Thrombospondin is the endogenous lectin of human platelets
Platelets activated by α-thrombin change shape from disks to spheres and aggregate. During this sequence of activation, platelets develop a membrane-bound lectin activity which is expressed after the secretion of intracellular granule contents. This lectin activity seems to be important in mediating platelet aggregation by binding to a specific receptor on other platelets. Gartner et al. have recently shown that fibrinogen is the receptor for the endogenous lectin secreted by activated platelets. Thrombospondin (also called glycoprotein G and thrombin-sensitive protein) is an α-granule constituent which has a molecular weight (MW) of 450,000 and is a disulphide-linked trimer of 160,000 MW subunits. Secreted thrombospondin binds to platelet membranes in a calcium-dependent manner. We show here that thrombospondin is the endogenous lectin of human platelets.