PHOSPHORYLATION OF PLATELET ACTIN-BINDING PROTEIN DURING PLATELET ACTIVATION

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 59  (3) , 466-471
Abstract
The 32P-labeling of actin-binding protein as a function of platelet activation was studied. Utilizing polyacrylamide-sodium dodecyl sulfate gel electrophoresis to resolve total platelet protein samples, 2-3-fold labeling increases in actin-binding protein 30-60 s were found after thrombin stimulation. Somewhat larger increases were observed for 40,000 and 20,000 apparent MW peptides. The actin-binding protein was identified on the gels by coelectrophoresis with purified actin-binding protein, its presence in cytoskeletal cores prepared by detergent extraction of activated 32P-labeled platelets, and by direct immunoprecipitation with antibodies against guinea pig vas deferens filamin (actin-binding protein). These cytoskeletal cores also indicated that the 32P-labeled actin-binding protein was closely associated with the activated platelet''s cytoskeleton. Following the 32P-labeling of actin-binding protein over an 8-min time course revealed that in aggregating platelet samples rapid dephosphorylation to almost initial levels occurred between 3 and 5 min. A similar curve was obtained for the 20,000 apparent MW peptide. However, rapid dephosphorylation was not observed if platelet aggregation was prevented by chelating external Ca or by using thrombasthenic platelets lacking the aggregation response. Cell-cell contact would seem to be crucial in intiating the rapid dephosphorylation response.