1
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Wang S, Sass MI, Kwon Y, Ludlam WG, Smith TM, Carter EJ, Gladden NE, Riggi M, Iwasa JH, Willardson BM, Shen PS. Visualizing the chaperone-mediated folding trajectory of the G protein β5 β-propeller. Mol Cell 2023; 83:3852-3868.e6. [PMID: 37852256 PMCID: PMC10841713 DOI: 10.1016/j.molcel.2023.09.032] [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: 05/17/2023] [Revised: 08/24/2023] [Accepted: 09/26/2023] [Indexed: 10/20/2023]
Abstract
The Chaperonin Containing Tailless polypeptide 1 (CCT) complex is an essential protein folding machine with a diverse clientele of substrates, including many proteins with β-propeller domains. Here, we determine the structures of human CCT in complex with its accessory co-chaperone, phosducin-like protein 1 (PhLP1), in the process of folding Gβ5, a component of Regulator of G protein Signaling (RGS) complexes. Cryoelectron microscopy (cryo-EM) and image processing reveal an ensemble of distinct snapshots that represent the folding trajectory of Gβ5 from an unfolded molten globule to a fully folded β-propeller. These structures reveal the mechanism by which CCT directs Gβ5 folding through initiating specific intermolecular contacts that facilitate the sequential folding of individual β sheets until the propeller closes into its native structure. This work directly visualizes chaperone-mediated protein folding and establishes that CCT orchestrates folding by stabilizing intermediates through interactions with surface residues that permit the hydrophobic core to coalesce into its folded state.
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Affiliation(s)
- Shuxin Wang
- Department of Biochemistry, School of Medicine, University of Utah, 15 N. Medical Drive East, Salt Lake City, UT 84112, USA
| | - Mikaila I Sass
- Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA
| | - Yujin Kwon
- Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA
| | - W Grant Ludlam
- Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA
| | - Theresa M Smith
- Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA
| | - Ethan J Carter
- Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA
| | - Nathan E Gladden
- Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA
| | - Margot Riggi
- Department of Biochemistry, School of Medicine, University of Utah, 15 N. Medical Drive East, Salt Lake City, UT 84112, USA
| | - Janet H Iwasa
- Department of Biochemistry, School of Medicine, University of Utah, 15 N. Medical Drive East, Salt Lake City, UT 84112, USA
| | - Barry M Willardson
- Department of Chemistry and Biochemistry, Brigham Young University, C100 BNSN, Provo, UT 84602, USA.
| | - Peter S Shen
- Department of Biochemistry, School of Medicine, University of Utah, 15 N. Medical Drive East, Salt Lake City, UT 84112, USA.
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2
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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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Wang S, Sass MI, Kwon Y, Ludlam WG, Smith TM, Carter EJ, Gladden NE, Riggi M, Iwasa JH, Willardson BM, Shen PS. Visualizing the chaperone-mediated folding trajectory of the G protein β5 β-propeller. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.04.539424. [PMID: 37205387 PMCID: PMC10187262 DOI: 10.1101/2023.05.04.539424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The cytosolic Chaperonin Containing Tailless polypeptide 1 (CCT) complex is an essential protein folding machine with a diverse clientele of substrates, including many proteins with β-propeller domains. Here, we determined structures of CCT in complex with its accessory co-chaperone, phosducin-like protein 1 (PhLP1), in the process of folding Gβ5, a component of Regulator of G protein Signaling (RGS) complexes. Cryo-EM and image processing revealed an ensemble of distinct snapshots that represent the folding trajectory of Gβ5 from an unfolded molten globule to a fully folded β-propeller. These structures reveal the mechanism by which CCT directs Gβ5 folding through initiating specific intermolecular contacts that facilitate the sequential folding of individual β-sheets until the propeller closes into its native structure. This work directly visualizes chaperone-mediated protein folding and establishes that CCT directs folding by stabilizing intermediates through interactions with surface residues that permit the hydrophobic core to coalesce into its folded state.
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Affiliation(s)
- Shuxin Wang
- Department of Biochemistry, 15 N. Medical Drive East, University of Utah, Salt Lake City, UT, 84112, USA
| | - Mikaila I. Sass
- Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA
| | - Yujin Kwon
- Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA
| | - W. Grant Ludlam
- Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA
| | - Theresa M. Smith
- Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA
| | - Ethan J. Carter
- Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA
| | - Nathan E. Gladden
- Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA
| | - Margot Riggi
- Department of Biochemistry, 15 N. Medical Drive East, University of Utah, Salt Lake City, UT, 84112, USA
| | - Janet H. Iwasa
- Department of Biochemistry, 15 N. Medical Drive East, University of Utah, Salt Lake City, UT, 84112, USA
| | - Barry M. Willardson
- Department of Chemistry and Biochemistry, C100 BNSN, Brigham Young University, Provo, UT, 84602, USA
| | - Peter S. Shen
- Department of Biochemistry, 15 N. Medical Drive East, University of Utah, Salt Lake City, UT, 84112, USA
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Kim KM. Unveiling the Differences in Signaling and Regulatory Mechanisms between Dopamine D2 and D3 Receptors and Their Impact on Behavioral Sensitization. Int J Mol Sci 2023; 24:ijms24076742. [PMID: 37047716 PMCID: PMC10095578 DOI: 10.3390/ijms24076742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 03/25/2023] [Accepted: 03/28/2023] [Indexed: 04/09/2023] Open
Abstract
Dopamine receptors are classified into five subtypes, with D2R and D3R playing a crucial role in regulating mood, motivation, reward, and movement. Whereas D2R are distributed widely across the brain, including regions responsible for motor functions, D3R are primarily found in specific areas related to cognitive and emotional functions, such as the nucleus accumbens, limbic system, and prefrontal cortex. Despite their high sequence homology and similar signaling pathways, D2R and D3R have distinct regulatory properties involving desensitization, endocytosis, posttranslational modification, and interactions with other cellular components. In vivo, D3R is closely associated with behavioral sensitization, which leads to increased dopaminergic responses. Behavioral sensitization is believed to result from D3R desensitization, which removes the inhibitory effect of D3R on related behaviors. Whereas D2R maintains continuous signal transduction through agonist-induced receptor phosphorylation, arrestin recruitment, and endocytosis, which recycle and resensitize desensitized receptors, D3R rarely undergoes agonist-induced endocytosis and instead is desensitized after repeated agonist exposure. In addition, D3R undergoes more extensive posttranslational modifications, such as glycosylation and palmitoylation, which are needed for its desensitization. Overall, a series of biochemical settings more closely related to D3R could be linked to D3R-mediated behavioral sensitization.
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Affiliation(s)
- Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 61186, Republic of Korea
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The Potential Role of R4 Regulators of G Protein Signaling (RGS) Proteins in Type 2 Diabetes Mellitus. Cells 2022; 11:cells11233897. [PMID: 36497154 PMCID: PMC9739376 DOI: 10.3390/cells11233897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/26/2022] [Accepted: 11/30/2022] [Indexed: 12/05/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) is a complex and heterogeneous disease that primarily results from impaired insulin secretion or insulin resistance (IR). G protein-coupled receptors (GPCRs) are proposed as therapeutic targets for T2DM. GPCRs transduce signals via the Gα protein, playing an integral role in insulin secretion and IR. The regulators of G protein signaling (RGS) family proteins can bind to Gα proteins and function as GTPase-activating proteins (GAP) to accelerate GTP hydrolysis, thereby terminating Gα protein signaling. Thus, RGS proteins determine the size and duration of cellular responses to GPCR stimulation. RGSs are becoming popular targeting sites for modulating the signaling of GPCRs and related diseases. The R4 subfamily is the largest RGS family. This review will summarize the research progress on the mechanisms of R4 RGS subfamily proteins in insulin secretion and insulin resistance and analyze their potential value in the treatment of T2DM.
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6
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G N S HS, Marise VLP, Rajalekshmi SG, Burri RR, Krishna Murthy TP. Articulating target-mining techniques to disinter Alzheimer's specific targets for drug repurposing. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 222:106931. [PMID: 35724476 DOI: 10.1016/j.cmpb.2022.106931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 03/14/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND AND OBJECTIVES Alzheimer's Disease (AD), an extremely progressive neurodegenerative disorder is an amalgamation of numerous intricate pathological networks. This century old disease is still an unmet medical condition owing to the modest efficacy of existing therapeutic agents in antagonizing the multi-targeted pathological pathways underlying AD. Given the paucity in AD specific drugs, fabricating comprehensive research strategies to envision disease specific targets to channelize and expedite drug discovery are mandated. However, the dwindling approval rates and stringent regulatory constraints concerning the approval of a new chemical entity is daunting the pharmaceutical industries from effectuating de novo research. To bridge the existing gaps in AD drug research, a promising contemporary way out could be drug repurposing. This drug repurposing investigation is intended to envisage AD specific targets and create drug libraries pertinent to the shortlisted targets via a series of avant-garde bioinformatics and computational strategies. METHODS Transcriptomic analysis of three AD specific datasets viz., GSE122063, GSE15222 and GSE5281 revealed significant Differentially Expressed Genes (DEGs) and subsequent Protein-Protein Interactions (PPI) network analysis captured crucial AD targets. Later, homology model was constructed through I-TASSER for a shortlisted target protein which lacked X-ray crystallographic structure and the built protein model was validated by molecular dynamic simulations. Further, drug library was created for the shortlisted target based on structural and side effect similarity with respective standard drugs. Finally, molecular docking, binding energy calculations and molecular dynamics studies were carried out to unravel the interactions exhibited by drugs from the created library with amino acids in active binding pocket of RGS4. RESULTS SST and RGS4 were shortlisted as potentially significant AD specific targets, however, the less explored target RGS4 was considered for further sequential analysis. Homology model constructed for RGS4 displayed best quality when validated through Ramachandran plot and ERRAT plot. Subsequent docking and molecular dynamics studies showcased substantial affinity demonstrated by three drugs viz., Ziprasidone, Melfoquine and Metaxalone from the created drug libraries, towards RGS4. CONCLUSION This virtual analysis forecasted the repurposable potential of Ziprasidone, Melfoquine and Metaxalone against AD based on their affinity towards RGS4, a key AD-specific target.
