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Wang Y, Gai S, Zhang W, Huang X, Ma S, Huo Y, Wu Y, Tu H, Pin JP, Rondard P, Xu C, Liu J. The GABA B receptor mediates neuroprotection by coupling to G 13. Sci Signal 2021; 14:eaaz4112. [PMID: 34665640 DOI: 10.1126/scisignal.aaz4112] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Yunyun Wang
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Siyu Gai
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Wenhua Zhang
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Xuetao Huang
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Shumin Ma
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Yujia Huo
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Yichen Wu
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Haijun Tu
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, 34094 Montpellier, France
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, 34094 Montpellier, France
| | - Chanjuan Xu
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Jianfeng Liu
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan, China.,Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, 510005 Guangzhou, China
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2
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Mechanistic diversity involved in the desensitization of G protein-coupled receptors. Arch Pharm Res 2021; 44:342-353. [PMID: 33761113 DOI: 10.1007/s12272-021-01320-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 03/14/2021] [Indexed: 01/14/2023]
Abstract
The desensitization of G protein-coupled receptors (GPCRs), which involves rapid loss of responsiveness due to repeated or chronic exposure to agonists, can occur through various mechanisms at different levels of signaling pathways. In this review, the mechanisms of GPCR desensitization are classified according to their occurrence at the receptor level and downstream to the receptor. The desensitization at the receptor level occurs in a phosphorylation-dependent manner, wherein the activated receptors are phosphorylated by GPCR kinases (GRKs), thereby increasing their affinities for arrestins. Arrestins bind to receptors through the cavity on the cytoplasmic region of heptahelical domains and interfere with the binding and activation of G-protein. Diverse mechanisms are involved in the desensitization that occurs downstream of the receptor. Some of these include the sequestration of G proteins, such as Gq and Gi/o by GRK2/3 and deubiquitinated arrestins, respectively. Mechanistically, GRK2/3 attenuates GPCR signaling by sequestering the Gα subunits of the Gq family and Gβγ via regulators of G protein signaling and pleckstrin homology domains, respectively. Moreover, studies on Gi/o-coupled D2-like receptors have reported that arrestins are deubiquitinated under desensitization condition and form a stable complex with Gβγ, thereby preventing them from coupling with Gα and the receptor, eventually leading to receptor signaling inhibition. Notably, the desensitization mechanism that involves arrestin deubiquitination is interesting; however, this is a new mechanism and needs to be explored further.
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3
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Ellaithy A, Gonzalez-Maeso J, Logothetis DA, Levitz J. Structural and Biophysical Mechanisms of Class C G Protein-Coupled Receptor Function. Trends Biochem Sci 2020; 45:1049-1064. [PMID: 32861513 PMCID: PMC7642020 DOI: 10.1016/j.tibs.2020.07.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 07/22/2020] [Accepted: 07/30/2020] [Indexed: 02/07/2023]
Abstract
Groundbreaking structural and spectroscopic studies of class A G protein-coupled receptors (GPCRs), such as rhodopsin and the β2 adrenergic receptor, have provided a picture of how structural rearrangements between transmembrane helices control ligand binding, receptor activation, and effector coupling. However, the activation mechanism of other GPCR classes remains more elusive, in large part due to complexity in their domain assembly and quaternary structure. In this review, we focus on the class C GPCRs, which include metabotropic glutamate receptors (mGluRs) and gamma-aminobutyric acid B (GABAB) receptors (GABABRs) most prominently. We discuss the unique biophysical questions raised by the presence of large extracellular ligand-binding domains (LBDs) and constitutive homo/heterodimerization. Furthermore, we discuss how recent studies have begun to unravel how these fundamental class C GPCR features impact the processes of ligand binding, receptor activation, signal transduction, regulation by accessory proteins, and crosstalk with other GPCRs.
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Affiliation(s)
- Amr Ellaithy
- Department of Neurology, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA; Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Javier Gonzalez-Maeso
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Diomedes A Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, USA; Department of Chemistry and Chemical Biology, College of Science and Center for Drug Discovery, Northeastern University, Boston, MA 02115, USA
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA.
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4
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Mechanisms and Regulation of Neuronal GABA B Receptor-Dependent Signaling. Curr Top Behav Neurosci 2020; 52:39-79. [PMID: 32808092 DOI: 10.1007/7854_2020_129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
γ-Aminobutyric acid B receptors (GABABRs) are broadly expressed throughout the central nervous system where they play an important role in regulating neuronal excitability and synaptic transmission. GABABRs are G protein-coupled receptors that mediate slow and sustained inhibitory actions via modulation of several downstream effector enzymes and ion channels. GABABRs are obligate heterodimers that associate with diverse arrays of proteins to form modular complexes that carry out distinct physiological functions. GABABR-dependent signaling is fine-tuned and regulated through a multitude of mechanisms that are relevant to physiological and pathophysiological states. This review summarizes the current knowledge on GABABR signal transduction and discusses key factors that influence the strength and sensitivity of GABABR-dependent signaling in neurons.
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5
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Papon MA, Le Feuvre Y, Barreda-Gómez G, Favereaux A, Farrugia F, Bouali-Benazzouz R, Nagy F, Rodríguez-Puertas R, Landry M. Spinal Inhibition of GABAB Receptors by the Extracellular Matrix Protein Fibulin-2 in Neuropathic Rats. Front Cell Neurosci 2020; 14:214. [PMID: 32765223 PMCID: PMC7378325 DOI: 10.3389/fncel.2020.00214] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 06/17/2020] [Indexed: 12/23/2022] Open
Abstract
In the central nervous system, the inhibitory GABAB receptor is the archetype of heterodimeric G protein-coupled receptors (GPCRs). Receptor interaction with partner proteins has emerged as a novel mechanism to alter GPCR signaling in pathophysiological conditions. We propose here that GABAB activity is inhibited through the specific binding of fibulin-2, an extracellular matrix protein, to the B1a subunit in a rat model of neuropathic pain. We demonstrate that fibulin-2 hampers GABAB activation, presumably through decreasing agonist-induced conformational changes. Fibulin-2 regulates the GABAB-mediated presynaptic inhibition of neurotransmitter release and weakens the GABAB-mediated inhibitory effect in neuronal cell culture. In the dorsal spinal cord of neuropathic rats, fibulin-2 is overexpressed and colocalized with B1a. Fibulin-2 may thus interact with presynaptic GABAB receptors, including those on nociceptive afferents. By applying anti-fibulin-2 siRNA in vivo, we enhanced the antinociceptive effect of intrathecal baclofen in neuropathic rats, thus demonstrating that fibulin-2 limits the action of GABAB agonists in vivo. Taken together, our data provide an example of an endogenous regulation of GABAB receptor by extracellular matrix proteins and demonstrate its functional impact on pathophysiological processes of pain sensitization.
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Affiliation(s)
- Marie-Amélie Papon
- Institut Interdisciplinaire de Neurosciences, University of Bordeaux, Bordeaux, France.,CNRS UMR 5297, Institut Interdisciplinaire de Neurosciences, Bordeaux, France
| | - Yves Le Feuvre
- Institut Interdisciplinaire de Neurosciences, University of Bordeaux, Bordeaux, France.,CNRS UMR 5297, Institut Interdisciplinaire de Neurosciences, Bordeaux, France
| | | | - Alexandre Favereaux
- Institut Interdisciplinaire de Neurosciences, University of Bordeaux, Bordeaux, France.,CNRS UMR 5297, Institut Interdisciplinaire de Neurosciences, Bordeaux, France
| | - Fanny Farrugia
- Institut Interdisciplinaire de Neurosciences, University of Bordeaux, Bordeaux, France.,CNRS UMR 5297, Institut Interdisciplinaire de Neurosciences, Bordeaux, France
| | - Rabia Bouali-Benazzouz
- Institut Interdisciplinaire de Neurosciences, University of Bordeaux, Bordeaux, France.,CNRS UMR 5297, Institut Interdisciplinaire de Neurosciences, Bordeaux, France
| | - Frédéric Nagy
- Institut Interdisciplinaire de Neurosciences, University of Bordeaux, Bordeaux, France.,CNRS UMR 5297, Institut Interdisciplinaire de Neurosciences, Bordeaux, France
| | | | - Marc Landry
- Institut Interdisciplinaire de Neurosciences, University of Bordeaux, Bordeaux, France.,CNRS UMR 5297, Institut Interdisciplinaire de Neurosciences, Bordeaux, France
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6
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Luo Y, Huang X, Yang J, Huang L, Li R, Wu Q, Jiang X. Proteomics analysis of G protein-coupled receptor kinase 4-inhibited cellular growth of HEK293 cells. J Proteomics 2019; 207:103445. [DOI: 10.1016/j.jprot.2019.103445] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 06/25/2019] [Accepted: 07/14/2019] [Indexed: 12/12/2022]
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7
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Liu M, Jiang Y, Wedow R, Li Y, Brazel DM, Chen F, Datta G, Davila-Velderrain J, McGuire D, Tian C, Zhan X, Choquet H, Docherty AR, Faul JD, Foerster JR, Fritsche LG, Gabrielsen ME, Gordon SD, Haessler J, Hottenga JJ, Huang H, Jang SK, Jansen PR, Ling Y, Mägi R, Matoba N, McMahon G, Mulas A, Orrù V, Palviainen T, Pandit A, Reginsson GW, Skogholt AH, Smith JA, Taylor AE, Turman C, Willemsen G, Young H, Young KA, Zajac GJM, Zhao W, Zhou W, Bjornsdottir G, Boardman JD, Boehnke M, Boomsma DI, Chen C, Cucca F, Davies GE, Eaton CB, Ehringer MA, Esko T, Fiorillo E, Gillespie NA, Gudbjartsson DF, Haller T, Harris KM, Heath AC, Hewitt JK, Hickie IB, Hokanson JE, Hopfer CJ, Hunter DJ, Iacono WG, Johnson EO, Kamatani Y, Kardia SLR, Keller MC, Kellis M, Kooperberg C, Kraft P, Krauter KS, Laakso M, Lind PA, Loukola A, Lutz SM, Madden PAF, Martin NG, McGue M, McQueen MB, Medland SE, Metspalu A, Mohlke KL, Nielsen JB, Okada Y, Peters U, Polderman TJC, Posthuma D, Reiner AP, Rice JP, Rimm E, Rose RJ, Runarsdottir V, Stallings MC, Stančáková A, Stefansson H, Thai KK, Tindle HA, Tyrfingsson T, Wall TL, Weir DR, Weisner C, Whitfield JB, Winsvold BS, Yin J, Zuccolo L, Bierut LJ, Hveem K, Lee JJ, Munafò MR, Saccone NL, Willer CJ, Cornelis MC, David SP, Hinds DA, Jorgenson E, Kaprio J, Stitzel JA, Stefansson K, Thorgeirsson TE, Abecasis G, Liu DJ, Vrieze S. Association studies of up to 1.2 million individuals yield new insights into the genetic etiology of tobacco and alcohol use. Nat Genet 2019; 51:237-244. [PMID: 30643251 PMCID: PMC6358542 DOI: 10.1038/s41588-018-0307-5] [Citation(s) in RCA: 1100] [Impact Index Per Article: 220.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Accepted: 11/06/2018] [Indexed: 12/21/2022]
Abstract
Tobacco and alcohol use are leading causes of mortality that influence risk for many complex diseases and disorders1. They are heritable2,3 and etiologically related4,5 behaviors that have been resistant to gene discovery efforts6-11. In sample sizes up to 1.2 million individuals, we discovered 566 genetic variants in 406 loci associated with multiple stages of tobacco use (initiation, cessation, and heaviness) as well as alcohol use, with 150 loci evidencing pleiotropic association. Smoking phenotypes were positively genetically correlated with many health conditions, whereas alcohol use was negatively correlated with these conditions, such that increased genetic risk for alcohol use is associated with lower disease risk. We report evidence for the involvement of many systems in tobacco and alcohol use, including genes involved in nicotinic, dopaminergic, and glutamatergic neurotransmission. The results provide a solid starting point to evaluate the effects of these loci in model organisms and more precise substance use measures.
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Affiliation(s)
- Mengzhen Liu
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Yu Jiang
- Department of Public Health Sciences, College of Medicine, Pennsylvania State University, Hershey, PA, USA
- Institute of Personalized Medicine, College of Medicine, Pennsylvania State University, Hershey, PA, USA
| | - Robbee Wedow
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Sociology, University of Colorado Boulder, Boulder, CO, USA
- Institute of Behavioral Science, University of Colorado Boulder, Boulder, CO, USA
| | - Yue Li
- Computer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge, MA, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - David M Brazel
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
- Interdisciplinary Quantitative Biology Graduate Group, University of Colorado Boulder, Boulder, CO, USA
| | - Fang Chen
- Department of Public Health Sciences, College of Medicine, Pennsylvania State University, Hershey, PA, USA
- Institute of Personalized Medicine, College of Medicine, Pennsylvania State University, Hershey, PA, USA
| | - Gargi Datta
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Jose Davila-Velderrain
- Computer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge, MA, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Daniel McGuire
- Department of Public Health Sciences, College of Medicine, Pennsylvania State University, Hershey, PA, USA
- Institute of Personalized Medicine, College of Medicine, Pennsylvania State University, Hershey, PA, USA
| | - Chao Tian
- 23andMe, Inc., Mountain View, CA, USA
| | - Xiaowei Zhan
- Quantitative Biomedical Research Center, Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Center for the Genetics of Host Defense, Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Hélène Choquet
- Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA
| | - Anna R Docherty
- Department of Psychiatry, Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA, USA
- Department of Psychiatry and Human Genetics, University of Utah, Salt Lake City, UT, USA
| | - Jessica D Faul
- Survey Research Center, Institute for Social Research, University of Michigan, Ann Arbor, MI, USA
| | - Johanna R Foerster
- Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Lars G Fritsche
- Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Maiken Elvestad Gabrielsen
- K.G. Jebsen Center for Genetic Epidemiology, Department of Public Health and Nursing, Norwegian University of Science and Technology, Trondheim, Norway
| | - Scott D Gordon
- Genetic Epidemiology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Jeffrey Haessler
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Jouke-Jan Hottenga
- Department of Biological Psychology, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Hongyan Huang
- Program in Genetic Epidemiology and Statistical Genetics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Seon-Kyeong Jang
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Philip R Jansen
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
- Department of Child and Adolescent Psychiatry, Erasmus MC Rotterdam, Rotterdam, the Netherlands
| | - Yueh Ling
- Department of Public Health Sciences, College of Medicine, Pennsylvania State University, Hershey, PA, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Reedik Mägi
- Estonian Genome Center, University of Tartu, Tartu, Estonia
| | - Nana Matoba
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Yokohama City, Japan
| | - George McMahon
- Department of Population Health Science, Bristol Medical School, Oakfield Grove, Bristol, UK
| | - Antonella Mulas
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche, Monserrato, Italy
| | - Valeria Orrù
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche, Monserrato, Italy
| | - Teemu Palviainen
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Anita Pandit
- Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA
| | | | - Anne Heidi Skogholt
- K.G. Jebsen Center for Genetic Epidemiology, Department of Public Health and Nursing, Norwegian University of Science and Technology, Trondheim, Norway
| | - Jennifer A Smith
- Survey Research Center, Institute for Social Research, University of Michigan, Ann Arbor, MI, USA
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | - Amy E Taylor
- Department of Population Health Science, Bristol Medical School, Oakfield Grove, Bristol, UK
| | - Constance Turman
- Program in Genetic Epidemiology and Statistical Genetics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Gonneke Willemsen
- Department of Biological Psychology, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Hannah Young
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Kendra A Young
- Department of Epidemiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Gregory J M Zajac
- Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Wei Zhao
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | - Wei Zhou
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
| | | | - Jason D Boardman
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Sociology, University of Colorado Boulder, Boulder, CO, USA
- Institute of Behavioral Science, University of Colorado Boulder, Boulder, CO, USA
| | - Michael Boehnke
- Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Dorret I Boomsma
- Department of Biological Psychology, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Chu Chen
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Francesco Cucca
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche, Monserrato, Italy
| | | | - Charles B Eaton
- Department of Family Medicine and Community Health, Alpert Medical School, Brown University, Providence, RI, USA
| | - Marissa A Ehringer
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - Tõnu Esko
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Estonian Genome Center, University of Tartu, Tartu, Estonia
| | - Edoardo Fiorillo
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche, Monserrato, Italy
| | - Nathan A Gillespie
- Department of Psychiatry, Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA, USA
- Genetic Epidemiology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Daniel F Gudbjartsson
- deCODE Genetics/Amgen, Inc., Reykjavik, Iceland
- School of Engineering and Natural Sciences, University of Iceland, Reykjavik, Iceland
| | - Toomas Haller
- Estonian Genome Center, University of Tartu, Tartu, Estonia
| | - Kathleen Mullan Harris
- Department of Sociology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Andrew C Heath
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO, USA
| | - John K Hewitt
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, CO, USA
| | - Ian B Hickie
- Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia
| | - John E Hokanson
- Department of Epidemiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Christian J Hopfer
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Psychiatry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - David J Hunter
- Program in Genetic Epidemiology and Statistical Genetics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Nuffield Department of Population Health, University of Oxford, Oxford, UK
| | - William G Iacono
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Eric O Johnson
- Fellows Program, RTI International, Research Triangle Park, NC, USA
| | - Yoichiro Kamatani
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Yokohama City, Japan
| | - Sharon L R Kardia
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | - Matthew C Keller
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, CO, USA
| | - Manolis Kellis
- Computer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge, MA, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Charles Kooperberg
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Peter Kraft
- Program in Genetic Epidemiology and Statistical Genetics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Kenneth S Krauter
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Markku Laakso
- Department of Internal Medicine, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
- Department of Medicine, Kuopio University Hospital, Kuopio, Finland
| | - Penelope A Lind
- Psychiatric Genetics, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Anu Loukola
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - Sharon M Lutz
- Department of Biostatistics and Bioinformatics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Pamela A F Madden
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO, USA
| | - Nicholas G Martin
- Genetic Epidemiology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Matt McGue
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Matthew B McQueen
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - Sarah E Medland
- Psychiatric Genetics, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | | | - Karen L Mohlke
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Jonas B Nielsen
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Yukinori Okada
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Yokohama City, Japan
- Department of Statistical Genetics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Ulrike Peters
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Department of Epidemiology, University of Washington, Seattle, WA, USA
| | - Tinca J C Polderman
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Danielle Posthuma
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
- Department of Clinical Genetics, VU Medical Centre Amsterdam, Amsterdam, the Netherlands
| | - Alexander P Reiner
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Department of Epidemiology, University of Washington, Seattle, WA, USA
| | - John P Rice
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA
| | - Eric Rimm
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
- Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Richard J Rose
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | | | - Michael C Stallings
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, CO, USA
| | - Alena Stančáková
- Department of Internal Medicine, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | | | - Khanh K Thai
- Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA
| | - Hilary A Tindle
- Department of Medicine, Vanderbilt University, Nashville, TN, USA
| | | | - Tamara L Wall
- Department of Psychiatry, University of California, San Diego, San Diego, CA, USA
| | - David R Weir
- Survey Research Center, Institute for Social Research, University of Michigan, Ann Arbor, MI, USA
| | - Constance Weisner
- Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA
| | - John B Whitfield
- Genetic Epidemiology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | | | - Jie Yin
- Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA
| | - Luisa Zuccolo
- Department of Population Health Science, Bristol Medical School, Oakfield Grove, Bristol, UK
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
| | - Laura J Bierut
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA
| | - Kristian Hveem
- K.G. Jebsen Center for Genetic Epidemiology, Department of Public Health and Nursing, Norwegian University of Science and Technology, Trondheim, Norway
- HUNT Research Centre, Department of Public Health and Nursing, Norwegian University of Science and Technology, Levanger, Norway
- Department of Medicine, Levanger Hospital, Nord-Trøndelag Hospital Trust, Levanger, Norway
| | - James J Lee
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA
| | - Marcus R Munafò
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
- UK Centre for Tobacco and Alcohol Studies, School of Psychological Science, University of Bristol, Bristol, UK
| | - Nancy L Saccone
- Department of Genetics, Washington University School of Medicine, St. Louis, MO, USA
| | - Cristen J Willer
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Marilyn C Cornelis
- Department of Preventative Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Sean P David
- Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | | | - Eric Jorgenson
- Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA
| | - Jaakko Kaprio
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
- Department of Public Health, University of Helsinki, Helsinki, Finland
| | - Jerry A Stitzel
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, USA
| | - Kari Stefansson
- deCODE Genetics/Amgen, Inc., Reykjavik, Iceland
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
| | | | - Gonçalo Abecasis
- Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Dajiang J Liu
- Department of Public Health Sciences, College of Medicine, Pennsylvania State University, Hershey, PA, USA.
- Institute of Personalized Medicine, College of Medicine, Pennsylvania State University, Hershey, PA, USA.
| | - Scott Vrieze
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, MN, USA.
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8
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Abstract
Information contained in the structure of extracellular ligands is transmitted across the cell membrane through allosterically induced changes in G protein-coupled receptor (GPCR) conformation that occur upon ligand binding. These changes, in turn, are imprinted upon intracellular effectors like arrestins and help determine which of its many functions are performed. Intramolecular fluorescein arsenical hairpin (FlAsH) bioluminescence resonance energy transfer (BRET), in which both the fluorescence donor and acceptor are contained within the same protein, can be used to report on activation-induced changes in protein conformation. Here, we describe a method using a series of Rluc-arrestin3-FlAsH-BRET biosensors to measure stimulus-induced changes in arrestin conformation in live cells. Each Rluc-arrestin3-FlAsH-BRET construct contains an N-terminal Renilla luciferase fluorescence donor that excites a fluorescent arsenical targeted to a different position within the protein by mutational insertion of a tetracysteine tag motif. Changes in net BRET upon GPCR stimulation can thus be viewed from multiple vantage points within the protein and used to develop an arrestin3 "conformational signature" that is receptor- and ligand-specific. This method can be used to determine how differences in GPCR and ligand structure influence information transfer across the plasma membrane and to classify GPCRs and/or ligands based on their capacity to induce different arrestin3 activation modes.
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9
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TERUNUMA M. Diversity of structure and function of GABA B receptors: a complexity of GABA B-mediated signaling. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2018; 94:390-411. [PMID: 30541966 PMCID: PMC6374141 DOI: 10.2183/pjab.94.026] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Accepted: 10/09/2018] [Indexed: 05/24/2023]
Abstract
γ-aminobutyric acid type B (GABAB) receptors are broadly expressed in the nervous system and play an important role in neuronal excitability. GABAB receptors are G protein-coupled receptors that mediate slow and prolonged inhibitory action, via activation of Gαi/o-type proteins. GABAB receptors mediate their inhibitory action through activating inwardly rectifying K+ channels, inactivating voltage-gated Ca2+ channels, and inhibiting adenylate cyclase. Functional GABAB receptors are obligate heterodimers formed by the co-assembly of R1 and R2 subunits. It is well established that GABAB receptors interact not only with G proteins and effectors but also with various proteins. This review summarizes the structure, subunit isoforms, and function of GABAB receptors, and discusses the complexity of GABAB receptors, including how receptors are localized in specific subcellular compartments, the mechanism regulating cell surface expression and mobility of the receptors, and the diversity of receptor signaling through receptor crosstalk and interacting proteins.
