Regulation of myosin phosphatase through phosphorylation of the myosin-binding subunit in platelet activation.
Human platelets were found to contain myosin phosphatase consisting of a 38-kD catalytic subunit of protein phosphatase type 1delta, a 130-kD myosin-binding subunit (MBS) and a 20-kD subunit, all of which cross-reacted with antibodies against these subunits of smooth muscle myosin phosphatase. Anti-MBS antibody coimmunoprecipitated RhoA and Rho-kinase of human platelets. Platelets MBS is a substrate for Rho-kinase and phosphorylation of MBS decreases the activity of myosin phosphatase. Treatment of intact platelets with 9, 11-epithio-11,12-methano-thromboxane A2 led to a dramatic increase in phosphorylation of MBS and a significant decrease in the activity of myosin phosphatase. These findings suggest a putative mechanism for agonist-induced regulation of myosin phosphatase activity in platelets.
Nakai
K
K
2nd Department of Internal Medicine, Mie University School of Medicine, Tsu Mie, Japan.
Suzuki
Y
Y
Kihira
H
H
Wada
H
H
Fujioka
M
M
Ito
M
M
Nakano
T
T
Kaibuchi
K
K
Shiku
H
H
Nishikawa
M
M
D001665:Binding Sites; D001792:Blood Platelets / Q000378:metabolism*; D006801:Humans; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D015539:Platelet Activation
D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins