Active Lyn protein tyrosine kinase is selectively enriched within membrane microdomains of resting platelets.
Circulating platelets are primed to respond very rapidly to thrombogenic stimuli, but most platelets complete their lifespan without ever becoming activated. Platelet activation is accompanied by waves of sequential tyrosine phosphorylation thought to involve members of the Src family of protein tyrosine kinases (PTKs). We show here that resting platelets contain highly active pp53/56(Lyn) PTK within membrane microdomains (rafts) isolated biochemically with or without the use of detergent. This fraction is also greatly enriched in the transmembrane glycoprotein CD36, known to associate with Lyn PTK, but in transfection studies we could find no evidence to suggest that CD36 affects the distribution or function of Lyn. Upon platelet activation Lyn activity remains constant or diminishes and pp60(c-src) PTK within this fraction becomes highly activated, indicating the dynamic nature of the membrane microdomains. It is suggested that the function of active Lyn PTK in the resting platelet is to allow prolonged survival of this anucleate cell.
Dorahy
D J
DJ
Cancer Research Unit, Faculty of Medicine and Health Sciences, University of Newcastle, Callaghan, 2308 NSW, Australia.
Burns
G F
GF
D000818:Animals; D001792:Blood Platelets / Q000201:enzymology*; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002384:Catalysis; D015536:Down-Regulation; D017830:Octoxynol; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D015539:Platelet Activation; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism*
D018955:CD36 Antigens; D009856:Oncogene Proteins, Viral; D017830:Octoxynol; D016392:Proto-Oncogene Proteins pp60(c-src); C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases