Fox J E, Phillips D R
J Biol Chem. 1982 Apr 25;257(8):4120-6.
The effect of myosin light chain phosphorylation on the association of myosin with the cytoskeletal structures of platelets was quantitated. In unstimulated platelets, little myosin light chain was phosphorylated and myosin remained in solution when cytoskeletons from Triton X-100 lysates of platelets were sedimented by centrifugation. In platelets activated by thrombin, the calcium ionophore A23187, or collagen, the rate and extent of myosin light chain phosphorylation paralleled the association of myosin with platelet cytoskeletal structures. Dephosphorylation of myosin light chain and myosin dissociation from the cytoskeleton occurred at comparable rates at longer times after addition of the stimulating agents to platelets. Quantitation of radioactive phosphate in the cytoskeleton-associated myosin and in the soluble myosin showed that the phosphorylated myosin light chain was selectively isolated with the Triton-insoluble cytoskeletons, whereas nonphosphorylated myosin was not associated. Inhibition of the light chain kinase with the calmodulin antagonist trifluoperazine inhibited myosin light chain phosphorylation and incorporation of myosin into the platelet cytoskeletons. Inhibition of light chain phosphorylation by prostaglandin E1 and prostacyclin produced similar effects. Thus, phosphorylation of the myosin light chain stabilizes the association of myosin with the contractile structures within platelets.
对肌球蛋白轻链磷酸化作用于肌球蛋白与血小板细胞骨架结构结合的效应进行了定量分析。在未受刺激的血小板中，很少有肌球蛋白轻链发生磷酸化，当通过离心使血小板经Triton X - 100裂解物中的细胞骨架沉降时，肌球蛋白仍留在溶液中。在由凝血酶、钙离子载体A23187或胶原蛋白激活的血小板中，肌球蛋白轻链磷酸化的速率和程度与肌球蛋白和血小板细胞骨架结构的结合情况平行。在向血小板添加刺激剂后的较长时间内，肌球蛋白轻链的去磷酸化以及肌球蛋白从细胞骨架上解离的速率相当。对与细胞骨架结合的肌球蛋白和可溶性肌球蛋白中的放射性磷酸盐进行定量分析表明，磷酸化的肌球蛋白轻链被选择性地分离到Triton不溶性细胞骨架中，而非磷酸化的肌球蛋白则未与之结合。用钙调蛋白拮抗剂三氟拉嗪抑制轻链激酶可抑制肌球蛋白轻链磷酸化以及肌球蛋白掺入血小板细胞骨架。前列腺素E1和前列环素对轻链磷酸化的抑制产生了类似的效果。因此，肌球蛋白轻链的磷酸化稳定了肌球蛋白与血小板内收缩结构的结合。
