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Li L, Xu Q, Tang C. RGS proteins and their roles in cancer: friend or foe? Cancer Cell Int 2023; 23:81. [PMID: 37118788 PMCID: PMC10148553 DOI: 10.1186/s12935-023-02932-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 04/21/2023] [Indexed: 04/30/2023] Open
Abstract
As negative modulators of G-protein-coupled receptors (GPCRs) signaling, regulators of G protein signaling (RGS) proteins facilitate various downstream cellular signalings through regulating kinds of heterotrimeric G proteins by stimulating the guanosine triphosphatase (GTPase) activity of G-protein α (Gα) subunits. The expression of RGS proteins is dynamically and precisely mediated by several different mechanisms including epigenetic regulation, transcriptional regulation -and post-translational regulation. Emerging evidence has shown that RGS proteins act as important mediators in controlling essential cellular processes including cell proliferation, survival -and death via regulating downstream cellular signaling activities, indicating that RGS proteins are fundamentally involved in sustaining normal physiological functions and dysregulation of RGS proteins (such as aberrant expression of RGS proteins) is closely associated with pathologies of many diseases such as cancer. In this review, we summarize the molecular mechanisms governing the expression of RGS proteins, and further discuss the relationship of RGS proteins and cancer.
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Affiliation(s)
- Lin Li
- National Clinical Research Center for Child Health of the Children's Hospital, Zhejiang University School of Medicine, No. 3333, Binsheng Rd., Hangzhou, 310052, People's Republic of China
- Department of Urology, Third Affiliated Hospital of the Second Military Medical University, Shanghai, 201805, China
| | - Qiang Xu
- National Clinical Research Center for Child Health of the Children's Hospital, Zhejiang University School of Medicine, No. 3333, Binsheng Rd., Hangzhou, 310052, People's Republic of China
| | - Chao Tang
- National Clinical Research Center for Child Health of the Children's Hospital, Zhejiang University School of Medicine, No. 3333, Binsheng Rd., Hangzhou, 310052, People's Republic of China.
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2
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Montañez-Miranda C, Perszyk RE, Harbin NH, Okalova J, Ramineni S, Traynelis SF, Hepler JR. Functional Assessment of Cancer-Linked Mutations in Sensitive Regions of Regulators of G Protein Signaling Predicted by Three-Dimensional Missense Tolerance Ratio Analysis. Mol Pharmacol 2023; 103:21-37. [PMID: 36384958 PMCID: PMC10955721 DOI: 10.1124/molpharm.122.000614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/04/2022] [Accepted: 10/18/2022] [Indexed: 11/18/2022] Open
Abstract
Regulators of G protein signaling (RGS) proteins modulate G protein-coupled receptor (GPCR) signaling by acting as negative regulators of G proteins. Genetic variants in RGS proteins are associated with many diseases, including cancers, although the impact of these mutations on protein function is uncertain. Here we analyze the RGS domains of 15 RGS protein family members using a novel bioinformatic tool that measures the missense tolerance ratio (MTR) using a three-dimensional (3D) structure (3DMTR). Subsequent permutation analysis can define the protein regions that are most significantly intolerant (P < 0.05) in each dataset. We further focused on RGS14, RGS10, and RGS4. RGS14 exhibited seven significantly tolerant and seven significantly intolerant residues, RGS10 had six intolerant residues, and RGS4 had eight tolerant and six intolerant residues. Intolerant and tolerant-control residues that overlap with pathogenic cancer mutations reported in the COSMIC cancer database were selected to define the functional phenotype. Using complimentary cellular and biochemical approaches, proteins were tested for effects on GPCR-Gα activation, Gα binding properties, and downstream cAMP levels. Identified intolerant residues with reported cancer-linked mutations RGS14-R173C/H and RGS4-K125Q/E126K, and tolerant RGS14-S127P and RGS10-S64T resulted in a loss-of-function phenotype in GPCR-G protein signaling activity. In downstream cAMP measurement, tolerant RGS14-D137Y and RGS10-S64T and intolerant RGS10-K89M resulted in change of function phenotypes. These findings show that 3DMTR identified intolerant residues that overlap with cancer-linked mutations cause phenotypic changes that negatively impact GPCR-G protein signaling and suggests that 3DMTR is a potentially useful bioinformatics tool for predicting functionally important protein residues. SIGNIFICANCE STATEMENT: Human genetic variant/mutation information has expanded rapidly in recent years, including cancer-linked mutations in regulator of G protein signaling (RGS) proteins. However, experimental testing of the impact of this vast catalogue of mutations on protein function is not feasible. We used the novel bioinformatics tool three-dimensional missense tolerance ratio (3DMTR) to define regions of genetic intolerance in RGS proteins and prioritize which cancer-linked mutants to test. We found that 3DMTR more accurately classifies loss-of-function mutations in RGS proteins than other databases thereby offering a valuable new research tool.
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Affiliation(s)
- Carolina Montañez-Miranda
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Riley E Perszyk
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Nicholas H Harbin
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Jennifer Okalova
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Suneela Ramineni
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - Stephen F Traynelis
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
| | - John R Hepler
- Department of Pharmacology and Chemical Biology (C.M.-M., R.E.P., N.H.H., S.R., S.F.T., J.R.H.) and Aflac Cancer and Blood Disorders Center, Department of Pediatrics (J.O.), Emory University School of Medicine, Atlanta, Georgia
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Foster SL, Lustberg DJ, Harbin NH, Bramlett SN, Hepler JR, Weinshenker D. RGS14 modulates locomotor behavior and ERK signaling induced by environmental novelty and cocaine within discrete limbic structures. Psychopharmacology (Berl) 2021; 238:2755-2773. [PMID: 34184126 PMCID: PMC8455459 DOI: 10.1007/s00213-021-05892-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 06/01/2021] [Indexed: 12/14/2022]
Abstract
RATIONALE In rodents, exposure to novel environments or psychostimulants promotes locomotion. Indeed, locomotor reactivity to novelty strongly predicts behavioral responses to psychostimulants in animal models of addiction. RGS14 is a plasticity-restricting protein with unique functional domains that enable it to suppress ERK-dependent signaling as well as regulate G protein activity. Although recent studies show that RGS14 is expressed in multiple limbic regions implicated in psychostimulant- and novelty-induced hyperlocomotion, its function has been examined mostly in the context of hippocampal physiology and memory. OBJECTIVE We investigated whether RGS14 modulates novelty- and cocaine-induced locomotion (NIL and CIL, respectively) and neuronal activity. METHODS We assessed Rgs14 knockout (RGS14 KO) mice and wild-type (WT) littermate controls using NIL and CIL behavioral tests, followed by quantification of c-fos and phosphorylated ERK (pERK) induction in limbic regions that normally express RGS14. RESULTS RGS14 KO mice were less active than WT controls in the NIL test, driven by avoidance of the center of the novel environment. By contrast, RGS14 KO mice demonstrated augmented peripheral locomotion in the CIL test conducted in either a familiar or novel environment. RGS14 KO mice exhibited increased thigmotaxis, as well as greater c-fos and pERK induction in the central amygdala and dorsal hippocampus, when cocaine and novelty were paired. CONCLUSIONS RGS14 KO mice exhibited anti-correlated locomotor responses to novelty and cocaine, but displayed increased thigmotaxis in response to either stimuli which was augmented by their combination. Our findings also suggest RGS14 may reduce neuronal activity in limbic subregions by inhibiting ERK-dependent signaling.
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Affiliation(s)
- Stephanie L. Foster
- Emory University School of Medicine, Department of Human Genetics, Atlanta, GA 30322
| | - Daniel J. Lustberg
- Emory University School of Medicine, Department of Human Genetics, Atlanta, GA 30322
| | - Nicholas H. Harbin
- Emory University School of Medicine, Department of Pharmacology and Chemical Biology, Atlanta, GA 30322
| | - Sara N. Bramlett
- Emory University School of Medicine, Department of Pharmacology and Chemical Biology, Atlanta, GA 30322
| | - John R. Hepler
- Emory University School of Medicine, Department of Pharmacology and Chemical Biology, Atlanta, GA 30322,Correspondence to: David Weinshenker, Ph.D., Department of Human Genetics, Emory University School of Medicine, 615 Michael St., Whitehead 301, Atlanta, GA 30322, ; John R. Hepler, Ph.D., Department of Pharmacology and Chemical Biology, Emory University School of Medicine, 1510 Clifton Rd., Atlanta, GA 30322,
| | - David Weinshenker
- , Department of Human Genetics, Emory University School of Medicine, 615 Michael St., Whitehead 301, Atlanta, GA, 30322, USA.
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Signaling Pathways Regulated by UBR Box-Containing E3 Ligases. Int J Mol Sci 2021; 22:ijms22158323. [PMID: 34361089 PMCID: PMC8346999 DOI: 10.3390/ijms22158323] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 12/31/2022] Open
Abstract
UBR box E3 ligases, also called N-recognins, are integral components of the N-degron pathway. Representative N-recognins include UBR1, UBR2, UBR4, and UBR5, and they bind destabilizing N-terminal residues, termed N-degrons. Understanding the molecular bases of their substrate recognition and the biological impact of the clearance of their substrates on cellular signaling pathways can provide valuable insights into the regulation of these pathways. This review provides an overview of the current knowledge of the binding mechanism of UBR box N-recognin/N-degron interactions and their roles in signaling pathways linked to G-protein-coupled receptors, apoptosis, mitochondrial quality control, inflammation, and DNA damage. The targeting of these UBR box N-recognins can provide potential therapies to treat diseases such as cancer and neurodegenerative diseases.
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Jeon JH, Oh TR, Park S, Huh S, Kim JH, Mai BK, Lee JH, Kim SH, Lee MJ. The Antipsychotic Drug Clozapine Suppresses the RGS4 Polyubiquitylation and Proteasomal Degradation Mediated by the Arg/N-Degron Pathway. Neurotherapeutics 2021; 18:1768-1782. [PMID: 33884581 PMCID: PMC8608952 DOI: 10.1007/s13311-021-01039-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2021] [Indexed: 02/04/2023] Open
Abstract
Although diverse antipsychotic drugs have been developed for the treatment of schizophrenia, most of their mechanisms of action remain elusive. Regulator of G-protein signaling 4 (RGS4) has been reported to be linked, both genetically and functionally, with schizophrenia and is a physiological substrate of the arginylation branch of the N-degron pathway (Arg/N-degron pathway). Here, we show that the atypical antipsychotic drug clozapine significantly inhibits proteasomal degradation of RGS4 proteins without affecting their transcriptional expression. In addition, the levels of Arg- and Phe-GFP (artificial substrates of the Arg/N-degron pathway) were significantly elevated by clozapine treatment. In silico computational model suggested that clozapine may interact with active sites of N-recognin E3 ubiquitin ligases. Accordingly, treatment with clozapine resulted in reduced polyubiquitylation of RGS4 and Arg-GFP in the test tube and in cultured cells. Clozapine attenuated the activation of downstream effectors of G protein-coupled receptor signaling, such as MEK1 and ERK1, in HEK293 and SH-SY5Y cells. Furthermore, intraperitoneal injection of clozapine into rats significantly stabilized the endogenous RGS4 protein in the prefrontal cortex. Overall, these results reveal an additional therapeutic mechanism of action of clozapine: this drug posttranslationally inhibits the degradation of Arg/N-degron substrates, including RGS4. These findings imply that modulation of protein post-translational modifications, in particular the Arg/N-degron pathway, may be a novel molecular therapeutic strategy against schizophrenia.
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Affiliation(s)
- Jun Hyoung Jeon
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Tae Rim Oh
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Seoyoung Park
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Sunghoo Huh
- Biomedical Research Institute, Seoul National University Hospital, Seoul, 03080, Korea
| | - Ji Hyeon Kim
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Binh Khanh Mai
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Jung Hoon Lee
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Korea
| | - Se Hyun Kim
- Biomedical Research Institute, Seoul National University Hospital, Seoul, 03080, Korea.
- Department of Psychiatry, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, 03080, Korea.
| | - Min Jae Lee
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul, 03080, Korea.
- Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, Korea.
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6
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Liu Y, Vashisth H. Allosteric Pathways Originating at Cysteine Residues in Regulators of G-Protein Signaling Proteins. Biophys J 2020; 120:517-526. [PMID: 33347886 PMCID: PMC7895990 DOI: 10.1016/j.bpj.2020.12.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 12/07/2020] [Accepted: 12/14/2020] [Indexed: 12/23/2022] Open
Abstract
Regulators of G-protein signaling (RGS) proteins play a central role in modulating signaling via G-protein coupled receptors (GPCRs). Specifically, RGS proteins bind to activated Gα subunits in G-proteins, accelerate the GTP hydrolysis, and thereby rapidly dampen GPCR signaling. Therefore, covalent molecules targeting conserved cysteine residues among RGS proteins have emerged as potential candidates to inhibit the RGS/Gα protein-protein interaction and enhance GPCR signaling. Although these inhibitors bind to conserved cysteine residues among RGS proteins, we have previously suggested [J. Am. Chem. Soc. 2018;140:3454–3460] that their potencies and specificities are related to differential protein dynamics among RGS proteins. Using data from all-atom molecular dynamics simulations, we reveal these differences in dynamics of RGS proteins by partitioning the protein structural space into a network of communities that allow allosteric signals to propagate along unique pathways originating at inhibitor binding sites and terminating at the RGS/Gα protein-protein interface.
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Affiliation(s)
- Yong Liu
- Department of Chemical Engineering, University of New Hampshire, Durham, New Hampshire
| | - Harish Vashisth
- Department of Chemical Engineering, University of New Hampshire, Durham, New Hampshire.
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McNabb HJ, Zhang Q, Sjögren B. Emerging Roles for Regulator of G Protein Signaling 2 in (Patho)physiology. Mol Pharmacol 2020; 98:751-760. [PMID: 32973086 DOI: 10.1124/molpharm.120.000111] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 09/08/2020] [Indexed: 12/11/2022] Open
Abstract
Since their discovery in the mid-1990s, regulator of G protein signaling (RGS) proteins have emerged as key regulators of signaling through G protein-coupled receptors. Among the over 20 known RGS proteins, RGS2 has received increasing interest as a potential therapeutic drug target with broad clinical implications. RGS2 is a member of the R4 subfamily of RGS proteins and is unique in that it is selective for Gα q Despite only having an RGS domain, responsible for the canonical GTPase activating protein activity, RGS2 can regulate additional processes, such as protein synthesis and adenylate cyclase activity, through protein-protein interactions. Here we provide an update of the current knowledge of RGS2 function as it relates to molecular mechanisms of regulation as well as its potential role in regulating a number of physiologic systems and pathologies, including cardiovascular disease and central nervous system disorders, as well as various forms of cancer. SIGNIFICANCE STATEMENT: Regulator of G protein signaling (RGS) proteins represent an exciting class of novel drug targets. RGS2, in particular, could have broad clinical importance. As more details are emerging on the regulation of RGS2 in various physiological systems, the potential utility of this small protein in therapeutic development is increasing.
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Affiliation(s)
- Harrison J McNabb
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana
| | - Qian Zhang
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana
| | - Benita Sjögren
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana
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Regulators of G protein signalling as pharmacological targets for the treatment of neuropathic pain. Pharmacol Res 2020; 160:105148. [PMID: 32858121 DOI: 10.1016/j.phrs.2020.105148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 07/24/2020] [Accepted: 08/10/2020] [Indexed: 12/30/2022]
Abstract
Neuropathic pain, a specific type of chronic pain resulting from persistent nervous tissue lesions, is a debilitating condition that affects about 7% of the population. This condition remains particularly difficult to treat because of the poor understanding of its underlying mechanisms. Drugs currently used to alleviate this chronic pain syndrome are of limited benefit due to their lack of efficacy and the elevated risk of side effects, especially after a prolonged period of treatment. Although drugs targeting G protein-coupled receptors (GPCR) also have several limitations, such as progressive loss of efficacy due to receptor desensitization or unavoidable side effects due to wide receptor distribution, the identification of several molecular partners that contribute to the fine-tuning of receptor activity has raised new opportunities for the development of alternative therapeutic approaches. Regulators of G protein signalling (RGS) act intracellularly by influencing the coupling process and activity of G proteins, and are amongst the best-characterized physiological modulators of GPCR. Changes in RGS expression have been documented in a range of models of neuropathic pain, or after prolonged treatment with diverse analgesics, and could participate in altered pain processing as well as impaired physiological or pharmacological control of nociceptive signals. The present review summarizes the experimental data that implicates RGS in the development of pain with focus on the pathological mechanisms of neuropathic pain, including the impact of neuropathic lesions on RGS expression and, reciprocally, the influence of modifying RGS on GPCRs involved in the modulation of nociception as well as on the outcome of pain. In this context, we address the question of the relevance of RGS as promising targets in the treatment of neuropathic pain.
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9
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Ni D, Lu S, Zhang J. Emerging roles of allosteric modulators in the regulation of protein-protein interactions (PPIs): A new paradigm for PPI drug discovery. Med Res Rev 2019; 39:2314-2342. [PMID: 30957264 DOI: 10.1002/med.21585] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Revised: 03/12/2019] [Accepted: 03/24/2019] [Indexed: 12/26/2022]
Abstract
Protein-protein interactions (PPIs) are closely implicated in various types of cellular activities and are thus pivotal to health and disease states. Given their fundamental roles in a wide range of biological processes, the modulation of PPIs has enormous potential in drug discovery. However, owing to the general properties of large, flat, and featureless interfaces of PPIs, previous attempts have demonstrated that the generation of therapeutic agents targeting PPI interfaces is challenging, rendering them almost "undruggable" for decades. To date, rapid progress in chemical and structural biology techniques has promoted the exploitation of allostery as a novel approach in drug discovery. By attaching to allosteric sites that are topologically and spatially distinct from PPI interfaces, allosteric modulators can achieve improved physiochemical properties. Thus, allosteric modulators may represent an alternative strategy to target intractable PPIs and have attracted intense pharmaceutical interest. In this review, we first briefly introduce the characteristics of PPIs and then present different approaches for investigating PPIs, as well as the latest methods for modulating PPIs. Importantly, we comprehensively review the recent progress in the development of allosteric modulators to inhibit or stabilize PPIs. Finally, we conclude with future perspectives on the discovery of allosteric PPI modulators, especially the application of computational methods to aid in allosteric PPI drug discovery.
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Affiliation(s)
- Duan Ni
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Clinical and Fundamental Research Center, Renji Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Shaoyong Lu
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Clinical and Fundamental Research Center, Renji Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China.,Medicinal Bioinformatics Center, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
| | - Jian Zhang
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Clinical and Fundamental Research Center, Renji Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China.,Medicinal Bioinformatics Center, Shanghai Jiao-Tong University School of Medicine, Shanghai, China.,Center for Single-Cell Omics, Shanghai Jiao-Tong University School of Medicine, Shanghai, China
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10
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RGS10 shapes the hemostatic response to injury through its differential effects on intracellular signaling by platelet agonists. Blood Adv 2019; 2:2145-2155. [PMID: 30150297 DOI: 10.1182/bloodadvances.2017008508] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 07/27/2018] [Indexed: 11/20/2022] Open
Abstract
Platelets express ≥2 members of the regulators of G protein signaling (RGS) family. Here, we have focused on the most abundant, RGS10, examining its impact on the hemostatic response in vivo and the mechanisms involved. We have previously shown that the hemostatic thrombi formed in response to penetrating injuries consist of a core of fully activated densely packed platelets overlaid by a shell of less-activated platelets responding to adenosine 5'-diphosphate (ADP) and thromboxane A2 (TxA2). Hemostatic thrombi formed in RGS10-/- mice were larger than in controls, with the increase due to expansion of the shell but not the core. Clot retraction was slower, and average packing density was reduced. Deleting RGS10 had agonist-specific effects on signaling. There was a leftward shift in the dose/response curve for the thrombin receptor (PAR4) agonist peptide AYPGKF but no increase in the maximum response. This contrasted with ADP and TxA2, both of which evoked considerably greater maximum responses in RGS10-/- platelets with enhanced Gq- and Gi-mediated signaling. Shape change, which is G13-mediated, was unaffected. Finally, we found that free RGS10 levels in platelets are actively regulated. In resting platelets, RGS10 was bound to 2 scaffold proteins: spinophilin and 14-3-3γ. Platelet activation caused an increase in free RGS10, as did the endothelium-derived platelet antagonist prostacyclin. Collectively, these observations show that RGS10 serves as an actively regulated node on the platelet signaling network, helping to produce smaller and more densely packed hemostatic thrombi with a greater proportion of fully activated platelets.
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11
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Mohammadi M, Mohammadiarani H, Shaw VS, Neubig RR, Vashisth H. Interplay of cysteine exposure and global protein dynamics in small-molecule recognition by a regulator of G-protein signaling protein. Proteins 2018; 87:146-156. [PMID: 30521141 DOI: 10.1002/prot.25642] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 11/07/2018] [Accepted: 11/29/2018] [Indexed: 02/06/2023]
Abstract
Regulator of G protein signaling (RGS) proteins play a pivotal role in regulation of G protein-coupled receptor (GPCR) signaling and are therefore becoming an increasingly important therapeutic target. Recently discovered thiadiazolidinone (TDZD) compounds that target cysteine residues have shown different levels of specificities and potencies for the RGS4 protein, thereby suggesting intrinsic differences in dynamics of this protein upon binding of these compounds. In this work, we investigated using atomistic molecular dynamics (MD) simulations the effect of binding of several small-molecule inhibitors on perturbations and dynamical motions in RGS4. Specifically, we studied two conformational models of RGS4 in which a buried cysteine residue is solvent-exposed due to side-chain motions or due to flexibility in neighboring helices. We found that TDZD compounds with aromatic functional groups perturb the RGS4 structure more than compounds with aliphatic functional groups. Moreover, small-molecules with aromatic functional groups but lacking sulfur atoms only transiently reside within the protein and spontaneously dissociate to the solvent. We further measured inhibitory effects of TDZD compounds using a protein-protein interaction assay on a single-cysteine RGS4 protein showing trends in potencies of compounds consistent with our simulation studies. Thermodynamic analyses of RGS4 conformations in the apo-state and on binding to TDZD compounds revealed links between both conformational models of RGS4. The exposure of cysteine side-chains appears to facilitate initial binding of TDZD compounds followed by migration of the compound into a bundle of four helices, thereby causing allosteric perturbations in the RGS/Gα protein-protein interface.
