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首页> 外文期刊>Biochemistry >INOSITOL 1,4,5-TRISPHOSPHATE-MEDIATED CA2+ RELEASE FROM PLATELET INTERNAL MEMBRANES IS REGULATED BY DIFFERENTIAL PHOSPHORYLATION
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INOSITOL 1,4,5-TRISPHOSPHATE-MEDIATED CA2+ RELEASE FROM PLATELET INTERNAL MEMBRANES IS REGULATED BY DIFFERENTIAL PHOSPHORYLATION

机译：血小板内膜的肌苷1,4,5-三磷酸介导的CA2 +释放通过差异磷酸化来调节

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摘要

Platelets are activated by an increase in cytosolic Ca2+, and a portion of this increase is derived from inositol 1,4,5-trisphosphate (InsP(3))-mediated Ca2+ release from internal stores via the InsP(3) receptor. Cytosolic cAMP inhibits platelet activation, and experiments were designed to determine if cAMP-dependent phosphorylation affects the rate of InsP(3)-mediated Ca2+ release. Western blotting of platelet internal membranes with anti-InsP(3) receptor and anti-actin binding protein antibodies revealed that the platelet contains type 1 InsP(3) receptor and that it is distinct from actin binding protein. The platelet InsP(3) receptor was shown to be phosphorylated by endogenous, membrane-bound kinases as well as by exogenous protein kinase A. Prior phosphorylation of the InsP(3) receptor by endogenous kinases inhibited additional protein kinase A-dependent phosphorylation by 60%. Furthermore, endogenous phosphorylation resulted in a 2-fold increase in the InsP(3)-mediated Ca2+ release rate relative to dephosphorylated controls. Following endogenous phosphorylation, additional phosphorylation by protein kinase A returned the Ca2+ release rate to control values, while protein kinase A-dependent phosphorylation of dephosphorylated membranes did not affect the release rate. These results suggest that the InsP(3) receptor within intact platelets is phosphorylated by endogenous kinases which results in a high InsP(3)-mediated Ca2+ release rate, and that increases in cAMP result in additional phosphorylation that inhibits Ca2+ release, thus contributing to inhibition of platelet activation.
机译：血小板被胞质内Ca2 +的增加所激活，这种增加的一部分来自肌醇1,4,5-三磷酸（InsP（3））介导的Ca2 +通过InsP（3）受体从内部储存区释放。胞质cAMP抑制血小板活化，并设计了实验以确定cAMP依赖性磷酸化是否影响InsP（3）介导的Ca2 +释放速率。抗InsP（3）受体和抗肌动蛋白结合蛋白抗体的血小板内膜的蛋白质印迹显示血小板含有1型InsP（3）受体，并且不同于肌动蛋白结合蛋白。血小板InsP（3）受体被内源性，膜结合激酶以及外源蛋白激酶A磷酸化。内源性激酶对InsP（3）受体的事先磷酸化抑制了额外的蛋白激酶A依赖性磷酸化，其作用为60 ％。此外，内源性磷酸化导致InsP（3）介导的Ca2 +释放速率相对于去磷酸化对照增加2倍。内源性磷酸化后，蛋白激酶A进行的额外磷酸化使Ca2 +释放速率恢复至控制值，而依赖蛋白激酶A的去磷酸化膜的磷酸化则不影响释放速率。这些结果表明完整血小板内的InsP（3）受体被内源性激酶磷酸化，导致高InsP（3）介导的Ca2 +释放速率，而cAMP的增加导致抑制Ca2 +释放的额外磷酸化，从而有助于抑制血小板活化。

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