MYOSIN AND CALDESMON PHOSPHORYLATION IN NONMUSCLE CELLS

Caldesmon是一种肌动蛋白结合蛋白，可以调节肌动蛋白为基础的 细胞过程这些活动包括胞质分裂，形状 变化、细胞运动性、细胞与细胞的相互作用、与基质的粘附以及 分泌物体外研究表明，钙调素可以抑制 肌动蛋白激活的肌球蛋白MgATP酶活性，这种抑制作用可以 通过钙调蛋白与钙调素结合来逆转。Caldesmon是一种底物， 各种激酶，并已被证明是磷酸化，在光滑 肌肉收缩。当人类血小板被激活时， 用佛波醇酯处理。 我们已经检测了钙调素的磷酸化， 血小板与生理激动剂如凝血酶、ADP和胶原 在用前列腺素PGI2治疗后，它提高了cAMP水平。 钙调素磷酸化的水平或位点没有增加 用凝血酶、ADP或胶原蛋白处理血小板后， 用PGI2处理导致磷酸化增加。胰蛋白 磷酸肽图谱显示，这种磷酸化主要发生在 在两个位点，其也在体外被cAMP依赖性 蛋白激酶

Caldesmon is an actin-binding protein which may modulate actin-based cellular processes. These include activities such as cytokinesis, shape change, cell motility, cell to cell interactions, adhesion to substrata and secretion. In vitro studies have shown that caldesmon can inhibit the actin-activated MgATPase activity of myosin and that this inhibition can be reversed by calmodulin binding to caldesmon. Caldesmon is a substrate for various kinases and has been shown to be phosphorylated during smooth muscle contraction. It is also phosphorylated when human platelets are treated with phorbol esters. We have examined the phosphorylation of caldesmon following treatment of platelets with physiological agonists such as thrombin, ADP and collagen and after treatment with the prostaglandin, PGI2, which raises cAMP levels. There is no increase in the level or sites of phosphorylation of caldesmon following treatment of platelets with thrombin, ADP or collagen, but treatment with PGI2 results in an increase in phosphorylation. Tryptic phosphopeptide maps show that this phosphorylation is primarily occurring at two sites which are also phosphorylated in vitro by cAMP-dependent protein kinase.