PKC、PKA和TPK在血小板激活中的作用

利用~（３２）Ｐ－ＮａＨ_２ＰＯ_４标记猪血小板，然后以ＰＭＡ、凝血酶、ＰＧＥ_１、腺苷等处理，结果表明，随着ＰＭＡ激活ＰＫＣ，血小板发生聚集。３５μｍｏｌ／ＬＰＧＥ_１或１ｍｍｏｌ／ＬｄｂｃＡＭＰ不能抑制５０ｎｍｏｌ／ＬＰＭＡ诱导的血小板聚集，腺苷却能抑制ＰＭＡ诱导的血小板聚集（ＥＣ_（５０）＝０．１ｍｍｏｌ／Ｌ），ｄｂ－ｃＡＭＰ、腺苷都不能抑制１００ｎｍｏｌ／ＬＰＭＡ诱导的４０ｋＤ蛋白磷酸化。ＰＫＡ激活不能抑制ＰＭＡ激活的ＰＫＣ。在ＰＭＡ、凝血酶激活的血小板中，ＰＫＣ、ＴＰＫ都发生激活，４０ｋＤ底物既是ＰＫＣ的底物又是ＴＰＫ的底物，ＰＫＣ和ＴＰＫ在血小板聚集中起着重要的调节作用。

The Role of PKC, PKA and TPK on Platelet Aggregation

Suspensions of aspirin-treated,￣(32)P-prelabeled, washed pig platelets containing ADP scavengers in the buffer were stimulated with PMA, thrombin,PGE_1 and db-cAMP.The phosphorylation of 40 kD, a subtrate of PKC, was increased dose-dependently with concentraction of PMA or thrombin, also, the phosphoryaltion of 26 kD, 38 kD was. Platelet aggregation induced by PMA occurred in parallel with PKC activation. PGE_1, a adenylate cyclase activator, could not inhibit platelet aggregation induced by 50 nmol/L PMA. db-cAMP,adenosine could not inhibit protein phosphorylation evoked by PKC. The result implies that protein kinase A (PKA) could not inhibit protein kinase C(PKC) when it was activated by PMA. In alkali treated PAGE gel, it was found that 40 kD, 57 kD polypeptides were more resistant to alkali than other polypeptides. Phosphoaminoacid analysis of 40 kD and 57 kD polypeptides indicated that it contained phosphoserine, phosphothreonine and phosphotyrosine. The 40 kD polypeptide may be a common substrate of PKC and TPK (tyrosine-protein kinase). The 40 kD polypeptide phosphorylation may play an important role in platelet aggreagation.