Role of PI3-K and Mlck during Activation of Thrombin Receptors

Object In order to compare the influences of wortmannin on platelet aggregation and platelet membrane surface glycoproteins GPIb expression after thrombin receptors activation, then to investigate the role of phosphatidylinositol 3-kinase (PI3-K) and myosin light chain kinase (MLCK) in the course of thrombin receptors activation.

Methods Peptide SFLLRN (PAR1-AP) and AYPGKF (PAR4-AP)were used for stimulating platelet, then the alterations of platelet aggregation and GPIb were analyzed in the involvement of 100nM wortmannin (inhibitor of PI3-K) and 10μM wortmannin (inhibitor of MLCK).

Results Platelet activation was influenced by either concentration of wortmannin in response to PARs stimulation. Platelet aggregation was apparently inhibited by 10μM wortmannin following both peptides, and slightly inhibited by 100nM wortmannin only upon PAR1-AP activation. In addition, GPIbα interalisation is partly inhibited by 100nM wortmannin in response to PAR1 (P <0.05 at 1, 2, 5min) and PAR4 (P <0.05 at 2, 5, 10min) activation. Meanwhile, 10μM wortmannin induces little alteration for GPIbα centralisation in the course of PAR activation, with a delayed restoration of surface GPIbα observed upon PAR1-AP activation, and no change of GPIbα redistribution exists upon PAR4-AP activation.

Conclusion All the results confirm different roles of PI3-K and MLCK in the course of thrombin receptors activation. PI3-K accelerates the short course of GPIb centralisation for two PARs signal pathways, while MLCK inhibites the restoration of GPIbα in PAR1 pathway