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Istiban MN, De Fruyt N, Kenis S, Beets I. Evolutionary conserved peptide and glycoprotein hormone-like neuroendocrine systems in C. elegans. Mol Cell Endocrinol 2024; 584:112162. [PMID: 38290646 PMCID: PMC11004728 DOI: 10.1016/j.mce.2024.112162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/11/2024] [Accepted: 01/15/2024] [Indexed: 02/01/2024]
Abstract
Peptides and protein hormones form the largest group of secreted signals that mediate intercellular communication and are central regulators of physiology and behavior in all animals. Phylogenetic analyses and biochemical identifications of peptide-receptor systems reveal a broad evolutionary conservation of these signaling systems at the molecular level. Substantial progress has been made in recent years on characterizing the physiological and putative ancestral roles of many peptide systems through comparative studies in invertebrate models. Several peptides and protein hormones are not only molecularly conserved but also have conserved roles across animal phyla. Here, we focus on functional insights gained in the nematode Caenorhabditis elegans that, with its compact and well-described nervous system, provides a powerful model to dissect neuroendocrine signaling networks involved in the control of physiology and behavior. We summarize recent discoveries on the evolutionary conservation and knowledge on the functions of peptide and protein hormone systems in C. elegans.
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Affiliation(s)
- Majdulin Nabil Istiban
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium
| | - Nathan De Fruyt
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium
| | - Signe Kenis
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium
| | - Isabel Beets
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium.
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Chang JP, Pemberton JG. Comparative aspects of GnRH-Stimulated signal transduction in the vertebrate pituitary - Contributions from teleost model systems. Mol Cell Endocrinol 2018; 463:142-167. [PMID: 28587765 DOI: 10.1016/j.mce.2017.06.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/31/2017] [Accepted: 06/01/2017] [Indexed: 02/07/2023]
Abstract
Gonadotropin-releasing hormone (GnRH) is a major regulator of reproduction through actions on pituitary gonadotropin release and synthesis. Although it is often thought that pituitary cells are exposed to only one GnRH, multiple GnRH forms are delivered to the pituitary of teleost fishes; interestingly this can include the cGnRH-II form usually thought to be non-hypophysiotropic. GnRHs can regulate other pituitary cell-types, both directly as well as indirectly, and multiple GnRH receptors (GnRHRs) may also be expressed in the pituitary, and even within a single pituitary cell-type. Literature on the differential actions of native GnRH isoforms in primary pituitary cells is largely derived from teleost fishes. This review will outline the diversity and complexity of GnRH-GnRHR signal transduction found within vertebrate gonadotropes as well as extra-gonadotropic sites with special emphasis on comparative studies from fish models. The implications that GnRHR transduction mechanisms are GnRH isoform-, function-, and cell-specific are also discussed.
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Affiliation(s)
- John P Chang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
| | - Joshua G Pemberton
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
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Griffiths K, Dolezal O, Cao B, Nilsson SK, See HB, Pfleger KDG, Roche M, Gorry PR, Pow A, Viduka K, Lim K, Lu BGC, Chang DHC, Murray-Rust T, Kvansakul M, Perugini MA, Dogovski C, Doerflinger M, Zhang Y, Parisi K, Casey JL, Nuttall SD, Foley M. i-bodies, Human Single Domain Antibodies That Antagonize Chemokine Receptor CXCR4. J Biol Chem 2016; 291:12641-12657. [PMID: 27036939 DOI: 10.1074/jbc.m116.721050] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Indexed: 01/20/2023] Open
Abstract
CXCR4 is a G protein-coupled receptor with excellent potential as a therapeutic target for a range of clinical conditions, including stem cell mobilization, cancer prognosis and treatment, fibrosis therapy, and HIV infection. We report here the development of a fully human single-domain antibody-like scaffold termed an "i-body," the engineering of which produces an i-body library possessing a long complementarity determining region binding loop, and the isolation and characterization of a panel of i-bodies with activity against human CXCR4. The CXCR4-specific i-bodies show antagonistic activity in a range of in vitro and in vivo assays, including inhibition of HIV infection, cell migration, and leukocyte recruitment but, importantly, not the mobilization of hematopoietic stem cells. Epitope mapping of the three CXCR4 i-bodies AM3-114, AM4-272, and AM3-523 revealed binding deep in the binding pocket of the receptor.
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Affiliation(s)
| | - Olan Dolezal
- Biomedical Manufacturing, CSIRO Manufacturing, 343 Royal Parade, Parkville, Victoria 3052
| | - Benjamin Cao
- the Australian Regenerative Medicine Institute, Monash University, Wellington Road, Clayton, Victoria 3800,; Biomedical Manufacturing, CSIRO Manufacturing, Bayview Avenue, Clayton, Victoria 3168
| | - Susan K Nilsson
- the Australian Regenerative Medicine Institute, Monash University, Wellington Road, Clayton, Victoria 3800,; Biomedical Manufacturing, CSIRO Manufacturing, Bayview Avenue, Clayton, Victoria 3168
| | - Heng B See
- the Harry Perkins Institute of Medical Research, Nedlands, Western Australia 6009,; the Centre for Medical Research, University of Western Australia, Crawley, Western Australia 6009
| | - Kevin D G Pfleger
- the Harry Perkins Institute of Medical Research, Nedlands, Western Australia 6009,; the Centre for Medical Research, University of Western Australia, Crawley, Western Australia 6009,; Dimerix Bioscience Ltd., Nedlands, Western Australia 6009
| | - Michael Roche
- the Doherty Institute for Infection and Immunity, University of Melbourne, 792 Elizabeth Street, Melbourne, Victoria 3000,; the Burnet Institute, 85 Commercial Road, Melbourne, Victoria 3004
| | - Paul R Gorry
- the School of Health and Biomedical Sciences, College of Science, Engineering and Health, RMIT University, Melbourne, Victoria 3001
| | - Andrew Pow
- From AdAlta Pty. Ltd., 15/2 Park Dr., Bundoora, Victoria 3083
| | - Katerina Viduka
- From AdAlta Pty. Ltd., 15/2 Park Dr., Bundoora, Victoria 3083
| | - Kevin Lim
- From AdAlta Pty. Ltd., 15/2 Park Dr., Bundoora, Victoria 3083
| | | | | | | | - Marc Kvansakul
- the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, and
| | - Matthew A Perugini
- the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, and
| | - Con Dogovski
- the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, and
| | | | - Yuan Zhang
- the Department of Medicine, St. Vincent's Hospital, University of Melbourne, Fitzroy, Victoria 3065, Australia
| | - Kathy Parisi
- From AdAlta Pty. Ltd., 15/2 Park Dr., Bundoora, Victoria 3083,; the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, and
| | - Joanne L Casey
- From AdAlta Pty. Ltd., 15/2 Park Dr., Bundoora, Victoria 3083
| | - Stewart D Nuttall
- Biomedical Manufacturing, CSIRO Manufacturing, 343 Royal Parade, Parkville, Victoria 3052
| | - Michael Foley
- From AdAlta Pty. Ltd., 15/2 Park Dr., Bundoora, Victoria 3083,; the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, and.
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Jaeger WC, Seeber RM, Eidne KA, Pfleger KDG. Molecular determinants of orexin receptor-arrestin-ubiquitin complex formation. Br J Pharmacol 2014; 171:364-74. [PMID: 24206104 PMCID: PMC3904257 DOI: 10.1111/bph.12481] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 09/11/2013] [Accepted: 10/15/2013] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND AND PURPOSE The orexin system regulates a multitude of key physiological processes, particularly involving maintenance of metabolic homeostasis. Consequently, there is considerable potential for pharmaceutical development for the treatment of disorders from narcolepsy to metabolic syndrome. It acts through the hormonal activity of two endogenous peptides, orexin A binding to orexin receptors 1 and 2 (OX₁ and OX₂) with similar affinity, and orexin B binding to OX₂ with higher affinity than OX₁ receptors. We have previously revealed data differentiating orexin receptor subtypes with respect to their relative stability in forming orexin receptor-arrestin-ubiquitin complexes measured by BRET. Recycling and cellular signalling distinctions were also observed. Here, we have investigated, using BRET, the molecular determinants involved in providing OX₂ receptors with greater β-arrestin-ubiquitin complex stability. EXPERIMENTAL APPROACH The contribution of the C-terminal tail of the OX receptors was investigated by bulk substitution and site-specific mutagenesis using BRET and inositol phosphate assays. KEY RESULTS Replacement of the OX₁ receptor C-terminus with that of the OX₂ receptor did not result in the expected gain of function, indicating a role for intracellular domain configuration in addition to primary structure. Furthermore, two out of the three putative serine/threonine clusters in the C-terminus were found to be involved in OX₂ receptor-β-arrestin-ubiquitin complex formation. CONCLUSIONS AND IMPLICATIONS This study provides fundamental insights into the molecular elements that influence receptor-arrestin-ubiquitin complex formation. Understanding how and why the orexin receptors can be functionally differentiated brings us closer to exploiting these receptors as drug targets.
