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Barrett JE, Shekarabi A, Inan S. Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments. Pharmacol Rev 2023; 75:1062-1118. [PMID: 37321860 PMCID: PMC10595024 DOI: 10.1124/pharmrev.121.000506] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 04/30/2023] [Accepted: 06/05/2023] [Indexed: 06/17/2023] Open
Abstract
Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.
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Affiliation(s)
- James E Barrett
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University. Philadelphia, Pennsylvania
| | - Aryan Shekarabi
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University. Philadelphia, Pennsylvania
| | - Saadet Inan
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University. Philadelphia, Pennsylvania
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2
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Serafini RA, Estill M, Pekarskaya EA, Sakloth F, Shen L, Javitch JA, Zachariou V. Tianeptine promotes lasting antiallodynic effects in a mouse model of neuropathic pain. Neuropsychopharmacology 2023; 48:1680-1689. [PMID: 37474762 PMCID: PMC10517169 DOI: 10.1038/s41386-023-01645-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 05/31/2023] [Accepted: 06/27/2023] [Indexed: 07/22/2023]
Abstract
Tricyclic antidepressants (TCAs), such as desipramine (DMI), are effective at managing neuropathic pain symptoms but often take several weeks to become effective and also lead to considerable side effects. Tianeptine (TIAN) is an atypical antidepressant that activates the mu-opioid receptor but does not produce analgesic tolerance or withdrawal in mice, nor euphoria in humans, at clinically-relevant doses. Here, we evaluate the efficacy of TIAN at persistently alleviating mechanical allodynia in the spared nerve injury (SNI) model of neuropathic pain, even well after drug clearance. After finding an accelerated onset of antiallodynic action compared to DMI, we used genetically modified mice to gain insight into RGS protein-associated pathways that modulate the efficacy of TIAN relative to DMI in models of neuropathic pain. Because we observed similar behavioral responses to both TIAN and DMI treatment in RGS4, RGSz1, and RGS9 knockout mice, we performed RNA sequencing on the NAc of TIAN- and DMI-treated mice after prolonged SNI to further clarify potential mechanisms underlying TIANs faster therapeutic actions. Our bioinformatic analysis revealed distinct transcriptomic signatures between the two drugs, with TIAN more directly reversing SNI-induced differentially expressed genes, and further predicted several upstream regulators that may be implicated in onset of action. This new understanding of the molecular pathways underlying TIAN action may enable the development of novel and more efficacious pharmacological approaches for the management of neuropathic pain.
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Affiliation(s)
- Randal A Serafini
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Pharmacology, Physiology and Biophysics, Chobanian & Avedisian School of Medicine at Boston University, Boston, MA, USA
| | - Molly Estill
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Elizabeth A Pekarskaya
- Department of Neuroscience, Columbia University, New York, NY, USA
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
| | - Farhana Sakloth
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Li Shen
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jonathan A Javitch
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
- Department of Molecular Pharmacology and Therapeutics, Columbia University, New York, NY, USA
| | - Venetia Zachariou
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Pharmacology, Physiology and Biophysics, Chobanian & Avedisian School of Medicine at Boston University, Boston, MA, USA.
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3
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Pisanò CA, Mercatelli D, Mazzocchi M, Brugnoli A, Morella I, Fasano S, Zaveri NT, Brambilla R, O'Keeffe GW, Neubig RR, Morari M. Regulator of G-Protein Signalling 4 (RGS4) negatively modulates nociceptin/orphanin FQ opioid receptor signalling: Implication for l-Dopa-induced dyskinesia. Br J Pharmacol 2023; 180:927-942. [PMID: 34767639 DOI: 10.1111/bph.15730] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 10/11/2021] [Accepted: 10/18/2021] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Regulator of G-protein signalling 4 (RGS4) is a signal transduction protein that accelerates intrinsic GTPase activity of Gαi/o and Gαq subunits, suppressing GPCR signalling. Here, we investigate whether RGS4 modulates nociceptin/orphanin FQ (N/OFQ) opioid (NOP) receptor signalling and if this modulation has relevance for l-Dopa-induced dyskinesia. EXPERIMENTAL APPROACH HEK293T cells transfected with NOP, NOP/RGS4 or NOP/RGS19 were challenged with N/OFQ and the small-molecule NOP agonist AT-403, using D1-stimulated cAMP levels as a readout. Primary rat striatal neurons and adult mouse striatal slices were challenged with either N/OFQ or AT-403 in the presence of the experimental RGS4 chemical probe, CCG-203920, and D1-stimulated cAMP or phosphorylated extracellular signal regulated kinase 1/2 (pERK) responses were monitored. In vivo, CCG-203920 was co-administered with AT-403 and l-Dopa to 6-hydroxydopamine hemilesioned rats, and dyskinetic movements, striatal biochemical correlates of dyskinesia (pERK and pGluR1 levels) and striatal RGS4 levels were measured. KEY RESULTS RGS4 expression reduced NOFQ and AT-403 potency and efficacy in HEK293T cells. CCG-203920 increased N/OFQ potency in primary rat striatal neurons and potentiated AT-403 response in mouse striatal slices. CCG-203920 enhanced AT-403-mediated inhibition of dyskinesia and its biochemical correlates, without compromising its motor-improving effects. Unilateral dopamine depletion caused bilateral reduction of RGS4 levels, which was reversed by l-Dopa. l-Dopa acutely up-regulated RGS4 in the lesioned striatum. CONCLUSIONS AND IMPLICATIONS RGS4 physiologically inhibits NOP receptor signalling. CCG-203920 enhanced NOP responses and improved the antidyskinetic potential of NOP receptor agonists, mitigating the effects of striatal RGS4 up-regulation occurring during dyskinesia expression. LINKED ARTICLES This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.
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Affiliation(s)
- Clarissa A Pisanò
- Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy
| | - Daniela Mercatelli
- Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy
| | - Martina Mazzocchi
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Alberto Brugnoli
- Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy
| | - Ilaria Morella
- Neuroscience and Mental Health Research Institute, Division of Neuroscience, School of Biosciences, Cardiff University, Cardiff, UK
| | - Stefania Fasano
- Neuroscience and Mental Health Research Institute, Division of Neuroscience, School of Biosciences, Cardiff University, Cardiff, UK
| | - Nurulain T Zaveri
- Astraea Therapeutics, Medicinal Chemistry Division, Mountain View, California, USA
| | - Riccardo Brambilla
- Neuroscience and Mental Health Research Institute, Division of Neuroscience, School of Biosciences, Cardiff University, Cardiff, UK
- Department of Biology and Biotechnology "L. Spallanzani", University of Pavia, Pavia, Italy
| | - Gerard W O'Keeffe
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Richard R Neubig
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
| | - Michele Morari
- Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy
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Kutchy NA, Palermo A, Ma R, Li Z, Ulanov A, Callen S, Siuzdak G, Roy S, Buch S, Hu G. Changes in Plasma Metabolic Signature upon Acute and Chronic Morphine Administration in Morphine-Tolerant Mice. Metabolites 2023; 13:metabo13030434. [PMID: 36984873 PMCID: PMC10053579 DOI: 10.3390/metabo13030434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/01/2023] [Accepted: 03/13/2023] [Indexed: 03/19/2023] Open
Abstract
Morphine administration causes system-level metabolic changes. Here, we show that morphine-tolerant mice exhibited distinct plasma metabolic signatures upon acute and chronic administration. We utilized a mouse model of morphine tolerance by exposing mice to increasing doses of the drug over 4 days. We collected plasma samples from mice undergoing acute or chronic morphine or saline injections and analyzed them using targeted GC–MS-based metabolomics to profile approximately 80 metabolites involved in the central carbon, amino acid, nucleotide, and lipid metabolism. Our findings reveal distinct alterations in plasma metabolite concentrations in response to acute or chronic morphine intake, and these changes were linked to the development of tolerance to morphine’s analgesic effects. We identified several metabolites that had been differentially affected by acute versus chronic morphine use, suggesting that metabolic changes may be mitigated by prolonged exposure to the drug. Morphine-tolerant mice showed a restoration of amino acid and glycolytic metabolites. Additionally, we conducted reconstructed metabolic network analysis on the first 30 VIP-ranked metabolites from the PLSDA of the saline, acute, and morphine-tolerant mice groups, which uncovered four interaction networks involving the amino acid metabolism, the TCA cycle, the glutamine-phenylalanine-tyrosine pathway, and glycolysis. These pathways were responsible for the metabolic differences observed following distinct morphine administration regimens. Overall, this study provides a valuable resource for future investigations into the role of metabolites in morphine-induced analgesia and associated effects following acute or chronic use in mice.
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Affiliation(s)
- Naseer A. Kutchy
- Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA (S.B.); (G.H.)
- Correspondence: (N.A.K.); (A.P.)
| | - Amelia Palermo
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
- Correspondence: (N.A.K.); (A.P.)
| | - Rong Ma
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA (S.B.); (G.H.)
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Zhong Li
- Department of Biostatistics & Bioinformatics, Duke University School of Medicine, Durham, NC 27710, USA
- Roy J. Carver Biotechnology Center, University of Illinois, Urbana, IL 61801, USA
| | - Alexandria Ulanov
- Roy J. Carver Biotechnology Center, University of Illinois, Urbana, IL 61801, USA
| | - Shannon Callen
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA (S.B.); (G.H.)
| | - Gary Siuzdak
- Center for Metabolomics and Mass Spectrometry, Scripps Research Institute, La Jolla, CA 92037, USA
| | - Sabita Roy
- Department of Surgery, University of Miami, Miami, FL 33136, USA
| | - Shilpa Buch
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA (S.B.); (G.H.)
| | - Guoku Hu
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA (S.B.); (G.H.)
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McPherson KB, Ingram SL. Cellular and circuit diversity determines the impact of endogenous opioids in the descending pain modulatory pathway. Front Syst Neurosci 2022; 16:963812. [PMID: 36045708 PMCID: PMC9421147 DOI: 10.3389/fnsys.2022.963812] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 07/15/2022] [Indexed: 01/31/2023] Open
Abstract
The descending pain modulatory pathway exerts important bidirectional control of nociceptive inputs to dampen and/or facilitate the perception of pain. The ventrolateral periaqueductal gray (vlPAG) integrates inputs from many regions associated with the processing of nociceptive, cognitive, and affective components of pain perception, and is a key brain area for opioid action. Opioid receptors are expressed on a subset of vlPAG neurons, as well as on both GABAergic and glutamatergic presynaptic terminals that impinge on vlPAG neurons. Microinjection of opioids into the vlPAG produces analgesia and microinjection of the opioid receptor antagonist naloxone blocks stimulation-mediated analgesia, highlighting the role of endogenous opioid release within this region in the modulation of nociception. Endogenous opioid effects within the vlPAG are complex and likely dependent on specific neuronal circuits activated by acute and chronic pain stimuli. This review is focused on the cellular heterogeneity within vlPAG circuits and highlights gaps in our understanding of endogenous opioid regulation of the descending pain modulatory circuits.
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Affiliation(s)
- Kylie B. McPherson
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy,Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States
| | - Susan L. Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States,*Correspondence: Susan L. Ingram
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6
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Fullerton EF, Karom MC, Streicher JM, Young LJ, Murphy AZ. Age-Induced Changes in µ-Opioid Receptor Signaling in the Midbrain Periaqueductal Gray of Male and Female Rats. J Neurosci 2022; 42:6232-6242. [PMID: 35790399 PMCID: PMC9374133 DOI: 10.1523/jneurosci.0355-22.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 04/08/2022] [Accepted: 04/16/2022] [Indexed: 11/21/2022] Open
Abstract
Opioids have decreased analgesic potency (but not efficacy) in aged rodents compared with adults; however, the neural mechanisms underlying this attenuated response are not yet known. The present study investigated the impact of advanced age and biological sex on opioid signaling in the ventrolateral periaqueductal gray (vlPAG) in the presence of chronic inflammatory pain. Assays measuring µ-opioid receptor (MOR) radioligand binding, GTPγS binding, receptor phosphorylation, cAMP inhibition, and regulator of G-protein signaling (RGS) protein expression were performed on vlPAG tissue from adult (2-3 months) and aged (16-18 months) male and female rats. Persistent inflammatory pain was induced by intraplantar injection of complete Freund's adjuvant (CFA). Adult males exhibited the highest MOR binding potential (BP) and highest G-protein activation (activation efficiency ratio) in comparison to aged males and females (adult and aged). No impact of advanced age or sex on MOR phosphorylation state was observed. DAMGO-induced cAMP inhibition was highest in the vlPAG of adult males compared with aged males and females (adult and aged). vlPAG levels of RGS4 and RGS9-2, critical for terminating G-protein signaling, were assessed using RNAscope. Adult rats (both males and females) exhibited lower levels of vlPAG RGS4 and RGS9-2 mRNA expression compared with aged males and females. The observed age-related reductions in vlPAG MOR BP, G-protein activation efficiency, and cAMP inhibition, along with the observed age-related increases in RGS4 and RGS9-2 vlPAG expression, provide potential mechanisms whereby the potency of opioids is decreased in the aged population.SIGNIFICANCE STATEMENT Opioids have decreased analgesic potency (but not efficacy) in aged rodents compared with adults; however, the neural mechanisms underlying this attenuated response are not yet known. In the present study, we observed age-related reductions in ventrolateral periaqueductal gray (vlPAG) µ-opioid receptor (MOR) binding potential (BP), G-protein activation efficiency, and cAMP inhibition, along with the observed age-related increases in regulator of G-protein signaling (RGS)4 and RGS9-2 vlPAG expression, providing potential mechanisms whereby the potency of opioids is decreased in the aged population. These coordinated decreases in opioid receptor signaling may explain the previously reported reduced potency of opioids to produce pain relief in females and aged rats.
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Affiliation(s)
- Evan F Fullerton
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30303
| | - Mary C Karom
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30303
| | - John M Streicher
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724
| | - Larry J Young
- Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Anne Z Murphy
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30303
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7
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Regulators of G protein signalling as pharmacological targets for the treatment of neuropathic pain. Pharmacol Res 2020; 160:105148. [PMID: 32858121 DOI: 10.1016/j.phrs.2020.105148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 07/24/2020] [Accepted: 08/10/2020] [Indexed: 12/30/2022]
Abstract
Neuropathic pain, a specific type of chronic pain resulting from persistent nervous tissue lesions, is a debilitating condition that affects about 7% of the population. This condition remains particularly difficult to treat because of the poor understanding of its underlying mechanisms. Drugs currently used to alleviate this chronic pain syndrome are of limited benefit due to their lack of efficacy and the elevated risk of side effects, especially after a prolonged period of treatment. Although drugs targeting G protein-coupled receptors (GPCR) also have several limitations, such as progressive loss of efficacy due to receptor desensitization or unavoidable side effects due to wide receptor distribution, the identification of several molecular partners that contribute to the fine-tuning of receptor activity has raised new opportunities for the development of alternative therapeutic approaches. Regulators of G protein signalling (RGS) act intracellularly by influencing the coupling process and activity of G proteins, and are amongst the best-characterized physiological modulators of GPCR. Changes in RGS expression have been documented in a range of models of neuropathic pain, or after prolonged treatment with diverse analgesics, and could participate in altered pain processing as well as impaired physiological or pharmacological control of nociceptive signals. The present review summarizes the experimental data that implicates RGS in the development of pain with focus on the pathological mechanisms of neuropathic pain, including the impact of neuropathic lesions on RGS expression and, reciprocally, the influence of modifying RGS on GPCRs involved in the modulation of nociception as well as on the outcome of pain. In this context, we address the question of the relevance of RGS as promising targets in the treatment of neuropathic pain.
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8
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Sakloth F, Polizu C, Bertherat F, Zachariou V. Regulators of G Protein Signaling in Analgesia and Addiction. Mol Pharmacol 2020; 98:739-750. [PMID: 32474445 DOI: 10.1124/mol.119.119206] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 05/19/2020] [Indexed: 12/11/2022] Open
Abstract
Regulator of G protein signaling (RGS) proteins are multifunctional proteins expressed in peripheral and neuronal cells, playing critical roles in development, physiologic processes, and pharmacological responses. RGS proteins primarily act as GTPase accelerators for activated Gα subunits of G-protein coupled receptors, but they may also modulate signal transduction by several other mechanisms. Over the last two decades, preclinical work identified members of the RGS family with unique and critical roles in intracellular responses to drugs of abuse. New information has emerged on the mechanisms by which RGS proteins modulate the efficacy of opioid analgesics in a brain region- and agonist-selective fashion. There has also been progress in the understanding of the protein complexes and signal transduction pathways regulated by RGS proteins in addiction and analgesia circuits. In this review, we summarize findings on the mechanisms by which RGS proteins modulate functional responses to opioids in models of analgesia and addiction. We also discuss reports on the regulation and function of RGS proteins in models of psychostimulant addiction. Using information from preclinical studies performed over the last 20 years, we highlight the diverse mechanisms by which RGS protein complexes control plasticity in response to opioid and psychostimulant drug exposure; we further discuss how the understanding of these pathways may lead to new opportunities for therapeutic interventions in G protein pathways. SIGNIFICANCE STATEMENT: Regulator of G protein signaling (RGS) proteins are signal transduction modulators, expressed widely in various tissues, including brain regions mediating addiction and analgesia. Evidence from preclinical work suggests that members of the RGS family act by unique mechanisms in specific brain regions to control drug-induced plasticity. This review highlights interesting findings on the regulation and function of RGS proteins in models of analgesia and addiction.
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Affiliation(s)
- Farhana Sakloth
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
| | - Claire Polizu
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
| | - Feodora Bertherat
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
| | - Venetia Zachariou
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
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9
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Senese NB, Kandasamy R, Kochan KE, Traynor JR. Regulator of G-Protein Signaling (RGS) Protein Modulation of Opioid Receptor Signaling as a Potential Target for Pain Management. Front Mol Neurosci 2020; 13:5. [PMID: 32038168 PMCID: PMC6992652 DOI: 10.3389/fnmol.2020.00005] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 01/09/2020] [Indexed: 12/23/2022] Open
Abstract
Opioid drugs are the gold standard for the management of pain, but their use is severely limited by dangerous and unpleasant side effects. All clinically available opioid analgesics bind to and activate the mu-opioid receptor (MOR), a heterotrimeric G-protein-coupled receptor, to produce analgesia. The activity of these receptors is modulated by a family of intracellular RGS proteins or regulators of G-protein signaling proteins, characterized by the presence of a conserved RGS Homology (RH) domain. These proteins act as negative regulators of G-protein signaling by serving as GTPase accelerating proteins or GAPS to switch off signaling by both the Gα and βγ subunits of heterotrimeric G-proteins. Consequently, knockdown or knockout of RGS protein activity enhances signaling downstream of MOR. In this review we discuss current knowledge of how this activity, across the different families of RGS proteins, modulates MOR activity, as well as activity of other members of the opioid receptor family, and so pain and analgesia in animal models, with particular emphasis on RGS4 and RGS9 families. We discuss inhibition of RGS proteins with small molecule inhibitors that bind to sensitive cysteine moieties in the RH domain and the potential for targeting this family of intracellular proteins as adjuncts to provide an opioid sparing effect or as standalone analgesics by promoting the activity of endogenous opioid peptides. Overall, we conclude that RGS proteins may be a novel drug target to provide analgesia with reduced opioid-like side effects, but that much basic work is needed to define the roles for specific RGS proteins, particularly in chronic pain, as well as a need to develop newer inhibitors.
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Affiliation(s)
- Nicolas B Senese
- Department of Pharmacology, Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, MI, United States.,Department of Psychiatry, Chicago, IL, United States
| | - Ram Kandasamy
- Department of Pharmacology, Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, MI, United States.,Department of Psychology, California State University, East Bay, Hayward, CA, United States
| | - Kelsey E Kochan
- Department of Pharmacology, Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, MI, United States
| | - John R Traynor
- Department of Pharmacology, Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, MI, United States.,Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI, United States
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10
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Squires KE, Montañez-Miranda C, Pandya RR, Torres MP, Hepler JR. Genetic Analysis of Rare Human Variants of Regulators of G Protein Signaling Proteins and Their Role in Human Physiology and Disease. Pharmacol Rev 2018; 70:446-474. [PMID: 29871944 DOI: 10.1124/pr.117.015354] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Regulators of G protein signaling (RGS) proteins modulate the physiologic actions of many neurotransmitters, hormones, and other signaling molecules. Human RGS proteins comprise a family of 20 canonical proteins that bind directly to G protein-coupled receptors/G protein complexes to limit the lifetime of their signaling events, which regulate all aspects of cell and organ physiology. Genetic variations account for diverse human traits and individual predispositions to disease. RGS proteins contribute to many complex polygenic human traits and pathologies such as hypertension, atherosclerosis, schizophrenia, depression, addiction, cancers, and many others. Recent analysis indicates that most human diseases are due to extremely rare genetic variants. In this study, we summarize physiologic roles for RGS proteins and links to human diseases/traits and report rare variants found within each human RGS protein exome sequence derived from global population studies. Each RGS sequence is analyzed using recently described bioinformatics and proteomic tools for measures of missense tolerance ratio paired with combined annotation-dependent depletion scores, and protein post-translational modification (PTM) alignment cluster analysis. We highlight selected variants within the well-studied RGS domain that likely disrupt RGS protein functions and provide comprehensive variant and PTM data for each RGS protein for future study. We propose that rare variants in functionally sensitive regions of RGS proteins confer profound change-of-function phenotypes that may contribute, in newly appreciated ways, to complex human diseases and/or traits. This information provides investigators with a valuable database to explore variation in RGS protein function, and for targeting RGS proteins as future therapeutic targets.
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Affiliation(s)
- Katherine E Squires
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Carolina Montañez-Miranda
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Rushika R Pandya
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Matthew P Torres
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - John R Hepler
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
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11
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Regulators of G-Protein Signaling (RGS) Proteins Promote Receptor Coupling to G-Protein-Coupled Inwardly Rectifying Potassium (GIRK) Channels. J Neurosci 2018; 38:8737-8744. [PMID: 30150362 DOI: 10.1523/jneurosci.0516-18.2018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 07/31/2018] [Accepted: 08/20/2018] [Indexed: 01/01/2023] Open
Abstract
Regulators of G-protein signaling (RGS) proteins negatively modulate presynaptic μ-opioid receptor inhibition of GABA release in the ventrolateral periaqueductal gray (vlPAG). Paradoxically, we find that G-protein-coupled receptor (GPCR) activation of G-protein-gated inwardly rectifying K+ channels (GIRKs) in the vlPAG is reduced in an agonist- and receptor-dependent manner in transgenic knock-in mice of either sex expressing mutant RGS-insensitive Gαo proteins. μ-Opioid receptor agonist activation of GIRK currents was reduced for DAMGO and fentanyl but not for [Met5]-enkephalin acetate salt hydrate (ME) in the RGS-insensitive heterozygous (Het) mice compared with wild-type mice. The GABAB agonist baclofen-induced GIRK currents were also reduced in the Het mice. We confirmed the role of Gαo proteins in μ-opioid receptor and GABAB receptor signaling pathways in wild-type mice using myristoylated peptide inhibitors of Gαo1 and Gαi1-3 The results using these inhibitors indicate that receptor activation of GIRK channels is dependent on the preference of the agonist-stimulated receptor for Gαo versus that for Gαi. DAMGO and fentanyl-mediated GIRK currents were reduced in the presence of the Gαo1 inhibitor, but not the Gαi1-3 inhibitors. In contrast, the Gαo1 peptide inhibitor did not affect ME activation of GIRK currents, which is consistent with results in the Het mice, but the Gαi1-3 inhibitors significantly reduced ME-mediated GIRK currents. Finally, the reduction in GIRK activation in the Het mice plays a role in opioid- and baclofen-mediated spinal antinociception, but not supraspinal antinociception. Thus, our studies indicate that RGS proteins have multiple mechanisms of modulating GPCR signaling that produce negative and positive regulation of signaling depending on the effector.SIGNIFICANCE STATEMENT Regulators of G-protein signaling (RGS) proteins positively modulate GPCR coupling to GIRKs, and this coupling is critical for opioid- and baclofen-mediated spinal antinociception, whereas μ-opioid receptor-mediated supraspinal antinociception depends on presynaptic inhibition that is negatively regulated by RGS proteins. The identification of these opposite roles for RGS proteins has implications for signaling via other GPCRs.
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Selective Role of RGS9-2 in Regulating Retrograde Synaptic Signaling of Indirect Pathway Medium Spiny Neurons in Dorsal Striatum. J Neurosci 2018; 38:7120-7131. [PMID: 30006367 DOI: 10.1523/jneurosci.0493-18.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 05/17/2018] [Accepted: 05/17/2018] [Indexed: 11/21/2022] Open
Abstract
In the striatum, medium spiny neurons (MSNs) are heavily involved in controlling movement and reward. MSNs form two distinct populations expressing either dopamine receptor 1 (D1-MSN) or dopamine receptor 2 (D2-MSN), which differ in their projection targets and neurochemical composition. The activity of both types of MSNs is shaped by multiple neuromodulatory inputs processed by GPCRs that fundamentally impact their synaptic properties biasing behavioral outcomes. How these GPCR signaling cascades are regulated and what downstream targets they recruit in D1-MSN and D2-MSN populations are incompletely understood. In this study, we examined the cellular and molecular mechanisms underlying the action of RGS9-2, a key GPCR regulator in MSNs implicated in both movement control and actions of addictive drugs. Imaging cultured striatal neurons, we found that ablation of RGS9-2 significantly reduced calcium influx through NMDARs. Electrophysiological recordings in slices confirmed inhibition of NMDAR function in MSNs, resulting in enhanced AMPAR/NMDAR ratio. Accordingly, male mice lacking RGS9-2 displayed behavioral hypersensitivity to NMDAR blockade by MK-801 or ketamine. Recordings from genetically identified populations of striatal neurons revealed that these changes were selective to D2-MSNs. Surprisingly, we found that these postsynaptic effects resulted in remodeling of presynaptic inputs to D2-MSNs increasing the frequency of mEPSC and inhibiting paired-pulse ratio. Pharmacological dissection revealed that these adaptations were mediated by the NMDAR-dependent inhibition of retrograde endocannabinoid signaling from D2-MSNs to CB1 receptor on presynaptic terminals. Together, these data demonstrate a novel mechanism for pathway selective regulation of synaptic plasticity in MSNs controlled by GPCR signaling.SIGNIFICANCE STATEMENT This study identifies a role for a major G-protein regulator in controlling synaptic properties of striatal neurons in a pathway selective fashion.
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13
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Gaspari S, Cogliani V, Manouras L, Anderson EM, Mitsi V, Avrampou K, Carr FB, Zachariou V. RGS9-2 Modulates Responses to Oxycodone in Pain-Free and Chronic Pain States. Neuropsychopharmacology 2017; 42:1548-1556. [PMID: 28074831 PMCID: PMC5436127 DOI: 10.1038/npp.2017.4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 11/28/2016] [Accepted: 12/23/2016] [Indexed: 12/11/2022]
Abstract
Regulator of G-protein signaling 9-2 (RGS9-2) is a striatal-enriched signal-transduction modulator known to have a critical role in the development of addiction-related behaviors following exposure to psychostimulants or opioids. RGS9-2 controls the function of several G-protein-coupled receptors, including dopamine receptor and mu opioid receptor (MOR). We previously showed that RGS9-2 complexes negatively control morphine analgesia, and promote the development of morphine tolerance. In contrast, RGS9-2 positively modulates the actions of other opioid analgesics, such as fentanyl and methadone. Here we investigate the role of RGS9-2 in regulating responses to oxycodone, an MOR agonist prescribed for the treatment of severe pain conditions that has addictive properties. Using mice lacking the Rgs9 gene (RGS9KO), we demonstrate that RGS9-2 positively regulates the rewarding effects of oxycodone in pain-free states, and in a model of neuropathic pain. Furthermore, although RGS9-2 does not affect the analgesic efficacy of oxycodone or the expression of physical withdrawal, it opposes the development of oxycodone tolerance, in both acute pain and chronic neuropathic pain models. Taken together, these data provide new information on the signal-transduction mechanisms that modulate the rewarding and analgesic actions of oxycodone.
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Affiliation(s)
- Sevasti Gaspari
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, New York, NY, USA
- University of Crete Faculty of Medicine, Department of Basic Sciences, Heraklion, Greece
| | - Valeria Cogliani
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, New York, NY, USA
| | - Lefteris Manouras
- University of Crete Faculty of Medicine, Department of Basic Sciences, Heraklion, Greece
| | - Ethan M Anderson
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, New York, NY, USA
| | - Vasiliki Mitsi
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, New York, NY, USA
| | - Kleopatra Avrampou
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, New York, NY, USA
| | - Fiona B Carr
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, New York, NY, USA
| | - Venetia Zachariou
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, New York, NY, USA
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Nibbeling EAR, Delnooz CCS, de Koning TJ, Sinke RJ, Jinnah HA, Tijssen MAJ, Verbeek DS. Using the shared genetics of dystonia and ataxia to unravel their pathogenesis. Neurosci Biobehav Rev 2017; 75:22-39. [PMID: 28143763 DOI: 10.1016/j.neubiorev.2017.01.033] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 12/09/2016] [Accepted: 01/24/2017] [Indexed: 12/13/2022]
Abstract
In this review we explore the similarities between spinocerebellar ataxias and dystonias, and suggest potentially shared molecular pathways using a gene co-expression network approach. The spinocerebellar ataxias are a group of neurodegenerative disorders characterized by coordination problems caused mainly by atrophy of the cerebellum. The dystonias are another group of neurological movement disorders linked to basal ganglia dysfunction, although evidence is now pointing to cerebellar involvement as well. Our gene co-expression network approach identified 99 shared genes and showed the involvement of two major pathways: synaptic transmission and neurodevelopment. These pathways overlapped in the two disorders, with a large role for GABAergic signaling in both. The overlapping pathways may provide novel targets for disease therapies. We need to prioritize variants obtained by whole exome sequencing in the genes associated with these pathways in the search for new pathogenic variants, which can than be used to help in the genetic counseling of patients and their families.
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Affiliation(s)
- Esther A R Nibbeling
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands
| | - Cathérine C S Delnooz
- University of Groningen, University Medical Center Groningen, Department of Neurology, Groningen, The Netherlands
| | - Tom J de Koning
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands; University of Groningen, University Medical Center Groningen, Department of Neurology, Groningen, The Netherlands
| | - Richard J Sinke
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands
| | - Hyder A Jinnah
- Departments of Neurology, Human Genetics and Pediatrics, Emory Clinic, Atlanta, USA
| | - Marina A J Tijssen
- University of Groningen, University Medical Center Groningen, Department of Neurology, Groningen, The Netherlands
| | - Dineke S Verbeek
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands.
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15
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Salaga M, Storr M, Martemyanov KA, Fichna J. RGS proteins as targets in the treatment of intestinal inflammation and visceral pain: New insights and future perspectives. Bioessays 2016; 38:344-54. [PMID: 26817719 PMCID: PMC4916644 DOI: 10.1002/bies.201500118] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Regulators of G protein signaling (RGS) proteins provide timely termination of G protein-coupled receptor (GPCR) responses. Serving as a central control point in GPCR signaling cascades, RGS proteins are promising targets for drug development. In this review, we discuss the involvement of RGS proteins in the pathophysiology of the gastrointestinal inflammation and their potential to become a target for anti-inflammatory drugs. Specifically, we evaluate the emerging evidence for modulation of selected receptor families: opioid, cannabinoid and serotonin by RGS proteins. We discuss how the regulation of RGS protein level and activity may modulate immunological pathways involved in the development of intestinal inflammation. Finally, we propose that RGS proteins may serve as a prognostic factor for survival rate in colorectal cancer. The ideas introduced in this review set a novel conceptual framework for the utilization of RGS proteins in the treatment of gastrointestinal inflammation, a growing major concern worldwide.
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Affiliation(s)
- Maciej Salaga
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Poland
| | - Martin Storr
- Walter Brendel Center of Experimental Medicine, University of Munich, Germany
| | - Kirill A. Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
- Corresponding authors: J.F. Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland, Phone: ++48 42 272 57 07, Fax: ++48 42 272 56 94, . K.A.M., Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way C347, Jupiter, FL 33458, USA, Phone: ++1 561 228 2770,
| | - Jakub Fichna
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Poland
- Corresponding authors: J.F. Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland, Phone: ++48 42 272 57 07, Fax: ++48 42 272 56 94, . K.A.M., Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way C347, Jupiter, FL 33458, USA, Phone: ++1 561 228 2770,
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16
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Gerber KJ, Squires KE, Hepler JR. Roles for Regulator of G Protein Signaling Proteins in Synaptic Signaling and Plasticity. Mol Pharmacol 2015; 89:273-86. [PMID: 26655302 DOI: 10.1124/mol.115.102210] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/10/2015] [Indexed: 11/22/2022] Open
Abstract
The regulator of G protein signaling (RGS) family of proteins serves critical roles in G protein-coupled receptor (GPCR) and heterotrimeric G protein signal transduction. RGS proteins are best understood as negative regulators of GPCR/G protein signaling. They achieve this by acting as GTPase activating proteins (GAPs) for Gα subunits and accelerating the turnoff of G protein signaling. Many RGS proteins also bind additional signaling partners that either regulate their functions or enable them to regulate other important signaling events. At neuronal synapses, GPCRs, G proteins, and RGS proteins work in coordination to regulate key aspects of neurotransmitter release, synaptic transmission, and synaptic plasticity, which are necessary for central nervous system physiology and behavior. Accumulating evidence has revealed key roles for specific RGS proteins in multiple signaling pathways at neuronal synapses, regulating both pre- and postsynaptic signaling events and synaptic plasticity. Here, we review and highlight the current knowledge of specific RGS proteins (RGS2, RGS4, RGS7, RGS9-2, and RGS14) that have been clearly demonstrated to serve critical roles in modulating synaptic signaling and plasticity throughout the brain, and we consider their potential as future therapeutic targets.
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Affiliation(s)
- Kyle J Gerber
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - Katherine E Squires
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - John R Hepler
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
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17
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Bosier B, Doyen PJ, Brolet A, Muccioli GG, Ahmed E, Desmet N, Hermans E, Deumens R. Inhibition of the regulator of G protein signalling RGS4 in the spinal cord decreases neuropathic hyperalgesia and restores cannabinoid CB1 receptor signalling. Br J Pharmacol 2015; 172:5333-46. [PMID: 26478461 PMCID: PMC5341217 DOI: 10.1111/bph.13324] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 07/24/2015] [Accepted: 09/04/2015] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND AND PURPOSE Regulators of G protein signalling (RGS) are major determinants of metabotropic receptor activity, reducing the lifespan of the GTP-bound state of G proteins. Because the reduced potency of analgesic agents in neuropathic pain may reflect alterations in RGS, we assessed the effects of CCG 63802, a specific RGS4 inhibitor, on pain hypersensitivity and signalling through cannabinoid receptors, in a model of neuropathic pain. EXPERIMENTAL APPROACH The partial sciatic nerve ligation (PSNL) model in male Sprague Dawley rats was used to measure paw withdrawal thresholds to mechanical (von Frey hairs) or thermal (Hargreaves method) stimuli, during and after intrathecal injection of CCG 63802. HEK293 cells expressing CB1 receptors and conditional expression of RGS4 were used to correlate cAMP production and ERK phosphorylation with receptor activation and RGS4 action. KEY RESULTS Treatment of PSNL rats with CCG 63802, twice daily for 7 days after nerve injury, attenuated thermal hyperalgesia during treatment. Spinal levels of anandamide were higher in PSNL animals, irrespective of the treatment. Although expression of CB1 receptors was unaffected, HU210-induced CB1 receptor signalling was inhibited in PSNL rats and restored after intrathecal CCG 63802. In transfected HEK cells expressing CB1 receptors and RGS4, inhibition of cAMP production, a downstream effect of CB1 receptor signalling, was blunted after RGS4 overexpression. RGS4 expression also attenuated the CB1 receptor-controlled activation of ERK1/2. CONCLUSIONS AND IMPLICATIONS Inhibition of spinal RGS4 restored endogenous analgesic signalling pathways and mitigated neuropathic pain. Signalling through CB1 receptors may be involved in this beneficial effect.
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Affiliation(s)
- Barbara Bosier
- Neuropharmacology Group, Institute of NeuroscienceUniversité catholique de LouvainBrusselsBelgium
| | - Pierre J. Doyen
- Neuropharmacology Group, Institute of NeuroscienceUniversité catholique de LouvainBrusselsBelgium
| | - Amandine Brolet
- Neuropharmacology Group, Institute of NeuroscienceUniversité catholique de LouvainBrusselsBelgium
| | - Giulio G. Muccioli
- Bioanalysis and Pharmacology of Bioactive Lipids Research Group, Louvain Drug Research InstituteUniversité catholique de LouvainBrusselsBelgium
| | - Eman Ahmed
- Neuropharmacology Group, Institute of NeuroscienceUniversité catholique de LouvainBrusselsBelgium
- Department of Clinical PharmacologyFaculty of Medicine, Suez Canal UniversityIsmailiaEgypt
| | - Nathalie Desmet
- Neuropharmacology Group, Institute of NeuroscienceUniversité catholique de LouvainBrusselsBelgium
| | - Emmanuel Hermans
- Neuropharmacology Group, Institute of NeuroscienceUniversité catholique de LouvainBrusselsBelgium
| | - Ronald Deumens
- Neuropharmacology Group, Institute of NeuroscienceUniversité catholique de LouvainBrusselsBelgium
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18
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Papakonstantinou MP, Karoussiotis C, Georgoussi Z. RGS2 and RGS4 proteins: New modulators of the κ-opioid receptor signaling. Cell Signal 2014; 27:104-14. [PMID: 25289860 DOI: 10.1016/j.cellsig.2014.09.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 09/10/2014] [Accepted: 09/23/2014] [Indexed: 01/22/2023]
Abstract
Previous studies have shown that RGS4 associates with the C-termini of μ- and δ-opioid receptors in living cells and plays a key role in Gi/Go protein coupling selectivity and signalling of these receptors [12,20]. To deduce whether similar effects also occur for the κ-opioid receptor (κ-ΟR) and define the ability of members of the Regulators of G protein Signaling (RGS) of the B/R4 subfamily to interact with κ-ΟR subdomains we generated glutathione S-transferase fusion peptides encompassing the carboxyl-termini of κ-OR (κ-CT). Results from pull down experiments indicated that RGS2 and RGS4 directly interact within different domains of the κ-CT. Co-precipitation studies in living cells indicated that RGS2 and RGS4 associate with κ-ΟR constitutively and upon receptor activation and confer selectivity for coupling with a specific subset of G proteins. Expression of both members, RGS2 and/or RGS4, in 293F cells attenuated κ-agonist mediated-adenylyl cyclase inhibition and extracellular signal regulated kinase (ERK1,2) phosphorylation with a different amplitude in their modulatory effect in κ-ΟR signaling. Our findings demonstrate that RGS2 and RGS4 are new interacting partners that play key roles in G protein coupling to negatively regulate κ-ΟR signaling.
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Affiliation(s)
- Maria-Pagona Papakonstantinou
- Laboratory of Cellular Signalling and Molecular Pharmacology, Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos", Athens, Greece
| | - Christos Karoussiotis
- Laboratory of Cellular Signalling and Molecular Pharmacology, Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos", Athens, Greece
| | - Zafiroula Georgoussi
- Laboratory of Cellular Signalling and Molecular Pharmacology, Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos", Athens, Greece.
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19
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Lamberts JT, Traynor JR. Opioid receptor interacting proteins and the control of opioid signaling. Curr Pharm Des 2014; 19:7333-47. [PMID: 23448476 DOI: 10.2174/138161281942140105160625] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 02/18/2013] [Indexed: 12/31/2022]
Abstract
Opioid receptors are seven-transmembrane domain receptors that couple to intracellular signaling molecules by activating heterotrimeric G proteins. However, the receptor and G protein do not function in isolation but their activities are modulated by several accessory and scaffolding proteins. Examples include arrestins, kinases, and regulators of G protein signaling proteins. Accessory proteins contribute to the observed potency and efficacy of agonists, but also to the direction of signaling and the phenomenon of biased agonism. This review will present current knowledge of such proteins and how they may provide targets for future drug design.
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Affiliation(s)
| | - John R Traynor
- Department of Pharmacology, University of Michigan Medical School, 1301 MSRB III, 1150 West Medical Center Drive, Ann Arbor, MI 48109-5632, USA.
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20
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Octeau JC, Schrader JM, Masuho I, Sharma M, Aiudi C, Chen CK, Kovoor A, Celver J. G protein beta 5 is targeted to D2-dopamine receptor-containing biochemical compartments and blocks dopamine-dependent receptor internalization. PLoS One 2014; 9:e105791. [PMID: 25162404 PMCID: PMC4146516 DOI: 10.1371/journal.pone.0105791] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 07/23/2014] [Indexed: 11/18/2022] Open
Abstract
G beta 5 (Gbeta5, Gβ5) is a unique G protein β subunit that is thought to be expressed as an obligate heterodimer with R7 regulator of G protein signaling (RGS) proteins instead of with G gamma (Gγ) subunits. We found that D2-dopamine receptor (D2R) coexpression enhances the expression of Gβ5, but not that of the G beta 1 (Gβ1) subunit, in HEK293 cells, and that the enhancement of expression occurs through a stabilization of Gβ5 protein. We had previously demonstrated that the vast majority of D2R either expressed endogenously in the brain or exogenously in cell lines segregates into detergent-resistant biochemical fractions. We report that when expressed alone in HEK293 cells, Gβ5 is highly soluble, but is retargeted to the detergent-resistant fraction after D2R coexpression. Furthermore, an in-cell biotin transfer proximity assay indicated that D2R and Gβ5 segregating into the detergent-resistant fraction specifically interacted in intact living cell membranes. Dopamine-induced D2R internalization was blocked by coexpression of Gβ5, but not Gβ1. However, the same Gβ5 coexpression levels had no effect on agonist-induced internalization of the mu opioid receptor (MOR), cell surface D2R levels, dopamine-mediated recruitment of β-arrestin to D2R, the amplitude of D2R-G protein coupling, or the deactivation kinetics of D2R-activated G protein signals. The latter data suggest that the interactions between D2R and Gβ5 are not mediated by endogenously expressed R7 RGS proteins.
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Affiliation(s)
- J. Christopher Octeau
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Joseph M. Schrader
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Meenakshi Sharma
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Christopher Aiudi
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Ching-Kang Chen
- Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States of America
| | - Abraham Kovoor
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
- * E-mail: (AK); (JC)
| | - Jeremy Celver
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
- * E-mail: (AK); (JC)
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21
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Terzi D, Gaspari S, Manouras L, Descalzi G, Mitsi V, Zachariou V. RGS9-2 modulates sensory and mood related symptoms of neuropathic pain. Neurobiol Learn Mem 2014; 115:43-8. [PMID: 25150149 DOI: 10.1016/j.nlm.2014.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 08/07/2014] [Accepted: 08/09/2014] [Indexed: 10/24/2022]
Abstract
The signal transduction modulator Rgs9-2 (Regulator of G protein signaling 9-2) plays a key role in dopaminergic and opioidergic transmission in the striatum. Rgs9-2 is a potent modulator of opiate reward and analgesia, but its role in chronic pain remains unknown. Here, we use the spared nerve injury model (SNI), to evaluate the influence of Rgs9-2 in sensory symptoms, as well as in anxiety and depression-like behaviors observed under neuropathic pain conditions. Our data demonstrate that knockout of the Rgs9 gene reduces the intensity of thermal hyperalgesia and mechanical allodynia the first few days after nerve injury. This small, but significant effect is only observed at early time points after nerve injury, whereas after the first week of SNI, Rgs9 knockout (Rgs9KO) and Rgs9 wildtype (Rgs9WT) mice show similar levels of mechanical allodynia and thermal hyperalgesia. Furthermore, Rgs9-2 deletion exacerbates anxiety and depression like behaviors several weeks after the emergence of the neuropathic pain symptoms. Our findings also reveal a temporal and regional regulation of Rgs9-2 protein expression by neuropathic pain, as Rgs9-2 levels are reduced in the spinal cord a few days after nerve injury, whereas decreased Rgs9-2 levels in the Nucleus Accumbens (NAc) are only observed several weeks after nerve injury. Thus, adaptations in Rgs9-2 activity in the spinal cord and in the NAc may contribute to sensory and affective components of neuropathic pain.
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Affiliation(s)
- Dimitra Terzi
- University of Crete Faculty of Medicine, Department of Basic Sciences, Heraklion, Crete 71003, Greece
| | - Sevasti Gaspari
- University of Crete Faculty of Medicine, Department of Basic Sciences, Heraklion, Crete 71003, Greece
| | - Lefteris Manouras
- University of Crete Faculty of Medicine, Department of Basic Sciences, Heraklion, Crete 71003, Greece
| | - Giannina Descalzi
- Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, Department of Pharmacology and Systems Therapeutics, United States
| | - Vassiliki Mitsi
- University of Crete Faculty of Medicine, Department of Basic Sciences, Heraklion, Crete 71003, Greece
| | - Venetia Zachariou
- University of Crete Faculty of Medicine, Department of Basic Sciences, Heraklion, Crete 71003, Greece; Icahn School of Medicine at Mount Sinai, Fishberg Department of Neuroscience and Friedman Brain Institute, Department of Pharmacology and Systems Therapeutics, United States.
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22
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Gaspari S, Papachatzaki MM, Koo JW, Carr FB, Tsimpanouli ME, Stergiou E, Bagot RC, Ferguson D, Mouzon E, Chakravarty S, Deisseroth K, Lobo MK, Zachariou V. Nucleus accumbens-specific interventions in RGS9-2 activity modulate responses to morphine. Neuropsychopharmacology 2014; 39:1968-77. [PMID: 24561386 PMCID: PMC4059906 DOI: 10.1038/npp.2014.45] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 01/31/2014] [Accepted: 02/03/2014] [Indexed: 12/20/2022]
Abstract
Regulator of G protein signalling 9-2 (Rgs9-2) modulates the actions of a wide range of CNS-acting drugs by controlling signal transduction of several GPCRs in the striatum. RGS9-2 acts via a complex mechanism that involves interactions with Gα subunits, the Gβ5 protein, and the adaptor protein R7BP. Our recent work identified Rgs9-2 complexes in the striatum associated with acute or chronic exposures to mu opioid receptor (MOR) agonists. In this study we use several new genetic tools that allow manipulations of Rgs9-2 activity in particular brain regions of adult mice in order to better understand the mechanism via which this protein modulates opiate addiction and analgesia. We used adeno-associated viruses (AAVs) to express forms of Rgs9-2 in the dorsal and ventral striatum (nucleus accumbens, NAc) in order to examine the influence of this protein in morphine actions. Consistent with earlier behavioural findings from constitutive Rgs9 knockout mice, we show that Rgs9-2 actions in the NAc modulate morphine reward and dependence. Notably, Rgs9-2 in the NAc affects the analgesic actions of morphine as well as the development of analgesic tolerance. Using optogenetics we demonstrate that activation of Channelrhodopsin2 in Rgs9-2-expressing neurons, or in D1 dopamine receptor (Drd1)-enriched medium spiny neurons, accelerates the development of morphine tolerance, whereas activation of D2 dopamine receptor (Drd2)-enriched neurons does not significantly affect the development of tolerance. Together, these data provide new information on the signal transduction mechanisms underlying opiate actions in the NAc.
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Affiliation(s)
- Sevasti Gaspari
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Maria M Papachatzaki
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Ja Wook Koo
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, Friedman Brain Institute, New York, NY, USA
| | - Fiona B Carr
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, Friedman Brain Institute, New York, NY, USA
| | | | - Eugenia Stergiou
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Rosemary C Bagot
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, Friedman Brain Institute, New York, NY, USA
| | - Deveroux Ferguson
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, Friedman Brain Institute, New York, NY, USA
| | - Ezekiell Mouzon
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, Friedman Brain Institute, New York, NY, USA
| | - Sumana Chakravarty
- Division of Chemical Biology, Indian Institute of Chemical Technology, Hyderabad, India
| | - Karl Deisseroth
- Departments of Bioengineering and Physiology and Behavioural Sciences, Stanford Univerity, Stanford, CA, USA
| | - Mary Kay Lobo
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Venetia Zachariou
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Greece
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, Friedman Brain Institute, New York, NY, USA
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, Friedman Brain Institute, New York, NY 10029, USA, Tel: +1 212 6598612; E-mail:
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23
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Differential control of opioid antinociception to thermal stimuli in a knock-in mouse expressing regulator of G-protein signaling-insensitive Gαo protein. J Neurosci 2013; 33:4369-77. [PMID: 23467353 DOI: 10.1523/jneurosci.5470-12.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Regulator of G-protein signaling (RGS) proteins classically function as negative modulators of G-protein-coupled receptor signaling. In vitro, RGS proteins have been shown to inhibit signaling by agonists at the μ-opioid receptor, including morphine. The goal of the present study was to evaluate the contribution of endogenous RGS proteins to the antinociceptive effects of morphine and other opioid agonists. To do this, a knock-in mouse that expresses an RGS-insensitive (RGSi) mutant Gαo protein, Gαo(G184S) (Gαo RGSi), was evaluated for morphine or methadone antinociception in response to noxious thermal stimuli. Mice expressing Gαo RGSi subunits exhibited a naltrexone-sensitive enhancement of baseline latency in both the hot-plate and warm-water tail-withdrawal tests. In the hot-plate test, a measure of supraspinal nociception, morphine antinociception was increased, and this was associated with an increased ability of opioids to inhibit presynaptic GABA neurotransmission in the periaqueductal gray. In contrast, antinociception produced by either morphine or methadone was reduced in the tail-withdrawal test, a measure of spinal nociception. In whole-brain and spinal cord homogenates from mice expressing Gαo RGSi subunits, there was a small loss of Gαo expression and an accompanying decrease in basal G-protein activity. Our results strongly support a role for RGS proteins as negative regulators of opioid supraspinal antinociception and also reveal a potential novel function of RGS proteins as positive regulators of opioid spinal antinociceptive pathways.
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Wang Q, Traynor JR. Modulation of μ-opioid receptor signaling by RGS19 in SH-SY5Y cells. Mol Pharmacol 2013; 83:512-20. [PMID: 23197645 PMCID: PMC3558815 DOI: 10.1124/mol.112.081992] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 11/29/2012] [Indexed: 02/03/2023] Open
Abstract
Regulator of G-protein signaling protein 19 (RGS19), also known as Gα-interacting protein (GAIP), acts as a GTPase accelerating protein for Gαz as well as Gαi/o subunits. Interactions with GAIP-interacting protein N-terminus and GAIP-interacting protein C-terminus (GIPC) link RGS19 to a variety of intracellular proteins. Here we show that RGS19 is abundantly expressed in human neuroblastoma SH-SY5Y cells that also express µ- and δ- opioid receptors (MORs and DORs, respectively) and nociceptin receptors (NOPRs). Lentiviral delivery of short hairpin RNA specifically targeted to RGS19 reduced RGS19 protein levels by 69%, with a similar reduction in GIPC. In RGS19-depleted cells, there was an increase in the ability of MOR (morphine) but not of DOR [(4-[(R)-[(2S,5R)-4-allyl-2,5-dimethylpiperazin-1-yl](3-methoxyphenyl)methyl]-N,N-diethylbenzamide (SNC80)] or NOPR (nociceptin) agonists to inhibit forskolin-stimulated adenylyl cyclase and increase mitogen-activated protein kinase (MAPK) activity. Overnight treatment with either MOR [D-Ala, N-Me-Phe, Gly-ol(5)-enkephalin (DAMGO) or morphine] or DOR (D-Pen(5)-enkephalin or SNC80) agonists increased RGS19 and GIPC protein levels in a time- and concentration-dependent manner. The MOR-induced increase in RGS19 protein was prevented by pretreatment with pertussis toxin or the opioid antagonist naloxone. Protein kinase C (PKC) activation alone increased the level of RGS19 and inhibitors of PKC 5,6,7,13-tetrahydro-13-methyl-5-oxo-12H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-12-propanenitrile and mitogen-activated protein kinase kinase 1 2-(2-amino-3-methoxyphenyl)-4H-chromen-4-one, but not protein kinase A (H89), completely blocked DAMGO-induced RGS19 protein accumulation. The findings show that RGS19 and GIPC are jointly regulated, that RGS19 is a GTPase accelerating protein for MOR with selectivity over DOR and NOPR, and that chronic MOR or DOR agonist treatment increases RGS19 levels by a PKC and the MAPK pathway-dependent mechanism.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Adenylyl Cyclases/genetics
- Adenylyl Cyclases/metabolism
- Animals
- Benzamides/pharmacology
- Colforsin/pharmacology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- HEK293 Cells
- Humans
- Mitogen-Activated Protein Kinases/genetics
- Mitogen-Activated Protein Kinases/metabolism
- Morphine/pharmacology
- Opioid Peptides/pharmacology
- PC12 Cells
- Piperazines/pharmacology
- Protein Kinase C/genetics
- Protein Kinase C/metabolism
- RGS Proteins/genetics
- RGS Proteins/metabolism
- Rats
- Receptors, Opioid/genetics
- Receptors, Opioid/metabolism
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/metabolism
- Signal Transduction/drug effects
- Nociceptin Receptor
- Nociceptin
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Affiliation(s)
- Qin Wang
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109-5632, USA
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25
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Kach J, Sethakorn N, Dulin NO. A finer tuning of G-protein signaling through regulated control of RGS proteins. Am J Physiol Heart Circ Physiol 2012; 303:H19-35. [PMID: 22542620 DOI: 10.1152/ajpheart.00764.2011] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Regulators of G-protein signaling (RGS) proteins are GTPase-activating proteins (GAP) for various Gα subunits of heterotrimeric G proteins. Through this mechanism, RGS proteins regulate the magnitude and duration of G-protein-coupled receptor signaling and are often referred to as fine tuners of G-protein signaling. Increasing evidence suggests that RGS proteins themselves are regulated through multiple mechanisms, which may provide an even finer tuning of G-protein signaling and crosstalk between G-protein-coupled receptors and other signaling pathways. This review summarizes the current data on the control of RGS function through regulated expression, intracellular localization, and covalent modification of RGS proteins, as related to cell function and the pathogenesis of diseases.
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Affiliation(s)
- Jacob Kach
- Department of Medicine, University of Chicago, Illinois, 60637, USA
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26
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Traynor J. μ-Opioid receptors and regulators of G protein signaling (RGS) proteins: from a symposium on new concepts in mu-opioid pharmacology. Drug Alcohol Depend 2012; 121:173-80. [PMID: 22129844 PMCID: PMC3288798 DOI: 10.1016/j.drugalcdep.2011.10.027] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 08/19/2011] [Accepted: 10/22/2011] [Indexed: 02/07/2023]
Abstract
Mu-opioid receptors (MOR) are the therapeutic target for opiate analgesic drugs and also mediate many of the side-effects and addiction liability of these compounds. MOR is a seven-transmembrane domain receptor that couples to intracellular signaling molecules by activating heterotrimeric G proteins. However, the receptor and G protein do not function in isolation but their activities are moderated by several accessory and scaffolding proteins. One important group of accessory proteins is the regulator of G protein signaling (RGS) protein family, a large family of more than thirty members which bind to the activated Gα subunit of the heterotrimeric G protein and serve to accelerate signal termination. This action negatively modulates receptor signaling and subsequent behavior. Several members of this family, in particular RGS4 and RGS9-2 have been demonstrated to influence MOR signaling and morphine-induced behaviors, including reward. Moreover, this interaction is not unidirectional since morphine has been demonstrated to modulate expression levels of RGS proteins, especially RGS4 and RGS9-2, in a tissue and time dependent manner. In this article, I will discuss our work on the regulation of MOR signaling by RGS protein activity in cultured cell systems in the context of other in vitro and behavioral studies. In addition I will consider implications of the bi-directional interaction between MOR receptor activation and RGS protein activity and whether RGS proteins might provide a suitable and novel target for medications to manage addictive behaviors.
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Affiliation(s)
- John Traynor
- Department of Pharmacology and Substance Abuse Research Center, University of Michigan, Ann Arbor, MI 48109-5632, United States.
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27
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Terzi D, Cao Y, Agrimaki I, Martemyanov KA, Zachariou V. R7BP modulates opiate analgesia and tolerance but not withdrawal. Neuropsychopharmacology 2012; 37:1005-12. [PMID: 22089315 PMCID: PMC3280654 DOI: 10.1038/npp.2011.284] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The adaptor protein R7 family binding protein (R7BP) modulates G protein coupled receptor (GPCR) signaling and desensitization by controlling the function of regulator of G protein signaling (RGS) proteins. R7BP is expressed throughout the brain and appears to modulate the membrane localization and stability of three proteins that belong to R7 RGS family: RGS6, RGS7, and RGS9-2. RGS9-2 is a potent negative modulator of opiate and psychostimulant addiction and promotes the development of analgesic tolerance to morphine, whereas the role of RGS6 and RGS7 in addiction remains unknown. Recent studies revealed that functional deletion of R7BP reduces R7 protein activity by preventing their anchoring to the cell membrane and enhances GPCR responsiveness in the basal ganglia. Here, we take advantage of R7BP knockout mice in order to examine the way interventions in R7 proteins function throughout the brain affect opiate actions. Our results suggest that R7BP is a negative modulator of the analgesic and locomotor activating actions of morphine. We also report that R7BP contributes to the development of morphine tolerance. Finally, our data suggest that although prevention of R7BP actions enhances the analgesic responses to morphine, it does not affect the severity of somatic withdrawal signs. Our data suggest that interventions in R7BP actions enhance the analgesic effect of morphine and prevent tolerance, without affecting withdrawal, pointing to R7BP complexes as potential new targets for analgesic drugs.
