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Spicer MM, Weber MA, Luo Z, Yang J, Narayanan NS, Fisher RA. Regulator of G protein signaling 6 (RGS6) in dopamine neurons promotes EtOH seeking, behavioral reward, and susceptibility to relapse. Psychopharmacology (Berl) 2024:10.1007/s00213-024-06631-8. [PMID: 38856764 DOI: 10.1007/s00213-024-06631-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 05/31/2024] [Indexed: 06/11/2024]
Abstract
Mesolimbic dopamine (DA) transmission is believed to play a critical role in mediating reward responses to drugs of abuse, including alcohol (EtOH). The neurobiological mechanisms underlying EtOH-seeking behavior and dependence are not fully understood, and abstinence remains the only effective way to prevent alcohol use disorders (AUDs). Here, we developed novel RGS6fl/fl; DAT-iCreER mice to determine the role of RGS6 in DA neurons on EtOH consumption, reward, and relapse behaviors. We found that RGS6 is expressed in DA neurons in both human and mouse ventral tegmental area (VTA), and that RGS6 loss in mice upregulates DA transporter (DAT) expression in VTA DA neuron synaptic terminals. Remarkably, loss of RGS6 in DA neurons significantly reduced EtOH consumption, preference, and reward in a manner indistinguishable from that seen in RGS6-/- mice. Strikingly, RGS6 loss from DA neurons before or after EtOH behavioral reward is established significantly reduced (~ 50%) re-instatement of reward following extinguishment, demonstrating distinct roles of RGS6 in promoting reward and relapse susceptibility to EtOH. These studies identify DA neurons as the locus of RGS6 action in promoting EtOH consumption, preference, reward, and relapse. RGS6 is unique among R7 RGS proteins in promoting rather than suppressing behavioral responses to drugs of abuse and to modulate EtOH behavioral reward. This is a result of RGS6's pre-synaptic actions that we hypothesize promote VTA DA transmission by suppressing GPCR-Gαi/o-DAT signaling in VTA DA neurons. These studies identify RGS6 as a potential therapeutic target for behavioral reward and relapse to EtOH.
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Affiliation(s)
- Mackenzie M Spicer
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, 51 Newton Rd. BSB 2-512, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, 169 Newton Rd., Iowa City, IA, 52242, USA
- Department of Neurology, University of Iowa Carver College of Medicine, 200 Hawkins Dr., Iowa City, IA, 52242, USA
| | - Matthew A Weber
- Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, 169 Newton Rd., Iowa City, IA, 52242, USA
- Department of Neurology, University of Iowa Carver College of Medicine, 200 Hawkins Dr., Iowa City, IA, 52242, USA
| | - Zili Luo
- Department of Pediatrics, University of Iowa Carver College of Medicine, 200 Hawkins Dr., Iowa City, IA, 52242, USA
| | - Jianqi Yang
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, 51 Newton Rd. BSB 2-512, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, 169 Newton Rd., Iowa City, IA, 52242, USA
| | - Nandakumar S Narayanan
- Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, 169 Newton Rd., Iowa City, IA, 52242, USA
- Department of Neurology, University of Iowa Carver College of Medicine, 200 Hawkins Dr., Iowa City, IA, 52242, USA
| | - Rory A Fisher
- Department of Neuroscience and Pharmacology, University of Iowa Carver College of Medicine, 51 Newton Rd. BSB 2-512, Iowa City, IA, 52242, USA.
- Iowa Neuroscience Institute, University of Iowa Carver College of Medicine, 169 Newton Rd., Iowa City, IA, 52242, USA.
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Spicer MM, Weber MA, Luo Z, Yang J, Narayanan NS, Fisher RA. Regulator of G protein signaling 6 (RGS6) in ventral tegmental area (VTA) dopamine neurons promotes EtOH seeking, behavioral reward and susceptibility to relapse. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.24.563844. [PMID: 37961154 PMCID: PMC10634791 DOI: 10.1101/2023.10.24.563844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Mesolimbic dopamine (DA) transmission is believed to play a critical role in mediating reward responses to drugs of abuse, including alcohol (EtOH). EtOH is the most abused substance worldwide with chronic consumption often leading to the development of dependence and abuse. Unfortunately, the neurobiological mechanisms underlying EtOH-seeking behavior and dependence are not fully understood, and abstinence remains the only effective way to prevent alcohol use disorders (AUDs). Here, we developed novel RGS6 fl/fl ; DAT-iCreER mice to determine the role of RGS6 in VTA DA neurons on EtOH consumption and reward behaviors. We found that RGS6 is expressed in DA neurons in both human and mouse VTA, and that RGS6 loss in mice upregulates DA transporter (DAT) expression in VTA DA neuron synaptic terminals. Remarkably, loss of RGS6 in VTA DA neurons significantly reduced EtOH consumption, preference, and reward in a manner indistinguishable from that seen in RGS6 -/- mice. Strikingly, RGS6 loss from VTA DA neurons before or after EtOH behavioral reward is established significantly reduced (∼50%) re-instatement of reward following extinguishment, demonstrating distinct roles of RGS6 in promoting reward and relapse susceptibility to EtOH. These studies illuminate a critical role of RGS6 in the mesolimbic circuit in promoting EtOH seeking, reward, and reinstatement. We propose that RGS6 functions to promote DA transmission through its function as a negative modulator of GPCR-Gα i/o -DAT signaling in VTA DA neurons. These studies identify RGS6 as a potential therapeutic target for behavioral reward and relapse to EtOH.
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DeBaker MC, Mitten EH, Rose TR, Marron Fernandez de Velasco E, Gao R, Lee AM, Wickman K. RGS6 negatively regulates inhibitory G protein signaling in dopamine neurons and positively regulates binge-like alcohol consumption in mice. Br J Pharmacol 2023; 180:2140-2155. [PMID: 36929333 PMCID: PMC10504421 DOI: 10.1111/bph.16071] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 02/02/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023] Open
Abstract
BACKGROUND AND PURPOSE Drugs of abuse, including alcohol, increase dopamine in the mesocorticolimbic system via actions on dopamine neurons in the ventral tegmental area (VTA). Increased dopamine transmission can activate inhibitory G protein signalling pathways in VTA dopamine neurons, including those controlled by GABAB and D2 receptors. Members of the R7 subfamily of regulator of G protein signalling (RGS) proteins can regulate inhibitory G protein signalling, but their influence on VTA dopamine neurons is unclear. Here, we investigated the influence of RGS6, an R7 RGS family memberthat has been implicated in the regulation of alcohol consumption in mice, on inhibitory G protein signalling in VTA dopamine neurons. EXPERIMENTAL APPROACH We used molecular, electrophysiological and genetic approaches to probe the impact of RGS6 on inhibitory G protein signalling in VTA dopamine neurons and on binge-like alcohol consumption in mice. KEY RESULTS RGS6 is expressed in adult mouse VTA dopamine neurons and it modulates inhibitory G protein signalling in a receptor-dependent manner, tempering D2 receptor-induced somatodendritic currents and accelerating deactivation of synaptically evoked GABAB receptor-dependent responses. RGS6-/- mice exhibit diminished binge-like alcohol consumption, a phenotype replicated in female (but not male) mice lacking RGS6 selectively in VTA dopamine neurons. CONCLUSIONS AND IMPLICATIONS RGS6 negatively regulates GABAB - and D2 receptor-dependent inhibitory G protein signalling pathways in mouse VTA dopamine neurons and exerts a sex-dependent positive influence on binge-like alcohol consumption in adult mice. As such, RGS6 may represent a new diagnostic and/or therapeutic target for alcohol use disorder.
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Affiliation(s)
- Margot C. DeBaker
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN
| | - Eric H. Mitten
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN
| | - Timothy R. Rose
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
| | | | - Runbo Gao
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
| | - Anna M. Lee
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
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The Potential Role of R4 Regulators of G Protein Signaling (RGS) Proteins in Type 2 Diabetes Mellitus. Cells 2022; 11:cells11233897. [PMID: 36497154 PMCID: PMC9739376 DOI: 10.3390/cells11233897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/26/2022] [Accepted: 11/30/2022] [Indexed: 12/05/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) is a complex and heterogeneous disease that primarily results from impaired insulin secretion or insulin resistance (IR). G protein-coupled receptors (GPCRs) are proposed as therapeutic targets for T2DM. GPCRs transduce signals via the Gα protein, playing an integral role in insulin secretion and IR. The regulators of G protein signaling (RGS) family proteins can bind to Gα proteins and function as GTPase-activating proteins (GAP) to accelerate GTP hydrolysis, thereby terminating Gα protein signaling. Thus, RGS proteins determine the size and duration of cellular responses to GPCR stimulation. RGSs are becoming popular targeting sites for modulating the signaling of GPCRs and related diseases. The R4 subfamily is the largest RGS family. This review will summarize the research progress on the mechanisms of R4 RGS subfamily proteins in insulin secretion and insulin resistance and analyze their potential value in the treatment of T2DM.
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Zhang P, Perez OC, Southey BR, Sweedler JV, Pradhan AA, Rodriguez-Zas SL. Alternative Splicing Mechanisms Underlying Opioid-Induced Hyperalgesia. Genes (Basel) 2021; 12:1570. [PMID: 34680965 PMCID: PMC8535871 DOI: 10.3390/genes12101570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 09/19/2021] [Accepted: 09/30/2021] [Indexed: 12/13/2022] Open
Abstract
Prolonged use of opioids can cause opioid-induced hyperalgesia (OIH). The impact of alternative splicing on OIH remains partially characterized. A study of the absolute and relative modes of action of alternative splicing further the understanding of the molecular mechanisms underlying OIH. Differential absolute and relative isoform profiles were detected in the trigeminal ganglia and nucleus accumbens of mice presenting OIH behaviors elicited by chronic morphine administration relative to control mice. Genes that participate in glutamatergic synapse (e.g., Grip1, Grin1, Wnk3), myelin protein processes (e.g., Mbp, Mpz), and axon guidance presented absolute and relative splicing associated with OIH. Splicing of genes in the gonadotropin-releasing hormone receptor pathway was detected in the nucleus accumbens while splicing in the vascular endothelial growth factor, endogenous cannabinoid signaling, circadian clock system, and metabotropic glutamate receptor pathways was detected in the trigeminal ganglia. A notable finding was the prevalence of alternatively spliced transcription factors and regulators (e.g., Ciart, Ablim2, Pbx1, Arntl2) in the trigeminal ganglia. Insights into the nociceptive and antinociceptive modulatory action of Hnrnpk were gained. The results from our study highlight the impact of alternative splicing and transcriptional regulators on OIH and expose the need for isoform-level research to advance the understanding of morphine-associated hyperalgesia.
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Affiliation(s)
- Pan Zhang
- Illinois Informatics Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA;
| | - Olivia C. Perez
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; (O.C.P.); (B.R.S.)
| | - Bruce R. Southey
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; (O.C.P.); (B.R.S.)
| | - Jonathan V. Sweedler
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA;
| | - Amynah A. Pradhan
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL 60612, USA;
| | - Sandra L. Rodriguez-Zas
- Illinois Informatics Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA;
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; (O.C.P.); (B.R.S.)
- Department of Statistics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Interruption of continuous opioid exposure exacerbates drug-evoked adaptations in the mesolimbic dopamine system. Neuropsychopharmacology 2020; 45:1781-1792. [PMID: 32079024 PMCID: PMC7608117 DOI: 10.1038/s41386-020-0643-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 02/10/2020] [Accepted: 02/13/2020] [Indexed: 12/14/2022]
Abstract
Drug-evoked adaptations in the mesolimbic dopamine system are postulated to drive opioid abuse and addiction. These adaptations vary in magnitude and direction following different patterns of opioid exposure, but few studies have systematically manipulated the pattern of opioid administration while measuring neurobiological and behavioral impact. We exposed male and female mice to morphine for one week, with administration patterns that were either intermittent (daily injections) or continuous (osmotic minipump infusion). We then interrupted continuous morphine exposure with either naloxone-precipitated or spontaneous withdrawal. Continuous morphine exposure caused tolerance to the psychomotor-activating effects of morphine, whereas both intermittent and interrupted morphine exposure caused long-lasting psychomotor sensitization. Given links between locomotor sensitization and mesolimbic dopamine signaling, we used fiber photometry and a genetically encoded dopamine sensor to conduct longitudinal measurements of dopamine dynamics in the nucleus accumbens. Locomotor sensitization caused by interrupted morphine exposure was accompanied by enhanced dopamine signaling in the nucleus accumbens. To further assess downstream consequences on striatal gene expression, we used next-generation RNA sequencing to perform genome-wide transcriptional profiling in the nucleus accumbens and dorsal striatum. The interruption of continuous morphine exposure exacerbated drug-evoked transcriptional changes in both nucleus accumbens and dorsal striatum, dramatically increasing differential gene expression and engaging unique signaling pathways. Our study indicates that opioid-evoked adaptations in brain function and behavior are critically dependent on the pattern of drug administration, and exacerbated by interruption of continuous exposure. Maintaining continuity of chronic opioid administration may, therefore, represent a strategy to minimize iatrogenic effects on brain reward circuits.
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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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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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Chakravarti B, Yang J, Ahlers-Dannen KE, Luo Z, Flaherty HA, Meyerholz DK, Anderson ME, Fisher RA. Essentiality of Regulator of G Protein Signaling 6 and Oxidized Ca 2+/Calmodulin-Dependent Protein Kinase II in Notch Signaling and Cardiovascular Development. J Am Heart Assoc 2017; 6:JAHA.117.007038. [PMID: 29079565 PMCID: PMC5721783 DOI: 10.1161/jaha.117.007038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background Congenital heart defects are the most common birth defects worldwide. Although defective Notch signaling is the major cause of mouse embryonic death from cardiovascular defects, how Notch signaling is regulated during embryonic vasculogenesis and heart development is poorly understood. Methods and Results Regulator of G protein signaling 6 (RGS6)−/−/Ca2+/calmodulin‐dependent protein kinase II (CaMKII)VV double mutant mice were developed by crossing RGS6−/− mice with mice expressing an oxidation‐resistant CaMKIIδ (CaMKIIVV), and the resulting embryonic defects/lethality were investigated using E7.5 to E15.5 embryos. While loss of either RGS6 or oxidized CaMKIIδ does not alter embryogenesis, their combined loss causes defective Notch signaling, severe cardiovascular defects, and embryonic lethality (≈E10.5–11.5). Embryos lacking RGS6 and expressing oxidation‐resistant CaMKIIδ exhibit reduced myocardial wall thickness, abnormal trabeculation, and arterial specification defects. Double mutants show vascular remodeling defects, including reduced neurovascularization, delayed neural tube maturation, and small dorsal aortae. These striking cardiovascular defects were accompanied by placental and yolk sac defects in angiogenesis, hematopoiesis, and vascular remodeling similar to what is seen with defective Notch1 signaling. Double mutant hearts, embryos, and yolk sacs exhibit profound downregulation of Notch1, Jagged 1, and Notch downstream target genes Hey1, Hey2, and Hey1L as well as impaired Notch1 signaling in embryos/hearts. Conclusions RGS6 and oxidized CaMKIIδ together function as novel critical upstream modulators of Notch signaling required for normal cardiovascular development and embryo survival. Their combined need indicates that they function in parallel pathways needed for Notch1 signaling in yolk sac, placenta and embryos. Thus, dysregulated embryonic RGS6 expression and oxidative activation of CaMKII may potentially contribute to congenital heart defects.
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Affiliation(s)
- Bandana Chakravarti
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Jianqi Yang
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA
| | | | - Zili Luo
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA
| | | | - David K Meyerholz
- Department of Pathology, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Mark E Anderson
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Rory A Fisher
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA
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Sutton LP, Ostrovskaya O, Dao M, Xie K, Orlandi C, Smith R, Wee S, Martemyanov KA. Regulator of G-Protein Signaling 7 Regulates Reward Behavior by Controlling Opioid Signaling in the Striatum. Biol Psychiatry 2016; 80:235-45. [PMID: 26364547 PMCID: PMC4753143 DOI: 10.1016/j.biopsych.2015.07.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 07/02/2015] [Accepted: 07/27/2015] [Indexed: 12/11/2022]
Abstract
BACKGROUND Morphine mediates its euphoric and analgesic effects by acting on the μ-opioid receptor (MOR). MOR belongs to the family of G-protein coupled receptors whose signaling efficiency is controlled by the regulator of G-protein signaling (RGS) proteins. Our understanding of the molecular diversity of RGS proteins that control MOR signaling, their circuit specific actions, and underlying cellular mechanisms is very limited. METHODS We used genetic approaches to ablate regulator of G-protein signaling 7 (RGS7) both globally and in specific neuronal populations. We used conditioned place preference and self-administration paradigms to examine reward-related behavior and a battery of tests to assess analgesia, tolerance, and physical dependence to morphine. Electrophysiology approaches were applied to investigate the impact of RGS7 on morphine-induced alterations in neuronal excitability and plasticity of glutamatergic synapses. At least three animals were used for each assessment. RESULTS Elimination of RGS7 enhanced reward, increased analgesia, delayed tolerance, and heightened withdrawal in response to morphine administration. RGS7 in striatal neurons was selectively responsible for determining the sensitivity of rewarding and reinforcing behaviors to morphine without affecting analgesia, tolerance, and withdrawal. In contrast, deletion of RGS7 in dopaminergic neurons did not influence morphine reward. RGS7 exerted its effects by controlling morphine-induced changes in excitability of medium spiny neurons in nucleus accumbens and gating the compositional plasticity of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and N-methyl-D-aspartate receptors. CONCLUSIONS This study identifies RGS7 as a novel regulator of MOR signaling by dissecting its circuit specific actions and pinpointing its role in regulating morphine reward by controlling the activity of nucleus accumbens neurons.
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Affiliation(s)
- Laurie P. Sutton
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458 USA
| | - Olga Ostrovskaya
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458 USA
| | - Maria Dao
- Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, FL 33458 USA,Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458 USA
| | - Keqiang Xie
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458 USA
| | - Cesare Orlandi
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458 USA
| | - Roy Smith
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458 USA
| | - Sunmee Wee
- Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, FL 33458 USA
| | - Kirill A. Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458 USA,Corresponding author: Dr. Kirill Martemyanov, Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, 3C2, Jupiter, FL 33458, Phone: (561) 228-2770,
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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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Ahlers KE, Chakravarti B, Fisher RA. RGS6 as a Novel Therapeutic Target in CNS Diseases and Cancer. AAPS JOURNAL 2016; 18:560-72. [PMID: 27002730 DOI: 10.1208/s12248-016-9899-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 02/25/2016] [Indexed: 12/17/2022]
Abstract
Regulator of G protein signaling (RGS) proteins are gatekeepers regulating the cellular responses induced by G protein-coupled receptor (GPCR)-mediated activation of heterotrimeric G proteins. Specifically, RGS proteins determine the magnitude and duration of GPCR signaling by acting as a GTPase-activating protein for Gα subunits, an activity facilitated by their semiconserved RGS domain. The R7 subfamily of RGS proteins is distinguished by two unique domains, DEP/DHEX and GGL, which mediate membrane targeting and stability of these proteins. RGS6, a member of the R7 subfamily, has been shown to specifically modulate Gαi/o protein activity which is critically important in the central nervous system (CNS) for neuronal responses to a wide array of neurotransmitters. As such, RGS6 has been implicated in several CNS pathologies associated with altered neurotransmission, including the following: alcoholism, anxiety/depression, and Parkinson's disease. In addition, unlike other members of the R7 subfamily, RGS6 has been shown to regulate G protein-independent signaling mechanisms which appear to promote both apoptotic and growth-suppressive pathways that are important in its tumor suppressor function in breast and possibly other tissues. Further highlighting the importance of RGS6 as a target in cancer, RGS6 mediates the chemotherapeutic actions of doxorubicin and blocks reticular activating system (Ras)-induced cellular transformation by promoting degradation of DNA (cytosine-5)-methyltransferase 1 (DNMT1) to prevent its silencing of pro-apoptotic and tumor suppressor genes. Together, these findings demonstrate the critical role of RGS6 in regulating both G protein-dependent CNS pathology and G protein-independent cancer pathology implicating RGS6 as a novel therapeutic target.
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Affiliation(s)
- Katelin E Ahlers
- Department of Pharmacology, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 2-505 Bowen Science Building, Iowa City, Iowa, 52242, USA
| | - Bandana Chakravarti
- Department of Pharmacology, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 2-505 Bowen Science Building, Iowa City, Iowa, 52242, USA
| | - Rory A Fisher
- Department of Pharmacology, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 2-505 Bowen Science Building, Iowa City, Iowa, 52242, USA. .,Department of Internal Medicine, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, 52242, USA.
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13
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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: 79] [Impact Index Per Article: 8.8] [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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14
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Stewart A, Maity B, Fisher RA. Two for the Price of One: G Protein-Dependent and -Independent Functions of RGS6 In Vivo. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 133:123-51. [PMID: 26123305 DOI: 10.1016/bs.pmbts.2015.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Regulator of G protein signaling 6 (RGS6) is unique among the members of the RGS protein family as it remains the only protein with the demonstrated capacity to control G protein-dependent and -independent signaling cascades in vivo. RGS6 inhibits signaling mediated by γ-aminobutyric acid B receptors, serotonin 1A receptors, μ opioid receptors, and muscarinic acetylcholine 2 receptors. RGS6 deletion triggers distinct behavioral phenotypes resulting from potentiated signaling by these G protein-coupled receptors namely ataxia, a reduction in anxiety and depression, enhanced analgesia, and increased parasympathetic tone, respectively. In addition, RGS6 possesses potent proapoptotic and growth suppressive actions. In heart, RGS6-dependent reactive oxygen species (ROS) production promotes doxorubicin (Dox)-induced cardiomyopathy, while in cancer cells RGS6/ROS signaling is necessary for activation of the ataxia telangiectasia mutated/p53/apoptosis pathway required for the chemotherapeutic efficacy of Dox. Further, by facilitating Tip60 (trans-acting regulator protein of HIV type 1-interacting protein 60 kDa)-dependent DNA methyltransferase 1 degradation, RGS6 suppresses cellular transformation in response to oncogenic Ras. The culmination of these G protein-independent actions results in potent tumor suppressor actions of RGS6 in the murine mammary epithelium. This work summarizes evidence from human genetic studies and model animals implicating RGS6 in normal physiology, disease, and the pharmacological actions of multiple drugs. Though efforts by multiple laboratories have contributed to the ever-growing RGS6 oeuvre, the pleiotropic nature of this gene will likely lead to additional work detailing the importance of RGS6 in neuropsychiatric disorders, cardiovascular disease, and cancer.
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Affiliation(s)
- Adele Stewart
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Biswanath Maity
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Rory A Fisher
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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15
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Regulator of G protein signaling 6 is a critical mediator of both reward-related behavioral and pathological responses to alcohol. Proc Natl Acad Sci U S A 2015; 112:E786-95. [PMID: 25646431 DOI: 10.1073/pnas.1418795112] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Alcohol is the most commonly abused drug worldwide, and chronic alcohol consumption is a major etiological factor in the development of multiple pathological sequelae, including alcoholic cardiomyopathy and hepatic cirrhosis. Here, we identify regulator of G protein signaling 6 (RGS6) as a critical regulator of both alcohol-seeking behaviors and the associated cardiac and hepatic morbidities through two mechanistically divergent signaling actions. RGS6(-/-) mice consume less alcohol when given free access and are less susceptible to alcohol-induced reward and withdrawal. Antagonism of GABA(B) receptors or dopamine D2 receptors partially reversed the reduction in alcohol consumption in RGS6(-/-) animals. Strikingly, dopamine transporter inhibition completely restored alcohol seeking in mice lacking RGS6. RGS6 deficiency was associated with alterations in the expression of genes controlling dopamine (DA) homeostasis and a reduction in DA levels in the striatum. Taken together, these data implicate RGS6 as an essential regulator of DA bioavailability. RGS6 deficiency also provided dramatic protection against cardiac hypertrophy and fibrosis, hepatic steatosis, and gastrointestinal barrier dysfunction and endotoxemia when mice were forced to consume alcohol. Although RGS proteins canonically function as G-protein regulators, RGS6-dependent, alcohol-mediated toxicity in the heart, liver, and gastrointestinal tract involves the ability of RGS6 to promote reactive oxygen species-dependent apoptosis, an action independent of its G-protein regulatory capacity. We propose that inhibition of RGS6 might represent a viable means to reduce alcohol cravings and withdrawal in human patients, while simultaneously protecting the heart and liver from further damage upon relapse.
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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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17
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Crowther NJ, Ferris WF. The impact of insulin resistance, gender, genes, glucocorticoids and ethnicity on body fat distribution. JOURNAL OF ENDOCRINOLOGY, METABOLISM AND DIABETES OF SOUTH AFRICA 2014. [DOI: 10.1080/22201009.2010.10872241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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18
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Masuho I, Xie K, Martemyanov KA. Macromolecular composition dictates receptor and G protein selectivity of regulator of G protein signaling (RGS) 7 and 9-2 protein complexes in living cells. J Biol Chem 2013; 288:25129-25142. [PMID: 23857581 DOI: 10.1074/jbc.m113.462283] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulator of G protein signaling (RGS) proteins play essential roles in the regulation of signaling via G protein-coupled receptors (GPCRs). With hundreds of GPCRs and dozens of G proteins, it is important to understand how RGS regulates selective GPCR-G protein signaling. In neurons of the striatum, two RGS proteins, RGS7 and RGS9-2, regulate signaling by μ-opioid receptor (MOR) and dopamine D2 receptor (D2R) and are implicated in drug addiction, movement disorders, and nociception. Both proteins form trimeric complexes with the atypical G protein β subunit Gβ5 and a membrane anchor, R7BP. In this study, we examined GTPase-accelerating protein (GAP) activity as well as Gα and GPCR selectivity of RGS7 and RGS9-2 complexes in live cells using a bioluminescence resonance energy transfer-based assay that monitors dissociation of G protein subunits. We showed that RGS9-2/Gβ5 regulated both Gi and Go with a bias toward Go, but RGS7/Gβ5 could serve as a GAP only for Go. Interestingly, R7BP enhanced GAP activity of RGS7 and RGS9-2 toward Go and Gi and enabled RGS7 to regulate Gi signaling. Neither RGS7 nor RGS9-2 had any activity toward Gz, Gs, or Gq in the absence or presence of R7BP. We also observed no effect of GPCRs (MOR and D2R) on the G protein bias of R7 RGS proteins. However, the GAP activity of RGS9-2 showed a strong receptor preference for D2R over MOR. Finally, RGS7 displayed an four times greater GAP activity relative to RGS9-2. These findings illustrate the principles involved in establishing G protein and GPCR selectivity of striatal RGS proteins.
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Affiliation(s)
- Ikuo Masuho
- From the Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, Florida 33410
| | - Keqiang Xie
- From the Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, Florida 33410
| | - Kirill A Martemyanov
- From the Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, Florida 33410.
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19
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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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20
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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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21
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Ballesta JJ, Cremades J, Rodríguez-Muñoz M, Garzón J, Faura CC. Sensitivity to μ-opioid receptor-mediated anti-nociception is determined by cross-regulation between μ- and δ-opioid receptors at supraspinal level. Br J Pharmacol 2012; 166:309-26. [PMID: 22023056 DOI: 10.1111/j.1476-5381.2011.01750.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The perception of pain and its inhibition varies considerably between individuals, and this variability is still unexplained. The aim of the present study is to determine whether functional interactions between opioid receptors are involved in the inter-individual variability in the sensitivity to μ-opioid receptor agonists. EXPERIMENTAL APPROACH Anti-nociceptive tests, radioligand binding, stimulation of [(35) S]GTP-γ-S binding, inhibition of cAMP production and co-immunoprecipitation experiments were performed in two strains of rat (Sprague-Dawley bred at our university - SDU - and Wistar) that differ in their sensitivity to opioids. KEY RESULTS The increased anti-nociceptive potency of µ-opioid receptor agonists in SDU rats was reversed by the δ-opioid receptor antagonist, naltrindole. Inhibition of the binding of [(3) H] naltrindole by µ-opioid receptor agonists was different in brain membranes from SDU and Wistar rats. Differences were also evident in the effect of δ-opioid receptor ligands on the binding of [(35) S]GTP-γ-S stimulated by µ-opioid receptors agonists. No strain-related differences were detected in spinal cord membranes. The potency of morphine to inhibit cAMP production in brain membranes varied between the strains, in the presence of deltorphin II and naltrindole. Co-immunoprecipitation experiments demonstrated that δ-opioid receptors were associated with μ-opioid receptors to a higher extent in brain synaptosomal fractions from SDU than in those from Wistar rats. CONCLUSIONS AND IMPLICATIONS There was increased supraspinal cross-talk between μ and δ-opioid receptors in SDU, as compared with Wistar rats. This was related to an enhanced sensitivity to anti-nociception induced by µ-opioid receptor agonists.
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Affiliation(s)
- J J Ballesta
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernandez, Alicante, Spain
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22
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Liapis E, Sandiford S, Wang Q, Gaidosh G, Motti D, Levay K, Slepak VZ. Subcellular localization of regulator of G protein signaling RGS7 complex in neurons and transfected cells. J Neurochem 2012; 122:568-81. [PMID: 22640015 DOI: 10.1111/j.1471-4159.2012.07811.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The R7 family of regulators of G protein signaling (RGS) is involved in many functions of the nervous system. This family includes RGS6, RGS7, RGS9, and RGS11 gene products and is defined by the presence of the characteristic first found in Disheveled, Egl-10, Pleckstrin (DEP), DEP helical extension (DHEX), Gγ-like, and RGS domains. Herein, we examined the subcellular localization of RGS7, the most broadly expressed R7 member. Our immunofluorescence studies of retinal and dorsal root ganglion neurons showed that RGS7 concentrated at the plasma membrane of cell bodies, in structures resembling lamellipodia or filopodia along the processes, and at the dendritic tips. At the plasma membrane of dorsal root ganglia neurons, RGS7 co-localized with its known binding partners R7 RGS binding protein (R7BP), Gαo, and Gαq. More than 50% of total RGS7-specific immunofluorescence was present in the cytoplasm, primarily within numerous small puncta that did not co-localize with R7BP. No specific RGS7 or R7BP immunoreactivity was detected in the nuclei. In transfected cell lines, ectopic RGS7 had both diffuse cytosolic and punctate localization patterns. RGS7 also localized in centrosomes. Structure-function analysis showed that the punctate localization was mediated by the DEP/DHEX domains, and centrosomal localization was dependent on the DHEX domain.
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Affiliation(s)
- Evangelos Liapis
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL, USA
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23
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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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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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25
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Sibbel SP, Talbert ME, Bowden DW, Haffner SM, Taylor KD, Chen YDI, Wagenknecht LE, Langefeld CD, Norris JM. RGS6 variants are associated with dietary fat intake in Hispanics: the IRAS Family Study. Obesity (Silver Spring) 2011; 19:1433-8. [PMID: 21233807 PMCID: PMC3683650 DOI: 10.1038/oby.2010.333] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recently, a genome-wide association scan was completed in the IRAS (Insulin Resistance Atherosclerosis Study) Family Study (IRASFS) Hispanic-American cohort. Multiple single-nucleotide polymorphisms (SNPs) in the G-protein signaling 6 (RGS6) gene were found to be associated with adiposity phenotypes. RGS6 has shown downstream antagonistic interplay with opioid receptors, targets of fatty/sugary food agonists. The possibility that RGS6 promotes tolerance and tachyphylaxis among the opioid receptor is a plausible pathway for overconsuming fat/sugar-laden food. Therefore, we hypothesized that RGS6 variants are associated with intake of fatty/sugary foods. In 932 Hispanics from San Antonio and San Luis Valley, CO, the following dietary intake variables were assessed using the Block Brief 2000 food frequency questionnaire: total calories, total fat, % calories from fat, % calories from saturated fat, protein, % calories from protein, carbohydrates, % calories from carbohydrates, and daily frequency of servings of fats/oils/sweets. We tested for association between 23 SNPs in RGS6 and dietary intake using a variance components measured genotype approach. All models were adjusted for gender, recruitment site, admixture, BMI, and age. Using an additive genetic model, rs1402064 was associated with higher intake of fats/oils/sweets, total calories, total fat and saturated fat (P = 0.0007, 0.026, 0.023, and 0.024). SNPs rs847330 and rs847354 were associated with higher intake of fats/oils/sweets (P = 0.002 and 0.018), total fat (P = 0.040 and 0.048) and saturated fat (P = 0.044 and 0.041). Finally, rs769148 was associated with higher intake of fats/oils/sweets (P = 0.002). RGS6 is a new candidate gene for adiposity traits that may be associated with a behavioral tendency toward fat-laden food intake.
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Affiliation(s)
- Scott P. Sibbel
- Department of Epidemiology, Colorado School of Public Health, University of Colorado Denver, Aurora, Colorado, USA
| | - Matthew E. Talbert
- Department of Biochemistry, Wake Forest University, Winston-Salem, North Carolina, USA
| | - Donald W. Bowden
- Department of Biochemistry, Wake Forest University, Winston-Salem, North Carolina, USA
| | - Steve M. Haffner
- Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Kent D. Taylor
- Medical Genetics Institute, Burns and Allen Cedars-Sinai Research Institute, Los Angeles, California, USA
| | - Yii-Der I. Chen
- Medical Genetics Institute, Burns and Allen Cedars-Sinai Research Institute, Los Angeles, California, USA
| | - Lynne E. Wagenknecht
- Department of Epidemiology, Division of Public Health Sciences, Wake Forest University, Winston-Salem, North Carolina, USA
| | - Carl D. Langefeld
- Department of Biostatistical Sciences, Division of Public Health Sciences, Wake Forest University, Winston-Salem, North Carolina, USA.
| | - Jill M. Norris
- Department of Epidemiology, Colorado School of Public Health, University of Colorado Denver, Aurora, Colorado, USA
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David M, Akerman L, Ziv M, Kadurina M, Gospodinov D, Pavlotsky F, Yankova R, Kouzeva V, Ramon M, Silverman M, Fishman P. Treatment of plaque-type psoriasis with oral CF101: data from an exploratory randomized phase 2 clinical trial. J Eur Acad Dermatol Venereol 2011; 26:361-7. [DOI: 10.1111/j.1468-3083.2011.04078.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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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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Masuho I, Celver J, Kovoor A, Martemyanov KA. Membrane anchor R9AP potentiates GTPase-accelerating protein activity of RGS11 x Gbeta5 complex and accelerates inactivation of the mGluR6-G(o) signaling. J Biol Chem 2009; 285:4781-7. [PMID: 20007977 DOI: 10.1074/jbc.m109.058511] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The R7 subfamily of RGS proteins critically regulates neuronal G protein-signaling pathways that are essential for vision, nociception, motor coordination, and reward processing. A member of the R7 RGS family, RGS11, is a GTPase-accelerating protein specifically expressed in retinal ON-bipolar cells where it forms complexes with the atypical G protein beta subunit, Gbeta(5), and transmembrane protein R9AP. Association with R9AP has been shown to be critical for the proteolytic stability of the complex in the retina. In this study we report that R9AP can in addition stimulate the GTPase-accelerating protein activity of the RGS11 x Gbeta(5) complex at Galpha(o). Single turnover GTPase assays reveal that R9AP co-localizes RGS11 x Gbeta(5) and Galpha(o) on the membrane and allosterically potentiates the GTPase-accelerating function of RGS11 x Gbeta(5). Reconstitution of mGluR6-Galpha(o) signaling in Xenopus oocytes indicates that RGS11 x Gbeta(5)-mediated GTPase acceleration in this system requires co-expression of R9AP. The results provide new insight into the regulation of mGluR6-Galpha(o) signaling by the RGS11 x Gbeta(5) x R9AP complex and establish R9AP as a general GTPase-accelerating protein activity regulator of R7 RGS complexes.
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Affiliation(s)
- Ikuo Masuho
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Talbot JN, Roman DL, Clark MJ, Roof RA, Tesmer JJG, Neubig RR, Traynor JR. Differential modulation of mu-opioid receptor signaling to adenylyl cyclase by regulators of G protein signaling proteins 4 or 8 and 7 in permeabilised C6 cells is Galpha subtype dependent. J Neurochem 2009; 112:1026-34. [PMID: 20002516 DOI: 10.1111/j.1471-4159.2009.06519.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Regulators of G protein signaling (RGS) proteins act as GTPase-accelerating protein to negatively modulate G protein signaling and are defined by a conserved RGS domain with considerable amino acid diversity. To determine the effects of specific, purified RGS proteins on mu-opioid signaling, C6 cells stably expressing a mu-opioid receptor were rendered permeable to proteins by treatment with digitonin. Mu-opioid inhibition of forskolin-stimulated adenylyl cyclase by [D-Ala(2),N-Me-Phe(4),Gly-ol]-enkephalin (DAMGO), a mu-specific opioid peptide, remained fully intact in permeabilized cells. Purified RGS domain of RGS4 added to permeabilized cells resulted in a twofold loss in DAMGO potency but had no effect in cells expressing RGS-insensitive G proteins. The inhibitory effect of DAMGO was reduced to the same extent by purified RGS4 and RGS8. In contrast, the RGS domain of RGS7 had no effect and inhibited the action of RGS8 as a result of weak physical association with Galphai2 and minimal GTPase-accelerating protein activity in C6 cell membranes. These data suggest that differences in conserved RGS domains of specific RGS proteins contribute to differential regulation of opioid signaling to adenylyl cyclase and that a permeabilized cell model is useful for studying the effects of specific RGS proteins on aspects of G protein-coupled receptor signaling.
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Affiliation(s)
- Jeffery N Talbot
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
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Effect of KEPI (Ppp1r14c) deletion on morphine analgesia and tolerance in mice of different genetic backgrounds: when a knockout is near a relevant quantitative trait locus. Neuroscience 2009; 165:882-95. [PMID: 19819304 DOI: 10.1016/j.neuroscience.2009.10.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 09/23/2009] [Accepted: 10/03/2009] [Indexed: 01/01/2023]
Abstract
We previously identified KEPI as a morphine-regulated gene using subtractive hybridization and differential display PCR. Upon phosphorylation by protein kinase C, KEPI becomes a powerful inhibitor of protein phosphatase 1. To gain insights into KEPI functions, we created KEPI knockout (KO) mice on mixed 129S6xC57BL/6 genetic backgrounds. KEPI maps onto mouse chromosome 10 close to the locus that contains the mu-opioid receptor (Oprm1) and provides a major quantitative trait locus for morphine effects. Analysis of single nucleotide polymorphisms in and near the Oprm1 locus identified a doubly-recombinant mouse with C57BL/6 markers within 1 Mb on either side of the KEPI deletion. This strategy minimized the amount of 129S6 DNA surrounding the transgene and documented the C57BL/6 origin of the Oprm1 gene in this founder and its offspring. Recombinant KEPIKO mice displayed (a) normal analgesic responses and normal locomotion after initial morphine treatments, (b) accelerated development of tolerance to analgesic effects of morphine, (c) elevated activity of protein phosphatase 1 in thalamus, (d) attenuated morphine reward as assessed by conditioned place preference. These data support roles for KEPI action in adaptive responses to repeated administration of morphine that include analgesic tolerance and drug reward.
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Norris JM, Langefeld CD, Talbert ME, Wing MR, Haritunians T, Fingerlin TE, Hanley AJG, Ziegler JT, Taylor KD, Haffner SM, Chen YDI, Bowden DW, Wagenknecht LE. Genome-wide association study and follow-up analysis of adiposity traits in Hispanic Americans: the IRAS Family Study. Obesity (Silver Spring) 2009; 17:1932-41. [PMID: 19461586 PMCID: PMC2832211 DOI: 10.1038/oby.2009.143] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We investigated candidate genomic regions associated with computed tomography (CT)-derived measures of adiposity in Hispanics from the Insulin Resistance Atherosclerosis Study Family Study (IRASFS). In 1,190 Hispanic individuals from 92 families 3 from the San Luis Valley, Colorado and San Antonio, Texas, we measured CT-derived visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and visceral:subcutaneous ratio (VSR). A genome-wide association study (GWAS) was completed using the Illumina HumanHap 300 BeadChip (approximately 317K single-nucleotide polymorphisms (SNPs)) in 229 individuals from the San Antonio site (stage 1). In total, 297 SNPs with evidence for association with VAT, SAT, or VSR, adjusting for age and sex (P<0.001), were genotyped in the remaining 961 Hispanic samples. The entire Hispanic cohort (n=1,190) was then tested for association, adjusting for age, sex, site of recruitment, and admixture estimates (stage 2). In stage 3, additional SNPs were genotyped in four genic regions showing evidence of association in stage 2. Several SNPs were associated in the GWAS (P<1x10(-5)) and were confirmed to be significantly associated in the entire Hispanic cohort (P<0.01), including: rs7543757 for VAT, rs4754373 and rs11212913 for SAT, and rs4541696 and rs4134351 for VSR. Numerous SNPs were associated with multiple adiposity phenotypes. Targeted analysis of four genes whose SNPs were significant in stage 2 suggests candidate genes for influencing the distribution (RGS6) and amount of adiposity (NGEF). Several candidate loci, including RGS6 and NGEF, are associated with CT-derived adipose fat measures in Hispanic Americans in a three-stage genetic association study.
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Affiliation(s)
- Jill M Norris
- Department of Epidemiology, Colorado School of Public Health, University of Colorado Denver, Aurora, Colorado, USA.
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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: 118] [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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Changes in striatal signaling induce remodeling of RGS complexes containing Gbeta5 and R7BP subunits. Mol Cell Biol 2009; 29:3033-44. [PMID: 19332565 DOI: 10.1128/mcb.01449-08] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neurotransmitter signaling via G protein coupled receptors is crucially controlled by regulators of G protein signaling (RGS) proteins that shape the duration and extent of the cellular response. In the striatum, members of the R7 family of RGS proteins modulate signaling via D2 dopamine and mu-opioid receptors controlling reward processing and locomotor coordination. Recent findings have established that R7 RGS proteins function as macromolecular complexes with two subunits: type 5 G protein beta (Gbeta5) and R7 binding protein (R7BP). In this study, we report that the subunit compositions of these complexes in striatum undergo remodeling upon changes in neuronal activity. We found that under normal conditions two equally abundant striatal R7 RGS proteins, RGS9-2 and RGS7, are unequally coupled to the R7BP subunit, which is present in complex predominantly with RGS9-2 rather than with RGS7. Changes in the neuronal excitability or oxygenation status resulting in extracellular calcium entry, uncouples RGS9-2 from R7BP, triggering its selective degradation. Concurrently, released R7BP binds to mainly intracellular RGS7 and recruits it to the plasma membrane and the postsynaptic density. These observations introduce activity-dependent remodeling of R7 RGS complexes as a new molecular plasticity mechanism in striatal neurons and suggest a general model for achieving rapid posttranslational subunit rearrangement in multisubunit complexes.
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Targeting of RGS7/Gbeta5 to the dendritic tips of ON-bipolar cells is independent of its association with membrane anchor R7BP. J Neurosci 2008; 28:10443-9. [PMID: 18842904 DOI: 10.1523/jneurosci.3282-08.2008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Complexes of regulator of G-protein signaling (RGS) proteins with G-protein beta5 (Gbeta5) subunits are essential components of signaling pathways that regulate the temporal characteristics of light-evoked responses in vertebrate retinal photoreceptors and ON-bipolar cells. Recent studies have found that RGS/Gbeta5 complexes bind to a new family of adapter proteins, R9AP (RGS9 anchor protein) and R7 family binding protein (R7BP), that in case of the RGS9/Gbeta5 complex were shown to determine its precise subcellular targeting to either the outer segment of photoreceptors or postsynaptic structures of striatal neurons, respectively. In this study, we establish that another trimeric complex consisting of RGS7, Gbeta5, and R7BP subunits is specifically targeted to the dendritic tips of retinal bipolar cells. However, examination of the mechanisms of complex targeting in vivo surprisingly revealed that the delivery of RGS7/Gbeta5 to the dendrites of ON-bipolar cells occurs independently of its association with R7BP. These findings provide a new mechanism for adapter-independent targeting of RGS/Gbeta5 complexes.
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35
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Psifogeorgou K, Papakosta P, Russo SJ, Neve RL, Kardassis D, Gold SJ, Zachariou V. RGS9-2 is a negative modulator of mu-opioid receptor function. J Neurochem 2007; 103:617-25. [PMID: 17725581 DOI: 10.1111/j.1471-4159.2007.04812.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Regulators of G-protein signaling (RGS) 9-2 is a striatal enriched protein that controls G protein coupled receptor signaling duration by accelerating Galpha subunit guanosine triphosphate hydrolysis. We have previously demonstrated that mice lacking the RGS9 gene show enhanced morphine analgesia and delayed development of tolerance. Here we extend these studies to understand the mechanism via which RGS9-2 modulates opiate actions. Our data suggest that RGS9-2 prevents several events triggered by mu-opioid receptor (MOR) activation. In transiently transfected PC12 cells, RGS9-2 delays agonist induced internalization of epitope HA-tagged mu-opioid receptor. This action of RGS9-2 requires localization of the protein near the cell membrane. Co-immunoprecipitation studies reveal that RGS9-2 interacts with HA-tagged mu-opioid receptor, and that this interaction is enhanced by morphine treatment. In addition, morphine promotes the association of RGS9-2 with another essential component of MOR desensitization, beta-arrestin-2. We also show that over-expression of RGS9-2 prevents opiate-induced extracellular signal-regulated kinase phosphorylation. Our data indicate that RGS9-2 plays an essential role in opiate actions, by negatively modulating MOR downstream signaling as well as the rate of MOR endocytosis.
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Affiliation(s)
- Kassi Psifogeorgou
- Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece
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36
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Xie Z, Li Z, Guo L, Ye C, Li J, Yu X, Yang H, Wang Y, Chen C, Zhang D, Liu-Chen LY. Regulator of G protein signaling proteins differentially modulate signaling of mu and delta opioid receptors. Eur J Pharmacol 2007; 565:45-53. [PMID: 17433292 PMCID: PMC2696627 DOI: 10.1016/j.ejphar.2007.03.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 02/28/2007] [Accepted: 03/06/2007] [Indexed: 10/23/2022]
Abstract
Effects of regulator of G protein signaling (RGS) proteins on mu and delta opioid receptors were investigated in HEK293 cells. Co-expression of RGS1, RGS2, RGS4, RGS9, RGS10 or RGS19 (Galpha-interacting protein (GAIP)) significantly reduced [Tyr-D-Ala-Gly-N-methyl-Phe-Gly-ol]-Enkephalin (DAMGO)-induced inhibition of adenylyl cyclase (AC) mediated by mu opioid receptor, but only RGS9 decreased the effects of [Tyr-D-Pen-Gly-p-Chloro-Phe-D-Pen]-Enkephalin (DPDPE) mediated by delta opioid receptor. When C-tails of the receptors were exchanged (mu/deltaC and delta/muC chimeras), RGS proteins decreased delta/muC-mediated AC inhibition, but none had significant effects on that via mu/deltaC receptor. Thus, the C-terminal domains of the receptors are critical for the differential effects of RGS proteins, which may be due to differences in receptor-G protein-RGS protein interactions in signaling complexes.
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Affiliation(s)
- Zhihua Xie
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Zhisong Li
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Lei Guo
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Caiying Ye
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Juan Li
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Xiaoli Yu
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Huifen Yang
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Yulin Wang
- Department of Pharmacology, Temple University, School of Medicine, Philadelphia, USA
| | - Chongguang Chen
- Department of Pharmacology, Temple University, School of Medicine, Philadelphia, USA
| | - Dechang Zhang
- Department of Pharmacology, School of Basic Medicine and Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Lee-Yuan Liu-Chen
- Department of Pharmacology, Temple University, School of Medicine, Philadelphia, USA
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Kim SD, Sung HJ, Park SK, Kim TW, Park SC, Kim SK, Cho JY, Rhee MH. The expression patterns of RGS transcripts in platelets. Platelets 2007; 17:493-7. [PMID: 17074726 DOI: 10.1080/09537100600758123] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Regulators of G protein signalling (RGS) are involved in the negative regulation of cell activation processes and are involved in the pathophysiology of cardiovascular diseases. To get some further evidence for a role of RGS proteins in platelets, we determined the expression profile of RGS-specific mRNA in rat platelets using reverse transcription-polymerase chain reaction (RT-PCR) with a poly dT18 primer and transcript-specific primers. We found that RGS2, RGS3, RGS5, RGS6, RGS10, RGS14, RGS16 and RGS18, Leukemia-associated Rho-GEF factor (LARG), and Galpha interacting protein (GAIP) were differentially expressed in platelets. The highest expression rate was found for RGS18 (about 1.3 fold when compared to GAPDH), followed by LARG, RGS6, RGS10 and RGS16 (0.7 to 0.95), whereas expression rates for RGS2, RGS3, RGS5, RGS14, and GAIP were in a range of 0.1 to 0.3. Our results suggest that G-protein-coupled receptor-mediated signalling in platelet may be regulated mainly by RGS 18, 16, 10, 6, and LARG.
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Affiliation(s)
- Sung Dae Kim
- Laboratory of Veterinary Physiology & Signalling, College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, Republic of Korea
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Piñeyro G, Archer-Lahlou E. Ligand-specific receptor states: Implications for opiate receptor signalling and regulation. Cell Signal 2007; 19:8-19. [PMID: 16842969 DOI: 10.1016/j.cellsig.2006.05.026] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Accepted: 05/29/2006] [Indexed: 10/24/2022]
Abstract
Opiate drugs produce their effects by acting upon G protein coupled receptors (GPCRs) and although they are among the most effective analgesics available, their clinical use is restricted by unwanted side effects such as tolerance, physical dependence, respiratory depression, nausea and constipation. As a class, opiates share a common profile of unwanted effects but there are also significant differences in ligand liability for producing these actions. A growing number of studies show that GPCRs may exist in multiple active states that differ in their signalling and regulatory properties and which may distinctively bind different agonists. In this review we summarize evidence supporting the existence of multiple active conformations for MORs and DORs, analyze information favouring the existence of ligand-specific receptor states and assess how ligand-selective efficacy may contribute to the production of longer lasting, better tolerated opiate analgesics.
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Affiliation(s)
- Graciela Piñeyro
- Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Canada.
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Xie GX, Palmer PP. How regulators of G protein signaling achieve selective regulation. J Mol Biol 2006; 366:349-65. [PMID: 17173929 PMCID: PMC1805491 DOI: 10.1016/j.jmb.2006.11.045] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 11/02/2006] [Accepted: 11/10/2006] [Indexed: 11/30/2022]
Abstract
The regulators of G protein signaling (RGS) are a family of cellular proteins that play an essential regulatory role in G protein-mediated signal transduction. There are multiple RGS subfamilies consisting of over 20 different RGS proteins. They are basically the guanosine triphosphatase (GTPase)-accelerating proteins that specifically interact with G protein alpha subunits. RGS proteins display remarkable selectivity and specificity in their regulation of receptors, ion channels, and other G protein-mediated physiological events. The molecular and cellular mechanisms underlying such selectivity are complex and cooperate at many different levels. Recent research data have provided strong evidence that the spatiotemporal-specific expression of RGS proteins and their target components, as well as the specific protein-protein recognition and interaction through their characteristic structural domains and functional motifs, are determinants for RGS selectivity and specificity. Other molecular mechanisms, such as alternative splicing and scaffold proteins, also significantly contribute to RGS selectivity. To pursue a thorough understanding of the mechanisms of RGS selective regulation will be of great significance for the advancement of our knowledge of molecular and cellular signal transduction.
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Affiliation(s)
| | - Pamela Pierce Palmer
- *Corresponding author: Pamela Pierce Palmer, M.D., Ph.D., University of California, San Francisco, Department of Anesthesia and Perioperative Care, 513 Parnassus Avenue, Box 0464, Room S-455, San Francisco, California 94143, USA, Telephone: (415)476-6783, FAX: (415)502-5375, E-mail:
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40
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Kim KS, Palmer PP, Kim KJ. RGS Proteins and Opioid Signaling. Korean J Pain 2006. [DOI: 10.3344/kjp.2006.19.1.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Kyung Seon Kim
- Department of Rehabilitation, Yonsei University College of Medicine, Seoul, Korea
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143, USA
| | - Pamela Pierce Palmer
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143, USA
| | - Ki Jun Kim
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143, USA
- Department of Anesthesiology and Pain Medicine, and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
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Kim KJ, Moriyama K, Han KR, Sharma M, Han X, Xie GX, Palmer PP. Differential expression of the regulator of G protein signaling RGS9 protein in nociceptive pathways of different age rats. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 160:28-39. [PMID: 16153714 DOI: 10.1016/j.devbrainres.2005.08.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 08/03/2005] [Accepted: 08/04/2005] [Indexed: 10/25/2022]
Abstract
Regulators of G protein signaling (RGS) proteins are GTPase-activating proteins which act as modulators of G-protein-coupled receptors. RGS9 has two alternative splicing variants. RGS9-1 is expressed in the retina. RGS9-2 is expressed in the brain, especially abundant in the striatum. It is believed to be an essential regulatory component of dopamine and opioid signaling. In this study, we compared the expression of RGS9 proteins in the nervous system of different age groups of rats employing immunocytochemistry. In both 3-week- and 1-year-old rats, RGS9 is expressed abundantly in caudate-putamen, nucleus accumbens, and olfactory tubercle. It is also expressed abundantly in the ventral horn of the spinal cord and the dorsal root ganglion (DRG) cells. Quantitative analysis showed that the intensities of RGS9 expression in 1-year-old rats are higher than those in the 3-week-old rats in caudate-putamen, nucleus accumbens, olfactory tubercle, periaqueductal gray, and gray matter of the spinal cord. In contrast, in thalamic nuclei and locus coeruleus, the intensities of RGS9 immunostaining in 3-week-old rats are higher than in 1-year-old rats. In DRG cells, there is no significant difference between the two age groups. These data suggest that RGS9 is differentially expressed with age. Such differential expression may play an important role in neuronal differentiation and development as well as in neuronal function, such as dopamine and opioid signaling.
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Affiliation(s)
- Ki Jun Kim
- University of California, San Francisco, Department of Anesthesia and Perioperative Care, 513 Parnassus Avenue, Box 0464, Room S-455, San Francisco, CA 94143, USA
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Garzón J, Rodríguez-Muñoz M, López-Fando A, Sánchez-Blázquez P. The RGSZ2 protein exists in a complex with mu-opioid receptors and regulates the desensitizing capacity of Gz proteins. Neuropsychopharmacology 2005; 30:1632-48. [PMID: 15827571 DOI: 10.1038/sj.npp.1300726] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The regulator of G-protein signaling RGS17(Z2) is a member of the RGS-Rz subfamily of GTPase-activating proteins (GAP) that efficiently deactivate GalphazGTP subunits. We have found that in the central nervous system (CNS), the levels of RGSZ2 mRNA and protein are elevated in the hypothalamus, midbrain, and pons-medulla, and that RGSZ2 is glycosylated in synaptosomal membranes isolated from CNS tissue. In analyzing the function of RGSZ2 in the CNS, we found that when the expression of RGSZ2 was impaired, the antinociceptive response to morphine and [D-Ala2, N-MePhe4, Gly-ol5]-enkephalin (DAMGO) augmented. This potentiation involved mu-opioid receptors and increased tolerance to further doses of these agonists administered 24 h later. High doses of morphine promoted agonist desensitization even within the analgesia time-course, a phenomenon that appears to be related to the great capacity of morphine to activate Gz proteins. In contrast, the knockdown of RGSZ2 proteins did not affect the activity of delta receptor agonists, [D-Pen2,5]-enkephalin (DPDPE), and [D-Ala2] deltorphin II. In membranes from periaqueductal gray matter (PAG), both RGSZ2 and the related RGS20(Z1) co-precipitated with mu-opioid receptors. While a morphine challenge reduced the association of Gi/o/z with mu receptors, it increased their association with the RGSZ2 and RGSZ1 proteins. However, only Galphaz subunits co-precipitated with RGSZ2. Doses of morphine that produced acute tolerance maintained the association of Galpha subunits with RGSZ proteins even after the analgesic effects had ceased. These results indicate that both RGSZ1 and RGSZ2 proteins influence mu receptor signaling by sequestering Galpha subunits, therefore behaving as effector antagonists.
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MESH Headings
- Analgesics, Opioid/pharmacology
- Analysis of Variance
- Animals
- Behavior, Animal
- Blotting, Northern
- Blotting, Western/methods
- Central Nervous System/anatomy & histology
- Central Nervous System/drug effects
- Central Nervous System/metabolism
- Dose-Response Relationship, Drug
- Drug Interactions
- Drug Tolerance
- GTP-Binding Protein alpha Subunits/metabolism
- GTP-Binding Proteins/metabolism
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/physiology
- Glycosylation/drug effects
- Immunoprecipitation/methods
- Mice
- Mice, Knockout
- Models, Biological
- Morphine/pharmacology
- Narcotics/pharmacology
- Oligodeoxyribonucleotides, Antisense/pharmacology
- Pain Measurement/drug effects
- RGS Proteins/chemistry
- RGS Proteins/genetics
- RGS Proteins/immunology
- RGS Proteins/metabolism
- RNA, Messenger/biosynthesis
- Receptors, Opioid, mu/metabolism
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Synaptosomes/drug effects
- Synaptosomes/metabolism
- Time Factors
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Affiliation(s)
- Javier Garzón
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, CSIC, Madrid, Spain.
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Garzón J, Rodríguez-Muñoz M, de la Torre-Madrid E, Sánchez-Blázquez P. Effector antagonism by the regulators of G protein signalling (RGS) proteins causes desensitization of mu-opioid receptors in the CNS. Psychopharmacology (Berl) 2005; 180:1-11. [PMID: 15830230 DOI: 10.1007/s00213-005-2248-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2004] [Accepted: 02/18/2005] [Indexed: 12/13/2022]
Abstract
RATIONALE In cell culture systems, agonists can promote the phosphorylation and internalization of receptors coupled to G proteins (GPCR), leading to their desensitization. However, in the CNS opioid agonists promote a profound desensitization of their analgesic effects without diminishing the presence of their receptors in the neuronal membrane. Recent studies have indicated that CNS proteins of the RGS family, specific regulators of G protein signalling, may be involved in mu-opioid receptor desensitization in vivo. OBJECTIVE In this work we review the role played by RGS proteins in the intensity and duration of the effects of mu-opioid receptor agonists, and how they influence the delayed tolerance that develops in response to specific doses of opioids. RESULTS RGS proteins are GTPase-activating proteins (GAP) that accelerate the hydrolysis of GalphaGTP to terminate signalling at effectors. The GAP activity of RGS-R4 and RGS-Rz proteins restricts the amplitude of opioid analgesia, and the efficient deactivation of GalphazGTP subunits by RGS-Rz proteins prevents mu receptor desensitization. However, RGS-R7 proteins antagonize effectors by binding to and sequestering mu receptor-activated Galphai/o/z subunits. Thus, they reduce the pool of receptor-regulated G proteins and hence, the effects of agonists. The delayed tolerance observed following morphine administration correlates with the transfer of Galpha subunits from mu receptors to RGS-R7 proteins and the subsequent stabilization of this association. CONCLUSION In the CNS, the RGS proteins control the activity of mu opioid receptors through GAP-dependent (RGS-R4 and RGS-Rz) as well as by GAP-independent mechanisms (RGS-R7). As a result, they can both antagonize effectors and desensitize receptors under certain circumstances.
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Affiliation(s)
- Javier Garzón
- Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Doctor Arce, 37, 28002, Madrid, Spain.
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Garzón J, Rodríguez-Muñoz M, Sánchez-Blázquez P. Morphine alters the selective association between mu-opioid receptors and specific RGS proteins in mouse periaqueductal gray matter. Neuropharmacology 2005; 48:853-68. [PMID: 15829256 DOI: 10.1016/j.neuropharm.2005.01.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 12/03/2004] [Accepted: 01/06/2005] [Indexed: 11/28/2022]
Abstract
In the CNS, several regulators of G-protein signalling (RGS) modulate the activity of mu-opioid receptors. In pull-down assays performed on membranes from mouse periaqueductal gray matter (PAG), mu-opioid receptors co-precipitated with delta-opioid receptors, Gi/o/z/q proteins, and the regulators of G-protein signalling RGS4, RGS9-2, RGS14, RGSZ1 and RGSZ2. No RGS2, RGS7, RGS10 and RGS11 proteins were associated with the mu receptors in these PAG membranes. In mice, an intracerebroventricular dose of 10 nmol morphine produced acute tolerance at mu receptors but did not disrupt the co-precipitation of mu-delta receptor complexes. However, this opioid reduced by more than 50% the co-precipitation of G alpha i/o/z subunits with mu receptors, and altered their association with some of the RGS proteins at 30 min, 3 h and 24 h after its administration. The association of RGS9-2 with mu receptors diminished by 30-40% 24 h after the administration of morphine, while that of RGSZ2 and of RGSZ1 increased. Morphine treatment recruited RGS4 to the PAG membranes, and 30 min and 3 h after the opioid challenge its association with mu receptors had increased. However, 24 h after morphine administration, the co-precipitation of RGS4 had decreased by about 30%. The opioid produced no change in the membrane levels of RGS9-2, RGS14, RGSZ1 and RGSZ2. Thus, in PAG synaptosomal membranes, a dynamic and selective link exists between, mu-opioid receptors, Gi/o/z proteins and certain RGS proteins.
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MESH Headings
- Analgesics, Opioid/pharmacology
- Animals
- Autoradiography
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Chemical Precipitation
- Chromatography, Affinity/methods
- Dose-Response Relationship, Drug
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Immunoblotting/methods
- Iodine Isotopes/pharmacology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Morphine/pharmacology
- Narcotics/pharmacology
- Periaqueductal Gray/drug effects
- Periaqueductal Gray/metabolism
- RGS Proteins/classification
- RGS Proteins/metabolism
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/deficiency
- Receptors, Opioid, mu/metabolism
- Time Factors
- beta-Endorphin/pharmacology
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Affiliation(s)
- Javier Garzón
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, Consejo Superior de Investigaciones Científicas, Doctor Arce 37, E-28002 Madrid, Spain.
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Sánchez-Blázquez P, Rodríguez-Muñoz M, Montero C, Garzón J. RGS-Rz and RGS9-2 proteins control mu-opioid receptor desensitisation in CNS: the role of activated Galphaz subunits. Neuropharmacology 2005; 48:134-50. [PMID: 15617734 DOI: 10.1016/j.neuropharm.2004.08.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Revised: 07/29/2004] [Accepted: 08/17/2004] [Indexed: 11/21/2022]
Abstract
Two consecutive i.c.v. administrations of analgesic doses of mu-opioid receptor agonists lead to a profound desensitisation of the latter receptors; a third dose produced less than 20% of the effect obtained with the first administration. Desensitisation was still effective 24h later. Impairing the activity of Galphaz but not Galphai2 subunits prevented tolerance developing after the administration of three consecutive doses of morphine. Further, the i.c.v. injection of Galphai2 subunits potentiated morphine analgesia and abolished acute tolerance, whereas i.c.v.-administered Galphaz subunits produced a rapid and robust loss of the response to morphine. The RGSZ1 and RGSZ2 proteins selectively deactivate GalphazGTP subunits, and their knockdown increased the effects produced by the first dose of morphine. However, impairing their activity also accelerated tachyphylaxis following successive doses of morphine, and facilitated the development of acute morphine tolerance. In contrast, inhibiting the RGS9-2 proteins, which bind to GalphaoGTP and GalphaiGTP but only weakly deactivates them, preserved the effects of consecutive morphine doses and abolished the generation of acute tolerance. Therefore, desensitisation of mu-opioid receptors can be achieved by reducing the responsiveness of post-receptor elements (via the possible action of activated Galphaz subunits) and/or by depleting the pool of receptor-regulated G proteins that agonists need to propagate their effects, e.g., through the activity of RGS9-2 proteins.
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46
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Abstract
In this article we review recent advances in our understanding of the crucial role of the Regulator of G protein Signaling (RGS) proteins in opioid signaling mechanisms and opioid tolerance development. Opioids exert their physiologic effects via complex G protein-coupled receptor-signaling mechanisms, and RGS proteins are now known to tightly regulate the G protein signaling cycle. RGS proteins contain GTPase-accelerating protein activity within their characteristic RGS domain and various other receptor signaling-related properties of their other functional domains. There have been more than 20 RGS proteins reported in the literature, and multiple RGS proteins have been shown to negatively regulate G protein-mediated opioid signaling, facilitate opioid receptor desensitization and internalization, and affect the rate at which opioid tolerance develops. Using RGS proteins as targets for future drug therapy aimed at modulating opioid effectiveness in both acute and chronic pain settings may be an important advance in the treatment of pain.
