1
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Sokrat B, Nguyen AH, Thomsen ARB, Huang LY, Kobayashi H, Kahsai AW, Kim J, Ho BX, Ma S, Little J, Ehrhart C, Pyne I, Hammond E, Bouvier M. Role of the V2R-βarrestin-Gβγ complex in promoting G protein translocation to endosomes. Commun Biol 2024; 7:826. [PMID: 38972875 PMCID: PMC11228049 DOI: 10.1038/s42003-024-06512-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 06/27/2024] [Indexed: 07/09/2024] Open
Abstract
Classically, G protein-coupled receptors (GPCRs) promote signaling at the plasma membrane through activation of heterotrimeric Gαβγ proteins, followed by the recruitment of GPCR kinases and βarrestin (βarr) to initiate receptor desensitization and internalization. However, studies demonstrated that some GPCRs continue to signal from internalized compartments, with distinct cellular responses. Both βarr and Gβγ contribute to such non-canonical endosomal G protein signaling, but their specific roles and contributions remain poorly understood. Here, we demonstrate that the vasopressin V2 receptor (V2R)-βarr complex scaffolds Gβγ at the plasma membrane through a direct interaction with βarr, enabling its transport to endosomes. Gβγ subsequently potentiates Gαs endosomal translocation, presumably to regenerate an endosomal pool of heterotrimeric Gs. This work shines light on the mechanism underlying G protein subunits translocation from the plasma membrane to the endosomes and provides a basis for understanding the role of βarr in mediating sustained G protein signaling.
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Affiliation(s)
- Badr Sokrat
- Department of Biochemistry and Molecular Medicine, University of Montreal, Montreal, QC, H3T 1J4, Canada
- Institute for Research in Immunology and Cancer, University of Montreal, Montreal, QC, H3T 1J4, Canada
- Department of Molecular Pathobiology, New York University School of Dentistry, New York, NY, 10010, USA
| | - Anthony H Nguyen
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Alex R B Thomsen
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
- Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
- Department of Molecular Pathobiology, New York University School of Dentistry, New York, NY, 10010, USA
| | - Li-Yin Huang
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Hiroyuki Kobayashi
- Institute for Research in Immunology and Cancer, University of Montreal, Montreal, QC, H3T 1J4, Canada
| | - Alem W Kahsai
- Department of Medicine, Duke University Medical Center, Durham, NC, 27710, USA
| | - Jihee Kim
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Bing X Ho
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Symon Ma
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - John Little
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Catherine Ehrhart
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Ian Pyne
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Emmery Hammond
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Michel Bouvier
- Department of Biochemistry and Molecular Medicine, University of Montreal, Montreal, QC, H3T 1J4, Canada.
- Institute for Research in Immunology and Cancer, University of Montreal, Montreal, QC, H3T 1J4, Canada.
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2
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Ashok S, Ramachandra Rao S. Updates on protein-prenylation and associated inherited retinopathies. FRONTIERS IN OPHTHALMOLOGY 2024; 4:1410874. [PMID: 39026984 PMCID: PMC11254824 DOI: 10.3389/fopht.2024.1410874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Accepted: 06/13/2024] [Indexed: 07/20/2024]
Abstract
Membrane-anchored proteins play critical roles in cell signaling, cellular architecture, and membrane biology. Hydrophilic proteins are post-translationally modified by a diverse range of lipid molecules such as phospholipids, glycosylphosphatidylinositol, and isoprenes, which allows their partition and anchorage to the cell membrane. In this review article, we discuss the biochemical basis of isoprenoid synthesis, the mechanisms of isoprene conjugation to proteins, and the functions of prenylated proteins in the neural retina. Recent discovery of novel prenyltransferases, prenylated protein chaperones, non-canonical prenylation-target motifs, and reversible prenylation is expected to increase the number of inherited systemic and blinding diseases with aberrant protein prenylation. Recent important investigations have also demonstrated the role of several unexpected regulators (such as protein charge, sequence/protein-chaperone interaction, light exposure history) in the photoreceptor trafficking of prenylated proteins. Technical advances in the investigation of the prenylated proteome and its application in vision research are discussed. Clinical updates and technical insights into known and putative prenylation-associated retinopathies are provided herein. Characterization of non-canonical prenylation mechanisms in the retina and retina-specific prenylated proteome is fundamental to the understanding of the pathogenesis of protein prenylation-associated inherited blinding disorders.
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Affiliation(s)
- Sudhat Ashok
- Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, State University of New York, University at Buffalo, Buffalo, NY, United States
| | - Sriganesh Ramachandra Rao
- Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, State University of New York, University at Buffalo, Buffalo, NY, United States
- Neuroscience Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York, University at Buffalo, Buffalo, NY, United States
- Research Service, VA Western New York Healthcare System, Buffalo, NY, United States
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3
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Nürnberg B, Beer-Hammer S, Reisinger E, Leiss V. Non-canonical G protein signaling. Pharmacol Ther 2024; 255:108589. [PMID: 38295906 DOI: 10.1016/j.pharmthera.2024.108589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 12/18/2023] [Accepted: 01/08/2024] [Indexed: 02/17/2024]
Abstract
The original paradigm of classical - also referred to as canonical - cellular signal transduction of heterotrimeric G proteins (G protein) is defined by a hierarchical, orthograde interaction of three players: the agonist-activated G protein-coupled receptor (GPCR), which activates the transducing G protein, that in turn regulates its intracellular effectors. This receptor-transducer-effector concept was extended by the identification of regulators and adapters such as the regulators of G protein signaling (RGS), receptor kinases like βARK, or GPCR-interacting arrestin adapters that are integrated into this canonical signaling process at different levels to enable fine-tuning. Finally, the identification of atypical signaling mechanisms of classical regulators, together with the discovery of novel modulators, added a new and fascinating dimension to the cellular G protein signal transduction. This heterogeneous group of accessory G protein modulators was coined "activators of G protein signaling" (AGS) proteins and plays distinct roles in canonical and non-canonical G protein signaling pathways. AGS proteins contribute to the control of essential cellular functions such as cell development and division, intracellular transport processes, secretion, autophagy or cell movements. As such, they are involved in numerous biological processes that are crucial for diseases, like diabetes mellitus, cancer, and stroke, which represent major health burdens. Although the identification of a large number of non-canonical G protein signaling pathways has broadened the spectrum of this cellular communication system, their underlying mechanisms, functions, and biological effects are poorly understood. In this review, we highlight and discuss atypical G protein-dependent signaling mechanisms with a focus on inhibitory G proteins (Gi) involved in canonical and non-canonical signal transduction, review recent developments and open questions, address the potential of new approaches for targeted pharmacological interventions.
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Affiliation(s)
- Bernd Nürnberg
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, D-72074 Tübingen, Germany.
| | - Sandra Beer-Hammer
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, D-72074 Tübingen, Germany
| | - Ellen Reisinger
- Gene Therapy for Hearing Impairment Group, Department of Otolaryngology - Head & Neck Surgery, University of Tübingen Medical Center, Elfriede-Aulhorn-Straße 5, D-72076 Tübingen, Germany
| | - Veronika Leiss
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, D-72074 Tübingen, Germany
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4
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Zhao C, MacKinnon R. Structural and functional analyses of a GPCR-inhibited ion channel TRPM3. Neuron 2023; 111:81-91.e7. [PMID: 36283409 DOI: 10.1016/j.neuron.2022.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 09/03/2022] [Accepted: 09/29/2022] [Indexed: 12/24/2022]
Abstract
G-protein coupled receptors (GPCRs) govern the physiological response to stimuli by modulating the activity of downstream effectors, including ion channels. TRPM3 is an ion channel inhibited by GPCRs through direct interaction with G protein (Gβγ) released upon their activation. This GPCR-TRPM3 signaling pathway contributes to the analgesic effect of morphine. Here, we characterized Gβγ inhibition of TRPM3 using electrophysiology and single particle cryo-electron microscopy (cryo-EM). From electrophysiology, we obtained a half inhibition constant (IC50) of ∼240 nM. Using cryo-EM, we determined structures of mouse TRPM3 expressed in human cells with and without Gβγ and with and without PIP2, a lipid required for TRPM3 activity, at resolutions of 2.7-4.7 Å. Gβγ-TRPM3 interfaces vary depending on PIP2 occupancy; however, in all cases, Gβγ appears loosely attached to TRPM3. The IC50 in electrophysiology experiments raises the possibility that additional unknown factors may stabilize the TRPM3-Gβγ complex.
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Affiliation(s)
- Chen Zhao
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, the Rockefeller University, New York, NY 10065, United States
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, the Rockefeller University, New York, NY 10065, United States.
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5
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Nubbemeyer B, Pepanian A, Paul George AA, Imhof D. Strategies towards Targeting Gαi/s Proteins: Scanning of Protein-Protein Interaction Sites To Overcome Inaccessibility. ChemMedChem 2021; 16:1696-1715. [PMID: 33615736 PMCID: PMC8252600 DOI: 10.1002/cmdc.202100039] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Indexed: 12/16/2022]
Abstract
Heterotrimeric G proteins are classified into four subfamilies and play a key role in signal transduction. They transmit extracellular signals to intracellular effectors subsequent to the activation of G protein-coupled receptors (GPCRs), which are targeted by over 30 % of FDA-approved drugs. However, addressing G proteins as drug targets represents a compelling alternative, for example, when G proteins act independently of the corresponding GPCRs, or in cases of complex multifunctional diseases, when a large number of different GPCRs are involved. In contrast to Gαq, efforts to target Gαi/s by suitable chemical compounds has not been successful so far. Here, a comprehensive analysis was conducted examining the most important interface regions of Gαi/s with its upstream and downstream interaction partners. By assigning the existing compounds and the performed approaches to the respective interfaces, the druggability of the individual interfaces was ranked to provide perspectives for selective targeting of Gαi/s in the future.
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Affiliation(s)
- Britta Nubbemeyer
- Pharmaceutical Biochemistry and BioanalyticsPharmaceutical InstituteUniversity of BonnAn der Immenburg 453121BonnGermany
| | - Anna Pepanian
- Pharmaceutical Biochemistry and BioanalyticsPharmaceutical InstituteUniversity of BonnAn der Immenburg 453121BonnGermany
| | | | - Diana Imhof
- Pharmaceutical Biochemistry and BioanalyticsPharmaceutical InstituteUniversity of BonnAn der Immenburg 453121BonnGermany
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6
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Tennakoon M, Senarath K, Kankanamge D, Ratnayake K, Wijayaratna D, Olupothage K, Ubeysinghe S, Martins-Cannavino K, Hébert TE, Karunarathne A. Subtype-dependent regulation of Gβγ signalling. Cell Signal 2021; 82:109947. [PMID: 33582184 PMCID: PMC8026654 DOI: 10.1016/j.cellsig.2021.109947] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) transmit information to the cell interior by transducing external signals to heterotrimeric G protein subunits, Gα and Gβγ subunits, localized on the inner leaflet of the plasma membrane. Though the initial focus was mainly on Gα-mediated events, Gβγ subunits were later identified as major contributors to GPCR-G protein signalling. A broad functional array of Gβγ signalling has recently been attributed to Gβ and Gγ subtype diversity, comprising 5 Gβ and 12 Gγ subtypes, respectively. In addition to displaying selectivity towards each other to form the Gβγ dimer, numerous studies have identified preferences of distinct Gβγ combinations for specific GPCRs, Gα subtypes and effector molecules. Importantly, Gβ and Gγ subtype-dependent regulation of downstream effectors, representing a diverse range of signalling pathways and physiological functions have been found. Here, we review the literature on the repercussions of Gβ and Gγ subtype diversity on direct and indirect regulation of GPCR/G protein signalling events and their physiological outcomes. Our discussion additionally provides perspective in understanding the intricacies underlying molecular regulation of subtype-specific roles of Gβγ signalling and associated diseases.
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Affiliation(s)
- Mithila Tennakoon
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kanishka Senarath
- Genetics and Molecular Biology Unit, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
| | - Dinesh Kankanamge
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kasun Ratnayake
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA; Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Dhanushan Wijayaratna
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Koshala Olupothage
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Sithurandi Ubeysinghe
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | | | - Terence E Hébert
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC H3G 1Y6, Canada.
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA.
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7
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Diversity of the Gβγ complexes defines spatial and temporal bias of GPCR signaling. Cell Syst 2021; 12:324-337.e5. [PMID: 33667409 DOI: 10.1016/j.cels.2021.02.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 12/09/2020] [Accepted: 02/04/2021] [Indexed: 01/04/2023]
Abstract
The signal transduction by G-protein-coupled receptors (GPCRs) is mediated by heterotrimeric G proteins composed from one of the 16 Gα subunits and the inseparable Gβγ complex assembled from a repertoire of 5 Gβ and 12 Gγ subunits. However, the functional role of compositional diversity in Gβγ complexes has been elusive. Using optical biosensors, we examined the function of all Gβγ combinations in living cells and uncovered two major roles of Gβγ diversity. First, we demonstrate that the identity of Gβγ subunits greatly influences the kinetics and efficacy of GPCR responses at the plasma membrane. Second, we show that different Gβγ combinations are selectively dispatched from the plasma membrane to various cellular organelles on a timescale from milliseconds to minutes. We describe the mechanisms regulating these processes and document their implications for GPCR signaling via various Gα subunits, thereby illustrating a role for the compositional diversity of G protein heterotrimers.
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8
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Calebiro D, Koszegi Z, Lanoiselée Y, Miljus T, O'Brien S. G protein-coupled receptor-G protein interactions: a single-molecule perspective. Physiol Rev 2020; 101:857-906. [PMID: 33331229 DOI: 10.1152/physrev.00021.2020] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
G protein-coupled receptors (GPCRs) regulate many cellular and physiological processes, responding to a diverse range of extracellular stimuli including hormones, neurotransmitters, odorants, and light. Decades of biochemical and pharmacological studies have provided fundamental insights into the mechanisms of GPCR signaling. Thanks to recent advances in structural biology, we now possess an atomistic understanding of receptor activation and G protein coupling. However, how GPCRs and G proteins interact in living cells to confer signaling efficiency and specificity remains insufficiently understood. The development of advanced optical methods, including single-molecule microscopy, has provided the means to study receptors and G proteins in living cells with unprecedented spatio-temporal resolution. The results of these studies reveal an unexpected level of complexity, whereby GPCRs undergo transient interactions among themselves as well as with G proteins and structural elements of the plasma membrane to form short-lived signaling nanodomains that likely confer both rapidity and specificity to GPCR signaling. These findings may provide new strategies to pharmaceutically modulate GPCR function, which might eventually pave the way to innovative drugs for common diseases such as diabetes or heart failure.
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Affiliation(s)
- Davide Calebiro
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Zsombor Koszegi
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Yann Lanoiselée
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Tamara Miljus
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Shannon O'Brien
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
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9
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Behrendt M, Gruss F, Enzeroth R, Dembla S, Zhao S, Crassous PA, Mohr F, Nys M, Louros N, Gallardo R, Zorzini V, Wagner D, Economou A, Rousseau F, Schymkowitz J, Philipp SE, Rohacs T, Ulens C, Oberwinkler J. The structural basis for an on-off switch controlling Gβγ-mediated inhibition of TRPM3 channels. Proc Natl Acad Sci U S A 2020; 117:29090-29100. [PMID: 33122432 PMCID: PMC7682392 DOI: 10.1073/pnas.2001177117] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
TRPM3 channels play important roles in the detection of noxious heat and in inflammatory thermal hyperalgesia. The activity of these ion channels in somatosensory neurons is tightly regulated by µ-opioid receptors through the signaling of Gβγ proteins, thereby reducing TRPM3-mediated pain. We show here that Gβγ directly binds to a domain of 10 amino acids in TRPM3 and solve a cocrystal structure of this domain together with Gβγ. Using these data and mutational analysis of full-length proteins, we pinpoint three amino acids in TRPM3 and their interacting partners in Gβ1 that are individually necessary for TRPM3 inhibition by Gβγ. The 10-amino-acid Gβγ-interacting domain in TRPM3 is subject to alternative splicing. Its inclusion in or exclusion from TRPM3 channel proteins therefore provides a mechanism for switching on or off the inhibitory action that Gβγ proteins exert on TRPM3 channels.
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Affiliation(s)
- Marc Behrendt
- Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037 Marburg, Germany
- Center for Mind, Brain and Behavior (CMBB), Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, 35032 Marburg, Germany
| | - Fabian Gruss
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Raissa Enzeroth
- Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037 Marburg, Germany
- Center for Mind, Brain and Behavior (CMBB), Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, 35032 Marburg, Germany
| | - Sandeep Dembla
- Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037 Marburg, Germany
- Center for Mind, Brain and Behavior (CMBB), Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, 35032 Marburg, Germany
| | - Siyuan Zhao
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103
| | - Pierre-Antoine Crassous
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103
| | - Florian Mohr
- Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Mieke Nys
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Nikolaos Louros
- Switch Laboratory, VIB Center for Brain and Disease Research, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Rodrigo Gallardo
- Switch Laboratory, VIB Center for Brain and Disease Research, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Valentina Zorzini
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, 3000 Leuven, Belgium
| | - Doris Wagner
- Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven, 3000 Leuven, Belgium
| | - Frederic Rousseau
- Switch Laboratory, VIB Center for Brain and Disease Research, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Joost Schymkowitz
- Switch Laboratory, VIB Center for Brain and Disease Research, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Stephan E Philipp
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103
| | - Chris Ulens
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, 3000 Leuven, Belgium;
| | - Johannes Oberwinkler
- Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037 Marburg, Germany;
- Center for Mind, Brain and Behavior (CMBB), Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, 35032 Marburg, Germany
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10
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Smrcka AV, Fisher I. G-protein βγ subunits as multi-functional scaffolds and transducers in G-protein-coupled receptor signaling. Cell Mol Life Sci 2019; 76:4447-4459. [PMID: 31435698 PMCID: PMC6842434 DOI: 10.1007/s00018-019-03275-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 08/05/2019] [Accepted: 08/12/2019] [Indexed: 02/08/2023]
Abstract
G-protein βγ subunits are key participants in G-protein signaling. These subunits facilitate interactions between receptors and G proteins that are critical for the G protein activation cycle at the plasma membrane. In addition, they play roles in directly transducing signals to an ever expanding range of downstream targets, including integral membrane and cytosolic proteins. Emerging data indicate that Gβγ may play additional roles at intracellular compartments including endosomes, the Golgi apparatus, and the nucleus. Here, we discuss the molecular and structural basis for their ability to coordinate this wide range of cellular activities.
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Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, 48104, USA.
| | - Isaac Fisher
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, 48104, USA
- Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, NY, 14629, USA
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11
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Mutual action by Gγ and Gβ for optimal activation of GIRK channels in a channel subunit-specific manner. Sci Rep 2019; 9:508. [PMID: 30679535 PMCID: PMC6346094 DOI: 10.1038/s41598-018-36833-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 11/29/2018] [Indexed: 01/06/2023] Open
Abstract
The tetrameric G protein-gated K+ channels (GIRKs) mediate inhibitory effects of neurotransmitters that activate Gi/o-coupled receptors. GIRKs are activated by binding of the Gβγ dimer, via contacts with Gβ. Gγ underlies membrane targeting of Gβγ, but has not been implicated in channel gating. We observed that, in Xenopus oocytes, expression of Gγ alone activated homotetrameric GIRK1* and heterotetrameric GIRK1/3 channels, without affecting the surface expression of GIRK or Gβ. Gγ and Gβ acted interdependently: the effect of Gγ required the presence of ambient Gβ and was enhanced by low doses of coexpressed Gβ, whereas excess of either Gβ or Gγ imparted suboptimal activation, possibly by sequestering the other subunit “away” from the channel. The unique distal C-terminus of GIRK1, G1-dCT, was important but insufficient for Gγ action. Notably, GIRK2 and GIRK1/2 were not activated by Gγ. Our results suggest that Gγ regulates GIRK1* and GIRK1/3 channel’s gating, aiding Gβ to trigger the channel’s opening. We hypothesize that Gγ helps to relax the inhibitory effect of a gating element (“lock”) encompassed, in part, by the G1-dCT; GIRK2 acts to occlude the effect of Gγ, either by setting in motion the same mechanism as Gγ, or by triggering an opposing gating effect.
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12
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Livingston KE, Mahoney JP, Manglik A, Sunahara RK, Traynor JR. Measuring ligand efficacy at the mu-opioid receptor using a conformational biosensor. eLife 2018; 7:32499. [PMID: 29932421 PMCID: PMC6042960 DOI: 10.7554/elife.32499] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 05/26/2018] [Indexed: 01/02/2023] Open
Abstract
The intrinsic efficacy of orthosteric ligands acting at G-protein-coupled receptors (GPCRs) reflects their ability to stabilize active receptor states (R*) and is a major determinant of their physiological effects. Here, we present a direct way to quantify the efficacy of ligands by measuring the binding of a R*-specific biosensor to purified receptor employing interferometry. As an example, we use the mu-opioid receptor (µ-OR), a prototypic class A GPCR, and its active state sensor, nanobody-39 (Nb39). We demonstrate that ligands vary in their ability to recruit Nb39 to µ-OR and describe methadone, loperamide, and PZM21 as ligands that support unique R* conformation(s) of µ-OR. We further show that positive allosteric modulators of µ-OR promote formation of R* in addition to enhancing promotion by orthosteric agonists. Finally, we demonstrate that the technique can be utilized with heterotrimeric G protein. The method is cell-free, signal transduction-independent and is generally applicable to GPCRs.
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Affiliation(s)
- Kathryn E Livingston
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, United States.,Edward F Domino Research Center, University of Michigan, Ann Arbor, United States
| | - Jacob P Mahoney
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, United States.,Edward F Domino Research Center, University of Michigan, Ann Arbor, United States
| | - Aashish Manglik
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California San Francisco, San Francisco, United States
| | - Roger K Sunahara
- Department of Pharmacology, University of California San Diego School of Medicine, La Jolla, United States
| | - John R Traynor
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, United States.,Edward F Domino Research Center, University of Michigan, Ann Arbor, United States
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13
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Brooks C, Murphy J, Belcastro M, Heller D, Kolandaivelu S, Kisselev O, Sokolov M. Farnesylation of the Transducin G Protein Gamma Subunit Is a Prerequisite for Its Ciliary Targeting in Rod Photoreceptors. Front Mol Neurosci 2018; 11:16. [PMID: 29410614 PMCID: PMC5787109 DOI: 10.3389/fnmol.2018.00016] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 01/10/2018] [Indexed: 12/26/2022] Open
Abstract
Primary cilia are microtubule-based organelles, which protrude from the plasma membrane and receive a wide range of extracellular signals. Various cilia use G protein-coupled receptors (GPCRs) for the detection of these signals. For instance, vertebrate rod photoreceptors use their cilia (also called outer segments) as antennae detecting photons by GPCR rhodopsin. Rhodopsin recognizes incoming light and activates its G protein, transducin, which is composed of three subunits α, β, and γ. Similar to all G protein γ subunits, the transducin Gγ1 subunit undergoes C-terminal prenylation resulting in the addition of an isoprenoid farnesyl; however, the significance of this posttranslational modification is unclear. To study the role of the farnesyl group, we genetically introduced a mutant Gγ1 that lacked the prenylation site into the retinal photoreceptors of mice. The biochemical and physiological analyses of these mice revealed that mutant Gγ1 dimerizes with the endogenous transducin Gβ1 subunit and that the resulting Gβγ dimers display reduced hydrophobicity. Although mutant Gβγ dimers could form a heterotrimeric G protein, they could not mediate phototransduction. This deficiency was due to a strong exclusion of non-farnesylated Gβγ complexes from the cilia (rod outer segments). Our results provide the first evidence that farnesylation is required for trafficking of G-protein βγ subunits to the cilium of rod photoreceptors.
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Affiliation(s)
- Celine Brooks
- Department of Ophthalmology, West Virginia University, Morgantown, WV, United States
| | - Joseph Murphy
- Department of Ophthalmology, West Virginia University, Morgantown, WV, United States
| | | | - Daniel Heller
- Department of Ophthalmology, West Virginia University, Morgantown, WV, United States
| | | | - Oleg Kisselev
- Department of Ophthalmology, Saint Louis University, St. Louis, MO, United States
| | - Maxim Sokolov
- Department of Ophthalmology, West Virginia University, Morgantown, WV, United States
- Department of Biochemistry, West Virginia University, Morgantown, WV, United States
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14
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Zhu Y, Zhang L, Zhang XC, Zhao Y. Structural dynamics of G iα protein revealed by single molecule FRET. Biochem Biophys Res Commun 2017; 491:603-608. [PMID: 28760338 DOI: 10.1016/j.bbrc.2017.07.156] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 07/27/2017] [Indexed: 01/13/2023]
Abstract
The heterotrimeric G proteins (Gαβγ) act as molecular switches to mediate signal transduction from G protein-coupled receptors to downstream effectors. Upon interaction with an activated receptor, G protein exchanges its bound GDP with GTP, stimulating downstream signal transmission. Release of GDP requires a structural rearrangement between the GTPase domain and helical domain of the Gα subunit. Here, we used single molecule fluorescence resonance energy transfer (smFRET) technique to study the conformational dynamics of these two domains in the apo state and in the binding of different ligands. Direct imaging of individual molecules showed that the Giα subunit is highly dynamic, and at least three major conformations of Giα could be observed in the apo state. Upon binding of GDP, Giα becomes dramatically less dynamic, resulting in a closed conformation between the two domains. We postulate that changes between the three conformations are sequential, and the three conformations appear to have distinct affinities toward GDP.
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Affiliation(s)
- Yongping Zhu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lei Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China
| | - Xuejun C Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Yongfang Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China
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15
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Gβ1 is required for neutrophil migration in zebrafish. Dev Biol 2017; 428:135-147. [PMID: 28554852 DOI: 10.1016/j.ydbio.2017.05.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 05/23/2017] [Accepted: 05/24/2017] [Indexed: 11/20/2022]
Abstract
Signaling mediated by G protein-coupled receptors (GPCRs) is essential for the migration of cells toward chemoattractants. The recruitment of neutrophils to injured tissues in zebrafish larvae is a useful model for studying neutrophil migration and trafficking in vivo. Indeed, the study of this process led to the discovery that PI3Kγ is required for the polarity and motility of neutrophils, features that are necessary for the directed migration of these cells to wounds. However, the mechanism by which PI3Kγ is activated remains to be determined. Here we show that signaling by specifically the heterotrimeric G protein subunit Gβ1 is critical for neutrophil migration in response to wounding. In embryos treated with small-molecule inhibitors of Gβγ signaling, neutrophils failed to migrate to wound sites. Although both the Gβ1 and Gβ4 isoforms are expressed in migrating neutrophils, only deficiency for the former (morpholino-based knockdown) interfered with the directed migration of neutrophils towards wounds. The Gβ1 deficiency also impaired the ability of cells to change cell shape and reduced their general motility, defects that are similar to those in neutrophils deficient for PI3Kγ. Transplantation assays showed that the requirement for Gβ1 in neutrophil migration is cell autonomous. Finally, live imaging revealed that Gβ1 is required for polarized activation of PI3K, and for the actin dynamics that enable neutrophil migration. Collectively, our data indicate that Gβ1 signaling controls proper neutrophil migration by activating PI3K and modulating actin dynamics. Moreover, they illustrate a role for a specific Gβ isoform in chemotaxis in vivo.
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16
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Chen M, Liu S, Li W, Zhang Z, Zhang X, Zhang XE, Cui Z. Three-Fragment Fluorescence Complementation Coupled with Photoactivated Localization Microscopy for Nanoscale Imaging of Ternary Complexes. ACS NANO 2016; 10:8482-8490. [PMID: 27584616 DOI: 10.1021/acsnano.6b03543] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Many cellular processes are governed by molecular machineries that involve multiple protein interactions. However, visualizing and identifying multiprotein complexes such as ternary complexes inside cells is always challenging, particularly in the subdiffraction cellular space. Here, we developed a three-fragment fluorescence complementation system (TFFC) based on the splitting of a photoactivatable fluorescent protein, mIrisFP, for the imaging of ternary complexes inside living cells. Using a combination of TFFC and photoactivated localization microscopy (PALM), namely, the TFFC-PALM technique, we are able to identify the multi-interaction of a ternary complex with nanometer-level spatial resolution and single-molecule sensitivity. The TFFC-PALM system has been further applied to the analysis of the Gs ternary complex, which is composed of αs, β1, and γ2 subunits, providing further insights into the subcellular localization and function of G protein subunits at the single-molecule level. The TFFC-PALM represents a valuable method for the visualization and identification of ternary complexes inside cells at the nanometer scale.
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Affiliation(s)
- Minghai Chen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Sanying Liu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Wei Li
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
| | - Zhiping Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
| | - Xiaowei Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
| | - Xian-En Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , Beijing 100101, China
| | - Zongqiang Cui
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences , Wuhan 430071, China
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Khan SM, Min A, Gora S, Houranieh GM, Campden R, Robitaille M, Trieu P, Pétrin D, Jacobi AM, Behlke MA, Angers S, Hébert TE. Gβ 4 γ 1 as a modulator of M3 muscarinic receptor signalling and novel roles of Gβ 1 subunits in the modulation of cellular signalling. Cell Signal 2015; 27:1597-608. [DOI: 10.1016/j.cellsig.2015.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 04/16/2015] [Accepted: 04/17/2015] [Indexed: 01/01/2023]
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18
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Brand CS, Sadana R, Malik S, Smrcka AV, Dessauer CW. Adenylyl Cyclase 5 Regulation by Gβγ Involves Isoform-Specific Use of Multiple Interaction Sites. Mol Pharmacol 2015. [PMID: 26206488 DOI: 10.1124/mol.115.099556] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Adenylyl cyclase (AC) converts ATP into cyclic AMP (cAMP), an important second messenger in cell signaling. Heterotrimeric G proteins and other regulators are important for control of AC activity. Depending on the AC isoform, Gβγ subunits can either conditionally stimulate or inhibit cAMP synthesis. We previously showed that the Gαs-βγ heterotrimer binds to the N terminus (NT) of type 5 AC (AC5). We now show that Gβγ binds to the NT of a wide variety of AC isoforms. We hypothesized that Gβγ/AC5 interactions involving inactive heterotrimer and Gβγ stimulation of AC5 were separable events. Mutations of the Gβγ "hotspot" show that this site is necessary for AC5 stimulation but not for interactions with the first 198 aa of AC5NT, which is a G protein scaffolding site. This contrasts with AC6, where the Gβγ hotspot is required for both interactions with AC6NT and for stimulation of AC6. Additionally, the SIGK hotspot peptide disrupts Gβγ regulation of AC isoforms 1, 2, and 6, but not AC5. Gβγ also binds the C1/C2 catalytic domains of AC5 and AC6. Finally, cellular interactions with full-length AC5 depend on multiple sites on Gβγ. This suggests an isoform-specific mechanism in which bound Gβγ at the AC5NT is ideally situated for spatiotemporal control of AC5. We propose Gβγ regulation of AC involves multiple binding events, and the role of the AC NT for mechanisms of regulation by heterotrimeric G protein subunits is isoform-specific.
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Affiliation(s)
- Cameron S Brand
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas (C.S.B., C.W.D.); Department of Natural Sciences, University of Houston-Downtown, Houston, Texas (R.S.); and Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, New York (S.M., A.V.S.)
| | - Rachna Sadana
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas (C.S.B., C.W.D.); Department of Natural Sciences, University of Houston-Downtown, Houston, Texas (R.S.); and Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, New York (S.M., A.V.S.)
| | - Sundeep Malik
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas (C.S.B., C.W.D.); Department of Natural Sciences, University of Houston-Downtown, Houston, Texas (R.S.); and Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, New York (S.M., A.V.S.)
| | - Alan V Smrcka
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas (C.S.B., C.W.D.); Department of Natural Sciences, University of Houston-Downtown, Houston, Texas (R.S.); and Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, New York (S.M., A.V.S.)
| | - Carmen W Dessauer
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas (C.S.B., C.W.D.); Department of Natural Sciences, University of Houston-Downtown, Houston, Texas (R.S.); and Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, New York (S.M., A.V.S.)
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19
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Comprehensive analysis of heterotrimeric G-protein complex diversity and their interactions with GPCRs in solution. Proc Natl Acad Sci U S A 2015; 112:E1181-90. [PMID: 25733868 DOI: 10.1073/pnas.1417573112] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Agonist binding to G-protein-coupled receptors (GPCRs) triggers signal transduction cascades involving heterotrimeric G proteins as key players. A major obstacle for drug design is the limited knowledge of conformational changes upon agonist binding, the details of interaction with the different G proteins, and the transmission to movements within the G protein. Although a variety of different GPCR/G protein complex structures would be needed, the transient nature of this complex and the intrinsic instability against dissociation make this endeavor very challenging. We have previously evolved GPCR mutants that display higher stability and retain their interaction with G proteins. We aimed at finding all G-protein combinations that preferentially interact with neurotensin receptor 1 (NTR1) and our stabilized mutants. We first systematically analyzed by coimmunoprecipitation the capability of 120 different G-protein combinations consisting of αi1 or αsL and all possible βγ-dimers to form a heterotrimeric complex. This analysis revealed a surprisingly unrestricted ability of the G-protein subunits to form heterotrimeric complexes, including βγ-dimers previously thought to be nonexistent, except for combinations containing β5. A second screen on coupling preference of all G-protein heterotrimers to NTR1 wild type and a stabilized mutant indicated a preference for those Gαi1βγ combinations containing γ1 and γ11. Heterotrimeric G proteins, including combinations believed to be nonexistent, were purified, and complexes with the GPCR were prepared. Our results shed new light on the combinatorial diversity of G proteins and their coupling to GPCRs and open new approaches to improve the stability of GPCR/G-protein complexes.
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20
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Charpentier TH, Waldo GL, Barrett MO, Huang W, Zhang Q, Harden TK, Sondek J. Membrane-induced allosteric control of phospholipase C-β isozymes. J Biol Chem 2014; 289:29545-57. [PMID: 25193662 PMCID: PMC4207972 DOI: 10.1074/jbc.m114.586784] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/13/2014] [Indexed: 11/06/2022] Open
Abstract
All peripheral membrane proteins must negotiate unique constraints intrinsic to the biological interface of lipid bilayers and the cytosol. Phospholipase C-β (PLC-β) isozymes hydrolyze the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) to propagate diverse intracellular responses that underlie the physiological action of many hormones, neurotransmitters, and growth factors. PLC-β isozymes are autoinhibited, and several proteins, including Gαq, Gβγ, and Rac1, directly engage distinct regions of these phospholipases to release autoinhibition. To understand this process, we used a novel, soluble analog of PIP2 that increases in fluorescence upon cleavage to monitor phospholipase activity in real time in the absence of membranes or detergents. High concentrations of Gαq or Gβ1γ2 did not activate purified PLC-β3 under these conditions despite their robust capacity to activate PLC-β3 at membranes. In addition, mutants of PLC-β3 with crippled autoinhibition dramatically accelerated the hydrolysis of PIP2 in membranes without an equivalent acceleration in the hydrolysis of the soluble analog. Our results illustrate that membranes are integral for the activation of PLC-β isozymes by diverse modulators, and we propose a model describing membrane-mediated allosterism within PLC-β isozymes.
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Affiliation(s)
| | | | | | - Weigang Huang
- the Division of Chemical Biology and Medicinal Chemistry, University of North Carolina School of Pharmacy, Chapel Hill, North Carolina 27599
| | - Qisheng Zhang
- the Division of Chemical Biology and Medicinal Chemistry, University of North Carolina School of Pharmacy, Chapel Hill, North Carolina 27599
| | | | - John Sondek
- From the Departments of Pharmacology and Biochemistry and Biophysics and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599 and
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Trusov Y, Chakravorty D, Botella JR. Diversity of heterotrimeric G-protein γ subunits in plants. BMC Res Notes 2012; 5:608. [PMID: 23113884 PMCID: PMC3508898 DOI: 10.1186/1756-0500-5-608] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 10/15/2012] [Indexed: 12/13/2022] Open
Abstract
Background Heterotrimeric G-proteins, consisting of three subunits Gα, Gβ and Gγ are present in most eukaryotes and mediate signaling in numerous biological processes. In plants, Gγ subunits were shown to provide functional selectivity to G-proteins. Three unconventional Gγ subunits were recently reported in Arabidopsis, rice and soybean but no structural analysis has been reported so far. Their relationship with conventional Gγ subunits and taxonomical distribution has not been yet demonstrated. Results After an extensive similarity search through plant genomes, transcriptomes and proteomes we assembled over 200 non-redundant proteins related to the known Gγ subunits. Structural analysis of these sequences revealed that most of them lack the obligatory C-terminal prenylation motif (CaaX). According to their C-terminal structures we classified the plant Gγ subunits into three distinct types. Type A consists of Gγ subunits with a putative prenylation motif. Type B subunits lack a prenylation motif and do not have any cysteine residues in the C-terminal region, while type C subunits contain an extended C-terminal domain highly enriched with cysteines. Comparative analysis of C-terminal domains of the proteins, intron-exon arrangement of the corresponding genes and phylogenetic studies suggested a common origin of all plant Gγ subunits. Conclusion Phylogenetic analyses suggest that types C and B most probably originated independently from type A ancestors. We speculate on a potential mechanism used by those Gγ subunits lacking isoprenylation motifs to anchor the Gβγ dimer to the plasma membrane and propose a new flexible nomenclature for plant Gγ subunits. Finally, in the light of our new classification, we give a word of caution about the interpretation of Gγ research in Arabidopsis and its generalization to other plant species.
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Affiliation(s)
- Yuri Trusov
- Plant Genetic Engineering Laboratory, School of Agriculture and Food Sciences, University of Queensland, Brisbane, Queensland, 4072, Australia
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22
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McGrath MF, Ogawa T, de Bold AJ. Ras dexamethasone-induced protein 1 is a modulator of hormone secretion in the volume overloaded heart. Am J Physiol Heart Circ Physiol 2012; 302:H1826-37. [PMID: 22408026 DOI: 10.1152/ajpheart.01085.2011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Because of the crucial role of the endocrine heart in maintaining homeostasis, considerable effort has been focused on the elucidation of the mechanistic underlying gene expression and secretion of the cardiac hormones atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP). However, much remains to be determined regarding specific molecular events involved in cardiocyte secretory function. In this work, we identified genes involved in the transcriptional response of the endocrine heart to volume overload (VO) and signaling pathways involved in its regulation. To this end, the cardiac atrial and ventricular transcriptomes were analyzed in the heart of rats subjected to experimentally induced aorto-caval shunt VO. Pathway analysis revealed unique gene expression profiles in the VO atria for G-protein signaling, notably a significant downregulation of Ras dexamethasone-induced protein 1 (RASD1). In vitro, knockdown of RASD1 in the atrial-derived HL-1 cells, significantly increased ANF secretion. Concurrent knockdown of RASD1 and its effectors Gα(o1) or Gβ(1)γ(2) abrogated the endocrine response, demonstrating a previously unknown negative modulator role for RASD1. RASD1 thus emerges as a tonic inhibitor of ANF secretion and illustrates for the first time the concept of inhibitory protein regulators of ANF release. The novel molecular function identified herein for RASD1 is of considerable importance given its therapeutic implications for cardiovascular disease.
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Affiliation(s)
- Monica Forero McGrath
- Cardiovascular Endocrinology Laboratory, University of Ottawa Heart Institute, University of Ottawa, Ottawa, Ontario, Canada
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Dingus J, Hildebrandt JD. Synthesis and assembly of G protein βγ dimers: comparison of in vitro and in vivo studies. Subcell Biochem 2012; 63:155-80. [PMID: 23161138 DOI: 10.1007/978-94-007-4765-4_9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The heterotrimeric GTP-binding proteins (G proteins) are the canonical cellular machinery used with the approximately 700 G protein-coupled receptors (GPCRs) in the human genome to transduce extracellular signals across the plasma membrane. The synthesis of the constituent G protein subunits, and their assembly into Gβγ dimers and G protein heterotrimers, determines the signaling repertoire for G-protein/GPCR signaling in cells. These synthesis/assembly -processes are intimately related to two other overlapping events in the intricate pathway leading to formation of G protein signaling complexes, posttranslational modification and intracellular trafficking of G proteins. The assembly of the Gβγ dimer is a complex process involving multiple accessory proteins and organelles. The mechanisms involved are becoming increasingly appreciated, but are still incompletely understood. In vitro and in vivo (cellular) studies provide different perspectives of these processes, and a comparison of them can provide insight into both our current level of understanding and directions to be taken in future investigations.
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Affiliation(s)
- Jane Dingus
- Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, SC, 29425, USA
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Mulligan T, Farber SA. Central and C-terminal domains of heterotrimeric G protein gamma subunits differentially influence the signaling necessary for primordial germ cell migration. Cell Signal 2011; 23:1617-24. [PMID: 21699975 DOI: 10.1016/j.cellsig.2011.05.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Accepted: 05/23/2011] [Indexed: 10/18/2022]
Abstract
Heterotrimeric G protein signaling is involved in many pathways essential to development including those controlling cell migration, proliferation, differentiation and apoptosis. One key developmental event known to rely on proper heterotrimeric G protein signaling is primordial germ cell (PGC) migration. We previously developed an in vivo PGC migration assay that identified differences in the signaling capacity of G protein gamma subunits. In this study we developed Gγ subunit chimeras to determine the regions of Gγ isoforms that are responsible for these differences. The central section of the Gγ subunit was found to be necessary for the ability of a Gγ subunit to mediate signaling involved in PGC migration. Residues found in the carboxy-terminal segment of Gγ transducin (gngt1) were found to be responsible for the ability of this subunit to disrupt PGC migration. The type of prenylation did not affect the ability of a Gγ subunit to reverse prenylation-deficient-Gγ-induced PGC migration defects. However, a version of gng2, engineered to be farnesylated instead of geranylgeranylated, still lacks the ability to reverse PGC migration defects known to result from treatment of zebrafish with geranylgeranyl transferase inhibitors (GGTI), supporting the notion that Gγ subunits are one of several protein targets that need to be geranylgeranylated to orchestrate the proper long-range migration of PGCs.
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Affiliation(s)
- Timothy Mulligan
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218, USA
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25
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Heterogeneous Prenyl Processing of the Heterotrimeric G protein Gamma Subunits. PROTEIN PRENYLATION PART A 2011. [DOI: 10.1016/b978-0-12-381339-8.00006-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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27
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Schwindinger WF, Mihalcik LJM, Giger KE, Betz KS, Stauffer AM, Linden J, Herve D, Robishaw JD. Adenosine A2A receptor signaling and golf assembly show a specific requirement for the gamma7 subtype in the striatum. J Biol Chem 2010; 285:29787-96. [PMID: 20639202 DOI: 10.1074/jbc.m110.142620] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The adenosine A(2A) receptor (A(2A)R) is increasingly recognized as a novel therapeutic target in Parkinson disease. In striatopallidal neurons, the G-protein α(olf) subtype is required to couple this receptor to adenylyl cyclase activation. It is now well established that the βγ dimer also performs an active role in this signal transduction process. In principal, sixty distinct βγ dimers could arise from combinatorial association of the five known β and 12 γ subunit genes. However, key questions regarding which βγ subunit combinations exist and whether they perform specific signaling roles in the context of the organism remain to be answered. To explore these questions, we used a gene targeting approach to specifically ablate the G-protein γ(7) subtype. Revealing a potentially new signaling paradigm, we show that the level of the γ(7) protein controls the hierarchial assembly of a specific G-protein α(olf)β(2)γ(7) heterotrimer in the striatum. Providing a probable basis for the selectivity of receptor signaling, we further demonstrate that loss of this specific G-protein heterotrimer leads to reduced A(2A)R activation of adenylyl cyclase. Finally, substantiating an important role for this signaling pathway in pyschostimulant responsiveness, we show that mice lacking the G-protein γ(7) subtype exhibit an attenuated behavioral response to caffeine. Collectively, these results further support the A(2A)R G-protein α(olf)β(2)γ(7) interface as a possible therapeutic target for Parkinson disease.
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28
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Yoshiura C, Kofuku Y, Ueda T, Mase Y, Yokogawa M, Osawa M, Terashima Y, Matsushima K, Shimada I. NMR Analyses of the Interaction between CCR5 and Its Ligand Using Functional Reconstitution of CCR5 in Lipid Bilayers. J Am Chem Soc 2010; 132:6768-77. [DOI: 10.1021/ja100830f] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Chie Yoshiura
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Yutaka Kofuku
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Takumi Ueda
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Yoko Mase
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Mariko Yokogawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Masanori Osawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Yuya Terashima
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Kouji Matsushima
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
| | - Ichio Shimada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Molecular Preventive Medicine, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, Effector Cell Institute, Inc., Tokyo 150-0036, Japan, and Biomedicinal Information Research Center (BIRC), National Institute of Advanced Industrial Science and Technology (AIST), Aomi 2-41-6, Koto-ku, Tokyo 135-0064, Japan
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29
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Prenylation-deficient G protein gamma subunits disrupt GPCR signaling in the zebrafish. Cell Signal 2009; 22:221-33. [PMID: 19786091 DOI: 10.1016/j.cellsig.2009.09.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 09/02/2009] [Accepted: 09/14/2009] [Indexed: 01/01/2023]
Abstract
Prenylation of G protein gamma (gamma) subunits is necessary for the membrane localization of heterotrimeric G proteins and for functional heterotrimeric G protein coupled receptor (GPCR) signaling. To evaluate GPCR signaling pathways during development, we injected zebrafish embryos with mRNAs encoding Ggamma subunits mutated so that they can no longer be prenylated. Low-level expression of these prenylation-deficient Ggamma subunits driven either ubiquitously or specifically in the primordial germ cells (PGCs) disrupts GPCR signaling and manifests as a PGC migration defect. This disruption results in a reduction of calcium accumulation in the protrusions of migrating PGCs and a failure of PGCs to directionally migrate. When co-expressed with a prenylation-deficient Ggamma, 8 of the 17 wildtype Ggamma isoforms individually confer the ability to restore calcium accumulation and directional migration. These results suggest that while the Ggamma subunits possess the ability to interact with G Beta (beta) proteins, only a subset of wildtype Ggamma proteins are stable within PGCs and can interact with key signaling components necessary for PGC migration. This in vivo study highlights the functional redundancy of these signaling components and demonstrates that prenylation-deficient Ggamma subunits are an effective tool to investigate the roles of GPCR signaling events during vertebrate development.
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30
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Dupré DJ, Robitaille M, Rebois RV, Hébert TE. The role of Gbetagamma subunits in the organization, assembly, and function of GPCR signaling complexes. Annu Rev Pharmacol Toxicol 2009; 49:31-56. [PMID: 18834311 DOI: 10.1146/annurev-pharmtox-061008-103038] [Citation(s) in RCA: 212] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The role of Gbetagamma subunits in cellular signaling has become well established in the past 20 years. Not only do they regulate effectors once thought to be the sole targets of Galpha subunits, but it has become clear that they also have a unique set of binding partners and regulate signaling pathways that are not always localized to the plasma membrane. However, this may be only the beginning of the story. Gbetagamma subunits interact with G protein-coupled receptors, Galpha subunits, and several different effector molecules during assembly and trafficking of receptor-based signaling complexes and not simply in response to ligand stimulation at sites of receptor cellular activity. Gbetagamma assembly itself seems to be tightly regulated via the action of molecular chaperones and in turn may serve a similar role in the assembly of specific signaling complexes. We propose that specific Gbetagamma subunits have a broader role in controlling the architecture, assembly, and activity of cellular signaling pathways.
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Affiliation(s)
- Denis J Dupré
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.
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31
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Ratnala VRP, Kobilka B. Understanding the ligand-receptor-G protein ternary complex for GPCR drug discovery. Methods Mol Biol 2009; 552:67-77. [PMID: 19513642 DOI: 10.1007/978-1-60327-317-6_5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Understanding the ternary complex between G protein-coupled receptors (GPCRs), cognate G proteins, and their ligands is an important landmark for drug discovery. Yet, little is known about the specific interactions between GPCRs and G proteins. For a better perspective on the ternary complex dynamics, we adapted a beta(2)-adrenergic receptor(beta(2)AR)-tetGs(alpha) reconstitution system and found evidence that for efficient coupling of the beta(2)AR to Gs does not require specific interactions between the betagamma-subunits and the beta(2)AR. Our results demonstrate that specific interactions between betagamma and the beta(2)AR are not required for G protein activation but likely serve to anchor Gs(alpha) to the plasma membrane. Our results also suggests that the advantages of analysis of G protein activation by using beta(2)AR receptor-tetGs(alpha) system in vitro at the close proximity of the receptor may constitute a simple screening system that avoids false positives and potentially adapted to screen drugs for other GPCRs.
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32
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Roychowdhury S, Rasenick MM. Submembraneous microtubule cytoskeleton: regulation of microtubule assembly by heterotrimeric Gproteins. FEBS J 2008; 275:4654-63. [PMID: 18754776 PMCID: PMC2782913 DOI: 10.1111/j.1742-4658.2008.06614.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Heterotrimeric Gproteins participate in signal transduction by transferring signals from cell surface receptors to intracellular effector molecules. Gproteins also interact with microtubules and participate in microtubule-dependent centrosome/chromosome movement during cell division, as well as neuronal differentiation. In recent years, significant progress has been made in our understanding of the biochemical/functional interactions between Gprotein subunits (alpha and betagamma) and microtubules, and the molecular details emerging from these studies suggest that alpha and betagamma subunits of Gproteins interact with tubulin/microtubules to regulate the assembly/dynamics of microtubules, providing a novel mechanism for hormone- or neurotransmitter-induced rapid remodeling of cytoskeleton, regulation of the mitotic spindle for centrosome/chromosome movements in cell division, and neuronal differentiation in which structural plasticity mediated by microtubules is important for appropriate synaptic connections and signal transmission.
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Affiliation(s)
- Sukla Roychowdhury
- Department of Biological Sciences, University of Texas, El Paso, TX, USA.
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33
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Vögler O, Barceló JM, Ribas C, Escribá PV. Membrane interactions of G proteins and other related proteins. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1778:1640-52. [PMID: 18402765 DOI: 10.1016/j.bbamem.2008.03.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Revised: 03/01/2008] [Accepted: 03/12/2008] [Indexed: 01/25/2023]
Abstract
Guanine nucleotide-binding proteins, G proteins, propagate incoming messages from receptors to effector proteins. They switch from an inactive to active state by exchanging a GDP molecule for GTP, and they return to the inactive form by hydrolyzing GTP to GDP. Small monomeric G proteins, such as Ras, are involved in controlling cell proliferation, differentiation and apoptosis, and they interact with membranes through isoprenyl moieties, fatty acyl moieties, and electrostatic interactions. This protein-lipid binding facilitates productive encounters of Ras and Raf proteins in defined membrane regions, so that signals can subsequently proceed through MEK and ERK kinases, which constitute the canonical MAP kinase signaling cassette. On the other hand, heterotrimeric G proteins undergo co/post-translational modifications in the alpha (myristic and/or palmitic acid) and the gamma (farnesol or geranylgeraniol) subunits. These modifications not only assist the G protein to localize to the membrane but they also help distribute the heterotrimer (Galphabetagamma) and the subunits generated upon activation (Galpha and Gbetagamma) to appropriate membrane microdomains. These proteins transduce messages from ubiquitous serpentine receptors, which control important functions such as taste, vision, blood pressure, body weight, cell proliferation, mood, etc. Moreover, the exchange of GDP by GTP is triggered by nucleotide exchange factors. Membrane receptors that activate G proteins can be considered as such, but other cytosolic, membranal or amphitropic proteins can accelerate the rate of G protein exchange or even activate this process in the absence of receptor-mediated activation. These and other protein-protein interactions of G proteins with other signaling proteins are regulated by their lipid preferences. Thus, G protein-lipid interactions control the features of messages and cell physiology.
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Affiliation(s)
- Oliver Vögler
- Molecular Cell Biomedicine, Department of Biology-IUNICS, Universitat de les Illes Balears, Palma de Mallorca, Spain
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34
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Hynes TR, Yost E, Mervine S, Berlot CH. Multicolor BiFC analysis of competition among G protein beta and gamma subunit interactions. Methods 2008; 45:207-13. [PMID: 18586104 DOI: 10.1016/j.ymeth.2008.06.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 05/23/2008] [Accepted: 06/16/2008] [Indexed: 12/19/2022] Open
Abstract
We have applied multicolor BiFC to study the association preferences of G protein beta and gamma subunits in living cells. Cells co-express multiple isoforms of beta and gamma subunits, most of which can form complexes. Although many betagamma complexes exhibit similar properties when assayed in reconstituted systems, knockout experiments in vivo suggest that individual isoforms have unique functions. BiFC makes it possible to correlate betagamma complex formation with functionality in intact cells by comparing the amounts of fluorescent betagamma complexes with their abilities to modulate effector proteins. The relative predominance of specific betagamma complexes in vivo is not known. To address this issue, multicolor BiFC can determine the association preferences of beta and gamma subunits by simultaneously visualizing the two fluorescent complexes formed when beta or gamma subunits fused to amino terminal fragments of yellow fluorescent protein (YFP-N) and cyan fluorescent protein (CFP-N) compete to interact with limiting amounts of a common gamma or beta subunit, respectively, fused to a carboxyl terminal fragment of CFP (CFP-C). Multicolor BiFC also makes it possible to determine the roles of interacting proteins in the subcellular targeting of complexes, study the formation of protein complexes that are unstable under isolation conditions, determine the roles of co-expressed proteins in regulating the association preferences of interacting proteins, and visualize dynamic events affecting multiple protein complexes. These approaches can be applied to studying the assembly and functions of a wide variety of protein complexes in the context of a living cell.
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Affiliation(s)
- Thomas R Hynes
- Weis Center for Research, Geisinger Clinic, 100 North Academy Avenue, Danville, PA 17822-2623, USA
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35
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Heterotrimeric G protein activation by G-protein-coupled receptors. Nat Rev Mol Cell Biol 2008; 9:60-71. [PMID: 18043707 DOI: 10.1038/nrm2299] [Citation(s) in RCA: 802] [Impact Index Per Article: 50.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Heterotrimeric G proteins have a crucial role as molecular switches in signal transduction pathways mediated by G-protein-coupled receptors. Extracellular stimuli activate these receptors, which then catalyse GTP-GDP exchange on the G protein alpha-subunit. The complex series of interactions and conformational changes that connect agonist binding to G protein activation raise various interesting questions about the structure, biomechanics, kinetics and specificity of signal transduction across the plasma membrane.
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36
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Kleuss C. Somatostatin modulates voltage-dependent Ca2+ channels in GH3 cells via a specific G(o) splice variant. CIBA FOUNDATION SYMPOSIUM 2007; 190:171-82; discussion 182-6. [PMID: 7587646 DOI: 10.1002/9780470514733.ch11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In rat pituitary GH3 cells Ca2+ current through L-type channels is reduced by somatostatin. This modulation of channel activity by somatostatin receptors is mediated by a guanine nucleotide-binding regulatory protein (G protein). It is sensitive to pertussis toxin, indicating the involvement of a G(o)- or Gi-type G protein in this pathway. The identity of this G protein was determined by suppressing the expression of endogenous G proteins individually via intranuclear injection of antisense oligonucleotides. This method was applied to GH3 cells to screen several G protein alpha, beta and gamma subunits for their roles in the defined signal transduction pathway. The loss of somatostatin's modulating activity on the voltage-dependent Ca2+ channel after oligonucleotide injection revealed the involvement of G(o) alpha 2 beta 1 gamma 3 to the exclusion of other closely related subtypes.
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Affiliation(s)
- C Kleuss
- Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Germany
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37
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Johnston CA, Siderovski DP. Receptor-mediated activation of heterotrimeric G-proteins: current structural insights. Mol Pharmacol 2007; 72:219-30. [PMID: 17430994 DOI: 10.1124/mol.107.034348] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) serve as catalytic activators of heterotrimeric G-proteins (Galphabetagamma) by exchanging GTP for the bound GDP on the Galpha subunit. This guanine nucleotide exchange factor activity of GPCRs is the initial step in the G-protein cycle and determines the onset of various intracellular signaling pathways that govern critical physiological responses to extracellular cues. Although the structural basis for many steps in the G-protein nucleotide cycle have been made clear over the past decade, the precise mechanism for receptor-mediated G-protein activation remains incompletely defined. Given that these receptors have historically represented a set of rich drug targets, a more complete understanding of their mechanism of action should provide further avenues for drug discovery. Several models have been proposed to explain the communication between activated GPCRs and Galphabetagamma leading to the structural changes required for guanine nucleotide exchange. This review is focused on the structural biology of G-protein signal transduction with an emphasis on the current hypotheses regarding Galphabetagamma activation. We highlight several recent results shedding new light on the structural changes in Galpha that may underlie GDP release.
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Affiliation(s)
- Christopher A Johnston
- Department of Pharmacology, University of North Carolina at Chapel Hill, CB# 7365, Chapel Hill, NC 27599-7365, USA
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38
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Abstract
The regulation of presynaptic, voltage-gated calcium channels by activation of heptahelical G protein-coupled receptors exerts a crucial influence on presynaptic calcium entry and hence on neurotransmitter release. Receptor activation subjects presynaptic N- and P/Q-type calcium channels to a rapid, membrane-delimited inhibition-mediated by direct, voltage-dependent interactions between G protein betagamma subunits and the channels-and to a slower, voltage-independent modulation involving soluble second messenger molecules. In turn, the direct inhibition of the channels is regulated as a function of many factors, including channel subtype, ancillary calcium channel subunits, and the types of G proteins and G protein regulatory factors involved. Twenty-five years after this mode of physiological regulation was first described, we review the investigations that have led to our current understanding of its molecular mechanisms.
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Affiliation(s)
- H William Tedford
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, Canada
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39
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Gao X, Sadana R, Dessauer CW, Patel TB. Conditional stimulation of type V and VI adenylyl cyclases by G protein betagamma subunits. J Biol Chem 2006; 282:294-302. [PMID: 17110384 DOI: 10.1074/jbc.m607522200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In a yeast two-hybrid screen of mouse brain cDNA library, using the N-terminal region of human type V adenylyl cyclase (hACV) as bait, we identified G protein beta2 subunit as an interacting partner. Additional yeast two-hybrid assays showed that the Gbeta(1) subunit also interacts with the N-terminal segments of hACV and human type VI adenylyl cyclase (hACVI). In vitro adenylyl cyclase (AC) activity assays using membranes of Sf9 cells expressing hACV or hACVI showed that Gbetagamma subunits enhance the activity of these enzymes provided either Galpha(s) or forskolin is present. Deletion of residues 77-151, but not 1-76, in the N-terminal region of hACVI obliterated the ability of Gbetagamma subunits to conditionally stimulate the enzyme. Likewise, activities of the recombinant, engineered, soluble forms of ACV and ACVI, which lack the N termini, were not enhanced by Gbetagamma subunits. Transfection of the C terminus of G protein receptor kinase 2 to sequester endogenous Gbetagamma subunits attenuated the ability of isoproterenol to increase cAMP accumulation in COS-7 cells overexpressing hACVI even when G(i) was inactivated by pertussis toxin. Therefore, we conclude that the N termini of human hACV and hACVI are necessary for interactions with, and regulation by, Gbetagamma subunits both in vitro and in intact cells. Moreover, Gbetagamma subunits derived from a source(s) other than G(i) are necessary for the full activation of hACVI by isoproterenol in intact cells.
