1
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Two-step structural changes in M3 muscarinic receptor activation rely on the coupled G q protein cycle. Nat Commun 2023; 14:1276. [PMID: 36882424 PMCID: PMC9992711 DOI: 10.1038/s41467-023-36911-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 02/23/2023] [Indexed: 03/09/2023] Open
Abstract
G protein-coupled receptors (GPCRs) regulate diverse intracellular signaling pathways through the activation of heterotrimeric G proteins. However, the effects of the sequential activation-deactivation cycle of G protein on the conformational changes of GPCRs remains unknown. By developing a Förster resonance energy transfer (FRET) tool for human M3 muscarinic receptor (hM3R), we find that a single-receptor FRET probe can display the consecutive structural conversion of a receptor by G protein cycle. Our results reveal that the G protein activation evokes a two-step change in the hM3R structure, including the fast step mediated by Gq protein binding and the subsequent slower step mediated by the physical separation of the Gαq and Gβγ subunits. We also find that the separated Gαq-GTP forms a stable complex with the ligand-activated hM3R and phospholipase Cβ. In sum, the present study uncovers the real-time conformational dynamics of innate hM3R during the downstream Gq protein cycle.
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2
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Hasan S, White NF, Tagliatela AC, Durall RT, Brown KM, McDiarmid GR, Meigs TE. Overexpressed Gα13 activates serum response factor through stoichiometric imbalance with Gβγ and mislocalization to the cytoplasm. Cell Signal 2023; 102:110534. [PMID: 36442589 DOI: 10.1016/j.cellsig.2022.110534] [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: 08/10/2022] [Revised: 11/21/2022] [Accepted: 11/21/2022] [Indexed: 11/26/2022]
Abstract
Gα13, a heterotrimeric G protein α subunit of the G12/13 subfamily, is an oncogenic driver in multiple cancer types. Unlike other G protein subfamilies that contribute to cancer progression via amino acid substitutions that abolish their deactivating, intrinsic GTPase activity, Gα13 rarely harbors such mutations in tumors and instead appears to stimulate aberrant cell growth via overexpression as a wildtype form. It is not known why this effect is exclusive to the G12/13 subfamily, nor has a mechanism been elucidated for overexpressed Gα13 promoting tumor progression. Using a reporter gene assay for serum response factor (SRF)-mediated transcription in HEK293 cells, we found that transiently expressed, wildtype Gα13 generates a robust SRF signal, approximately half the amplitude observed for GTPase-defective Gα13. When epitope-tagged, wildtype Gα13 was titrated upward in cells, a sharp increase in SRF stimulation was observed coincident with a "spillover" of Gα13 from membrane-associated to a soluble fraction. Overexpressing G protein β and γ subunits caused both a decrease in this signal and a shift of wildtype Gα13 back to the membranous fraction, suggesting that stoichiometric imbalance in the αβγ heterotrimer results in aberrant subcellular localization and signalling by overexpressed Gα13. We also examined the acylation requirements of wildtype Gα13 for signalling to SRF. Similar to GTPase-defective Gα13, S-palmitoylation of the wildtype α subunit was necessary for SRF activation but could be replaced functionally by an engineered site for N-terminal myristoylation. However, a key difference was observed between wildtype and GTPase-defective Gα13: whereas the latter protein lacking palmitoylation sites was rescued in its SRF signalling by either an engineered polybasic sequence or a C-terminal isoprenylation site, these motifs failed to restore signalling by wildtype, non-palmitoylated Gα13. These findings illuminate several components of the mechanism in which overexpressed, wildtype Gα13 contributes to growth and tumorigenic signalling, and reveal greater stringency in its requirements for post-translational modification in comparison to GTPase-defective Gα13.
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Affiliation(s)
- Sharmin Hasan
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Nicholas F White
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Alicia C Tagliatela
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - R Taylor Durall
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Katherine M Brown
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Gray R McDiarmid
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Thomas E Meigs
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA.
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3
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Subedi B, Schrick K. EYFP fusions to HD-Zip IV transcription factors enhance their stability and lead to phenotypic changes in Arabidopsis. PLANT SIGNALING & BEHAVIOR 2022; 17:2119013. [PMID: 36154907 PMCID: PMC9519029 DOI: 10.1080/15592324.2022.2119013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 08/22/2022] [Accepted: 08/23/2022] [Indexed: 06/16/2023]
Abstract
Green fluorescent protein (GFP) and its derivatives are extensively used for labeling cells, monitoring gene expression and/or tracking the localization or interactions of proteins. Previous reports of detrimental effects of fluorescent protein (FP) expression include cytotoxicity and interference with fusion protein function or localization. Only a few studies have documented the fluorescent tag-specific effects in plants. Here, we show that placing an enhanced yellow FP (EYFP) tag on the amino-terminus of GLABRA2 (GL2) and PROTODERMAL FACTOR2 (PDF2), two developmentally important HD-Zip IV transcription factors from Arabidopsis, enhances their protein stability. Additionally, expression of EYFP:GL2 not only rescued the gl2 null mutant but also resulted in the abnormal development of abaxially curled leaves associated with EYFP-tag induced GL2 overexpression. Our study raises concerns on the use of FPs regarding their effects on the native properties of target proteins as well as biological consequences of fusion protein expression on morphology.
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Affiliation(s)
- Bibek Subedi
- Division of Biology, Molecular, Cellular and Developmental Biology, Kansas State University, Manhattan, KS, USA
| | - Kathrin Schrick
- Division of Biology, Molecular, Cellular and Developmental Biology, Kansas State University, Manhattan, KS, USA
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4
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Randolph CE, Dwyer MB, Aumiller JL, Dixon AJ, Inoue A, Osei-Owusu P, Wedegaertner PB. Enhanced membrane binding of oncogenic G protein αqQ209L confers resistance to inhibitor YM-254890. J Biol Chem 2022; 298:102538. [PMID: 36174676 PMCID: PMC9626947 DOI: 10.1016/j.jbc.2022.102538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 09/15/2022] [Accepted: 09/18/2022] [Indexed: 11/29/2022] Open
Abstract
Heterotrimeric G proteins couple activated G protein–coupled receptors (GPCRs) to intracellular signaling pathways. They can also function independently of GPCR activation upon acquiring mutations that prevent GTPase activity and result in constitutive signaling, as occurs with the αqQ209L mutation in uveal melanoma. YM-254890 (YM) can inhibit signaling by both GPCR-activated WT αq and GPCR-independent αqQ209L. Although YM inhibits WT αq by binding to αq-GDP and preventing GDP/GTP exchange, the mechanism of YM inhibition of cellular αqQ209L remains to be fully understood. Here, we show that YM promotes a subcellular redistribution of αqQ209L from the plasma membrane (PM) to the cytoplasm. To test if this loss of PM localization could contribute to the mechanism of inhibition of αqQ209L by YM, we developed and examined N-terminal mutants of αqQ209L, termed PM-restricted αqQ209L, in which the addition of membrane-binding motifs enhanced PM localization and prevented YM-promoted redistribution. Treatment of cells with YM failed to inhibit signaling by these PM-restricted αqQ209L. Additionally, pull-down experiments demonstrated that YM promotes similar conformational changes in both αqQ209L and PM-restricted αqQ209L, resulting in increased binding to βγ and decreased binding to regulator RGS2, and effectors p63RhoGEF-DH/PH and phospholipase C-β. GPCR-dependent signaling by PM-restricted WT αq is strongly inhibited by YM, demonstrating that resistance to YM inhibition by membrane-binding mutants is specific to constitutively active αqQ209L. Together, these results indicate that changes in membrane binding impact the ability of YM to inhibit αqQ209L and suggest that YM contributes to inhibition of αqQ209L by promoting its relocalization.
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Affiliation(s)
- Clinita E Randolph
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA
| | - Morgan B Dwyer
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA
| | - Jenna L Aumiller
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA
| | - Alethia J Dixon
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Patrick Osei-Owusu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Philip B Wedegaertner
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA.
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5
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Flöser A, Becker K, Kostenis E, König G, Krasel C, Kolb P, Bünemann M. Disentangling bias between G q, GRK2, and arrestin3 recruitment to the M 3 muscarinic acetylcholine receptor. eLife 2021; 10:58442. [PMID: 34851820 PMCID: PMC8635974 DOI: 10.7554/elife.58442] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 11/18/2021] [Indexed: 12/11/2022] Open
Abstract
G protein-coupled receptors (GPCRs) transmit extracellular signals to the inside by activation of intracellular effector proteins. Different agonists can promote differential receptor-induced signaling responses – termed bias – potentially by eliciting different levels of recruitment of effector proteins. As activation and recruitment of effector proteins might influence each other, thorough analysis of bias is difficult. Here, we compared the efficacy of seven agonists to induce G protein, G protein-coupled receptor kinase 2 (GRK2), as well as arrestin3 binding to the muscarinic acetylcholine receptor M3 by utilizing FRET-based assays. In order to avoid interference between these interactions, we studied GRK2 binding in the presence of inhibitors of Gi and Gq proteins and analyzed arrestin3 binding to prestimulated M3 receptors to avoid differences in receptor phosphorylation influencing arrestin recruitment. We measured substantial differences in the agonist efficacies to induce M3R-arrestin3 versus M3R-GRK2 interaction. However, the rank order of the agonists for G protein- and GRK2-M3R interaction was the same, suggesting that G protein and GRK2 binding to M3R requires similar receptor conformations, whereas requirements for arrestin3 binding to M3R are distinct.
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Affiliation(s)
- Anja Flöser
- Department of Pharmaceutical Chemistry, Philipps-University Marburg, Marburg, Germany.,Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany
| | - Katharina Becker
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany
| | - Evi Kostenis
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Gabriele König
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Cornelius Krasel
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany
| | - Peter Kolb
- Department of Pharmaceutical Chemistry, Philipps-University Marburg, Marburg, Germany
| | - Moritz Bünemann
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany
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6
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Qifti A, Jackson L, Singla A, Garwain O, Scarlata S. Stimulation of phospholipase Cβ1 by Gα q promotes the assembly of stress granule proteins. Sci Signal 2021; 14:eaav1012. [PMID: 34665639 DOI: 10.1126/scisignal.aav1012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
[Figure: see text].
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Affiliation(s)
- Androniqi Qifti
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Lela Jackson
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Ashima Singla
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Osama Garwain
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Suzanne Scarlata
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
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7
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Jelinek V, Mösslein N, Bünemann M. Structures in G proteins important for subtype selective receptor binding and subsequent activation. Commun Biol 2021; 4:635. [PMID: 34045638 PMCID: PMC8160216 DOI: 10.1038/s42003-021-02143-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 04/26/2021] [Indexed: 11/09/2022] Open
Abstract
G protein-coupled receptors (GPCRs) selectively couple to specific heterotrimeric G proteins comprised of four subfamilies in order to induce appropriate physiological responses. However, structural determinants in Gα subunits responsible for selective recognition by approximately 800 human GPCRs have remained elusive. Here, we directly compare the influence of subtype-specific Gα structures on the stability of GPCR-G protein complexes and the activation by two Gq-coupled receptors. We used FRET-assays designed to distinguish multiple Go and Gq-based Gα chimeras in their ability to be selectively bound and activated by muscarinic M3 and histaminic H1 receptors. We identify the N-terminus including the αN/β1-hinge, the β2/β3-loop and the α5 helix of Gα to be key selectivity determinants which differ in their impact on selective binding to GPCRs and subsequent activation depending on the specific receptor. Altogether, these findings provide new insights into the molecular basis of G protein-coupling selectivity even beyond the Gα C-terminus.
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Affiliation(s)
- Volker Jelinek
- Institute of Pharmacology and Clinical Pharmacy, Philipps-University Marburg, Marburg, Germany
| | - Nadja Mösslein
- Institute of Pharmacology and Clinical Pharmacy, Philipps-University Marburg, Marburg, Germany
| | - Moritz Bünemann
- Institute of Pharmacology and Clinical Pharmacy, Philipps-University Marburg, Marburg, Germany.
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8
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Kumar S, Olson AC, Koelle MR. The neural G protein Gαo tagged with GFP at an internal loop is functional in C. elegans. G3-GENES GENOMES GENETICS 2021; 11:6277897. [PMID: 34003969 PMCID: PMC8496287 DOI: 10.1093/g3journal/jkab167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 05/01/2021] [Indexed: 11/23/2022]
Abstract
Gαo is the alpha subunit of the major heterotrimeric G protein in neurons and mediates signaling by every known neurotransmitter, yet the signaling mechanisms activated by Gαo remain to be fully elucidated. Genetic analysis in Caenorhabditis elegans has shown that Gαo signaling inhibits neuronal activity and neurotransmitter release, but studies of the molecular mechanisms underlying these effects have been limited by lack of tools to complement genetic studies with other experimental approaches. Here, we demonstrate that inserting the green fluorescent protein (GFP) into an internal loop of the Gαo protein results in a tagged protein that is functional in vivo and that facilitates cell biological and biochemical studies of Gαo. Transgenic expression of Gαo-GFP rescues the defects caused by loss of endogenous Gαo in assays of egg laying and locomotion behaviors. Defects in body morphology caused by loss of Gαo are also rescued by Gαo-GFP. The Gαo-GFP protein is localized to the plasma membrane of neurons, mimicking localization of endogenous Gαo. Using GFP as an epitope tag, Gαo-GFP can be immunoprecipitated from C. elegans lysates to purify Gαo protein complexes. The Gαo-GFP transgene reported in this study enables studies involving in vivo localization and biochemical purification of Gαo to compliment the already well-developed genetic analysis of Gαo signaling.
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Affiliation(s)
- Santosh Kumar
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 USA
| | - Andrew C Olson
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 USA
| | - Michael R Koelle
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 USA
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9
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Bondar A, Lazar J. Optical sensors of heterotrimeric G protein signaling. FEBS J 2020; 288:2570-2584. [DOI: 10.1111/febs.15655] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/26/2020] [Accepted: 12/03/2020] [Indexed: 01/14/2023]
Affiliation(s)
- Alexey Bondar
- Center for Nanobiology and Structural Biology Institute of Microbiology of the Czech Academy of Sciences Nove Hrady Czech Republic
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Prague Czech Republic
- Faculty of Science University of South Bohemia Ceske Budejovice Czech Republic
| | - Josef Lazar
- Center for Nanobiology and Structural Biology Institute of Microbiology of the Czech Academy of Sciences Nove Hrady Czech Republic
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Prague Czech Republic
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10
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Blankenbach KV, Claas RF, Aster NJ, Spohner AK, Trautmann S, Ferreirós N, Black JL, Tesmer JJG, Offermanns S, Wieland T, Meyer zu Heringdorf D. Dissecting G q/11-Mediated Plasma Membrane Translocation of Sphingosine Kinase-1. Cells 2020; 9:cells9102201. [PMID: 33003441 PMCID: PMC7599897 DOI: 10.3390/cells9102201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/25/2020] [Accepted: 09/27/2020] [Indexed: 12/24/2022] Open
Abstract
Diverse extracellular signals induce plasma membrane translocation of sphingosine kinase-1 (SphK1), thereby enabling inside-out signaling of sphingosine-1-phosphate. We have shown before that Gq-coupled receptors and constitutively active Gαq/11 specifically induced a rapid and long-lasting SphK1 translocation, independently of canonical Gq/phospholipase C (PLC) signaling. Here, we further characterized Gq/11 regulation of SphK1. SphK1 translocation by the M3 receptor in HEK-293 cells was delayed by expression of catalytically inactive G-protein-coupled receptor kinase-2, p63Rho guanine nucleotide exchange factor (p63RhoGEF), and catalytically inactive PLCβ3, but accelerated by wild-type PLCβ3 and the PLCδ PH domain. Both wild-type SphK1 and catalytically inactive SphK1-G82D reduced M3 receptor-stimulated inositol phosphate production, suggesting competition at Gαq. Embryonic fibroblasts from Gαq/11 double-deficient mice were used to show that amino acids W263 and T257 of Gαq, which interact directly with PLCβ3 and p63RhoGEF, were important for bradykinin B2 receptor-induced SphK1 translocation. Finally, an AIXXPL motif was identified in vertebrate SphK1 (positions 100–105 in human SphK1a), which resembles the Gαq binding motif, ALXXPI, in PLCβ and p63RhoGEF. After M3 receptor stimulation, SphK1-A100E-I101E and SphK1-P104A-L105A translocated in only 25% and 56% of cells, respectively, and translocation efficiency was significantly reduced. The data suggest that both the AIXXPL motif and currently unknown consequences of PLCβ/PLCδ(PH) expression are important for regulation of SphK1 by Gq/11.
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Affiliation(s)
- Kira Vanessa Blankenbach
- Institut für Allgemeine Pharmakologie und Toxikologie, Universitätsklinikum, Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (K.V.B.); (R.F.C.); (N.J.A.); (A.K.S.)
| | - Ralf Frederik Claas
- Institut für Allgemeine Pharmakologie und Toxikologie, Universitätsklinikum, Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (K.V.B.); (R.F.C.); (N.J.A.); (A.K.S.)
| | - Natalie Judith Aster
- Institut für Allgemeine Pharmakologie und Toxikologie, Universitätsklinikum, Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (K.V.B.); (R.F.C.); (N.J.A.); (A.K.S.)
| | - Anna Katharina Spohner
- Institut für Allgemeine Pharmakologie und Toxikologie, Universitätsklinikum, Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (K.V.B.); (R.F.C.); (N.J.A.); (A.K.S.)
| | - Sandra Trautmann
- Institut für Klinische Pharmakologie, Universitätsklinikum, Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (S.T.); (N.F.)
| | - Nerea Ferreirós
- Institut für Klinische Pharmakologie, Universitätsklinikum, Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (S.T.); (N.F.)
| | - Justin L. Black
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA;
| | - John J. G. Tesmer
- Departments of Biological Sciences and of Medicinal Chemistry and Molecular Pharmacology, Purdue University West Lafayette, West Lafayette, IN 47907-2054, USA;
| | - Stefan Offermanns
- Abteilung für Pharmakologie, Max-Planck-Institut für Herz- und Lungenforschung, 61231 Bad Nauheim, Germany;
| | - Thomas Wieland
- Experimentelle Pharmakologie Mannheim, European Center for Angioscience, Universität Heidelberg, 68167 Mannheim, Germany;
| | - Dagmar Meyer zu Heringdorf
- Institut für Allgemeine Pharmakologie und Toxikologie, Universitätsklinikum, Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (K.V.B.); (R.F.C.); (N.J.A.); (A.K.S.)
- Correspondence: ; Tel.: +49-69-6301-3906
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11
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Olsen RHJ, DiBerto JF, English JG, Glaudin AM, Krumm BE, Slocum ST, Che T, Gavin AC, McCorvy JD, Roth BL, Strachan RT. TRUPATH, an open-source biosensor platform for interrogating the GPCR transducerome. Nat Chem Biol 2020; 16:841-849. [PMID: 32367019 PMCID: PMC7648517 DOI: 10.1038/s41589-020-0535-8] [Citation(s) in RCA: 273] [Impact Index Per Article: 68.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 03/30/2020] [Indexed: 12/18/2022]
Abstract
G-protein-coupled receptors (GPCRs) remain major drug targets, despite our incomplete understanding of how they signal through 16 non-visual G-protein signal transducers (collectively named the transducerome) to exert their actions. To address this gap, we have developed an open-source suite of 14 optimized bioluminescence resonance energy transfer (BRET) Gαβγ biosensors (named TRUPATH) to interrogate the transducerome with single pathway resolution in cells. Generated through exhaustive protein engineering and empirical testing, the TRUPATH suite of Gαβγ biosensors includes the first Gα15 and GαGustducin probes. In head-to-head studies, TRUPATH biosensors outperformed first-generation sensors at multiple GPCRs and in different cell lines. Benchmarking studies with TRUPATH biosensors recapitulated previously documented signaling bias and revealed new coupling preferences for prototypic and understudied GPCRs with potential in vivo relevance. To enable a greater understanding of GPCR molecular pharmacology by the scientific community, we have made TRUPATH biosensors easily accessible as a kit through Addgene.
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Affiliation(s)
- Reid H J Olsen
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Jeffrey F DiBerto
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Justin G English
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Alexis M Glaudin
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Brian E Krumm
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Samuel T Slocum
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
- National Institute of Mental Health Psychoactive Drug Screening Program, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Tao Che
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Ariana C Gavin
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - John D McCorvy
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Bryan L Roth
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA.
- National Institute of Mental Health Psychoactive Drug Screening Program, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA.
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, USA.
| | - Ryan T Strachan
- Department of Pharmacology, University of North Carolina Chapel Hill School of Medicine, Chapel Hill, NC, USA.
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12
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Zaccor NW, Sumner CJ, Snyder SH. The nonselective cation channel TRPV4 inhibits angiotensin II receptors. J Biol Chem 2020; 295:9986-9997. [PMID: 32493776 PMCID: PMC7380189 DOI: 10.1074/jbc.ra120.014325] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/01/2020] [Indexed: 12/14/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are a ubiquitously expressed family of receptor proteins that regulate many physiological functions and other proteins. They act through two dissociable signaling pathways: the exchange of GDP to GTP by linked G-proteins and the recruitment of β-arrestins. GPCRs modulate several members of the transient receptor potential (TRP) channel family of nonselective cation channels. How TRP channels reciprocally regulate GPCR signaling is less well-explored. Here, using an array of biochemical approaches, including immunoprecipitation and fluorescence, calcium imaging, phosphate radiolabeling, and a β-arrestin-dependent luciferase assay, we characterize a GPCR-TRP channel pair, angiotensin II receptor type 1 (AT1R), and transient receptor potential vanilloid 4 (TRPV4), in primary murine choroid plexus epithelial cells and immortalized cell lines. We found that AT1R and TRPV4 are binding partners and that activation of AT1R by angiotensin II (ANGII) elicits β-arrestin-dependent inhibition and internalization of TRPV4. Activating TRPV4 with endogenous and synthetic agonists inhibited angiotensin II-mediated G-protein-associated second messenger accumulation, AT1R receptor phosphorylation, and β-arrestin recruitment. We also noted that TRPV4 inhibits AT1R phosphorylation by activating the calcium-activated phosphatase calcineurin in a Ca2+/calmodulin-dependent manner, preventing β-arrestin recruitment and receptor internalization. These findings suggest that when TRP channels and GPCRs are co-expressed in the same tissues, many of these channels can inhibit GPCR desensitization.
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Affiliation(s)
- Nicholas W Zaccor
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Charlotte J Sumner
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Solomon H Snyder
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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13
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Jose AM. The analysis of living systems can generate both knowledge and illusions. eLife 2020; 9:56354. [PMID: 32553111 PMCID: PMC7302876 DOI: 10.7554/elife.56354] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 06/12/2020] [Indexed: 12/20/2022] Open
Abstract
Life relies on phenomena that range from changes in molecules that occur within nanoseconds to changes in populations that occur over millions of years. Researchers have developed a vast range of experimental techniques to analyze living systems, but a given technique usually only works over a limited range of length or time scales. Therefore, gaining a full understanding of a living system usually requires the integration of information obtained at multiple different scales by two or more techniques. This approach has undoubtedly led to a much better understanding of living systems but, equally, the staggering complexity of these systems, the sophistication and limitations of the techniques available in modern biology, and the need to use two or more techniques, can lead to persistent illusions of knowledge. Here, in an effort to make better use of the experimental techniques we have at our disposal, I propose a broad classification of techniques into six complementary approaches: perturbation, visualization, substitution, characterization, reconstitution, and simulation. Such a taxonomy might also help increase the reproducibility of inferences and improve peer review.
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Affiliation(s)
- Antony M Jose
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
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14
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Kurz M, Krett AL, Bünemann M. Voltage Dependence of Prostanoid Receptors. Mol Pharmacol 2020; 97:267-277. [DOI: 10.1124/mol.119.118372] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 01/25/2020] [Indexed: 12/16/2022] Open
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15
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Son YE, Park HS. Conserved Roles of MonA in Fungal Growth and Development in Aspergillus Species. MYCOBIOLOGY 2019; 47:457-465. [PMID: 32010467 PMCID: PMC6968623 DOI: 10.1080/12298093.2019.1677380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/24/2019] [Accepted: 09/24/2019] [Indexed: 06/10/2023]
Abstract
MonA is a subunit of a guanine nucleotide exchange factor that is important for vacuole passing and autophagy processes in eukaryotes. In this study, we characterized the function of MonA, an orthologue of Saccharomyces cerevisiae Mon1, in the model fungus Aspergillus nidulans and a toxigenic fungus A. flavus. In A. nidulans, the absence of AnimonA led to decreased fungal growth, reduced asexual reproduction, and defective cleistothecia production. In addition, AnimonA deletion mutants exhibited decreased spore viability, had reduced trehalose contents in conidia, and were sensitive to thermal stress. In A. flavus, deletion of AflmonA caused decreased fungal growth and defective production of asexual spores and sclerotia structures. Moreover, the absence of monA affected vacuole morphology in both species. Taken together, these results indicate that MonA plays conserved roles in controlling fungal growth, development and vacuole morphology in A. nidulans and A. flavus.
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Affiliation(s)
- Ye-Eun Son
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, South Korea
| | - Hee-Soo Park
- School of Food Science and Biotechnology, Institute of Agricultural Science and Technology, Kyungpook National University, Daegu, South Korea
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16
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Mattern A, Machka F, Wickleder MS, Ilyaskina OS, Bünemann M, Diener M, Pouokam E. Potentiation of the activation of cholinergic receptors by multivalent presentation of ligands supported on gold nanoparticles. Org Biomol Chem 2018; 16:6680-6687. [PMID: 30177977 DOI: 10.1039/c8ob01686k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Gold nanoparticles (NP) with a functionalized ligand shell offer the possibility to potentiate the action of agonists at the receptor site by multivalency. In order to find out whether this can be realized for the pharmacologically important class of cholinergic receptors known to be involved in the regulation of most organ functions, carbachol-functionalized gold NPs (Au-MUDA-CCh) with an average diameter of 14 nm were synthesized. As functional read-out, cholinergic agonist-induced anion secretion was measured as increase in short-circuit current (Isc) across rat proximal colon in Ussing chambers. Similarly to the corresponding native agonist acetylcholine, Au-MUDA-CCh induced a concentration-dependent increase in Isc, which represents chloride secretion across the epithelium. This response was inhibited by atropine and hexamethonium indicating the activation of muscarinic and nicotinic receptors by the functionalized NPs. A strong potentiation of ligand-receptor interaction was a key benefit of functionalized NPs over native agonists. This was observed with physiological approaches as measurements of changes in Isc revealed a nearly equivalent response evoked by 1 pM Au-MUDA-CCh and 500 nM native CCh. To better determine this potentiation at the receptor level, pharmacological approaches based on the signaling cascade of ACh-induced activation of muscarinic receptors were used. FRET (Förster Resonance Energy Transfer) measurements performed on HEK293T cells transiently transfected with M3-R, Gαq-YFP, Gβ1-wt and CFP-Gγ2, revealed that both Au-MUDA-CCh and native CCh activated G-proteins with EC50 amounting to 127 ± 0.44 fM and 224 ± 7.12 nM, respectively. Thus, the functionalization of the NPs with CCh yields a potentiation by over 106, a property that could find usage in specific targeting, activation and compensation of pathologically reduced expression of receptors of interest.
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Affiliation(s)
- A Mattern
- Institute of Inorganic Chemistry, University of Cologne, Cologne, Germany
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17
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Onken MD, Makepeace CM, Kaltenbronn KM, Kanai SM, Todd TD, Wang S, Broekelmann TJ, Rao PK, Cooper JA, Blumer KJ. Targeting nucleotide exchange to inhibit constitutively active G protein α subunits in cancer cells. Sci Signal 2018; 11:eaao6852. [PMID: 30181242 PMCID: PMC6279241 DOI: 10.1126/scisignal.aao6852] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Constitutively active G protein α subunits cause cancer, cholera, Sturge-Weber syndrome, and other disorders. Therapeutic intervention by targeted inhibition of constitutively active Gα subunits in these disorders has yet to be achieved. We found that constitutively active Gαq in uveal melanoma (UM) cells was inhibited by the cyclic depsipeptide FR900359 (FR). FR allosterically inhibited guanosine diphosphate-for-guanosine triphosphate (GDP/GTP) exchange to trap constitutively active Gαq in inactive, GDP-bound Gαβγ heterotrimers. Allosteric inhibition of other Gα subunits was achieved by the introduction of an FR-binding site. In UM cells driven by constitutively active Gαq, FR inhibited second messenger signaling, arrested cell proliferation, reinstated melanocytic differentiation, and stimulated apoptosis. In contrast, FR had no effect on BRAF-driven UM cells. FR promoted UM cell differentiation by reactivating polycomb repressive complex 2 (PRC2)-mediated gene silencing, a heretofore unrecognized effector system of constitutively active Gαq in UM. Constitutively active Gαq and PRC2 therefore provide therapeutic targets for UM. The development of FR analogs specific for other Gα subunit subtypes may provide novel therapeutic approaches for diseases driven by constitutively active Gα subunits or multiple G protein-coupled receptors (GPCRs) where targeting a single receptor is ineffective.
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Affiliation(s)
- Michael D Onken
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Carol M Makepeace
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Kevin M Kaltenbronn
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stanley M Kanai
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Tyson D Todd
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Shiqi Wang
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Thomas J Broekelmann
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Prabakar Kumar Rao
- Department of Ophthalmology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - John A Cooper
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Kendall J Blumer
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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18
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Ilyaskina OS, Lemoine H, Bünemann M. Lifetime of muscarinic receptor-G-protein complexes determines coupling efficiency and G-protein subtype selectivity. Proc Natl Acad Sci U S A 2018; 115:5016-5021. [PMID: 29686069 PMCID: PMC5948956 DOI: 10.1073/pnas.1715751115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are essential for the detection of extracellular stimuli by cells and transfer the encoded information via the activation of functionally distinct subsets of heterotrimeric G proteins into intracellular signals. Despite enormous achievements toward understanding GPCR structures, major aspects of the GPCR-G-protein selectivity mechanism remain unresolved. As this can be attributed to the lack of suitable and broadly applicable assays, we set out to develop a quantitative FRET-based assay to study kinetics and affinities of G protein binding to activated GPCRs in membranes of permeabilized cells in the absence of nucleotides. We measured the association and dissociation kinetics of agonist-induced binding of Gi/o, Gq/11, Gs, and G12/13 proteins to muscarinic M1, M2, and M3 receptors in the absence of nucleotides between fluorescently labeled G proteins and receptors expressed in mammalian cells. Our results show a strong quantitative correlation between not the on-rates of G-protein-M3-R interactions but rather the affinities of Gq and Go proteins to M3-Rs, their GPCR-G-protein lifetime and their coupling efficiencies determined in intact cells, suggesting that the G-protein subtype-specific affinity to the activated receptor in the absence of nucleotides is, in fact, a major determinant of the coupling efficiency. Our broadly applicable FRET-based assay represents a fast and reliable method to quantify the intrinsic affinity and relative coupling selectivity of GPCRs toward all G-protein subtypes.
