Nguyen G, Self S J, Camani C, Kruithof E K
Department of Internal Medecine, CHUV, Lausanne, Switzerland.
Biochem J. 1992 Nov 1;287 ( Pt 3)(Pt 3):911-5. doi: 10.1042/bj2870911.
The binding of tissue-type plasminogen activator (t-PA) to membranes prepared from human liver was investigated, and a specific, saturable, high-affinity binding site (Kd = 3.4 nM) was identified. The binding of t-PA to liver membranes was not affected by an excess of D-mannose or D-galactose, or by active urokinase (u-PA), whereas binding of t-PA to membranes prepared from human HepG2 hepatoma cells was inhibited by u-PA. HepG2-membrane-bound t-PA was fully complexed to PA inhibitor 1 (PAI-1), whereas liver-membrane-bound t-PA was not complexed. Gel filtration on Sephacryl S300 of membrane proteins solubilized in deoxycholate revealed that high-affinity t-PA binding activity elutes at an apparent molecular mass of 40 kDa. Monoclonal antibodies specific for the growth factor and the kringle 2 domains inhibited the binding of t-PA to liver membranes and the catabolism of t-PA by rat hepatoma cells. Human liver membranes also bound u-PA; binding was inhibited by pro-u-PA, the N-terminal fragment of u-PA, but not by the 33 kDa form of u-PA or by t-PA. Our results show that human liver membranes contain a specific 40 kDa binding protein for t-PA that is different from the PAI-1-dependent receptor described on HepG2 cells and the mannose receptor isolated from human liver.
研究了组织型纤溶酶原激活剂（t-PA）与人肝制备的膜的结合情况，鉴定出一个特异性、可饱和、高亲和力的结合位点（Kd = 3.4 nM）。t-PA与肝细胞膜的结合不受过量D-甘露糖或D-半乳糖或活性尿激酶（u-PA）的影响，而t-PA与人类HepG2肝癌细胞制备的膜的结合则受到u-PA的抑制。HepG2膜结合的t-PA与纤溶酶原激活剂抑制剂1（PAI-1）完全复合，而肝膜结合的t-PA则未复合。对用脱氧胆酸盐溶解的膜蛋白在Sephacryl S300上进行凝胶过滤显示，高亲和力的t-PA结合活性在表观分子量为40 kDa处洗脱。针对生长因子和kringle 2结构域的单克隆抗体抑制t-PA与肝细胞膜的结合以及大鼠肝癌细胞对t-PA的分解代谢。人肝细胞膜也结合u-PA；结合受到单链尿激酶型纤溶酶原激活剂（pro-u-PA）、u-PA的N端片段的抑制，但不受33 kDa形式的u-PA或t-PA的抑制。我们的结果表明，人肝细胞膜含有一种特异性的40 kDa的t-PA结合蛋白，它不同于在HepG2细胞上描述的PAI-1依赖性受体和从人肝中分离的甘露糖受体。
