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Minagawa I, Sagata D, Pitia AM, Kohriki H, Shibata M, Sasada H, Hasegawa Y, Kohsaka T. Dynamics of insulin-like factor 3 and its receptor expression in boar testes. J Endocrinol 2014; 220:247-61. [PMID: 24464024 DOI: 10.1530/joe-13-0430] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Relaxin-like factor (RLF), now mainly known as insulin-like factor 3 (INSL3), is essential for testis descent during fetal development; however, its function in the adult testis is still being elucidated. As a major step toward understanding the as-yet-unknown function of INSL3 in boars, this study aimed to develop a time-resolved fluoroimmunoassay for boar INSL3, characterize the dynamics of INSL3 expression during development, and demonstrate the expression of the INSL3 hormone-receptor system in the testis. All samples were collected from Duroc boars. The sensitivity of the assay system established was 8.2 pg/well (164 pg/ml), and no cross-reactivity with other hormones, such as porcine relaxin, was observed. Circulating INSL3 was shown to increase progressively during development. INSL3 secreted from the Leydig cells was released not only into the blood circulation but also into the interstitial and seminiferous compartments in sufficient concentrations. A testicular fractionation study revealed that its receptor RXFP2 transcripts were expressed mainly in testicular germ cells. In addition, INSL3 bound to the germ cell membranes in a hormone-specific and saturable manner. These results reveal that INSL3 secreted into the interstitial compartment from the Leydig cells is transported into the seminiferous compartments, where its receptor RXFP2 is expressed mainly in the germ cells to which INSL3 binds, suggesting that INSL3 functions as a paracrine factor on seminiferous germ cells.
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Affiliation(s)
- Itaru Minagawa
- Laboratory of Animal Reproduction and Physiology, Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan Division of Animal Resource Production, The United Graduate School of Agricultural Science, Gifu University, Gifu, Japan Shizuoka Swine and Poultry Experimental Station, Kikugawa, Shizuoka, Japan Laboratory of Animal Reproduction, School of Veterinary Medicine, Kitasato University, Towada, Japan School of Veterinary Medicine, Animal Sciences High-Tech Research Center, Kitasato University, Towada, Japan
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52
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Chan LJ, Smith CM, Chua BE, Lin F, Bathgate RAD, Separovic F, Gundlach AL, Hossain MA, Wade JD. Synthesis of fluorescent analogs of relaxin family peptides and their preliminary in vitro and in vivo characterization. Front Chem 2013; 1:30. [PMID: 24790958 PMCID: PMC3982560 DOI: 10.3389/fchem.2013.00030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/18/2013] [Indexed: 12/13/2022] Open
Abstract
Relaxin, a heterodimeric polypeptide hormone, is a key regulator of collagen metabolism and multiple vascular control pathways in humans and rodents. Its actions are mediated via its cognate G-protein-coupled receptor, RXFP1 although it also "pharmacologically" activates RXFP2, the receptor for the related, insulin-like peptide 3 (INSL3), which has specific actions on reproduction and bone metabolism. Therefore, experimental tools to facilitate insights into the distinct biological actions of relaxin and INSL3 are required, particularly for studies of tissues containing both RXFP1 and RXFP2. Here, we chemically functionalized human (H2) relaxin, the RXFP1-selective relaxin analog H2:A(4-24)(F23A), and INSL3 to accommodate a fluorophore without marked reduction in binding or activation propensity. Chemical synthesis of the two chains for each peptide was followed by sequential regioselective formation of their three disulfide bonds. Click chemistry conjugation of Cy5.5 at the B-chain N-terminus, with conservation of the disulfide bonds, yielded analogs displaying appropriate selective binding affinity and ability to activate RXFP1 and/or RXFP2 in vitro. The in vivo biological activity of Cy5.5-H2 relaxin and Cy5.5-H2:A(4-24)(F23A) was confirmed in mice, as acute intracerebroventricular (icv) infusion of these peptides (but not Cy5.5-INSL3) stimulated water drinking, an established behavioral response elicited by central RXFP1 activation. The central distribution of Cy5.5-conjugated peptides was examined in mice killed 30 min after infusion, revealing higher fluorescence within brain tissue near-adjacent to the cerebral ventricle walls relative to deeper brain areas. Production of fluorophore-conjugated relaxin family peptides will facilitate future pharmacological studies to probe the function of H2 relaxin/RXFP1 and INSL3/RXFP2 signaling in vivo while tracking their distribution following central or peripheral administration.
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Affiliation(s)
- Linda J Chan
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia ; School of Chemistry, The University of Melbourne VIC, Australia
| | - Craig M Smith
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia ; Florey Department of Neuroscience and Mental Health, The University of Melbourne VIC, Australia
| | - Berenice E Chua
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia
| | - Feng Lin
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia
| | - Ross A D Bathgate
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia ; Florey Department of Neuroscience and Mental Health, The University of Melbourne VIC, Australia ; Department of Biochemistry and Molecular Biology, The University of Melbourne VIC, Australia
| | | | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia ; Florey Department of Neuroscience and Mental Health, The University of Melbourne VIC, Australia
| | - Mohammed Akhter Hossain
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia ; School of Chemistry, The University of Melbourne VIC, Australia ; Florey Department of Neuroscience and Mental Health, The University of Melbourne VIC, Australia
| | - John D Wade
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne VIC, Australia ; School of Chemistry, The University of Melbourne VIC, Australia ; Florey Department of Neuroscience and Mental Health, The University of Melbourne VIC, Australia
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53
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: G protein-coupled receptors. Br J Pharmacol 2013; 170:1459-581. [PMID: 24517644 PMCID: PMC3892287 DOI: 10.1111/bph.12445] [Citation(s) in RCA: 505] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. G protein-coupled receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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Kong RCK, Petrie EJ, Mohanty B, Ling J, Lee JCY, Gooley PR, Bathgate RAD. The relaxin receptor (RXFP1) utilizes hydrophobic moieties on a signaling surface of its N-terminal low density lipoprotein class A module to mediate receptor activation. J Biol Chem 2013; 288:28138-51. [PMID: 23926099 DOI: 10.1074/jbc.m113.499640] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The peptide hormone relaxin is showing potential as a treatment for acute heart failure. Although it is known that relaxin mediates its actions through the G protein-coupled receptor relaxin family peptide receptor 1 (RXFP1), little is known about the molecular mechanisms by which relaxin binding results in receptor activation. Previous studies have highlighted that the unique N-terminal low density lipoprotein class A (LDLa) module of RXFP1 is essential for receptor activation, and it has been hypothesized that this module is the true "ligand" of the receptor that directs the conformational changes necessary for G protein coupling. In this study, we confirmed that an RXFP1 receptor lacking the LDLa module binds ligand normally but cannot signal through any characterized G protein-coupled receptor signaling pathway. Furthermore, we comprehensively examined the contributions of amino acids in the LDLa module to RXFP1 activity using both gain-of-function and loss-of-function mutational analysis together with NMR structural analysis of recombinant LDLa modules. Gain-of-function studies with an inactive RXFP1 chimera containing the LDLa module of the human LDL receptor (LB2) demonstrated two key N-terminal regions of the module that were able to rescue receptor signaling. Loss-of-function mutations of residues in these regions demonstrated that Leu-7, Tyr-9, and Lys-17 all contributed to the ability of the LDLa module to drive receptor activation, and judicious amino acid substitutions suggested this involves hydrophobic interactions. Our results demonstrate that these key residues contribute to interactions driving the active receptor conformation, providing further evidence of a unique mode of G protein-coupled receptor activation.
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Affiliation(s)
- Roy C K Kong
- From the Florey Institute of Neuroscience and Mental Health and Florey Department of Neuroscience and Mental Health
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55
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Bathgate RAD, Halls ML, van der Westhuizen ET, Callander GE, Kocan M, Summers RJ. Relaxin family peptides and their receptors. Physiol Rev 2013; 93:405-80. [PMID: 23303914 DOI: 10.1152/physrev.00001.2012] [Citation(s) in RCA: 376] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.
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Affiliation(s)
- R A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences & Department of Pharmacology, Monash University, Victoria, Australia
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56
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Cernaro V, Lacquaniti A, Lupica R, Buemi A, Trimboli D, Giorgianni G, Bolignano D, Buemi M. Relaxin: new pathophysiological aspects and pharmacological perspectives for an old protein. Med Res Rev 2013; 34:77-105. [PMID: 23401142 DOI: 10.1002/med.21277] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Human relaxin-2 (hereafter simply defined as "relaxin") is a 6-kDa peptidic hormone best known for the physiological role played during pregnancy in the growth and differentiation of the reproductive tract and in the renal and systemic hemodynamic changes. This factor can also be involved in the pathophysiology of arterial hypertension and heart failure, in the molecular pathways of fibrosis and cancer, and in angiogenesis and bone remodeling. It belongs to the relaxin peptide family, whose members comprehensively exert numerous effects through interaction with different types of receptors, classified as relaxin family peptide (RXFP) receptors (RXFP1, RXFP2, RXFP3, RXFP4). Research looks toward the in-depth examination and complete understanding of relaxin in its various pleiotropic actions. The intent is to evaluate the likelihood of employing this substance for therapeutic purposes, for instance in diseases where a deficit could be part of the underlying pathophysiological mechanisms, also avoiding any adverse effect. Relaxin is already being considered as a promising drug, especially in acute heart failure. A careful study of the different RXFPs and their receptors and the comprehension of all biological activities of these hormones will probably provide new drugs with a potential wide range of therapeutic applications in the near future.
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Affiliation(s)
- Valeria Cernaro
- Department of Internal Medicine, University of Messina, Via Consolare Valeria, 1, 98100, Italy
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57
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Preliminary Structure–Function Relationship Studies on Insulin-Like Peptide 5 (INSL5). Int J Pept Res Ther 2013. [DOI: 10.1007/s10989-013-9341-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Bathgate RAD, Oh MHY, Ling WJJ, Kaas Q, Hossain MA, Gooley PR, Rosengren KJ. Elucidation of relaxin-3 binding interactions in the extracellular loops of RXFP3. Front Endocrinol (Lausanne) 2013; 4:13. [PMID: 23440673 PMCID: PMC3579193 DOI: 10.3389/fendo.2013.00013] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 01/31/2013] [Indexed: 12/28/2022] Open
Abstract
Relaxin-3 is a highly conserved neuropeptide in vertebrate species and binds to the Class A G protein-coupled receptor (GPCR) RXFP3. Relaxin-3 is involved in a wide range of behaviors, including feeding, stress responses, arousal, and cognitive processes and therefore targeting of RXFP3 may be relevant for a range of neurological diseases. Structural knowledge of RXFP3 and its interaction with relaxin-3 would both increase our understanding of ligand recognition in GPCRs that respond to protein ligands and enable acceleration of the design of drug leads. In this study we have used comparative sequence analysis, molecular modeling and receptor mutagenesis to investigate the binding site of the native ligand human relaxin-3 (H3 relaxin) on the human RXFP3 receptor. Previous structure function studies have demonstrated that arginine residues in the H3 relaxin B-chain are critical for binding interactions with the receptor extracellular loops and/or N-terminal domain. Hence we have concentrated on determining the ligand interacting sites in these domains and have focused on glutamic (E) and aspartic acid (D) residues in these regions that may form electrostatic interactions with these critical arginine residues. Conserved D/E residues identified from vertebrate species multiple sequence alignments were mutated to Ala in human RXFP3 to test the effect of loss of amino acid side chain on receptor binding using a Eu-labeled relaxin-3 agonist. Finally data from mutagenesis experiments have been used in ligand docking simulations to a homology model of human RXFP3 based on the peptide-bound chemokine receptor 4 (CXCR4) structure. These studies have resulted in a model of the relaxin-3 interaction with RXFP3 which will inform further interrogation of the agonist binding site.
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Affiliation(s)
- Ross A. D. Bathgate
- Florey Institute of Neuroscience and Mental Health, University of MelbourneParkville, VIC, Australia
- Department of Biochemistry and Molecular Biology, University of MelbourneParkville, VIC, Australia
- *Correspondence: Ross A. D. Bathgate, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 3010 Victoria, Australia. e-mail:
| | - Maria H. Y. Oh
- Florey Institute of Neuroscience and Mental Health, University of MelbourneParkville, VIC, Australia
- Department of Biochemistry and Molecular Biology, University of MelbourneParkville, VIC, Australia
| | - W. J. Jason Ling
- Florey Institute of Neuroscience and Mental Health, University of MelbourneParkville, VIC, Australia
- Department of Biochemistry and Molecular Biology, University of MelbourneParkville, VIC, Australia
| | - Quentin Kaas
- Institute for Molecular Bioscience, The University of QueenslandBrisbane, QLD, Australia
| | - M. Akhter Hossain
- Florey Institute of Neuroscience and Mental Health, University of MelbourneParkville, VIC, Australia
- School of Chemistry, University of MelbourneParkville, VIC, Australia
| | - Paul R. Gooley
- Department of Biochemistry and Molecular Biology, University of MelbourneParkville, VIC, Australia
| | - K. Johan Rosengren
- School of Biomedical Sciences, The University of QueenslandBrisbane, QLD, Australia
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59
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Bruell S, Kong RCK, Petrie EJ, Hoare B, Wade JD, Scott DJ, Gooley PR, Bathgate RAD. Chimeric RXFP1 and RXFP2 Receptors Highlight the Similar Mechanism of Activation Utilizing Their N-Terminal Low-Density Lipoprotein Class A Modules. Front Endocrinol (Lausanne) 2013; 4:171. [PMID: 24273532 PMCID: PMC3822782 DOI: 10.3389/fendo.2013.00171] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 10/25/2013] [Indexed: 11/13/2022] Open
Abstract
Relaxin family peptide (RXFP) receptors 1 and 2 are unique G-protein coupled receptors in that they contain an N-terminal low-density lipoprotein type A (LDLa) module which is necessary for receptor activation. The current hypothesis suggests that upon ligand binding the LDLa module interacts with the transmembrane (TM) domain of a homodimer partner receptor to induce the active receptor conformations. We recently demonstrated that three residues in the N-terminus of the RXFP1 LDLa module are potentially involved in hydrophobic interactions with the receptor to drive activation. RXFP2 shares two out of three of the residues implicated, suggesting that the two LDLa modules could be interchanged without adversely affecting activity. However, in 2007 it was shown that a chimera consisting of the RXFP1 receptor with its LDLa swapped for that of RXFP2 did not signal. We noticed this construct also contained the RXFP2 region linking the LDLa to the leucine-rich repeats. We therefore constructed chimeric RXFP1 and RXFP2 receptors with their LDLa modules swapped immediately C-terminally to the final cysteine residue of the module, retaining the native linker. In addition, we exchanged the TM domains of the chimeras to explore if matching the LDLa module with the TM domain of its native receptor altered activity. All of the chimeras were expressed at the surface of HEK293T cells with ligand binding profiles similar to the wild-type receptors. Importantly, as predicted, ligand binding was able to induce cAMP-based signaling. Chimeras of RXFP1 with the LDLa of RXFP2 demonstrated reduced H2 relaxin potency with the pairing of the RXFP2 TM with the RXFP2 LDLa necessary for full ligand efficacy. In contrast the ligand-mediated potencies and efficacies on the RXFP2 chimeras were similar suggesting the RXFP1 LDLa module has similar efficacy on the RXFP2 TM domain. Our studies demonstrate the LDLa modules of RXFP1 and RXFP2 modulate receptor activation via a similar mechanism.
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Affiliation(s)
- Shoni Bruell
- Florey Department of Neuroscience and Mental Health, Florey Institute of Neuroscience and Mental Health , Melbourne, VIC , Australia ; Department of Biochemistry and Molecular Biology , Melbourne, VIC , Australia
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60
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Lin F, Tailhades J, Chan LJ, Bathgate RA, Hossain MA, Wade JD. Preparation of canine relaxin by Fmoc-solid phase synthesis and regioselective disulfide bond formation within the A- and B-chains. ACTA ACUST UNITED AC 2013. [DOI: 10.7243/2052-9341-1-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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61
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Chen CZ, Southall N, Xiao J, Marugan JJ, Ferrer M, Hu X, Jones RE, Feng S, Agoulnik IU, Zheng W, Agoulnik AI. Identification of small-molecule agonists of human relaxin family receptor 1 (RXFP1) by using a homogenous cell-based cAMP assay. ACTA ACUST UNITED AC 2012; 18:670-7. [PMID: 23212924 DOI: 10.1177/1087057112469406] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The relaxin hormone is involved in a variety of biological functions, including female reproduction and parturition, as well as regulation of cardiovascular, renal, pulmonary, and hepatic functions. It regulates extracellular matrix remodeling, cell invasiveness, proliferation, differentiation, and overall tissue homeostasis. The G protein-coupled receptor (GPCR) relaxin family receptor 1 (RXFP1) is a cognate relaxin receptor that mainly signals through cyclic AMP second messenger. Although agonists of the receptor could have a wide range of pharmacologic utility, until now there have been no reported small-molecule agonists for relaxin receptors. Here, we report the development of a quantitative high-throughput platform for an RXFP1 agonist screen based on homogenous cell-based HTRF cyclic AMP (cAMP) assay technology. Two small molecules of similar structure were independently identified from a screen of more than 365 677 compounds. Neither compound showed activity in a counterscreen with HEK293T cells transfected with an unrelated GPCR vasopressin 1b receptor. These small-molecule agonists also demonstrated selectivity against the RXFP2 receptor, providing a basis for future medicinal chemistry optimization of selective relaxin receptor agonists.
