Sano K, Nakamura H, Matsuo T, Kawahara Y, Fukuzaki H, Kaibuchi K, Takai Y
FEBS Lett. 1985 Nov 11;192(1):4-8. doi: 10.1016/0014-5793(85)80031-4.
In human platelets, the Ca2+ ionophore A23187 stimulated the phosphorylation of a 40 kDa protein and myosin light chain (MLC) to the same extents as those induced by thrombin, but the doses of A23187 for 40 kDa protein phosphorylation were higher than those for MLC phosphorylation, although the doses of thrombin for both reactions were nearly the same. Moreover, A23187 produced much less diacylglycerol than thrombin. However, the sites of the 40 kDa protein phosphorylated by the action of A23187 and thrombin were identical, and the 40 kDa protein phosphorylation induced by A23187 and thrombin was inhibited by tetracaine, an inhibitor for protein kinase C. Neither A23187 nor thrombin induced the production of a catalytic fragment of protein kinase C which might be generated by limited proteolysis with Ca2+-dependent protease. These results indicate that A23187 induces protein kinase C activation which phosphorylates the 40 kDa protein, but higher doses of A23187 are required for the activation of this enzyme than for the activation of MLC kinase.
在人血小板中，Ca2+离子载体A23187刺激40 kDa蛋白和肌球蛋白轻链（MLC）磷酸化的程度与凝血酶诱导的相同，但诱导40 kDa蛋白磷酸化所需的A23187剂量高于MLC磷酸化所需剂量，尽管两种反应中凝血酶的剂量几乎相同。此外，A23187产生的二酰甘油比凝血酶少得多。然而，A23187和凝血酶作用下磷酸化的40 kDa蛋白的位点相同，且A23187和凝血酶诱导的40 kDa蛋白磷酸化被蛋白激酶C抑制剂丁卡因抑制。A23187和凝血酶均未诱导可能由Ca2+依赖性蛋白酶有限水解产生的蛋白激酶C催化片段的产生。这些结果表明，A23187诱导蛋白激酶C激活，使40 kDa蛋白磷酸化，但激活该酶所需的A23187剂量高于激活MLC激酶所需剂量。
