Phosphorylation of CPI-17, an inhibitory phosphoprotein of smooth muscle myosin phosphatase, by Rho-kinase.
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 Thr(38) (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 Ca(2+) sensitization of smooth muscle contraction as a downstream effector of Rho-kinase.
Koyama
M
M
First Department of Internal Medicine, Mie University School of Medicine, Tsu, Mie 514-8507, Japan.
Ito
M
M
Feng
J
J
Seko
T
T
Shiraki
K
K
Takase
K
K
Hartshorne
D J
DJ
Nakano
T
T
D000818:Animals; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism*; D043263:Myosin-Light-Chain Phosphatase; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D054460:rho-Associated Kinases
D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase