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Zhang J, Pandey M, Awe A, Lue N, Kittock C, Fikse E, Degner K, Staples J, Mokhasi N, Chen W, Yang Y, Adikaram P, Jacob N, Greenfest-Allen E, Thomas R, Bomeny L, Zhang Y, Petros TJ, Wang X, Li Y, Simonds WF. The association of GNB5 with Alzheimer disease revealed by genomic analysis restricted to variants impacting gene function. Am J Hum Genet 2024; 111:473-486. [PMID: 38354736 PMCID: PMC10940018 DOI: 10.1016/j.ajhg.2024.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 02/16/2024] Open
Abstract
Disease-associated variants identified from genome-wide association studies (GWASs) frequently map to non-coding areas of the genome such as introns and intergenic regions. An exclusive reliance on gene-agnostic methods of genomic investigation could limit the identification of relevant genes associated with polygenic diseases such as Alzheimer disease (AD). To overcome such potential restriction, we developed a gene-constrained analytical method that considers only moderate- and high-risk variants that affect gene coding sequences. We report here the application of this approach to publicly available datasets containing 181,388 individuals without and with AD and the resulting identification of 660 genes potentially linked to the higher AD prevalence among Africans/African Americans. By integration with transcriptome analysis of 23 brain regions from 2,728 AD case-control samples, we concentrated on nine genes that potentially enhance the risk of AD: AACS, GNB5, GNS, HIPK3, MED13, SHC2, SLC22A5, VPS35, and ZNF398. GNB5, the fifth member of the heterotrimeric G protein beta family encoding Gβ5, is primarily expressed in neurons and is essential for normal neuronal development in mouse brain. Homozygous or compound heterozygous loss of function of GNB5 in humans has previously been associated with a syndrome of developmental delay, cognitive impairment, and cardiac arrhythmia. In validation experiments, we confirmed that Gnb5 heterozygosity enhanced the formation of both amyloid plaques and neurofibrillary tangles in the brains of AD model mice. These results suggest that gene-constrained analysis can complement the power of GWASs in the identification of AD-associated genes and may be more broadly applicable to other polygenic diseases.
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Affiliation(s)
- Jianhua Zhang
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Mritunjay Pandey
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Adam Awe
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nicole Lue
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Claire Kittock
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Emma Fikse
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Katherine Degner
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jenna Staples
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Neha Mokhasi
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Weiping Chen
- Genomic Core, National Institute of Diabetes and Digestive and Kidney Diseases, Bldg. 8/Rm 1A11, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yanqin Yang
- Laboratory of Transplantation Genomics, National Heart Lung and Blood Institute, Bldg. 10/Rm 7S261, National Institutes of Health, Bethesda, MD 20892, USA
| | - Poorni Adikaram
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nirmal Jacob
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Emily Greenfest-Allen
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Rachel Thomas
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Laura Bomeny
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yajun Zhang
- Unit on Cellular and Molecular Neurodevelopment, Bldg. 35/Rm 3B 1002, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Timothy J Petros
- Unit on Cellular and Molecular Neurodevelopment, Bldg. 35/Rm 3B 1002, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Xiaowen Wang
- Partek Incorporated, 12747 Olive Boulevard, St. Louis, MO 63141, USA
| | - Yulong Li
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA
| | - William F Simonds
- Metabolic Diseases Branch, Bldg. 10/Rm 8C-101, National Institutes of Health, Bethesda, MD 20892, USA.
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Haley TL, Hecht RM, Ren G, Carroll JR, Aicher SA, Duvoisin RM, Morgans CW. Light-dependent changes in the outer plexiform layer of the mouse retina. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1226224. [PMID: 38983050 PMCID: PMC11182082 DOI: 10.3389/fopht.2023.1226224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Accepted: 08/17/2023] [Indexed: 07/11/2024]
Abstract
The ability of the visual system to relay meaningful information over a wide range of lighting conditions is critical to functional vision, and relies on mechanisms of adaptation within the retina that adjust sensitivity and gain as ambient light changes. Photoreceptor synapses represent the first stage of image processing in the visual system, thus activity-driven changes at this site are a potentially powerful, yet under-studied means of adaptation. To gain insight into these mechanisms, the abundance and distribution of key synaptic proteins involved in photoreceptor to ON-bipolar cell transmission were compared between light-adapted mice and mice subjected to prolonged dark exposure (72 hours), by immunofluorescence confocal microscopy and immunoblotting. We also tested the effects on protein abundance and distribution of 0.5-4 hours of light exposure following prolonged darkness. Proteins examined included the synaptic ribbon protein, ribeye, and components of the ON-bipolar cell signal transduction pathway (mGluR6, TRPM1, RGS11, GPR179, Goα). The results indicate a reduction in immunoreactivity for ribeye, TRPM1, mGluR6, and RGS11 following prolonged dark exposure compared to the light-adapted state, but a rapid restoration of the light-adapted pattern upon light exposure. Electron microscopy revealed similar ultrastructure of light-adapted and dark-adapted photoreceptor terminals, with the exception of electron dense vesicles in dark-adapted but not light-adapted ON-bipolar cell dendrites. To assess synaptic transmission from photoreceptors to ON-bipolar cells, we recorded electroretinograms after different dark exposure times (2, 16, 24, 48, 72 hours) and measured the b-wave to a-wave ratios. Consistent with the reduction in synaptic proteins, the b/a ratios were smaller following prolonged dark exposure (48-72 hours) compared to 16 hours dark exposure (13-21%, depending on flash intensity). Overall, the results provide evidence of light/dark-dependent plasticity in photoreceptor synapses at the biochemical, morphological, and physiological levels.
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Affiliation(s)
| | | | | | | | | | | | - Catherine W. Morgans
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR, United States
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Basak M, Das K, Mahata T, Kumar D, Nagar N, Poluri KM, Kumar P, Das P, Stewart A, Maity B. RGS7 balances acetylation/de-acetylation of p65 to control chemotherapy-dependent cardiac inflammation. Cell Mol Life Sci 2023; 80:255. [PMID: 37589751 PMCID: PMC11071981 DOI: 10.1007/s00018-023-04895-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 06/28/2023] [Accepted: 07/22/2023] [Indexed: 08/18/2023]
Abstract
Cardiotoxicity remains a major limitation in the clinical utility of anthracycline chemotherapeutics. Regulator of G-protein Signaling 7 (RGS7) and inflammatory markers are up-regulated in the hearts of patients with a history of chemotherapy particularly those with reduced left-ventricular function. RGS7 knockdown in either the murine myocardium or isolated murine ventricular cardiac myocytes (VCM) or cultured human VCM provided marked protection against doxorubicin-dependent oxidative stress, NF-κB activation, inflammatory cytokine production, and cell death. In exploring possible mechanisms causally linking RGS7 to pro-inflammatory signaling cascades, we found that RGS7 forms a complex with acetylase Tip60 and deacetylase sirtuin 1 (SIRT1) and controls the acetylation status of the p65 subunit of NF-κB. In VCM, the detrimental impact of RGS7 could be mitigated by inhibiting Tip60 or activating SIRT1, indicating that the ability of RGS7 to modulate cellular acetylation capacity is critical for its pro-inflammatory actions. Further, RGS7-driven, Tip60/SIRT1-dependent cytokines released from ventricular cardiac myocytes and transplanted onto cardiac fibroblasts increased oxidative stress, markers of transdifferentiation, and activity of extracellular matrix remodelers emphasizing the importance of the RGS7-Tip60-SIRT1 complex in paracrine signaling in the myocardium. Importantly, while RGS7 overexpression in heart resulted in sterile inflammation, fibrotic remodeling, and compromised left-ventricular function, activation of SIRT1 counteracted the detrimental impact of RGS7 in heart confirming that RGS7 increases acetylation of SIRT1 substrates and thereby drives cardiac dysfunction. Together, our data identify RGS7 as an amplifier of inflammatory signaling in heart and possible therapeutic target in chemotherapeutic drug-induced cardiotoxicity.
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Affiliation(s)
- Madhuri Basak
- Centre of Biomedical Research (CBMR), SGPGI, SGPGI Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Kiran Das
- Centre of Biomedical Research (CBMR), SGPGI, SGPGI Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Tarun Mahata
- Centre of Biomedical Research (CBMR), SGPGI, SGPGI Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Dinesh Kumar
- Centre of Biomedical Research (CBMR), SGPGI, SGPGI Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Nupur Nagar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, 247667, India
| | - Krishna Mohan Poluri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, 247667, India
| | - Pranesh Kumar
- Institute of Pharmaceutical Sciences, University of Lucknow, Lucknow, Uttar Pradesh, 226025, India
| | - Priyadip Das
- Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur, Chennai, Tamilnadu, 603203, India
| | - Adele Stewart
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, FL, 33458, USA.
| | - Biswanath Maity
- Centre of Biomedical Research (CBMR), SGPGI, SGPGI Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India.
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DeBaker MC, Mitten EH, Rose TR, Marron Fernandez de Velasco E, Gao R, Lee AM, Wickman K. RGS6 negatively regulates inhibitory G protein signaling in dopamine neurons and positively regulates binge-like alcohol consumption in mice. Br J Pharmacol 2023; 180:2140-2155. [PMID: 36929333 PMCID: PMC10504421 DOI: 10.1111/bph.16071] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 02/02/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023] Open
Abstract
BACKGROUND AND PURPOSE Drugs of abuse, including alcohol, increase dopamine in the mesocorticolimbic system via actions on dopamine neurons in the ventral tegmental area (VTA). Increased dopamine transmission can activate inhibitory G protein signalling pathways in VTA dopamine neurons, including those controlled by GABAB and D2 receptors. Members of the R7 subfamily of regulator of G protein signalling (RGS) proteins can regulate inhibitory G protein signalling, but their influence on VTA dopamine neurons is unclear. Here, we investigated the influence of RGS6, an R7 RGS family memberthat has been implicated in the regulation of alcohol consumption in mice, on inhibitory G protein signalling in VTA dopamine neurons. EXPERIMENTAL APPROACH We used molecular, electrophysiological and genetic approaches to probe the impact of RGS6 on inhibitory G protein signalling in VTA dopamine neurons and on binge-like alcohol consumption in mice. KEY RESULTS RGS6 is expressed in adult mouse VTA dopamine neurons and it modulates inhibitory G protein signalling in a receptor-dependent manner, tempering D2 receptor-induced somatodendritic currents and accelerating deactivation of synaptically evoked GABAB receptor-dependent responses. RGS6-/- mice exhibit diminished binge-like alcohol consumption, a phenotype replicated in female (but not male) mice lacking RGS6 selectively in VTA dopamine neurons. CONCLUSIONS AND IMPLICATIONS RGS6 negatively regulates GABAB - and D2 receptor-dependent inhibitory G protein signalling pathways in mouse VTA dopamine neurons and exerts a sex-dependent positive influence on binge-like alcohol consumption in adult mice. As such, RGS6 may represent a new diagnostic and/or therapeutic target for alcohol use disorder.
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Affiliation(s)
- Margot C. DeBaker
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN
| | - Eric H. Mitten
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN
| | - Timothy R. Rose
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
| | | | - Runbo Gao
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
| | - Anna M. Lee
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN
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Das K, Basak M, Mahata T, Biswas S, Mukherjee S, Kumar P, Moniruzzaman M, Stewart A, Maity B. Cardiac RGS7 and RGS11 drive TGFβ1-dependent liver damage following chemotherapy exposure. FASEB J 2023; 37:e23064. [PMID: 37440271 DOI: 10.1096/fj.202300094r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 06/03/2023] [Accepted: 06/15/2023] [Indexed: 07/14/2023]
Abstract
Off target damage to vital organ systems is an unfortunate side effect of cancer chemotherapy and remains a major limitation to the use of these essential drugs in the clinic. Despite decades of research, the mechanisms conferring susceptibility to chemotherapy driven cardiotoxicity and hepatotoxicity remain unclear. In the livers of patients with a history of chemotherapy, we observed a twofold increase in expression of G protein regulator RGS7 and a corresponding decrease in fellow R7 family member RGS11. Knockdown of RGS7 via introduction of RGS7 shRNA via tail vein injection decreased doxorubicin-induced hepatic collagen and lipid deposition, glycogen accumulation, and elevations in ALT, AST, and triglycerides by approximately 50%. Surprisingly, a similar result could be achieved via introduction of RGS7 shRNA directly to the myocardium without impacting RGS7 levels in the liver directly. Indeed, doxorubicin-treated cardiomyocytes secrete the endocrine factors transforming growth factor β1 (TGFβ1) and TGFβ superfamily binding protein follistatin-related protein 1 (FSTL1). Importantly, RGS7 overexpression in the heart was sufficient to recapitulate the impacts of doxorubicin on the liver and inhibition of TGFβ1 signaling with the receptor blocker GW788388 ameliorated the effect of cardiac RGS7 overexpression on hepatic fibrosis, steatosis, oxidative stress, and cell death as well as the resultant elevation in liver enzymes. Together these data demonstrate that RGS7 controls both the release of TGFβ1 from the heart and the profibrotic and pro-oxidant actions of TGFβ1 in the liver and emphasize the functional significance of endocrine cardiokine signaling in the pathogenesis of chemotherapy drive multiorgan damage.