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Affiliation(s)
- Olga S Ilyaskina
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, University of Marburg, 35032 Marburg, Germany
| | - Horst Lemoine
- Department of Laser Medicine, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Moritz Bünemann
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, University of Marburg, 35032 Marburg, Germany;
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19
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Garwain O, Valla K, Scarlata S. Phospholipase Cβ1 regulates proliferation of neuronal cells. FASEB J 2018; 32:2891-2898. [PMID: 29401590 DOI: 10.1096/fj.201701284r] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cells have developed lineage-specific mechanisms to control proliferation and drive morphologic changes upon differentiation. A hallmark of differentiation is the assembly of signaling molecules that transduce extracellular signals, such as the production of the G protein-regulated enzyme phospholipase Cβ (PLCβ), which generates calcium signals from sensory stimuli. We found that in most cancerous cell lines there is positive correlation between PLCβ1 levels and cell proliferation. In cells of neuronal lineage, however, reducing PLCβ1 levels increases the rate of proliferation. Using a combination of biochemical and biophysical methods, we find that, in the G1 phase, a cytosolic population of PLCβ1 associates with cyclin-dependent kinase 16 (CDK16), a neuron-specific enzyme that is activated by cyclin Y to inactivate the antioncogenic protein p27Kip1. Binding of PLCβ1 directly inhibits CDK16 activity and in turn reduces the ability of cells to enter the S phase. Activation of Gαq by carbachol causes movement of PLCβ from the cytosol to the plasma membrane, reducing its association with CDK16. Similarly, the overexpression of activated Gαq moves PLCβ1 to the membrane, reverses G1 arrest, and promotes proliferation, thereby connecting external stimuli with cell proliferation. Our results present a model in which the transient high expression of PLCβ1 that occurs at the onset of differentiation arrests cells in the G1 phase through its association with CDK16 and allows CDK16 to transition to its postmitotic function of neurite outgrowth and trafficking of synaptic vesicles. The novel role of PLCβ1 in neuronal cell proliferation offers a unique interaction that can be manipulated to guide cells into a neuronal phenotype or to develop therapies for neuroblastomas.-Garwain, O., Valla, K., Scarlata, S. Phospholipase Cβ1 regulates proliferation of neuronal cells.
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Affiliation(s)
- Osama Garwain
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts, USA
| | - Kaitlyn Valla
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts, USA
| | - Suzanne Scarlata
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts, USA.,Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
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20
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Yano H, Provasi D, Cai NS, Filizola M, Ferré S, Javitch JA. Development of novel biosensors to study receptor-mediated activation of the G-protein α subunits G s and G olf. J Biol Chem 2017; 292:19989-19998. [PMID: 29042444 PMCID: PMC5723988 DOI: 10.1074/jbc.m117.800698] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 10/02/2017] [Indexed: 11/06/2022] Open
Abstract
Gαs (Gs) and Gαolf (Golf) are highly homologous G-protein α subunits that activate adenylate cyclase, thereby serving as crucial mediators of intracellular signaling. Because of their dramatically different brain expression patterns, we studied similarities and differences between their activation processes with the aim of comparing their receptor coupling mechanisms. We engineered novel luciferase- and Venus-fused Gα constructs that can be used in bioluminescence resonance energy transfer assays. In conjunction with molecular simulations, these novel biosensors were used to determine receptor activation-induced changes in conformation. Relative movements in Gs were consistent with the crystal structure of β2 adrenergic receptor in complex with Gs Conformational changes in Golf activation are shown to be similar to those in Gs Overall the current study reveals general similarities between Gs and Golf activation at the molecular level and provides a novel set of tools to search for Gs- and Golf-specific receptor pharmacology. In view of the wide functional and pharmacological roles of Gs- and Golf-coupled dopamine D1 receptor and adenosine A2A receptor in the brain and other organs, elucidating their differential structure-function relationships with Gs and Golf might provide new approaches for the treatment of a variety of neuropsychiatric disorders. In particular, these novel biosensors can be used to reveal potentially therapeutic dopamine D1 receptor and adenosine A2A receptor ligands with functionally selective properties between Gs and Golf signaling.
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Affiliation(s)
- Hideaki Yano
- National Institute on Drug Abuse, Baltimore, Maryland 21224.
| | - Davide Provasi
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Ning Sheng Cai
- National Institute on Drug Abuse, Baltimore, Maryland 21224
| | - Marta Filizola
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Sergi Ferré
- National Institute on Drug Abuse, Baltimore, Maryland 21224
| | - Jonathan A Javitch
- Departments of Psychiatry and Pharmacology, College of Physicians & Surgeons, Columbia University, New York, New York 10032; Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032.
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21
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Navaratnarajah P, Gershenson A, Ross EM. The binding of activated Gα q to phospholipase C-β exhibits anomalous affinity. J Biol Chem 2017; 292:16787-16801. [PMID: 28842497 DOI: 10.1074/jbc.m117.809673] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 08/22/2017] [Indexed: 01/01/2023] Open
Abstract
Upon activation by the Gq family of Gα subunits, Gβγ subunits, and some Rho family GTPases, phospholipase C-β (PLC-β) isoforms hydrolyze phosphatidylinositol 4,5-bisphosphate to the second messengers inositol 1,4,5-trisphosphate and diacylglycerol. PLC-β isoforms also function as GTPase-activating proteins, potentiating Gq deactivation. To elucidate the mechanism of this mutual regulation, we measured the thermodynamics and kinetics of PLC-β3 binding to Gαq FRET and fluorescence correlation spectroscopy, two physically distinct methods, both yielded Kd values of about 200 nm for PLC-β3-Gαq binding. This Kd is 50-100 times greater than the EC50 for Gαq-mediated PLC-β3 activation and for the Gαq GTPase-activating protein activity of PLC-β. The measured Kd was not altered either by the presence of phospholipid vesicles, phosphatidylinositol 4,5-bisphosphate and Ca2+, or by the identity of the fluorescent labels. FRET-based kinetic measurements were also consistent with a Kd of 200 nm We determined that PLC-β3 hysteresis, whereby PLC-β3 remains active for some time following either Gαq-PLC-β3 dissociation or PLC-β3-potentiated Gαq deactivation, is not sufficient to explain the observed discrepancy between EC50 and Kd These results indicate that the mechanism by which Gαq and PLC-β3 mutually regulate each other is far more complex than a simple, two-state allosteric model and instead is probably kinetically determined.
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Affiliation(s)
- Punya Navaratnarajah
- From the Department of Pharmacology and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 and
| | - Anne Gershenson
- the Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003-9292
| | - Elliott M Ross
- From the Department of Pharmacology and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 and
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22
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Scherer SL, Cain MD, Kanai SM, Kaltenbronn KM, Blumer KJ. Regulation of neurite morphogenesis by interaction between R7 regulator of G protein signaling complexes and G protein subunit Gα 13. J Biol Chem 2017; 292:9906-9918. [PMID: 28432124 DOI: 10.1074/jbc.m116.771923] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 04/19/2017] [Indexed: 02/06/2023] Open
Abstract
The R7 regulator of G protein signaling family (R7-RGS) critically regulates nervous system development and function. Mice lacking all R7-RGS subtypes exhibit diverse neurological phenotypes, and humans bearing mutations in the retinal R7-RGS isoform RGS9-1 have vision deficits. Although each R7-RGS subtype forms heterotrimeric complexes with Gβ5 and R7-RGS-binding protein (R7BP) that regulate G protein-coupled receptor signaling by accelerating deactivation of Gi/o α-subunits, several neurological phenotypes of R7-RGS knock-out mice are not readily explained by dysregulated Gi/o signaling. Accordingly, we used tandem affinity purification and LC-MS/MS to search for novel proteins that interact with R7-RGS heterotrimers in the mouse brain. Among several proteins detected, we focused on Gα13 because it had not been linked to R7-RGS complexes before. Split-luciferase complementation assays indicated that Gα13 in its active or inactive state interacts with R7-RGS heterotrimers containing any R7-RGS isoform. LARG (leukemia-associated Rho guanine nucleotide exchange factor (GEF)), PDZ-RhoGEF, and p115RhoGEF augmented interaction between activated Gα13 and R7-RGS heterotrimers, indicating that these effector RhoGEFs can engage Gα13·R7-RGS complexes. Because Gα13/R7-RGS interaction required R7BP, we analyzed phenotypes of neuronal cell lines expressing RGS7 and Gβ5 with or without R7BP. We found that neurite retraction evoked by Gα12/13-dependent lysophosphatidic acid receptors was augmented in R7BP-expressing cells. R7BP expression blunted neurite formation evoked by serum starvation by signaling mechanisms involving Gα12/13 but not Gαi/o These findings provide the first evidence that R7-RGS heterotrimers interact with Gα13 to augment signaling pathways that regulate neurite morphogenesis. This mechanism expands the diversity of functions whereby R7-RGS complexes regulate critical aspects of nervous system development and function.
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Affiliation(s)
- Stephanie L Scherer
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Matthew D Cain
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Stanley M Kanai
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Kevin M Kaltenbronn
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Kendall J Blumer
- From the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
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23
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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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24
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Abstract
AKAP-Lbc is a Rho-activating guanine nucleotide exchange factor (RhoGEF) important in heart development and pro-fibrotic signaling in cardiomyocytes. Heterotrimeric G proteins of the G12/13 subfamily, comprising Gα12 and Gα13, are well characterized as stimulating a specialized group of RhoGEFs through interaction with their RGS-homology (RH) domain. Despite lacking an RH domain, AKAP-Lbc is bound by Gα12 through an unknown mechanism to activate Rho signaling. We identified a Gα12-binding region near the C-terminus of AKAP-Lbc, closely homologous to a region of p114RhoGEF that we also discovered to interact with Gα12. This binding mechanism is distinct from the well-studied interface between RH-RhoGEFs and G12/13 α subunits, as demonstrated by Gα12 mutants selectively impaired in binding either this AKAP-Lbc/p114RhoGEF region or RH-RhoGEFs. AKAP-Lbc and p114RhoGEF showed high specificity for binding Gα12 in comparison to Gα13, and experiments using chimeric G12/13 α subunits mapped determinants of this selectivity to the N-terminal region of Gα12. In cultured cells expressing constitutively GDP-bound Gα12 or Gα13, the Gα12 construct was more potent in exerting a dominant-negative effect on serum-mediated signaling to p114RhoGEF, demonstrating coupling of these signaling proteins in a cellular pathway. In addition, charge-reversal of conserved residues in AKAP-Lbc and p114RhoGEF disrupted Gα12 binding for both proteins, suggesting they harbor a common structural mechanism for interaction with this α subunit. Our results provide the first evidence of p114RhoGEF as a Gα12 signaling effector, and define a novel region conserved between AKAP-Lbc and p114RhoGEF that allows Gα12 signaling input to these non-RH RhoGEFs.
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25
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Phospholipase Cβ connects G protein signaling with RNA interference. Adv Biol Regul 2015; 61:51-7. [PMID: 26746047 DOI: 10.1016/j.jbior.2015.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 11/19/2015] [Accepted: 11/20/2015] [Indexed: 11/24/2022]
Abstract
Phosphoinositide-specific-phospholipase Cβ (PLCβ) is the main effector of Gαq stimulation which is coupled to receptors that bind acetylcholine, bradykinin, dopamine, angiotensin II as well as other hormones and neurotransmitters. Using a yeast two-hybrid and other approaches, we have recently found that the same region of PLCβ that binds Gαq also interacts with Component 3 Promoter of RNA induced silencing complex (C3PO), which is required for efficient activity of the RNA-induced silencing complex. In purified form, C3PO competes with Gαq for PLCβ binding and at high concentrations can quench PLCβ activation. Additionally, we have found that the binding of PLCβ to C3PO inhibits its nuclease activity leading to reversal of RNA-induced silencing of specific genes. In cells, we found that PLCβ distributes between the plasma membrane where it localizes with Gαq, and in the cytosol where it localizes with C3PO. When cells are actively processing small interfering RNAs the interaction between PLCβ and C3PO gets stronger and leads to changes in the cellular distribution of PLCβ. The magnitude of attenuation is specific for different silencing RNAs. Our studies imply a direct link between calcium responses mediated through Gαq and post-transcriptional gene regulation through PLCβ.
