Yeh C H, Wang W C, Hsieh T T, Huang T F
Department of Pharmacology, College of Medicine, National Taiwan University, Chang Gung Memorial Hospital, Taipei 100, Taiwan.
J Biol Chem. 2000 Jun 23;275(25):18615-8. doi: 10.1074/jbc.C000234200.
Glycoprotein (GP) Ib, an adhesion receptor expressed on both platelets and endothelial cells, mediates the binding of von Willebrand factor (vWF). Platelet GPIb plays an important role in platelet adhesion and activation, whereas the interaction of vWF and endothelial GPIb is not fully understood. We report here that agkistin, a snake venom protein, selectively blocks the interaction of vWF with human endothelial GPIb and inhibits angiogenesis in vivo. Agkistin specifically blocked human umbilical vein endothelial cell (HUVEC) adhesion to immobilized vWF in a concentration-dependent manner. Fluorescein isothiocyanate (FITC)-conjugated agkistin bound to HUVECs in a saturable manner. AP1, a monoclonal antibody (mAb) raised against GPIb, specifically inhibited the binding of FITC-conjugated agkistin to HUVECs in a dose-dependent manner, but other anti-integrin mAbs raised against alpha(v)beta(3), alpha(2)beta(1), and alpha(5)beta(1) did not affect this binding reaction. However, neither agkistin (2 microgram/ml) nor AP1 (40 microgram/ml) apparently reduced HUVEC viability. Both agkistin and AP1 exhibited a profound anti-angiogenic effect in vivo when assayed by using the 10-day-old embryo chick chorioallantoic membrane model. These results suggest endothelial GPIb plays a role in spontaneous angiogenesis in vivo, and the anti-angiogenic effect of agkistin may be because of disruption of the interaction of endogenous vWF with endothelial GPIb.
糖蛋白（GP）Ib是一种在血小板和内皮细胞上均有表达的黏附受体，介导血管性血友病因子（vWF）的结合。血小板糖蛋白Ib在血小板黏附和激活中起重要作用，而vWF与内皮糖蛋白Ib之间的相互作用尚未完全明确。我们在此报告，蛇毒蛋白阿吉斯汀能选择性阻断vWF与人内皮糖蛋白Ib的相互作用，并在体内抑制血管生成。阿吉斯汀以浓度依赖的方式特异性阻断人脐静脉内皮细胞（HUVEC）与固定化vWF的黏附。异硫氰酸荧光素（FITC）偶联的阿吉斯汀以饱和方式与HUVEC结合。AP1是一种针对糖蛋白Ib产生的单克隆抗体（mAb），能以剂量依赖的方式特异性抑制FITC偶联的阿吉斯汀与HUVEC的结合，但针对α(v)β(3)、α(2)β(1)和α(5)β(1)产生的其他抗整合素单克隆抗体不影响这种结合反应。然而，阿吉斯汀（2微克/毫升）和AP1（40微克/毫升）均未明显降低HUVEC的活力。当使用10日龄鸡胚绒毛尿囊膜模型进行检测时，阿吉斯汀和AP1在体内均表现出显著的抗血管生成作用。这些结果表明内皮糖蛋白Ib在体内自发性血管生成中起作用，阿吉斯汀的抗血管生成作用可能是由于内源性vWF与内皮糖蛋白Ib的相互作用被破坏。