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Affiliation(s)
- Catherine Z Chen
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD, USA
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62
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The Importance of Tryptophan B28 in H2 Relaxin for RXFP2 Binding and Activation. Int J Pept Res Ther 2012. [DOI: 10.1007/s10989-012-9332-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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63
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Chan LJ, Rosengren KJ, Layfield SL, Bathgate RAD, Separovic F, Samuel CS, Hossain MA, Wade JD. Identification of key residues essential for the structural fold and receptor selectivity within the A-chain of human gene-2 (H2) relaxin. J Biol Chem 2012; 287:41152-64. [PMID: 23024363 DOI: 10.1074/jbc.m112.409284] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human gene-2 (H2) relaxin is currently in Phase III clinical trials for the treatment of acute heart failure. It is a 53-amino acid insulin-like peptide comprising two chains and three disulfide bonds. It interacts with two of the relaxin family peptide (RXFP) receptors. Although its cognate receptor is RXFP1, it is also able to cross-react with RXFP2, the native receptor for a related peptide, insulin-like peptide 3. In order to understand the basis of this cross-reactivity, it is important to elucidate both binding and activation mechanisms of this peptide. The primary binding mechanism of this hormone has been extensively studied and well defined. H2 relaxin binds to the leucine-rich repeats of RXFP1 and RXFP2 using B-chain-specific residues. However, little is known about the secondary interaction that involves the A-chain of H2 relaxin and transmembrane exoloops of the receptors. We demonstrate here through extensive mutation of the A-chain that the secondary interaction between H2 relaxin and RXFP1 is not driven by any single amino acid, although residues Tyr-3, Leu-20, and Phe-23 appear to contribute. Interestingly, these same three residues are important drivers of the affinity and activity of H2 relaxin for RXFP2 with additional minor contributions from Lys-9, His-12, Lys-17, Arg-18, and Arg-22. Our results provide new insights into the mechanism of secondary activation interaction of RXFP1 and RXFP2 by H2 relaxin, leading to a potent and RXFP1-selective analog, H2:A(4-24)(F23A), which was tested in vitro and in vivo and found to significantly inhibit collagen deposition similar to native H2 relaxin.
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Affiliation(s)
- Linda J Chan
- Florey Neuroscience Institutes, University of Melbourne, Victoria 3010, Australia
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64
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Scott DJ, Rosengren KJ, Bathgate RAD. The different ligand-binding modes of relaxin family peptide receptors RXFP1 and RXFP2. Mol Endocrinol 2012; 26:1896-906. [PMID: 22973049 DOI: 10.1210/me.2012-1188] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Relaxin and insulin-like peptide 3 (INSL3) are peptide hormones with a number of important physiological roles in reproduction, regulation of extracellular matrix turnover, and cardiovascular function. Relaxin and INSL3 mediate their actions through the closely related G-protein coupled receptors, relaxin family peptide receptors 1 and 2 (RXFP1 and RXFP2), respectively. These receptors have large extracellular domains (ECD) that contain high-affinity ligand-binding sites within their 10 leucine-rich repeat (LRR)-containing modules. Although relaxin can bind and activate both RXFP1 and RXFP2, INSL3 can only bind and activate RXFP2. To investigate whether this difference is related to the nature of the high-affinity ECD binding site or to differences in secondary binding sites involving the receptor transmembrane (TM) domain, we created a suite of constructs with RXFP1/2 chimeric ECD attached to single TM helices. We show that by changing as little as one LRR, representing four amino acid substitutions, we were able to engineer a high-affinity INSL3-binding site into the ECD of RXFP1. Molecular modeling of the INSL3-RXFP2 interaction based on extensive experimental data highlights the differences in the binding mechanisms of relaxin and INSL3 to the ECD of their cognate receptors. Interestingly, when the engineered RXFP1/2 ECD were introduced into full-length RXFP1 constructs, INSL3 exhibited only low affinity and efficacy on these receptors. These results highlight critical differences both in the ECD binding and in the coordination of the ECD-binding site with the TM domain, and provide new mechanistic insights into the binding and activation events of RXFP1 and RXFP2 by their native hormone ligands.
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Affiliation(s)
- Daniel J Scott
- Florey Neuroscience Institutes and the Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
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65
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Halls ML. Constitutive formation of an RXFP1-signalosome: a novel paradigm in GPCR function and regulation. Br J Pharmacol 2012; 165:1644-1658. [PMID: 21557732 DOI: 10.1111/j.1476-5381.2011.01470.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The classical second messenger cAMP is important in diverse physiological processes, where its spatial and temporal compartmentalization allows precise control over multiple cellular events. Within this context, G-protein-coupled receptors (GPCRs) govern specialized pools of cAMP, which are functionally specific for the unique cellular effects attributed to a particular system. The relaxin receptor, RXFP1, is a GPCR that exerts pleiotropic physiological effects including a potent anti-fibrotic response, increased cancer metastases, and has efficacy as a vasodilator in heart failure. On a cellular level, relaxin stimulation of RXFP1 results in the activation of multiple G-protein pathways affecting cAMP accumulation. Specificity and diversity in the cAMP signal generated by RXFP1 is controlled by differential G-protein coupling dependent upon the background of cellular expression, and cAMP compartmentalization. Further complexity in cAMP signalling results from the constitutive assembly of an RXFP1-signalosome, which specifically responds to low concentrations of relaxin, and activates a distinct cAMP pathway. The RXFP1-signalosome is a higher-order protein complex that facilitates receptor sensitivity to attomolar concentration of peptide, exhibits constitutive activity and dual coupling to G-proteins and β-arrestins and reveals a concentration-biased agonism mediated by relaxin. The specific and directed formation of GPCR-centered signalosomes allows an even greater spatial and temporal control of cAMP, thus rationalizing the considerable physiological scope of this ubiquitous second messenger.
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Affiliation(s)
- Michelle L Halls
- Department of Pharmacology, University of Cambridge, Cambridge, UK
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66
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Vodstrcil LA, Tare M, Novak J, Dragomir N, Ramirez RJ, Wlodek ME, Conrad KP, Parry LJ. Relaxin mediates uterine artery compliance during pregnancy and increases uterine blood flow. FASEB J 2012; 26:4035-44. [PMID: 22744867 DOI: 10.1096/fj.12-210567] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Normal pregnancy involves dramatic remodeling of the uterine vasculature, with abnormal vascular adaptations contributing to pregnancy diseases such as preeclampsia. The peptide hormone relaxin is important for the renal and systemic hemodynamic adaptations to pregnancy, and has been shown to increase arterial compliance and outward hypertrophic remodeling. Therefore, we investigated the possibility that relaxin acts on its receptor, RXFP1, to mediate uterine artery compliance in late pregnancy and increase uterine blood flow velocity in rats. RXFP1 was predominantly localized to the tunica media vascular smooth muscle cells in the uterine artery, although receptors were also detected in endothelial cells. Highest expression of Rxfp1 in the uterine artery occurred in estrus and early pregnancy. Isolated uterine arteries from late pregnant rats treated with a monoclonal antibody against circulating relaxin (MCA1) had significantly increased vessel wall stiffness compared with controls, with no reduction in wall thickness. Chronic infusion of relaxin (4 μg/h, osmotic minipump) for 5 d in nonpregnant rats significantly increased uterine artery blood flow velocity. Overall, these data demonstrate a functional role for relaxin in mediating uterine artery compliance in pregnant rats, which may be necessary to maintain adequate uterine blood flow to the uterus and placenta.