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26
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Myeong J, Kwak M, Jeon JP, Hong C, Jeon JH, So I. Close spatio-association of the transient receptor potential canonical 4 (TRPC4) channel with Gαi in TRPC4 activation process. Am J Physiol Cell Physiol 2015; 308:C879-89. [PMID: 25788576 DOI: 10.1152/ajpcell.00374.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 03/12/2015] [Indexed: 01/03/2023]
Abstract
TPRC channels are Ca(2+)-permeable, nonselective cation channels that are activated by a wide variety of stimuli, including G protein-coupled receptors (GPCRs). TRPC4 is commonly assumed to be activated by Gq/phospholipase C-coupled receptors. However, the other molecular mechanisms by which Gα proteins regulate TRPC4 remain unclear. Here, we found that Gαi2 regulates TRPC4 activation by direct binding. To investigate this mechanism, we used whole patch clamp and fluorescence resonance energy transfer (FRET). We tagged an isoform of mTRPC4 and G protein with CFP and YFP, respectively, and transiently transfected cells with the FRET pair. The FRET efficiency between TRPC4β-CFP and the constitutively active mutant form of Gαi2 was nearly 15% and was greater than that observed with wild-type Gαi2 (nearly 5%). Gβγ and the TRPC4 channel showed a FRET efficiency lower than 6%. In HEK293 cells transfected with the M2 muscarinic receptor, the application of carbachol increased the FRET efficiency between TRPC4β-CFP and Gαi2(WT)-YFP from 4.7 ± 0.4% (n = 7) to 12.6 ± 1.4% (n = 7). We also found that the TRPC4 channel directly interacts with Gαi2, but not with Gαq, when the channel is open. We analyzed the calcium levels in HEK293 cells expressing the channels and Gαi2 or Gαq using the calcium indicator YC6.1 (Yellow Cameleon 6.1). In response to the muscarinic agonist carbachol, M2-, Gαi2-, and TRPC4-expressing cells showed a prolonged Ca(2+) influx compared with cells expressing only M2. Together, these data suggest that Gαi2 activates the TRPC4 channel by direct binding, which then induces Ca(2+) entry.
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Affiliation(s)
- JongYun Myeong
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Misun Kwak
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Jae-Pyo Jeon
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas
| | - Chansik Hong
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Ju-Hong Jeon
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Insuk So
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
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Wolters V, Krasel C, Brockmann J, Bünemann M. Influence of gαq on the dynamics of m3-acetylcholine receptor-g-protein-coupled receptor kinase 2 interaction. Mol Pharmacol 2014; 87:9-17. [PMID: 25316767 DOI: 10.1124/mol.114.094722] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G-protein-coupled receptor kinase 2 (GRK2) is a serine/threonine kinase with an important function in the desensitization of G-protein-coupled receptors. Based on its ability to bind G-protein βγ subunits as well as activated Gαq subunits, it can be considered as an effector for G-proteins. The recruitment of GRK2 to activated receptors is well known to be mediated by Gβγ together with negatively charged membrane phospholipids. In the current study, we address the role of Gαq on the interaction of GRK2 with activated Gq-protein-coupled receptors. Therefore, we established new Förster resonance energy transfer (FRET)-based assays to study the interaction of GRK2 with the M3-acetylcholine (M3-ACh) receptor as well as Gq-protein subunits with high spatiotemporal resolution in single living human embryonic kidney 293T cells. M3-ACh receptor stimulation with 10 µM acetylcholine resulted in distinct changes in FRET, which reflects interaction of the respective proteins. GRK2 mutants with reduced binding affinity toward Gαq [GRK2(D110A)] and Gβγ [GRK2(R587Q)] were used to determine the specific role of Gq-protein-binding by GRK2. Comparison of absolute FRET amplitudes demonstrated that Gαq enhances the extent and stability of the GRK2-M3-ACh receptor interaction, and that not only Gβγ but also Gαq can target GRK2 to the membrane. This reveals an important role of Gαq in efficient recruitment of GRK2 to M3-ACh receptors. Furthermore, interactions between Gαq and GRK2 were associated with a prolongation of the interaction between GRK2 and the M3-ACh receptor and enhanced arrestin recruitment by these receptors, indicating that Gαq influences signaling and desensitization.
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Affiliation(s)
- Valerie Wolters
- Institute for Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany (V.W., C.K., M.B.); and Department of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (J.B.)
| | - Cornelius Krasel
- Institute for Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany (V.W., C.K., M.B.); and Department of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (J.B.)
| | - Jörg Brockmann
- Institute for Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany (V.W., C.K., M.B.); and Department of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (J.B.)
| | - Moritz Bünemann
- Institute for Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Philipps-University Marburg, Marburg, Germany (V.W., C.K., M.B.); and Department of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (J.B.)
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Dynamics of Gαq-protein-p63RhoGEF interaction and its regulation by RGS2. Biochem J 2014; 458:131-40. [PMID: 24299002 DOI: 10.1042/bj20130782] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Some G-protein-coupled receptors regulate biological processes via Gα12/13- or Gαq/11-mediated stimulation of RhoGEFs (guanine-nucleotide-exchange factors). p63RhoGEF is known to be specifically activated by Gαq/11 and mediates a major part of the acute response of vascular smooth muscle cells to angiotensin II treatment. In order to gain information about the dynamics of receptor-mediated activation of p63RhoGEF, we developed a FRET-based assay to study interactions between Gαq-CFP and Venus-p63RhoGEF in single living cells. Upon activation of histaminergic H1 or muscarinic M3 receptors, a robust FRET signal occurred that allowed for the first time the analysis of the kinetics of this interaction in detail. On- and off-set kinetics of Gαq-p63RhoGEF interactions closely resembled the kinetics of Gαq activity. Analysis of the effect of RGS2 (regulator of G-protein signalling 2) on the dynamics of Gαq activity and their interaction with p63RhoGEF showed that RGS2 is able to accelerate both deactivation of Gαq proteins and dissociation of Gαq and p63RhoGEF to a similar extent. Furthermore, we were able to detect activation-dependent FRET between RGS2 and p63RhoGEF and observed a reduced p63RhoGEF-mediated downstream signalling in the presence of RGS2. In summary, these observations support the concept of a functional activation-dependent p63RhoGEF-Gαq-RGS2 complex.
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29
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Sahu S, Philip F, Scarlata S. Hydrolysis rates of different small interfering RNAs (siRNAs) by the RNA silencing promoter complex, C3PO, determines their regulation by phospholipase Cβ. J Biol Chem 2013; 289:5134-44. [PMID: 24338081 DOI: 10.1074/jbc.m113.531467] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C3PO plays a key role in promoting RNA-induced gene silencing. C3PO consists of two subunits of the endonuclease translin-associated factor X (TRAX) and six subunits of the nucleotide-binding protein translin. We have found that TRAX binds strongly to phospholipase Cβ (PLCβ), which transmits G protein signals from many hormones and sensory inputs. The association between PLCβ and TRAX is thought to underlie the ability of PLCβ to reverse gene silencing by small interfering RNAs. However, this reversal only occurs for some genes (e.g. GAPDH and LDH) but not others (e.g. Hsp90 and cyclophilin A). To understand this specificity, we carried out studies using fluorescence-based methods. In cells, we find that PLCβ, TRAX, and their complexes are identically distributed through the cytosol suggesting that selectivity is not due to large scale sequestration of either the free or complexed proteins. Using purified proteins, we find that PLCβ binds ∼5-fold more weakly to translin than to TRAX but ∼2-fold more strongly to C3PO. PLCβ does not alter TRAX-translin assembly to C3PO, and brightness studies suggest one PLCβ binds to one C3PO octamer without a change in the number of TRAX/translin molecules suggesting that PLCβ binds to an external site. Functionally, we find that C3PO hydrolyzes siRNA(GAPDH) at a faster rate than siRNA(Hsp90). However, when PLCβ is bound to C3PO, the hydrolysis rate of siRNA(GAPDH) becomes comparable with siRNA(Hsp90). Our results show that the selectivity of PLCβ toward certain genes lies in the rate at which the RNA is hydrolyzed by C3PO.
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Affiliation(s)
- Shriya Sahu
- From the Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661
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Hultman R, Kumari U, Michel N, Casey PJ. Gαz regulates BDNF-induction of axon growth in cortical neurons. Mol Cell Neurosci 2013; 58:53-61. [PMID: 24321455 DOI: 10.1016/j.mcn.2013.12.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 11/27/2013] [Accepted: 12/03/2013] [Indexed: 01/26/2023] Open
Abstract
The disruption of neurotransmitter and neurotrophic factor signaling in the central nervous system (CNS) is implicated as the root cause of neuropsychiatric disorders, including schizophrenia, epilepsy, chronic pain, and depression. Therefore, identifying the underlying molecular mechanisms by which neurotransmitter and neurotrophic factor signaling regulates neuronal survival or growth may facilitate identification of more effective therapies for these disorders. Previously, our lab found that the heterotrimeric G protein, Gz, mediates crosstalk between G protein-coupled receptors and neurotrophin signaling in the neural cell line PC12. These data, combined with Gαz expression profiles--predominantly in neuronal cells with higher expression levels corresponding to developmental times of target tissue innervation--suggested that Gαz may play an important role in neurotrophin signaling and neuronal development. Here, we provide evidence in cortical neurons, both manipulated ex vivo and those cultured from Gz knockout mice, that Gαz is localized to axonal growth cones and plays a significant role in the development of axons of cortical neurons in the CNS. Our findings indicate that Gαz inhibits BDNF-stimulated axon growth in cortical neurons, establishing an endogenous role for Gαz in regulating neurotrophin signaling in the CNS.
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Affiliation(s)
- Rainbo Hultman
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA; Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, Singapore 169857, Republic of Singapore
| | - Udhaya Kumari
- Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, Singapore 169857, Republic of Singapore
| | - Nadine Michel
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA
| | - Patrick J Casey
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA; Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, Singapore 169857, Republic of Singapore.
