The effect of platelet surface protein phosphorylation on collagen-platelet interaction

Phosphorylation of the surface proteins of human platelets by treatment with human plasma kinase and exogenous ATP enhances their aggregation response to collagen. This effect can be reversed by treatment of the phosphorylated platelets with acid phosphatase. Moreover, acid phosphatase treatment of normal human platelets results in a decreased aggregation response to collagen. The increased responsiveness of phosphorylated platelets to collagen is associated with a concomitant increase in Thromboxane A2 formation. These results suggest that the platelet surface protein phosphorylation/dephosphorylation plays an important role in modulating platelet function.