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Affiliation(s)
- Miho TERUNUMA
- Division of Oral Biochemistry, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
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10
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Pin JP, Bettler B. Organization and functions of mGlu and GABAB receptor complexes. Nature 2016; 540:60-68. [DOI: 10.1038/nature20566] [Citation(s) in RCA: 155] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 10/21/2016] [Indexed: 02/08/2023]
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11
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Lahaie N, Kralikova M, Prézeau L, Blahos J, Bouvier M. Post-endocytotic Deubiquitination and Degradation of the Metabotropic γ-Aminobutyric Acid Receptor by the Ubiquitin-specific Protease 14. J Biol Chem 2016; 291:7156-70. [PMID: 26817839 DOI: 10.1074/jbc.m115.686907] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Indexed: 02/01/2023] Open
Abstract
Mechanisms controlling the metabotropic γ-aminobutyric acid receptor (GABAB) cell surface stability are still poorly understood. In contrast with many other G protein-coupled receptors (GPCR), it is not subject to agonist-promoted internalization, but is constitutively internalized and rapidly down-regulated. In search of novel interacting proteins regulating receptor fate, we report that the ubiquitin-specific protease 14 (USP14) interacts with the GABAB(1b)subunit's second intracellular loop. Probing the receptor for ubiquitination using bioluminescence resonance energy transfer (BRET), we detected a constitutive and phorbol 12-myristate 13-acetate (PMA)-induced ubiquitination of the receptor at the cell surface. PMA also increased internalization and accelerated receptor degradation. Overexpression of USP14 decreased ubiquitination while treatment with a small molecule inhibitor of the deubiquitinase (IU1) increased receptor ubiquitination. Treatment with the internalization inhibitor Dynasore blunted both USP14 and IU1 effects on the receptor ubiquitination state, suggesting a post-endocytic site of action. Overexpression of USP14 also led to an accelerated degradation of GABABin a catalytically independent fashion. We thus propose a model whereby cell surface ubiquitination precedes endocytosis, after which USP14 acts as an ubiquitin-binding protein that targets the ubiquitinated receptor to lysosomal degradation and promotes its deubiquitination.
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Affiliation(s)
- Nicolas Lahaie
- From the Department of Biochemistry and Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec H3T 1J4, Canada
| | - Michaela Kralikova
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, 14220 Prague 4, Czech Republic, and
| | - Laurent Prézeau
- Institut de Génomique Fonctionnelle, Université de Montpellier 1 and 2, 34090 Montpellier, France
| | - Jaroslav Blahos
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, 14220 Prague 4, Czech Republic, and
| | - Michel Bouvier
- From the Department of Biochemistry and Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec H3T 1J4, Canada,
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12
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Jean-Charles PY, Snyder JC, Shenoy SK. Chapter One - Ubiquitination and Deubiquitination of G Protein-Coupled Receptors. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:1-55. [PMID: 27378754 DOI: 10.1016/bs.pmbts.2016.05.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The seven-transmembrane containing G protein-coupled receptors (GPCRs) constitute the largest family of cell-surface receptors. Transmembrane signaling by GPCRs is fundamental to many aspects of physiology including vision, olfaction, cardiovascular, and reproductive functions as well as pain, behavior and psychomotor responses. The duration and magnitude of signal transduction is tightly controlled by a series of coordinated trafficking events that regulate the cell-surface expression of GPCRs at the plasma membrane. Moreover, the intracellular trafficking profiles of GPCRs can correlate with the signaling efficacy and efficiency triggered by the extracellular stimuli that activate GPCRs. Of the various molecular mechanisms that impart selectivity, sensitivity and strength of transmembrane signaling, ubiquitination of the receptor protein plays an important role because it defines both trafficking and signaling properties of the activated GPCR. Ubiquitination of proteins was originally discovered in the context of lysosome-independent degradation of cytosolic proteins by the 26S proteasome; however a large body of work suggests that ubiquitination also orchestrates the downregulation of membrane proteins in the lysosomes. In the case of GPCRs, such ubiquitin-mediated lysosomal degradation engenders long-term desensitization of transmembrane signaling. To date about 40 GPCRs are known to be ubiquitinated. For many GPCRs, ubiquitination plays a major role in postendocytic trafficking and sorting to the lysosomes. This chapter will focus on the patterns and functional roles of GPCR ubiquitination, and will describe various molecular mechanisms involved in GPCR ubiquitination.
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Affiliation(s)
- P-Y Jean-Charles
- Department of Medicine (Cardiology), Duke University Medical Center, Durham, NC, United States
| | - J C Snyder
- Department of Cell Biology, Duke University Medical Center, Durham, NC, United States
| | - S K Shenoy
- Department of Medicine (Cardiology), Duke University Medical Center, Durham, NC, United States; Department of Cell Biology, Duke University Medical Center, Durham, NC, United States.
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13
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Butt S, Ashraf F, Porter LA, Zhang H. Sodium salicylate reduces the level of GABAB receptors in the rat's inferior colliculus. Neuroscience 2015; 316:41-52. [PMID: 26705739 DOI: 10.1016/j.neuroscience.2015.12.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 12/08/2015] [Accepted: 12/11/2015] [Indexed: 10/22/2022]
Abstract
Previous studies have indicated that sodium salicylate (SS) can cause hearing abnormalities through affecting the central auditory system. In order to understand central effects of the drug, we examined how a single intraperitoneal injection of the drug changed the level of subunits of the type-B γ-aminobutyric acid receptor (GABAB receptor) in the rat's inferior colliculus (IC). Immunohistochemical and western blotting experiments were conducted three hours following a drug injection, as previous studies indicated that a tinnitus-like behavior could be reliably induced in rats within this time period. Results revealed that both subunits of the receptor, GABABR1 and GABABR2, reduced their level over the entire area of the IC. Such a reduction was observed in both cell body and neuropil regions. In contrast, no changes were observed in other brain structures such as the cerebellum. Thus, a coincidence existed between a structure-specific reduction in the level of GABAB receptor subunits in the IC and the presence of a tinnitus-like behavior. This coincidence likely suggests that a reduction in the level of GABAB receptor subunits was involved in the generation of a tinnitus-like behavior and/or used by the nervous system to restore normal hearing following application of SS.
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Affiliation(s)
- S Butt
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada
| | - F Ashraf
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada
| | - L A Porter
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada
| | - H Zhang
- Department of Biological Sciences, University of Windsor, Windsor, ON, Canada.
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14
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Maurin T, Melko M, Abekhoukh S, Khalfallah O, Davidovic L, Jarjat M, D'Antoni S, Catania MV, Moine H, Bechara E, Bardoni B. The FMRP/GRK4 mRNA interaction uncovers a new mode of binding of the Fragile X mental retardation protein in cerebellum. Nucleic Acids Res 2015; 43:8540-50. [PMID: 26250109 PMCID: PMC4787806 DOI: 10.1093/nar/gkv801] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 07/28/2015] [Indexed: 11/13/2022] Open
Abstract
Fragile X syndrome (FXS), the most common form of inherited intellectual disability, is caused by the silencing of the FMR1 gene encoding an RNA-binding protein (FMRP) mainly involved in translational control. We characterized the interaction between FMRP and the mRNA of GRK4, a member of the guanine nucleotide-binding protein (G protein)-coupled receptor kinase super-family, both in vitro and in vivo. While the mRNA level of GRK4 is unchanged in the absence or in the presence of FMRP in different regions of the brain, GRK4 protein level is increased in Fmr1-null cerebellum, suggesting that FMRP negatively modulates the expression of GRK4 at the translational level in this brain region. The C-terminal region of FMRP interacts with a domain of GRK4 mRNA, that we called G4RIF, that is folded in four stem loops. The SL1 stem loop of G4RIF is protected by FMRP and is part of the S1/S2 sub-domain that directs translation repression of a reporter mRNA by FMRP. These data confirm the role of the G4RIF/FMRP complex in translational regulation. Considering the role of GRK4 in GABAB receptors desensitization, our results suggest that an increased GRK4 levels in FXS might contribute to cerebellum-dependent phenotypes through a deregulated desensitization of GABAB receptors.
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Affiliation(s)
- Thomas Maurin
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
| | - Mireille Melko
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
| | - Sabiha Abekhoukh
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
| | - Olfa Khalfallah
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
| | - Laetitia Davidovic
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
| | - Marielle Jarjat
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
| | - Simona D'Antoni
- Institute of Neurological Sciences, The National Research Council of Italy, 95126 Catania, Italy
| | - Maria Vincenza Catania
- Institute of Neurological Sciences, The National Research Council of Italy, 95126 Catania, Italy IRCCS Oasi Maria SS, 94018 Troina (EN), Italy
| | - Hervé Moine
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), CNRS, UMR7104, Inserm U596, Collège de France, Strasbourg University, 67400 Illkirch-Graffenstaden, France
| | - Elias Bechara
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
| | - Barbara Bardoni
- CNRS UMR 7275, Institute of Molecular and Cellular Pharmacology, 06560 Valbonne Sophia-Antipolis, France University of Nice Sophia-Antipolis, 06103 Nice, FRANCE CNRS LIA 'Neogenex', 06560 Valbonne Sophia-Antipolis, France
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15
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Allen SJ, Parthasarathy G, Darke PL, Diehl RE, Ford RE, Hall DL, Johnson SA, Reid JC, Rickert KW, Shipman JM, Soisson SM, Zuck P, Munshi SK, Lumb KJ. Structure and Function of the Hypertension Variant A486V of G Protein-coupled Receptor Kinase 4. J Biol Chem 2015; 290:20360-73. [PMID: 26134571 DOI: 10.1074/jbc.m115.648907] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Indexed: 11/06/2022] Open
Abstract
G-protein-coupled receptor (GPCR) kinases (GRKs) bind to and phosphorylate GPCRs, initiating the process of GPCR desensitization and internalization. GRK4 is implicated in the regulation of blood pressure, and three GRK4 polymorphisms (R65L, A142V, and A486V) are associated with hypertension. Here, we describe the 2.6 Å structure of human GRK4α A486V crystallized in the presence of 5'-adenylyl β,γ-imidodiphosphate. The structure of GRK4α is similar to other GRKs, although slight differences exist within the RGS homology (RH) bundle subdomain, substrate-binding site, and kinase C-tail. The RH bundle subdomain and kinase C-terminal lobe form a strikingly acidic surface, whereas the kinase N-terminal lobe and RH terminal subdomain surfaces are much more basic. In this respect, GRK4α is more similar to GRK2 than GRK6. A fully ordered kinase C-tail reveals interactions linking the C-tail with important determinants of kinase activity, including the αB helix, αD helix, and the P-loop. Autophosphorylation of wild-type GRK4α is required for full kinase activity, as indicated by a lag in phosphorylation of a peptide from the dopamine D1 receptor without ATP preincubation. In contrast, this lag is not observed in GRK4α A486V. Phosphopeptide mapping by mass spectrometry indicates an increased rate of autophosphorylation of a number of residues in GRK4α A486V relative to wild-type GRK4α, including Ser-485 in the kinase C-tail.
