1
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Vps37a regulates hepatic glucose production by controlling glucagon receptor localization to endosomes. Cell Metab 2022; 34:1824-1842.e9. [PMID: 36243006 DOI: 10.1016/j.cmet.2022.09.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 08/04/2022] [Accepted: 09/21/2022] [Indexed: 01/11/2023]
Abstract
During mammalian energy homeostasis, the glucagon receptor (Gcgr) plays a key role in regulating both glucose and lipid metabolisms. However, the mechanisms by which these distinct signaling arms are differentially regulated remain poorly understood. Using a Cy5-glucagon agonist, we show that the endosomal protein Vps37a uncouples glucose production from lipid usage downstream of Gcgr signaling by altering intracellular receptor localization. Hepatocyte-specific knockdown of Vps37a causes an accumulation of Gcgr in endosomes, resulting in overactivation of the cAMP/PKA/p-Creb signaling pathway to gluconeogenesis without affecting β-oxidation. Shifting the receptor back to the plasma membrane rescues the differential signaling and highlights the importance of the spatiotemporal localization of Gcgr for its metabolic effects. Importantly, since Vps37a knockdown in animals fed with a high-fat diet leads to hyperglycemia, although its overexpression reduces blood glucose levels, these data reveal a contribution of endosomal signaling to metabolic diseases that could be exploited for treatments of type 2 diabetes.
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2
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Josephs TM, Belousoff MJ, Liang YL, Piper SJ, Cao J, Garama DJ, Leach K, Gregory KJ, Christopoulos A, Hay DL, Danev R, Wootten D, Sexton PM. Structure and dynamics of the CGRP receptor in apo and peptide-bound forms. Science 2021; 372:science.abf7258. [DOI: 10.1126/science.abf7258] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 02/11/2021] [Indexed: 12/11/2022]
Affiliation(s)
- Tracy M. Josephs
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Matthew J. Belousoff
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Yi-Lynn Liang
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Sarah J. Piper
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Jianjun Cao
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Daniel J. Garama
- Hudson Institute of Medical Research, Clayton 3168, Victoria, Australia
- Department of Molecular and Translational Science, Monash University, Clayton 3168, Victoria, Australia
| | - Katie Leach
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Karen J. Gregory
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Arthur Christopoulos
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Debbie L. Hay
- Department of Pharmacology and Toxicology, University of Otago, Dunedin 9054, New Zealand
| | - Radostin Danev
- Graduate School of Medicine, University of Tokyo, N415, 7-3-1 Hongo, Bunkyo-ku, 113-0033 Tokyo, Japan
| | - Denise Wootten
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
| | - Patrick M. Sexton
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, Victoria, Australia
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3
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Yang B, Gelfanov VM, Perez-Tilve D, DuBois B, Rohlfs R, Levy J, Douros JD, Finan B, Mayer JP, DiMarchi RD. Optimization of Truncated Glucagon Peptides to Achieve Selective, High Potency, Full Antagonists. J Med Chem 2021; 64:4697-4708. [PMID: 33821647 DOI: 10.1021/acs.jmedchem.0c02069] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Antagonism of glucagon's biological action is a proven strategy for decreasing glucose in diabetic animals and patients. To achieve full, potent, and selective suppression, we chemically optimized N-terminally truncated glucagon fragments for the identification and establishment of the minimum sequence peptide, [Glu9]glucagon(6-29) amide (11) as a full antagonist in cellular signaling and receptor binding (IC50 = 36 nM). Substitution of Phe6 with l-3-phenyllactic acid (Pla) produced [Pla6, Glu9]glucagon(6-29) amide (21), resulting in a 3-fold improvement in receptor binding (IC50 = 12 nM) and enhanced antagonist potency. Further substitution of Glu9 and Asn28 with aspartic acid yielded [Pla6, Asp28]glucagon amide (26), which demonstrated a further increase in inhibitory potency (IC50 = 9 nM), and improved aqueous solubility. Peptide 26 and a palmitoylated analogue, [Pla6, Lys10(γGluγGlu-C16), Asp28]glucagon(6-29) amide (31), displayed sustained duration in vivo action that successfully reversed glucagon-induced glucose elevation in mice.
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Affiliation(s)
- Bin Yang
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.,Novo Nordisk Research Center Indianapolis, Indianapolis, Indiana 46241, United States
| | - Vasily M Gelfanov
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.,Novo Nordisk Research Center Indianapolis, Indianapolis, Indiana 46241, United States
| | - Diego Perez-Tilve
- Department of Medicine, University of Cincinnati, Cincinnati, Ohio 45267, United States
| | - Barent DuBois
- Novo Nordisk Research Center Indianapolis, Indianapolis, Indiana 46241, United States
| | - Rebecca Rohlfs
- Novo Nordisk Research Center Indianapolis, Indianapolis, Indiana 46241, United States
| | - Jay Levy
- Novo Nordisk Research Center Indianapolis, Indianapolis, Indiana 46241, United States
| | - Jonathan D Douros
- Novo Nordisk Research Center Indianapolis, Indianapolis, Indiana 46241, United States
| | - Brian Finan
- Novo Nordisk Research Center Indianapolis, Indianapolis, Indiana 46241, United States
| | - John P Mayer
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Richard D DiMarchi
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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4
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Xiao X, Qin M, Zhang F, Su Y, Zhou B, Zhou Z. Understanding the Mechanism of Activation/Deactivation of GLP-1R via Accelerated Molecular Dynamics Simulation. Aust J Chem 2021. [DOI: 10.1071/ch20127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Glucagon-like peptide-1 receptor (GLP-1R), as a member of the class B G protein-coupled receptors (GPCRs), plays a crucial role in regulating blood glucose level signal recognition through its activation. The conformation changes during the activation pathway are of particular importance for its function. To investigate the activation mechanism of GLP-1R, the crystal structures of active and inactive forms are chosen to perform a total of 2 μs of accelerated molecular dynamics (aMD) simulations and 400ns of conventional molecular dynamics (cMD) simulations. With the aid of structural analysis and potential of mean force (PMF) calculations, we reveal the role of different helices in the activation and deactivation process and obtain the intermediate states during activation and deactivation that are difficult to capture in experiments. Protein structure network (PSN) was utilised to clarify the allosteric communication pathways of activation and deactivation and reveal the mechanisms of its activation and deactivation. The results could advance our understanding of the activation mechanism of GLP-1R and the related drug design.
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5
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Cryo-EM structure of an activated VIP1 receptor-G protein complex revealed by a NanoBiT tethering strategy. Nat Commun 2020; 11:4121. [PMID: 32807782 PMCID: PMC7431577 DOI: 10.1038/s41467-020-17933-8] [Citation(s) in RCA: 116] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 07/17/2020] [Indexed: 02/06/2023] Open
Abstract
Vasoactive intestinal polypeptide receptor (VIP1R) is a widely expressed class B G protein-coupled receptor and a drug target for the treatment of neuronal, metabolic, and inflammatory diseases. However, our understanding of its mechanism of action and the potential of drug discovery targeting this receptor is limited by the lack of structural information of VIP1R. Here we report a cryo-electron microscopy structure of human VIP1R bound to PACAP27 and Gs heterotrimer, whose complex assembly is stabilized by a NanoBiT tethering strategy. Comparison with other class B GPCR structures reveals that PACAP27 engages VIP1R with its N-terminus inserting into the ligand binding pocket at the transmembrane bundle of the receptor, which subsequently couples to the G protein in a receptor-specific manner. This structure has provided insights into the molecular basis of PACAP27 binding and VIP receptor activation. The methodology of the NanoBiT tethering may help to provide structural information of unstable complexes. Vasoactive intestinal polypeptide receptor (VIP1R) is a widely expressed class B G protein-coupled receptor and a drug target for the treatment of inflammatory diseases. Here authors report a cryoelectron microscopy structure of human VIP1R bound to PACAP27 and Gs heterotrimer, which provides insights into PACAP27 binding and VIP receptor activation.
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6
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Mattedi G, Acosta-Gutiérrez S, Clark T, Gervasio FL. A combined activation mechanism for the glucagon receptor. Proc Natl Acad Sci U S A 2020; 117:15414-15422. [PMID: 32571939 PMCID: PMC7355025 DOI: 10.1073/pnas.1921851117] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We report on a combined activation mechanism for a class B G-protein-coupled receptor (GPCR), the glucagon receptor. By computing the conformational free-energy landscape associated with the activation of the receptor-agonist complex and comparing it with that obtained with the ternary complex (receptor-agonist-G protein) we show that the agonist stabilizes the receptor in a preactivated complex, which is then fully activated upon binding of the G protein. The proposed mechanism contrasts with the generally assumed GPCR activation mechanism, which proceeds through an opening of the intracellular region allosterically elicited by the binding of the agonist. The mechanism found here is consistent with electron cryo-microscopy structural data and might be general for class B GPCRs. It also helps us to understand the mode of action of the numerous allosteric antagonists of this important drug target.
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Affiliation(s)
- Giulio Mattedi
- Department of Chemistry, University College London, London WC1E 6BT, United Kingdom
| | | | - Timothy Clark
- Computer-Chemistry Center, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen 91052, Germany
| | - Francesco Luigi Gervasio
- Department of Chemistry, University College London, London WC1E 6BT, United Kingdom;
- Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, United Kingdom
- Pharmaceutical Sciences, University of Geneva, Geneva CH-1211, Switzerland
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7
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Noda H, Guo J, Khatri A, Dean T, Reyes M, Armanini M, Brooks DJ, Martins JS, Schipani E, Bouxsein ML, Demay MB, Potts JT, Jüppner H, Gardella TJ. An Inverse Agonist Ligand of the PTH Receptor Partially Rescues Skeletal Defects in a Mouse Model of Jansen's Metaphyseal Chondrodysplasia. J Bone Miner Res 2020; 35:540-549. [PMID: 31693237 PMCID: PMC8050614 DOI: 10.1002/jbmr.3913] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 10/14/2019] [Accepted: 10/24/2019] [Indexed: 01/09/2023]
Abstract
Jansen's metaphyseal chondrodysplasia (JMC) is a rare disease of bone and mineral ion physiology that is caused by activating mutations in PTHR1. Ligand-independent signaling by the mutant receptors in cells of bone and kidney results in abnormal skeletal growth, excessive bone turnover, and chronic hypercalcemia and hyperphosphaturia. Clinical features further include short stature, limb deformities, nephrocalcinosis, and progressive losses in kidney function. There is no effective treatment option available for JMC. In previous cell-based assays, we found that certain N-terminally truncated PTH and PTHrP antagonist peptides function as inverse agonists and thus can reduce the high rates of basal cAMP signaling exhibited by the mutant PTHR1s of JMC in vitro. Here we explored whether one such inverse agonist ligand, [Leu11 ,dTrp12 ,Trp23 ,Tyr36 ]-PTHrP(7-36)NH2 (IA), can be effective in vivo and thus ameliorate the skeletal abnormalities that occur in transgenic mice expressing the PTHR1-H223R allele of JMC in osteoblastic cells via the collagen-1α1 promoter (C1HR mice). We observed that after 2 weeks of twice-daily injection and relative to vehicle controls, the IA analog resulted in significant improvements in key skeletal parameters that characterize the C1HR mice, because it reduced the excess trabecular bone mass, bone marrow fibrosis, and levels of bone turnover markers in blood and urine. The overall findings provide proof-of-concept support for the notion that inverse agonist ligands targeted to the mutant PTHR1 variants of JMC can have efficacy in vivo. Further studies of such PTHR1 ligand analogs could help open paths toward the first treatment option for this debilitating skeletal disorder. © 2019 American Society for Bone and Mineral Research.
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Affiliation(s)
- Hiroshi Noda
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - Jun Guo
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - Ashok Khatri
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - Thomas Dean
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - Monica Reyes
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - Michael Armanini
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA.,Department of Orthopedic Surgery, Harvard Medical School, Boston, MA, USA.,Center for Advanced Orthopedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Daniel J Brooks
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA.,Department of Orthopedic Surgery, Harvard Medical School, Boston, MA, USA.,Center for Advanced Orthopedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Janaina S Martins
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | | | - Mary L Bouxsein
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA.,Department of Orthopedic Surgery, Harvard Medical School, Boston, MA, USA.,Center for Advanced Orthopedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - John T Potts
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - Harald Jüppner
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
| | - Thomas J Gardella
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
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8
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Zhang Y, Sun B, Feng D, Hu H, Chu M, Qu Q, Tarrasch JT, Li S, Sun Kobilka T, Kobilka BK, Skiniotis G. Cryo-EM structure of the activated GLP-1 receptor in complex with a G protein. Nature 2017; 546:248-253. [PMID: 28538729 PMCID: PMC5587415 DOI: 10.1038/nature22394] [Citation(s) in RCA: 405] [Impact Index Per Article: 57.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Accepted: 04/25/2017] [Indexed: 02/06/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) is a hormone with essential roles in regulating insulin secretion, carbohydrate metabolism and appetite. GLP-1 effects are mediated through binding to GLP-1R, a family B G protein-coupled receptor (GPCR) signaling primarily through the stimulatory G protein Gs. Family B GPCRs are important therapeutic targets, however our understanding of their mechanism of action is limited by the lack of structural information on activated and full-length receptors. Here we show the electron cryo-microscopy structure of the peptide-activated GLP-1R:Gs complex at near atomic resolution. The peptide is clasped between the N-terminal domain and transmembrane core of the receptor, further stabilized by extracellular loops. Conformational changes in the transmembrane domain result in a sharp kink in the middle of transmembrane helix 6, which pivots its intracellular half outward to accommodate the α5 helix of GαsRas. These results provide a structural framework for understanding family B receptor activation through hormone binding.
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Affiliation(s)
- Yan Zhang
- Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Bingfa Sun
- ConfometRx, 3070 Kenneth St, Santa Clara, California 95054, USA
| | - Dan Feng
- ConfometRx, 3070 Kenneth St, Santa Clara, California 95054, USA
| | - Hongli Hu
- Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Matthew Chu
- ConfometRx, 3070 Kenneth St, Santa Clara, California 95054, USA
| | - Qianhui Qu
- Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Jeffrey T Tarrasch
- Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Shane Li
- ConfometRx, 3070 Kenneth St, Santa Clara, California 95054, USA
| | | | - Brian K Kobilka
- ConfometRx, 3070 Kenneth St, Santa Clara, California 95054, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Georgios Skiniotis
- Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
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9
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Yin Y, de Waal PW, He Y, Zhao LH, Yang D, Cai X, Jiang Y, Melcher K, Wang MW, Xu HE. Rearrangement of a polar core provides a conserved mechanism for constitutive activation of class B G protein-coupled receptors. J Biol Chem 2017; 292:9865-9881. [PMID: 28356352 DOI: 10.1074/jbc.m117.782987] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 03/20/2017] [Indexed: 11/06/2022] Open
Abstract
The glucagon receptor (GCGR) belongs to the secretin-like (class B) family of G protein-coupled receptors (GPCRs) and is activated by the peptide hormone glucagon. The structures of an activated class B GPCR have remained unsolved, preventing a mechanistic understanding of how these receptors are activated. Using a combination of structural modeling and mutagenesis studies, we present here two modes of ligand-independent activation of GCGR. First, we identified a GCGR-specific hydrophobic lock comprising Met-338 and Phe-345 within the IC3 loop and transmembrane helix 6 (TM6) and found that this lock stabilizes the TM6 helix in the inactive conformation. Disruption of this hydrophobic lock led to constitutive G protein and arrestin signaling. Second, we discovered a polar core comprising conserved residues in TM2, TM3, TM6, and TM7, and mutations that disrupt this polar core led to constitutive GCGR activity. On the basis of these results, we propose a mechanistic model of GCGR activation in which TM6 is held in an inactive conformation by the conserved polar core and the hydrophobic lock. Mutations that disrupt these inhibitory elements allow TM6 to swing outward to adopt an active TM6 conformation similar to that of the canonical β2-adrenergic receptor complexed with G protein and to that of rhodopsin complexed with arrestin. Importantly, mutations in the corresponding polar core of several other members of class B GPCRs, including PTH1R, PAC1R, VIP1R, and CRFR1, also induce constitutive G protein signaling, suggesting that the rearrangement of the polar core is a conserved mechanism for class B GPCR activation.
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Affiliation(s)
- Yanting Yin
- From the Van Andel Research Institute - Shanghai Institute of Materia Medica (VARI-SIMM) Center, Center for Structure and Function of Drug Targets, The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CAS), Shanghai 201203, China.,the Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, Michigan 49503.,the University of Chinese Academy of Sciences, Number 19A Yuquan Road, Beijing 100049, China
| | - Parker W de Waal
- the Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, Michigan 49503
| | - Yuanzheng He
- the Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, Michigan 49503
| | - Li-Hua Zhao
- From the Van Andel Research Institute - Shanghai Institute of Materia Medica (VARI-SIMM) Center, Center for Structure and Function of Drug Targets, The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CAS), Shanghai 201203, China
| | - Dehua Yang
- The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China, and
| | - Xiaoqing Cai
- The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China, and
| | - Yi Jiang
- From the Van Andel Research Institute - Shanghai Institute of Materia Medica (VARI-SIMM) Center, Center for Structure and Function of Drug Targets, The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CAS), Shanghai 201203, China
| | - Karsten Melcher
- the Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, Michigan 49503
| | - Ming-Wei Wang
- The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China, and .,the School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
| | - H Eric Xu
- From the Van Andel Research Institute - Shanghai Institute of Materia Medica (VARI-SIMM) Center, Center for Structure and Function of Drug Targets, The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CAS), Shanghai 201203, China, .,the Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, Michigan 49503.,the University of Chinese Academy of Sciences, Number 19A Yuquan Road, Beijing 100049, China
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10
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Culhane KJ, Liu Y, Cai Y, Yan ECY. Transmembrane signal transduction by peptide hormones via family B G protein-coupled receptors. Front Pharmacol 2015; 6:264. [PMID: 26594176 PMCID: PMC4633518 DOI: 10.3389/fphar.2015.00264] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 10/23/2015] [Indexed: 01/28/2023] Open
Abstract
Although family B G protein-coupled receptors (GPCRs) contain only 15 members, they play key roles in transmembrane signal transduction of hormones. Family B GPCRs are drug targets for developing therapeutics for diseases ranging from metabolic to neurological disorders. Despite their importance, the molecular mechanism of activation of family B GPCRs remains largely unexplored due to the challenges in expression and purification of functional receptors to the quantity for biophysical characterization. Currently, there is no crystal structure available of a full-length family B GPCR. However, structures of key domains, including the extracellular ligand binding regions and seven-helical transmembrane regions, have been solved by X-ray crystallography and NMR, providing insights into the mechanisms of ligand recognition and selectivity, and helical arrangements within the cell membrane. Moreover, biophysical and biochemical methods have been used to explore functions, key residues for signaling, and the kinetics and dynamics of signaling processes. This review summarizes the current knowledge of the signal transduction mechanism of family B GPCRs at the molecular level and comments on the challenges and outlook for mechanistic studies of family B GPCRs.
