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Jeon JH, Oh TR, Park S, Huh S, Kim JH, Mai BK, Lee JH, Kim SH, Lee MJ. The Antipsychotic Drug Clozapine Suppresses the RGS4 Polyubiquitylation and Proteasomal Degradation Mediated by the Arg/N-Degron Pathway. Neurotherapeutics 2021; 18:1768-1782. [PMID: 33884581 PMCID: PMC8608952 DOI: 10.1007/s13311-021-01039-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2021] [Indexed: 02/04/2023] Open
Abstract
Although diverse antipsychotic drugs have been developed for the treatment of schizophrenia, most of their mechanisms of action remain elusive. Regulator of G-protein signaling 4 (RGS4) has been reported to be linked, both genetically and functionally, with schizophrenia and is a physiological substrate of the arginylation branch of the N-degron pathway (Arg/N-degron pathway). Here, we show that the atypical antipsychotic drug clozapine significantly inhibits proteasomal degradation of RGS4 proteins without affecting their transcriptional expression. In addition, the levels of Arg- and Phe-GFP (artificial substrates of the Arg/N-degron pathway) were significantly elevated by clozapine treatment. In silico computational model suggested that clozapine may interact with active sites of N-recognin E3 ubiquitin ligases. Accordingly, treatment with clozapine resulted in reduced polyubiquitylation of RGS4 and Arg-GFP in the test tube and in cultured cells. Clozapine attenuated the activation of downstream effectors of G protein-coupled receptor signaling, such as MEK1 and ERK1, in HEK293 and SH-SY5Y cells. Furthermore, intraperitoneal injection of clozapine into rats significantly stabilized the endogenous RGS4 protein in the prefrontal cortex. Overall, these results reveal an additional therapeutic mechanism of action of clozapine: this drug posttranslationally inhibits the degradation of Arg/N-degron substrates, including RGS4. These findings imply that modulation of protein post-translational modifications, in particular the Arg/N-degron pathway, may be a novel molecular therapeutic strategy against schizophrenia.
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Affiliation(s)
- Jun Hyoung Jeon
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Tae Rim Oh
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Seoyoung Park
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Sunghoo Huh
- Biomedical Research Institute, Seoul National University Hospital, Seoul, 03080, Korea
| | - Ji Hyeon Kim
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Binh Khanh Mai
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Jung Hoon Lee
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Se Hyun Kim
- Biomedical Research Institute, Seoul National University Hospital, Seoul, 03080, Korea.
- Department of Psychiatry, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, 03080, Korea.
| | - Min Jae Lee
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea.
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Korea.
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2
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Fina ME, Wang J, Nikonov SS, Sterling S, Vardi N, Kashina A, Dong DW. Arginyltransferase (Ate1) regulates the RGS7 protein level and the sensitivity of light-evoked ON-bipolar responses. Sci Rep 2021; 11:9376. [PMID: 33931669 PMCID: PMC8087773 DOI: 10.1038/s41598-021-88628-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 04/14/2021] [Indexed: 12/16/2022] Open
Abstract
Regulator of G-protein signaling 7 (RGS7) is predominately present in the nervous system and is essential for neuronal signaling involving G-proteins. Prior studies in cultured cells showed that RGS7 is regulated via proteasomal degradation, however no protein is known to facilitate proteasomal degradation of RGS7 and it has not been shown whether this regulation affects G-protein signaling in neurons. Here we used a knockout mouse model with conditional deletion of arginyltransferase (Ate1) in the nervous system and found that in retinal ON bipolar cells, where RGS7 modulates a G-protein to signal light increments, deletion of Ate1 raised the level of RGS7. Electroretinographs revealed that lack of Ate1 leads to increased light-evoked response sensitivities of ON-bipolar cells, as well as their downstream neurons. In cultured mouse embryonic fibroblasts (MEF), RGS7 was rapidly degraded via proteasome pathway and this degradation was abolished in Ate1 knockout MEF. Our results indicate that Ate1 regulates RGS7 protein level by facilitating proteasomal degradation of RGS7 and thus affects G-protein signaling in neurons.
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Affiliation(s)
- Marie E Fina
- Department of Biomedical Sciences, School of Veterinary Medicines, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Junling Wang
- Department of Biomedical Sciences, School of Veterinary Medicines, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Sergei S Nikonov
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Stephanie Sterling
- Department of Biomedical Sciences, School of Veterinary Medicines, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Noga Vardi
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Anna Kashina
- Department of Biomedical Sciences, School of Veterinary Medicines, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Dawei W Dong
- Department of Biomedical Sciences, School of Veterinary Medicines, University of Pennsylvania, Philadelphia, PA, 19104, USA.
- Institute for Biomedical Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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3
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Michaelides M, Miller ML, Egervari G, Primeaux SD, Gomez JL, Ellis RJ, Landry JA, Szutorisz H, Hoffman AF, Lupica CR, Loos RJF, Thanos PK, Bray GA, Neumaier JF, Zachariou V, Wang GJ, Volkow ND, Hurd YL. Striatal Rgs4 regulates feeding and susceptibility to diet-induced obesity. Mol Psychiatry 2020; 25:2058-2069. [PMID: 29955167 PMCID: PMC6310669 DOI: 10.1038/s41380-018-0120-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 05/10/2018] [Accepted: 05/14/2018] [Indexed: 12/16/2022]
Abstract
Consumption of high fat, high sugar (western) diets is a major contributor to the current high levels of obesity. Here, we used a multidisciplinary approach to gain insight into the molecular mechanisms underlying susceptibility to diet-induced obesity (DIO). Using positron emission tomography (PET), we identified the dorsal striatum as the brain area most altered in DIO-susceptible rats and molecular studies within this region highlighted regulator of G-protein signaling 4 (Rgs4) within laser-capture micro-dissected striatonigral (SN) and striatopallidal (SP) medium spiny neurons (MSNs) as playing a key role. Rgs4 is a GTPase accelerating enzyme implicated in plasticity mechanisms of SP MSNs, which are known to regulate feeding and disturbances of which are associated with obesity. Compared to DIO-resistant rats, DIO-susceptible rats exhibited increased striatal Rgs4 with mRNA expression levels enriched in SP MSNs. siRNA-mediated knockdown of striatal Rgs4 in DIO-susceptible rats decreased food intake to levels comparable to DIO-resistant animals. Finally, we demonstrated that the human Rgs4 gene locus is associated with increased body weight and obesity susceptibility phenotypes, and that overweight humans exhibit increased striatal Rgs4 protein. Our findings highlight a novel role for involvement of Rgs4 in SP MSNs in feeding and DIO-susceptibility.
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Affiliation(s)
- Michael Michaelides
- Departments of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Biobehavioral Imaging & Molecular Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA
- Department of Psychiatry, Johns Hopkins School of Medicine, Baltimore, MD, 21205, USA
- Biobehavioral Imaging & Molecular Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA
| | - Michael L Miller
- Departments of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Gabor Egervari
- Departments of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Stefany D Primeaux
- Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, LA, 70112, USA
- Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - Juan L Gomez
- Biobehavioral Imaging & Molecular Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA
| | - Randall J Ellis
- Biobehavioral Imaging & Molecular Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA
| | - Joseph A Landry
- Departments of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Henrietta Szutorisz
- Departments of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Alexander F Hoffman
- Electrophysiology Research Section, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA
| | - Carl R Lupica
- Electrophysiology Research Section, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, 21224, USA
| | - Ruth J F Loos
- The Charles Bronfman Institute for Personalized Medicine, The Mindich Child Health and Development Institute, The Genetics of Obesity and Related Metabolic Traits Program, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Panayotis K Thanos
- Research Institute on Addictions, University at Buffalo, Buffalo, NY, 14203, USA
| | - George A Bray
- Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
| | - John F Neumaier
- Departments of Psychiatry and Pharmacology, University of Washington, Seattle, WA, 98195, USA
| | - Venetia Zachariou
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Gene-Jack Wang
- Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Nora D Volkow
- Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Yasmin L Hurd
- Departments of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
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Lur G, Fariborzi M, Higley MJ. Ketamine disrupts neuromodulatory control of glutamatergic synaptic transmission. PLoS One 2019; 14:e0213721. [PMID: 30865708 PMCID: PMC6415832 DOI: 10.1371/journal.pone.0213721] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 02/27/2019] [Indexed: 12/21/2022] Open
Abstract
A growing body of literature has demonstrated the potential for ketamine in the treatment of major depression. Sub-anesthetic doses produce rapid and sustained changes in depressive behavior, both in patients and rodent models, associated with reorganization of glutamatergic synapses in the prefrontal cortex (PFC). While ketamine is known to regulate N-methyl-D-aspartate (NMDA) -type glutamate receptors (NMDARs), the full complement of downstream cellular consequences for ketamine administration are not well understood. Here, we combine electrophysiology with 2-photon imaging and glutamate uncaging in acute slices of mouse PFC to further examine how ketamine alters glutamatergic synaptic transmission. We find that four hours after ketamine treatment, glutamatergic synapses themselves are not significantly affected. However, levels of the neuromodulatory Regulator of G-protein Signaling (RGS4) are dramatically reduced. This loss of RGS4 activity is associated with disruption of the normal compartmentalization of synaptic neuromodulation. Thus, under control conditions, α2 adrenergic receptors and type B γ-aminobutyric acid (GABAB) receptors selectively inhibit α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) -type glutamate receptors (AMPARs) and NMDARs, respectively. After ketamine administration and reduction in RGS4 activity, this selectivity is lost, with both modulatory systems broadly inhibiting glutamatergic transmission. These results suggest a novel mechanism by which ketamine may influence synaptic signaling and provide new avenues for the exploration of therapeutics directed at treating neuropsychiatric disorders, such as depression.
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Affiliation(s)
- Gyorgy Lur
- Department of Neuroscience, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, California, United States of America
- * E-mail:
| | - Mona Fariborzi
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, California, United States of America
| | - Michael J. Higley
- Department of Neuroscience, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, Connecticut, United States of America
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Doyen PJ, Vergouts M, Pochet A, Desmet N, van Neerven S, Brook G, Hermans E. Inflammation-associated regulation of RGS in astrocytes and putative implication in neuropathic pain. J Neuroinflammation 2017; 14:209. [PMID: 29078779 PMCID: PMC5658970 DOI: 10.1186/s12974-017-0971-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 09/26/2017] [Indexed: 02/07/2023] Open
Abstract
Background Regulators of G-protein signaling (RGS) are major physiological modulators of G-protein-coupled receptors (GPCR) signaling. Several GPCRs expressed in both neurons and astrocytes participate in the central control of pain processing, and the reduced efficacy of analgesics in neuropathic pain conditions may rely on alterations in RGS function. The expression and the regulation of RGS in astrocytes is poorly documented, and we herein hypothesized that neuroinflammation which is commonly observed in neuropathic pain could influence RGS expression in astrocytes. Methods In a validated model of neuropathic pain, the spared nerve injury (SNI), the regulation of RGS2, RGS3, RGS4, and RGS7 messenger RNA (mRNA) was examined up to 3 weeks after the lesion. Changes in the expression of the same RGS were also studied in cultured astrocytes exposed to defined activation protocols or to inflammatory cytokines. Results We evidenced a differential regulation of these RGS in the lumbar spinal cord of animals undergoing SNI. In particular, RGS3 appeared upregulated at early stages after the lesion whereas expression of RGS2 and RGS4 was decreased at later stages. Decrease in RGS7 expression was already observed after 3 days and outlasted until 21 days after the lesion. In cultured astrocytes, we observed that changes in the culture conditions distinctly influenced the constitutive expression of these RGS. Also, brief exposures (4 to 8 h) to either interleukin-1β, interleukin-6, or tumor necrosis factor α caused rapid changes in the mRNA levels of the RGS, which however did not strictly recapitulate the regulations observed in the spinal cord of lesioned animals. Longer exposure (48 h) to inflammatory cytokines barely influenced RGS expression, confirming the rapid but transient regulation of these cell signaling modulators. Conclusion Changes in the environment of astrocytes mimicking the inflammation observed in the model of neuropathic pain can affect RGS expression. Considering the role of astrocytes in the onset and progression of neuropathic pain, we propose that the inflammation-mediated modulation of RGS in astrocytes constitutes an adaptive mechanism in a context of neuroinflammation and may participate in the regulation of nociception.
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Affiliation(s)
- Pierre J Doyen
- Neuropharmacology, Institute of Neuroscience, Université Catholique de Louvain, Avenue Hippocrate B1.54.10, 1200, Brussels, Belgium
| | - Maxime Vergouts
- Neuropharmacology, Institute of Neuroscience, Université Catholique de Louvain, Avenue Hippocrate B1.54.10, 1200, Brussels, Belgium
| | - Amandine Pochet
- Neuropharmacology, Institute of Neuroscience, Université Catholique de Louvain, Avenue Hippocrate B1.54.10, 1200, Brussels, Belgium
| | - Nathalie Desmet
- Neuropharmacology, Institute of Neuroscience, Université Catholique de Louvain, Avenue Hippocrate B1.54.10, 1200, Brussels, Belgium
| | - Sabien van Neerven
- Neuropharmacology, Institute of Neuroscience, Université Catholique de Louvain, Avenue Hippocrate B1.54.10, 1200, Brussels, Belgium
| | - Gary Brook
- Institute for Neuropathology, University Hospital, RWTH Aachen University, Aachen, Germany
| | - Emmanuel Hermans
- Neuropharmacology, Institute of Neuroscience, Université Catholique de Louvain, Avenue Hippocrate B1.54.10, 1200, Brussels, Belgium.
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Park HJ, Kim SH, Moon DO. Growth inhibition of human breast carcinoma cells by overexpression of regulator of G-protein signaling 4. Oncol Lett 2017; 13:4357-4363. [PMID: 28588709 DOI: 10.3892/ol.2017.6009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 07/15/2016] [Indexed: 01/05/2023] Open
Abstract
Breast cancer remains the second largest cause of mortality in women with cancer and does not respond well to conventional therapies. Regulator of G-protein signaling 4 (RGS4) is a GTPase-activating protein of the heterotrimeric Gq and Gi proteins. Altered levels of RGS4 are reportedly linked with several human diseases, including cancer. The present study investigated whether overexpression of RGS4 inhibited the growth of human breast cancer cells. Protein expression was investigated by western blot analysis. Cell viability and apoptosis were analyzed by MTT assay and flow cytometric analysis, respectively. Cell cycle analysis was performed using propidium iodide staining in order to examine the anti-proliferative function of increased RGS4 levels. Next, changes in the expression levels of G2/M cell cycle-related proteins were examined. Overexpression of RGS4 led to the upregulation of phosphorylayed (p)-Ser216 cell division cycle (Cdc)25C and p-Tyr15 Cdc2. Importantly, MG132-induced proteasome blockade prevented degradation of RGS4. Suppression of proliferation was associated with G2/M-phase cell cycle arrest. Furthermore, enhanced endogenous RGS4 protein levels significantly inhibited breast cancer cell growth, which was reversed by a pharmacological inhibitor of RGS4. Taken together, these results suggest that overexpression of RGS4 in human breast cancer cells by molecular means may offer a potential therapeutic approach.
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Affiliation(s)
- Hyun-Jung Park
- Department of Biology Education, Daegu University, Gyeongsan, Gyeongsangbuk-do 38453, Republic of Korea
| | - Seung-Hyun Kim
- Department of Biology Education, Daegu University, Gyeongsan, Gyeongsangbuk-do 38453, Republic of Korea
| | - Dong-Oh Moon
- Department of Biology Education, Daegu University, Gyeongsan, Gyeongsangbuk-do 38453, Republic of Korea
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7
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Zhang Y, Li F, Wang H, Yin C, Huang J, Mahavadi S, Murthy KS, Hu W. Immune/Inflammatory Response and Hypocontractility of Rabbit Colonic Smooth Muscle After TNBS-Induced Colitis. Dig Dis Sci 2016; 61:1925-40. [PMID: 26879904 PMCID: PMC4920730 DOI: 10.1007/s10620-016-4078-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 02/03/2016] [Indexed: 12/13/2022]
Abstract
BACKGROUND The contractility of colonic smooth muscle is dysregulated due to immune/inflammatory responses in inflammatory bowel diseases. Inflammation in vitro induces up-regulation of regulator of G-protein signaling 4 (RGS4) expression in colonic smooth muscle cells. AIMS To characterize the immune/inflammatory responses and RGS4 expression pattern in colonic smooth muscle after induction of colitis. METHODS Colitis was induced in rabbits by intrarectal instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Innate/adaptive immune response RT-qPCR array was performed using colonic circular muscle strips. At 1-9 weeks after colonic intramuscular microinjection of lentivirus, the distal and proximal colons were collected, and muscle strips and dispersed muscle cells were prepared from circular muscle layer. Expression levels of RGS4 and NFκB signaling components were determined by Western blot analysis. The biological consequences of RGS4 knockdown were assessed by measurement of muscle contraction and phospholipase C (PLC)-β activity in response to acetylcholine (ACh). RESULTS Contraction in response to ACh was significantly inhibited in the inflamed colonic circular smooth muscle cells. RGS4, IL-1, IL-6, IL-8, CCL3, CD1D, and ITGB2 were significantly up-regulated, while IL-18, CXCR4, CD86, and C3 were significantly down-regulated in the inflamed muscle strips. RGS4 protein expression in the inflamed smooth muscles was dramatically increased. RGS4 stable knockdown in vivo augmented ACh-stimulated PLC-β activity and contraction in colonic smooth muscle cells. CONCLUSION Inflamed smooth muscle exhibits up-regulation of IL-1-related signaling components, Th1 cytokines and RGS4, and inhibition of contraction. Stable knockdown of endogenous RGS4 in colonic smooth muscle increases PLC-β activity and contractile responses.
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Affiliation(s)
- Yonggang Zhang
- Department of Neuroscience, Temple University School of Medicine, 3500 N Broad Street, Philadelphia, PA 19140, USA
| | - Fang Li
- Department of Neuroscience, Temple University School of Medicine, 3500 N Broad Street, Philadelphia, PA 19140, USA
| | - Hong Wang
- Department of Neuroscience, Temple University School of Medicine, 3500 N Broad Street, Philadelphia, PA 19140, USA
| | - Chaoran Yin
- Department of Neuroscience, Temple University School of Medicine, 3500 N Broad Street, Philadelphia, PA 19140, USA
| | - JieAn Huang
- Department of Gastroenterology, First Affiliated Hospital, Guangxi Medical University, No. 6 Shuangyong Rd, Nanning 530021, Guangxi, China
| | - Sunila Mahavadi
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, 1101 East Marshall Street, Richmond, VA 23298, USA
| | - Karnam S. Murthy
- Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, 1101 East Marshall Street, Richmond, VA 23298, USA
| | - Wenhui Hu
- Department of Neuroscience, Temple University School of Medicine, 3500 N Broad Street, Philadelphia, PA 19140, USA
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8
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Santhappan R, Crowder AT, Gouty S, Cox BM, Côté TE. Mu opioid receptor activation enhances regulator of G protein signaling 4 association with the mu opioid receptor/G protein complex in a GTP-dependent manner. J Neurochem 2015; 135:76-87. [PMID: 26119705 PMCID: PMC5034817 DOI: 10.1111/jnc.13222] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 06/19/2015] [Accepted: 06/25/2015] [Indexed: 11/26/2022]
Abstract
The interaction of Regulator of G protein Signaling 4 (RGS4) with the rat mu opioid receptor (MOR)/G protein complex was investigated. Solubilized MOR from rat brain membranes was immunoprecipitated in the presence of RGS4 with antibodies against the N-terminus of MOR (anti-MOR10-70 ). Activation of MOR with [D-Ala(2) , N-Me-Phe(4) , Gly(5) -ol] enkephalin (DAMGO) during immunoprecipitation caused a 150% increase in Goα and a 50% increase in RGS4 in the pellet. When 10 μM GTP was included with DAMGO, there was an additional 72% increase in RGS4 co-immunoprecipitating with MOR (p = 0.003). Guanosine 5'-O-(3-thiotriphosphate) (GTPγS) increased the amount of co-precipitating RGS4 by 93% (compared to DAMGO alone, p = 0.008), and the inclusion of GTPγS caused the ratio of MOR to RGS4 to be 1 : 1 (31 fmoles : 28 fmoles, respectively). GTPγS also increased the association of endogenous RGS4 with MOR. In His6 RGS4/Ni(2+) -NTA agarose pull down experiments, 0.3 μM GTPγS tripled the binding of Goα to His6 RGS4, whereas the addition of 100 μM GDP blocked this effect. Importantly, activation of solubilized MOR with DAMGO in the presence of 100 μM GDP and 0.3 μM GTPγS increased Goα binding to His6 RGS4/Ni(2+) -NTA agarose (p = 0.001). Regulators of G protein Signaling (RGS) shorten the time that G proteins are active. Activation of the mu opioid receptor (MOR) causes GTP to bind to and to activate Go (αoβγ). RGS4 then binds to the activated αo-GTP/MOR complex and accelerates the intrinsic GTPase of αo. After αo dissociates from MOR, RGS4 remains bound to the C-terminal region of MOR.
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Affiliation(s)
- Rema Santhappan
- Department of Pharmacology, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Alicia Tamara Crowder
- Department of Pharmacology, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.,Neuroscience Program, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Shawn Gouty
- Department of Pharmacology, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Brian M Cox
- Department of Pharmacology, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.,Neuroscience Program, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Thomas E Côté
- Department of Pharmacology, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.,Neuroscience Program, The Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
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9
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Li SJ, Li Y, Cui SC, Qi Y, Zhao JJ, Liu XY, Xu P, Chen XH. Splicing factor transformer-2β (Tra2β) regulates the expression of regulator of G protein signaling 4 (RGS4) gene and is induced by morphine. PLoS One 2013; 8:e72220. [PMID: 23977258 PMCID: PMC3747076 DOI: 10.1371/journal.pone.0072220] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 07/08/2013] [Indexed: 12/19/2022] Open
Abstract
Regulator of G protein signaling 4 (RGS4) is a critical modulator of G protein-coupled receptor (GPCR)-mediated signaling and plays important roles in many neural process and diseases. Particularly, drug-induced alteration in RGS4 protein levels is associated with acute and chronic effects of drugs of abuse. However, the precise mechanism underlying the regulation of RGS4 expression is largely unknown. Here, we demonstrated that the expression of RGS4 gene was subject to regulation by alternative splicing of the exon 6. Transformer-2β (Tra2β), an important splicing factor, bound to RGS4 mRNA and increased the relative level of RGS4-1 mRNA isoform by enhancing the inclusion of exon 6. Meanwhile, Tra2β increased the expression of full-length RGS4 protein. In rat brain, Tra2β was co-localized with RGS4 in multiple opioid action-related brain regions. In addition, the acute and chronic morphine treatment induced alteration in the expression level of Tra2β in rat locus coerulus (LC) in parallel to that of RGS4 proteins. It suggests that induction of this splicing factor may contribute to the change of RGS4 level elicited by morphine. Taken together, the results provide the evidence demonstrating the function of Tra2β as a new mediator in opioid-induced signaling pathway via regulating RGS4 expression.
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Affiliation(s)
- Shu-Jing Li
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
- Laboratory of Genomic Physiology and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
| | - Ya Li
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Shi-chao Cui
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Yao Qi
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Jing-Jing Zhao
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Xiao-Yan Liu
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Ping Xu
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
| | - Xian-Hua Chen
- State Key Laboratory of Medical Neurobiology and Department of Neurobiology,School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, China
- Laboratory of Genomic Physiology and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
- * E-mail:
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10
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Ruiz de Azua I, Nakajima KI, Rossi M, Cui Y, Jou W, Gavrilova O, Wess J. Spinophilin as a novel regulator of M3 muscarinic receptor-mediated insulin release in vitro and in vivo. FASEB J 2012; 26:4275-86. [PMID: 22730439 DOI: 10.1096/fj.12-204644] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Spinophilin (SPL), a multidomain scaffolding protein known to modulate the activity of different G-protein-coupled receptors, regulates various central nervous system (CNS) functions. However, little is known about the role of SPL expressed in peripheral cell types including pancreatic β cells. In this study, we examined the ability of SPL to modulate the activity of β-cell M(3) muscarinic acetylcholine receptors (M3Rs), which play an important role in facilitating insulin release and maintaining normal blood glucose levels. We demonstrated, by using both in vitro and in vivo approaches (mouse insulinoma cells and SPL-deficient mice), that SPL is a potent negative regulator of M3R-mediated signaling and insulin release. Additional biochemical and biophysical studies, including the use of bioluminescence resonance energy transfer technology, suggested that SPL is able to recruit regulator of G-protein signaling 4 (RGS4) to the M3R signaling complex in an agonist-dependent fashion. Since RGS4 is a member of the RGS family of proteins that act to reduce the lifetime of activated G proteins, these findings support the concept that the inhibitory effects of SPL on M3R activity are mediated by RGS4. These data suggest that SPL or other G-protein-coupled receptor-associated proteins may serve as novel targets for drug therapy aimed at improving β-cell function for the treatment of type 2 diabetes.
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Affiliation(s)
- Inigo Ruiz de Azua
- Molecular Signaling Section, Mouse Metabolic Core Facility, Laboratory of Bioorganic Chemistry, NIH-NIDDK, Bldg. 8A, Rm. B1A-05, 8 Center Dr. MSC 0810 Bethesda, MD 20892-0810, USA
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11
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Sjögren B, Parra S, Heath LJ, Atkins KB, Xie ZJ, Neubig RR. Cardiotonic steroids stabilize regulator of G protein signaling 2 protein levels. Mol Pharmacol 2012; 82:500-9. [PMID: 22695717 DOI: 10.1124/mol.112.079293] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Regulator of G protein signaling 2 (RGS2), a G(q)-specific GTPase-activating protein, is strongly implicated in cardiovascular function. RGS2(-/-) mice are hypertensive and prone to heart failure, and several rare human mutations that accelerate RGS2 degradation have been identified among patients with hypertension. Therefore, pharmacological up-regulation of RGS2 protein levels might be beneficial. We used a β-galactosidase complementation method to screen several thousand compounds with known pharmacological functions for those that increased RGS2 protein levels. Several cardiotonic steroids (CTSs), including ouabain and digoxin, increased RGS2 but not RGS4 protein levels. CTSs increased RGS2 protein levels through a post-transcriptional mechanism, by slowing protein degradation. RGS2 mRNA levels in primary vascular smooth muscle cells were unaffected by CTS treatment, whereas protein levels were increased 2- to 3-fold. Na(+)/K(+)-ATPase was required for the increase in RGS2 protein levels, because the effect was lost in Na(+)/K(+)-ATPase-knockdown cells. Furthermore, we demonstrated that CTS-induced increases in RGS2 levels were functional and reduced receptor-stimulated, G(q)-dependent, extracellular signal-regulated kinase phosphorylation. Finally, we showed that in vivo treatment with digoxin led to increased RGS2 protein levels in heart and kidney. CTS-induced increases in RGS2 protein levels and function might modify several deleterious mechanisms in hypertension and heart failure. This novel CTS mechanism might contribute to the beneficial actions of low-dose digoxin treatment in heart failure. Our results support the concept of small-molecule modulation of RGS2 protein levels as a new strategy for cardiovascular therapy.
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Affiliation(s)
- Benita Sjögren
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
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12
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Kach J, Sethakorn N, Dulin NO. A finer tuning of G-protein signaling through regulated control of RGS proteins. Am J Physiol Heart Circ Physiol 2012; 303:H19-35. [PMID: 22542620 DOI: 10.1152/ajpheart.00764.2011] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Regulators of G-protein signaling (RGS) proteins are GTPase-activating proteins (GAP) for various Gα subunits of heterotrimeric G proteins. Through this mechanism, RGS proteins regulate the magnitude and duration of G-protein-coupled receptor signaling and are often referred to as fine tuners of G-protein signaling. Increasing evidence suggests that RGS proteins themselves are regulated through multiple mechanisms, which may provide an even finer tuning of G-protein signaling and crosstalk between G-protein-coupled receptors and other signaling pathways. This review summarizes the current data on the control of RGS function through regulated expression, intracellular localization, and covalent modification of RGS proteins, as related to cell function and the pathogenesis of diseases.
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Affiliation(s)
- Jacob Kach
- Department of Medicine, University of Chicago, Illinois, 60637, USA
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13
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MEKK1-MKK4-JNK-AP1 pathway negatively regulates Rgs4 expression in colonic smooth muscle cells. PLoS One 2012; 7:e35646. [PMID: 22545125 PMCID: PMC3335800 DOI: 10.1371/journal.pone.0035646] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 03/19/2012] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Regulator of G-protein Signaling 4 (RGS4) plays an important role in regulating smooth muscle contraction, cardiac development, neural plasticity and psychiatric disorder. However, the underlying regulatory mechanisms remain elusive. Our recent studies have shown that upregulation of Rgs4 by interleukin (IL)-1β is mediated by the activation of NFκB signaling and modulated by extracellular signal-regulated kinases, p38 mitogen-activated protein kinase, and phosphoinositide-3 kinase. Here we investigate the effect of the c-Jun N-terminal kinase (JNK) pathway on Rgs4 expression in rabbit colonic smooth muscle cells. METHODOLOGY/PRINCIPAL FINDINGS Cultured cells at first passage were treated with or without IL-1β (10 ng/ml) in the presence or absence of the selective JNK inhibitor (SP600125) or JNK small hairpin RNA (shRNA). The expression levels of Rgs4 mRNA and protein were determined by real-time RT-PCR and Western blot respectively. SP600125 or JNK shRNA increased Rgs4 expression in the absence or presence of IL-1β stimulation. Overexpression of MEKK1, the key upstream kinase of JNK, inhibited Rgs4 expression, which was reversed by co-expression of JNK shRNA or dominant-negative mutants for MKK4 or JNK. Both constitutive and inducible upregulation of Rgs4 expression by SP600125 was significantly inhibited by pretreatment with the transcription inhibitor, actinomycin D. Dual reporter assay showed that pretreatment with SP600125 sensitized the promoter activity of Rgs4 in response to IL-1β. Mutation of the AP1-binding site within Rgs4 promoter increased the promoter activity. Western blot analysis confirmed that IL-1β treatment increased the phosphorylation of JNK, ATF-2 and c-Jun. Gel shift and chromatin immunoprecipitation assays validated that IL-1β increased the in vitro and ex vivo binding activities of AP1 within rabbit Rgs4 promoter. CONCLUSION/SIGNIFICANCE Activation of MEKK1-MKK4-JNK-AP1 signal pathway plays a tonic inhibitory role in regulating Rgs4 transcription in rabbit colonic smooth muscle cells. This negative regulation may aid in maintaining the transient level of RGS4 expression.
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14
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Davies JS, Klein DC, Carter DA. Selective genomic targeting by FRA-2/FOSL2 transcription factor: regulation of the Rgs4 gene is mediated by a variant activator protein 1 (AP-1) promoter sequence/CREB-binding protein (CBP) mechanism. J Biol Chem 2011; 286:15227-39. [PMID: 21367864 PMCID: PMC3083148 DOI: 10.1074/jbc.m110.201996] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 01/12/2011] [Indexed: 01/21/2023] Open
Abstract
FRA-2/FOSL2 is a basic region-leucine zipper motif transcription factor that is widely expressed in mammalian tissues. The functional repertoire of this factor is unclear, partly due to a lack of knowledge of genomic sequences that are targeted. Here, we identified novel, functional FRA-2 targets across the genome through expression profile analysis in a knockdown transgenic rat. In this model, a nocturnal rhythm of pineal gland FRA-2 is suppressed by a genetically encoded, dominant negative mutant protein. Bioinformatic analysis of validated sets of FRA-2-regulated and -nonregulated genes revealed that the FRA-2 regulon is limited by genomic target selection rules that, in general, transcend core cis-sequence identity. However, one variant AP-1-related (AP-1R) sequence was common to a subset of regulated genes. The functional activity and protein binding partners of a candidate AP-1R sequence were determined for a novel FRA-2-repressed gene, Rgs4. FRA-2 protein preferentially associated with a proximal Rgs4 AP-1R sequence as demonstrated by ex vivo ChIP and in vitro EMSA analysis; moreover, transcriptional repression was blocked by mutation of the AP-1R sequence, whereas mutation of an upstream consensus AP-1 family sequence did not affect Rgs4 expression. Nocturnal changes in protein complexes at the Rgs4 AP-1R sequence are associated with FRA-2-dependent dismissal of the co-activator, CBP; this provides a mechanistic basis for Rgs4 gene repression. These studies have also provided functional insight into selective genomic targeting by FRA-2, highlighting discordance between predicted and actual targets. Future studies should address FRA-2-Rgs4 interactions in other systems, including the brain, where FRA-2 function is poorly understood.
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Affiliation(s)
- Jeff S. Davies
- From the School of Biosciences, Cardiff University, Cardiff CF10 3AX, Wales, United Kingdom and
| | - David C. Klein
- the Section on Neuroendocrinology, Program on Developmental Endocrinology and Genetics, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - David A. Carter
- From the School of Biosciences, Cardiff University, Cardiff CF10 3AX, Wales, United Kingdom and
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15
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Wang Q, Traynor JR. Opioid-induced down-regulation of RGS4: role of ubiquitination and implications for receptor cross-talk. J Biol Chem 2011; 286:7854-7864. [PMID: 21209077 PMCID: PMC3048672 DOI: 10.1074/jbc.m110.160911] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 11/29/2010] [Indexed: 01/05/2023] Open
Abstract
Regulator of G protein signaling protein 4 (RGS4) acts as a GTPase accelerating protein to modulate μ- and δ- opioid receptor (MOR and DOR, respectively) signaling. In turn, exposure to MOR agonists leads to changes in RGS4 at the mRNA and/or protein level. Here we have used human neuroblastoma SH-SY5Y cells that endogenously express MOR, DOR, and RGS4 to study opioid-mediated down-regulation of RGS4. Overnight treatment of SH-SY5Y cells with the MOR agonist DAMGO or the DOR agonist DPDPE decreased RGS4 protein by ∼60% accompanied by a profound loss of opioid receptors but with no change in RGS4 mRNA. The decrease in RGS4 protein was prevented by the pretreatment with pertussis toxin or the opioid antagonist naloxone. The agonist-induced down-regulation of RGS4 proteins was completely blocked by treatment with the proteasome inhibitors MG132 or lactacystin or high concentrations of leupeptin, indicating involvement of ubiquitin-proteasome and lysosomal degradation. Polyubiquitinated RGS4 protein was observed in the presence of MG132 or the specific proteasome inhibitor lactacystin and promoted by opioid agonist. The loss of opioid receptors was not prevented by MG132, demonstrating a different degradation pathway. RGS4 is a GTPase accelerating protein for both Gα(i/o) and Gα(q) proteins. After overnight treatment with DAMGO to reduce RGS4 protein, signaling at the Gα(i/o)-coupled DOR and the Gα(q)-coupled M(3) muscarinic receptor (M(3)R) was increased but not signaling of the α(2) adrenergic receptor or bradykinin BK(2) receptor, suggesting the development of cross-talk between the DOR and M(3)R involving RGS4.
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MESH Headings
- Acetylcysteine/analogs & derivatives
- Acetylcysteine/pharmacology
- Analgesics, Opioid/pharmacology
- Cell Line, Tumor
- Cysteine Proteinase Inhibitors/pharmacology
- Down-Regulation/drug effects
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- HEK293 Cells
- Humans
- Leupeptins/pharmacology
- Naloxone/pharmacology
- Narcotic Antagonists/pharmacology
- Pertussis Toxin/pharmacology
- Proteasome Endopeptidase Complex/metabolism
- Proteasome Inhibitors
- RGS Proteins/biosynthesis
- Receptor, Muscarinic M3/metabolism
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Bradykinin/metabolism
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/metabolism
- Signal Transduction/drug effects
- Time Factors
- Ubiquitination/drug effects
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Affiliation(s)
- Qin Wang
- From the Department of Pharmacology and
| | - John R Traynor
- From the Department of Pharmacology and; Substance Abuse Research Center, University of Michigan, Ann Arbor, Michigan 48109.
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16
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Yang Z, Cooper PR, Damera G, Mukhopadhyay I, Cho H, Kehrl JH, Panettieri RA, Druey KM. Beta-agonist-associated reduction in RGS5 expression promotes airway smooth muscle hyper-responsiveness. J Biol Chem 2011; 286:11444-55. [PMID: 21278382 DOI: 10.1074/jbc.m110.212480] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Although short-acting and long-acting inhaled β(2)-adrenergic receptor agonists (SABA and LABA, respectively) relieve asthma symptoms, use of either agent alone without concomitant anti-inflammatory drugs (corticosteroids) may increase the risk of disease exacerbation in some patients. We found previously that pretreatment of human precision-cut lung slices (PCLS) with SABA impaired subsequent β(2)-agonist-induced bronchodilation, which occurred independently of changes in receptor quantities. Here we provide evidence that prolonged exposure of cultured human airway smooth muscle (HuASM) cells to β(2)-agonists directly augments procontractile signaling pathways elicited by several compounds including thrombin, bradykinin, and histamine. Such treatment did not increase surface receptor amounts or expression of G proteins and downstream effectors (phospholipase Cβ and myosin light chain). In contrast, β-agonists decreased expression of regulator of G protein signaling 5 (RGS5), which is an inhibitor of G-protein-coupled receptor (GPCR) activity. RGS5 knockdown in HuASM increased agonist-evoked intracellular calcium flux and myosin light chain (MLC) phosphorylation, which are prerequisites for contraction. PCLS from Rgs5(-/-) mice contracted more to carbachol than those from WT mice, indicating that RGS5 negatively regulates bronchial smooth muscle contraction. Repetitive β(2)-agonist use may not only lead to reduced bronchoprotection but also to sensitization of excitation-contraction signaling pathways as a result of reduced RGS5 expression.
