these hormonal effects, ultimately blocking proliferative estrogen signaling (i.e., oral contraceptives/antagonization of human gonadotropin-releasing hormone receptor [hGnRH-R] activity). Full hGnRH-R blockade, however, results in menopausal symptoms and affects bone mineralization, thus limiting treatment duration or demanding estrogen add-back approaches. To overcome such issues, we aimed to identify novel, small-molecule hGnRH-R antagonists. This led to the discovery of compound BAY 1214784, an orally available, potent, and selective hGnRH-R antagonist. Altering the geminal dimethylindoline core of the initial hit compound to a spiroindoline system significantly improved GnRH-R antagonist potencies across several species, mandatory for a successful compound optimization in vivo. In a first-in-human study in postmenopausal women, once daily treatment with BAY 1214784 effectively lowered plasma luteinizing hormone levels by up to 49%, at the same time being associated with low pharmacokinetic variability and good tolerability.
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Affiliation(s)
- Olaf Panknin
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Andrea Wagenfeld
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Wilhelm Bone
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Eckhard Bender
- Research & Development, Pharmaceuticals, Bayer AG, Aprather Weg 18a, 42113 Wuppertal, Germany
| | - Katrin Nowak-Reppel
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | | | - Reinhard Nubbemeyer
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Stefan Bäurle
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Sven Ring
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Norbert Schmees
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Olaf Prien
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Martina Schäfer
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Christian Friedrich
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Thomas M Zollner
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Andreas Steinmeyer
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
| | - Thomas Mueller
- Research & Development, Pharmaceuticals, Bayer AG, Aprather Weg 18a, 42113 Wuppertal, Germany
| | - Gernot Langer
- Research & Development, Pharmaceuticals, Bayer AG, Müllerstrasse 170, 13342 Berlin, Germany
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6
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Coss D. Regulation of reproduction via tight control of gonadotropin hormone levels. Mol Cell Endocrinol 2018; 463:116-130. [PMID: 28342855 PMCID: PMC6457911 DOI: 10.1016/j.mce.2017.03.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/16/2017] [Accepted: 03/21/2017] [Indexed: 01/04/2023]
Abstract
Mammalian reproduction is controlled by the hypothalamic-pituitary-gonadal axis. GnRH from the hypothalamus regulates synthesis and secretion of gonadotropins, LH and FSH, which then control steroidogenesis and gametogenesis. In females, serum LH and FSH levels exhibit rhythmic changes throughout the menstrual or estrous cycle that are correlated with pulse frequency of GnRH. Lack of gonadotropins leads to infertility or amenorrhea. Dysfunctions in the tightly controlled ratio due to levels slightly outside the normal range occur in a larger number of women and are correlated with polycystic ovaries and premature ovarian failure. Since the etiology of these disorders is largely unknown, studies in cell and mouse models may provide novel candidates for investigations in human population. Hence, understanding the mechanisms whereby GnRH regulates gonadotropin hormone levels will provide insight into the physiology and pathophysiology of the reproductive system. This review discusses recent advances in our understanding of GnRH regulation of gonadotropin synthesis.
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Affiliation(s)
- Djurdjica Coss
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA 92521, United States.
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7
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Wang C, Xu C, Liu M, Pan Y, Bai B, Chen J. C-terminus of OX2R significantly affects downstream signaling pathways. Mol Med Rep 2017; 16:159-166. [PMID: 28487995 PMCID: PMC5482145 DOI: 10.3892/mmr.2017.6557] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 03/30/2017] [Indexed: 12/11/2022] Open
Abstract
The human orexin 2 receptor (OX2R) is a G-protein‑coupled receptor (GPCR) that has been implicated in a number of diverse physiological functions. Recent studies have identified a number of functions of the C‑termini of GPCRs. However, the importance of the OX2R C‑terminus in regulating signaling and surface expression remains unclear. In the present study, the function of the OX2R C‑terminus was investigated using three C‑terminal mutants, which were truncated at residues 368, 384 and 414, respectively, and the wild‑type control, which expressed the full‑length OX2R. HEK‑293 cells were transfected with the mutated and control OX2R constructs. ELISA, western blot analysis and calcium assays were used to investigate the effects of the mutations on OX2R function. The present results demonstrated that residues 385‑414 and 415‑444 exhibited a cumulative effect on the surface expression of OX2R. Residues 369‑384 exhibited a significant influence on inositol phosphate production and extracellular signal‑regulated kinase 1/2 phosphorylation. Residues 385‑414 significantly influenced agonist‑induced internalization, whereas residues 369‑384 and 385‑414 significantly influenced Ca2+ release. The results of the present study suggest that the C‑terminus of OX2R is important for its role in various physiological and pathological processes, and may therefore be associated with such disorders as depression and anorexia.
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Affiliation(s)
- Chunmei Wang
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Chao Xu
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Minghui Liu
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Yanyou Pan
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Bo Bai
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Jing Chen
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
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Madziva MT, Mkhize NN, Flanagan CA, Katz AA. The carboxy-terminal tail or the intracellular loop 3 is required for β-arrestin-dependent internalization of a mammalian type II GnRH receptor. Mol Cell Endocrinol 2015; 411:187-97. [PMID: 25957085 DOI: 10.1016/j.mce.2015.04.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 04/08/2015] [Accepted: 04/29/2015] [Indexed: 10/23/2022]
Abstract
The type II GnRH receptor (GnRH-R2) in contrast to mammalian type I GnRH receptor (GnRH-R1) has a cytosolic carboxy-terminal tail. We investigated the role of β-arrestin 1 in GnRH-R2-mediated signalling and mapped the regions in GnRH-R2 required for recruitment of β-arrestin, employing internalization assays. We show that GnRH-R2 activation of ERK is dependent on β-arrestin and protein kinase C. Appending the tail of GnRH-R2 to GnRH-R1 enabled GRK- and β-arrestin-dependent internalization of the chimaeric receptor. Surprisingly, carboxy-terminally truncated GnRH-R2 retained β-arrestin and GRK-dependent internalization, suggesting that β-arrestin interacts with additional elements of GnRH-R2. Mutating serine and threonine or basic residues of intracellular loop 3 did not abolish β-arrestin 1-dependent internalization but a receptor lacking these basic residues and the carboxy-terminus showed no β-arrestin 1-dependent internalization. Our results suggest that basic residues at the amino-terminal end of intracellular loop 3 or the carboxy-terminal tail are required for β-arrestin dependent internalization.
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Affiliation(s)
- Michael T Madziva
- Medical Research Council Research Unit for Receptor Biology, Institute of Infectious Disease and Molecular Medicine and Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Observatory, 7925 Cape Town, South Africa; School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, 7 York Road, Parktown 2193, Johannesburg, South Africa
| | - Nonhlanhla N Mkhize
- Medical Research Council Research Unit for Receptor Biology, Institute of Infectious Disease and Molecular Medicine and Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Observatory, 7925 Cape Town, South Africa
| | - Colleen A Flanagan
- Medical Research Council Research Unit for Receptor Biology, Institute of Infectious Disease and Molecular Medicine and Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Observatory, 7925 Cape Town, South Africa; School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Medical School, 7 York Road, Parktown 2193, Johannesburg, South Africa
| | - Arieh A Katz
- Medical Research Council Research Unit for Receptor Biology, Institute of Infectious Disease and Molecular Medicine and Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Observatory, 7925 Cape Town, South Africa.
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Hothersall JD, Brown AJ, Dale I, Rawlins P. Can residence time offer a useful strategy to target agonist drugs for sustained GPCR responses? Drug Discov Today 2015; 21:90-96. [PMID: 26226643 DOI: 10.1016/j.drudis.2015.07.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 06/24/2015] [Accepted: 07/21/2015] [Indexed: 01/28/2023]
Abstract
Residence time describes the how long a ligand is bound to its target, and is attracting interest in drug discovery as a potential means of improving clinical efficacy by increasing target coverage. This concept, as originally applied to antagonists, is more complicated for G-protein-coupled receptor (GPCR) agonists because of the transiency of receptor responses (via desensitization and internalization). However, in some cases sustained GPCR agonist responses have been observed, with evidence consistent with a role for slow binding kinetics. We propose a model to explain our understanding of how residence time and rebinding might influence sustained signaling by internalized receptors. We also highlight the anticipated benefit for drug discovery of fully understanding and exploiting these phenomena to target desirable receptor response profiles selectively.
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Affiliation(s)
| | | | - Ian Dale
- AstraZeneca, Discovery Sciences, Cambridge Science Park, Cambridge CB4 0WG, UK
| | - Philip Rawlins
- AstraZeneca, Discovery Sciences, Cambridge Science Park, Cambridge CB4 0WG, UK.
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Hothersall JD, Bussey CE, Brown AJ, Scott JS, Dale I, Rawlins P. Sustained wash-resistant receptor activation responses of GPR119 agonists. Eur J Pharmacol 2015; 762:430-42. [PMID: 26101059 DOI: 10.1016/j.ejphar.2015.06.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 06/15/2015] [Accepted: 06/16/2015] [Indexed: 12/16/2022]
Abstract
G protein-coupled receptor 119 (GPR119) is involved in regulating metabolic homoeostasis, with GPR119 agonists targeted for the treatment of type-2 diabetes and obesity. Using the endogenous agonist oleoylethanolamide and a number of small molecule synthetic agonists we have investigated the temporal dynamics of receptor signalling. Using both a dynamic luminescence biosensor-based assay and an endpoint cAMP accumulation assay we show that agonist-driven desensitization is not a major regulatory mechanism for GPR119 despite robust activation responses, regardless of the agonist used. Temporal analysis of the cAMP responses demonstrated sustained signalling resistant to washout for some, but not all of the agonists tested. Further analysis indicated that the sustained effects of one synthetic agonist AR-231,453 were consistent with a role for slow dissociation kinetics. In contrast, the sustained responses to MBX-2982 and AZ1 appeared to involve membrane deposition. We also detect wash-resistant responses to AR-231,453 at the level of physiologically relevant responses in an endogenous expression system (GLP-1 secretion in GLUTag cells). In conclusion, our findings indicate that in a recombinant expression system GPR119 activation is sustained, with little evidence of pronounced receptor desensitization, and for some ligands persistent agonist responses continue despite removal of excess agonist. This provides novel understanding of the temporal responses profiles of potential drug candidates targetting GPR119, and highlights the importance of carefully examining the the mechanisms through which GPCRs generate sustained responses.
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Affiliation(s)
| | | | - Alastair J Brown
- AstraZeneca, Alderley Park, Macclesfield SK10 4TG, UK; Heptares Therapeutics Limited, Welwyn Garden City AL7 3AX, UK
| | - James S Scott
- AstraZeneca, Alderley Park, Macclesfield SK10 4TG, UK
| | - Ian Dale
- AstraZeneca, Cambridge Science Park, Cambridge CB4 0WG, UK
| | - Philip Rawlins
- AstraZeneca, Cambridge Science Park, Cambridge CB4 0WG, UK
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11
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Williams BL, Akazome Y, Oka Y, Eisthen HL. Dynamic evolution of the GnRH receptor gene family in vertebrates. BMC Evol Biol 2014; 14:215. [PMID: 25344287 PMCID: PMC4232701 DOI: 10.1186/s12862-014-0215-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 09/25/2014] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Elucidating the mechanisms underlying coevolution of ligands and receptors is an important challenge in molecular evolutionary biology. Peptide hormones and their receptors are excellent models for such efforts, given the relative ease of examining evolutionary changes in genes encoding for both molecules. Most vertebrates possess multiple genes for both the decapeptide gonadotropin releasing hormone (GnRH) and for the GnRH receptor. The evolutionary history of the receptor family, including ancestral copy number and timing of duplications and deletions, has been the subject of controversy. RESULTS We report here for the first time sequences of three distinct GnRH receptor genes in salamanders (axolotls, Ambystoma mexicanum), which are orthologous to three GnRH receptors from ranid frogs. To understand the origin of these genes within the larger evolutionary context of the gene family, we performed phylogenetic analyses and probabilistic protein homology searches of GnRH receptor genes in vertebrates and their near relatives. Our analyses revealed four points that alter previous views about the evolution of the GnRH receptor gene family. First, the "mammalian" pituitary type GnRH receptor, which is the sole GnRH receptor in humans and previously presumed to be highly derived because it lacks the cytoplasmic C-terminal domain typical of most G-protein coupled receptors, is actually an ancient gene that originated in the common ancestor of jawed vertebrates (Gnathostomata). Second, unlike previous studies, we classify vertebrate GnRH receptors into five subfamilies. Third, the order of subfamily origins is the inverse of previous proposed models. Fourth, the number of GnRH receptor genes has been dynamic in vertebrates and their ancestors, with multiple duplications and losses. CONCLUSION Our results provide a novel evolutionary framework for generating hypotheses concerning the functional importance of structural characteristics of vertebrate GnRH receptors. We show that five subfamilies of vertebrate GnRH receptors evolved early in the vertebrate phylogeny, followed by several independent instances of gene loss. Chief among cases of gene loss are humans, best described as degenerate with respect to GnRH receptors because we retain only a single, ancient gene.
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12
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Thompson IR, Kaiser UB. GnRH pulse frequency-dependent differential regulation of LH and FSH gene expression. Mol Cell Endocrinol 2014; 385:28-35. [PMID: 24056171 PMCID: PMC3947649 DOI: 10.1016/j.mce.2013.09.012] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 09/10/2013] [Accepted: 09/10/2013] [Indexed: 12/14/2022]
Abstract
The pituitary gonadotropin hormones, FSH and LH, are essential for fertility. Containing an identical α-subunit (CGA), they are comprised of unique β-subunits, FSHβ and LHβ, respectively. These two hormones are regulated by the hypothalamic decapeptide, GnRH, which is released in a pulsatile manner from GnRH neurons located in the hypothalamus. Varying frequencies of pulsatile GnRH stimulate distinct signaling pathways and transcriptional machinery after binding to the receptor, GnRHR, on the cell surface of anterior pituitary gonadotropes. This ligand-receptor binding and activation orchestrates the synthesis and release of FSH and LH, in synergy with other effectors of gonadotropin production, such as activin, inhibin and steroids. Current research efforts aim to discover the mechanisms responsible for the decoding of the GnRH pulse signal by the gonadotrope. Modulating the response to GnRH has the potential to lead to new therapies for patients with altered gonadotropin secretion, such as those with hypothalamic amenorrhea or polycystic ovarian syndrome.
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Affiliation(s)
- Iain R Thompson
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Ursula B Kaiser
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, United States.
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13
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Ortmann O, Weiss JM, Diedrich K. Gonadotrophin-releasing hormone (GnRH) and GnRH agonists: mechanisms of action. Reprod Biomed Online 2013; 5 Suppl 1:1-7. [PMID: 12537774 DOI: 10.1016/s1472-6483(11)60210-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hypothalamic decapeptide gonadotrophin-releasing hormone (GnRH) binds to specific receptors on pituitary gonadotrophs. These receptors belong to the family of G protein-coupled receptors. Their activation leads to phosphoinositide breakdown with generation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and diacylglycerol. These second messengers initiate Ca2+ release from intracellular stores and activation of protein kinase C, both of which are important for gonadotrophin secretion and synthesis. Prolonged activation of GnRH receptors by GnRH leads to desensitization and consequently to suppressed gonadotrophin secretion. This is the primary mechanism of action of agonistic GnRH analogues. By contrast, GnRH antagonists compete with GnRH for receptors on gonadotroph cell membranes, inhibit GnRH-induced signal transduction and consequently gonadotrophin secretion. These compounds are free of agonistic actions, which might be beneficial in certain clinical applications.
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Affiliation(s)
- O Ortmann
- Department of Obstetrics and Gynecology, Medical University of Lübeck, 23538 Lübeck, Germany.
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Avet C, Garrel G, Denoyelle C, Laverrière JN, Counis R, Cohen-Tannoudji J, Simon V. SET protein interacts with intracellular domains of the gonadotropin-releasing hormone receptor and differentially regulates receptor signaling to cAMP and calcium in gonadotrope cells. J Biol Chem 2012; 288:2641-54. [PMID: 23233674 DOI: 10.1074/jbc.m112.388876] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In mammals, the receptor of the neuropeptide gonadotropin-releasing hormone (GnRHR) is unique among the G protein-coupled receptor (GPCR) family because it lacks the carboxyl-terminal tail involved in GPCR desensitization. Therefore, mechanisms involved in the regulation of GnRHR signaling are currently poorly known. Here, using immunoprecipitation and GST pull-down experiments, we demonstrated that SET interacts with GnRHR and targets the first and third intracellular loops. We delineated, by site-directed mutagenesis, SET binding sites to the basic amino acids (66)KRKK(69) and (246)RK(247), located next to sequences required for receptor signaling. The impact of SET on GnRHR signaling was assessed by decreasing endogenous expression of SET with siRNA in gonadotrope cells. Using cAMP and calcium biosensors in gonadotrope living cells, we showed that SET knockdown specifically decreases GnRHR-mediated mobilization of intracellular cAMP, whereas it increases its intracellular calcium signaling. This suggests that SET influences signal transfer between GnRHR and G proteins to enhance GnRHR signaling to cAMP. Accordingly, complexing endogenous SET by introduction of the first intracellular loop of GnRHR in αT3-1 cells significantly reduced GnRHR activation of the cAMP pathway. Furthermore, decreasing SET expression prevented cAMP-mediated GnRH stimulation of Gnrhr promoter activity, highlighting a role of SET in gonadotropin-releasing hormone regulation of gene expression. In conclusion, we identified SET as the first direct interacting partner of mammalian GnRHR and showed that SET contributes to a switch of GnRHR signaling toward the cAMP pathway.
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Affiliation(s)
- Charlotte Avet
- Université Paris Diderot, Sorbonne Paris Cité, Biologie Fonctionnelle et Adaptative, Equipe Physiologie de l'Axe Gonadotrope, Case Courrier 7007, CNRS-EAC 4413, 4 Rue MA Lagroua Weill Hallé, 75013 Paris, France
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15
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Caunt CJ, Perett RM, Fowkes RC, McArdle CA. Mechanisms of GnRH-induced extracellular signal-regulated kinase nuclear localization. PLoS One 2012; 7:e40077. [PMID: 22808094 PMCID: PMC3395631 DOI: 10.1371/journal.pone.0040077] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 06/05/2012] [Indexed: 12/11/2022] Open
Abstract
Gonadotropin-releasing hormone receptors (GnRHR) mediate activation and nuclear translocation of the extracellular signal regulated kinases 1 and 2 (ERK) by phosphorylation on the TEY motif. This is necessary for GnRH to initiate transcriptional programmes controlling fertility, but mechanisms that govern ERK targeting are unclear. Using automated microscopy to explore ERK regulation in single cells, we find that GnRHR activation induces marked redistribution of ERK to the nucleus and that this effect can be uncoupled from the level of TEY phosphorylation of ERK. Thus, 5 min stimulation with 100 nM GnRH increased phospho-ERK levels (from 89 ± 34 to 555 ± 45 arbitrary fluorescence units) and increased the nuclear:cytoplasmic (N:C) ERK ratio (from 1.36 ± 0.06 to 2.16 ± 0.05) in the whole cell population, but it also significantly increased N:C ERK in cells binned according to phospho-ERK levels. This phosphorylation unattributable component of the ERK translocation response occurs at a broad range of GnRHR expression levels, in the presence of tyrosine phosphatase and protein synthesis inhibitors, and in ERK mutants unable to undergo catalytic activation. It also occurred in mutants incapable of binding the DEF (docking site for ERK, F/Y-X-F/Y-P) domains found in many ERK binding partners. It was however, reduced by MEK or PKC inhibition and by mutations preventing TEY phosphorylation or that abrogate ERK binding to D (docking) domain partners. We therefore show that TEY phosphorylation of ERK is necessary, but not sufficient for the full nuclear localization response. We further show that this "phosphorylation unattributable" component of GnRH-mediated ERK nuclear translocation requires both PKC activity and association with partner proteins via the D-domain.
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Affiliation(s)
- Christopher J. Caunt
- Department of Biology and Biochemistry, University of Bath, Bath, United Kingdom
| | - Rebecca M. Perett
- School of Clinical Sciences, University of Bristol, Bristol, United Kingdom
| | - Robert C. Fowkes
- Endocrine Signaling Group, Royal Veterinary College, London, United Kingdom
| | - Craig A. McArdle
- School of Clinical Sciences, University of Bristol, Bristol, United Kingdom
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16
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Cohen-Tannoudji J, Avet C, Garrel G, Counis R, Simon V. Decoding high Gonadotropin-releasing hormone pulsatility: a role for GnRH receptor coupling to the cAMP pathway? Front Endocrinol (Lausanne) 2012; 3:107. [PMID: 22969749 PMCID: PMC3431540 DOI: 10.3389/fendo.2012.00107] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 08/15/2012] [Indexed: 01/06/2023] Open
Abstract
The gonadotropin-releasing hormone (GnRH) pulsatile pattern is critical for appropriate regulation of gonadotrope activity but only little is known about the signaling mechanisms by which gonadotrope cells decode such pulsatile pattern. Here, we review recent lines of evidence showing that the GnRH receptor (GnRH-R) activates the cyclic AMP (cAMP) pathway in gonadotrope cells, thus ending a long-lasting controversy. Interestingly, coupling of GnRH-R to the cAMP pathway as well as induction of nitric oxide synthase 1 (NOS1) or follistatin through this signaling pathway take place preferentially under high GnRH pulsatility. The preovulatory surge of GnRH in vivo is indeed associated with an important increase of pituitary cAMP and NOS1 expression levels, both being markedly inhibited by treatment with a GnRH antagonist. Altogether, this suggests that due to its atypical structure and desensitization properties, the GnRH-R may continue to signal through the cAMP pathway under conditions inducing desensitization for most other receptors. Such a mechanism may contribute to decode high GnRH pulsatile pattern and enable gonadotrope cell plasticity during the estrus cycle.
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Affiliation(s)
- Joëlle Cohen-Tannoudji
- *Correspondence: Joëlle Cohen-Tannoudji, Equipe Physiologie de l’Axe Gonadotrope, Unité de Biologie Fonctionnelle et Adaptative, CNRS-EAC 4413, Sorbonne Paris Cité, Université Paris Diderot-Paris 7, Case courrier 7007, 4 rue Marie-Andrée Lagroua- Weill-Hallé, 75013 Paris, France. e-mail:
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17
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Crawford JL, McLeod BJ, Eckery DC. The hypothalamic-pituitary-ovarian axis and manipulations of the oestrous cycle in the brushtail possum. Gen Comp Endocrinol 2011; 170:424-48. [PMID: 21074534 DOI: 10.1016/j.ygcen.2010.10.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 10/31/2010] [Indexed: 11/23/2022]
Abstract
The main purpose of this review is to provide a comprehensive update on what is known about the regulatory mechanisms of the hypothalamic-pituitary-ovarian axis in the brushtail possum, and to report on the outcomes of attempts made to manipulate by hormonal means, these processes in the possum. Over the last 15 years, several unique features of possum reproductive physiology have been discovered. These include an extended follicular phase despite elevated concentrations of FSH during the luteal phase, and early expression of LH receptors on granulosa cells of small antral follicles, suggesting a different mechanism for the selection of a dominant follicle. The use of routine synchronisation protocols that are effective in eutherians has failed to be effective in possums, and so the ability to reliably synchronise oestrus in this species remains a challenge.
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Affiliation(s)
- Janet L Crawford
- School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
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Armstrong S, Caunt C, Finch A, McArdle C. Using automated imaging to interrogate gonadotrophin-releasing hormone receptor trafficking and function. Mol Cell Endocrinol 2011; 331:194-204. [PMID: 20688134 PMCID: PMC3021717 DOI: 10.1016/j.mce.2010.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 05/07/2010] [Accepted: 07/13/2010] [Indexed: 01/03/2023]
Abstract
Gonadotrophin-releasing hormone (GnRH) acts via seven transmembrane receptors on gonadotrophs to stimulate gonadotrophin synthesis and secretion, and thereby mediates central control of reproduction. Type I mammalian GnRHR are unique, in that they lack C-terminal tails. This is thought to underlie their resistance to rapid homologous desensitisation as well as their slow rate of internalisation and inability to provoke G-protein-independent (arrestin-mediated) signalling. More recently it has been discovered that the vast majority of human GnRHR are actually intracellular, in spite of the fact that they are activated at the cell surface by a membrane impermeant peptide hormone. This apparently reflects inefficient exit from the endoplasmic reticulum and again, the absence of the C-tail likely contributes to their intracellular localisation. This review is intended to cover some of these novel aspects of GnRHR biology, focusing on ways that we have used automated fluorescence microscopy (high content imaging) to explore GnRHR localisation and trafficking as well as spatial and temporal aspects of GnRH signalling via the Ca(2+)/calmodulin/calcineurin/NFAT and Raf/MEK/ERK pathways.
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Affiliation(s)
- S.P. Armstrong
- University of Bristol, School of Clinical Sciences, Labs. for Integrative Neuroscience and Endocrinology, 1 Whitson Street, Bristol BS1 3NY, UK
| | - C.J. Caunt
- Department of Biology & Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - A.R. Finch
- University of Bristol, School of Clinical Sciences, Labs. for Integrative Neuroscience and Endocrinology, 1 Whitson Street, Bristol BS1 3NY, UK
| | - C.A. McArdle
- University of Bristol, School of Clinical Sciences, Labs. for Integrative Neuroscience and Endocrinology, 1 Whitson Street, Bristol BS1 3NY, UK
- Corresponding author.
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Walker JJ, Terry JR, Tsaneva-Atanasova K, Armstrong SP, McArdle CA, Lightman SL. Encoding and decoding mechanisms of pulsatile hormone secretion. J Neuroendocrinol 2010; 22:1226-38. [PMID: 21054582 DOI: 10.1111/j.1365-2826.2010.02087.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Ultradian pulsatile hormone secretion underlies the activity of most neuroendocrine systems, including the hypothalamic-pituitary adrenal (HPA) and gonadal (HPG) axes, and this pulsatile mode of signalling permits the encoding of information through both amplitude and frequency modulation. In the HPA axis, glucocorticoid pulse amplitude increases in anticipation of waking, and, in the HPG axis, changing gonadotrophin-releasing hormone pulse frequency is the primary means by which the body alters its reproductive status during development (i.e. puberty). The prevalence of hormone pulsatility raises two crucial questions: how are ultradian pulses encoded (or generated) by these systems, and how are these pulses decoded (or interpreted) at their target sites? We have looked at mechanisms within the HPA axis responsible for encoding the pulsatile mode of glucocorticoid signalling that we observe in vivo. We review evidence regarding the 'hypothalamic pulse generator' hypothesis, and describe an alternative model for pulse generation, which involves steroid feedback-dependent endogenous rhythmic activity throughout the HPA axis. We consider the decoding of hormone pulsatility by taking the HPG axis as a model system and focussing on molecular mechanisms of frequency decoding by pituitary gonadotrophs.
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Affiliation(s)
- J J Walker
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, UK.
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Bliss SP, Navratil AM, Xie J, Roberson MS. GnRH signaling, the gonadotrope and endocrine control of fertility. Front Neuroendocrinol 2010; 31:322-40. [PMID: 20451543 PMCID: PMC2923852 DOI: 10.1016/j.yfrne.2010.04.002] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2010] [Revised: 04/26/2010] [Accepted: 04/30/2010] [Indexed: 11/28/2022]
Abstract
Mammalian reproductive cycles are controlled by an intricate interplay between the hypothalamus, pituitary and gonads. Central to the function of this axis is the ability of the pituitary gonadotrope to appropriately respond to stimulation by gonadotropin-releasing hormone (GnRH). This review focuses on the role of cell signaling and in particular, mitogen-activated protein kinase (MAPK) activities regulated by GnRH that are necessary for normal fertility. Recently, new mouse models making use of conditional gene deletion have shed new light on the relationships between GnRH signaling and fertility in both male and female mice. Within the reproductive axis, GnRH signaling is initiated through discrete membrane compartments in which the receptor resides leading to the activation of the extracellular signal-regulated kinases (ERKs 1/2). As defined by gonadotrope-derived cellular models, the ERKs appear to play a central role in the regulation of a cohort of immediate early genes that regulate the expression of late genes that, in part, define the differentiated character of the gonadotrope. Recent data would suggest that in vivo, conditional, pituitary-specific disruption of ERK signaling by GnRH leads to a gender-specific perturbation of fertility. Double ERK knockout in the anterior pituitary leads to female infertility due to LH biosynthesis deficiency and a failure in ovulation. In contrast, male mice are modestly LH deficient; however, this does not have an appreciable impact on fertility.
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Affiliation(s)
- Stuart P Bliss
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, United States
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21
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Fink MY, Pincas H, Choi SG, Nudelman G, Sealfon SC. Research resource: Gonadotropin-releasing hormone receptor-mediated signaling network in LbetaT2 cells: a pathway-based web-accessible knowledgebase. Mol Endocrinol 2010; 24:1863-71. [PMID: 20592162 DOI: 10.1210/me.2009-0530] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The GnRH receptor (GnRHR), expressed at the cell surface of the anterior pituitary gonadotrope, is critical for normal secretion of gonadotropins LH and FSH, pubertal development, and reproduction. The signaling network downstream of the GnRHR and the molecular bases of the regulation of gonadotropin expression have been the subject of intense research. The murine LbetaT2 cell line represents a mature gonadotrope and therefore is an important model for the study of GnRHR-signaling pathways and modulation of the gonadotrope cell by physiological regulators. In order to facilitate access to the information contained in this complex and evolving literature, we have developed a pathway-based knowledgebase that is web hosted. At present, using 106 relevant primary publications, we curated a comprehensive knowledgebase of the GnRHR signaling in the LbetaT2 cell in the form of a process diagram. Positive and negative controls of gonadotropin gene expression, which included GnRH itself, hypothalamic factors, gonadal steroids and peptides, as well as other hormones, were illustrated. The knowledgebase contains 187 entities and 206 reactions. It was assembled using CellDesigner software, which provides an annotated graphic representation of interactions, stored in Systems Biology Mark-up Language. We then utilized Biological Pathway Publisher, a software suite previously developed in our laboratory, to host the knowledgebase in a web-accessible format as a public resource. In addition, the network entities were linked to a public wiki, providing a forum for discussion, updating, and error correction. The GnRHR-signaling network is openly accessible at http://tsb.mssm.edu/pathwayPublisher/GnRHR_Pathway/GnRHR_Pathway_ index.html.
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Affiliation(s)
- Marc Y Fink
- Center for Translational Systems Biology and Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029, USA
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22
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Armstrong SP, Caunt CJ, Fowkes RC, Tsaneva-Atanasova K, McArdle CA. Pulsatile and sustained gonadotropin-releasing hormone (GnRH) receptor signaling: does the ERK signaling pathway decode GnRH pulse frequency? J Biol Chem 2010; 285:24360-71. [PMID: 20507982 PMCID: PMC2915671 DOI: 10.1074/jbc.m110.115964] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) acts via G-protein-coupled receptors on gonadotrophs to stimulate synthesis and secretion of luteinizing hormone and follicle-stimulating hormone. It is secreted in pulses, and its effects depend on pulse frequency, but decoding mechanisms are unknown. Here we have used an extracellular signal regulated kinase-green fluorescent protein (ERK2-GFP) reporter to monitor GnRH signaling. GnRH caused dose-dependent ERK2-GFP translocation to the nucleus, providing a live-cell readout for activation. Pulsatile GnRH caused dose- and frequency-dependent ERK2-GFP translocation. These responses were rapid and transient, showed only digital tracking, and did not desensitize under any condition tested (dose, frequency, and receptor number varied). We also tested for the effects of cycloheximide (to prevent induction of nuclear-inducible MAPK phosphatases) and used GFP fusions containing ERK mutations (D319N, which prevents docking domain-dependent binding to MAPK phosphatases, and K52R, which prevents catalytic activity). These manipulations had little or no effect on the translocation responses, arguing against a role for MAPK phosphatases or ERK-mediated feedback in shaping ERK activation during pulsatile stimulation. GnRH also caused dose- and frequency-dependent activation of the alpha-gonadotropin subunit-, luteinizing hormone beta-, and follicle-stimulating hormone beta- luciferase reporters, and the latter response was inhibited by ERK1/2 knockdown. Moreover, GnRH caused frequency-dependent activation of an Egr1-luciferase reporter, but the response was proportional to cumulative pulse duration. Our data suggest that frequency decoding is not due to negative feedback shaping ERK signaling in this model.
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Affiliation(s)
- Stephen P Armstrong
- Laboratories for Integrative Neuroscience and Endocrinology, Department of Clinical Sciences at South Bristol, University of Bristol, Whitson Street, Bristol BS1 3NY, United Kingdom
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Tsutsumi R, Mistry D, Webster NJG. Signaling responses to pulsatile gonadotropin-releasing hormone in LbetaT2 gonadotrope cells. J Biol Chem 2010; 285:20262-72. [PMID: 20406815 DOI: 10.1074/jbc.m110.132662] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH) is secreted in a pulsatile fashion by hypothalamic neurons, and alterations in pulse frequency and amplitude differentially regulate gonadotropin synthesis and release. In this study, we investigated the kinetics of G(s) and G(q) signaling in response to continuous or pulsatile GnRH using fluorescence resonance energy transfer reporters in live mouse LbetaT2 gonadotrope cells. cAMP and protein kinase A-dependent reporters showed a rapid but transient increase in fluorescence resonance energy transfer signal with increasing doses of constant GnRH, and in contrast diacylglycerol (DAG) and calcium reporters showed a rapid and sustained signal. Multiple pulses of GnRH caused multiple pulses of cAMP and protein kinase A activation without desensitization, but the DAG and calcium reporters were rapidly desensitized resulting in inhibition of calcium and DAG responses. At the transcriptional level, both a cAMP-dependent cAMP-response element reporter and a DAG/calcium-dependent AP-1 reporter showed a pulse frequency-dependent increase in luciferase activity. However, constant GnRH stimulation gave very little cAMP-response element activation but very strong AP-1 activation. Based on these data, we propose that both the GnRH-R-G(s) and G(q) pathways are responsive to pulses of GnRH, but only the G(q) pathway is responsive to constant GnRH. Furthermore, the G(q) pathway is subject to desensitization with multiple GnRH pulses, but the G(s) pathway is not.
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Affiliation(s)
- Rie Tsutsumi
- Medical Research Service, Veterans Affairs San Diego Healthcare System, San Diego, California 92161, USA
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Armstrong SP, Caunt CJ, Fowkes RC, Tsaneva-Atanasova K, McArdle CA. Pulsatile and sustained gonadotropin-releasing hormone (GnRH) receptor signaling: does the Ca2+/NFAT signaling pathway decode GnRH pulse frequency? J Biol Chem 2010; 284:35746-57. [PMID: 19858197 PMCID: PMC2791005 DOI: 10.1074/jbc.m109.063917] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) acts via 7 transmembrane region receptors on gonadotrophs to stimulate synthesis and secretion of the luteinizing hormone and follicle-stimulating hormone. It is secreted in pulses, and its effects depend on pulse frequency, but decoding mechanisms are unknown. Here we have used (nuclear factor of activated T-cells 2 (NFAT2)-emerald fluorescent protein) to monitor GnRH signaling. Increasing [Ca2+]i causes calmodulin/calcineurin-dependent nuclear NFAT translocation, a response involving proteins (calmodulins and NFATs) that decode frequency in other systems. Using live cell imaging, pulsatile GnRH caused dose- and frequency-dependent increases in nuclear NFAT2-emerald fluorescent protein, and at low frequency, translocation simply tracked GnRH exposure (albeit with slower kinetics). At high frequency (30-min intervals), failure to return to basal conditions before repeat stimulation caused integrative tracking, illustrating how the relative dynamics of up- and downstream signals can increase efficiency of GnRH action. Mathematical modeling predicted desensitization of GnRH effects on [Ca2+]i and that desensitization would increase with dose, frequency, and receptor number, but no such desensitization was seen in HeLa and/or LβT2 cells possibly because pulsatile GnRH did not reduce receptor expression (measured by immunofluorescence). GnRH also caused dose- and frequency-dependent activation of αGSU, luteinizing hormone β, and follicle-stimulating hormone β luciferase reporters, effects that were blocked by calcineurin inhibition. Pulsatile GnRH also activated an NFAT-responsive luciferase reporter, but this response was directly related to cumulative pulse duration. This together with the lack of desensitization of translocation responses suggests that NFAT may mediate GnRH action but is not a genuine decoder of GnRH pulse frequency.
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Affiliation(s)
- Stephen P Armstrong
- Laboratories for Integrative Neuroscience and Endocrinology, Department of Clinical Science at South Bristol, University of Bristol, Whitson Street, Bristol BS1 3NY
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Abstract
PURPOSE OF REVIEW To discuss recent progress in our understanding of pituitary gonadotroph development and gonadotropin gene regulation, with an emphasis on differential luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion and subunit synthesis, and the implications this may have on female reproductive health. RECENT FINDINGS In the mature gonadotroph, there is an emerging concept that differential synthesis of gonadotropin beta-subunit genes, essential for cyclic reproductive function, is associated with modification of activation and/or stability of important regulatory proteins and transcription factors. Recent studies suggest that cellular events, which affect histone modification, play an essential role in both gonadotroph development and the ontogeny of gonadotropin subunit gene expression. Such dynamic events are under the orchestration of the hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH), potentially through the ability of GnRH to activate several distinct signaling cascades within the gonadotroph. SUMMARY Greater insight into the cellular events that are key to gonadotroph physiology will contribute to our understanding of abnormal gonadotropin secretion in disorders such as hypothalamic amenorrhea and polycystic ovarian syndrome (PCOS), and provide a context for the design of novel therapeutic approaches.
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Affiliation(s)
- Nick A Ciccone
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital and Harvard Medical School, 221 Longwood Avenue, Boston, Massachusetts 02115, USA
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Signaling by G-protein-coupled receptor (GPCR): studies on the GnRH receptor. Front Neuroendocrinol 2009; 30:10-29. [PMID: 18708085 DOI: 10.1016/j.yfrne.2008.07.001] [Citation(s) in RCA: 199] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Revised: 04/28/2008] [Accepted: 07/21/2008] [Indexed: 01/22/2023]
Abstract
Gonadotropin-releasing hormone (GnRH) is the first key hormone of reproduction. GnRH analogs are extensively used in in vitro fertilization, and treatment of sex hormone-dependent cancers, due to their ability to bring about 'chemical castration'. The interaction of GnRH with its cognate type I receptor (GnRHR) in pituitary gonadotropes results in the activation of Gq/G(11), phospholipase Cbeta (PLCbetaI), PLA(2), and PLD. Sequential activation of the phospholipases generates the second messengers inositol 1, 4, 5-trisphosphate (IP(3)), diacylglycerol (DAG), and arachidonic acid (AA), which are required for Ca(2+) mobilization, the activation of various protein kinase C isoforms (PKCs), and the production of prostaglandin (PG) and other metabolites of AA, respectively. PKC isoforms are the major mediators of the downstream activation of a number of mitogen-activated protein kinase (MAPK) cascades by GnRH, namely: extracellular signal-regulated kinase (ERK), jun-N-terminal kinase (JNK), and p38MAPK. The activated MAPKs phosphorylate both cytosolic and nuclear proteins to initiate the transcriptional activation of the gonadotropin subunit genes and the GnRHR. While Ca(2+) mobilization has been found to initiate rapid gonadotropin secretion, Ca(2+), together with various PKC isoforms, MAPKs and AA metabolites also serve as key nodes, in the GnRH-stimulated signaling network that enables the gonadotropes to decode GnRH pulse frequencies and translating that into differential gonadotropin synthesis and release. Even though pulsatility of GnRH is recognized as a major determinant for differential gonadotropin subunit gene expression and gonadotropin secretion very little is yet known about the signaling circuits governing GnRH action at the 'Systems Biology' level. Direct apoptotic and metastatic effects of GnRH analogs in gonadal steroid-dependent cancers expressing the GnRHR also seem to be mediated by the activation of the PKC/MAPK pathways. However, the mechanisms dictating life (pituitary) vs. death (cancer) decisions made by the same GnRHR remain elusive. Understanding these molecular mechanisms triggered by the GnRHR through biochemical and 'Systems Biology' approaches would provide the basis for the construction of the dynamic connectivity maps, which operate in the various cell types (endocrine, cancer, and immune system) targeted by GnRH. The connectivity maps will open a new vista for exploring the direct effects of GnRH analogs in tumors and the design of novel combined therapies for fertility control, reproductive disorders and cancers.
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27
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Larivière S, Garrel-Lazayres G, Simon V, Shintani N, Baba A, Counis R, Cohen-Tannoudji J. Gonadotropin-releasing hormone inhibits pituitary adenylyl cyclase-activating polypeptide coupling to 3',5'-cyclic adenosine-5'-monophosphate pathway in LbetaT2 gonadotrope cells through novel protein kinase C isoforms and phosphorylation of pituitary adenylyl cyclase-activating polypeptide type I receptor. Endocrinology 2008; 149:6389-98. [PMID: 18755795 DOI: 10.1210/en.2008-0504] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Gonadotrope cells are primarily regulated by GnRH but are also targets of the pituitary adenylyl cyclase-activating polypeptide (PACAP). Although it has been reported that reciprocal interactions between both neuropeptides contribute to regulation of gonadotrope function, the underlying mechanisms remain poorly understood. In this study, we reevaluated PACAP coupling to the cAMP pathway in LbetaT2 gonadotrope cells and analyzed GnRH effect on PACAP signaling. We established that PACAP38 markedly increases intracellular cAMP levels (EC50 of 4.7 +/- 1.3 nm) through the PACAP type 1 receptor (PAC1-R), as evidenced by pharmacological and RT-PCR studies. Interestingly, although GnRH couples to cAMP pathway in LbetaT2 cells, the effects of both neuropeptides were not synergistic. Instead, the GnRH agonist (GnRHa) triptorelin rapidly and strongly inhibited (70% inhibition as early as 5 min) PACAP38-induced cAMP production. Inhibition was calcium independent, mimicked by the phorbol ester phorbol 12-myristate 13-acetate, and blocked by the protein kinase C (PKC) inhibitor bisindoylmaleimide, indicating that GnRHa inhibitory action relies on PKC. Selective down-regulation of both conventional and novel PKC prevented a GnRHa effect, whereas pharmacological inhibition of conventional PKC only was ineffective, strongly suggesting the involvement of novel PKC isoforms. GnRHa did not inhibit forskolin- or cholera toxin-stimulated cAMP accumulation, suggesting that PAC1-R is the predominant target of GnRH. Accordingly, we demonstrated for the first time that GnRH increases PAC1-R phosphorylation through PKC, providing a potential molecular mechanism which may account for GnRH inhibitory effect.
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Affiliation(s)
- Sigolène Larivière
- Unité Mixte de Recherche-Centre National de la Recherche Scientifique 7079 Physiologie and Physiopathologie, Université Pierre and Marie Curie-Paris 6, Case 256, 4 Place Jussieu, 75252 Paris cedex 05, France
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Karakoula A, Tovey SC, Brighton PJ, Willars GB. Lack of receptor-selective effects of either RGS2, RGS3 or RGS4 on muscarinic M3- and gonadotropin-releasing hormone receptor-mediated signalling through G alpha q/11. Eur J Pharmacol 2008; 587:16-24. [PMID: 18457830 DOI: 10.1016/j.ejphar.2008.03.047] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 02/26/2008] [Accepted: 03/10/2008] [Indexed: 10/22/2022]
Abstract
Termination of signalling by G-protein-coupled receptors requires inactivation of the G alpha-subunits of heterotrimeric G-proteins and the re-association of G alpha- and G betagamma-subunits. Inactivation of G alpha-subunits is achieved by the hydrolysis of bound GTP by an intrinsic GTPase activity, which is considerably enhanced by GTPase activating proteins. Regulators of G-protein signalling (RGS) proteins are a large family of GTPase activating proteins, many of which have structures indicating roles beyond GTPase activating protein activity and suggesting that the identity of the RGS protein recruited may also be critical to other aspects of signalling. There is some evidence of selective effects of RGS proteins against different G-protein-coupled receptors coupling to the same signalling pathways and growing evidence of physical interactions between RGS proteins and G-protein-coupled receptors. However, it is unclear as to how common such interactions are and the circumstances under which they are functionally relevant. Here we have examined potential selectivity of RGS2, 3 and 4 against signalling mediated by G alpha q/11-coupled muscarinic M3 receptors and gonadotropin-releasing hormone in an immortalised mouse pituitary cell line. Despite major structural differences between these two receptor types and agonist-dependent phosphorylation of the muscarinic M3- but not gonadotropin-releasing hormone receptor, signalling by both receptors was similarly inhibited by expression of either RGS2 or RGS3, whereas RGS4 has little effect. Thus, at least in these circumstances, RGS protein-dependent inhibition of signalling is not influenced by the nature of the G-protein-coupled receptor through which the signalling is mediated.
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Affiliation(s)
- Aikaterini Karakoula
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom
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Pawson AJ, Faccenda E, Maudsley S, Lu ZL, Naor Z, Millar RP. Mammalian type I gonadotropin-releasing hormone receptors undergo slow, constitutive, agonist-independent internalization. Endocrinology 2008; 149:1415-22. [PMID: 18039780 DOI: 10.1210/en.2007-1159] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Regulatory elements present in the cytoplasmic carboxyl-terminal tails of G protein-coupled receptors contribute to agonist-dependent receptor desensitization, internalization, and association with accessory proteins such as beta-arrestin. The mammalian type I GnRH receptors are unique among the rhodopsin-like G protein-coupled receptors because they lack a cytoplasmic carboxyl-terminal tail. In addition, they do not recruit beta-arrestin, nor do they undergo rapid desensitization. By measuring the internalization of labeled GnRH agonists, previous studies have reported that mammalian type I GnRH receptors undergo slow agonist-dependent internalization. In the present study, we have measured the internalization of epitope-tagged GnRH receptors, both in the absence and presence of GnRH stimulation. We demonstrate that mammalian type I GnRH receptors exhibit a low level of constitutive agonist-independent internalization. Stimulation with GnRH agonist did not significantly enhance the level of receptor internalization above the constitutive level. In contrast, the catfish GnRH and rat TRH receptors, which have cytoplasmic carboxyl-terminal tails, displayed similar levels of constitutive agonist-independent internalization but underwent robust agonist-dependent internalization, as did chimeras of the mammalian type I GnRH receptor with the cytoplasmic carboxyl-terminal tails of the catfish GnRH receptor or the rat TRH receptor. When the carboxyl-terminal Tyr325 and Leu328 residues of the mammalian type I GnRH receptor were replaced with alanines, these two mutant receptors underwent significantly impaired internalization, suggesting a function for the Tyr-X-X-Leu sequence in mediating the constitutive agonist-independent internalization of mammalian type I GnRH receptors. These findings provide further support for the underlying notion that the absence of the cytoplasmic carboxyl-terminal tail of the mammalian type I GnRH receptors has been selected for during evolution to prevent rapid receptor desensitization and internalization to allow protracted GnRH signaling in mammals.
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Affiliation(s)
- Adam J Pawson
- Medical Research Council Human Reproductive Sciences Unit, The Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, United Kingdom.
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30
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Conn PM, Ulloa-Aguirre A, Ito J, Janovick JA. G Protein-Coupled Receptor Trafficking in Health and Disease: Lessons Learned to Prepare for Therapeutic Mutant Rescue in Vivo. Pharmacol Rev 2007; 59:225-50. [PMID: 17878512 DOI: 10.1124/pr.59.3.2] [Citation(s) in RCA: 200] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
G protein-coupled receptors (GPCR) comprise the largest family of drug targets. This is not surprising as many signaling systems rely on this class of receptor to convert external and internal stimuli to intracellular responses. As is the case with other membrane proteins, GPCRs are subjected to a stringent quality control mechanism at the endoplasmic reticulum, which ensures that only correctly folded proteins enter the secretory pathway. Because of this quality control system, point mutations resulting in protein sequence variations may result in the production of misfolded and disease-causing proteins that are unable to reach their functional destinations in the cell. There is now a wealth of information demonstrating the functional rescue of misfolded mutant receptors by small nonpeptide molecules originally designed to serve as receptor antagonists; these small molecules ("pharmacoperones") serve as molecular templates, promoting correct folding and allowing the mutants to pass the scrutiny of the cellular quality control system and be expressed at the cell surface membrane. Two of these systems are especially well characterized: the gonadotropin-releasing hormone and the vasopressin type 2 receptors, which play important roles in regulating reproduction and water homeostasis, respectively. Mutations in these receptors can lead to well defined diseases that are recognized as being caused by receptor misfolding that may potentially be amenable to treatment with pharmacoperones. This review is focused on protein misfolding and misrouting related to various disease states, with special emphasis on these two receptors, which have proved to be of value for development of drugs potentially useful in regulating GPCR trafficking in healthy and disease states.
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Affiliation(s)
- P Michael Conn
- Divisions of Neuroscience and Reproductive Biology, ONPRC/OHSU, Beaverton, OR 97006, USA.
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31
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Jones BW, Song GJ, Greuber EK, Hinkle PM. Phosphorylation of the endogenous thyrotropin-releasing hormone receptor in pituitary GH3 cells and pituitary tissue revealed by phosphosite-specific antibodies. J Biol Chem 2007; 282:12893-906. [PMID: 17329249 DOI: 10.1074/jbc.m610854200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To study phosphorylation of the endogenous type I thyrotropin-releasing hormone receptor in the anterior pituitary, we generated phosphosite-specific polyclonal antibodies. The major phosphorylation site of receptor endogenously expressed in pituitary GH3 cells was Thr(365) in the receptor tail; distal sites were more phosphorylated in some heterologous models. beta-Arrestin 2 reduced thyrotropin-releasing hormone (TRH)-stimulated inositol phosphate production and accelerated internalization of the wild type receptor but not receptor mutants where the critical phosphosites were mutated to Ala. Phosphorylation peaked within seconds and was maximal at 100 nm TRH. Based on dominant negative kinase and small interfering RNA approaches, phosphorylation was mediated primarily by G protein-coupled receptor kinase 2. Phosphorylated receptor, visualized by immunofluorescence microscopy, was initially at the plasma membrane, and over 5-30 min it moved to intracellular vesicles in GH3 cells. Dephosphorylation was rapid (t((1/2)) approximately 1 min) if agonist was removed while receptor was at the surface. Dephosphorylation was slower (t((1/2)) approximately 4 min) if agonist was withdrawn after receptor had internalized. After agonist removal and dephosphorylation, a second pulse of agonist caused extensive rephosphorylation, particularly if most receptor was still on the plasma membrane. Phosphorylated receptor staining was visible in prolactin- and thyrotropin-producing cells in rat pituitary tissue from untreated rats and much stronger in tissue from animals injected with TRH. Our results show that the TRH receptor can rapidly cycle between a phosphorylated and nonphosphorylated state in response to changing agonist concentrations and that phosphorylation can be used as an indicator of receptor activity in vivo.