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Affiliation(s)
- Samantha J Allen
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Gopal Parthasarathy
- Structural Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486
| | - Paul L Darke
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Ronald E Diehl
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Rachael E Ford
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Dawn L Hall
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Scott A Johnson
- Structural Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486
| | - John C Reid
- Structural Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486
| | - Keith W Rickert
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Jennifer M Shipman
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Stephen M Soisson
- Structural Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486
| | - Paul Zuck
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Sanjeev K Munshi
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
| | - Kevin J Lumb
- From Screening and Protein Sciences, Merck Research Laboratories, North Wales, Pennsylvania 19454 and
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16
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Zhang Z, Zhang W, Huang S, Sun Q, Wang Y, Hu Y, Sun N, Zhang Y, Jiang Z, Minato N, Pin JP, Su L, Liu J. GABAB receptor promotes its own surface expression by recruiting a Rap1-dependent signaling cascade. J Cell Sci 2015; 128:2302-13. [DOI: 10.1242/jcs.167056] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 05/05/2015] [Indexed: 12/11/2022] Open
Abstract
ABSTRACT
G-protein-coupled receptors (GPCRs) are key players in cell signaling, and their cell surface expression is tightly regulated. For many GPCRs such as β2-AR (β2-adrenergic receptor), receptor activation leads to downregulation of receptor surface expression, a phenomenon that has been extensively characterized. By contrast, some other GPCRs, such as GABAB receptor, remain relatively stable at the cell surface even after prolonged agonist treatment; however, the underlying mechanisms are unclear. Here, we identify the small GTPase Rap1 as a key regulator for promoting GABAB receptor surface expression. Agonist stimulation of GABAB receptor signals through Gαi/o to inhibit Rap1GAPII (also known as Rap1GAP1b, an isoform of Rap1GAP1), thereby activating Rap1 (which has two isoforms, Rap1a and Rap1b) in cultured cerebellar granule neurons (CGNs). The active form of Rap1 is then recruited to GABAB receptor through physical interactions in CGNs. This Rap1-dependent signaling cascade promotes GABAB receptor surface expression by stimulating receptor recycling. Our results uncover a new mechanism regulating GPCR surface expression and also provide a potential explanation for the slow, long-lasting inhibitory action of GABA neurotransmitter.
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Affiliation(s)
- Zongyong Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Wenhua Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Siluo Huang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qian Sun
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yunyun Wang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yongjian Hu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Ninghua Sun
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yilei Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhihua Jiang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Nagahiro Minato
- Department of Immunology and Cell Biology, Kyoto University, Kyoto 606-8501, Japan
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université Montpellier 1 et 2, Montpellier cedex 5 34094, France
| | - Li Su
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jianfeng Liu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
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17
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Role of post-translational modifications on structure, function and pharmacology of class C G protein-coupled receptors. Eur J Pharmacol 2015; 763:233-40. [PMID: 25981296 DOI: 10.1016/j.ejphar.2015.05.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 03/06/2015] [Accepted: 05/11/2015] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors are divided into three classes (A, B and C) based on homology of their seven transmembrane domains. Class C is the smallest class with 22 human receptor subtypes including eight metabotropic glutamate (mGlu1-8) receptors, two GABAB receptors (GABAB1 and GABAB2), three taste receptors (T1R1-3), one calcium-sensing (CaS) receptor, one GPCR, class C, group 6, subtype A (GPRC6) receptor, and seven orphan receptors. G protein-coupled receptors undergo a number of post-translational modifications, which regulate their structure, function and/or pharmacology. Here, we review the existence of post-translational modifications in class C G protein-coupled receptors and their regulatory roles, with particular focus on glycosylation, phosphorylation, ubiquitination, SUMOylation, disulphide bonding and lipidation.
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18
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Isovaline does not activate GABA(B) receptor-coupled potassium currents in GABA(B) expressing AtT-20 cells and cultured rat hippocampal neurons. PLoS One 2015; 10:e0118497. [PMID: 25706125 PMCID: PMC4337901 DOI: 10.1371/journal.pone.0118497] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 01/19/2015] [Indexed: 01/13/2023] Open
Abstract
Isovaline is a non-proteinogenic amino acid that has analgesic properties. R-isovaline is a proposed agonist of the γ-aminobutyric acid type B (GABAB) receptor in the thalamus and peripheral tissue. Interestingly, the responses to R-isovaline differ from those of the canonical GABAB receptor agonist R-baclofen, warranting further investigation. Using whole cell recording techniques we explored isovaline actions on GABAB receptors coupled to rectifying K+ channels in cells of recombinant and native receptor preparations. In AtT-20 cells transfected with GABAB receptor subunits, bath application of the GABAB receptor agonists, GABA (1 μM) and R-baclofen (5 μM) produced inwardly rectifying currents that reversed approximately at the calculated reversal potential for K+ R- isovaline (50 μM to 1 mM) and S-isovaline (500 μM) did not evoke a current. R-isovaline applied either extracellularly (250 μM) or intracellularly (10 μM) did not alter responses to GABA at 1 μM. Co-administration of R-isovaline (250 μM) with a low concentration (10 nM) of GABA did not result in a response. In cultured rat hippocampal neurons that natively express GABAB receptors, R-baclofen (5 μM) induced GABAB receptor-dependent inward currents. Under the same conditions R-isovaline (1 or 50 μM) did not evoke a current or significantly alter R-baclofen-induced effects. Therefore, R-isovaline does not interact with recombinant or native GABAB receptors to open K+ channels in these preparations.
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Tang J, Dong J, Yang L, Gao L, Zheng J. Paroxetine alleviates rat limb post-ischemia induced allodynia through GRK2 upregulation in superior cervical ganglia. Int J Clin Exp Med 2015; 8:2065-2076. [PMID: 25932137 PMCID: PMC4402784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 01/17/2015] [Indexed: 06/04/2023]
Abstract
Long-lasting neuroplastic changes induced by transient decrease in G protein-coupled receptor kinase 2 (GRK2) in nociceptors enhances and prolongs inflammatory hyperalgesia. Here, we investigated the effects of paroxetine (a selective serotonin reuptake inhibitor and GRK2 inhibitor) on GRK2 expression in superior cervical ganglion (SCG) in a rat model of complex regional pain syndrome type I (CRPS-I). After ischemia-reperfusion (I/R) injury, the ipsilateral 50% paw withdrawal thresholds (PWTs) to mechanical stimuli and the expression levels of GRK2 protein and mRNA in the ipsilateral SCGs all decreased significantly; the ipsilateral cold allodynia scores increased significantly. No significant differences were found in the contralateral side except GRK2 mRNA reduced significantly at day 2-day 9 after I/R injury, but still higher than those in ipsilateral SCGs. After paroxetine administration, the ipsilateral 50% PWTs at day 2, 7, 14, and 21 were significantly higher than those in control group; The GRK2 protein and mRNA levels in ipsilateral SCGs were also significantly up-regulated after day1; The ipsilateral cold allodynia scores were significantly reduced after day7. No significant differences were found in the contralateral 50% PWTs, cold allodynia scores, and GRK2 protein level except GRK2 mRNA levels increased significantly at day1-day7 after paroxetine administration. Therefore, a transient decrease of GRK2 expression in SCG neurons might be involved in the development and maintenance of allodynia in CRPS-I and paroxetine might alleviate this allodynia through GRK2 protein upregulation in SCGs.
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Affiliation(s)
- Jun Tang
- Department of Anesthesiology, Jinshan Hospital, Fudan UniversityShanghai, China
| | - Jing Dong
- Department of Anesthesiology, Shanghai First People’s Hospital, Shanghai Jiaotong University Affiliated Shanghai First People’s Hospital650 Xin Songjiang Road, Shanghai 201620, China
| | - Li Yang
- Department of Anesthesiology, Jinshan Hospital, Fudan UniversityShanghai, China
| | - Lingqi Gao
- Department of Anesthesiology, Shanghai First People’s Hospital, Shanghai Jiaotong University Affiliated Shanghai First People’s Hospital650 Xin Songjiang Road, Shanghai 201620, China
| | - Jijian Zheng
- Department of Anesthesiology, Shanghai First People’s Hospital, Shanghai Jiaotong University Affiliated Shanghai First People’s Hospital650 Xin Songjiang Road, Shanghai 201620, China
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20
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Hanack C, Moroni M, Lima WC, Wende H, Kirchner M, Adelfinger L, Schrenk-Siemens K, Tappe-Theodor A, Wetzel C, Kuich PH, Gassmann M, Roggenkamp D, Bettler B, Lewin GR, Selbach M, Siemens J. GABA blocks pathological but not acute TRPV1 pain signals. Cell 2015; 160:759-770. [PMID: 25679765 DOI: 10.1016/j.cell.2015.01.022] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 11/16/2014] [Accepted: 01/06/2015] [Indexed: 01/01/2023]
Abstract
Sensitization of the capsaicin receptor TRPV1 is central to the initiation of pathological forms of pain, and multiple signaling cascades are known to enhance TRPV1 activity under inflammatory conditions. How might detrimental escalation of TRPV1 activity be counteracted? Using a genetic-proteomic approach, we identify the GABAB1 receptor subunit as bona fide inhibitor of TRPV1 sensitization in the context of diverse inflammatory settings. We find that the endogenous GABAB agonist, GABA, is released from nociceptive nerve terminals, suggesting an autocrine feedback mechanism limiting TRPV1 sensitization. The effect of GABAB on TRPV1 is independent of canonical G protein signaling and rather relies on close juxtaposition of the GABAB1 receptor subunit and TRPV1. Activating the GABAB1 receptor subunit does not attenuate normal functioning of the capsaicin receptor but exclusively reverts its sensitized state. Thus, harnessing this mechanism for anti-pain therapy may prevent adverse effects associated with currently available TRPV1 blockers.
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Affiliation(s)
- Christina Hanack
- Department of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany; Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Mirko Moroni
- Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Wanessa C Lima
- Department of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Hagen Wende
- Department of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Marieluise Kirchner
- Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Lisa Adelfinger
- Department of Biomedicine, University of Basel, CH-4056 Basel, Switzerland
| | - Katrin Schrenk-Siemens
- Department of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Anke Tappe-Theodor
- Department of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Christiane Wetzel
- Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - P Henning Kuich
- Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Martin Gassmann
- Department of Biomedicine, University of Basel, CH-4056 Basel, Switzerland
| | - Dennis Roggenkamp
- Beiersdorf AG, Research & Development, Unnastrasse 48, 20245 Hamburg, Germany
| | - Bernhard Bettler
- Department of Biomedicine, University of Basel, CH-4056 Basel, Switzerland
| | - Gary R Lewin
- Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Matthias Selbach
- Max Delbrück Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Jan Siemens
- Department of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany.
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21
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Montpas N, Cabana J, St-Onge G, Gravel S, Morin G, Kuroyanagi T, Lavigne P, Fujii N, Oishi S, Heveker N. Mode of binding of the cyclic agonist peptide TC14012 to CXCR7: identification of receptor and compound determinants. Biochemistry 2015; 54:1505-15. [PMID: 25669416 DOI: 10.1021/bi501526s] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The chemokine receptor CXCR7 is an atypical CXCL12 receptor that, as opposed to the classical CXCL12 receptor CXCR4, signals preferentially via the β-arrestin pathway and does not mediate chemotaxis. We previously reported that the cyclic peptide TC14012, a potent CXCR4 antagonist, also engaged CXCR7, albeit with lower potency. Surprisingly, the compound activated the CXCR7-arrestin pathway. The reason underlying the opposite effects of TC14012 on CXCR4 and CXCR7, and the mode of binding of TC14012 to CXCR7, remained unclear. The mode of binding of TC14012 to CXCR4 is known from cocrystallization of its analogue CVX15 with CXCR4. We here report the the mode of binding of TC14012 to CXCR7 by combining the use of compound analogues, receptor mutants, and molecular modeling. We find that the mode of binding of TC14012 to CXCR7 is indeed similar to that of CVX15 to CXCR4, with compound positions Arg2 and Arg14 engaging CXCR7 key residues D179(4.60) (on the tip of transmembrane domain 4) and D275(6.58) (on the tip of transmembrane domain 6), respectively. Interestingly, the TC14012 parent compound T140 is not a CXCR7 agonist, because of conformational constraints in its pharmacophore, which in TC14012 are relieved through C-terminal amidation. However, an engineered salt bridge between the CXCR7 ECL2 substitution R197D and compound residue Arg1 permitted T140 agonism by repositioning the compound in the binding pocket. In conclusion, our results show that the opposite effect of TC14012 on CXCR4 and CXCR7 is not explained by different binding modes. Rather, engagement of the interface between transmembrane domains and extracellular loops readily triggers CXCR7, but not CXCR4, activation.