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Affiliation(s)
- Kiran Das
- Centre of Biomedical Research (CBMR), Lucknow, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Madhuri Basak
- Centre of Biomedical Research (CBMR), Lucknow, India
| | - Tarun Mahata
- Centre of Biomedical Research (CBMR), Lucknow, India
| | - Sayan Biswas
- Forensic Medicine, College of Medicine and Sagore Dutta Hospital, Kolkata, India
| | | | - Pranesh Kumar
- Institute of Pharmaceutical Sciences, University of Lucknow, Lucknow, India
| | | | - Adele Stewart
- Department of Biomedical Science, Florida Atlantic University, Jupiter, Florida, USA
| | - Biswanath Maity
- Centre of Biomedical Research (CBMR), Lucknow, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
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Pandey M, Zhang JH, Adikaram PR, Kittock C, Lue N, Awe A, Degner K, Jacob N, Staples J, Thomas R, Kohnen AB, Ganesan S, Kabat J, Chen CK, Simonds WF. Specific regulation of mechanical nociception by Gβ5 involves GABA-B receptors. JCI Insight 2023; 8:e134685. [PMID: 37219953 PMCID: PMC10371342 DOI: 10.1172/jci.insight.134685] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 05/19/2023] [Indexed: 05/24/2023] Open
Abstract
Mechanical, thermal, and chemical pain sensation is conveyed by primary nociceptors, a subset of sensory afferent neurons. The intracellular regulation of the primary nociceptive signal is an area of active study. We report here the discovery of a Gβ5-dependent regulatory pathway within mechanical nociceptors that restrains antinociceptive input from metabotropic GABA-B receptors. In mice with conditional knockout (cKO) of the gene that encodes Gβ5 (Gnb5) targeted to peripheral sensory neurons, we demonstrate the impairment of mechanical, thermal, and chemical nociception. We further report the specific loss of mechanical nociception in Rgs7-Cre+/- Gnb5fl/fl mice but not in Rgs9-Cre+/- Gnb5fl/fl mice, suggesting that Gβ5 might specifically regulate mechanical pain in regulator of G protein signaling 7-positive (Rgs7+) cells. Additionally, Gβ5-dependent and Rgs7-associated mechanical nociception is dependent upon GABA-B receptor signaling since both were abolished by treatment with a GABA-B receptor antagonist and since cKO of Gβ5 from sensory cells or from Rgs7+ cells potentiated the analgesic effects of GABA-B agonists. Following activation by the G protein-coupled receptor Mrgprd agonist β-alanine, enhanced sensitivity to inhibition by baclofen was observed in primary cultures of Rgs7+ sensory neurons harvested from Rgs7-Cre+/- Gnb5fl/fl mice. Taken together, these results suggest that the targeted inhibition of Gβ5 function in Rgs7+ sensory neurons might provide specific relief for mechanical allodynia, including that contributing to chronic neuropathic pain, without reliance on exogenous opioids.
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Affiliation(s)
- Mritunjay Pandey
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Jian-Hua Zhang
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Poorni R. Adikaram
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Claire Kittock
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Nicole Lue
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Adam Awe
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Katherine Degner
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Nirmal Jacob
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Jenna Staples
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Rachel Thomas
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Allison B. Kohnen
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Sundar Ganesan
- Research Technologies Branch, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA
| | - Juraj Kabat
- Research Technologies Branch, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA
| | - Ching-Kang Chen
- Department of Molecular Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - William F. Simonds
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
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Li L, Xu Q, Tang C. RGS proteins and their roles in cancer: friend or foe? Cancer Cell Int 2023; 23:81. [PMID: 37118788 PMCID: PMC10148553 DOI: 10.1186/s12935-023-02932-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 04/21/2023] [Indexed: 04/30/2023] Open
Abstract
As negative modulators of G-protein-coupled receptors (GPCRs) signaling, regulators of G protein signaling (RGS) proteins facilitate various downstream cellular signalings through regulating kinds of heterotrimeric G proteins by stimulating the guanosine triphosphatase (GTPase) activity of G-protein α (Gα) subunits. The expression of RGS proteins is dynamically and precisely mediated by several different mechanisms including epigenetic regulation, transcriptional regulation -and post-translational regulation. Emerging evidence has shown that RGS proteins act as important mediators in controlling essential cellular processes including cell proliferation, survival -and death via regulating downstream cellular signaling activities, indicating that RGS proteins are fundamentally involved in sustaining normal physiological functions and dysregulation of RGS proteins (such as aberrant expression of RGS proteins) is closely associated with pathologies of many diseases such as cancer. In this review, we summarize the molecular mechanisms governing the expression of RGS proteins, and further discuss the relationship of RGS proteins and cancer.
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Affiliation(s)
- Lin Li
- National Clinical Research Center for Child Health of the Children's Hospital, Zhejiang University School of Medicine, No. 3333, Binsheng Rd., Hangzhou, 310052, People's Republic of China
- Department of Urology, Third Affiliated Hospital of the Second Military Medical University, Shanghai, 201805, China
| | - Qiang Xu
- National Clinical Research Center for Child Health of the Children's Hospital, Zhejiang University School of Medicine, No. 3333, Binsheng Rd., Hangzhou, 310052, People's Republic of China
| | - Chao Tang
- National Clinical Research Center for Child Health of the Children's Hospital, Zhejiang University School of Medicine, No. 3333, Binsheng Rd., Hangzhou, 310052, People's Republic of China.
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A RGS7-CaMKII complex drives myocyte-intrinsic and myocyte-extrinsic mechanisms of chemotherapy-induced cardiotoxicity. Proc Natl Acad Sci U S A 2023; 120:e2213537120. [PMID: 36574707 PMCID: PMC9910480 DOI: 10.1073/pnas.2213537120] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Dose-limiting cardiotoxicity remains a major limitation in the clinical use of cancer chemotherapeutics. Here, we describe a role for Regulator of G protein Signaling 7 (RGS7) in chemotherapy-dependent heart damage, the demonstration for a functional role of RGS7 outside of the nervous system and retina. Though expressed at low levels basally, we observed robust up-regulation of RGS7 in the human and murine myocardium following chemotherapy exposure. In ventricular cardiomyocytes (VCM), RGS7 forms a complex with Ca2+/calmodulin-dependent protein kinase (CaMKII) supported by key residues (K412 and P391) in the RGS domain of RGS7. In VCM treated with chemotherapeutic drugs, RGS7 facilitates CaMKII oxidation and phosphorylation and CaMKII-dependent oxidative stress, mitochondrial dysfunction, and apoptosis. Cardiac-specific RGS7 knockdown protected the heart against chemotherapy-dependent oxidative stress, fibrosis, and myocyte loss and improved left ventricular function in mice treated with doxorubicin. Conversely, RGS7 overexpression induced fibrosis, reactive oxygen species generation, and cell death in the murine myocardium that were mitigated following CaMKII inhibition. RGS7 also drives production and release of the cardiokine neuregulin-1, which facilitates paracrine communication between VCM and neighboring vascular endothelial cells (EC), a maladaptive mechanism contributing to VCM dysfunction in the failing heart. Importantly, while RGS7 was both necessary and sufficient to facilitate chemotherapy-dependent cytotoxicity in VCM, RGS7 is dispensable for the cancer-killing actions of these same drugs. These selective myocyte-intrinsic and myocyte-extrinsic actions of RGS7 in heart identify RGS7 as an attractive therapeutic target in the mitigation of chemotherapy-driven cardiotoxicity.
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Basak M, Das K, Mahata T, Sengar AS, Verma SK, Biswas S, Bhadra K, Stewart A, Maity B. RGS7-ATF3-Tip60 Complex Promotes Hepatic Steatosis and Fibrosis by Directly Inducing TNFα. Antioxid Redox Signal 2023; 38:137-159. [PMID: 35521658 DOI: 10.1089/ars.2021.0174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Aims: The pathophysiological mechanism(s) underlying non-alcoholic fatty liver disease (NAFLD) have yet to be fully delineated and only a single drug, peroxisome proliferator-activated receptor (PPAR) α/γ agonist saroglitazar, has been approved. Here, we sought to investigate the role of Regulator of G Protein Signaling 7 (RGS7) in hyperlipidemia-dependent hepatic dysfunction. Results: RGS7 is elevated in the livers of NAFLD patients, particularly those with severe hepatic damage, pronounced insulin resistance, and high inflammation. In the liver, RGS7 forms a unique complex with transcription factor ATF3 and histone acetyltransferase Tip60, which is implicated in NAFLD. The removal of domains is necessary for ATF3/Tip60 binding compromises RGS7-dependent reactive oxygen species generation and cell death. Hepatic RGS7 knockdown (KD) prevented ATF3/Tip60 induction, and it provided protection against fibrotic remodeling and inflammation in high-fat diet-fed mice translating to improvements in liver function. Hyperlipidemia-dependent oxidative stress and metabolic dysfunction were largely reversed in RGS7 KD mice. Interestingly, saroglitazar failed to prevent RGS7/ATF3 upregulation but it did partially restore Tip60 levels. RGS7 drives the release of particularly tumor necrosis factor α (TNFα) from isolated hepatocytes, stellate cells and its depletion reverses steatosis, oxidative stress by direct TNFα exposure. Conversely, RGS7 overexpression in the liver is sufficient to trigger oxidative stress in hepatocytes that can be mitigated via TNFα inhibition. Innovation: We discovered a novel non-canonical function for an R7RGS protein, which usually functions to regulate G protein coupled receptor (GPCR) signaling. This is the first demonstration for a functional role of RGS7 outside the retina and central nervous system. Conclusion: RGS7 represents a potential novel target for the amelioration of NAFLD. Antioxid. Redox Signal. 38, 137-159.
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Affiliation(s)
| | - Kiran Das
- Centre of Biomedical Research, Lucknow, India
| | | | | | | | - Sayan Biswas
- Department of Forensic Medicine, College of Medicine and Sagore Dutta Hospital, Kolkata, India
| | - Kakali Bhadra
- Department of Zoology, University of Kalyani, Kalyani, India
| | - Adele Stewart
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, Florida, USA
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Das K, Basak M, Mahata T, Kumar M, Kumar D, Biswas S, Chatterjee S, Moniruzzaman M, Saha NC, Mondal K, Kumar P, Das P, Stewart A, Maity B. RGS11-CaMKII complex mediated redox control attenuates chemotherapy-induced cardiac fibrosis. Redox Biol 2022; 57:102487. [PMID: 36228439 PMCID: PMC9557029 DOI: 10.1016/j.redox.2022.102487] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 09/20/2022] [Indexed: 12/06/2022] Open
Abstract
Dose limiting cardiotoxicity remains a major limiting factor in the clinical use of several cancer chemotherapeutics including anthracyclines and the antimetabolite 5-fluorouracil (5-FU). Prior work has demonstrated that chemotherapeutics increase expression of R7 family regulator of G protein signaling (RGS) protein-binding partner Gβ5, which drives myocyte cytotoxicity. However, though several R7 family members are expressed in heart, the exact role of each protein in chemotherapy driven heart damage remains unclear. Here, we demonstrate that RGS11, downregulated in the human heart following chemotherapy exposure, possesses potent anti-apoptotic actions, in direct opposition to the actions of fellow R7 family member RGS6. RGS11 forms a direct complex with the apoptotic kinase CaMKII and stress responsive transcription factor ATF3 and acts to counterbalance the ability of CaMKII and ATF3 to trigger oxidative stress, mitochondrial dysfunction, cell death, and release of the cardiokine neuregulin-1 (NRG1), which mediates pathological intercommunication between myocytes and endothelial cells. Doxorubicin triggers RGS11 depletion in the murine myocardium, and cardiac-specific OE of RGS11 decreases doxorubicin-induced fibrosis, myocyte hypertrophy, apoptosis, oxidative stress, and cell loss and aids in the maintenance of left ventricular function. Conversely, RGS11 knockdown in heart promotes cardiac fibrosis associated with CaMKII activation and ATF3/NRG1 induction. Indeed, inhibition of CaMKII largely prevents the fibrotic remodeling resulting from cardiac RGS11 depletion underscoring the functional importance of the RGS11-CaMKII interaction in the pathogenesis of cardiac fibrosis. These data describe an entirely new role for RGS11 in heart and identify RGS11 as a potential new target for amelioration of chemotherapy-induced cardiotoxicity.
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Affiliation(s)
- Kiran Das
- Centre of Biomedical Research, SGPGIMS Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India; Academy of Scientific and Innovative Research (AcSIR), India
| | - Madhuri Basak
- Centre of Biomedical Research, SGPGIMS Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Tarun Mahata
- Centre of Biomedical Research, SGPGIMS Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Manish Kumar
- Centre of Biomedical Research, SGPGIMS Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Dinesh Kumar
- Centre of Biomedical Research, SGPGIMS Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Sayan Biswas
- Forensic Medicine, College of Medicine and Sagore Dutta Hospital, B.T. Road, Kamarhati, Kolkata, West Bengal, 700058, India
| | | | | | | | - Kausik Mondal
- Zoology, University of Kalyani, Nadia, West Bengal, 741235, India
| | - Pranesh Kumar
- Pharmaceutical Sciences, Aryakul College of Pharmacy & Research, Natkur, Aryakul College Road, Lucknow, Uttar Pradesh, 226002, India
| | - Priyadip Das
- Chemistry, SRM Institute of Science and Technology, Kattankulathur, Tamilnadu, 603203, India
| | - Adele Stewart
- Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, FL, 33458, USA
| | - Biswanath Maity
- Centre of Biomedical Research, SGPGIMS Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India; Academy of Scientific and Innovative Research (AcSIR), India.