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Affiliation(s)
- Dimitra Terzi
- Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete, Greece
| | - Yan Cao
- Department of Neuroscience, The Scripps Research Institute—Florida, Jupiter, FL, USA
| | - Ioanna Agrimaki
- Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete, Greece
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute—Florida, Jupiter, FL, USA,Department of Neuroscience, The Scripps Research Institute—Florida, 130 Scripps Way 3C2, Jupiter, FL 33458, USA, Tel:+561 228 2770, E-mail:
| | - Venetia Zachariou
- Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete, Greece,Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete 71003, Greece, Tel: +30 2810 394527, Fax: +30 2810 394530, E-mail:
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28
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Membrane attachment is key to protecting transducin GTPase-activating complex from intracellular proteolysis in photoreceptors. J Neurosci 2011; 31:14660-8. [PMID: 21994382 DOI: 10.1523/jneurosci.3516-11.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The members of the R7 regulator of G-protein signaling (RGS) protein subfamily are versatile regulators of G-protein signaling throughout the nervous system. Recent studies indicate that they are often found in complexes with membrane anchor proteins that serve as versatile modulators of their activity, intracellular targeting, and stability. One striking example is the interplay between the membrane anchor R9AP and the RGS9-1 · Gβ5 GTPase-activating complex responsible for the rapid inactivation of the G-protein transducin in vertebrate photoreceptor cells during their recovery from light excitation. The amount of this complex in photoreceptors sets their temporal resolution and is precisely regulated by the expression level of R9AP, which serves to protect the RGS9-1 and Gβ5 subunits from intracellular proteolysis. In this study, we investigated the mechanism by which R9AP performs its protective function in mouse rods and found that it is entirely confined to recruiting RGS9-1 · Gβ5 to cellular membranes. Furthermore, membrane attachment of RGS9-1 · Gβ5 is sufficient for its stable expression in rods even in the absence of R9AP. Our second finding is that RGS9-1 · Gβ5 possesses targeting information that specifies its exclusion from the outer segment and that this information is neutralized by association with R9AP to allow outer segment targeting. Finally, we demonstrate that the ability of R9AP · RGS9-1 · Gβ5 to accelerate GTP hydrolysis on transducin is independent of its means of membrane attachment, since replacing the transmembrane domain of R9AP with a site for lipid modification did not impair the catalytic activity of this complex.
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29
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Waugh JL, Celver J, Sharma M, Dufresne RL, Terzi D, Risch SC, Fairbrother WG, Neve RL, Kane JP, Malloy MJ, Pullinger CR, Gu HF, Tsatsanis C, Hamilton SP, Gold SJ, Zachariou V, Kovoor A. Association between regulator of G protein signaling 9-2 and body weight. PLoS One 2011; 6:e27984. [PMID: 22132185 PMCID: PMC3223194 DOI: 10.1371/journal.pone.0027984] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 10/28/2011] [Indexed: 12/15/2022] Open
Abstract
Regulator of G protein signaling 9-2 (RGS9-2) is a protein that is highly enriched in the striatum, a brain region that mediates motivation, movement and reward responses. We identified a naturally occurring 5 nucleotide deletion polymorphism in the human RGS9 gene and found that the mean body mass index (BMI) of individuals with the deletion was significantly higher than those without. A splicing reporter minigene assay demonstrated that the deletion had the potential to significantly decrease the levels of correctly spliced RGS9 gene product. We measured the weights of rats after virally transduced overexpression of RGS9-2 or the structurally related RGS proteins, RGS7, or RGS11, in the nucleus accumbens (NAc) and observed a reduction in body weight after overexpression of RGS9-2 but not RGS7 or 11. Conversely, we found that the RGS9 knockout mice were heavier than their wild-type littermates and had significantly higher percentages of abdominal fat. The constituent adipocytes were found to have a mean cross-sectional area that was more than double that of corresponding cells from wild-type mice. However, food intake and locomotion were not significantly different between the two strains. These studies with humans, rats and mice implicate RGS9-2 as a factor in regulating body weight.
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Affiliation(s)
- Jeffrey L. Waugh
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Jeremy Celver
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
- Kovogen LLC, Mystic, Connecticut, United States of America
| | - Meenakshi Sharma
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Robert L. Dufresne
- Department of Pharmacy Practice, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Dimitra Terzi
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece
| | - S. Craig Risch
- Department of Psychiatry, University of California San Francisco, San Francisco, California, United States of America
| | - William G. Fairbrother
- Department of Molecular and Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Rachael L. Neve
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - John P. Kane
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, United States of America
- Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, United States of America
| | - Mary J. Malloy
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, United States of America
| | - Clive R. Pullinger
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, United States of America
- Department of Physiological Nursing, University of California San Francisco, San Francisco, California, United States of America
| | - Harvest F. Gu
- Department of Molecular Medicine and Surgery, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden
| | - Christos Tsatsanis
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece
| | - Steven P. Hamilton
- Department of Psychiatry, University of California San Francisco, San Francisco, California, United States of America
| | - Stephen J. Gold
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Venetia Zachariou
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece
| | - Abraham Kovoor
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America
- Kovogen LLC, Mystic, Connecticut, United States of America
- * E-mail:
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30
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Differential regulation of RGS proteins in the prefrontal cortex of short- and long-term human opiate abusers. Neuropharmacology 2011; 62:1044-51. [PMID: 22056472 DOI: 10.1016/j.neuropharm.2011.10.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 10/20/2011] [Accepted: 10/24/2011] [Indexed: 12/20/2022]
Abstract
Opiate addiction is characterized by drug tolerance and dependence which involve adaptive changes in μ-opioid receptors (MORs) signaling. Regulators of G-protein signaling RGS9, RGS4 and RGS10 proteins negatively regulate G(αi/o) protein activity modulating MOR function. An important role of RGS proteins in drug addiction has been described but the status of RGS proteins in human brain of opiate addicts remains unknown. The present study evaluated the immunoreactivity levels of RGS4, RGS9 and RGS10 proteins in prefrontal cortex of short- (n = 15) and long-term (n = 21) opiate abusers and in matched control subjects. RGS4 protein was not altered in short-term opiate abusers but, in long-term abusers it was significantly up-regulated (Δ = 29 ± 6%). RGS10 protein expression was significantly decreased in short-term (Δ = -42 ± 7%) but remained unaltered in long-term opiate abusers. RGS9 protein levels in opiate abusers did not differ from matched controls either in the short-term or in the long-term opiate abuser groups. RGS4, RGS9 and RGS10 levels were also studied in brains (frontal cortex) of rats submitted to acute and chronic morphine treatment and to spontaneous and naloxone-precipitated opiate withdrawal. Chronic morphine treatment in rats was associated with an increase in RGS4 protein immunoreactivity (Δ = 28 ± 7%), which persisted in spontaneous (Δ = 35 ± 8%) and naloxone-precipitated withdrawal (Δ = 30 ± 9%) without significant changes in RGS9 and RGS10 proteins. The specific modulation of RGS4 and RGS10 protein expression observed in the prefrontal cortex of opiate abusers might be relevant in the neurobiology of opiate tolerance, dependence and withdrawal. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.
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31
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β-arrestin2 plays permissive roles in the inhibitory activities of RGS9-2 on G protein-coupled receptors by maintaining RGS9-2 in the open conformation. Mol Cell Biol 2011; 31:4887-901. [PMID: 22006018 DOI: 10.1128/mcb.05690-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Together with G protein-coupled receptor (GPCR) kinases (GRKs) and β-arrestins, RGS proteins are the major family of molecules that control the signaling of GPCRs. The expression pattern of one of these RGS family members, RGS9-2, coincides with that of the dopamine D(3) receptor (D(3)R) in the brain, and in vivo studies have shown that RGS9-2 regulates the signaling of D2-like receptors. In this study, β-arrestin2 was found to be required for scaffolding of the intricate interactions among the dishevelled-EGL10-pleckstrin (DEP) domain of RGS9-2, Gβ5, R7-binding protein (R7BP), and D(3)R. The DEP domain of RGS9-2, under the permission of β-arrestin2, inhibited the signaling of D(3)R in collaboration with Gβ5. β-Arrestin2 competed with R7BP and Gβ5 so that RGS9-2 is placed in the cytosolic region in an open conformation which is able to inhibit the signaling of GPCRs. The affinity of the receptor protein for β-arrestin2 was a critical factor that determined the selectivity of RGS9-2 for the receptor it regulates. These results show that β-arrestins function not only as mediators of receptor-G protein uncoupling and initiators of receptor endocytosis but also as scaffolding proteins that control and coordinate the inhibitory effects of RGS proteins on the signaling of certain GPCRs.
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32
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Philibin SD, Hernandez A, Self DW, Bibb JA. Striatal signal transduction and drug addiction. Front Neuroanat 2011; 5:60. [PMID: 21960960 PMCID: PMC3176395 DOI: 10.3389/fnana.2011.00060] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 09/01/2011] [Indexed: 11/23/2022] Open
Abstract
Drug addiction is a severe neuropsychiatric disorder characterized by loss of control over motivated behavior. The need for effective treatments mandates a greater understanding of the causes and identification of new therapeutic targets for drug development. Drugs of abuse subjugate normal reward-related behavior to uncontrollable drug-seeking and -taking. Contributions of brain reward circuitry are being mapped with increasing precision. The role of synaptic plasticity in addiction and underlying molecular mechanisms contributing to the formation of the addicted state are being delineated. Thus we may now consider the role of striatal signal transduction in addiction from a more integrative neurobiological perspective. Drugs of abuse alter dopaminergic and glutamatergic neurotransmission in medium spiny neurons of the striatum. Dopamine receptors important for reward serve as principle targets of drugs abuse, which interact with glutamate receptor signaling critical for reward learning. Complex networks of intracellular signal transduction mechanisms underlying these receptors are strongly stimulated by addictive drugs. Through these mechanisms, repeated drug exposure alters functional and structural neuroplasticity, resulting in transition to the addicted biological state and behavioral outcomes that typify addiction. Ca2+ and cAMP represent key second messengers that initiate signaling cascades, which regulate synaptic strength and neuronal excitability. Protein phosphorylation and dephosphorylation are fundamental mechanisms underlying synaptic plasticity that are dysregulated by drugs of abuse. Increased understanding of the regulatory mechanisms by which protein kinases and phosphatases exert their effects during normal reward learning and the addiction process may lead to novel targets and pharmacotherapeutics with increased efficacy in promoting abstinence and decreased side effects, such as interference with natural reward, for drug addiction.
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Affiliation(s)
- Scott D Philibin
- Department of Psychiatry, University of Texas Southwestern Medical Center Dallas, TX, USA
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33
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Xie K, Martemyanov KA. Control of striatal signaling by g protein regulators. Front Neuroanat 2011; 5:49. [PMID: 21852966 PMCID: PMC3151604 DOI: 10.3389/fnana.2011.00049] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2011] [Accepted: 07/23/2011] [Indexed: 12/03/2022] Open
Abstract
Signaling via heterotrimeric G proteins plays a crucial role in modulating the responses of striatal neurons that ultimately shape core behaviors mediated by the basal ganglia circuitry, such as reward valuation, habit formation, and movement coordination. Activation of G protein-coupled receptors (GPCRs) by extracellular signals activates heterotrimeric G proteins by promoting the binding of GTP to their α subunits. G proteins exert their effects by influencing the activity of key effector proteins in this region, including ion channels, second messenger enzymes, and protein kinases. Striatal neurons express a staggering number of GPCRs whose activation results in the engagement of downstream signaling pathways and cellular responses with unique profiles but common molecular mechanisms. Studies over the last decade have revealed that the extent and duration of GPCR signaling are controlled by a conserved protein family named regulator of G protein signaling (RGS). RGS proteins accelerate GTP hydrolysis by the α subunits of G proteins, thus promoting deactivation of GPCR signaling. In this review, we discuss the progress made in understanding the roles of RGS proteins in controlling striatal G protein signaling and providing integration and selectivity of signal transmission. We review evidence on the formation of a macromolecular complex between RGS proteins and other components of striatal signaling pathways, their molecular regulatory mechanisms and impacts on GPCR signaling in the striatum obtained from biochemical studies and experiments involving genetic mouse models. Special emphasis is placed on RGS9-2, a member of the RGS family that is highly enriched in the striatum and plays critical roles in drug addiction and motor control.