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Affiliation(s)
- Kelly J Culhane
- Department of Molecular Biophysics and Biochemistry, Yale University New Haven, CT, USA
| | - Yuting Liu
- Department of Chemistry, Yale University New Haven, CT, USA
| | - Yingying Cai
- Department of Chemistry, Yale University New Haven, CT, USA
| | - Elsa C Y Yan
- Department of Chemistry, Yale University New Haven, CT, USA
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11
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Sun X, Cheng J, Wang X, Tang Y, Ågren H, Tu Y. Residues remote from the binding pocket control the antagonist selectivity towards the corticotropin-releasing factor receptor-1. Sci Rep 2015; 5:8066. [PMID: 25628267 PMCID: PMC4308710 DOI: 10.1038/srep08066] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 01/02/2015] [Indexed: 01/01/2023] Open
Abstract
The corticotropin releasing factors receptor-1 and receptor-2 (CRF1R and CRF2R) are therapeutic targets for treating neurological diseases. Antagonists targeting CRF1R have been developed for the potential treatment of anxiety disorders and alcohol addiction. It has been found that antagonists targeting CRF1R always show high selectivity, although CRF1R and CRF2R share a very high rate of sequence identity. This has inspired us to study the origin of the selectivity of the antagonists. We have therefore built a homology model for CRF2R and carried out unbiased molecular dynamics and well-tempered metadynamics simulations for systems with the antagonist CP-376395 in CRF1R or CRF2R to address this issue. We found that the side chain of Tyr(6.63) forms a hydrogen bond with the residue remote from the binding pocket, which allows Tyr(6.63) to adopt different conformations in the two receptors and results in the presence or absence of a bottleneck controlling the antagonist binding to or dissociation from the receptors. The rotameric switch of the side chain of Tyr356(6.63) allows the breaking down of the bottleneck and is a perquisite for the dissociation of CP-376395 from CRF1R.
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Affiliation(s)
- Xianqiang Sun
- Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
| | - Jianxin Cheng
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Xu Wang
- Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
| | - Yun Tang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Hans Ågren
- Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
| | - Yaoquan Tu
- Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
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12
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Bai Q, Shi D, Zhang Y, Liu H, Yao X. Exploration of the antagonist CP-376395 escape pathway for the corticotropin-releasing factor receptor 1 by random acceleration molecular dynamics simulations. MOLECULAR BIOSYSTEMS 2015; 10:1958-67. [PMID: 24820411 DOI: 10.1039/c4mb00037d] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Corticotropin-releasing factor receptor 1 (CRF1R), a member of class B G-protein-coupled receptors (GPCRs), plays an important role in the treatment of osteoporosis, diabetes, depression, migraine and anxiety. To explore the escape pathway of the antagonist CP-376395 in the binding pocket of CRF1R, molecular dynamics (MD) simulations, dynamical network analysis, random acceleration molecular dynamics (RAMD) simulations and adaptive biasing force (ABF) calculations were performed on the crystal structure of CRF1R in complex with CP-376395. The results of dynamical network analysis show that TM7 of CRF1R has the strongest edges during MD simulation. The bent part of TM7 forms a V-shape pocket with Gly356(7.50). Asn283(5.50) has high hydrogen bond occupancy during 100 ns MD simulations and is the key interaction residue with the antagonist in the binding pocket of CRF1R. RAMD simulation has identified three possible pathways (PW1, PW2 and PW3) for CP-376395 to escape from the binding pocket of CRF1R. The PW3 pathway was proved to be the most likely escape pathway for CP-376395. The free energy along the PW3 pathway was calculated by using ABF simulations. Two energy barriers were found along the reaction coordinates. Residues Leu323(6.49), Asn283(5.50) and Met206(3.47) contribute to the steric hindrance for the first energy barrier. Residues His199(3.40) and Gln355(7.49) contribute to the second energy barrier through the hydrogen bonding interaction between CP-376395 and CRF1R. The results of our study can not only provide useful information to understand the interaction mechanism between CP-376395 and CRF1R, but also provide the details about the possible escape pathway and the free energy profile of CP-376395 in the pocket of CRF1R.
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Affiliation(s)
- Qifeng Bai
- College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000, P. R. China.
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13
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Bortolato A, Doré AS, Hollenstein K, Tehan BG, Mason JS, Marshall FH. Structure of Class B GPCRs: new horizons for drug discovery. Br J Pharmacol 2015; 171:3132-45. [PMID: 24628305 DOI: 10.1111/bph.12689] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 03/04/2014] [Accepted: 03/10/2014] [Indexed: 01/15/2023] Open
Abstract
Class B GPCRs of the secretin family are important drug targets in many human diseases including diabetes, neurodegeneration, cardiovascular disease and psychiatric disorders. X-ray crystal structures for the glucagon receptor and corticotropin-releasing factor receptor 1 have now been published. In this review, we analyse the new structures and how they compare with each other and with Class A and F receptors. We also consider the differences in druggability and possible similarity in the activation mechanisms. Finally, we discuss the potential for the design of small-molecule modulators for these important targets in drug discovery. This new structural insight allows, for the first time, structure-based drug design methods to be applied to Class B GPCRs.
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Affiliation(s)
- Andrea Bortolato
- Heptares Therapeutics Limited, Welwyn Garden City, Hertfordshire, UK
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Xu J, Wang Z, Liu P, Li D, Lin J. An insight into antagonist binding and induced conformational dynamics of class B GPCR corticotropin-releasing factor receptor 1. MOLECULAR BIOSYSTEMS 2015; 11:2042-50. [DOI: 10.1039/c5mb00159e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The binding of small-molecule antagonists, CP-376395 and MTIP, would induce conformational dynamics behaviors of CRF1R.
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Affiliation(s)
- Junli Xu
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy
- Nankai University
- Tianjin 300071
- China
- Pharmaceutical Intelligence Platform
| | - Zhonghua Wang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy
- Nankai University
- Tianjin 300071
- China
| | - Pi Liu
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy
- Nankai University
- Tianjin 300071
- China
| | - Dongmei Li
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy
- Nankai University
- Tianjin 300071
- China
| | - Jianping Lin
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy
- Nankai University
- Tianjin 300071
- China
- Pharmaceutical Intelligence Platform
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Hollenstein K, de Graaf C, Bortolato A, Wang MW, Marshall FH, Stevens RC. Insights into the structure of class B GPCRs. Trends Pharmacol Sci 2013; 35:12-22. [PMID: 24359917 DOI: 10.1016/j.tips.2013.11.001] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/30/2013] [Accepted: 11/01/2013] [Indexed: 02/08/2023]
Abstract
The secretin-like (class B) family of G protein-coupled receptors (GPCRs) are key players in hormonal homeostasis and are interesting drug targets for the treatment of several metabolic disorders (such as type 2 diabetes, osteoporosis, and obesity) and nervous system diseases (such as migraine, anxiety, and depression). The recently solved crystal structures of the transmembrane domains of the human glucagon receptor and human corticotropin-releasing factor receptor 1 have opened up new opportunities to study the structure and function of class B GPCRs. The current review shows how these structures offer more detailed explanations to previous biochemical and pharmacological studies of class B GPCRs, and provides new insights into their interactions with ligands.
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Affiliation(s)
- Kaspar Hollenstein
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, UK
| | - Chris de Graaf
- Division of Medicinal Chemistry, Faculty of Sciences, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Andrea Bortolato
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, UK
| | - Ming-Wei Wang
- The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CAS), 189 Guo Shou Jing Road, Shanghai, 201203, China
| | - Fiona H Marshall
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, UK.
| | - Raymond C Stevens
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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Hollenstein K, Kean J, Bortolato A, Cheng RKY, Doré AS, Jazayeri A, Cooke RM, Weir M, Marshall FH. Structure of class B GPCR corticotropin-releasing factor receptor 1. Nature 2013; 499:438-43. [PMID: 23863939 DOI: 10.1038/nature12357] [Citation(s) in RCA: 344] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 06/07/2013] [Indexed: 12/17/2022]
Abstract
Structural analysis of class B G-protein-coupled receptors (GPCRs), cell-surface proteins that respond to peptide hormones, has been restricted to the amino-terminal extracellular domain, thus providing little understanding of the membrane-spanning signal transduction domain. The corticotropin-releasing factor receptor type 1 is a class B receptor which mediates the response to stress and has been considered a drug target for depression and anxiety. Here we report the crystal structure of the transmembrane domain of the human corticotropin-releasing factor receptor type 1 in complex with the small-molecule antagonist CP-376395. The structure provides detailed insight into the architecture of class B receptors. Atomic details of the interactions of the receptor with the non-peptide ligand that binds deep within the receptor are described. This structure provides a model for all class B GPCRs and may aid in the design of new small-molecule drugs for diseases of brain and metabolism.
