Adunyah S E, Dean W L
Department of Biochemistry, University of Louisville School of Medicine, KY 40292.
Biochim Biophys Acta. 1987 Oct 1;930(3):401-9. doi: 10.1016/0167-4889(87)90013-9.
We have examined the effects of added cAMP-dependent protein kinase and endogenous calmodulin-dependent kinase on Ca2+ transport in purified internal membranes from human platelets. Both Ca2+ uptake and Ca2+-ATPase activity were maximally stimulated about 2-fold by addition of cAMP-dependent protein kinase. Cyclic AMP-dependent protein kinase inhibitor reduced both Ca2+ uptake and Ca2+-ATPase activities at concentrations which also inhibited cAMP-dependent protein phosphorylation. In addition, concerted stimulation of Ca2+-ATPase by exogenous calmodulin and added catalytic subunit of cAMP-dependent protein kinase was observed. A 22-kDa protein was phosphorylated by both cAMP-dependent and calmodulin-dependent kinases at the same rate as stimulation of the Ca2+-ATPase. Cyclic AMP-dependent phosphorylation of the 22-kDa polypeptide was inhibited by the protein kinase inhibitor and calmodulin-dependent phosphorylation was inhibited by chlorpromazine and EGTA. These results are consistent with the hypothesis that one mode of control of Ca2+ homeostasis in platelets may be similar to the phospholamban system in cardiac muscle.
我们研究了添加的环磷酸腺苷（cAMP）依赖性蛋白激酶和内源性钙调蛋白依赖性激酶对人血小板纯化内膜中钙离子转运的影响。添加cAMP依赖性蛋白激酶后，钙离子摄取和钙离子ATP酶活性均受到最大约2倍的刺激。环磷酸腺苷依赖性蛋白激酶抑制剂在抑制cAMP依赖性蛋白磷酸化的浓度下，降低了钙离子摄取和钙离子ATP酶活性。此外，观察到外源性钙调蛋白和添加的cAMP依赖性蛋白激酶催化亚基对钙离子ATP酶有协同刺激作用。一种22 kDa的蛋白质被cAMP依赖性激酶和钙调蛋白依赖性激酶磷酸化的速率与钙离子ATP酶的刺激速率相同。蛋白激酶抑制剂抑制了22 kDa多肽的cAMP依赖性磷酸化，氯丙嗪和乙二醇双四乙酸（EGTA）抑制了钙调蛋白依赖性磷酸化。这些结果与以下假设一致：血小板中钙离子稳态的一种控制模式可能类似于心肌中的受磷蛋白系统。
