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Zhang MY, Ao JY, Liu N, Chen T, Lu SY. Exploring the constitutive activation mechanism of the class A orphan GPR20. Acta Pharmacol Sin 2024:10.1038/s41401-024-01385-7. [PMID: 39256608 DOI: 10.1038/s41401-024-01385-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2024] [Accepted: 08/22/2024] [Indexed: 09/12/2024] Open
Abstract
GPR20, an orphan G protein-coupled receptor (GPCR), shows significant expression in intestinal tissue and represents a potential therapeutic target to treat gastrointestinal stromal tumors. GPR20 performs high constitutive activity when coupling with Gi. Despite the pharmacological importance of GPCR constitutive activation, determining the mechanism has long remained unclear. In this study, we explored the constitutive activation mechanism of GPR20 through large-scale unbiased molecular dynamics simulations. Our results unveil the allosteric nature of constitutively activated GPCR signal transduction involving extracellular and intracellular domains. Moreover, the constitutively active state of the GPR20 requires both the N-terminal cap and Gi protein. The N-terminal cap of GPR20 functions like an agonist and mediates long-range activated conformational shift. Together with the previous study, this study enhances our knowledge of the self-activation mechanism of the orphan receptor, facilitates the drug discovery efforts that target GPR20.
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Affiliation(s)
- Ming-Yang Zhang
- Key Laboratory of Protection, Development and Utilization of Medicinal Resources in Liupanshan Area, Ministry of Education, Peptide & Protein Drug Research Center, School of Pharmacy, Ningxia Medical University, Yinchuan, 750004, China
- Medicinal Chemistry and Bioinformatics Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Jian-Yang Ao
- Department of Hepatobiliary and Pancreatic Surgery, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, 200120, China
- Institute of Hepatobiliary and Pancreatic Surgery, Tongji University School of Medicine, Shanghai, 200120, China
| | - Ning Liu
- Key Laboratory of Protection, Development and Utilization of Medicinal Resources in Liupanshan Area, Ministry of Education, Peptide & Protein Drug Research Center, School of Pharmacy, Ningxia Medical University, Yinchuan, 750004, China
| | - Ting Chen
- Department of Cardiology, Changzheng Hospital, Affiliated to Naval Medical University, Shanghai, 200003, China.
| | - Shao-Yong Lu
- Key Laboratory of Protection, Development and Utilization of Medicinal Resources in Liupanshan Area, Ministry of Education, Peptide & Protein Drug Research Center, School of Pharmacy, Ningxia Medical University, Yinchuan, 750004, China.
- Medicinal Chemistry and Bioinformatics Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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2
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Wei S, Pour NG, Tiruvadi-Krishnan S, Ray AP, Thakur N, Eddy MT, Lamichhane R. Single-molecule visualization of human A 2A adenosine receptor activation by a G protein and constitutively activating mutations. Commun Biol 2023; 6:1218. [PMID: 38036689 PMCID: PMC10689853 DOI: 10.1038/s42003-023-05603-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 11/17/2023] [Indexed: 12/02/2023] Open
Abstract
Mutations that constitutively activate G protein-coupled receptors (GPCRs), known as constitutively activating mutations (CAMs), modify cell signaling and interfere with drugs, resulting in diseases with limited treatment options. We utilize fluorescence imaging at the single-molecule level to visualize the dynamic process of CAM-mediated activation of the human A2A adenosine receptor (A2AAR) in real time. We observe an active-state population for all CAMs without agonist stimulation. Importantly, activating mutations significantly increase the population of an intermediate state crucial for receptor activation, notably distinct from the addition of a partner G protein. Activation kinetics show that while CAMs increase the frequency of transitions to the intermediate state, mutations altering sodium sensitivity increase transitions away from it. These findings indicate changes in GPCR function caused by mutations may be predicted based on whether they favor or disfavor formation of an intermediate state, providing a framework for designing receptors with altered functions or therapies that target intermediate states.
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Affiliation(s)
- Shushu Wei
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts and Sciences, University of Tennessee, Knoxville, TN, USA
| | - Niloofar Gopal Pour
- Department of Chemistry, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, USA
| | - Sriram Tiruvadi-Krishnan
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts and Sciences, University of Tennessee, Knoxville, TN, USA
| | - Arka Prabha Ray
- Department of Chemistry, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, USA
| | - Naveen Thakur
- Department of Chemistry, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, USA
| | - Matthew T Eddy
- Department of Chemistry, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, USA.
| | - Rajan Lamichhane
- Department of Biochemistry & Cellular and Molecular Biology, College of Arts and Sciences, University of Tennessee, Knoxville, TN, USA.
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3
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Ligand-Free Signaling of G-Protein-Coupled Receptors: Relevance to μ Opioid Receptors in Analgesia and Addiction. Molecules 2022; 27:molecules27185826. [PMID: 36144565 PMCID: PMC9503102 DOI: 10.3390/molecules27185826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 09/04/2022] [Accepted: 09/06/2022] [Indexed: 11/17/2022] Open
Abstract
Numerous G-protein-coupled receptors (GPCRs) display ligand-free basal signaling with potential physiological functions, a target in drug development. As an example, the μ opioid receptor (MOR) signals in ligand-free form (MOR-μ*), influencing opioid responses. In addition, agonists bind to MOR but can dissociate upon MOR activation, with ligand-free MOR-μ* carrying out signaling. Opioid pain therapy is effective but incurs adverse effects (ADRs) and risk of opioid use disorder (OUD). Sustained opioid agonist exposure increases persistent basal MOR-μ* activity, which could be a driving force for OUD and ADRs. Antagonists competitively prevent resting MOR (MOR-μ) activation to MOR-μ*, while common antagonists, such as naloxone and naltrexone, also bind to and block ligand-free MOR-μ*, acting as potent inverse agonists. A neutral antagonist, 6β-naltrexol (6BN), binds to but does not block MOR-μ*, preventing MOR-μ activation only competitively with reduced potency. We hypothesize that 6BN gradually accelerates MOR-μ* reversal to resting-state MOR-μ. Thus, 6BN potently prevents opioid dependence in rodents, at doses well below those blocking antinociception or causing withdrawal. Acting as a ‘retrograde addiction modulator’, 6BN could represent a novel class of therapeutics for OUD. Further studies need to address regulation of MOR-μ* and, more broadly, the physiological and pharmacological significance of ligand-free signaling in GPCRs.
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4
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APLNR regulates IFN-γ signaling via β-arrestin 1 mediated JAK-STAT1 pathway in melanoma cells. Biochem J 2022; 479:385-399. [PMID: 35084016 DOI: 10.1042/bcj20210813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/17/2022] [Accepted: 01/27/2022] [Indexed: 11/17/2022]
Abstract
The apelin receptor (APLNR) regulates many biological processes including metabolism, angiogenesis, circulating blood volume and cardiovascular function. Additionally, APLNR is overexpressed in various types of cancer and influences cancer progression. APLNR is reported to regulate tumor recognition during immune surveillance by modulating the IFN-γ response. However, the mechanism of APLNR crosstalk with intratumoral IFN-γ signaling remains unknown. Here, we show that activation of APLNR upregulates IFN-γ signaling in melanoma cells through APLNR mediated β-arrestin 1 but not β-arrestin 2 recruitment. Our data suggests that β-arrestin 1 directly interacts with STAT1 to inhibit STAT1 phosphorylation to attenuate IFN-γ signaling. The APLNR mutant receptor, I109A, which is deficient in β-arrestins recruitment, is unable to enhance intratumoral IFN-γ signaling. While APLNR N112G, a constitutively active mutant receptor, increases intratumoral sensitivity to IFN-γ signaling by enhancing STAT1 phosphorylation upon IFN-γ exposure. We also demonstrate in a co-culture system that APLNR regulates tumor survival rate. Taken together, our findings reveal that APLNR modulates IFN-γ signaling in melanoma cells and suggests that APLNR may be a potential target to enhance the efficacy of immunotherapy.
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5
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Stoddart LA, Kilpatrick LE, Corriden R, Kellam B, Briddon SJ, Hill SJ. Efficient G protein coupling is not required for agonist-mediated internalization and membrane reorganization of the adenosine A 3 receptor. FASEB J 2021; 35:e21211. [PMID: 33710641 PMCID: PMC9328438 DOI: 10.1096/fj.202001729rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 11/03/2020] [Accepted: 11/09/2020] [Indexed: 01/09/2023]
Abstract
Organization of G protein‐coupled receptors at the plasma membrane has been the focus of much recent attention. Advanced microscopy techniques have shown that these receptors can be localized to discrete microdomains and reorganization upon ligand activation is crucial in orchestrating their signaling. Here, we have compared the membrane organization and downstream signaling of a mutant (R108A, R3.50A) of the adenosine A3 receptor (A3AR) to that of the wild‐type receptor. Fluorescence Correlation Spectroscopy (FCS) studies with a fluorescent agonist (ABEA‐X‐BY630) demonstrated that both wild‐type and mutant receptors bind agonist with high affinity but in subsequent downstream signaling assays the R108A mutation abolished agonist‐mediated inhibition of cAMP production and ERK phosphorylation. In further FCS studies, both A3AR and A3AR R108A underwent similar agonist‐induced increases in receptor density and molecular brightness which were accompanied by a decrease in membrane diffusion after agonist treatment. Using bimolecular fluorescence complementation, experiments showed that the R108A mutant retained the ability to recruit β‐arrestin and these receptor/arrestin complexes displayed similar membrane diffusion and organization to that observed with wild‐type receptors. These data demonstrate that effective G protein signaling is not a prerequisite for agonist‐stimulated β‐arrestin recruitment and membrane reorganization of the A3AR.
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Affiliation(s)
- Leigh A Stoddart
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| | - Laura E Kilpatrick
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK.,School of Pharmacy, Biodiscovery Institute, University Park Nottingham, Nottingham, UK
| | - Ross Corriden
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| | - Barrie Kellam
- Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK.,School of Pharmacy, Biodiscovery Institute, University Park Nottingham, Nottingham, UK
| | - Stephen J Briddon
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
| | - Stephen J Hill
- Cell Signalling and Pharmacology Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, UK.,Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
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6
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Schöneberg T, Liebscher I. Mutations in G Protein-Coupled Receptors: Mechanisms, Pathophysiology and Potential Therapeutic Approaches. Pharmacol Rev 2020; 73:89-119. [PMID: 33219147 DOI: 10.1124/pharmrev.120.000011] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
There are approximately 800 annotated G protein-coupled receptor (GPCR) genes, making these membrane receptors members of the most abundant gene family in the human genome. Besides being involved in manifold physiologic functions and serving as important pharmacotherapeutic targets, mutations in 55 GPCR genes cause about 66 inherited monogenic diseases in humans. Alterations of nine GPCR genes are causatively involved in inherited digenic diseases. In addition to classic gain- and loss-of-function variants, other aspects, such as biased signaling, trans-signaling, ectopic expression, allele variants of GPCRs, pseudogenes, gene fusion, and gene dosage, contribute to the repertoire of GPCR dysfunctions. However, the spectrum of alterations and GPCR involvement is probably much larger because an additional 91 GPCR genes contain homozygous or hemizygous loss-of-function mutations in human individuals with currently unidentified phenotypes. This review highlights the complexity of genomic alteration of GPCR genes as well as their functional consequences and discusses derived therapeutic approaches. SIGNIFICANCE STATEMENT: With the advent of new transgenic and sequencing technologies, the number of monogenic diseases related to G protein-coupled receptor (GPCR) mutants has significantly increased, and our understanding of the functional impact of certain kinds of mutations has substantially improved. Besides the classical gain- and loss-of-function alterations, additional aspects, such as biased signaling, trans-signaling, ectopic expression, allele variants of GPCRs, uniparental disomy, pseudogenes, gene fusion, and gene dosage, need to be elaborated in light of GPCR dysfunctions and possible therapeutic strategies.
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Affiliation(s)
- Torsten Schöneberg
- Rudolf Schönheimer Institute of Biochemistry, Molecular Biochemistry, Medical Faculty, Leipzig, Germany
| | - Ines Liebscher
- Rudolf Schönheimer Institute of Biochemistry, Molecular Biochemistry, Medical Faculty, Leipzig, Germany
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7
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Cell-autonomous light sensitivity via Opsin3 regulates fuel utilization in brown adipocytes. PLoS Biol 2020; 18:e3000630. [PMID: 32040503 PMCID: PMC7034924 DOI: 10.1371/journal.pbio.3000630] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 02/21/2020] [Accepted: 01/27/2020] [Indexed: 01/15/2023] Open
Abstract
Opsin3 (Opn3) is a transmembrane heptahelical G protein–coupled receptor (GPCR) with the potential to produce a nonvisual photoreceptive effect. Interestingly, anatomical profiling of GPCRs reveals that Opn3 mRNA is highly expressed in adipose tissue. The photosensitive functions of Opn3 in mammals are poorly understood, and whether Opn3 has a role in fat is entirely unknown. In this study, we found that Opn3-knockout (Opn3-KO) mice were prone to diet-induced obesity and insulin resistance. At the cellular level, Opn3-KO brown adipocytes cultured in darkness had decreased glucose uptake and lower nutrient-induced mitochondrial respiration than wild-type (WT) cells. Light exposure promoted mitochondrial activity and glucose uptake in WT adipocytes but not in Opn3-KO cells. Brown adipocytes carrying a defective mutation in Opn3’s putative G protein–binding domain also exhibited a reduction in glucose uptake and mitochondrial respiration in darkness. Using RNA-sequencing, we identified several novel light-sensitive and Opn3-dependent molecular signatures in brown adipocytes. Importantly, direct exposure of brown adipose tissue (BAT) to light in living mice significantly enhanced thermogenic capacity of BAT, and this effect was diminished in Opn3-KO animals. These results uncover a previously unrecognized cell-autonomous, light-sensing mechanism in brown adipocytes via Opn3-GPCR signaling that can regulate fuel metabolism and mitochondrial respiration. Our work also provides a molecular basis for developing light-based treatments for obesity and its related metabolic disorders. Brown adipose tissue plays a pivotal role in energy homeostasis and serves as a metabolic sink for glucose and fatty acid. This study demonstrates a novel light-sensing mechanism in mice via the photoreceptor Opsin3 that regulates fuel utilization and mitochondrial activity of brown adipocytes.
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8
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Berg KA, Clarke WP. Making Sense of Pharmacology: Inverse Agonism and Functional Selectivity. Int J Neuropsychopharmacol 2018; 21:962-977. [PMID: 30085126 PMCID: PMC6165953 DOI: 10.1093/ijnp/pyy071] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 08/04/2018] [Indexed: 12/12/2022] Open
Abstract
Constitutive receptor activity/inverse agonism and functional selectivity/biased agonism are 2 concepts in contemporary pharmacology that have major implications for the use of drugs in medicine and research as well as for the processes of new drug development. Traditional receptor theory postulated that receptors in a population are quiescent unless activated by a ligand. Within this framework ligands could act as agonists with various degrees of intrinsic efficacy, or as antagonists with zero intrinsic efficacy. We now know that receptors can be active without an activating ligand and thus display "constitutive" activity. As a result, a new class of ligand was discovered that can reduce the constitutive activity of a receptor. These ligands produce the opposite effect of an agonist and are called inverse agonists. The second topic discussed is functional selectivity, also commonly referred to as biased agonism. Traditional receptor theory also posited that intrinsic efficacy is a single drug property independent of the system in which the drug acts. However, we now know that a drug, acting at a single receptor subtype, can have multiple intrinsic efficacies that differ depending on which of the multiple responses coupled to a receptor is measured. Thus, a drug can be simultaneously an agonist, an antagonist, and an inverse agonist acting at the same receptor. This means that drugs have an additional level of selectivity (signaling selectivity or "functional selectivity") beyond the traditional receptor selectivity. Both inverse agonism and functional selectivity need to be considered when drugs are used as medicines or as research tools.
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Affiliation(s)
- Kelly A Berg
- Department of Pharmacology, University of Texas Health, San Antonio, Texas
| | - William P Clarke
- Department of Pharmacology, University of Texas Health, San Antonio, Texas,Correspondence: William P. Clarke, PhD, Department of Pharmacology, Mail Stop 7764, UT Health at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229 ()
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9
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Gao N, Liang T, Yuan Y, Xiao X, Zhao Y, Guo Y, Li M, Pu X. Exploring the mechanism of F282L mutation-caused constitutive activity of GPCR by a computational study. Phys Chem Chem Phys 2018; 18:29412-29422. [PMID: 27735961 DOI: 10.1039/c6cp03710k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
G-protein-coupled receptors (GPCRs) are important drug targets and generally activated by ligands. However, some experiments found that GPCRs also give rise to constitutive activity through some mutations (viz., CAM), which are usually associated with different kinds of diseases. However, the mechanisms of CAMs and their roles in interactions with drug-ligands are unclear in experiments. Herein, we used microsecond molecular dynamics simulations to study the effect of one important F282L mutation on β2AR in order to address the questions above. With the aid of principle component and correlation analysis, our results revealed that the F282L mutation could increase the instability of the overall structure, increase the dramatic fluctuations of NPxxY and extracellular loops, and decrease restraint of the helices through weakening interhelical H-bonding and correlations between residues, which could partly contribute to the constitutive activity reported by the experiments. The observations from the protein structure network (PSN) analysis indicate that the mutant exhibits less information flow than the wild β2AR and weakens the role of TM5 and TM6 in the signal transmission, but it enhances the impact of TM3 on the orthosteric pathway and TM4 on the allosteric one. In addition, the results from the virtual screening reveal that the mutant prefers to select agonists rather than antagonists, similar to the active state but opposite of the inactive state, further confirming that the F282L mutation advances the activation of β2AR. Our observations provide valuable information for understanding the mechanism of the mutation-caused constitutive activity of GPCR and related drug-design.
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Affiliation(s)
- Nan Gao
- Faculty of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People's Republic of China.
| | - Tao Liang
- Faculty of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People's Republic of China.
| | - Yuan Yuan
- College of Management, Southwest University for Nationalities, Chengdu 610041, P. R. China
| | - Xiuchan Xiao
- Department of Architecture and Environmental Engineering, Chengdu Technological University, Chengdu, Sichuan 611730, China
| | - Yihuan Zhao
- Faculty of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People's Republic of China.
| | - Yanzhi Guo
- Faculty of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People's Republic of China.
| | - Menglong Li
- Faculty of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People's Republic of China.
| | - Xuemei Pu
- Faculty of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People's Republic of China.
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Purcell RH, Toro C, Gahl WA, Hall RA. A disease-associated mutation in the adhesion GPCR BAI2 (ADGRB2) increases receptor signaling activity. Hum Mutat 2017; 38:1751-1760. [PMID: 28891236 DOI: 10.1002/humu.23336] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 08/01/2017] [Accepted: 09/03/2017] [Indexed: 12/15/2022]
Abstract
Mutations in G protein-coupled receptors (GPCRs) that increase constitutive signaling activity can cause human disease. A de novo C-terminal mutation (R1465W) in the adhesion GPCR BAI2 (also known as ADGRB2) was identified in a patient suffering from progressive spastic paraparesis and other neurological symptoms. In vitro studies revealed that this mutation strongly increases the constitutive signaling activity of an N-terminally cleaved form of BAI2, which represents the activated form of the receptor. Further studies dissecting the mechanism(s) underling this effect revealed that wild-type BAI2 primarily couples to Gαz , with the R1465W mutation conferring increased coupling to Gαi . The R1465W mutation also increases the total and surface expression of BAI2. The mutation has no effect on receptor binding to β-arrestins, but does perturb binding to the endocytic protein endophilin A1, identified here as a novel interacting partner for BAI2. These studies provide new insights into the signaling capabilities of the adhesion GPCR BAI2/ADGRB2 and shed light on how an apparent gain-of-function mutation to the receptor's C-terminus may lead to human disease.
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Affiliation(s)
- Ryan H Purcell
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia
| | - Camilo Toro
- NIH Undiagnosed Diseases Program, Office of the Director, NIH, Bethesda, Maryland
| | - William A Gahl
- NIH Undiagnosed Diseases Program, Office of the Director, NIH, Bethesda, Maryland
| | - Randy A Hall
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia
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11
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Le Stunff C, Tilotta F, Sadoine J, Le Denmat D, Briet C, Motte E, Clauser E, Bougnères P, Chaussain C, Silve C. Knock-In of the Recurrent R368X Mutation of PRKAR1A that Represses cAMP-Dependent Protein Kinase A Activation: A Model of Type 1 Acrodysostosis. J Bone Miner Res 2017; 32:333-346. [PMID: 27589370 DOI: 10.1002/jbmr.2987] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/19/2016] [Accepted: 09/01/2016] [Indexed: 12/13/2022]
Abstract
In humans, activating mutations in the PRKAR1A gene cause acrodysostosis 1 (ACRDYS1). These mutations result in a reduction in PKA activation caused by an impaired ability of cAMP to dissociate mutant PRKAR1A from catalytic PKA subunits. Two striking features of this rare developmental disease are renal resistance to PTH and chondrodysplasia resulting from the constitutive inhibition of PTHR1/Gsa/AC/cAMP/PKA signaling. We developed a knock-in of the recurrent ACRDYS1 R368X PRKAR1A mutation in the mouse. No litters were obtained from [R368X]/[+] females (thus no homozygous [R368X]/[R368X] mice). In [R368X]/[+] mice, Western blot analysis confirmed mutant allele heterozygous expression. Growth retardation, peripheral acrodysostosis (including brachydactyly affecting all digits), and facial dysostosis were shown in [R368X]/[+] mice by weight curves and skeletal measurements (μCT scan) as a function of time. [R368X]/[+] male and female mice were similarly affected. Unexpected, however, whole-mount skeletal preparations revealed a striking delay in mineralization in newborn mutant mice, accompanied by a decrease in the height of terminal hypertrophic chondrocyte layer, an increase in the height of columnar proliferative prehypertrophic chondrocyte layer, and changes in the number and spatial arrangement of proliferating cell nuclear antigen (PCNA)-positive chondrocytes. Plasma PTH and basal urinary cAMP were significantly higher in [R368X]/[+] compared to WT mice. PTH injection increased urinary cAMP similarly in [R368X]/[+] and WT mice. PRKACA expression was regulated in a tissue (kidney not bone and liver) manner. This model, the first describing the germline expression of a PRKAR1A mutation causing dominant repression of cAMP-dependent PKA, reproduced the main features of ACRDYS1 in humans. It should help decipher the specificity of the cAMP/PKA signaling pathway, crucial for numerous stimuli. In addition, our results indicate that PRKAR1A, by tempering intracellular cAMP levels, is a molecular switch at the crossroads of signaling pathways regulating chondrocyte proliferation and differentiation. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Catherine Le Stunff
- INSERM U1169, University Paris Sud, Hôpital Bicêtre, Le Kremlin Bicêtre, France
| | - Francoise Tilotta
- EA 2496 Laboratory Orofacial Pathologies, Imagery and Biotherapies, Dental School and Life imaging Platform (PIV), University Paris Descartes Sorbonne Paris Cité, Montrouge, France
| | - Jérémy Sadoine
- EA 2496 Laboratory Orofacial Pathologies, Imagery and Biotherapies, Dental School and Life imaging Platform (PIV), University Paris Descartes Sorbonne Paris Cité, Montrouge, France
| | - Dominique Le Denmat
- EA 2496 Laboratory Orofacial Pathologies, Imagery and Biotherapies, Dental School and Life imaging Platform (PIV), University Paris Descartes Sorbonne Paris Cité, Montrouge, France
| | - Claire Briet
- INSERM U1169, University Paris Sud, Hôpital Bicêtre, Le Kremlin Bicêtre, France
| | - Emmanuelle Motte
- INSERM U1169, University Paris Sud, Hôpital Bicêtre, Le Kremlin Bicêtre, France
| | - Eric Clauser
- INSERM U970, University Paris Descartes, Paris Centre de Recherche Cardiovasculaire (PARCC), Paris, France
| | - Pierre Bougnères
- INSERM U1169, University Paris Sud, Hôpital Bicêtre, Le Kremlin Bicêtre, France
| | - Catherine Chaussain
- EA 2496 Laboratory Orofacial Pathologies, Imagery and Biotherapies, Dental School and Life imaging Platform (PIV), University Paris Descartes Sorbonne Paris Cité, Montrouge, France.,Assistance Publique-Hôpitaux de Paris (AP-HP) Odontology Department Bretonneau, Louis Mourier, Hôpitaux Universitaires Paris Nord Val de Seine, Paris, France.,Centre de Référence des Maladies Rares du Métabolisme du Phosphore et du Calcium and Filière de Santé Maladies Rares OSCAR, AP-HP, Paris, France
| | - Caroline Silve
- INSERM U1169, University Paris Sud, Hôpital Bicêtre, Le Kremlin Bicêtre, France.,Centre de Référence des Maladies Rares du Métabolisme du Phosphore et du Calcium and Filière de Santé Maladies Rares OSCAR, AP-HP, Paris, France.,Service de Biochimie et Génétique Moléculaire, Hôpital Cochin, AP-HP, Paris, France
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12
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Krumm BE, Lee S, Bhattacharya S, Botos I, White CF, Du H, Vaidehi N, Grisshammer R. Structure and dynamics of a constitutively active neurotensin receptor. Sci Rep 2016; 6:38564. [PMID: 27924846 PMCID: PMC5141500 DOI: 10.1038/srep38564] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 11/03/2016] [Indexed: 11/09/2022] Open
Abstract
Many G protein-coupled receptors show constitutive activity, resulting in the production of a second messenger in the absence of an agonist; and naturally occurring constitutively active mutations in receptors have been implicated in diseases. To gain insight into mechanistic aspects of constitutive activity, we report here the 3.3 Å crystal structure of a constitutively active, agonist-bound neurotensin receptor (NTSR1) and molecular dynamics simulations of agonist-occupied and ligand-free receptor. Comparison with the structure of a NTSR1 variant that has little constitutive activity reveals uncoupling of the ligand-binding domain from conserved connector residues, that effect conformational changes during GPCR activation. Furthermore, molecular dynamics simulations show strong contacts between connector residue side chains and increased flexibility at the intracellular receptor face as features that coincide with robust signalling in cells. The loss of correlation between the binding pocket and conserved connector residues, combined with altered receptor dynamics, possibly explains the reduced neurotensin efficacy in the constitutively active NTSR1 and a facilitated initial engagement with G protein in the absence of agonist.
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Affiliation(s)
- Brian E Krumm
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Sangbae Lee
- Department of Molecular Immunology, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, California 91010, United States
| | - Supriyo Bhattacharya
- Department of Molecular Immunology, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, California 91010, United States
| | - Istvan Botos
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, United States
| | - Courtney F White
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Haijuan Du
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Nagarajan Vaidehi
- Department of Molecular Immunology, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, California 91010, United States
| | - Reinhard Grisshammer
- Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
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13
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Fischer L, Wilde C, Schöneberg T, Liebscher I. Functional relevance of naturally occurring mutations in adhesion G protein-coupled receptor ADGRD1 (GPR133). BMC Genomics 2016; 17:609. [PMID: 27516204 PMCID: PMC4982218 DOI: 10.1186/s12864-016-2937-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 07/14/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A large number of human inherited and acquired diseases and phenotypes are caused by mutations in G protein-coupled receptors (GPCR). Genome-wide association studies (GWAS) have shown that variations in the ADGRD1 (GPR133) locus are linked with differences in metabolism, human height and heart frequency. ADGRD1 is a Gs protein-coupled receptor belonging to the class of adhesion GPCRs. RESULTS Analysis of more than 1000 sequenced human genomes revealed approximately 9000 single nucleotide polymorphisms (SNPs) in the human ADGRD1 as listed in public data bases. Approximately 2.4 % of these SNPs are located in exons resulting in 129 non-synonymous SNPs (nsSNPs) at 119 positions of ADGRD1. However, the functional relevance of those variants is unknown. In-depth characterization of these amino acid changes revealed several nsSNPs (A448D, Q600stop, C632fs [frame shift], A761E, N795K) causing full or partial loss of receptor function, while one nsSNP (F383S) significantly increased basal activity of ADGRD1. CONCLUSION Our results show that a broad spectrum of functionally relevant ADGRD1 variants is present in the human population which may cause clinically relevant phenotypes, while being compatible with life when heterozygous.
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Affiliation(s)
- Liane Fischer
- From the Section of Molecular Biochemistry, Institute of Biochemistry, Medical Faculty, University of Leipzig, Johannisallee 30, 04103, Leipzig, Germany
| | - Caroline Wilde
- From the Section of Molecular Biochemistry, Institute of Biochemistry, Medical Faculty, University of Leipzig, Johannisallee 30, 04103, Leipzig, Germany
| | - Torsten Schöneberg
- From the Section of Molecular Biochemistry, Institute of Biochemistry, Medical Faculty, University of Leipzig, Johannisallee 30, 04103, Leipzig, Germany.
| | - Ines Liebscher
- From the Section of Molecular Biochemistry, Institute of Biochemistry, Medical Faculty, University of Leipzig, Johannisallee 30, 04103, Leipzig, Germany.
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14
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Bitter taste receptors: Novel insights into the biochemistry and pharmacology. Int J Biochem Cell Biol 2016; 77:184-96. [PMID: 26995065 DOI: 10.1016/j.biocel.2016.03.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 03/14/2016] [Accepted: 03/15/2016] [Indexed: 01/14/2023]
Abstract
Bitter taste receptors (T2Rs) belong to the super family of G protein-coupled receptors (GPCRs). There are 25 T2Rs expressed in humans, and these interact with a large and diverse group of bitter ligands. T2Rs are expressed in many extra-oral tissues and can perform diverse physiological roles. Structure-function studies led to the identification of similarities and dissimilarities between T2Rs and Class A GPCRs including amino acid conservation and novel motifs. However, the efficacy of most of the T2R ligands is not yet elucidated and the biochemical pharmacology of T2Rs is poorly understood. Recent studies on T2Rs characterized novel ligands including blockers for these receptors that include inverse agonist and antagonists. In this review we discuss the techniques used for elucidating bitter blockers, concept of ligand bias, generic amino acid numbering, the role of cholesterol, and conserved water molecules in the biochemistry and pharmacology of T2Rs.
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Rhayem Y, Le Stunff C, Abdel Khalek W, Auzan C, Bertherat J, Linglart A, Couvineau A, Silve C, Clauser E. Functional Characterization of PRKAR1A Mutations Reveals a Unique Molecular Mechanism Causing Acrodysostosis but Multiple Mechanisms Causing Carney Complex. J Biol Chem 2015; 290:27816-28. [PMID: 26405036 PMCID: PMC4646027 DOI: 10.1074/jbc.m115.656553] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Indexed: 02/05/2023] Open
Abstract
The main target of cAMP is PKA, the main regulatory subunit of which (PRKAR1A) presents mutations in two genetic disorders: acrodysostosis and Carney complex. In addition to the initial recurrent mutation (R368X) of the PRKAR1A gene, several missense and nonsense mutations have been observed recently in acrodysostosis with hormonal resistance. These mutations are located in one of the two cAMP-binding domains of the protein, and their functional characterization is presented here. Expression of each of the PRKAR1A mutants results in a reduction of forskolin-induced PKA activation (measured by a reporter assay) and an impaired ability of cAMP to dissociate PRKAR1A from the catalytic PKA subunits by BRET assay. Modeling studies and sensitivity to cAMP analogs specific for domain A (8-piperidinoadenosine 3',5'-cyclic monophosphate) or domain B (8-(6-aminohexyl)aminoadenosine-3',5'-cyclic monophosphate) indicate that the mutations impair cAMP binding locally in the domain containing the mutation. Interestingly, two of these mutations affect amino acids for which alternative amino acid substitutions have been reported to cause the Carney complex phenotype. To decipher the molecular mechanism through which homologous substitutions can produce such strikingly different clinical phenotypes, we studied these mutations using the same approaches. Interestingly, the Carney mutants also demonstrated resistance to cAMP, but they expressed additional functional defects, including accelerated PRKAR1A protein degradation. These data demonstrate that a cAMP binding defect is the common molecular mechanism for resistance of PKA activation in acrodysosotosis and that several distinct mechanisms lead to constitutive PKA activation in Carney complex.
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Affiliation(s)
- Yara Rhayem
- From the INSERM U970, Université Paris Descartes, Paris Centre de Recherche Cardiovasculaire, 56 Rue Leblanc, 75015 Paris, France, the Service de Biochimie et Génétique Moléculaire and
| | - Catherine Le Stunff
- INSERM U1169, Université Paris Sud, Hôpital Bicêtre, 94270 Le Kremlin Bicêtre, France
| | - Waed Abdel Khalek
- From the INSERM U970, Université Paris Descartes, Paris Centre de Recherche Cardiovasculaire, 56 Rue Leblanc, 75015 Paris, France
| | - Colette Auzan
- From the INSERM U970, Université Paris Descartes, Paris Centre de Recherche Cardiovasculaire, 56 Rue Leblanc, 75015 Paris, France
| | - Jerome Bertherat
- Service d'Endocrinologie, Hôpital Cochin, Assistance Publique, Hôpitaux de Paris, 75014 Paris, France, the Institut Cochin, INSERM U1060, Université Paris Descartes, 75014 Paris, France
| | - Agnès Linglart
- the Service d'Endocrinologie Pédiatrique, Hôpital Bicêtre, Assistance Publique, Hôpitaux de Paris, 94270 Le Kremlin Bicêtre, France, and
| | - Alain Couvineau
- UMR 1149 INSERM, Université Paris Diderot, ERL CNRS 8252, Faculté de Médecine Site Bichat, 75018 Paris, France
| | - Caroline Silve
- the Service de Biochimie et Génétique Moléculaire and INSERM U1169, Université Paris Sud, Hôpital Bicêtre, 94270 Le Kremlin Bicêtre, France
| | - Eric Clauser
- From the INSERM U970, Université Paris Descartes, Paris Centre de Recherche Cardiovasculaire, 56 Rue Leblanc, 75015 Paris, France, the Service de Biochimie et Génétique Moléculaire and
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Frentzou GA, Drinkhill MJ, Turner NA, Ball SG, Ainscough JFX. A state of reversible compensated ventricular dysfunction precedes pathological remodelling in response to cardiomyocyte-specific activity of angiotensin II type-1 receptor in mice. Dis Model Mech 2015; 8:783-94. [PMID: 26092119 PMCID: PMC4527284 DOI: 10.1242/dmm.019174] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 05/26/2015] [Indexed: 12/12/2022] Open
Abstract
Cardiac dysfunction is commonly associated with high-blood-pressure-induced cardiomyocyte hypertrophy, in response to aberrant renin-angiotensin system (RAS) activity. Ensuing pathological remodelling promotes cardiomyocyte death and cardiac fibroblast activation, leading to cardiac fibrosis. The initiating cellular mechanisms that underlie this progressive disease are poorly understood. We previously reported a conditional mouse model in which a human angiotensin II type-I receptor transgene (HART) was expressed in differentiated cardiomyocytes after they had fully matured, but not during development. Twelve-month-old HART mice exhibited ventricular dysfunction and cardiomyocyte hypertrophy with interstitial fibrosis following full receptor stimulation, without affecting blood pressure. Here, we show that chronic HART activity in young adult mice causes ventricular dysfunction without hypertrophy, fibrosis or cardiomyocyte death. Dysfunction correlated with reduced expression of pro-hypertrophy markers and increased expression of pro-angiogenic markers in the cardiomyocytes experiencing increased receptor load. This stimulates responsive changes in closely associated non-myocyte cells, including the downregulation of pro-angiogenic genes, a dampened inflammatory response and upregulation of Tgfβ. Importantly, this state of compensated dysfunction was reversible. Furthermore, increased stimulation of the receptors on the cardiomyocytes caused a switch in the secondary response from the non-myocyte cells. Progressive cardiac remodelling was stimulated through hypertrophy and death of individual cardiomyocytes, with infiltration, proliferation and activation of fibroblast and inflammatory cells, leading to increased angiogenic and inflammatory signalling. Together, these data demonstrate that a state of pre-hypertrophic compensated dysfunction can exist in affected individuals before common markers of heart disease are detectable. The data also suggest that there is an initial response from the housekeeping cells of the heart to signals emanating from distressed neighbouring cardiomyocytes to suppress those changes most commonly associated with progressive heart disease. We suggest that the reversible nature of this state of compensated dysfunction presents an ideal window of opportunity for personalised therapeutic intervention. Highlighted Article: A novel conditional mouse model was used to investigate early initiating stages of heart disease that are commonly overlooked, and identifies a ‘window of opportunity’ for personalised therapeutic intervention.
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Affiliation(s)
- Georgia A Frentzou
- Leeds Institute of Cardiovascular & Metabolic Medicine, and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds LS2 9JT, UK
| | - Mark J Drinkhill
- Leeds Institute of Cardiovascular & Metabolic Medicine, and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds LS2 9JT, UK
| | - Neil A Turner
- Leeds Institute of Cardiovascular & Metabolic Medicine, and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds LS2 9JT, UK
| | - Stephen G Ball
- Leeds Institute of Cardiovascular & Metabolic Medicine, and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds LS2 9JT, UK
| | - Justin F X Ainscough
- Leeds Institute of Cardiovascular & Metabolic Medicine, and Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds LS2 9JT, UK
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Stoy H, Gurevich VV. How genetic errors in GPCRs affect their function: Possible therapeutic strategies. Genes Dis 2015; 2:108-132. [PMID: 26229975 PMCID: PMC4516391 DOI: 10.1016/j.gendis.2015.02.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 02/07/2015] [Indexed: 01/14/2023] Open
Abstract
Activating and inactivating mutations in numerous human G protein-coupled receptors (GPCRs) are associated with a wide range of disease phenotypes. Here we use several class A GPCRs with a particularly large set of identified disease-associated mutations, many of which were biochemically characterized, along with known GPCR structures and current models of GPCR activation, to understand the molecular mechanisms yielding pathological phenotypes. Based on this mechanistic understanding we also propose different therapeutic approaches, both conventional, using small molecule ligands, and novel, involving gene therapy.
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18
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Trafficking of β-Adrenergic Receptors: Implications in Intracellular Receptor Signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 132:151-88. [PMID: 26055058 DOI: 10.1016/bs.pmbts.2015.03.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
β-Adrenergic receptors (βARs), prototypical G-protein-coupled receptors, play a pivotal role in regulating neuronal and cardiovascular responses to catecholamines during stress. Agonist-induced receptor endocytosis is traditionally considered as a primary mechanism to turn off the receptor signaling (or receptor desensitization). However, recent progress suggests that intracellular trafficking of βAR presents a mean to translocate receptor signaling machinery to intracellular organelles/compartments while terminating the signaling at the cell surface. Moreover, the apparent multidimensionality of ligand efficacy in space and time in a cell has forecasted exciting pathophysiological implications, which are just beginning to be explored. As we begin to understand how these pathways impact downstream cellular programs, this will have significant implications for a number of pathophysiological conditions in heart and other systems, that in turn open up new therapeutic opportunities.
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19
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Michel MC, Seifert R. Selectivity of pharmacological tools: implications for use in cell physiology. A review in the theme: Cell signaling: proteins, pathways and mechanisms. Am J Physiol Cell Physiol 2015; 308:C505-20. [PMID: 25631871 DOI: 10.1152/ajpcell.00389.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/24/2015] [Indexed: 01/08/2023]
Abstract
Pharmacological inhibitors are frequently used to identify the receptors, receptor subtypes, and associated signaling pathways involved in physiological cell responses. Based on the effects of such inhibitors conclusions are drawn about the involvement of their assumed target or lack thereof. While such inhibitors can be useful tools for a better physiological understanding, their uncritical use can lead to incorrect conclusions. This article reviews the concept of inhibitor selectivity and its implication for cell physiology. Specifically, we discuss the implications of using inhibitor vs. activator approaches, issues of direct vs. indirect pathway modulation, implications of inverse agonism and biased signaling, and those of orthosteric vs. allosteric, competitive vs. noncompetitive, and reversible vs. irreversible inhibition. Additional problems can result from inconsistent estimates of inhibitor potency and differences in potency between cell-free systems and intact cells. These concepts are illustrated by several examples of inhibitors displaying affinity for related but distinct targets or even unrelated targets. Of note, many of the issues being addressed are also applicable to genetic inhibition strategies. The main practical conclusion following from these concepts is that investigators should be critical in the choice of inhibitor, its concentrations, and its mode of application. When this advice is adhered to, small-molecule pharmacological inhibitors can be important experimental tools in the hand of physiologists.
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Affiliation(s)
- Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany; and
| | - Roland Seifert
- Department of Pharmacology, Hannover Medical School, Hannover, Germany
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20
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Marott SCW, Nordestgaard BG, Jensen GB, Tybjaerg-Hansen A, Benn M. AT1 mutations and risk of atrial fibrillation based on genotypes from 71,000 individuals from the general population. Br J Clin Pharmacol 2014; 76:114-24. [PMID: 23210602 DOI: 10.1111/bcp.12050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 11/25/2012] [Indexed: 11/30/2022] Open
Abstract
AIMS Activation of the angiotensin II type 1 (AT1 ) receptor has been shown to mediate the structural and electrical remodelling of the atrial myocardium associated with atrial fibrillation. We hypothesized that AT1 genotypic variation is associated with atrial fibrillation or diseases predisposing to atrial fibrillation, such as hypertension, heart failure, ischaemic heart disease and myocardial infarction, in the general population. METHODS We resequenced the AT1 gene in 760 individuals with atrial fibrillation and identified two nonsynonymous variants (I103T and A244S), which were subsequently genotyped in the prospective Copenhagen City Heart Study (n = 10 603) and the prospective Copenhagen General Population Study (n = 60 647). RESULTS Risk of atrial fibrillation for heterozygotes for AT1 genetic variants A244S and I103T/A244S vs. noncarriers was increased by 2.7-fold (95% confidence interval 1.5- to 5.1-fold) and 2.6-fold (95% confidence interval 1.6- to 4.2-fold), respectively, for men. CONCLUSIONS Heterozygosity for the nonsynonymous AT1 genetic variants A244S and I103T/A244S was associated with increased risk of atrial fibrillation in men. The AT1 recptor might be a target for the pharmaceutical industry. This finding needs to be validated in independent studies.
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Affiliation(s)
- Sarah C W Marott
- Department of Clinical Biochemistry, Herlev Hospital, Herlev, Denmark
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21
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Randazzo PA, Jian X, Chen PW, Zhai P, Soubias O, Northup JK. Quantitative Analysis of Guanine Nucleotide Exchange Factors (GEFs) as Enzymes. CELLULAR LOGISTICS 2014; 3:e27609. [PMID: 25332840 PMCID: PMC4187004 DOI: 10.4161/cl.27609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 12/19/2013] [Accepted: 12/20/2013] [Indexed: 11/19/2022]
Abstract
The proteins that possess guanine nucleotide exchange factor (GEF) activity, which include about ~800 G protein coupled receptors (GPCRs),1 15 Arf GEFs,2 81 Rho GEFs,3 8 Ras GEFs,4 and others for other families of GTPases,5 catalyze the exchange of GTP for GDP on all regulatory guanine nucleotide binding proteins. Despite their importance as catalysts, relatively few exchange factors (we are aware of only eight for ras superfamily members) have been rigorously characterized kinetically.5-13 In some cases, kinetic analysis has been simplistic leading to erroneous conclusions about mechanism (as discussed in a recent review14). In this paper, we compare two approaches for determining the kinetic properties of exchange factors: (i) examining individual equilibria, and; (ii) analyzing the exchange factors as enzymes. Each approach, when thoughtfully used,14,15 provides important mechanistic information about the exchange factors. The analysis as enzymes is described in further detail. With the focus on the production of the biologically relevant guanine nucleotide binding protein complexed with GTP (G•GTP), we believe it is conceptually simpler to connect the kinetic properties to cellular effects. Further, the experiments are often more tractable than those used to analyze the equilibrium system and, therefore, more widely accessible to scientists interested in the function of exchange factors.
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Affiliation(s)
- Paul A Randazzo
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Peng Zhai
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics; National Institute on Alcohol Abuse and Alcoholism; Rockville, MD USA
| | - John K Northup
- Laboratory of Membrane Biochemistry and Biophysics; National Institute on Alcohol Abuse and Alcoholism; Rockville, MD USA
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22
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Kleinau G, Biebermann H. Constitutive activities in the thyrotropin receptor: regulation and significance. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 70:81-119. [PMID: 24931193 DOI: 10.1016/b978-0-12-417197-8.00003-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The thyroid-stimulating hormone receptor (TSHR, or thyrotropin receptor) is a family A G protein-coupled receptor. It not only binds thyroid-stimulating hormone (TSH, or thyrotropin) but also interacts with autoantibodies under pathological conditions. The TSHR and TSH are essential for thyroid growth and function and thus for all thyroid hormone-associated physiological superordinated processes, including metabolism and development of the central nervous system. In vitro studies have found that the TSHR permanently stimulates ligand-independent (constitutive) activation of Gs, which ultimately leads to intracellular cAMP accumulation. Furthermore, a vast variety of constitutively activating mutations of TSHR-at more than 50 different amino acid positions-have been reported to enhance basal signaling. These lead in vivo to a "gain-of-function" phenotype of nonautoimmune hyperthyroidism or toxic adenomas. Moreover, many naturally occurring inactivating mutations are known to cause a "loss-of-function" phenotype, resulting in resistance to thyroid hormone or hyperthyrotropinemia. Several of these mutations are also characterized by impaired basal signaling, and these are designated here as "constitutively inactivating mutations" (CIMs). More than 30 amino acid positions with CIMs have been identified so far. Moreover, the permanent TSHR signaling capacity can also be blocked by inverse agonistic antibodies or small drug-like molecules, which both have a potential for clinical usage. In this chapter, information on constitutive activity in the TSHR is described, including up- and downregulation, linked protein conformations, physiological and pathophysiological conditions, and related intracellular signaling.
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Affiliation(s)
- Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
| | - Heike Biebermann
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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23
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Coll AP. “Are melanocortin receptors constitutively active in vivo?”. Eur J Pharmacol 2013; 719:202-207. [DOI: 10.1016/j.ejphar.2013.04.051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 03/22/2013] [Accepted: 04/03/2013] [Indexed: 10/26/2022]
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Kleinau G, Neumann S, Grüters A, Krude H, Biebermann H. Novel insights on thyroid-stimulating hormone receptor signal transduction. Endocr Rev 2013; 34:691-724. [PMID: 23645907 PMCID: PMC3785642 DOI: 10.1210/er.2012-1072] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The TSH receptor (TSHR) is a member of the glycoprotein hormone receptors, a subfamily of family A G protein-coupled receptors. The TSHR is of great importance for the growth and function of the thyroid gland. The TSHR and its endogenous ligand TSH are pivotal proteins with respect to a variety of physiological functions and malfunctions. The molecular events of TSHR regulation can be summarized as a process of signal transduction, including signal reception, conversion, and amplification. The steps during signal transduction from the extra- to the intracellular sites of the cell are not yet comprehensively understood. However, essential new insights have been achieved in recent years on the interrelated mechanisms at the extracellular region, the transmembrane domain, and intracellular components. This review contains a critical summary of available knowledge of the molecular mechanisms of signal transduction at the TSHR, for example, the key amino acids involved in hormone binding or in the structural conformational changes that lead to G protein activation or signaling regulation. Aspects of TSHR oligomerization, signaling promiscuity, signaling selectivity, phenotypes of genetic variations, and potential extrathyroidal receptor activity are also considered, because these are relevant to an understanding of the overall function of the TSHR, including physiological, pathophysiological, and pharmacological perspectives. Directions for future research are discussed.
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Affiliation(s)
- Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, Ostring 3, Augustenburger Platz 1, 13353 Berlin, Germany.
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25
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Gilliland CT, Salanga CL, Kawamura T, Trejo J, Handel TM. The chemokine receptor CCR1 is constitutively active, which leads to G protein-independent, β-arrestin-mediated internalization. J Biol Chem 2013; 288:32194-32210. [PMID: 24056371 DOI: 10.1074/jbc.m113.503797] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of G protein-coupled receptors by their associated ligands has been extensively studied, and increasing structural information about the molecular mechanisms underlying ligand-dependent receptor activation is beginning to emerge with the recent expansion in GPCR crystal structures. However, some GPCRs are also able to adopt active conformations in the absence of agonist binding that result in the initiation of signal transduction and receptor down-modulation. In this report, we show that the CC-type chemokine receptor 1 (CCR1) exhibits significant constitutive activity leading to a variety of cellular responses. CCR1 expression is sufficient to induce inhibition of cAMP formation, increased F-actin content, and basal migration of human and murine leukocytes. The constitutive activity leads to basal phosphorylation of the receptor, recruitment of β-arrestin-2, and subsequent receptor internalization. CCR1 concurrently engages Gαi and β-arrestin-2 in a multiprotein complex, which may be accommodated by homo-oligomerization or receptor clustering. The data suggest the presence of two functional states for CCR1; whereas receptor coupled to Gαi functions as a canonical GPCR, albeit with high constitutive activity, the CCR1·β-arrestin-2 complex is required for G protein-independent constitutive receptor internalization. The pertussis toxin-insensitive uptake of chemokine by the receptor suggests that the CCR1·β-arrestin-2 complex may be related to a potential scavenging function of the receptor, which may be important for maintenance of chemokine gradients and receptor responsiveness in complex fields of chemokines during inflammation.
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Affiliation(s)
| | | | | | - JoAnn Trejo
- the Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Tracy M Handel
- From the Skaggs School of Pharmacy and Pharmaceutical Sciences.
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de Voux A, Chan MC, Folefoc AT, Madziva MT, Flanagan CA. Constitutively active CCR5 chemokine receptors differ in mediating HIV envelope-dependent fusion. PLoS One 2013; 8:e54532. [PMID: 23355876 PMCID: PMC3552960 DOI: 10.1371/journal.pone.0054532] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 12/12/2012] [Indexed: 11/18/2022] Open
Abstract
The CCR5 chemokine receptor is a rhodopsin-like G protein-coupled receptor that mediates the effects of pro-inflammatory β-chemokines. CCR5 is also the major co-receptor for entry of human immunodeficiency virus (HIV) into human cells. G protein-coupled receptors exist in ensembles of active and inactive conformations. Active receptor conformations can be stabilized by mutations. Although binding of the HIV envelope protein to CCR5 stimulates cellular signaling, the CCR5 conformation that induces fusion of the viral membrane with cellular membranes is not known. We mutated conserved amino acids to generate constitutively active CCR5 receptors, which are stabilized in active conformations, and tested the ability of constitutively active CCR5 receptors to mediate HIV envelope-directed membrane fusion. Mutation of the Asp3.49(125) and Arg6.32(225) residues of CCR5 did not cause constitutive activity, but Lys or Pro substitutions for Thr2.56(82), in the TxP motif, caused high basal inositol phosphate signaling. Signaling did not increase in response to MIP-1β, suggesting that the Thr2.56(82) mutants were fully stabilized in active conformations. The Thr2.56(82)Lys mutation severely decreased cell surface CCR5 expression. Combining the Thr2.56(82)Lys mutation with an Arg6.32(225)Gln mutation partially reversed the decrease in expression. Mutants with Thr2.56(82)Lys substitutions were poor mediators of HIV envelope-directed membrane fusion, but mutants with the Thr2.65(82)Pro substitution exhibited full co-receptor function. Our results suggest that the Thr2.65(82)Lys and Thr2.65(82)Pro mutations stabilize distinct constitutively active CCR5 conformations. Lys in position 2.65(82) stabilizes activated receptor conformations that appear to be constitutively internalized and do not induce envelope-dependent membrane fusion, whereas Pro stabilizes activated conformations that are not constitutively internalized and fully mediate envelope-directed membrane fusion.
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Affiliation(s)
- Alex de Voux
- Medical Research Council Receptor Biology Research Unit, Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Mei-Chi Chan
- Medical Research Council Receptor Biology Research Unit, Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Asongna T. Folefoc
- Medical Research Council Receptor Biology Research Unit, Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Michael T. Madziva
- Medical Research Council Receptor Biology Research Unit, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
| | - Colleen A. Flanagan
- Medical Research Council Receptor Biology Research Unit, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- * E-mail:
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27
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Müller A, Kleinau G, Piechowski CL, Müller TD, Finan B, Pratzka J, Grüters A, Krude H, Tschöp M, Biebermann H. G-protein coupled receptor 83 (GPR83) signaling determined by constitutive and zinc(II)-induced activity. PLoS One 2013; 8:e53347. [PMID: 23335960 PMCID: PMC3546042 DOI: 10.1371/journal.pone.0053347] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 11/27/2012] [Indexed: 12/31/2022] Open
Abstract
The G-protein coupled receptor 83 (GPR83) is an orphan G-protein coupled receptor for which the natural ligand(s) and signaling pathway(s) remain to be identified. Previous studies suggest a role of GPR83 in the regulation of thermogenesis and the control of circulating adiponectin. The aim of this study was to gain insights into the molecular underpinnings underlying GPR83 signaling. In particular, we aimed to assess the underlying G-protein activated signaling pathway of GPR83 and how this pathway is affected by mutational activation and zinc(II) challenge. Finally, we assessed the capacity of GPR83 for homodimerization. Our results show for the first time that mouse (m) GPR83 has high basal Gq/11 activity without affecting Gi or Gs signaling. Furthermore, we found that, under physiological conditions, zinc(II) (but not calcium(II) and magnesium(II)) potently activates mGPR83, thus identifying zinc(II) as an endogenous molecule with agonistic capability to activate mGPR83. In line with the observation that zinc(II)-ions activate mGPR83, we identified a cluster of ion-binding sensitive amino acids (e.g. His145, His204, Cys207, Glu217) in an activation sensitive receptor region of mGPR83. The occurrence of a constitutive activating mutant and a zinc(II)-binding residue at the N-terminal part corroborate the importance of this region in mGPR83 signal regulation. Finally, our results indicate that mGPR83 forms homodimers, which extend the current knowledge and molecular facets of GPR83 signaling.
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Affiliation(s)
- Anne Müller
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Carolin L. Piechowski
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Timo D. Müller
- Institute of Diabetes and Obesity, Helmholtz Center Munich, German Research Center for Environmental Health (GmbH), Munich, Germany
| | - Brian Finan
- Institute of Diabetes and Obesity, Helmholtz Center Munich, German Research Center for Environmental Health (GmbH), Munich, Germany
| | - Juliane Pratzka
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Annette Grüters
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Heiko Krude
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Matthias Tschöp
- Institute of Diabetes and Obesity, Helmholtz Center Munich, German Research Center for Environmental Health (GmbH), Munich, Germany
- Department of Metabolic Diseases, Technical University, Munich, Germany
| | - Heike Biebermann
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Berlin, Germany
- * E-mail:
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28
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Casas-González P, Scaglia HE, Pérez-Solís MA, Durand G, Scaglia J, Zariñán T, Dias JA, Reiter E, Ulloa-Aguirre A. Normal testicular function without detectable follicle-stimulating hormone. A novel mutation in the follicle-stimulating hormone receptor gene leading to apparent constitutive activity and impaired agonist-induced desensitization and internalization. Mol Cell Endocrinol 2012; 364:71-82. [PMID: 22954680 DOI: 10.1016/j.mce.2012.08.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 08/15/2012] [Accepted: 08/16/2012] [Indexed: 11/15/2022]
Abstract
Activating mutations in the follicle-stimulating hormone (FSH) receptor (FSHR) gene are rarely detected due to the absence of a clearly defined phenotype, particularly in men. We here report the biochemical features of a novel mutation in the first extracellular loop of the FSHR. The mutation (N431I) was detected in an asymptomatic man exhibiting normal spermatogenesis, suppressed serum FSH, and normal or elevated levels of biochemical markers of FSH action. Employing different experimental strategies on HEK-293 cells transiently expressing the N431I FSHR mutant, we found that the mutation led to decreased cell surface plasma membrane expression of the receptor protein, but conferred a low level of constitutive activity associated with markedly altered agonist-stimulated desensitization and internalization. These latter features may contribute and/or amplify the persistent activation of the receptor in both absence and presence of agonist and provide new insights into opportunities for adjuvant therapies based on disruption of these processes.
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Affiliation(s)
- Patricia Casas-González
- Research Unit in Reproductive Medicine, Hospital de Ginecobstetricia Luis Castelazo Ayala, Instituto Mexicano del Seguro Social, Mexico 01090, DF, Mexico.
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29
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Northup JK, Jian X, Randazzo PA. Nucleotide exchange factors: Kinetic analyses and the rationale for studying kinetics of GEFs. CELLULAR LOGISTICS 2012. [PMID: 23181196 PMCID: PMC3498072 DOI: 10.4161/cl.21627] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Exchange factors are enzymes that catalyze the exchange of GTP for GDP on guanine nucleotide binding proteins. Progress in understanding the molecular basis of action and the cellular functions of these enzymes has largely come from structural determinations (e.g., crystal structures) and studying effects on cells when expression levels of the exchange factors are perturbed or mutated exchange factors are expressed. Proportionally little effort has been expended on studying the kinetics of exchange; however, reaction rates are central to understanding enzymes. Here, we discuss the importance of kinetic analysis of exchange factors for guanine nucleotide binding proteins, with a focus on ADP-ribosylation factor (Arf) and heterotrimeric G proteins, for providing unique insights into molecular mechanisms and regulation as well as how kinetic analyses are used to complement other approaches.
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Affiliation(s)
- John K Northup
- Laboratory of Cellular Biology; National Institute of Deafness and Other Communication Disorders; Rockville, MD USA
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30
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Miura SI, Kiya Y, Hanzawa H, Nakao N, Fujino M, Imaizumi S, Matsuo Y, Yanagisawa H, Koike H, Komuro I, Karnik SS, Saku K. Small molecules with similar structures exhibit agonist, neutral antagonist or inverse agonist activity toward angiotensin II type 1 receptor. PLoS One 2012; 7:e37974. [PMID: 22719858 PMCID: PMC3375280 DOI: 10.1371/journal.pone.0037974] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 05/01/2012] [Indexed: 11/29/2022] Open
Abstract
Small differences in the chemical structures of ligands can be responsible for agonism, neutral antagonism or inverse agonism toward a G-protein-coupled receptor (GPCR). Although each ligand may stabilize the receptor conformation in a different way, little is known about the precise conformational differences. We synthesized the angiotensin II type 1 receptor blocker (ARB) olmesartan, R239470 and R794847, which induced inverse agonism, antagonism and agonism, respectively, and then investigated the ligand-specific changes in the receptor conformation with respect to stabilization around transmembrane (TM)3. The results of substituted cysteine accessibility mapping studies support the novel concept that ligand-induced changes in the conformation of TM3 play a role in stabilizing GPCR. Although the agonist-, neutral antagonist and inverse agonist-binding sites in the AT(1) receptor are similar, each ligand induced specific conformational changes in TM3. In addition, all of the experimental data were obtained with functional receptors in a native membrane environment (in situ).
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Affiliation(s)
- Shin-ichiro Miura
- Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan.
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31
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Taslimi A, Mathew E, Celić A, Wessel S, Dumont ME. Identifying functionally important conformational changes in proteins: activation of the yeast α-factor receptor Ste2p. J Mol Biol 2012; 418:367-78. [PMID: 22387470 DOI: 10.1016/j.jmb.2012.02.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2011] [Revised: 02/13/2012] [Accepted: 02/18/2012] [Indexed: 11/29/2022]
Abstract
We have developed a procedure in which disulfide cross-links are used to identify regions of proteins that undergo functionally important intramolecular motion. The approach was applied to the identification of disulfide bonds that stabilize the active state of the yeast α-mating pheromone receptor Ste2p, a member of the superfamily of G protein-coupled receptors. Cysteine residues were introduced at random positions in targeted regions of a starting allele of Ste2p that completely lacks cysteines. Libraries of mutated receptors were then screened for alleles that exhibit constitutive signaling. Two strongly activated alleles were recovered containing cysteine residues in transmembrane (TM) segments 5 and 6. Constitutive activity of these alleles was dependent on the presence of both introduced cysteines and was sensitive to reducing agent. Cross-linked peptides derived from the mutant receptors were detected by immunoblotting. Additional sites of cross-linking between TM segments 5 and 6 that did not lead to constitutive activation were also identified. These results indicate that relative motion of the TM segments 5 and 6 in the extracellular half of the membrane is sufficient to activate the receptor and that TM segment 6, but not TM segment 5, exhibits rotational mobility that is not associated with receptor activation.
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Affiliation(s)
- Amir Taslimi
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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32
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33
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Kleinau G, Hoyer I, Kreuchwig A, Haas AK, Rutz C, Furkert J, Worth CL, Krause G, Schülein R. From molecular details of the interplay between transmembrane helices of the thyrotropin receptor to general aspects of signal transduction in family a G-protein-coupled receptors (GPCRs). J Biol Chem 2011; 286:25859-71. [PMID: 21586576 PMCID: PMC3138303 DOI: 10.1074/jbc.m110.196980] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 05/10/2011] [Indexed: 12/24/2022] Open
Abstract
Transmembrane helices (TMHs) 5 and 6 are known to be important for signal transduction by G-protein-coupled receptors (GPCRs). Our aim was to characterize the interface between TMH5 and TMH6 of the thyrotropin receptor (TSHR) to gain molecular insights into aspects of signal transduction and regulation. A proline at TMH5 position 5.50 is highly conserved in family A GPCRs and causes a twist in the helix structure. Mutation of the TSHR-specific alanine (Ala-593⁵·⁵⁰) at this position to proline resulted in a 20-fold reduction of cell surface expression. This indicates that TMH5 in the TSHR might have a conformation different from most other family A GPCRs by forming a regular α-helix. Furthermore, linking our own and previous data from directed mutagenesis with structural information led to suggestions of distinct pairs of interacting residues between TMH5 and TMH6 that are responsible for stabilizing either the basal or the active state. Our insights suggest that the inactive state conformation is constrained by a core set of polar interactions among TMHs 2, 3, 6, and 7 and in contrast that the active state conformation is stabilized mainly by non-polar interactions between TMHs 5 and 6. Our findings might be relevant for all family A GPCRs as supported by a statistical analysis of residue properties between the TMHs of a vast number of GPCR sequences.
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Affiliation(s)
- Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie, 13125 Berlin, Germany.
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34
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Steyaert J, Kobilka BK. Nanobody stabilization of G protein-coupled receptor conformational states. Curr Opin Struct Biol 2011; 21:567-72. [PMID: 21782416 DOI: 10.1016/j.sbi.2011.06.011] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 06/28/2011] [Accepted: 06/30/2011] [Indexed: 11/30/2022]
Abstract
Remarkable progress has been made in the field of G protein-coupled receptor (GPCR) structural biology during the past four years. Several obstacles to generating diffraction quality crystals of GPCRs have been overcome by combining innovative methods ranging from protein engineering to lipid-based screens and microdiffraction technology. The initial GPCR structures represent energetically stable inactive-state conformations. However, GPCRs signal through different G protein isoforms or G protein-independent effectors upon ligand binding suggesting the existence of multiple ligand-specific active states. These active-state conformations are unstable in the absence of specific cytosolic signaling partners representing new challenges for structural biology. Camelid single chain antibody fragments (nanobodies) show promise for stabilizing active GPCR conformations and as chaperones for crystallogenesis.
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Affiliation(s)
- Jan Steyaert
- Department of Molecular and Cellular Interactions, Vlaams Instituut voor Biotechnologie & Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
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35
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Shim JY. Understanding functional residues of the cannabinoid CB1. Curr Top Med Chem 2011; 10:779-98. [PMID: 20370713 DOI: 10.2174/156802610791164210] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 10/27/2009] [Indexed: 02/07/2023]
Abstract
The brain cannabinoid (CB(1)) receptor that mediates numerous physiological processes in response to marijuana and other psychoactive compounds is a G protein coupled receptor (GPCR) and shares common structural features with many rhodopsin class GPCRs. For the rational development of therapeutic agents targeting the CB(1) receptor, understanding of the ligand-specific CB(1) receptor interactions responsible for unique G protein signals is crucial. For a more than a decade, a combination of mutagenesis and computational modeling approaches has been successfully employed to study the ligand-specific CB(1) receptor interactions. In this review, after a brief discussion about recent advances in understanding of some structural and functional features of GPCRs commonly applicable to the CB(1) receptor, the CB(1) receptor functional residues reported from mutational studies are divided into three different types, ligand binding (B), receptor stabilization (S) and receptor activation (A) residues, to delineate the nature of the binding pockets of anandamide, CP55940, WIN55212-2 and SR141716A and to describe the molecular events of the ligand-specific CB(1) receptor activation from ligand binding to G protein signaling. Taken these CB(1) receptor functional residues, some of which are unique to the CB(1) receptor, together with the biophysical knowledge accumulated for the GPCR active state, it is possible to propose the early stages of the CB(1) receptor activation process that not only provide some insights into understanding molecular mechanisms of receptor activation but also are applicable for identifying new therapeutic agents by applying the validated structure-based approaches, such as virtual high throughput screening (HTS) and fragment-based approach (FBA).
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Affiliation(s)
- Joong-Youn Shim
- J.L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, 700 George Street, Durham, NC 27707, USA.
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36
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Corander MP, Rimmington D, Challis BG, O'Rahilly S, Coll AP. Loss of agouti-related peptide does not significantly impact the phenotype of murine POMC deficiency. Endocrinology 2011; 152:1819-28. [PMID: 21363936 PMCID: PMC3137464 DOI: 10.1210/en.2010-1450] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 01/31/2011] [Indexed: 11/19/2022]
Abstract
The hypothalamic melanocortin system is unique among neuropeptide systems controlling energy homeostasis, in that both anorexigenic proopiomelanocortin (POMC)-derived and orexigenic Agouti related-peptide (AgRP)-derived ligands act at the same receptors, namely melanocortin 3 and 4 receptors (MC3/4R). AgRP clearly acts as a competitive antagonist at MC3R and MC4R but may also have an inverse agonist action at these receptors. The physiological relevance of this remains uncertain. We generated a mouse lacking both POMC and AgRP [double knockout (DKO) mouse]. Phenotyping was performed in the absence and presence of glucocorticoids, and the response to central peptide administration was studied. The phenotype of DKO mice is indistinguishable from that of mice lacking Pomc alone, with both exhibiting highly similar degrees of hyperphagia and increased body length, fat, and lean mass compared with wild-type controls. After a 24-h fast, there was no difference in the refeeding response between Pomc(-/-) and DKO mice. Similarly, corticosterone supplementation caused an equivalent increase in food intake and body weight in both genotypes. Although the central administration of [Nle⁴, d-Phe⁷]-α-MSH to DKO mice caused a decrease in food intake and an increase in brown adipose tissue Ucp1 expression, both of which could be antagonized with the coadministration of AgRP, there was no effect of AgRP alone. These data suggest AgRP acts predominantly as a melanocortin antagonist. If AgRP has significant melanocortin-independent actions, these are of insufficient magnitude in vivo to impact any of the detailed phenotypes we have measured under a wide variety of conditions.
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MESH Headings
- Adipose Tissue/drug effects
- Adipose Tissue/metabolism
- Agouti-Related Protein/genetics
- Agouti-Related Protein/metabolism
- Agouti-Related Protein/pharmacology
- Animals
- Body Weight/drug effects
- Corticosterone/pharmacology
- Eating/drug effects
- Energy Metabolism
- Female
- Gene Expression
- Genotype
- Hypothalamus/metabolism
- Injections, Intraventricular
- Male
- Mice
- Mice, 129 Strain
- Mice, Knockout
- Phenotype
- Pro-Opiomelanocortin/deficiency
- Pro-Opiomelanocortin/genetics
- Pro-Opiomelanocortin/metabolism
- Protein Binding
- Receptor, Melanocortin, Type 3/agonists
- Receptor, Melanocortin, Type 3/antagonists & inhibitors
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/antagonists & inhibitors
- Receptor, Melanocortin, Type 4/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Time Factors
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Affiliation(s)
- Marcus P Corander
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Level 4, Addenbrooke's Hospital, Cambridge, UK.
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37
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Łukasiewicz S, Faron-Górecka A, Kędracka-Krok S, Dziedzicka-Wasylewska M. Effect of clozapine on the dimerization of serotonin 5-HT(2A) receptor and its genetic variant 5-HT(2A)H425Y with dopamine D(2) receptor. Eur J Pharmacol 2011; 659:114-23. [PMID: 21496455 DOI: 10.1016/j.ejphar.2011.03.038] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 03/03/2011] [Accepted: 03/22/2011] [Indexed: 11/25/2022]
Abstract
Oligomerization of G protein-coupled receptors has become a very important issue in a present molecular pharmacology. In the present study the level of the serotonin 5-HT(2A) and the dopamine D(2) receptor interactions have been studied since it may have a key significance in understanding the mechanism of action of drugs used to treat schizophrenia. With the use of fluorescence resonance energy transfer we demonstrated that the serotonin 5-HT(2A) receptors form homo- and hetero-dimers with the dopamine D(2) receptors and polymorphism H452Y within the 5-HT(2A) receptor, implicated as a cause of altered response to antipsychotic treatment, disturbs both processes. Clozapine affected the hetero-dimers (5-HT(2A)H452Y/D(2)) complexes and increased the otherwise weakened dimerization to the value observed for combination of both wild type receptors, and had no effect on the serotonin receptor homo-dimers (5-HT(2A)H452Y/5-HT(2A)), while haloperidol has restored the weakened interaction within homo-complexes and did not effect the hetero-complexes. The obtained data suggest that H452Y polymorphism has an influence not only on the level of constitutive oligomerization of investigated receptors but also it changes their pharmacological properties within both homo- and hetero-complexes.
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Affiliation(s)
- Sylwia Łukasiewicz
- Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 7 Gronostajowa Street, Krakow, Poland.
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38
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Rasmussen SGF, Choi HJ, Fung JJ, Pardon E, Casarosa P, Chae PS, Devree BT, Rosenbaum DM, Thian FS, Kobilka TS, Schnapp A, Konetzki I, Sunahara RK, Gellman SH, Pautsch A, Steyaert J, Weis WI, Kobilka BK. Structure of a nanobody-stabilized active state of the β(2) adrenoceptor. Nature 2011; 469:175-80. [PMID: 21228869 PMCID: PMC3058308 DOI: 10.1038/nature09648] [Citation(s) in RCA: 1313] [Impact Index Per Article: 101.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 11/01/2010] [Indexed: 11/16/2022]
Abstract
G protein coupled receptors (GPCRs) exhibit a spectrum of functional behaviors in response to natural and synthetic ligands. Recent crystal structures provide insights into inactive states of several GPCRs. Efforts to obtain an agonist-bound active-state GPCR structure have proven difficult due to the inherent instability of this state in the absence of a G protein. We generated a camelid antibody fragment (nanobody) to the human β2 adrenergic receptor (β2AR) that exhibits G protein-like behavior, and obtained an agonist-bound, active-state crystal structure of the receptor-nanobody complex. Comparison with the inactive β2AR structure reveals subtle changes in the binding pocket; however, these small changes are associated with an 11Å outward movement of the cytoplasmic end of transmembrane segment 6, and rearrangements of transmembrane segments 5 and 7 that are remarkably similar to those observed in opsin, an active form of rhodopsin. This structure provides insights into the process of agonist binding and activation.
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Affiliation(s)
- Søren G F Rasmussen
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, California 94305, USA
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39
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Lado-Abeal J, Quisenberry LR, Castro-Piedras I. Identification and evaluation of constitutively active thyroid stimulating hormone receptor mutations. Methods Enzymol 2011; 484:375-95. [PMID: 21036242 DOI: 10.1016/b978-0-12-381298-8.00019-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
Abstract
Thyroid stimulating hormone receptor (TSHR) is a guanine nucleotide-binding protein-coupled seven-transmembrane-domain receptor that controls the differentiation, growth, and function of the thyroid gland through stimulation of adenylyl cyclase and phospholipase C pathways. Thyroid stimulating hormone (TSH) is the main TSHR ligand, and unliganded receptor remains silent due to the interaction of its large extracellular domain with the extracellular loops of the serpentine. The TSHR gene is highly mutagenic and constitutively active mutations have been extensively described. Naturally occurring TSHR-activating mutations can affect any part of the receptor, but most activating mutations affect the serpentine region, and the majority of these are located in the third intracellular loop or transmembrane domain six. We describe several simple and relatively cheap methods used in our laboratory to study constitutive TSHR mutations that include (1) screening of TSHR gene mutations in paraffin-embedded thyroid tissue samples, (2) measurement of TSHR constitutive activity in vitro, (3) measurement of TSHR expression at cell surface by flow cytometry analysis, (4) TSH binding to TSHR, and (5) TSHR phosphorylation analysis.
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Affiliation(s)
- Joaquin Lado-Abeal
- Department of Internal Medicine, Tech University Health Sciences Center-SOM, Lubbock, Texas, USA
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40
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Sharma M, Afrin F, Satija N, Tripathi RP, Gangenahalli GU. Stromal-derived factor-1/CXCR4 signaling: indispensable role in homing and engraftment of hematopoietic stem cells in bone marrow. Stem Cells Dev 2011; 20:933-46. [PMID: 21186999 DOI: 10.1089/scd.2010.0263] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Homing and engraftment of hematopoietic stem/progenitor cells (HSPCs) in bone marrow is the major determining factor in success of hematopoietic stem cell transplantation. This is a complex, multistep process orchestrated by the coordinated interplay between adhesion molecules, cytokines, growth factors, and regulatory cofactors, many of which remain to be defined. Recent studies have highlighted the pivotal role of unique stromal-derived factor-1 (SDF-1)/CXCR4 signaling in the regulation of HSPC homing and subsequent engraftment. In addition, studies suggest that SDF-1/CXCR4 signaling acts as an essential survival-promoting factor of transplanted HSPCs as well as maintenance of quiescent HSCs in bone marrow niche. These pleiotropic effects exerted by SDF-1/CXCR4 axis make this unique signaling initiator very promising, not only for optimal hematopoietic reconstitution but also for the development of innovative approaches to achieve restoration, regeneration, or repair of other damaged tissues potentially amendable to reversal by stem cell transplantation. This goal can only be achieved when the role of SDF-1/CXCR4 axis in hematopoietic transplantation is clearly defined. Hence, this review presents current knowledge of the mechanisms through which SDF-1/CXCR4 signaling promotes restoration of hematopoiesis by regulating the homing and engraftment of HSPCs.
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Affiliation(s)
- Menka Sharma
- Stem Cell and Gene Therapy Research Group, Division of Radiation Biosciences, Institute of Nuclear Medicine and Allied Sciences, Defense Research and Development Organization, New Delhi, India
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41
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Nikiforovich GV, Marshall GR, Baranski TJ. Simplified modeling approach suggests structural mechanisms for constitutive activation of the C5a receptor. Proteins 2010; 79:787-802. [PMID: 21287612 DOI: 10.1002/prot.22918] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 10/11/2010] [Accepted: 10/13/2010] [Indexed: 11/07/2022]
Abstract
Molecular modeling of conformational changes occurring in the transmembrane region of the complement factor 5a receptor (C5aR) during receptor activation was performed by comparing two constitutively active mutants (CAMs) of C5aR, NQ (I124N/L127Q), and F251A, to those of the wild-type C5aR and NQ-N296A (I124N/L127Q/N296A), which have the wild-type phenotype. Modeling involved comprehensive sampling of various rotations of TM helices aligned to the crystal template of the dark-adapted rhodopsin along their long axes. By assuming that the relative energies of the spontaneously activated states of CAMs should be lower or at least comparable to energies characteristic for the ground states, we selected the plausible models for the conformational states associated with constitutive activation in C5aR. The modeling revealed that the hydrogen bonds between the side chains of D82-N119, S85-N119, and S131-C221 characteristic for the ground state were replaced by the hydrogen bonds D82-N296, N296-Y300, and S131-R134, respectively, in the activated states. Also, conformational transitions that occurred upon activation were hindered by contacts between the side chains of L127 and F251. The results rationalize the available data of mutagenesis in C5aR and offer the first specific molecular mechanism for the loss of constitutive activity in NQ-N296A. Our results also contributed to understanding the general structural mechanisms of activation in G-protein-coupled receptors lacking the "ionic lock", R(3.50) and E/D(6.30). Importantly, these results were obtained by modeling approaches that deliberately simplify many elements in order to explore potential conformations of GPCRs involving large-scale molecular movements.
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Nishihara E, Chen CR, Higashiyama T, Mizutori-Sasai Y, Ito M, Kubota S, Amino N, Miyauchi A, Rapoport B. Subclinical nonautoimmune hyperthyroidism in a family segregates with a thyrotropin receptor mutation with weakly increased constitutive activity. Thyroid 2010; 20:1307-14. [PMID: 20929407 PMCID: PMC2974847 DOI: 10.1089/thy.2010.0261] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Subclinical hyperthyroidism is usually associated with Graves' disease or toxic nodular goiter. Here we report a family with hereditary subclinical hyperthyroidism caused by a constitutively activating germline mutation of the thyrotropin receptor (TSHR) gene. METHODS The proband was a 64-year-old Japanese woman who presented with a thyroid nodule and was found to be euthyroid with a suppressed serum TSH. The nodule was not hot. Although antibodies to thyroid peroxidase and thyroglobulin antibodies were present, TSHR antibodies were not detected by TSH-binding inhibition or by bioassay. Two of her middle-aged sons, but not her daughter, also had subclinical hyperthyroidism without TSHR antibodies. Without therapy, the clinical condition of the affected individuals remained unchanged over 3 years without development of overt hyperthyroidism. RESULTS A novel heterozygous TSHR point mutation causing a glutamic acid to lysine substitution at codon 575 (E575K) in the second extracellular loop was detected in the three family members with subclinical hyperthyroidism, but was absent in her one daughter with normal thyroid function. In vitro functional studies of the E575K TSHR mutation demonstrated a weak, but significant, increase in constitutive activation of the cAMP pathway. CONCLUSION Although hereditary nonautoimmune overt hyperthyroidism is very rare, TSHR activating mutations as a cause of subclinical hyperthyroidism may be more common and should be considered in the differential diagnosis, especially if familial.
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Affiliation(s)
- Eijun Nishihara
- Center for Excellence in Thyroid Care, Kuma Hospital, Kobe, Japan.
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Gozé C, Bergé G, M'Kadmi C, Floquet N, Gagne D, Galleyrand JC, Fehrentz JA, Martinez J. Involvement of tryptophan W276 and of two surrounding amino acid residues in the high constitutive activity of the ghrelin receptor GHS-R1a. Eur J Pharmacol 2010; 643:153-61. [PMID: 20599926 DOI: 10.1016/j.ejphar.2010.06.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 06/07/2010] [Accepted: 06/10/2010] [Indexed: 10/19/2022]
Abstract
The human ghrelin receptor (GHS-R1a) is known to display a high level of signaling in the absence of ligand. The Trp276, located in the fully conserved CWXP motif of G protein-coupled receptors, is believed to function as a rotameric switch in these receptors. A comparative modelling of GHS-R1a with the motilin receptor, the most related G protein-coupled receptor to GHS-R1a known to date, but characterized by a very low ligand-independent signaling level, revealed that only two surrounding residues of Trp276, that are Val131 and Ile134, were different from these receptors. We mutated them at once in GHS-R1a to create a "motilin receptor-like" environment of Trp276 in order to study the consequences on GHS-R1a activation. We studied the pharmacological properties of the W276A, V131L-I134M GHS-R1a mutants. Basal as well as maximal ghrelin-induced signaling was assessed both by inositol-phosphate accumulation and SRE pathways. As compared to the wild type receptor, the SRE-luciferase assay displayed a markedly impaired basal activity for W276A whereas that of V131L-I134M was, strikingly, two fold increased. Nevertheless, the efficacy of ghrelin to bind or to stimulate mutant receptors remained unchanged. It is concluded that Trp276, Val131 and Ile134 have a significant impact on constitutive signaling of GHS-R1a, V131L-I134M being the first example of a GHS-R1a mutant with a higher basal activity than the wild type receptor.
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Affiliation(s)
- Catherine Gozé
- Institut des Biomolécules Max Mousseron, UMR, CNRS, Universités Montpellier, France.
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Kleinau G, Haas AK, Neumann S, Worth CL, Hoyer I, Furkert J, Rutz C, Gershengorn MC, Schülein R, Krause G. Signaling-sensitive amino acids surround the allosteric ligand binding site of the thyrotropin receptor. FASEB J 2010; 24:2347-54. [PMID: 20179143 DOI: 10.1096/fj.09-149146] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The thyrotropin receptor [thyroid-stimulating hormone receptor (TSHR)], a G-protein-coupled receptor (GPCR), is endogenously activated by thyrotropin, which binds to the extracellular region of the receptor. We previously identified a low-molecular-weight (LMW) agonist of the TSHR and predicted its allosteric binding pocket within the receptor's transmembrane domain. Because binding of the LMW agonist probably disrupts interactions or leads to formation of new interactions among amino acid residues surrounding the pocket, we tested whether mutation of residues at these positions would lead to constitutive signaling activity. Guided by molecular modeling, we performed site-directed mutagenesis of 24 amino acids in this spatial region, followed by functional characterization of the mutant receptors in terms of expression and signaling, measured as cAMP accumulation. We found that mutations V421I, Y466A, T501A, L587V, M637C, M637W, S641A, Y643F, L645V, and Y667A located in several helices exhibit constitutive activity. Of note is mutation M637W at position 6.48 in transmembrane helix 6, which has a significant effect on the interaction of the receptor with the LMW agonist. In summary, we found that a high proportion of residues in several helices surrounding the allosteric binding site of LMW ligands in the TSHR when mutated lead to constitutively active receptors. Our findings of signaling-sensitive residues in this region of the transmembrane bundle may be of general importance as this domain appears to be evolutionarily retained among GPCRs.
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Affiliation(s)
- Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, D-13125 Berlin, Germany
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Nikiforovich GV, Baranski TJ. Computational Modeling of Constitutively Active Mutants of GPCRs. Methods Enzymol 2010; 485:369-91. [DOI: 10.1016/b978-0-12-381296-4.00021-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Cogé F, Guenin SP, Fery I, Migaud M, Devavry S, Slugocki C, Legros C, Ouvry C, Cohen W, Renault N, Nosjean O, Malpaux B, Delagrange P, Boutin JA. The end of a myth: cloning and characterization of the ovine melatonin MT(2) receptor. Br J Pharmacol 2009; 158:1248-62. [PMID: 19814723 DOI: 10.1111/j.1476-5381.2009.00453.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE For many years, it was suspected that sheep expressed only one melatonin receptor (closely resembling MT(1) from other mammal species). Here we report the cloning of another melatonin receptor, MT(2), from sheep. EXPERIMENTAL APPROACH Using a thermo-resistant reverse transcriptase and polymerase chain reaction primer set homologous to the bovine MT(2) mRNA sequence, we have cloned and characterized MT(2) receptors from sheep retina. KEY RESULTS The ovine MT(2) receptor presents 96%, 72% and 67% identity with cattle, human and rat respectively. This MT(2) receptor stably expressed in CHO-K1 cells showed high-affinity 2[(125)I]-iodomelatonin binding (K(D)= 0.04 nM). The rank order of inhibition of 2[(125)I]-iodomelatonin binding by melatonin, 4-phenyl-2-propionamidotetralin and luzindole was similar to that exhibited by MT(2) receptors of other species (melatonin > 4-phenyl-2-propionamidotetralin > luzindole). However, its pharmacological profile was closer to that of rat, rather than human MT(2) receptors. Functionally, the ovine MT(2) receptors were coupled to G(i) proteins leading to inhibition of adenylyl cyclase, as the other melatonin receptors. In sheep brain, MT(2) mRNA was expressed in pars tuberalis, choroid plexus and retina, and moderately in mammillary bodies. Real-time polymerase chain reaction showed that in sheep pars tuberalis, premammillary hypothalamus and mammillary bodies, the temporal pattern of expression of MT(1) and MT(2) mRNA was not parallel in the three tissues. CONCLUSION AND IMPLICATIONS Co-expression of MT(1) and MT(2) receptors in all analysed sheep brain tissues suggests that MT(2) receptors may participate in melatonin regulation of seasonal anovulatory activity in ewes by modulating MT(1) receptor action.
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Affiliation(s)
- F Cogé
- Pharmacologie Moléculaire et Cellulaire, Institut de Recherches SERVIER, Suresnes, France
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Pathe-Neuschäfer-Rube A, Neuschäfer-Rube F, Püschel G. Role of the ERC motif in the proximal part of the second intracellular loop and the C-terminal domain of the human prostaglandin F2alpha receptor (hFP-R) in G-protein coupling control. Biochem J 2009; 388:317-24. [PMID: 15651980 PMCID: PMC1186721 DOI: 10.1042/bj20041321] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The human FP-R (F2alpha prostaglandin receptor) is a Gq-coupled heptahelical ectoreceptor, which is of significant medical interest, since it is a potential target for the treatment of glaucoma and preterm labour. On agonist exposure, it mediates an increase in intracellular inositol phosphate formation. Little is known about the structures that govern the agonist-dependent receptor activation. In other prostanoid receptors, the C-terminal domain has been inferred in the control of agonist-dependent receptor activation. A DRY motif at the beginning of the second intracellular loop is highly conserved throughout the G-protein-coupled receptor family and appears to be crucial for controlling agonist-dependent receptor activation. It is replaced by an ERC motif in the FP-R and no evidence for the relevance of this motif in ligand-dependent activation of prostanoid receptors has been provided so far. The aim of the present study was to elucidate the potential role of the C-terminal domain and the ERC motif in agonist-controlled intracellular signalling in FP-R mutants generated by site-directed mutagenesis. It was found that substitution of the acidic Glu(132) in the ERC motif by a threonine residue led to full constitutive activation, whereas truncation of the receptor's C-terminal domain led to partial constitutive activation of all three intracellular signal pathways that had previously been shown to be activated by the FP-R, i.e. inositol trisphosphate formation, focal adhesion kinase activation and T-cell factor signalling. Inositol trisphosphate formation and focal adhesion kinase phosphorylation were further enhanced by ligand binding in cells expressing the truncation mutant but not the E132T (Glu132-->Thr) mutant. Thus C-terminal truncation appeared to result in a receptor with partial constitutive activation, whereas substitution of Glu132 by threonine apparently resulted in a receptor with full constitutive activity.
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Affiliation(s)
- Andrea Pathe-Neuschäfer-Rube
- Institut für Ernährungswissenschaft, Abteilung Biochemie der Ernährung, Universität Potsdam, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Frank Neuschäfer-Rube
- Institut für Ernährungswissenschaft, Abteilung Biochemie der Ernährung, Universität Potsdam, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Gerhard P. Püschel
- Institut für Ernährungswissenschaft, Abteilung Biochemie der Ernährung, Universität Potsdam, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
- To whom correspondence should be addressed (email )
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Lee PH. Label-free optical biosensor: A tool for G protein-coupled receptors pharmacology profiling and inverse agonists identification. J Recept Signal Transduct Res 2009; 29:146-53. [DOI: 10.1080/10799890903064390] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Hu LA, Tang PM, Eslahi NK, Zhou T, Barbosa J, Liu Q. Identification of surrogate agonists and antagonists for orphan G-protein-coupled receptor GPR139. ACTA ACUST UNITED AC 2009; 14:789-97. [PMID: 19525486 DOI: 10.1177/1087057109335744] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
GPR139 is an orphan G-protein-coupled receptor (GPCR) that is expressed nearly exclusively in the central nervous system and may play a role in the control of locomotor activity. The signal transduction pathway and pharmacological function of GPR139, however, are still controversial due to the lack of natural or synthetic ligands. The authors report the characterization of human GPR139 signaling pathway and identification of surrogate agonists and antagonists. In both transient and stable transfections of HEK293F cells, overexpression of GPR139 increased basal intracellular cAMP concentrations compared to control cells. Furthermore, forskolin and isoproterenol-stimulated cAMP responses were enhanced in GPR139-expressing cells, suggesting that GPR139 is predominantly coupled to Galpha(s). The authors screened a large library of small molecules for compounds that increase cAMP levels in GPR139-expressing cells and identified a compound with GPR139 agonist activity. This compound increased cAMP production specifically in cells expressing GPR139 but not in cells expressing its highly homologous receptor GPR142. Furthermore, this compound did not induce calcium mobilization in GPR139 cells, indicating no Galpha(q)-mediated response. In addition, antagonist screening with the identified agonist yielded 2 classes of compounds as antagonists. The identification of surrogate agonists and antagonists of human GPR139 provides important tools for further study of this orphan GPCR.
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Affiliation(s)
- Liaoyuan A Hu
- Department of Pharmaceutical Discovery, Lexicon Pharmaceuticals, The Woodlands, Texas 77381, USA.
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Toyooka M, Tujii T, Takeda S. The N-terminal domain of GPR61, an orphan G-protein-coupled receptor, is essential for its constitutive activity. J Neurosci Res 2009; 87:1329-33. [PMID: 19025769 DOI: 10.1002/jnr.21955] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
G-protein-coupled receptor 61 (GPR61) is an orphan receptor that is abundantly expressed in the brain, which suggests its involvement in various physiological functions in the central nervous system. It couples with Gs and shows constitutive activity. To investigate the role of the N-terminal segment in the constitutive activity of GPR61, we measured [(35)S]GTPgammaS binding using a GPR61-Gs fusion protein and derivatives that had a deletion or alanine mutation in the N-terminal segment. We found that deletion of the N-terminal 25 amino acids and the V19A mutation in GPR61 impaired its constitutive activity. Moreover, the loss of the constitutive activity of the mutants could be restored by adding a fusion protein containing a C-terminal CD8 single transmembrane domain and the N-terminal 48-amino-acid segment of GPR61, i.e., CD8-48. We conclude that the N-terminal domain of GPR61 is required for maintaining its constitutive activity and functions as a tethered intramolecular ligand.
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Affiliation(s)
- Masaru Toyooka
- Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Gunma, Japan
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