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Affiliation(s)
- Kaspar Hollenstein
- Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City AL7 3AX, UK
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Vohra S, Taddese B, Conner AC, Poyner DR, Hay DL, Barwell J, Reeves PJ, Upton GJG, Reynolds CA. Similarity between class A and class B G-protein-coupled receptors exemplified through calcitonin gene-related peptide receptor modelling and mutagenesis studies. J R Soc Interface 2012; 10:20120846. [PMID: 23235263 PMCID: PMC3565703 DOI: 10.1098/rsif.2012.0846] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Modelling class B G-protein-coupled receptors (GPCRs) using class A GPCR structural templates is difficult due to lack of homology. The plant GPCR, GCR1, has homology to both class A and class B GPCRs. We have used this to generate a class A–class B alignment, and by incorporating maximum lagged correlation of entropy and hydrophobicity into a consensus score, we have been able to align receptor transmembrane regions. We have applied this analysis to generate active and inactive homology models of the class B calcitonin gene-related peptide (CGRP) receptor, and have supported it with site-directed mutagenesis data using 122 CGRP receptor residues and 144 published mutagenesis results on other class B GPCRs. The variation of sequence variability with structure, the analysis of polarity violations, the alignment of group-conserved residues and the mutagenesis results at 27 key positions were particularly informative in distinguishing between the proposed and plausible alternative alignments. Furthermore, we have been able to associate the key molecular features of the class B GPCR signalling machinery with their class A counterparts for the first time. These include the [K/R]KLH motif in intracellular loop 1, [I/L]xxxL and KxxK at the intracellular end of TM5 and TM6, the NPXXY/VAVLY motif on TM7 and small group-conserved residues in TM1, TM2, TM3 and TM7. The equivalent of the class A DRY motif is proposed to involve Arg2.39, His2.43 and Glu3.46, which makes a polar lock with T6.37. These alignments and models provide useful tools for understanding class B GPCR function.
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Affiliation(s)
- Shabana Vohra
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, UK
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18
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Garcia GL, Dong M, Miller LJ. Differential determinants for coupling of distinct G proteins with the class B secretin receptor. Am J Physiol Cell Physiol 2012; 302:C1202-12. [PMID: 22277758 DOI: 10.1152/ajpcell.00273.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The secretin receptor is a prototypic class B G protein-coupled receptor that is activated by binding of its natural peptide ligand. The signaling effects of this receptor are mediated by coupling with Gs, which activates cAMP production, and Gq, which activates intracellular calcium mobilization. We have explored the molecular basis for the coupling of each of these G proteins to this receptor using systematic site-directed mutagenesis of key residues within each of the intracellular loop regions, and studying ligand binding and secretin-stimulated cAMP and calcium responses. Mutation of a conserved histidine in the first intracellular loop (H157A and H157R) markedly reduced cell surface expression, resulting in marked reduction in cAMP and elimination of measurable calcium responses. Mutation of an arginine (R153A) in the first intracellular loop reduced calcium, but not cAMP responses. Mutation of a dibasic motif in the second intracellular loop (R231A/K232A) had no significant effects on any measured responses. Mutations in the third intracellular loop involving adjacent lysine and leucine residues (K302A/L303A) or two arginine residues separated by a leucine and an alanine (R318A/R321A) significantly reduced cAMP responses, while the latter also reduced calcium responses. Additive effects were elicited by combining the effective mutations, while combining all the effective mutations resulted in a construct that continued to bind secretin normally, but that elicited no significant cAMP or calcium responses. These data suggest that, while some receptor determinants are clearly shared, there are also distinct determinants for coupling with each of these G proteins.
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Affiliation(s)
- Gene L Garcia
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, USA
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Lueblinghoff J, Mueller S, Sontheimer J, Paschke R. Lack of consistent association of thyrotropin receptor mutations in vitro activity with the clinical course of patients with sporadic non-autoimmune hyperthyroidism. J Endocrinol Invest 2010; 33:228-33. [PMID: 19636218 DOI: 10.1007/bf03345784] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND Up to date, 14 patients with sporadic non-autoimmune hyperthyroidism (SNAH) caused by sporadic germline mutations in the TSH receptor (TSHR) gene have been reported. Despite considerable differences in the activity of hyperthyroidism, all SNAH case reports concluded that the demonstrated constitutive activity explains the phenotype. AIM Recently, linear regression analysis (LRA) of constitutive activity as a function of TSHR expression determined by 125I-bTSH binding or fluorescence activated cell sorting analysis was described as a more reliable way of characterizing the in vitro activity (IVA) of a constitutively activating TSHR mutation. Therefore, we analyzed a possible genotype-phenotype correlation in a systematic review of the case reports and investigated the TSHR mutation's LRA in selected cases. MATERIAL AND METHODS We determined the LRA for all sporadic germline mutations which had not previously been reported. Moreover, we systematically evaluated all case reports of SNAH for evidence of an association of the clinical course (CC) with the IVA of the mutated TSHR. RESULTS The LRA determined were: M453T (5.2+/-0.8), L512Q (4.5+/-0.7), I568T (25.6+/-6.3), F631L (45.9+/-9.4), T632I (14.5+/-2.7), D633Y (16.4+/-6.4). None of the 10 examined clinical signs showed a significant association with the LRA. Moreover, the comparison of the CC of patients harboring the same mutation (S281N, M453T, I568T, S505N) also showed no relation of the clinical activity with a high LRA. CONCLUSION Considering the different diagnostic circumstances, therapeutic strategies and the limitations of a systematic analysis of case reports due to the restricted number of case reports and limited follow-up we found no consistent relation of the TSHR mutation's IVA determined by LRA with the CC of patients with SNAH. This may also be due to the action of genetic, epigenetic, and environmental modifiers.
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Affiliation(s)
- J Lueblinghoff
- III Medical Department, University of Leipzig, D- 04103 Leipzig, Germany
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Bonde MM, Yao R, Ma JN, Madabushi S, Haunsø S, Burstein ES, Whistler JL, Sheikh SP, Lichtarge O, Hansen JL. An angiotensin II type 1 receptor activation switch patch revealed through evolutionary trace analysis. Biochem Pharmacol 2010; 80:86-94. [PMID: 20227396 DOI: 10.1016/j.bcp.2010.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 02/08/2010] [Accepted: 03/04/2010] [Indexed: 12/21/2022]
Abstract
Seven transmembrane (7TM) or G protein-coupled receptors constitute a large superfamily of cell surface receptors sharing a structural motif of seven transmembrane spanning alpha helices. Their activation mechanism most likely involves concerted movements of the transmembrane helices, but remains to be completely resolved. Evolutionary Trace (ET) analysis is a computational method, which identifies clusters of functionally important residues by integrating information on evolutionary important residue variations with receptor structure. Combined with known mutational data, ET predicted a patch of residues in the cytoplasmic parts of TM2, TM3, and TM6 to form an activation switch that is common to all family A 7TM receptors. We tested this hypothesis in the rat Angiotensin II (Ang II) type 1a (AT1a) receptor. The receptor has important roles in the cardiovascular system, but has also frequently been applied as a model for 7TM receptor activation and signaling. Six mutations: F66A, L67R, L70R, L119R, D125A, and I245F were targeted to the putative switch and assayed for changes in activation state by their ligand binding, signaling, and trafficking properties. All but one receptor mutant (that was not expressed well) displayed phenotypes associated with changed activation state, such as increased agonist affinity or basal activity, promiscuous activation, or constitutive internalization highlighting the importance of testing different signaling pathways. We conclude that this evolutionary important patch mediates interactions important for maintaining the inactive state. More broadly, these observations in the AT1 receptor are consistent with computational predictions of a generic role for this patch in 7TM receptor activation.
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Affiliation(s)
- Marie Mi Bonde
- Laboratory for Molecular Cardiology, The Danish National Research Foundation Centre for Cardiac Arrhythmia, The Heart Centre, Copenhagen University Hospital, Rigshospitalet, Juliane Mariesvej 20, section 9312, DK-2100 Copenhagen, Denmark
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21
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Tao YX. Constitutive activation of G protein-coupled receptors and diseases: insights into mechanisms of activation and therapeutics. Pharmacol Ther 2008; 120:129-48. [PMID: 18768149 DOI: 10.1016/j.pharmthera.2008.07.005] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 07/22/2008] [Indexed: 01/17/2023]
Abstract
The existence of constitutive activity for G protein-coupled receptors (GPCRs) was first described in 1980s. In 1991, the first naturally occurring constitutively active mutations in GPCRs that cause diseases were reported in rhodopsin. Since then, numerous constitutively active mutations that cause human diseases were reported in several additional receptors. More recently, loss of constitutive activity was postulated to also cause diseases. Animal models expressing some of these mutants confirmed the roles of these mutations in the pathogenesis of the diseases. Detailed functional studies of these naturally occurring mutations, combined with homology modeling using rhodopsin crystal structure as the template, lead to important insights into the mechanism of activation in the absence of crystal structure of GPCRs in active state. Search for inverse agonists on these receptors will be critical for correcting the diseases cause by activating mutations in GPCRs. Theoretically, these inverse agonists are better therapeutics than neutral antagonists in treating genetic diseases caused by constitutively activating mutations in GPCRs.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, 212 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
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22
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Gozu HI, Mueller S, Bircan R, Krohn K, Ekinci G, Yavuzer D, Sargin H, Sargin M, Ones T, Gezen C, Orbay E, Cirakoglu B, Paschke R. A new silent germline mutation of the TSH receptor: coexpression in a hyperthyroid family member with a second activating somatic mutation. Thyroid 2008; 18:499-508. [PMID: 18466076 DOI: 10.1089/thy.2007.0335] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Up to date, three thyroid-stimulating hormone receptor (TSHR) germline variants have been reported for which no functional consequences have been detected by in vitro characterizations. However, familial nonautoimmune hyperthyroidism and hot nodules are clearly associated with constitutively activating TSHR germline mutations. We describe a family with a new TSHR germline mutation that is associated with euthyroidism in 13 family members and hyperthyroidism in 1 family member. METHODS Mutation analysis of the TSHR gene was performed by denaturing gradient gel electrophoresis. TSHR constructs were characterized by determination of cell surface expression, 3'-5'-cyclic adenosine monophosphate (cAMP) accumulation, and constitutive cAMP activity. RESULTS A novel TSHR germline mutation (N372T) was found in a man who presented with thyrotoxicosis. The mutation was also detected in 13 family members, all of whom were euthyroid. Interestingly, an additional constitutively active somatic mutation (S281N) was identified on the second parental TSHR allele of the hyperthyroid index patient. Linear regression analysis showed a lack of constitutive activity for N372T. Moreover, coexpression studies of N372T with S281N did not reveal any evidence for a functional influence of N372T on the constitutively active mutation (CAM). CONCLUSIONS N372T is unlikely to cause altered thyroid function. This is consistent with the finding that only the index patient with the additional somatic mutation S281N was hyperthyroid.
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Affiliation(s)
- Hulya Iliksu Gozu
- Section of Endocrinology and Metabolism, Dr. Lutfi Kirdar Kartal Education and Research Hospital, Istanbul, Turkey
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Significance of Ectodomain Cysteine Boxes 2 and 3 for the Activation Mechanism of the Thyroid-stimulating Hormone Receptor. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84077-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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24
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Ringkananont U, Van Durme J, Montanelli L, Ugrasbul F, Yu YM, Weiss RE, Refetoff S, Grasberger H. Repulsive Separation of the Cytoplasmic Ends of Transmembrane Helices 3 and 6 Is Linked to Receptor Activation in a Novel Thyrotropin Receptor Mutant (M626I). Mol Endocrinol 2006; 20:893-903. [PMID: 16339276 DOI: 10.1210/me.2005-0339] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
AbstractLigand-dependent activation of G protein-coupled receptors (GPCRs) involves repositioning of the juxtacytoplasmic ends of transmembrane helices TM3 and TM6. This concept, inferred from site-directed spin labeling studies, is supported by chemical cross-linking of the cytoplasmic ends of TM3 and TM6 blocking GPCR activation. Here we report a novel constitutive active mutation (M626I) in TM6 of the TSH receptor (TSHR), identified in affected members of a family with nonautoimmune hyperthyroidism. The specific constitutive activity of M626I, measured by its basal cAMP generation corrected for cell surface expression, was 13-fold higher than that of wild-type TSHR. Homology modeling of the TSHR serpentine domain based on the rhodopsin crystal structure suggests that M626 faces the side chain of I515 of TM3 near the membrane-cytoplasmic junction. Steric hindrance of the introduced isoleucine by I515 is consistent with the fact that shorter or more flexible side chains at position 626 did not increase constitutivity. Furthermore, a reciprocal mutation at position 515 (I515M), when introduced into the M626I background, acts as revertant mutation by allowing accommodation of the isoleucine sidechain at position 626 and fully restoring the constitutive activity to the level of wild-type TSHR. Thus, repulsive separation of the juxtacytoplasmic TM6 and TM3 in the M626I model conclusively demonstrates a direct link between the opening of this cytoplasmic face of the receptor structure and G protein coupling.
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Affiliation(s)
- Usanee Ringkananont
- Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA
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25
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Martin B, Lopez de Maturana R, Brenneman R, Walent T, Mattson MP, Maudsley S. Class II G protein-coupled receptors and their ligands in neuronal function and protection. Neuromolecular Med 2005; 7:3-36. [PMID: 16052036 PMCID: PMC2636744 DOI: 10.1385/nmm:7:1-2:003] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2005] [Accepted: 01/26/2005] [Indexed: 12/20/2022]
Abstract
G protein-coupled receptors (GPCRs) play pivotal roles in regulating the function and plasticity of neuronal circuits in the nervous system. Among the myriad of GPCRs expressed in neural cells, class II GPCRs which couples predominantly to the Gs-adenylate cyclase-cAMP signaling pathway, have recently received considerable attention for their involvement in regulating neuronal survival. Neuropeptides that activate class II GPCRs include secretin, glucagon-like peptides (GLP-1 and GLP-2), growth hormone-releasing hormone (GHRH), pituitary adenylate cyclase activating peptide (PACAP), corticotropin-releasing hormone (CRH), vasoactive intestinal peptide (VIP), parathyroid hormone (PTH), and calcitonin-related peptides. Studies of patients and animal and cell culture models, have revealed possible roles for class II GPCRs signaling in the pathogenesis of several prominent neurodegenerative conditions including stroke, Alzheimer's, Parkinson's, and Huntington's diseases. Many of the peptides that activate class II GPCRs promote neuron survival by increasing the resistance of the cells to oxidative, metabolic, and excitotoxic injury. A better understanding of the cellular and molecular mechanisms by which class II GPCRs signaling modulates neuronal survival and plasticity will likely lead to novel therapeutic interventions for neurodegenerative disorders.
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Affiliation(s)
- Bronwen Martin
- Laboratory of Neurosciences, National Institute on Ageing Intramural Research Program, Gerontology Research Center, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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26
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Bywater RP. Location and nature of the residues important for ligand recognition in G-protein coupled receptors. J Mol Recognit 2005; 18:60-72. [PMID: 15386622 DOI: 10.1002/jmr.685] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The overall structure of the biogenic amine subclass of the G-protein-coupled receptors, and of their ligand binding sites, is discussed with the aim of highlighting the major structural features of these receptors that are responsible for ligand recognition. A comparison is made between biogenic amine receptors, peptide receptors of the rhodopsin class, and the secretin receptors which all have peptide ligands. The question of where the peptide ligands bind, whether at extracellular sites or within the transmembrane helix bundle, is discussed. The suitability of the rhodopsin crystal structure as a template for construction of homology models is discussed and it is concluded that there are many reasons why a caution should be issued against using it uncritically.
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Affiliation(s)
- Robert P Bywater
- Adelard Institute, London, UK and Division of Molecular Neurobiology, Wallenberg Neuroscience Center, Lund University, Lund, Sweden.
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27
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Strudwick N, Bhogal N, Evans NA, Blaney FE, Findlay JBC. Evidence to support a spectrum of active states for the glucagon receptor. Biochem Soc Trans 2005; 32:1037-9. [PMID: 15506957 DOI: 10.1042/bst0321037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The ternary complex model suggests that G-protein-coupled receptors resonate between inactive (R) and active (R*) forms. Physiologically, R sites ordinarily predominate with a few R* sites giving rise to basal activity. Agonists recognize, stabilize and increase the R* population, thus altering intracellular activity. There is evidence to suggest the possibility of a spectrum of conformations between R and R*. Our aim is to study the consequences of putative GR (glucagon receptor)-activating mutations using glucagon and partial agonist des-His(1)-[Glu(9)]glucagon amide (glucagon-NH(2)). Alanine substitution in TM (transmembrane) helix 2 of Arg(173) or of His(177) detrimentally affected glucagon and glucagon-NH(2) response maxima. TM2 receptor mutant, Phe(181)-Ala, displayed reduced maximum cAMP accumulation in response to glucagon-NH(2). Thr(353)-Cys (TM6) and Glu(406)-Ala (TM7) receptors demonstrated constitutive activity and enhanced EC(50) values for glucagon-NH(2); Arg(346)-Ala (TM6) and Asn(404)-Ala (TM7) receptors were activated by sub-fmol glucagon concentrations, yet were not constitutively active and demonstrated wild-type receptor-like EC(50) values for glucagon-NH(2). Unlike Arg(346)-Ala receptors, Thr(353)-Cys, Asn(404)-Ala and Glu(406)-Ala receptors demonstrated improved EC(50) values for glucagon, whereas their maximal responses to and their affinity for glucagon were comparable with the wild-type receptor. In contrast, despite slightly reduced glucagon-NH(2) affinity, Arg(346)-Ala, Thr(353)-Cys, Asn(404)-Ala and Glu(406)-Ala receptors displayed glucagon-NH(2) response maxima that exceeded those seen for wild-type receptors. Interestingly, we observed biphasic glucagon-mediated signalling responses. Our results are consistent with the concept of different agonists promoting the formation of distinct active states from partially active R*(low) to fully active R*(high) forms.