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Affiliation(s)
- Hema Sree G N S
- Pharmacological Modelling and Simulation Centre, M. S. Ramaiah University of Applied Sciences, Bangalore, Karnataka 560094, India
| | - V Lakshmi Prasanna Marise
- Pharmacological Modelling and Simulation Centre, M. S. Ramaiah University of Applied Sciences, Bangalore, Karnataka 560094, India; Department of Pharmacy Practice, Faculty of Pharmacy, M. S. Ramaiah University of Applied Sciences, Bangalore, Karnataka 560094, India
| | - Saraswathy Ganesan Rajalekshmi
- Pharmacological Modelling and Simulation Centre, M. S. Ramaiah University of Applied Sciences, Bangalore, Karnataka 560094, India; Department of Pharmacy Practice, Faculty of Pharmacy, M. S. Ramaiah University of Applied Sciences, Bangalore, Karnataka 560094, India.
| | | | - T P Krishna Murthy
- Department of Biotechnology, M. S. Ramaiah Institute of Technology, Bangalore, Karnataka 560054, India
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Luo H, Marron Fernandez de Velasco E, Wickman K. Neuronal G protein-gated K + channels. Am J Physiol Cell Physiol 2022; 323:C439-C460. [PMID: 35704701 PMCID: PMC9362898 DOI: 10.1152/ajpcell.00102.2022] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels exert a critical inhibitory influence on neurons. Neuronal GIRK channels mediate the G protein-dependent, direct/postsynaptic inhibitory effect of many neurotransmitters including γ-aminobutyric acid (GABA), serotonin, dopamine, adenosine, somatostatin, and enkephalin. In addition to their complex regulation by G proteins, neuronal GIRK channel activity is sensitive to PIP2, phosphorylation, regulator of G protein signaling (RGS) proteins, intracellular Na+ and Ca2+, and cholesterol. The application of genetic and viral manipulations in rodent models, together with recent progress in the development of GIRK channel modulators, has increased our understanding of the physiological and behavioral impact of neuronal GIRK channels. Work in rodent models has also revealed that neuronal GIRK channel activity is modified, transiently or persistently, by various stimuli including exposure drugs of abuse, changes in neuronal activity patterns, and aversive experience. A growing body of preclinical and clinical evidence suggests that dysregulation of GIRK channel activity contributes to neurological diseases and disorders. The primary goals of this review are to highlight fundamental principles of neuronal GIRK channel biology, mechanisms of GIRK channel regulation and plasticity, the nascent landscape of GIRK channel pharmacology, and the potential relevance of GIRK channels to the pathophysiology and treatment of neurological diseases and disorders.
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Affiliation(s)
- Haichang Luo
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
| | | | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
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8
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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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Jeong E, Kim Y, Jeong J, Cho Y. Structure of the class C orphan GPCR GPR158 in complex with RGS7-Gβ5. Nat Commun 2021; 12:6805. [PMID: 34815401 PMCID: PMC8611064 DOI: 10.1038/s41467-021-27147-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 11/04/2021] [Indexed: 11/22/2022] Open
Abstract
GPR158, a class C orphan GPCR, functions in cognition, stress-induced mood control, and synaptic development. Among class C GPCRs, GPR158 is unique as it lacks a Venus flytrap-fold ligand-binding domain and terminates Gαi/o protein signaling through the RGS7-Gβ5 heterodimer. Here, we report the cryo-EM structures of GPR158 alone and in complex with one or two RGS7-Gβ5 heterodimers. GPR158 dimerizes through Per-Arnt-Sim-fold extracellular and transmembrane (TM) domains connected by an epidermal growth factor-like linker. The TM domain (TMD) reflects both inactive and active states of other class C GPCRs: a compact intracellular TMD, conformations of the two intracellular loops (ICLs) and the TMD interface formed by TM4/5. The ICL2, ICL3, TM3, and first helix of the cytoplasmic coiled-coil provide a platform for the DHEX domain of one RGS7 and the second helix recruits another RGS7. The unique features of the RGS7-binding site underlie the selectivity of GPR158 for RGS7.
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Affiliation(s)
- Eunyoung Jeong
- grid.49100.3c0000 0001 0742 4007Department of Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Yoojoong Kim
- grid.49100.3c0000 0001 0742 4007Department of Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Jihong Jeong
- grid.49100.3c0000 0001 0742 4007Department of Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Yunje Cho
- Department of Life Science, Pohang University of Science and Technology, Pohang, Republic of Korea.
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Photoreceptor phosphodiesterase (PDE6): activation and inactivation mechanisms during visual transduction in rods and cones. Pflugers Arch 2021; 473:1377-1391. [PMID: 33860373 DOI: 10.1007/s00424-021-02562-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 03/27/2021] [Accepted: 03/30/2021] [Indexed: 01/16/2023]
Abstract
Rod and cone photoreceptors of the vertebrate retina utilize cGMP as the primary intracellular messenger for the visual signaling pathway that converts a light stimulus into an electrical response. cGMP metabolism in the signal-transducing photoreceptor outer segment reflects the balance of cGMP synthesis (catalyzed by guanylyl cyclase) and degradation (catalyzed by the photoreceptor phosphodiesterase, PDE6). Upon light stimulation, rapid activation of PDE6 by the heterotrimeric G-protein (transducin) triggers a dramatic drop in cGMP levels that lead to cell hyperpolarization. Following cessation of the light stimulus, the lifetime of activated PDE6 is also precisely regulated by additional processes. This review summarizes recent advances in the structural characterization of the rod and cone PDE6 catalytic and regulatory subunits in the context of previous biochemical studies of the enzymological properties and allosteric regulation of PDE6. Emphasis is given to recent advances in understanding the structural and conformational changes underlying the mechanism by which the activated transducin α-subunit binds to-and relieves inhibition of-PDE6 catalysis that is controlled by its intrinsically disordered, inhibitory γ-subunit. The role of the regulator of G-protein signaling 9-1 (RGS9-1) in regulating the lifetime of the transducin-PDE6 is also briefly covered. The therapeutic potential of pharmacological compounds acting as inhibitors or activators targeting PDE6 is discussed in the context of inherited retinal diseases resulting from mutations in rod and cone PDE6 genes as well as other inherited defects that arise from excessive cGMP accumulation in retinal photoreceptor cells.
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11
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Gao Y, Eskici G, Ramachandran S, Poitevin F, Seven AB, Panova O, Skiniotis G, Cerione RA. Structure of the Visual Signaling Complex between Transducin and Phosphodiesterase 6. Mol Cell 2020; 80:237-245.e4. [PMID: 33007200 DOI: 10.1016/j.molcel.2020.09.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 08/04/2020] [Accepted: 09/09/2020] [Indexed: 12/21/2022]
Abstract
Heterotrimeric G proteins communicate signals from activated G protein-coupled receptors to downstream effector proteins. In the phototransduction pathway responsible for vertebrate vision, the G protein-effector complex is composed of the GTP-bound transducin α subunit (GαT·GTP) and the cyclic GMP (cGMP) phosphodiesterase 6 (PDE6), which stimulates cGMP hydrolysis, leading to hyperpolarization of the photoreceptor cell. Here we report a cryo-electron microscopy (cryoEM) structure of PDE6 complexed to GTP-bound GαT. The structure reveals two GαT·GTP subunits engaging the PDE6 hetero-tetramer at both the PDE6 catalytic core and the PDEγ subunits, driving extensive rearrangements to relieve all inhibitory constraints on enzyme catalysis. Analysis of the conformational ensemble in the cryoEM data highlights the dynamic nature of the contacts between the two GαT·GTP subunits and PDE6 that supports an alternating-site catalytic mechanism.
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Affiliation(s)
- Yang Gao
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Gözde Eskici
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sekar Ramachandran
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA; Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Frédéric Poitevin
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Alpay Burak Seven
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Ouliana Panova
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Georgios Skiniotis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA; Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA.
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12
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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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13
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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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14
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Unique retinal signaling defect in GNB5-related disease. Doc Ophthalmol 2019; 140:273-277. [PMID: 31720979 DOI: 10.1007/s10633-019-09735-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/05/2019] [Indexed: 10/25/2022]
Abstract
OBJECTIVE To report a unique retinal signaling defect in GNB5-related disease. METHODS A 3-year-old female child underwent detailed systemic and ophthalmological evaluation. The eye examination included fundus photography, spectral domain optical coherence tomography and an extended protocol full-field electroretinography (ERG) including the ISCEV recommended standard steps. The dark-adapted (DA) ERGs were performed to a series of white flashes (range 0.006-30.0 cd s m-2) and two red flashes. The DA ERGs to higher stimulus intensities (3.0, 10.0 and 30.0 cd s m-2) were tested using a range of inter-stimulus intervals (ISI) of up to 60 s. In addition to standard light-adapted (LA) ERGs, a short-duration (0.5 s) LA 3.0 30-Hz flicker ERG and a long-duration LA ON-OFF ERG were also performed. Genetic testing included microarray, mitochondrial genome testing and whole exome sequencing. RESULTS The child was diagnosed to have status epilepticus and bradycardia at 6 months of age. Subsequently, she was diagnosed to have global developmental delay and hypotonia. On ophthalmological evaluation, the child fixes and follows light. Fundus evaluation showed mild optic disk pallor; macular SD-OCT was normal. The dim flash DA ERGs (DA 0.006 and DA 0.01 cd s m-2) were non-detectable. DA red flash ERGs showed the presence of an x-wave (cone component) and no rod component. The DA 3.0, 10.0 and 30.0 ERGs showed electronegative configuration regardless of the ISI; the averaged a-wave amplitude (4 flashes) was smaller at shorter ISI but became normal at a prolonged ISI (60 s). The LA 30-Hz flicker ERG was severely reduced but detectable for the initial 0.5 s; this became non-detectable after 5 s of averaging. The LA 3.0 2-Hz ERG showed markedly reduced a- and b-wave amplitudes and a reduced b:a ratio; the LA ON-OFF ERGs were non-detectable. WES identified a homozygous null mutation in G protein subunit beta 5 (GNB5; c.1032C>A/p.Tyr344*). CONCLUSION This report identifies for the first time a unique retinopathy associated with biallelic mutations in GNB5. The observed phenotype is consistent with a dual retinal signaling defect reminiscent of features of bradyopsia and rod ON-bipolar dysfunction.
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15
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Adikaram PR, Zhang JH, Kittock CM, Pandey M, Hassan SA, Lue NG, Wang G, Gucek M, Simonds WF. Development of R7BP inhibitors through cross-linking coupled mass spectrometry and integrated modeling. Commun Biol 2019; 2:338. [PMID: 31531399 PMCID: PMC6744478 DOI: 10.1038/s42003-019-0585-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 08/21/2019] [Indexed: 02/08/2023] Open
Abstract
Protein-protein interaction (PPI) networks are known to be valuable targets for therapeutic intervention; yet the development of PPI modulators as next-generation drugs to target specific vertices, edges, and hubs has been impeded by the lack of structural information of many of the proteins and complexes involved. Building on recent advancements in cross-linking mass spectrometry (XL-MS), we describe an effective approach to obtain relevant structural data on R7BP, a master regulator of itch sensation, and its interfaces with other proteins in its network. This approach integrates XL-MS with a variety of modeling techniques to successfully develop antibody inhibitors of the R7BP and RGS7/Gβ5 duplex interaction. Binding and inhibitory efficiency are studied by surface plasmon resonance spectroscopy and through an R7BP-derived dominant negative construct. This approach may have broader applications as a tool to facilitate the development of PPI modulators in the absence of crystal structures or when structural information is limited.
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Affiliation(s)
- Poorni R. Adikaram
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bldg. 10/Rm 8C-101, Bethesda, MD 20892 USA
| | - Jian-Hua Zhang
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bldg. 10/Rm 8C-101, Bethesda, MD 20892 USA
| | - Claire M. Kittock
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bldg. 10/Rm 8C-101, Bethesda, MD 20892 USA
| | - Mritunjay Pandey
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bldg. 10/Rm 8C-101, Bethesda, MD 20892 USA
| | - Sergio A. Hassan
- Center for Molecular Modeling, Center for Information Technology, Bldg. 12/Rm 2049, Bethesda, MD 20892 USA
| | - Nicole G. Lue
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bldg. 10/Rm 8C-101, Bethesda, MD 20892 USA
| | - Guanghui Wang
- Proteomics Core, National Heart Lung and Blood Institute, National Institutes of Health, Bldg. 10/Rm 8C-103A, Bethesda, MD 20892 USA
| | - Marjan Gucek
- Proteomics Core, National Heart Lung and Blood Institute, National Institutes of Health, Bldg. 10/Rm 8C-103A, Bethesda, MD 20892 USA
| | - William F. Simonds
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bldg. 10/Rm 8C-101, Bethesda, MD 20892 USA
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16
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Rademacher N, Kuropka B, Kunde SA, Wahl MC, Freund C, Shoichet SA. Intramolecular domain dynamics regulate synaptic MAGUK protein interactions. eLife 2019; 8:41299. [PMID: 30864948 PMCID: PMC6438691 DOI: 10.7554/elife.41299] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 03/12/2019] [Indexed: 12/25/2022] Open
Abstract
PSD-95 MAGUK family scaffold proteins are multi-domain organisers of synaptic transmission that contain three PDZ domains followed by an SH3-GK domain tandem. This domain architecture allows coordinated assembly of protein complexes composed of neurotransmitter receptors, synaptic adhesion molecules and downstream signalling effectors. Here we show that binding of monomeric CRIPT-derived PDZ3 ligands to the third PDZ domain of PSD-95 induces functional changes in the intramolecular SH3-GK domain assembly that influence subsequent homotypic and heterotypic complex formation. We identify PSD-95 interactors that differentially bind to the SH3-GK domain tandem depending on its conformational state. Among these interactors, we further establish the heterotrimeric G protein subunit Gnb5 as a PSD-95 complex partner at dendritic spines of rat hippocampal neurons. The PSD-95 GK domain binds to Gnb5, and this interaction is triggered by CRIPT-derived PDZ3 ligands binding to the third PDZ domain of PSD-95, unraveling a hierarchical binding mechanism of PSD-95 complex formation.
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Affiliation(s)
- Nils Rademacher
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Benno Kuropka
- Institute of Chemistry and Biochemistry, Laboratory of Protein Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Stella-Amrei Kunde
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Markus C Wahl
- Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin, Berlin, Germany.,Macromolecular Crystallography, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - Christian Freund
- Institute of Chemistry and Biochemistry, Laboratory of Protein Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Sarah A Shoichet
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
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17
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Patil DN, Rangarajan ES, Novick SJ, Pascal BD, Kojetin DJ, Griffin PR, Izard T, Martemyanov KA. Structural organization of a major neuronal G protein regulator, the RGS7-Gβ5-R7BP complex. eLife 2018; 7:42150. [PMID: 30540250 PMCID: PMC6310461 DOI: 10.7554/elife.42150] [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: 09/18/2018] [Accepted: 12/12/2018] [Indexed: 01/03/2023] Open
Abstract
Signaling by the G-protein-coupled receptors (GPCRs) plays fundamental role in a vast number of essential physiological functions. Precise control of GPCR signaling requires action of regulators of G protein signaling (RGS) proteins that deactivate heterotrimeric G proteins. RGS proteins are elaborately regulated and comprise multiple domains and subunits, yet structural organization of these assemblies is poorly understood. Here, we report a crystal structure and dynamics analyses of the multisubunit complex of RGS7, a major regulator of neuronal signaling with key roles in controlling a number of drug target GPCRs and links to neuropsychiatric disease, metabolism, and cancer. The crystal structure in combination with molecular dynamics and mass spectrometry analyses reveals unique organizational features of the complex and long-range conformational changes imposed by its constituent subunits during allosteric modulation. Notably, several intermolecular interfaces in the complex work in synergy to provide coordinated modulation of this key GPCR regulator.
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Affiliation(s)
- Dipak N Patil
- Department of Neuroscience, The Scripps Research Institute, Jupiter, United States
| | - Erumbi S Rangarajan
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, United States
| | - Scott J Novick
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, United States
| | - Bruce D Pascal
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, United States
| | - Douglas J Kojetin
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, United States
| | - Patrick R Griffin
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, United States.,Department of Molecular Medicine, The Scripps Research Institute, Jupiter, United States
| | - Tina Izard
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, United States
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, United States
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18
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Qutob N, Masuho I, Alon M, Emmanuel R, Cohen I, Di Pizio A, Madore J, Elkahloun A, Ziv T, Levy R, Gartner JJ, Hill VK, Lin JC, Hevroni Y, Greenberg P, Brodezki A, Rosenberg SA, Kosloff M, Hayward NK, Admon A, Niv MY, Scolyer RA, Martemyanov KA, Samuels Y. RGS7 is recurrently mutated in melanoma and promotes migration and invasion of human cancer cells. Sci Rep 2018; 8:653. [PMID: 29330521 PMCID: PMC5766496 DOI: 10.1038/s41598-017-18851-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 12/19/2017] [Indexed: 11/14/2022] Open
Abstract
Analysis of 501 melanoma exomes revealed RGS7, which encodes a GTPase-accelerating protein (GAP), to be a tumor-suppressor gene. RGS7 was mutated in 11% of melanomas and was found to harbor three recurrent mutations (p.R44C, p.E383K and p.R416Q). Structural modeling of the most common recurrent mutation of the three (p.R44C) predicted that it destabilizes the protein due to the loss of an H-bond and salt bridge network between the mutated position and the serine and aspartic acid residues at positions 58 as 61, respectively. We experimentally confirmed this prediction showing that the p.R44C mutant protein is indeed destabilized. We further show RGS7 p.R44C has weaker catalytic activity for its substrate Gαo, thus providing a dual mechanism for its loss of function. Both of these effects are expected to contribute to loss of function of RGS7 resulting in increased anchorage-independent growth, migration and invasion of melanoma cells. By mutating position 56 in the R44C mutant from valine to cysteine, thereby enabling the formation of a disulfide bridge between the two mutated positions, we slightly increased the catalytic activity and reinstated protein stability, leading to the rescue of RGS7′s function as a tumor suppressor. Our findings identify RGS7 as a novel melanoma driver and point to the clinical relevance of using strategies to stabilize the protein and, thereby, restore its function.
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Affiliation(s)
- Nouar Qutob
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute, FL, 33458, USA
| | - Michal Alon
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Rafi Emmanuel
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Isadora Cohen
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Antonella Di Pizio
- Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University, Rehovot, Israel
| | - Jason Madore
- Melanoma Institute Australia, University of Sydney, NSW, Australia.,Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, NSW, Australia
| | - Abdel Elkahloun
- National Human Genome Research Institute, US National Institutes of Health, Bethesda, Maryland, USA
| | - Tamar Ziv
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Ronen Levy
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Jared J Gartner
- National Cancer Institute, Surgery Branch, US National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Victoria K Hill
- National Human Genome Research Institute, US National Institutes of Health, Bethesda, Maryland, USA
| | - Jimmy C Lin
- National Human Genome Research Institute, US National Institutes of Health, Bethesda, Maryland, USA
| | - Yael Hevroni
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Polina Greenberg
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Alexandra Brodezki
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel
| | - Steven A Rosenberg
- National Human Genome Research Institute, US National Institutes of Health, Bethesda, Maryland, USA
| | - Mickey Kosloff
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Nicholas K Hayward
- Melanoma Institute Australia, University of Sydney, NSW, Australia.,QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Arie Admon
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Masha Y Niv
- Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University, Rehovot, Israel
| | - Richard A Scolyer
- Melanoma Institute Australia, University of Sydney, NSW, Australia.,Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, NSW, Australia.,Disciplines of Surgery and Pathology, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia
| | | | - Yardena Samuels
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot, Israel.
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19
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Huang H, Zhu CT, Skuja LL, Hayden DJ, Hart AC. Genome-Wide Screen for Genes Involved in Caenorhabditis elegans Developmentally Timed Sleep. G3 (BETHESDA, MD.) 2017; 7:2907-2917. [PMID: 28743807 PMCID: PMC5592919 DOI: 10.1534/g3.117.300071] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 07/21/2017] [Indexed: 12/24/2022]
Abstract
In Caenorhabditis elegans, Notch signaling regulates developmentally timed sleep during the transition from L4 larval stage to adulthood (L4/A) . To identify core sleep pathways and to find genes acting downstream of Notch signaling, we undertook the first genome-wide, classical genetic screen focused on C. elegans developmentally timed sleep. To increase screen efficiency, we first looked for mutations that suppressed inappropriate anachronistic sleep in adult hsp::osm-11 animals overexpressing the Notch coligand OSM-11 after heat shock. We retained suppressor lines that also had defects in L4/A developmentally timed sleep, without heat shock overexpression of the Notch coligand. Sixteen suppressor lines with defects in developmentally timed sleep were identified. One line carried a new allele of goa-1; loss of GOA-1 Gαo decreased C. elegans sleep. Another line carried a new allele of gpb-2, encoding a Gβ5 protein; Gβ5 proteins have not been previously implicated in sleep. In other scenarios, Gβ5 GPB-2 acts with regulators of G protein signaling (RGS proteins) EAT-16 and EGL-10 to terminate either EGL-30 Gαq signaling or GOA-1 Gαo signaling, respectively. We found that loss of Gβ5 GPB-2 or RGS EAT-16 decreased L4/A sleep. By contrast, EGL-10 loss had no impact. Instead, loss of RGS-1 and RGS-2 increased sleep. Combined, our results suggest that, in the context of L4/A sleep, GPB-2 predominantly acts with EAT-16 RGS to inhibit EGL-30 Gαq signaling. These results confirm the importance of G protein signaling in sleep and demonstrate that these core sleep pathways function genetically downstream of the Notch signaling events promoting sleep.
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Affiliation(s)
- Huiyan Huang
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
| | - Chen-Tseh Zhu
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island 02912
| | - Lukas L Skuja
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
| | - Dustin J Hayden
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
| | - Anne C Hart
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912
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20
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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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Shamseldin HE, Masuho I, Alenizi A, Alyamani S, Patil DN, Ibrahim N, Martemyanov KA, Alkuraya FS. GNB5 mutation causes a novel neuropsychiatric disorder featuring attention deficit hyperactivity disorder, severely impaired language development and normal cognition. Genome Biol 2016; 17:195. [PMID: 27677260 PMCID: PMC5037613 DOI: 10.1186/s13059-016-1061-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 09/12/2016] [Indexed: 11/23/2022] Open
Abstract
Background Neuropsychiatric disorders are common forms of disability in humans. Despite recent progress in deciphering the genetics of these disorders, their phenotypic complexity continues to be a major challenge. Mendelian neuropsychiatric disorders are rare but their study has the potential to unravel novel mechanisms that are relevant to their complex counterparts. Results In an extended consanguineous family, we identified a novel neuropsychiatric phenotype characterized by severe speech impairment, variable expressivity of attention deficit hyperactivity disorder (ADHD), and motor delay. We identified the disease locus through linkage analysis on 15q21.2, and exome sequencing revealed a novel missense variant in GNB5. GNB5 encodes an atypical β subunit of the heterotrimeric GTP-binding proteins (Gβ5). Gβ5 is enriched in the central nervous system where it forms constitutive complexes with members of the regulator of G protein signaling family of proteins to modulate neurotransmitter signaling that affects a number of neurobehavioral outcomes. Here, we show that the S81L mutant form of Gβ5 has significantly impaired activity in terminating responses that are elicited by dopamine. Conclusions We demonstrate that these deficits originate from the impaired expression of the mutant Gβ5 protein, resulting in the decreased ability to stabilize regulator of G protein signaling complexes. Our data suggest that this novel neuropsychiatric phenotype is the human equivalent of Gnb5 deficiency in mice, which manifest motor deficits and hyperactivity, and highlight a critical role of Gβ5 in normal behavior as well as language and motor development in humans. Electronic supplementary material The online version of this article (doi:10.1186/s13059-016-1061-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hanan E Shamseldin
- Department of Genetics, King Faisal Specialist Hospital and Research Center, MBC-03, PO Box 3354, Riyadh, 11211, Saudi Arabia
| | - Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, #3C2, Jupiter, FL, 33458, USA
| | - Ahmed Alenizi
- Department of Pediatrics, King Saud Medical City, Riyadh, Saudi Arabia
| | - Suad Alyamani
- Department of Neurosciences, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Dipak N Patil
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, #3C2, Jupiter, FL, 33458, USA
| | - Niema Ibrahim
- Department of Genetics, King Faisal Specialist Hospital and Research Center, MBC-03, PO Box 3354, Riyadh, 11211, Saudi Arabia
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, #3C2, Jupiter, FL, 33458, USA.
| | - Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, MBC-03, PO Box 3354, Riyadh, 11211, Saudi Arabia. .,Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia.
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GNB5 Mutations Cause an Autosomal-Recessive Multisystem Syndrome with Sinus Bradycardia and Cognitive Disability. Am J Hum Genet 2016; 99:704-710. [PMID: 27523599 DOI: 10.1016/j.ajhg.2016.06.025] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 06/24/2016] [Indexed: 11/20/2022] Open
Abstract
GNB5 encodes the G protein β subunit 5 and is involved in inhibitory G protein signaling. Here, we report mutations in GNB5 that are associated with heart-rate disturbance, eye disease, intellectual disability, gastric problems, hypotonia, and seizures in nine individuals from six families. We observed an association between the nature of the variants and clinical severity; individuals with loss-of-function alleles had more severe symptoms, including substantial developmental delay, speech defects, severe hypotonia, pathological gastro-esophageal reflux, retinal disease, and sinus-node dysfunction, whereas related heterozygotes harboring missense variants presented with a clinically milder phenotype. Zebrafish gnb5 knockouts recapitulated the phenotypic spectrum of affected individuals, including cardiac, neurological, and ophthalmological abnormalities, supporting a direct role of GNB5 in the control of heart rate, hypotonia, and vision.
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23
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Vincent A, Audo I, Tavares E, Maynes J, Tumber A, Wright T, Li S, Michiels C, Condroyer C, MacDonald H, Verdet R, Sahel JA, Hamel CP, Zeitz C, Héon E, Banin E, Bocquet B, De Baere E, Casteels I, Defoort-Dhellemmes S, Drumare I, Friedburg C, Gottlob I, Jacobson S, Kellner U, Koenekoop R, Kohl S, Leroy B, Lorenz B, McLean R, Meire F, Meunier I, Munier F, de Ravel T, Reiff C, Mohand-Saïd S, Sharon D, Schorderet D, Schwartz S, Zanlonghi X. Biallelic Mutations in GNB3 Cause a Unique Form of Autosomal-Recessive Congenital Stationary Night Blindness. Am J Hum Genet 2016; 98:1011-1019. [PMID: 27063057 DOI: 10.1016/j.ajhg.2016.03.021] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 03/18/2016] [Indexed: 01/13/2023] Open
Abstract
Congenital stationary night blindness (CSNB) is a heterogeneous group of non-progressive inherited retinal disorders with characteristic electroretinogram (ERG) abnormalities. Riggs and Schubert-Bornschein are subtypes of CSNB and demonstrate distinct ERG features. Riggs CSNB demonstrates selective rod photoreceptor dysfunction and occurs due to mutations in genes encoding proteins involved in rod phototransduction cascade; night blindness is the only symptom and eye examination is otherwise normal. Schubert-Bornschein CSNB is a consequence of impaired signal transmission between the photoreceptors and bipolar cells. Schubert-Bornschein CSNB is subdivided into complete CSNB with an ON bipolar signaling defect and incomplete CSNB with both ON and OFF pathway involvement. Both subtypes are associated with variable degrees of night blindness or photophobia, reduced visual acuity, high myopia, and nystagmus. Whole-exome sequencing of a family screened negative for mutations in genes associated with CSNB identified biallelic mutations in the guanine nucleotide-binding protein subunit beta-3 gene (GNB3). Two siblings were compound heterozygous for a deletion (c.170_172delAGA [p.Lys57del]) and a nonsense mutation (c.1017G>A [p.Trp339(∗)]). The maternal aunt was homozygous for the nonsense mutation (c.1017G>A [p.Trp339(∗)]). Mutational analysis of GNB3 in a cohort of 58 subjects with CSNB identified a sporadic case individual with a homozygous GNB3 mutation (c.200C>T [p.Ser67Phe]). GNB3 encodes the β subunit of G protein heterotrimer (Gαβγ) and is known to modulate ON bipolar cell signaling and cone transducin function in mice. Affected human subjects showed an unusual CSNB phenotype with variable degrees of ON bipolar dysfunction and reduced cone sensitivity. This unique retinal disorder with dual anomaly in visual processing expands our knowledge about retinal signaling.
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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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25
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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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26
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Coleman BD, Marivin A, Parag-Sharma K, DiGiacomo V, Kim S, Pepper JS, Casler J, Nguyen LT, Koelle MR, Garcia-Marcos M. Evolutionary Conservation of a GPCR-Independent Mechanism of Trimeric G Protein Activation. Mol Biol Evol 2015; 33:820-37. [PMID: 26659249 PMCID: PMC4760084 DOI: 10.1093/molbev/msv336] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Trimeric G protein signaling is a fundamental mechanism of cellular communication in eukaryotes. The core of this mechanism consists of activation of G proteins by the guanine-nucleotide exchange factor (GEF) activity of G protein coupled receptors. However, the duration and amplitude of G protein-mediated signaling are controlled by a complex network of accessory proteins that appeared and diversified during evolution. Among them, nonreceptor proteins with GEF activity are the least characterized. We recently found that proteins of the ccdc88 family possess a Gα-binding and activating (GBA) motif that confers GEF activity and regulates mammalian cell behavior. A sequence similarity-based search revealed that ccdc88 genes are highly conserved across metazoa but the GBA motif is absent in most invertebrates. This prompted us to investigate whether the GBA motif is present in other nonreceptor proteins in invertebrates. An unbiased bioinformatics search in Caenorhabditis elegans identified GBAS-1 (GBA and SPK domain containing-1) as a GBA motif-containing protein with homologs only in closely related worm species. We demonstrate that GBAS-1 has GEF activity for the nematode G protein GOA-1 and that the two proteins are coexpressed in many cells of living worms. Furthermore, we show that GBAS-1 can activate mammalian Gα-subunits and provide structural insights into the evolutionarily conserved determinants of the GBA–G protein interface. These results demonstrate that the GBA motif is a functional GEF module conserved among highly divergent proteins across evolution, indicating that the GBA-Gα binding mode is strongly constrained under selective pressure to mediate receptor-independent G protein activation in metazoans.