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Affiliation(s)
- Lenka A Vodstrcil
- Department of Zoology, The University of Melbourne, Gate 12, Royal Parade, Parkville, VIC, 3010, Australia
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67
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Nagarathnam B, Kalaimathy S, Balakrishnan V, Sowdhamini R. Cross-Genome Clustering of Human and C. elegans G-Protein Coupled Receptors. Evol Bioinform Online 2012; 8:229-59. [PMID: 22807621 PMCID: PMC3396462 DOI: 10.4137/ebo.s9405] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
G-protein coupled receptors (GPCRs) are one of the largest groups of membrane proteins and are popular drug targets. The work reported here attempts to perform cross-genome phylogeny on GPCRs from two widely different taxa, human versus C. elegans genomes and to address the issues on evolutionary plasticity, to identify functionally related genes, orthologous relationship, and ligand binding properties through effective bioinformatic approaches. Through RPS blast around 1106 nematode GPCRs were given chance to associate with previously established 8 types of human GPCR profiles at varying E-value thresholds and resulted 32 clusters were illustrating co-clustering and class-specific retainsionship. In the significant thresholds, 81% of the C. elegans GPCRs were associated with 32 clusters and 27 C. elegans GPCRs (2%) inferred for orthology. 177 hypothetical proteins were observed in cluster association and could be reliably associated with one of 32 clusters. Several nematode-specific GPCR clades were observed suggesting lineage-specific functional recruitment in response to environment.
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Affiliation(s)
- Balasubramanian Nagarathnam
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India
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Hossain MA, Wade JD, Bathgate RAD. Chimeric relaxin peptides highlight the role of the A-chain in the function of H2 relaxin. Peptides 2012; 35:102-6. [PMID: 22414484 DOI: 10.1016/j.peptides.2012.02.021] [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: 01/27/2012] [Revised: 02/23/2012] [Accepted: 02/24/2012] [Indexed: 11/25/2022]
Abstract
Human gene-2 (H2) relaxin is a member of the insulin-relaxin peptide superfamily. Because of the potential clinical applications of H2 relaxin, there is a need for novel analogs that have improved biological activity and receptor specificity. In this respect, we have chemically assembled chimeric peptides consisting of the B-chain of H2 relaxin in combination with A-chains from other insulin/relaxin family members. The peptides were prepared using solid phase peptide synthesis together with regioselective disulfide bond formation and characterized by RP-HPLC, MALDI-TOF MS and amino acid analysis. Their in vitro activity was assessed in RXFP1 or RXFP2 expressing cells. Replacement of the H2 relaxin A-chain resulted in parallel losses of binding affinity and activity on RXFP1. Not surprisingly H1A-H2B demonstrated the highest activity as the H1 A-chain shares high homology with H2 relaxin whereas INSLA-H2B, which shows low homology, had very poor activity. Importantly A-chain replacements had a dramatic effect on RXFP2 activity similar to previous results demonstrating different modes of activation of A-chain variants on RXFP1 and RXFP2. H3A-H2B is particularly interesting as it displays moderate activity at RXFP1 but poor activity at RXFP2 indicating that it may be a template for specific RXFP1 agonist development. Our study confirms that the activity of H2 relaxin at both RXFP1 and RXFP2 relies on interactions with both the B- and A-chains, and also provide new biochemical insights into the mechanism of relaxin action that the A-chain needs to be in native or near-native form for strong RXFP1 or RXFP2 agonist activity.
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Horton JS, Yamamoto SY, Bryant-Greenwood GD. Relaxin augments the inflammatory IL6 response in the choriodecidua. Placenta 2012; 33:399-407. [PMID: 22386961 DOI: 10.1016/j.placenta.2012.02.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 01/16/2012] [Accepted: 02/03/2012] [Indexed: 11/25/2022]
Abstract
UNLABELLED Intrauterine infection frequently leads to preterm birth (PTB), with the pathophysiology involving activation of the innate immune system and its associated inflammatory response. The choriodecidua produces relaxin (RLN) and elevated levels are associated with preterm premature rupture of the fetal membranes. However, it is not increased in bacterially-mediated PTB, but may act as an endogenous sterile inflammatory mediator. Elevated systemic RLN levels from the corpus luteum are also associated with PTB, but the mechanism is unknown. In clinical obstetrics, intrauterine inflammation or infection can coexist with elevated RLN. Therefore, in this study, we further characterized the effects of RLN alone or together with an inflammatory mediator on the production of IL1B, CSF2 (GM-CSF), IL6, IL8 and TNF, from chorionic cytotrophoblasts (CyT), decidual fibroblasts (DF) and stromal cells (DSC), using interleukin-1 beta (IL1B) to mimic sterile inflammation or lipopolysaccharide (LPS) for bacterial infection. Endogenous differences between the cells showed that the CyT expressed more RLN, its receptor RXFP1 and the RXFP1 splice variant D. CyT also showed the most robust cAMP response to RLN with increased IL6 secreted after 4 h, preceded by increased transcription at 1 h, likely due to activation of RXFP1 and cAMP. When all cell types were treated with IL1B and RLN, RLN augmented secretion of IL6 and IL8 from CyT and DF, but not DSC. Similarly, RLN augmented LPS-induced IL6 secretion from CyT and DF. Despite the structural similarity between TLR4 and RXFP1, blocking TLR4 in CyT had no effect on RLN-induced IL6 secretion, suggesting specific activation of RXFP1. Thus, we have shown that in the presence of a low level of intrauterine inflammation/infection, elevated RLN could act on the CyT and DF to augment the inflammatory response, contributing to the pathophysiology of PTB. SUMMARY RLN augments the inflammatory responses induced by IL1B or LPS in chorionic cytotrophoblasts and decidual fibroblasts.
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Affiliation(s)
- J S Horton
- Department of Cell and Molecular Biology, University of Hawaii, John A. Burns School of Medicine, 651 Ilalo Street, Bioscience Building, Honolulu, HI 96813, USA.
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Shabanpoor F, Akhter Hossain M, Ryan PJ, Belgi A, Layfield S, Kocan M, Zhang S, Samuel CS, Gundlach AL, Bathgate RAD, Separovic F, Wade JD. Minimization of human relaxin-3 leading to high-affinity analogues with increased selectivity for relaxin-family peptide 3 receptor (RXFP3) over RXFP1. J Med Chem 2012; 55:1671-81. [PMID: 22257012 DOI: 10.1021/jm201505p] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Relaxin-3 is a neuropeptide that is implicated in the regulation of stress responses and memory. The elucidation of its precise physiological role(s) has, however, been hampered by cross-activation of the relaxin-2 receptor, RXFP1, in the brain. The current study undertook to develop analogues of human relaxin-3 (H3 relaxin) that can selectively bind and activate its receptor, RXFP3. We developed a high-affinity selective agonist (analogue 2) by removal of the intra-A chain disulfide bond and deletion of 10 residues from the N terminus of the A chain. Further truncation of this analogue from the C terminus of the B chain to Cys(B22) and addition of an Arg(B23) led to a high-affinity, RXFP3-selective, competitive antagonist (analogue 3). Central administration of analogue 2 in rats increased food intake, which was blocked by prior coadministration of analogue 3. These novel RXFP3-selective peptides represent valuable pharmacological tools to study the physiological roles of H3 relaxin/RXFP3 systems in the brain and important leads for the development of novel compounds for the treatment of affective and cognitive disorders.
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Affiliation(s)
- Fazel Shabanpoor
- Florey Neuroscience Institutes, The University of Melbourne, Victoria 3010, Australia
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71
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Bathgate RAD, Zhang S, Hughes RA, Rosengren KJ, Wade JD. The structural determinants of insulin-like Peptide 3 activity. Front Endocrinol (Lausanne) 2012; 3:11. [PMID: 22654853 PMCID: PMC3356098 DOI: 10.3389/fendo.2012.00011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 01/12/2012] [Indexed: 11/24/2022] Open
Abstract
Insulin-like peptide 3 (INSL3) is a hormone and/or paracrine factor which is a member of the relaxin peptide family. It has key roles as a fertility regulator in both males and females. The receptor for INSL3 is the leucine rich repeat (LRR) containing G-protein coupled receptor 8 (LGR8) which is now known as relaxin family peptide receptor 2 (RXFP2). Receptor activation by INSL3 involves binding to the LRRs in the large ectodomain of RXFP2 by residues within the B-chain of INSL3 as well as an interaction with the transmembrane exoloops of the receptor. Although the binding to the LRRs is well characterized the features of the peptide and receptor involved in the exoloop interaction are currently unknown. This study was designed to determine the key INSL3 determinants for RXFP2 activation. A chimeric peptide approach was first utilized to demonstrate that the A-chain is critical for receptor activation. Replacement of the INSL3 A-chain with that from the related peptides INSL5 and INSL6 resulted in complete loss of activity despite only minor changes in binding affinity. Subsequent replacement of specific A-chain residues with those from the INSL5 peptide highlighted that the N-terminus of the A-chain of INSL3 is critical for its activity. Remarkably, replacement of the entire N-terminus with four or five alanine residues resulted in peptides with near native activity suggesting that specific residues are not necessary for activity. Additionally removal of two amino acids at the C-terminus of the A-chain and mutation of Lys-8 in the B-chain also resulted in minor decreases in peptide activity. Therefore we have demonstrated that the activity of the INSL3 peptide is driven predominantly by residues 5-9 in the A-chain, with minor additional contributions from the two C-terminal A-chain residues and Lys-8 in the B-chain. Using this new knowledge, we were able to produce a truncated INSL3 peptide structure which retained native activity, despite having 14 fewer residues than the parent peptide.
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Affiliation(s)
- Ross A. D. Bathgate
- Florey Neuroscience Institutes, University of MelbourneMelbourne, VIC, Australia
- Department of Biochemistry and Molecular Biology, University of MelbourneMelbourne, VIC, Australia
- *Correspondence: Ross A. D. Bathgate and John D. Wade, Florey Neuroscience Institutes, University of Melbourne, Melbourne, VIC 3031, Australia. e-mail: ;
| | - Soude Zhang
- Florey Neuroscience Institutes, University of MelbourneMelbourne, VIC, Australia
| | - Richard A. Hughes
- Department of Pharmacology, University of MelbourneMelbourne, VIC, Australia
| | - K. Johan Rosengren
- School of Biomedical Sciences, The University of QueenslandBrisbane, QLD, Australia
| | - John D. Wade
- Florey Neuroscience Institutes, University of MelbourneMelbourne, VIC, Australia
- School of Chemistry, University of MelbourneMelbourne, VIC, Australia
- *Correspondence: Ross A. D. Bathgate and John D. Wade, Florey Neuroscience Institutes, University of Melbourne, Melbourne, VIC 3031, Australia. e-mail: ;
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72
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Belgi A, Hossain MA, Shabanpoor F, Chan L, Zhang S, Bathgate RAD, Tregear GW, Wade JD. Structure and Function Relationship of Murine Insulin-like Peptide 5 (INSL5): Free C-Terminus Is Essential for RXFP4 Receptor Binding and Activation. Biochemistry 2011; 50:8352-61. [DOI: 10.1021/bi201093m] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alessia Belgi
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
| | - Mohammed A. Hossain
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
| | - Fazel Shabanpoor
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
| | - Linda Chan
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
| | - Suode Zhang
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
| | - Ross A. D. Bathgate
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
| | - Geoffrey W. Tregear
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
| | - John D. Wade
- Florey
Neuroscience Institutes, ‡Department of Biochemistry and Molecular Biology, and §School of Chemistry, The University of Melbourne, Victoria
3010, Australia
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Hossain MA, Rosengren KJ, Samuel CS, Shabanpoor F, Chan LJ, Bathgate RAD, Wade JD. The minimal active structure of human relaxin-2. J Biol Chem 2011; 286:37555-65. [PMID: 21878627 DOI: 10.1074/jbc.m111.282194] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
H2 relaxin is a peptide hormone associated with a number of therapeutically relevant physiological effects, including regulation of collagen metabolism and multiple vascular control pathways. It is currently in phase III clinical trials for the treatment of acute heart failure due to its ability to induce vasodilation and influence renal function. It comprises 53 amino acids and is characterized by two separate polypeptide chains (A-B) that are cross-linked by three disulfide bonds. This size and complex structure represents a considerable challenge for the chemical synthesis of H2 relaxin, a major limiting factor for the exploration of modifications and derivatizations of this peptide, to optimize effect and drug-like characteristics. To address this issue, we describe the solid phase peptide synthesis and structural and functional evaluation of 24 analogues of H2 relaxin with truncations at the termini of its peptide chains. We show that it is possible to significantly truncate both the N and C termini of the B-chain while still retaining potent biological activity. This suggests that these regions are not critical for interactions with the H2 relaxin receptor, RXFP1. In contrast, truncations do reduce the activity of H2 relaxin for the related receptor RXFP2 by improving RXFP1 selectivity. In addition to new mechanistic insights into the function of H2 relaxin, this study identifies a critical active core with 38 amino acids. This minimized core shows similar antifibrotic activity as native H2 relaxin when tested in human BJ3 cells and thus represents an attractive receptor-selective lead for the development of novel relaxin therapeutics.
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74
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Shabanpoor F, Zhang S, Hughes RA, Hossain MA, Layfield S, Ferraro T, Bathgate RAD, Separovic F, Wade JD. Design and development of analogues of dimers of insulin-like peptide 3 B-chain as high-affinity antagonists of the RXFP2 receptor. Biopolymers 2011; 96:81-7. [PMID: 20560146 DOI: 10.1002/bip.21484] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Insulin-like peptide 3 (INSL3) is one of 10 members of the human relaxin-insulin superfamily of peptides. It is a peptide hormone that is expressed by fetal and postnatal testicular Leydig cells and postnatal ovarian thecal cells. It mediates testicular descent during fetal life and suppresses sperm apoptosis in adult males, whereas, in females, it causes oocyte maturation. INSL3 has also been shown to promote thyroid tumor growth and angiogenesis in human. These actions of INSL3 are mediated through its G protein-coupled receptor, RXFP2. INSL3, a two-chained peptide, binds to its receptor primarily via its B-chain, whereas elements of the A-chain are essential for receptor activation. In an attempt to design a high-affinity antagonist with potential clinical application as an anticancer agent as well as a contraceptive, we have previously prepared a synthetic parallel dimer of INSL3 B-chain and demonstrated that it binds to RXFP2 with high affinity. In this work, we undertook full pharmacological characterization of this peptide and show that it can antaogonize INSL3-mediated cAMP signaling through RXFP2. Further refinement by truncation of 18 residues yielded a minimized analogue that retained full binding affinity and INSL3 antagonism. It is an attractive lead peptide for in vivo evaluation as an inhibitor of male and female fertility and of INSL3-mediated carcinogenesis.
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Affiliation(s)
- Fazel Shabanpoor
- Howard Florey Institute, University of Melbourne, Melbourne, VIC 3010, Australia
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75
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Branch DR. Role of G protein-coupled vasoactive intestinal peptide receptors in HIV integration. Future Virol 2011. [DOI: 10.2217/fvl.11.42] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The pathogenesis of HIV infection is closely linked to the replication of the virus in vivo. Even though the progress in anti-HIV-1 chemotherapy in the past several years has been dramatic, the efficient protection against HIV-1 infection still remains one of the most important global challenges. The complete blockage of AIDS progression appears to be difficult with current treatment due to the rapid occurrence of viral drug-resistance, increasing cost and the likelihood of adverse side effects. Furthermore, although originally regarded with high hope, development of a suitable vaccine appears to be years away. The purpose of this article is to describe previous findings regarding a potentially important role of the vasoactive intestinal peptide/pituitary adenylate cyclase-activating polypeptide (VPAC) family of G protein-coupled receptors in HIV-1 infection, to provide evidence for the involvement of these receptors in providing signals that can control the integration of the virus into the host DNA and to report new findings that support a role for VPAC receptors in the facilitation of HIV integration.