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Schwarz J, Bringmann H. Reduced sleep-like quiescence in both hyperactive and hypoactive mutants of the Galphaq Gene egl-30 during lethargus in Caenorhabditis elegans. PLoS One 2013; 8:e75853. [PMID: 24073282 PMCID: PMC3779211 DOI: 10.1371/journal.pone.0075853] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 08/22/2013] [Indexed: 11/30/2022] Open
Abstract
Sleep-like states are characterized by massively reduced behavioral activity. Little is known about genetic control of sleep-like behavior. It is also not clear how general activity levels during wake-like behavior influence activity levels during sleep-like behavior. Mutations that increase wake-like activity are generally believed to also increase activity during sleep-like behavior and mutations that decrease wake-like activity are believed to have decreased activity during sleep-like behavior. We studied sleep-like behavior during lethargus in larvae of Caenorhabditis elegans. We looked through a small set of known mutants with altered activity levels. As expected, mutants with increased activity levels typically showed less sleep-like behavior. Among these hyperactive mutants was a gain-of-function mutant of the conserved heterotrimeric G protein subunit Galphaq gene egl-30. We found, however, that an unusual semidominant hypoactive mutant of egl-30 also had reduced sleep-like behavior. While movement was severely reduced and impaired in the semidominant egl-30 mutant, sleep-like behavior was severely reduced: the semidominant egl-30 mutant lacked prolonged periods of complete immobility, reduced spontaneous neural activity less, and reduced responsiveness to stimulation less. egl-30 is a well-known regulator of behavior. Our results suggest that egl-30 controls not only general activity levels, but also differences between wake-like and sleep-like behavior.
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Affiliation(s)
- Juliane Schwarz
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Henrik Bringmann
- Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- * E-mail:
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Philip F, Sahu S, Caso G, Scarlata S. Role of phospholipase C-β in RNA interference. Adv Biol Regul 2013; 53:319-330. [PMID: 23916604 PMCID: PMC3805765 DOI: 10.1016/j.jbior.2013.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 06/02/2023]
Abstract
Phospholipase C-β (PLCβ) enzymes are activated by G proteins in response to agents such as hormones and neurotransmitters, and have been implicated in leukemias and neurological disorders. PLCβ activity causes an increase in intracellular calcium which ultimately leads to profound changes in the cell. PLCβ localizes to three cellular compartments: the plasma membrane, the cytosol and the nucleus. Under most cell conditions, the majority of PLCβ localizes to the plasma membrane where it interacts with G proteins. In trying to determine the factors that localize PLCβ to the cytosol and nucleus, we have recently identified the binding partner, TRAX. TRAX is a nuclease and part of the machinery involved in RNA interference. This review discusses the interaction between PLCβ and TRAX, and its repercussions in G protein signaling and RNA silencing.
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Affiliation(s)
- Finly Philip
- Department of Physiology & Biophysics, Stony Brook University, Stony Brook, NY 11794-8661, USA
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Chishiki K, Kamakura S, Yuzawa S, Hayase J, Sumimoto H. Ubiquitination of the heterotrimeric G protein α subunits Gαi2 and Gαq is prevented by the guanine nucleotide exchange factor Ric-8A. Biochem Biophys Res Commun 2013; 435:414-9. [DOI: 10.1016/j.bbrc.2013.04.103] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Accepted: 04/30/2013] [Indexed: 01/01/2023]
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Ritchie BJ, Smolski WC, Montgomery ER, Fisher ES, Choi TY, Olson CM, Foster LA, Meigs TE. Determinants at the N- and C-termini of Gα12 required for activation of Rho-mediated signaling. J Mol Signal 2013; 8:3. [PMID: 23531275 PMCID: PMC3636079 DOI: 10.1186/1750-2187-8-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 03/17/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Heterotrimeric guanine nucleotide binding proteins of the G12/13 subfamily, which includes the α-subunits Gα12 and Gα13, stimulate the monomeric G protein RhoA through interaction with a distinct subset of Rho-specific guanine nucleotide exchange factors (RhoGEFs). The structural features that mediate interaction between Gα13 and RhoGEFs have been examined in crystallographic studies of the purified complex, whereas a Gα12:RhoGEF complex has not been reported. Several signaling responses and effector interactions appear unique to Gα12 or Gα13, despite their similarity in amino acid sequence. METHODS To comprehensively examine Gα12 for regions involved in RhoGEF interaction, we screened a panel of Gα12 cassette substitution mutants for binding to leukemia-associated RhoGEF (LARG) and for activation of serum response element mediated transcription. RESULTS We identified several cassette substitutions that disrupt Gα12 binding to LARG and the related p115RhoGEF. These Gα12 mutants also were impaired in activating serum response element mediated signaling, a Rho-dependent response. Most of these mutants matched corresponding regions of Gα13 reported to contact p115RhoGEF, but unexpectedly, several RhoGEF-uncoupling mutations were found within the N- and C-terminal regions of Gα12. Trypsin protection assays revealed several mutants in these regions as retaining conformational activation. In addition, charge substitutions near the Gα12 N-terminus selectively disrupted binding to LARG but not p115RhoGEF. CONCLUSIONS Several structural aspects of the Gα12:RhoGEF interface differ from the reported Gα13:RhoGEF complex, particularly determinants within the C-terminal α5 helix and structurally uncharacterized N-terminus of Gα12. Furthermore, key residues at the Gα12 N-terminus may confer selectivity for LARG as a downstream effector.
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Affiliation(s)
- Benjamin J Ritchie
- Department of Biology, University of North Carolina at Asheville, One University Heights, Asheville, NC 28804, USA.
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Philip F, Guo Y, Aisiku O, Scarlata S. Phospholipase Cβ1 is linked to RNA interference of specific genes through translin-associated factor X. FASEB J 2012; 26:4903-13. [PMID: 22889834 PMCID: PMC3509058 DOI: 10.1096/fj.12-213934] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 08/06/2012] [Indexed: 12/26/2022]
Abstract
Phospholipase Cβ1 (PLCβ1) is a G-protein-regulated enzyme whose activity results in proliferative and mitogenic changes in the cell. We have previously found that in solution PLCβ1 binds to the RNA processing protein translin-associated factor X (TRAX) with nanomolar affinity and that this binding competes with G proteins. Here, we show that endogenous PLCβ1 and TRAX interact in SK-N-SH cells and also in HEK293 cells induced to overexpress PLCβ1. In HEK293 cells, TRAX overexpression ablates Ca(2+) signals generated by G protein-PLCβ1 activation. TRAX plays a key role in down-regulation of proteins by small, interfering RNA, and PLCβ1 overexpression completely reverses the 2- to 4-fold down-regulation of GAPDH by siRNA in HEK293 and HeLa cells as seen by an ∼4-fold recovery in both the transcript and protein levels. Also, down-regulation of endogenous PLCβ1 in HEK293 and HeLa cells allows for an ∼20% increase in siRNA(GAPDH) silencing. While PLCβ1 overexpression results in a 50% reversal of cell death caused by siRNA(LDH), it does not affect cell survival or silencing of other genes (e.g., cyclophilin, Hsp90, translin). PLCβ1 overexpression in HEK293 and HeLa cells causes a 30% reduction in the total amount of small RNAs. LDH and GAPDH are part of a complex that promotes H2B synthesis that allows cells to progress through the S phase. We find that PLCβ1 reverses the cell death and completely rescues H2B levels caused by siRNA knockdown of LDH or GAPDH. Taken together, our study shows a novel role of PLCβ1 in gene regulation through TRAX association.
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Affiliation(s)
- Finly Philip
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Yuanjian Guo
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | | | - Suzanne Scarlata
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
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Rebois RV, Maki K, Meeks JA, Fishman PH, Hébert TE, Northup JK. D2-like dopamine and β-adrenergic receptors form a signaling complex that integrates Gs- and Gi-mediated regulation of adenylyl cyclase. Cell Signal 2012; 24:2051-60. [PMID: 22759790 PMCID: PMC3432756 DOI: 10.1016/j.cellsig.2012.06.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 06/13/2012] [Accepted: 06/22/2012] [Indexed: 12/20/2022]
Abstract
β-Adrenergic receptors (βAR) and D(2)-like dopamine receptors (which include D(2)-, D(3)- and D(4)-dopamine receptors) activate G(s) and G(i), the stimulatory and inhibitory heterotrimeric G proteins, respectively, which in turn regulate the activity of adenylyl cyclase (AC). β(2)-Adrenergic receptors (β(2)AR) and D(4)-dopamine receptors (D(4)DR) co-immunoprecipitated when co-expressed in HEK 293 cells, suggesting the existence of a signaling complex containing both receptors. In order to determine if these receptors are closely associated with each other, and with other components involved in G protein-mediated signal transduction, β(2)AR, D(4)DR, G protein subunits (Gα(i1) and the Gβ(1)γ(2) heterodimer) and AC were tagged so that bioluminescence resonance energy transfer (BRET) could be used to monitor their interactions. All of the tagged proteins retained biological function. For the first time, FlAsH-labeled proteins were used in BRET experiments as fluorescent acceptors for the energy transferred from Renilla luciferase-tagged donor proteins. Our experiments revealed that β(2)AR, D(4)DR, G proteins and AC were closely associated in a functional signaling complex in cellulo. Furthermore, BRET experiments indicated that although activation of G(i) caused a conformational change within the heterotrimeric protein, it did not cause the Gβγ heterodimer to dissociate from the Gα(i1) subunit. Evidence for the presence of a signaling complex in vivo was obtained by purifying βAR from detergent extracts of mouse brain with alprenolol-Sepharose and showing that the precipitate also contained both D(2)-like dopamine receptors and AC.
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Affiliation(s)
- R Victor Rebois
- Laboratory of Cellular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, United States.
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Hoffmann C, Nuber S, Zabel U, Ziegler N, Winkler C, Hein P, Berlot CH, Bünemann M, Lohse MJ. Comparison of the activation kinetics of the M3 acetylcholine receptor and a constitutively active mutant receptor in living cells. Mol Pharmacol 2012; 82:236-45. [PMID: 22564786 PMCID: PMC11037427 DOI: 10.1124/mol.112.077578] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 05/07/2012] [Indexed: 12/26/2022] Open
Abstract
Activation of G-protein-coupled receptors is the first step of the signaling cascade triggered by binding of an agonist. Here we compare the activation kinetics of the G(q)-coupled M(3) acetylcholine receptor (M(3)-AChR) with that of a constitutively active mutant receptor (M(3)-AChR-N514Y) using M(3)-AChR constructs that report receptor activation by changes in the fluorescence resonance energy transfer (FRET) signal. We observed a leftward shift in the concentration-dependent FRET response for acetylcholine and carbachol with M(3)-AChR-N514Y. Consistent with this result, at submaximal agonist concentrations, the activation kinetics of M(3)-AChR-N514Y were significantly faster, whereas at maximal agonist concentrations the kinetics of receptor activation were identical. Receptor deactivation was significantly faster with carbachol than with acetylcholine and was significantly delayed by the N514Y mutation. Receptor-G-protein interaction was measured by FRET between M(3)-AChR-yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP)-Gγ(2). Agonist-induced receptor-G-protein coupling was of a time scale similar to that of receptor activation. As observed for receptor deactivation, receptor-G-protein dissociation was slower for acetylcholine than that for carbachol. Acetylcholine-stimulated increases in receptor-G-protein coupling of M(3)-AChR-N514Y reached only 12% of that of M(3)-AChR and thus cannot be kinetically analyzed. G-protein activation was measured using YFP-tagged Gα(q) and CFP-tagged Gγ(2). Activation of G(q) was significantly slower than receptor activation and indistinguishable for the two agonists. However, G(q) deactivation was significantly prolonged for acetylcholine compared with that for carbachol. Consistent with decreased agonist-stimulated coupling to G(q), agonist-stimulated G(q) activation by M(3)-AChR-N514Y was not detected. Taken together, these results indicate that the N514Y mutation produces constitutive activation of M(3)-AChR by decreasing the rate of receptor deactivation, while having minimal effect on receptor activation.
