Dobner P, Koller E, Engelmann B
Physiologisches Institut der Universität München, Munich, Germany.
FEBS Lett. 1999 Feb 12;444(2-3):270-4. doi: 10.1016/s0014-5793(98)01687-1.
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 125I-LDL by up to 80%. The transfer of pyrene (py)-labeled sphingomyelin (SM), phosphatidylcholine and phosphatidylethanolamine from LDL to the platelets was unaffected by the antibody. The lectin wheat germ agglutinin (WGA) reduced the binding of 125I-LDL to the platelets by approximately 80%. In contrast, the lectin stimulated the transfer of SM from LDL into the platelets by about three-fold. WGA also specifically augmented the transfer of py-SM between lipid vesicles and the platelets, the stimulation being abolished in the presence of N-acetylglucosamine. Dextran sulfate (DS) increased the specific binding of 125I-LDL to the platelets by up to 2.8-fold. On the other hand, the import of LDL-derived py-phospholipids was unaffected by DS. Together, the results indicate that the phospholipid transfer from LDL to the platelets is independent of the high affinity 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.
低密度脂蛋白（LDL）与血小板细胞膜的结合可促进磷脂从LDL向血小板的转移。一种针对血小板糖蛋白IIb/IIIa的多克隆抗体可将125I-LDL的高亲和力结合抑制达80%。芘（py）标记的鞘磷脂（SM）、磷脂酰胆碱和磷脂酰乙醇胺从LDL向血小板的转移不受该抗体影响。凝集素麦胚凝集素（WGA）使125I-LDL与血小板的结合减少约80%。相反，该凝集素使SM从LDL向血小板的转移增加约三倍。WGA还特异性增强了脂质囊泡与血小板之间py-SM的转移，在存在N-乙酰葡糖胺的情况下这种刺激作用消失。硫酸葡聚糖（DS）使125I-LDL与血小板的特异性结合增加达2.8倍。另一方面，LDL衍生的py-磷脂的导入不受DS影响。总之，结果表明磷脂从LDL向血小板的转移独立于LDL与血小板的高亲和力结合，且受到WGA的特异性刺激。因此，血小板与LDL磷脂的相互作用与它们与脂蛋白载脂蛋白成分的相互作用明显不同。
