1
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Wu D, Casey PJ. GPCR-Gα13 Involvement in Mitochondrial Function, Oxidative Stress, and Prostate Cancer. Int J Mol Sci 2024; 25:7162. [PMID: 39000269 PMCID: PMC11241654 DOI: 10.3390/ijms25137162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 06/20/2024] [Accepted: 06/26/2024] [Indexed: 07/16/2024] Open
Abstract
Gα13 and Gα12, encoded by the GNA13 and GNA12 genes, respectively, are members of the G12 family of Gα proteins that, along with their associated Gβγ subunits, mediate signaling from specific G protein-coupled receptors (GPCRs). Advanced prostate cancers have increased expression of GPCRs such as CXC Motif Chemokine Receptor 4 (CXCR4), lysophosphatidic acid receptor (LPAR), and protease activated receptor 1 (PAR-1). These GPCRs signal through either the G12 family, or through Gα13 exclusively, often in addition to other G proteins. The effect of Gα13 can be distinct from that of Gα12, and the role of Gα13 in prostate cancer initiation and progression is largely unexplored. The oncogenic effect of Gα13 on cell migration and invasion in prostate cancer has been characterized, but little is known about other biological processes such as mitochondrial function and oxidative stress. Current knowledge on the link between Gα13 and oxidative stress is based on animal studies in which GPCR-Gα13 signaling decreased superoxide levels, and the overexpression of constitutively active Gα13 promoted antioxidant gene activation. In human samples, mitochondrial superoxide dismutase 2 (SOD2) correlates with prostate cancer risk and prognostic Gleason grade. However, overexpression of SOD2 in prostate cancer cells yielded conflicting results on cell growth and survival under basal versus oxidative stress conditions. Hence, it is necessary to explore the effect of Gα13 on prostate cancer tumorigenesis, as well as the effect of Gα13 on SOD2 in prostate cancer cell growth under oxidative stress conditions.
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Affiliation(s)
- Di Wu
- Programme in Cancer and Stem Cell Biology, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore;
| | - Patrick J. Casey
- Programme in Cancer and Stem Cell Biology, Duke-NUS Medical School, 8 College Road, Singapore 169857, Singapore;
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, 308 Research Drive, Durham, NC 27710, USA
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2
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Hasan S, White NF, Tagliatela AC, Durall RT, Brown KM, McDiarmid GR, Meigs TE. Overexpressed Gα13 activates serum response factor through stoichiometric imbalance with Gβγ and mislocalization to the cytoplasm. Cell Signal 2023; 102:110534. [PMID: 36442589 DOI: 10.1016/j.cellsig.2022.110534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 11/21/2022] [Accepted: 11/21/2022] [Indexed: 11/26/2022]
Abstract
Gα13, a heterotrimeric G protein α subunit of the G12/13 subfamily, is an oncogenic driver in multiple cancer types. Unlike other G protein subfamilies that contribute to cancer progression via amino acid substitutions that abolish their deactivating, intrinsic GTPase activity, Gα13 rarely harbors such mutations in tumors and instead appears to stimulate aberrant cell growth via overexpression as a wildtype form. It is not known why this effect is exclusive to the G12/13 subfamily, nor has a mechanism been elucidated for overexpressed Gα13 promoting tumor progression. Using a reporter gene assay for serum response factor (SRF)-mediated transcription in HEK293 cells, we found that transiently expressed, wildtype Gα13 generates a robust SRF signal, approximately half the amplitude observed for GTPase-defective Gα13. When epitope-tagged, wildtype Gα13 was titrated upward in cells, a sharp increase in SRF stimulation was observed coincident with a "spillover" of Gα13 from membrane-associated to a soluble fraction. Overexpressing G protein β and γ subunits caused both a decrease in this signal and a shift of wildtype Gα13 back to the membranous fraction, suggesting that stoichiometric imbalance in the αβγ heterotrimer results in aberrant subcellular localization and signalling by overexpressed Gα13. We also examined the acylation requirements of wildtype Gα13 for signalling to SRF. Similar to GTPase-defective Gα13, S-palmitoylation of the wildtype α subunit was necessary for SRF activation but could be replaced functionally by an engineered site for N-terminal myristoylation. However, a key difference was observed between wildtype and GTPase-defective Gα13: whereas the latter protein lacking palmitoylation sites was rescued in its SRF signalling by either an engineered polybasic sequence or a C-terminal isoprenylation site, these motifs failed to restore signalling by wildtype, non-palmitoylated Gα13. These findings illuminate several components of the mechanism in which overexpressed, wildtype Gα13 contributes to growth and tumorigenic signalling, and reveal greater stringency in its requirements for post-translational modification in comparison to GTPase-defective Gα13.
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Affiliation(s)
- Sharmin Hasan
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Nicholas F White
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Alicia C Tagliatela
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - R Taylor Durall
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Katherine M Brown
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Gray R McDiarmid
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA
| | - Thomas E Meigs
- Department of Biology, University of North Carolina Asheville, 220 Campus Drive, Asheville, NC 28804, USA.
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3
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Tutunea-Fatan E, Lee JC, Denker BM, Gunaratnam L. Heterotrimeric Gα 12/13 proteins in kidney injury and disease. Am J Physiol Renal Physiol 2020; 318:F660-F672. [PMID: 31984793 DOI: 10.1152/ajprenal.00453.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Gα12 and Gα13 are ubiquitous members of the heterotrimeric guanine nucleotide-binding protein (G protein) family that play central and integrative roles in the regulation of signal transduction cascades within various cell types in the kidney. Gα12/Gα13 proteins enable the kidney to adapt to an ever-changing environment by transducing stimuli from cell surface receptors and accessory proteins to effector systems. Therefore, perturbations in Gα12/Gα13 levels or their activity can contribute to the pathogenesis of various renal diseases, including renal cancer. This review will highlight and discuss the complex and expanding roles of Gα12/Gα13 proteins on distinct renal pathologies, with emphasis on more recently reported findings. Deciphering how the different Gα12/Gα13 interaction networks participate in the onset and development of renal diseases may lead to the discovery of new therapeutic strategies.
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Affiliation(s)
- Elena Tutunea-Fatan
- Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada
| | - Jasper C Lee
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Bradley M Denker
- Beth Israel Deaconess Medical Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Lakshman Gunaratnam
- Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada.,Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.,Division of Nephrology, Department of Medicine, University of Western Ontario, London, Ontario, Canada
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4
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Lecointre C, Desrues L, Joubert JE, Perzo N, Guichet PO, Le Joncour V, Brulé C, Chabbert M, Leduc R, Prézeau L, Laquerrière A, Proust F, Gandolfo P, Morin F, Castel H. Signaling switch of the urotensin II vasosactive peptide GPCR: prototypic chemotaxic mechanism in glioma. Oncogene 2015; 34:5080-94. [PMID: 25597409 DOI: 10.1038/onc.2014.433] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 11/25/2014] [Accepted: 11/25/2014] [Indexed: 12/12/2022]
Abstract
Multiform glioblastomas (GBM) are the most frequent and aggressive primary brain tumors in adults. The poor prognosis is due to neo-angiogenesis and cellular invasion, processes that require complex chemotaxic mechanisms involving motility, migration and adhesion. Understanding these different cellular events implies identifying receptors and transduction pathways that lead to and promote either migration or adhesion. Here we establish that glioma express the vasoactive peptide urotensin II (UII) and its receptor UT and that UT-mediated signaling cascades are involved in glioma cell migration and adhesion. Components of the urotensinergic systems, UII and UT, are widely expressed in patient-derived GBM tissue sections, glioma cell lines and fresh biopsy explants. Interestingly, gradient concentrations of UII produced chemoattracting migratory/motility effects in glioma as well as HEK293 cells expressing human UT. These effects mainly involved the G13/Rho/rho kinase pathway while partially requiring Gi/o/PI3K components. In contrast, we observed that homogeneous concentrations of UII drastically blocked cell motility and stimulated cell-matrix adhesions through a UT/Gi/o signaling cascade, partially involving phosphatidylinositol-3 kinase. Finally, we provide evidence that, in glioma cells, homogeneous concentration of UII allowed translocation of Gα13 to the UT receptor at the plasma membrane and increased actin stress fibers, lamellipodia formation and vinculin-stained focal adhesions. UII also provoked a re-localization of UT precoupled to Gαi in filipodia and initiated integrin-stained focal points. Altogether, these findings suggest that UT behaves as a chemotaxic receptor, relaying a signaling switch between directional migration and cell adhesion under gradient or homogeneous concentrations, thereby redefining sequential mechanisms affecting tumor cells during glioma invasion. Taken together, our results allow us to propose a model in order to improve the design of compounds that demonstrate signaling bias for therapies that target specifically the Gi/o signaling pathway.
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Affiliation(s)
- C Lecointre
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - L Desrues
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - J E Joubert
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - N Perzo
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France.,Department of Pharmacology, Institut of Pharmacology, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - P-O Guichet
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - V Le Joncour
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - C Brulé
- Department of Pharmacology, Institut of Pharmacology, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada.,IGF, Institut of Functional Genomic, CNRS UMR 5203, Inserm U661, University of Montpellier 1 and 2, Montpellier, France
| | - M Chabbert
- UMR CNRS 6214, Inserm 1083, Faculté de Médecine 3, Angers, France
| | - R Leduc
- Department of Pharmacology, Institut of Pharmacology, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - L Prézeau
- IGF, Institut of Functional Genomic, CNRS UMR 5203, Inserm U661, University of Montpellier 1 and 2, Montpellier, France
| | - A Laquerrière
- Service of Anatomocytopathology, CHU of Rouen, ERI28 Inserm, IRIB, Rouen, France
| | - F Proust
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France.,Service of Neurosurgery, CHU of Rouen, Rouen, France
| | - P Gandolfo
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - F Morin
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - H Castel
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
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5
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Nishida M, Ohba M, Nakaya M, Kurose H. [Molecular mechanism underlying the development of heart failure mediated by heterotrimeric G protein signaling]. Nihon Yakurigaku Zasshi 2010; 135:179-183. [PMID: 20467166 DOI: 10.1254/fpj.135.179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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6
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Sabbatini ME, Bi Y, Ji B, Ernst SA, Williams JA. CCK activates RhoA and Rac1 differentially through Galpha13 and Galphaq in mouse pancreatic acini. Am J Physiol Cell Physiol 2009; 298:C592-601. [PMID: 19940064 DOI: 10.1152/ajpcell.00448.2009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cholecystokinin (CCK) has been shown to activate RhoA and Rac1, as well as reorganize the actin cytoskeleton and, thereby, modify acinar morphology and amylase secretion in mouse pancreatic acini. The aim of the present study was to determine which heterotrimeric G proteins activate RhoA and Rac1 upon CCK stimulation. Galpha(13), but not Galpha(12), was identified in mouse pancreatic acini by RT-PCR and Western blotting. Using specific assays for RhoA and Rac1 activation, we showed that only active Galpha(13) activated RhoA. By contrast, active Galpha(13) and Galpha(q), but not Galpha(s), slightly increased GTP-bound Rac1 levels. A greater increase in Rac1 activation was observed when active Galpha(13) and active Galpha(q) were coexpressed. Galpha(i) was not required for CCK-induced RhoA or Rac1 activation. The regulator of G protein signaling (RGS) domain of p115-Rho guanine nucleotide exchange factor (p115-RGS), a specific inhibitor of Galpha(12/13)-mediated signaling, abolished CCK-stimulated RhoA activation. By contrast, both RGS-2, an inhibitor of Galpha(q), and p115-RGS abolished CCK-induced Rac1 activation, which was PLC pathway-independent. Active Galpha(q) and Galpha(13), but not Galpha(s), induced morphological changes and actin redistribution similar to 1 nM CCK. CCK-induced actin cytoskeletal reorganization was inhibited by RGS-2, but not by p115-RGS, whereas CCK-induced amylase secretion was blocked by both inhibitors. Together, these findings indicate that, in mouse pancreatic acini, Galpha(13) links CCK stimulation to the activation of RhoA, whereas both Galpha(13) and Galpha(q) link CCK stimulation to the activation of Rac1. CCK-induced actin cytoskeletal reorganization is mainly mediated by Galpha(q). By contrast, Galpha(13) and Galpha(q) signaling are required for CCK-induced amylase secretion.
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Affiliation(s)
- Maria E Sabbatini
- Department of Molecular and Integrative Physiology, The University of Michigan, Ann Arbor, Michigan, USA.
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7
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Yamazaki J, Katoh H, Negishi M. Lysophosphatidic acid and thrombin receptors require both G alpha12 and G alpha13 to regulate axonal morphology in hippocampal neurons. Biol Pharm Bull 2009; 31:2216-22. [PMID: 19043202 DOI: 10.1248/bpb.31.2216] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The G alpha subunits of the G(12) family of heterotrimeric guanine nucleotide-binding proteins (G proteins), defined by G alpha(12) and G alpha(13), have many cellular functions in common, including stimulation of stress fiber formation and focal adhesion assembly via the small GTPase RhoA activation. We and others previously showed that G alpha(12) and G alpha(13) mediate neurite retraction in neuronal cell lines, but their roles in primary cultured neurons have not been adequately understood. Here, we found that expression of constitutively active mutants of G alpha(12) or G alpha(13) caused growth cone collapse dependent on Rho-kinase activity in hippocampal neurons. The stimulation of thrombin and lysophosphatidic acid (LPA) receptors, which have been thought to selectively couple to G alpha(12) and G alpha(13), respectively, caused growth cone collapse and suppressed axon branching dependent on Rho-kinase activity in hippocampal neurons. Thrombin- and LPA-induced growth cone collapse was suppressed by both single knockdown of G alpha(12) and G alpha(13) with short hairpin RNAs and this suppression was augmented by double knockdown of both G alpha(12) and G alpha(13). These results suggest that thrombin and LPA receptors couple to both G alpha(12) and G alpha(13) for growth cone collapse.
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Affiliation(s)
- Junya Yamazaki
- Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Japan
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8
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Porchia F, Papucci M, Gargini C, Asta A, De Marco G, Agretti P, Tonacchera M, Mazzoni MR. Endothelin-1 up-regulates p115RhoGEF in embryonic rat cardiomyocytes during the hypertrophic response. J Recept Signal Transduct Res 2008; 28:265-83. [PMID: 18569527 DOI: 10.1080/10799890802084515] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
In cardiomyocytes, certain extracellular stimuli that activate heterotrimeric G protein-coupled receptors (GPCRs) can induce hypertrophy by regulating gene expression and increasing protein synthesis. We investigated if rat embryonic cardiomyocytes (H9c2) underwent variations in the expression levels and subcellular distribution of key components of GPCR-activated signaling pathways during endothelin-1 (ET-1)-induced hypertrophic response. A significant increase of p115RhoGEF protein level was evident in ET-1-treated cells. Real-time quantitative PCR showed RhoGEF mRNA levels were significantly increased. Inhibition of the Rho-associated kinase (ROCK) caused a significant decrease of p115RhoGEF protein in the nuclear fraction, whereas an inhibitor of PKC induced a redistribution of the protein between membrane/organelle and nuclear fractions. The ROCK inhibitor also decreased H9c2 cell hypertrophic response. These results indicate that ROCK and its downstream target molecules, which are involved in inducing the hypertrophic response, are also implicated in signaling the up-regulation of the p115RhoGEF protein.
