Vanadate activates Rho A translocation in association with contracting effects in ileal longitudinal smooth muscle of guinea pig.
We characterized the effects of vanadate, an inhibitor of tyrosine phosphatase, on the tension, the level of myosin light chain (MLC) phosphorylation, and Rho A activation in intact ileal longitudinal smooth muscle of the guinea pig to study the role of tyrosine phosphorylation in contraction signaling. Vanadate exerted a sustained contraction with a slow onset of tension development, in a concentration-dependent manner. The contractile effects of vanadate were accompanied by increases in the level of MLC phosphorylation. The tyrosine kinase inhibitor genistein; the MLC kinase inhibitor 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9); and the Rho kinase inhibitor (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride, monohydrate (Y-27632) inhibited the vanadate-induced contraction and MLC phosphorylation. Vanadate caused Rho A translocation from the cytosol to the membrane fraction, which was inhibited by genistein, but not by ML-9 and Y-27632. These data indicate that vanadate induces Rho A activation probably via protein tyrosine phosphorylation and the subsequent contraction through increases in the level of MLC phosphorylation.
Department of Cellular and Molecular Pharmacology, Nagoya City University, Graduate School of Medical Sciences, Nagoya 467-8601, Japan. mkawabe@med.nagoya-cu.ac.jp
Mayumi
M
Mori
Hiromi
H
Tsushima
D000818:Animals; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D014638:Vanadates / Q000494:pharmacology*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D018994:Myosin Light Chains; D014638:Vanadates; D017027:Protein Tyrosine Phosphatases; D020742:rhoA GTP-Binding Protein