Interaction Of Plasminogen With Human Platelets

血凝块的溶解（纤维蛋白溶解）需要纤溶酶，纤溶酶是一种来源于组织纤溶酶原激活剂（tPA）激活纤溶酶原的蛋白酶。已知纤溶酶原和tPA都与血小板表面结合，在那里它们的相互作用大大加速。因此，血小板是纤维蛋白溶解的重要促进剂。我们实验室一直在研究纤溶酶原与血小板结合的一些细节。我们使用经典的平衡结合实验，目的是建立结合位点的数量和结合亲和力。我们还将生物素化纤溶酶原与血小板化学交联，然后通过Western印迹法检测纤溶酶原-受体复合物，目的是鉴定将纤溶酶原与活化和静息细胞结合的血小板膜蛋白。文献表明，血小板活化可增强纤溶酶原，并且增加的结合不是直接与血小板结合，而是与血小板结合的纤维蛋白结合。然而，我们的数据表明，有直接纤溶酶原结合血小板，无论是当他们休息时，当他们被激活。结合位点的数量似乎未被活化而改变，但结合亲和力大大增加。然而，单克隆抗体对纤溶酶原与静息血小板和活化血小板结合的影响是不同的。

Dissolution of blood clots (fibrinolysis) requires plasmin, a protease derived from the activation of plasminogen by tissue plasminogen activator (tPA). Both plasminogen and tPA are known to bind to the surface of platelets, where their interaction becomes greatly accelerated. Therefore, platelets are important promoters of fibrinolysis. Our laboratory has been examining plasminogen binding to platelets in some detail. We use classical equilibrium binding experiments with the goal of establishing the number of binding sites and the binding affinity. We are also chemically crosslinking biotinylated plasminogen to platelets and then testing for plasminogen-receptor complexes by Western blotting, with the goal of identifying the platelet membrane protein(s) that binds plasminogen to activated and resting cells. The literature indicates that platelet activation enhances plasminogen and that the increased binding is not directly to the platelets but to platelet-bound fibrin. However, our data suggest that there is direct plasminogen binding to platelets, both when they are resting and when they are activated. The number of binding sites appears to be unchanged by activation but binding affinity is greatly increased. However, the effect of monoclonal antibodies on plasminogen binding to resting and activated platelets is different.