Adelman B, Michelson A D, Greenberg J, Handin R I
Blood. 1986 Dec;68(6):1280-4.
We have characterized the effects of plasmin on glycoprotein Ib (GpIb), a platelet membrane receptor for von Willebrand factor (vWF), and on glycocalicin, a fragment of the alpha chain of GpIb that contains the vWF-binding region. The addition of 4.5 X 10(-7) mol/L plasmin to washed platelets caused a time-dependent decrease in ristocetin-induced, vWF-dependent platelet agglutination. epsilon-Aminocaproic acid (EACA) inhibited plasmin release of glycocalicin-related antigen from washed platelets and preserved vWF-dependent platelet agglutination, thus indicating that the lysine-binding sites on plasmin facilitated its degradation of GpIb. To demonstrate a direct interaction between plasmin and the vWF-binding region of GpIb we incubated purified glycocalicin with plasmin. Plasmin degraded the glycocalicin into two small carbohydrate-poor peptides and into a larger carbohydrate-rich fragment. EACA was able to inhibit plasmin-mediated degradation of glycocalicin in a concentration-dependent fashion. These studies indicated that plasmin degradation of GpIb was due to a direct interaction between plasmin and GpIb and that this effect was mediated by the lysine-binding region of the plasmin molecule.
我们已对纤溶酶对糖蛋白Ib（GpIb）和糖钙蛋白（一种含有血管性血友病因子（vWF）结合区域的GpIbα链片段）的作用进行了表征。向洗涤过的血小板中添加4.5×10⁻⁷mol/L的纤溶酶会导致瑞斯托菌素诱导的、vWF依赖的血小板凝集随时间下降。ε-氨基己酸（EACA）抑制了洗涤过的血小板中纤溶酶释放糖钙蛋白相关抗原，并保留了vWF依赖的血小板凝集，因此表明纤溶酶上的赖氨酸结合位点促进了其对GpIb的降解。为了证明纤溶酶与GpIb的vWF结合区域之间的直接相互作用，我们将纯化的糖钙蛋白与纤溶酶一起孵育。纤溶酶将糖钙蛋白降解为两个小的低糖肽和一个较大的富含糖的片段。EACA能够以浓度依赖的方式抑制纤溶酶介导的糖钙蛋白降解。这些研究表明，GpIb的纤溶酶降解是由于纤溶酶与GpIb之间的直接相互作用，并且这种作用是由纤溶酶分子的赖氨酸结合区域介导的。
