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Tian M, Wu N, Xie X, Liu T, You Y, Ma S, Bian H, Cao H, Wang L, Liu C, Qi J. Phosphorylation of RGS16 at Tyr168 promote HBeAg-mediated macrophage activation by ERK pathway to accelerate liver injury. J Mol Med (Berl) 2024; 102:257-272. [PMID: 38141114 DOI: 10.1007/s00109-023-02405-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 11/03/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023]
Abstract
Liver injury is closely associated with macrophage activation following HBV infection. Our previous study showed that only HBeAg, but not HBsAg and HBcAg, stably enhances inflammatory cytokine production in macrophages. And we also indicated that HBeAg could induce macrophage activation via TLR2 and thus aggravate the progression of liver fibrosis. However, the specific molecular mechanism of HBeAg in macrophage activation is not clear. We screened significantly overexpressed RGS16 from RNASeq results of HBeAg-stimulated macrophages and validated them with cellular assays, GSE83148 microarray dataset, and in clinical samples. Meanwhile, small interference, plasmid, and lentivirus transfection assays were used to establish cell models for knockdown and overexpression of RGS16, and q-PCR, ELISA, Transwell, and CCK-8 assays were used to analyze the role of RGS16 in HBeAg-induced macrophage activation. In addition, the upstream and downstream mechanisms of RGS16 in HBeAg-treated macrophage activation were explored using inhibitors, phostag gels, and RGS16 phosphorylation mutant plasmids. Finally, the effect of RGS16 on hepatic inflammation in murine tissues was evaluated by H&E staining, liver enzyme assay and immunofluorescence. RGS16 was significantly upregulated in HBeAg-induced macrophage activation, and its expression was enhanced with increasing HBeAg content and treatment time. Functional experiments showed that overexpression of RGS16 promoted the production of inflammatory factors TNF-α and IL-6 and boosted macrophage proliferation and migration, while knockdown of RGS16 exhibited the opposite effect. Mechanistically, we discovered that RGS16 is regulated by the TLR2/P38/STAT5 signaling pathway. Meanwhile, RGS16 enhanced ERK phosphorylation via its own Tyr168 phosphorylation to contribute to macrophage activation, thereby accelerating liver injury. Finally, in mice, overexpression of RGS16 markedly strengthened liver inflammation. HBeAg upregulates RGS16 expression through the TLR2-P38-STAT5 axis, and the upregulated expression of RGS16 enhances macrophage activation and accelerates liver injury by promoting ERK phosphorylation. In this process, phosphorylation of Tyr168 is necessary for RGS16 to function. KEY MESSAGES: RGS16 boosted HBeAg-induced macrophage inflammation, proliferation, and migration. Tyr168 phosphorylation of RGS16 affected by ERK promoted macrophage activation. HBeAg upregulated the expression of RGS16 through TLR2/P38/STAT5 signal pathway. RGS16 promoted liver injury by regulating macrophage functions in mouse model.
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Affiliation(s)
- Miaomiao Tian
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China
| | - Nijin Wu
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China
| | - Xiaoyu Xie
- Shandong Provincial Clinical Research Center for Digestive Diseases, Qilu Hospital of Shandong University, Jinan, Shandong, 250012, People's Republic of China
| | - Tiantian Liu
- Shandong Provincial Hospital, Shandong University, Jinan, Shandong, 250021, People's Republic of China
| | - Yajing You
- Shandong Provincial Hospital, Shandong University, Jinan, Shandong, 250021, People's Republic of China
| | - Shujun Ma
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China
| | - Hongjun Bian
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China
| | - Huiling Cao
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China
| | - Le Wang
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China
| | - Chenxi Liu
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China.
- Shandong Provincial Engineering and Technological Research Center for Liver Diseases Prevention and Control, Jinan, Shandong, 250021, People's Republic of China.
| | - Jianni Qi
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, 324 Jingwu Road, Jinan, Shandong, 250021, People's Republic of China.
- Shandong Provincial Engineering and Technological Research Center for Liver Diseases Prevention and Control, Jinan, Shandong, 250021, People's Republic of China.
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Tian M, Ma Y, Li T, Wu N, Li J, Jia H, Yan M, Wang W, Bian H, Tan X, Qi J. Functions of regulators of G protein signaling 16 in immunity, inflammation, and other diseases. Front Mol Biosci 2022; 9:962321. [PMID: 36120550 PMCID: PMC9478547 DOI: 10.3389/fmolb.2022.962321] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 08/08/2022] [Indexed: 11/13/2022] Open
Abstract
Regulators of G protein signaling (RGS) act as guanosine triphosphatase activating proteins to accelerate guanosine triphosphate hydrolysis of the G protein α subunit, leading to the termination of the G protein-coupled receptor (GPCR) downstream signaling pathway. RGS16, which is expressed in a number of cells and tissues, belongs to one of the small B/R4 subfamilies of RGS proteins and consists of a conserved RGS structural domain with short, disordered amino- and carboxy-terminal extensions and an α-helix that classically binds and de-activates heterotrimeric G proteins. However, with the deepening of research, it has been revealed that RGS16 protein not only regulates the classical GPCR pathway, but also affects immune, inflammatory, tumor and metabolic processes through other signaling pathways including the mitogen-activated protein kinase, phosphoinositide 3-kinase/protein kinase B, Ras homolog family member A and stromal cell-derived factor 1/C-X-C motif chemokine receptor 4 pathways. Additionally, the RGS16 protein may be involved in the Hepatitis B Virus -induced inflammatory response. Therefore, given the continuous expansion of knowledge regarding its role and mechanism, the structure, characteristics, regulatory mechanisms and known functions of the small RGS proteinRGS16 are reviewed in this paper to prepare for diagnosis, treatment, and prognostic evaluation of different diseases such as inflammation, tumor, and metabolic disorders and to better study its function in other diseases.
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Affiliation(s)
- Miaomiao Tian
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Yan Ma
- Zibo Central Hospital, Zibo, China
| | - Tao Li
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Nijin Wu
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Jiaqi Li
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Huimin Jia
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Meizhu Yan
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Wenwen Wang
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Hongjun Bian
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Xu Tan
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
- *Correspondence: Jianni Qi, ; Xu Tan,
| | - Jianni Qi
- Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
- Shandong Provincial Engineering and Technological Research Center for Liver Diseases Prevention and Control, Jinan, China
- *Correspondence: Jianni Qi, ; Xu Tan,
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3
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Sjögren B. The evolution of regulators of G protein signalling proteins as drug targets - 20 years in the making: IUPHAR Review 21. Br J Pharmacol 2017; 174:427-437. [PMID: 28098342 DOI: 10.1111/bph.13716] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 12/11/2016] [Accepted: 01/08/2017] [Indexed: 12/11/2022] Open
Abstract
Regulators of G protein signalling (RGS) proteins are celebrating the 20th anniversary of their discovery. The unveiling of this new family of negative regulators of G protein signalling in the mid-1990s solved a persistent conundrum in the G protein signalling field, in which the rate of deactivation of signalling cascades in vivo could not be replicated in exogenous systems. Since then, there has been tremendous advancement in the knowledge of RGS protein structure, function, regulation and their role as novel drug targets. RGS proteins play an important modulatory role through their GTPase-activating protein (GAP) activity at active, GTP-bound Gα subunits of heterotrimeric G proteins. They also possess many non-canonical functions not related to G protein signalling. Here, an update on the status of RGS proteins as drug targets is provided, highlighting advances that have led to the inclusion of RGS proteins in the IUPHAR/BPS Guide to PHARMACOLOGY database of drug targets.
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Affiliation(s)
- B Sjögren
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
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Regulation of Gβγi-dependent PLC-β3 activity in smooth muscle: inhibitory phosphorylation of PLC-β3 by PKA and PKG and stimulatory phosphorylation of Gαi-GTPase-activating protein RGS2 by PKG. Cell Biochem Biophys 2015; 70:867-80. [PMID: 24777815 DOI: 10.1007/s12013-014-9992-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In gastrointestinal smooth muscle, agonists that bind to Gi-coupled receptors activate preferentially PLC-β3 via Gβγ to stimulate phosphoinositide (PI) hydrolysis and generate inositol 1,4,5-trisphosphate (IP3) leading to IP3-dependent Ca(2+) release and muscle contraction. In the present study, we identified the mechanism of inhibition of PLC-β3-dependent PI hydrolysis by cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG). Cyclopentyl adenosine (CPA), an adenosine A1 receptor agonist, caused an increase in PI hydrolysis in a concentration-dependent fashion; stimulation was blocked by expression of the carboxyl-terminal sequence of GRK2(495-689), a Gβγ-scavenging peptide, or Gαi minigene but not Gαq minigene. Isoproterenol and S-nitrosoglutathione (GSNO) induced phosphorylation of PLC-β3 and inhibited CPA-induced PI hydrolysis, Ca(2+) release, and muscle contraction. The effect of isoproterenol on all three responses was inhibited by PKA inhibitor, myristoylated PKI, or AKAP inhibitor, Ht-31, whereas the effect of GSNO was selectively inhibited by PKG inhibitor, Rp-cGMPS. GSNO, but not isoproterenol, also phosphorylated Gαi-GTPase-activating protein, RGS2, and enhanced association of Gαi3-GTP and RGS2. The effect of GSNO on PI hydrolysis was partly reversed in cells (i) expressing constitutively active GTPase-resistant Gαi mutant (Q204L), (ii) phosphorylation-site-deficient RGS2 mutant (S46A/S64A), or (iii) siRNA for RGS2. We conclude that PKA and PKG inhibit Gβγi-dependent PLC-β3 activity by direct phosphorylation of PLC-β3. PKG, but not PKA, also inhibits PI hydrolysis indirectly by a mechanism involving phosphorylation of RGS2 and its association with Gαi-GTP. This allows RGS2 to accelerate Gαi-GTPase activity, enhance Gαβγi trimer formation, and inhibit Gβγi-dependent PLC-β3 activity.
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Raveh A, Schultz PJ, Aschermann L, Carpenter C, Tamayo-Castillo G, Cao S, Clardy J, Neubig RR, Sherman DH, Sjögren B. Identification of protein kinase C activation as a novel mechanism for RGS2 protein upregulation through phenotypic screening of natural product extracts. Mol Pharmacol 2014; 86:406-16. [PMID: 25086086 DOI: 10.1124/mol.114.092403] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Biochemical high-throughput screening is widely used in drug discovery, using a variety of small molecule libraries. However, broader screening strategies may be more beneficial to identify novel biologic mechanisms. In the current study we used a β-galactosidase complementation method to screen a selection of microbial-derived pre-fractionated natural product extracts for those that increase regulator of G protein signaling 2 (RGS2) protein levels. RGS2 is a member of a large family of proteins that all regulate signaling through G protein-coupled receptors (GPCRs) by accelerating GTPase activity on active Gα as well as through other mechanisms. RGS2(-/-) mice are hypertensive, show increased anxiety, and are prone to heart failure. RGS2 has a very short protein half-life due to rapid proteasomal degradation, and we propose that enhancement of RGS2 protein levels could be a beneficial therapeutic strategy. Bioassay-guided fractionation of one of the hit strains yielded a pure compound, Indolactam V, a known protein kinase C (PKC) activator, which selectively increased RGS2 protein levels in a time- and concentration-dependent manner. Similar results were obtained with phorbol 12-myristate 13-acetate as well as activation of the Gq-coupled muscarinic M3 receptor. The effect on RGS2 protein levels was blocked by the nonselective PKC inhibitor Gö6983 (3-[1-[3-(dimethylamino)propyl]-5-methoxy-1H-indol-3-yl]-4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione), the PKCβ-selective inhibitor Ruboxastaurin, as well as small interfering RNA-mediated knockdown of PKCβ. Indolactam V-mediated increases in RGS2 protein levels also had functional effects on GPCR signaling. This study provides important proof-of-concept for our screening strategy and could define a negative feedback mechanism in Gq/Phospholipase C signaling through RGS2 protein upregulation.
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Affiliation(s)
- Avi Raveh
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Pamela J Schultz
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Lauren Aschermann
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Colleen Carpenter
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Giselle Tamayo-Castillo
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Shugeng Cao
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Jon Clardy
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Richard R Neubig
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - David H Sherman
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
| | - Benita Sjögren
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan (A.R., P.J.S., D.H.S.); Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan (L.A., R.R.N., B.S.); Department of Pharmacology (C.C.), Department of Medicinal Chemistry (D.H.S.), Department of Microbiology and Immunology (D.H.S.), Department of Chemistry (D.H.S.), Center for Chemical Genomics, University of Michigan, Ann Arbor, Michigan (D.H.S.); Unidad Estrategica de Bioprospección, Instituto Nacional de Biodiversidad, Santo Domingo de Heredia, Costa Rica & CIPRONA, Escuela de Química, Universidad de Costa Rica, San Pedro, Costa Rica (G.T-C.); Harvard Medical School, Boston, Massachusetts (S.C., J.C.); and University of Hawaii Cancer Center, Honolulu, Hawaii (S.C.)
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Gat-Viks I, Chevrier N, Wilentzik R, Eisenhaure T, Raychowdhury R, Steuerman Y, Shalek AK, Hacohen N, Amit I, Regev A. Deciphering molecular circuits from genetic variation underlying transcriptional responsiveness to stimuli. Nat Biotechnol 2013; 31:342-9. [PMID: 23503680 PMCID: PMC3622156 DOI: 10.1038/nbt.2519] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 02/04/2013] [Indexed: 01/24/2023]
Abstract
Individual genetic variation affects gene responsiveness to stimuli, often by influencing complex molecular circuits. Here we combine genomic and intermediate-scale transcriptional profiling with computational methods to identify variants that affect the responsiveness of genes to stimuli (responsiveness quantitative trait loci or reQTLs) and to position these variants in molecular circuit diagrams. We apply this approach to study variation in transcriptional responsiveness to pathogen components in dendritic cells from recombinant inbred mouse strains. We identify reQTLs that correlate with particular stimuli and position them in known pathways. For example, in response to a virus-like stimulus, a trans-acting variant responds as an activator of the antiviral response; using RNA interference, we identify Rgs16 as the likely causal gene. Our approach charts an experimental and analytic path to decipher the mechanisms underlying genetic variation in circuits that control responses to stimuli.
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Affiliation(s)
- Irit Gat-Viks
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA.
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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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Kach J, Sethakorn N, Dulin NO. A finer tuning of G-protein signaling through regulated control of RGS proteins. Am J Physiol Heart Circ Physiol 2012; 303:H19-35. [PMID: 22542620 DOI: 10.1152/ajpheart.00764.2011] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Regulators of G-protein signaling (RGS) proteins are GTPase-activating proteins (GAP) for various Gα subunits of heterotrimeric G proteins. Through this mechanism, RGS proteins regulate the magnitude and duration of G-protein-coupled receptor signaling and are often referred to as fine tuners of G-protein signaling. Increasing evidence suggests that RGS proteins themselves are regulated through multiple mechanisms, which may provide an even finer tuning of G-protein signaling and crosstalk between G-protein-coupled receptors and other signaling pathways. This review summarizes the current data on the control of RGS function through regulated expression, intracellular localization, and covalent modification of RGS proteins, as related to cell function and the pathogenesis of diseases.
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Affiliation(s)
- Jacob Kach
- Department of Medicine, University of Chicago, Illinois, 60637, USA
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9
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Stewart A, Huang J, Fisher RA. RGS Proteins in Heart: Brakes on the Vagus. Front Physiol 2012; 3:95. [PMID: 22685433 PMCID: PMC3368389 DOI: 10.3389/fphys.2012.00095] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 03/27/2012] [Indexed: 12/14/2022] Open
Abstract
It has been nearly a century since Otto Loewi discovered that acetylcholine (ACh) release from the vagus produces bradycardia and reduced cardiac contractility. It is now known that parasympathetic control of the heart is mediated by ACh stimulation of G(i/o)-coupled muscarinic M2 receptors, which directly activate G protein-coupled inwardly rectifying potassium (GIRK) channels via Gβγ resulting in membrane hyperpolarization and inhibition of action potential (AP) firing. However, expression of M2R-GIRK signaling components in heterologous systems failed to recapitulate native channel gating kinetics. The missing link was identified with the discovery of regulator of G protein signaling (RGS) proteins, which act as GTPase-activating proteins to accelerate the intrinsic GTPase activity of Gα resulting in termination of Gα- and Gβγ-mediated signaling to downstream effectors. Studies in mice expressing an RGS-insensitive Gα(i2) mutant (G184S) implicated endogenous RGS proteins as key regulators of parasympathetic signaling in heart. Recently, two RGS proteins have been identified as critical regulators of M2R signaling in heart. RGS6 exhibits a uniquely robust expression in heart, especially in sinoatrial (SAN) and atrioventricular nodal regions. Mice lacking RGS6 exhibit increased bradycardia and inhibition of SAN AP firing in response to CCh as well as a loss of rapid activation and deactivation kinetics and current desensitization for ACh-induced GIRK current (I(KACh)). Similar findings were observed in mice lacking RGS4. Thus, dysregulation in RGS protein expression or function may contribute to pathologies involving aberrant electrical activity in cardiac pacemaker cells. Moreover, RGS6 expression was found to be up-regulated in heart under certain pathological conditions, including doxorubicin treatment, which is known to cause life-threatening cardiotoxicity and atrial fibrillation in cancer patients. On the other hand, increased vagal tone may be cardioprotective in heart failure where acetylcholinesterase inhibitors and vagal stimulation have been proposed as potential therapeutics. Together, these studies identify RGS proteins, especially RGS6, as new therapeutic targets for diseases such as sick sinus syndrome or other maladies involving abnormal autonomic control of the heart.
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Affiliation(s)
- Adele Stewart
- Department of Pharmacology, Carver College of Medicine, University of Iowa Iowa City, IA, USA
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10
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Chidiac P, Roy AA. Activity, Regulation, and Intracellular Localization of RGS Proteins. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820308244] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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11
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Sjögren B. Regulator of G protein signaling proteins as drug targets: current state and future possibilities. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2011; 62:315-47. [PMID: 21907914 DOI: 10.1016/b978-0-12-385952-5.00002-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Regulators of G protein signaling (RGS) proteins have emerged in the past two decades as novel drug targets in many areas of research. Their importance in regulating signaling via G protein-coupled receptors has become evident as numerous studies have been published on the structure and function of RGS proteins. A number of genetic models have also been developed, demonstrating the potential clinical importance of RGS proteins in various disease states, including central nervous system disorders, cardiovascular disease, diabetes, and several types of cancer. Apart from their classical mechanism of action as GTPase-activating proteins (GAPs), RGS proteins can also serve other noncanonical functions. This opens up a new approach to targeting RGS proteins in drug discovery as the view on the function of these proteins is constantly evolving. This chapter summarizes the latest development in RGS protein drug discovery with special emphasis on noncanonical functions and regulatory mechanisms of RGS protein expression. As more reports are being published on this group of proteins, it is becoming clear that modulation of GAP activity might not be the only way to therapeutically target RGS proteins.
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Affiliation(s)
- Benita Sjögren
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA
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12
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Miyoshi N, Ishii H, Sekimoto M, Doki Y, Mori M. RGS16 is a marker for prognosis in colorectal cancer. Ann Surg Oncol 2009; 16:3507-14. [PMID: 19760045 DOI: 10.1245/s10434-009-0690-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Revised: 07/02/2009] [Accepted: 07/03/2009] [Indexed: 01/15/2023]
Abstract
BACKGROUND The RGS family, comprising 22 homologues of proteins, plays a role in cellular proliferation, differentiation, membrane trafficking, and embryonic development through the involvement of the mitogen-activated protein kinase signaling pathway. METHODS In order to demonstrate the importance of RGS16 expression for the prediction of prognosis of colorectal cancer (CRC), we analyzed RGS16 gene expression in 22 human gastrointestinal cell lines and 124 paired cases of CRC and noncancerous regions. RESULTS RGS16 was expressed in 17 human gastrointestinal cancer cell lines examined in this study. RGS16 expression was higher in colorectal cancer tissue than in corresponding normal tissue (P < 0.001) in messenger RNA (mRNA) and protein levels. Patients in the RGS16 high-expression group showed a poorer overall survival rate than those in the low-expression group (P < 0.001), indicating that high RGS16 expression was an independent prognostic factor. CONCLUSION The present study suggests that RGS16 is useful as a predictive marker for patient prognosis of CRC.
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Affiliation(s)
- Norikatsu Miyoshi
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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13
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Osei-Owusu P, Sun X, Drenan RM, Steinberg TH, Blumer KJ. Regulation of RGS2 and Second Messenger Signaling in Vascular Smooth Muscle Cells by cGMP-dependent Protein Kinase. J Biol Chem 2007; 282:31656-65. [PMID: 17681944 DOI: 10.1074/jbc.m706360200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RGS2, a GTPase-activating protein (GAP) for G(q)alpha, regulates vascular relaxation and blood pressure. RGS2 can be phosphorylated by type Ialpha cGMP-dependent protein kinase (cGKIalpha), increasing its GAP activity. To understand how RGS2 and cGKIalpha regulate vascular smooth muscle signaling and function, we identified signaling pathways that are controlled by cGMP in an RGS2-dependent manner and discovered new mechanisms whereby cGK activity regulates RGS2. We show that RGS2 regulates vasoconstrictor-stimulated Ca(2+) store release, capacitative Ca(2+) entry, and noncapacitative Ca(2+) entry and that RGS2 is required for cGMP-mediated inhibition of vasoconstrictor-elicited phospholipase Cbeta activation, Ca(2+) store release, and capacitative Ca(2+) entry. RGS2 is degraded in vascular smooth muscle cells via the proteasome. Inhibition of cGK activity blunts RGS2 degradation. However, inactivation of the cGKIalpha phosphorylation sites in RGS2 does not stabilize the protein, suggesting that cGK activity regulates RGS2 degradation by other mechanisms. cGK activation promotes association of RGS2 with the plasma membrane by a mechanism requiring its cGKIalpha phosphorylation sites. By regulating GAP activity, plasma membrane association, and degradation, cGKIalpha therefore may control a cycle of RGS2 activation and inactivation. By diminishing cGK activity, endothelial dysfunction may impair RGS2 activation, thereby blunting vascular relaxation and contributing to hypertension.
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Affiliation(s)
- Patrick Osei-Owusu
- Cell Biology and Physiology and Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Hooks SB, Martemyanov K, Zachariou V. A role of RGS proteins in drug addiction. Biochem Pharmacol 2007; 75:76-84. [PMID: 17880927 DOI: 10.1016/j.bcp.2007.07.045] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 07/24/2007] [Accepted: 07/26/2007] [Indexed: 11/22/2022]
Abstract
The diverse family of Regulators of G protein signaling (RGS) proteins are widely distributed proteins with multiple functions, including GAP activity for heterotrimeric G protein alpha subunits. Three members of the RGS family, RGS9-2, RGS4 and RGSz, have been shown to play an essential modulatory role in psychostimulant and opiate drug actions. Interestingly, these proteins show distinct structure, distribution pattern and cellular localization. In addition, each of these proteins is differentially regulated by drugs of abuse in particular brain networks and appears to modulate distinct signal transduction events. The striatal enriched RGS9 plays a prominent role in opiate and psychostimulant drug reward; RGS4 appears to modulate opiate dependence via actions in the locus coeruleus, whereas RGSz modulates analgesia via activation of the PKC pathway.
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Affiliation(s)
- Shelley B Hooks
- University of Georgia, Department of Pharmaceutical and Biomedical Sciences, Athens, GA, USA
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15
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Moroi K, Nishiyama M, Kawabata SI, Ichiba H, Yajima T, Kimura S. Phosphorylation of Ser166 in RGS5 by protein kinase C causes loss of RGS function. Life Sci 2007; 81:40-50. [PMID: 17540411 DOI: 10.1016/j.lfs.2007.04.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 03/31/2007] [Accepted: 04/17/2007] [Indexed: 11/30/2022]
Abstract
RGS5 is a member of regulators of G protein signaling (RGS) proteins that attenuate heterotrimeric G protein signaling by functioning as GTPase-activating proteins (GAPs). We investigated phosphorylation of RGS5 and the resulting change of its function. In 293T cells, transiently expressed RGS5 was phosphorylated by endogenous protein kinases in the basal state. The phosphorylation was enhanced by phorbol 12-myristate 13-acetate (PMA) and endothelin-1 (ET-1), and suppressed by protein kinase C (PKC) inhibitors, H7, calphostin C and staurosporine. These results suggest involvement of PKC in phosphorylation of RGS5. In in vitro experiments, PKC phosphorylated recombinant RGS5 protein at serine residues. RGS5 protein phosphorylated by PKC showed much lower binding capacity for and GAP activity toward Galpha subunits than did the unphosphorylated RGS5. In cells expressing RGS5, the inhibitory effect of RGS5 on ET-1-induced Ca(2+) responses was enhanced by staurosporine. Mass spectrometric analysis of the phosphorylated RGS5 revealed that Ser166 was one of the predominant phosphorylation sites. Substitution of Ser166 by aspartic acid abolished the binding capacity to Galpha subunits and the GAP activity, and markedly reduced the inhibitory effect on ET-1-induced Ca(2+) responses. These results indicate that phosphorylation at Ser166 of RGS5 by PKC causes loss of the function of RGS5 in G protein signaling. Since this serine residue is conserved in RGS domains of many RGS proteins, the phosphorylation at Ser166 by PKC might act as a molecular switch and have functional significance.
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Affiliation(s)
- Kayoko Moroi
- Department of Biochemistry and Molecular Pharmacology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan
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16
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Ajit SK, Ramineni S, Edris W, Hunt RA, Hum WT, Hepler JR, Young KH. RGSZ1 interacts with protein kinase C interacting protein PKCI-1 and modulates mu opioid receptor signaling. Cell Signal 2006; 19:723-30. [PMID: 17126529 DOI: 10.1016/j.cellsig.2006.09.008] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 09/15/2006] [Accepted: 09/15/2006] [Indexed: 11/26/2022]
Abstract
Protein kinase C interacting protein (PKCI-1) was identified among the potential interactors from a yeast two hybrid screen of human brain library using N terminal of RGSZ1 as a bait. The cysteine string region, unique to the RZ subfamily, contributes to the observed interaction because PKCI-1 interacted with N-terminus of RGS17 and GAIP, but not with that of RGS2 or RGS7 where cysteine string motif is absent. The interaction between RGSZ1 and PKCI-1 was confirmed by coimmunoprecipitation and immunofluorescence. PKCI-1 and RGSZ1 could be detected by coimmunoprecipitation using 14-3-3 antibody in cells transfected with PKCI-1 or RGSZ1 respectively, but when transfected with PKCI-1 and RGSZ1 together, only RGSZ1 could be detected. Phosphorylation of Galphaz by protein kinase C (PKC) reduces the ability of the RGS to effectively function as GTPase accelerating protein for Galphaz, and interferes with ability of Galphaz to interact with betagamma complex. We investigated the roles of 14-3-3 and PKCI-1 in phosphorylation of Galphaz. Phosphorylation of Galphaz by PKC was inhibited by 14-3-3 and the presence of PKCI-1 did not provide any further inhibition. PKCI-1 interacts with mu opioid receptor and suppresses receptor desensitization and PKC related mu opioid receptor phosphorylation [W. Guang, H. Wang, T. Su, I.B. Weinstein, J.B. Wang, Mol. Pharmacol. 66 (2004) 1285.]. Previous studies have also shown that mu opioid receptor co-precipitates with RGSZ1 and influence mu receptor signaling by acting as effector antagonists [J. Garzon, M. Rodriguez-Munoz, P. Sanchez-Blazquez, Neuropharmacology 48 (2005) 853., J. Garzon, M. Rodriguez-Munoz, A. Lopez-Fando, P. Sanchez-Blazquez Neuropsychopharmacology 30 (2005) 1632.]. Inhibition of cAMP by mu opioid receptor was significantly reduced by RGSZ1 and this effect was enhanced in combination with PKCI-1. Our studies thus provide a link between the previous observations mentioned above and indicate that the major function of PKCI-1 is to modulate mu opioid receptor signaling pathway along with RGSZ1, rather than directly mediating the Galphaz RGSZ1 interaction.
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Affiliation(s)
- Seena K Ajit
- Neuroscience Discovery, Wyeth Research CN 8000, Princeton NJ 08543, USA.
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17
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Abstract
Regulators of G-protein signalling (RGS) proteins are a large and diverse family initially identified as GTPase activating proteins (GAPs) of heterotrimeric G-protein Galpha-subunits. At least some can also influence Galpha activity through either effector antagonism or by acting as guanine nucleotide dissociation inhibitors (GDIs). As our understanding of RGS protein structure and function has developed, so has the realisation that they play roles beyond G-protein regulation. Such diversity of function is enabled by the variety of RGS protein structure and their ability to interact with other cellular molecules including phospholipids, receptors, effectors and scaffolds. The activity, sub-cellular distribution and expression levels of RGS proteins are dynamically regulated, providing a layer of complexity that has yet to be fully elucidated.
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Affiliation(s)
- Gary B Willars
- Department of Cell Physiology and Pharmacology, University of Leicester, University Road, Leicester LE1 9HN, UK.
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18
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Liu T, Bohlken A, Kuljaca S, Lee M, Nguyen T, Smith S, Cheung B, Norris MD, Haber M, Holloway AJ, Bowtell DDL, Marshall GM. The retinoid anticancer signal: mechanisms of target gene regulation. Br J Cancer 2005; 93:310-8. [PMID: 16012519 PMCID: PMC2361573 DOI: 10.1038/sj.bjc.6602700] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Retinoids induce growth arrest, differentiation, and cell death in many cancer cell types. One factor determining the sensitivity or resistance to the retinoid anticancer signal is the transcriptional response of retinoid-regulated target genes in cancer cells. We used cDNA microarray to identify 31 retinoid-regulated target genes shared by two retinoid-sensitive neuroblastoma cell lines, and then sought to determine the relevance of the target gene responses to the retinoid anticancer signal. The pattern of retinoid responsiveness for six of 13 target genes (RARβ2, CYP26A1, CRBP1, RGS16, DUSP6, EGR1) correlated with phenotypic retinoid sensitivity, across a panel of retinoid-sensitive or -resistant lung and breast cancer cell lines. Retinoid treatment of MYCN transgenic mice bearing neuroblastoma altered the expression of five of nine target genes examined (RARβ2, CYP26A1, CRBP1, DUSP6, PLAT) in neuroblastoma tumour tissue in vivo. In retinoid-sensitive neuroblastoma, lung and breast cancer cell lines, direct inhibition of retinoid-induced RARβ2 expression blocked induction of only one of eight retinoid target genes (CYP26A1). DNA demethylation, histone acetylation, and exogenous overexpression of RARβ2 partially restored retinoid-responsive CYP26A1 expression in RA-resistant MDA-MB-231 breast, but not SK-MES-1 lung, cancer cells. Combined, rather than individual, inhibition of DUSP6 and RGS16 was required to block retinoid-induced growth inhibition in neuroblastoma cells, through phosphorylation of extracellular-signal-regulated kinase. In conclusion, sensitivity to the retinoid anticancer signal is determined in part by the transcriptional response of key retinoid-regulated target genes, such as RARβ2, DUSP6, and RGS16.
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Affiliation(s)
- T Liu
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - A Bohlken
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - S Kuljaca
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - M Lee
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - T Nguyen
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - S Smith
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - B Cheung
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - M D Norris
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - M Haber
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
| | - A J Holloway
- Peter MacCallum Cancer Centre, East Melbourne VIC 8006, Australia
| | - D D L Bowtell
- Peter MacCallum Cancer Centre, East Melbourne VIC 8006, Australia
| | - G M Marshall
- Children's Cancer Institute Australia for Medical Research, Randwick NSW 2031, Australia
- Centre for Children's Cancer and Blood Disorders, Sydney Children's Hospital, High Street, Randwick NSW 2031, Australia
- Centre for Children's Cancer and Blood Disorders, Sydney Children's Hospital, High Street, Randwick NSW 2031, Australia. E-mail:
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19
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Ward RJ, Milligan G. A Key Serine for the GTPase-Activating Protein Function of Regulator of G Protein Signaling Proteins Is Not a General Target for 14-3-3 Interactions. Mol Pharmacol 2005; 68:1821-30. [PMID: 16160139 DOI: 10.1124/mol.105.015073] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mammalian regulator of G protein signaling (RGS) proteins are highly conserved within the RGS domain. Of amino acids that are universal, a serine residue at the C terminus of this domain has been described as the binding site in RGS7 for 14-3-3 proteins. However, studies with the related RGS3 indicate that the site of interaction is not within the RGS domain. We confirm that the interaction of RGS3 with 14-3-3tau and 14-3-3zeta requires Ser264 and not the RGS domain and show both that mutation of the conserved RGS domain serine, Ser496 in RGS3, to either alanine or aspartate does not prevent binding of 14-3-3 proteins and that 14-3-3 proteins do not inhibit GTPase-activating protein (GAP) activity against receptor-activated Galpha(o1). However, mutation of Ser496 does directly impair the action of RGS3 as a GAP against receptor-activated Galpha(o1). We mutated the equivalent serine residue in the family B/R4 RGS proteins RGS1 and RGS16. Using two distinct assay formats, conversion to aspartate virtually abolished GAP activity, whereas conversion to alanine decreased potency 20-fold. Neither alteration modulated interactions with 14-3-3tau or 14-3-3zeta, but the 14-3-3 proteins did not modulate the GAP activity of the wild-type or mutant RGS proteins. Although interactions between 14-3-3 proteins and many RGS proteins can be observed, this does not involve this conserved serine and does not inherently modify GAP function.
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Affiliation(s)
- Richard J Ward
- Molecular Pharmacolofy Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Davidson Building, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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20
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Abstract
Regulator of G-protein-signaling (RGS) proteins play a key role in the regulation of G-protein-coupled receptor (GPCR) signaling. The characteristic hallmark of RGS proteins is a conserved approximately 120-aa RGS region that confers on these proteins the ability to serve as GTPase-activating proteins (GAPs) for G(alpha) proteins. Most RGS proteins can serve as GAPs for multiple isoforms of G(alpha) and therefore have the potential to influence many cellular signaling pathways. However, RGS proteins can be highly regulated and can demonstrate extreme specificity for a particular signaling pathway. RGS proteins can be regulated by altering their GAP activity or subcellular localization; such regulation is achieved by phosphorylation, palmitoylation, and interaction with protein and lipid-binding partners. Many RGS proteins have GAP-independent functions that influence GPCR and non-GPCR-mediated signaling, such as effector regulation or action as an effector. Hence, RGS proteins should be considered multifunctional signaling regulators. GPCR-mediated signaling is critical for normal function in the cardiovascular system and is currently the primary target for the pharmacological treatment of disease. Alterations in RGS protein levels, in particular RGS2 and RGS4, produce cardiovascular phenotypes. Thus, because of the importance of GPCR-signaling pathways and the profound influence of RGS proteins on these pathways, RGS proteins are regulators of cardiovascular physiology and potentially novel drug targets as well.
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Affiliation(s)
- Evan L Riddle
- Department of Pharmacology, University of California San Diego, La Jolla, USA
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21
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García A, Prabhakar S, Hughan S, Anderson TW, Brock CJ, Pearce AC, Dwek RA, Watson SP, Hebestreit HF, Zitzmann N. Differential proteome analysis of TRAP-activated platelets: involvement of DOK-2 and phosphorylation of RGS proteins. Blood 2004; 103:2088-95. [PMID: 14645010 DOI: 10.1182/blood-2003-07-2392] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Abstract
We have applied a proteomics approach to analyze signaling cascades in human platelets stimulated by thrombin receptor activating peptide (TRAP). By analyzing basal and TRAP-activated platelets using 2-dimensional gel electrophoresis (2-DE), we detected 62 differentially regulated protein features. From these, 41 could be identified by liquid chromatography–coupled tandem mass spectrometry (LC-MS/MS) and were found to derive from 31 different genes, 8 of which had not previously been reported in platelets, including the adapter downstream of tyrosine kinase 2 (Dok-2). Further studies revealed that the change in mobility of Dok-2 was brought about by tyrosine phosphorylation. Dok-2 tyrosine phosphorylation was also found to be involved in collagen receptor, glycoprotein VI (GPVI), signaling as well as in outside-in signaling through the major platelet integrin, αIIbβ3. These studies also provided the first demonstration of posttranslational modification of 2 regulator of G protein signaling (RGS) proteins, RGS10 and 18. Phosphorylation of RGS18 was mapped to Ser49 by MS/MS analysis. This study provides a new approach for the identification of novel signaling molecules in activated platelets, providing new insights into the mechanisms of platelet activation and building the basis for the development of therapeutic agents for thrombotic diseases.
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Affiliation(s)
- Angel García
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, United Kingdom.
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22
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Anger T, Zhang W, Mende U. Differential Contribution of GTPase Activation and Effector Antagonism to the Inhibitory Effect of RGS Proteins on Gq-mediated Signaling in Vivo. J Biol Chem 2004; 279:3906-15. [PMID: 14630933 DOI: 10.1074/jbc.m309496200] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RGS proteins act as negative regulators of G protein signaling by serving as GTPase-activating proteins (GAP) for alpha subunits of heterotrimeric G proteins (Galpha), thereby accelerating G protein inactivation. RGS proteins can also block Galpha-mediated signal production by competing with downstream effectors for Galpha binding. Little is known about the relative contribution of GAP and effector antagonism to the inhibitory effect of RGS proteins on G protein-mediated signaling. By comparing the inhibitory effect of RGS2, RGS3, RGS5, and RGS16 on Galpha(q)-mediated phospholipase Cbeta (PLCbeta) activation under conditions where GTPase activation is possible versus nonexistent, we demonstrate that members of the R4 RGS subfamily differ significantly in their dependence on GTPase acceleration. COS-7 cells were transiently transfected with either muscarinic M3 receptors, which couple to endogenous Gq protein and mediate a stimulatory effect of carbachol on PLCbeta, or constitutively active Galphaq*, which is inert to GTP hydrolysis and activates PLCbeta independent of receptor activation. In M3-expressing cells, all of the RGS proteins significantly blunted the efficacy and potency of carbachol. In contrast, Galphaq* -induced PLCbeta activation was inhibited by RGS2 and RGS3 but not RGS5 and RGS16. The observed differential effects were not due to changes in M3, Galphaq/Galphaq*, PLCbeta, or RGS expression, as shown by receptor binding assays and Western blots. We conclude that closely related R4 RGS family members differ in their mechanism of action. RGS5 and RGS16 appear to depend on G protein inactivation, whereas GAP-independent mechanisms (such as effector antagonism) are sufficient to mediate the inhibitory effect of RGS2 and RGS3.
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Affiliation(s)
- Thomas Anger
- Cardiovascular Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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Kaushik R, Yu F, Chia W, Yang X, Bahri S. Subcellular localization of LGN during mitosis: evidence for its cortical localization in mitotic cell culture systems and its requirement for normal cell cycle progression. Mol Biol Cell 2003; 14:3144-55. [PMID: 12925752 PMCID: PMC181556 DOI: 10.1091/mbc.e03-04-0212] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mammalian LGN/AGS3 proteins and their Drosophila Pins orthologue are cytoplasmic regulators of G-protein signaling. In Drosophila, Pins localizes to the lateral cortex of polarized epithelial cells and to the apical cortex of neuroblasts where it plays important roles in their asymmetric division. Using overexpression studies in different cell line systems, we demonstrate here that, like Drosophila Pins, LGN can exhibit enriched localization at the cell cortex, depending on the cell cycle and the culture system used. We find that in WISH, PC12, and NRK but not COS cells, LGN is largely directed to the cell cortex during mitosis. Overexpression of truncated protein domains further identified the Galpha-binding C-terminal portion of LGN as a sufficient domain for cortical localization in cell culture. In mitotic COS cells that normally do not exhibit cortical LGN localization, LGN is redirected to the cell cortex upon overexpression of Galpha subunits of heterotrimeric G-proteins. The results also show that the cortical localization of LGN is dependent on microfilaments and that interfering with LGN function in cultured cell lines causes early disruption to cell cycle progression.
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Affiliation(s)
- Rachna Kaushik
- Institute of Molecular and Cell Biology, Singapore 117609
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24
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Osterhout JL, Waheed AA, Hiol A, Ward RJ, Davey PC, Nini L, Wang J, Milligan G, Jones TLZ, Druey KM. Palmitoylation regulates regulator of G-protein signaling (RGS) 16 function. II. Palmitoylation of a cysteine residue in the RGS box is critical for RGS16 GTPase accelerating activity and regulation of Gi-coupled signalling. J Biol Chem 2003; 278:19309-16. [PMID: 12642592 DOI: 10.1074/jbc.m210124200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Palmitoylation is a reversible post-translational modification used by cells to regulate protein activity. The regulator of G-protein signaling (RGS) proteins RGS4 and RGS16 share conserved cysteine (Cys) residues that undergo palmitoylation. In the accompanying article (Hiol, A., Davey, P. C., Osterhout, J. L., Waheed, A. A., Fischer, E. R., Chen, C. K., Milligan, G., Druey, K. M., and Jones, T. L. Z. (2003) J. Biol. Chem. 278, 19301-19308), we determined that mutation of NH2-terminal cysteine residues in RGS16 (Cys-2 and Cys-12) reduced GTPase accelerating (GAP) activity toward a 5-hydroxytryptamine (5-HT1A)/G alpha o1 receptor fusion protein in cell membranes. NH2-terminal acylation also permitted palmitoylation of a cysteine residue in the RGS box of RGS16 (Cys-98). Here we investigated the role of internal palmitoylation in RGS16 localization and GAP activity. Mutation of RGS16 Cys-98 or RGS4 Cys-95 to alanine reduced GAP activity on the 5-HT1A/G alpha o1 fusion protein and regulation of adenylyl cyclase inhibition. The C98A mutation had no effect on RGS16 localization or GAP activity toward purified G-protein alpha subunits. Enzymatic palmitoylation of RGS16 resulted in internal palmitoylation on residue Cys-98. Palmitoylated RGS16 or RGS4 WT but not C98A or C95A preincubated with membranes expressing 5-HT1a/G alpha o1 displayed increased GAP activity over time. These results suggest that palmitoylation of a Cys residue in the RGS box is critical for RGS16 and RGS4 GAP activity and their ability to regulate Gi-coupled signaling in mammalian cells.
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Affiliation(s)
- James L Osterhout
- Molecular Signal Transduction Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20892, USA
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Derrien A, Zheng B, Osterhout JL, Ma YC, Milligan G, Farquhar MG, Druey KM. Src-mediated RGS16 tyrosine phosphorylation promotes RGS16 stability. J Biol Chem 2003; 278:16107-16. [PMID: 12588871 DOI: 10.1074/jbc.m210371200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The amplitude of signaling evoked by stimulation of G protein-coupled receptors may be controlled in part by the GTPase accelerating activity of the regulator of G protein signaling (RGS) proteins. In turn, subcellular targeting, protein-protein interactions, or post-translational modifications such as phosphorylation may shape RGS activity and specificity. We found previously that RGS16 undergoes tyrosine phosphorylation on conserved tyrosine residues in the RGS box. Phosphorylation on Tyr(168) was mediated by the epidermal growth factor receptor (EGFR). We show here that endogenous RGS16 is phosphorylated after epidermal growth factor stimulation of MCF-7 cells. In addition, p60-Src or Lyn kinase phosphorylated recombinant RGS16 in vitro, and RGS16 underwent phosphorylation in the presence of constitutively active Src (Y529F) in EGFR(-) CHO-K1 cells. Blockade of endogenous Src activity by selective inhibitors attenuated RGS16 phosphorylation induced by pervanadate or receptor stimulation. Furthermore, the rate of RGS16 degradation was reduced in cells expressing active Src or treated with pervanadate or a G protein-coupled receptor ligand (CXCL12). Induction of RGS16 tyrosine phosphorylation was associated with increased RGS16 protein levels and enhanced GAP activity in cell membranes. These results suggest that Src mediates RGS16 tyrosine phosphorylation, which may promote RGS16 stability.
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Affiliation(s)
- Alexandrine Derrien
- Laboratory of Allergic Diseases, NIAID/National Institutes of Health, 12441 Parklawn Drive, Rockville, MD 20852, USA
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Geymonat M, Spanos A, Walker PA, Johnston LH, Sedgwick SG. In vitro regulation of budding yeast Bfa1/Bub2 GAP activity by Cdc5. J Biol Chem 2003; 278:14591-4. [PMID: 12637549 DOI: 10.1074/jbc.c300059200] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Cdc5 protein of budding yeast is a polo-like kinase that has multiple roles in mitosis including control of the mitotic exit network (MEN). MEN activity brings about loss of mitotic kinase activity so that the mitotic spindle is disassembled and cytokinesis can proceed. Activity of the MEN is regulated by a small GTPase, Tem1, which in turn is controlled by a two-component GTPase-activating protein (GAP) formed by Bfa1 and Bub2. Bfa1 has been identified as a regulatory target of Cdc5 but there are conflicting deductions from indirect in vivo assays as to whether phosphorylation inhibits or stimulates Bfa1 activity. To resolve this question, we have used direct in vitro assays to observe the effects of phosphorylation on Bfa1 activity. We show that when Bfa1 is phosphorylated by Cdc5, its GAP activity with Bub2 is inhibited although its ability to interact with Tem1 is unaffected. Thus, in vivo inactivation of Bfa1-Bub2 by Cdc5 would have a positive regulatory effect by increasing levels of Tem1-GTP so stimulating exit from mitosis.
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Affiliation(s)
- Marco Geymonat
- Divisions of Yeast Genetics and Protein Structure, National Institute for Medical Research, Mill Hill, London NW7 1AA, Great Britain
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Wieland T, Mittmann C. Regulators of G-protein signalling: multifunctional proteins with impact on signalling in the cardiovascular system. Pharmacol Ther 2003; 97:95-115. [PMID: 12559385 DOI: 10.1016/s0163-7258(02)00326-1] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Regulator of G-protein signalling (RGS) proteins form a superfamily of at least 25 proteins, which are highly diverse in structure, expression patterns, and function. They share a 120 amino acid homology domain (RGS domain), which exhibits GTPase accelerating activity for alpha-subunits of heterotrimeric G-proteins, and thus, are negative regulators of G-protein-mediated signalling. Based on the organisation of the Rgs genes, structural similarities, and differences in functions, they can be divided into at least six subfamilies of RGS proteins and three more families of RGS-like proteins. Many of these proteins regulate signalling processes within cells, not only via interaction with G-protein alpha-subunits, but are G-protein-regulated effectors, Gbetagamma scavenger, or scaffolding proteins in signal transduction complexes as well. The expression of at least 16 different RGS proteins in the mammalian or human myocardium have been described. A subgroup of at least eight was detected in a single atrial myocyte. The exact functions of these proteins remain mostly elusive, but RGS proteins such as RGS4 are involved in the regulation of G(i)-protein betagamma-subunit-gated K(+) channels. An up-regulation of RGS4 expression has been consistently found in human heart failure and some animal models. Evidence is increasing that the enhanced RGS4 expression counter-regulates the G(q/11)-induced signalling caused by hypertrophic stimuli. In the vascular system, RGS5 seems to be an important signalling regulator. It is expressed in vascular endothelial cells, but not in cultured smooth muscle cells. Its down-regulation, both in a model of capillary morphogenesis and in an animal model of stroke, render it a candidate gene, which may be involved in the regulation of capillary growth, angiogenesis, and in the pathophysiology of stroke.
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Affiliation(s)
- Thomas Wieland
- Institut für Pharmakologie und Toxikologie, Fakultät für Klinische Medizin Mannheim der Universität Heidelberg, Maybachstrasse 14-16, D-68169 Mannheim, Germany.
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Niu J, Scheschonka A, Druey KM, Davis A, Reed E, Kolenko V, Bodnar R, Voyno-Yasenetskaya T, Du X, Kehrl J, Dulin NO. RGS3 interacts with 14-3-3 via the N-terminal region distinct from the RGS (regulator of G-protein signalling) domain. Biochem J 2002; 365:677-84. [PMID: 11985497 PMCID: PMC1222729 DOI: 10.1042/bj20020390] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2002] [Revised: 04/17/2002] [Accepted: 05/01/2002] [Indexed: 11/17/2022]
Abstract
RGS3 belongs to a family of the regulators of G-protein signalling (RGS), which bind and inhibit the G alpha subunits of heterotrimeric G-proteins via a homologous RGS domain. Increasing evidence suggests that RGS proteins can also interact with targets other than G-proteins. Employing yeast two-hybrid screening of a cDNA library, we identified an interaction between RGS3 and the phosphoserine-binding protein 14-3-3. This interaction was confirmed by in vitro binding and co-immunoprecipitation experiments. RGS3-deletion analysis revealed the presence of a single 14-3-3-binding site located outside of the RGS domain. Ser(264) was then identified as the 14-3-3-binding site of RGS3. The S(264)A mutation resulted in the loss of RGS3 binding to 14-3-3, without affecting its ability to bind G alpha(q). Signalling studies showed that the S(264)A mutant was more potent than the wild-type RGS3 in inhibition of G-protein-mediated signalling. Binding experiments revealed that RGS3 exists in two separate pools, either 14-3-3-bound or G-protein-bound, and that the 14-3-3-bound RGS3 is unable to interact with G-proteins. These data are consistent with the model wherein 14-3-3 serves as a scavenger of RGS3, regulating the amounts of RGS3 available for binding G-proteins. This study describes a new level in the regulation of G-protein signalling, in which the inhibitors of G-proteins, RGS proteins, can themselves be regulated by phosphorylation and binding 14-3-3.
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Affiliation(s)
- Jiaxin Niu
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, IL 60612, U.S.A
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Derrien A, Druey KM. RGS16 function is regulated by epidermal growth factor receptor-mediated tyrosine phosphorylation. J Biol Chem 2001; 276:48532-8. [PMID: 11602604 DOI: 10.1074/jbc.m108862200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Galpha(i)-coupled receptor stimulation results in epidermal growth factor receptor (EGFR) phosphorylation and MAPK activation. Regulators of G protein signaling (RGS proteins) inhibit G protein-dependent signal transduction by accelerating Galpha(i) GTP hydrolysis, shortening the duration of G protein effector stimulation. RGS16 contains two conserved tyrosine residues in the RGS box, Tyr(168) and Tyr(177), which are predicted sites of phosphorylation. RGS16 underwent phosphorylation in response to m2 muscarinic receptor or EGFR stimulation in HEK 293T or COS-7 cells, which required EGFR kinase activity. Mutational analysis suggested that RGS16 was phosphorylated on both tyrosine residues (Tyr(168) Tyr(177)) after EGF stimulation. RGS16 co-immunoprecipitated with EGFR, and the interaction did not require EGFR activation. Purified EGFR phosphorylated only recombinant RGS16 wild-type or Y177F in vitro, implying that EGFR-mediated phosphorylation depended on residue Tyr(168). Phosphorylated RGS16 demonstrated enhanced GTPase accelerating (GAP) activity on Galpha(i). Mutation of Tyr(168) to phenylalanine resulted in a 30% diminution in RGS16 GAP activity but completely eliminated its ability to regulate G(i)-mediated MAPK activation or adenylyl cyclase inhibition in HEK 293T cells. In contrast, mutation of Tyr(177) to phenylalanine had no effect on RGS16 GAP activity but also abolished its regulation of G(i)-mediated signal transduction in these cells. These data suggest that tyrosine phosphorylation regulates RGS16 function and that EGFR may potentially inhibit Galpha(i)-dependent MAPK activation in a feedback loop by enhancing RGS16 activity through tyrosine phosphorylation.
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Affiliation(s)
- A Derrien
- Molecular Signal Transduction Section, Laboratory of Allergic Diseases, National Institutes of Health, Rockville, Maryland 20852, USA
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