LYSOSOMAL DEGRADATION OF RECEPTOR-BOUND UROKINASE-TYPE PLASMINOGEN-ACTIVATOR IS ENHANCED BY ITS INHIBITORS IN HUMAN TROPHOBLASTIC CHORIOCARCINOMA CELLS
LYSOSOMAL DEGRADATION OF RECEPTOR-BOUND UROKINASE-TYPE PLASMINOGEN-ACTIVATOR IS ENHANCED BY ITS INHIBITORS IN HUMAN TROPHOBLASTIC CHORIOCARCINOMA CELLS
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DOI：
10.1091/mbc.1.13.1043
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发表时间：
1990-12-01
期刊：
影响因子：
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通讯作者：
ANDREASEN, PA
中科院分区：
文献类型：
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作者：
JENSEN, PH;CHRISTENSEN, EI;ANDREASEN, PA
我们研究了纤溶酶原激活剂抑制剂PAl-1(1)和PAl-2对人绒毛膜癌细胞系JAR中尿激酶型纤溶酶原激活剂(u-PA)与其受体结合的影响。 在全细胞结合测定中使用 I-125 标记的配体时，未复合的 u-PA 和 u-PA 抑制剂复合物均在 4℃ 下以大约 100 pM 的 K(d) 与受体结合。 将细胞转移至 37 摄氏度，导致高达 50% 的细胞结合 u-PA 抑制剂复合物降解为氨基酸，而未复合的 u-PA 降解率为 15%；剩余的配体在培养基中以明显完整的形式回收或者仍然与细胞相关。 囊泡运输和溶酶体水解酶抑制剂可以抑制降解。 通过电子显微镜放射自显影，I-125-u-PA 和 I-125-u-PA 抑制剂复合物均位于 4 摄氏度下的细胞膜上，细胞间期膜上的颗粒密度最高，但在 37 摄氏度下孵育后，u-PA 和 u-PA-PA1-1 复合物的颗粒分别有 17% 和 27% 出现在细胞膜上。溶酶体样小体。 这些发现表明，u-PA 受体在与特定抑制剂形成复合物后具有清除 u-PA 的清除功能。 这些数据表明了一种新的机制，通过第二配体的结合来启动受体介导的内吞作用。
We have studied the effect of plasminogen activator inhibitors PAl-1(1) and PAl-2 on the binding of urokinase-type plasminogen activator (u-PA) to its receptor in the human choriocarcinoma cell line JAR. With I-125-labelled ligands in whole-cell binding assays, both uncomplexed u-PA and u-PA-inhibitor complexes bound to the receptor with a K(d) of approximately 100 pM at 4-degrees-C. Transferring the cells to 37-degrees-C led to degradation to amino acids of up to 50% of the cell-bound u-PA-inhibitor complexes, whereas the degradation of uncomplexed u-PA was 15%; the remaining ligand was recovered in an apparently intact form in the medium or was still cell associated. The degradation could be inhibited by inhibitors of vesicle transport and lysosomal hydrolases. By electron microscopic autoradiography, both I-125-u-PA and I-125-u-PA-inhibitor complexes were located over the cell membrane at 4-degrees-C, with the highest density of grains over the membrane at cell-cell interphases, but, after incubation at 37-degrees-C, 17 and 27% of the grains for u-PA and u-PA-PAl-1 complexes, respectively, appeared over lysosomal-like bodies. These findings suggest that the u-PA receptor possesses a clearance function for the removal of u-PA after its complex formation with a specific inhibitor. The data suggest a novel mechanism by which receptor-mediated endocytosis is initiated by the binding of a secondary ligand.