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Affiliation(s)
- Nicolas Montpas
- Research Centre, Sainte-Justine Hospital, University of Montreal , Montréal H3T 1C5, Canada
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22
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Raveh A, Turecek R, Bettler B. Mechanisms of fast desensitization of GABA(B) receptor-gated currents. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2015; 73:145-65. [PMID: 25637440 DOI: 10.1016/bs.apha.2014.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABA(B) receptors (GABA(B)Rs) regulate the excitability of most neurons in the central nervous system by modulating the activity of enzymes and ion channels. In the sustained presence of the neurotransmitter γ-aminobutyric acid, GABA(B)Rs exhibit a time-dependent decrease in the receptor response-a phenomenon referred to as homologous desensitization. Desensitization prevents excessive receptor influences on neuronal activity. Much work focused on the mechanisms of GABA(B)R desensitization that operate at the receptor and control receptor expression at the plasma membrane. Over the past few years, it became apparent that GABA(B)Rs additionally evolved mechanisms for faster desensitization. These mechanisms operate at the G protein rather than at the receptor and inhibit G protein signaling within seconds of agonist exposure. The mechanisms for fast desensitization are ideally suited to regulate receptor-activated ion channel responses, which influence neuronal activity on a faster timescale than effector enzymes. Here, we provide an update on the mechanisms for fast desensitization of GABA(B)R responses and discuss physiological and pathophysiological implications.
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Affiliation(s)
- Adi Raveh
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland
| | - Rostislav Turecek
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland; Department of Auditory Neuroscience, Institute of Experimental Medicine, ASCR, Prague, Czech Republic
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland.
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23
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Xu C, Zhang W, Rondard P, Pin JP, Liu J. Complex GABAB receptor complexes: how to generate multiple functionally distinct units from a single receptor. Front Pharmacol 2014; 5:12. [PMID: 24575041 PMCID: PMC3920572 DOI: 10.3389/fphar.2014.00012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 01/22/2014] [Indexed: 01/05/2023] Open
Abstract
The main inhibitory neurotransmitter, GABA, acts on both ligand-gated and G protein-coupled receptors, the GABAA/C and GABAB receptors, respectively. The later play important roles in modulating many synapses, both at the pre- and post-synaptic levels, and are then still considered as interesting targets to treat a number of brain diseases, including addiction. For many years, several subtypes of GABAB receptors were expected, but cloning revealed only two genes that work in concert to generate a single type of GABAB receptor composed of two subunits. Here we will show that the signaling complexity of this unit receptor type can be largely increased through various ways, including receptor stoichiometry, subunit isoforms, cell-surface expression and localization, crosstalk with other receptors, or interacting proteins. These recent data revealed how complexity of a receptor unit can be increased, observation that certainly are not unique to the GABAB receptor.
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Affiliation(s)
- Chanjuan Xu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology Wuhan, China
| | - Wenhua Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology Wuhan, China
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, Universités de Montpellier I & II Montpellier, France
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, Universités de Montpellier I & II Montpellier, France
| | - Jianfeng Liu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology Wuhan, China
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24
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Sauvageau E, Rochdi MD, Oueslati M, Hamdan FF, Percherancier Y, Simpson JC, Pepperkok R, Bouvier M. CNIH4 interacts with newly synthesized GPCR and controls their export from the endoplasmic reticulum. Traffic 2014; 15:383-400. [PMID: 24405750 DOI: 10.1111/tra.12148] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 12/24/2013] [Accepted: 01/09/2013] [Indexed: 01/02/2023]
Abstract
The molecular mechanisms regulating G protein-coupled receptors (GPCRs) trafficking from their site of synthesis in the endoplasmic reticulum (ER) to their site of function (the cell surface) remain poorly characterized. Using a bioluminescence resonance energy transfer-based proteomic screen, we identified a novel GPCR-interacting protein; the human cornichon homologue 4 (CNIH4). This previously uncharacterized protein is localized in the early secretory pathway where it interacts with members of the 3 family of GPCRs. Both overexpression and knockdown expression of CNIH4 caused the intracellular retention of GPCRs, indicating that this ER-resident protein plays an important role in GPCR export. Overexpression of CNIH4 at low levels rescued the maturation and cell surface expression of an intracellularly retained mutant form of the β2-adrenergic receptor, further demonstrating a positive role of CNIH4 in GPCR trafficking. Taken with the co-immunoprecipitation of CNIH4 with Sec23 and Sec24, components of the COPII coat complex responsible for ER export, these data suggest that CNIH4 acts as a cargo-sorting receptor, recruiting GPCRs into COPII vesicles.
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Affiliation(s)
- Etienne Sauvageau
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Canada; Department of Biochemistry, Université de Montréal, Montréal, Canada
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25
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Ivankova K, Turecek R, Fritzius T, Seddik R, Prezeau L, Comps-Agrar L, Pin JP, Fakler B, Besseyrias V, Gassmann M, Bettler B. Up-regulation of GABA(B) receptor signaling by constitutive assembly with the K+ channel tetramerization domain-containing protein 12 (KCTD12). J Biol Chem 2013; 288:24848-56. [PMID: 23843457 PMCID: PMC3750179 DOI: 10.1074/jbc.m113.476770] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
GABAB receptors are the G-protein coupled receptors (GPCRs) for GABA, the main inhibitory neurotransmitter in the central nervous system. Native GABAB receptors comprise principle and auxiliary subunits that regulate receptor properties in distinct ways. The principle subunits GABAB1a, GABAB1b, and GABAB2 form fully functional heteromeric GABAB(1a,2) and GABAB(1b,2) receptors. Principal subunits regulate forward trafficking of the receptors from the endoplasmic reticulum to the plasma membrane and control receptor distribution to axons and dendrites. The auxiliary subunits KCTD8, -12, -12b, and -16 are cytosolic proteins that influence agonist potency and G-protein signaling of GABAB(1a,2) and GABAB(1b,2) receptors. Here, we used transfected cells to study assembly, surface trafficking, and internalization of GABAB receptors in the presence of the KCTD12 subunit. Using bimolecular fluorescence complementation and metabolic labeling, we show that GABAB receptors associate with KCTD12 while they reside in the endoplasmic reticulum. Glycosylation experiments support that association with KCTD12 does not influence maturation of the receptor complex. Immunoprecipitation and bioluminescence resonance energy transfer experiments demonstrate that KCTD12 remains associated with the receptor during receptor activity and receptor internalization from the cell surface. We further show that KCTD12 reduces constitutive receptor internalization and thereby increases the magnitude of receptor signaling at the cell surface. Accordingly, knock-out or knockdown of KCTD12 in cultured hippocampal neurons reduces the magnitude of the GABAB receptor-mediated K+ current response. In summary, our experiments support that the up-regulation of functional GABAB receptors at the neuronal plasma membrane is an additional physiological role of the auxiliary subunit KCTD12.
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Affiliation(s)
- Klara Ivankova
- Department of Biomedicine, University of Basel, CH-4056 Basel, Switzerland
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26
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Zhang Z, Xue L, Guo H, Li Y, Ding H, Huang S. Phosphorylation-independent desensitization of metabotropic glutamate receptor 5 by G protein-coupled receptor kinase 2 in HEK 293 cells. Mol Biol 2013. [DOI: 10.1134/s0026893313010160] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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27
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Berthouze-Duquesnes M, Lucas A, Saulière A, Sin YY, Laurent AC, Galés C, Baillie G, Lezoualc'h F. Specific interactions between Epac1, β-arrestin2 and PDE4D5 regulate β-adrenergic receptor subtype differential effects on cardiac hypertrophic signaling. Cell Signal 2012; 25:970-80. [PMID: 23266473 DOI: 10.1016/j.cellsig.2012.12.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 12/17/2012] [Indexed: 12/24/2022]
Abstract
β1 and β2 adrenergic receptors (βARs) are highly homologous but fulfill distinct physiological and pathophysiological roles. Here we show that both βAR subtypes activate the cAMP-binding protein Epac1, but they differentially affect its signaling. The distinct effects of βARs on Epac1 downstream effectors, the small G proteins Rap1 and H-Ras, involve different modes of interaction of Epac1 with the scaffolding protein β-arrestin2 and the cAMP-specific phosphodiesterase (PDE) variant PDE4D5. We found that β-arrestin2 acts as a scaffold for Epac1 and is necessary for Epac1 coupling to H-Ras. Accordingly, knockdown of β-arrestin2 prevented Epac1-induced histone deacetylase 4 (HDAC4) nuclear export and cardiac myocyte hypertrophy upon β1AR activation. Moreover, Epac1 competed with PDE4D5 for interaction with β-arrestin2 following β2AR activation. Dissociation of the PDE4D5-β-arrestin2 complex allowed the recruitment of Epac1 to β2AR and induced a switch from β2AR non-hypertrophic signaling to a β1AR-like pro-hypertrophic signaling cascade. These findings have implications for understanding the molecular basis of cardiac myocyte remodeling and other cellular processes in which βAR subtypes exert opposing effects.
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MESH Headings
- Animals
- Arrestins/antagonists & inhibitors
- Arrestins/genetics
- Arrestins/metabolism
- Cardiomegaly/metabolism
- Cardiomegaly/pathology
- Cells, Cultured
- Cyclic Nucleotide Phosphodiesterases, Type 3/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 4
- Fluorescence Resonance Energy Transfer
- Guanine Nucleotide Exchange Factors/metabolism
- HEK293 Cells
- Humans
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/metabolism
- Protein Interaction Maps
- Proto-Oncogene Proteins p21(ras)/metabolism
- RNA Interference
- RNA, Small Interfering/metabolism
- Rats
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-2/metabolism
- Signal Transduction
- beta-Arrestins
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Affiliation(s)
- Magali Berthouze-Duquesnes
- Inserm, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, 31432 Toulouse Cedex 04, France
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28
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Nimitvilai S, Arora DS, McElvain MA, Brodie MS. Reversal of inhibition of putative dopaminergic neurons of the ventral tegmental area: interaction of GABA(B) and D2 receptors. Neuroscience 2012; 226:29-39. [PMID: 22986166 PMCID: PMC3490029 DOI: 10.1016/j.neuroscience.2012.08.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 08/21/2012] [Accepted: 08/23/2012] [Indexed: 10/27/2022]
Abstract
Neurons of the ventral tegmental area (VTA) are critical in the rewarding and reinforcing properties of drugs of abuse. Desensitization of VTA neurons to moderate extracellular concentrations of dopamine (DA) is dependent on protein kinase C (PKC) and intracellular calcium levels. This desensitization is called DA inhibition reversal, as it requires concurrent activation of D2 and D1-like receptors; activation of D2 receptors alone does not result in desensitization. Activation of other G-protein-linked receptors can substitute for D1 activation. Like D2 receptors, GABA(B) receptors in the VTA are coupled to G-protein-linked potassium channels. In the present study, we examined interactions between a GABA(B) agonist, baclofen, and dopamine agonists, dopamine and quinpirole, to determine whether there was some interaction in the processes of desensitization of GABA(B) and D2 responses. Long-duration administration of baclofen alone produced reversal of the baclofen-induced inhibition indicative of desensitization, and this desensitization persisted for at least 60 min after baclofen washout. Desensitization to baclofen was dependent on PKC. Dopamine inhibition was reduced for 30 min after baclofen-induced desensitization and conversely, the magnitude of baclofen inhibition was reduced for 30 min by long-duration application of dopamine, but not quinpirole. These results indicate that D2 and GABA(B) receptors share some PKC-dependent mechanisms of receptor desensitization.