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Affiliation(s)
- Werner C Jaeger
- Laboratory for Molecular Endocrinology-G Protein-Coupled Receptors, Western Australian Institute for Medical Research (WAIMR) and Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
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Dupakuntla M, Pathak B, Roy BS, Mahale SD. Extracellular loop 2 in the FSH receptor is crucial for ligand mediated receptor activation. Mol Cell Endocrinol 2012; 362:60-8. [PMID: 22641019 DOI: 10.1016/j.mce.2012.05.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Revised: 05/17/2012] [Accepted: 05/18/2012] [Indexed: 10/28/2022]
Abstract
The present study aims to determine the role of the specific residues of the extracellular loops (ELs) of the FSH receptor (FSHR) in hormone binding and receptor activation. By substituting the sequences of each of the ELs of human FSHR with those of the luteinizing hormone/choriogonadotropin receptor (LH/CGR), we generated three mutant constructs where the three ELs were individually replaced. A fourth construct had all the three substituted ELs. The receptor expression and hormone binding ability of the mutants were comparable to that of the wild type. Hormone-induced signaling and internalization were lower in the EL2 substitution mutant (EL2M). In this mutant, the EL2 of FSHR was substituted with the corresponding loop of LH/CGR. Interestingly, homology modeling revealed a change in the orientation of EL2 in the mutant receptor. Thus, disruption of EL2 affected overall receptor function, suggesting the role of FSHR specific residues of the loop in ligand mediated signaling.
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Affiliation(s)
- Madhavi Dupakuntla
- Division of Structural Biology, National Institute for Research in Reproductive Health (Indian Council of Medical Research), Parel, Mumbai 400 012, India
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Maya-Núñez G, Janovick JA, Aguilar-Rojas A, Jardón-Valadez E, Leaños-Miranda A, Zariñan T, Ulloa-Aguirre A, Conn PM. Biochemical mechanism of pathogenesis of human gonadotropin-releasing hormone receptor mutants Thr104Ile and Tyr108Cys associated with familial hypogonadotropic hypogonadism. Mol Cell Endocrinol 2011; 337:16-23. [PMID: 21277937 PMCID: PMC3073020 DOI: 10.1016/j.mce.2011.01.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 01/18/2011] [Accepted: 01/19/2011] [Indexed: 12/28/2022]
Abstract
The pathogenic mechanisms whereby the Thr104Ile and Tyr108Cys mutations in the gonadotropin-releasing hormone receptor (GnRHR) gene cause hypogonadotropic hypogonadism in humans are unknown. Transient expression of Thr104Ile and Tyr108Cys mutants in COS-7 cells revealed that both GnRHR mutants neither bind nor respond to agonist. Removal of Lys191 rescued function of both mutants, while addition of a carboxyl-terminal targeting sequence only rescued function of the Thr104Ile mutant. Exposure to the pharmacoperone In3 rescued almost completely Thr104Ile mutant function to wild-type levels, whereas rescue was partial for the Tyr108Cys GnRHR. Additional mutations that block formation of bridges involving Cys108 showed that a Cys108-Cys200 disulfide bridge is the predominant moiety formed in the Tyr108Cys mutant. Thr104Ile and Tyr108Cys GnRHRs are misfolded structures whose function is rescuable by genetic and/or pharmacological strategies. The Tyr108Cys mutant forms an aberrant disulfide bridge that prevents formation of the required Cys14-Cys200 bridge essential for GnRHR plasma membrane expression.
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Affiliation(s)
- Guadalupe Maya-Núñez
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Jo Ann Janovick
- Oregon National Primate Research Center, 505 NW 185th Avenue, Beaverton, OR, 97006
| | - Arturo Aguilar-Rojas
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
- Centro de Investigación Biomédica del Sur (CIBIS), Instituto Mexicano del Seguro Social, Xochitepec, Mor., Mexico
| | - Eduardo Jardón-Valadez
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Alfredo Leaños-Miranda
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Teresa Zariñan
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
| | - Alfredo Ulloa-Aguirre
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
- Oregon National Primate Research Center, 505 NW 185th Avenue, Beaverton, OR, 97006
| | - P. Michael Conn
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia “Luis Castelazo Ayala”, Instituto Mexicano del Seguro Social, México D.F., Mexico
- Oregon National Primate Research Center, 505 NW 185th Avenue, Beaverton, OR, 97006
- Departments of Physiology and Pharmacology, Cell and Development Biology and Obstetrics and Gynecology, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR.97239
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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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Endokrine Therapie der Zukunft. GYNAKOLOGISCHE ENDOKRINOLOGIE 2010. [DOI: 10.1007/s10304-009-0327-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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10
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Abstract
I (R.P.M.) presented "The Year In G Protein-Coupled Receptor Research" at ENDO 2009. I first described the diversity of ligands and the five families into which the approximately 800 G protein-coupled receptors (GPCRs) are grouped, their basic structural architectures, their preeminent role in signaling, and the enormous scope for developing drugs targeted at GPCRs. I then spoke about some of the exciting breakthroughs in solving the atomic level structures of the active state of rhodopsin, beta(2)-adrenergic, beta(1)-adrenergic, and A(2A)-adenosine receptors. I also described studies on the structural changes accompanying the activation of the rhodopsin family of GPCRs. From these recent technical advances, we can anticipate that many more GPCR structures will emerge, which will afford us greater insight into their common and unique structural features and, particularly, the mechanisms underlying their activation. These insights will guide us in our understanding of how GPCRs operate, both in the normal and pathological situation. Although these crystal structures are highly informative, it is important to recognize that they represent static frozen conformations of a single GPCR state. New biophysical techniques are therefore being utilized to facilitate the dynamic monitoring of GPCR structural changes in relation to ligand activation. Solving of the crystal structures of GPCRs has also presented the real possibility of using the information of the ligand-binding pocket to allow in silico screening for novel small-molecule ligands. I then reviewed the concept of ligand-induced selective signaling of GPCRs, which is opening up new insights into more selective drug development. The assembly of GPCRs as homo- and heterooligomers and their phosphorylation and association with a vast array of trafficking and signal-modulating proteins are emerging as major mechanisms underlying the functioning of GPCRs. Differential expression and recruitment of these proteins provide a mechanism for subtle physiological regulation of cellular activity. Finally, I mentioned some of the GPCRs that have lately come to the fore as novel regulators in endocrinology. These included fatty acid-specific GPCRs expressed in pancreatic beta-cells and novel neuroendocrine GPCRs regulating reproduction.
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Affiliation(s)
- Robert P Millar
- Medical Research Council (MRC) Human Reproductive Sciences Unit, The Queen's Medical Research Institute, Edinburgh, Scotland, United Kingdom.
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Light activation of rhodopsin: insights from molecular dynamics simulations guided by solid-state NMR distance restraints. J Mol Biol 2009; 396:510-27. [PMID: 20004206 DOI: 10.1016/j.jmb.2009.12.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Revised: 10/09/2009] [Accepted: 12/02/2009] [Indexed: 11/20/2022]
Abstract
Structural restraints provided by solid-state NMR measurements of the metarhodopsin II intermediate are combined with molecular dynamics simulations to help visualize structural changes in the light activation of rhodopsin. Since the timescale for the formation of the metarhodopsin II intermediate (>1 ms) is beyond that readily accessible by molecular dynamics, we use NMR distance restraints derived from 13C dipolar recoupling measurements to guide the simulations. The simulations yield a working model for how photoisomerization of the 11-cis retinylidene chromophore bound within the interior of rhodopsin is coupled to transmembrane helix motion and receptor activation. The mechanism of activation that emerges is that multiple switches on the extracellular (or intradiscal) side of rhodopsin trigger structural changes that converge to disrupt the ionic lock between helices H3 and H6 on the intracellular side of the receptor.
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GABAergic transmission to gonadotropin-releasing hormone (GnRH) neurons is regulated by GnRH in a concentration-dependent manner engaging multiple signaling pathways. J Neurosci 2009; 29:9809-18. [PMID: 19657033 DOI: 10.1523/jneurosci.2509-09.2009] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) neurons are the central regulators of fertility. GnRH stimulates or inhibits GnRH neuronal activity depending on dose. The mechanisms for these actions remain unknown. We hypothesized GnRH acts in part by altering fast synaptic transmission to GnRH neurons. GABAergic and glutamatergic postsynaptic currents (PSCs), both of which can excite these neurons, were recorded from GnRH neurons in brain slices from adult intact and orchidectomized (ORX) males. ORX enhanced the frequency of GABA transmission to GnRH neurons, but had no effect on glutamatergic transmission. Effects of ORX on GABAergic transmission were reversed by estradiol replacement, suggesting GABA is a mediator of steroid feedback in males. GABAergic neurons express type-1 GnRH receptor (GnRHR-1). Low GnRH (20 nm) reduced GABAergic PSC frequency in GnRH neurons from both ORX and intact mice. High GnRH (2 microm) had no effect on either GABAergic or glutamatergic transmission to GnRH neurons. To investigate mechanisms mediating low-dose GnRH suppression of GABAergic transmission, GABAergic PSCs were recorded after arresting G(alphai) activity with pertussis toxin (PTX). PTX abolished the suppressive effect of low GnRH. Moreover, PTX uncovered a stimulatory effect of high GnRH on GABAergic transmission. These data suggest low-dose GnRH suppresses GnRH firing rate in part by decreasing GABAergic transmission to the GnRH neurons, independent of gonadal hormone milieu. Low-dose GnRH appears to exert the suppressive effect by activating GnRHR-I coupled to G(alphai). The concentration-dependent effects of GnRH may be mediated in part by changes in affinity of GnRH to GnRHR-I coupled to different G(alpha) proteins.
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Liu J, Maccalman CD, Wang YL, Leung PCK. Promotion of human trophoblasts invasion by gonadotropin-releasing hormone (GnRH) I and GnRH II via distinct signaling pathways. Mol Endocrinol 2009; 23:1014-21. [PMID: 19372239 DOI: 10.1210/me.2008-0451] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The potential roles of GnRH I and GnRH II have been assigned in promoting the invasive capacity of human trophoblasts by regulating matrix metalloproteinases-2 and -9, type I tissue inhibitor of matrix metalloproteinase, and urokinase plasminogen activator/plasminogen activator inhibitor protease systems during human placentation, and GnRH II has been shown to be more potent than GnRH I. However, the mechanisms for the differential effects of these two hormones remain unclear. In this study, we examined the invasion-promoting effects and the signaling pathways of GnRH I and GnRH II in human trophoblasts. The data revealed that both GnRH I and GnRH II were key autocrine and/or paracrine regulators in facilitating trophoblast invasion. The GnRH receptor antagonist (Antide) and specific small interfering RNA for GnRH receptor inhibited the regulatory effects of GnRH I, but not GnRH II, on trophoblast invasion. Both GnRH I and II activated protein kinase C, ERK1/2, and c-Jun N-terminal kinase to mediate their effects on trophoblast invasion, whereas only GnRH II elicited invasion-promoting action through transactivating the tyrosine kinase activity of epidermal growth factor receptor in trophoblasts. Our observations elucidate a ligand-dependent selective cross-communication between GnRH receptor and epidermal growth factor receptor signaling systems in human trophoblastic cell, and this would further our understanding on the differentially biological significance of these two forms of GnRH in extrapituitary tissues.
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Affiliation(s)
- Jing Liu
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, People's Republic of China
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Ahuja S, Hornak V, Yan ECY, Syrett N, Goncalves JA, Hirshfeld A, Ziliox M, Sakmar TP, Sheves M, Reeves PJ, Smith SO, Eilers M. Helix movement is coupled to displacement of the second extracellular loop in rhodopsin activation. Nat Struct Mol Biol 2009; 16:168-75. [PMID: 19182802 PMCID: PMC2705779 DOI: 10.1038/nsmb.1549] [Citation(s) in RCA: 176] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2008] [Accepted: 01/02/2009] [Indexed: 11/30/2022]
Abstract
The second extracellular loop (EL2) of rhodopsin forms a cap over the binding site of its photoreactive 11-cis retinylidene chromophore. A critical question has been whether EL2 forms a reversible gate that opens upon activation or acts as a rigid barrier. Distance measurements using solid-state 13C NMR spectroscopy between the retinal chromophore and the β4 strand of EL2 show the loop is displaced from the retinal binding site upon activation, and there is a rearrangement in the hydrogen-bonding networks connecting EL2 with the extracellular ends of transmembrane helices H4, H5 and H6. NMR measurements further reveal that structural changes in EL2 are coupled to the motion of helix H5 and breaking of the ionic lock that regulates activation. These results provide a comprehensive view of how retinal isomerization triggers helix motion and activation in this prototypical G protein-coupled receptor.
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Affiliation(s)
- Shivani Ahuja
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-5215, USA
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