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Affiliation(s)
- Keqiang Xie
- The Scripps Research Institute Jupiter, FL, USA
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Wang Q, Levay K, Chanturiya T, Dvoriantchikova G, Anderson KL, Bianco SDC, Ueta CB, Molano RD, Pileggi A, Gurevich EV, Gavrilova O, Slepak VZ. Targeted deletion of one or two copies of the G protein β subunit Gβ5 gene has distinct effects on body weight and behavior in mice. FASEB J 2011; 25:3949-57. [PMID: 21804131 DOI: 10.1096/fj.11-190157] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We investigated the physiological role of Gβ5, a unique G protein β subunit that dimerizes with regulators of G protein signaling (RGS) proteins of the R7 family instead of Gγ. Gβ5 is essential for stability of these complexes, so that its knockout (KO)causes degradation of the entire Gβ5-R7 family. We report that the Gβ5-KO mice remain leaner than the wild type (WT) throughout their lifetime and are resistant to a high-fat diet. They have a 5-fold increase in locomotor activity, increased thermogenesis, and lower serum insulin, all of which correlate with a higher level of secreted epinephrine. Heterozygous (HET) mice are 2-fold more active than WT mice. Surprisingly, with respect to body weight, the HET mice display a phenotype opposite to that of the KO mice: by the age of 6 mo, they are ≥ 15% heavier than the WT and have increased adiposity, insulin resistance, and liver steatosis. These changes occur in HET mice fed a normal diet and without apparent hyperphagia, mimicking basic characteristics of human metabolic syndrome. We conclude that even a partial reduction in Gβ5-R7 level can perturb normal animal metabolism and behavior. Our data on Gβ5 haploinsufficient mice may explain earlier observations of genetic linkage between R7 family mutations and obesity in humans.
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Affiliation(s)
- Qiang Wang
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida, 33136, USA
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Papachatzaki MM, Antal Z, Terzi D, Szücs P, Zachariou V, Antal M. RGS9-2 modulates nociceptive behaviour and opioid-mediated synaptic transmission in the spinal dorsal horn. Neurosci Lett 2011; 501:31-4. [PMID: 21741448 DOI: 10.1016/j.neulet.2011.06.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 06/21/2011] [Accepted: 06/21/2011] [Indexed: 11/17/2022]
Abstract
The regulator of G protein signaling 9-2 (RGS9-2) is a constituent of G protein-coupled receptor (GPCR) macromolecular complexes with a major role in regulation of GPCR activity in the central nervous system. Previous in situ hybridization and Western blot studies revealed that RGS9-2 is expressed in the superficial dorsal horn of the spinal cord. In the present study, we monitored tail withdrawal latencies to noxious thermal stimuli and performed in vitro whole-cell patch clamp electrophysiological recordings from neurons in lamina II of the spinal dorsal horn to examine the role of RGS9-2 in the dorsal horn of the spinal cord in nociceptive behaviours and opiate mediated modulation of synaptic transmission. Our findings obtained from RGS9 knockout mice indicate that the lack of RGS9-2 protein decreases sensitivity to thermal stimuli and to the analgesic actions of morphine in the tail immersion paradigm. This modulatory role of RGS9-2 on opiate-mediated responses was further supported by electrophysiological studies showing that hyperpolarization of neurons in lamina II of the spinal dorsal horn evoked by application of DAMGO ([d-Ala2, N-MePhe4, Gly-ol]-enkephalin, a mu opioid receptor agonist) was diminished in RGS9 knockout mice. The results indicate that RGS9-2 enhances the effect of morphine and may play a crucial role in opiate-mediated analgesic mechanisms at the level of the spinal cord.
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Affiliation(s)
- Maria Martha Papachatzaki
- Department of Basic Science, University of Crete, Faculty of Medicine, Heraklion, Crete 71003, Greece
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A unique role of RGS9-2 in the striatum as a positive or negative regulator of opiate analgesia. J Neurosci 2011; 31:5617-24. [PMID: 21490202 DOI: 10.1523/jneurosci.4146-10.2011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The signaling molecule RGS9-2 is a potent modulator of G-protein-coupled receptor function in striatum. Our earlier work revealed a critical role for RGS9-2 in the actions of the μ-opioid receptor (MOR) agonist morphine. In this study, we demonstrate that RGS9-2 may act as a positive or negative modulator of MOR-mediated behavioral responses in mice depending on the agonist administered. Paralleling these findings we use coimmunoprecipitation assays to show that the signaling complexes formed between RGS9-2 and Gα subunits in striatum are determined by the MOR agonist, and we identify RGS9-2 containing complexes associated with analgesic tolerance. In striatum, MOR activation promotes the formation of complexes between RGS9-2 and several Gα subunits, but morphine uniquely promotes an association between RGS9-2 and Gαi3. In contrast, RGS9-2/Gαq complexes assemble after acute application of several MOR agonists but not after morphine application. Repeated morphine administration leads to the formation of distinct complexes, which contain RGS9-2, Gβ5, and Gαq. Finally, we use simple pharmacological manipulations to disrupt RGS9-2 complexes formed during repeated MOR activation to delay the development of analgesic tolerance to morphine. Our data provide a better understanding of the brain-region-specific signaling events associated with opiate analgesia and tolerance and point to pharmacological approaches that can be readily tested for improving chronic analgesic responsiveness.
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Sjögren B. Regulator of G protein signaling proteins as drug targets: current state and future possibilities. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2011; 62:315-47. [PMID: 21907914 DOI: 10.1016/b978-0-12-385952-5.00002-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Regulators of G protein signaling (RGS) proteins have emerged in the past two decades as novel drug targets in many areas of research. Their importance in regulating signaling via G protein-coupled receptors has become evident as numerous studies have been published on the structure and function of RGS proteins. A number of genetic models have also been developed, demonstrating the potential clinical importance of RGS proteins in various disease states, including central nervous system disorders, cardiovascular disease, diabetes, and several types of cancer. Apart from their classical mechanism of action as GTPase-activating proteins (GAPs), RGS proteins can also serve other noncanonical functions. This opens up a new approach to targeting RGS proteins in drug discovery as the view on the function of these proteins is constantly evolving. This chapter summarizes the latest development in RGS protein drug discovery with special emphasis on noncanonical functions and regulatory mechanisms of RGS protein expression. As more reports are being published on this group of proteins, it is becoming clear that modulation of GAP activity might not be the only way to therapeutically target RGS proteins.
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Affiliation(s)
- Benita Sjögren
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
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Posokhova E, Uversky V, Martemyanov KA. Proteomic identification of Hsc70 as a mediator of RGS9-2 degradation by in vivo interactome analysis. J Proteome Res 2010; 9:1510-21. [PMID: 20095651 DOI: 10.1021/pr901022m] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Changes in interactions between signaling proteins underlie many cellular functions. In the mammalian nervous system, a member of the Regulator of G protein Signaling family, RGS9-2 (Regulator of G protein Signaling, type 9), is a key regulator of dopamine and opioid signaling pathways that mediate motor control and reward behavior. Dynamic association of RGS9-2 with a neuronal protein R7BP (R7 family Binding Protein) has been found to be critically important for the regulation of the expression level of the complex by proteolytic mechanisms. Changes in RGS9-2 expression are observed in response to a number of signaling events and are thought to contribute to the plasticity of the neurotransmitter action. In this study, we report an identification of molecular chaperone Hsc70 (Heat shock cognate protein 70) as a critical mediator of RGS9-2 expression that is specifically recruited to the intrinsically disordered C-terminal domain of RGS9-2 following its dissociation from R7BP. Hsc70 was identified by a novel application of the quantitative proteomics approach developed to monitor interactome dynamics in mice using a set of controls contributed by knockout strains. We propose this application to be a useful tool for studying the dynamics of protein assemblies in complex models, such as signaling in the mammalian nervous system.
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Affiliation(s)
- Ekaterina Posokhova
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Celver J, Sharma M, Kovoor A. RGS9-2 mediates specific inhibition of agonist-induced internalization of D2-dopamine receptors. J Neurochem 2010; 114:739-49. [PMID: 20477943 DOI: 10.1111/j.1471-4159.2010.06805.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Regulator of G protein signaling 9-2 (RGS9-2), a member of the RGS family of GTPase accelerating proteins, is expressed specifically in the striatum, a brain region involved in controlling movement, motivation, mood and addiction. RGS9-2 can be found co-localized with D(2)-class dopamine receptors in medium spiny striatal neurons and altered functioning of both RGS9-2 and D(2)-like dopamine receptors have been implicated in schizophrenia, movement disorders and reward responses. Previously we showed that RGS9-2 can specifically co-localize with D(2)-dopamine receptors (D2R). Here we provide further evidence of the specificity of RGS9-2 for regulating D2R cellular functions: the expression of RGS9-2 inhibits dopamine-mediated cellular internalization of D2R, while the expression of another RGS protein, RGS4, had no effect. In addition, the agonist-mediated internalization of the G protein coupled delta opioid receptor was unaffected by RGS9-2 expression. We utilized mutant constructs of RGS9-2 to show that the RGS9-2 DEP (for Disheveled, EGL-10, Pleckstrin homology) domain and the GTPase accelerating activity of RGS9-2 were necessary for mediating specific inhibition of D2R internalization.
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Affiliation(s)
- Jeremy Celver
- Department of Biomedical and Pharmacological Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, USA
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Brain region specific actions of regulator of G protein signaling 4 oppose morphine reward and dependence but promote analgesia. Biol Psychiatry 2010; 67:761-9. [PMID: 19914603 PMCID: PMC3077672 DOI: 10.1016/j.biopsych.2009.08.041] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Revised: 07/01/2009] [Accepted: 08/19/2009] [Indexed: 11/22/2022]
Abstract
BACKGROUND Regulator of G protein signaling 4 (RGS4) is one of the smaller members of the RGS family of proteins, which are known to control signaling amplitude and duration via interactions with G protein alpha subunits or other signaling molecules. Earlier evidence suggests dynamic regulation of RGS4 levels in neuronal networks mediating actions of opiates and other drugs of abuse, but the consequences of RGS4 actions in vivo are largely unknown. METHODS In this study, we use constitutive and nucleus accumbens-inducible RGS4 knockout mice as well as mice overexpressing RGS4 in the nucleus accumbens via viral mediated gene transfer, to examine the influence of RGS4 on behavioral responses to opiates. We also use electrophysiology and immunoprecipitation assays to further understand the mechanisms underlying the tissue-specific actions of RGS4. RESULTS Inducible knockout or selective overexpression of RGS4 in the nucleus accumbens reveals that, in this brain region, RGS4 acts as a negative regulator of morphine reward, whereas in the locus coeruleus RGS4 opposes morphine physical dependence. In contrast, we show that RGS4 does not affect morphine analgesia or tolerance but is a positive modulator of certain opiate analgesics, such as methadone and fentanyl. CONCLUSIONS These findings provide fundamentally novel information concerning the role of RGS4 in the cellular mechanisms underlying the diverse actions of opiate drugs in the nervous system.
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Abstract
Regulator of G protein-signaling (RGS) proteins are a family of more than 30 intracellular proteins that negatively modulate intracellular signaling of receptors in the G protein-coupled receptor family. This family includes receptors for opioids, cannabinoids, and dopamine that mediate the acute effects of addictive drugs or behaviors and chronic effects leading to the development of addictive disease. Members of the RGS protein family, by negatively modulating receptor signaling, influence the intracellular processes that lead to addiction. In turn, addictive drugs control the expression levels of several RGS proteins. This review will consider the distribution and mechanisms of action of RGS proteins, particularly the R4 and R7 families that have been implicated in the actions of addictive drugs, how knowledge of these proteins is contributing to an understanding of addictive processes, and whether specific RGS proteins could provide targets for the development of medications to manage and/or treat addiction.
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Affiliation(s)
- John Traynor
- Department of Pharmacology and Substance Abuse Research Center, University of Michigan, Ann Arbor, Michigan 48109-5632, USA.
