title: Rho-kinase contributes to sustained RhoA activation through phosphorylation of p190A RhoGAP.
abstract: RhoA is transiently activated by specific extracellular signals such as endothelin-1 (ET-1) in vascular smooth muscle cells. RhoGAP negatively regulates RhoA activity: thus, RhoA becomes the GDP-bound inactive form afterward. Sustained activation of RhoA is induced with high doses of the extracellular signals and is implicated in certain diseases such as vasospasms. However, it remains largely unknown how prolonged activation of RhoA is induced. Here we show that Rho-kinase, an effector of RhoA, phosphorylated p190A RhoGAP at Ser(1150) and attenuated p190A RhoGAP activity in COS7 cells. Binding of Rnd to p190A RhoGAP is thought to enhance its activation. Phosphorylation of p190A RhoGAP by Rho-kinase impaired Rnd binding. Stimulation of vascular smooth muscle cells with a high dose of ET-1 provoked sustained RhoA activation and p190A RhoGAP phosphorylation, both of which were prohibited by a Rho-kinase inhibitor. The phosphomimic mutation of p190A RhoGAP weakened Rnd binding and RhoGAP activities. Taken together, these results suggest that ET-1 induces Rho-kinase activation and subsequent phosphorylation of p190A RhoGAP, leading to prolonged RhoA activation.
authors.affiliation: Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa-ku, Nagoya 466-8550, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mori
authors.forename: Mutsuki
authors.initials: M
authors.lastname: Amano
authors.forename: Mikito
authors.initials: M
authors.lastname: Takefuji
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Kato
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Morita
authors.forename: Tomoki
authors.initials: T
authors.lastname: Nishioka
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Matsuura
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Murohara
authors.forename: Kozo
authors.initials: K
authors.lastname: Kaibuchi
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D009154:Mutation; D010766:Phosphorylation / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D014661:Vasoconstriction; D054460:rho-Associated Kinases / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C074560:ARHGAP35 protein, human; D019332:Endothelin-1; D020662:Guanine Nucleotide Exchange Factors; D009124:Muscle Proteins; D012097:Repressor Proteins; C066737:RHOA protein, human; D006153:Guanosine Diphosphate; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein