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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: 14] [Impact Index Per Article: 1.8] [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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Hayes MP, Roman DL. Regulator of G Protein Signaling 17 as a Negative Modulator of GPCR Signaling in Multiple Human Cancers. AAPS JOURNAL 2016; 18:550-9. [PMID: 26928451 DOI: 10.1208/s12248-016-9894-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 02/15/2016] [Indexed: 02/08/2023]
Abstract
Regulators of G protein signaling (RGS) proteins modulate G protein-coupled receptor (GPCR) signaling networks by terminating signals produced by active Gα subunits. RGS17, a member of the RZ subfamily of RGS proteins, is typically only expressed in appreciable amounts in the human central nervous system, but previous works have shown that RGS17 expression is selectively upregulated in a number of malignancies, including lung, breast, prostate, and hepatocellular carcinoma. In addition, this upregulation of RGS17 is associated with a more aggressive cancer phenotype, as increased proliferation, migration, and invasion are observed. Conversely, decreased RGS17 expression diminishes the response of ovarian cancer cells to agents commonly used during chemotherapy. These somewhat contradictory roles of RGS17 in cancer highlight the need for selective, high-affinity inhibitors of RGS17 to use as chemical probes to further the understanding of RGS17 biology. Based on current evidence, these compounds could potentially have clinical utility as novel chemotherapeutics in the treatment of lung, prostate, breast, and liver cancers. Recent advances in screening technologies to identify potential inhibitors coupled with increasing knowledge of the structural requirements of RGS-Gα protein-protein interaction inhibitors make the future of drug discovery efforts targeting RGS17 promising. This review highlights recent findings related to RGS17 as both a canonical and atypical RGS protein, its role in various human disease states, and offers insights on small molecule inhibition of RGS17.
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Affiliation(s)
- Michael P Hayes
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa, USA
| | - David L Roman
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa, USA. .,Cancer Signaling and Experimental Therapeutics Program, Holden Comprehensive Cancer Center, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA. .,, 115 S. Grand Avenue, S327 PHAR, Iowa City, Iowa, 52242, USA.
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3
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Woodard GE, Jardín I, Berna-Erro A, Salido GM, Rosado JA. Regulators of G-protein-signaling proteins: negative modulators of G-protein-coupled receptor signaling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 317:97-183. [PMID: 26008785 DOI: 10.1016/bs.ircmb.2015.02.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Regulators of G-protein-signaling (RGS) proteins are a category of intracellular proteins that have an inhibitory effect on the intracellular signaling produced by G-protein-coupled receptors (GPCRs). RGS along with RGS-like proteins switch on through direct contact G-alpha subunits providing a variety of intracellular functions through intracellular signaling. RGS proteins have a common RGS domain that binds to G alpha. RGS proteins accelerate GTPase and thus enhance guanosine triphosphate hydrolysis through the alpha subunit of heterotrimeric G proteins. As a result, they inactivate the G protein and quickly turn off GPCR signaling thus terminating the resulting downstream signals. Activity and subcellular localization of RGS proteins can be changed through covalent molecular changes to the enzyme, differential gene splicing, and processing of the protein. Other roles of RGS proteins have shown them to not be solely committed to being inhibitors but behave more as modulators and integrators of signaling. RGS proteins modulate the duration and kinetics of slow calcium oscillations and rapid phototransduction and ion signaling events. In other cases, RGS proteins integrate G proteins with signaling pathways linked to such diverse cellular responses as cell growth and differentiation, cell motility, and intracellular trafficking. Human and animal studies have revealed that RGS proteins play a vital role in physiology and can be ideal targets for diseases such as those related to addiction where receptor signaling seems continuously switched on.
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Affiliation(s)
- Geoffrey E Woodard
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, Bethesda, MD, USA
| | - Isaac Jardín
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - A Berna-Erro
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Gines M Salido
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Juan A Rosado
- Department of Physiology, University of Extremadura, Caceres, Spain
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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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Nitric Oxide and Zinc-Mediated Protein Assemblies Involved in Mu Opioid Receptor Signaling. Mol Neurobiol 2013; 48:769-82. [DOI: 10.1007/s12035-013-8465-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 04/18/2013] [Indexed: 01/06/2023]
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Yu JZ, Rasenick MM. Receptor signaling and the cell biology of synaptic transmission. HANDBOOK OF CLINICAL NEUROLOGY 2012; 106:9-35. [PMID: 22608613 DOI: 10.1016/b978-0-444-52002-9.00002-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
This volume describes a series of psychiatric and neuropsychiatric disorders, connects some aspects of somatic and psychiatric medicine, and describes various current and emerging therapies. The purpose of this chapter is to set the stage for the volume by developing the theoretical basis of synaptic transmission and introducing the various neurotransmitters and their receptors involved in the process. The intent is to provide not only a historical context through which to understand neurotransmitters, but a current contextual basis for understanding neuronal signal transduction and applying this knowledge to facilitate treatment of maladies of the brain and mind.
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Affiliation(s)
- Jiang-Zhou Yu
- Department of Physiology, University of Illinois, Chicago, IL, USA
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Sánchez-Blázquez P, Rodríguez-Muñoz M, Garzón J. Mu-opioid receptors transiently activate the Akt-nNOS pathway to produce sustained potentiation of PKC-mediated NMDAR-CaMKII signaling. PLoS One 2010; 5:e11278. [PMID: 20585660 PMCID: PMC2890584 DOI: 10.1371/journal.pone.0011278] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 06/03/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In periaqueductal grey (PAG) matter, cross-talk between the Mu-opioid receptor (MOR) and the glutamate N-methyl-D-Aspartate receptor (NMDAR)-CaMKII pathway supports the development of analgesic tolerance to morphine. In neurons, histidine triad nucleotide binding protein 1 (HINT1) connects the regulators of G protein signaling RGSZ1 and RGSZ2 to the C terminus of the MOR. In response to morphine, this HINT1-RGSZ complex binds PKCgamma, and afterwards, the interplay between PKCgamma, Src and Gz/Gi proteins leads to sustained potentiation of NMDAR-mediated glutamate responses. METHODOLOGY/PRINCIPAL FINDINGS Following an intracerebroventricular (icv) injection of 10 nmol morphine, Akt was recruited to the synaptosomal membrane and activated by Thr308 and Ser473 phosphorylation. The Akt activation was immediately transferred to neural Nitric Oxide Synthase (nNOS) Ser1417. Afterwards, nitric oxide (NO)-released zinc ions recruited PKCgamma to the MOR to promote the Src-mediated phosphorylation of the Tyr1325 NMDAR2A subunit. This action increased NMDAR calcium flux and CaMKII was activated in a calcium-calmodulin dependent manner. CaMKII then acted on nNOS Ser847 to produce a sustained reduction in NO levels. The activation of the Akt-nNOS pathway was also reduced by the binding of these proteins to the MOR-HINT1 complex where they remained inactive. Tolerance to acute morphine developed as a result of phosphorylation of MOR cytosolic residues, uncoupling from the regulated G proteins which are transferred to RGSZ2 proteins. The diminished effect of morphine was prevented by LNNA, an inhibitor of nNOS function, and naltrindole, a delta-opioid receptor antagonist that also inhibits Akt. CONCLUSIONS/SIGNIFICANCE Analysis of the regulatory phosphorylation of the proteins included in the study indicated that morphine produces a transient activation of the Akt/PKB-nNOS pathway. This activation occurs upstream of PKCgamma and Src mediated potentiation of NMDAR activity, ultimately leading to morphine tolerance. In summary, the Akt-nNOS pathway acts as a primer for morphine-triggered events which leads to the sustained potentiation of the NMDAR-CaMKII pathway and MOR inhibition.
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Affiliation(s)
- Pilar Sánchez-Blázquez
- Neuropharmacology, Cajal Institute, CSIC, Madrid, Spain
- CIBER of Mental Health (CIBERSAM) G09, ISCIII, Madrid, Spain
| | | | - Javier Garzón
- Neuropharmacology, Cajal Institute, CSIC, Madrid, Spain
- CIBER of Mental Health (CIBERSAM) G09, ISCIII, Madrid, Spain
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Brain-specific Gαz interacts with Src tyrosine kinase to regulate Mu-opioid receptor-NMDAR signaling pathway. Cell Signal 2009; 21:1444-54. [DOI: 10.1016/j.cellsig.2009.05.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 05/06/2009] [Accepted: 05/06/2009] [Indexed: 11/20/2022]
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Garzón J, de la Torre-Madrid E, Rodríguez-Muñoz M, Vicente-Sánchez A, Sánchez-Blázquez P. Gz mediates the long-lasting desensitization of brain CB1 receptors and is essential for cross-tolerance with morphine. Mol Pain 2009; 5:11. [PMID: 19284549 PMCID: PMC2657119 DOI: 10.1186/1744-8069-5-11] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Accepted: 03/10/2009] [Indexed: 12/14/2022] Open
Abstract
Background Although the systemic administration of cannabinoids produces antinociception, their chronic use leads to analgesic tolerance as well as cross-tolerance to morphine. These effects are mediated by cannabinoids binding to peripheral, spinal and supraspinal CB1 and CB2 receptors, making it difficult to determine the relevance of each receptor type to these phenomena. However, in the brain, the CB1 receptors (CB1Rs) are expressed at high levels in neurons, whereas the expression of CB2Rs is marginal. Thus, CB1Rs mediate the effects of smoked cannabis and are also implicated in emotional behaviors. We have analyzed the production of supraspinal analgesia and the development of tolerance at CB1Rs by the direct injection of a series of cannabinoids into the brain. The influence of the activation of CB1Rs on supraspinal analgesia evoked by morphine was also evaluated. Results Intracerebroventricular (icv) administration of cannabinoid receptor agonists, WIN55,212-2, ACEA or methanandamide, generated a dose-dependent analgesia. Notably, a single administration of these compounds brought about profound analgesic tolerance that lasted for more than 14 days. This decrease in the effect of cannabinoid receptor agonists was not mediated by depletion of CB1Rs or the loss of regulated G proteins, but, nevertheless, it was accompanied by reduced morphine analgesia. On the other hand, acute morphine administration produced tolerance that lasted only 3 days and did not affect the CB1R. We found that both neural mu-opioid receptors (MORs) and CB1Rs interact with the HINT1-RGSZ module, thereby regulating pertussis toxin-insensitive Gz proteins. In mice with reduced levels of these Gz proteins, the CB1R agonists produced no such desensitization or morphine cross-tolerance. On the other hand, experimental enhancement of Gz signaling enabled an acute icv administration of morphine to produce a long-lasting tolerance at MORs that persisted for more than 2 weeks, and it also impaired the analgesic effects of cannabinoids. Conclusion In the brain, cannabinoids can produce analgesic tolerance that is not associated with the loss of surface CB1Rs or their uncoupling from regulated transduction. Neural specific Gz proteins are essential mediators of the analgesic effects of supraspinal CB1R agonists and morphine. These Gz proteins are also responsible for the long-term analgesic tolerance produced by single doses of these agonists, as well as for the cross-tolerance between CB1Rs and MORs.
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Modulation of phosphodiesterase6 turnoff during background illumination in mouse rod photoreceptors. J Neurosci 2008; 28:2064-74. [PMID: 18305241 DOI: 10.1523/jneurosci.2973-07.2008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In rod photoreceptors of wild-type mice, background light produces an acceleration of the decay of responses to brief flashes, accompanied by a decrease in the rate-limiting time constant for response decay. In rods in which phosphodiesterase gamma (PDEgamma) lacks one of its sites of phosphorylation (T35A rods), both the waveform of response decay and the rate-limiting time constant are nearly unaffected by backgrounds. These effects are not the result of the removal of the phosphorylation site per se, because rods lacking both of the phosphorylation sites of PDEgamma (T22A/T35A rods) adapt to light in a nearly normal manner. Because PDEgamma is one of the proteins of the GTPase activating protein (GAP) complex, our experiments argue for a novel mechanism of photoreceptor light adaptation produced by modulation of GAP-dependent hydrolysis of transducin alpha GTP. In PDEgamma T35A rods, a change in the conformation of the PDEgamma subunit may hinder or mask this mechanism, which in mammals appears to be primarily responsible for the quickening of the temporal resolution of the rod response in backgrounds. Modulation of PDE turnoff also helps to prevent premature saturation of the rod in bright backgrounds, thus making an important contribution to light adaptation. Our experiments provide evidence for modulation of GAP protein-dependent response turnoff, which may also play a role in controlling signal duration at hormone receptors and synapses in the CNS.
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Maple AM, Perna MK, Parlaman JP, Stanwood GD, Brown RW. Ontogenetic quinpirole treatment produces long-lasting decreases in the expression of Rgs9, but increases Rgs17 in the striatum, nucleus accumbens and frontal cortex. Eur J Neurosci 2007; 26:2532-8. [DOI: 10.1111/j.1460-9568.2007.05860.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Rodríguez-Muñoz M, de la Torre-Madrid E, Gaitán G, Sánchez-Blázquez P, Garzón J. RGS14 prevents morphine from internalizing Mu-opioid receptors in periaqueductal gray neurons. Cell Signal 2007; 19:2558-71. [PMID: 17825524 DOI: 10.1016/j.cellsig.2007.08.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 08/06/2007] [Indexed: 01/24/2023]
Abstract
Opioid agonists display different capacities to stimulate mu-opioid receptor (MOR) endocytosis, which is related to their ability to provoke the phosphorylation of specific cytosolic residues in the MORs. Generally, opioids that efficiently promote MOR endocytosis and recycling produce little tolerance, as is the case for [D-Ala(2), N-MePhe(4),Gly-ol(5)] encephalin (DAMGO). However, morphine produces rapid and profound antinociceptive desensitization in the adult mouse brain associated with little MOR internalization. The regulator of G-protein signaling, the RGS14 protein, associates with MORs in periaqueductal gray matter (PAG) neurons, and when RGS14 is silenced morphine increased the serine 375 phosphorylation in the C terminus of the MOR, a GRK substrate. Subsequently, these receptors were internalized and recycled back to the membrane where they accumulated on cessation of antinociception. These mice now exhibited a resensitized response to morphine and little tolerance developed. Thus, in morphine-activated MORs the RGS14 prevents GRKs from phosphorylating those residues required for beta-arresting-mediated endocytosis. Moreover morphine but not DAMGO triggered a process involving calcium/calmodulin-dependent kinase II (CaMKII) in naïve mice, which contributes to MOR desensitization in the plasma membrane. In RGS14 knockdown mice morphine failed to activate this kinase. It therefore appears that phosphorylation and internalization of MORs disrupts the CaMKII-mediated negative regulation of these opioid receptors.
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MESH Headings
- Amino Acid Sequence
- Analgesics, Opioid/administration & dosage
- Analgesics, Opioid/pharmacology
- Animals
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Drug Tolerance
- Endocytosis/drug effects
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Enzyme Activation
- G-Protein-Coupled Receptor Kinases/metabolism
- Gene Silencing
- Hot Temperature/adverse effects
- Injections, Intraventricular
- Male
- Mice
- Molecular Sequence Data
- Morphine/administration & dosage
- Morphine/pharmacology
- Neurons/drug effects
- Neurons/enzymology
- Neurons/metabolism
- Oligonucleotides, Antisense/metabolism
- Pain/etiology
- Pain/physiopathology
- Pain/prevention & control
- Pain Measurement
- Pain Threshold/drug effects
- Periaqueductal Gray/cytology
- Periaqueductal Gray/drug effects
- Periaqueductal Gray/enzymology
- Periaqueductal Gray/metabolism
- Phosphorylation
- RGS Proteins/genetics
- RGS Proteins/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/metabolism
- Serine/metabolism
- Synaptosomes/drug effects
- Synaptosomes/metabolism
- Time Factors
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Affiliation(s)
- María Rodríguez-Muñoz
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, Madrid E-28002, Spain
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Rodríguez-Muñoz M, de la Torre-Madrid E, Sánchez-Blázquez P, Garzón J. Morphine induces endocytosis of neuronal mu-opioid receptors through the sustained transfer of Galpha subunits to RGSZ2 proteins. Mol Pain 2007; 3:19. [PMID: 17634133 PMCID: PMC1947952 DOI: 10.1186/1744-8069-3-19] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Accepted: 07/17/2007] [Indexed: 12/11/2022] Open
Abstract
Background In general, opioids that induce the recycling of μ-opioid receptors (MORs) promote little desensitization, although morphine is one exception to this rule. While morphine fails to provoke significant internalization of MORs in cultured cells, it does stimulate profound desensitization. In contrast, morphine does promote some internalization of MORs in neurons although this does not prevent this opioid from inducing strong antinociceptive tolerance. Results In neurons, morphine stimulates the long-lasting transfer of MOR-activated Gα subunits to proteins of the RGS-R7 and RGS-Rz subfamilies. We investigated the influence of this regulatory process on the capacity of morphine to promote desensitization and its association with MOR recycling in the mature nervous system. In parallel, we also studied the effects of [D-Ala2, N-MePhe4, Gly-ol5] encephalin (DAMGO), a potent inducer of MOR internalization that promotes little tolerance. We observed that the initial exposure to icv morphine caused no significant internalization of MORs but rather, a fraction of the Gα subunits was stably transferred to RGS proteins in a time-dependent manner. As a result, the antinociception produced by a second dose of morphine administered 6 h after the first was weaker. However, this opioid now stimulated the phosphorylation, internalization and recycling of MORs, and further exposure to morphine promoted little tolerance to this moderate antinociception. In contrast, the initial dose of DAMGO stimulated intense phosphorylation and internalization of the MORs associated with a transient transfer of Gα subunits to the RGS proteins, recovering MOR control shortly after the effects of the opioid had ceased. Accordingly, the recycled MORs re-established their association with G proteins and the neurons were rapidly resensitized to DAMGO. Conclusion In the nervous system, morphine induces a strong desensitization before promoting the phosphorylation and recycling of MORs. The long-term sequestering of morphine-activated Gα subunits by certain RGS proteins reduces the responses to this opioid in neurons. This phenomenon probably increases free Gβγ dimers in the receptor environment and leads to GRK phosphorylation and internalization of the MORs. Although, the internalization of the MORs permits the transfer of opioid-activated Gα subunits to the RGSZ2 proteins, it interferes with the stabilization of this regulatory process and recycled MORs recover the control on these Gα subunits and opioid tolerance develops slowly.
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Affiliation(s)
- María Rodríguez-Muñoz
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, Madrid E-28002, Spain
| | | | - Pilar Sánchez-Blázquez
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, Madrid E-28002, Spain
| | - Javier Garzón
- Neurofarmacología, Instituto de Neurobiología Santiago Ramón y Cajal, Madrid E-28002, Spain
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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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Abstract
This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, USA.
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17
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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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18
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Stanwood GD, Parlaman JP, Levitt P. Genetic or pharmacological inactivation of the dopamine D
1
receptor differentially alters the expression of regulator of G‐protein signalling (Rgs) transcripts. Eur J Neurosci 2006; 24:806-18. [PMID: 16930410 DOI: 10.1111/j.1460-9568.2006.04970.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dysregulation of dopamine (DA) receptor signalling induces specific changes in behaviour, neuronal circuitry and gene expression in the mammalian forebrain. In order to better understand signalling adaptations at the molecular level, we used high-density oligonucleotide microarrays (Codelink Mouse 20K) to define alterations in the expression of transcripts encoding regulator of G-protein coupled receptor signalling in dopamine D1 receptor knockout mice (Drd1a-KO). Regulator of G-protein signalling (Rgs) 2, Rgs4, and Rgs9 were significantly decreased in the striatum (STR) of Drd1a-KO mice. These changes were confirmed by in situ hybridization, and were also observed in the nucleus accumbens (NAc). In contrast, analysis of the medial frontal cortex (MFC) revealed a significant decrease in Rgs17 expression exclusively, and a modest up-regulation of Rgs5 transcript. The expression of these gene products were not significantly altered in the dopamine-poor visual cortex (VC). The Drd1a-KO mouse, and a rabbit model of in utero cocaine exposure, in which D1R signalling is permanently reduced, possess analogous morphological and functional alterations in dopamine-modulated brain circuits; thus we also examined long-lasting changes in RGS transcript expression following prenatal exposure to cocaine. In sharp contrast to the Drd1a-KO, Rgs2 and Rgs4 were unchanged, and Rgs9 and Rgs17 transcripts were increased in prenatal cocaine-exposed progeny. These data suggest that an absolute absence of D1R signalling (Drd1a-KO) and hypomorphic D1R signalling (prenatal cocaine) produce common alterations in neuronal morphology, but distinct outcomes in molecular neuroadaptations.
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Affiliation(s)
- Gregg D Stanwood
- Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville TN 37203, USA.
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19
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Nunn C, Mao H, Chidiac P, Albert PR. RGS17/RGSZ2 and the RZ/A family of regulators of G-protein signaling. Semin Cell Dev Biol 2006; 17:390-9. [PMID: 16765607 DOI: 10.1016/j.semcdb.2006.04.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Regulators of G-protein signaling (RGS proteins) comprise over 20 different proteins that have been classified into subfamilies on the basis of structural homology. The RZ/A family includes RGSZ2/RGS17 (the most recently discovered member of this family), GAIP/RGS19, RGSZ1/RGS20, and the RGSZ1 variant Ret-RGS. The RGS proteins are GTPase activating proteins (GAPs) that turn off G-proteins and thus negatively regulate the signaling of G-protein coupled receptors (GPCRs). In addition, some RZ/A family RGS proteins are able to modify signaling through interactions with adapter proteins (such as GIPC and GIPN). The RZ/A proteins have a simple structure that includes a conserved amino-terminal cysteine string motif, RGS box and short carboxyl-terminal, which confer GAP activity (RGS box) and the ability to undergo covalent modification and interact with other proteins (amino-terminal). This review focuses on RGS17 and its RZ/A sibling proteins and discusses the similarities and differences among these proteins in terms of their palmitoylation, phosphorylation, intracellular localization and interactions with GPCRs and adapter proteins. The specificity of these RGS protein for different Galpha proteins and receptors, and the consequences for signaling are discussed. The tissue and brain distribution, and the evolving understanding of the roles of this family of RGS proteins in receptor signaling and brain function are highlighted.
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Affiliation(s)
- Caroline Nunn
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ont., Canada, N6A 5C1
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20
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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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21
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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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22
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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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23
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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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24
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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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