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Affiliation(s)
- Guo-Xi Xie
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, California
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Garzón J, Rodríguez-Muñoz M, López-Fando A, Sánchez-Blázquez P. Activation of μ-Opioid Receptors Transfers Control of Gα Subunits to the Regulator of G-protein Signaling RGS9-2. J Biol Chem 2005; 280:8951-60. [PMID: 15632124 DOI: 10.1074/jbc.m407005200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In mouse periaqueductal gray matter (PAG) membranes, the mu-opioid receptor (MOR) coprecipitated the alpha-subunits of the Gi/o/z/q/11 proteins, the Gbeta1/2 subunits, and the regulator of G-protein signaling RGS9-2 and its partner protein Gbeta5. RGS7 and RGS11 present in this neural structure showed no association with MOR. In vivo intracerebroventricular injection of morphine did not alter MOR immunoreactivity, but 30 min and 3 h after administration, the coprecipitation of Galpha subunits with MORs was reduced by up to 50%. Furthermore, the association between Galpha subunits and RGS9-2 proteins was increased. Twenty-four hours after receiving intracerebroventricular morphine, the Galpha subunits left the RGS9-2 proteins and re-associated with the MORs. However, doses of the opioid able to induce tolerance promoted the stable transfer of Galpha subunits to the RGS9-2 control. This was accompanied by Ser phosphorylation of RGS9-2 proteins, which increased their co-precipitation with 14-3-3 proteins. In the PAG membranes of morphine-desensitized mice, the capacity of the opioid to stimulate G-protein-related guanosine 5'-O-(3-[35S]thiotriphosphate) binding as well as low Km GTPase activity was attenuated. The in vivo knockdown of RGS9-2 expression prevented morphine from altering the association between MORs and G-proteins, and tolerance did not develop. In PAG membranes from RGS9-2 knockdown mice, morphine showed full capacity to activate G-proteins. Thus, the tolerance that develops following an adequate dose of morphine is caused by the stabilization and retention of MOR-activated Galpha subunits by RGS9-2 proteins. This multistep process is initiated by the morphine-induced transfer of MOR-associated Galpha subunits to the RGS9-2 proteins, followed by Ser phosphorylation of the latter and their binding to 14-3-3 proteins. This regulatory mechanism probably precedes the loss of MORs from the cell membrane, which has been observed with other opioid agonists.
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Affiliation(s)
- Javier Garzón
- Department of Neuropharmacology, Cajal Institute, Consejo Superior de Investigaciones Científicas, E-28002 Madrid, Spain.
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48
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López-Fando A, Rodríguez-Muñoz M, Sánchez-Blázquez P, Garzón J. Expression of neural RGS-R7 and Gbeta5 Proteins in Response to Acute and Chronic Morphine. Neuropsychopharmacology 2005; 30:99-110. [PMID: 15199376 DOI: 10.1038/sj.npp.1300515] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The R7 subfamily of regulators of G-protein signaling (RGS) proteins (RGS6, RGS7, RGS9-2, and RGS11), and its binding protein Gbeta5, are found in neural structures of mouse brain. A single intracerebroventricular priming dose of 10 nmol morphine gave rise to acute tolerance to the analgesic effects of successive identical test doses of the opioid. At 2 h after administering the acute opioid, RGS7 mRNA levels in the striatum plus those of RGS9-2 in the striatum and thalamus were increased, whereas RGS9-2 and RGS11 mRNA were reduced in the cortex. Similar but attenuated RGS-R7 mRNA changes persisted 24 h after acute morphine administration. No changes in Gbeta5 mRNA levels were observed. At 2 days after commencing sustained morphine treatment, the levels of mRNA for RGS7, RGS9-2, RGS11, and Gbeta5 increased in most of the brain structures studied (striatum, thalamus, periaqueductal gray matter (PAG), and cortex). In these morphine tolerant-dependent mice, the greater changes were found for RGS9-2 in the thalamus (>500%) and PAG (>200%). In post-dependent mice, the increases in RGS-R7 and Gbeta5 mRNA still persisted in the PAG and striatum at 8 and 16 days after starting the chronic opioid treatment. The raised mRNA levels promoted by chronic, but not by acute, morphine, were accompanied by increases in the encoded proteins. This is probably a result of the costabilization of the RGS-R7 and Gbeta5 proteins forming heterodimers. Opioid-induced adaptations of RGS-R7 and Gbeta5 genes may regulate the severity of morphine-induced tolerance/dependence and the duration of the post-dependent period, helping to recover the normal response.
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Affiliation(s)
- Almudena López-Fando
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, CSIC, Madrid, Spain
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49
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Clark MJ, Traynor JR. Endogenous regulator of g protein signaling proteins reduce {mu}-opioid receptor desensitization and down-regulation and adenylyl cyclase tolerance in C6 cells. J Pharmacol Exp Ther 2004; 312:809-15. [PMID: 15383633 DOI: 10.1124/jpet.104.074641] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic exposure of cells to mu-opioid agonists leads to tolerance which can be measured by a reduced ability to activate signaling pathways in the cell. Cell signaling through inhibitory G proteins is negatively regulated by RGS (regulator of G protein signaling) proteins. Here we examine the hypothesis that the GTPase accelerating activity of RGS proteins, by altering the lifetime of Galpha and Gbetagamma, plays a role in the development of cellular tolerance to mu-opioids. C6 glioma cells were stably transfected with mu-opioid receptor and pertussis toxin (PTX)-insensitive Galpha(o) that was either sensitive or insensitive to endogenous RGS proteins. Cells were treated with PTX to uncouple endogenous Galpha proteins followed by exposure to the mu-opioid agonists [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) or morphine. Receptor desensitization as measured by agonist-stimulated [(35)S]GTPgammaS binding and receptor down-regulation as measured by [(3)H]diprenorphine binding were increased in cells expressing RGS-insensitive Galpha(o). Exposure to high concentrations of morphine or the peptidic mu-opioid agonist DAMGO led to a tolerance to inhibit adenylyl cyclase activity in both cell types with a rapid (30 min) and a slower component. Using a submaximal concentration of DAMGO to induce a reduced level of tolerance, a shift in the concentration-effect curve for DAMGO to inhibit adenylyl cyclase activity was seen in the cells expressing RGS-insensitive Galpha(o), but not in the cells expressing RGS-sensitive Galpha(o), which can be partly explained by an increased supersensitization of the adenylyl cyclase response. The results show that RGS proteins endogenously expressed in C6 cells reduce agonist-induced mu-opioid receptor desensitization, down-regulation, and sensitivity to tolerance to inhibit adenylyl cyclase activity.
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Affiliation(s)
- Mary J Clark
- Department of Pharmacology, University of Michigan Medical School, 1301 Medical Science Research Building III, 1150 West Medical Center Drive, Ann Arbor, MI 48109-0632, USA
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50
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Garzón J, Rodríguez-Muñoz M, López-Fando A, García-España A, Sánchez-Blázquez P. RGSZ1 and GAIP regulate mu- but not delta-opioid receptors in mouse CNS: role in tachyphylaxis and acute tolerance. Neuropsychopharmacology 2004; 29:1091-104. [PMID: 14997173 DOI: 10.1038/sj.npp.1300408] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the CNS, the regulators of G-protein signaling (RGS) proteins belonging to the Rz subfamily, RGS19 (G(alpha) interacting protein (GAIP)) and RGS20 (Z1), control the activity of opioid agonists at mu but not at delta receptors. Rz proteins show high selectivity in deactivating G(alpha)z-GTP subunits. After reducing the expression of RGSZ1 with antisense oligodeoxynucleotides (ODN), the supraspinal antinociception produced by morphine, heroin, DAMGO ([D-Ala2, N-MePhe4,Gly-ol5]-enkephalin), and endomorphin-1 was notably increased. No change was observed in the effect of endomorphin-2. This agrees with the proposed existence of different mu receptors for the endomorphins. The activities of DPDPE ([D-Pen2,5]-enkephalin) and [D-Ala2] deltorphin II, agonists at delta receptors, were also unchanged. Knockdown of GAIP and of the GAIP interacting protein C-terminus (GIPC) led to changes in agonist effects at mu but not at delta receptors. The impairment of RGSZ1 extended the duration of morphine analgesia by at least 1 h beyond that observed in control animals. CTOP (Cys2, Tyr3, Orn5, Pen7-amide) antagonized morphine analgesia when given during the period in which the effect of morphine was enhanced by RGSZ1 knockdown. Thus, in naive mice, morphine tachyphylaxis originated in the presence of the opioid agonist and during the analgesia time course. The knockdown of RGSZ1 facilitated the development of tolerance to a single dose of morphine and accelerated tolerance to continuous delivery of the opioid. These results indicate that mu but not delta receptors are linked to Rz regulation. The mu receptor-mediated activation of Gz proteins is effective at recruiting the adaptive mechanisms leading to the development of opioid desensitization.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Analgesics, Opioid/pharmacology
- Animals
- Behavior, Animal
- Blotting, Northern/methods
- Blotting, Western/methods
- Carrier Proteins/adverse effects
- Carrier Proteins/chemistry
- Carrier Proteins/physiology
- Central Nervous System/anatomy & histology
- Central Nervous System/drug effects
- Central Nervous System/metabolism
- Dose-Response Relationship, Drug
- Drug Interactions
- Drug Tolerance/physiology
- GTP-Binding Proteins/classification
- GTP-Binding Proteins/pharmacology
- Glycosylation/drug effects
- Male
- Mice
- Neuropeptides/adverse effects
- Neuropeptides/chemistry
- Neuropeptides/physiology
- Oligodeoxyribonucleotides, Antisense/pharmacology
- Pain Measurement/drug effects
- RGS Proteins/adverse effects
- RGS Proteins/chemistry
- RGS Proteins/physiology
- RNA, Messenger/biosynthesis
- Reaction Time/drug effects
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/metabolism
- Recombinant Fusion Proteins/metabolism
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Somatostatin/analogs & derivatives
- Somatostatin/pharmacology
- Tachyphylaxis/physiology
- Time Factors
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Affiliation(s)
- Javier Garzón
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, CSIC, Madrid, Spain.
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