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Anderson GR, Cao Y, Davidson S, Truong HV, Pravetoni M, Thomas MJ, Wickman K, Giesler GJ, Martemyanov KA. R7BP complexes with RGS9-2 and RGS7 in the striatum differentially control motor learning and locomotor responses to cocaine. Neuropsychopharmacology 2010; 35:1040-50. [PMID: 20043004 PMCID: PMC2887292 DOI: 10.1038/npp.2009.212] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the striatum, signaling through G protein-coupled dopamine receptors mediates motor and reward behavior, and underlies the effects of addictive drugs. The extent of receptor responses is determined by RGS9-2/Gbeta5 complexes, a striatally enriched regulator that limits the lifetime of activated G proteins. Recent studies suggest that the function of RGS9-2/Gbeta5 is controlled by the association with an additional subunit, R7BP, making elucidation of its contribution to striatal signaling essential for understanding molecular mechanisms of behaviors mediated by the striatum. In this study, we report that elimination of R7BP in mice results in motor coordination deficits and greater locomotor response to morphine administration, consistent with the essential role of R7BP in maintaining RGS9-2 expression in the striatum. However, in contrast to previously reported observations with RGS9-2 knockouts, mice lacking R7BP do not show higher sensitivity to locomotor-stimulating effects of cocaine. Using a striatum-specific knockdown approach, we show that the sensitivity of motor stimulation to cocaine is instead dependent on RGS7, whose complex formation with R7BP is dictated by RGS9-2 expression. These results indicate that dopamine signaling in the striatum is controlled by concerted interplay between two RGS proteins, RGS7 and RGS9-2, which are balanced by a common subunit, R7BP.
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Affiliation(s)
- Garret R Anderson
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
| | - Yan Cao
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
| | - Steve Davidson
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
| | - Hai V Truong
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
| | - Marco Pravetoni
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
| | - Mark J Thomas
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA
| | - Glenn J Giesler
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
| | - Kirill A Martemyanov
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA,Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street S.E., Minneapolis, MN 55455, USA. Tel: +612 626 5309; Fax: +612 625 8408; E-mail:
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Regulators of G Protein Signaling Proteins as Targets for Drug Discovery. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2010; 91:81-119. [DOI: 10.1016/s1877-1173(10)91004-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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McCoy KL, Hepler JR. Regulators of G protein signaling proteins as central components of G protein-coupled receptor signaling complexes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:49-74. [PMID: 20374713 DOI: 10.1016/s1877-1173(09)86003-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The regulators of G protein signaling (RGS) proteins bind directly to G protein alpha (Gα) subunits to regulate the signaling functions of Gα and their linked G protein-coupled receptors (GPCRs). Recent studies indicate that RGS proteins also interact with GPCRs, not just G proteins, to form preferred functional pairs. Interactions between GPCRs and RGS proteins may be direct or indirect (via a linker protein) and are dictated by the receptors, rather than the linked G proteins. Emerging models suggest that GPCRs serve as platforms for assembling an overlapping and distinct constellation of signaling proteins that perform receptor-specific signaling tasks. Compelling evidence now indicates that RGS proteins are central components of these GPCR signaling complexes. This review will outline recent discoveries of GPCR/RGS pairs as well as new data in support of the idea that GPCRs serve as platforms for the formation of multiprotein signaling complexes.
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Affiliation(s)
- Kelly L McCoy
- Department of Pharmacology, G205 Rollins Research Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Terzi D, Stergiou E, King SL, Zachariou V. Regulators of G protein signaling in neuropsychiatric disorders. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:299-333. [PMID: 20374720 DOI: 10.1016/s1877-1173(09)86010-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Regulators of G protein signaling (RGS) comprise a diverse group of about 40 proteins which determine signaling amplitude and duration via modulation of receptor/G protein or receptor/effector coupling. Several members of the RGS family are expressed in the brain, where they have precise roles in regulation of important physiological processes. The unique functions of each RGS can be attributed to its structure, distinct pattern of expression, and regulation, and its preferential interactions with receptors, Galpha subunits and other signaling proteins. Evidence suggests dysfunction of RGS proteins is related to several neuropathological conditions. Moreover, clinical and preclinical work reveals that the efficacy and/or side effects of treatments are highly influenced by RGS activity. This article summarizes findings on RGS proteins in vulnerability to several neuropsychiatric disorders, the mechanism via which RGS proteins control neuronal responses and their potential use as drug targets.
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Affiliation(s)
- Dimitra Terzi
- Department of Pharmacology, Faculty of Medicine, University of Crete, Heraklion 71003, Crete, Greece
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Retina-specific GTPase accelerator RGS11/G beta 5S/R9AP is a constitutive heterotrimer selectively targeted to mGluR6 in ON-bipolar neurons. J Neurosci 2009; 29:9301-13. [PMID: 19625520 DOI: 10.1523/jneurosci.1367-09.2009] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Members of the R7 family of the regulators of G-protein signaling (R7 RGS) proteins form multi-subunit complexes that play crucial roles in processing the light responses of retinal neurons. The disruption of these complexes has been shown to lead to the loss of temporal resolution in retinal photoreceptors and deficient synaptic transmission to downstream neurons. Despite the well established role of one member of this family, RGS9-1, in controlling vertebrate phototransduction, the roles and organizational principles of other members in the retina are poorly understood. Here we investigate the composition, localization, and function of complexes containing RGS11, the closest homolog of RGS9-1. We find that RGS11 forms a novel obligatory trimeric complex with the short splice isoform of the type 5 G-protein beta subunit (G beta 5) and the RGS9 anchor protein (R9AP). The complex is expressed exclusively in the dendritic tips of ON-bipolar cells in which its localization is accomplished through a direct association with mGluR6, the glutamate receptor essential for the ON-bipolar light response. Although association with both R9AP and mGluR6 contributed to the proteolytic stabilization of the complex, postsynaptic targeting of RGS11 was not determined by its membrane anchor R9AP. Electrophysiological recordings of the light response in mouse rod ON-bipolar cells reveal that the genetic elimination of RGS11 has little effect on the deactivation of G alpha(o) in dark-adapted cells or during adaptation to background light. These results suggest that the deactivation of mGluR6 cascade during the light response may require the contribution of multiple GTPase activating proteins.
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The R7 RGS protein family: multi-subunit regulators of neuronal G protein signaling. Cell Biochem Biophys 2009; 54:33-46. [PMID: 19521673 DOI: 10.1007/s12013-009-9052-9] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 05/27/2009] [Indexed: 01/09/2023]
Abstract
G protein-coupled receptor signaling pathways mediate the transmission of signals from the extracellular environment to the generation of cellular responses, a process that is critically important for neurons and neurotransmitter action. The ability to promptly respond to rapidly changing stimulation requires timely inactivation of G proteins, a process controlled by a family of specialized proteins known as regulators of G protein signaling (RGS). The R7 group of RGS proteins (R7 RGS) has received special attention due to their pivotal roles in the regulation of a range of crucial neuronal processes such as vision, motor control, reward behavior, and nociception in mammals. Four proteins in this group, RGS6, RGS7, RGS9, and RGS11, share a common molecular organization of three modules: (i) the catalytic RGS domain, (ii) a GGL domain that recruits G beta(5), an outlying member of the G protein beta subunit family, and (iii) a DEP/DHEX domain that mediates interactions with the membrane anchor proteins R7BP and R9AP. As heterotrimeric complexes, R7 RGS proteins not only associate with and regulate a number of G protein signaling pathway components, but have also been found to form complexes with proteins that are not traditionally associated with G protein signaling. This review summarizes our current understanding of the biology of the R7 RGS complexes including their structure/functional organization, protein-protein interactions, and physiological roles.
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Wang Q, Liu-Chen LY, Traynor JR. Differential modulation of mu- and delta-opioid receptor agonists by endogenous RGS4 protein in SH-SY5Y cells. J Biol Chem 2009; 284:18357-67. [PMID: 19416973 DOI: 10.1074/jbc.m109.015453] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulator of G-protein signaling (RGS) proteins are a family of molecules that control the duration of G protein signaling. A variety of RGS proteins have been reported to modulate opioid receptor signaling. Here we show that RGS4 is abundantly expressed in human neuroblastoma SH-SY5Y cells that endogenously express mu- and delta-opioid receptors and test the hypothesis that the activity of opioids in these cells is modulated by RGS4. Endogenous RGS4 protein was reduced by approximately 90% in SH-SY5Y cells stably expressing short hairpin RNA specifically targeted to RGS4. In these cells, the potency and maximal effect of delta-opioid receptor agonist (SNC80)-mediated inhibition of forskolin-stimulated cAMP accumulation was increased compared with control cells. This effect was reversed by transient transfection of a stable RGS4 mutant (HA-RGS4C2S). Furthermore, MAPK activation by SNC80 was increased in cells with knockdown of RGS4. In contrast, there was no change in the mu-opioid (morphine) response at adenylyl cyclase or MAPK. FLAG-tagged opioid receptors and HA-RGS4C2S were transiently expressed in HEK293T cells, and co-immunoprecipitation experiments showed that the delta-opioid receptor but not the mu-opioid receptor could be precipitated together with the stable RGS4. Using chimeras of the delta- and mu-opioid receptors, the C-tail and third intracellular domain of the delta-opioid receptor were suggested to be the sites of interaction with RGS4. The findings demonstrate a role for endogenous RGS4 protein in modulating delta-opioid receptor signaling in SH-SY5Y cells and provide evidence for a receptor-specific effect of RGS4.
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Affiliation(s)
- Qin Wang
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
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Leontiadis LJ, Papakonstantinou MP, Georgoussi Z. Regulator of G protein signaling 4 confers selectivity to specific G proteins to modulate mu- and delta-opioid receptor signaling. Cell Signal 2009; 21:1218-28. [PMID: 19324084 DOI: 10.1016/j.cellsig.2009.03.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 03/12/2009] [Accepted: 03/15/2009] [Indexed: 10/21/2022]
Abstract
In vitro studies have shown that the Regulator of G protein Signaling 4 (RGS4) interacts with the C-termini of mu- and delta-opioid receptors (mu-OR, delta-OR) (Georgoussi et al., 2006, Cell. Signal.18, 771-782). Herein we demonstrate that RGS4 associates with these receptors in living cells and forms selective complexes with Gi/Go proteins in a receptor dependent manner. This interaction occurs within the predicted fourth intracellular loop of mu, delta-ORs as part of a signaling complex consisting of the opioid receptor, activated Galpha and RGS4. RGS4 is recruited to the plasma membrane upon opioid receptor stimulation. Expression of RGS4 in HEK293 cells attenuated agonist-mediated extracellular signal regulated kinase (ERK1,2) phosphorylation for both receptors and accelerated agonist-induced internalization of the delta-OR. RGS4 lacking its N-terminal domain failed to interact with both opioid receptors and to modulate opioid receptor signaling. Our findings demonstrate that RGS4 plays a key role in G protein coupling selectivity and signaling of the mu- and delta-OmicronRs.
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Affiliation(s)
- Leonidas J Leontiadis
- Laboratory of Cellular Signaling and Molecular Pharmacology, Institute of Biology, National Center for Scientific Research Demokritos, Ag. Paraskevi-Attikis, Athens, Greece
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Traynor JR, Terzi D, Caldarone BJ, Zachariou V. RGS9-2: probing an intracellular modulator of behavior as a drug target. Trends Pharmacol Sci 2009; 30:105-11. [PMID: 19211160 PMCID: PMC3394094 DOI: 10.1016/j.tips.2008.11.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2008] [Revised: 11/12/2008] [Accepted: 11/13/2008] [Indexed: 10/21/2022]
Abstract
Regulators of G-protein signaling (RGS proteins) comprise a large family of signal transduction molecules that modulate G-protein-coupled-receptor (GPCR) function. Among the RGS proteins expressed in the brain, RGS9-2 is very abundant in the striatum, a brain region involved in movement, motivation, mood and addiction. This protein negatively modulates signal transduction thus playing a key part in striatal function and resultant behavioral responses. In particular, there is evidence of important interactions with mu-opioid- and dopamine D(2)-receptor signaling pathways. Several studies indicate that manipulations of RGS9-2 levels in the striatum might greatly affect pharmacological responses. These findings indicate that treatment strategies targeting RGS9-2 levels or activity might be used to enhance responses to drugs acting at GPCRs and/or prevent undesired drug actions.
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Affiliation(s)
- John R Traynor
- Department of Pharmacology and Substance Abuse Research Center, University of Michigan, Ann Arbor, MI 48109, USA
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