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Affiliation(s)
| | | | - Vincent S Shaw
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Richard R Neubig
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Harish Vashisth
- Department of Chemical Engineering, University of New Hampshire, Durham, New Hampshire
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12
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Hannanta-anan P, Chow BY. Optogenetic Inhibition of Gα q Protein Signaling Reduces Calcium Oscillation Stochasticity. ACS Synth Biol 2018; 7:1488-1495. [PMID: 29792810 PMCID: PMC6311707 DOI: 10.1021/acssynbio.8b00065] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As fast terminators of G-protein coupled receptor (GPCR) signaling, regulators of G-protein signaling (RGS) serve critical roles in fine-tuning second messenger levels and, consequently, cellular responses to external stimuli. Here, we report the creation of an optogenetic RGS2 (opto-RGS2) that suppresses agonist-evoked calcium oscillations by the inactivation of Gαq protein. In this system, cryptochrome-mediated heterodimerization of the catalytic RGS2-box with its N-terminal amphipathic helix reconstitutes a functional membrane-localized complex that can dynamically suppress store-operated release of calcium. Engineered opto-RGS2 cell lines were used to establish the role of RGS2 as a key inhibitory feedback regulator of the stochasticity of the Gαq-mediated calcium spike timing. RGS2 reduced the stochasticity of carbachol-stimulated calcium oscillations, and the feedback inhibition was coupled to the global calcium elevation by calmodulin/RGS2 interactions. The identification of a critical negative feedback circuit exemplifies the utility of optogenetic approaches for interrogating RGS/GPCR biology and calcium encoding principles through temporally precise molecular gain-of-function.
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Affiliation(s)
| | - Brian Y. Chow
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104
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13
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Bodle CR, Schamp JH, O'Brien JB, Hayes MP, Wu M, Doorn JA, Roman DL. Screen Targeting Lung and Prostate Cancer Oncogene Identifies Novel Inhibitors of RGS17 and Problematic Chemical Substructures. SLAS DISCOVERY 2018; 23:363-374. [PMID: 29351497 DOI: 10.1177/2472555217752301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Regulator of G protein signaling (RGS) proteins temporally regulate heterotrimeric G protein signaling cascades elicited by G protein-coupled receptor activation and thus are essential for cell homeostasis. The dysregulation of RGS protein expression has been linked to several pathologies, spurring discovery efforts to identify small-molecule inhibitors of these proteins. Presented here are the results of a high-throughput screening (HTS) campaign targeting RGS17, an RGS protein reported to be inappropriately upregulated in several cancers. A screen of over 60,000 small molecules led to the identification of five hit compounds that inhibit the RGS17-Gαo protein-protein interaction. Chemical and biochemical characterization demonstrated that three of these hits inhibited the interaction through the decomposition of parent compound into reactive products under normal chemical library storage/usage conditions. Compound substructures susceptible to decomposition are reported and the decomposition process characterized, adding to the armamentarium of tools available to the screening field, allowing for the conservation of resources in follow-up efforts and more efficient identification of potentially decomposed compounds. Finally, analogues of one hit compound were tested, and the results establish the first ever structure-activity relationship (SAR) profile for a small-molecule inhibitor of RGS17.
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Affiliation(s)
- Christopher R Bodle
- 1 Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA, USA
| | - Josephine H Schamp
- 1 Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA, USA
| | - Joseph B O'Brien
- 1 Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA, USA
| | - Michael P Hayes
- 1 Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA, USA
| | - Meng Wu
- 1 Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA, USA.,2 University of Iowa High Throughput Screening Facility (UIHTS), University of Iowa, Iowa City, IA, USA.,3 Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Jonathan A Doorn
- 1 Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA, USA
| | - David L Roman
- 1 Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, IA, USA.,4 Cancer Signaling and Experimental Therapeutics Program, Holden Comprehensive Cancer Center, UIHC, University of Iowa, Iowa City, IA, USA
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14
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Hong K, Li M, Nourian Z, Meininger GA, Hill MA. Angiotensin II Type 1 Receptor Mechanoactivation Involves RGS5 (Regulator of G Protein Signaling 5) in Skeletal Muscle Arteries: Impaired Trafficking of RGS5 in Hypertension. Hypertension 2017; 70:1264-1272. [PMID: 29061726 DOI: 10.1161/hypertensionaha.117.09757] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 06/11/2017] [Accepted: 09/20/2017] [Indexed: 01/07/2023]
Abstract
Studies suggest that arteriolar pressure-induced vasoconstriction can be initiated by GPCRs (G protein-coupled receptors), including the AT1R (angiotensin II type 1 receptor). This raises the question, are such mechanisms regulated by negative feedback? The present studies examined whether RGS (regulators of G protein signaling) proteins in vascular smooth muscle cells are colocalized with the AT1R when activated by mechanical stress or angiotensin II and whether this modulates AT1R-mediated vasoconstriction. To determine whether activation of the AT1R recruits RGS5, an in situ proximity ligation assay was performed in primary cultures of cremaster muscle arteriolar vascular smooth muscle cells treated with angiotensin II or hypotonic solution in the absence or presence of candesartan (an AT1R blocker). Proximity ligation assay results revealed a concentration-dependent increase in trafficking/translocation of RGS5 toward the activated AT1R, which was attenuated by candesartan. In intact arterioles, knockdown of RGS5 enhanced constriction to angiotensin II and augmented myogenic responses to increased intraluminal pressure. Myogenic constriction was attenuated to a higher degree by candesartan in RGS5 siRNA-transfected arterioles, consistent with RGS5 contributing to downregulation of AT1R-mediated signaling. Further, translocation of RGS5 was impaired in vascular smooth muscle cells of spontaneously hypertensive rats. This is consistent with dysregulated (RGS5-mediated) AT1R signaling that could contribute to excessive vasoconstriction in hypertension. In intact vessels, candesartan reduced myogenic vasoconstriction to a greater extent in spontaneously hypertensive rats compared with controls. Collectively, these findings suggest that AT1R activation results in translocation of RGS5 toward the plasma membrane, limiting AT1R-mediated vasoconstriction through its role in Gq/11 protein-dependent signaling.
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Affiliation(s)
- Kwangseok Hong
- From the Department of Medical Pharmacology and Physiology (K.H., M.L., G.A.M., M.A.H.) and Dalton Cardiovascular Research Center (K.H., Z.N., G.A.M., M.A.H.), University of Missouri, Columbia; and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville (K.H.)
| | - Min Li
- From the Department of Medical Pharmacology and Physiology (K.H., M.L., G.A.M., M.A.H.) and Dalton Cardiovascular Research Center (K.H., Z.N., G.A.M., M.A.H.), University of Missouri, Columbia; and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville (K.H.)
| | - Zahra Nourian
- From the Department of Medical Pharmacology and Physiology (K.H., M.L., G.A.M., M.A.H.) and Dalton Cardiovascular Research Center (K.H., Z.N., G.A.M., M.A.H.), University of Missouri, Columbia; and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville (K.H.)
| | - Gerald A Meininger
- From the Department of Medical Pharmacology and Physiology (K.H., M.L., G.A.M., M.A.H.) and Dalton Cardiovascular Research Center (K.H., Z.N., G.A.M., M.A.H.), University of Missouri, Columbia; and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville (K.H.)
| | - Michael A Hill
- From the Department of Medical Pharmacology and Physiology (K.H., M.L., G.A.M., M.A.H.) and Dalton Cardiovascular Research Center (K.H., Z.N., G.A.M., M.A.H.), University of Missouri, Columbia; and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville (K.H.).
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15
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Chen Y, Booth C, Wang H, Wang RX, Terzi D, Zachariou V, Jiao K, Zhang J, Wang Q. Effective Attenuation of Adenosine A1R Signaling by Neurabin Requires Oligomerization of Neurabin. Mol Pharmacol 2017; 92:630-639. [PMID: 28954816 DOI: 10.1124/mol.117.109462] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 09/25/2017] [Indexed: 12/17/2022] Open
Abstract
The adenosine A1 receptor (A1R) is a key mediator of the neuroprotective effect by endogenous adenosine. Yet targeting this receptor for neuroprotection is challenging due to its broad expression throughout the body. A mechanistic understanding of the regulation of A1R signaling is necessary for the future design of therapeutic agents that can selectively enhance A1R-mediated responses in the nervous system. In this study, we demonstrate that A1R activation leads to a sustained localization of regulator of G protein signaling 4 (RGS4) at the plasma membrane, a process that requires neurabin (a neural tissue-specific protein). A1R and RGS4 interact with the overlapping regions of neurabin. In addition, neurabin domains required for oligomerization are essential for formation of the A1R/neurabin/RGS4 ternary complex, as well as for stable localization of RGS4 at the plasma membrane and attenuation of A1R signaling. Thus, A1R and RGS4 each likely interact with one neurabin molecule in a neurabin homo-oligomer to form a ternary complex, representing a novel mode of regulation of G protein-coupled receptor signaling by scaffolding proteins. Our mechanistic analysis of neurabin-mediated regulation of A1R signaling in this study will be valuable for the future design of therapeutic agents that can selectively enhance A1R-mediated responses in the nervous system.
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Affiliation(s)
- Yunjia Chen
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Christopher Booth
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Hongxia Wang
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Raymond X Wang
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Dimitra Terzi
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Venetia Zachariou
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Kai Jiao
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Jin Zhang
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
| | - Qin Wang
- Departments of Cell, Developmental, and Integrative Biology (Y.C., H.W., R.X.W., Q.W.) and Genetics (K.J.), University of Alabama, Birmingham, Alabama; Department of Pharmacology, University of California, San Diego, California (C.B., J.Z.); and Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York (D.T., V.Z.)
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16
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Bodle CR, Mackie DI, Hayes MP, Schamp JH, Miller MR, Henry MD, Doorn JA, Houtman JCD, James MA, Roman DL. Natural Products Discovered in a High-Throughput Screen Identified as Inhibitors of RGS17 and as Cytostatic and Cytotoxic Agents for Lung and Prostate Cancer Cell Lines. JOURNAL OF NATURAL PRODUCTS 2017. [PMID: 28621943 PMCID: PMC5567870 DOI: 10.1021/acs.jnatprod.7b00112] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Regulator of G Protein Signaling (RGS) 17 is an overexpressed promoter of cancer survival in lung and prostate tumors, the knockdown of which results in decreased tumor cell proliferation in vitro. Identification of drug-like molecules inhibiting this protein could ameliorate the RGS17's pro-tumorigenic effect. Using high-throughput screening, a chemical library containing natural products was interrogated for inhibition of the RGS17-Gαo interaction. Initial hits were verified in control and counter screens. Leads were characterized via biochemical, mass spectrometric, Western blot, microscopic, and cytotoxicity measures. Four known compounds (1-4) were identified with IC50 values ranging from high nanomolar to low micromolar. Three compounds were extensively characterized biologically, demonstrating cellular activity determined by confocal microscopy, and two compounds were assessed via ITC exhibiting high nanomolar to low micromolar dissociation constants. The compounds were found to have a cysteine-dependent mechanism of binding, verified through site-directed mutagenesis and cysteine reactivity assessment. Two compounds, sanguinarine (1) and celastrol (2), were found to be cytostatic against lung and prostate cancer cell lines and cytotoxic against prostate cancer cell lines in vitro, although the dependence of RGS17 on these phenomena remains elusive, a result that is perhaps not surprising given the multimodal cytostatic and cytotoxic activities of many natural products.
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Affiliation(s)
- Christopher R. Bodle
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa 52242, United States
| | - Duncan I. Mackie
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa 52242, United States
- Holden Comprehensive Cancer Center, UIHC, University of Iowa, Iowa City, Iowa 52242, United States
| | - Michael P. Hayes
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa 52242, United States
| | - Josephine H Schamp
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa 52242, United States
| | - Michael R. Miller
- Holden Comprehensive Cancer Center, UIHC, University of Iowa, Iowa City, Iowa 52242, United States
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, United States
| | - Michael D. Henry
- Department of Molecular Physiology, Biophysics, and Pathology, Holden Comprehensive Cancer Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, United States
| | - Jonathan A. Doorn
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa 52242, United States
| | - Jon C. D. Houtman
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, United States
- Interdisciplinary Graduate Program in Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, United States
| | - Michael A. James
- Department of Surgery, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, United States
- Pancreatic Cancer Program at the Medical College of Wisconsin, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, United States
| | - David L. Roman
- Department of Pharmaceutical Sciences and Experimental Therapeutics, University of Iowa, Iowa City, Iowa 52242, United States
- Cancer Signaling and Experimental Therapeutics Program, Holden Comprehensive Cancer Center, UIHC, University of Iowa, Iowa City, Iowa 52242, United States
- Corresponding Author. Tel: 319-335-6920. Fax: 319-335-8766.
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17
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Lee KN, Lu X, Nguyen C, Feng Q, Chidiac P. Cardiomyocyte specific overexpression of a 37 amino acid domain of regulator of G protein signalling 2 inhibits cardiac hypertrophy and improves function in response to pressure overload in mice. J Mol Cell Cardiol 2017. [PMID: 28641980 DOI: 10.1016/j.yjmcc.2017.06.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Regulator of G protein signalling 2 (RGS2) is known to play a protective role in maladaptive cardiac hypertrophy and heart failure via its ability to inhibit Gq- and Gs- mediated GPCR signalling. We previously demonstrated that RGS2 can also inhibit protein translation and can thereby attenuate cell growth. This G protein-independent inhibitory effect has been mapped to a 37 amino acid domain (RGS2eb) within RGS2 that binds to eukaryotic initiation factor 2B (eIF2B). When expressed in neonatal rat cardiomyocytes, RGS2eb attenuates both protein synthesis and hypertrophy induced by Gq- and Gs- activating agents. In the current study, we investigated the potential cardioprotective role of RGS2eb by determining whether RGS2eb transgenic (RGS2eb TG) mice with cardiomyocyte specific overexpression of RGS2eb show resistance to the development of hypertrophy in comparison to wild-type (WT) controls. Using transverse aortic constriction (TAC) in a pressure-overload hypertrophy model, we demonstrated that cardiac hypertrophy was inhibited in RGS2eb TG mice compared to WT controls following four weeks of TAC. Expression of the hypertrophic markers atrial natriuretic peptide (ANP) and β-myosin heavy chain (MHC-β) was also reduced in RGS2eb TG compared to WT TAC animals. Furthermore, cardiac function in RGS2eb TG TAC mice was significantly improved compared to WT TAC mice. Notably, cardiomyocyte cell size was significantly decreased in TG compared to WT TAC mice. These results suggest that RGS2 may limit pathological cardiac hypertrophy at least in part via the function of its eIF2B-binding domain.
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Affiliation(s)
- Katherine N Lee
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, N6A5C1, Canada
| | - Xiangru Lu
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, N6A5C1, Canada
| | - Chau Nguyen
- School of Pharmacy, D'Youville College, Buffalo, New York 14201, USA
| | - Qingping Feng
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, N6A5C1, Canada
| | - Peter Chidiac
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, N6A5C1, Canada.
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18
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Rorabaugh BR, Chakravarti B, Mabe NW, Seeley SL, Bui AD, Yang J, Watts SW, Neubig RR, Fisher RA. Regulator of G Protein Signaling 6 Protects the Heart from Ischemic Injury. J Pharmacol Exp Ther 2016; 360:409-416. [PMID: 28035008 DOI: 10.1124/jpet.116.238345] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 12/28/2016] [Indexed: 01/07/2023] Open
Abstract
Gαi-coupled receptors play important roles in protecting the heart from ischemic injury. Regulator of G protein signaling (RGS) proteins suppress Gαi signaling by accelerating the GTPase activity of Gαi subunits. However, the roles of individual RGS proteins in modulating ischemic injury are unknown. In this study, we investigated the effect of RGS6 deletion on myocardial sensitivity to ischemic injury. Hearts from RGS6 knockout (RGS6-/-) and RGS6 wild-type (RGS6+/+) mice were subjected to 30 minutes of ischemia and 2 hours of reperfusion on a Langendorff heart apparatus. Infarcts in RGS6-/- hearts were significantly larger than infarcts in RGS6+/+ hearts. RGS6-/- hearts also exhibited increased phosphorylation of β2-adrenergic receptors and G protein-coupled receptor kinase 2 (GRK2). Mitochondrial GRK2 as well as caspase-3 cleavage were increased significantly in RGS6-/- hearts compared with RGS6+/+ hearts after ischemia. Chronic propranolol treatment of mice prevented the observed increases in ischemic injury and the GRK2 phosphorylation observed in RGS6-/- hearts. Our findings suggest that loss of RGS6 predisposes the ventricle to prodeath signaling through a β2AR-GRK2-dependent signaling mechanism, and they provide evidence for a protective role of RGS6 in the ischemic heart. Individuals expressing genetic polymorphisms that suppress the activity of RGS6 may be at increased risk of cardiac ischemic injury. Furthermore, the development of agents that increase RGS6 expression or activity might provide a novel strategy for the treatment of ischemic heart disease.
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Affiliation(s)
- Boyd R Rorabaugh
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Bandana Chakravarti
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Nathaniel W Mabe
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Sarah L Seeley
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Albert D Bui
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Jianqi Yang
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Stephanie W Watts
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Richard R Neubig
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Rory A Fisher
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
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19
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Masuda K, Kitakami JI, Kozasa T, Kodama T, Ihara S, Hamakubo T. Visualization of ligand‐induced G
i
‐protein activation in chemotaxing cells. FASEB J 2016; 31:910-919. [DOI: 10.1096/fj.201601102r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 11/07/2016] [Indexed: 01/29/2023]
Affiliation(s)
- Kazuyuki Masuda
- Department of Quantitative Biology and MedicineResearch Center for Advanced Science and TechnologyUniversity of Tokyo Tokyo Japan
| | - Jun-Ichi Kitakami
- Laboratory of Systems Biology and MedicineResearch Center for Advanced Science and TechnologyUniversity of Tokyo Tokyo Japan
| | - Tohru Kozasa
- Department of Quantitative Biology and MedicineResearch Center for Advanced Science and TechnologyUniversity of Tokyo Tokyo Japan
| | - Tatsuhiko Kodama
- Laboratory of Systems Biology and MedicineResearch Center for Advanced Science and TechnologyUniversity of Tokyo Tokyo Japan
| | - Sigeo Ihara
- Laboratory of Systems Biology and MedicineResearch Center for Advanced Science and TechnologyUniversity of Tokyo Tokyo Japan
| | - Takao Hamakubo
- Department of Quantitative Biology and MedicineResearch Center for Advanced Science and TechnologyUniversity of Tokyo Tokyo Japan
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20
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RGS10 Negatively Regulates Platelet Activation and Thrombogenesis. PLoS One 2016; 11:e0165984. [PMID: 27829061 PMCID: PMC5102365 DOI: 10.1371/journal.pone.0165984] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2016] [Accepted: 10/20/2016] [Indexed: 01/08/2023] Open
Abstract
Regulators of G protein signaling (RGS) proteins act as GTPase activating proteins to negatively regulate G protein-coupled receptor (GPCR) signaling. Although several RGS proteins including RGS2, RGS16, RGS10, and RGS18 are expressed in human and mouse platelets, the respective unique function(s) of each have not been fully delineated. RGS10 is a member of the D/R12 subfamily of RGS proteins and is expressed in microglia, macrophages, megakaryocytes, and platelets. We used a genetic approach to examine the role(s) of RGS10 in platelet activation in vitro and hemostasis and thrombosis in vivo. GPCR-induced aggregation, secretion, and integrin activation was much more pronounced in platelets from Rgs10-/- mice relative to wild type (WT). Accordingly, these mice had markedly reduced bleeding times and were more susceptible to vascular injury-associated thrombus formation than control mice. These findings suggest a unique, non-redundant role of RGS10 in modulating the hemostatic and thrombotic functions of platelets in mice. RGS10 thus represents a potential therapeutic target to control platelet activity and/or hypercoagulable states.
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21
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Postula M, Janicki PK, Milanowski L, Pordzik J, Eyileten C, Karlinski M, Wylezol P, Solarska M, Czlonkowka A, Kurkowska-Jastrzebka I, Sugino S, Imamura Y, Mirowska-Guzel D. Association of frequent genetic variants in platelet activation pathway genes with large-vessel ischemic stroke in Polish population. Platelets 2016; 28:66-73. [DOI: 10.1080/09537104.2016.1203404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Marek Postula
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
- Perioperative Genomics Laboratory, Penn State University, College of Medicine, Hershey, PA, USA
| | - Piotr K. Janicki
- Perioperative Genomics Laboratory, Penn State University, College of Medicine, Hershey, PA, USA
| | - Lukasz Milanowski
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
| | - Justyna Pordzik
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
| | - Ceren Eyileten
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
| | - Michal Karlinski
- 2nd Department of Neurology, Institute of Psychiatry and Neurology, Warsaw, Poland
| | - Pawel Wylezol
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
| | - Marta Solarska
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
| | - Anna Czlonkowka
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
- 2nd Department of Neurology, Institute of Psychiatry and Neurology, Warsaw, Poland
| | | | - Shigekazu Sugino
- Perioperative Genomics Laboratory, Penn State University, College of Medicine, Hershey, PA, USA
| | - Yuka Imamura
- Genome Sciences Facility, Penn State University, College of Medicine, Hershey, PA, USA
| | - Dagmara Mirowska-Guzel
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Center for Preclinical Research and Technology CEPT, Warsaw, Poland
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Sjögren B, Parra S, Atkins KB, Karaj B, Neubig RR. Digoxin-Mediated Upregulation of RGS2 Protein Protects against Cardiac Injury. J Pharmacol Exp Ther 2016; 357:311-9. [PMID: 26941169 PMCID: PMC4851323 DOI: 10.1124/jpet.115.231571] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Accepted: 03/01/2016] [Indexed: 12/31/2022] Open
Abstract
Regulator of G protein signaling (RGS) proteins have emerged as novel drug targets since their discovery almost two decades ago. RGS2 has received particular interest in cardiovascular research due to its role in regulating Gqsignaling in the heart and vascular smooth muscle. RGS2(-/-)mice are hypertensive, prone to heart failure, and display accelerated kidney fibrosis. RGS2 is rapidly degraded through the proteasome, and human mutations leading to accelerated RGS2 protein degradation correlate with hypertension. Hence, stabilizing RGS2 protein expression could be a novel route in treating cardiovascular disease. We previously identified cardiotonic steroids, including digoxin, as selective stabilizers of RGS2 protein in vitro. In the current study we investigated the functional effects of digoxin-mediated RGS2 protein stabilization in vivo. Using freshly isolated myocytes from wild-type and RGS2(-/-)mice treated with vehicle or low-dose digoxin (2µg/kg/day for 7 days) we demonstrated that agonist-induced cAMP levels and cardiomyocyte contractility was inhibited by digoxin in wild-type but not in RGS2(-/-)mice. This inhibition was accompanied by an increase in RGS2 protein levels in cardiomyocytes as well as in whole heart tissue. Furthermore, digoxin had protective effects in a model of cardiac injury in wild-type mice and this protection was lost in RGS2(-/-)mice. Digoxin is the oldest known therapy for heart failure; however, beyond its activity at the Na(+)/K(+)-ATPase, the exact mechanism of action is not known. The current study adds a novel mechanism, whereby through stabilizing RGS2 protein levels digoxin could exert its protective effects in the failing heart.
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Affiliation(s)
- Benita Sjögren
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (B.S., B.K., R.R.N.); and Department of Pharmacology (S.P.) and Department of Internal Medicine (K.B.A.), University of Michigan, Ann Arbor, Michigan
| | - Sergio Parra
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (B.S., B.K., R.R.N.); and Department of Pharmacology (S.P.) and Department of Internal Medicine (K.B.A.), University of Michigan, Ann Arbor, Michigan
| | - Kevin B Atkins
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (B.S., B.K., R.R.N.); and Department of Pharmacology (S.P.) and Department of Internal Medicine (K.B.A.), University of Michigan, Ann Arbor, Michigan
| | - Behirda Karaj
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (B.S., B.K., R.R.N.); and Department of Pharmacology (S.P.) and Department of Internal Medicine (K.B.A.), University of Michigan, Ann Arbor, Michigan
| | - Richard R Neubig
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (B.S., B.K., R.R.N.); and Department of Pharmacology (S.P.) and Department of Internal Medicine (K.B.A.), University of Michigan, Ann Arbor, Michigan
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23
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Salaga M, Storr M, Martemyanov KA, Fichna J. RGS proteins as targets in the treatment of intestinal inflammation and visceral pain: New insights and future perspectives. Bioessays 2016; 38:344-54. [PMID: 26817719 PMCID: PMC4916644 DOI: 10.1002/bies.201500118] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Regulators of G protein signaling (RGS) proteins provide timely termination of G protein-coupled receptor (GPCR) responses. Serving as a central control point in GPCR signaling cascades, RGS proteins are promising targets for drug development. In this review, we discuss the involvement of RGS proteins in the pathophysiology of the gastrointestinal inflammation and their potential to become a target for anti-inflammatory drugs. Specifically, we evaluate the emerging evidence for modulation of selected receptor families: opioid, cannabinoid and serotonin by RGS proteins. We discuss how the regulation of RGS protein level and activity may modulate immunological pathways involved in the development of intestinal inflammation. Finally, we propose that RGS proteins may serve as a prognostic factor for survival rate in colorectal cancer. The ideas introduced in this review set a novel conceptual framework for the utilization of RGS proteins in the treatment of gastrointestinal inflammation, a growing major concern worldwide.
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Affiliation(s)
- Maciej Salaga
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Poland
| | - Martin Storr
- Walter Brendel Center of Experimental Medicine, University of Munich, Germany
| | - Kirill A. Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
- Corresponding authors: J.F. Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland, Phone: ++48 42 272 57 07, Fax: ++48 42 272 56 94, . K.A.M., Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way C347, Jupiter, FL 33458, USA, Phone: ++1 561 228 2770,
| | - Jakub Fichna
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Poland
- Corresponding authors: J.F. Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland, Phone: ++48 42 272 57 07, Fax: ++48 42 272 56 94, . K.A.M., Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way C347, Jupiter, FL 33458, USA, Phone: ++1 561 228 2770,
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24
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Zhang H, Wheat H, Wang P, Jiang S, Baghdoyan HA, Neubig RR, Shi XY, Lydic R. RGS Proteins and Gαi2 Modulate Sleep, Wakefulness, and Disruption of Sleep/ Wake States after Isoflurane and Sevoflurane Anesthesia. Sleep 2016; 39:393-404. [PMID: 26564126 DOI: 10.5665/sleep.5450] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/17/2015] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES This study tested the hypothesis that Regulators of G protein Signaling (RGS) proteins contribute to the regulation of wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep, and to sleep disruption caused by volatile anesthetics. METHODS The three groups used in this study included wild-type (WT; n = 7) mice and knock-in mice that were heterozygous (+/GS; n = 7) or homozygous (GS/GS; n = 7) for an RGS-insensitive allele that causes prolonged Gαi2 signaling. Mice were implanted with electrodes for recording sleep and conditioned for 1 week or more to sleep in the laboratory. Using within and between groups designs, 24-h recordings of wakefulness, NREM sleep, and REM sleep were compared across three interventions: (1) baseline (control) and after 3 h of being anesthetized with (2) isoflurane or (3) sevoflurane. RESULTS Baseline recordings during the light phase revealed that relative to WT mice, homozygous RGS-insensitive (GS/GS) mice exhibit significantly increased wakefulness and decreased NREM and REM sleep. During the dark phase, these state-specific differences remained significant but reversed direction of change. After cessation of isoflurane and sevoflurane anesthesia there was a long-lasting and significant disruption of sleep and wakefulness. The durations of average episodes of wakefulness, NREM sleep, and REM sleep were significantly altered as a function of genotype and isoflurane and sevoflurane anesthesia. CONCLUSIONS RGS proteins and Gαi2 play a significant role in regulating states of wakefulness, NREM sleep, and REM sleep. Genotype-specific differences demonstrate that RGS proteins modulate sleep disruption caused by isoflurane and sevoflurane anesthesia. The results also support the conclusion that isoflurane and sevoflurane anesthesia do not satisfy the homeostatic drive for sleep.
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Affiliation(s)
- Hao Zhang
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI.,Department of Anesthesiology, The Second Artillery General Hospital, Beijing, China
| | - Heather Wheat
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI
| | - Peter Wang
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI
| | - Sha Jiang
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI
| | - Helen A Baghdoyan
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI.,Departments of Anesthesiology and Psychology, University of Tennessee, Knoxville, TN
| | - Richard R Neubig
- Department of Pharmacology and Toxicology, Michigan State University, Lansing, MI
| | - X Y Shi
- Department of Anesthesiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Ralph Lydic
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI.,Departments of Anesthesiology and Psychology, University of Tennessee, Knoxville, TN
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25
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Gerber KJ, Squires KE, Hepler JR. Roles for Regulator of G Protein Signaling Proteins in Synaptic Signaling and Plasticity. Mol Pharmacol 2015; 89:273-86. [PMID: 26655302 DOI: 10.1124/mol.115.102210] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/10/2015] [Indexed: 11/22/2022] Open
Abstract
The regulator of G protein signaling (RGS) family of proteins serves critical roles in G protein-coupled receptor (GPCR) and heterotrimeric G protein signal transduction. RGS proteins are best understood as negative regulators of GPCR/G protein signaling. They achieve this by acting as GTPase activating proteins (GAPs) for Gα subunits and accelerating the turnoff of G protein signaling. Many RGS proteins also bind additional signaling partners that either regulate their functions or enable them to regulate other important signaling events. At neuronal synapses, GPCRs, G proteins, and RGS proteins work in coordination to regulate key aspects of neurotransmitter release, synaptic transmission, and synaptic plasticity, which are necessary for central nervous system physiology and behavior. Accumulating evidence has revealed key roles for specific RGS proteins in multiple signaling pathways at neuronal synapses, regulating both pre- and postsynaptic signaling events and synaptic plasticity. Here, we review and highlight the current knowledge of specific RGS proteins (RGS2, RGS4, RGS7, RGS9-2, and RGS14) that have been clearly demonstrated to serve critical roles in modulating synaptic signaling and plasticity throughout the brain, and we consider their potential as future therapeutic targets.
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Affiliation(s)
- Kyle J Gerber
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - Katherine E Squires
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
| | - John R Hepler
- Programs in Molecular and Systems Pharmacology (K.J.G., K.E.S., J.R.H.) and Neuroscience (J.R.H.), Department of Pharmacology (K.J.G., K.E.S., J.R.H.), Emory University School of Medicine, Atlanta, Georgia
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26
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Lee JH, Jiang Y, Kwon YT, Lee MJ. Pharmacological Modulation of the N-End Rule Pathway and Its Therapeutic Implications. Trends Pharmacol Sci 2015; 36:782-797. [PMID: 26434644 DOI: 10.1016/j.tips.2015.07.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 07/13/2015] [Accepted: 07/16/2015] [Indexed: 11/26/2022]
Abstract
The N-end rule pathway is a proteolytic system in which single N-terminal amino acids of short-lived substrates determine their metabolic half-lives. Substrates of this pathway have been implicated in the pathogenesis of many diseases, including malignancies, neurodegeneration, and cardiovascular disorders. This review provides a comprehensive overview of current knowledge about the mechanism and functions of the N-end rule pathway. Pharmacological strategies for the modulation of target substrate degradation are also reviewed, with emphasis on their in vivo implications. Given the rapid advances in structural and biochemical understanding of the recognition components (N-recognins) of the N-end rule pathway, small-molecule inhibitors and activating ligands of N-recognins emerge as therapeutic agents with novel mechanisms of action.
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Affiliation(s)
- Jung Hoon Lee
- Department of Biochemistry and Molecular Biology, Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Yanxialei Jiang
- Department of Biochemistry and Molecular Biology, Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Yong Tae Kwon
- Protein Metabolism Medical Research Center, Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea.
| | - Min Jae Lee
- Department of Biochemistry and Molecular Biology, Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Protein Metabolism Medical Research Center, Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Neuroscience Research Institute, Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea.
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27
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Modulating platelet reactivity through control of RGS18 availability. Blood 2015; 126:2611-20. [PMID: 26407691 DOI: 10.1182/blood-2015-04-640037] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 09/22/2015] [Indexed: 01/13/2023] Open
Abstract
Most platelet agonists activate platelets by binding to G-protein-coupled receptors. We have shown previously that a critical node in the G-protein signaling network in platelets is formed by a scaffold protein, spinophilin (SPL), the tyrosine phosphatase, Src homology region 2 domain-containing phosphatase-1 (SHP-1), and the regulator of G-protein signaling family member, RGS18. Here, we asked whether SPL and other RGS18 binding proteins such as 14-3-3γ regulate platelet reactivity by sequestering RGS18 and, if so, how this is accomplished. The results show that, in resting platelets, free RGS18 levels are relatively low, increasing when platelets are activated by thrombin. Free RGS18 levels also rise when platelets are rendered resistant to activation by exposure to prostaglandin I2 (PGI2) or forskolin, both of which increase platelet cyclic adenosine monophosphate (cAMP) levels. However, the mechanism for raising free RGS18 is different in these 2 settings. Whereas thrombin activates SHP-1 and causes dephosphorylation of SPL tyrosine residues, PGI2 and forskolin cause phosphorylation of SPL Ser94 without reducing tyrosine phosphorylation. Substituting alanine for Ser94 blocks cAMP-induced dissociation of the SPL/RGS/SHP-1 complex. Replacing Ser94 with aspartate prevents formation of the complex and produces a loss-of-function phenotype when expressed in mouse platelets. Together with the defect in platelet function we previously observed in SPL(-/-) mice, these data show that (1) regulated sequestration and release of RGS18 by intracellular binding proteins provides a mechanism for coordinating activating and inhibitory signaling networks in platelets, and (2) differential phosphorylation of SPL tyrosine and serine residues provides a key to understanding both.
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28
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Doupnik CA. RGS Redundancy and Implications in GPCR-GIRK Signaling. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:87-116. [PMID: 26422983 DOI: 10.1016/bs.irn.2015.05.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Regulators of G protein signaling (RGS proteins) are key components of GPCR complexes, interacting directly with G protein α-subunits to enhance their intrinsic GTPase activity. The functional consequence is an accelerated termination of G protein effectors including certain ion channels. RGS proteins have a profound impact on the membrane-delimited gating behavior of G-protein-activated inwardly rectifying K(+) (GIRK) channels as demonstrated in reconstitution assays and recent RGS knockout mice studies. Akin to GPCRs and G protein αβγ subunits, multiple RGS isoforms are expressed within single GIRK-expressing neurons, suggesting functional redundancy and/or specificity in GPCR-GIRK channel signaling. The extent and impact of RGS redundancy in neuronal GPCR-GIRK channel signaling is currently not fully appreciated; however, recent studies from RGS knockout mice are providing important new clues on the impact of individual endogenous RGS proteins and the extent of RGS functional redundancy. Incorporating "tools" such as engineered RGS-resistant Gαi/o subunits provide an important assessment method for determining the impact of all endogenous RGS proteins on a given GPCR response and an accounting benchmark to assess the impact of individual RGS knockouts on overall RGS redundancy within a given neuron. Elucidating the degree of regulation attributable to specific RGS proteins in GIRK channel function will aid in the assessment of individual RGS proteins as viable therapeutic targets in epilepsy, ataxia's, memory disorders, and a growing list of neurological disorders.
