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Bettegazzi B, Bellani S, Cattaneo S, Codazzi F, Grohovaz F, Zacchetti D. Gα13 Contributes to LPS-Induced Morphological Alterations and Affects Migration of Microglia. Mol Neurobiol 2021; 58:6397-6414. [PMID: 34529232 DOI: 10.1007/s12035-021-02553-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 08/26/2021] [Indexed: 11/24/2022]
Abstract
Microglia are the resident immune cells of the CNS that are activated in response to a variety of stimuli. This phenotypical change is aimed to maintain the local homeostasis, also by containing the insults and repair the damages. All these processes are tightly regulated and coordinated and a failure in restoring homeostasis by microglia can result in the development of neuroinflammation that can facilitate the progression of pathological conditions. Indeed, chronic microglia activation is commonly recognized as a hallmark of many neurological disorders, especially at an early stage. Many complex pathways, including cytoskeletal remodeling, are involved in the control of the microglial phenotypical and morphological changes that occur during activation. In this work, we focused on the small GTPase Gα13 and its role at the crossroad between RhoA and Rac1 signaling when microglia is exposed to pro-inflammatory stimulation. We propose the direct involvement of Gα13 in the cytoskeletal rearrangements mediated by FAK, LIMK/cofilin, and Rac1 during microglia activation. In fact, we show that Gα13 knockdown significantly inhibited LPS-induced microglial cell activation, in terms of both changes in morphology and migration, through the modulation of FAK and one of its downstream effectors, Rac1. In conclusion, we propose Gα13 as a critical factor in the regulation of morphological and functional properties of microglia during activation, which might become a target of intervention for the control of microglia inflammation.
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Affiliation(s)
- Barbara Bettegazzi
- IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milan, Italy. .,Vita-Salute San Raffaele University, via Olgettina 58, 20132, Milan, Italy.
| | - Serena Bellani
- IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milan, Italy
| | - Stefano Cattaneo
- IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milan, Italy.,Vita-Salute San Raffaele University, via Olgettina 58, 20132, Milan, Italy
| | - Franca Codazzi
- IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milan, Italy.,Vita-Salute San Raffaele University, via Olgettina 58, 20132, Milan, Italy
| | - Fabio Grohovaz
- IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milan, Italy.,Vita-Salute San Raffaele University, via Olgettina 58, 20132, Milan, Italy
| | - Daniele Zacchetti
- IRCCS San Raffaele Scientific Institute, via Olgettina 60, 20132, Milan, Italy.
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2
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Ranieri M, Venneri M, Pellegrino T, Centrone M, Di Mise A, Cotecchia S, Tamma G, Valenti G. The Vasopressin Receptor 2 Mutant R137L Linked to the Nephrogenic Syndrome of Inappropriate Antidiuresis (NSIAD) Signals through an Alternative Pathway that Increases AQP2 Membrane Targeting Independently of S256 Phosphorylation. Cells 2020; 9:cells9061354. [PMID: 32486031 PMCID: PMC7349359 DOI: 10.3390/cells9061354] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 05/26/2020] [Accepted: 05/27/2020] [Indexed: 12/18/2022] Open
Abstract
NSIAD is a rare X-linked condition, caused by activating mutations in the AVPR2 gene coding for the vasopressin V2 receptor (V2R) associated with hyponatremia, despite undetectable plasma vasopressin levels. We have recently provided in vitro evidence that, compared to V2R-wt, expression of activating V2R mutations R137L, R137C and F229V cause a constitutive redistribution of the AQP2 water channel to the plasma membrane, higher basal water permeability and significantly higher basal levels of p256-AQP2 in the F229V mutant but not in R137L or R137C. In this study, V2R mutations were expressed in collecting duct principal cells and the associated signalling was dissected. V2R-R137L and R137C mutants had significantly higher basal pT269-AQP2 levels -independently of S256 and PKA-which were reduced to control by treatment with Rho kinase (ROCK) inhibitor. Interestingly, ROCK activity was found significantly higher in V2R-R137L along with activation of the Gα12/13–Rho–ROCK pathway. Of note, inhibition of ROCK reduced the basal elevated osmotic water permeability to control. To conclude, our data demonstrate for the first time that the gain-of-function mutation of the V2R, R137L causing NSIAD, signals through an alternative PKA-independent pathway that increases AQP2 membrane targeting through ROCK-induced phosphorylation at S/T269 independently of S256 of AQP2.
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Affiliation(s)
- Marianna Ranieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
| | - Maria Venneri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
| | - Tommaso Pellegrino
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
| | - Mariangela Centrone
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
| | - Annarita Di Mise
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
| | - Susanna Cotecchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
| | - Grazia Tamma
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
- Istituto Nazionale di Biostrutture e Biosistemi, 00136 Roma, Italy
| | - Giovanna Valenti
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70125 Bari, Italy; (M.R.); (M.V.); (T.P.); (M.C.); (A.D.M.); (S.C.); (G.T.)
- Istituto Nazionale di Biostrutture e Biosistemi, 00136 Roma, Italy
- Center of Excellence in Comparative Genomics (CEGBA), University of Bari, 70125 Bari, Italy
- Correspondence: ; Tel.: +39-080-5443444
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3
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Stecky RC, Quick CR, Fleming TL, Mull ML, Vinson VK, Whitley MS, Dover EN, Meigs TE. Divergent C-terminal motifs in Gα12 and Gα13 provide distinct mechanisms of effector binding and SRF activation. Cell Signal 2020; 72:109653. [PMID: 32330601 DOI: 10.1016/j.cellsig.2020.109653] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 04/19/2020] [Accepted: 04/19/2020] [Indexed: 11/18/2022]
Abstract
The G12/13 subfamily of heterotrimeric guanine nucleotide binding proteins comprises the α subunits Gα12 and Gα13, which transduce signals for cell growth, cytoskeletal rearrangements, and oncogenic transformation. In an increasing range of cancers, overexpressed Gα12 or Gα13 are implicated in aberrant cell proliferation and/or metastatic invasion. Although Gα12 and Gα13 bind non-redundant sets of effector proteins and participate in unique signalling pathways, the structural features responsible for functional differences between these α subunits are largely unknown. Invertebrates encode a single G12/13 homolog that participates in cytoskeletal changes yet appears to lack signalling to SRF (serum response factor), a transcriptional activator stimulated by mammalian Gα12 and Gα13 to promote growth and tumorigenesis. Our previous studies identified an evolutionarily divergent region in Gα12 for which replacement by homologous sequence from Drosophila melanogaster abolished SRF signalling, whereas the same invertebrate substitution was fully tolerated in Gα13 [Montgomery et al. (2014) Mol. Pharmacol. 85: 586]. These findings prompted our current approach of evolution-guided mutagenesis to identify fine structural features of Gα12 and Gα13 that underlie their respective SRF activation mechanisms. Our results identified two motifs flanking the α4 helix that play a key role in Gα12 signalling to SRF. We found the region encompassing these motifs to provide an interacting surface for multiple Gα12-specific target proteins that fail to bind Gα13. Adjacent to this divergent region, a highly-conserved domain was vital for SRF activation by both Gα12 and Gα13. However, dissection of this domain using invertebrate substitutions revealed different signalling mechanisms in these α subunits and identified Gα13-specific determinants of binding Rho-specific guanine nucleotide exchange factors. Furthermore, invertebrate substitutions in the C-terminal, α5 helical region were selectively disruptive to Gα12 signalling. Taken together, our results identify key structural features near the C-terminus that evolved after the divergence of Gα12 and Gα13, and should aid the development of agents to selectively manipulate signalling by individual α subunits of the G12/13 subfamily.
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Affiliation(s)
- Rebecca C Stecky
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America
| | - Courtney R Quick
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America
| | - Todd L Fleming
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America
| | - Makenzy L Mull
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America
| | - Vanessa K Vinson
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America
| | - Megan S Whitley
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America
| | - E Nicole Dover
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America
| | - Thomas E Meigs
- Department of Biology, University of North Carolina Asheville, One University Heights, Asheville, NC 28804, United States of America.
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Domeier PP, Chodisetti SB, Schell SL, Kawasawa YI, Fasnacht MJ, Soni C, Rahman ZSM. B-Cell-Intrinsic Type 1 Interferon Signaling Is Crucial for Loss of Tolerance and the Development of Autoreactive B Cells. Cell Rep 2019; 24:406-418. [PMID: 29996101 PMCID: PMC6089613 DOI: 10.1016/j.celrep.2018.06.046] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 04/09/2018] [Accepted: 06/11/2018] [Indexed: 01/03/2023] Open
Abstract
Type 1 interferon (T1IFN) signaling promotes inflammation and lupus pathology, but its role in autoreactive B cell development in the antibody-forming cell (AFC) and germinal center (GC) pathways is unclear. Using a lupus model that allows for focused study of the AFC and GC responses, we show that T1IFN signaling is crucial for autoreactive B cell development in the AFC and GC pathways. Through bone marrow chimeras, DNA-reactive B cell transfer, and GC-specific Cre mice, we confirm that IFNαR signaling in B cells promotes autoreactive B cell development into both pathways. Transcriptomic analysis reveals gene expression alterations in multiple signaling pathways in non-GC and GC B cells in the absence of IFNαR. Finally, we find that T1IFN signaling promotes autoreactive B cell development in the AFC and GC pathways by regulating BCR signaling. These data suggest value for anti-IFNαR therapy in individuals with elevated T1IFN activity before clinical disease onset. The B-cell-intrinsic mechanisms of type 1 interferon (T1IFN) signaling in regulating B cell tolerance is unclear. Domeier et al. show that T1IFN signaling in B cells causes loss of B cell tolerance, promoting autoreactive B cell development into the antibody-forming cell and germinal center pathways by regulating BCR signaling.
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Affiliation(s)
- Phillip P Domeier
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-0850, USA
| | - Sathi Babu Chodisetti
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-0850, USA
| | - Stephanie L Schell
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-0850, USA
| | - Yuka Imamura Kawasawa
- Departments of Pharmacology and Biochemistry and Molecular Biology, Institute for Personalized Medicine, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-0850, USA
| | - Melinda J Fasnacht
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-0850, USA
| | - Chetna Soni
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-0850, USA
| | - Ziaur S M Rahman
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-0850, USA.
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5
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Toro-Tapia G, Villaseca S, Beyer A, Roycroft A, Marcellini S, Mayor R, Torrejón M. The Ric-8A/Gα13/FAK signalling cascade controls focal adhesion formation during neural crest cell migration in Xenopus. Development 2018; 145:dev.164269. [PMID: 30297374 DOI: 10.1242/dev.164269] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 09/23/2018] [Indexed: 12/22/2022]
Abstract
Ric-8A is a pleiotropic guanine nucleotide exchange factor involved in the activation of various heterotrimeric G-protein pathways during adulthood and early development. Here, we sought to determine the downstream effectors of Ric-8A during the migration of the vertebrate cranial neural crest (NC) cells. We show that the Gα13 knockdown phenocopies the Ric-8A morphant condition, causing actin cytoskeleton alteration, protrusion instability, and a strong reduction in the number and dynamics of focal adhesions. In addition, the overexpression of Gα13 is sufficient to rescue Ric-8A-depleted cells. Ric-8A and Gα13 physically interact and colocalize in protrusions of the cells leading edge. The focal adhesion kinase FAK colocalizes and interacts with the endogenous Gα13, and a constitutively active form of Src efficiently rescues the Gα13 morphant phenotype in NC cells. We propose that Ric-8A-mediated Gα13 signalling is required for proper cranial NC cell migration by regulating focal adhesion dynamics and protrusion formation.
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Affiliation(s)
- Gabriela Toro-Tapia
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción 4030000, Chile
| | - Soraya Villaseca
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción 4030000, Chile
| | - Andrea Beyer
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción 4030000, Chile
| | - Alice Roycroft
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Sylvain Marcellini
- Departamento de Biología Cellular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción 4030000, Chile
| | - Roberto Mayor
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Marcela Torrejón
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción 4030000, Chile
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6
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G-Protein Gα 13 Functions with Abl Kinase to Regulate Actin Cytoskeletal Reorganization. J Mol Biol 2017; 429:3836-3849. [PMID: 29079481 DOI: 10.1016/j.jmb.2017.10.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/17/2017] [Accepted: 10/18/2017] [Indexed: 11/23/2022]
Abstract
Heterotrimeric G-proteins are essential cellular signal transducers. One of the G-proteins, Gα13, is critical for actin cytoskeletal reorganization, cell migration, cell proliferation, and apoptosis. Previously, we have shown that Gα13 is essential for both G-protein-coupled receptor and receptor tyrosine kinase-induced actin cytoskeletal reorganization such as dynamic dorsal ruffle turnover and cell migration. However, the mechanism by which Gα13 signals to actin cytoskeletal reorganization is not completely understood. Here we show that Gα13 directly interacts with Abl tyrosine kinase, which is a critical regulator of actin cytoskeleton. This interaction is critical for Gα13-induced dorsal ruffle turnover, endothelial cell remodeling, and cell migration. Our data uncover a new molecular signaling pathway by which Gα13 controls actin cytoskeletal reorganization.
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7
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Russo A, Ranieri M, Di Mise A, Dossena S, Pellegrino T, Furia E, Nofziger C, Debellis L, Paulmichl M, Valenti G, Tamma G. Interleukin-13 increases pendrin abundance to the cell surface in bronchial NCI-H292 cells via Rho/actin signaling. Pflugers Arch 2017; 469:1163-1176. [PMID: 28378089 DOI: 10.1007/s00424-017-1970-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 03/20/2017] [Accepted: 03/22/2017] [Indexed: 11/28/2022]
Abstract
Interleukin-13 (IL13) is a major player in the development of airway hyperresponsiveness in several respiratory disorders. Emerging data suggest that an increased expression of pendrin in airway epithelia is associated with elevated airway hyperreactivity in asthma. Here, we investigate the effect of IL13 on pendrin localization and function using bronchiolar NCI-H292 cells. The data obtained revealed that IL13 increases the cell surface expression of pendrin. This effect was paralleled by a significant increase in the intracellular pH, possibly via indirect stimulation of NHE. IL13 effect on pendrin localization and intracellular pH was reversed by theophylline, a bronchodilator compound used to treat asthma. IL13 upregulated RhoA activity, a crucial protein controlling actin dynamics, via G-alpha-13. Specifically, IL13 stabilized actin cytoskeleton and promoted co-localization and a direct molecular interaction between pendrin and F-actin in the plasma membrane region. These effects were reversed following exposure of cells to theophylline. Selective inhibition of Rho kinase, a downstream effector of Rho, reduced the IL13-dependent cell surface expression of pendrin. Together, these data indicate that IL13 increases pendrin abundance to the cell surface via Rho/actin signaling, an effect reversed by theophylline.
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Affiliation(s)
- Annamaria Russo
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy
| | - Marianna Ranieri
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy.
| | - Annarita Di Mise
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy
| | - Silvia Dossena
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Tommaso Pellegrino
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy
| | - Emilia Furia
- Department of Chemistry and Chemical Technologies, University of Calabria, Rende, Italy
| | - Charity Nofziger
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Lucantonio Debellis
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy
| | - Markus Paulmichl
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Giovanna Valenti
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy.,Istituto Nazionsale di Biostrutture e Biosistemi (I.N.B.B.), Rome, Italy.,Centre of Excellence Genomic and Proteomics GEBCA, University of Bari, Bari, Italy
| | - Grazia Tamma
- Department of Biosciences Biotechnologies and Biopharmaceutics, University of Bari, Via Orabona 4, 70125, Bari, Italy. .,Istituto Nazionsale di Biostrutture e Biosistemi (I.N.B.B.), Rome, Italy.
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8
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Schiemer J, Bohm A, Lin L, Merrill-Skoloff G, Flaumenhaft R, Huang JS, Le Breton GC, Chishti AH. Gα13 Switch Region 2 Relieves Talin Autoinhibition to Activate αIIbβ3 Integrin. J Biol Chem 2016; 291:26598-26612. [PMID: 27803165 DOI: 10.1074/jbc.m116.747279] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 10/28/2016] [Indexed: 11/06/2022] Open
Abstract
Integrins function as bi-directional signaling transducers that regulate cell-cell and cell-matrix signals across the membrane. A key modulator of integrin activation is talin, a large cytoskeletal protein that exists in an autoinhibited state in quiescent cells. Talin is a large 235-kDa protein composed of an N-terminal 45-kDa FERM (4.1, ezrin-, radixin-, and moesin-related protein) domain, also known as the talin head domain, and a series of helical bundles known as the rod domain. The talin head domain consists of four distinct lobes designated as F0-F3. Integrin binding and activation are mediated through the F3 region, a critically regulated domain in talin. Regulation of the F3 lobe is accomplished through autoinhibition via anti-parallel dimerization. In the anti-parallel dimerization model, the rod domain region of one talin molecule binds to the F3 lobe on an adjacent talin molecule, thus achieving the state of autoinhibition. Platelet functionality requires integrin activation for adherence and thrombus formation, and thus regulation of talin presents a critical node where pharmacological intervention is possible. A major mechanism of integrin activation in platelets is through heterotrimeric G protein signaling regulating hemostasis and thrombosis. Here, we provide evidence that switch region 2 (SR2) of the ubiquitously expressed G protein (Gα13) directly interacts with talin, relieves its state of autoinhibition, and triggers integrin activation. Biochemical analysis of Gα13 shows SR2 binds directly to the F3 lobe of talin's head domain and competes with the rod domain for binding. Intramolecular FRET analysis shows Gα13 can relieve autoinhibition in a cellular milieu. Finally, a myristoylated SR2 peptide shows demonstrable decrease in thrombosis in vivo Altogether, we present a mechanistic basis for the regulation of talin through Gα13.
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Affiliation(s)
- James Schiemer
- From the Department of Developmental, Molecular, and Chemical Biology.,Sackler School of Graduate Biomedical Sciences, Programs in Cellular and Molecular Physiology
| | - Andrew Bohm
- From the Department of Developmental, Molecular, and Chemical Biology
| | - Li Lin
- From the Department of Developmental, Molecular, and Chemical Biology.,Pharmacology and Experimental Therapeutics and Molecular Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Glenn Merrill-Skoloff
- the Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115
| | - Robert Flaumenhaft
- the Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115
| | - Jin-Sheng Huang
- the Research Resources Center, Protein Research Laboratory, University of Illinois at Chicago, Chicago, Illinois 60612, and
| | - Guy C Le Breton
- the Department of Pharmacology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612
| | - Athar H Chishti
- From the Department of Developmental, Molecular, and Chemical Biology, .,Sackler School of Graduate Biomedical Sciences, Programs in Cellular and Molecular Physiology.,Pharmacology and Experimental Therapeutics and Molecular Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111
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9
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Wu KX, Phuektes P, Kumar P, Goh GYL, Moreau D, Chow VTK, Bard F, Chu JJH. Human genome-wide RNAi screen reveals host factors required for enterovirus 71 replication. Nat Commun 2016; 7:13150. [PMID: 27748395 PMCID: PMC5071646 DOI: 10.1038/ncomms13150] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 09/08/2016] [Indexed: 12/31/2022] Open
Abstract
Enterovirus 71 (EV71) is a neurotropic enterovirus without antivirals or vaccine, and its host-pathogen interactions remain poorly understood. Here we use a human genome-wide RNAi screen to identify 256 host factors involved in EV71 replication in human rhabdomyosarcoma cells. Enrichment analyses reveal overrepresentation in processes like mitotic cell cycle and transcriptional regulation. We have carried out orthogonal experiments to characterize the roles of selected factors involved in cell cycle regulation and endoplasmatic reticulum-associated degradation. We demonstrate nuclear egress of CDK6 in EV71 infected cells, and identify CDK6 and AURKB as resistance factors. NGLY1, which co-localizes with EV71 replication complexes at the endoplasmatic reticulum, supports EV71 replication. We confirm importance of these factors for EV71 replication in a human neuronal cell line and for coxsackievirus A16 infection. A small molecule inhibitor of NGLY1 reduces EV71 replication. This study provides a comprehensive map of EV71 host factors and reveals potential antiviral targets. Enterovirus 71 (EV71) infection causes a spectrum of symptoms including neurological disease. To improve our understanding of EV71-host interactions, Wu et al. here perform a genome-wide RNAi screen, which implicates cell cycle regulation and ER-associated degradation as important factors in EV71 replication.
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Affiliation(s)
- Kan Xing Wu
- Department of Microbiology and Immunology, National University of Singapore, Singapore 117597, Singapore
| | - Patchara Phuektes
- Department of Microbiology and Immunology, National University of Singapore, Singapore 117597, Singapore
| | - Pankaj Kumar
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore
| | - Germaine Yen Lin Goh
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore
| | - Dimitri Moreau
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore
| | - Vincent Tak Kwong Chow
- Department of Microbiology and Immunology, National University of Singapore, Singapore 117597, Singapore
| | - Frederic Bard
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore
| | - Justin Jang Hann Chu
- Department of Microbiology and Immunology, National University of Singapore, Singapore 117597, Singapore.,Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore
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10
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Syrovatkina V, Alegre KO, Dey R, Huang XY. Regulation, Signaling, and Physiological Functions of G-Proteins. J Mol Biol 2016; 428:3850-68. [PMID: 27515397 DOI: 10.1016/j.jmb.2016.08.002] [Citation(s) in RCA: 250] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Revised: 07/31/2016] [Accepted: 08/03/2016] [Indexed: 12/31/2022]
Abstract
Heterotrimeric guanine-nucleotide-binding regulatory proteins (G-proteins) mainly relay the information from G-protein-coupled receptors (GPCRs) on the plasma membrane to the inside of cells to regulate various biochemical functions. Depending on the targeted cell types, tissues, and organs, these signals modulate diverse physiological functions. The basic schemes of heterotrimeric G-proteins have been outlined. In this review, we briefly summarize what is known about the regulation, signaling, and physiological functions of G-proteins. We then focus on a few less explored areas such as the regulation of G-proteins by non-GPCRs and the physiological functions of G-proteins that cannot be easily explained by the known G-protein signaling pathways. There are new signaling pathways and physiological functions for G-proteins to be discovered and further interrogated. With the advancements in structural and computational biological techniques, we are closer to having a better understanding of how G-proteins are regulated and of the specificity of G-protein interactions with their regulators.
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Affiliation(s)
- Viktoriya Syrovatkina
- Department of Physiology and Biophysics, Weill Cornell Medical College, of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Kamela O Alegre
- Department of Physiology and Biophysics, Weill Cornell Medical College, of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Raja Dey
- Department of Physiology and Biophysics, Weill Cornell Medical College, of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Xin-Yun Huang
- Department of Physiology and Biophysics, Weill Cornell Medical College, of Cornell University, 1300 York Avenue, New York, NY 10065, USA.
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Park F. Accessory proteins for heterotrimeric G-proteins in the kidney. Front Physiol 2015; 6:219. [PMID: 26300785 PMCID: PMC4528294 DOI: 10.3389/fphys.2015.00219] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 07/20/2015] [Indexed: 11/17/2022] Open
Abstract
Heterotrimeric G-proteins play a fundamentally important role in regulating signal transduction pathways in the kidney. Accessory proteins are being identified as direct binding partners for heterotrimeric G-protein α or βγ subunits to promote more diverse mechanisms by which G-protein signaling is controlled. In some instances, accessory proteins can modulate the signaling magnitude, localization, and duration following the activation of cell membrane-associated receptors. Alternatively, accessory proteins complexed with their G-protein α or βγ subunits can promote non-canonical models of signaling activity within the cell. In this review, we will highlight the expression profile, localization and functional importance of these newly identified accessory proteins to control the function of select G-protein subunits under normal and various disease conditions observed in the kidney.
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Affiliation(s)
- Frank Park
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center Memphis, TN, USA
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12
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Abstract
The G12 family of heterotrimeric G proteins is defined by their α-subunits,
Gα12 and Gα13. These α-subunits
regulate cellular homeostasis, cell migration, and oncogenesis in a
context-specific manner primarily through their interactions with distinct
proteins partners that include diverse effector molecules and scaffold proteins.
With a focus on identifying any other novel regulatory protein(s) that can
directly interact with Gα13, we subjected Gα13
to tandem affinity purification-coupled mass spectrometric analysis. Our results
from such analysis indicate that Gα13 potently interacts with
mammalian Ric-8A. Our mass spectrometric analysis data also indicates that
Ric-8A, which was tandem affinity purified along with Gα13, is
phosphorylated at Ser-436, Thr-441, Thr-443 and Tyr-435. Using a serial deletion
approach, we have defined that the C-terminus of Gα13 containing
the guanine-ring interaction site is essential and sufficient for its
interaction with Ric-8A. Evaluation of Gα13-specific signaling
pathways in SKOV3 or HeyA8 ovarian cancer cell lines indicate that Ric-8A
potentiates Gα13-mediated activation of RhoA, Cdc42, and the
downstream p38MAPK. We also establish that the tyrosine phosphorylation of
Ric-8A, thus far unidentified, is potently stimulated by Gα13.
Our results also indicate that the stimulation of tyrosine-phosphorylation of
Ric-8A by Gα13 is partially sensitive to inhibitors of
Src-family of kinases, namely PP2 and SI. Furthermore, we demonstrate that
Gα13 promotes the translocation of Ric-8A to plasma membrane
and this translocation is attenuated by the Src-inhibitors, SI1 and PP2. Thus,
our results demonstrate for the first time that Gα13 stimulates
the tyrosine phosphorylation of Ric-8A and Gα13-mediated
tyrosine-phosphorylation plays a critical role in the translocation of Ric-8A to
plasma membrane.
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13
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Orecchia A, Mettouchi A, Uva P, Simon GC, Arcelli D, Avitabile S, Ragone G, Meneguzzi G, Pfenninger KH, Zambruno G, Failla CM. Endothelial cell adhesion to soluble vascular endothelial growth factor receptor‐1 triggers a cell dynamic and angiogenic phenotype. FASEB J 2013; 28:692-704. [DOI: 10.1096/fj.12-225771] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Angela Orecchia
- Molecular and Cell Biology LaboratoryIstituto Dermopatico dell'Immacolata (IDI)–Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)RomeItaly
| | - Amel Mettouchi
- Institut National de la Santé et de la Recherche Médicale (INSERM) U634NiceFrance
| | - Paolo Uva
- Center for Advanced Studies, Research, and Development in Sardinia (CRS4)Bioinformatics LaboratoryCagliariItaly
| | - Glenn C. Simon
- Department of PediatricsUniversity of ColoradoAuroraColoradoUSA
| | - Diego Arcelli
- Molecular Oncology LaboratoryIstituto Dermopatico dell'Immacolata (IDI)–Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)RomeItaly
| | - Simona Avitabile
- Molecular and Cell Biology LaboratoryIstituto Dermopatico dell'Immacolata (IDI)–Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)RomeItaly
| | - Gianluca Ragone
- Molecular Oncology LaboratoryIstituto Dermopatico dell'Immacolata (IDI)–Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)RomeItaly
| | - Guerrino Meneguzzi
- Institut National de la Santé et de la Recherche Médicale (INSERM) U634NiceFrance
| | | | - Giovanna Zambruno
- Molecular and Cell Biology LaboratoryIstituto Dermopatico dell'Immacolata (IDI)–Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)RomeItaly
| | - Cristina Maria Failla
- Molecular and Cell Biology LaboratoryIstituto Dermopatico dell'Immacolata (IDI)–Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)RomeItaly
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Testosterone promotes vascular endothelial cell migration via upregulation of ROCK-2/moesin cascade. Mol Biol Rep 2013; 40:6729-35. [PMID: 24065547 DOI: 10.1007/s11033-013-2788-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Accepted: 09/14/2013] [Indexed: 01/20/2023]
Abstract
Cross-sectional studies have demonstrated a reverse relationship between serum level of testosterone (T) and the incidence rate of cardiovascular disease in men, indicating that T exerts beneficial effects in cardiovascular system. However, the endothelial effects of T are poorly understood. Actin remodeling is essential for endothelial cell movement and vascular repair and this process is controlled by the actin-binding protein moesin. In the present study, we studied the effects of T on actin remodeling, moesin expression and phosphorylation, as well as cell migration in cultured human umbilical endothelial cells (hUVECs). We found that T provoked the formation of cortical actin complexes and membrane protrusions in endothelial cells. Treatment with T induced dose- and time-dependent increase of moesin expression and phosphorylation, which was inhibited by the addition of androgen receptor antagonist hydroxyflutamide (HF). Moreover, T enhanced ROCK-2 activity. The ROCK-2 inhibitor Y27632 or the transfection of ROCK-2 siRNA largely inhibited T-induced moesin expression and phosphorylation, indicating that ROCK-2 pathway is crucial for these effects. T promoted endothelial cell migration, which was inhibited by the addition of HF or Y27632. In conclusion, T induces actin cytoskeleton remodeling by regulating moesin expression and activation, resulting in enhanced endothelial cell migration. Our work adds new insights into endothelial mechanisms of T, which is relevant for its vascular actions.
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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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16
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Hansen MDH, Kwiatkowski AV. Control of actin dynamics by allosteric regulation of actin binding proteins. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 303:1-25. [PMID: 23445807 DOI: 10.1016/b978-0-12-407697-6.00001-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The regulated assembly and organization of actin filaments allows the cell to construct a large diversity of actin-based structures specifically suited to a range of cellular processes. A vast array of actin regulatory proteins must work in concert to form specific actin networks within cells, and spatial and temporal requirements for actin assembly necessitate rapid regulation of protein activity. This chapter explores a common mechanism of controlling the activity of actin binding proteins: allosteric autoinhibition by interdomain head-tail interactions. Intramolecular interactions maintain these proteins in a closed conformation that masks protein domains needed to regulate actin dynamics. Autoinhibition is typically relieved by two or more ligand binding and/or posttranslational modification events that expose key protein domains. Regulation through multiple inputs permits precise temporal and spatial control of protein activity to guide actin network formation.
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Affiliation(s)
- Marc D H Hansen
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, USA.
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17
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Kashimoto R, Yamanaka H, Kobayashi K, Okubo M, Yagi H, Mimura O, Noguchi K. Phosphorylation of ezrin/radixin/moesin (ERM) protein in spinal microglia following peripheral nerve injury and lysophosphatidic acid administration. Glia 2012; 61:338-48. [PMID: 23065679 DOI: 10.1002/glia.22436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 09/18/2012] [Indexed: 11/09/2022]
Abstract
Peripheral nerve injury activates spinal glial cells, which may contribute to the development of pain behavioral hypersensitivity. There is growing evidence that activated microglia show dynamic changes in cell morphology; however, the molecular mechanisms that underlie the modification of the membrane and cytoskeleton of microglia are not known. Here, we investigated the phosphorylation of ezrin, radixin, and moesin (ERM) proteins in the spinal cord after peripheral nerve injury. ERM is known to function as membrane-cytoskeletal linkers and be localized at filopodia- and microvilli-like structures. ERM proteins must be phosphorylated at a specific C-terminal threonine residue to be in the active state. The nature of ERM proteins in the spinal cord of animals in a neuropathic pain model has not been investigated and characterized. In the present study, we observed an increase in the phosphorylated ERM in the spinal microglia following spared nerve injury. The intrathecal administration of lysophosphatidic acid induced the phosphorylation of ERM proteins in microglia along with the development of mechanical pain hypersensitivity. Intrathecal administration of ERM antisense locked nucleic acid suppressed nerve injury-induced tactile allodynia and decreased the phosphorylation of ERM, but not the Iba1 staining pattern, in spinal glial cells. These findings suggest that lysophosphatidic acid induced the phosphorylation of ERM proteins in spinal microglia and may be involved in the emergence of neuropathic pain. These findings may underlie the pathological mechanisms of nerve injury-induced neuropathic pain.
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Affiliation(s)
- Ryosuke Kashimoto
- Department of Ophthalmology, Hyogo College of Medicine, Nishinomiya, Japan
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18
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Carloni V, Mazzocca A, Mello T, Galli A, Capaccioli S. Cell fusion promotes chemoresistance in metastatic colon carcinoma. Oncogene 2012; 32:2649-60. [PMID: 22751128 DOI: 10.1038/onc.2012.268] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chemoresistance is an important concern in the treatment of metastatic colon cancer. It may emerge through selection of clones that are inherently resistant from the outset or through mechanisms acquired during treatment. Cell fusion represents an efficient means of rapid phenotypic evolution that make cells with new properties at a rate exceeding that achievable by random mutagenesis. Here, we first identified a number of proteins involved in cell fusion using a shotgun proteomics approach, then we investigated the role of these proteins namely tetraspanin CD81/CD9, ADAM10, GTP-binding protein α13, radixin, myosin regulatory light chain and RhoA in the regulation of colon cancer cell fusion. We also found a previously unrecognized role of ADAM10, Gα13 and RhoA in promoting cell fusion. Finally, we show that the occurrence of cell fusion in a metastatic model of colon carcinoma causes the appearance of cells resistant to both 5-fluorouracil and oxaliplatin. These findings highlight the importance of cell fusion in cancer progression and raise significant implications for overcoming chemoresistance in metastatic colon cancer.
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Affiliation(s)
- V Carloni
- Department of Internal Medicine, Center for Research, Transfer and High Education, DENOthe, University of Florence, Florence, Italy.
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19
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Hewavitharana T, Wedegaertner PB. Non-canonical signaling and localizations of heterotrimeric G proteins. Cell Signal 2012; 24:25-34. [PMID: 21907280 PMCID: PMC3205251 DOI: 10.1016/j.cellsig.2011.08.014] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Accepted: 08/20/2011] [Indexed: 10/17/2022]
Abstract
Heterotrimeric G proteins typically transduce signals from G protein-coupled receptors (GPCRs) to effector proteins. In the conventional G protein signaling paradigm, the G protein is located at the cytoplasmic surface of the plasma membrane, where, after activation by an agonist-bound GPCR, the GTP-bound Gα and free Gβγ bind to and regulate a number of well-studied effectors, including adenylyl cyclase, phospholipase Cβ, RhoGEFs and ion channels. However, research over the past decade or more has established that G proteins serve non-canonical roles in the cell, whereby they regulate novel effectors, undergo activation independently of a GPCR, and/or function at subcellular locations other than the plasma membrane. This review will highlight some of these non-canonical aspects of G protein signaling, focusing on direct interactions of G protein subunits with cytoskeletal and cell adhesion proteins, the role of G proteins in cell division, and G protein signaling at diverse organelles.
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Affiliation(s)
- Thamara Hewavitharana
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, United States
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20
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Thennes T, Mehta D. Heterotrimeric G proteins, focal adhesion kinase, and endothelial barrier function. Microvasc Res 2011; 83:31-44. [PMID: 21640127 DOI: 10.1016/j.mvr.2011.05.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 05/04/2011] [Accepted: 05/12/2011] [Indexed: 12/18/2022]
Abstract
Ligands by binding to G protein coupled receptors (GPCRs) stimulate dissociation of heterotrimeric G proteins into Gα and Gβγ subunits. Released Gα and Gβγ subunits induce discrete signaling cues that differentially regulate focal adhesion kinase (FAK) activity and endothelial barrier function. Activation of G proteins downstream of receptors such as protease activated receptor 1 (PAR1) and histamine receptors rapidly increases endothelial permeability which reverses naturally within the following 1-2 h. However, activation of G proteins coupled to the sphingosine-1-phosphate receptor 1 (S1P1) signal cues that enhance basal barrier endothelial function and restore endothelial barrier function following the increase in endothelial permeability by edemagenic agents. Intriguingly, both PAR1 and S1P1 activation stimulates FAK activity, which associates with alteration in endothelial barrier function by these agonists. In this review, we focus on the role of the G protein subunits downstream of PAR1 and S1P1 in regulating FAK activity and endothelial barrier function.
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Affiliation(s)
- Tracy Thennes
- Department of Pharmacology, University of Illinois at Chicago, Chicago, IL 60612, USA
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21
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Hochbaum D, Barila G, Ribeiro-Neto F, Altschuler DL. Radixin assembles cAMP effectors Epac and PKA into a functional cAMP compartment: role in cAMP-dependent cell proliferation. J Biol Chem 2010; 286:859-66. [PMID: 21047789 DOI: 10.1074/jbc.m110.163816] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
cAMP is an ubiquitous second messenger. Localized areas with high cAMP concentration, i.e. cAMP microdomains, provide an elegant mechanism to generate signaling specificity and transduction efficiency. However, the mechanisms underlying cAMP effector targeting into these compartments is still unclear. Here we report the identification of radixin as a scaffolding unit for both cAMP effectors, Epac and PKA. This complex localizes in a submembrane compartment where cAMP synthesis occurs. Compartment disruption by shRNA and dominant negative approaches negatively affects cAMP action. Inhibition can be rescued by expression of Rap1b, a substrate for both Epac1 and PKA, but only in its GTP-bound and phosphorylated state. We propose that radixin scaffolds both cAMP effectors in a functional cAMP-sensing compartment for efficient signal transduction, using Rap1 as a downstream signal integrator.
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Affiliation(s)
- Daniel Hochbaum
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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22
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He M, Cheng Y, Li W, Liu Q, Liu J, Huang J, Fu X. Vascular endothelial growth factor C promotes cervical cancer metastasis via up-regulation and activation of RhoA/ROCK-2/moesin cascade. BMC Cancer 2010; 10:170. [PMID: 20429915 PMCID: PMC2873393 DOI: 10.1186/1471-2407-10-170] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 04/29/2010] [Indexed: 01/01/2023] Open
Abstract
Background The elevated expression of vascular endothelial growth factor C (VEGF-C) is correlated with clinical cervical cancer metastasis and patient survival, which is interpreted by VEGF-C functions to stimulate angiogenesis and lymphatic genesis. However, the direct impact of VEGF-C on cervical cancer cell motility remains largely unknown. Methods In this study, we investigated the effects of VEGF-C on actin cytoskeleton remodeling and on cervical cancer cell migration and invasion and how the actin-regulatory protein, moesin regulated these effects through RhoA/ROCK-2 signaling pathway. Results On cervical carcinoma cell line SiHa cells, exposure of VEGF-C triggered remodeling of the actin cytoskeleton and the formation of membrane ruffles, which was required for cell movement. VEGF-C significantly enhanced SiHa cells horizontal migration and three-dimensional invasion into matrices. These actions were dependent on increased expression and phosphorylation of the actin-regulatory protein moesin and specific moesin siRNA severely impaired VEGF-C stimulated-cell migration. The extracellular small GTPase RhoA/ROCK-2 cascade mediated the increased moesin expression and phosphorylation, which was discovered by the use of Y-27632, a specific inhibitor of Rho kinase and by transfected constitutively active, dominant-negative RhoA as well as ROCK-2 SiRNA. Furthermore, in the surgical cervical specimen from the patients with FIGO stage at cervical intra-epithelial neoplasia and I-II cervical squamous cell carcinoma, the expression levels of moesin were found to be significantly correlated with tumor malignancy and metastasis. Conclusions These results implied that VEGF-C promoted cervical cancer metastasis by upregulation and activation of moesin protein through RhoA/ROCK-2 pathway. Our findings offer new insight into the role of VEGF-C on cervical cancer progression and may provide potential targets for cervical cancer therapy.
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Affiliation(s)
- Mian He
- Department of Gynecology and obstetrics, the first affiliated hospital of Sun Yat-sen University, Guangdong, Guangzhou, 510089, China.
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Marty C, Ye RD. Heterotrimeric G protein signaling outside the realm of seven transmembrane domain receptors. Mol Pharmacol 2010; 78:12-8. [PMID: 20404072 DOI: 10.1124/mol.110.063453] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Heterotrimeric G proteins, consisting of the guanine nucleotide-binding Galpha subunits with GTPase activity and the closely associated Gbeta and Ggamma subunits, are important signaling components for receptors with seven transmembrane domains (7TMRs). These receptors, also termed G protein-coupled receptors (GPCRs), act as guanine nucleotide exchange factors upon agonist stimulation. There is now accumulating evidence for noncanonical functions of heterotrimeric G proteins independent of 7TMR coupling. Galpha proteins belonging to all 4 subfamilies, including G(s), G(i), G(q), and G(12) are found to play important roles in receptor tyrosine kinase signaling, regulation of oxidant production, development, and cell migration, through physical and functional interaction with proteins other than 7TMRs. Association of Galpha with non-7TMR proteins also facilitates presentation of these G proteins to specific cellular microdomains. This Minireview aims to summarize our current understanding of the noncanonical roles of Galpha proteins in cell signaling and to discuss unresolved issues including regulation of Galpha activation by proteins other than the 7TMRs.
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Affiliation(s)
- Caroline Marty
- Institut National de la Santé et de la Recherche Médicale, Université Paris XI, Institut Gustave Roussy, Villejuif, France
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24
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Grzelinski M, Pinkenburg O, Büch T, Gold M, Stohr S, Kalwa H, Gudermann T, Aigner A. Critical role of G(alpha)12 and G(alpha)13 for human small cell lung cancer cell proliferation in vitro and tumor growth in vivo. Clin Cancer Res 2010; 16:1402-15. [PMID: 20160064 DOI: 10.1158/1078-0432.ccr-09-1873] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE In small cell lung cancer cells (SCLC), various autocrine stimuli lead to the parallel activation of G(q/11) and G(12/13) proteins. Although the contribution of the G(q/11)-phospholipase C-beta cascade to mitogenic effects in SCLC cells is well established, the relevance of G(12/13) signaling is still elusive. In other tumor entities, G(12/13) activation promotes invasiveness without affecting cellular proliferation. Here, we investigate the role of G(12/13)-dependent signaling in SCLC. EXPERIMENTAL DESIGN We used small hairpin RNA-mediated targeting of G(alpha)(12), G(alpha)(13), or both in H69 and H209 cells and analyzed the effects of G(alpha)(12) and/or G(alpha)(13) knockdown on tumor cells in vitro, tumor growth in vivo, and mitogen-activated protein kinase (MAPK) activation. RESULTS Lentiviral expression of small hairpin RNAs resulted in robust and specific G(alpha)(12) and G(alpha)(13) knockdown as well as markedly inhibited proliferation, colony formation, and bradykinin-promoted stimulation of cell growth. Analyzing the activation status of all three major MAPK families revealed nonredundant functions of G(alpha)(12) and G(alpha)(13) in SCLC and a marked p42/p44 activation upon G(alpha)(12)/G(alpha)(13) knockdown. In a s.c. tumor xenograft mouse model, G(alpha)(12) or G(alpha)(13) downregulation led to decreased tumor growth due to reduced tumor cell proliferation. More importantly, G(alpha)(12)/G(alpha)(13) double knockdown completely abolished H69 tumorigenicity in mice. CONCLUSIONS G(alpha)(12) and G(alpha)13) exert a complex pattern of nonredundant effects in SCLC, and in contrast to other tumor types, SCLC cell proliferation in vitro and tumorigenicity in vivo critically depend on G(12/13) signaling. Due to the complete abolishment of tumorgenicity in our study, RNAi-mediated double knockdown may provide a promising new avenue in SCLC treatment.
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Affiliation(s)
- Marius Grzelinski
- Department of Pharmacology and Toxicology, Philipps-University School of Medicine, Marburg, Germany
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25
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Persson A, Lindwall C, Curtis MA, Kuhn HG. Expression of ezrin radixin moesin proteins in the adult subventricular zone and the rostral migratory stream. Neuroscience 2010; 167:312-22. [PMID: 20109539 DOI: 10.1016/j.neuroscience.2010.01.035] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 01/15/2010] [Accepted: 01/19/2010] [Indexed: 12/24/2022]
Abstract
Continuous proliferation occurs in the adult subventricular zone (SVZ) of the lateral ventricles throughout life. In the SVZ, progenitor cells differentiate into neuroblasts, which migrate tangentially along the rostral migratory stream (RMS) to reach their final destination in the olfactory bulb. These progenitor cells mature and integrate into the existing neural network of the olfactory bulb. Long distance migration of neuroblasts in the RMS requires a highly dynamic cytoskeleton with the ability to respond to surrounding stimuli. Radixin is a member of the ERM (Ezrin, Radixin, Moesin) family, which connect the actin cytoskeleton to the extracellular matrix through transmembrane proteins. The membrane-cytoskeleton linker proteins of the ERM family may regulate cellular events with a high demand on cytoskeleton plasticity, such as cell motility. Recently, specific expression of the ERM protein ezrin was shown in the RMS. Radixin however has not been characterized in this region. Here we used immunohistochemistry and confocal microscopy to examine the expression of radixin in the different cell types of the adult subventricular zone niche and in the RMS. Our findings indicate that radixin is strongly expressed in neuroblasts of the adult RMS and subventricular zone, and also in Olig2-positive cells. We also demonstrate the presence of radixin in the cerebral cortex, striatum, cerebellum, thalamus, hippocampus as well as the granular and periglomerular layers of the olfactory bulb. Our studies also reveal the localization of radixin in neurosphere culture studies and we reveal the specificity of our labeling using Western blotting. The expression pattern demonstrated here suggests a role for radixin in neuronal migration and differentiation in the adult RMS. Understanding how adult neuronal migration is regulated is of importance for the development of new therapeutic interventions using endogenous repair for neurodegenerative diseases.
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Affiliation(s)
- A Persson
- Center for Brain Repair and Rehabilitation, Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden
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26
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Kahsai AW, Zhu S, Fenteany G. G protein-coupled receptor kinase 2 activates radixin, regulating membrane protrusion and motility in epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1803:300-10. [PMID: 19913059 DOI: 10.1016/j.bbamcr.2009.11.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 11/03/2009] [Accepted: 11/04/2009] [Indexed: 12/11/2022]
Abstract
Ezrin/radixin/moesin (ERM) proteins are membrane-cytoskeleton linkers that also have roles in signal transduction. Here we show that G protein-coupled receptor kinase 2 (GRK2) regulates membrane protrusion and cell migration during wound closure in Madin-Darby canine kidney (MDCK) epithelial cell monolayers at least partly through activating phosphorylation of radixin on a conserved, regulatory C-terminal Thr residue. GRK2 phosphorylated radixin exclusively on Thr 564 in vitro. Expression of a phosphomimetic (Thr-564-to-Asp) mutant of radixin resulted in increased Rac1 activity, membrane protrusion and cell motility in MDCK cells, suggesting that radixin functions "upstream" of Rac1, presumably as a scaffolding protein. Phosphorylation of ERM proteins was highest during the most active phase of epithelial cell sheet migration over the course of wound closure. In view of these results, we explored the mode of action of quinocarmycin/quinocarcin analog DX-52-1, an inhibitor of cell migration and radixin function with considerable selectivity for radixin over the other ERM proteins, finding that its mechanism of inhibition of radixin does not appear to involve binding and antagonism at the site of regulatory phosphorylation.
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Affiliation(s)
- Alem W Kahsai
- Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA
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Han J, Liu G, Profirovic J, Niu J, Voyno-Yasenetskaya T. Zyxin is involved in thrombin signaling via interaction with PAR-1 receptor. FASEB J 2009; 23:4193-206. [PMID: 19690217 DOI: 10.1096/fj.09-131862] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Protease-activated receptor 1 (PAR-1) mediates thrombin signaling in human endothelial cells. As a G-protein-coupled receptor, PAR-1 transmits thrombin signal through activation of the heterotrimeric G proteins, Gi, Gq, and G12/13. In this study, we demonstrated that zyxin, a LIM-domain-containing protein, is involved in thrombin-mediated actin cytoskeleton remodeling and serum response element (SRE)-dependent gene transcription. We determined that zyxin binds to the C-terminal domain of PAR-1, providing a possible mechanism of involvement of zyxin as a signal transducer in PAR-1 signaling. Data showing that disruption of PAR-1-zyxin interaction inhibited thrombin-induced stress fiber formation and SRE activation supports this hypothesis. Similarly, depletion of zyxin using siRNA inhibited thrombin-induced actin stress fiber formation and SRE-dependent gene transcription. In addition, depletion of zyxin resulted in delay of endothelial barrier restoration after thrombin treatment. Notably, down-regulation of zyxin did not affect thrombin-induced activation of RhoA or Gi, Gq, and G12/13 heterotrimeric G proteins, implicating a novel signaling pathway regulated by PAR-1 that is not mediated by G-proteins. The observation that zyxin targets VASP, a partner of zyxin in regulation of actin assembly and dynamics, to focal adhesions and along stress fibers on thrombin stimulation suggests that zyxin may participate in thrombin-induced cytoskeletal remodeling through recruitment of VASP. In summary, this study establishes a crucial role of zyxin in thrombin signaling in endothelial cells and provides evidence for a novel PAR-1 signaling pathway mediated by zyxin.
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Affiliation(s)
- Jingyan Han
- Department of Pharmacology (MC 868), University of Illinois at Chicago, 909 S. Wolcott Ave., Chicago, IL 60612, USA
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28
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Krawetz R, Kelly GM. Coordinate Gα13 and Wnt6-β-catenin signaling in F9 embryonal carcinoma cells is required for primitive endoderm differentiation. Biochem Cell Biol 2009; 87:567-80. [DOI: 10.1139/o09-014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The mouse F9 embryonal carcinoma cell line is ideally suited to study the epithelial-to-mesenchymal transition accompanying the differentiation of primitive to parietal extraembryonic endoderm. In F9 cells, the application of exogenous agents including retinoic acid or activation of signal transduction cascades downstream of G-proteins triggers widespread changes in gene expression and leads to the formation of primitive endoderm. The epithelial-to-mesenchymal transition is completed and parietal endoderm develops as of result of increasing PKA activity in primitive endoderm cells. Expression of a constitutively active form of Gα13(Q226L) is sufficient to induce F9 cells into parietal endoderm and a model is emerging that a signaling axis linking G-protein signaling to RhoA and the ERM protein moesin is required for differentiation. In this study, we found that expression of either p115RhoGEF or a constitutively active, GTPase-deficient form of RhoA(L63) promoted primitive, but not parietal, endoderm formation. The overexpression of Gα13(Q226L) or p115RhoGEF, but not Rho(L63), caused β-catenin to translocate to the nucleus. Surprisingly, the stimulation of the Wnt-β-catenin pathway was accompanied by nuclear β-catenin and primitive endoderm formation, even when a dominant negative was used to block the signaling axis at the level of p115RhoGEF or when ROCK activity was inhibited using the pharmacological agent Y-27632. Together, results indicate that the coordinate signaling by two independent pathways, one involving canonical Wnt-β-catenin activation of target genes and the other with Gα13 signaling to ERM proteins to modulate cytoarchitectural changes, is required during the retinoic acid induced differentiation of F9 cells to primitive endoderm.
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Affiliation(s)
- Roman Krawetz
- Department of Biology, Molecular Genetics Unit, University of Western Ontario, London, ON N6A 5B7, Canada
- Child Health Research Institute, University of Western Ontario, London, ON N6A 5B7, Canada
| | - Gregory M. Kelly
- Department of Biology, Molecular Genetics Unit, University of Western Ontario, London, ON N6A 5B7, Canada
- Child Health Research Institute, University of Western Ontario, London, ON N6A 5B7, Canada
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29
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Abstract
The G12 subfamily of heterotrimeric guanine nucleotide-binding proteins consists of two alpha subunits, G alpha12 and G alpha13. These proteins mediate signalling via G protein-coupled receptors and have been implicated in various physiological and pathophysiological processes. A number of direct and indirect effectors of G alpha12 and G alpha13 have been identified that mediate, or have been proposed to mediate, the diverse cellular responses accompanying activation of G12 proteins. This review describes the signalling pathways and cellular events stimulated by G12 proteins, with a particular emphasis on processes that are important in regulating cell migration and invasion, and could potentially be involved in the pathophysiology of cancer metastasis. Experimental findings directly implicating G12 proteins in the spread of metastatic disease are also summarized, indicating the importance of targeted inhibition of G12 signalling as a potential therapeutic option for locally advanced and metastatic disease.
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Affiliation(s)
- Juhi Juneja
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710-3813, USA
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30
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Suzuki N, Hajicek N, Kozasa T. Regulation and physiological functions of G12/13-mediated signaling pathways. Neurosignals 2009; 17:55-70. [PMID: 19212140 DOI: 10.1159/000186690] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Accepted: 10/10/2008] [Indexed: 12/12/2022] Open
Abstract
Accumulating data indicate that G12 subfamily (Galpha12/13)-mediated signaling pathways play pivotal roles in a variety of physiological processes, while aberrant regulation of this pathway has been identified in various human diseases. It has been demonstrated that Galpha12/13-mediated signals form networks with other signaling proteins at various levels, from cell surface receptors to transcription factors, to regulate cellular responses. Galpha12/13 have slow rates of nucleotide exchange and GTP hydrolysis, and specifically target RhoGEFs containing an amino-terminal RGS homology domain (RH-RhoGEFs), which uniquely function both as a GAP and an effector for Galpha12/13. In this review, we will focus on the mechanisms regulating the Galpha12/13 signaling system, particularly the Galpha12/13-RH-RhoGEF-Rho pathway, which can regulate a wide variety of cellular functions from migration to transformation.