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11
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Darira SV, Sutton LP. The interaction, mechanism and function of GPR158-RGS7 cross-talk. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2022; 193:167-176. [PMID: 36357076 DOI: 10.1016/bs.pmbts.2022.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
GPR158 is an orphan G protein-coupled receptor (GPCR) that is broadly expressed in the brain and displays unique structural characteristics and signaling mechanisms. GPR158 is a binding partner for the regulator of G protein signaling 7 (RGS7) and augments its expression, subcellular localization, and catalytic activity. Recent cryo-electron microscopy (cryo-EM) studies have revealed the structure of GPR158 alone and in complex with RGS7. The GPR158-RGS7 complex is shown to be regulated by chronic stress exposure and is a modulator of stress-induced depression. This review highlights the signaling mechanism and function of GPR158-RGS7 and provides a context for the unique formation of GPCR-RGS complexes.
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Affiliation(s)
- Shradha V Darira
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, United States
| | - Laurie P Sutton
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, United States.
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12
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Sheng Y, Chen L, Ren X, Jiang Z, Yau KW. Molecular determinants of response kinetics of mouse M1 intrinsically-photosensitive retinal ganglion cells. Sci Rep 2021; 11:23424. [PMID: 34873237 PMCID: PMC8648817 DOI: 10.1038/s41598-021-02832-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/19/2021] [Indexed: 11/28/2022] Open
Abstract
Intrinsically-photosensitive retinal ganglion cells (ipRGCs) are non-rod/non-cone retinal photoreceptors expressing the visual pigment, melanopsin, to detect ambient irradiance for various non-image-forming visual functions. The M1-subtype, amongst the best studied, mediates primarily circadian photoentrainment and pupillary light reflex. Their intrinsic light responses are more prolonged than those of rods and cones even at the single-photon level, in accordance with the typically slower time course of non-image-forming vision. The short (OPN4S) and long (OPN4L) alternatively-spliced forms of melanopsin proteins are both present in M1-ipRGCs, but their functional difference is unclear. We have examined this point by genetically removing the Opn4 gene (Opn4-/-) in mouse and re-expressing either OPN4S or OPN4L singly in Opn4-/- mice by using adeno-associated virus, but found no obvious difference in their intrinsic dim-flash responses. Previous studies have indicated that two dominant slow steps in M1-ipRGC phototransduction dictate these cells' intrinsic dim-flash-response kinetics, with time constants (τ1 and τ2) at room temperature of ~ 2 s and ~ 20 s, respectively. Here we found that melanopsin inactivation by phosphorylation or by β-arrestins may not be one of these two steps, because their genetic disruptions did not prolong the two time constants or affect the response waveform. Disruption of GAP (GTPase-Activating-Protein) activity on the effector enzyme, PLCβ4, in M1-ipRGC phototransduction to slow down G-protein deactivation also did not prolong the response decay, but caused its rising phase to become slightly sigmoidal by giving rise to a third time constant, τ3, of ~ 2 s (room temperature). This last observation suggests that GAP-mediated G-protein deactivation does partake in the flash-response termination, although normally with a time constant too short to be visible in the response waveform.
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Affiliation(s)
- Yanghui Sheng
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 North Wolfe St, Baltimore, MD, 21205, USA
- Graduate Neuroscience Program, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Lujing Chen
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 North Wolfe St, Baltimore, MD, 21205, USA
- Graduate Neuroscience Program, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Department of Neurobiology, Harvard Medical School, 220 Longwood Ave, Boston, MA, 02115, USA
| | - Xiaozhi Ren
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 North Wolfe St, Baltimore, MD, 21205, USA
- Vedere Bio II, Inc., 700 Main St, Cambridge, MA, 02139, USA
| | - Zheng Jiang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 North Wolfe St, Baltimore, MD, 21205, USA
- Department of Ophthalmology, Baylor College of Medicine, 6565 Fannin St, Houston, TX, 77030, USA
| | - King-Wai Yau
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 North Wolfe St, Baltimore, MD, 21205, USA.
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13
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De Nittis P, Efthymiou S, Sarre A, Guex N, Chrast J, Putoux A, Sultan T, Raza Alvi J, Ur Rahman Z, Zafar F, Rana N, Rahman F, Anwar N, Maqbool S, Zaki MS, Gleeson JG, Murphy D, Galehdari H, Shariati G, Mazaheri N, Sedaghat A, Lesca G, Chatron N, Salpietro V, Christoforou M, Houlden H, Simonds WF, Pedrazzini T, Maroofian R, Reymond A. Inhibition of G-protein signalling in cardiac dysfunction of intellectual developmental disorder with cardiac arrhythmia (IDDCA) syndrome. J Med Genet 2021; 58:815-831. [PMID: 33172956 PMCID: PMC8639930 DOI: 10.1136/jmedgenet-2020-107015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 08/30/2020] [Accepted: 09/04/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND Pathogenic variants of GNB5 encoding the β5 subunit of the guanine nucleotide-binding protein cause IDDCA syndrome, an autosomal recessive neurodevelopmental disorder associated with cognitive disability and cardiac arrhythmia, particularly severe bradycardia. METHODS We used echocardiography and telemetric ECG recordings to investigate consequences of Gnb5 loss in mouse. RESULTS We delineated a key role of Gnb5 in heart sinus conduction and showed that Gnb5-inhibitory signalling is essential for parasympathetic control of heart rate (HR) and maintenance of the sympathovagal balance. Gnb5-/- mice were smaller and had a smaller heart than Gnb5+/+ and Gnb5+/- , but exhibited better cardiac function. Lower autonomic nervous system modulation through diminished parasympathetic control and greater sympathetic regulation resulted in a higher baseline HR in Gnb5-/- mice. In contrast, Gnb5-/- mice exhibited profound bradycardia on treatment with carbachol, while sympathetic modulation of the cardiac stimulation was not altered. Concordantly, transcriptome study pinpointed altered expression of genes involved in cardiac muscle contractility in atria and ventricles of knocked-out mice. Homozygous Gnb5 loss resulted in significantly higher frequencies of sinus arrhythmias. Moreover, we described 13 affected individuals, increasing the IDDCA cohort to 44 patients. CONCLUSIONS Our data demonstrate that loss of negative regulation of the inhibitory G-protein signalling causes HR perturbations in Gnb5-/- mice, an effect mainly driven by impaired parasympathetic activity. We anticipate that unravelling the mechanism of Gnb5 signalling in the autonomic control of the heart will pave the way for future drug screening.
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Affiliation(s)
| | - Stephanie Efthymiou
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Alexandre Sarre
- Cardiovascular Assessment Facility, University of Lausanne, Lausanne, Switzerland
| | - Nicolas Guex
- Bioinformatics Competence Center, University of Lausanne, Lausanne, Switzerland
| | - Jacqueline Chrast
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Audrey Putoux
- Service de Génétique, Hopital Femme Mere Enfant, Bron, France
| | - Tipu Sultan
- Department of Pediatric Neurology, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Javeria Raza Alvi
- Department of Pediatric Neurology, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Zia Ur Rahman
- Department of Pediatric Neurology, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Faisal Zafar
- Department of Paediatric Neurology, Children's Hospital and Institute of Child Health, Multan, Pakistan
| | - Nuzhat Rana
- Department of Paediatric Neurology, Children's Hospital and Institute of Child Health, Multan, Pakistan
| | - Fatima Rahman
- Department of Developmental-Behavioural Paediatrics, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Najwa Anwar
- Department of Developmental-Behavioural Paediatrics, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Shazia Maqbool
- Department of Developmental-Behavioural Paediatrics, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Joseph G Gleeson
- Department of Neuroscience and Pediatrics, Howard Hughes Medical Institute, La Jolla, California, USA
| | - David Murphy
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Hamid Galehdari
- Department of Genetics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahwaz, Iran (the Islamic Republic of)
| | - Gholamreza Shariati
- Department of Medical Genetics, Faculty of Medicine, Ahvaz Jondishapour University of Medical Sciences, Ahvaz, Iran (the Islamic Republic of)
| | - Neda Mazaheri
- Department of Genetics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahwaz, Iran (the Islamic Republic of)
| | - Alireza Sedaghat
- Health Research Institute, Diabetes Research Center, Ahvaz Jundishapur University of medical Sciences, Ahvaz, Iran (the Islamic Republic of)
| | - Gaetan Lesca
- Service de Genetique, Hospices Civils de Lyon, Lyon, France
| | - Nicolas Chatron
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
- Service de Genetique, Hospices Civils de Lyon, Lyon, France
| | - Vincenzo Salpietro
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Marilena Christoforou
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Henry Houlden
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - William F Simonds
- Metabolic Diseases Branch/NIDDK, National Institutes of Health, Bethesda, MD, USA
| | - Thierry Pedrazzini
- Experimental Cardiology Unit, Department of Cardiovascular Medicine, University of Lausanne, Lausanne, Switzerland
| | - Reza Maroofian
- Department of Neuromuscular Disorders, Queen Square Institute of Neurology, University College London, London, UK
| | - Alexandre Reymond
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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14
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Mahata T, Sengar AS, Basak M, Das K, Pramanick A, Verma SK, Singh PK, Biswas S, Sarkar S, Saha S, Chatterjee S, Das M, Stewart A, Maity B. Hepatic Regulator of G Protein Signaling 6 (RGS6) drives non-alcoholic fatty liver disease by promoting oxidative stress and ATM-dependent cell death. Redox Biol 2021; 46:102105. [PMID: 34534913 PMCID: PMC8446788 DOI: 10.1016/j.redox.2021.102105] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 08/14/2021] [Indexed: 12/15/2022] Open
Abstract
The pathophysiological mechanism(s) driving non-alcoholic fatty liver disease, the most prevalent chronic liver disease globally, have yet to be fully elucidated. Here, we identify regulator of G protein signaling 6 (RGS6), up-regulated in the livers of NAFLD patients, as a critical mediator of hepatic steatosis, fibrosis, inflammation, and cell death. Human patients with high hepatic RGS6 expression exhibited a corresponding high inflammatory burden, pronounced insulin resistance, and poor liver function. In mice, liver-specific RGS6 knockdown largely ameliorated high fat diet (HFD)-driven oxidative stress, fibrotic remodeling, inflammation, lipid deposition and cell death. RGS6 depletion allowed for maintenance of mitochondrial integrity restoring redox balance, improving fatty acid oxidation, and preventing loss of insulin receptor sensitivity in hepatocytes. RGS6 is both induced by ROS and increases ROS generation acting as a key amplification node to exacerbate oxidative stress. In liver, RGS6 forms a direct complex with ATM kinase supported by key aspartate residues in the RGS domain and is both necessary and sufficient to drive hyperlipidemia-dependent ATM phosphorylation. pATM and markers of DNA damage (γH2AX) were also elevated in livers from NAFLD patients particularly in samples with high RGS6 protein content. Unsurprisingly, RGS6 knockdown prevented ATM phosphorylation in livers from HFD-fed mice. Further, RGS6 mutants lacking the capacity for ATM binding fail to facilitate palmitic acid-dependent hepatocyte apoptosis underscoring the importance of the RGS6-ATM complex in hyperlipidemia-dependent cell death. Inhibition of RGS6, then, may provide a viable means to prevent or reverse liver damage by mitigating oxidative liver damage.
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Affiliation(s)
- Tarun Mahata
- Centre of Biomedical Research, Sanjay Gandhi Post-Graduate Institute of Medical Sciences Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Abhishek Singh Sengar
- Centre of Biomedical Research, Sanjay Gandhi Post-Graduate Institute of Medical Sciences Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Madhuri Basak
- Centre of Biomedical Research, Sanjay Gandhi Post-Graduate Institute of Medical Sciences Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Kiran Das
- Centre of Biomedical Research, Sanjay Gandhi Post-Graduate Institute of Medical Sciences Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Arnab Pramanick
- Centre of Biomedical Research, Sanjay Gandhi Post-Graduate Institute of Medical Sciences Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Sumit Kumar Verma
- Centre of Biomedical Research, Sanjay Gandhi Post-Graduate Institute of Medical Sciences Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Praveen Kumar Singh
- Department of Surgery, Millers School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Sayan Biswas
- Department of Forensic Medicine, College of Medicine and Sagore Dutta Hospital, B.T. Road, Kamarhati, Kolkata, West Bengal, 700058, India
| | - Subhasish Sarkar
- Department of Surgery, College of Medicine and Sagore Dutta Hospital, B.T. Road, Kamarhati, Kolkata, West Bengal, 700058, India
| | - Sudipta Saha
- Department of Pharmaceutical Sciences, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Raebareli Road, Lucknow, Uttar Pradesh, 226025, India
| | - Suvro Chatterjee
- Department of Biotechnology, Anna University and Vascular Biology Laboratory, AU-KBC Research Centre, MIT Campus, Chennai, 600044, India
| | - Madhusudan Das
- Department of Zoology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, West Bengal, 700019, India.
| | - Adele Stewart
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, FL, 33458, USA
| | - Biswanath Maity
- Centre of Biomedical Research, Sanjay Gandhi Post-Graduate Institute of Medical Sciences Campus, Raebareli Road, Lucknow, Uttar Pradesh, 226014, India.
