Higashihara M, Takahata K, Kurokawa K, Ikebe M
First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
FEBS Lett. 1992 Jul 28;307(2):206-10. doi: 10.1016/0014-5793(92)80768-c.
Okadaic acid (OA), a potent inhibitor of protein phosphatases type 1 and type 2A, inhibited thrombin-induced platelet aggregation (IC50 = 0.8 microM), [14C]serotonin release and increase in intracellular Ca2+ ([Ca2+]i) in the same dose dependence. In the absence of thrombin OA increased the phosphorylation of 50-kDa protein and 20-kDa myosin light chain (MLC20). The 50-kDa protein phosphorylation was accomplished within a shorter time period and at a lower concentration than was the MLC20. OA decreased the thrombin-induced phosphorylation of 47-kDa protein and MLC20, although phosphorylation of MLC20 reincreased at higher concentrations of OA (5-10 microM). Since type 2A phosphatase is more sensitive to OA than type 1, these results suggest that type 2A phosphatases are involved in the regulation of Ca2+ signaling in thrombin-induced platelet activation.
冈田酸（OA）是一种强效的蛋白磷酸酶1型和2A型抑制剂，以相同的剂量依赖性抑制凝血酶诱导的血小板聚集（IC50 = 0.8微摩尔）、[14C]5-羟色胺释放以及细胞内Ca2+（[Ca2+]i）升高。在没有凝血酶的情况下，OA增加了50-kDa蛋白和20-kDa肌球蛋白轻链（MLC20）的磷酸化。50-kDa蛋白的磷酸化在比MLC20更短的时间内且在更低的浓度下完成。OA降低了凝血酶诱导的47-kDa蛋白和MLC20的磷酸化，尽管在更高浓度的OA（5 - 10微摩尔）下MLC20的磷酸化再次增加。由于2A型磷酸酶比1型对OA更敏感，这些结果表明2A型磷酸酶参与凝血酶诱导的血小板激活过程中Ca2+信号的调节。
