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Tzoupis H, Nteli A, Androutsou ME, Tselios T. Gonadotropin-Releasing Hormone and GnRH Receptor: Structure, Function and Drug Development. Curr Med Chem 2021; 27:6136-6158. [PMID: 31309882 DOI: 10.2174/0929867326666190712165444] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 06/18/2019] [Accepted: 06/19/2019] [Indexed: 01/11/2023]
Abstract
BACKGROUND Gonadotropin-Releasing Hormone (GnRH) is a key element in sexual maturation and regulation of the reproductive cycle in the human organism. GnRH interacts with the pituitary cells through the activation of the Gonadotropin Releasing Hormone Receptors (GnRHR). Any impairments/dysfunctions of the GnRH-GnRHR complex lead to the development of various cancer types and disorders. Furthermore, the identification of GnRHR as a potential drug target has led to the development of agonist and antagonist molecules implemented in various treatment protocols. The development of these drugs was based on the information derived from the functional studies of GnRH and GnRHR. OBJECTIVE This review aims at shedding light on the versatile function of GnRH and GnRH receptor and offers an apprehensive summary regarding the development of different agonists, antagonists and non-peptide GnRH analogues. CONCLUSION The information derived from these studies can enhance our understanding of the GnRH-GnRHR versatile nature and offer valuable insight into the design of new more potent molecules.
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Affiliation(s)
| | - Agathi Nteli
- Department of Chemistry, University of Patras, Rion GR-26504, Greece
| | - Maria-Eleni Androutsou
- Vianex S.A., Tatoiou Str., 18th km Athens-Lamia National Road, Nea Erythrea 14671, Greece
| | - Theodore Tselios
- Department of Chemistry, University of Patras, Rion GR-26504, Greece
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Targeting luteinizing hormone-releasing hormone: A potential therapeutics to treat gynecological and other cancers. J Control Release 2018; 269:277-301. [DOI: 10.1016/j.jconrel.2016.11.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 11/04/2016] [Accepted: 11/05/2016] [Indexed: 01/05/2023]
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Mayevu NMI, Choe H, Abagyan R, Seong JY, Millar RP, Katz AA, Flanagan CA. Histidine(7.36(305)) in the conserved peptide receptor activation domain of the gonadotropin releasing hormone receptor couples peptide binding and receptor activation. Mol Cell Endocrinol 2015; 402:95-106. [PMID: 25583361 DOI: 10.1016/j.mce.2015.01.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 01/06/2015] [Accepted: 01/06/2015] [Indexed: 12/29/2022]
Abstract
Transmembrane helix seven residues of G protein-coupled receptors (GPCRs) couple agonist binding to a conserved receptor activation mechanism. Amino-terminal residues of the GnRH peptide determine agonist activity. We investigated GnRH interactions with the His(7.36(305)) residue of the GnRH receptor, using functional and computational analysis of modified GnRH receptors and peptides. Non-polar His(7.36(305)) substitutions decreased receptor affinity for GnRH four- to forty-fold, whereas GnRH signaling potency was more decreased (~150-fold). Uncharged polar His(7.36(305)) substitutions decreased GnRH potency, but not affinity. [2-Nal(3)]-GnRH retained high affinity at receptors with non-polar His(7.36(305)) substitutions, supporting a role for His(7.36(305)) in recognizing Trp(3) of GnRH. Compared with GnRH, [2-Nal(3)]-GnRH potency was lower at the wild type GnRH receptor, but unchanged or higher at mutant receptors. Results suggest that His(7.36(305)) of the GnRH receptor forms two distinct interactions that determine binding to Trp(3) and couple agonist binding to the conserved transmembrane domain network that activates GPCRs.