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Affiliation(s)
| | - Arthur Marivin
- Department of Biochemistry, Boston University School of Medicine
| | | | | | - Seongseop Kim
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine
| | - Judy S Pepper
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine
| | - Jason Casler
- Department of Biochemistry, Boston University School of Medicine
| | - Lien T Nguyen
- Department of Biochemistry, Boston University School of Medicine
| | - Michael R Koelle
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine
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Generating Recombinant Antibodies against Putative Biomarkers of Retinal Injury. PLoS One 2015; 10:e0124492. [PMID: 25902199 PMCID: PMC4406585 DOI: 10.1371/journal.pone.0124492] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 03/10/2015] [Indexed: 01/08/2023] Open
Abstract
Candidate biomarkers, indicative of disease or injury, are beginning to overwhelm the process of validation through immunological means. Recombinant antibodies developed through phage-display offer an alternative means of generating monoclonal antibodies faster than traditional immunization of animals. Peptide segments of putative biomarkers of laser induced injury in the rabbit, discovered through mass spectrometry, were used as targets for a selection against a library of phage-displayed human single-chain variable fragment (scFv) antibodies. Highly specific antibodies were isolated to four of these unique peptide sequences. One antibody against the retinal protein, Guanine Nucleotide-Binding Protein Beta 5 (GBB5), had a dissociation constant ~300 nM and recognized the full-length endogenous protein in retinal homogenates of three different animal species by western blot. Alanine scanning of the peptide target identified three charged and one hydrophobic amino acid as the critical binding residues for two different scFvs. To enhance the utility of the reagent, one scFv was dimerized through a Fragment-crystallizable hinge region (i.e., Fc) and expressed in HEK-293 cells. This dimeric reagent yielded a 25-fold lower detection limit in western blots.
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28
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Stewart A, Maity B, Fisher RA. Two for the Price of One: G Protein-Dependent and -Independent Functions of RGS6 In Vivo. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 133:123-51. [PMID: 26123305 DOI: 10.1016/bs.pmbts.2015.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Regulator of G protein signaling 6 (RGS6) is unique among the members of the RGS protein family as it remains the only protein with the demonstrated capacity to control G protein-dependent and -independent signaling cascades in vivo. RGS6 inhibits signaling mediated by γ-aminobutyric acid B receptors, serotonin 1A receptors, μ opioid receptors, and muscarinic acetylcholine 2 receptors. RGS6 deletion triggers distinct behavioral phenotypes resulting from potentiated signaling by these G protein-coupled receptors namely ataxia, a reduction in anxiety and depression, enhanced analgesia, and increased parasympathetic tone, respectively. In addition, RGS6 possesses potent proapoptotic and growth suppressive actions. In heart, RGS6-dependent reactive oxygen species (ROS) production promotes doxorubicin (Dox)-induced cardiomyopathy, while in cancer cells RGS6/ROS signaling is necessary for activation of the ataxia telangiectasia mutated/p53/apoptosis pathway required for the chemotherapeutic efficacy of Dox. Further, by facilitating Tip60 (trans-acting regulator protein of HIV type 1-interacting protein 60 kDa)-dependent DNA methyltransferase 1 degradation, RGS6 suppresses cellular transformation in response to oncogenic Ras. The culmination of these G protein-independent actions results in potent tumor suppressor actions of RGS6 in the murine mammary epithelium. This work summarizes evidence from human genetic studies and model animals implicating RGS6 in normal physiology, disease, and the pharmacological actions of multiple drugs. Though efforts by multiple laboratories have contributed to the ever-growing RGS6 oeuvre, the pleiotropic nature of this gene will likely lead to additional work detailing the importance of RGS6 in neuropsychiatric disorders, cardiovascular disease, and cancer.
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Affiliation(s)
- Adele Stewart
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Biswanath Maity
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Rory A Fisher
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
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Orlandi C, Xie K, Masuho I, Fajardo-Serrano A, Lujan R, Martemyanov KA. Orphan Receptor GPR158 Is an Allosteric Modulator of RGS7 Catalytic Activity with an Essential Role in Dictating Its Expression and Localization in the Brain. J Biol Chem 2015; 290:13622-39. [PMID: 25792749 DOI: 10.1074/jbc.m115.645374] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 11/06/2022] Open
Abstract
Regulators of G protein signaling control the duration and extent of signaling via G protein-coupled receptor (GPCR) pathways by accelerating the GTP hydrolysis on G protein α subunits thereby promoting termination of GPCR signaling. A member of this family, RGS7, plays a critical role in the nervous system where it regulates multiple neurotransmitter GPCRs that mediate vision, memory, and the action of addictive drugs. Previous studies have established that in vivo RGS7 forms mutually exclusive complexes with the membrane protein RGS7-binding protein or the orphan receptor GPR158. In this study, we examine the impact of GPR158 on RGS7 in the brain. We report that knock-out of GPR158 in mice results in marked post-transcriptional destabilization of RGS7 and substantial loss of its association with membranes in several brain regions. We further identified the RGS7-binding site in the C terminus of GPR158 and found that it shares significant homology with the RGS7-binding protein. The proximal portion of the GPR158 C terminus additionally contained a conserved sequence that was capable of enhancing RGS7 GTPase-activating protein activity in solution by an allosteric mechanism acting in conjunction with the regulators of the G protein signaling-binding domain. The distal portion of the GPR158 C terminus contained several phosphodiesterase E γ-like motifs and selectively recruited G proteins in their activated state. The results of this study establish GPR158 as an essential regulator of RGS7 in the native nervous system with a critical role in controlling its expression, membrane localization, and catalytic activity.
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Affiliation(s)
- Cesare Orlandi
- From the Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458 and
| | - Keqiang Xie
- From the Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458 and
| | - Ikuo Masuho
- From the Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458 and
| | - Ana Fajardo-Serrano
- the Instituto de Investigación en Descapacidades Neuronales (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, 02006 Albacete, Spain
| | - Rafael Lujan
- the Instituto de Investigación en Descapacidades Neuronales (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, 02006 Albacete, Spain
| | - Kirill A Martemyanov
- From the Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458 and
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de Velasco EMF, McCall N, Wickman K. GIRK Channel Plasticity and Implications for Drug Addiction. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:201-38. [DOI: 10.1016/bs.irn.2015.05.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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31
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Ostrovskaya O, Xie K, Masuho I, Fajardo-Serrano A, Lujan R, Wickman K, Martemyanov KA. RGS7/Gβ5/R7BP complex regulates synaptic plasticity and memory by modulating hippocampal GABABR-GIRK signaling. eLife 2014; 3:e02053. [PMID: 24755289 PMCID: PMC3988575 DOI: 10.7554/elife.02053] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In the hippocampus, the inhibitory neurotransmitter GABA shapes the activity of the output pyramidal neurons and plays important role in cognition. Most of its inhibitory effects are mediated by signaling from GABAB receptor to the G protein-gated Inwardly-rectifying K+ (GIRK) channels. Here, we show that RGS7, in cooperation with its binding partner R7BP, regulates GABABR-GIRK signaling in hippocampal pyramidal neurons. Deletion of RGS7 in mice dramatically sensitizes GIRK responses to GABAB receptor stimulation and markedly slows channel deactivation kinetics. Enhanced activity of this signaling pathway leads to decreased neuronal excitability and selective disruption of inhibitory forms of synaptic plasticity. As a result, mice lacking RGS7 exhibit deficits in learning and memory. We further report that RGS7 is selectively modulated by its membrane anchoring subunit R7BP, which sets the dynamic range of GIRK responses. Together, these results demonstrate a novel role of RGS7 in hippocampal synaptic plasticity and memory formation. DOI:http://dx.doi.org/10.7554/eLife.02053.001 Neurons communicate with one another at junctions called synapses. The arrival of an electrical signal known as an action potential at the first cell causes molecules known as neurotransmitters to be released into the synapse. These molecules diffuse across the gap between the neurons and bind to receptors on the receiving cell. Some neurotransmitters, such as glutamate, activate cells when they bind to receptors, thus making it easier for the second neuron to ‘fire’ (i.e., to generate an action potential). By contrast, other neurotransmitters, such as GABA, usually make it harder for the second neuron to fire. Many of the effects of GABA involve a type of receptor called GABAB. When GABA binds to one of these receptors, a molecule called a G-protein is recruited to the receptor. This activates the G-protein, triggering a cascade of events inside the cell that lead ultimately to the opening of potassium ion channels, which as known as GIRKs, in the cell membrane. Positively charged potassium ions then leave the cell through these channels, and this makes it more difficult for the cell to fire. Now, Ostrovskaya et al. have revealed that a complex of three proteins regulates the interaction between GABAB receptors and GIRK channels. In neurons that lack either of these proteins, the receptors have less influence on GIRKs than in normal cells. Moreover, mice that lack one of the proteins (called RGS7) perform less well in various learning and memory tests: for example, they take longer than normal animals to learn the location of an escape platform in a water maze, or to retain a memory of a fearful event. By identifying the proteins that regulate the interaction between GABAB receptors and GIRKs, Ostrovskaya et al. have helped to unravel a key signaling cascade relevant to cognition. Given that GIRK channels have recently been implicated in Down’s syndrome, these insights may also increase understanding of cognitive impairments in neuropsychiatric disorders. DOI:http://dx.doi.org/10.7554/eLife.02053.002
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Affiliation(s)
- Olga Ostrovskaya
- Department of Neuroscience, The Scripps Research Institute, Jupiter, United States
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Abstract
The Dishevelled, EGL-10 and pleckstrin (DEP) domain is a globular protein domain that is present in about ten human protein families with well-defined structural features. A picture is emerging that DEP domains mainly function in the spatial and temporal control of diverse signal transduction events by recruiting proteins to the plasma membrane. DEP domains can interact with various partners at the membrane, including phospholipids and membrane receptors, and their binding is subject to regulation.
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Karpinsky-Semper D, Volmar CH, Brothers SP, Slepak VZ. Differential effects of the Gβ5-RGS7 complex on muscarinic M3 receptor-induced Ca2+ influx and release. Mol Pharmacol 2014; 85:758-68. [PMID: 24586057 DOI: 10.1124/mol.114.091843] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The G protein β subunit Gβ5 uniquely forms heterodimers with R7 family regulators of G protein signaling (RGS) proteins (RGS6, RGS7, RGS9, and RGS11) instead of Gγ. Although the Gβ5-RGS7 complex attenuates Ca(2+) signaling mediated by the muscarinic M3 receptor (M3R), the route of Ca(2+) entry (i.e., release from intracellular stores and/or influx across the plasma membrane) is unknown. Here, we show that, in addition to suppressing carbachol-stimulated Ca(2+) release, Gβ5-RGS7 enhanced Ca(2+) influx. This novel effect of Gβ5-RGS7 was blocked by nifedipine and 2-aminoethoxydiphenyl borate. Experiments with pertussis toxin, an RGS domain-deficient mutant of RGS7, and UBO-QIC {L-threonine,(3R)-N-acetyl-3-hydroxy-L-leucyl-(aR)-a-hydroxybenzenepropanoyl-2,3-idehydro-N-methylalanyl-L-alanyl-N-methyl-L-alanyl-(3R)-3-[[(2S,3R)-3-hydroxy-4- methyl-1-oxo-2-[(1-oxopropyl)amino]pentyl]oxy]-L-leucyl-N,O-dimethyl-,(7→1)-lactone (9CI)}, a novel inhibitor of Gq, showed that Gβ5-RGS7 modulated a Gq-mediated pathway. These studies indicate that Gβ5-RGS7, independent of RGS7 GTPase-accelerating protein activity, couples M3R to a nifedipine-sensitive Ca(2+) channel. We also compared the action of Gβ5-RGS7 on M3R-induced Ca(2+) influx and release elicited by different muscarinic agonists. Responses to Oxo-M [oxotremorine methiodide N,N,N,-trimethyl-4-(2-oxo-1-pyrrolidinyl)-2-butyn-1-ammonium iodide] were insensitive to Gβ5-RGS7. Pilocarpine responses consisted of a large release and modest influx components, of which the former was strongly inhibited whereas the latter was insensitive to Gβ5-RGS7. McN-A-343 [(4-hydroxy-2-butynyl)-1-trimethylammonium-3-chlorocarbanilate chloride] was the only compound whose total Ca(2+) response was enhanced by Gβ5-RGS7, attributed to, in part, by the relatively small Ca(2+) release this partial agonist stimulated. Together, these results show that distinct agonists not only have differential M3R functional selectivity, but also confer specific sensitivity to the Gβ5-RGS7 complex.
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Affiliation(s)
- Darla Karpinsky-Semper
- Department of Molecular and Cellular Pharmacology (D.K.-S., V.Z.S.) and Center for Therapeutic Innovation, Department of Psychiatry and Behavioral Sciences (C.-H.V., S.P.B.), University of Miami Miller School of Medicine, Miami, Florida
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Luján R, Marron Fernandez de Velasco E, Aguado C, Wickman K. New insights into the therapeutic potential of Girk channels. Trends Neurosci 2013; 37:20-9. [PMID: 24268819 DOI: 10.1016/j.tins.2013.10.006] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 10/24/2013] [Accepted: 10/25/2013] [Indexed: 01/01/2023]
Abstract
G protein-dependent signaling pathways control the activity of excitable cells of the nervous system and heart, and are the targets of neurotransmitters, clinically relevant drugs, and drugs of abuse. G protein-gated inwardly rectifying potassium (K(+)) (Girk/Kir3) channels are a key effector in inhibitory signaling pathways. Girk-dependent signaling contributes to nociception and analgesia, reward-related behavior, mood, cognition, and heart-rate regulation, and has been linked to epilepsy, Down syndrome, addiction, and arrhythmias. We discuss recent advances in our understanding of Girk channel structure, organization in signaling complexes, and plasticity, as well as progress on the development of subunit-selective Girk modulators. These findings offer new hope for the selective manipulation of Girk channels to treat a variety of debilitating afflictions.
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Affiliation(s)
- Rafael Luján
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain.
| | | | - Carolina Aguado
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, 321 Church Street South East, Minneapolis, MN 55455, USA.
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Arshavsky VY, Wensel TG. Timing is everything: GTPase regulation in phototransduction. Invest Ophthalmol Vis Sci 2013; 54:7725-33. [PMID: 24265205 DOI: 10.1167/iovs.13-13281] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
As the molecular mechanisms of vertebrate phototransduction became increasingly clear in the 1980s, a persistent problem was the discrepancy between the slow GTP hydrolysis catalyzed by the phototransduction G protein, transducin, and the much more rapid physiological recovery of photoreceptor cells from light stimuli. Beginning with a report published in 1989, a series of studies revealed that transducin GTPase activity could approach the rate needed to explain physiological recovery kinetics in the presence of one or more factors present in rod outer segment membranes. One by one, these factors were identified, beginning with PDEγ, the inhibitory subunit of the cGMP phosphodiesterase activated by transducin. There followed the discovery of the crucial role played by the regulator of G protein signaling, RGS9, a member of a ubiquitous family of GTPase-accelerating proteins, or GAPs, for heterotrimeric G proteins. Soon after, the G protein β isoform Gβ5 was identified as an obligate partner subunit, followed by the discovery or R9AP, a transmembrane protein that anchors the RGS9 GAP complex to the disk membrane, and is essential for the localization, stability, and activity of this complex in vivo. The physiological importance of all of the members of this complex was made clear first by knockout mouse models, and then by the discovery of a human visual defect, bradyopsia, caused by an inherited deficiency in one of the GAP components. Further insights have been gained by high-resolution crystal structures of subcomplexes, and by extensive mechanistic studies both in vitro and in animal models.
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Affiliation(s)
- Vadim Y Arshavsky
- Albert Eye Research Institute, Duke University, Durham, North Carolina
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36
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Lin YG, Weadick CJ, Santini F, Chang BSW. Molecular evolutionary analysis of vertebrate transducins: a role for amino acid variation in photoreceptor deactivation. J Mol Evol 2013; 77:231-45. [PMID: 24145862 DOI: 10.1007/s00239-013-9589-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 09/25/2013] [Indexed: 01/05/2023]
Abstract
Transducin is a heterotrimeric G protein that plays a critical role in phototransduction in the rod and cone photoreceptor cells of the vertebrate retina. Rods, highly sensitive cells that recover from photoactivation slowly, underlie dim-light vision, whereas cones are less sensitive, recover more quickly, and underlie bright-light vision. Transducin deactivation is a critical step in photoreceptor recovery and may underlie the functional distinction between rods and cones. Rods and cones possess distinct transducin α subunits, yet they share a common deactivation mechanism, the GTPase activating protein (GAP) complex. Here, we used codon models to examine patterns of sequence evolution in rod (GNAT1) and cone (GNAT2) α subunits. Our results indicate that purifying selection is the dominant force shaping GNAT1 and GNAT2 evolution, but that GNAT2 has additionally been subject to positive selection operating at multiple phylogenetic scales; phylogeny-wide analysis identified several sites in the GNAT2 helical domain as having substantially elevated dN/dS estimates, and branch-site analysis identified several nearby sites as targets of strong positive selection during early vertebrate history. Examination of aligned GNAT and GAP complex crystal structures revealed steric clashes between several positively selected sites and the deactivating GAP complex. This suggests that GNAT2 sequence variation could play an important role in adaptive evolution of the vertebrate visual system via effects on photoreceptor deactivation kinetics and provides an alternative perspective to previous work that focused instead on the effect of GAP complex concentration. Our findings thus further the understanding of the molecular biology, physiology, and evolution of vertebrate visual systems.
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Affiliation(s)
- Yi G Lin
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
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37
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Moreira IS. Structural features of the G-protein/GPCR interactions. Biochim Biophys Acta Gen Subj 2013; 1840:16-33. [PMID: 24016604 DOI: 10.1016/j.bbagen.2013.08.027] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 01/07/2023]
Abstract
BACKGROUND The details of the functional interaction between G proteins and the G protein coupled receptors (GPCRs) have long been subjected to extensive investigations with structural and functional assays and a large number of computational studies. SCOPE OF REVIEW The nature and sites of interaction in the G-protein/GPCR complexes, and the specificities of these interactions selecting coupling partners among the large number of families of GPCRs and G protein forms, are still poorly defined. MAJOR CONCLUSIONS Many of the contact sites between the two proteins in specific complexes have been identified, but the three dimensional molecular architecture of a receptor-Gα interface is only known for one pair. Consequently, many fundamental questions regarding this macromolecular assembly and its mechanism remain unanswered. GENERAL SIGNIFICANCE In the context of current structural data we review the structural details of the interfaces and recognition sites in complexes of sub-family A GPCRs with cognate G-proteins, with special emphasis on the consequences of activation on GPCR structure, the prevalence of preassembled GPCR/G-protein complexes, the key structural determinants for selective coupling and the possible involvement of GPCR oligomerization in this process.
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Affiliation(s)
- Irina S Moreira
- REQUIMTE/Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.
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Huang J, Stewart A, Maity B, Hagen J, Fagan RL, Yang J, Quelle DE, Brenner C, Fisher RA. RGS6 suppresses Ras-induced cellular transformation by facilitating Tip60-mediated Dnmt1 degradation and promoting apoptosis. Oncogene 2013; 33:3604-11. [PMID: 23995786 DOI: 10.1038/onc.2013.324] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 04/16/2013] [Accepted: 07/04/2013] [Indexed: 12/17/2022]
Abstract
The RAS protooncogene has a central role in regulation of cell proliferation, and point mutations leading to oncogenic activation of Ras occur in a large number of human cancers. Silencing of tumor-suppressor genes by DNA methyltransferase 1 (Dnmt1) is essential for oncogenic cellular transformation by Ras, and Dnmt1 is overexpressed in numerous human cancers. Here we provide new evidence that the pleiotropic regulator of G protein signaling (RGS) family member RGS6 suppresses Ras-induced cellular transformation by facilitating Tip60-mediated degradation of Dmnt1 and promoting apoptosis. Employing mouse embryonic fibroblasts from wild-type and RGS6(-/-) mice, we found that oncogenic Ras induced upregulation of RGS6, which in turn blocked Ras-induced cellular transformation. RGS6 functions to suppress cellular transformation in response to oncogenic Ras by downregulating Dnmt1 protein expression leading to inhibition of Dnmt1-mediated anti-apoptotic activity. Further experiments showed that RGS6 functions as a scaffolding protein for both Dnmt1 and Tip60 and is required for Tip60-mediated acetylation of Dnmt1 and subsequent Dnmt1 ubiquitylation and degradation. The RGS domain of RGS6, known only for its GTPase-activating protein activity toward Gα subunits, was sufficient to mediate Tip60 association with RGS6. This work demonstrates a novel signaling action for RGS6 in negative regulation of oncogene-induced transformation and provides new insights into our understanding of the mechanisms underlying Ras-induced oncogenic transformation and regulation of Dnmt1 expression. Importantly, these findings identify RGS6 as an essential cellular defender against oncogenic stress and a potential therapeutic target for developing new cancer treatments.
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Affiliation(s)
- J Huang
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - A Stewart
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - B Maity
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - J Hagen
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - R L Fagan
- Department of Biochemistry, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - J Yang
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - D E Quelle
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - C Brenner
- Department of Biochemistry, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - R A Fisher
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
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X-ray structure of the mammalian GIRK2-βγ G-protein complex. Nature 2013; 498:190-7. [PMID: 23739333 PMCID: PMC4654628 DOI: 10.1038/nature12241] [Citation(s) in RCA: 234] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 05/03/2013] [Indexed: 01/09/2023]
Abstract
G protein-gated inward rectifier K+ (GIRK) channels allow neurotransmitters, via G protein-coupled receptor stimulation, to control cellular electrical excitability. In cardiac and neuronal cells this control regulates heart rate and neural circuit activity. We present the 3.5 Å resolution crystal structure of the mammalian GIRK2 channel in complex with βγ G protein subunits, the central signaling complex that links G protein-coupled receptor stimulation to K+ channel activity. Short-range atomic and long-range electrostatic interactions stabilize four βγ G protein subunits at the interfaces between four K+ channel subunits, inducing a pre-open state of the channel. The pre-open state exhibits a conformation that is intermediate between the closed and constitutively active mutant, open conformations. The resultant structural picture is compatible with “membrane delimited” activation of GIRK channels by G proteins and the characteristic burst kinetics of channel gating. The structures also permit a conceptual understanding of how the signaling lipid PIP2 and intracellular Na+ ions participate in multi-ligand regulation of GIRK channels.
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40
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Light-induced translocation of RGS9-1 and Gβ5L in mouse rod photoreceptors. PLoS One 2013; 8:e58832. [PMID: 23555598 PMCID: PMC3610756 DOI: 10.1371/journal.pone.0058832] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 02/07/2013] [Indexed: 01/09/2023] Open
Abstract
The transducin GTPase-accelerating protein complex, which determines the photoresponse duration of photoreceptors, is composed of RGS9-1, Gβ5L and R9AP. Here we report that RGS9-1 and Gβ5L change their distribution in rods during light/dark adaptation. Upon prolonged dark adaptation, RGS9-1 and Gβ5L are primarily located in rod inner segments. But very dim-light exposure quickly translocates them to the outer segments. In contrast, their anchor protein R9AP remains in the outer segment at all times. In the dark, Gβ5L's interaction with R9AP decreases significantly and RGS9-1 is phosphorylated at S(475) to a significant degree. Dim light exposure leads to quick de-phosphorylation of RGS9-1. Furthermore, after prolonged dark adaptation, RGS9-1 and transducin Gα are located in different cellular compartments. These results suggest a previously unappreciated mechanism by which prolonged dark adaptation leads to increased light sensitivity in rods by dissociating RGS9-1 from R9AP and redistributing it to rod inner segments.
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41
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GIRK channel modulation by assembly with allosterically regulated RGS proteins. Proc Natl Acad Sci U S A 2012; 109:19977-82. [PMID: 23169654 DOI: 10.1073/pnas.1214337109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
G-protein-activated inward-rectifying K(+) (GIRK) channels hyperpolarize neurons to inhibit synaptic transmission throughout the nervous system. By accelerating G-protein deactivation kinetics, the regulator of G-protein signaling (RGS) protein family modulates the timing of GIRK activity. Despite many investigations, whether RGS proteins modulate GIRK activity in neurons by mechanisms involving kinetic coupling, collision coupling, or macromolecular complex formation has remained unknown. Here we show that GIRK modulation occurs by channel assembly with R7-RGS/Gβ5 complexes under allosteric control of R7 RGS-binding protein (R7BP). Elimination of R7BP occludes the Gβ5 subunit that interacts with GIRK channels. R7BP-bound R7-RGS/Gβ5 complexes and Gβγ dimers interact noncompetitively with the intracellular domain of GIRK channels to facilitate rapid activation and deactivation of GIRK currents. By disrupting this allosterically regulated assembly mechanism, R7BP ablation augments GIRK activity. This enhanced GIRK activity increases the drug effects of agonists acting at G-protein-coupled receptors that signal via GIRK channels, as indicated by greater antinociceptive effects of GABA(B) or μ-opioid receptor agonists. These findings show that GIRK current modulation in vivo requires channel assembly with allosterically regulated RGS protein complexes, which provide a target for modulating GIRK activity in neurological disorders in which these channels have crucial roles, including pain, epilepsy, Parkinson's disease and Down syndrome.
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Liapis E, Sandiford S, Wang Q, Gaidosh G, Motti D, Levay K, Slepak VZ. Subcellular localization of regulator of G protein signaling RGS7 complex in neurons and transfected cells. J Neurochem 2012; 122:568-81. [PMID: 22640015 DOI: 10.1111/j.1471-4159.2012.07811.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The R7 family of regulators of G protein signaling (RGS) is involved in many functions of the nervous system. This family includes RGS6, RGS7, RGS9, and RGS11 gene products and is defined by the presence of the characteristic first found in Disheveled, Egl-10, Pleckstrin (DEP), DEP helical extension (DHEX), Gγ-like, and RGS domains. Herein, we examined the subcellular localization of RGS7, the most broadly expressed R7 member. Our immunofluorescence studies of retinal and dorsal root ganglion neurons showed that RGS7 concentrated at the plasma membrane of cell bodies, in structures resembling lamellipodia or filopodia along the processes, and at the dendritic tips. At the plasma membrane of dorsal root ganglia neurons, RGS7 co-localized with its known binding partners R7 RGS binding protein (R7BP), Gαo, and Gαq. More than 50% of total RGS7-specific immunofluorescence was present in the cytoplasm, primarily within numerous small puncta that did not co-localize with R7BP. No specific RGS7 or R7BP immunoreactivity was detected in the nuclei. In transfected cell lines, ectopic RGS7 had both diffuse cytosolic and punctate localization patterns. RGS7 also localized in centrosomes. Structure-function analysis showed that the punctate localization was mediated by the DEP/DHEX domains, and centrosomal localization was dependent on the DHEX domain.
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Affiliation(s)
- Evangelos Liapis
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL, USA
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43
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Huang PS, Yeh HS, Yi HP, Lin CJ, Yang CS. Fluorescence-based assay probing regulator of G protein signaling partner proteins. Anal Biochem 2012; 423:133-40. [PMID: 22310500 DOI: 10.1016/j.ab.2012.01.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 01/09/2012] [Accepted: 01/13/2012] [Indexed: 10/14/2022]
Abstract
The regulator of G protein signaling (RGS) proteins are one of the essential modulators for the G protein system. Besides regulating G protein signaling by accelerating the GTPase activity of Gα subunits, RGS proteins are implicated in exerting other functions; they are also known to be involved in several diseases. Moreover, the existence of a single RGS protein in plants and its seven-transmembrane domain found in 2003 triggered efforts to unveil detailed structural and functional information of RGS proteins. We present a method for real-time examination of the protein-protein interactions between RGS and Gα subunits. AtRGS1 from plants and RGS4 from mammals were site-directedly labeled with the fluorescent probe Lucifer yellow on engineered cysteine residues and used to interact with different Gα subunits. The physical interactions can be revealed by monitoring the real-time fluorescence changes (8.6% fluorescence increase in mammals and 27.6% in plants); their correlations to functional exertion were shown with a GTPase accelerating activity assay and further confirmed by measurement of K(d). We validate the effectiveness of this method and suggest its application to the exploration of more RGS signaling partner proteins in physiological and pathological studies.
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Affiliation(s)
- Po-Shiun Huang
- Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei 10617, Taiwan
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44
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Terzi D, Cao Y, Agrimaki I, Martemyanov KA, Zachariou V. R7BP modulates opiate analgesia and tolerance but not withdrawal. Neuropsychopharmacology 2012; 37:1005-12. [PMID: 22089315 PMCID: PMC3280654 DOI: 10.1038/npp.2011.284] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The adaptor protein R7 family binding protein (R7BP) modulates G protein coupled receptor (GPCR) signaling and desensitization by controlling the function of regulator of G protein signaling (RGS) proteins. R7BP is expressed throughout the brain and appears to modulate the membrane localization and stability of three proteins that belong to R7 RGS family: RGS6, RGS7, and RGS9-2. RGS9-2 is a potent negative modulator of opiate and psychostimulant addiction and promotes the development of analgesic tolerance to morphine, whereas the role of RGS6 and RGS7 in addiction remains unknown. Recent studies revealed that functional deletion of R7BP reduces R7 protein activity by preventing their anchoring to the cell membrane and enhances GPCR responsiveness in the basal ganglia. Here, we take advantage of R7BP knockout mice in order to examine the way interventions in R7 proteins function throughout the brain affect opiate actions. Our results suggest that R7BP is a negative modulator of the analgesic and locomotor activating actions of morphine. We also report that R7BP contributes to the development of morphine tolerance. Finally, our data suggest that although prevention of R7BP actions enhances the analgesic responses to morphine, it does not affect the severity of somatic withdrawal signs. Our data suggest that interventions in R7BP actions enhance the analgesic effect of morphine and prevent tolerance, without affecting withdrawal, pointing to R7BP complexes as potential new targets for analgesic drugs.
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Affiliation(s)
- Dimitra Terzi
- Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete, Greece
| | - Yan Cao
- Department of Neuroscience, The Scripps Research Institute—Florida, Jupiter, FL, USA
| | - Ioanna Agrimaki
- Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete, Greece
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute—Florida, Jupiter, FL, USA,Department of Neuroscience, The Scripps Research Institute—Florida, 130 Scripps Way 3C2, Jupiter, FL 33458, USA, Tel:+561 228 2770, E-mail:
| | - Venetia Zachariou
- Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete, Greece,Department of Basic Sciences, University of Crete, Faculty of Medicine, Laboratory of Pharmacology, Heraklion, Crete 71003, Greece, Tel: +30 2810 394527, Fax: +30 2810 394530, E-mail:
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45
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Shim H, Wang CT, Chen YL, Chau VQ, Fu KG, Yang J, McQuiston AR, Fisher RA, Chen CK. Defective retinal depolarizing bipolar cells in regulators of G protein signaling (RGS) 7 and 11 double null mice. J Biol Chem 2012; 287:14873-9. [PMID: 22371490 DOI: 10.1074/jbc.m112.345751] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Two members of the R7 subfamily of regulators of G protein signaling, RGS7 and RGS11, are present at dendritic tips of retinal depolarizing bipolar cells (DBCs). Their involvement in the mGluR6/Gα(o)/TRPM1 pathway that mediates DBC light responses has been implicated. However, previous genetic studies employed an RGS7 mutant mouse that is hypomorphic, and hence the exact role of RGS7 in DBCs remains unclear. We have made a true RGS7-null mouse line with exons 6-8 deleted. The RGS7(-/-) mouse is viable and fertile but smaller in body size. Electroretinogram (ERG) b-wave implicit time in young RGS7(-/-) mice is prolonged at eye opening, but the phenotype disappears at 2 months of age. Expression levels of RGS6 and RGS11 are unchanged in RGS7(-/-) retina, but the Gβ5S level is significantly reduced. By characterizing a complete RGS7 and RGS11 double knock-out (711dKO) mouse line, we found that Gβ5S expression in the retinal outer plexiform layer is eliminated, as is the ERG b-wave. Ultrastructural defects akin to those of Gβ5(-/-) mice are evident in 711dKO mice. In retinas of mice lacking RGS6, RGS7, and RGS11, Gβ5S is undetectable, whereas levels of the photoreceptor-specific Gβ5L remain unchanged. Whereas RGS6 alone sustains a significant amount of Gβ5S expression in retina, the DBC-related defects in Gβ5(-/-) mice are caused solely by a combined loss of RGS7 and RGS11. Our data support the notion that the role of Gβ5 in the retina, and likely in the entire nervous system, is mediated exclusively by R7 RGS proteins.
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Affiliation(s)
- Hoon Shim
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, USA
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46
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Xie K, Ge S, Collins VE, Haynes CL, Renner KJ, Meisel RL, Lujan R, Martemyanov KA. Gβ5-RGS complexes are gatekeepers of hyperactivity involved in control of multiple neurotransmitter systems. Psychopharmacology (Berl) 2012; 219:823-34. [PMID: 21766168 PMCID: PMC3260372 DOI: 10.1007/s00213-011-2409-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 07/01/2011] [Indexed: 12/25/2022]
Abstract
RATIONALE AND OBJECTIVES Our knowledge about genes involved in the control of basal motor activity that may contribute to the pathology of the hyperactivity disorders, e.g., attention deficit hyperactivity disorder (ADHD), is limited. Disruption of monoamine neurotransmitter signaling through G protein-coupled receptors (GPCR) is considered to be a major contributing factor to the etiology of the ADHD. Genetic association evidence and functional data suggest that regulators of G protein signaling proteins of the R7 family (R7 RGS) that form obligatory complexes with type 5 G protein beta subunit (Gβ5) and negatively regulate signaling downstream from monoamine GPCRs may play a role in controlling hyperactivity. METHODS To test this hypothesis, we conducted behavioral, pharmacological, and neurochemical studies using a genetic mouse model that lacked Gβ5, a subunit essential for the expression of the entire R7 RGS family. RESULTS Elimination of Gβ5-RGS complexes led to a striking level of hyperactivity that far exceeds activity levels previously observed in animal models. This hyperactivity was accompanied by motor learning deficits and paradoxical behavioral sensitization to a novel environment. Neurochemical studies indicated that Gβ5-RGS-deficient mice had higher sensitivity of inhibitory GPCR signaling and deficits in basal levels, release, and reuptake of dopamine. Surprisingly, pharmacological treatment with monoamine reuptake inhibitors failed to alter hyperactivity. In contrast, blockade of NMDA receptors reversed the expression of hyperactivity in Gβ5-RGS-deficient mice. CONCLUSIONS These findings establish that Gβ5-RGS complexes are critical regulators of monoamine-NMDA receptor signaling cross-talk and link these complexes to disorders that manifest as hyperactivity, impaired learning, and motor dysfunctions.
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Affiliation(s)
- Keqiang Xie
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455 USA
| | - Shencheng Ge
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455 USA
| | | | - Christy L. Haynes
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455 USA
| | - Kenneth J. Renner
- Department of Biology, University of South Dakota, Vermillion, SD 57069
| | - Robert L. Meisel
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455 USA
| | - Rafael Lujan
- Departamento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, 02006 Albacete, Spain
| | - Kirill A. Martemyanov
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455 USA,Address for correspondence: Dr. Kirill Martemyanov, Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, 3C2, Jupiter, Florida 33458 Phone: (612) 245-7567,
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Abstract
G protein signaling depends on the ability of the individual subunits of the G protein heterotrimer to assemble into functional complexes. Formation of the G protein βγ (Gβγ) dimer is particularly challenging because it is an obligate dimer in which the individual subunits are unstable on their own. Recent studies have revealed an intricate chaperone system that brings the Gβ and Gγ subunits together. This system includes the cytosolic chaperonin containing TCP-1 (CCT) and its co-chaperone phosducin-like protein 1 (PhLP1). CCT assists Gβ in achieving its β-propeller structure, while PhLP1 releases Gβ from CCT and facilitates its interaction with Gγ. Once Gβγ is formed, PhLP1 remains bound until it is displaced by the Gα subunit and the G protein heterotrimer is brought together. Another obligate dimer is the complex between the G protein β(5) subunit and a regulator of G protein signaling protein (Gβ(5)-RGS). Gβ(5)-RGS also requires CCT for Gβ(5) folding, but PhLP1 plays a different role. It stabilizes the interaction between Gβ(5) and CCT, perhaps to increase folding efficiency. After Gβ(5) folding PhLP1 must subsequently release, allowing the RGS protein to bind and form the Gβ(5)-RGS dimer directly on CCT. Gβ(5)-RGS is then freed from CCT to interact with its membrane anchoring protein and form a stable complex that turns off the G protein signal by catalyzing GTP hydrolysis on Gα.
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Affiliation(s)
- Barry M Willardson
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA,
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β-arrestin2 plays permissive roles in the inhibitory activities of RGS9-2 on G protein-coupled receptors by maintaining RGS9-2 in the open conformation. Mol Cell Biol 2011; 31:4887-901. [PMID: 22006018 DOI: 10.1128/mcb.05690-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Together with G protein-coupled receptor (GPCR) kinases (GRKs) and β-arrestins, RGS proteins are the major family of molecules that control the signaling of GPCRs. The expression pattern of one of these RGS family members, RGS9-2, coincides with that of the dopamine D(3) receptor (D(3)R) in the brain, and in vivo studies have shown that RGS9-2 regulates the signaling of D2-like receptors. In this study, β-arrestin2 was found to be required for scaffolding of the intricate interactions among the dishevelled-EGL10-pleckstrin (DEP) domain of RGS9-2, Gβ5, R7-binding protein (R7BP), and D(3)R. The DEP domain of RGS9-2, under the permission of β-arrestin2, inhibited the signaling of D(3)R in collaboration with Gβ5. β-Arrestin2 competed with R7BP and Gβ5 so that RGS9-2 is placed in the cytosolic region in an open conformation which is able to inhibit the signaling of GPCRs. The affinity of the receptor protein for β-arrestin2 was a critical factor that determined the selectivity of RGS9-2 for the receptor it regulates. These results show that β-arrestins function not only as mediators of receptor-G protein uncoupling and initiators of receptor endocytosis but also as scaffolding proteins that control and coordinate the inhibitory effects of RGS proteins on the signaling of certain GPCRs.
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Adams DR, Ron D, Kiely PA. RACK1, A multifaceted scaffolding protein: Structure and function. Cell Commun Signal 2011; 9:22. [PMID: 21978545 PMCID: PMC3195729 DOI: 10.1186/1478-811x-9-22] [Citation(s) in RCA: 324] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Accepted: 10/06/2011] [Indexed: 12/17/2022] Open
Abstract
The Receptor for Activated C Kinase 1 (RACK1) is a member of the tryptophan-aspartate repeat (WD-repeat) family of proteins and shares significant homology to the β subunit of G-proteins (Gβ). RACK1 adopts a seven-bladed β-propeller structure which facilitates protein binding. RACK1 has a significant role to play in shuttling proteins around the cell, anchoring proteins at particular locations and in stabilising protein activity. It interacts with the ribosomal machinery, with several cell surface receptors and with proteins in the nucleus. As a result, RACK1 is a key mediator of various pathways and contributes to numerous aspects of cellular function. Here, we discuss RACK1 gene and structure and its role in specific signaling pathways, and address how posttranslational modifications facilitate subcellular location and translocation of RACK1. This review condenses several recent studies suggesting a role for RACK1 in physiological processes such as development, cell migration, central nervous system (CN) function and circadian rhythm as well as reviewing the role of RACK1 in disease.
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Affiliation(s)
- David R Adams
- Department of Life Sciences, and Materials and Surface Science Institute, University of Limerick, Limerick, Ireland.
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50
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Abstract
Signal transduction through G-protein-coupled receptors (GPCRs) is central for the regulation of virtually all cellular functions and has been widely implicated in human disease. Regulators of G-protein signaling (RGS proteins) belong to a diverse protein family that was originally discovered for their ability to accelerate signal termination in response to GPCR stimulation, thereby reducing the amplitude and duration of GPCR effects. All RGS proteins share a common RGS domain that interacts with G protein α subunits and mediates their biological regulation of GPCR signaling. However, RGS proteins differ widely in size and the organization of their sequences flanking the RGS domain, which contain several additional functional domains that facilitate protein-protein (or protein-lipid) interactions. RGS proteins are subject to posttranslational modifications, and, in addition, their expression, activity, and subcellular localization can be dynamically regulated. Thus, there exists a wide array of mechanisms that facilitate their proper function as modulators and integrators of G-protein signaling. Several RGS proteins have been implicated in the cardiac remodeling response and heart rate regulation, and changes in RGS protein expression and/or function are believed to participate in the pathophysiology of cardiac hypertrophy, failure and arrhythmias as well as hypertension. This review is based on recent advances in our understanding of the expression pattern, regulation, and functional role of canonical RGS proteins, with a special focus on the healthy heart and the diseased heart. In addition, we discuss their potential and promise as therapeutic targets as well as strategies to modulate their expression and function.
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Affiliation(s)
- Peng Zhang
- Cardiovascular Research Center, Rhode Island Hospital and Alpert Medical School of Brown University, 1 Hoppin St, Providence, RI 02903, USA
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