CD36 associates with CD9 and integrins on human blood platelets

The membrane glycoprotein CD36 is involved in platelet aggregation, inhibit ion of angiogenesis, atherosclerosis, and sequestration of malaria-parasiti zed erythrocytes. In this study, immunoprecipitations with anti-CD36 antibo dies were performed to identify proteins that associate with CD36 in the pl atelet membrane. Platelets were solubilized in 1% Triton X-100, 3-[(3-chola midopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), Brij 96, or Brij 99 , and the proteins that coprecipitated with CD36 were identified by peptide mass spectrometry and Western blotting. The tetraspanin protein CD9 and th e integrins alpha IIb beta3 and alpha6 beta1 specifically coprecipitated wi th CD36 from platelets that were solubilized in CHAPS and Brij 99 but not f rom platelets that were solubilized in Triton X-100. Only CD9 is coprecipit ated with CD36 from platelets that were solubilized in Brij 96. Reciprocal immunoprecipitations with antibodies to CD9, alpha6, alpha IIb, or beta3 fr om Brij 99-solubilized platelets coprecipitated CD36. Coprecipitation of CD 36, CD9, and alpha6 beta1 was also observed on platelets from a patient wit h Glanzmann thrombasthenia, indicating that alpha IIb beta3 is not required for the other proteins to associate. Colocalization of alpha6 and CD36, of CD9 and CD36, and of alpha6 and CD9 was observed on intact platelets prior to solubilization, using double immunofluorescence microscopy. These data indicate that CD36 associates with CD9 and integrins on human blood platele ts. These associated proteins may mediate or participate in some of the div erse biological functions of CD36. (Blood. 2001;97:1689-1696) (C) 2001 by T he American Society of Hematology.