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15
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Extended Phenotyping and Functional Validation Facilitate Diagnosis of a Complex Patient Harboring Genetic Variants in MCCC1 and GNB5 Causing Overlapping Phenotypes. Genes (Basel) 2021; 12:genes12091352. [PMID: 34573334 PMCID: PMC8469011 DOI: 10.3390/genes12091352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 08/26/2021] [Accepted: 08/26/2021] [Indexed: 12/22/2022] Open
Abstract
Identifying multiple ultra-rare genetic syndromes with overlapping phenotypes is a diagnostic conundrum in clinical genetics. This study investigated the pathogenicity of a homozygous missense variant in GNB5 (GNB5L; NM_016194.4: c.920T > G (p. Leu307Arg); GNB5S; NM_006578.4: c.794T > G (p. Leu265Arg)) identified through exome sequencing in a female child who also had 3-methylcrotonyl-CoA carboxylase (3-MCC) deficiency (newborn screening positive) and hemoglobin E trait. The proband presented with early-onset intellectual disability, the severity of which was more in keeping with GNB5-related disorder than 3-MCC deficiency. She later developed bradycardia and cardiac arrest, and upon re-phenotyping showed cone photo-transduction recovery deficit, all known only to GNB5-related disorders. Patient-derived fibroblast assays showed preserved GNB5S expression, but bioluminescence resonance energy transfer assay showed abolished function of the variant reconstituted Gβ5S containing RGS complexes for deactivation of D2 dopamine receptor activity, confirming variant pathogenicity. This study highlights the need for precise phenotyping and functional assays to facilitate variant classification and clinical diagnosis in patients with complex medical conditions.
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16
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Stoveken HM, Fernandez-Vega V, Muntean BS, Patil DN, Shumate J, Bannister TD, Scampavia L, Spicer TP, Martemyanov KA. Identification of Potential Modulators of the RGS7/Gβ5/R7BP Complex. SLAS DISCOVERY 2021; 26:1177-1188. [PMID: 34112017 DOI: 10.1177/24725552211020679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Regulators of G protein signaling (RGS) proteins serve as critical regulatory nodes to limit the lifetime and extent of signaling via G protein-coupled receptors (GPCRs). Previously, approaches to pharmacologically inhibit RGS activity have mostly focused on the inhibition of GTPase activity by interrupting the interaction of RGS proteins with the G proteins they regulate. However, several RGS proteins are also regulated by association with binding partners. A notable example is the mammalian RGS7 protein, which has prominent roles in metabolic control, vision, reward, and actions of opioid analgesics. In vivo, RGS7 exists in complex with the binding partners type 5 G protein β subunit (Gβ5) and R7 binding protein (R7BP), which control its stability and activity, respectively. Targeting the whole RGS7/Gβ5/R7BP protein complex affords the opportunity to allosterically tune opioid receptor signaling following opioid engagement while potentially bypassing undesirable side effects. Hence, we implemented a novel strategy to pharmacologically target the interaction between RGS7/Gβ5 and R7BP. To do so, we searched for protein complex inhibitors using a time-resolved fluorescence resonance energy transfer (FRET)-based high-throughput screening (HTS) assay that measures compound-mediated alterations in the FRET signal between RGS7/Gβ5 and R7BP. We performed two HTS campaigns, each screening ~100,000 compounds from the Scripps Drug Discovery Library (SDDL). Each screen yielded more than 100 inhibitors, which will be described herein.
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Affiliation(s)
- Hannah M Stoveken
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | | | - Brian S Muntean
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | - Dipak N Patil
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | - Justin Shumate
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, USA
| | - Thomas D Bannister
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, USA
| | - Louis Scampavia
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, USA
| | - Timothy P Spicer
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, USA
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17
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Tennakoon M, Senarath K, Kankanamge D, Ratnayake K, Wijayaratna D, Olupothage K, Ubeysinghe S, Martins-Cannavino K, Hébert TE, Karunarathne A. Subtype-dependent regulation of Gβγ signalling. Cell Signal 2021; 82:109947. [PMID: 33582184 PMCID: PMC8026654 DOI: 10.1016/j.cellsig.2021.109947] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) transmit information to the cell interior by transducing external signals to heterotrimeric G protein subunits, Gα and Gβγ subunits, localized on the inner leaflet of the plasma membrane. Though the initial focus was mainly on Gα-mediated events, Gβγ subunits were later identified as major contributors to GPCR-G protein signalling. A broad functional array of Gβγ signalling has recently been attributed to Gβ and Gγ subtype diversity, comprising 5 Gβ and 12 Gγ subtypes, respectively. In addition to displaying selectivity towards each other to form the Gβγ dimer, numerous studies have identified preferences of distinct Gβγ combinations for specific GPCRs, Gα subtypes and effector molecules. Importantly, Gβ and Gγ subtype-dependent regulation of downstream effectors, representing a diverse range of signalling pathways and physiological functions have been found. Here, we review the literature on the repercussions of Gβ and Gγ subtype diversity on direct and indirect regulation of GPCR/G protein signalling events and their physiological outcomes. Our discussion additionally provides perspective in understanding the intricacies underlying molecular regulation of subtype-specific roles of Gβγ signalling and associated diseases.
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Affiliation(s)
- Mithila Tennakoon
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kanishka Senarath
- Genetics and Molecular Biology Unit, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
| | - Dinesh Kankanamge
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kasun Ratnayake
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA; Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Dhanushan Wijayaratna
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Koshala Olupothage
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Sithurandi Ubeysinghe
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | | | - Terence E Hébert
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC H3G 1Y6, Canada.
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA.
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18
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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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19
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G protein β5-ATM complexes drive acetaminophen-induced hepatotoxicity. Redox Biol 2021; 43:101965. [PMID: 33933881 PMCID: PMC8105674 DOI: 10.1016/j.redox.2021.101965] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 03/30/2021] [Accepted: 03/30/2021] [Indexed: 12/14/2022] Open
Abstract
Excessive ingestion of the common analgesic acetaminophen (APAP) leads to severe hepatotoxicity. Here we identify G protein β5 (Gβ5), elevated in livers from APAP overdose patients, as a critical regulator of cell death pathways and autophagic signaling in APAP-exposed liver. Liver-specific knockdown of Gβ5 in mice protected the liver from APAP-dependent fibrosis, cell loss, oxidative stress, and inflammation following either acute or chronic APAP administration. Conversely, overexpression of Gβ5 in liver was sufficient to drive hepatocyte dysfunction and loss. In hepatocytes, Gβ5 depletion ameliorated mitochondrial dysfunction, allowed for maintenance of ATP generation and mitigated APAP-induced cell death. Further, Gβ5 knockdown also reversed impacts of APAP on kinase cascades (e.g. ATM/AMPK) signaling to mammalian target of rapamycin (mTOR), a master regulator of autophagy and, as a result, interrupted autophagic flux. Though canonically relegated to nuclear DNA repair pathways, ATM also functions in the cytoplasm to control cell death and autophagy. Indeed, we now show that Gβ5 forms a direct, stable complex with the FAT domain of ATM, important for autophosphorylation-dependent kinase activation. These data provide a viable explanation for these novel, G protein-independent actions of Gβ5 in liver. Thus, Gβ5 sits at a critical nexus in multiple pathological sequelae driving APAP-dependent liver damage.
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20
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Calebiro D, Koszegi Z, Lanoiselée Y, Miljus T, O'Brien S. G protein-coupled receptor-G protein interactions: a single-molecule perspective. Physiol Rev 2020; 101:857-906. [PMID: 33331229 DOI: 10.1152/physrev.00021.2020] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
G protein-coupled receptors (GPCRs) regulate many cellular and physiological processes, responding to a diverse range of extracellular stimuli including hormones, neurotransmitters, odorants, and light. Decades of biochemical and pharmacological studies have provided fundamental insights into the mechanisms of GPCR signaling. Thanks to recent advances in structural biology, we now possess an atomistic understanding of receptor activation and G protein coupling. However, how GPCRs and G proteins interact in living cells to confer signaling efficiency and specificity remains insufficiently understood. The development of advanced optical methods, including single-molecule microscopy, has provided the means to study receptors and G proteins in living cells with unprecedented spatio-temporal resolution. The results of these studies reveal an unexpected level of complexity, whereby GPCRs undergo transient interactions among themselves as well as with G proteins and structural elements of the plasma membrane to form short-lived signaling nanodomains that likely confer both rapidity and specificity to GPCR signaling. These findings may provide new strategies to pharmaceutically modulate GPCR function, which might eventually pave the way to innovative drugs for common diseases such as diabetes or heart failure.
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Affiliation(s)
- Davide Calebiro
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Zsombor Koszegi
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Yann Lanoiselée
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Tamara Miljus
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Shannon O'Brien
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
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21
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Sciacca FL, Ciaccio C, Fontana F, Strano C, Gilardoni F, Pantaleoni C, D'Arrigo S. Severe Phenotype in a Patient With Homozygous 15q21.2 Microdeletion Involving BCL2L10, GNB5, and MYO5C Genes, Resembling Infantile Developmental Disorder With Cardiac Arrhythmias (IDDCA). Front Genet 2020; 11:399. [PMID: 32477400 PMCID: PMC7237723 DOI: 10.3389/fgene.2020.00399] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 03/30/2020] [Indexed: 11/29/2022] Open
Abstract
Homozygous and compound heterozygous mutations in GNB5 gene have been associated with a wide spectrum of clinical presentations, ranging from neurodevelopmental issues with or without cardiac arrhythmia (LADCI) to severe developmental delay with epileptic encephalopathy, retinal dystrophy, and heart rhythm abnormalities (IDDCA). While missense or missense/non-sense mutations usually lead to milder form, the biallelic loss of function of GNB5 gene causes the severe multisystemic IDDCA phenotype. So far, only 27 patients have been described with GNB5-associated disease. We report the first case of a patient carrying a homozygous 15q21.2 microdeletion, encompassing GNB5 and the two contiguous genes BCL2L10 and MYO5C. The clinical features of the child are consistent with the severe IDDCA phenotype, thus confirming the GNB5 loss-of-function mechanism in determining such presentation of the disease.
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Affiliation(s)
- Francesca L Sciacca
- Neurological Biochemistry and Neuropharmacology Unit, Laboratory of Cytogenetic, Department of Diagnostic and Technology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Claudia Ciaccio
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Federica Fontana
- Neurological Biochemistry and Neuropharmacology Unit, Laboratory of Cytogenetic, Department of Diagnostic and Technology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Camilla Strano
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Francesca Gilardoni
- Neurological Biochemistry and Neuropharmacology Unit, Laboratory of Cytogenetic, Department of Diagnostic and Technology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Chiara Pantaleoni
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Stefano D'Arrigo
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
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22
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Sakloth F, Polizu C, Bertherat F, Zachariou V. Regulators of G Protein Signaling in Analgesia and Addiction. Mol Pharmacol 2020; 98:739-750. [PMID: 32474445 DOI: 10.1124/mol.119.119206] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 05/19/2020] [Indexed: 12/11/2022] Open
Abstract
Regulator of G protein signaling (RGS) proteins are multifunctional proteins expressed in peripheral and neuronal cells, playing critical roles in development, physiologic processes, and pharmacological responses. RGS proteins primarily act as GTPase accelerators for activated Gα subunits of G-protein coupled receptors, but they may also modulate signal transduction by several other mechanisms. Over the last two decades, preclinical work identified members of the RGS family with unique and critical roles in intracellular responses to drugs of abuse. New information has emerged on the mechanisms by which RGS proteins modulate the efficacy of opioid analgesics in a brain region- and agonist-selective fashion. There has also been progress in the understanding of the protein complexes and signal transduction pathways regulated by RGS proteins in addiction and analgesia circuits. In this review, we summarize findings on the mechanisms by which RGS proteins modulate functional responses to opioids in models of analgesia and addiction. We also discuss reports on the regulation and function of RGS proteins in models of psychostimulant addiction. Using information from preclinical studies performed over the last 20 years, we highlight the diverse mechanisms by which RGS protein complexes control plasticity in response to opioid and psychostimulant drug exposure; we further discuss how the understanding of these pathways may lead to new opportunities for therapeutic interventions in G protein pathways. SIGNIFICANCE STATEMENT: Regulator of G protein signaling (RGS) proteins are signal transduction modulators, expressed widely in various tissues, including brain regions mediating addiction and analgesia. Evidence from preclinical work suggests that members of the RGS family act by unique mechanisms in specific brain regions to control drug-induced plasticity. This review highlights interesting findings on the regulation and function of RGS proteins in models of analgesia and addiction.
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Affiliation(s)
- Farhana Sakloth
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
| | - Claire Polizu
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
| | - Feodora Bertherat
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
| | - Venetia Zachariou
- Nash Family Department of Neuroscience, and Friedman Brain Institute (F.S., C.P., F.B., V.Z.) and Department of Pharmacological Sciences (V.Z.), Icahn School of Medicine at Mount Sinai, New York, New York
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23
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Wang Q, Henry TAN, Pronin AN, Jang GF, Lubaczeuski C, Crabb JW, Bernal-Mizrachi E, Slepak VZ. The regulatory G protein signaling complex, Gβ5-R7, promotes glucose- and extracellular signal-stimulated insulin secretion. J Biol Chem 2020; 295:7213-7223. [PMID: 32229584 PMCID: PMC7247291 DOI: 10.1074/jbc.ra119.011534] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 03/05/2020] [Indexed: 12/29/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are important modulators of glucose-stimulated insulin secretion, essential for maintaining energy homeostasis. Here we investigated the role of Gβ5-R7, a protein complex consisting of the atypical G protein β subunit Gβ5 and a regulator of G protein signaling of the R7 family. Using the mouse insulinoma MIN6 cell line and pancreatic islets, we investigated the effects of G protein subunit β 5 (Gnb5) knockout on insulin secretion. Consistent with previous work, Gnb5 knockout diminished insulin secretion evoked by the muscarinic cholinergic agonist Oxo-M. We found that the Gnb5 knockout also attenuated the activity of other GPCR agonists, including ADP, arginine vasopressin, glucagon-like peptide 1, and forskolin, and, surprisingly, the response to high glucose. Experiments with MIN6 cells cultured at different densities provided evidence that Gnb5 knockout eliminated the stimulatory effect of cell adhesion on Oxo-M-stimulated glucose-stimulated insulin secretion; this effect likely involved the adhesion GPCR GPR56. Gnb5 knockout did not influence cortical actin depolymerization but affected protein kinase C activity and the 14-3-3ϵ substrate. Importantly, Gnb5-/- islets or MIN6 cells had normal total insulin content and released normal insulin amounts in response to K+-evoked membrane depolarization. These results indicate that Gβ5-R7 plays a role in the insulin secretory pathway downstream of signaling via all GPCRs and glucose. We propose that the Gβ5-R7 complex regulates a phosphorylation event participating in the vesicular trafficking pathway downstream of G protein signaling and actin depolymerization but upstream of insulin granule release.
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Affiliation(s)
- Qiang Wang
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, Florida 33136
| | - Taylor A N Henry
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, Florida 33136
| | - Alexey N Pronin
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, Florida 33136
| | - Geeng-Fu Jang
- Cole Eye Institute and Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Camila Lubaczeuski
- Division of Endocrinology, Diabetes, and Metabolism, University of Miami School of Medicine, Miami, Florida 33136
| | - John W Crabb
- Cole Eye Institute and Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Ernesto Bernal-Mizrachi
- Division of Endocrinology, Diabetes, and Metabolism, University of Miami School of Medicine, Miami, Florida 33136
| | - Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, Florida 33136.
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24
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Ahlers-Dannen KE, Spicer MM, Fisher RA. RGS Proteins as Critical Regulators of Motor Function and Their Implications in Parkinson's Disease. Mol Pharmacol 2020; 98:730-738. [PMID: 32015009 DOI: 10.1124/mol.119.118836] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 01/25/2020] [Indexed: 11/22/2022] Open
Abstract
Parkinson disease (PD) is a devastating, largely nonfamilial, age-related disorder caused by the progressive loss of dopamine (DA) neurons in the substantia nigra pars compacta (SNc). Release of DA from these neurons into the dorsal striatum is crucial for regulating movement and their loss causes PD. Unfortunately, the mechanisms underlying SNc neurodegeneration remain unclear, and currently there is no cure for PD, only symptomatic treatments. Recently, several regulator of G protein signaling (RGS) proteins have emerged as critical modulators of PD pathogenesis and/or motor dysfunction and dyskinesia: RGSs 4, 6, 9, and 10. Striatal RGS4 has been shown to exacerbate motor symptoms of DA loss by suppressing M4-autoreceptor-Gα i/o signaling in striatal cholinergic interneurons. RGS6 and RGS9 are key regulators of D2R-Gα i/o signaling in SNc DA neurons and striatal medium spiny neurons, respectively. RGS6, expressed in human and mouse SNc DA neurons, suppresses characteristic PD hallmarks in aged mice, including SNc DA neuron loss, motor deficits, and α-synuclein accumulation. After DA depletion, RGS9 (through its inhibition of medium spiny neuron D2R signaling) suppresses motor dysfunction induced by L-DOPA or D2R-selective agonists. RGS10 is highly expressed in microglia, the brain's resident immune cells. Within the SNc, RGS10 may promote DA neuron survival through the upregulation of prosurvival genes and inhibition of microglial inflammatory factor expression. Thus, RGSs 4, 6, 9, and 10 are critical modulators of cell signaling pathways that promote SNc DA neuron survival and/or proper motor control. Accordingly, these RGS proteins represent novel therapeutic targets for the treatment of PD pathology. SIGNIFICANCE STATEMENT: Parkinson disease (PD), the most common movement disorder, is a progressive neurodegenerative disease characterized by substantia nigra pars compacta (SNc) dopamine (DA) neuron loss and subsequent motor deficits. Current PD therapies only target disease motor symptomology and are fraught with side effects. Therefore, researchers have begun to explore alternative therapeutic options. Regulator of G protein signaling (RGS) proteins, whether primarily expressed in SNc DA neurons (RGS6), striatal neurons (RGSs 4 and 9), or microglia (RGS10), modulate key signaling pathways important for SNc DA neuron survival and/or proper motor control. As such, RGS proteins represent novel therapeutic targets in PD.
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Affiliation(s)
- Katelin E Ahlers-Dannen
- Department of Neuroscience and Pharmacology (K.E.A.-D., M.M.S., R.A.F.), Iowa Neuroscience Institute (R.A.F.), and Interdisciplinary Graduate Program in Molecular Medicine (M.M.S., R.A.F.), University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Mackenzie M Spicer
- Department of Neuroscience and Pharmacology (K.E.A.-D., M.M.S., R.A.F.), Iowa Neuroscience Institute (R.A.F.), and Interdisciplinary Graduate Program in Molecular Medicine (M.M.S., R.A.F.), University of Iowa Carver College of Medicine, Iowa City, Iowa
| | - Rory A Fisher
- Department of Neuroscience and Pharmacology (K.E.A.-D., M.M.S., R.A.F.), Iowa Neuroscience Institute (R.A.F.), and Interdisciplinary Graduate Program in Molecular Medicine (M.M.S., R.A.F.), University of Iowa Carver College of Medicine, Iowa City, Iowa
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25
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Malerba N, De Nittis P, Merla G. The Emerging Role of Gβ Subunits in Human Genetic Diseases. Cells 2019; 8:E1567. [PMID: 31817184 PMCID: PMC6952978 DOI: 10.3390/cells8121567] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 11/23/2019] [Accepted: 11/29/2019] [Indexed: 12/20/2022] Open
Abstract
Environmental stimuli are perceived and transduced inside the cell through the activation of signaling pathways. One common type of cell signaling transduction network is initiated by G-proteins. G-proteins are activated by G-protein-coupled receptors (GPCRs) and transmit signals from hormones, neurotransmitters, and other signaling factors, thus controlling a number of biological processes that include synaptic transmission, visual photoreception, hormone and growth factors release, regulation of cell contraction and migration, as well as cell growth and differentiation. G-proteins mainly act as heterotrimeric complexes, composed of alpha, beta, and gamma subunits. In the last few years, whole exome sequencing and biochemical studies have shown causality of disease-causing variants in genes encoding G-proteins and human genetic diseases. This review focuses on the G-protein β subunits and their emerging role in the etiology of genetically inherited rare diseases in humans.
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Affiliation(s)
- Natascia Malerba
- Division of Medical Genetics Unit, IRCCS Casa Sollievo della Sofferenza, Viale Cappuccini, 71013 San Giovanni Rotondo (FG), Italy;
| | - Pasquelena De Nittis
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland;
| | - Giuseppe Merla
- Division of Medical Genetics Unit, IRCCS Casa Sollievo della Sofferenza, Viale Cappuccini, 71013 San Giovanni Rotondo (FG), Italy;
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26
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Muntean BS, Patil DN, Madoux F, Fossetta J, Scampavia L, Spicer TP, Martemyanov KA. A High-Throughput Time-Resolved Fluorescence Energy Transfer Assay to Screen for Modulators of RGS7/Gβ5/R7BP Complex. Assay Drug Dev Technol 2019; 16:150-161. [PMID: 29658790 DOI: 10.1089/adt.2017.839] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are excellent drug targets exploited by majority of the Food and Drug Administration-approved medications, but when modulated, are often accompanied by significant adverse effects. Targeting of other elements in GPCR pathways for improved safety and efficacy is thus an unmet need. The strength of GPCR signaling is tightly regulated by regulators of G protein signaling (RGS) proteins, making them attractive drug targets. We focused on a prominent RGS complex in the brain consisting of RGS7 and its binding partners Gβ5 and R7BP. These complexes play critical roles in regulating multiple GPCRs and essential physiological processes, yet no small molecule modulators are currently available to modify its function. In this study, we report a novel high-throughput approach to screen for small molecule modulators of the intramolecular transitions in the RGS7/Gβ5/R7BP complex known to be involved in its allosteric regulation. We developed a time-resolved fluorescence energy transfer-based in vitro assay that utilizes full-length recombinant proteins and shows consistency, excellent assay statistics, and high level of sensitivity. We demonstrated the potential of this approach by screening two compound libraries (LOPAC 1280 and MicroSource Spectrum). This study confirms the feasibility of the chosen strategy for identifying small molecule modulators of RGS7/Gβ5/R7BP complex for impacting signaling downstream of the GPCRs.
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Affiliation(s)
- Brian S Muntean
- 1 Department of Neuroscience, The Scripps Research Institute , Jupiter, Florida
| | - Dipak N Patil
- 1 Department of Neuroscience, The Scripps Research Institute , Jupiter, Florida
| | - Franck Madoux
- 2 Department of Molecular Medicine, The Scripps Research Institute , Jupiter, Florida
| | | | - Louis Scampavia
- 2 Department of Molecular Medicine, The Scripps Research Institute , Jupiter, Florida
| | - Timothy P Spicer
- 2 Department of Molecular Medicine, The Scripps Research Institute , Jupiter, Florida
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27
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Israeli R, Asli A, Avital-Shacham M, Kosloff M. RGS6 and RGS7 Discriminate between the Highly Similar Gα i and Gα o Proteins Using a Two-Tiered Specificity Strategy. J Mol Biol 2019; 431:3302-3311. [PMID: 31153905 DOI: 10.1016/j.jmb.2019.05.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 05/12/2019] [Accepted: 05/23/2019] [Indexed: 11/15/2022]
Abstract
RGS6 and RGS7 are regulators of G protein signaling (RGS) proteins that inactivate heterotrimeric (αβγ) G proteins and mediate diverse biological functions, such as cardiac and neuronal signaling. Uniquely, both RGS6 and RGS7 can discriminate between Gαo and Gαi1-two similar Gα subunits that belong to the same Gi sub-family. Here, we show that the isolated RGS domains of RGS6 and RGS7 are sufficient to achieve this specificity. We identified three specific RGS6/7 "disruptor residues" that can attenuate RGS interactions toward Gα subunits and demonstrated that their insertion into a representative high-activity RGS causes a significant, yet non-specific, reduction in activity. We further identified a unique "modulatory" residue that bypasses this negative effect, specifically toward Gαo. Hence, the exquisite specificity of RGS6 and RGS7 toward closely related Gα subunits is achieved via a two-tier specificity system, whereby a Gα-specific modulatory motif overrides the inhibitory effect of non-specific disruptor residues. Our findings expand the understanding of the molecular toolkit used by the RGS family to achieve specific interactions with selected Gα subunits-emphasizing the functional importance of the RGS domain in determining the activity and selectivity of RGS R7 sub-family members toward particular Gα subunits.
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Affiliation(s)
- Ran Israeli
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel
| | - Ali Asli
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel
| | - Meirav Avital-Shacham
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel
| | - Mickey Kosloff
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa 3498838, Israel.
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28
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Zurawski Z, Yim YY, Alford S, Hamm HE. The expanding roles and mechanisms of G protein-mediated presynaptic inhibition. J Biol Chem 2019; 294:1661-1670. [PMID: 30710014 PMCID: PMC6364771 DOI: 10.1074/jbc.tm118.004163] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Throughout the past five decades, tremendous advancements have been made in our understanding of G protein signaling and presynaptic inhibition, many of which were published in the Journal of Biological Chemistry under the tenure of Herb Tabor as Editor-in-Chief. Here, we identify these critical advances, including the formulation of the ternary complex model of G protein-coupled receptor signaling and the discovery of Gβγ as a critical signaling component of the heterotrimeric G protein, along with the nature of presynaptic inhibition and its physiological role. We provide an overview for the discovery and physiological relevance of the two known Gβγ-mediated mechanisms for presynaptic inhibition: first, the action of Gβγ on voltage-gated calcium channels to inhibit calcium influx to the presynaptic active zone and, second, the direct binding of Gβγ to the SNARE complex to displace synaptotagmin downstream of calcium entry, which has been demonstrated to be important in neurons and secretory cells. These two mechanisms act in tandem with each other in a synergistic manner to provide more complete spatiotemporal control over neurotransmitter release.
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Affiliation(s)
- Zack Zurawski
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600; Department of Anatomy and Cell Biology, University of Illinois, Chicago, Illinois 60612-7308
| | - Yun Young Yim
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600
| | - Simon Alford
- Department of Anatomy and Cell Biology, University of Illinois, Chicago, Illinois 60612-7308
| | - Heidi E Hamm
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600.
