HDL binding to human platelets and purified GpIIb/IIa

Abstract

Early studies considered that fibrinogen receptor glycoprotein (Gp) IIb/IIIa is the binding site for both low-density lipoprotein (LDL) and high-density lipoprotein3 (HDL3). Our recent invastigation support the hypotesis that the binding of LDL to human platelets is related to GpIIb/IIIa. However no evidence is found supporting specific binding of HDL to GpIIb/IIIa. In this study, we present evidence that purified integrin GpIIb/IIIa is not the receptor for HDL on platelets. Binding of FITC-conjugated HDL to isolated human platelets and to purified GpIIb/IIIa was detected by using flow cytometry. Binding of HDL to isolated platelets was found to be independent of the state of platelet activation. On the other hand concentration dependent binding of FITC-conjugated HDL to isolated platelets was observed. GpIIb/IIIa, purified from human platelets by afinity chromatography coated to polystyrene microbeads showed no binding activity to HDL-FITC. Therefore GpIIb/IIIa complex is not the receptor for HDL.