Phosphorylation of CPI‐17, an inhibitory phosphoprotein of smooth muscle myosin phosphatase, by Rho‐kinase

[摘要]

Phosphorylation of CPI-17 by Rho-associated kinase (Rho-kinase) and its effect on myosin phosphatase (MP) activity were investigated. CPI-17 was phosphorylated by Rho-kinase to 0.92 mol of P/mol of CPI-17 in vitro. The inhibitory phosphorylation site was Thr³⁸ (as reported previously) and was identified using a point mutant of CPI-17 and a phosphorylation state-specific antibody. Phosphorylation by Rho-kinase dramatically increased the inhibitory effect of CPI-17 on MP activity. Thus, CPI-17 as a substrate of Rho-kinase could be involved in the Ca²⁺ sensitization of smooth muscle contraction as a downstream effector of Rho-kinase.

[学科分类] 生物化学/生物物理

[关键词] Rho-kinase;Myosin phosphatase;CPI-17;Smooth muscle;Ca2+ sensitization;Rho-kinase;Rho-associated kinase;MP;myosin phosphatase;PP1;type 1 protein phosphatase;PP1cδ;the δ isoform of the catalytic subunit of PP1;MLCK;myosin light chain kinase;MLC20;20 kDa myosin light chain;PKC;protein kinase C;GST;glutathione S-transferase;GTPγS;guanosine 5′-3-O-(thio)triphosphate;SDS;sodium dodecyl sulfate;PAGE;polyacrylamide gel electrophoresis