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Affiliation(s)
- Donald R Branch
- Research & Development, Canadian Blood Services, Immunology Hub, Toronto Centre, Toronto, Ontario M5G 2M1, Canada
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76
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Haugaard-Kedström LM, Shabanpoor F, Hossain MA, Clark RJ, Ryan PJ, Craik DJ, Gundlach AL, Wade JD, Bathgate RAD, Rosengren KJ. Design, Synthesis, and Characterization of a Single-Chain Peptide Antagonist for the Relaxin-3 Receptor RXFP3. J Am Chem Soc 2011; 133:4965-74. [DOI: 10.1021/ja110567j] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | - Richard J. Clark
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | | | - David J. Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | | | | | | | - K. Johan Rosengren
- School of Natural Sciences, Linnaeus University, SE-391 82 Kalmar, Sweden
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
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77
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Feugang JM, Rodriguez-Munoz JC, Willard ST, Bathgate RA, Ryan PL. Examination of relaxin and its receptors expression in pig gametes and embryos. Reprod Biol Endocrinol 2011; 9:10. [PMID: 21251292 PMCID: PMC3032664 DOI: 10.1186/1477-7827-9-10] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 01/20/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Relaxin is a small peptide also known as pregnancy hormone in many mammals. It is synthesized by both male and female tissues, and its secretions are found in various body fluids such as plasma serum, ovarian follicular fluid, utero-oviduct secretions, and seminal plasma of many mammals, including pigs. However, the presence and effects of relaxin in porcine gametes and embryos are still not well-known. The purpose of this study was to assess the presence of relaxin and its receptors RXFP1 and RXFP2 in pig gametes and embryos. METHODS Immature cumulus-oocyte complexes (COCs) were aspirated from sows' ovaries collected at the abattoir. After in vitro-maturation, COCs were in vitro-fertilized and cultured. For studies, immature and mature COCs were separately collected, and oocytes were freed from their surrounding cumulus cells. Denuded oocytes, cumulus cells, mature boar spermatozoa, zygotes, and embryos (cleaved and blastocysts) were harvested for temporal and spatial gene expression studies. Sections of ovary, granulosa and neonatal porcine uterine cells were also collected to use as controls. RESULTS Using both semi-quantitative and quantitative PCRs, relaxin transcripts were not detected in all tested samples, while RXFP1 and RXFP2 mRNA were present. Both receptor gene products were found at higher levels in oocytes compared to cumulus cells, irrespective of the maturation time. Cleaved-embryos contained higher levels of RXFP2 mRNA, whereas, blastocysts were characterized by a higher RXFP1 mRNA content. Using western-immunoblotting or in situ immunofluorescence, relaxin and its receptor proteins were detected in all samples. Their fluorescence intensities were consistently more important in mature oocytes than immature ones. The RXFP1 and RXFP2 signal intensities were mostly located in the plasma membrane region, while the relaxin ones appeared homogeneously distributed within the oocytes and embryonic cells. Furthermore, spermatozoa displayed stronger RXFP2 signal than RXFP1 after western-immunoblotting. CONCLUSION All together, our findings suggest potential roles of relaxin and its receptors during oocyte maturation, early embryo development, and beyond.
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Affiliation(s)
- Jean M Feugang
- Department of Animal & Dairy Sciences, Mississippi State University, 4025 Wise Center, Mississippi State, MS 38762, USA
| | - Juan C Rodriguez-Munoz
- Department of Animal & Dairy Sciences, Mississippi State University, 4025 Wise Center, Mississippi State, MS 38762, USA
| | - Scott T Willard
- Department of Biochemistry & Molecular Biology, Mississippi State University, 402 Dorman Hall, Mississippi, MS 38762, USA
| | - Ross A Bathgate
- Florey Neuroscience Institutes, University of Melbourne, Gate 11, Royal Parade, Victoria, 3010, Australia
| | - Peter L Ryan
- Department of Animal & Dairy Sciences, Mississippi State University, 4025 Wise Center, Mississippi State, MS 38762, USA
- Department of Pathobiology & Population Medicine, Mississippi State University, 240 Wise Center Dr., Mississippi State, MS 38762, USA
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Abstract
Relaxin is an approximately 6-kilodalton peptide hormone secreted by the corpus luteum, and circulates in the maternal blood during pregnancy. Relaxin administration to awake, chronically instrumented, nonpregnant rats mimics the vasodilatory phenomena of pregnancy. Furthermore, immunoneutralization of relaxin or its elimination from the circulation during midterm pregnancy in awake rats prevents maternal systemic and renal vasodilation, and the increase in global arterial compliance. Human investigation, albeit limited through 2010, also reveals vasodilatory effects of relaxin in the nonpregnant condition and observations consistent with a role for relaxin in gestational renal hyperfiltration. Evidence suggests that the vasodilatory responses of relaxin are mediated by its major receptor, the relaxin/insulin-like family peptide 1 receptor, RFXP1. The molecular mechanisms of relaxin vasodilation depend on the duration of hormone exposure (ie, there are rapid and sustained vasodilatory responses). Newly emerging data support the role of Gα(i/o) protein coupling to phosphatidylinositol-3 kinase/Akt (protein kinase B)-dependent phosphorylation and activation of endothelial nitric oxide synthase in the rapid vasodilatory responses of relaxin. Sustained vasodilatory responses critically depend on vascular endothelial and placental growth factors, and increases in arterial gelatinase(s) activity. Gelatinases hydrolyze big endothelin (ET) at a gly-leu bond to form ET(1-32), which activates the endothelial ET(B)/nitric oxide vasodilatory pathway. Although the relevance of relaxin biology to preeclampsia is largely speculative at this time, there are potential tantalizing links that are discussed in the context of our current understanding of the etiology and pathophysiology of the disease.
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Affiliation(s)
- Kirk P Conrad
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Road, Gainesville, FL 32610, USA.
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79
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Vodstrcil LA, Shynlova O, Verlander JW, Wlodek ME, Parry LJ. Decreased Expression of the Rat Myometrial Relaxin Receptor (RXFP1) in Late Pregnancy Is Partially Mediated by the Presence of the Conceptus1. Biol Reprod 2010; 83:818-24. [DOI: 10.1095/biolreprod.110.083931] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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80
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A missense mutation in LRR8 of RXFP2 is associated with cryptorchidism. Mamm Genome 2010; 21:442-9. [DOI: 10.1007/s00335-010-9291-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 09/20/2010] [Indexed: 01/29/2023]
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81
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Ivell R, Kotula-Balak M, Glynn D, Heng K, Anand-Ivell R. Relaxin family peptides in the male reproductive system--a critical appraisal. Mol Hum Reprod 2010; 17:71-84. [DOI: 10.1093/molehr/gaq086] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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82
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Zhang S, Hughes RA, Bathgate RAD, Shabanpoor F, Hossain MA, Lin F, van Lierop B, Robinson AJ, Wade JD. Role of the intra-A-chain disulfide bond of insulin-like peptide 3 in binding and activation of its receptor, RXFP2. Peptides 2010; 31:1730-6. [PMID: 20570702 DOI: 10.1016/j.peptides.2010.05.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 05/29/2010] [Accepted: 05/29/2010] [Indexed: 10/19/2022]
Abstract
INSL3 is a member of the insulin-IGF-relaxin superfamily and plays a key role in male fetal development and in adult germ cell maturation. It is the cognate ligand for RXFP2, a leucine-rich repeat containing G-protein coupled receptor. To date, and in contrast to our current knowledge of the key structural features that are required for the binding of INSL3 to RXFP2, comparatively little is known about the key residues that are required to elicit receptor activation and downstream cell signaling. Early evidence suggests that these are contained principally within the A-chain. To further explore this hypothesis, we have undertaken an examination of the functional role of the intra-A-chain disulfide bond. Using solid-phase peptide synthesis together with regioselective disulfide bond formation, two analogs of human INSL3 were prepared in which the intra-chain disulfide bond was replaced, one in which the corresponding Cys residues were substituted with the isosteric Ser and the other in which the Cys were removed altogether. Both of these peptides retained nearly full RXFP2 receptor binding but were devoid of cAMP activity (receptor activation), indicating that the intra-A-chain disulfide bond makes a significant contribution to the ability of INSL3 to act as an RXFP2 agonist. Replacement of the disulfide bond with a metabolically stable dicarba bond yielded two isomers of INSL3 that each exhibited bioactivity similar to native INSL3. This study highlights the critical structural role played by the intra-A-chain disulfide bond of INSL3 in mediating agonist actions through the RXFP2 receptor.
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Affiliation(s)
- Suode Zhang
- Howard Florey Institute, University of Melbourne, Victoria 3010, Australia
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83
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Hombach-Klonisch S, Bialek J, Radestock Y, Truong A, Agoulnik AI, Fiebig B, Willing C, Weber E, Hoang-Vu C, Klonisch T. INSL3 has tumor-promoting activity in thyroid cancer. Int J Cancer 2010; 127:521-31. [PMID: 19950223 DOI: 10.1002/ijc.25068] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The functional role of INSL3 and its receptor RXFP2 in carcinogenesis is largely unknown. We have previously demonstrated (pro-)cathepsin-L as a target of INSL3 in human thyroid cancer cells facilitating penetration of tumor cells through elastin matrices. We demonstrate the expression of RXFP2 in human thyroid tissues and in mouse follicular thyroid epithelial cells using Cre-recombinase transgene driven by Rxfp2 promoter. Recombinant and secreted INSL3 increased the motility of thyroid carcinoma (TC) cells in an autocrine/paracrine manner. This effect required the presence of RXFP2. We identified S100A4 as a novel INSL3 target molecule and showed that S100A4 facilitated INSL3-induced enhanced motility. Stable transfectants of the human follicular TC cell line FTC-133 expressing and secreting bioactive human INSL3 displayed enhanced anchorage-independent growth in soft agar assays. Xenotransplant experiments in nude mice showed that INSL3, but not EGFP-mock transfectants, developed fast-growing and highly vascularized xenografts. We used human umbilical vein endothelial cells in capillary tube formation assays to demonstrate increased 2-dimensional tube formations induced by recombinant human INSL3 and human S100A4 comparable to the effect of vascular endothelial growth factor used as positive control. We conclude that INSL3 is a powerful and multifunctional promoter of tumor growth and angiogenesis in human thyroid cancer cell xenografts. INSL3 actions involve RXFP2 activation and the secretion of S100A4 and (pro-)cathepsin-L.
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84
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Callander GE, Bathgate RAD. Relaxin family peptide systems and the central nervous system. Cell Mol Life Sci 2010; 67:2327-41. [PMID: 20213277 PMCID: PMC11115692 DOI: 10.1007/s00018-010-0304-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 01/13/2010] [Accepted: 02/03/2010] [Indexed: 11/24/2022]
Abstract
Since its discovery in the 1920s, relaxin has enjoyed a reputation as a peptide hormone of pregnancy. However, relaxin and other relaxin family peptides are now associated with numerous non-reproductive physiologies and disease states. The new millennium bought with it the sequence of the human genome and subsequently new directions for relaxin research. In 2002, the ancestral relaxin gene RLN3 was identified from genome databases. The relaxin-3 peptide is highly expressed in a small region of the brain and in species from teleost to primates and has both conserved sequence and sites of expression. Combined with the discovery of the relaxin family peptide receptors, interest in the role of the relaxin family peptides in the central nervous system has been reignited. This review explores the relaxin family peptides that are expressed in or act upon the brain, the receptors that mediate their actions, and what is currently known of their functions.
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Affiliation(s)
- G. E. Callander
- Florey Neuroscience Institutes and Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, VIC 3010 Australia
| | - R. A. D. Bathgate
- Florey Neuroscience Institutes and Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, VIC 3010 Australia
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85
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Kong RCK, Shilling PJ, Lobb DK, Gooley PR, Bathgate RAD. Membrane receptors: structure and function of the relaxin family peptide receptors. Mol Cell Endocrinol 2010; 320:1-15. [PMID: 20138959 DOI: 10.1016/j.mce.2010.02.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 12/14/2009] [Accepted: 02/02/2010] [Indexed: 01/17/2023]
Abstract
The receptors for members of the relaxin peptide family have only recently been discovered and are G-protein-coupled receptors (GPCRs). Relaxin and insulin-like peptide 3 (INSL3) interact with the leucine-rich-repeat-containing GPCRs (LGRs) LGR7 and LGR8, respectively. These receptors show closest similarity to the glycoprotein hormone receptors and contain large ectodomains with 10 leucine-rich repeats (LRRs) but are unique members of the LGR family (class C) as they have an LDL class A (LDLa) module at their N-terminus. In contrast, relaxin-3 and INSL5 interact with another class of type I GPCRs which lack a large ectodomain, the peptide receptors GPCR135 and GPCR142, respectively. These receptors are now classified as relaxin family peptide (RXFP) receptors, RXFP1 (LGR7), RXFP2 (LGR8), RXFP3 (GPCR135) and RXFP4 (GPCR142). This review outlines the identification of the peptides and receptors, their expression profiles and physiological roles and the functional interactions of the peptides with their unique receptors.
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Affiliation(s)
- Roy C K Kong
- Florey Neuroscience Institutes, University of Melbourne, Victoria 3010, Australia
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86
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Hossain MA, Samuel CS, Binder C, Hewitson TD, Tregear GW, Wade JD, Bathgate RAD. The chemically synthesized human relaxin-2 analog, B-R13/17K H2, is an RXFP1 antagonist. Amino Acids 2009; 39:409-16. [DOI: 10.1007/s00726-009-0454-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Accepted: 12/17/2009] [Indexed: 01/06/2023]
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87
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88
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89
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Relaxin family peptide. Br J Pharmacol 2009. [DOI: 10.1111/j.1476-5381.2009.00501_57.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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90
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Markovic D, Challiss RAJ. Alternative splicing of G protein-coupled receptors: physiology and pathophysiology. Cell Mol Life Sci 2009; 66:3337-52. [PMID: 19629391 PMCID: PMC11115665 DOI: 10.1007/s00018-009-0093-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 06/30/2009] [Accepted: 07/03/2009] [Indexed: 12/16/2022]
Abstract
The G protein-coupled receptors (GPCRs) are a superfamily of transmembrane receptors that have a broad distribution and can collectively recognise a diverse array of ligands. Activation or inhibition of GPCR signalling can affect many (patho)physiological processes, and consequently they are a major target for existing and emerging drug therapies. A common observation has been that the pharmacological, signalling and regulatory properties of GPCRs can differ in a cell- and tissue-specific manner. Such "phenotypic" diversity might be attributable to post-translational modifications and/or association of GPCRs with accessory proteins, however, post-transcriptional mechanisms are also likely to contribute. Although approximately 50% of GPCR genes are intronless, those that possess introns can undergo alternative splicing, generating GPCR subtype isoforms that may differ in their pharmacological, signalling and regulatory properties. In this review we shall highlight recent research into GPCR splice variation and discuss the potential consequences this might have for GPCR function in health and disease.
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Affiliation(s)
- Danijela Markovic
- Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Leicester, UK.
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91
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Avellar MCW, Lázari MFM, Porto CS. Expression and function of G-protein-coupled receptorsin the male reproductive tract. AN ACAD BRAS CIENC 2009; 81:321-44. [DOI: 10.1590/s0001-37652009000300002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2008] [Accepted: 08/14/2008] [Indexed: 11/22/2022] Open
Abstract
This review focuses on the expression and function of muscarinic acetylcholine receptors (mAChRs), α1-adrenoceptors and relaxin receptors in the male reproductive tract. The localization and differential expression of mAChR and α1-adrenoceptor subtypes in specific compartments of the efferent ductules, epididymis, vas deferens, seminal vesicle and prostate of various species indicate a role for these receptors in the modulation of luminal fluid composition and smooth muscle contraction, including effects on male fertility. Furthermore, the activation of mAChRs induces transactivation of the epidermal growth factor receptor (EGFR) and the Sertoli cell proliferation. The relaxin receptors are present in the testis, RXFP1 in elongated spermatids and Sertoli cells from rat, and RXFP2 in Leydig and germ cells from rat and human, suggesting a role for these receptors in the spermatogenic process. The localization of both receptors in the apical portion of epithelial cells and smooth muscle layers of the vas deferens suggests an involvement of these receptors in the contraction and regulation of secretion.
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92
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Luo X, Bathgate RAD, Liu YL, Shao XX, Wade JD, Guo ZY. Recombinant expression of an insulin-like peptide 3 (INSL3) precursor and its enzymatic conversion to mature human INSL3. FEBS J 2009; 276:5203-11. [PMID: 19674100 DOI: 10.1111/j.1742-4658.2009.07216.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Insulin-like peptide 3 (INSL3), which is primarily expressed in the Leydig cells of the testes, is a member of the insulin superfamily of peptide hormones. One of its primary functions is to initiate and mediate descent of the testes of the male fetus via interaction with its G protein-coupled receptor, RXFP2. Study of the peptide has relied upon chemical synthesis of the separate A- and B-chains and subsequent chain recombination. To establish an alternative approach to the preparation of human INSL3, we designed and recombinantly expressed a single-chain INSL3 precursor in Escherichia coli cells. The precursor was solubilized from the inclusion body, purified almost to homogeneity by immobilized metal-ion affinity chromatography and refolded efficiently in vitro. The refolded precursor was subsequently converted to mature human INSL3 by sequential endoproteinase Lys-C and carboxypeptidase B treatment. CD spectroscopic analysis and peptide mapping showed that the refolded INSL3 possessed an insulin-like fold with the expected disulfide linkages. Recombinant human INSL3 demonstrated full activity in stimulating cAMP activity in RXFP2-expressing cells. Interestingly, the activity of the single-chain precursor was comparable with that of the mature two-chain INSL3, suggesting that the receptor-binding region within the mid- to C-terminal of B-chain is maintained in an active conformation in the precursor. This study not only provides an efficient approach for mature INSL3 preparation, but also resulted in the acquisition of a useful single-chain template for additional structural and functional studies of the peptide.
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Affiliation(s)
- Xiao Luo
- Institute of Protein Research, East Hospital, Tongji University, Shanghai, China
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93
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Kern A, Bryant-Greenwood GD. Mechanisms of relaxin receptor (LGR7/RXFP1) expression and function. Ann N Y Acad Sci 2009; 1160:60-6. [PMID: 19416160 DOI: 10.1111/j.1749-6632.2008.03826.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The LGR7/RXFP1 and LGR8/RXFP2 receptors are unique receptors among the G-protein-coupled receptors (GPCRs) in having a low-density lipoprotein class A (LDL-A) module. Their complex gene organization, among the intron-richest of the GPCRs, suggests that alternative splicing is a common occurrence. We have therefore investigated the role of the LDL-A module and shown the identity, expression, and functions of three LGR7 splice variants in the human decidua. Point mutations of conserved residues or complete deletion of the LDL-A module resulted in loss of the cAMP response to relaxin. Its glycosylation also impacted LGR7 cell surface delivery and therefore receptor activation. The wild-type (WT) LGR7 was expressed as both precursor and mature forms, but deletion of the LDL-A module resulted in expression of only the mature form. Three new alternatively spliced variants of LGR7 were identified, all containing a truncated extracellular region. Their functional characterization showed them exerting dominant negative effects on the WT LGR7 by preventing its homodimerization, maturation, and subsequent trafficking to the cell surface, resulting in loss of function. In summary, different mechanisms have been identified for controlling the cell surface expression and function of the LGR7 protein which are likely to be significant for the role of relaxin in human parturition.
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Affiliation(s)
- András Kern
- The Pacific Biosciences Research Center, University of Hawaii, Honolulu, Hawaii 96822, USA.
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94
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Schwabe C, Büllesbach EE. The "hot wires" of the relaxin-like factor (Insl3). Ann N Y Acad Sci 2009; 1160:93-8. [PMID: 19416166 DOI: 10.1111/j.1749-6632.2008.03779.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The discovery of the total separation of receptor-binding and signal-generating regions of the relaxin-like factor (RLF) has provided an opportunity to investigate the mechanism of transmembrane signaling. The receptor-binding residues of RLF are in the B chain of the two-chain molecule and extend from the midregion of the central helix to the tryptophan in position B27. The signal initiation site resides in two residues before the N-terminal cysteine in each chain. For optimal signaling the RLF requires five L-alpha-amino acids preceding cysteine A10, whereas the B chain requires only three. The nature of the side chains of these amino acids is not critical for the signaling function. Heuristic arguments lead us to suggest that the peptide bond is the signal-generating feature of RLF and possibly of other peptide hormones.
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Affiliation(s)
- Christian Schwabe
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.
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95
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Feng S, Agoulnik IU, Li Z, Han HD, Lopez-Berestein G, Sood A, Ittmann MM, Agoulnik AI. Relaxin/RXFP1 signaling in prostate cancer progression. Ann N Y Acad Sci 2009; 1160:379-80. [PMID: 19416223 DOI: 10.1111/j.1749-6632.2008.03793.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We found that relaxin peptide expression is significantly elevated in recurrent human prostate cancer. Stimulation with relaxin increased migration, invasiveness, proliferation, and adhesion of LNCaP and PC3 cells in vitro. Opposite effects on cellular phenotype were observed after suppression of endogenous relaxin/RXFP1 expression or signaling. We showed an accelerated progression of prostate cancer in TRAMP males with transgenic relaxin overexpression and a longer survival of TRAMP, RXFP1-deficient males. Suppression of RXFP1 expression in PC3 xenografts in nude mice by intratumoral injections of short interfering RNA resulted in decreased tumor size, cell proliferation, and metastasis rate.
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Affiliation(s)
- Shu Feng
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas 77030, USA
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96
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Kern A, Bryant-Greenwood GD. Characterization of relaxin receptor (RXFP1) desensitization and internalization in primary human decidual cells and RXFP1-transfected HEK293 cells. Endocrinology 2009; 150:2419-28. [PMID: 19116340 PMCID: PMC2671891 DOI: 10.1210/en.2008-1385] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We report here the desensitization and internalization of the relaxin receptor (RXFP1) after agonist activation in both primary human decidual cells and HEK293 cells stably transfected with RXFP1. The importance of beta-arrestin 2 in these processes has also been demonstrated. Thus, in HEK-RXFP1 cells the desensitization of RXFP1 was significantly increased when beta-arrestin 2 was overexpressed. After relaxin activation, beta-arrestin 2 was translocated to the cell membrane and RXFP1 underwent rapid internalization. We have previously shown that RXFP1 forms dimers/oligomers during its biosynthesis and trafficking to the plasma membrane, we now show that internalization of RXFP1 occurs through this dimerization/oligomerization. In nonagonist stimulated cells, it is known that the majority of the RXFP1 is located intracellularly and was confirmed in the cells used here. Constitutive internalization of RXFP1 could account for this and indeed, slow but robust constitutive internalization, which was increased after agonist stimulation was demonstrated. A carboxyl-terminal deleted RXFP1 variant had a similar level of constitutive agonist-independent internalization as the wild-type RXFP1 but lost sensitivity to agonist stimulation. This demonstrated the importance of the carboxyl terminus in agonist-stimulated receptor internalization. These data suggest that the autocrine/paracrine actions of relaxin in the decidua are under additional controls at the level of expression of its receptor on the surface of its target cells.
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MESH Headings
- Arrestins/pharmacology
- Autocrine Communication/genetics
- Autocrine Communication/physiology
- Cell Culture Techniques
- Cell Line/drug effects
- Cell Line/metabolism
- Cells, Cultured
- Decidua/drug effects
- Decidua/metabolism
- Dimerization
- Female
- Gene Expression/physiology
- Humans
- Models, Biological
- Paracrine Communication/genetics
- Paracrine Communication/physiology
- Protein Structure, Tertiary/physiology
- Protein Transport/drug effects
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Peptide/agonists
- Receptors, Peptide/chemistry
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Relaxin/pharmacology
- Transfection
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Affiliation(s)
- András Kern
- The Pacific Biosciences Research Center, University of Hawaii, Honolulu, Hawaii 96822, USA.
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97
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Callander GE, Thomas WG, Bathgate RAD. Development and Optimization of MicroRNA against Relaxin-3. Ann N Y Acad Sci 2009; 1160:261-4. [DOI: 10.1111/j.1749-6632.2008.03816.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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98
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Scott DJ, Tregear GW, Bathgate RAD. Modeling the Primary Hormone-Binding Site of RXFP1 and RXFP2. Ann N Y Acad Sci 2009; 1160:74-7. [DOI: 10.1111/j.1749-6632.2009.03950.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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99
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Tregear GW, Bathgate RAD, Hossain MA, Lin F, Zhang S, Shabanpoor F, Scott DJ, Ma S, Gundlach AL, Samuel CS, Wade JD. Structure and Activity in the Relaxin Family of Peptides. Ann N Y Acad Sci 2009; 1160:5-10. [DOI: 10.1111/j.1749-6632.2009.03955.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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100
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Hartley BJ, Scott DJ, Callander GE, Wilkinson TN, Ganella DE, Kong CK, Layfield S, Ferraro T, Petrie EJ, Bathgate RAD. Resolving the Unconventional Mechanisms Underlying RXFP1 and RXFP2 Receptor Function. Ann N Y Acad Sci 2009; 1160:67-73. [DOI: 10.1111/j.1749-6632.2009.03949.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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