Activation of Hippo Pathway Proteins in Thrombin-Stimulated Platelets and Regutates Platelets Activation in Vitro

Abstract

To investigate the phosphorylation levels of Hippo pathway proteins in thrombin stimulated platelets and to explore its effects on platelet activation. The phosphorylation levels of Hippo pathway proteins - Mammalian STE20-like kinase 1/2 (MST1/2), Nuclear Dbf2 related kinase 1/2 (NDR1/2) and Mps one binder 1(MOB1) in human thrombin stimulated platelets was detected by Western blot. The effect of MST1/2 inhibitor XMU-MP-1 on platelet aggregation was detected by Platelet Aggregometer. The effect of XMU-MP-1 on platelet integrin αIIbβ3 activation and CD62p expression was detected by flow cytometry. The effect of XMU-MP-1 on the "outside-in" signal of platelet integrin was detected by blood clot retraction test. The effects of XMU-MP-1 on platelet Hippo pathway proteins and p38 phosphorylation levels was detected by Western blot. The phosphorylation levels of MST1/2, NDR1/2 and MOB1 were significantly increased in thrombin activated platelets; XMU-MP-1 inhibited thrombin-induced platelet aggregation and αIIbβ3 activation, but did not affect α-granules release and clot retraction. In addition, thrombin induced phosphorylation of the Hippo proteins were decreased in XMU-MP-1 treated platelets, while the phosphorylation of p38 was not affected. In thrombin stimulated platelets, Hippo pathway proteins were activated and contributed to platelets activation.