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Affiliation(s)
- Xianlong Gao
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois 60153, USA
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40
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Mervine SM, Yost EA, Sabo JL, Hynes TR, Berlot CH. Analysis of G protein betagamma dimer formation in live cells using multicolor bimolecular fluorescence complementation demonstrates preferences of beta1 for particular gamma subunits. Mol Pharmacol 2006; 70:194-205. [PMID: 16641313 DOI: 10.1124/mol.106.022616] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The specificity of G protein betagamma signaling demonstrated by in vivo knockouts is greater than expected based on in vitro assays of betagamma function. In this study, we investigated the basis for this discrepancy by comparing the abilities of seven beta1gamma complexes containing gamma1, gamma2, gamma5, gamma7, gamma10, gamma11, or gamma12 to interact with alphas and of these gamma subunits to compete for interaction with beta1 in live human embryonic kidney (HEK) 293 cells. betagamma complexes were imaged using bimolecular fluorescence complementation, in which fluorescence is produced by two nonfluorescent fragments (N and C) of cyan fluorescent protein (CFP) or yellow fluorescent protein (YFP) when brought together by proteins fused to each fragment. Plasma membrane targeting of alphas-CFP varied inversely with its expression level, and the abilities of YFP-N-beta1YFP-C-gamma complexes to increase this targeting varied by 2-fold or less. However, there were larger differences in the abilities of the CFP-N-gamma subunits to compete for association with CFP-C-beta1. When the intensities of coexpressed CFP-C-beta1CFP-N-gamma (cyan) and CFP-C-beta1YFP-N-gamma2 (yellow) complexes were compared under conditions in which CFP-C-beta1 was limiting, the CFP-N-gamma subunits exhibited a 4.5-fold range in their abilities to compete with YFP-N-gamma2 for association with CFP-C-beta1. CFP-N-gamma12 and CFP-N-gamma1 were the strongest and weakest competitors, respectively. Taken together with previous demonstrations of a role for betagamma in the specificity of receptor signaling, these results suggest that differences in the association preferences of coexpressed beta and gamma subunits for each other can determine which complexes predominate and participate in signaling pathways in intact cells.
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Affiliation(s)
- Stacy M Mervine
- Weis Center for Research, Geisinger Clinic, 100 North Academy Avenue, Danville, PA 17822-2623, USA
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41
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Lamango NS. Liver prenylated methylated protein methyl esterase is an organophosphate-sensitive enzyme. J Biochem Mol Toxicol 2006; 19:347-57. [PMID: 16292756 DOI: 10.1002/jbt.20100] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Prenylation and subsequent methylation are essential modifications on a significant proportion of eucaryotic proteins. Proteins such as the G-gamma subunits of G-protein coupled receptors, nuclear lamins, and guanine nucleotide-binding proteins such as Ras are prenylated and undergo methylation. Prenylated methylated protein methyl esterase (PMPMEase) readily hydrolyses the prenylated protein methyl esters, thus making this step reversible and possibly regulatory. Benzoyl-glycyl-farnesyl-cysteine methyl ester (BzGFCM) was developed as a specific PMPMEase substrate and characterized by electron spray ionization mass spectrometry (ESI-MS) to be of the calculated molecular mass. Rat liver and brain PMPMEase hydrolyzed BzGFCM, forming benzoyl-glycyl-farnesyl-cysteine (BzGFC) in a time- and concentration-dependent manner. Both enzymes cleaved BzGFCM with K(m) values of 4.58 +/- 0.30 and 25.57 +/- 2.36 microM and V(max) values of 2.21 +/- 0.03 and 0.17 +/- 0.003 nmol/min/mg, respectively. The liver enzyme eluted from a gel-filtration column as a single peak of apparent size, 89 kDa. The brain enzyme eluted as two main peaks of 53 and 890 kDa. Organophosphorus pesticides (OPs), which are suspected to be involved in human disorders such as parkinsonism, neuronal, and retinal degeneration, inhibited the liver enzyme with IC(50) values from 4.77 muM for parathion to 0.04 microM for paraoxon, respectively. Only about 25% of the brain enzyme was inhibited by 0.5-1 mM solutions of mipafox, while 0.1 and 1 mM paraoxon inhibited over 50% and 95% of the enzyme, respectively. Paraoxon is thus about 2,250 times less potent against the brain than the liver PMPMEase. BzGFCM was not hydrolyzed by various cholinesterases, indicating its specificity for PMPMEase. Perturbations in prenylated protein metabolism might play a role in noncholinergic OPs-induced toxicity, since prenylated proteins play such important roles in cell signaling, proliferation, differentiation, and apoptosis.
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Affiliation(s)
- Nazarius S Lamango
- College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, Tallahassee, 32307, USA.
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42
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Mittal V, Linder M. Biochemical characterization of RGS14: RGS14 activity towards G-protein alpha subunits is independent of its binding to Rap2A. Biochem J 2006; 394:309-15. [PMID: 16246175 PMCID: PMC1386029 DOI: 10.1042/bj20051086] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RGS (regulators of G-protein signalling) modulate signalling by acting as GAPs (GTPase-activating proteins) for alpha subunits of heterotrimeric G-proteins. RGS14 accelerates GTP hydrolysis by G(ialpha) family members through its RGS domain and suppresses guanine nucleotide dissociation from G(ialpha1) and G(ialpha3) subunits through its C-terminal GoLoco domain. Additionally, RGS14 binds the activated forms of the small GTPases Rap1 and Rap2 by virtue of tandem RBDs (Raf-like Ras/Rap binding domains). RGS14 was identified in a screen for Rap2 effectors [Traver, Splingard, Gaudriault and De Gunzburg (2004) Biochem. J. 379, 627-632]. In the present study, we tested whether Rap binding regulates RGS14's biochemical activities. We found that RGS14 activity towards heterotrimeric G-proteins, as either a GAP or a GDI (guanine nucleotide dissociation inhibitor), was unaffected by Rap binding. Extending our biochemical characterization of RGS14, we also examined whether RGS14 can suppress guanine nucleotide exchange on G(ialpha1) in the context of the heterotrimer. We found that a heterotrimer composed of N-myristoylated G(ialpha1) and prenylated G(betagamma) is resistant to the GDI activity of the GoLoco domain of RGS14. This is consistent with models of GoLoco domain action on free G(alpha) and suggests that RGS14 alone cannot induce subunit dissociation to promote receptor-independent activation of G(betagamma)-mediated signalling pathways.
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Affiliation(s)
- Vivek Mittal
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Ave., Campus Box 8228, St. Louis, MO 63110, U.S.A
| | - Maurine E. Linder
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Ave., Campus Box 8228, St. Louis, MO 63110, U.S.A
- To whom correspondence should be addressed (email )
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Abstract
The G protein gamma13 subunit (Ggamma13) is expressed in taste and retinal and neuronal tissues and plays a key role in taste transduction. We identified PSD95, Veli-2, and other PDZ domain-containing proteins as binding partners for Ggamma13 by yeast two-hybrid and pull-down assays. In two-hybrid assays, Ggamma13 interacted specifically with the third PDZ domain of PSD95, the sole PDZ domain of Veli-2, and the third PDZ domain of SAP97, a PSD95-related protein. Ggamma13 did not interact with the other PDZ domains of PSD95. Coexpression of Ggamma13 with its Gbeta1 partner did not interfere with these two-hybrid interactions. The physical interaction of Ggamma13 with PSD95 in the cellular milieu was confirmed in pull-down assays following heterologous expression in HEK293 cells. The interaction of Ggamma13 with the PDZ domain of PSD95 was via the C-terminal CAAX tail of Ggamma13 (where AA indicates the aliphatic amino acid); alanine substitution of the CTAL sequence at the C terminus of Ggamma13 abolished its interactions with PSD95 in two-hybrid and pull-down assays. Veli-2 and SAP97 were identified in taste tissue and in Ggamma13-expressing taste cells. Coimmunoprecipitation of Ggamma13 and PSD95 from brain and of Ggamma13 and SAP97 from taste tissue indicates that Ggamma13 interacts with these proteins endogenously. This is the first demonstration that PDZ domain proteins interact with heterotrimeric G proteins via the CAAX tail of Ggamma subunits. The interaction of Ggamma13 with PDZ domain-containing proteins may provide a means to target particular Gbetagamma subunits to specific subcellular locations and/or macromolecular complexes involved in signaling pathways.
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Affiliation(s)
- Zairong Li
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York 10029, USA
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44
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Roychowdhury S, Martinez L, Salgado L, Das S, Rasenick MM. G protein activation is prerequisite for functional coupling between Gα/Gβγ and tubulin/microtubules. Biochem Biophys Res Commun 2006; 340:441-8. [PMID: 16380086 DOI: 10.1016/j.bbrc.2005.12.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2005] [Accepted: 12/03/2005] [Indexed: 11/29/2022]
Abstract
Heterotrimeric G proteins participate in signal transduction by transferring signals from cell surface receptors to intracellular effector molecules. Interestingly, recent results suggest that G proteins also interact with microtubules and participate in cell division and differentiation. It has been shown earlier that both alpha and betagamma subunits of G proteins modulate microtubule assembly in vitro. Since G protein activation and subsequent dissociation of alpha and betagamma subunits are necessary for G proteins to participate in signaling processes, here we asked if similar activation is required for modulation of microtubule assembly by G proteins. We reconstituted Galphabetagamma heterotrimer from myristoylated-Galpha and prenylated-Gbetagamma, and found that the heterotrimer blocks Gi1alpha activation of tubulin GTPase and inhibits the ability of Gbeta1gamma2 to promote in vitro microtubule assembly. Results suggest that G protein activation is required for functional coupling between Galpha/Gbetagamma and tubulin/microtubules, and supports the notion that regulation of microtubules is an integral component of G protein mediated signaling.
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Affiliation(s)
- Sukla Roychowdhury
- Neurological and Metabolic Disorder, University of Texas, El Paso, TX 79968, USA.
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45
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Myung CS, Lim WK, DeFilippo JM, Yasuda H, Neubig RR, Garrison JC. Regions in the G Protein γ Subunit Important for Interaction with Receptors and Effectors. Mol Pharmacol 2005; 69:877-87. [PMID: 16319284 DOI: 10.1124/mol.105.018994] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G betagamma dimers containing the gamma11 or gamma1 subunits are often less potent and effective in their ability to regulate effectors compared with dimers containing the gamma2 subunit. To explore the regions of the gamma subunit that affect the activity of the betagamma dimer, we constructed eight chimeric gamma subunits from the gamma1 and gamma2 subunits. Two chimeras were made in which the N-terminal regions of gamma1 and gamma2 were exchanged and two in which the C-terminal regions were transposed. Another set of chimeras was made in which the CAAX motifs of the chimeras were altered to direct modification with different prenyl groups. All eight gamma chimeras were expressed in Sf9 cells with the beta1 subunit, G betagamma dimers were purified, and then they were assayed in vitro for their ability to bind to the G alpha(i1) subunit, to couple G alpha(i1) to the A1 adenosine receptor, to stimulate phospholipase C-beta, and to regulate type I or type II adenyl cyclases. Dimers containing the C-terminal sequence of the gamma2 subunit modified with the geranylgeranyl lipid had the highest affinity for G(i1)alpha (range, 0.5-1.2 nM) and were most effective at coupling the G(i1)alpha subunit to receptor. These dimers were most effective at stimulating the phosphatidylinositol-specific phospholipase C-beta isoform and inhibiting type I adenyl cyclase. In contrast, betagamma dimers containing the N-terminal sequence of the gamma2 subunit and a geranylgeranyl group are most effective at activating type II adenyl cyclase. The results indicate that both the N- and C-terminal regions of the gamma subunit impart specificity to receptor and effector interactions.
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Affiliation(s)
- Chang-Seon Myung
- Department of Pharmacology, College of Pharmacy, Chungnam National University Daejeon, Korea
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46
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Abstract
One of the first hurdles to be negotiated in the postgenomic era involves the description of the entire protein content of the cell, the proteome. Such efforts are presently complicated by the various posttranslational modifications that proteins can experience, including glycosylation, lipid attachment, phosphorylation, methylation, disulfide bond formation, and proteolytic cleavage. Whereas these and other posttranslational protein modifications have been well characterized in Eucarya and Bacteria, posttranslational modification in Archaea has received far less attention. Although archaeal proteins can undergo posttranslational modifications reminiscent of what their eucaryal and bacterial counterparts experience, examination of archaeal posttranslational modification often reveals aspects not previously observed in the other two domains of life. In some cases, posttranslational modification allows a protein to survive the extreme conditions often encountered by Archaea. The various posttranslational modifications experienced by archaeal proteins, the molecular steps leading to these modifications, and the role played by posttranslational modification in Archaea form the focus of this review.
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Affiliation(s)
- Jerry Eichler
- Dept. of Life Sciences, Ben Gurion University, P.O. Box 653, Beersheva 84105, Israel.
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Kino T, Kozasa T, Chrousos GP. Statin-induced blockade of prenylation alters nucleocytoplasmic shuttling of GTP-binding proteins gamma2 and beta2 and enhances their suppressive effect on glucocorticoid receptor transcriptional activity. Eur J Clin Invest 2005; 35:508-13. [PMID: 16101671 DOI: 10.1111/j.1365-2362.2005.01539.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND We previously reported that the guanine tri-phosphate-binding proteins (G) beta and gamma are both localized in the nucleus, in addition to their expected cytoplasmic/plasma membrane localization. These proteins, as a heterodimeric complex, suppress glucocorticoid response element-mediated transcriptional activity of the glucocorticoid receptor through direct physical interactions between Gbeta and the glucocorticoid receptor. MATERIALS AND METHODS As Ggamma is prenylated at a cysteine residue in its C-terminal portion, and as this post-translational modification is required for many of the known Gbeta/Ggamma activities, we examined the effect of its absence or diminution on Gbeta/Ggamma-induced suppression of glucocorticoid receptor-induced transcriptional activity. RESULTS In a functional reporter assay, Ggamma2C68S, which is defective at the prenylation site, was more potent than the wild-type Ggamma2 at increasing Gbeta2-induced suppression of glucocorticoid receptor transactivation. Interestingly, the enhanced green fluorescent protein fusion of this mutant Ggamma2 was localized preferentially in the nucleus, while it was absent from the plasma membrane. Lovastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor that abrogates the prenylation of Ggamma, shifted the subcellular localization of enhanced green fluorescence protein-fused Ggamma2 and Gbeta2 from the cytoplasm/plasma membrane to the nucleus and further suppressed glucocorticoid receptor-induced transcriptional activity. CONCLUSIONS These findings indicate that not only is the natural covalent addition of the prenyl residue to Ggamma unnecessary for the transcriptional suppression induced by Gbeta/Ggamma on the glucocorticoid receptor, but rather helps retain the Gbeta/Ggamma complex away from the nucleus decreasing its antiglucocorticoid actions.
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Affiliation(s)
- T Kino
- National Institutes of Health, Bethesda, MD 20892, USA.
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48
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Steiner D, Saya D, Schallmach E, Simonds WF, Vogel Z. Adenylyl cyclase type-VIII activity is regulated by G(betagamma) subunits. Cell Signal 2005; 18:62-8. [PMID: 15925485 DOI: 10.1016/j.cellsig.2005.03.014] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2005] [Accepted: 03/15/2005] [Indexed: 10/25/2022]
Abstract
The Ca2+-activated adenylyl cyclase type VIII (AC-VIII) has been implicated in several forms of neural plasticity, including drug addiction and learning and memory. It has not been clear whether Gi/o proteins and G-protein coupled receptors regulate the activity of AC-VIII. Here we show in intact mammalian cell system that AC-VIII is inhibited by mu-opioid receptor activation and that this inhibition is pertussis toxin sensitive. Moreover, we show that G(betagamma) subunits inhibit AC-VIII activity, while constitutively active alphai/o subunits do not. Different Gbeta isoforms varied in their efficacies, with Gbeta1gamma2 or Gbeta2gamma2 being more efficient than Gbeta3gamma2 and Gbeta4gamma2, while Gbeta5 (transfected with gamma2) had no effect. As for the Ggamma subunits, Gbeta1 inhibited AC-VIII activity in the presence of all gamma subunits tested except for gamma5 that had only a marginal activity. Moreover, cotransfection with proteins known to serve as scavengers of Gbetagamma dimers, or to reduce Gbetagamma plasma membrane anchorage, markedly attenuated the mu-opioid receptor-induced inhibition of AC-VIII. These results demonstrate that Gbetagamma (originating from agonist activation of these receptors) and probably not Galphai/o subunits are involved in the agonist inhibition of AC-VIII.
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Affiliation(s)
- Debora Steiner
- Department of Neurobiology, The Weizmann Institute of Science, Rehovot 76100, Israel
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49
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Vadakkadathmeethal K, Felczak A, Davignon I, Collins J, Sunahara RK. Cloning and characterization of the G protein betagamma subunits from Trichoplusia ni (High Five cells). INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2005; 35:333-345. [PMID: 15763469 DOI: 10.1016/j.ibmb.2004.12.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2004] [Revised: 12/01/2004] [Accepted: 12/17/2004] [Indexed: 05/24/2023]
Abstract
Baculoviral-mediated expression in insect cells has become a method of choice where high-level protein expression is desired and where expression in Escherichia coliform (E. coli.) is unsuitable. Genes of interest are inserted into the baculoviral genome of Autographa californica nuclear polyhedrosis virus (AcNPV) under the extremely strong, but very late polyhedron gene (PolH). The preferred host lines are derived from Spodoptera frugiperda (Sf9 or Sf21) or Tricoplusia ni (High Five, Invitrogen). Viral expression in insect cells is commonly used in the signal transduction field, due to the more than satisfactory capacity to express membrane proteins. However, co-association and/or co-purification of contaminating endogenous host G protein subunits, for example, may potentially threaten the functional and structural homogeneity of membrane preparations. The undefined G protein composition is complicated by the limited sequence data of either the S. frugiperda or Tricoplusia ni genomes. Here we report the isolation of cDNAs encoding two members of the heterotrimeric G protein family, Gbeta (Tn-Gbeta) and Ggamma (Tn-Ggamma), from Tricoplusia ni. Tn-Gbeta shares approximately 90% amino acid sequence identity with Gbeta from Drosophila melanogaster and 84% identity with mammalian Gbeta (human Gbeta1). Tn-Ggamma shares approximately 71% amino acid identity with D. melanogaster Ggamma1 and 42% identity with mammalian Ggamma (human Ggamma2). Tn-Gbetagamma is also functionally similar to mammalian Gbeta1gamma2 by virtue of their capacity to form a complex with mammalian Galpha subunits, support G-protein-dependent agonist binding to a mammalian G protein-coupled receptor (beta2-adrenergic receptor) and directly regulate effectors such as adenylyl cyclase.
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Affiliation(s)
- Kannan Vadakkadathmeethal
- Department of Pharmacology, University of Michigan Medical School, 1301 Medical Sciences Research Building III, Ann Arbor, MI 48104 734-647-6277, USA
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Schwindinger WF, Giger KE, Betz KS, Stauffer AM, Sunderlin EM, Sim-Selley LJ, Selley DE, Bronson SK, Robishaw JD. Mice with deficiency of G protein gamma3 are lean and have seizures. Mol Cell Biol 2004; 24:7758-68. [PMID: 15314181 PMCID: PMC506985 DOI: 10.1128/mcb.24.17.7758-7768.2004] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Emerging evidence suggests that the gamma subunit composition of an individual G protein contributes to the specificity of the hundreds of known receptor signaling pathways. Among the twelve gamma subtypes, gamma3 is abundantly and widely expressed in the brain. To identify specific functions and associations for gamma3, a gene-targeting approach was used to produce mice lacking the Gng3 gene (Gng3-/-). Confirming the efficacy and specificity of gene targeting, Gng3-/- mice show no detectable expression of the Gng3 gene, but expression of the divergently transcribed Bscl2 gene is not affected. Suggesting unique roles for gamma3 in the brain, Gng3-/- mice display increased susceptibility to seizures, reduced body weights, and decreased adiposity compared to their wild-type littermates. Predicting possible associations for gamma3, these phenotypic changes are associated with significant reductions in beta2 and alphai3 subunit levels in certain regions of the brain. The finding that the Gng3-/- mice and the previously reported Gng7-/- mice display distinct phenotypes and different alphabetagamma subunit associations supports the notion that even closely related gamma subtypes, such as gamma3 and gamma7, perform unique functions in the context of the organism.
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Affiliation(s)
- William F. Schwindinger
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Kathryn E. Giger
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Kelly S. Betz
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Anna M. Stauffer
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Elaine M. Sunderlin
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Laura J. Sim-Selley
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Dana E. Selley
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Sarah K. Bronson
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Janet D. Robishaw
- Weis Center for Research, Geisinger Clinic, Danville, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, Hershey, Pennsylvania, Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
- Corresponding author. Mailing address: Geisinger Clinic, Weis Center for Research, 100 North Academy Ave., Danville, PA 17822. Phone: (570) 271-6684. Fax: (570) 271-6701. E-mail:
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