PI3K调控血小板聚集过程中RhoA活性及其与mDia1相互作用

a 本研究探讨RhoA／mDia1通路在血小板聚集过程中的作用及PI3K抑制剂对该过程的调控作用。分离人外周血中血小板，采用GSTpull-down法及免疫共沉淀法检测血小板聚集过程中RhoA、Rac1及Cdc42活性的变化；采用免疫共沉淀法检测血小板聚集过程中RhoA、Rac1及Cdc42是否与mDia1相互结合并形成复合体，并进一步检测PI3K抑制剂对上述过程的影响。结果表明：凝血酶能够诱导聚集血小板中RhoA活性上调，且与mDial相结合的RhoA-GTP显著增高；渥曼青霉素（wortmnnin）能够阻断由凝血酶诱导的聚集血小板中RhoA活性上调，并阻断凝血酶诱导的RhoA—GTP与mDia1的结合。凝血酶能上调聚集血小板中Rac1和Cdc42生物活性，但并未诱发其与mDia1结合，该过程也不能被wortmannin阻断。结论：PI3K通过RhoA／mDia1参与调控凝血酶诱导的血小板聚集等actin细胞骨架重构过程。

PI3-kinase Mediates Activity of RhoA and Interaction of RhoA with mDia1 in Thrombin-induced Piatelet Aggregation

The aim of this study was to investigate the role of RhoA/mDial pathway in the process of thrombininduced platelet aggregation and regulatory effect of PI3K inhibitor on this process. The human platelets were isolated from peripheral blood, the activation of RhoA, Racl and Cdc42 in the platelet aggregation was detected by GST pulldown assay and immune co-precipitation, the interaction of RhoA, Racl and Cdc42 with raDial and the formation of complex in the process of platelet aggregation were determined by immune coprecipitation, and the effect of PI3K inhibitor （wortmannin） on above-mentioned process was assayed. The results showed that thrombin elevated the activity of RhoA and the binding capability of RhoA with raDial during thrombin-induced platelet aggregation and spreading on Fg coated coverslips. Wortmannin inhibited the rising of RhoA activity and the binding level of RhoA with mDial induced by thrombin. Thrombin elevated the activity of Racl and Cdc42 during thrombin-induced platelet aggregation, but could not induce binding of Racl or Cdc42 with mDial. Wortmannin could not inhibit the rising of Racl and Cdc42 activity induced by thrombin. It is concluded that the PI3-kinase regulates the thrombin-induced actin cytoskeleton reconstitution in platelets by RhoA-mDial pathway.