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Affiliation(s)
- S Nimitvilai
- Department of Physiology and Biophysics, University of Illinois at Chicago, 835 S. Wolcott, Room E-202, M/C 901, Chicago, IL 60612-7342, USA
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29
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Seddik R, Jungblut SP, Silander OK, Rajalu M, Fritzius T, Besseyrias V, Jacquier V, Fakler B, Gassmann M, Bettler B. Opposite effects of KCTD subunit domains on GABA(B) receptor-mediated desensitization. J Biol Chem 2012; 287:39869-77. [PMID: 23035119 DOI: 10.1074/jbc.m112.412767] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GABA(B) receptors assemble from principle and auxiliary subunits. The principle subunits GABA(B1) and GABA(B2) form functional heteromeric GABA(B(1,2)) receptors that associate with homotetramers of auxiliary KCTD8, -12, -12b, or -16 (named after their K(+) channel tetramerization domain) subunits. These auxiliary subunits constitute receptor subtypes with distinct functional properties. KCTD12 and -12b generate desensitizing receptor responses while KCTD8 and -16 generate largely non-desensitizing receptor responses. The structural elements of the KCTDs underlying these differences in desensitization are unknown. KCTDs are modular proteins comprising a T1 tetramerization domain, which binds to GABA(B2), and a H1 homology domain. KCTD8 and -16 contain an additional C-terminal H2 homology domain that is not sequence-related to the H1 domains. No functions are known for the H1 and H2 domains. Here we addressed which domains and sequence motifs in KCTD proteins regulate desensitization of the receptor response. We found that the H1 domains in KCTD12 and -12b mediate desensitization through a particular sequence motif, T/NFLEQ, which is not present in the H1 domains of KCTD8 and -16. In addition, the H2 domains in KCTD8 and -16 inhibit desensitization when expressed C-terminal to the H1 domains but not when expressed as a separate protein in trans. Intriguingly, the inhibitory effect of the H2 domain is sequence-independent, suggesting that the H2 domain sterically hinders desensitization by the H1 domain. Evolutionary analysis supports that KCTD12 and -12b evolved desensitizing properties by liberating their H1 domains from antagonistic H2 domains and acquisition of the T/NFLEQ motif.
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Affiliation(s)
- Riad Seddik
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
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30
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Heaney CF, Bolton MM, Murtishaw AS, Sabbagh JJ, Magcalas CM, Kinney JW. Baclofen administration alters fear extinction and GABAergic protein levels. Neurobiol Learn Mem 2012; 98:261-71. [PMID: 23010137 DOI: 10.1016/j.nlm.2012.09.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 09/06/2012] [Accepted: 09/13/2012] [Indexed: 12/14/2022]
Abstract
The investigation of GABAergic systems in learning and extinction has principally focused on ionotropic GABA(A) receptors. Less well characterized is the metabotropic GABA(B) receptor, which when activated, induces a more sustained inhibitory effect and has been implicated in regulating oscillatory activity. Few studies have been carried out utilizing GABA(B) ligands in learning, and investigations of GABA(B) in extinction have primarily focused on interactions with drugs of abuse. The current study examined changes in GABA(B) receptor function using the GABA(B) agonist baclofen (2 mg/mL) or the GABA(B) antagonist phaclofen (0.3 mg/mL) on trace cued and contextual fear conditioning and extinction. The compounds were either administered during training and throughout extinction in Experiment 1, or starting 24 h after training and throughout extinction in Experiment 2. All drugs were administered 1 mL/kg via intraperitoneal injection. These studies demonstrated that the administration of baclofen during training and extinction trials impaired animals' ability to extinguish the fear association to the CS, whereas the animals that were administered baclofen starting 24 h after training (Experiment 2) did display some extinction. Further, contextual fear extinction was impaired by baclofen in both experiments. Tissue analyses suggest the cued fear extinction deficit may be related to changes in the GABA(B2) receptor subunit in the amygdala. The data in the present investigation demonstrate that GABA(B) receptors play an important role in trace cued and contextual fear extinction, and may function differently than GABA(A) receptors in learning, memory, and extinction.
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Affiliation(s)
- Chelcie F Heaney
- Behavioral Neuroscience Laboratory, Department of Psychology, University of Nevada, Las Vegas, United States
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Moutin E, Raynaud F, Roger J, Pellegrino E, Homburger V, Bertaso F, Ollendorff V, Bockaert J, Fagni L, Perroy J. Dynamic remodeling of scaffold interactions in dendritic spines controls synaptic excitability. ACTA ACUST UNITED AC 2012; 198:251-63. [PMID: 22801779 PMCID: PMC3410417 DOI: 10.1083/jcb.201110101] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Synaptic activity–dependent remodeling of the glutamate receptor scaffold complex generates a negative feedback loop that limits further NMDA receptor activation. Scaffolding proteins interact with membrane receptors to control signaling pathways and cellular functions. However, the dynamics and specific roles of interactions between different components of scaffold complexes are poorly understood because of the dearth of methods available to monitor binding interactions. Using a unique combination of single-cell bioluminescence resonance energy transfer imaging in living neurons and electrophysiological recordings, in this paper, we depict the role of glutamate receptor scaffold complex remodeling in space and time to control synaptic transmission. Despite a broad colocalization of the proteins in neurons, we show that spine-confined assembly/disassembly of this scaffold complex, physiologically triggered by sustained activation of synaptic NMDA (N-methyl-d-aspartate) receptors, induces physical association between ionotropic (NMDA) and metabotropic (mGlu5a) synaptic glutamate receptors. This physical interaction results in an mGlu5a receptor–mediated inhibition of NMDA currents, providing an activity-dependent negative feedback loop on NMDA receptor activity. Such protein scaffold remodeling represents a form of homeostatic control of synaptic excitability.
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Affiliation(s)
- Enora Moutin
- Centre national de la recherche scientifique, UMR-5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, Cedex 16, France
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Impairment of GABAB receptor dimer by endogenous 14-3-3ζ in chronic pain conditions. EMBO J 2012; 31:3239-51. [PMID: 22692127 DOI: 10.1038/emboj.2012.161] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 05/07/2012] [Indexed: 11/09/2022] Open
Abstract
In the central nervous system, the inhibitory GABAB receptor is the archetype of heterodimeric G protein-coupled receptors (GPCRs). However, the regulation of GABAB dimerization, and more generally of GPCR oligomerization, remains largely unknown. We propose a novel mechanism for inhibition of GPCR activity through de-dimerization in pathological conditions. We show here that 14-3-3ζ, a GABAB1-binding protein, dissociates the GABAB heterodimer, resulting in the impairment of GABAB signalling in spinal neurons. In the dorsal spinal cord of neuropathic rats, 14-3-3ζ is overexpressed and weakens GABAB inhibition. Using anti-14-3-3ζ siRNA or competing peptides disrupts 14-3-3ζ/GABAB1 interaction and restores functional GABAB heterodimers in the dorsal horn. Importantly, both strategies greatly enhance the anti-nociceptive effect of intrathecal Baclofen in neuropathic rats. Taken together, our data provide the first example of endogenous regulation of a GPCR oligomeric state and demonstrate its functional impact on the pathophysiological process of neuropathic pain sensitization.
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GABAB receptors do not internalize after baclofen treatment, possibly due to a lack of β-arrestin association: Study with a real-time visualizing assay. Synapse 2012; 66:759-69. [DOI: 10.1002/syn.21565] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 04/11/2012] [Indexed: 11/07/2022]
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Benke D, Zemoura K, Maier PJ. Modulation of cell surface GABA(B) receptors by desensitization, trafficking and regulated degradation. World J Biol Chem 2012; 3:61-72. [PMID: 22558486 PMCID: PMC3342575 DOI: 10.4331/wjbc.v3.i4.61] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2011] [Revised: 12/08/2011] [Accepted: 12/15/2011] [Indexed: 02/05/2023] Open
Abstract
Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity. γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system, and mediates its effects via two classes of receptors: the GABA(A) and GABA(B) receptors. GABA(A) receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission. GABA(B) receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission. The extent of inhibitory neurotransmission is determined by a variety of factors, such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g., phosphorylation), as well as by the number of receptors present in the plasma membrane available for signal transduction. The level of GABA(B) receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation. In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA(B) receptors in the plasma membrane, and thereby signaling strength.
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Affiliation(s)
- Dietmar Benke
- Dietmar Benke, Khaled Zemoura, Patrick J Maier, Institute of Pharmacology and Toxicology, University of Zürich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Busnelli M, Saulière A, Manning M, Bouvier M, Galés C, Chini B. Functional selective oxytocin-derived agonists discriminate between individual G protein family subtypes. J Biol Chem 2011; 287:3617-29. [PMID: 22069312 DOI: 10.1074/jbc.m111.277178] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We used a bioluminescence resonance energy transfer biosensor to screen for functional selective ligands of the human oxytocin (OT) receptor. We demonstrated that OT promoted the direct engagement and activation of G(q) and all the G(i/o) subtypes at the OT receptor. Other peptidic analogues, chosen because of specific substitutions in key OT structural/functional residues, all showed biased activation of G protein subtypes. No ligand, except OT, activated G(oA) or G(oB), and, with only one exception, all of the peptides that activated G(q) also activated G(i2) and G(i3) but not G(i1), G(oA), or G(oB), indicating a strong bias toward these subunits. Two peptides (DNalOVT and atosiban) activated only G(i1) or G(i3), failed to recruit β-arrestins, and did not induce receptor internalization, providing the first clear examples of ligands differentiating individual G(i/o) family members. Both analogs inhibited cell proliferation, showing that a single G(i) subtype-mediated pathway is sufficient to prompt this physiological response. These analogs represent unique tools for examining the contribution of G(i/o) members in complex biological responses and open the way to the development of drugs with peculiar selectivity profiles. This is of particular relevance because OT has been shown to improve symptoms in neurodevelopmental and psychiatric disorders characterized by abnormal social behaviors, such as autism. Functional selective ligands, activating a specific G protein signaling pathway, may possess a higher efficacy and specificity on OT-based therapeutics.
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Affiliation(s)
- Marta Busnelli
- Consiglio Nazionale delle Ricerche Institute of Neuroscience, Via Vanvitelli 32, Milan 20143, Italy
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Hannan S, Wilkins ME, Dehghani-Tafti E, Thomas P, Baddeley SM, Smart TG. Gamma-aminobutyric acid type B (GABA(B)) receptor internalization is regulated by the R2 subunit. J Biol Chem 2011; 286:24324-35. [PMID: 21724853 PMCID: PMC3129212 DOI: 10.1074/jbc.m110.220814] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 04/20/2011] [Indexed: 01/04/2023] Open
Abstract
γ-Aminobutyric acid type B (GABA(B)) receptors are important for slow synaptic inhibition in the CNS. The efficacy of inhibition is directly related to the stability of cell surface receptors. For GABA(B) receptors, heterodimerization between R1 and R2 subunits is critical for cell surface expression and signaling, but how this determines the rate and extent of receptor internalization is unknown. Here, we insert a high affinity α-bungarotoxin binding site into the N terminus of the R2 subunit and reveal its dominant role in regulating the internalization of GABA(B) receptors in live cells. To simultaneously study R1a and R2 trafficking, a new α-bungarotoxin binding site-labeling technique was used, allowing α-bungarotoxin conjugated to different fluorophores to selectively label R1a and R2 subunits. This approach demonstrated that R1a and R2 are internalized as dimers. In heterologous expression systems and neurons, the rates and extents of internalization for R1aR2 heteromers and R2 homomers are similar, suggesting a regulatory role for R2 in determining cell surface receptor stability. The fast internalization rate of R1a, which has been engineered to exit the endoplasmic reticulum, was slowed to that of R2 by truncating the R1a C-terminal tail or by removing a dileucine motif in its coiled-coil domain. Slowing the rate of internalization by co-assembly with R2 represents a novel role for GPCR heterodimerization whereby R2 subunits, via their C terminus coiled-coil domain, mask a dileucine motif on R1a subunits to determine the surface stability of the GABA(B) receptor.
