Separable assembly of platelet pseudopodal and contractile cytoskeletons.
Unactivated platelets contain about 69% G actin and less than 10% of the contractile proteins in a cytoskeletal core resistant to extraction with 1% Triton X-100. Activation by thrombin leads, within 1 min, to the formation of pseudopodia and contractile gels, accompanied by the reduction of the G-actin content to about 22% and the development of cytoskeletal cores containing 70%-80% of the total actin and 60%-80% of the total myosin and actin-binding protein. Inhibition of pseudopodal formation by pretreatment with cytochalasin B before thrombin activation results in the loss of most of the actin-binding protein and about one third of the actin from the cytoskeletal core. Myosin incorporation and contractile gel formation are unaltered by this treatment. Conversely, activation with phorbol 12-myristate 13-acetate leads to pseudopodal but not contractile gel formation, with cytoskeletal cores containing mostly actin and actin-binding protein. These results demonstrate that there are separable cytoskeletal assembly processes in platelets for pseudopodal and contractile gel formation.
D000199:Actins / Q000378:metabolism; D001792:Blood Platelets / Q000648:ultrastructure*; D002352:Carrier Proteins / Q000378:metabolism; D003285:Contractile Proteins / Q000378:metabolism; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D005782:Gels; D018260:Gelsolin; D006801:Humans; D008840:Microfilament Proteins; D009218:Myosins / Q000378:metabolism; D011108:Polymers; D011554:Pseudopodia / Q000648:ultrastructure*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
D000199:Actins; D002352:Carrier Proteins; D003285:Contractile Proteins; D005782:Gels; D018260:Gelsolin; D008840:Microfilament Proteins; D011108:Polymers; C016953:brevin; D003571:Cytochalasin B; D013917:Thrombin; D009218:Myosins; D013755:Tetradecanoylphorbol Acetate