Cytoskeletal proteins and platelet signaling

The actin filament network fills the cytoplasm of unstimulated platelets an d connects with a submembranous latticework of short cross-linked actin fil aments, known as the membrane skeleton. One function of the cytoskeleton is to direct the contours of the membrane in the unstimulated platelet and th e rapid changes in shape in the activated platelet. Activation-induced chan ges result from events such as phosphorylation or calpain-induced cleavage of cytoskeletal proteins. The specific reorganizations depend upon the comb ination of signals to which platelets are exposed. A second function of the cytoskeleton is to bind other cellular components; it binds signaling mole cules, localizing them to specific cellular locations; it binds the plasma membrane regulating properties of the membrane, maintaining microdomains in the membrane, or regulating activities of membrane proteins. In this way, the cytoskeleton plays a critical role in regulation of spatial organizatio ns and, thus, in the integration of cellular activities.