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Affiliation(s)
- Carsten Hoffmann
- Department of Pharmacology and Toxicology, University of Wuerzburg, Versbacher Strasse 9, Wuerzburg, Germany.
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Boutin A, Allen MD, Neumann S, Gershengorn MC. Persistent signaling by thyrotropin-releasing hormone receptors correlates with G-protein and receptor levels. FASEB J 2012; 26:3473-82. [PMID: 22593547 DOI: 10.1096/fj.12-207860] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
G-protein-coupled receptors with dissociable agonists for thyrotropin, parathyroid hormone, and sphingosine-1-phosphate were found to signal persistently hours after agonist withdrawal. Here we show that mouse thyrotropin-releasing hormone (TRH) receptors, subtypes 2 and 1(TRH-R2 and TRH-R1), can signal persistently in HEK-EM293 cells under appropriate conditions, but TRH-R2 exhibits higher persistent signaling activity. Both receptors couple primarily to Gα(q/11). To gain insight into the mechanism of persistent signaling, we compared proximal steps of inositolmonophosphate (IP1) signaling by TRH-Rs. Persistent signaling was not caused by slower dissociation of TRH from TRH-R2 (t(1/2)=77 ± 8.1 min) compared with TRH-R1 (t(1/2)=82 ± 12 min) and was independent of internalization, as inhibition of internalization did not affect persistent signaling (115% of control), but required continuously activated receptors, as an inverse agonist decreased persistent signaling by 60%. Gα(q/11) knockdown decreased persistent signaling by TRH-R2 by 82%, and overexpression of Gα(q/11) induced persistent signaling in cells expressing TRH-R1. Lastly, persistent signaling was induced in cells expressing high levels of TRH-R1. We suggest that persistent signaling by TRHRs is exhibited when sufficient levels of agonist/receptor/G-protein complexes are established and maintained and that TRH-R2 forms and maintains these complexes more efficiently than TRH-R1.
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Affiliation(s)
- Alisa Boutin
- Laboratory of Endocrinology and Receptor Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-8029, USA
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Lohse MJ, Nuber S, Hoffmann C. Fluorescence/bioluminescence resonance energy transfer techniques to study G-protein-coupled receptor activation and signaling. Pharmacol Rev 2012; 64:299-336. [PMID: 22407612 DOI: 10.1124/pr.110.004309] [Citation(s) in RCA: 251] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fluorescence and bioluminescence resonance energy transfer (FRET and BRET) techniques allow the sensitive monitoring of distances between two labels at the nanometer scale. Depending on the placement of the labels, this permits the analysis of conformational changes within a single protein (for example of a receptor) or the monitoring of protein-protein interactions (for example, between receptors and G-protein subunits). Over the past decade, numerous such techniques have been developed to monitor the activation and signaling of G-protein-coupled receptors (GPCRs) in both the purified, reconstituted state and in intact cells. These techniques span the entire spectrum from ligand binding to the receptors down to intracellular second messengers. They allow the determination and the visualization of signaling processes with high temporal and spatial resolution. With these techniques, it has been demonstrated that GPCR signals may show spatial and temporal patterning. In particular, evidence has been provided for spatial compartmentalization of GPCRs and their signals in intact cells and for distinct physiological consequences of such spatial patterning. We review here the FRET and BRET technologies that have been developed for G-protein-coupled receptors and their signaling proteins (G-proteins, effectors) and the concepts that result from such experiments.
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Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, Versbacher Str. 9, 97078 Würzburg, Germany.
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Abstract
The classical view of heterotrimeric G protein signaling places G -proteins at the cytoplasmic surface of the cell's plasma membrane where they are activated by an appropriate G protein-coupled receptor. Once activated, the GTP-bound Gα and the free Gβγ are able to regulate plasma membrane-localized effectors, such as adenylyl cyclase, phospholipase C-β, RhoGEFs and ion channels. Hydrolysis of GTP by the Gα subunit returns the G protein to the inactive Gαβγ heterotrimer. Although all of these events in the G protein cycle can be restricted to the cytoplasmic surface of the plasma membrane, G protein localization is dynamic. Thus, it has become increasingly clear that G proteins are able to move to diverse subcellular locations where they perform non-canonical signaling functions. This chapter will highlight our current understanding of trafficking pathways that target newly synthesized G proteins to the plasma membrane, activation-induced and reversible translocation of G proteins from the plasma membrane to intracellular locations, and constitutive trafficking of G proteins.
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Protein palmitoylation and subcellular trafficking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2981-94. [DOI: 10.1016/j.bbamem.2011.07.009] [Citation(s) in RCA: 257] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 07/06/2011] [Accepted: 07/12/2011] [Indexed: 02/07/2023]
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Gabay M, Pinter ME, Wright FA, Chan P, Murphy AJ, Valenzuela DM, Yancopoulos GD, Tall GG. Ric-8 proteins are molecular chaperones that direct nascent G protein α subunit membrane association. Sci Signal 2011; 4:ra79. [PMID: 22114146 DOI: 10.1126/scisignal.2002223] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ric-8A (resistance to inhibitors of cholinesterase 8A) and Ric-8B are guanine nucleotide exchange factors that enhance different heterotrimeric guanine nucleotide-binding protein (G protein) signaling pathways by unknown mechanisms. Because transgenic disruption of Ric-8A or Ric-8B in mice caused early embryonic lethality, we derived viable Ric-8A- or Ric-8B-deleted embryonic stem (ES) cell lines from blastocysts of these mice. We observed pleiotropic G protein signaling defects in Ric-8A(-/-) ES cells, which resulted from reduced steady-state amounts of Gα(i), Gα(q), and Gα(13) proteins to <5% of those of wild-type cells. The amounts of Gα(s) and total Gβ protein were partially reduced in Ric-8A(-/-) cells compared to those in wild-type cells, and only the amount of Gα(s) was reduced substantially in Ric-8B(-/-) cells. The abundances of mRNAs encoding the G protein α subunits were largely unchanged by loss of Ric-8A or Ric-8B. The plasma membrane residence of G proteins persisted in the absence of Ric-8 but was markedly reduced compared to that in wild-type cells. Endogenous Gα(i) and Gα(q) were efficiently translated in Ric-8A(-/-) cells but integrated into endomembranes poorly; however, the reduced amounts of G protein α subunits that reached the membrane still bound to nascent Gβγ. Finally, Gα(i), Gα(q), and Gβ(1) proteins exhibited accelerated rates of degradation in Ric-8A(-/-) cells compared to those in wild-type cells. Together, these data suggest that Ric-8 proteins are molecular chaperones required for the initial association of nascent Gα subunits with cellular membranes.
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Affiliation(s)
- Meital Gabay
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
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43
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Quantitative co-expression of proteins at the single cell level--application to a multimeric FRET sensor. PLoS One 2011; 6:e27321. [PMID: 22114669 PMCID: PMC3219669 DOI: 10.1371/journal.pone.0027321] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 10/13/2011] [Indexed: 01/05/2023] Open
Abstract
Background Co-expression of proteins is generally achieved by introducing two (or more) independent plasmids into cells, each driving the expression of a different protein of interest. However, the relative expression levels may vary strongly between individual cells and cannot be controlled. Ideally, co-expression occurs at a defined ratio, which is constant among cells. This feature is of particular importance for quantitative single cell studies, especially those employing bimolecular Förster Resonance Energy Transfer (FRET) sensors. Methodology/Principal Findings Four co-expression strategies based on co-transfection, a dual promotor plasmid, an internal ribosome entry site (IRES) and a viral 2A peptide were selected. Co-expression of two spectrally separable fluorescent proteins in single living cells was quantified. It is demonstrated that the 2A peptide strategy can be used for robust equimolar co-expression, while the IRES sequence allows expression of two proteins at a ratio of approximately 3:1. Combined 2A and IRES elements were used for the construction of a single plasmid that drives expression of three individual proteins, which generates a FRET sensor for measuring heterotrimeric G-protein activation. The plasmid drives co-expression of donor and acceptor tagged subunits, with reduced heterogeneity, and can be used to measure G-protein activation in single living cells. Conclusions/Significance Quantitative co-expression of two or more proteins can be achieved with little cell-to-cell variability. This finding enables reliable co-expression of donor and acceptor tagged proteins for FRET studies, which is of particular importance for the development of novel bimolecular sensors that can be expressed from single plasmid.
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44
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Vellano CP, Maher EM, Hepler JR, Blumer JB. G protein-coupled receptors and resistance to inhibitors of cholinesterase-8A (Ric-8A) both regulate the regulator of g protein signaling 14 RGS14·Gαi1 complex in live cells. J Biol Chem 2011; 286:38659-38669. [PMID: 21880739 PMCID: PMC3207400 DOI: 10.1074/jbc.m111.274928] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 08/19/2011] [Indexed: 01/10/2023] Open
Abstract
Regulator of G protein Signaling 14 (RGS14) is a multifunctional scaffolding protein that integrates both conventional and unconventional G protein signaling pathways. Like other RGS (regulator of G protein signaling) proteins, RGS14 acts as a GTPase accelerating protein to terminate conventional Gα(i/o) signaling. However, unlike other RGS proteins, RGS14 also contains a G protein regulatory/GoLoco motif that specifically binds Gα(i1/3)-GDP in cells and in vitro. The non-receptor guanine nucleotide exchange factor Ric-8A can bind and act on the RGS14·Gα(i1)-GDP complex to play a role in unconventional G protein signaling independent of G protein-coupled receptors (GPCRs). Here we demonstrate that RGS14 forms a Gα(i/o)-dependent complex with a G(i)-linked GPCR and that this complex is regulated by receptor agonist and Ric-8A (resistance to inhibitors of cholinesterase-8A). Using live cell bioluminescence resonance energy transfer, we show that RGS14 functionally associates with the α(2A)-adrenergic receptor (α(2A)-AR) in a Gα(i/o)-dependent manner. This interaction is markedly disrupted after receptor stimulation by the specific agonist UK14304, suggesting complex dissociation or rearrangement. Agonist-mediated dissociation of the RGS14·α(2A)-AR complex occurs in the presence of Gα(i/o) but not Gα(s) or Gα(q). Unexpectedly, RGS14 does not dissociate from Gα(i1) in the presence of stimulated α(2A)-AR, suggesting preservation of RGS14·Gα(i1) complexes after receptor activation. However, Ric-8A facilitates dissociation of both the RGS14·Gα(i1) complex and the Gα(i1)-dependent RGS14·α(2A)-AR complex after receptor activation. Together, these findings indicate that RGS14 can form complexes with GPCRs in cells that are dependent on Gα(i/o) and that these RGS14·Gα(i1)·GPCR complexes may be substrates for other signaling partners such as Ric-8A.