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Affiliation(s)
- N Strudwick
- School of Biochemistry and Microbiology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
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28
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Gensure RC, Shimizu N, Tsang J, Gardella TJ. Identification of a contact site for residue 19 of parathyroid hormone (PTH) and PTH-related protein analogs in transmembrane domain two of the type 1 PTH receptor. Mol Endocrinol 2003; 17:2647-58. [PMID: 12947048 DOI: 10.1210/me.2003-0275] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Recent functional studies have suggested that position 19 in PTH interacts with the portion of the PTH-1 receptor (P1R) that contains the extracellular loops and seven transmembrance helices (TMs) (the J domain). We tested this hypothesis using the photoaffinity cross-linking approach. A PTHrP(1-36) analog and a conformationally constrained PTH(1-21) analog, each containing para-benzoyl-l-phenylalanine (Bpa) at position 19, each cross-linked efficiently to the P1R expressed in COS-7 cells, and digestive mapping analysis localized the cross-linked site to the interval (Leu232-Lys240) at the extracellular end of TM2. Point mutation analysis identified Ala234, Val235, and Lys240 as determinants of cross-linking efficiency, and the Lys240-->Ala mutation selectively impaired the binding of PTH(1-21) and PTH(1-19) analogs, relative to that of PTH(1-15) analogs. The findings support the hypothesis that residue 19 of the receptor-bound ligand contacts, or is close to, the P1R J domain-specifically, Lys240 at the extracellular end of TM2. The findings also support a molecular model in which the 1-21 region of PTH binds to the extracellular face of the P1R J domain as an alpha-helix.
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Affiliation(s)
- Robert C Gensure
- Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts 02114, USA
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29
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Runge S, Gram C, Brauner-Osborne H, Madsen K, Knudsen LB, Wulff BS. Three distinct epitopes on the extracellular face of the glucagon receptor determine specificity for the glucagon amino terminus. J Biol Chem 2003; 278:28005-10. [PMID: 12724331 DOI: 10.1074/jbc.m301085200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The glucagon and glucagon-like peptide-1 (GLP-1) receptors are homologous family B seven-transmembrane (7TM) G protein-coupled receptors, and they selectively recognize the homologous peptide hormones glucagon (29 amino acids) and GLP-1 (30-31 amino acids), respectively. The amino-terminal extracellular domain of the glucagon and GLP-1 receptors (140-150 amino acids) determines specificity for the carboxyl terminus of glucagon and GLP-1, respectively. In addition, the glucagon receptor core domain (7TM helices and connecting loops) strongly determines specificity for the glucagon amino terminus. Only 4 of 15 residues are divergent in the glucagon and GLP-1 amino termini; Ser2, Gln3, Tyr10, and Lys12 in glucagon and the corresponding Ala8, Glu9, Val16, and Ser18 in GLP-1. In this study, individual substitution of these four residues of glucagon with the corresponding residues of GLP-1 decreased the affinity and potency at the glucagon receptor relative to glucagon. Substitution of distinct segments of the glucagon receptor core domain with the corresponding segments of the GLP-1 receptor rescued the affinity and potency of specific glucagon analogs. Site-directed mutagenesis identified the Asp385 --> Glu glucagon receptor mutant that specifically rescued Ala2-glucagon. The results show that three distinct epitopes of the glucagon receptor core domain determine specificity for the N terminus of glucagon. We suggest a glucagon receptor binding model in which the extracellular ends of TM2 and TM7 are close to and determine specificity for Gln3 and Ser2 of glucagon, respectively. Furthermore, the second extracellular loop and/or proximal segments of TM4 and/or TM5 are close to and determine specificity for Lys12 of glucagon.
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Affiliation(s)
- Steffen Runge
- Molecular Pharmacology, Novo Nordisk, DK-2760 Maaloev, Denmark
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30
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Abstract
A 29-amino acid polypeptide hormone, glucagon has been one of the most prolific models in the study of hormone action. The key biologic function of glucagon is to counterbalance the actions of insulin and maintain a normal level of serum glucose. Diabetes mellitus can thus be considered a bihormonal disorder with an excess of glucagon contributing to the hyperglycemic state. The effects of glucagon are mediated by the glucagon receptor, which is itself a prototypical member of a distinct category called family B receptors within the G protein-coupled superfamily of seven-helical transmembrane receptors (GPCRs). At the structural level, the peptide ligands of family B receptors are highly homologous, in particular in the N-terminal region of the molecules. The mechanism by which highly homologous peptide ligands selectively recognize their receptors involves distinct molecular interactions that are gradually being elucidated. This review focuses on structural determinants of the glucagon receptor that are important for its activity with respect to interaction with its ligand and G proteins. Information about the glucagon receptor is presented within the context of what is known about other members of the family B GPCRs.
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Affiliation(s)
- Cecilia G Unson
- The Rockefeller University, 1230 York Avenue, Box 294, New York, NY 10021, USA.
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31
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Haywood M, Tymchenko N, Spaliviero J, Koch A, Jimenez M, Gromoll J, Simoni M, Nordhoff V, Handelsman DJ, Allan CM. An activated human follicle-stimulating hormone (FSH) receptor stimulates FSH-like activity in gonadotropin-deficient transgenic mice. Mol Endocrinol 2002; 16:2582-91. [PMID: 12403847 DOI: 10.1210/me.2002-0032] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
FSH mediates its testicular actions via a specific Sertoli cell G protein-coupled receptor. We created a novel transgenic model to investigate a mutant human FSH receptor (FSHR(+)) containing a single amino acid substitution (Asp567Gly) equivalent to activating mutations in related glycoprotein hormone receptors. To examine the ligand-independent gonadal actions of FSHR(+), the rat androgen-binding protein gene promoter was used to direct FSHR(+) transgene expression to Sertoli cells of gonadotropin-deficient hypogonadal (hpg) mice. Both normal and hpg mouse testes expressed FSHR(+) mRNA. Testis weights of transgenic FSHR(+) hpg mice were increased approximately 2-fold relative to hpg controls (P < 0.02) and contained mature Sertoli cells and postmeiotic germ cells absent in controls, revealing FSHR(+)-initiated autonomous FSH-like testicular activity. Isolated transgenic Sertoli cells had significantly higher basal ( approximately 2-fold) and FSH-stimulated ( approximately 50%) cAMP levels compared with controls, demonstrating constitutive signaling and cell-surface expression of FSHR(+), respectively. Transgenic FSHR(+) also elevated testosterone production in hpg testes, in the absence of circulating LH (or FSH), and it was not expressed functionally on steroidogenic cells, suggesting a paracrine effect mediated by Sertoli cells. The FSHR(+) response was additive with a maximal testosterone dose on hpg testicular development, demonstrating FSHR(+) activity independent of androgen-specific actions. The FSHR(+) response was male specific as ovarian expression of FSHR(+) had no effect on hpg ovary size. These findings reveal transgenic FSHR(+) stimulated a constitutive FSH-like Sertoli cell response in gonadotropin-deficient testes, and pathways that induced LH-independent testicular steroidogenesis. This novel transgenic paradigm provides a unique approach to investigate the in vivo actions of mutated activating gonadotropin receptors.
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Affiliation(s)
- Miriam Haywood
- Andrology Laboratory, ANZAC Research Institute, Sydney, New South Wales 2139, Australia
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32
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Abstract
Reproduction cannot take place without the proper functioning of the lutropin/choriogonadotropin receptor (LHR). When the LHR does not work properly, ovulation does not occur in females and Leydig cells do not develop normally in the male. Also, because the LHR is essential for sustaining the elevated levels of progesterone needed to maintain pregnancy during the first trimester, disruptions in the functions of the LHR during pregnancy have catastrophic consequences. As such, a full understanding of the biology of the LHR is essential to the survival of our species. In this review we summarize our current knowledge of the structure, functions, and regulation of this important receptor.
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Affiliation(s)
- Mario Ascoli
- Department of Pharmacology, The University of Iowa, Iowa City, 52242-1109, USA.
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33
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Vlaeminck-Guillem V, Ho SC, Rodien P, Vassart G, Costagliola S. Activation of the cAMP pathway by the TSH receptor involves switching of the ectodomain from a tethered inverse agonist to an agonist. Mol Endocrinol 2002; 16:736-46. [PMID: 11923470 DOI: 10.1210/mend.16.4.0816] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Several lines of evidence indicate that constraining intramolecular interactions between transmembrane domains are required to maintain G protein-coupled receptors in an inactive conformation in the absence of agonist. For the glycoprotein hormone receptors, which harbor a long amino-terminal ectodomain responsible for hormone binding, it has been suggested that the ectodomain could contribute to these negative constraints. To test this hypothesis, we expressed at the surface of COS-7 cells mutants of the TSH receptor in which variable portions of the amino-terminal ectodomain are replaced by a 19-residue tag from bovine rhodopsin. Whereas none of the rhodopsin-tagged truncated mutants could be activated by saturating concentrations of TSH, the constructs with the shortest amino-terminal extension displayed increased constitutive activity toward the cAMP pathway, when compared with the wild-type holoreceptor. The shortest truncated construct was strongly activated by the introduction of mutations in transmembrane segment VI (D633A), or in the third intracellular loop (A623I) of the receptor. The magnitude of the stimulation was similar to that observed when the same mutations were introduced in the intact wild-type receptor. On the contrary, the shortest truncated construct was unaffected by activating mutations affecting residues of the extracellular loop region (I486F, I568T) or the top of transmembrane segment VII (del658-661). Together, our results are compatible with a model in which activation of the cAMP pathway by the TSH receptor involves switching of the ectodomain from a tethered inverse agonist to a true agonist.
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Affiliation(s)
- Virginie Vlaeminck-Guillem
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Nucléaire, Université Libre de Bruxelles, Campus Erasme, B-1070 Bruxelles, Belgium.
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34
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Ballesteros JA, Jensen AD, Liapakis G, Rasmussen SG, Shi L, Gether U, Javitch JA. Activation of the beta 2-adrenergic receptor involves disruption of an ionic lock between the cytoplasmic ends of transmembrane segments 3 and 6. J Biol Chem 2001; 276:29171-7. [PMID: 11375997 DOI: 10.1074/jbc.m103747200] [Citation(s) in RCA: 499] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The movements of transmembrane segments (TMs) 3 and 6 at the cytoplasmic side of the membrane play an important role in the activation of G-protein-coupled receptors. Here we provide evidence for the existence of an ionic lock that constrains the relative mobility of the cytoplasmic ends of TM3 and TM6 in the inactive state of the beta(2)-adrenergic receptor. We propose that the highly conserved Arg-131(3.50) at the cytoplasmic end of TM3 interacts both with the adjacent Asp-130(3.49) and with Glu-268(6.30) at the cytoplasmic end of TM6. Such a network of ionic interactions has now been directly supported by the high-resolution structure of the inactive state of rhodopsin. We hypothesized that the network of interactions would serve to constrain the receptor in the inactive state, and the release of this ionic lock could be a key step in receptor activation. To test this hypothesis, we made charge-neutralizing mutations of Glu-268(6.30) and of Asp-130(3.49) in the beta(2)-adrenergic receptor. Alone and in combination, we observed a significant increase in basal and pindolol-stimulated cAMP accumulation in COS-7 cells transiently transfected with the mutant receptors. Moreover, based on the increased accessibility of Cys-285(6.47) in TM6, we provide evidence for a conformational rearrangement of TM6 that is highly correlated with the extent of constitutive activity of the different mutants. The present experimental data together with the recent high-resolution structure of rhodopsin suggest that ionic interactions between Asp/Glu(3.49), Arg(3.50), and Glu(6.30) may constitute a common switch governing the activation of many rhodopsin-like G-protein-coupled receptors.
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Affiliation(s)
- J A Ballesteros
- Novasite Pharmaceuticals, Inc., San Diego, California 92121, USA
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35
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Nielsen SM, Nielsen LZ, Hjorth SA, Perrin MH, Vale WW. Constitutive activation of tethered-peptide/corticotropin-releasing factor receptor chimeras. Proc Natl Acad Sci U S A 2000; 97:10277-81. [PMID: 10963687 PMCID: PMC27874 DOI: 10.1073/pnas.97.18.10277] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2000] [Indexed: 12/24/2022] Open
Abstract
Constitutive activity, or ligand-independent activity, of mutant G protein-coupled receptors (GPCRs) has been described extensively and implicated in the pathology of many diseases. Using the corticotropin-releasing factor (CRF) receptor and the thrombin receptor as a model, we present a ligand-dependent constitutive activation of a GPCR. A chimera in which the N-terminal domain of the CRF receptor is replaced by the amino-terminal 16 residues of CRF displays significant levels of constitutive activation. The activity, as measured by intracellular levels of cAMP, is blocked in a dose-dependent manner by the nonpeptide antagonist antalarmin. These results support a propinquity effect in CRF receptor activation, in which the amino-terminal portion of the CRF peptide is presented to the body of the receptor in the proper proximity for activation. This form of ligand-dependent constitutive activation may be of general applicability for the creation of constitutively activated GPCRs that are regulated by peptide ligands such as CRF. These chimeras may prove useful in analyzing mechanisms of receptor regulation and in the structural analysis of ligand activated receptors.
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Affiliation(s)
- S M Nielsen
- The Clayton Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Science, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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36
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Rosenkilde MM, Kledal TN, Holst PJ, Schwartz TW. Selective elimination of high constitutive activity or chemokine binding in the human herpesvirus 8 encoded seven transmembrane oncogene ORF74. J Biol Chem 2000; 275:26309-15. [PMID: 10842179 DOI: 10.1074/jbc.m003800200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Open reading frame 74 (ORF74) encoded by human herpesvirus 8 is a highly constitutively active seven transmembrane (7TM) receptor stimulated by angiogenic chemokines, e.g. growth-related oncogene-alpha, and inhibited by angiostatic chemokines e.g. interferon-gamma-inducible protein. Transgenic mice expressing ORF74 under control of the CD2 promoter develop highly vascularized Kaposi's sarcoma-like tumors. Through targeted mutagenesis we here create three distinct phenotypes of ORF74: a receptor with normal, high constitutive signaling through the phospholipase C pathway but deprived of binding and action of chemokines obtained through deletion of 22 amino acids from the N-terminal extension; an ORF74 with high constitutive activity but with selective elimination of stimulatory regulation by angiogenic chemokines obtained through substitution of basic residues at the extracellular ends of TM-V or TM-VI; and an ORF74 lacking constitutive activity but with preserved ability to be stimulated by agonist chemokines obtained through introduction of an Asp residue on the hydrophobic, presumed membrane-exposed face of TM-II. It is concluded that careful molecular dissection can selectively eliminate either agonist or inverse agonist modulation as well as high constitutive activity of the virally encoded oncogene ORF74 and that these mutant forms presumably can be used in transgenic animals to identify the molecular mechanism of its transforming activity.
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Affiliation(s)
- M M Rosenkilde
- Laboratory for Molecular Pharmacology, Department of Pharmacology, The Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark
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37
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Unson CG, Wu CR, Sakmar TP, Merrifield RB. Selective stabilization of the high affinity binding conformation of glucagon receptor by the long splice variant of Galpha(s). J Biol Chem 2000; 275:21631-8. [PMID: 10791965 DOI: 10.1074/jbc.m002093200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To analyze functional differences in the interactions of the glucagon receptor (GR) with the two predominant splice variants of Galpha(s), GR was covalently linked to the short and the long forms Galpha(s)-S and Galpha(s)-L to produce the fusion proteins GR-Galpha(s)-S and GR-Galpha(s)-L. GR-Galpha(s)-S bound glucagon with an affinity similar to that of GR, while GR-Galpha(s)-L showed a 10-fold higher affinity for glucagon. In the presence of GTPgammaS, GR-Galpha(s)-L reverted to the low affinity glucagon binding conformation. Both GR-Galpha(s)-L and GR-Galpha(s)-S were constitutively active, causing elevated basal levels of cAMP even in the absence of glucagon. A mutant GR that failed to activate G(s) (G23D1R) was fused to Galpha(s)-L. G23D1R-Galpha(s)-L bound glucagon with high affinity, but failed to elevate cAMP levels, suggesting that the mechanisms of GR-mediated Galpha(s)-L activation and Galpha(s)-L-induced high affinity glucagon binding are independent. Both GR-Galpha(s)-S and GR-Galpha(s)-L bound the antagonist desHis(1)[Nle(9),Ala(11),Ala(16)]glucagon amide with affinities similar to GR. The antagonist displayed partial agonist activity with GR-Galpha(s)-L, but not with GR-Galpha(s)-S. Therefore, the partial agonist activity of the antagonist observed in intact cells appears to be due to GRs coupled to Galpha(s)-L. We conclude that Galpha(s)-S and Galpha(s)-L interact differently with GR and that specific coupling of GR to Galpha(s)-L may account for GTP-sensitive high affinity glucagon binding.
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Affiliation(s)
- C G Unson
- Rockefeller University and the Howard Hughes Medical Institute, Laboratory of Molecular Biology and Biochemistry, Rockefeller University, New York, New York 10021, USA.
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38
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Cao YJ, Gimpl G, Fahrenholz F. A mutation in the second intracellular loop of the pituitary adenylate cyclase activating polypeptide type I receptor confers constitutive receptor activation. FEBS Lett 2000; 469:142-6. [PMID: 10713259 DOI: 10.1016/s0014-5793(00)01269-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor belongs to the glucagon/secretin/vasoactive intestinal polypeptide (VIP) receptor family. We mutated and deleted an amino acid residue (E261) which is located within the second intracellular loop of the rat PACAP type I receptor and which is highly conserved among the receptor family. The wild-type receptor and the mutant receptors were efficiently expressed at the surface of COS-7 cells at nearly the same level and revealed the same high affinity for the agonist PACAP-27. The cAMP contents of COS cells transfected with the E261A, E261Q, and the deletion mutant receptor were 4.6-, 5.7-, and 6.7-fold higher as compared with COS cells transfected with the wild-type receptor. Thus, all the mutant PACAP receptors were constitutively active. The data suggest that the glutamic acid in the second intracellular loop of the PACAP receptor may be a key residue to constrain the receptor in the inactive conformation with respect to its coupling to G(s) proteins.