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Affiliation(s)
- Saad Hannan
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
- GlaxoSmithKline R&D, Medicines Research Centre, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Megan E. Wilkins
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
| | - Ebrahim Dehghani-Tafti
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
| | - Philip Thomas
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
| | - Stuart M. Baddeley
- GlaxoSmithKline R&D, Medicines Research Centre, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Trevor G. Smart
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
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Hannan S, Wilkins ME, Dehghani-Tafti E, Thomas P, Baddeley SM, Smart TG. γ-Aminobutyric Acid Type B (GABAB) Receptor Internalization Is Regulated by the R2 Subunit. J Biol Chem 2011. [DOI: 10.1074/jbc.m111.220814] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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Abstract
Dopamine is an important regulator of systemic blood pressure via multiple mechanisms. It affects fluid and electrolyte balance by its actions on renal hemodynamics and epithelial ion and water transport and by regulation of hormones and humoral agents. The kidney synthesizes dopamine from circulating or filtered L-DOPA independently from innervation. The major determinants of the renal tubular synthesis/release of dopamine are probably sodium intake and intracellular sodium. Dopamine exerts its actions via two families of cell surface receptors, D1-like receptors comprising D1R and D5R, and D2-like receptors comprising D2R, D3R, and D4R, and by interactions with other G protein-coupled receptors. D1-like receptors are linked to vasodilation, while the effect of D2-like receptors on the vasculature is variable and probably dependent upon the state of nerve activity. Dopamine secreted into the tubular lumen acts mainly via D1-like receptors in an autocrine/paracrine manner to regulate ion transport in the proximal and distal nephron. These effects are mediated mainly by tubular mechanisms and augmented by hemodynamic mechanisms. The natriuretic effect of D1-like receptors is caused by inhibition of ion transport in the apical and basolateral membranes. D2-like receptors participate in the inhibition of ion transport during conditions of euvolemia and moderate volume expansion. Dopamine also controls ion transport and blood pressure by regulating the production of reactive oxygen species and the inflammatory response. Essential hypertension is associated with abnormalities in dopamine production, receptor number, and/or posttranslational modification.
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Affiliation(s)
- Ines Armando
- Children’s National Medical Center—Center for Molecular Physiology Research, Washington, District of Columbia
| | - Van Anthony M. Villar
- Children’s National Medical Center—Center for Molecular Physiology Research, Washington, District of Columbia
| | - Pedro A. Jose
- Children’s National Medical Center—Center for Molecular Physiology Research, Washington, District of Columbia
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Breton B, Lagacé M, Bouvier M. Combining resonance energy transfer methods reveals a complex between the α 2A‐adrenergic receptor, Gα i1β 1γ 2, and GRK2. FASEB J 2010. [DOI: 10.1096/fj.10.164061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Billy Breton
- Department of BiochemistryInstitute for Research in Immunology and CancerGroupe de Recherche Universitaire sur le MédicamentUniversité de Montréal Montréal Québec Canada
| | - Monique Lagacé
- Department of BiochemistryInstitute for Research in Immunology and CancerGroupe de Recherche Universitaire sur le MédicamentUniversité de Montréal Montréal Québec Canada
| | - Michel Bouvier
- Department of BiochemistryInstitute for Research in Immunology and CancerGroupe de Recherche Universitaire sur le MédicamentUniversité de Montréal Montréal Québec Canada
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40
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Padgett CL, Slesinger PA. GABAB receptor coupling to G-proteins and ion channels. ADVANCES IN PHARMACOLOGY 2010; 58:123-47. [PMID: 20655481 DOI: 10.1016/s1054-3589(10)58006-2] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
GABA(B) receptors have been found to play a key role in regulating membrane excitability and synaptic transmission in the brain. The GABA(B) receptor is a G-protein coupled receptor (GPCR) that associates with a subset of G-proteins (pertussis toxin sensitive Gi/o family), that in turn regulate specific ion channels and trigger cAMP cascades. In this review, we describe the relationships between the GABA(B) receptor, its effectors and associated proteins that mediate GABA(B) receptor function within the brain. We discuss a unique feature of the GABA(B) receptor, the requirement for heterodimerization to produce functional receptors, as well as an increasing body of evidence that suggests GABA(B) receptors comprise a macromolecular signaling heterocomplex, critical for efficient targeting and function of the receptors. Within this complex, GABA(B) receptors associate specifically with Gi/o G-proteins that regulate voltage-gated Ca(2+) (Ca(V)) channels, G-protein activated inwardly rectifying K(+) (GIRK) channels, and adenylyl cyclase. Numerous studies have revealed that lipid rafts, scaffold proteins, targeting motifs in the receptor, and regulators of G-protein signaling (RGS) proteins also contribute to the function of GABA(B) receptors and affect cellular processes such as receptor trafficking and activity-dependent desensitization. This complex regulation of GABA(B) receptors in the brain may provide opportunities for new ways to regulate GABA-dependent inhibition in normal and diseased states of the nervous system.
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Affiliation(s)
- Claire L Padgett
- Peptide Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, USA
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41
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Gravel S, Malouf C, Boulais PE, Berchiche YA, Oishi S, Fujii N, Leduc R, Sinnett D, Heveker N. The peptidomimetic CXCR4 antagonist TC14012 recruits beta-arrestin to CXCR7: roles of receptor domains. J Biol Chem 2010; 285:37939-43. [PMID: 20956518 DOI: 10.1074/jbc.c110.147470] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
CXCR7 is an atypical chemokine receptor that signals through β-arrestin in response to agonists without detectable activation of heterotrimeric G-proteins. Its cognate chemokine ligand CXCL12 also binds CXCR4, a chemokine receptor of considerable clinical interest. Here we report that TC14012, a peptidomimetic inverse agonist of CXCR4, is an agonist on CXCR7. The potency of β-arrestin recruitment to CXCR7 by TC14012 is much higher than that of the previously reported CXCR4 antagonist AMD3100 and differs only by one log from that of the natural ligand CXCL12 (EC(50) 350 nM for TC14012, as compared with 30 nM for CXCL12 and 140 μM for AMD3100). Moreover, like CXCL12, TC14012 leads to Erk 1/2 activation in U373 glioma cells that express only CXCR7, but not CXCR4. Given that with TC14012 and AMD3100 two structurally unrelated CXCR4 antagonists turn out to be agonists on CXCR7, this likely reflects differences in the activation mechanism of the arrestin pathway by both receptors. To identify the receptor domain responsible for these opposed effects, we investigated CXCR4 and CXCR7 C terminus-swapping chimeras. Using quantitative bioluminescence resonance energy transfer, we find that the CXCR7 receptor core formed by the seven-transmembrane domains and the connecting loops determines the agonistic activity of both TC14012 and AMD3100. Moreover, we find that the CXCR7 chimera bearing the CXCR4 C-terminal constitutively associates with arrestin in the absence of ligands. Our data suggest that the CXCR4 and CXCR7 cores share ligand-binding surfaces for the binding of the synthetic ligands, indicating that CXCR4 inhibitors should be tested also on CXCR7.
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Affiliation(s)
- Stéphanie Gravel
- Department of Biochemistry, Université de Montréal, Montréal, Québec H3T 1J4, Canada
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42
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Breton B, Lagacé M, Bouvier M. Combining resonance energy transfer methods reveals a complex between the alpha2A-adrenergic receptor, Galphai1beta1gamma2, and GRK2. FASEB J 2010; 24:4733-43. [PMID: 20696855 DOI: 10.1096/fj.10-164061] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Traditionally, G-protein-coupled receptor (GPCR) interactions with their G proteins and regulatory proteins, GPCR kinases (GRKs) and arrestins, are described as sequential events involving rapid assemblies/disassemblies. To directly monitor the dynamics of these interactions in living cells, we combined two spectrally resolved bioluminescence and one fluorescence resonance energy transfer (RET) methods. The RET combination analysis revealed that stimulation of the α(2A)-adrenergic receptor (α(2A)AR) leads to the recruitment of GRK2 at a receptor still associated with the Gα(i1)β(1)γ(2) complex. The interaction kinetics of GRKs with Gγ(2) (2.8 ± 0.4 s) and α(2A)AR (5.2 ± 0.5 s) were similar to that of the receptor-promoted change in RET between Gα(i1) and Gγ(2) (5.2 ± 1.2 s), and persisted until the translocation of βarrestin2 to the receptor, indicating that GRK2 remains associated to the receptor/G-protein complex for longer periods than anticipated. Moreover, GRK2 or a kinase-deficient GRK2 mutant, but not GRK5, potentiated the receptor-promoted changes in RET between Gα(i1) and Gγ(2) and abrogated the α(2A)AR-stimulated calcium response, suggesting that the recruitment of GRK2 to the complex contributes to the structural rearrangement and functional regulation of the signaling unit, independently of the kinase activity. RET combination analysis revealed unanticipated dynamics in GPCR signaling and will be applicable to many biological systems.
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Affiliation(s)
- Billy Breton
- Department of Biochemistry, Institute for Research in Immunology and Cancer, and Groupe de Recherche Universitaire sur le Médicament, Université de Montréal, Montréal, Québec, Canada
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Prolonged activation of NMDA receptors promotes dephosphorylation and alters postendocytic sorting of GABAB receptors. Proc Natl Acad Sci U S A 2010; 107:13918-23. [PMID: 20643948 DOI: 10.1073/pnas.1000853107] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Slow and persistent synaptic inhibition is mediated by metabotropic GABAB receptors (GABABRs). GABABRs are responsible for the modulation of neurotransmitter release from presynaptic terminals and for hyperpolarization at postsynaptic sites. Postsynaptic GABABRs are predominantly found on dendritic spines, adjacent to excitatory synapses, but the control of their plasma membrane availability is still controversial. Here, we explore the role of glutamate receptor activation in regulating the function and surface availability of GABABRs in central neurons. We demonstrate that prolonged activation of NMDA receptors (NMDA-Rs) leads to endocytosis, a diversion from a recycling route, and subsequent lysosomal degradation of GABABRs. These sorting events are paralleled by a reduction in GABABR-dependent activation of inwardly rectifying K+ channel currents. Postendocytic sorting is critically dependent on phosphorylation of serine 783 (S783) within the GABABR2 subunit, an established substrate of AMP-dependent protein kinase (AMPK). NMDA-R activation leads to a rapid increase in phosphorylation of S783, followed by a slower dephosphorylation, which results from the activity of AMPK and protein phosphatase 2A, respectively. Agonist activation of GABABRs counters the effects of NMDA. Thus, NMDA-R activation alters the phosphorylation state of S783 and acts as a molecular switch to decrease the abundance of GABABRs at the neuronal plasma membrane. Such a mechanism may be of significance during synaptic plasticity or pathological conditions, such as ischemia or epilepsy, which lead to prolonged activation of glutamate receptors.
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Saenz del Burgo L, Milligan G. Heterodimerisation of G protein-coupled receptors: implications for drug design and ligand screening. Expert Opin Drug Discov 2010; 5:461-74. [PMID: 22823130 DOI: 10.1517/17460441003720467] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
IMPORTANCE OF THE FIELD In recent times many G protein-coupled receptors (GPCRs) have been shown to dimerise/oligomerise and, in some cases, such structural organization has been found to be essential for receptor function or to play a modulatory role in living cells. The fact that these complexes may display differential pharmacology through, for example, the formation of a new binding pocket or signalling properties, as well as different functions or regulation in physiological tissues, offers novel opportunities for drug discovery. As a consequence, it seems necessary to develop new approaches suitable for GPCR heterodimer identification and selective ligand screening. AREAS COVERED IN THIS REVIEW This review gives an overview of new strategies that have been developed in an effort to incorporate the possibilities added by GPCR hetero-oligomerisation on the screening of compounds as drug candidates. WHAT THE READER WILL GAIN The reader will gain a wider knowledge about how the current understanding of GPCR oligomeric structure and function has mandated that hetero-oligomeric receptors must be considered as novel targets in the identification of future lead compounds. TAKE HOME MESSAGE For the improvement of novel drug discovery, more structural and functional information on the process of receptor oligomerisation is needed, and the realisation that the function of GPCRs can be greatly influenced by other interacting receptors or proteins also demands consideration in the lead-compound developing process in order to achieve better therapeutic agents.
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Affiliation(s)
- Laura Saenz del Burgo
- University of Glasgow, Faculty of Biomedical and Life Sciences, Wolfson Building, Glasgow G12 8QQ, Scotland, UK
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45
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Martel C, Dugré-Brisson S, Boulay K, Breton B, Lapointe G, Armando S, Trépanier V, Duchaîne T, Bouvier M, Desgroseillers L. Multimerization of Staufen1 in live cells. RNA (NEW YORK, N.Y.) 2010; 16:585-97. [PMID: 20075165 PMCID: PMC2822923 DOI: 10.1261/rna.1664210] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Transport of mRNA is an efficient mechanism to target proteins to specific regions of a cell. Although it is well documented that mRNAs are transported in ribonucleoprotein (RNP) complexes, several of the mechanisms involved in complex formation and localization are poorly understood. Staufen (Stau) 1, a double-stranded RNA-binding protein, is a well accepted marker of mRNA transport complexes. In this manuscript, we provide evidence that Stau1 self-associates in live cells using immunoprecipitation and bioluminescence resonance energy transfer (BRET) assays. The double-stranded RNA-binding domains dsRBD3 and dsRBD4 contributed about half of the signal, suggesting that Stau1 RNA-binding activity is involved in Stau1 self-association. Protein-protein interaction also occurred, via dsRBD5 and dsRBD2, as shown by in vitro pull-down, yeast two-hybrid, and BRET assays in live cells. Interestingly, Stau1 self-association contributes to the formation of oligomeric complexes as evidenced by the coexpression of split Renilla luciferase halves covalently linked to Stau1 in a protein complementation assay (PCA) combined with a BRET assay with Stau1-YFP. Moreover, we showed that these higher-order Stau1-containing complexes carry RNAs when the RNA stain SYTO 14 was used as the energy acceptor in the PCA/BRET assay. The oligomeric composition of Stau1-containing complexes and the presence of specific mRNAs have been confirmed by biochemical approaches involving two successive immunoprecipitations of Stau1-tagged molecules followed by qRT-PCR amplification. Altogether, these results indicate that Stau1 self-associates in mRNPs via its multiple functional domains that can select mRNAs to be transported and establish protein-protein interaction.
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Affiliation(s)
- Catherine Martel
- Département de Biochimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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Jose PA, Soares-da-Silva P, Eisner GM, Felder RA. Dopamine and G protein-coupled receptor kinase 4 in the kidney: role in blood pressure regulation. Biochim Biophys Acta Mol Basis Dis 2010; 1802:1259-67. [PMID: 20153824 DOI: 10.1016/j.bbadis.2010.02.004] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Revised: 02/05/2010] [Accepted: 02/07/2010] [Indexed: 12/11/2022]
Abstract
Complex interactions between genes and environment result in a sodium-induced elevation in blood pressure (salt sensitivity) and/or hypertension that lead to significant morbidity and mortality affecting up to 25% of the middle-aged adult population worldwide. Determining the etiology of genetic and/or environmentally-induced high blood pressure has been difficult because of the many interacting systems involved. Two main pathways have been implicated as principal determinants of blood pressure since they are located in the kidney (the key organ responsible for blood pressure regulation), and have profound effects on sodium balance: the dopaminergic and renin-angiotensin systems. These systems counteract or modulate each other, in concert with a host of intracellular second messenger pathways to regulate sodium and water balance. In particular, the G protein-coupled receptor kinase type 4 (GRK4) appears to play a key role in regulating dopaminergic-mediated natriuresis. Constitutively activated GRK4 gene variants (R65L, A142V, and A486V), by themselves or by their interaction with other genes involved in blood pressure regulation, are associated with essential hypertension and/or salt-sensitive hypertension in several ethnic groups. GRK4γ 142Vtransgenic mice are hypertensive on normal salt intake while GRK4γ 486V transgenic mice develop hypertension only with an increase in salt intake. GRK4 gene variants have been shown to hyperphosphorylate, desensitize, and internalize two members of the dopamine receptor family, the D(1) (D(1)R) and D(3) (D(3)R) dopamine receptors, but also increase the expression of a key receptor of the renin-angiotensin system, the angiotensin type 1 receptor (AT(1)R). Knowledge of the numerous blood pressure regulatory pathways involving angiotensin and dopamine may provide new therapeutic approaches to the pharmacological regulation of sodium excretion and ultimately blood pressure control.
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Affiliation(s)
- Pedro A Jose
- Children's National Medical Center, George Washington University for the Health Sciences, Washington, DC, USA.
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47
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Benke D. Mechanisms of GABAB receptor exocytosis, endocytosis, and degradation. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2010; 58:93-111. [PMID: 20655479 DOI: 10.1016/s1054-3589(10)58004-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABA(B) receptors belong to the family of G-protein-coupled receptors, which mediate slow inhibitory neurotransmission in the central nervous system. They are promising drug targets for a variety of neurological disorders and play important functions in regulating synaptic plasticity. Signaling strength is critically dependent on the availability of the receptors at the cell surface. Several distinct highly regulated trafficking mechanisms ensure the presence of adequate receptor numbers in the plasma membrane. The rate of exocytosis of newly synthesized receptors from the endoplasmic reticulum via the Golgi apparatus to the cell surface as well as the rates of their endocytosis and degradation determines the retention time of receptors at the cell surface. This chapter focuses on the recently emerged mechanisms of GABA(B) receptor exocytosis, endocytosis, recycling, and degradation.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
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GABAB receptors: physiological functions and mechanisms of diversity. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2010; 58:231-55. [PMID: 20655485 DOI: 10.1016/s1054-3589(10)58010-4] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
GABA(B) receptors are the G-protein-coupled receptors (GPCRs) for gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the central nervous system. GABA(B) receptors are implicated in the etiology of a variety of psychiatric disorders and are considered attractive drug targets. With the cloning of GABA(B) receptor subunits 13 years ago, substantial progress was made in the understanding of the molecular structure, physiology, and pharmacology of these receptors. However, it remained puzzling that native studies demonstrated a heterogeneity of GABA(B) responses that contrasted with a very limited diversity of cloned GABA(B) receptor subunits. Until recently, the only firmly established molecular diversity consisted of two GABA(B1) subunit isoforms, GABA(B1a) and GABA(B1b), which assemble with GABA(B2) subunits to generate heterodimeric GABA(B(1a,2)) and GABA(B(1b,2)) receptors. Using genetic, ultrastructural, biochemical, and electrophysiological approaches, it has been possible to identify functional properties that segregate with these two receptors. Moreover, receptor modifications and factors that can alter the receptor response have been identified. Most importantly, recent data reveal the existence of a family of auxiliary GABA(B) receptor subunits that assemble as tetramers with the C-terminal domain of GABA(B2) subunits and drastically alter pharmacology and kinetics of the receptor response. The data are most consistent with native GABA(B) receptors minimally forming dimeric assemblies of units composed of GABA(B1), GABA(B2), and a tetramer of auxiliary subunits. This represents a substantial departure from current structural concepts for GPCRs.
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Terunuma M, Pangalos MN, Moss SJ. Functional modulation of GABAB receptors by protein kinases and receptor trafficking. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2010; 58:113-22. [PMID: 20655480 DOI: 10.1016/s1054-3589(10)58005-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABA(B) receptors (GABA(B)R) are heterodimeric G protein-coupled receptors (GPCRs) that mediate slow and prolonged inhibitory signals in the central nervous system. The signaling of GPCRs is under stringent control and is subject to regulation by multiple posttranslational mechanisms. The beta-adrenergic receptor is a prototypic GPCR. Like most GPCRs, prolonged exposure of this receptor to agonist induces phosphorylation of multiple intracellular residues that is largely dependent upon the activity of G protein-coupled receptor kinases (GRKs). Phosphorylation terminates receptor-effector coupling and promotes both interaction with beta-arrestins and removal from the plasma membrane via clathrin-dependent endocytosis. Emerging evidence for GABA(B)Rs suggests that these GPCRs do not conform to this mode of regulation. Studies using both native and recombinant receptor preparations have demonstrated that GABA(B)Rs do not undergo agonist-induced internalization and are not GRK substrates. Moreover, whilst GABA(B)Rs undergo clathrin-dependent constitutive endocytosis, it is generally accepted that their rates of internalization are not modified by prolonged agonist exposure. Biochemical studies have revealed that GABA(B)Rs are phosphorylated on multiple residues within the cytoplasmic domains of both the R1 and R2 subunits by cAMP-dependent protein kinase and 5'AMP-dependent protein kinase (AMPK). Here we discuss the role that this phosphorylation plays in determining GABA(B)R effector coupling and their trafficking within the endocytic pathway and go on to evaluate the significance of GABA(B)R phosphorylation in controlling neuronal excitability under normal and pathological conditions.
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Affiliation(s)
- Miho Terunuma
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
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Namkung Y, Dipace C, Urizar E, Javitch JA, Sibley DR. G protein-coupled receptor kinase-2 constitutively regulates D2 dopamine receptor expression and signaling independently of receptor phosphorylation. J Biol Chem 2009; 284:34103-15. [PMID: 19815545 DOI: 10.1074/jbc.m109.055707] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated the regulatory effects of GRK2 on D(2) dopamine receptor signaling and found that this kinase inhibits both receptor expression and functional signaling in a phosphorylation-independent manner, apparently through different mechanisms. Overexpression of GRK2 was found to suppress receptor expression at the cell surface and enhance agonist-induced internalization, whereas short interfering RNA knockdown of endogenous GRK2 led to an increase in cell surface receptor expression and decreased agonist-mediated endocytosis. These effects were not due to GRK2-mediated phosphorylation of the D(2) receptor as a phosphorylation-null receptor mutant was regulated similarly, and overexpression of a catalytically inactive mutant of GRK2 produced the same effects. The suppression of receptor expression is correlated with constitutive association of GRK2 with the receptor complex as we found that GRK2 and several of its mutants were able to co-immunoprecipitate with the D(2) receptor. Agonist pretreatment did not enhance the ability of GRK2 to co-immunoprecipitate with the receptor. We also found that overexpression of GRK2 attenuated the functional coupling of the D(2) receptor and that this activity required the kinase activity of GRK2 but did not involve receptor phosphorylation, thus suggesting the involvement of an additional GRK2 substrate. Interestingly, we found that the suppression of functional signaling also required the G betagamma binding activity of GRK2 but did not involve the GRK2 N-terminal RH domain. Our results suggest a novel mechanism by which GRK2 negatively regulates G protein-coupled receptor signaling in a manner that is independent of receptor phosphorylation.
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Affiliation(s)
- Yoon Namkung
- Molecular Neuropharmacology Section, NINDS, National Institutes of Health, Bethesda, Maryland 20892-9405, USA
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