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Affiliation(s)
- Christopher P Vellano
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322.
| | - Ellen M Maher
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, South Carolina 29425
| | - John R Hepler
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Joe B Blumer
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, South Carolina 29425.
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Qin K, Dong C, Wu G, Lambert NA. Inactive-state preassembly of G(q)-coupled receptors and G(q) heterotrimers. Nat Chem Biol 2011; 7:740-7. [PMID: 21873996 PMCID: PMC3177959 DOI: 10.1038/nchembio.642] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 06/29/2011] [Indexed: 12/29/2022]
Abstract
G protein-coupled receptors (GPCRs) transmit signals by forming active-state complexes with heterotrimeric G proteins. It has been suggested that some GPCRs also assemble with G proteins before ligand-induced activation and that inactive-state preassembly facilitates rapid and specific G protein activation. However, no mechanism of preassembly has been described, and no functional consequences of preassembly have been demonstrated. Here we show that M(3) muscarinic acetylcholine receptors (M3R) form inactive-state complexes with G(q) heterotrimers in intact cells. The M3R C terminus is sufficient, and a six-amino-acid polybasic sequence distal to helix 8 ((565)KKKRRK(570)) is necessary for preassembly with G(q). Replacing this sequence with six alanine residues prevents preassembly, slows the rate of G(q) activation and decreases steady-state agonist sensitivity. That other G(q)-coupled receptors possess similar polybasic regions and also preassemble with G(q) suggests that these GPCRs may use a common preassembly mechanism to facilitate activation of G(q) heterotrimers.
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Affiliation(s)
- Kou Qin
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, USA
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46
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Aittaleb M, Nishimura A, Linder ME, Tesmer JJG. Plasma membrane association of p63 Rho guanine nucleotide exchange factor (p63RhoGEF) is mediated by palmitoylation and is required for basal activity in cells. J Biol Chem 2011; 286:34448-56. [PMID: 21832057 DOI: 10.1074/jbc.m111.273342] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of G protein-coupled receptors at the cell surface leads to the activation or inhibition of intracellular effector enzymes, which include various Rho guanine nucleotide exchange factors (RhoGEFs). RhoGEFs activate small molecular weight GTPases at the plasma membrane (PM). Many of the known G protein-coupled receptor-regulated RhoGEFs are found in the cytoplasm of unstimulated cells, and PM recruitment is a critical aspect of their regulation. In contrast, p63RhoGEF, a Gα(q)-regulated RhoGEF, appears to be constitutively localized to the PM. The objective of this study was to determine the molecular basis for the localization of p63RhoGEF and the impact of its subcellular localization on its regulation by Gα(q). Herein, we show that the pleckstrin homology domain of p63RhoGEF is not involved in its PM targeting. Instead, a conserved string of cysteines (Cys-23/25/26) at the N terminus of the enzyme is palmitoylated and required for membrane localization and full basal activity in cells. Conversion of these residues to serine relocates p63RhoGEF from the PM to the cytoplasm, diminishes its basal activity, and eliminates palmitoylation. The activity of palmitoylation-deficient p63RhoGEF can be rescued by targeting to the PM by fusion with tandem phospholipase C-δ1 pleckstrin homology domains or by co-expression with wild-type Gα(q) but not with palmitoylation-deficient Gα(q). Our data suggest that p63RhoGEF is regulated chiefly through allosteric control by Gα(q), as opposed to other known Gα-regulated RhoGEFs, which are instead sequestered in the cytoplasm, perhaps because of their high basal activity.
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Affiliation(s)
- Mohamed Aittaleb
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109-2216, USA
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47
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Adjobo-Hermans MJW, Goedhart J, van Weeren L, Nijmeijer S, Manders EMM, Offermanns S, Gadella TWJ. Real-time visualization of heterotrimeric G protein Gq activation in living cells. BMC Biol 2011; 9:32. [PMID: 21619590 PMCID: PMC3129320 DOI: 10.1186/1741-7007-9-32] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Accepted: 05/27/2011] [Indexed: 12/28/2022] Open
Abstract
Background Gq is a heterotrimeric G protein that plays an important role in numerous physiological processes. To delineate the molecular mechanisms and kinetics of signalling through this protein, its activation should be measurable in single living cells. Recently, fluorescence resonance energy transfer (FRET) sensors have been developed for this purpose. Results In this paper, we describe the development of an improved FRET-based Gq activity sensor that consists of a yellow fluorescent protein (YFP)-tagged Gγ2 subunit and a Gαq subunit with an inserted monomeric Turquoise (mTurquoise), the best cyan fluorescent protein variant currently available. This sensor enabled us to determine, for the first time, the kon (2/s) of Gq activation. In addition, we found that the guanine nucleotide exchange factor p63RhoGEF has a profound effect on the number of Gq proteins that become active upon stimulation of endogenous histamine H1 receptors. The sensor was also used to measure ligand-independent activation of the histamine H1 receptor (H1R) upon addition of a hypotonic stimulus. Conclusions Our observations reveal that the application of a truncated mTurquoise as donor and a YFP-tagged Gγ2 as acceptor in FRET-based Gq activity sensors substantially improves their dynamic range. This optimization enables the real-time single cell quantification of Gq signalling dynamics, the influence of accessory proteins and allows future drug screening applications by virtue of its sensitivity.
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Affiliation(s)
- Merel J W Adjobo-Hermans
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
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Boutin A, Allen MD, Geras-Raaka E, Huang W, Neumann S, Gershengorn MC. Thyrotropin receptor stimulates internalization-independent persistent phosphoinositide signaling. Mol Pharmacol 2011; 80:240-6. [PMID: 21525174 DOI: 10.1124/mol.111.072157] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The thyrotropin [thyroid-stimulating hormone (TSH)] receptor (TSHR) is known to acutely and persistently stimulate cAMP signaling and at higher TSH concentrations to acutely stimulate phosphoinositide signaling. We measured persistent signaling by stimulating TSHR-expressing human embryonic kidney-EM293 cells with TSH and measuring cAMP or inositol monophosphate (IP1) production, a measure of phosphoinositide signaling, 60 min or longer after TSH removal. In contrast to persistent cAMP production, persistent IP1 production increased progressively when TSH exposure was increased from 1 to 30 min, whereas the rates of decay of persistent signaling were similar. A small-molecule agonist and a thyroid-stimulating antibody also caused persistent IP1 and cAMP signaling. A small-molecule inverse agonist and a neutral antagonist inhibited TSH-stimulated persistent IP1 production, whereas the inverse agonist but not the neutral antagonist inhibited persistent cAMP production. As with persistent cAMP production, persistent IP1 production was not affected when TSHR internalization was inhibited or enhanced. Moreover, Alexa546-TSH-activated TSHR internalization was not accompanied by Gα(q) coupling protein internalization. Thus, transient exposure to high concentrations of TSH causes persistent phosphoinositide and cAMP signaling that is not dependent on internalization. To our knowledge, this is the first demonstration of persistent activation by any G protein-coupled receptor (GPCR) via the Gα(q) pathway and of two G protein-mediated pathways by any GPCR.
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Affiliation(s)
- Alisa Boutin
- NIDDK, CEB, National Institutes of Health, 50 South Drive, Bethesda, MD 20892-8029, USA.
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Golebiewska U, Johnston JM, Devi L, Filizola M, Scarlata S. Differential response to morphine of the oligomeric state of μ-opioid in the presence of δ-opioid receptors. Biochemistry 2011; 50:2829-37. [PMID: 21361347 DOI: 10.1021/bi101701x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Prolonged morphine treatment induces extensive desensitization of the μ-opioid receptor (μOR) which is the G-protein-coupled receptor that primarily mediates the cellular response to morphine. To date, the molecular mechanism underlying this process is unknown. Here, we have used live cell fluorescence imaging to investigate whether prolonged morphine treatment affects the physical environment of μOR, or its coupling with G-proteins, in two neuronal cell lines. We find that chronic morphine treatment does not change the amount of enhanced yellow fluorescence protein (eYFP)-tagged μOR on the plasma membrane, and only slightly decreases its association with G-protein subunits. Additionally, morphine treatment does not have a detectable effect on the diffusion coefficient of eYFP-μOR. However, in the presence of another family member, the δ-opioid receptor (δOR), prolonged morphine exposure results in a significant increase in the diffusion rate of μOR. Number and brightness measurements suggest that μOR exists primarily as a dimer that will oligomerize with δOR into tetramers, and morphine promotes the dissociation of these tetramers. To provide a plausible structural context to these data, we used homology modeling techniques to generate putative configurations of μOR-δOR tetramers. Overall, our studies provide a possible rationale for morphine sensitivity.
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Affiliation(s)
- Urszula Golebiewska
- Department of Biological Sciences and Geology, Queensboro Community College, Bayside, New York 11364-1497, United States
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50
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Aisiku O, Dowal L, Scarlata S. Protein kinase C phosphorylation of PLCβ1 regulates its cellular localization. Arch Biochem Biophys 2011; 509:186-90. [PMID: 21338571 DOI: 10.1016/j.abb.2011.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 10/18/2022]
Abstract
Activation of phospholipase Cβ (PLCβ) by G proteins leads to a chain of events that result in an increase in intracellular calcium and activation of protein kinase C (PKC). It has been found that PKC phosphorylates PLCβ1 on S887 in vitro without affecting its enzymatic activity or its ability to be activated by Gα(q) proteins. To understand whether S887 phosphorylation affects the enzyme's activity in cells, we constructed two mutants that mimic the wild type and PKC-phosphorylated enzymes (S887A and S887D). We find that these constructs bind similarly to Gα(q) in vitro. When expressed in HEK293 cells, both mutants associate identically to Gα(q) in both the basal and stimulated states. Both mutants diffuse with similar rates and also interact identically with another known binding partner, translin-associated factor X (TRAX), which associates with PLCβ1 in the cytosol and nucleus. However, the two mutants localize differently in the cell. We find that S887A has a much higher nuclear localization than its S887D counterpart both in HEK293 cells and PC12 cells. Our studies suggest that PKC phosphorylation regulates the level of PLCβ1 cytosolic and nuclear activity by regulating its cellular compartmentalization.
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Affiliation(s)
- Omozuanvbo Aisiku
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794-8661, USA
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