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Affiliation(s)
- Y J Cao
- Institut für Biochemie, Johannes Gutenberg-Universität Mainz, Becherweg 30, D-55099, Mainz, Germany
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39
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Hinke SA, Pospisilik JA, Demuth HU, Mannhart S, Kühn-Wache K, Hoffmann T, Nishimura E, Pederson RA, McIntosh CH. Dipeptidyl peptidase IV (DPIV/CD26) degradation of glucagon. Characterization of glucagon degradation products and DPIV-resistant analogs. J Biol Chem 2000; 275:3827-34. [PMID: 10660533 DOI: 10.1074/jbc.275.6.3827] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Over the past decade, numerous studies have been targeted at defining structure-activity relationships of glucagon. Recently, we have found that glucagon(1-29) is hydrolyzed by dipeptidyl peptidase IV (DPIV) to produce glucagon(3-29) and glucagon(5-29); in human serum, [pyroglutamyl (pGlu)(3)]glucagon(3-29) is formed from glucagon(3-29), and this prevents further hydrolysis of glucagon by DPIV (H.-U. Demuth, K. Glund, U. Heiser, J. Pospisilik, S. Hinke, T. Hoffmann, F. Rosche, D. Schlenzig, M. Wermann, C. McIntosh, and R. Pederson, manuscript in preparation). In the current study, the biological activity of these peptides was examined in vitro. The amino-terminally truncated peptides all behaved as partial agonists in cyclic AMP stimulation assays, with Chinese hamster ovary K1 cells overexpressing the human glucagon receptor (potency: glucagon(1-29) > [pGlu(3)]glu- cagon(3-29) > glucagon(3-29) > glucagon(5-29) > [Glu(9)]glu- cagon(2-29)). In competition binding experiments, [pGlu(3)]glucagon(3-29) and glucagon(5-29) both demonstrated 5-fold lower affinity for the receptor than glucagon(1-29), whereas glucagon(3-29) exhibited 18-fold lower affinity. Of the peptides tested, only glucagon(5-29) showed antagonist activity, and this was weak compared with the classical glucagon antagonist, [Glu(9)]glucagon(2-29). Hence, DPIV hydrolysis of glucagon yields low affinity agonists of the glucagon receptor. As a corollary to evidence indicating that DPIV degrades glucagon (Demuth, et al., manuscript in preparation), DPIV-resistant analogs were synthesized. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry was used to assess DPIV resistance, and it allowed kinetic analysis of degradation. Of several analogs generated, only [D-Ser(2)] and [Gly(2)]glucagon retained high affinity binding and biological potency, similar to native glucagon in vitro. [D-Ser(2)]Glucagon exhibited enhanced hyperglycemic activity in a bioassay, whereas [Gly(2)]glucagon was not completely resistant to DPIV degradation.
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Affiliation(s)
- S A Hinke
- Department of Physiology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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40
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Abstract
G protein-coupled, seven-transmembrane segment receptors (GPCRs or 7TM receptors), with more than 1000 different members, comprise the largest superfamily of proteins in the body. Since the cloning of the first receptors more than a decade ago, extensive experimental work has uncovered multiple aspects of their function and challenged many traditional paradigms. However, it is only recently that we are beginning to gain insight into some of the most fundamental questions in the molecular function of this class of receptors. How can, for example, so many chemically diverse hormones, neurotransmitters, and other signaling molecules activate receptors believed to share a similar overall tertiary structure? What is the nature of the physical changes linking agonist binding to receptor activation and subsequent transduction of the signal to the associated G protein on the cytoplasmic side of the membrane and to other putative signaling pathways? The goal of the present review is to specifically address these questions as well as to depict the current awareness about GPCR structure-function relationships in general.
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Affiliation(s)
- U Gether
- Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
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41
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Abstract
The glucagon receptor gene is a member of a gene family, the expression of which is strongly upregulated by glucose. This review deals with the structure of both the glucagon receptor gene and its promoter. Attention is focused on the glucose regulatory element that we discovered in the promoter of this gene. Regulation by glucose of genes implicated in glucose homeostasis represents one mechanism contributing to the control of fuel utilization. Its deficiency or imbalance could potentially lead to or participate in pathological situations such as diabetes mellitus. On the other hand, the regulatory element of the glucagon receptor gene promoter could be used as a tool for the glucose-regulated expression of other genes. Indeed, an analysis of the glucagon receptor gene promoter demonstrated that only a short fragment of the genomic DNA, easy to subclone, contains all required elements for activation by glucose. Its potential use for gene therapy is also considered, therefore, in this report.
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Affiliation(s)
- M Svoboda
- Laboratory of Biochemistry and Nutrition, Université Libre de Bruxelles, Brussels, B-1070, Belgium. msvobod@.ulb.ac.be
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42
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Latronico AC, Segaloff DL. Naturally occurring mutations of the luteinizing-hormone receptor: lessons learned about reproductive physiology and G protein-coupled receptors. Am J Hum Genet 1999; 65:949-58. [PMID: 10486313 PMCID: PMC1288265 DOI: 10.1086/302602] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Affiliation(s)
- Ana Claudia Latronico
- Developmental Endocrinology Unit, Hospital das Clinicas, São Paulo University Medical School, São Paulo; and Department of Physiology and Biophysics, The University of Iowa College of Medicine, Iowa City
| | - Deborah L. Segaloff
- Developmental Endocrinology Unit, Hospital das Clinicas, São Paulo University Medical School, São Paulo; and Department of Physiology and Biophysics, The University of Iowa College of Medicine, Iowa City
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43
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Cypess AM, Unson CG, Wu CR, Sakmar TP. Two cytoplasmic loops of the glucagon receptor are required to elevate cAMP or intracellular calcium. J Biol Chem 1999; 274:19455-64. [PMID: 10383462 DOI: 10.1074/jbc.274.27.19455] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The glucagon receptor is a member of a distinct class of G protein-coupled receptors (GPCRs) sharing little amino acid sequence homology with the larger rhodopsin-like GPCR family. To identify the components of the glucagon receptor necessary for G-protein coupling, we replaced sequentially all or part of each intracellular loop (i1, i2, and i3) and the C-terminal tail of the glucagon receptor with the 11 amino acids comprising the first intracellular loop of the D4 dopamine receptor. When expressed in transiently transfected COS-1 cells, the mutant receptors fell into two different groups with respect to hormone-mediated signaling. The first group included the loop i1 mutants, which bound glucagon and signaled normally. The second group comprised the loop i2 and i3 chimeras, which caused no detectable adenylyl cyclase activation in COS-1 cells. However, when expressed in HEK 293T cells, the loop i2 or i3 chimeras caused very small glucagon-mediated increases in cAMP levels and intracellular calcium concentrations, with EC50 values nearly 100-fold higher than those measured for wild-type receptor. Replacement of both loops i2 and i3 simultaneously was required to completely abolish G protein signaling as measured by both cAMP accumulation and calcium flux assays. These results show that the i2 and i3 loops play a role in glucagon receptor signaling, consistent with recent models for the mechanism of activation of G proteins by rhodopsin-like GPCRs.
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Affiliation(s)
- A M Cypess
- The Rockefeller University, New York, New York 10021, USA
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44
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45
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Abell AN, McCormick DJ, Segaloff DL. Certain activating mutations within helix 6 of the human luteinizing hormone receptor may be explained by alterations that allow transmembrane regions to activate Gs. Mol Endocrinol 1998; 12:1857-69. [PMID: 9849960 DOI: 10.1210/mend.12.12.0202] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Male-limited gonadotropin-independent precocious puberty (MPP) is frequently associated with mutations of the human LH/CG receptor (hLHR) that result in constitutively active hLHRs. Many such activating mutations have been identified in transmembrane 6 of the hLHR, with the substitution of Asp-578 being the most frequently observed mutation. Mutagenesis of a transmembrane helix of a G protein-coupled receptor can cause local alterations in the conformation near the mutated residue, allosteric changes elsewhere in the protein, and/or changes in the interhelical packing of the receptor. Therefore, while it has been hypothesized that activation of the receptor by mutations of Asp-578 may arise via alterations in the interactions of helix 6 with other transmembrane helices and/or by allosterically altering the conformation of the third intracellular loop, it has not been possible to ascertain the role of the sixth transmembrane helix per se in activating Gs in the mutated full-length receptor. Recently, however, we have shown that a peptide KMAILIFT, corresponding to the juxtacytoplasmic portion of helix 6 of the hLHR, is capable of activating Gs. These results suggest that helix 6 itself can directly interact with Gs. Importantly, the KMAILIFT peptide did not include Asp-578, which lies just C-terminal to this sequence. We show herein that a peptide extended to include Asp-578 (KMAILIFTDFT) is a poor activator of Gs. However, if the peptide is synthesized with the aspartate replaced with either a glycine or tyrosine, substitutions that are found in some patients with MPP, these peptides have Gs-stimulating activity. Additionally, a transmembrane 6 peptide with the substitution of Ile-575 with leucine, another mutation found in MPP, mimicked the activating effects of this mutation in the full-length receptor. The ability of peptides in which Asp-578 or Ile-575 is substituted to mimic the activating effects of these mutations in the full-length receptor suggests that the sixth transmembrane helix represents a site for direct interaction with Gs. In addition to the stimulatory effects of transmembrane 6 peptides, peptides corresponding to the juxtacytoplasmic portions of the fourth, fifth, and seventh helices were also able to stimulate Gs. These results are consistent with the hypothesis that the transmembrane helices may form a pocket for interaction with Gs and that constitutive activation of the hLHR may involve the opening of the pocket formed by these helices, thus exposing Gs-binding sites on these helices.
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Affiliation(s)
- A N Abell
- Department of Physiology and Biophysics, The University of Iowa College of Medicine, Iowa City 52242, USA
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Sandberg K, Ji H, Clark A, Shapira H, Catt K. Cloning and expression of a novel angiotensin II receptor subtype. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50109-0] [Citation(s) in RCA: 199] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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