Immunocytochemical Study on the Redistribution of Signal Molecules in Human Platelet Adherent to Extracellular Matrices

点击翻译按钮获取中文摘要

Using immunofluorescence microscopy, we have examined the cytoskeletal patterns in human platelets adherent to collagen. Vinculin was detected as aligned patches, and located along actin filaments. Although talin was not detected at the ends of actin filaments, it was concentrated at the periphery of the platelets where the platelets were in close contact with adjacent platelets. pp125^<FAK> was detected as small spots, all of which, as a whole, formed a ring at the central areas of adherent platelets. These results suggest that the adherent platelets fail to form typical focal contacts.Focal adhesion kinase (FAK) is phosphorylated on tyrosine during agonist-induced platelet aggregation or spreading on matrices. In this study, using a immunocytochemical method, we focused on (re)distribution of FAK during platelet activation and aggregation induced by thrombin. We found that FAK translocates to submembrane zone just beneath plasma membrane from cytoplasm prior to both aggregation and tyrosine phosphorylation of the kinase.Next, we have examined the role of phosphoinositide 3-kinase (P13-K) in platelet adhesion and aggregation using wortmannin and LY294002, two unrelated inhibitors of P13-K.Pretreatment of the platelets with the inhibitors prevented platelet spreading on collagen and aggregation induced by thrombin receptor activator peptide. These results suggest that P13-K is necessary for the activation of αllbβ3 integrin and maintenance of the integrin in its active state.