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Affiliation(s)
- Craig A Doupnik
- Department of Molecular Pharmacology & Physiology, University of South Florida College of Medicine, Tampa, Florida, USA.
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29
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Neubig RR. RGS-Insensitive G Proteins as In Vivo Probes of RGS Function. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 133:13-30. [PMID: 26123300 DOI: 10.1016/bs.pmbts.2015.04.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Guanine nucleotide-binding proteins of the inhibitory (Gi/o) class play critical physiological roles and the receptors that activate them are important therapeutic targets (e.g., mu opioid, serotonin 5HT1a, etc.). Gi/o proteins are negatively regulated by regulator of G protein signaling (RGS) proteins. The redundant actions of the 20 different RGS family members have made it difficult to establish their overall physiological role. A unique G protein mutation (G184S in Gαi/o) prevents RGS binding to the Gα subunit and blocks all RGS action at that particular Gα subunit. The robust phenotypes of mice expressing these RGS-insensitive (RGSi) mutant G proteins illustrate the profound action of RGS proteins in cardiovascular, metabolic, and central nervous system functions. Specifically, the enhanced Gαi2 signaling through the RGSi Gαi2(G184S) mutant knock-in mice shows protection against cardiac ischemia/reperfusion injury and potentiation of serotonin-mediated antidepressant actions. In contrast, the RGSi Gαo mutant knock-in produces enhanced mu-opioid receptor-mediated analgesia but also a seizure phenotype. These genetic models provide novel insights into potential therapeutic strategies related to RGS protein inhibitors and/or G protein subtype-biased agonists at particular GPCRs.
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Affiliation(s)
- Richard R Neubig
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan, USA.
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30
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Wamsteeker Cusulin JI, Bains JS. Embedded synaptic feedback in the neuroendocrine stress axis. J Neuroendocrinol 2015; 27:481-6. [PMID: 25612538 DOI: 10.1111/jne.12260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 01/07/2015] [Accepted: 01/15/2015] [Indexed: 11/28/2022]
Abstract
Neural regulation of blood glucocorticoid levels is critical for defence of homeostasis during physiological or psychoemotional challenges. In mammals, this function is carried out by the neuroendocrine stress axis, coordinated by parvocellular neuroendocrine cells (PNCs) of the paraventricular hypothalamic nucleus. Feedback regulation of PNCs by glucocorticoids provides complex experience-dependent shaping of neuroendocrine responses. We review recent evidence for metaplastic actions of glucocorticoids as 'circuit breakers' at synapses directly regulating PNC excitability and explore how such mechanisms may serve as substrates for stress adaptation.
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Affiliation(s)
- J I Wamsteeker Cusulin
- Hotchkiss Brain Institute and the Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - J S Bains
- Hotchkiss Brain Institute and the Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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31
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Sjögren B, Swaney S, Neubig RR. FBXO44-Mediated Degradation of RGS2 Protein Uniquely Depends on a Cullin 4B/DDB1 Complex. PLoS One 2015; 10:e0123581. [PMID: 25970626 PMCID: PMC4430315 DOI: 10.1371/journal.pone.0123581] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 03/05/2015] [Indexed: 12/30/2022] Open
Abstract
The ubiquitin-proteasome system for protein degradation plays a major role in regulating cell function and many signaling proteins are tightly controlled by this mechanism. Among these, Regulator of G Protein Signaling 2 (RGS2) is a target for rapid proteasomal degradation, however, the specific enzymes involved are not known. Using a genomic siRNA screening approach, we identified a novel E3 ligase complex containing cullin 4B (CUL4B), DNA damage binding protein 1 (DDB1) and F-box protein 44 (FBXO44) that mediates RGS2 protein degradation. While the more typical F-box partners CUL1 and Skp1 can bind FBXO44, that E3 ligase complex does not bind RGS2 and is not involved in RGS2 degradation. These observations define an unexpected DDB1/CUL4B-containing FBXO44 E3 ligase complex. Pharmacological targeting of this mechanism provides a novel therapeutic approach to hypertension, anxiety, and other diseases associated with RGS2 dysregulation.
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Affiliation(s)
- Benita Sjögren
- Department of Pharmacology & Toxicology, Michigan State University, 1355 Bogue Street, East Lansing, MI 48824, United States of America
| | - Steven Swaney
- Center for Chemical Genomics, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109, United States of America
| | - Richard R Neubig
- Department of Pharmacology & Toxicology, Michigan State University, 1355 Bogue Street, East Lansing, MI 48824, United States of America
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32
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The regulator of G-protein signaling 18 regulates platelet aggregation, hemostasis and thrombosis. Biochem Biophys Res Commun 2015; 462:378-82. [PMID: 25969426 DOI: 10.1016/j.bbrc.2015.04.143] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 04/30/2015] [Indexed: 11/23/2022]
Abstract
Regulators of G protein signaling (RGS) proteins are known to interact with and negatively regulate/turn-off G protein activation. RGS18 is identified as an R4 subfamily member of this family with specific expression in hematopoietic progenitors, myeloerythroid cells, megakaryocytes and platelets. Studies focused on understanding its function in platelet biology have been limited, in part, due to lack of pharmacological inhibitors. Thus, the present study investigated the function of RGS18 in platelets, using the RGS18 knockout mouse model (RGS18(-/-)). We identified phenotypic differences between RGS18(-/-) and wild-type (WT) mice, and show that RGS18 plays a significant role in hemostasis and thrombosis. Hence, RGS18 deficiency markedly shortened bleeding as well as occlusion times (in vivo). Furthermore, RGS18(-/-) platelets displayed hyper-responsiveness with regards to agonist induced aggregation (in vitro). This gain of function phenotype may serve as the mechanism or explain, at least in part, the enhanced hemostasis and thrombosis phenotype observed in the RGS18 deletion mice. Collectively, our findings provide valuable insight and highlight a critical and direct role for RGS18 in modulating platelet function.
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Banaei-Esfahani A, Moazzeni H, Nosar PN, Amin S, Arefian E, Soleimani M, Yazdani S, Elahi E. MicroRNAs that target RGS5. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2015; 18:108-14. [PMID: 25810883 PMCID: PMC4366720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 09/16/2014] [Indexed: 11/22/2022]
Abstract
OBJECTIVES An earlier meta-analysis on gene expression data derived from four microarray, two cDNA library, and one SAGE experiment had identified RGS5 as one of only ten non-housekeeping genes that were reported to be expressed in human trabecular meshwork (TM) cells by all studies. RGS5 encodes regulator of G-protein signaling-5. The TM tissue is the route of aqueous fluid outflow, and is relevant to the pathology of glaucoma. MicroRNAs constitute the most recently identified components of the cellular machinery for gene regulation in eukaryotic cells. Given our long standing interest in glaucoma, we aimed to identify miRNAs that may target RGS5. MATERIALS AND METHODS Eight miRNAs were selected for study using bioinformatics tools and available data on miRNAs expressed in the eye. Their effects were assessed using the dual luciferase assay. 3'-UTR segments of RGS5 mRNA were cloned downstream of a luciferase coding gene in psiCHECK2 vectors, and these were co-transfected with each of the miRNAs into HEK293 cells. RESULTS The outcomes evidenced that one or more of the segments are in fact targeted by miR-7, miR-9, miR-96, miR-23a, miR-23b, miR-204, and miR-211. Down regulations by the miRNAs were statistically significant. The effect of miR-204 is considered particularly important as this miRNA is well known to regulate eye development and to affect multiple ocular functions. CONCLUSION Our results justify further studies on regulation of RGS5 expression and RGS5 downstream functions by these miRNAs.
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Affiliation(s)
- Amir Banaei-Esfahani
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
| | - Hamidreza Moazzeni
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Pooya Naseri Nosar
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
| | - Sadaf Amin
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
| | - Ehsan Arefian
- School of Biology, College of Science, University of Tehran, Tehran, Iran
| | | | - Shahin Yazdani
- Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Elahe Elahi
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran,School of Biology, College of Science, University of Tehran, Tehran, Iran,*Corresponding author: Elahe Elahi. College of Science, University of Tehran, Tehran, Iran. Tel: +98-9122181251; Fax: +98-21-66405141; ,
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34
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Ganss R. Keeping the Balance Right. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 133:93-121. [DOI: 10.1016/bs.pmbts.2015.02.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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35
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Delesque-Touchard N, Pendaries C, Volle-Challier C, Millet L, Salel V, Hervé C, Pflieger AM, Berthou-Soulie L, Prades C, Sorg T, Herbert JM, Savi P, Bono F. Regulator of G-protein signaling 18 controls both platelet generation and function. PLoS One 2014; 9:e113215. [PMID: 25405900 PMCID: PMC4236145 DOI: 10.1371/journal.pone.0113215] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/24/2014] [Indexed: 01/10/2023] Open
Abstract
RGS18 is a myeloerythroid lineage-specific regulator of G-protein signaling, highly expressed in megakaryocytes (MKs) and platelets. In the present study, we describe the first generation of a RGS18 knockout mouse model (RGS18-/-). Interesting phenotypic differences between RGS18-/- and wild-type (WT) mice were identified, and show that RGS18 plays a significant role in both platelet generation and function. RGS18 deficiency produced a gain of function phenotype in platelets. In resting platelets, the level of CD62P expression was increased in RGS18-/- mice. This increase correlated with a higher level of plasmatic serotonin concentration. RGS18-/- platelets displayed a higher sensitivity to activation in vitro. RGS18 deficiency markedly increased thrombus formation in vivo. In addition, RGS18-/- mice presented a mild thrombocytopenia, accompanied with a marked deficit in MK number in the bone marrow. Analysis of MK maturation in vitro and in vivo revealed a defective megakaryopoiesis in RGS18-/- mice, with a lower bone marrow content of only the most committed MK precursors. Finally, RGS18 deficiency was correlated to a defect of platelet recovery in vivo under acute conditions of thrombocytopenia. Thus, we highlight a role for RGS18 in platelet generation and function, and provide additional insights into the physiology of RGS18.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Tania Sorg
- Department of Scientific Operations PhenoPro, Mouse Clinical Institute (MCI), Strasbourg, France
| | | | - Pierre Savi
- Early to Candidate (E2C), Sanofi, Toulouse, France
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Zhao P, Nunn C, Ramineni S, Hepler JR, Chidiac P. The Ras-binding domain region of RGS14 regulates its functional interactions with heterotrimeric G proteins. J Cell Biochem 2014; 114:1414-23. [PMID: 23255434 DOI: 10.1002/jcb.24483] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 12/06/2012] [Indexed: 12/28/2022]
Abstract
RGS14 is a 60 kDa protein that contains a regulator of G protein signaling (RGS) domain near its N-terminus, a central region containing a pair of tandem Ras-binding domains (RBD), and a GPSM (G protein signaling modulator) domain (a.k.a. Gi/o-Loco binding [GoLoco] motif) near its C-terminus. The RGS domain of RGS14 exhibits GTPase accelerating protein (GAP) activity toward Gαi/o proteins, while its GPSM domain acts as a guanine nucleotide dissociation inhibitor (GDI) on Gαi1 and Gαi3. In the current study, we investigate the contribution of different domains of RGS14 to its biochemical functions. Here we show that the full-length protein has a greater GTPase activating activity but a weaker inhibition of nucleotide dissociation relative to its isolated RGS and GPSM regions, respectively. Our data suggest that these differences may be attributable to an inter-domain interaction within RGS14 that promotes the activity of the RGS domain, but simultaneously inhibits the activity of the GPSM domain. The RBD region seems to play an essential role in this regulatory activity. Moreover, this region of RGS14 is also able to bind to members of the B/R4 subfamily of RGS proteins and enhance their effects on GPCR-activated Gi/o proteins. Overall, our results suggest a mechanism wherein the RBD region associates with the RGS domain region, producing an intramolecular interaction within RGS14 that enhances the GTPase activating function of its RGS domain while disfavoring the negative effect of its GPSM domain on nucleotide dissociation.
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Affiliation(s)
- Peishen Zhao
- Department of Physiology, University of Western Ontario, London, Ontario, Canada
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37
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Lamberts JT, Traynor JR. Opioid receptor interacting proteins and the control of opioid signaling. Curr Pharm Des 2014; 19:7333-47. [PMID: 23448476 DOI: 10.2174/138161281942140105160625] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 02/18/2013] [Indexed: 12/31/2022]
Abstract
Opioid receptors are seven-transmembrane domain receptors that couple to intracellular signaling molecules by activating heterotrimeric G proteins. However, the receptor and G protein do not function in isolation but their activities are modulated by several accessory and scaffolding proteins. Examples include arrestins, kinases, and regulators of G protein signaling proteins. Accessory proteins contribute to the observed potency and efficacy of agonists, but also to the direction of signaling and the phenomenon of biased agonism. This review will present current knowledge of such proteins and how they may provide targets for future drug design.
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Affiliation(s)
| | - John R Traynor
- Department of Pharmacology, University of Michigan Medical School, 1301 MSRB III, 1150 West Medical Center Drive, Ann Arbor, MI 48109-5632, USA.
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A new non-canonical pathway of Gα(q) protein regulating mitochondrial dynamics and bioenergetics. Cell Signal 2014; 26:1135-46. [PMID: 24444709 DOI: 10.1016/j.cellsig.2014.01.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 01/09/2014] [Indexed: 12/12/2022]
Abstract
Contrary to previous assumptions, G proteins do not permanently reside on the plasma membrane, but are constantly monitoring the cytoplasmic surfaces of the plasma membrane and endomembranes. Here, we report that the Gαq and Gα11 proteins locate at the mitochondria and play a role in a complex signaling pathway that regulates mitochondrial dynamics. Our results provide evidence for the presence of the heteromeric G protein (Gαq/11βγ) at the outer mitochondrial membrane and for Gαq at the inner membrane. Both localizations are necessary to maintain the proper equilibrium between fusion and fission; which is achieved by altering the activity of mitofusin proteins, Drp1, OPA1 and the membrane potential at both the outer and inner mitochondrial membranes. As a result of the absence of Gαq/11, there is a decrease in mitochondrial fusion rates and a decrease in overall respiratory capacity, ATP production and OXPHOS-dependent growth. These findings demonstrate that the presence of Gαq proteins at the mitochondria serves as a physiological function: stabilizing elongated mitochondria and regulating energy production in Drp1 and Opa1 dependent mechanisms. This thereby links organelle dynamics and physiology.
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39
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Vashisth H, Storaska AJ, Neubig RR, Brooks CL. Conformational dynamics of a regulator of G-protein signaling protein reveals a mechanism of allosteric inhibition by a small molecule. ACS Chem Biol 2013; 8:2778-84. [PMID: 24093330 DOI: 10.1021/cb400568g] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Regulators of G protein signaling (RGS) proteins are key players in regulating signaling via G protein-coupled receptors. RGS proteins directly bind to the Gα-subunits of activated heterotrimeric G-proteins, and accelerate the rate of GTP hydrolysis, thereby rapidly deactivating G-proteins. Using atomistic simulations and NMR spectroscopy, we have studied in molecular detail the mechanism of action of CCG-50014, a potent small molecule inhibitor of RGS4 that covalently binds to cysteine residues on RGS4. We apply temperature-accelerated molecular dynamics (TAMD) to carry out enhanced conformational sampling of apo RGS4 structures, and consistently find that the α5-α6 helix pair of RGS4 can spontaneously span open-like conformations, allowing binding of CCG-50014 to the buried side-chain of Cys95. Both NMR experiments and MD simulations reveal chemical shift perturbations in residues in the vicinity of inhibitor binding site as well as in the RGS4-Gα binding interface. Consistent with a loss of G-protein binding, GAP activity, and allosteric mechanism of action of CCG-50014, our simulations of the RGS4-Gα complex in the presence of inhibitor suggest a relatively unstable protein-protein interaction. These results have potential implications for understanding how the conformational dynamics among RGS proteins may play a key role in the sensitivity of inhibitors.
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Affiliation(s)
- Harish Vashisth
- Department
of Chemical Engineering, University of New Hampshire, Durham, New Hampshire 03824, United States of America
| | - Andrew J. Storaska
- Department
of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109, United States of America
| | - Richard R. Neubig
- Department
of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, United States of America
| | - Charles L. Brooks
- Department
of Chemistry and Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109, United States of America
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40
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Zhang P, Mende U. Functional role, mechanisms of regulation, and therapeutic potential of regulator of G protein signaling 2 in the heart. Trends Cardiovasc Med 2013; 24:85-93. [PMID: 23962825 DOI: 10.1016/j.tcm.2013.07.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 07/08/2013] [Accepted: 07/10/2013] [Indexed: 12/22/2022]
Abstract
G protein-mediated signal transduction is essential for the regulation of cardiovascular function, including heart rate, growth, contraction, and vascular tone. Regulators of G protein Signaling (RGS proteins) fine-tune G protein-coupled receptor-induced signaling by regulating its magnitude and duration through direct interaction with the α subunits of heterotrimeric G proteins. Changes in the RGS protein expression and/or function in the heart often lead to pathophysiological changes and are associated with cardiac disease in animals and humans, including hypertrophy, fibrosis development, heart failure, and arrhythmias. This article focuses on Regulator of G protein Signaling 2 (RGS2), which is widely expressed in many tissues and is highly regulated in its expression and function. Most information to date has been obtained in biochemical, cellular, and animal studies, but data from humans is emerging. We review recent advances on the functional role of cardiovascular RGS2 and the mechanisms that determine its signaling selectivity, expression, and functionality. We highlight key unanswered questions and discuss the potential of RGS2 as a therapeutic target.
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Affiliation(s)
- Peng Zhang
- Cardiovascular Research Center, Cardiology Division, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, USA
| | - Ulrike Mende
- Cardiovascular Research Center, Cardiology Division, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, USA.
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41
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Croft W, Hill C, McCann E, Bond M, Esparza-Franco M, Bennett J, Rand D, Davey J, Ladds G. A physiologically required G protein-coupled receptor (GPCR)-regulator of G protein signaling (RGS) interaction that compartmentalizes RGS activity. J Biol Chem 2013; 288:27327-27342. [PMID: 23900842 DOI: 10.1074/jbc.m113.497826] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors (GPCRs) can interact with regulator of G protein signaling (RGS) proteins. However, the effects of such interactions on signal transduction and their physiological relevance have been largely undetermined. Ligand-bound GPCRs initiate by promoting exchange of GDP for GTP on the Gα subunit of heterotrimeric G proteins. Signaling is terminated by hydrolysis of GTP to GDP through intrinsic GTPase activity of the Gα subunit, a reaction catalyzed by RGS proteins. Using yeast as a tool to study GPCR signaling in isolation, we define an interaction between the cognate GPCR (Mam2) and RGS (Rgs1), mapping the interaction domains. This reaction tethers Rgs1 at the plasma membrane and is essential for physiological signaling response. In vivo quantitative data inform the development of a kinetic model of the GTPase cycle, which extends previous attempts by including GPCR-RGS interactions. In vivo and in silico data confirm that GPCR-RGS interactions can impose an additional layer of regulation through mediating RGS subcellular localization to compartmentalize RGS activity within a cell, thus highlighting their importance as potential targets to modulate GPCR signaling pathways.
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Affiliation(s)
- Wayne Croft
- Division of Biomedical Cell Biology, Warwick Medical School
| | | | - Eilish McCann
- Division of Biomedical Cell Biology, Warwick Medical School
| | - Michael Bond
- Division of Biomedical Cell Biology, Warwick Medical School
| | | | | | - David Rand
- Systems Biology Centre, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - John Davey
- Division of Biomedical Cell Biology, Warwick Medical School
| | - Graham Ladds
- Division of Biomedical Cell Biology, Warwick Medical School.
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42
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Jaba IM, Zhuang ZW, Li N, Jiang Y, Martin KA, Sinusas AJ, Papademetris X, Simons M, Sessa WC, Young LH, Tirziu D. NO triggers RGS4 degradation to coordinate angiogenesis and cardiomyocyte growth. J Clin Invest 2013; 123:1718-31. [PMID: 23454748 DOI: 10.1172/jci65112] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 01/10/2013] [Indexed: 12/11/2022] Open
Abstract
Myocardial hypertrophy is an adaptation to increased hemodynamic demands. An increase in heart tissue must be matched by a corresponding expansion of the coronary vasculature to maintain and adequate supply of oxygen and nutrients for the heart. The physiological mechanisms that underlie the coordination of angiogenesis and cardiomyocyte growth are unknown. We report that induction of myocardial angiogenesis promotes cardiomyocyte growth and cardiac hypertrophy through a novel NO-dependent mechanism. We used transgenic, conditional overexpression of placental growth factor (PlGF) in murine cardiac tissues to stimulate myocardial angiogenesis and increase endothelial-derived NO release. NO production, in turn, induced myocardial hypertrophy by promoting proteasomal degradation of regulator of G protein signaling type 4 (RGS4), thus relieving the repression of the Gβγ/PI3Kγ/AKT/mTORC1 pathway that stimulates cardiomyocyte growth. This hypertrophic response was prevented by concomitant transgenic expression of RGS4 in cardiomyocytes. NOS inhibitor L-NAME also significantly attenuated RGS4 degradation, and reduced activation of AKT/mTORC1 signaling and induction of myocardial hypertrophy in PlGF transgenic mice, while conditional cardiac-specific PlGF expression in eNOS knockout mice did not induce myocardial hypertrophy. These findings describe a novel NO/RGS4/Gβγ/PI3Kγ/AKT mechanism that couples cardiac vessel growth with myocyte growth and heart size.
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Affiliation(s)
- Irina M Jaba
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut 06510, USA
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43
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Smrcka AV. Molecular targeting of Gα and Gβγ subunits: a potential approach for cancer therapeutics. Trends Pharmacol Sci 2013; 34:290-8. [PMID: 23557963 DOI: 10.1016/j.tips.2013.02.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 02/21/2013] [Accepted: 02/26/2013] [Indexed: 11/26/2022]
Abstract
G-Protein-coupled receptors (GPCRs) signal through G protein α and βγ subunit families to regulate a wide range of physiological and pathophysiological processes. As such, GPCRs are major targets for therapeutic drugs. Downstream targets of GPCRs have also gained interest as a therapeutic approach to complex pathologies involving multiple GPCRs. One such approach involves targeting of the G proteins themselves. Several small molecule Gα and Gβγ modulators have been developed and been tested in various animal models of disease. Here we will discuss the requirements for targeting Gα and Gβγ subunits, the mechanisms of action of currently identified inhibitors, and focus on the potential utility of Gα and Gβγ inhibitors in the treatment of various cancers.
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Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
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44
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Holobotovskyy V, Manzur M, Tare M, Burchell J, Bolitho E, Viola H, Hool LC, Arnolda LF, McKitrick DJ, Ganss R. Regulator of G-protein signaling 5 controls blood pressure homeostasis and vessel wall remodeling. Circ Res 2013; 112:781-91. [PMID: 23303165 DOI: 10.1161/circresaha.111.300142] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Regulator of G-protein signaling 5 (RGS5) modulates G-protein-coupled receptor signaling and is prominently expressed in arterial smooth muscle cells. Our group first reported that RGS5 is important in vascular remodeling during tumor angiogenesis. We hypothesized that RGS5 may play an important role in vessel wall remodeling and blood pressure regulation. OBJECTIVE To demonstrate that RGS5 has a unique and nonredundant role in the pathogenesis of hypertension and to identify crucial RGS5-regulated signaling pathways. METHODS AND RESULTS We observed that arterial RGS5 expression is downregulated with chronically elevated blood pressure after angiotensin II infusion. Using a knockout mouse model, radiotelemetry, and pharmacological inhibition, we subsequently showed that loss of RGS5 results in profound hypertension. RGS5 signaling is linked to the renin-angiotensin system and directly controls vascular resistance, vessel contractility, and remodeling. RGS5 deficiency aggravates pathophysiological features of hypertension, such as medial hypertrophy and fibrosis. Moreover, we demonstrate that protein kinase C, mitogen-activated protein kinase/extracellular signal-regulated kinase, and Rho kinase signaling pathways are major effectors of RGS5-mediated hypertension. CONCLUSIONS Loss of RGS5 results in hypertension. Loss of RGS5 signaling also correlates with hyper-responsiveness to vasoconstrictors and vascular stiffening. This establishes a significant, distinct, and causal role of RGS5 in vascular homeostasis. RGS5 modulates signaling through the angiotensin II receptor 1 and major Gαq-coupled downstream pathways, including Rho kinase. So far, activation of RhoA/Rho kinase has not been associated with RGS molecules. Thus, RGS5 is a crucial regulator of blood pressure homeostasis with significant clinical implications for vascular pathologies, such as hypertension.
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Affiliation(s)
- Vasyl Holobotovskyy
- Western Australian Institute for Medical Research, Rear, 50 Murray St, Perth, WA 6010, Australia
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46
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Louwette S, Van Geet C, Freson K. Regulators of G protein signaling: role in hematopoiesis, megakaryopoiesis and platelet function. J Thromb Haemost 2012; 10:2215-22. [PMID: 22908964 DOI: 10.1111/j.1538-7836.2012.04903.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Regulators of G protein signaling (RGS) are intracellular signaling regulators that bind activated G protein α subunits (Gα) and increase their intrinsic GTPase activity via their common RGS homology domain. In addition to their GTPase accelerating activity (GAP), RGS proteins also contain other domains that regulate their receptor selectivity, their interaction with other proteins such as adenylyl cyclase or their subcellular localization via interaction with scaffold proteins such as tubulin, 14-3-3 or spinophilin. There are at least 37 different RGS family members in humans and numerous physiological functions have been assigned to these proteins, which have rather a tissue-specific expression pattern. The role of some RGS proteins was shown to be important for hematopoiesis. More recent studies also focused on their expression in platelets, and for R4 RGS subfamily members RGS2, RGS16 and RGS18, it could be demonstrated that they regulate megakaryopoiesis and/or platelet function. These functional studies mostly comprised in vitro experiments and in vivo studies using small animal models. Their role in human pathology related to platelet dysfunction remains still largely unknown, except for a case report with a RGS2 gain of function mutation. In addition to an introduction on RGS signaling and different effectors with a special focus on the R4 subfamily members, we here will give an overview of the studies related to the role of RGS proteins in hematopoiesis, megakaryopoiesis and platelet function.
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Affiliation(s)
- S Louwette
- Center for Molecular and Vascular Biology Departement of Pediatrics, University of Leuven, Leuven, Belgium
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47
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Magalhaes AC, Dunn H, Ferguson SS. Regulation of GPCR activity, trafficking and localization by GPCR-interacting proteins. Br J Pharmacol 2012; 165:1717-1736. [PMID: 21699508 DOI: 10.1111/j.1476-5381.2011.01552.x] [Citation(s) in RCA: 245] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
GPCRs represent the largest family of integral membrane proteins and were first identified as receptor proteins that couple via heterotrimeric G-proteins to regulate a vast variety of effector proteins to modulate cellular function. It is now recognized that GPCRs interact with a myriad of proteins that not only function to attenuate their signalling but also function to couple these receptors to heterotrimeric G-protein-independent signalling pathways. In addition, intracellular and transmembrane proteins associate with GPCRs and regulate their processing in the endoplasmic reticulum, trafficking to the cell surface, compartmentalization to plasma membrane microdomains, endocytosis and trafficking between intracellular membrane compartments. The present review will overview the functional consequence of β-arrestin, receptor activity-modifying proteins (RAMPS), regulators of G-protein signalling (RGS), GPCR-associated sorting proteins (GASPs), Homer, small GTPases, PSD95/Disc Large/Zona Occludens (PDZ), spinophilin, protein phosphatases, calmodulin, optineurin and Src homology 3 (SH3) containing protein interactions with GPCRs.
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Affiliation(s)
- Ana C Magalhaes
- J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, London, ON, CanadaThe Department of Physiology & Pharmacology, the University of Western Ontario, London, ON, Canada
| | - Henry Dunn
- J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, London, ON, CanadaThe Department of Physiology & Pharmacology, the University of Western Ontario, London, ON, Canada
| | - Stephen Sg Ferguson
- J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, London, ON, CanadaThe Department of Physiology & Pharmacology, the University of Western Ontario, London, ON, Canada
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48
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Mighiu AS, Heximer SP. Controlling Parasympathetic Regulation of Heart Rate: A Gatekeeper Role for RGS Proteins in the Sinoatrial Node. Front Physiol 2012; 3:204. [PMID: 22707940 PMCID: PMC3374348 DOI: 10.3389/fphys.2012.00204] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 05/23/2012] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitters released from sympathetic and parasympathetic nerve terminals in the sinoatrial node (SAN) exert their effects via G-protein-coupled receptors. Integration of these different G-protein signals within pacemaker cells of the SAN is critical for proper regulation of heart rate and function. For example, excessive parasympathetic signaling can be associated with sinus node dysfunction (SND) and supraventricular arrhythmias. Our previous work has shown that one member of the regulator of G-protein signaling (RGS) protein family, RGS4, is highly and selectively expressed in pacemaker cells of the SAN. Consistent with its role as an inhibitor of parasympathetic signaling, RGS4-knockout mice have reduced basal heart rates and enhanced negative chronotropic responses to parasympathetic agonists. Moreover, RGS4 appears to be an important part of SA nodal myocyte signaling pathways that mediate G-protein-coupled inwardly rectifying potassium channel (GIRK) channel activation/deactivation and desensitization. Since RGS4 acts immediately downstream of M2 muscarinic receptors, it is tempting to speculate that RGS4 functions as a master regulator of parasympathetic signaling upstream of GIRKs, HCNs, and L-type Ca2+ channels in the SAN. Thus, loss of RGS4 function may lead to increased susceptibility to conditions associated with increased parasympathetic signaling, including bradyarrhythmia, SND, and atrial fibrillation.
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Affiliation(s)
- Alexandra S Mighiu
- Department of Physiology, Heart and Stroke/Richard Lewar Centre of Excellence in Cardiovascular Research, University of Toronto Toronto, ON, Canada
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49
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Sjögren B, Parra S, Heath LJ, Atkins KB, Xie ZJ, Neubig RR. Cardiotonic steroids stabilize regulator of G protein signaling 2 protein levels. Mol Pharmacol 2012; 82:500-9. [PMID: 22695717 DOI: 10.1124/mol.112.079293] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Regulator of G protein signaling 2 (RGS2), a G(q)-specific GTPase-activating protein, is strongly implicated in cardiovascular function. RGS2(-/-) mice are hypertensive and prone to heart failure, and several rare human mutations that accelerate RGS2 degradation have been identified among patients with hypertension. Therefore, pharmacological up-regulation of RGS2 protein levels might be beneficial. We used a β-galactosidase complementation method to screen several thousand compounds with known pharmacological functions for those that increased RGS2 protein levels. Several cardiotonic steroids (CTSs), including ouabain and digoxin, increased RGS2 but not RGS4 protein levels. CTSs increased RGS2 protein levels through a post-transcriptional mechanism, by slowing protein degradation. RGS2 mRNA levels in primary vascular smooth muscle cells were unaffected by CTS treatment, whereas protein levels were increased 2- to 3-fold. Na(+)/K(+)-ATPase was required for the increase in RGS2 protein levels, because the effect was lost in Na(+)/K(+)-ATPase-knockdown cells. Furthermore, we demonstrated that CTS-induced increases in RGS2 levels were functional and reduced receptor-stimulated, G(q)-dependent, extracellular signal-regulated kinase phosphorylation. Finally, we showed that in vivo treatment with digoxin led to increased RGS2 protein levels in heart and kidney. CTS-induced increases in RGS2 protein levels and function might modify several deleterious mechanisms in hypertension and heart failure. This novel CTS mechanism might contribute to the beneficial actions of low-dose digoxin treatment in heart failure. Our results support the concept of small-molecule modulation of RGS2 protein levels as a new strategy for cardiovascular therapy.
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Affiliation(s)
- Benita Sjögren
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
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50
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Verkerk AO, Geuzebroek GSC, Veldkamp MW, Wilders R. Effects of acetylcholine and noradrenalin on action potentials of isolated rabbit sinoatrial and atrial myocytes. Front Physiol 2012; 3:174. [PMID: 22754533 PMCID: PMC3385584 DOI: 10.3389/fphys.2012.00174] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/12/2012] [Indexed: 01/07/2023] Open
Abstract
The autonomic nervous system controls heart rate and contractility through sympathetic and parasympathetic inputs to the cardiac tissue, with acetylcholine (ACh) and noradrenalin (NA) as the chemical transmitters. In recent years, it has become clear that specific Regulators of G protein Signaling proteins (RGS proteins) suppress muscarinic sensitivity and parasympathetic tone, identifying RGS proteins as intriguing potential therapeutic targets. In the present study, we have identified the effects of 1 μM ACh and 1 μM NA on the intrinsic action potentials of sinoatrial (SA) nodal and atrial myocytes. Single cells were enzymatically isolated from the SA node or from the left atrium of rabbit hearts. Action potentials were recorded using the amphotericin-perforated patch-clamp technique in the absence and presence of ACh, NA, or a combination of both. In SA nodal myocytes, ACh increased cycle length and decreased diastolic depolarization rate, whereas NA decreased cycle length and increased diastolic depolarization rate. Both ACh and NA increased maximum upstroke velocity. Furthermore, ACh hyperpolarized the maximum diastolic potential. In atrial myocytes stimulated at 2 Hz, both ACh and NA hyperpolarized the maximum diastolic potential, increased the action potential amplitude, and increased the maximum upstroke velocity. Action potential duration at 50 and 90% repolarization was decreased by ACh, but increased by NA. The effects of both ACh and NA on action potential duration showed a dose dependence in the range of 1-1000 nM, while a clear-cut frequency dependence in the range of 1-4 Hz was absent. Intermediate results were obtained in the combined presence of ACh and NA in both SA nodal and atrial myocytes. Our data uncover the extent to which SA nodal and atrial action potentials are intrinsically dependent on ACh, NA, or a combination of both and may thus guide further experiments with RGS proteins.
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Affiliation(s)
- Arie O Verkerk
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
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