High molecular weight kininogen regulates prekallikrein assembly and activation on endothelial cells: A novel mechanism for contact activation
High molecular weight kininogen regulates prekallikrein assembly and activation on endothelial cells: A novel mechanism for contact activation
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DOI：
10.1182/blood.v91.2.516.516_516_528
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发表时间：
1998-01-15
期刊：
影响因子：
20.3
通讯作者：
Schmaier, AH
中科院分区：
文献类型：
--
作者：
Motta, G;Rojkjaer, R;Schmaier, AH
在血管细胞表面组装蛋白质接触系统的后果几乎没有得到研究。我们询问这些蛋白质在培养的人内皮细胞（HUVEC 5）表面上的组装是否导致前激肽释放酶（PK）及其依赖性途径的激活。在存在高分子量激肽原（HK）的情况下，生物素化PK与HUVEC特异性可逆结合（表观Kd为23 +/- 11 nmol/L，B-max为1.7 +/- 0.5 x 10（7）个位点/细胞[平均值+/- SD，n = 5次实验]）。细胞相关PK迅速转化为激肽释放酶。令人惊讶的是，细胞相关的HK.PK复合物的活化完全不依赖于外源性因子XII（K-m = 30 nmol/L，V-max = 12 +/- 3 pmol/L/min，在不存在时v K-m = 20 nmol/L，V-max = 9.2 +/- 2.1 pmol/L/min，在存在因子XII时）。相反，激肽释放酶的形成是由内皮细胞相关的巯基蛋白酶介导的。细胞相关HK在前激肽释放酶活化过程中被蛋白水解，从表面释放激肽释放酶。此外，与HUVEC上HK结合的PK的活化促进尿激酶原的激肽释放酶依赖性活化，导致纤溶酶的形成。这些结果表明，存在一个以前未描述的，因子XII独立的途径，接触因子激活HUVEC，调节缓激肽的生产，并可能有助于细胞相关的纤溶酶原激活体内。(C)1998年，美国血液学会。
The consequences of assembling the contact system of proteins on the surface of vascular cells has received little study. We asked whether assembly of these proteins on the surface of cultured human endothelial cells (HUVEC5) results in the activation of prekallikrein (PK) and its dependent pathways. Biotinylated PK binds specifically and reversibly to HUVECs in the presence of high molecular weight kininogen (HK) (apparent K-d of 23 +/- 11 nmol/L, B-max of 1.7 +/- 0.5 x 10(7) sites per cell [mean +/- SD, n = 5 experiments]). Cell-associated PK is rapidly converted to kallikrein. Surprisingly, the activation of cell-associated HK.PK complexes is entirely independent of exogenous factor XII (K-m = 30 nmol/L, V-max = 12 +/- 3 pmol/L/min in the absence v K-m = 20 nmol/L, V-max = 9.2 +/- 2.1 pmol/L/min in the presence of factor XII). Rather, kallikrein formation is mediated by an endothelial cell-associated, thiol protease. Cell-associated HK is proteolyzed during the course of prekallikrein activation, releasing kallikrein from the surface. Furthermore, activation of PK bound to HK on HUVECs promotes kallikrein-dependent activation of pro-urokinase, resulting in the formation of plasmin. These results indicate the existence of a previously undescribed, factor XII-independent pathway for contact factor activation on HUVECs that regulates the production of bradykinin and may contribute to cell-associated plasminogen activation in vivo. (C) 1998 by The American Society of Hematology.