Platelet high affinity low density lipoprotein binding and import of lipoprotein derived phospholipids

The binding of low density lipoprotein (LDL) to the platelet cell membrane could facilitate the transfer of phospholipids from LDL to the platelets. A polyclonal antibody against the platelet glycoproteins IIb/IIIa inhibited the high affinity binding of I-125-LDL by up to 80%. The transfer of pyrene (py)-labeled sphingomyelin (SM), phosphatidylcholine and phosphatidylethan olamine from LDL to the platelets was unaffected by the antibody. The lecti n wheat germ agglutinin (WGA) reduced the binding of I-125-LDL to the plate lets by approximately 80%. In contrast, the lectin stimulated the transfer of SM from LDL into the platelets ba about three-fold. WGA also specificall y augmented the transfer of py-SM between lipid vesicles and the platelets, the stimulation being abolished in the presence of N-acetylglucosamine, De xtran sulfate (DS) increased the specific binding of I-125-LDL to the plate lets by up to 2.8-fold. On the other hand, the import of LBL-derived py-pho spholipids was unaffected by DS. Together, the results indicate that the ph ospholipid transfer from LDL to the platelets is independent of the high af finity LDL binding to the platelets and is specifically stimulated by WGA. Thus, the interactions of platelets with LDL phospholipids differ markedly from those with the apoprotein components of the lipoproteins. (C) 1999 Fed eration of European Biochemical Societies.