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Affiliation(s)
- Zhao Yang
- Molecular Signal Transduction Section, Laboratory of Allergic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892, USA
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17
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Li J, Zhao H, Luo P, Gu Y. Functional cooperation of of IL-1β and RGS4 in the brachial plexus avulsion mediated brain reorganization. J Brachial Plex Peripher Nerve Inj 2010; 5:18. [PMID: 21138588 PMCID: PMC3017042 DOI: 10.1186/1749-7221-5-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 12/07/2010] [Indexed: 01/27/2023] Open
Abstract
BACKGROUNDS There is considerable evidence that central nervous system is continuously modulated by activity, behavior and skill acquisition. This study is to examine the reorganization in cortical and subcortical regions in response to brachial plexus avulsion. METHODS Adult C57BL/6 mice were divided into four groups: control, 1, 3 and 6 month of brachial plexus avulsion. IL-1β, IL-6 and RGS4 expression in cortex, brainstem and spinal cord were detected by BiostarM-140 s microarray and real-time PCR. RGS4 subcellular distribution and modulation were further analyzed by primary neuron culture and Western Blot. RESULTS After 1, 3 and 6 months of brachial plexus avulsion, 49 (0 up, 49 down), 29 (17 up, 12 down), 13 (9 up, 4 down) genes in cerebral cortex, 40 (8 up, 32 down), 11 (7 up, 4 down), 137 (63 up, 74 down) in brainstem, 27 (14 up, 13 down), 33 (18 up, 15 down), 60 (29 up, 31 down) in spinal cord were identified. Among the regulated gene, IL-1β and IL-6 were sustainable enhanced in brain stem, while PKACβ and RGS4 were up-regulated throughout cerebral cortex, brainstem and spinal cord in 3 and 6 month of nerve injury. Intriguingly, subcellular distribution of RGS4 in above three regions was dependent on the functional correlation of PKA and IL-1β. CONCLUSION Data herein indicated that brachial plexus avulsion could efficiently initiate and perpetuate the brain reorganization. Network involved IL-1β and RGS4 signaling might implicate in the re-establish and strengthening of the local circuits at the cortical and subcortical levels.
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Affiliation(s)
- Jifeng Li
- Lab of Hand function reconstruction, Huashan Hospital, Fudan University, Shanghai, China
| | - Hui Zhao
- Lab of Hand function reconstruction, Huashan Hospital, Fudan University, Shanghai, China
| | - Pengbo Luo
- Lab of Hand function reconstruction, Huashan Hospital, Fudan University, Shanghai, China
| | - Yudong Gu
- Lab of Hand function reconstruction, Huashan Hospital, Fudan University, Shanghai, China
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18
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Rivero G, Gabilondo AM, García-Sevilla JA, La Harpe R, Morentín B, Javier Meana J. Characterization of regulators of G-protein signaling RGS4 and RGS10 proteins in the postmortem human brain. Neurochem Int 2010; 57:722-9. [DOI: 10.1016/j.neuint.2010.08.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 07/29/2010] [Accepted: 08/11/2010] [Indexed: 10/19/2022]
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19
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Xie Z, Yang Z, Druey KM. Phosphorylation of RGS13 by the cyclic AMP-dependent protein kinase inhibits RGS13 degradation. J Mol Cell Biol 2010; 2:357-65. [PMID: 20974683 DOI: 10.1093/jmcb/mjq031] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Regulators of G-protein signaling (RGS) proteins are scaffolds that control diverse signaling pathways by modulating signalosome formation and by accelerating the GTPase activity of heterotrimeric G proteins. Although expression of many RGS proteins is relatively low in quiescent cells, transcriptional and post-translational responses to environmental cues regulate both their abundance and activity. We found previously that RGS13, one of the smallest RGS proteins in the family, inhibited cyclic AMP-dependent protein kinase (PKA)-induced gene expression through interactions with the transcription factor cAMP-response element-binding (CREB) protein. Here, we show that PKA activation also leads to increased steady-state RGS13 expression through RGS13 phosphorylation, which inhibits RGS13 protein degradation. RGS13 turnover was significantly reduced in cells stimulated with cAMP, which was reversed by expression of the PKA-specific inhibitory peptide PKI. RGS13 phosphorylation was diminished by mutation of an N-terminal Thr residue (T41) identified as a phosphorylation site by mass spectrometry. Mutation of Thr41 in RGS13 to Ala (T41A) reduced steady-state RGS13 levels and its ability to inhibit M2 muscarinic receptor-mediated Erk phosphorylation compared with wild-type RGS13 by attenuating the protective effect of cAMP on RGS13 degradation. RGS13 underwent ubiquitylation, indicating that it is a likely target of the proteasome. These studies are the first to demonstrate post-translational mechanisms controlling the expression of RGS13. Stabilization of RGS13 through PKA-mediated phosphorylation could enhance RGS13 functions, providing negative feedback regulation that promotes cellular desensitization.
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Affiliation(s)
- Zhihui Xie
- Molecular Signal Transduction Section, Laboratory of Allergic Diseases, NIAID/NIH, 10 Center Drive, Room 11N242, Bethesda, MD 20892, USA
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20
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Li F, Hu DY, Liu S, Mahavadi S, Yen W, Murthy KS, Khalili K, Hu W. RNA-binding protein HuR regulates RGS4 mRNA stability in rabbit colonic smooth muscle cells. Am J Physiol Cell Physiol 2010; 299:C1418-29. [PMID: 20881234 DOI: 10.1152/ajpcell.00093.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Regulator of G protein signaling 4 (RGS4) regulates the strength and duration of G protein signaling and plays an important role in smooth muscle contraction, cardiac development, and psychiatric disorders. Little is known about the posttranscriptional regulation of RGS4 expression. We cloned the full-length cDNA of rabbit RGS4, which contains a long 3'-untranslated region (UTR) with several AU-rich elements (AREs). We determined whether RGS4 mRNA stability is mediated by the RNA-binding protein human antigen R (HuR) and contributes to IL-1β-induced upregulation of RGS4 expression. We show that IL-1β treatment in colonic smooth muscle cells doubled the half-life of RGS4 mRNA. Addition of RGS4 3'-UTR to the downstream of Renilla luciferase reporter induced dramatic reduction in the enzyme activity and mRNA expression of luciferase, which was attenuated by the site-directed mutation of the two 3'-most ARE sites. IL-1β increased luciferase mRNA stability in a UTR-dependent manner. Knockdown of HuR significantly aggravated UTR-mediated instability of luciferase and inhibited IL-1β-induced upregulation of RGS4 mRNA. In addition, IL-1β increased cytosolic translocation and RGS4 mRNA binding of HuR. These findings suggest that 3'-most ARE sites within RGS4 3'-UTR are essential for the instability of RGS4 mRNA and IL-1β promotes the stability of RGS4 mRNA through HuR.
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Affiliation(s)
- Fang Li
- Department of Neuroscience, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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21
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Yang J, Huang J, Chatterjee TK, Twait E, Fisher RA. A novel mechanism involving coordinated regulation of nuclear levels and acetylation of NF-YA and Bcl6 activates RGS4 transcription. J Biol Chem 2010; 285:29760-9. [PMID: 20630860 PMCID: PMC2943308 DOI: 10.1074/jbc.m110.121459] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 07/13/2010] [Indexed: 11/06/2022] Open
Abstract
Neuronally enriched RGS4 plays a critical role attenuating G protein signaling in brain, although the mechanisms regulating RGS4 expression are unknown. Here we describe a novel mechanism for transcriptional activation of RGS4 in neuron-like PC6 cells, where RGS4 is markedly induced during confluence-induced growth arrest. Transcriptional activation of RGS4 in confluent PC6 cells was accompanied by impaired G(i/o)-dependent MAPK activation. In the human RGS4 gene promoter, we identified three phylogenetically conserved cis-elements: an inverted CCAAT box element (ICE), a cAMP response element, and a B-cell lymphoma 6 (Bcl6)-binding site. The ICE and the cAMP response element mediate activation, and the Bcl6 site mediates repression of RGS4 transcription. Activation of RGS4 transcription in confluent PC6 cells is accompanied by increases in NF-YA and C/EBPβ and decreases in Bcl6 levels in the nucleus. Increases in NF-YA and C/EBPβ lead to their increased binding to the RGS4 promoter in vivo, and dominant negative forms of these proteins repressed RGS4 promoter activity. Acetylation of NF-YA and Bcl6 were increased in postconfluent cells. Trichostatin A stimulation of RGS4 promoter activity, accompanied by increased binding of NF-YA and decreased binding of Bcl6 to the promoter, was abolished by mutation of the ICE and enhanced by mutation of the Bcl6 site. These findings demonstrate a dynamic and coordinated regulation of nuclear levels and acetylation status of trans-acting factors critical in determining the off/on state of the RGS4 promoter.
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Affiliation(s)
| | - Jie Huang
- From the Departments of Pharmacology and
| | - Tapan K. Chatterjee
- the Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio 45221
| | - Erik Twait
- Surgery, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242 and
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22
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Roman DL, Blazer LL, Monroy CA, Neubig RR. Allosteric inhibition of the regulator of G protein signaling-Galpha protein-protein interaction by CCG-4986. Mol Pharmacol 2010; 78:360-5. [PMID: 20530129 DOI: 10.1124/mol.109.063388] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulator of G protein signaling (RGS) proteins act to temporally modulate the activity of G protein subunits after G protein-coupled receptor activation. RGS proteins exert their effect by directly binding to the activated Galpha subunit of the G protein, catalyzing the accelerated hydrolysis of GTP and returning the G protein to its inactive, heterotrimeric form. In previous studies, we have sought to inhibit this GTPase-accelerating protein activity of the RGS protein by using small molecules. In this study, we investigated the mechanism of CCG-4986 [methyl-N-[(4-chlorophenyl)sulfonyl]-4-nitro-benzenesulfinimidoate], a previously reported small-molecule RGS inhibitor. Here, we find that CCG-4986 inhibits RGS4 function through the covalent modification of two spatially distinct cysteine residues on RGS4. We confirm that modification of Cys132, located near the RGS/Galpha interaction surface, modestly inhibits Galpha binding and GTPase acceleration. In addition, we report that modification of Cys148, a residue located on the opposite face of RGS4, can disrupt RGS/Galpha interaction through an allosteric mechanism that almost completely inhibits the Galpha-RGS protein-protein interaction. These findings demonstrate three important points: 1) the modification of the Cys148 allosteric site results in significant changes to the RGS interaction surface with Galpha; 2) this identifies a "hot spot" on RGS4 for binding of small molecules and triggering an allosteric change that may be significantly more effective than targeting the actual protein-protein interaction surface; and 3) because of the modification of a positional equivalent of Cys148 in RGS8 by CCG-4986, lack of inhibition indicates that RGS proteins exhibit fundamental differences in their responses to small-molecule ligands.
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Affiliation(s)
- David L Roman
- Division of Medicinal and Natural Products Chemistry, University of Iowa College of Pharmacy, Iowa City, Iowa 52242, USA.
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23
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RGS4 is a negative regulator of insulin release from pancreatic beta-cells in vitro and in vivo. Proc Natl Acad Sci U S A 2010; 107:7999-8004. [PMID: 20385802 DOI: 10.1073/pnas.1003655107] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Therapeutic strategies that augment insulin release from pancreatic beta-cells are considered beneficial in the treatment of type 2 diabetes. We previously demonstrated that activation of beta-cell M(3) muscarinic receptors (M3Rs) greatly promotes glucose-stimulated insulin secretion (GSIS), suggesting that strategies aimed at enhancing signaling through beta-cell M3Rs may become therapeutically useful. M3R activation leads to the stimulation of G proteins of the G(q) family, which are under the inhibitory control of proteins known as regulators of G protein signaling (RGS proteins). At present, it remains unknown whether RGS proteins play a role in regulating insulin release. To address this issue, we initially demonstrated that MIN6 insulinoma cells express functional M3Rs and that RGS4 was by far the most abundant RGS protein expressed by these cells. Strikingly, siRNA-mediated knockdown of RGS4 expression in MIN6 cells greatly enhanced M3R-mediated augmentation of GSIS and calcium release. We obtained similar findings using pancreatic islets prepared from RGS4-deficient mice. Interestingly, RGS4 deficiency had little effect on insulin release caused by activation of other beta-cell GPCRs. Finally, treatment of mutant mice selectively lacking RGS4 in pancreatic beta-cells with a muscarinic agonist (bethanechol) led to significantly increased plasma insulin and reduced blood glucose levels, as compared to control littermates. Studies with beta-cell-specific M3R knockout mice showed that these responses were mediated by beta-cell M3Rs. These findings indicate that RGS4 is a potent negative regulator of M3R function in pancreatic beta-cells, suggesting that RGS4 may represent a potential target to promote insulin release for therapeutic purposes.
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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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25
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Cloning and characterization of rabbit Rgs4 promoter in gut smooth muscle. Gene 2009; 451:45-53. [PMID: 19945517 DOI: 10.1016/j.gene.2009.11.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2009] [Revised: 11/19/2009] [Accepted: 11/19/2009] [Indexed: 11/23/2022]
Abstract
Regulator of G-protein signaling 4 (Rgs4) regulates the strength and duration of G-protein signaling, and plays an important role in cardiac development, smooth muscle contraction and psychiatric disorders. Rgs4 expression is regulated at both mRNA and protein levels. In order to examine the transcriptional mechanism of Rgs4 expression, we have cloned and characterized rabbit Rgs4 promoter. The coding sequence of rabbit Rgs4 was obtained by degenerative RT-PCR and used for Northern blot and 5'-RACE analysis. A single transcript was identified in rabbit colonic smooth muscle cells. The 5'-untranslated region (UTR) extended 120 bp nucleotides upstream of the Rgs4 start codon. A putative promoter sequence (1389 bp) showed a consensus TATA box and cis-acting binding sites for several potential transcriptional factors. Reporter gene assay identified strong promoter activity in various cell types. Further analysis by deletion mutagenesis suggested that the proximal region had a highest core promoter activity while the distal region is suppressive. IL-1beta significantly increased the promoter activity. The in vitro and in vivo binding activities for NF-kappaB transcription factor were validated by electrophoretic mobility shift assay and chromatin immunoprecipitation assay respectively. Mutation of NF-kappaB site reduced the promoter activity. These data suggest that the cloned rabbit Rgs4 promoter is functionally active and NF-kappaB binding site possesses enhancer activity in regulating Rgs4 transcription. Our studies provide an important basis for further understanding of Rgs4 regulation and function in different diseases.
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Terzi D, Stergiou E, King SL, Zachariou V. Regulators of G protein signaling in neuropsychiatric disorders. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:299-333. [PMID: 20374720 DOI: 10.1016/s1877-1173(09)86010-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Regulators of G protein signaling (RGS) comprise a diverse group of about 40 proteins which determine signaling amplitude and duration via modulation of receptor/G protein or receptor/effector coupling. Several members of the RGS family are expressed in the brain, where they have precise roles in regulation of important physiological processes. The unique functions of each RGS can be attributed to its structure, distinct pattern of expression, and regulation, and its preferential interactions with receptors, Galpha subunits and other signaling proteins. Evidence suggests dysfunction of RGS proteins is related to several neuropathological conditions. Moreover, clinical and preclinical work reveals that the efficacy and/or side effects of treatments are highly influenced by RGS activity. This article summarizes findings on RGS proteins in vulnerability to several neuropsychiatric disorders, the mechanism via which RGS proteins control neuronal responses and their potential use as drug targets.
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Affiliation(s)
- Dimitra Terzi
- Department of Pharmacology, Faculty of Medicine, University of Crete, Heraklion 71003, Crete, Greece
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27
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Slepak VZ. Structure, function, and localization of Gβ5-RGS complexes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:157-203. [PMID: 20374716 DOI: 10.1016/s1877-1173(09)86006-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Members of the R7 subfamily of regulator of G protein signaling (RGS) proteins (RGS6, 7, 9, and 11) exist as heterodimers with the G protein beta subunit Gβ5. These protein complexes are only found in neurons and are defined by the presence of three domains: DEP/DHEX, Gβ5/GGL, and RGS. This article summarizes published work in the following areas: (1) the functional significance of structural organization of Gβ5-R7 complexes, (2) regional distribution of Gβ5-R7 in the nervous system and regulation of R7 family expression, (3) subcellular localization of Gβ5-R7 complexes, and (4) novel binding partners of Gβ5-R7 proteins. The review points out some contradictions between observations made by different research groups and highlights the importance of using alternative experimental approaches to obtain conclusive information about Gβ5-R7 function in vivo.
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Affiliation(s)
- Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology and the Neuroscience Program, University of Miami School of Medicine, Miami, Florida 33136, USA
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Xie Y, Wolff DW, Wei T, Wang B, Deng C, Kirui JK, Jiang H, Qin J, Abel PW, Tu Y. Breast cancer migration and invasion depend on proteasome degradation of regulator of G-protein signaling 4. Cancer Res 2009; 69:5743-51. [PMID: 19549919 DOI: 10.1158/0008-5472.can-08-3564] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Aberrant signaling through G-protein coupled receptors promotes metastasis, the major cause of breast cancer death. We identified regulator of G-protein signaling 4 (RGS4) as a novel suppressor of breast cancer migration and invasion, important steps of metastatic cascades. By blocking signals initiated through G(i)-coupled receptors, such as protease-activated receptor 1 and CXC chemokine receptor 4, RGS4 disrupted Rac1-dependent lamellipodia formation, a key step involved in cancer migration and invasion. RGS4 has GTPase-activating protein (GAP) activity, which inhibits G-protein coupled receptor signaling by deactivating G-proteins. An RGS4 GAP-deficient mutant failed to inhibit migration and invasion of breast cancer cells in both in vitro assays and a mouse xenograft model. Interestingly, both established breast cancer cell lines and human breast cancer specimens showed that the highest levels of RGS4 protein were expressed in normal breast epithelia and that RGS4 down-regulation by proteasome degradation is an index of breast cancer invasiveness. Proteasome blockade increased endogenous RGS4 protein to levels that markedly inhibit breast cancer cell migration and invasion, which was reversed by an RGS4-targeted short hairpin RNA. Our findings point to the existence of a mechanism for posttranslational regulation of RGS4 function, which may have important implications for the acquisition of a metastatic phenotype by breast cancer cells. Preventing degradation of RGS4 protein should attenuate aberrant signal inputs from multiple G(i)-coupled receptors, thereby retarding the spread of breast cancer cells and making them targets for surgery, radiation, and immune treatment.
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Affiliation(s)
- Yan Xie
- Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
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Activation of the JAK-STAT pathway is necessary for desensitization of 5-HT2A receptor-stimulated phospholipase C signalling by olanzapine, clozapine and MDL 100907. Int J Neuropsychopharmacol 2009; 12:651-65. [PMID: 18976543 PMCID: PMC3733235 DOI: 10.1017/s1461145708009590] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We have previously demonstrated that olanzapine-induced desensitization of 5-HT2A receptor-stimulated phospholipase C (PLC) activity is associated with increases in RGS7 protein levels both in vivo and in cells in culture, and the increase in RGS7 is dependent on activation of the JAK-STAT pathway in cells in culture. In the present study, we found that desensitization of 5-HT2A receptor-stimulated PLC activity induced by olanzapine is dependent on activation of the JAK-STAT pathway. Similar to olanzapine, clozapine-induced desensitization of 5-HT2A receptor signalling is accompanied by increases in RGS7 and activation of JAK2. Treatment with the selective 5-HT2A receptor antagonist MDL 100907 also increased RGS7 protein levels and JAK2 activation. Using a JAK2 inhibitor AG490, we found that clozapine and MDL 100907-induced increases in RGS7 are dependent on activation of the JAK-STAT pathway. Olanzapine, clozapine, and MDL 100907 treatment increased mRNA levels of RGS7. Using a chromatin immunoprecipitation assay we found STAT3 binding to the putative RGS7 promoter region. Taken together, olanzapine-induced activation of the JAK-STAT pathway, and STAT3 binding to the RGS7 gene could underlie the increase in RGS7 mRNA which could subsequently increase protein expression. Furthermore, the increase in RGS7 protein could play a role in the desensitization of 5-HT2A receptor signalling by terminating the activated Galphaq/11 proteins more rapidly. Overall, our data suggest that the complete desensitization of 5-HT2A receptor-stimulated PLC activity by olanzapine, clozapine and MDL 100907 requires activation of the JAK-STAT pathway, which in turn increases RGS7 expression probably by direct transcriptional activity of STAT3.
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Wang Q, Liu-Chen LY, Traynor JR. Differential modulation of mu- and delta-opioid receptor agonists by endogenous RGS4 protein in SH-SY5Y cells. J Biol Chem 2009; 284:18357-67. [PMID: 19416973 DOI: 10.1074/jbc.m109.015453] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulator of G-protein signaling (RGS) proteins are a family of molecules that control the duration of G protein signaling. A variety of RGS proteins have been reported to modulate opioid receptor signaling. Here we show that RGS4 is abundantly expressed in human neuroblastoma SH-SY5Y cells that endogenously express mu- and delta-opioid receptors and test the hypothesis that the activity of opioids in these cells is modulated by RGS4. Endogenous RGS4 protein was reduced by approximately 90% in SH-SY5Y cells stably expressing short hairpin RNA specifically targeted to RGS4. In these cells, the potency and maximal effect of delta-opioid receptor agonist (SNC80)-mediated inhibition of forskolin-stimulated cAMP accumulation was increased compared with control cells. This effect was reversed by transient transfection of a stable RGS4 mutant (HA-RGS4C2S). Furthermore, MAPK activation by SNC80 was increased in cells with knockdown of RGS4. In contrast, there was no change in the mu-opioid (morphine) response at adenylyl cyclase or MAPK. FLAG-tagged opioid receptors and HA-RGS4C2S were transiently expressed in HEK293T cells, and co-immunoprecipitation experiments showed that the delta-opioid receptor but not the mu-opioid receptor could be precipitated together with the stable RGS4. Using chimeras of the delta- and mu-opioid receptors, the C-tail and third intracellular domain of the delta-opioid receptor were suggested to be the sites of interaction with RGS4. The findings demonstrate a role for endogenous RGS4 protein in modulating delta-opioid receptor signaling in SH-SY5Y cells and provide evidence for a receptor-specific effect of RGS4.
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Affiliation(s)
- Qin Wang
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
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31
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Paspalas CD, Selemon LD, Arnsten AFT. Mapping the regulator of G protein signaling 4 (RGS4): presynaptic and postsynaptic substrates for neuroregulation in prefrontal cortex. ACTA ACUST UNITED AC 2009; 19:2145-55. [PMID: 19153107 DOI: 10.1093/cercor/bhn235] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Regulator of G protein signaling 4 (RGS4) regulates intracellular signaling via G proteins and is markedly reduced in the prefrontal cortex (PFC) of patients with schizophrenia. Characterizing the expression of RGS4 within individual neuronal compartments is thus key to understanding its actions on individual G protein-coupled receptors (GPCRs). Here we present an ultrastructural reference map of RGS4 protein in macaque PFC based on immunogold electron microscopic analysis. At the soma, all labeling was asynaptic and affiliated with subsurface cistern microdomains of pyramidal neurons. The nucleus displayed most of immunoreactivity. RGS4 levels were particularly high along proximal apical dendrites and markedly decreased with distance from the soma; clustered label was present at the bifurcation into second-order branches. In distal dendrites and in spines, the protein was found flanking or directly facing the postsynaptic density of symmetric and asymmetric synapses. Axons also expressed RGS4. In fact, the density and distribution of pre- and postsynaptic labeling was correlated with the axon ultrastructure and the type of established synapses. The data indicate that RGS4 is strategically positioned to regulate not only postsynaptic but also presynaptic signaling in response to synaptic and nonsynaptic GPCR activation, having broad yet highly selective influences on multiple aspects of PFC cellular physiology.
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Kuntz-Melcavage KL, Freeman WM, Vrana KE. CNS genes implicated in relapse. SUBSTANCE ABUSE-RESEARCH AND TREATMENT 2008; 2:1-12. [PMID: 25922574 PMCID: PMC4395042 DOI: 10.4137/sart.s1042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Drug abuse is a condition that impacts not only the individual drug user, but society as a whole. Although prevention of initial drug use is the most effective way to prevent addiction, avoiding relapse is a crucial component of drug addiction recovery. Recent studies suggest that there is a set of genes whose expression is robustly and stably altered following drug use and ensuing abstinence. Such stable changes in gene expression correlate with ultrastructural changes in brain as well as alterations in behavior. As persistent molecular changes, these genes may provide targets for the development of therapeutics. Developing a list of well-characterized candidate genes and examining the effect of manipulating these genes will contribute to the ultimate goal of developing effective treatments to prevent relapse to drug use.
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Affiliation(s)
- Kara L Kuntz-Melcavage
- Department of Pharmacology, Pennsylvania State University College of Medicine, R130, 500 University Drive, Hershey, PA 17033, U.S.A
| | - Willard M Freeman
- Department of Pharmacology, Pennsylvania State University College of Medicine, R130, 500 University Drive, Hershey, PA 17033, U.S.A
| | - Kent E Vrana
- Department of Pharmacology, Pennsylvania State University College of Medicine, R130, 500 University Drive, Hershey, PA 17033, U.S.A
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Roof RA, Sobczyk-Kojiro K, Turbiak AJ, Roman DL, Pogozheva ID, Blazer LL, Neubig RR, Mosberg HI. Novel peptide ligands of RGS4 from a focused one-bead, one-compound library. Chem Biol Drug Des 2008; 72:111-9. [PMID: 18637987 DOI: 10.1111/j.1747-0285.2008.00687.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Regulators of G protein signaling accelerate GTP hydrolysis by G alpha subunits and profoundly inhibit signaling by G protein-coupled receptors. The distinct expression patterns and pathophysiologic regulation of regulators of G protein signaling proteins suggest that inhibitors may have therapeutic potential. We previously reported the design, mechanistic evaluation, and structure-activity relationships of a disulfide-containing cyclic peptide inhibitor of RGS4, YJ34 (Ac-Val-Lys-c[Cys-Thr-Gly-Ile-Cys]-Glu-NH(2), S-S) (Roof et al., Chem Biol Drug Des, 67, 2006, 266). Using a focused one-bead, one-compound peptide library that contains features known to be necessary for the activity of YJ34, we now identify peptides that bind to RGS4. Six peptides showed confirmed binding to RGS4 by flow cytometry. Two analogs of peptide 2 (Gly-Thr-c[Cys-Phe-Gly-Thr-Cys]-Trp-NH(2), S-S with a free or acetylated N-terminus) inhibited RGS4-stimulated G alpha(o) GTPase activity at 25-50 microM. They selectively inhibit RGS4 but not RGS7, RGS16, and RGS19. Their inhibition of RGS4 does not depend on cysteine-modification of RGS4, as they do not lose activity when all cysteines are removed from RGS4. Peptide 2 has been modeled to fit in the same binding pocket predicted for YJ34 but in the reverse orientation.
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Affiliation(s)
- Rebecca A Roof
- Department of Pharmacology, University of Michigan, 1301 MSRB III/SPC5632, Ann Arbor, MI 48103, USA
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Jedema HP, Gold SJ, Gonzalez-Burgos G, Sved AF, Tobe BJ, Wensel T, Grace AA. Chronic cold exposure increases RGS7 expression and decreases alpha(2)-autoreceptor-mediated inhibition of noradrenergic locus coeruleus neurons. Eur J Neurosci 2008; 27:2433-43. [PMID: 18461718 DOI: 10.1111/j.1460-9568.2008.06208.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Chronic stress exposure alters the central noradrenergic neurons originating from the locus coeruleus (LC). Previously, we demonstrated that evoked increases in the firing rate of LC neurons and their release of norepinephrine are enhanced following chronic cold exposure. In the present studies, we tested the hypothesis that reduced feedback inhibition of LC neurons might underlie these alterations in LC activity by examining the effect of alpha(2)-autoreceptor stimulation on LC activity in chronically stressed rats using in vivo and in vitro single unit recordings. Given that regulators of G-protein signaling (RGS) proteins can impact the coupling of alpha(2)-autoreceptors to downstream signaling cascades, we also explored the expression of several RGS proteins following chronic stress exposure. We observed that the alpha(2)-autoreceptor-evoked inhibition of LC neurons was reduced and that the expression of RGS7 was increased following chronic stress exposure. Finally, we demonstrated that intracellular administration of RGS7 via patch clamp electrodes mimicked the stress-induced decrease in clonidine-evoked autoreceptor-mediated inhibition. These novel data provide a mechanism to explain how chronic stress-induced alterations in receptor coupling can result in changes in alpha(2)-autoreceptor control of noradrenergic function throughout the central nervous system, potentially leading to alterations in anxiety-related behaviors, and may suggest novel therapeutic targets for the treatment of mood and anxiety disorders.
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Affiliation(s)
- Hank P Jedema
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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Interleukin-1beta up-regulates RGS4 through the canonical IKK2/IkappaBalpha/NF-kappaB pathway in rabbit colonic smooth muscle. Biochem J 2008; 412:35-43. [PMID: 18260825 DOI: 10.1042/bj20080042] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Initial Ca2+-dependent contraction of the intestinal smooth muscle mediated by G(q)-coupled receptors is attenuated by RGS4 (regulator of G-protein signalling 4). Treatment of colonic muscle cells with IL-1beta (interleukin-1beta) inhibits acetylcholine-stimulated initial contraction through increasing the expression of RGS4. NF-kappaB (nuclear factor kappaB) signalling is the dominant pathway activated by IL-1beta. In the present study we show that RGS4 is a new target gene regulated by IL-1beta/NF-kappaB signalling. Exposure of cultured rabbit colonic muscle cells to IL-1beta induced a rapid increase in RGS4 mRNA expression, which was abolished by pretreatment with a transcription inhibitor, actinomycin D, implying a transcription-dependent mechanism. Existence of the canonical IKK2 [IkappaB (inhibitor of NF-kappaB) kinase 2]/IkappaBalpha pathway of NF-kappaB activation induced by IL-1beta in rabbit colonic muscle cells was validated with multiple approaches, including the induction of reporter luciferase activity and endogenous NF-kappaB-target gene expression, NF-kappaB-DNA binding activity, p65 nuclear translocation, IkappaBalpha degradation and the phosphorylation of IKK2 at Ser(177/181) and p65 at Ser(536). RGS4 up-regulation by IL-1beta was blocked by selective inhibitors of IKK2, IkappaBalpha or NF-kappaB activation, by effective siRNA (small interfering RNA) of IKK2, and in cells expressing either the kinase-inactive IKK2 mutant (K44A) or the phosphorylation-deficient IkappaBalpha mutant (S32A/S36A). An IKK2-specific inhibitor or effective siRNA prevented IL-1beta-induced inhibition of acetylcholine-stimulated PLC-beta (phopsholipase C-beta) activation. These results suggest that the canonical IKK2/IkappaBalpha pathway of NF-kappaB activation mediates the up-regulation of RGS4 expression in response to IL-1beta and contributes to the inhibitory effect of IL-1beta on acetylcholine-stimulated PLC-beta-dependent initial contraction in rabbit colonic smooth muscle.
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Gold SJ, Hoang CV, Potts BW, Porras G, Pioli E, Kim KW, Nadjar A, Qin C, LaHoste GJ, Li Q, Bioulac BH, Waugh JL, Gurevich E, Neve RL, Bezard E. RGS9-2 negatively modulates L-3,4-dihydroxyphenylalanine-induced dyskinesia in experimental Parkinson's disease. J Neurosci 2007; 27:14338-48. [PMID: 18160641 PMCID: PMC6673430 DOI: 10.1523/jneurosci.4223-07.2007] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Accepted: 11/11/2007] [Indexed: 11/21/2022] Open
Abstract
Chronic L-dopa treatment of Parkinson's disease (PD) often leads to debilitating involuntary movements, termed L-dopa-induced dyskinesia (LID), mediated by dopamine (DA) receptors. RGS9-2 is a GTPase accelerating protein that inhibits DA D2 receptor-activated G proteins. Herein, we assess the functional role of RGS9-2 on LID. In monkeys, Western blot analysis of striatal extracts shows that RGS9-2 levels are not altered by MPTP-induced DA denervation and/or chronic L-dopa administration. In MPTP monkeys with LID, striatal RGS9-2 overexpression--achieved by viral vector injection into the striatum--diminishes the involuntary movement intensity without lessening the anti-parkinsonian effects of the D1/D2 receptor agonist L-dopa. In contrasts, in these animals, striatal RGS9-2 overexpression diminishes both the involuntary movement intensity and the anti-parkinsonian effects of the D2/D3 receptor agonist ropinirole. In unilaterally 6-OHDA-lesioned rats with LID, we show that the time course of viral vector-mediated striatal RGS9-2 overexpression parallels the time course of improvement of L-dopa-induced involuntary movements. We also find that unilateral 6-OHDA-lesioned RGS9-/- mice are more susceptible to L-dopa-induced involuntary movements than unilateral 6-OHDA-lesioned RGS9+/+ mice, albeit the rotational behavior--taken as an index of the anti-parkinsonian response--is similar between the two groups of mice. Together, these findings suggest that RGS9-2 plays a pivotal role in LID pathophysiology. However, the findings also suggest that increasing RGS9-2 expression and/or function in PD patients may only be a suitable therapeutic strategy to control involuntary movements induced by nonselective DA agonist such as L-dopa.
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Affiliation(s)
- Stephen J. Gold
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Chau V. Hoang
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Bryan W. Potts
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Gregory Porras
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Universite Victor Segalen-Bordeaux 2, 33076 Bordeaux, France
| | - Elsa Pioli
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Universite Victor Segalen-Bordeaux 2, 33076 Bordeaux, France
| | - Ki Woo Kim
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Agnes Nadjar
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Universite Victor Segalen-Bordeaux 2, 33076 Bordeaux, France
| | - Chuan Qin
- Institute of Lab Animal Sciences, Chinese Academy of Medical Sciences, 100021 Beijing, China
| | - Gerald J. LaHoste
- Department of Psychology, University of New Orleans, New Orleans, Louisiana 70148
| | - Qin Li
- Institute of Lab Animal Sciences, Chinese Academy of Medical Sciences, 100021 Beijing, China
| | - Bernard H. Bioulac
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Universite Victor Segalen-Bordeaux 2, 33076 Bordeaux, France
| | - Jeffrey L. Waugh
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Eugenia Gurevich
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, and
| | - Rachael L. Neve
- Department of Genetics, Harvard Medical School, Belmont, Massachusetts 02478
| | - Erwan Bezard
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Universite Victor Segalen-Bordeaux 2, 33076 Bordeaux, France
- Institute of Lab Animal Sciences, Chinese Academy of Medical Sciences, 100021 Beijing, China
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Hu W, Mahavadi S, Li F, Murthy KS. Upregulation of RGS4 and downregulation of CPI-17 mediate inhibition of colonic muscle contraction by interleukin-1beta. Am J Physiol Cell Physiol 2007; 293:C1991-2000. [PMID: 17959727 PMCID: PMC4123227 DOI: 10.1152/ajpcell.00300.2007] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The pro-inflammatory cytokine IL-1beta contributes to the reduced contractile responses of gut smooth muscle observed in both animal colitis models and human inflammatory bowel diseases. However, the mechanisms are not well understood. The effects of IL-1beta on the signaling targets mediating acetylcholine (ACh)-induced initial and sustained contraction were examined using rabbit colonic circular muscle strips and cultured muscle cells. The contraction was assessed through cell length decrease, myosin light chain (MLC(20)) phosphorylation, and activation of PLC-beta and Rho kinase. Expression levels of the signaling targets were determined by Western blot analysis and real-time RT-PCR. Short interfering RNAs (siRNAs) for regulator of G protein signaling 4 (RGS4) were used to silence endogenous RGS4 in muscle strips or cultured muscle cells. IL-1beta treatment of muscle strips inhibited both initial and sustained contraction and MLC(20) phosphorylation in isolated muscle cells. IL-1beta treatment increased RGS4 expression but had no effect on muscarinic receptor binding or Galpha(q) expression. In contrast, IL-1beta decreased the expression and phosphorylation of CPI-17 but had no effect on RhoA expression or ACh-induced Rho kinase activity. Upregulation of RGS4 and downregulation of CPI-17 by IL-1beta in muscle strips were corroborated in cultured muscle cells. Knockdown of RGS4 by siRNA in both muscle strips and cultured muscle cells blocked the inhibitory effect of IL-1beta on initial contraction and PLC-beta activation, whereas overexpression of RGS4 inhibited PLC-beta activation. These data suggest that IL-1beta upregulates RGS4 expression, resulting in the inhibition of initial contraction and downregulation of CPI-17 expression during sustained contraction in colonic smooth muscle.
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Affiliation(s)
- Wenhui Hu
- Department of Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA.
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Muma NA, Singh RK, Vercillo MS, D'Souza DN, Zemaitaitis B, Garcia F, Damjanoska KJ, Zhang Y, Battaglia G, Van de Kar LD. Chronic olanzapine activates the Stat3 signal transduction pathway and alters expression of components of the 5-HT2A receptor signaling system in rat frontal cortex. Neuropharmacology 2007; 53:552-62. [PMID: 17675105 PMCID: PMC2075101 DOI: 10.1016/j.neuropharm.2007.06.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 06/12/2007] [Accepted: 06/20/2007] [Indexed: 12/19/2022]
Abstract
The mechanisms underlying desensitization of serotonin 2A (5-HT(2A)) receptor signaling by antagonists are unclear but may involve changes in gene expression mediated via signal transduction pathways. In cells in culture, olanzapine causes desensitization of 5-HT(2A) receptor signaling and increases the levels of regulators of G protein signaling (RGS) 7 protein dependent on phosphorylation/activation of the Janus kinase 2 (Jak2)/signal transducers and activators of transcription 3 (Stat3) signaling pathway. In the current study, the 5-HT(2A) receptor signaling system in rat frontal cortex was examined following 7 days of daily treatment with 0.5, 2.0 or 10.0 mg/kg i.p. olanzapine. Olanzapine increased phosphorylation of Stat3 in rats treated daily with 10 mg/kg olanzapine and caused a dose-dependent desensitization of 5-HT(2A) receptor-mediated phospholipase C activity. There were dose-dependent increases in the levels of membrane-associated 5-HT(2A) receptor, G(alpha11) and G(alphaq) protein levels but no changes in the G(beta) protein levels. With olanzapine treatment, RGS4 protein levels increase in the membrane-fraction and decrease in the cytosolic fraction by similar amounts suggesting a redistribution of RGS4 protein within neurons. RGS7 protein levels increase in both the membrane and cytosolic fractions in rats treated daily with 10mg/kg olanzapine. The olanzapine-induced increase in Stat3 activity could underlie the increase in RGS7 protein expression in vivo as previously demonstrated in cultured cells. Furthermore, the increases in membrane-associated RGS proteins could play a role in desensitization of signaling by terminating the activated G(alphaq/11) proteins more rapidly.
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Affiliation(s)
- N A Muma
- Department of Pharmacology, Loyola University Medical Center, Maywood, IL 60153, USA.
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Schwendt M, McGinty JF. Regulator of G-Protein Signaling 4 Interacts with Metabotropic Glutamate Receptor Subtype 5 in Rat Striatum: Relevance to Amphetamine Behavioral Sensitization. J Pharmacol Exp Ther 2007; 323:650-7. [PMID: 17693584 DOI: 10.1124/jpet.107.128561] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulator of G-protein signaling (RGS) 4 negatively modulates signaling of several Galpha(q)-coupled receptors, including metabotropic glutamate receptor (mGluR) subtype 5 in neuronal and non-neuronal cell lines. In the brain, both RGS4 and mGluR5 receptors are enriched in the striatum, and their functions have been linked to psychostimulant-induced behavior and synaptic plasticity. However, it is not known whether RGS4 and mGluR5 interactions occur in rat striatum and whether chronic amphetamine (AMPH) treatment produces changes in RGS4 levels that are correlated with mGluR5 receptor activity. Using coimmunoprecipitation, the present study demonstrated that endogenous RGS4 binds mGluR5 receptors as well as key mGluR5-associated proteins, Galpha(q/11), and phospholipase C-beta1 (PLCbeta1) in preparations from rat striatum. In the next experiment, rats were treated with AMPH (5 mg/kg i.p. daily) for 5 days followed by 3 weeks of abstinence. At this time point, animals pretreated with AMPH displayed sensitized behavioral responses to AMPH challenge and decreased RGS4 protein in dorsal striatum and nucleus accumbens. Behavioral sensitization to AMPH was also accompanied by an increase in Galpha(q/11) and PLCbeta1 in dorsal striatum. In contrast, total levels of mGluR5 receptors in the striatum were not altered by any AMPH treatment. In conclusion, the present study demonstrates that RGS4 protein is an integral part of the mGluR5 protein complex in the striatum. This study further suggests that AMPH-induced changes in mGluR5-associated protein levels (RGS4, Galpha(q/11), and PLCbeta1) may be related to altered coupling of striatal mGluR5 receptors in animals sensitized to AMPH.
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Affiliation(s)
- Marek Schwendt
- Department of Neurosciences, Medical University of South Carolina, 173 Ashley Ave., BSB 403, Charleston, SC 29425, USA.
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40
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Singh RK, Shi J, Zemaitaitis BW, Muma NA. Olanzapine increases RGS7 protein expression via stimulation of the Janus tyrosine kinase-signal transducer and activator of transcription signaling cascade. J Pharmacol Exp Ther 2007; 322:133-40. [PMID: 17392403 DOI: 10.1124/jpet.107.120386] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Atypical antipsychotics such as olanzapine have high affinity for multiple monoamine neurotransmitter receptors and are the mainstay of pharmacological therapy for treatment of schizophrenia. In addition to blocking monoamine receptors, these drugs also affect intracellular signaling cascades. We now report that 24-h treatment with 300 nM olanzapine causes desensitization of serotonin (5-HT)(2A) receptors in A1A1v cells, a rat cortical cell line, as indicated by a reduction in inositol phosphate accumulation following stimulation with a 5-HT(2A/2C) receptor agonist (-)-1-(2,5-dimethoxy-4-lodophenyl)-2-aminopropane HCl. Olanzapine treatment for 24 h increased the levels of 5-HT(2A) receptors in both cytosol (234 +/- 34% of control level) and membrane fractions (206 +/- 14% of control levels) and RGS7 proteins in both cytosol (193 +/- 32% of control levels) and membrane fractions (160 +/- 18% of control levels) as measured on Western blots. Increased phosphorylation of Janus tyrosine kinase (JAK) 2 and increased phosphorylation and nuclear translocation of signal transducer and activator of transcription (STAT) 3 with 24-h olanzapine treatment demonstrate activation of the JAK-STAT signaling cascade. Pretreatment with a JAK inhibitor, AG490 [alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide], prevented the olanzapine-induced increase in membrane RGS7 protein levels; AG490 alone had no effect on RGS7 protein levels. We verified that treatment with AG490 reduced phosphorylation of JAK2 and inhibited the nuclear localization of phospho-STAT3. Interestingly, treatment with the JAK inhibitor had no effect on 5-HT(2A) receptor protein levels. These data suggest that olanzapine-induced activation of the JAK-STAT signaling cascade causes increased expression of RGS7 protein, which in turn could mediate desensitization of 5-HT(2A) receptor signaling caused by olanzapine because RGS7 binds to Galpha(q) protein and accelerates GTP hydrolysis.
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Affiliation(s)
- Rakesh K Singh
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois, USA
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Gu Z, Jiang Q, Yan Z. RGS4 Modulates Serotonin Signaling in Prefrontal Cortex and Links to Serotonin Dysfunction in a Rat Model of Schizophrenia. Mol Pharmacol 2007; 71:1030-9. [PMID: 17220354 DOI: 10.1124/mol.106.032490] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulator of G protein signaling 4 (RGS4) has recently been identified as one of the genes linked to the susceptibility of schizophrenia. However, the functional roles of RGS4 and how it may be involved in the pathophysiology of schizophrenia remain largely unknown. In this study, we investigated the possible impact of RGS4 on the function of serotonin and dopamine receptors, two main targets for schizophrenia treatment. Activation of serotonin 5-HT(1A) receptors or dopamine D(4) receptors down-regulates the function of NMDA receptor (NMDAR) channel, a key player controlling cognition and emotion, in pyramidal neurons of prefrontal cortex (PFC). Blocking RGS4 function significantly potentiated the 5-HT(1A) regulation of NMDAR current; conversely, overexpression of RGS4 attenuated the 5-HT(1A) effect. In contrast, the D(4) regulation of NMDAR current was not altered by RGS4 manipulation. Moreover, the 5-HT(1A) regulation of NMDA receptors was significantly enhanced in a subset of PFC pyramidal neurons from rats treated with subchronic phencyclidine, an animal model of schizophrenia, which was found to be associated with specifically decreased RGS4 expression in these cells. Thus, our study has revealed an important coupling of RGS4 to serotonin signaling in cortical neurons and provided a molecular and cellular mechanism underlying the potential involvement of RGS4 in the pathophysiology of schizophrenia.
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Affiliation(s)
- Zhenglin Gu
- Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 124 Sherman Hall, Buffalo NY 14214.
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42
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Bodenstein J, Sunahara RK, Neubig RR. N-terminal residues control proteasomal degradation of RGS2, RGS4, and RGS5 in human embryonic kidney 293 cells. Mol Pharmacol 2007; 71:1040-50. [PMID: 17220356 DOI: 10.1124/mol.106.029397] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulator of G protein signaling (RGS) proteins modulate G protein-coupled receptor (GPCR) signaling. The N termini of some RGS4-family proteins provide receptor specificity and also contain an N-end rule determinant that results in ubiquitylation and decreased protein expression. The relevance of these mechanisms to other RGS proteins is not fully understood. Thus we examined function, receptor specificity, and expression of R4 subfamily RGS proteins (RGS2, -3, -4, -5, and -8). Although the N terminus plays a key role in protein stability in human embryonic kidney (HEK) 293 cells, we were unable to demonstrate specificity of RGS2, -3, -4, -5, or -8 for muscarinic receptors (M(1), M(3), and M(5)). However, cellular RGS activity (8 = 3 > 2) was strongly correlated with expression; RGS4 and -5 had minimal expression and activity. Stabilizing mutations of RGS4 and -5 (C2S) enhanced expression and function with a greater influence on RGS4 than on RGS5. We were surprised to find that a predicted destabilizing mutation in RGS8 (A2C) did not markedly affect expression and had no effect on function. In contrast, a destabilizing mutation in RGS2 (RGS2-Q2L) recently identified as a rare N-terminal genetic variant in a Japanese hypertensive cohort (J Hypertens 23:1497-1505, 2005) showed significantly reduced expression and inhibition of angiotensin II (AT(1)) receptor-stimulated accumulation of inositol phosphates. We were surprised to find that RGS2-Q2R, also predicted to be destabilizing, showed nearly normal expression and function. Thus, proteasomal regulation of RGS expression in HEK293 cells strongly controls RGS function and a novel RGS2 mutation with decreased protein expression could be relevant to the pathophysiology of hypertension in humans.
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Affiliation(s)
- Johannes Bodenstein
- Department of Pharmacology, 1301 MSRB III/Box 0632, 1150 W. Medical Center Drive, University of Michigan Medical School, Ann Arbor, MI 48109-0632, USA
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Huang J, Pashkov V, Kurrasch DM, Yu K, Gold SJ, Wilkie TM. Feeding and fasting controls liver expression of a regulator of G protein signaling (Rgs16) in periportal hepatocytes. COMPARATIVE HEPATOLOGY 2006; 5:8. [PMID: 17123436 PMCID: PMC1687201 DOI: 10.1186/1476-5926-5-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2006] [Accepted: 11/23/2006] [Indexed: 11/10/2022]
Abstract
BACKGROUND Heterotrimeric G protein signaling in liver helps maintain carbohydrate and lipid homeostasis. G protein signaling is activated by binding of extracellular ligands to G protein coupled receptors and inhibited inside cells by regulators of G protein signaling (RGS) proteins. RGS proteins are GTPase activating proteins, and thereby regulate Gi and/or Gq class G proteins. RGS gene expression can be induced by the ligands they feedback regulate, and RGS gene expression can be used to mark tissues and cell-types when and where Gi/q signaling occurs. We characterized the expression of mouse RGS genes in liver during fasting and refeeding to identify novel signaling pathways controlling changes in liver metabolism. RESULTS Rgs16 is the only RGS gene that is diurnally regulated in liver of ad libitum fed mice. Rgs16 transcription, mRNA and protein are up regulated during fasting and rapidly down regulated after refeeding. Rgs16 is expressed in periportal hepatocytes, the oxygen-rich zone of the liver where lipolysis and gluconeogenesis predominates. Restricting feeding to 4 hr of the light phase entrained Rgs16 expression in liver but did not affect circadian regulation of Rgs16 expression in the suprachiasmatic nuclei (SCN). CONCLUSION Rgs16 is one of a subset of genes that is circadian regulated both in SCN and liver. Rgs16 mRNA expression in liver responds rapidly to changes in feeding schedule, coincident with key transcription factors controlling the circadian clock. Rgs16 expression can be used as a marker to identify and investigate novel G-protein mediated metabolic and circadian pathways, in specific zones within the liver.
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Affiliation(s)
- Jie Huang
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Dr., Dallas TX 75390-9041, USA
| | - Victor Pashkov
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Dr., Dallas TX 75390-9041, USA
| | - Deborah M Kurrasch
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Dr., Dallas TX 75390-9041, USA
- Department of Physiology, University of California, San Francisco 94143-2611, USA
| | - Kan Yu
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Dr., Dallas TX 75390-9041, USA
- Department of Neurology, University of Mississippi Medical Center, Jackson MS 39216, USA
| | - Stephen J Gold
- Department of Psychiatry, UT Southwestern Medical Center, 6001 Forest Park Dr., Dallas TX 75390-9070, USA
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., Ft. Worth TX 76107, USA
| | - Thomas M Wilkie
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Dr., Dallas TX 75390-9041, USA
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Jaén C, Doupnik CA. RGS3 and RGS4 Differentially Associate with G Protein-coupled Receptor-Kir3 Channel Signaling Complexes Revealing Two Modes of RGS Modulation. J Biol Chem 2006; 281:34549-60. [PMID: 16973624 DOI: 10.1074/jbc.m603177200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RGS3 and RGS4 are GTPase-activating proteins expressed in the brain and heart that accelerate the termination of G(i/o)- and G(q)-mediated signaling. We report here the determinants mediating selective association of RGS4 with several G protein-coupled receptors (GPCRs) that form macromolecular complexes with neuronal G protein-gated inwardly rectifying potassium (Kir3 or GIRK) channels. Kir3 channels are instrumental in regulating neuronal firing in the central and peripheral nervous system and pacemaker activity in the heart. By using an epitope-tagged degradation-resistant RGS4 mutant, RGS4(C2V), immunoprecipitation of several hemagglutinin-tagged G(i/o)-coupled and G(q)-coupled receptors expressed in Chinese hamster ovary (CHO-K1) cells readily co-precipitated both Kir3.1/Kir3.2a channels and RGS4(C2V). In contrast to RGS4(C2V), the closely related and functionally active RGS3 "short" isoform (RGS3s) did not interact with any of the GPCR-Kir3 channel complexes examined. Deletion and chimeric RGS constructs indicate both the N-terminal domain and the RGS domain of RGS4(C2V) are necessary for association with m2 receptor-Kir3.1/Kir3.2a channel complexes, where the GPCR was found to be the major target for RGS4(C2V) interaction. The functional impact of RGS4(C2V) "precoupling" to the GPCR-Kir3 channel complex versus RGS3s "collision coupling" was a 100-fold greater potency in the acceleration of G protein-dependent Kir3 channel-gating kinetics with no attenuation in current amplitude. These findings demonstrate that RGS4, a highly regulated modulator and susceptibility gene for schizophrenia, can directly associate with multiple GPCR-Kir3 channel complexes and may affect a wide range of neurotransmitter-mediated inhibitory and excitatory events in the nervous and cardiovascular systems.
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MESH Headings
- Amino Acid Sequence
- Animals
- CHO Cells
- Cells, Cultured
- Cricetinae
- Electrophoretic Mobility Shift Assay
- G Protein-Coupled Inwardly-Rectifying Potassium Channels/genetics
- G Protein-Coupled Inwardly-Rectifying Potassium Channels/metabolism
- GTP-Binding Protein alpha Subunit, Gi2/genetics
- GTP-Binding Protein alpha Subunit, Gi2/metabolism
- GTP-Binding Proteins/genetics
- GTP-Binding Proteins/metabolism
- GTPase-Activating Proteins/genetics
- GTPase-Activating Proteins/metabolism
- Gene Expression Regulation
- Hemagglutinins/genetics
- Hemagglutinins/metabolism
- Humans
- Immunoblotting
- Immunoprecipitation
- Ion Channel Gating
- Kinetics
- Mice
- Molecular Sequence Data
- Oocytes/metabolism
- RGS Proteins/genetics
- RGS Proteins/metabolism
- Receptor, Muscarinic M2/genetics
- Receptor, Muscarinic M2/metabolism
- Receptor, Serotonin, 5-HT1A/genetics
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptors, Lysophosphatidic Acid/genetics
- Receptors, Lysophosphatidic Acid/metabolism
- Sequence Deletion
- Sequence Homology, Amino Acid
- Serotonin/pharmacology
- Signal Transduction
- Transfection
- Xenopus laevis/metabolism
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Affiliation(s)
- Cristina Jaén
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida 33612, USA
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45
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Roman DL, Talbot JN, Roof RA, Sunahara RK, Traynor JR, Neubig RR. Identification of small-molecule inhibitors of RGS4 using a high-throughput flow cytometry protein interaction assay. Mol Pharmacol 2006; 71:169-75. [PMID: 17012620 DOI: 10.1124/mol.106.028670] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Regulators of G-protein signaling (RGS) proteins are important components of signal transduction pathways initiated through G-protein-coupled receptors (GPCRs). RGS proteins accelerate the intrinsic GTPase activity of G-protein alpha-subunits (Galpha) and thus shorten the time course and reduce the magnitude of G-protein alpha- and betagamma-subunit signaling. Inhibiting RGS action has been proposed as a means to enhance the activity and specificity of GPCR agonist drugs, but pharmacological targeting of protein-protein interactions has typically been difficult. The aim of this project was to identify inhibitors of RGS4. Using a Luminex 96-well plate bead analyzer and a novel flow-cytometric protein interaction assay to assess Galpha-RGS interactions in a high-throughput screen, we identified the first small-molecule inhibitor of an RGS protein. Of 3028 compounds screened, 1, methyl N-[(4-chlorophenyl)sulfonyl]-4-nitrobenzenesulfinimidoate (CCG-4986), inhibited RGS4/Galpha(o) binding with 3 to 5 muM potency. It binds to RGS4, inhibits RGS4 stimulation of Galpha(o) GTPase activity in vitro, and prevents RGS4 regulation of mu-opioid-inhibited adenylyl cyclase activity in permeabilized cells. Furthermore, CCG-4986 is selective for RGS4 and does not inhibit RGS8. Thus, we demonstrate the feasibility of targeting RGS/Galpha protein-protein interactions with small molecules as a novel means to modulate GPCR-mediated signaling processes.
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Affiliation(s)
- David L Roman
- Department of Pharmacology, University of Michigan Medical School, 1150 W. Medical Center Drive, 1303 MSRB III, Ann Arbor, MI 41809, USA
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46
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Lipska BK, Mitkus S, Caruso M, Hyde TM, Chen J, Vakkalanka R, Straub RE, Weinberger DR, Kleinman JE. RGS4 mRNA expression in postmortem human cortex is associated with COMT Val158Met genotype and COMT enzyme activity. Hum Mol Genet 2006; 15:2804-12. [PMID: 16905560 DOI: 10.1093/hmg/ddl222] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Linkage, association and postmortem studies have implicated regulator of G-protein signaling 4 (RGS4), which negatively modulates signal transduction at G-protein-coupled receptors, as a candidate schizophrenia susceptibility gene. We compared RGS4 mRNA expression in the dorsolateral prefrontal cortex (DLPFC), between normal controls and patients with schizophrenia in two independent cohorts (>100 subjects each) (the CBDB/NIMH Collection and the Stanley Array Collection), and in the hippocampus in the CBDB/NIMH Collection. We also examined the effects of the four previously identified putative RGS4 risk SNPs (rs10917670, rs951436, rs951439, rs2661319) on RGS4 expression levels in these cohorts. As dopamine signaling is linked to RGS4 expression and there is evidence for statistical epistasis between COMT Val158Met polymorphism and RGS4 alleles, we also examined relationships between the COMT Val158Met genotype and RGS4 expression in the DLPFC. We did not detect a difference in RGS4 expression levels between schizophrenic patients (or bipolar disorder patients in the Stanley Collection) and controls and found no significant association between any of the RGS4 risk SNPs and RGS4 expression. However, COMT Val158Met genotype was associated with prefrontal and hippocampal RGS4 mRNA expression in an allele dose-dependent manner, with carriers of the COMT Val allele showing significantly lower expression than heterozygous individuals or subjects homozygous for the Met allele. Consistent with these genotype effects, RGS4 mRNA was inversely correlated with the COMT enzyme activity in the DLPFC. These data suggest that RGS4 mRNA expression is associated with cortical dopamine signaling and illustrate the importance of genetic and/or environmental background in gene expression studies in schizophrenia.
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Affiliation(s)
- Barbara K Lipska
- Clinical Brain Disorders Branch, Genes, Cognition and Psychosis Program, National Institute for Mental Health, NIH, DHHS, Bethesda, MD 20892-1385, USA.
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Roof RA, Jin Y, Roman DL, Sunahara RK, Ishii M, Mosberg HI, Neubig RR. Mechanism of action and structural requirements of constrained peptide inhibitors of RGS proteins. Chem Biol Drug Des 2006; 67:266-74. [PMID: 16629824 DOI: 10.1111/j.1747-0285.2006.00373.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Regulators of G-protein signaling (RGS) accelerate guanine triphosphate hydrolysis by Galpha-subunits and profoundly inhibit signaling by G protein-coupled receptors. The distinct expression patterns and pathophysiologic regulation of RGS proteins suggest that inhibitors may have therapeutic potential. We previously reported the design of a constrained peptide inhibitor of RGS4 (1: Ac-Val-Lys-[Cys-Thr-Gly-Ile-Cys]-Glu-NH2, S-S) based on the structure of the Galphai switch 1 region but its mechanism of action was not established. In the present study, we show that 1 inhibits RGS4 by mimicking and competing for binding with the switch 1 region of Galphai and that peptide 1 shows selectivity for RGS4 and RGS8 versus RGS7. Structure-activity relationships of analogs related to 1 are described that illustrate key features for RGS inhibition. Finally, we demonstrate activity of the methylene dithioether-bridged peptide inhibitor, 2, to modulate muscarinic receptor-regulated potassium currents in atrial myocytes. These data support the proposed mechanism of action of peptide RGS inhibitors, demonstrate their action in native cells, and provide a starting point for the design of RGS inhibitor drugs.
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Affiliation(s)
- Rebecca A Roof
- Department of Pharmacology, 1150 W. Medical Center Dr, University of Michigan, Ann Arbor, MI 48109, USA
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48
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Abstract
There is accumulating evidence that regulators of G-protein signalling (RGS) can have roles in signal transduction that are not related to GAP activity. Furthermore, RGSs have much more selective effects in vivo than might be anticipated from their behaviour in in vitro assays. I discuss the molecular mechanisms by which these phenomena might be explained including specific interactions between the RGS and G-protein coupled receptor, G-protein and effector.
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Affiliation(s)
- Andrew Tinker
- BHF Laboratories and Department of Medicine, University College London, 5 University Street, London WC1E 6JJ, UK.
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49
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Fu Y, Huang X, Zhong H, Mortensen RM, D'Alecy LG, Neubig RR. Endogenous RGS Proteins and Gα Subtypes Differentially Control Muscarinic and Adenosine-Mediated Chronotropic Effects. Circ Res 2006; 98:659-66. [PMID: 16456099 DOI: 10.1161/01.res.0000207497.50477.60] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiac automaticity is controlled by G protein-coupled receptors, such as adrenergic, muscarinic, and adenosine receptors. The strength and duration of G protein signaling is attenuated by regulator of G protein signaling (RGS) proteins acting as GTPase-activating proteins for Galpha subunits; however, little is known about the role of endogenous RGS proteins in cardiac function. We created point mutations in Galpha subunits that disrupt Galpha-RGS binding and introduced them into embryonic stem (ES) cells by homologous recombination. Spontaneously contacting cardiocytes derived from the ES cells were used to evaluate the role of endogenous RGS proteins in chronotropic regulation. The RGS-insensitive GalphaoG184S homozygous knock-in (GalphaoGS/GS) cells demonstrated enhanced adenosine A1 and muscarinic M2 receptor-mediated bradycardic responses. In contrast, Galphai2GS/GS cells showed enhanced responses to M2 but not A1 receptors. Similarly M2 but not A1 bradycardic responses were dramatically enhanced in Galphai2GS/GS mice. Blocking G protein-coupled inward rectifying K+ (GIRK) channels largely abolished the mutation-induced enhancement of the M2 receptor-mediated response but had a minimal effect on A1 responses. The Galphas-dependent stimulation of beating rate by the beta2 adrenergic receptor agonist procaterol was significantly attenuated in GalphaoGS/GS and nearly abolished in Galphai2GS/GS cells because of enhanced signaling via a pertussis toxin sensitive mechanism. Thus, endogenous RGS proteins potently reduce the actions of Galpha(i/o)-linked receptors on cardiac automaticity. Furthermore, M2 and A1 receptors differentially use Galphai2 and Galphao and associated downstream effectors. Thus, alterations in RGS function may play a role in pathophysiological processes and RGS proteins could represent novel cardiovascular therapeutic targets.
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Affiliation(s)
- Ying Fu
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
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Schwendt M, Gold SJ, McGinty JF. Acute amphetamine down-regulates RGS4 mRNA and protein expression in rat forebrain: distinct roles of D1and D2dopamine receptors. J Neurochem 2006; 96:1606-15. [PMID: 16539683 DOI: 10.1111/j.1471-4159.2006.03669.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Administration of psychostimulants modulates mRNA of several regulators of guanine nucleotide-binding protein signaling (RGSs) proteins in the brain. In the present study, the regulation of amphetamine-induced decrease of RGS4 expression in the rat forebrain was evaluated. RGS4 mRNA was reduced by amphetamine in an inverse, dose-dependent manner. The lowest dose (2.5 mg/kg) decreased RGS4 mRNA in caudate putamen for up to 6 h after injection whereas the decrease in several frontal cortical areas was detected at 3 h only. Analysis of RGS4 immunoreactivity by western blotting revealed a decrease 3 h after amphetamine solely in the caudate putamen. Systemic administration of D(1) (SCH23390) or D(2) (eticlopride) receptor antagonists blocked amphetamine-induced locomotion but amphetamine augmented both the SCH23390-induced increase and the eticlopride-induced decrease in RGS4 mRNA in the caudate putamen. Further, the down-regulation of RGS4 immunoreactivity by eticlopride was robust whereas the effect of SCH23390 was blunted as compared with its effect on mRNA. These data suggest that, by decreasing RGS4 expression in the caudate putamen via D(1) receptors, acute amphetamine could disinhibit RGS4-sensitive guanine nucleotide-binding protein alpha-subunit i- and/or q-coupled signaling pathways and favor mechanisms that counterbalance D(1) receptor stimulation.
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MESH Headings
- Amphetamine/pharmacology
- Amphetamine-Related Disorders/genetics
- Amphetamine-Related Disorders/metabolism
- Amphetamine-Related Disorders/physiopathology
- Animals
- Benzazepines/pharmacology
- Cerebral Cortex/drug effects
- Cerebral Cortex/metabolism
- Disease Models, Animal
- Dopamine/metabolism
- Dopamine Antagonists/pharmacology
- Dose-Response Relationship, Drug
- Down-Regulation/drug effects
- Down-Regulation/physiology
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- Male
- Neostriatum/drug effects
- Neostriatum/metabolism
- Prosencephalon/drug effects
- Prosencephalon/metabolism
- Prosencephalon/physiopathology
- RGS Proteins/drug effects
- RGS Proteins/genetics
- RGS Proteins/metabolism
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Dopamine/drug effects
- Receptors, Dopamine/metabolism
- Receptors, Dopamine D1/drug effects
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D2/drug effects
- Receptors, Dopamine D2/metabolism
- Salicylamides/pharmacology
- Signal Transduction/drug effects
- Signal Transduction/physiology
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Affiliation(s)
- Marek Schwendt
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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