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Affiliation(s)
- Francesca Porchia
- Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, University of Pisa, Pisa, Italy
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9
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Kilts JD, Lin SS, Lowe JE, Kwatra MM. Selective activation of human atrial Galpha12 and Galpha13 by Galphaq-coupled angiotensin and endothelin receptors. J Cardiovasc Pharmacol 2007; 50:299-303. [PMID: 17878759 DOI: 10.1097/fjc.0b013e3180a72632] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Galphaq-coupled receptors such as alpha1-adrenergic, angiotensin, and endothelin receptors, play key roles in cardiac physiology. These receptors have also been shown to couple to G proteins of the G12 family, including Galpha12 and Galpha13. In this report, we determined whether these G proteins interact with endothelin, angiotensin, and alpha1-adrenergic receptors in the human heart. We find that these receptors activate cardiac Galpha12 and Galpha13 differentially; endothelin receptors activate only Galpha12 (to 218 +/- 22% of unstimulated levels), angiotensin receptors activate only Galpha13 (to 236 +/- 49% of unstimulated levels), and alpha1-adrenergic receptors activate neither Galpha12 (123 +/- 18% of unstimulated levels) nor Galpha13 (113 +/- 12% of unstimulated levels). Consistent with these data, translocation of guanine nucleotide exchange factor p115RhoGEF, which responds to Galpha13, occurs only after stimulation of angiotensin receptors (shifting from 73 +/- 12% to 41 +/- 10% cytosolic). These differences in the activation of Galpha12 and Galpha13 by Galphaq-coupled receptors may underlie reported differences in the functions of these receptors.
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MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Angiotensins/physiology
- Atrial Appendage/metabolism
- Atrial Appendage/physiology
- Blotting, Western
- Endothelins/physiology
- Female
- GTP-Binding Protein alpha Subunits, G12-G13/metabolism
- GTP-Binding Protein alpha Subunits, G12-G13/physiology
- Guanine Nucleotide Exchange Factors/metabolism
- Guanine Nucleotide Exchange Factors/physiology
- Humans
- Male
- Middle Aged
- Phenylephrine/pharmacology
- Photoaffinity Labels
- Protein Transport
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Adrenergic, alpha-1/physiology
- Receptors, Angiotensin/metabolism
- Receptors, Angiotensin/physiology
- Receptors, Endothelin/metabolism
- Receptors, Endothelin/physiology
- Rho Guanine Nucleotide Exchange Factors
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Affiliation(s)
- Jason D Kilts
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
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10
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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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11
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Johansson BB, Minsaas L, Aragay AM. Proteasome involvement in the degradation of the G(q) family of Galpha subunits. FEBS J 2005; 272:5365-77. [PMID: 16218966 DOI: 10.1111/j.1742-4658.2005.04934.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metabolically unstable proteins are involved in a multitude of regulatory networks, including those that control cell signaling, the cell cycle and in many responses to physiological stress. In the present study, we have determined the stability and characterized the degradation process of some members of the G(q) class of heterotrimeric G proteins. Pulse-chase experiments in HEK293 cells indicated a rapid turnover of endogenously expressed Galpha(q) and overexpressed Galpha(q) and Galpha(16) subunits. Pretreatment with proteasome inhibitors attenuated the degradation of both G alpha subunits. In contrast, pretreatment of cells with inhibitors of lysosomal proteases and nonproteasomal cysteine proteases had very little effect on the stability of the proteins. Significantly, the turnover of these proteins is not affected by transient activation of their associated receptors. Fractionation studies showed that the rates of Galpha(q) and Galpha16 degradation are accelerated in the cytosol. In fact, we show that a mutant Galpha(q) which lacks its palmitoyl modification site, and which is localized almost entirely in the cytoplasm, has a marked increase in the rate of degradation. Taken together, these results suggest that the G(q) class proteins are degraded through the proteasome pathway and that cellular localization and/or other protein interactions determine their stability.
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Affiliation(s)
- Bente B Johansson
- Department of Biomedicine, Faculty of Medicine, University of Bergen, Norway
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