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Affiliation(s)
- Brian W Jones
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USA
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Bliss SP, Navratil AM, Breed M, Skinner DC, Clay CM, Roberson MS. Signaling complexes associated with the type I gonadotropin-releasing hormone (GnRH) receptor: colocalization of extracellularly regulated kinase 2 and GnRH receptor within membrane rafts. Mol Endocrinol 2006; 21:538-49. [PMID: 17068198 DOI: 10.1210/me.2006-0289] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Our previous work demonstrated that the type I GnRH receptor (GnRHR) resides exclusively and constitutively within membrane rafts in alphaT3-1 gonadotropes and that this association was necessary for the ability of the receptor to couple to the ERK signaling pathway. G(alphaq), c-raf, and calmodulin have also been shown to reside in this compartment, implicating a raft-associated multiprotein signaling complex as a functional link between the GnRHR and ERK signaling. In the studies reported here, we used subcellular fractionation and coimmunoprecipitation to analyze the behavior of ERKs with respect to this putative signaling platform. ERK 2 associated partially and constitutively with low-density membranes both in alphaT3-1 cells and in whole mouse pituitary. Cholesterol depletion of alphaT3-1 cells reversibly blocked the association of both the GnRHR and ERKs with low-density membranes and uncoupled the ability of GnRH to activate ERK. Analysis of the kinetics of recovery of ERK inducibility after cholesterol normalization supported the conclusion that reestablishment of the association of the GnRHR and ERKs with the membrane raft compartment was not sufficient for reconstitution of signaling activity. In alphaT3-1 cells, the GnRHR and ERK2 coimmunoprecipitated from low-density membrane fractions prepared either in the presence or absence of detergent. The GnRHR also partitioned into low-density, detergent-resistant membrane fractions in mouse pituitary and coimmunoprecipitated with ERK2 from these fractions. Collectively, these data support a model in which coupling of the GnRHR to the ERK pathway in gonadotropes involves the assembly of a multiprotein signaling complex in association with specialized microdomains of the plasma membrane.
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Affiliation(s)
- Stuart P Bliss
- Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853, USA
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33
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Song JA, Oh DY, Moon JS, Geum D, Kwon HB, Seong JY. Involvement of the ser-glu-pro motif in ligand species-dependent desensitisation of the rat gonadotrophin-releasing hormone receptor. J Neuroendocrinol 2006; 18:757-66. [PMID: 16965294 DOI: 10.1111/j.1365-2826.2006.01469.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There are two forms of gonadotrophin-releasing hormone (GnRH), GnRH-I and GnRH-II, in the vertebrate brain. Both GnRH-I and GnRH-II are thought to interact with the type-I GnRH receptor (GnRHR). The present study attempted to demonstrate whether GnRH-I and GnRH-II induce differential desensitisation of GnRHR and to identify the motif involved. Time course inositol phosphate (IP) accumulation assay reveals that, in cells expressing the wild-type rat GnRHR, GnRH-I induced continuous increase in IP production, whereas GnRH-II-induced IP production rate at later time points (30-120 min after ligand treatment) became attenuated. However, in cells expressing the mutant receptor in which the Ser-Glu-Pro (SEP) motif in extracellular loop 3 was replaced by Pro-Glu-Val (PEV), IP accumulation rates at later time points were more decreased by GnRH-I than GnRH-II. Ca2+ responses to repetitive GnRH applications reveal that GnRH-II desensitised the wild-type receptor faster than GnRH-I, whereas the opposite situation was observed in the PEV mutant. In addition, cell surface loss of GFP-tagged wild-type receptor was more facilitated by GnRH-II than GnRH-I, whereas that of the GFP-tagged PEV mutant receptor was more enhanced by GnRH-I than GnRH-II. The present study indicates that the SEP motif is potentially responsible for ligand species-dependent receptor desensitisation. Together, these results suggest that GnRH-I and GnRH-II may have different effects on mammalian type-I GnRHR via modulation of desensitisation rates.
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Affiliation(s)
- J A Song
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea
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34
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Weiss JM, König SJ, Polack S, Emons G, Schulz KD, Diedrich K, Ortmann O. Actions of gonadotropin-releasing hormone analogues in pituitary gonadotrophs and their modulation by ovarian steroids. J Steroid Biochem Mol Biol 2006; 101:118-26. [PMID: 16891115 DOI: 10.1016/j.jsbmb.2006.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Recently, GnRH antagonists (GnRHant) like cetrorelix and ganirelix have been introduced in protocols of controlled ovarian hyperstimulation for assisted reproductive techniques to prevent premature luteinizing hormone (LH) surges. Here we tested, whether the actions of cetrorelix and the GnRH agonist (GnRHag) triptorelin in gonadotrophs are dependent on the steroid milieu. Furthermore, we characterized the actions of cetrorelix and triptorelin on LH secretion and the total LH pool. Female rat pituitary cells were treated either with 0.1 nM triptorelin for 1, 2, 4 and 6 days or for 1, 3, 5 and 6 h or with 1, 10 or 100 nM cetrorelix for 1, 2, 3 and 5 h or for 10 min. Cells were stimulated for 3h with different concentrations of GnRH (10 pM-1 microM). For analysis of the total LH pool, which is composed of stored and released LH, cells were lysed with 0.1% Triton X-100 at -80 degrees C overnight. To test, whether the steroid milieu affects the actions of cetrorelix and triptorelin, cells were incubated for 52 h with 1 nM estradiol (E) alone or with combinations of 100 nM progesterone (P) for 4 or 52 h, respectively. Cells were then treated with 0.1 nM triptorelin for 9 h or 1 nM cetrorelix for 3 h and stimulated for 3 h with different concentrations of GnRH (10 pM-1 microM). The suppressive effect of triptorelin on LH secretion was fully accomplished after 3 h of treatment, for cetrorelix only 10 min were sufficient. The concentration of cetrorelix must be at least equimolar to GnRH to block LH secretion. Cetrorelix shifted the EC50s of the GnRH dose-response curve to the right. Triptorelin suppressed total LH significantly (from 137 to 36 ng/ml) after 1 h in a time-dependent manner. In contrast, only high concentrations of cetrorelix increased total LH. In steroid treated cells the suppressive effects of triptorelin were more distinct. One nanomolar cetrorelix suppressed GnRH-stimulated LH secretion of cells not treated with steroids from 10.1 to 3.5 ng/ml. In cells, additionally treated with estradiol alone or estradiol and short-term progesterone, LH levels were higher (from 3.5 to 5.4 or 4.5 ng/ml, respectively). In cells co-treated with estradiol and progesterone for 52 h LH secretion was only suppressed from 10.1 to 9.5 ng/ml. Steroid treatments diminished the suppressive effect of cetrorelix on LH secretion. In conclusion, the depletion of the total LH pool contributes to the desensitizing effect of triptorelin. The actions of cetrorelix and triptorelin are dependent on the steroid milieu.
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Affiliation(s)
- Juergen M Weiss
- Department of Obstetrics and Gynecology, Medical University Luebeck, Ratzeburger Allee 160, 23538 Luebeck, and Department of Obstetrics and Gynecology, Caritas St. Josef Hospital, Regensburg, Germany.
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35
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Ferris HA, Shupnik MA. Mechanisms for pulsatile regulation of the gonadotropin subunit genes by GNRH1. Biol Reprod 2006; 74:993-8. [PMID: 16481592 DOI: 10.1095/biolreprod.105.049049] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The frequency of gonadotropin-releasing hormone (GNRH1, or GnRH) pulses secreted from the hypothalamus determine the ratios of the gonadotropin subunit genes luteinizing hormone beta (Lhb), follicle-stimulating hormone beta (Fshb) and the common alpha-glycoprotein subunit gene (Cga) transcribed in the anterior pituitaries of mammals. Fshb is preferentially transcribed at slower GNRH1 pulse frequencies, whereas Lhb and Cga are preferentially transcribed at more rapid pulse frequencies. Producing the gonadotropins in the correct proportions is critical for normal fertility. Currently, there is no definitive explanation for how GNRH1 pulses differentially activate gonadotropin subunit gene transcription. Several pathways may contribute to this regulation. For example, GNRH1-regulated GNRH1-receptor concentrations may lead to variable signaling pathway activation. Several signaling pathways are activated by GnRH, including mitogen-activated protein kinase, protein kinase C, calcium influx, and calcium-calmodulin kinase, and these may be preferentially regulated under certain conditions. In addition, some signaling proteins feed back to downregulate their own levels. Other arms of gonadotroph signaling appear to be regulated by synthesis, modification, and degradation of either transcription factors or regulatory proteins. Finally, the dynamic binding of proteins to the chromatin, and how that might be regulated by chromatin-modifying proteins, is addressed. Oscillations in expression, modification, and chromatin binding of the proteins involved in gonadotropin gene expression are likely a link between GNRH1 pulsatility and differential gonadotropin transcription.
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MESH Headings
- Animals
- Chromatin/physiology
- Follicle Stimulating Hormone, beta Subunit/genetics
- Follicle Stimulating Hormone, beta Subunit/metabolism
- Follicle Stimulating Hormone, beta Subunit/physiology
- Gene Expression Regulation/physiology
- Glycoprotein Hormones, alpha Subunit/genetics
- Glycoprotein Hormones, alpha Subunit/metabolism
- Glycoprotein Hormones, alpha Subunit/physiology
- Gonadotropin-Releasing Hormone/physiology
- Gonadotropins/genetics
- Gonadotropins/metabolism
- Gonadotropins/physiology
- Gonads/physiology
- Humans
- Hypothalamo-Hypophyseal System/physiology
- Hypothalamus/metabolism
- Luteinizing Hormone, beta Subunit/genetics
- Luteinizing Hormone, beta Subunit/metabolism
- Luteinizing Hormone, beta Subunit/physiology
- Protein Processing, Post-Translational/genetics
- Protein Processing, Post-Translational/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Transcription, Genetic/genetics
- Transcription, Genetic/physiology
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Affiliation(s)
- Heather A Ferris
- Department of Physiology, University of Virginia, Charlottesville, Virginia 22908, USA
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36
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Rispoli LA, Nett TM. Pituitary gonadotropin-releasing hormone (GnRH) receptor: structure, distribution and regulation of expression. Anim Reprod Sci 2005; 88:57-74. [PMID: 15993012 DOI: 10.1016/j.anireprosci.2005.05.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Reproduction in mammals is controlled by interactions between the hypothalamus, anterior pituitary and gonads. Interaction of GnRH with its cognate receptor is essential to regulating reproduction. Characterization of the structure, distribution and expression of GnRH receptors (GnRH-R) has furthered our understanding of the physiological consequences of GnRH stimulation of pituitary gonadotropes. Based on the putative topology of the amino acid sequence of the GnRH-R and point mutation studies, key elements of the GnRH-R have been identified to play a role in ligand recognition and binding, G-protein activation and internalization. Normally, reproductive function is mediated by GnRH-R expressed only on the membranes of pituitary gonadotropes. The density of GnRH-R on gonadotropes determines their ability to respond to GnRH. This density is highest just prior to ovulation and likely is important for complete expression of the pre-ovulatory surge of LH. Therefore, knowledge regarding what regulates the density of GnRH-R is essential to understanding changes in pituitary sensitivity to GnRH and ultimately, to expression of the LH surge. Regulation of GnRH-R gene expression is influenced by a multitude of factors including gonadal steroid hormones, inhibin, activin and perhaps most importantly GnRH itself.
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Affiliation(s)
- L A Rispoli
- Department of Biomedical Sciences, Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, CO 80523, USA
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37
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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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38
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Shacham S, Cheifetz MN, Fridkin M, Pawson AJ, Millar RP, Naor Z. Identification of Ser153 in ICL2 of the gonadotropin-releasing hormone (GnRH) receptor as a phosphorylation-independent site for inhibition of Gq coupling. J Biol Chem 2005; 280:28981-8. [PMID: 15964850 DOI: 10.1074/jbc.m500312200] [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: 11/06/2022] Open
Abstract
Type I gonadotropin-releasing hormone (GnRH) receptor (GnRHR) is unique among mammalian G-protein-coupled receptors (GPCRs) in lacking a C-terminal tail, which is involved in desensitization in GPCRs. Therefore, we searched for inhibitory sites in the intracellular loops (ICLs) of the GnRHR. Synthetic peptides corresponding to the three ICLs were inserted into permeabilized alphaT3-1 gonadotrope cells, and GnRH-induced inositol phosphate (InsP) formation was determined. GnRH-induced InsP production was potentiated by ICL2 > ICL3 but not by the ICL1 peptides, suggesting they are acting as decoy peptides. We examined the effects of six peptides in which only one of the Ser or Thr residues was substituted with Ala or Glu. Only substitution of Ser153 with Ala or Glu ablated the potentiating effect upon GnRH-induced InsP elevation. ERK activation was enhanced, and the rate of GnRH-induced InsP formation was about 6.5-fold higher in the first 10 min in COS-1 cells that were transfected with mutants of the GnRHR in which the ICL2 Ser/Thr residues (Ser151, Ser153, and Thr142) or only Ser153 was mutated to Ala as compared with the wild type GnRHR. The data indicate that ICL2 harbors an inhibitory domain, such that exogenous ICL2 peptide serves as a decoy for the inhibitory site (Ser153) of the GnRHR, thus enabling further activation. GnRH does not induce receptor phosphorylation in alphaT3-1 cells. Because the phosphomimetic ICL2-S153E peptide did not mimic the stimulatory effect of the ICL2 peptide, the inhibitory effect of Ser153 operates through a phosphorylation-independent mechanism.
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Affiliation(s)
- Sharon Shacham
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel
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Levavi-Sivan B, Avitan A. Sequence analysis, endocrine regulation, and signal transduction of GnRH receptors in teleost fish. Gen Comp Endocrinol 2005; 142:67-73. [PMID: 15862550 DOI: 10.1016/j.ygcen.2005.01.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 01/16/2005] [Accepted: 01/31/2005] [Indexed: 11/29/2022]
Abstract
Three gonadotropin-releasing hormones (GnRHs) and three cognate receptors have been identified in vertebrates, with distinct distributions and functions. According to their sequences, the receptors can be grouped into distinct classes: types I, II, and III. One branch contains all type-I GnRH receptors (GnRH-R-I) from mammals and fish; another branch clusters mainly amphibian and human type-II GnRH receptors; and a third branch includes evolved fish, mainly perciform species, type-III GnRH receptors. Taken tilapia GnRH receptors as a model, the present study summarizes the information regarding the amino-acid residues assumed to be involved in the receptors' structure, binding, activation, and intracellular signal transduction, including arrangement of the disulfide bonds, glycosylation sites, coupling to G proteins, and protein kinase A or protein kinase C phosphorylation sites.
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Affiliation(s)
- Berta Levavi-Sivan
- Department of Animal Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
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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: 173] [Impact Index Per Article: 9.1] [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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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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Tien JH, Lyles D, Zeeman ML. A potential role of modulating inositol 1,4,5-trisphosphate receptor desensitization and recovery rates in regulating ovulation. J Theor Biol 2005; 232:105-17. [PMID: 15498598 DOI: 10.1016/j.jtbi.2004.08.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Revised: 07/21/2004] [Accepted: 08/04/2004] [Indexed: 11/22/2022]
Abstract
Regulation of the human menstrual cycle is a frequency dependent process controlled in part by the pulsatile release of gonadotropin releasing hormone (GnRH) from the hypothalamus. The binding of GnRH to gonadotroph cells in the pituitary stimulates inositol 1,4,5-trisphosphate (IP3) mediated release of calcium from the endoplasmic reticulum, resulting in calcium oscillations and the secretion of luteinizing hormone (LH). A sudden increase in serum LH concentrations known as the LH surge triggers ovulation. Here we model the intracellular calcium dynamics of gonadotroph cells by adapting the model of Li and Rinzel (J. Theor. Biol. 166 (1994) 461) to include the desensitization of IP3 receptors to IP3. Allowing the resensitization rate of these receptors to vary over the course of the cycle suffices to explain the LH surge in both the normal menstrual cycle, and in the treatment of Kallmann's syndrome (a condition where endogenous production of GnRH is absent).
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Affiliation(s)
- Joseph H Tien
- Center for Applied Mathematics, Cornell University, 657 Frank HT Rhodes Hall, Ithaca, NY 14853, USA.
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43
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Pfleger KDG, Kroeger KM, Eidne KA. Receptors for hypothalamic releasing hormones TRH and GnRH: oligomerization and interactions with intracellular proteins. Semin Cell Dev Biol 2004; 15:269-80. [PMID: 15125890 DOI: 10.1016/j.semcdb.2003.12.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Studies of TRH and GnRH receptors have revealed much information about the roles of G-proteins and beta-arrestins, as well as receptor residues important for signaling, desensitization and internalization. However, the proteins involved are only just beginning to be identified and characterized. Additional complexity now exists with the observation that these receptors form oligomers in live cells. Indeed, hetero-oligomerization of TRH receptor subtypes 1 and 2 potentially alters interactions with intracellular regulatory proteins. Knowledge of proteins that interact with TRH or GnRH receptors will increase our understanding of receptor function and provide potential drug targets for a range of receptor-associated conditions.
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Affiliation(s)
- Kevin Donald George Pfleger
- Molecular Endocrinology Research Group/7TM Receptor Laboratory, Western Australian Institute for Medical Research, Centre for Medical Research, Sir Charles Gairdner Hospital, University of Western Australia, Nedlands, Perth, 6009, Australia
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Janovick JA, Ulloa-Aguirre A, Conn PM. Evolved regulation of gonadotropin-releasing hormone receptor cell surface expression. Endocrine 2003; 22:317-27. [PMID: 14709805 DOI: 10.1385/endo:22:3:317] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Accepted: 10/28/2003] [Indexed: 01/21/2023]
Abstract
Dominant negative effects of mutant gonadotropin-releasing hormone (GnRH) receptors (GnRHR; isolated from patients with idiopathic hypogonadotropic hypogonadism) on plasma membrane expression (PME) and function of the wt GnRHR were examined. In addition, we assessed the effect of mutants on wt GnRHR with receptor modifications that, by themselves, diminished PME. Among such mechanisms that restrict PME of GnRHR in primates are: (a) addition of the primate-specific K191 and (b) deletion of the carboxyl tail ("Ctail") found in pre-mammalian species (fish, birds) of GnRHR. We prepared rat (r) and human (h) GnRHR plasmids (88% homologous), each with or without the K191; chimeras were then made with C-tail or each of four truncated fragments (selected to isolate consensus sites for palmitoylation or phosphorylation) of the 51-amino-acid Ser-rich piscine GnRHR C-tail and then expressed in COS-7 cells. The data suggest that the dominant negative effect of the mutants on the hGnRHR requires intrinsic low PME that co-evolved with the dominant-negative effect. The data further reveal that additional modifications must have occurred in primates that are important for both the diminution of the PME and the development of the dominant negative effect of the mutants.
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Affiliation(s)
- Jo Ann Janovick
- Oregon Health & Science University, Portland, OR 97239-3098, USA
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Navratil AM, Bliss SP, Berghorn KA, Haughian JM, Farmerie TA, Graham JK, Clay CM, Roberson MS. Constitutive localization of the gonadotropin-releasing hormone (GnRH) receptor to low density membrane microdomains is necessary for GnRH signaling to ERK. J Biol Chem 2003; 278:31593-602. [PMID: 12791688 DOI: 10.1074/jbc.m304273200] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Specialized membrane microdomains known as lipid rafts are thought to contribute to G-protein coupled receptor (GPCR) signaling by organizing receptors and their cognate signaling molecules into discrete membrane domains. To determine if the GnRHR, an unusual member of the GPCR superfamily, partitions into lipid rafts, homogenates of alpha T3-1 cells expressing endogenous GnRHR or Chinese hamster ovary cells expressing an epitope-tagged GnRHR were fractionated through a sucrose gradient. We found the GnRHR and c-raf kinase constitutively localized to low density fractions independent of hormone treatment. Partitioning of c-raf kinase into lipid rafts was also observed in whole mouse pituitary glands. Consistent with GnRH induced phosphorylation and activation of c-raf kinase, GnRH treatment led to a decrease in the apparent electrophoretic mobility of c-raf kinase that partitioned into lipid rafts compared with unstimulated cells. Cholesterol depletion of alpha T3-1 cells using methyl-beta-cyclodextrin disrupted GnRHR but not c-raf kinase association with rafts and shifted the receptor into higher density fractions. Cholesterol depletion also significantly attenuated GnRH but not phorbol ester-mediated activation of extracellular signal-related kinase (ERK) and c-fos gene induction. Raft localization and GnRHR signaling to ERK and c-Fos were rescued upon repletion of membrane cholesterol. Thus, the organization of the GnRHR into low density membrane microdomains appears critical in mediating GnRH induced intracellular signaling.
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Affiliation(s)
- Amy M Navratil
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA
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Oh DY, Wang L, Ahn RS, Park JY, Seong JY, Kwon HB. Differential G protein coupling preference of mammalian and nonmammalian gonadotropin-releasing hormone receptors. Mol Cell Endocrinol 2003; 205:89-98. [PMID: 12890570 DOI: 10.1016/s0303-7207(03)00204-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Recently, we have identified three distinct types of gonadotropin-releasing hormone receptor (GnRHR) in the bullfrog (designated bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3). In the present study, we compared G protein coupling preference of mammalian and nonmammalian GnRHRs. In a transient expression system, stimulation of either bfGnRHRs or rat GnRHR by GnRH significantly increased both inositol phosphates (IP) and cAMP productions, but ratios of IP to cAMP induction levels were quite different among the receptors, indicating differential G protein coupling preference. Using cAMP-dependent protein kinase A (PKA)-specific (CRE-luc) or protein kinase C (PKC)-specific reporter (c-fos-luc) systems, we further examined G(s) and G(q/11) coupling preference of these GnRHRs. Since activities of CRE-luc and c-fos-luc were highly dependent on cell types, GnRH-induced CRE-luc or c-fos-luc activity was normalized by forskolin-induced CRE-luc or 12-O-tetradecanoylphenol-13-acetate (TPA)-induced c-fos-luc activity, respectively. This normalized result indicated that bfGnRHR-2 couples to G(s) more actively than G(q/11), while bfGnRHR-1 and -3 couple to G(s) and G(q/11) with similar strength. However, the rat GnRHR appeared to couple to G(q/11) more efficiently than G(s). This study was further confirmed by an experiment in which GnRH augmented CRE-driven luciferase activity in alphaT3-1 cells when CRE-luc was cotransfected with bfGnRHRs but not with vehicle or rat GnRHR. Collectively, these results indicate that mammalian and nonmammalian GnRHRs may induce diverse cellular and physiological responses through differential activation of PKA and PKC signaling pathways.
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Affiliation(s)
- Da Young Oh
- Hormone Research Center, Chonnam National University, 500-757 Gwangju, South Korea
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Ruf F, Fink MY, Sealfon SC. Structure of the GnRH receptor-stimulated signaling network: insights from genomics. Front Neuroendocrinol 2003; 24:181-99. [PMID: 14596811 DOI: 10.1016/s0091-3022(03)00027-x] [Citation(s) in RCA: 57] [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: 10/27/2022]
Abstract
The GnRH receptor influences gene expression in the gonadotrope through activating signaling cascades that modulate transcription factor expression and activity. A longstanding question in neuroendocrinology is how instructions received at the membrane in the form of the pattern of receptor stimulation are processed into specific biosynthetic changes at each gonadotropin promoter. Signal transduction from the membrane to preformed transcription factors relies on recognition of altered conformations. Signal transduction through the layers of the gene network also requires the biosynthesis of new transcription factors. The signal processing of this system depends on its molecular connectivity map and its feedback and feed-forward loops. Review of signal transduction, gene control, and genomic studies provide evidence of key loops that cross between cellular and nuclear compartments. Genomic studies suggest that the signal transduction and gene network form a continuum. We propose that information transfer in the gonadotrope depends on robust signaling modules that serve to integrate events at different time scales across cytoplasmic and nuclear compartments.
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Affiliation(s)
- Frederique Ruf
- Department of Neurology, Box 1137, Mount Sinai School of Medicine, New York, NY 10029, USA
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48
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Farshori PQ, Shah BH, Arora KK, Martinez-Fuentes A, Catt KJ. Activation and nuclear translocation of PKCdelta, Pyk2 and ERK1/2 by gonadotropin releasing hormone in HEK293 cells. J Steroid Biochem Mol Biol 2003; 85:337-47. [PMID: 12943720 DOI: 10.1016/s0960-0760(03)00226-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mechanism of agonist-induced activation of Pyk2 and its relationship with ERK1/2 phosphorylation was analyzed in HEK293 cells stably expressing the gonadotropin releasing hormone (GnRH) receptor. GnRH stimulation caused rapid and sustained phosphorylation of ERK1/2 and Pyk2 that was accompanied by their nuclear translocation. Pyk2 was also localized on cell membranes and at focal adhesions. Dominant negative Pyk2 (PKM) had no effect on GnRH-induced ERK1/2 phosphorylation and c-fos expression. These actions of GnRH on ERK1/2 and Pyk2 were mimicked by activation of protein kinase C (PKC) and were abolished by its inhibition. GnRH caused translocation of PKCalpha and delta, but not of epsilon, iota and lambda, to the cell membrane, as well as phosphorylation of Raf at Ser338, a major site in the activation of MEK/ERK1/2. Stimulation of HEK293 cells by EGF caused marked ERK1/2 phosphorylation that was attenuated by the selective EGFR receptor (EGF-R) kinase inhibitor, AG1478. However, GnRH-induced ERK1/2 activation was independent of EGF-R activation. These results indicate that activation of PKC is responsible for GnRH-induced phosphorylation of both ERK1/2 and Pyk2, and that Pyk2 activation does not contribute to GnRH signaling. Moreover, GnRH-induced phosphorylation of ERK1/2 and expression of c-fos in HEK293 cells is independent of Src and EGF-R transactivation, and is mediated through the PKC/Raf/MEK cascade.
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Affiliation(s)
- Parvaiz Q Farshori
- Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Building 49, Room 6A-36, Bethesda, MD 20892-4510, USA
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49
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Shah BH, Farshori MP, Jambusaria A, Catt KJ. Roles of Src and epidermal growth factor receptor transactivation in transient and sustained ERK1/2 responses to gonadotropin-releasing hormone receptor activation. J Biol Chem 2003; 278:19118-26. [PMID: 12642580 DOI: 10.1074/jbc.m212932200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The duration as well as the magnitude of mitogen-activated protein kinase activation has been proposed to regulate gene expression and other specific intracellular responses in individual cell types. Activation of ERK1/2 by the hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH) is relatively sustained in alpha T3-1 pituitary gonadotropes and HEK293 cells but is transient in immortalized GT1-7 neurons. Each of these cell types expresses the epidermal growth factor receptor (EGFR) and responds to EGF stimulation with significant but transient ERK1/2 phosphorylation. However, GnRH-induced ERK1/2 phosphorylation caused by EGFR transactivation was confined to GT1-7 cells and was attenuated by EGFR kinase inhibition. Neither EGF nor GnRH receptor activation caused translocation of phospho-ERK1/2 into the nucleus in GT1-7 cells. In contrast, agonist stimulation of GnRH receptors expressed in HEK293 cells caused sustained phosphorylation and nuclear translocation of ERK1/2 by a protein kinase C-dependent but EGFR-independent pathway. GnRH-induced activation of ERK1/2 was attenuated by the selective Src kinase inhibitor PP2 and the negative regulatory C-terminal Src kinase in GT1-7 cells but not in HEK293 cells. In GT1-7 cells, GnRH stimulated phosphorylation and nuclear translocation of the ERK1/2-dependent protein, p90RSK-1 (RSK-1). These results indicate that the duration of ERK1/2 activation depends on the signaling pathways utilized by GnRH in specific target cells. Whereas activation of the Gq/protein kinase C pathway in HEK293 cells causes sustained phosphorylation and translocation of ERK1/2 to the nucleus, transactivation of the EGFR by GnRH in GT1-7 cells elicits transient ERK1/2 signals without nuclear accumulation. These findings suggest that transactivation of the tightly regulated EGFR can account for the transient ERK1/2 responses that are elicited by stimulation of certain G protein-coupled receptors.
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Affiliation(s)
- Bukhtiar H Shah
- Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510, USA
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Pierantoni R, Cobellis G, Meccariello R, Fasano S. Evolutionary aspects of cellular communication in the vertebrate hypothalamo-hypophysio-gonadal axis. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 218:69-141. [PMID: 12199520 DOI: 10.1016/s0074-7696(02)18012-0] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
This review emphasizes the comparative approach for developing insight into knowledge related to cellular communications occurring in the hypothalamus-pituitary-gonadal axis. Indeed, research on adaptive phenomena leads to evolutionary tracks. Thus, going through recent results, we suggest that pheromonal communication precedes local communication which, in turn, precedes communication via the blood stream. Furthermore, the use of different routes of communication by a certain mediator leads to a conceptual change related to what hormones are. Nevertheless, endocrine communication should leave out of consideration the source (glandular or not) of mediator. Finally, we point out that the use of lower vertebrate animal models is fundamental to understanding general physiological mechanisms. In fact, different anatomical organization permits access to tissues not readily approachable in mammals.
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