title: RhoA phosphorylation induces Rac1 release from guanine dissociation inhibitor alpha and stimulation of vascular smooth muscle cell migration.
abstract: Although overactivation of RhoA is recognized as a common component of vascular disorders, the molecular mechanisms regulating RhoA activity in vascular smooth muscle cells (VSMC) are still unclear. We have previously shown that in VSMC, RhoA is phosphorylated on Ser188 by nitric oxide (NO)-stimulated cGMP-dependent kinase (PKG), which leads to RhoA-Rho kinase pathway inhibition. In this study, we showed that expression of phosphoresistant RhoA mutants prevented the stimulation of VSMC migration and adhesion induced by NO-PKG pathway activation. In contrast, under basal conditions, phosphomimetic RhoA mutants stimulated VSMC adhesion and migration through a signaling pathway requiring Rac1 and the Rho exchange factor Vav3. RhoA phosphorylation or phosphomimetic RhoA mutants induced Rac1 activation but did not activate Vav3. Indeed, phosphorylated RhoA or phosphomimetic mutants trapped guanine dissociation inhibitor α (GDIα), leading to the release of Rac1 and its translocation to the membrane, where it was then activated by the basal Vav3 nucleotide exchange activity. In vivo, RhoA phosphorylation induced by PKG activation in the aortas of rats treated with sildenafil induced dissociation of Rac1 from GDIα and activation of the Rac1 signaling pathway. These results suggest that the phosphorylation of RhoA represents a novel potent and physiological GDIα displacement factor that leads to Rac1 activation and regulation of Rac1-dependent VSMC functions.
authors.affiliation: INSERM UMR915, l'Institut du Thorax, IRTUN, Nantes, France. malvyne.derkinderen@univ-nantes.fr
authors.forename: Malvyne
authors.initials: M
authors.lastname: Rolli-Derkinderen
authors.forename: Gilles
authors.initials: G
authors.lastname: Toumaniantz
authors.forename: Pierre
authors.initials: P
authors.lastname: Pacaud
authors.forename: Gervaise
authors.initials: G
authors.lastname: Loirand
mesh_terms: D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D051567:Proto-Oncogene Proteins c-vav / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology; D014945:Wound Healing / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C086796:GDP dissociation inhibitor 1; D020730:Guanine Nucleotide Dissociation Inhibitors; D051567:Proto-Oncogene Proteins c-vav; D034741:RNA, Small Interfering; D013873:Thionucleotides; C550255:VAV3 protein, rat; D009569:Nitric Oxide; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; D017869:Cyclic GMP-Dependent Protein Kinases; C499134:Rac1 protein, rat; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; D006152:Cyclic GMP