Shannon Oonagh, Flock Jan-Ingmar
Division of Clinical bacteriology, Department of Laboratory Medicine, Huddinge University Hospital F82, Karolinska Institute, S-141 86 Stockholm, Sweden.
Thromb Haemost. 2004 Apr;91(4):779-89. doi: 10.1160/TH03-05-0287.
S. aureus produces and secretes a protein, extracellular fibrinogen binding protein (Efb), which contributes to virulence in wound infection. We have shown here that Efb is a potent inhibitor of platelet aggregation. Efb can bind specifically to platelets by two mechanisms; 1) to fibrinogen naturally bound to the surface of activated platelets and 2) also directly to a surface localized component on the platelets. This latter binding of Efb is independent of fibrinogen. The specific binding of Efb to the putative receptor on the platelet surface results in a stimulated, non-functional binding of fibrinogen in a dose dependent manner, distinct from natural binding of fibrinogen to platelets. The natural binding of fibrinogen to GPIIb/IIIa on activated platelets could be blocked by a monoclonal antibody against this integrin, whereas the Efb-mediated fibrinogen binding could not be blocked. The enhanced Efb-dependent fibrinogen binding to platelets is of a nature that does not promote aggregation of the platelets; instead it inhibits aggregation. The anti-thrombotic action of Efb may explain the effect of Efb on wound healing, which is delayed in the presence of Efb.
金黄色葡萄球菌产生并分泌一种蛋白质，即细胞外纤维蛋白原结合蛋白（Efb），它在伤口感染中对毒力有影响。我们在此已表明Efb是血小板聚集的强效抑制剂。Efb可通过两种机制特异性结合血小板：1）与天然结合在活化血小板表面的纤维蛋白原结合；2）也直接与血小板表面的一种定位成分结合。Efb的后一种结合不依赖于纤维蛋白原。Efb与血小板表面假定受体的特异性结合导致纤维蛋白原以剂量依赖方式进行受刺激的、无功能的结合，这与纤维蛋白原与血小板的天然结合不同。活化血小板上纤维蛋白原与糖蛋白IIb/IIIa的天然结合可被针对该整合素的单克隆抗体阻断，而Efb介导的纤维蛋白原结合则不能被阻断。Efb依赖的纤维蛋白原与血小板结合增强，其性质并不促进血小板聚集；相反，它抑制聚集。Efb的抗血栓作用可能解释了Efb对伤口愈合的影响，在有Efb存在时伤口愈合会延迟。
