CD36 IS SPATIALLY ASSOCIATED WITH GLYCOPROTEIN IIB-IIIA (ALPHA-IIB-BETA-3) ON THE SURFACE OF RESTING PLATELETS

Platelet activation and aggregation induced by agonists such as thromb in are accompanied by the phosphorylation of several proteins on tyros ine. Such tyrosine phosphorylation is dependent upon activation and li gand engagement of the major integrin receptor on the surface of plate lets, glycoprotein (GP) IIb-IIIa (alpha IIb beta 3), but how this is a ccomplished is not known. The only platelet membrane GP known to assoc iate with non receptor tyrosine kinases is CD36 (GPIV) which forms ass ociations with pp60(Fyn), pp62(Yes), and pp54/58(Lyn), and antibodies directed against CD36 activate platelets in a process dependent upon G PIIb-IIIa. These and other data suggest physical association between t he two membrane GPs, IIb-IIIa and CD36. By the use of immunoprecipitat ion of lysates of platelets that have been surface labeled and chemica lly crosslinked we show here that CD36 and GPIIb-IIIa are spatially as sociated on the surface of resting platelets. (C) 1996 Academic Press, Inc.