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Affiliation(s)
- Nkateko M I Mayevu
- Medical Research Council Receptor Biology Research Unit, Institute of Infectious Diseases and Molecular Medicine, Division of Medical Biochemistry, University of Cape Town Health Sciences Faculty, Observatory, Cape Town 7925, South Africa
| | - Han Choe
- Department of Physiology and Bio-Medical Institute of Technology, University of Ulsan College of Medicine, Seoul 138-736, Korea
| | - Ruben Abagyan
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92039, USA
| | - Jae Young Seong
- Graduate School of Medicine, Korea University, Seoul 136-705, Korea
| | - Robert P Millar
- Medical Research Council Receptor Biology Research Unit, Institute of Infectious Diseases and Molecular Medicine, Division of Medical Biochemistry, University of Cape Town Health Sciences Faculty, Observatory, Cape Town 7925, South Africa; Mammal Research Institute, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
| | - Arieh A Katz
- Medical Research Council Receptor Biology Research Unit, Institute of Infectious Diseases and Molecular Medicine, Division of Medical Biochemistry, University of Cape Town Health Sciences Faculty, Observatory, Cape Town 7925, South Africa
| | - Colleen A Flanagan
- Medical Research Council Receptor Biology Research Unit, Institute of Infectious Diseases and Molecular Medicine, Division of Medical Biochemistry, University of Cape Town Health Sciences Faculty, Observatory, Cape Town 7925, South Africa; School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Private bag 3, Wits 2050, South Africa.
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Maione L, Albarel F, Bouchard P, Gallant M, Flanagan CA, Bobe R, Cohen-Tannoudji J, Pivonello R, Colao A, Brue T, Millar RP, Lombes M, Young J, Guiochon-Mantel A, Bouligand J. R31C GNRH1 mutation and congenital hypogonadotropic hypogonadism. PLoS One 2013; 8:e69616. [PMID: 23936060 PMCID: PMC3723855 DOI: 10.1371/journal.pone.0069616] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 06/11/2013] [Indexed: 01/27/2023] Open
Abstract
Normosmic congenital hypogonadotropic hypogonadism (nCHH) is a rare reproductive disease leading to lack of puberty and infertility. Loss-of-function mutations of GNRH1 gene are a very rare cause of autosomal recessive nCHH. R31C GNRH1 is the only missense mutation that affects the conserved GnRH decapeptide sequence. This mutation was identified in a CpG islet in nine nCHH subjects from four unrelated families, giving evidence for a putative “hot spot”. Interestingly, all the nCHH patients carry this mutation in heterozygosis that strikingly contrasts with the recessive inheritance associated with frame shift and non-sense mutations. Therefore, after exclusion of a second genetic event, a comprehensive functional characterization of the mutant R31C GnRH was undertaken. Using different cellular models, we clearly demonstrate a dramatic reduction of the mutant decapeptide capacity to bind GnRH-receptor, to activate MAPK pathway and to trigger inositol phosphate accumulation and intracellular calcium mobilization. In addition it is less able than wild type to induce lh-beta transcription and LH secretion in gonadotrope cells. Finally, the absence of a negative dominance in vitro offers a unique opportunity to discuss the complex in vivo patho-physiology of this form of nCHH.
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Affiliation(s)
- Luigi Maione
- Université Paris-Sud, Faculté de Médecine Paris-Sud Unité mixte de Recherche en Santé 693, Le Kremlin Bicetre, France
- Service d'Endocrinologie et des Maladies de la Reproduction, Hopital Bicetre, Assistance Publique Hopitaux de Paris, Le Kremlin-Bicêtre, France
- Università degli Studi di Napoli Federico II, Dipartimento di Medicina Clinica e Chirurgia, Sezione di Endocrinologia e Metabolismo, Napoli, Italy
| | - Frederique Albarel
- Département d'Endocrinologie et Centre de Référence des Maladies Rares d'Origine Hypophysaire, Hopital de la Timone, Marseille, France
| | - Philippe Bouchard
- Service d'Endocrinologie, diabétologie et endocrinologie de la reproduction, Hopital Saint-Antoine, Assistance Publique-Hopitaux de Paris, Paris, France
| | - Megan Gallant
- University of Cape Town Medical School, Medical Research Council, Receptor Biology Research Unit, Institute of Infectious Diseases and Molecular Medicine, Observatory, Cape Town, South Africa
| | - Colleen A. Flanagan
- University of Cape Town Medical School, Medical Research Council, Receptor Biology Research Unit, Institute of Infectious Diseases and Molecular Medicine, Observatory, Cape Town, South Africa
- School of Physiology, University of the Witwatersrand Faculty of Health Sciences, Parktown, Johannesburg, South Africa
| | - Regis Bobe
- Université Paris-Sud, Unité mixte de Recherche en Santé 770, Le Kremlin-Bicetre, France
| | - Joelle Cohen-Tannoudji
- Equipe Physiologie de l'Axe Gonadotrope, Unité de Biologie Fonctionnelle et Adaptative, Sorbonne Paris Cité, Université Paris Diderot-Paris 7, Paris, France
| | - Rosario Pivonello
- Università degli Studi di Napoli Federico II, Dipartimento di Medicina Clinica e Chirurgia, Sezione di Endocrinologia e Metabolismo, Napoli, Italy
| | - Annamaria Colao
- Università degli Studi di Napoli Federico II, Dipartimento di Medicina Clinica e Chirurgia, Sezione di Endocrinologia e Metabolismo, Napoli, Italy
| | - Thierry Brue
- Département d'Endocrinologie et Centre de Référence des Maladies Rares d'Origine Hypophysaire, Hopital de la Timone, Marseille, France
| | - Robert P. Millar
- University of Cape Town Medical School, Medical Research Council, Receptor Biology Research Unit, Institute of Infectious Diseases and Molecular Medicine, Observatory, Cape Town, South Africa
- Mammal Research Institute, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa and Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, Scotland
| | - Marc Lombes
- Université Paris-Sud, Faculté de Médecine Paris-Sud Unité mixte de Recherche en Santé 693, Le Kremlin Bicetre, France
| | - Jacques Young
- Université Paris-Sud, Faculté de Médecine Paris-Sud Unité mixte de Recherche en Santé 693, Le Kremlin Bicetre, France
- Service d'Endocrinologie et des Maladies de la Reproduction, Hopital Bicetre, Assistance Publique Hopitaux de Paris, Le Kremlin-Bicêtre, France
| | - Anne Guiochon-Mantel
- Université Paris-Sud, Faculté de Médecine Paris-Sud Unité mixte de Recherche en Santé 693, Le Kremlin Bicetre, France
- Laboratoire de Génétique moléculaire, Pharmacogénétique et Hormonologie, Hopital Bicetre, Assistance Publique Hopitaux de Paris, Le Kremlin-Bicetre, France
| | - Jerome Bouligand
- Université Paris-Sud, Faculté de Médecine Paris-Sud Unité mixte de Recherche en Santé 693, Le Kremlin Bicetre, France
- Laboratoire de Génétique moléculaire, Pharmacogénétique et Hormonologie, Hopital Bicetre, Assistance Publique Hopitaux de Paris, Le Kremlin-Bicetre, France
- * E-mail:
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Pfleger KDG, Pawson AJ, Millar RP. Changes to gonadotropin-releasing hormone (GnRH) receptor extracellular loops differentially affect GnRH analog binding and activation: evidence for distinct ligand-stabilized receptor conformations. Endocrinology 2008; 149:3118-29. [PMID: 18356273 DOI: 10.1210/en.2008-0002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GnRH and its structural variants bind to GnRH receptors from different species with different affinities and specificities. By investigating chimeric receptors that combine regions of mammalian and nonmammalian GnRH receptors, a greater understanding of how different domains influence ligand binding and receptor activation can be achieved. Using human-catfish and human-chicken chimeric receptors, we demonstrate the importance of extracellular loop conformation for ligand binding and agonist potency, providing further evidence for GnRH and GnRH II stabilization of distinct active receptor conformations. We demonstrate examples of GnRH receptor gain-of-function mutations that apparently improve agonist potency independently of affinity, implicating a role for extracellular loops in stabilizing the inactive receptor conformation. We also show that entire extracellular loop substitution can overcome the detrimental effects of localized mutations, thereby demonstrating the importance of considering the conformation of entire domains when drawing conclusions from point-mutation studies. Finally, we present evidence implicating the configuration of extracellular loops 2 and 3 in combination differentiating GnRH analog binding modes. Because there are two endogenous forms of GnRH ligand but only one functional form of full-length GnRH receptor in humans, understanding how GnRH and GnRH II can elicit distinct functional effects through the same receptor is likely to provide important insights into how these ligands can have differential effects in both physiological and pathological situations.
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Affiliation(s)
- Kevin D G Pfleger
- Medical Research Council Human Reproductive Sciences Unit, Centre for Reproductive Biology, The Queen's Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom.
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Flanagan CA, Chen CC, Coetsee M, Mamputha S, Whitlock KE, Bredenkamp N, Grosenick L, Fernald RD, Illing N. Expression, structure, function, and evolution of gonadotropin-releasing hormone (GnRH) receptors GnRH-R1SHS and GnRH-R2PEY in the teleost, Astatotilapia burtoni. Endocrinology 2007; 148:5060-71. [PMID: 17595228 DOI: 10.1210/en.2006-1400] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Multiple GnRH receptors are known to exist in nonmammalian species, but it is uncertain which receptor type regulates reproduction via the hypothalamic-pituitary-gonadal axis. The teleost fish, Astatotilapia burtoni, is useful for identifying the GnRH receptor responsible for reproduction, because only territorial males reproduce. We have cloned a second GnRH receptor in A. burtoni, GnRH-R1(SHS) (SHS is a peptide motif in extracellular loop 3), which is up-regulated in pituitaries of territorial males. We have shown that GnRH-R1(SHS) is expressed in many tissues and specifically colocalizes with LH in the pituitary. In A. burtoni brain, mRNA levels of both GnRH-R1(SHS) and a previously identified receptor, GnRH-R2(PEY), are highly correlated with mRNA levels of all three GnRH ligands. Despite its likely role in reproduction, we found that GnRH-R1(SHS) has the highest affinity for GnRH2 in vitro and low responsivity to GnRH1. Our phylogenetic analysis shows that GnRH-R1(SHS) is less closely related to mammalian reproductive GnRH receptors than GnRH-R2(PEY). We correlated vertebrate GnRH receptor amino acid sequences with receptor function and tissue distribution in many species and found that GnRH receptor sequences predict ligand responsiveness but not colocalization with pituitary gonadotropes. Based on sequence analysis, tissue localization, and physiological response we propose that the GnRH-R1(SHS) receptor controls reproduction in teleosts, including A. burtoni. We propose a GnRH receptor classification based on gene sequence that correlates with ligand selectivity but not with reproductive control. Our results suggest that different duplicated GnRH receptor genes have been selected to regulate reproduction in different vertebrate lineages.
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Affiliation(s)
- Colleen A Flanagan
- Department of Biological Sciences and Program in Neuroscience, Stanford University, Stanford, CA 94305-2130, USA
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Mamputha S, Lu ZL, Roeske RW, Millar RP, Katz AA, Flanagan CA. Conserved amino acid residues that are important for ligand binding in the type I gonadotropin-releasing hormone (GnRH) receptor are required for high potency of GnRH II at the type II GnRH receptor. Mol Endocrinol 2006; 21:281-92. [PMID: 16973761 DOI: 10.1210/me.2006-0150] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GnRH I regulates reproduction. A second form, designated GnRH II, selectively binds type II GnRH receptors. Amino acids of the type I GnRH receptor required for binding of GnRH I (Asp2.61(98), Asn2.65(102), and Lys3.32(121)) are conserved in the type II GnRH receptor, but their roles in receptor function are unknown. We have delineated their functions using mutagenesis, signaling and binding assays, immunoblotting, and computational modeling. Mutating Asp2.61(97) to Glu or Ala, Asn2.65(101) to Ala, or Lys3.32(120) to Gln decreased potency of GnRH II-stimulated inositol phosphate production. Consistent with proposed roles in ligand recognition, mutations eliminated measurable binding of GnRH II, whereas expression of mutant receptors was not decreased. In detailed analysis of how these residues affect ligand-dependent signaling, [Trp2]-GnRH I showed lesser decreases in potency than GnRH I at the Asp2.61(97)Glu mutant. In contrast, [Trp2]-GnRH II showed the same loss of potency as GnRH II at this mutant. This suggests that Asp2.61(97) contributes to recognition of His2 of GnRH I, but not of GnRH II. GnRH II showed a large decrease in potency at the Asn2.65(101)Ala mutant compared with analogs lacking the CO group of Gly10NH2. This suggests that Asn2.65(101) recognizes Gly10NH2 of GnRH II. GnRH agonists showed large decreases in potency at the Lys3.32(120)Gln mutant, but antagonist activity was unaffected. This suggests that Lys3.32(120) recognizes agonists, but not antagonists, as in the type I receptor. These data indicate that roles of conserved residues are similar, but not identical, in the type I and II GnRH receptors.
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Affiliation(s)
- Sipho Mamputha
- Medical Research Council/University of Cape Town Research Group for Receptor Biology, Institute for Infectious Diseases and Molecular Medicine and Division of Medical Biochemistry, Cape Town, South Africa
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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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Söderhäll JA, Polymeropoulos EE, Paulini K, Günther E, Kühne R. Antagonist and agonist binding models of the human gonadotropin-releasing hormone receptor. Biochem Biophys Res Commun 2005; 333:568-82. [PMID: 15950933 DOI: 10.1016/j.bbrc.2005.05.142] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2005] [Accepted: 05/07/2005] [Indexed: 10/25/2022]
Abstract
G-protein-coupled receptors (GPCRs) constitute one of the most important classes of drug targets. Since the first high-resolution structure of a GPCR was determined by Palczewski and co-workers [K. Palczewski, T. Kumasaka, T. Hori, C.A. Behnke, H. Motoshima, B.A. Fox, I. Le Trong, D.C. Teller, T. Okada, R.E. Stenkamp, M. Yamamoto, M. Miyano, Crystal structure of rhodopsin: a G-protein-coupled receptor, Science 289 (2000) 739-745], development of in silico models of rhodopsin-like GPCRs could be rationally founded. In this work, we present a model of the human gonadotropin-releasing hormone receptor based on the rhodopsin structure. The transmembrane helices are modeled by homology, while the extra- and intra-cellular loops are modeled in such a way that experimentally determined interactions and microdomains (e.g., hydrophobic cores) are retained. We conclude that specifically tailored models, compared to more automatic approaches, have the benefit that known interactions are easily introduced early in the homology modeling. Furthermore, tailored models, although more tedious to construct, are better suited for drug lead finding and for compound optimization. To test the stability of the receptor, we performed a 1 ns molecular dynamics simulation. Moreover, we docked two agonists (native GnRH and Triptorelin, [dTrp(6)]-GnRH) and two antagonists (Cetrorelix, dNal(1)-dCpa(2)-dPal(3)-Ser(4)-Tyr(5)-dCit(6)-Leu(7)-Arg(8)-Pro(9)-dAla(10)), and the covalently constrained dicyclic decapeptide dicyclo(1,1'-5/4-10)[Ac-Glu(1)(Gly(1)')-dCpa(2)-dTrp(3)-Asp(4)-dbu(5)-dNal(6)-Leu(7)-Arg(8)-Pro(9)-dpr(10)-NH(2)] into the putative receptor binding site. The docked ligand conformations result in ligand-receptor interactions that are generally in good agreement with site-directed mutagenesis and ligand-binding studies presented in the literature. Our results indicate that the binding conformation of the antagonists differs from that of the agonists. This difference can be linked to the activation or inhibition of the receptor.
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MESH Headings
- Binding Sites
- Computer Simulation
- Gonadotropin-Releasing Hormone/analogs & derivatives
- Gonadotropin-Releasing Hormone/chemistry
- Humans
- Models, Chemical
- Models, Molecular
- Protein Binding
- Protein Conformation
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/analysis
- Receptors, G-Protein-Coupled/antagonists & inhibitors
- Receptors, G-Protein-Coupled/chemistry
- Receptors, LHRH/agonists
- Receptors, LHRH/analysis
- Receptors, LHRH/antagonists & inhibitors
- Receptors, LHRH/chemistry
- Sequence Analysis, Protein/methods
- Triptorelin Pamoate/chemistry
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Affiliation(s)
- J Arvid Söderhäll
- Institute for Molecular Pharmacology, Robert-Rössle-Strasse 10, D-13125 Berlin, Germany
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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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