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29
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Malerba N, Towner S, Keating K, Squeo GM, Wilson W, Merla G. A NGS-Targeted Autism/ID Panel Reveals Compound Heterozygous GNB5 Variants in a Novel Patient. Front Genet 2018; 9:626. [PMID: 30631341 PMCID: PMC6315145 DOI: 10.3389/fgene.2018.00626] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/23/2018] [Indexed: 11/13/2022] Open
Abstract
Homozygous and compound heterozygous pathogenic variants in GNB5 have been recently associated with a spectrum of clinical presentations varying from a severe multisystem form of the disorder including intellectual disability, early infantile developmental and epileptic encephalopathy, retinal abnormalities and cardiac arrhythmias (IDDCA) to a milder form with language delay, attention-deficit/hyperactivity disorder, cognitive impairment, with or without cardiac arrhythmia (LADCI). Approximately twenty patients have been described so far; here we report a novel case of a 2.5-year-old female who is a compound heterozygote for a frameshift and a missense variant in the GNB5 gene. Her clinical presentation is consistent with a moderate phenotype, corroborating the direct correlation between the type and pathogenic mechanism of the GNB5 genetic variant and the severity of related phenotype.
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Affiliation(s)
- Natascia Malerba
- Division of Medical Genetics, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | - Shelley Towner
- Division of Medical Genetics, University of Virginia, Charlottesville, VA, United States
| | - Katherine Keating
- Division of Medical Genetics, University of Virginia, Charlottesville, VA, United States
| | - Gabriella Maria Squeo
- Division of Medical Genetics, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
| | - William Wilson
- Division of Medical Genetics, University of Virginia, Charlottesville, VA, United States
| | - Giuseppe Merla
- Division of Medical Genetics, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
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30
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Squires KE, Montañez-Miranda C, Pandya RR, Torres MP, Hepler JR. Genetic Analysis of Rare Human Variants of Regulators of G Protein Signaling Proteins and Their Role in Human Physiology and Disease. Pharmacol Rev 2018; 70:446-474. [PMID: 29871944 DOI: 10.1124/pr.117.015354] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Regulators of G protein signaling (RGS) proteins modulate the physiologic actions of many neurotransmitters, hormones, and other signaling molecules. Human RGS proteins comprise a family of 20 canonical proteins that bind directly to G protein-coupled receptors/G protein complexes to limit the lifetime of their signaling events, which regulate all aspects of cell and organ physiology. Genetic variations account for diverse human traits and individual predispositions to disease. RGS proteins contribute to many complex polygenic human traits and pathologies such as hypertension, atherosclerosis, schizophrenia, depression, addiction, cancers, and many others. Recent analysis indicates that most human diseases are due to extremely rare genetic variants. In this study, we summarize physiologic roles for RGS proteins and links to human diseases/traits and report rare variants found within each human RGS protein exome sequence derived from global population studies. Each RGS sequence is analyzed using recently described bioinformatics and proteomic tools for measures of missense tolerance ratio paired with combined annotation-dependent depletion scores, and protein post-translational modification (PTM) alignment cluster analysis. We highlight selected variants within the well-studied RGS domain that likely disrupt RGS protein functions and provide comprehensive variant and PTM data for each RGS protein for future study. We propose that rare variants in functionally sensitive regions of RGS proteins confer profound change-of-function phenotypes that may contribute, in newly appreciated ways, to complex human diseases and/or traits. This information provides investigators with a valuable database to explore variation in RGS protein function, and for targeting RGS proteins as future therapeutic targets.
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Affiliation(s)
- Katherine E Squires
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Carolina Montañez-Miranda
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Rushika R Pandya
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Matthew P Torres
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - John R Hepler
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
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Abstract
Modulation of neurotransmitter exocytosis by activated Gi/o coupled G-protein coupled receptors (GPCRs) is a universal regulatory mechanism used both to avoid overstimulation and to influence circuitry. One of the known modulation mechanisms is the interaction between Gβγ and the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNAREs). There are 5 Gβ and 12 Gγ subunits, but specific Gβγs activated by a given GPCR and the specificity to effectors, such as SNARE, in vivo are not known. Although less studied, Gβγ binding to the exocytic fusion machinery (i.e. SNARE) provides a more direct regulatory mechanism for neurotransmitter release. Here, we review some recent insights in the architecture of the synaptic terminal, modulation of synaptic transmission, and implications of G protein modulation of synaptic transmission in diseases. Numerous presynaptic proteins are involved in the architecture of synaptic terminals, particularly the active zone, and their importance in the regulation of exocytosis is still not completely understood. Further understanding of the Gβγ-SNARE interaction and the architecture and mechanisms of exocytosis may lead to the discovery of novel therapeutic targets to help patients with various disorders such as hypertension, attention-deficit/hyperactivity disorder, post-traumatic stress disorder, and acute/chronic pain.
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Affiliation(s)
- Yun Young Yim
- Department of Pharmacology, Vanderbilt University, Nashville 37232-6600, TN, United States
| | - Zack Zurawski
- Department of Pharmacology, Vanderbilt University, Nashville 37232-6600, TN, United States
| | - Heidi Hamm
- Department of Pharmacology, Vanderbilt University, Nashville 37232-6600, TN, United States.
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Inhibitory Signaling to Ion Channels in Hippocampal Neurons Is Differentially Regulated by Alternative Macromolecular Complexes of RGS7. J Neurosci 2018; 38:10002-10015. [PMID: 30315127 DOI: 10.1523/jneurosci.1378-18.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/01/2018] [Accepted: 09/26/2018] [Indexed: 12/14/2022] Open
Abstract
The neuromodulatory effects of GABA on pyramidal neurons are mediated by GABAB receptors (GABABRs) that signal via a conserved G-protein-coupled pathway. Two prominent effectors regulated by GABABRs include G-protein inwardly rectifying K+ (GIRK) and P/Q/N type voltage-gated Ca2+ (CaV2) ion channels that control excitability and synaptic output of these neurons, respectively. Regulator of G-protein signaling 7 (RGS7) has been shown to control GABAB effects, yet the specificity of its impacts on effector channels and underlying molecular mechanisms is poorly understood. In this study, we show that hippocampal RGS7 forms two distinct complexes with alternative subunit configuration bound to either membrane protein R7BP (RGS7 binding protein) or orphan receptor GPR158. Quantitative biochemical experiments show that both complexes account for targeting nearly the entire pool of RGS7 to the plasma membrane. We analyzed the effect of genetic elimination in mice of both sexes and overexpression of various components of RGS7 complex by patch-clamp electrophysiology in cultured neurons and brain slices. We report that RGS7 prominently regulates GABABR signaling to CaV2, in addition to its known involvement in modulating GIRK. Strikingly, only complexes containing R7BP, but not GPR158, accelerated the kinetics of both GIRK and CaV2 modulation by GABABRs. In contrast, GPR158 overexpression exerted the opposite effect and inhibited RGS7-assisted temporal modulation of GIRK and CaV2 by GABA. Collectively, our data reveal mechanisms by which distinctly composed macromolecular complexes modulate the activity of key ion channels that mediate the inhibitory effects of GABA on hippocampal CA1 pyramidal neurons.SIGNIFICANCE STATEMENT This study identifies the contributions of distinct macromolecular complexes containing a major G-protein regulator to controlling key ion channel function in hippocampal neurons with implications for understanding molecular mechanisms underlying synaptic plasticity, learning, and memory.
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Abstract
The transient receptor potential channel TRPM1 is required for synaptic transmission between photoreceptors and the ON subtype of bipolar cells (ON-BPC), mediating depolarization in response to light. TRPM1 is present in the somas and postsynaptic dendritic tips of ON-BPCs. Monoclonal antibodies generated against full-length TRPM1 were found to have differential labeling patterns when used to immunostain the mouse retina, with some yielding reduced labeling of dendritic tips relative to the labeling of cell bodies. Epitope mapping revealed that those antibodies that poorly label the dendritic tips share a binding site (N2d) in the N-terminal arm near the transmembrane domain. A major splice variant of TRPM1 lacking exon 19 does not contain the N2d binding site, but quantitative immunoblotting revealed no enrichment of this variant in synaptsomes. One explanation of the differential labeling is masking of the N2d epitope by formation of a synapse-specific multiprotein complex. Identifying the binding partners that are specific for the fraction of TRPM1 present at the synapses is an ongoing challenge for understanding TRPM1 function.
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34
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Yang J, Platt LT, Maity B, Ahlers KE, Luo Z, Lin Z, Chakravarti B, Ibeawuchi SR, Askeland RW, Bondaruk J, Czerniak BA, Fisher RA. RGS6 is an essential tumor suppressor that prevents bladder carcinogenesis by promoting p53 activation and DNMT1 downregulation. Oncotarget 2018; 7:69159-69172. [PMID: 27713144 PMCID: PMC5342467 DOI: 10.18632/oncotarget.12473] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 09/26/2016] [Indexed: 12/26/2022] Open
Abstract
Urinary bladder cancer (UBC) is largely caused by exposure to toxic chemicals including those in cigarette smoke (i.e. BBN). An activating SNP in RGS6 is associated with a pronounced reduction in UBC risk, especially among smokers. However, the mechanism underlying this reduction remains unknown. Here we demonstrate that RGS6 is robustly expressed in human urothelium, where urothelial cell carcinoma originates, and is downregulated in human UBC. Utilizing RGS6-/- mice we interrogated a possible role for RGS6 as a tumor suppressor using the BBN-induced bladder carcinogenesis model that closely recapitulates human disease. As in humans, RGS6 is robustly expressed in mouse urothelium. RGS6 loss dramatically accelerates BBN-induced bladder carcinogenesis, with RGS6-/- mice consistently displaying more advanced pathological lesions than RGS6+/+ mice. Furthermore, BBN treatment promotes urothelial RGS6 mRNA and protein downregulation. RGS6 loss impairs p53 activation and promotes aberrant accumulation of oncogenic protein DNMT1 in urothelium. Tumor suppressor RASSF1A, a DNMT1-regulated gene, is also silenced, likely via methylation of its promoter during BBN exposure. We hypothesize that this BBN-induced RGS6 loss represents a critical hit in UBC as it irrevocably impairs the anti-proliferative actions of the ATM/p53 and RASSF1A pathways. Consistent with these findings, RGS6-/- mice treated with CP-31398, a p53-stablizing agent, and/or 5-Aza, a DNMT1 inhibitor, are protected from BBN-induced tumorigenesis. Together, our data identify RGS6 as a master tumor suppressor modulating two critical signaling pathways that are often dysregulated in UBC; therefore, RGS6 represents a potential novel biomarker for UBC diagnosis/prognosis and an appealing new target in its treatment.
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Affiliation(s)
- Jianqi Yang
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Lance T Platt
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Biswanath Maity
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Katelin E Ahlers
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Zili Luo
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Zhibo Lin
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Bandana Chakravarti
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Stella-Rita Ibeawuchi
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Ryan W Askeland
- Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Jolanta Bondaruk
- Department of Pathology, MD Anderson Cancer Center, the University of Texas, Houston, TX, USA
| | - Bogdan A Czerniak
- Department of Pathology, MD Anderson Cancer Center, the University of Texas, Houston, TX, USA
| | - Rory A Fisher
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
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Alqinyah M, Hooks SB. Regulating the regulators: Epigenetic, transcriptional, and post-translational regulation of RGS proteins. Cell Signal 2017; 42:77-87. [PMID: 29042285 DOI: 10.1016/j.cellsig.2017.10.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 10/06/2017] [Accepted: 10/13/2017] [Indexed: 12/11/2022]
Abstract
Regulators of G protein signaling (RGS) are a family of proteins classically known to accelerate the intrinsic GTPase activity of G proteins, which results in accelerated inactivation of heterotrimeric G proteins and inhibition of G protein coupled receptor signaling. RGS proteins play major roles in essential cellular processes, and dysregulation of RGS protein expression is implicated in multiple diseases, including cancer, cardiovascular and neurodegenerative diseases. The expression of RGS proteins is highly dynamic and is regulated by epigenetic, transcriptional and post-translational mechanisms. This review summarizes studies that report dysregulation of RGS protein expression in disease states, and presents examples of drugs that regulate RGS protein expression. Additionally, this review discusses, in detail, the transcriptional and post-transcriptional mechanisms regulating RGS protein expression, and further assesses the therapeutic potential of targeting these mechanisms. Understanding the molecular mechanisms controlling the expression of RGS proteins is essential for the development of therapeutics that indirectly modulate G protein signaling by regulating expression of RGS proteins.
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Affiliation(s)
- Mohammed Alqinyah
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA, USA
| | - Shelley B Hooks
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA, USA.
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36
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Yim YY, McDonald WH, Hyde K, Cruz-Rodríguez O, Tesmer JJG, Hamm HE. Quantitative Multiple-Reaction Monitoring Proteomic Analysis of Gβ and Gγ Subunits in C57Bl6/J Brain Synaptosomes. Biochemistry 2017; 56:5405-5416. [PMID: 28880079 DOI: 10.1021/acs.biochem.7b00433] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Gβγ dimers are one of the essential signaling units of activated G protein-coupled receptors (GPCRs). There are five Gβ and 12 Gγ subunits in humans; numerous studies have demonstrated that different Gβ and Gγ subunits selectively interact to form unique Gβγ dimers, which in turn may target specific receptors and effectors. Perturbation of Gβγ signaling can lead to impaired physiological responses. Moreover, previous targeted multiple-reaction monitoring (MRM) studies of Gβ and Gγ subunits have shown distinct regional and subcellular localization patterns in four brain regions. Nevertheless, no studies have quantified or compared their individual protein levels. In this study, we have developed a quantitative MRM method not only to quantify but also to compare the protein abundance of neuronal Gβ and Gγ subunits. In whole and fractionated crude synaptosomes, we were able to identify the most abundant neuronal Gβ and Gγ subunits and their subcellular localizations. For example, Gβ1 was mostly localized at the membrane while Gβ2 was evenly distributed throughout synaptosomal fractions. The protein expression levels and subcellular localizations of Gβ and Gγ subunits may affect the Gβγ dimerization and Gβγ-effector interactions. This study offers not only a new tool for quantifying and comparing Gβ and Gγ subunits but also new insights into the in vivo distribution of Gβ and Gγ subunits, and Gβγ dimer assembly in normal brain function.
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Affiliation(s)
- Yun Young Yim
- Department of Pharmacology, Vanderbilt University , Nashville, Tennessee 37232-6600, United States
| | - W Hayes McDonald
- Department of Biochemistry, Vanderbilt University , Nashville, Tennessee 37232-6600, United States
| | - Karren Hyde
- Department of Pharmacology, Vanderbilt University , Nashville, Tennessee 37232-6600, United States
| | | | | | - Heidi E Hamm
- Department of Pharmacology, Vanderbilt University , Nashville, Tennessee 37232-6600, United States
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37
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Martemyanov KA, Sampath AP. The Transduction Cascade in Retinal ON-Bipolar Cells: Signal Processing and Disease. Annu Rev Vis Sci 2017; 3:25-51. [PMID: 28715957 DOI: 10.1146/annurev-vision-102016-061338] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Our robust visual experience is based on the reliable transfer of information from our photoreceptor cells, the rods and cones, to higher brain centers. At the very first synapse of the visual system, information is split into two separate pathways, ON and OFF, which encode increments and decrements in light intensity, respectively. The importance of this segregation is borne out in the fact that receptive fields in higher visual centers maintain a separation between ON and OFF regions. In the past decade, the molecular mechanisms underlying the generation of ON signals have been identified, which are unique in their use of a G-protein signaling cascade. In this review, we consider advances in our understanding of G-protein signaling in ON-bipolar cell (BC) dendrites and how insights about signaling have emerged from visual deficits, mostly night blindness. Studies of G-protein signaling in ON-BCs reveal an intricate mechanism that permits the regulation of visual sensitivity over a wide dynamic range.
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Affiliation(s)
| | - Alapakkam P Sampath
- Jules Stein Eye Institute, University of California, Los Angeles, California 90095;
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38
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Wang Q, Pronin AN, Levay K, Almaca J, Fornoni A, Caicedo A, Slepak VZ. Regulator of G-protein signaling Gβ5-R7 is a crucial activator of muscarinic M3 receptor-stimulated insulin secretion. FASEB J 2017; 31:4734-4744. [PMID: 28687610 DOI: 10.1096/fj.201700197rr] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 06/27/2017] [Indexed: 12/20/2022]
Abstract
In pancreatic β cells, muscarinic cholinergic receptor M3 (M3R) stimulates glucose-induced secretion of insulin. Regulator of G-protein signaling (RGS) proteins are critical modulators of GPCR activity, yet their role in β cells remains largely unknown. R7 subfamily RGS proteins are stabilized by the G-protein subunit Gβ5, such that the knockout of the Gnb5 gene results in degradation of all R7 subunits. We found that Gnb5 knockout in mice or in the insulin-secreting MIN6 cell line almost completely eliminates insulinotropic activity of M3R. Moreover, overexpression of Gβ5-RGS7 strongly promotes M3R-stimulated insulin secretion. Examination of this noncanonical mechanism in Gnb5-/- MIN6 cells showed that cAMP, diacylglycerol, or Ca2+ levels were not significantly affected. There was no reduction in the amplitude of free Ca2+ responses in islets from the Gnb5-/- mice, but the frequency of Ca2+ oscillations induced by cholinergic agonist was lowered by more than 30%. Ablation of Gnb5 impaired M3R-stimulated phosphorylation of ERK1/2. Stimulation of the ERK pathway in Gnb5-/- cells by epidermal growth factor restored M3R-stimulated insulin release to near normal levels. Identification of the novel role of Gβ5-R7 in insulin secretion may lead to a new therapeutic approach for improving pancreatic β-cell function.-Wang, Q., Pronin, A. N., Levay, K., Almaca, J., Fornoni, A., Caicedo, A., Slepak, V. Z. Regulator of G-protein signaling Gβ5-R7 is a crucial activator of muscarinic M3 receptor-stimulated insulin secretion.
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Affiliation(s)
- Qiang Wang
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
| | - Alexey N Pronin
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
| | - Konstantin Levay
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
| | - Joana Almaca
- Department of Medicine, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Alessia Fornoni
- Department of Medicine, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Alejandro Caicedo
- Department of Medicine, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
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Scherer SL, Cain MD, Kanai SM, Kaltenbronn KM, Blumer KJ. Regulation of neurite morphogenesis by interaction between R7 regulator of G protein signaling complexes and G protein subunit Gα 13. J Biol Chem 2017; 292:9906-9918. [PMID: 28432124 DOI: 10.1074/jbc.m116.771923] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 04/19/2017] [Indexed: 02/06/2023] Open
Abstract
The R7 regulator of G protein signaling family (R7-RGS) critically regulates nervous system development and function. Mice lacking all R7-RGS subtypes exhibit diverse neurological phenotypes, and humans bearing mutations in the retinal R7-RGS isoform RGS9-1 have vision deficits. Although each R7-RGS subtype forms heterotrimeric complexes with Gβ5 and R7-RGS-binding protein (R7BP) that regulate G protein-coupled receptor signaling by accelerating deactivation of Gi/o α-subunits, several neurological phenotypes of R7-RGS knock-out mice are not readily explained by dysregulated Gi/o signaling. Accordingly, we used tandem affinity purification and LC-MS/MS to search for novel proteins that interact with R7-RGS heterotrimers in the mouse brain. Among several proteins detected, we focused on Gα13 because it had not been linked to R7-RGS complexes before. Split-luciferase complementation assays indicated that Gα13 in its active or inactive state interacts with R7-RGS heterotrimers containing any R7-RGS isoform. LARG (leukemia-associated Rho guanine nucleotide exchange factor (GEF)), PDZ-RhoGEF, and p115RhoGEF augmented interaction between activated Gα13 and R7-RGS heterotrimers, indicating that these effector RhoGEFs can engage Gα13·R7-RGS complexes. Because Gα13/R7-RGS interaction required R7BP, we analyzed phenotypes of neuronal cell lines expressing RGS7 and Gβ5 with or without R7BP. We found that neurite retraction evoked by Gα12/13-dependent lysophosphatidic acid receptors was augmented in R7BP-expressing cells. R7BP expression blunted neurite formation evoked by serum starvation by signaling mechanisms involving Gα12/13 but not Gαi/o These findings provide the first evidence that R7-RGS heterotrimers interact with Gα13 to augment signaling pathways that regulate neurite morphogenesis. This mechanism expands the diversity of functions whereby R7-RGS complexes regulate critical aspects of nervous system development and function.
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Affiliation(s)
- Stephanie L Scherer
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Matthew D Cain
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Stanley M Kanai
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Kevin M Kaltenbronn
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Kendall J Blumer
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
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40
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Sjögren B. The evolution of regulators of G protein signalling proteins as drug targets - 20 years in the making: IUPHAR Review 21. Br J Pharmacol 2017; 174:427-437. [PMID: 28098342 DOI: 10.1111/bph.13716] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 12/11/2016] [Accepted: 01/08/2017] [Indexed: 12/11/2022] Open
Abstract
Regulators of G protein signalling (RGS) proteins are celebrating the 20th anniversary of their discovery. The unveiling of this new family of negative regulators of G protein signalling in the mid-1990s solved a persistent conundrum in the G protein signalling field, in which the rate of deactivation of signalling cascades in vivo could not be replicated in exogenous systems. Since then, there has been tremendous advancement in the knowledge of RGS protein structure, function, regulation and their role as novel drug targets. RGS proteins play an important modulatory role through their GTPase-activating protein (GAP) activity at active, GTP-bound Gα subunits of heterotrimeric G proteins. They also possess many non-canonical functions not related to G protein signalling. Here, an update on the status of RGS proteins as drug targets is provided, highlighting advances that have led to the inclusion of RGS proteins in the IUPHAR/BPS Guide to PHARMACOLOGY database of drug targets.
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Affiliation(s)
- B Sjögren
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
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41
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Development of a bimolecular luminescence complementation assay for RGS: G protein interactions in cells. Anal Biochem 2017; 522:10-17. [PMID: 28115169 DOI: 10.1016/j.ab.2017.01.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 01/10/2017] [Accepted: 01/18/2017] [Indexed: 02/03/2023]
Abstract
Cell based assessment tools and screening platforms are the preferred paradigm for small molecule identification and validation due to selectively identifying molecules with cellular activity and validation of compound activity against target proteins in their native environment. With respect to Regulator of G Protein Signaling (RGS) proteins, current cell based methodologies are either low throughput or monitor downstream signaling consequences. The increasing number of reports indicating RGS function in various disease pathogeneses highlights the need for a robust RGS inhibitor discovery and characterization paradigm. Promega's NanoBit Protein Complementation Assay utilizes NanoLuc, an engineered luciferase with enhanced luminescence characteristics which allow for both robust and kinetic assessment of protein interaction formation and disruption. Here we characterized 15 separate RGS: G protein interactions using this system. The binding profile of RGS: Gα interactions correlates to prior published biochemical binding profiles of these proteins. Additionally, we demonstrated this system is suitable for high throughput screening efforts via calculation of Z-factors for three of the interactions and demonstrated that a known small molecule inhibitor of RGS4 disrupts the RGS4: Gαi1 protein-protein interaction. In conclusion, the NanoBit Protein Complementation Assay holds promise as a robust platform for discovery and characterization of RGS inhibitors.
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42
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Aguado C, Orlandi C, Fajardo-Serrano A, Gil-Minguez M, Martemyanov KA, Luján R. Cellular and Subcellular Localization of the RGS7/Gβ5/R7BP Complex in the Cerebellar Cortex. Front Neuroanat 2016; 10:114. [PMID: 27965545 PMCID: PMC5127842 DOI: 10.3389/fnana.2016.00114] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 11/10/2016] [Indexed: 11/13/2022] Open
Abstract
A member of regulator of G-protein signaling family, RGS7, is an essential modulator of signaling through GABAB receptors. RGS7 functions as a macromolecular complex with type 5 G protein β (Gβ5) and R7 binding protein (R7BP) to control the localization and function of the resultant heterotrimeric complexes. Here, we used co-immunoprecipitation, in situ hybridization, histoblot and immunohistochemical techniques at the light and electron microscopic level to advance understanding of RGS7-Gβ5-R7BP complexes in the central nervous system, focusing on distinct neuronal populations in the cerebellar cortex. Histoblot analysis showed that RGS7, Gβ5 and R7BP proteins were widely expressed in the brain, with mostly an overlapping pattern and showing a high expression level in the molecular layer of the cerebellar cortex. Co-immunoprecipitation experiments established that the RGS7/Gβ5 forms complexes with R7BP in the cerebellum. At the cellular level, RGS7 and R7BP mRNAs were expressed at the highest level in Purkinje cells (PCs) and Golgi cells, and at low levels in granule cells. Immunohistochemistry confirmed that labeling for RGS7, Gβ5 and R7BP were present in the three neuronal populations and concentrated in dendrites and spines. At the electron microscopic level, immunolabeling for RGS7, Gβ5 and R7BP proteins was found both at postsynaptic and presynaptic sites and showed similar distribution patterns. Immunoreactivity for the three proteins was mostly localized along the extrasynaptic plasma membrane of dendritic shafts and spines of PCs and to a lesser extent, in axon terminals (AT) establishing excitatory synapses. Quantitative analysis of immunogold particles for RGS7, Gβ5 and R7BP revealed that they are non-uniformly distributed along the surface of PCs, and show enrichment around excitatory synapses on dendritic spines. We further report that deletion of R7BP in mice reduced the targeting of both RGS7 and Gβ5 to the plasma membrane. Altogether, these data support the existence of macromolecular complexes composed of RGS7-Gβ5-R7BP in PCs. The location at post- and pre-synaptic sites in PCs spines-parallel fiber synapses suggests their involvement in the modulation of glutamatergic neurotransmission in the cerebellar cortex.
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Affiliation(s)
- Carolina Aguado
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | - Cesare Orlandi
- Department of Neuroscience, The Scripps Research Institute Jupiter, FL, USA
| | - Ana Fajardo-Serrano
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | - Mercedes Gil-Minguez
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | | | - Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
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Intermolecular Interaction between Anchoring Subunits Specify Subcellular Targeting and Function of RGS Proteins in Retina ON-Bipolar Neurons. J Neurosci 2016; 36:2915-25. [PMID: 26961947 DOI: 10.1523/jneurosci.3833-15.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In vertebrate retina, light responses generated by the rod photoreceptors are transmitted to the second-order neurons, the ON-bipolar cells (ON-BC), and this communication is indispensible for vision in dim light. In ON-BCs, synaptic transmission is initiated by the metabotropic glutamate receptor, mGluR6, that signals via the G-protein Go to control opening of the effector ion channel, TRPM1. A key role in this process belongs to the GTPase Activating Protein (GAP) complex that catalyzes Go inactivation upon light-induced suppression of glutamate release in rod photoreceptors, thereby driving ON-BC depolarization to changes in synaptic input. The GAP complex has a striking molecular complexity. It contains two Regulator of G-protein Signaling (RGS) proteins RGS7 and RGS11 that directly act on Go and two adaptor subunits: RGS Anchor Protein (R9AP) and the orphan receptor, GPR179. Here we examined the organizational principles of the GAP complex in ON-BCs. Biochemical experiments revealed that RGS7 binds to a conserved site in GPR179 and that RGS11 in vivo forms a complex only with R9AP. R9AP and GPR179 are further integrated via direct protein-protein interactions involving their cytoplasmic domains. Elimination of GPR179 prevents postsynaptic accumulation of R9AP. Furthermore, concurrent knock-out of both R9AP and RGS7 does not reconfigure the GAP complex and completely abolishes synaptic transmission, resulting in a novel mouse model of night blindness. Based on these results, we propose a model of hierarchical assembly and function of the GAP complex that supports ON-BCs visual signaling.
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Gβγ subunits-Different spaces, different faces. Pharmacol Res 2016; 111:434-441. [PMID: 27378564 DOI: 10.1016/j.phrs.2016.06.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Revised: 06/27/2016] [Accepted: 06/28/2016] [Indexed: 11/20/2022]
Abstract
Gβγ subunits play key roles in modulation of canonical effectors in G protein-coupled receptor (GPCR)-dependent signalling at the cell surface. However, a number of recent studies of Gβγ function have revealed that they regulate a large number of molecules at distinct subcellular sites. These novel, non-canonical Gβγ roles have reshaped our understanding of how important Gβγ signalling is compared to our original notion of Gβγ subunits as simple negative regulators of Gα subunits. Gβγ dimers have now been identified as regulators of transcription, anterograde and retrograde trafficking and modulators of second messenger molecule generation in intracellular organelles. Here, we review some recent advances in our understanding of these novel non-canonical roles of Gβγ.
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Aissani B, Wiener HW, Zhang K. Fine Mapping of the Body Fat QTL on Human Chromosome 1q43. PLoS One 2016; 11:e0153794. [PMID: 27111224 PMCID: PMC4844098 DOI: 10.1371/journal.pone.0153794] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 04/04/2016] [Indexed: 11/20/2022] Open
Abstract
Introduction Evidence for linkage and association of obesity-related quantitative traits to chromosome 1q43 has been reported in the Quebec Family Study (QFS) and in populations of Caribbean Hispanic ancestries yet no specific candidate locus has been replicated to date. Methods Using a set of 1,902 single nucleotide polymorphisms (SNPs) genotyped in 525 African American (AA) and 391 European American (EA) women enrolled in the NIEHS uterine fibroid study (NIEHS-UFS), we generated a fine association map for the body mass index (BMI) across a 2.3 megabase-long interval delimited by RGS7 (regulator of G-protein signaling 7) and PLD5 (Phospholipase D, member 5). Multivariable-adjusted linear regression models were fitted to the data to evaluate the association in race-stratified analyses and meta-analysis. Results The strongest associations were observed in a recessive genetic model and peaked in the 3’ end of RGS7 at intronic rs261802 variant in the AA group (p = 1.0 x 10−4) and in meta-analysis of AA and EA samples (p = 9.0 x 10−5). In the EA group, moderate associations peaked at rs6429264 (p = 2.0 x 10−3) in the 2 Kb upstream sequence of RGS7. In the reference populations for the European ancestry in the 1,000 genomes project, rs6429264 occurs in strong linkage disequilibrium (D’ = 0.94) with rs1341467, the strongest candidate SNP for total body fat in QFS that failed genotyping in the present study. Additionally we report moderate associations at the 3’ end of PLD5 in meta-analysis (3.2 x 10−4 ≤ p ≤ 5.8 x 10−4). Conclusion We report replication data suggesting that RGS7, a gene abundantly expressed in the brain, might be a putative body fat QTL on human chromosome 1q43. Future genetic and functional studies are required to substantiate our observations and to potentially link them to the neurobehavioral phenotypes associated with the RGS7 region.
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Affiliation(s)
- Brahim Aissani
- Department of Epidemiology, University of Alabama at Birmingham School of Public Health, Birmingham, Alabama, United States of America
- * E-mail:
| | - Howard W. Wiener
- Department of Epidemiology, University of Alabama at Birmingham School of Public Health, Birmingham, Alabama, United States of America
| | - Kui Zhang
- Department of Mathematical Sciences, Michigan Technological University, Houghton, Michigan, United States of America
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Muntean BS, Martemyanov KA. Association with the Plasma Membrane Is Sufficient for Potentiating Catalytic Activity of Regulators of G Protein Signaling (RGS) Proteins of the R7 Subfamily. J Biol Chem 2016; 291:7195-204. [PMID: 26811338 PMCID: PMC4807299 DOI: 10.1074/jbc.m115.713446] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 01/21/2016] [Indexed: 12/23/2022] Open
Abstract
Regulators of G protein Signaling (RGS) promote deactivation of heterotrimeric G proteins thus controlling the magnitude and kinetics of responses mediated by G protein-coupled receptors (GPCR). In the nervous system, RGS7 and RGS9-2 play essential role in vision, reward processing, and movement control. Both RGS7 and RGS9-2 belong to the R7 subfamily of RGS proteins that form macromolecular complexes with R7-binding protein (R7BP). R7BP targets RGS proteins to the plasma membrane and augments their GTPase-accelerating protein (GAP) activity, ultimately accelerating deactivation of G protein signaling. However, it remains unclear if R7BP serves exclusively as a membrane anchoring subunit or further modulates RGS proteins to increase their GAP activity. To directly answer this question, we utilized a rapidly reversible chemically induced protein dimerization system that enabled us to control RGS localization independent from R7BP in living cells. To monitor kinetics of Gα deactivation, we coupled this strategy with measuring changes in the GAP activity by bioluminescence resonance energy transfer-based assay in a cellular system containing μ-opioid receptor. This approach was used to correlate changes in RGS localization and activity in the presence or absence of R7BP. Strikingly, we observed that RGS activity is augmented by membrane recruitment, in an orientation independent manner with no additional contributions provided by R7BP. These findings argue that the association of R7 RGS proteins with the membrane environment provides a major direct contribution to modulation of their GAP activity.
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Affiliation(s)
- Brian S Muntean
- From the Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458
| | - Kirill A Martemyanov
- From the Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458
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Ahlers KE, Chakravarti B, Fisher RA. RGS6 as a Novel Therapeutic Target in CNS Diseases and Cancer. AAPS JOURNAL 2016; 18:560-72. [PMID: 27002730 DOI: 10.1208/s12248-016-9899-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 02/25/2016] [Indexed: 12/17/2022]
Abstract
Regulator of G protein signaling (RGS) proteins are gatekeepers regulating the cellular responses induced by G protein-coupled receptor (GPCR)-mediated activation of heterotrimeric G proteins. Specifically, RGS proteins determine the magnitude and duration of GPCR signaling by acting as a GTPase-activating protein for Gα subunits, an activity facilitated by their semiconserved RGS domain. The R7 subfamily of RGS proteins is distinguished by two unique domains, DEP/DHEX and GGL, which mediate membrane targeting and stability of these proteins. RGS6, a member of the R7 subfamily, has been shown to specifically modulate Gαi/o protein activity which is critically important in the central nervous system (CNS) for neuronal responses to a wide array of neurotransmitters. As such, RGS6 has been implicated in several CNS pathologies associated with altered neurotransmission, including the following: alcoholism, anxiety/depression, and Parkinson's disease. In addition, unlike other members of the R7 subfamily, RGS6 has been shown to regulate G protein-independent signaling mechanisms which appear to promote both apoptotic and growth-suppressive pathways that are important in its tumor suppressor function in breast and possibly other tissues. Further highlighting the importance of RGS6 as a target in cancer, RGS6 mediates the chemotherapeutic actions of doxorubicin and blocks reticular activating system (Ras)-induced cellular transformation by promoting degradation of DNA (cytosine-5)-methyltransferase 1 (DNMT1) to prevent its silencing of pro-apoptotic and tumor suppressor genes. Together, these findings demonstrate the critical role of RGS6 in regulating both G protein-dependent CNS pathology and G protein-independent cancer pathology implicating RGS6 as a novel therapeutic target.
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Affiliation(s)
- Katelin E Ahlers
- Department of Pharmacology, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 2-505 Bowen Science Building, Iowa City, Iowa, 52242, USA
| | - Bandana Chakravarti
- Department of Pharmacology, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 2-505 Bowen Science Building, Iowa City, Iowa, 52242, USA
| | - Rory A Fisher
- Department of Pharmacology, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 2-505 Bowen Science Building, Iowa City, Iowa, 52242, USA. .,Department of Internal Medicine, The Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, 52242, USA.
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Tayou J, Wang Q, Jang GF, Pronin AN, Orlandi C, Martemyanov KA, Crabb JW, Slepak VZ. Regulator of G Protein Signaling 7 (RGS7) Can Exist in a Homo-oligomeric Form That Is Regulated by Gαo and R7-binding Protein. J Biol Chem 2016; 291:9133-47. [PMID: 26895961 DOI: 10.1074/jbc.m115.694075] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Indexed: 11/06/2022] Open
Abstract
RGS (regulator of G protein signaling) proteins of the R7 subfamily (RGS6, -7, -9, and -11) are highly expressed in neurons where they regulate many physiological processes. R7 RGS proteins contain several distinct domains and form obligatory dimers with the atypical Gβ subunit, Gβ5 They also interact with other proteins such as R7-binding protein, R9-anchoring protein, and the orphan receptors GPR158 and GPR179. These interactions facilitate plasma membrane targeting and stability of R7 proteins and modulate their activity. Here, we investigated RGS7 complexes using in situ chemical cross-linking. We found that in mouse brain and transfected cells cross-linking causes formation of distinct RGS7 complexes. One of the products had the apparent molecular mass of ∼150 kDa on SDS-PAGE and did not contain Gβ5 Mass spectrometry analysis showed no other proteins to be present within the 150-kDa complex in the amount close to stoichiometric with RGS7. This finding suggested that RGS7 could form a homo-oligomer. Indeed, co-immunoprecipitation of differentially tagged RGS7 constructs, with or without chemical cross-linking, demonstrated RGS7 self-association. RGS7-RGS7 interaction required the DEP domain but not the RGS and DHEX domains or the Gβ5 subunit. Using transfected cells and knock-out mice, we demonstrated that R7-binding protein had a strong inhibitory effect on homo-oligomerization of RGS7. In contrast, our data indicated that GPR158 could bind to the RGS7 homo-oligomer without causing its dissociation. Co-expression of constitutively active Gαo prevented the RGS7-RGS7 interaction. These results reveal the existence of RGS protein homo-oligomers and show regulation of their assembly by R7 RGS-binding partners.
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Affiliation(s)
- Junior Tayou
- From the Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Qiang Wang
- From the Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Geeng-Fu Jang
- the Cole Eye Institute Cleveland Clinic, Cleveland, Ohio 44195, and
| | - Alexey N Pronin
- From the Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Cesare Orlandi
- the Department of Neuroscience, Scripps Research Institute, Jupiter, Florida 33458
| | - Kirill A Martemyanov
- the Department of Neuroscience, Scripps Research Institute, Jupiter, Florida 33458
| | - John W Crabb
- the Cole Eye Institute Cleveland Clinic, Cleveland, Ohio 44195, and
| | - Vladlen Z Slepak
- From the Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136,
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Gerber KJ, Squires KE, Hepler JR. Roles for Regulator of G Protein Signaling Proteins in Synaptic Signaling and Plasticity. Mol Pharmacol 2015; 89:273-86. [PMID: 26655302 DOI: 10.1124/mol.115.102210] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/10/2015] [Indexed: 11/22/2022] Open
Abstract
The regulator of G protein signaling (RGS) family of proteins serves critical roles in G protein-coupled receptor (GPCR) and heterotrimeric G protein signal transduction. RGS proteins are best understood as negative regulators of GPCR/G protein signaling. They achieve this by acting as GTPase activating proteins (GAPs) for Gα subunits and accelerating the turnoff of G protein signaling. Many RGS proteins also bind additional signaling partners that either regulate their functions or enable them to regulate other important signaling events. At neuronal synapses, GPCRs, G proteins, and RGS proteins work in coordination to regulate key aspects of neurotransmitter release, synaptic transmission, and synaptic plasticity, which are necessary for central nervous system physiology and behavior. Accumulating evidence has revealed key roles for specific RGS proteins in multiple signaling pathways at neuronal synapses, regulating both pre- and postsynaptic signaling events and synaptic plasticity. Here, we review and highlight the current knowledge of specific RGS proteins (RGS2, RGS4, RGS7, RGS9-2, and RGS14) that have been clearly demonstrated to serve critical roles in modulating synaptic signaling and plasticity throughout the brain, and we consider their potential as future therapeutic targets.
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Affiliation(s)
- Kyle J Gerber
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - Katherine E Squires
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - John R Hepler
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
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Khan SM, Min A, Gora S, Houranieh GM, Campden R, Robitaille M, Trieu P, Pétrin D, Jacobi AM, Behlke MA, Angers S, Hébert TE. Gβ 4 γ 1 as a modulator of M3 muscarinic receptor signalling and novel roles of Gβ 1 subunits in the modulation of cellular signalling. Cell Signal 2015; 27:1597-608. [DOI: 10.1016/j.cellsig.2015.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 04/16/2015] [Accepted: 04/17/2015] [Indexed: 01/01/2023]
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