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Affiliation(s)
- Nobuchika Suzuki
- Laboratory of Systems Biology and Medicine, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan.
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31
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Cho H, Kehrl JH. Chapter 9 Regulation of Immune Function by G Protein‐Coupled Receptors, Trimeric G Proteins, and RGS Proteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:249-98. [DOI: 10.1016/s1877-1173(09)86009-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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32
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Kahsai AW, Cui J, Kaniskan HU, Garner PP, Fenteany G. Analogs of tetrahydroisoquinoline natural products that inhibit cell migration and target galectin-3 outside of its carbohydrate-binding site. J Biol Chem 2008; 283:24534-45. [PMID: 18556657 DOI: 10.1074/jbc.m800006200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cell migration is central to a number of normal and disease processes. Small organic molecules that inhibit cell migration have potential as both research probes and therapeutic agents. We have identified two tetrahydroisoquinoline natural product analogs with antimigratory activities on Madin-Darby canine kidney epithelial cells: a semisynthetic derivative of quinocarmycin (also known as quinocarcin), DX-52-1, and a more complex synthetic molecule, HUK-921, related to the naphthyridinomycin family. It has been assumed that the cellular effects of reactive tetrahydroisoquinolines result from the alkylation of DNA. We have reported previously that the primary target of DX-52-1 relevant to cell migration appears to be the membrane-cytoskeleton linker protein radixin. Here we extend the analysis of the protein targets of DX-52-1, reporting that the multifunctional carbohydrate-binding protein galectin-3 is a secondary target of DX-52-1 that may also be relevant to the antimigratory effects of both DX-52-1 and HUK-921. All known inhibitors of galectin-3 target its beta-galactoside-binding site in the carbohydrate recognition domain. However, we found that DX-52-1 and HUK-921 bind galectin-3 outside of its beta-galactoside-binding site. Intriguingly HUK-921, although a less potent inhibitor of cell migration than DX-52-1, had far greater selectivity for galectin-3 over radixin, exhibiting little binding to radixin, both in vitro and in cells. Overexpression of galectin-3 in cells led to a dramatic increase in cell adhesion on different extracellular matrix substrata as well as changes in cell-cell adhesion and cell motility. Galectin-3-overexpressing cells had greatly reduced sensitivity to DX-52-1 and HUK-921, and these compounds caused a change in localization of the overexpressed galectin-3 and reversion of the cells to a more normal morphology. The converse manipulation, RNA interference-based silencing of galectin-3 expression, resulted in reduced cell-matrix adhesion and cell migration. In aggregate, the data suggest that DX-52-1 and HUK-921 inhibit a carbohydrate binding-independent function of galectin-3 that is involved in cell migration.
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Affiliation(s)
- Alem W Kahsai
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA
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33
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Andreeva AV, Kutuzov MA, Voyno-Yasenetskaya TA. Scaffolding proteins in G-protein signaling. J Mol Signal 2007; 2:13. [PMID: 17971232 PMCID: PMC2211295 DOI: 10.1186/1750-2187-2-13] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 10/30/2007] [Indexed: 11/18/2022] Open
Abstract
Heterotrimeric G proteins are ubiquitous signaling partners of seven transmembrane-domain G-protein-coupled receptors (GPCRs), the largest (and most important pharmacologically) receptor family in mammals. A number of scaffolding proteins have been identified that regulate various facets of GPCR signaling. In this review, we summarize current knowledge concerning those scaffolding proteins that are known to directly bind heterotrimeric G proteins, and discuss the composition of the protein complexes they assemble and their effects on signal transduction. Emerging evidence about possible ways of regulation of activity of these scaffolding proteins is also discussed.
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Affiliation(s)
- Alexandra V Andreeva
- Department of Pharmacology, College of Medicine, University of Illinois at Chicago, 909 S, Wolcott Ave, Chicago, Illinois 60612, USA.
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34
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Morphogenic Signaling in Neurons Via Neurotransmitter Receptors and Small GTPases. Mol Neurobiol 2007; 35:278-87. [DOI: 10.1007/s12035-007-0023-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 11/30/1999] [Accepted: 12/08/2006] [Indexed: 01/21/2023]
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35
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Kelly P, Casey PJ, Meigs TE. Biologic functions of the G12 subfamily of heterotrimeric g proteins: growth, migration, and metastasis. Biochemistry 2007; 46:6677-87. [PMID: 17503779 DOI: 10.1021/bi700235f] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The G12 subfamily of heterotrimeric G proteins has been the subject of intense scientific interest for more than 15 years. During this period, studies have revealed more than 20 potential G12-interacting proteins and numerous signaling axes emanating from the G12 proteins, Galpha12 and Galpha13. In addition, more recent studies have begun to illuminate the various and sundry functions that the G12 subfamily plays in biology. In this review, we summarize the diverse range of proteins that have been identified as Galpha12 and/or Galpha13 interactors and describe ongoing studies designed to dissect the biological roles of specific Galpha-effector protein interactions. Further, we describe and discuss the expanding role of G12 proteins in the biology of cells, focusing on the distinct properties of this subfamily in regulating cell proliferation, cell migration, and metastatic invasion.
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Affiliation(s)
- Patrick Kelly
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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36
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Krawetz R, MacKenzie MJ, Sun Q, Walton PA, Kelly GM. Gα13 activation rescues moesin-depletion induced apoptosis in F9 teratocarcinoma cells. Exp Cell Res 2006; 312:3224-40. [PMID: 16860319 DOI: 10.1016/j.yexcr.2006.06.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2006] [Revised: 05/25/2006] [Accepted: 06/14/2006] [Indexed: 11/17/2022]
Abstract
Mouse F9 cells differentiate into primitive endoderm when treated with retinoic acid (RA) and into parietal endoderm in response to RA and dibutyryl (db-) cAMP. G protein signaling either blocks or mimics RA-induced differentiation, the latter signaling through the Wnt-beta-catenin pathway. In our study, we found that a constitutively active Galpha13 mutant induces F9 cells to differentiate into parietal endoderm in the absence of exogenous agents. Galpha13 expression and subsequent differentiation are accompanied by beta-catenin translocation to the nucleus. Differentiation and changes in cell morphology are supported by rearrangements to the F-actin cytoskeleton. ERM (ezrin-radixin-moesin) proteins, known to link F-actin to transmembrane receptors, are also redistributed during differentiation. Furthermore, morpholino antisense and shRNA approaches show that moesin expression is essential since its knockdown leads to altered F-actin distribution and subsequent apoptosis. Moesin-depleted cells, however, remain attached to the substrate when Galpha13 is constitutively expressed, but they do not differentiate into extraembryonic endoderm. Our study demonstrates a link between Galpha13 signaling that regulates differentiation of F9 cells through primitive to parietal endoderm and a moesin requirement for cell survival.
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Affiliation(s)
- Roman Krawetz
- Department of Biology, Molecular Genetics Unit, University of Western Ontario, London, ON, Canada N6A 5B7
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37
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Kahsai AW, Zhu S, Wardrop DJ, Lane WS, Fenteany G. Quinocarmycin Analog DX-52-1 Inhibits Cell Migration and Targets Radixin, Disrupting Interactions of Radixin with Actin and CD44. ACTA ACUST UNITED AC 2006; 13:973-83. [PMID: 16984887 DOI: 10.1016/j.chembiol.2006.07.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 07/13/2006] [Accepted: 07/20/2006] [Indexed: 12/25/2022]
Abstract
In the course of screening for new small-molecule modulators of cell motility, we discovered that quinocarmycin (also known as quinocarcin) analog DX-52-1 is an inhibitor of epithelial cell migration. While it has been assumed that the main target of DX-52-1 is DNA, we identified and confirmed radixin as the relevant molecular target of DX-52-1 in the cell. Radixin is a member of the ezrin/radixin/moesin family of membrane-actin cytoskeleton linker proteins that also participate in signal transduction pathways. DX-52-1 binds specifically and covalently to the C-terminal region of radixin, which contains the domain that interacts with actin filaments. Overexpression of radixin in cells abrogates their sensitivity to DX-52-1's antimigratory activity. Small interfering RNA-mediated silencing of radixin expression reduces the rate of cell migration. Finally, we found that DX-52-1 disrupts radixin's ability to interact with both actin and the cell adhesion molecule CD44.
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Affiliation(s)
- Alem W Kahsai
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA
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38
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Shan D, Chen L, Wang D, Tan YC, Gu JL, Huang XY. The G protein G alpha(13) is required for growth factor-induced cell migration. Dev Cell 2006; 10:707-18. [PMID: 16740474 DOI: 10.1016/j.devcel.2006.03.014] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 11/17/2005] [Accepted: 03/23/2006] [Indexed: 01/25/2023]
Abstract
Heterotrimeric G proteins are critical cellular signal transducers. They are known to directly relay signals from seven-transmembrane G protein-coupled receptors (GPCRs) to downstream effectors. On the other hand, receptor tyrosine kinases (RTKs), a different family of membrane receptors, signal through docking sites in their carboxy-terminal tails created by autophosphorylated tyrosine residues. Here we show that a heterotrimeric G protein, G alpha(13), is essential for RTK-induced migration of mouse fibroblast and endothelial cells. G alpha(13) activity in cell migration is retained in a C-terminal mutant that is defective in GPCR coupling, suggesting that the migration function is independent of GPCR signaling. Thus, G alpha(13) appears to be a critical signal transducer for RTKs as well as GPCRs. This broader role of G alpha(13) in cell migration initiated by two types of receptors could provide a molecular basis for the vascular system defects exhibited by G alpha(13) knockout mice.
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MESH Headings
- Animals
- Cell Line
- Cell Movement/drug effects
- Cell Movement/physiology
- Cells, Cultured
- Embryo, Mammalian
- Endothelium, Vascular/cytology
- Endothelium, Vascular/metabolism
- Enzyme Activation
- Epidermal Growth Factor/pharmacology
- Fibroblasts/drug effects
- Fibroblasts/physiology
- GTP-Binding Protein alpha Subunits, G12-G13/deficiency
- GTP-Binding Protein alpha Subunits, G12-G13/genetics
- GTP-Binding Protein alpha Subunits, G12-G13/metabolism
- GTP-Binding Protein alpha Subunits, G12-G13/physiology
- Gene Deletion
- Glutathione Transferase/metabolism
- Humans
- Mice
- Mice, Knockout
- Mitogen-Activated Protein Kinase 3/metabolism
- Models, Biological
- Platelet-Derived Growth Factor/pharmacology
- Receptor Protein-Tyrosine Kinases/metabolism
- Recombinant Proteins/metabolism
- rac GTP-Binding Proteins/metabolism
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Affiliation(s)
- Dandan Shan
- Department of Physiology, Weill Medical College, Cornell University, New York, New York 10021, USA
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39
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Hu Y, Lu Y, Zhou Z, Du Y, Xing J, Wang L, Lin M, Sha J. Defective expression of Gα12 in the testes of azoospermia patients and in the spermatozoa with low motility. J Mol Med (Berl) 2006; 84:416-24. [PMID: 16612612 DOI: 10.1007/s00109-005-0028-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Accepted: 11/11/2005] [Indexed: 10/24/2022]
Abstract
Antibody to the Galpha12-subunit of guanine nucleotide regulatory proteins was used to determine whether the Galpha12 is present in adult human spermatogenic cells and to determine its role in dyszoospermia. Immunoblots from testes and spermatozoa demonstrated the presence of Galpha12 in the samples. Immunohistochemical analyses of testes found that Galpha12 was expressed in the cytoplasm of Leydig cells and was expressed in spermatids from the elongating Sb phase to mature sperm. Indirect immunofluorescence of human spermatozoa revealed the presence of Galpha12 in the neck region and the midpiece of the sperm. Galpha12 in spermatids and spermatozoa partially co-localized with F-actin and alpha-tubulin. Immunohistochemical analyses of tissues from three patients with non-obstructive azoospermia showed abnormal expression of Galpha12 in more than 45% of spermatids. Furthermore, Western blots and indirect immunofluorescence found defective expression of Galpha12 in low-motility spermatozoa with midpieces that were bent on themselves. Therefore, it suggests that Galpha12 plays a role in polarity and tail formation as spermatids mature. Furthermore, Galpha12 may be a candidate protein responsible for azoospermia caused by spermatogenic disturbance or midpiece deformities.
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Affiliation(s)
- Yanqiu Hu
- Laboratory of Reproductive Medicine, Department of Histology and Embryology, Nanjing Medical University, 140 Hanzhong Road, Nanjing, Jiangsu Province, People's Republic of China
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40
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Simoncini T, Scorticati C, Mannella P, Fadiel A, Giretti MS, Fu XD, Baldacci C, Garibaldi S, Caruso A, Fornari L, Naftolin F, Genazzani AR. Estrogen receptor alpha interacts with Galpha13 to drive actin remodeling and endothelial cell migration via the RhoA/Rho kinase/moesin pathway. Mol Endocrinol 2006; 20:1756-71. [PMID: 16601072 DOI: 10.1210/me.2005-0259] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Sex steroids control cell movement and tissue organization; however, little is known of the involved mechanisms. This report describes the ongoing dynamic regulation by estrogen of the actin cytoskeleton and cell movement in human vascular endothelial cells that depends on rapid activation of the actin-regulatory protein moesin. Moesin activation is triggered by the interaction of the C-terminal portion of cell membrane estrogen receptor alpha with the G protein Galpha(13), leading to activation of the small GTPase RhoA and of the downstream effector Rho-associated kinase. The resulting phosphorylation of moesin on Thr(558) is the means of moesin's binding to actin and the remodeling of the actin cytoskeleton. This cascade of events ensues within minutes of estradiol administration and results in changes in cell morphology and to the development of specialized cell membrane structures such as ruffles and pseudopodia that are necessary for cell movement. These findings expand our knowledge of the basis of estrogen's effects on human cells, including the regulation of actin assembly, cell movement and migration. They highlight novel pathways of signal transduction of estrogen receptor alpha through nontranscriptional mechanisms. Furthermore, exposure of this estrogen receptor-dependent, nongenomic action of estrogen on human vascular endothelial cells is especially relevant to the present interest in the role of estrogen in cardiovascular protection.
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Affiliation(s)
- Tommaso Simoncini
- Molecular and Cellular Gynecological Endocrinology Laboratory, Department of Reproductive Medicine and Child Development, University of Pisa, Italy.
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41
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Loebrich S, Bähring R, Katsuno T, Tsukita S, Kneussel M. Activated radixin is essential for GABAA receptor alpha5 subunit anchoring at the actin cytoskeleton. EMBO J 2006; 25:987-99. [PMID: 16467845 PMCID: PMC1409722 DOI: 10.1038/sj.emboj.7600995] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 01/16/2006] [Indexed: 11/09/2022] Open
Abstract
Neurotransmitter receptor clustering is thought to represent a critical parameter for neuronal transmission. Little is known about the mechanisms that anchor and concentrate inhibitory neurotransmitter receptors in neurons. GABAA receptor (GABAAR) alpha5 subunits mainly locate at extrasynaptic sites and are thought to mediate tonic inhibition. Notably, similar as synaptic GABAARs, these receptor subtypes also appear in cluster formations at neuronal surface membranes and are of particular interest in cognitive processing. GABAAR alpha5 mutation or depletion facilitates trace fear conditioning or improves spatial learning in mice, respectively. Here, we identified the actin-binding protein radixin, a member of the ERM family, as the first directly interacting molecule that anchors GABAARs at cytoskeletal elements. Intramolecular activation of radixin is a functional prerequisite for GABAAR alpha5 subunit binding and both depletion of radixin expression as well as replacement of the radixin F-actin binding motif interferes with GABAAR alpha5 cluster formation. Our data suggest radixin to represent a critical factor in receptor localization and/or downstream signaling.
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Affiliation(s)
- Sven Loebrich
- Zentrum für Molekulare Neurobiologie Hamburg (ZMNH), Universität Hamburg, Hamburg, Germany
| | - Robert Bähring
- Zentrum für Molekulare Neurobiologie Hamburg (ZMNH), Universität Hamburg, Hamburg, Germany
| | - Tatsuya Katsuno
- Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Sachiko Tsukita
- Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
- School of Health Sciences, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Matthias Kneussel
- Zentrum für Molekulare Neurobiologie Hamburg (ZMNH), Universität Hamburg, Hamburg, Germany
- Zentrum für Molekulare Neurobiologie Hamburg (ZMNH), Universität Hamburg, Falkenried 94, 20251 Hamburg, Germany. Tel.: +49 40 42803 6275; Fax: +49 40 42803 7700; E-mail:
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42
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Abstract
The microvascular endothelial cell monolayer localized at the critical interface between the blood and vessel wall has the vital functions of regulating tissue fluid balance and supplying the essential nutrients needed for the survival of the organism. The endothelial cell is an exquisite “sensor” that responds to diverse signals generated in the blood, subendothelium, and interacting cells. The endothelial cell is able to dynamically regulate its paracellular and transcellular pathways for transport of plasma proteins, solutes, and liquid. The semipermeable characteristic of the endothelium (which distinguishes it from the epithelium) is crucial for establishing the transendothelial protein gradient (the colloid osmotic gradient) required for tissue fluid homeostasis. Interendothelial junctions comprise a complex array of proteins in series with the extracellular matrix constituents and serve to limit the transport of albumin and other plasma proteins by the paracellular pathway. This pathway is highly regulated by the activation of specific extrinsic and intrinsic signaling pathways. Recent evidence has also highlighted the importance of the heretofore enigmatic transcellular pathway in mediating albumin transport via transcytosis. Caveolae, the vesicular carriers filled with receptor-bound and unbound free solutes, have been shown to shuttle between the vascular and extravascular spaces depositing their contents outside the cell. This review summarizes and analyzes the recent data from genetic, physiological, cellular, and morphological studies that have addressed the signaling mechanisms involved in the regulation of both the paracellular and transcellular transport pathways.
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Affiliation(s)
- Dolly Mehta
- Center of Lung and Vascular Biology, Dept. of Pharmacology (M/C 868), University of Illinois, 835 S. Wolcott Avenue, Chicago, IL 60612, USA
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43
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Andreeva AV, Vaiskunaite R, Kutuzov MA, Profirovic J, Skidgel RA, Voyno-Yasenetskaya T. Novel mechanisms of G protein-dependent regulation of endothelial nitric-oxide synthase. Mol Pharmacol 2005; 69:975-82. [PMID: 16326932 DOI: 10.1124/mol.105.018846] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelial nitric-oxide synthase (eNOS) plays a crucial role in the regulation of a variety of cardiovascular and pulmonary functions in both normal and pathological conditions. Multiple signaling inputs, including calcium, caveolin-1, phosphorylation by several kinases, and binding to the 90-kDa heat shock protein (Hsp90), regulate eNOS activity. Here, we report a novel mechanism of G protein-dependent regulation of eNOS. We demonstrate that in mammalian cells, the alpha subunit of heterotrimeric G12 protein (G alpha12) can form a complex with eNOS in an activation- and Hsp90-independent manner. Our data show that G alpha12 does not affect eNOS-specific activity, but it strongly enhances total eNOS activity by increasing cellular levels of eNOS. Experiments using inhibition of protein or mRNA synthesis show that G alpha12 increases the expression of eNOS by increasing half-life of both eNOS protein and eNOS mRNA. Small interfering RNA-mediated depletion of endogenous G alpha12 decreases eNOS levels. A quantitative correlation can be detected between the extent of down-regulation of G alpha12 and eNOS in endothelial cells after prolonged treatment with thrombin. G protein-dependent increase of eNOS expression represents a novel mechanism by which heterotrimeric G proteins can regulate the activity of downstream signaling molecules.
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MESH Headings
- Animals
- Cells, Cultured
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/enzymology
- Enzyme Activation
- Enzyme Stability
- GTP-Binding Protein alpha Subunits, G12-G13/antagonists & inhibitors
- GTP-Binding Protein alpha Subunits, G12-G13/genetics
- GTP-Binding Protein alpha Subunits, G12-G13/metabolism
- HSP90 Heat-Shock Proteins/metabolism
- Humans
- Nitric Oxide Synthase Type III/genetics
- Nitric Oxide Synthase Type III/metabolism
- RNA Stability
- RNA, Messenger/analysis
- RNA, Messenger/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/pharmacology
- Thrombin/pharmacology
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Affiliation(s)
- Alexandra V Andreeva
- Department of Pharmacology, University of Illinois, College of Medicine, Chicago, IL 60612, USA
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Liu G, Voyno-Yasenetskaya TA. Radixin Stimulates Rac1 and Ca2+/Calmodulin-dependent Kinase, CaMKII. J Biol Chem 2005; 280:39042-9. [PMID: 16186118 DOI: 10.1074/jbc.m504341200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The ERM (ezrin, radixin, moesin) proteins function as cross-linkers between cell membrane and cytoskeleton by binding to membrane proteins via their N-terminal domain and to F-actin via their C-terminal domain. Previous studies from our laboratory have shown that the alpha-subunit of heterotrimeric G(13) protein induces conformational activation of radixin via interaction with its N-terminal domain (Vaiskunaite, R., Adarichev, V., Furthmayr, H., Kozasa, T., Gudkov, A., and Voyno-Yasenetskaya, T. A. (2000) J. Biol. Chem. 275, 26206-26212). In the present study, we tested whether radixin can regulate Galpha(13)-mediated signaling pathways. We determined the effects of the N-terminal domain (amino acids 1-318) and C-terminal domain (amino acids 319-583) of radixin on serum response element (SRE)-dependent gene transcription initiated by a constitutively activated Galpha(13)Q226L. The N-terminal domain potentiated SRE activation induced by Galpha(13)Q226L; RhoGDI inhibited this effect. Surprisingly, the C-terminal domain also stimulated the SRE-dependent gene transcription. When co-transfected with Galpha(13)Q226L, the C-terminal domain of radixin synergistically stimulated the SRE activation; RhoGDI inhibited this effect. Using in vivo pull-down assays, we have determined that the C-terminal domain of radixin activated Rac1 but not RhoA or Cdc42 proteins. By contrast, Galpha(13)Q226L activated RhoA but not Rac1 or Cdc42. We have also shown that both the C-terminal domain of radixin and Galpha(13)Q226L can stimulate Ca(2+)/calmodulin-dependent kinase, CaMKII. Activated mutant that mimics the phosphorylated state of radixin (T564E) stimulated Rac1, induced the phosphorylation of CaMKII, and stimulated SRE-dependent gene transcription. Down-regulation of endogenous radixin using small interference RNA inhibited SRE-dependent gene transcription and phosphorylation of CaMKII induced by Galpha(13)Q226L. Overall, our results indicated that radixin via its C-terminal domain mediates SRE-dependent gene transcription through activation of Rac1 and CaMKII. In addition, the radixin-CaMKII signaling pathway is involved in Galpha(13)-mediated SRE-dependent gene transcription, suggesting that radixin could be involved in novel signaling pathway regulated by G(13) protein.
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Affiliation(s)
- Guoquan Liu
- Department of Pharmacology, University of Illinois, Chicago, Illinois 60612, USA
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Abstract
Heterotrimeric G proteins are key players in transmembrane signaling by coupling a huge variety of receptors to channel proteins, enzymes, and other effector molecules. Multiple subforms of G proteins together with receptors, effectors, and various regulatory proteins represent the components of a highly versatile signal transduction system. G protein-mediated signaling is employed by virtually all cells in the mammalian organism and is centrally involved in diverse physiological functions such as perception of sensory information, modulation of synaptic transmission, hormone release and actions, regulation of cell contraction and migration, or cell growth and differentiation. In this review, some of the functions of heterotrimeric G proteins in defined cells and tissues are described.
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Affiliation(s)
- Nina Wettschureck
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany
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46
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Profirovic J, Gorovoy M, Niu J, Pavlovic S, Voyno-Yasenetskaya T. A Novel Mechanism of G Protein-dependent Phosphorylation of Vasodilator-stimulated Phosphoprotein. J Biol Chem 2005; 280:32866-76. [PMID: 16046415 DOI: 10.1074/jbc.m501361200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vasodilator-stimulated phosphoprotein (VASP) is a major substrate of protein kinase A (PKA). Here we described the novel mechanism of VASP phosphorylation via cAMP-independent PKA activation. We showed that in human umbilical vein endothelial cells (HUVECs) alpha-thrombin induced phosphorylation of VASP. Specific inhibition of Galpha13 protein by the RGS domain of a guanine nucleotide exchange factor, p115RhoGEF, inhibited thrombin-dependent phosphorylation of VASP. More importantly, Galpha13-induced VASP phosphorylation was dependent on activation of RhoA and mitogen-activated protein kinase kinase kinase, MEKK1, leading to the stimulation of the NF-kappaB signaling pathway. alpha-Thrombin-dependent VASP phosphorylation was inhibited by small interfering RNA-mediated knockdown of RhoA, whereas Galpha13-dependent VASP phosphorylation was inhibited by a specific RhoA inhibitor botulinum toxin C3 and by a dominant negative mutant of MEKK1. We determined that Galpha13-dependent VASP phosphorylation was also inhibited by specific PKA inhibitors, PKI and H-89. In addition, the expression of phosphorylation-deficient IkappaB and pretreatment with the proteasome inhibitor MG-132 abolished Galpha13- and alpha-thrombin-induced VASP phosphorylation. In summary, we have described a novel pathway of Galpha13-induced VASP phosphorylation that involves activation of RhoA and MEKK1, phosphorylation and degradation of IkappaB, release of PKA catalytic subunit from the complex with IkappaB and NF-kappaB, and subsequent phosphorylation of VASP.
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Affiliation(s)
- Jasmina Profirovic
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
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47
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Tamma G, Carmosino M, Svelto M, Valenti G. Bradykinin signaling counteracts cAMP-elicited aquaporin 2 translocation in renal cells. J Am Soc Nephrol 2005; 16:2881-9. [PMID: 16093449 DOI: 10.1681/asn.2005020190] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Bradykinin (BK) is one of the most important peptides regulating vascular tone, water, and ionic balance in the body, playing a key role in controlling BP. It is interesting that patients with essential hypertension excrete less BK than normotensive individuals. For elucidating the mechanism by which BK regulates renal water transport that contributes to its antihypertensive effect, aquaporin 2 (AQP2)-transfected collecting duct CD8 cells, expressing the BK type II receptor (BK2R), were used as an experimental model. In CD8 cells, BK pretreatment impaired forskolin-induced AQP2 translocation to the apical plasma membrane. For clarifying the signal transduction cascade associated with this effect, whether BK induced an increase in cytosolic calcium, via the G protein Gq, known to be coupled to BK2R, first was investigated. Spectrofluorometry using fura-2-AM revealed that 100 nM BK elicited a significant increase in Ca(i), which was abolished by the receptor antagonist HOE-140. BK acts through BK2R coupled to both Gq and Galpha13, a known upstream effector of Rho protein. In CD8 cells, BK causes an increase in Rho activity, likely as a result of Galpha13 activation. This results in stabilization of the cortical F-actin network, thus impairing AQP2 trafficking. These effects counteract physiologic vasopressin stimulation, which instead has an opposite effect on actin network organization through Rho inactivation.
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Affiliation(s)
- Grazia Tamma
- Dipartimento di Fisiologia Generale e Ambientale, Via Amendola 165/A, Bari 70126, Italy
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48
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Andreeva AV, Kutuzov MA, Vaiskunaite R, Profirovic J, Meigs TE, Predescu S, Malik AB, Voyno-Yasenetskaya T. G alpha12 interaction with alphaSNAP induces VE-cadherin localization at endothelial junctions and regulates barrier function. J Biol Chem 2005; 280:30376-83. [PMID: 15980433 DOI: 10.1074/jbc.m502844200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The involvement of heterotrimeric G proteins in the regulation of adherens junction function is unclear. We identified alphaSNAP as an interactive partner of G alpha12 using yeast two-hybrid screening. Glutathione S-transferase pull-down assays showed the selective interaction of alphaSNAP with G alpha12 in COS-7 as well as in human umbilical vein endothelial cells. Using domain swapping experiments, we demonstrated that the N-terminal region of G alpha12 (1-37 amino acids) was necessary and sufficient for its interaction with alphaSNAP. G alpha13 with its N-terminal extension replaced by that of G alpha12 acquired the ability to bind to alphaSNAP, whereas G alpha12 with its N terminus replaced by that of G alpha13 lost this ability. Using four point mutants of alphaSNAP, which alter its ability to bind to the SNARE complex, we determined that the convex rather than the concave surface of alphaSNAP was involved in its interaction with G alpha12. Co-transfection of human umbilical vein endothelial cells with G alpha12 and alphaSNAP stabilized VE-cadherin at the plasma membrane, whereas down-regulation of alphaSNAP with siRNA resulted in the loss of VE-cadherin from the cell surface and, when used in conjunction with G alpha12 overexpression, decreased endothelial barrier function. Our results demonstrate a direct link between the alpha subunit of G12 and alphaSNAP, an essential component of the membrane fusion machinery, and implicate a role for this interaction in regulating the membrane localization of VE-cadherin and endothelial barrier function.
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Affiliation(s)
- Alexandra V Andreeva
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
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49
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Meigs TE, Juneja J, DeMarco CT, Stemmle LN, Kaplan DD, Casey PJ. Selective Uncoupling of Gα12 from Rho-mediated Signaling. J Biol Chem 2005; 280:18049-55. [PMID: 15746095 DOI: 10.1074/jbc.m500445200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The heterotrimeric G protein G(12) has been implicated in such cellular regulatory processes as cytoskeletal rearrangement, cell-cell adhesion, and oncogenic transformation. Although the activated alpha-subunit of G(12) has been shown to interact directly with a number of protein effectors, the roles of many of these protein-protein interactions in G(12)-mediated cell physiology are poorly understood. To begin dissecting the specific cellular pathways engaged upon G(12) activation, we produced a series of substitution mutants in the regions of Galpha(12) predicted to play a role in effector binding. Here we report the identification and characterization of an altered form of Galpha(12) that is functionally uncoupled from signaling through the monomeric G protein Rho, a protein known to propagate several Galpha(12)-mediated signals. This mutant of Galpha(12) fails to bind the Rho-specific guanine nucleotide exchange factors p115RhoGEF and LARG (leukemia-associated RhoGEF), fails to stimulate Rho-dependent transcriptional activation, and fails to trigger activation of RhoA and the Rho-mediated cellular responses of cell rounding and c-jun N-terminal kinase activation. Importantly, this mutant of Galpha(12) retains coupling to the effector protein E-cadherin, as evidenced by its ability both to bind E-cadherin in vitro and to disrupt E-cadherin-mediated cell-cell adhesion. Furthermore, this mutant retains the ability to trigger beta-catenin release from the cytoplasmic domain of cadherin. This identification of a variant of Galpha(12) that is selectively uncoupled from one signaling pathway while retaining signaling capacity through a separate pathway will facilitate investigations into the mechanisms through which G(12) proteins mediate diverse biological responses.
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Affiliation(s)
- Thomas E Meigs
- Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA
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50
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Riobo NA, Manning DR. Receptors coupled to heterotrimeric G proteins of the G12 family. Trends Pharmacol Sci 2005; 26:146-54. [PMID: 15749160 DOI: 10.1016/j.tips.2005.01.007] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Much regarding the engagement of the G(12) family of heterotrimeric G proteins (G(12) and G(13)) by agonist-activated receptors remains unclear. For example, the identity of receptors that couple unequivocally to G(12) and G(13) and how signals are allocated among these and other G proteins remain open questions. Part of the problem in understanding signaling through G(12) and G(13) is that the activation of these G proteins is rarely demonstrated directly and is instead presumed usually from far removed downstream events. Furthermore, receptors that couple to G(12) and G(13) invariably couple to additional G proteins, and thus few events can be linked unambiguously to one G protein or another. In this article, we document receptors that reportedly couple to G(12), G(13) or both G(12) and G(13), evaluate the methodology used to understand the coupling of these receptors, and discuss the ability of these receptors to couple also to G(q).
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Affiliation(s)
- Natalia A Riobo
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
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