Fibroblasts, glial, and neuronal cells are involved in extravascular prothrombin activation
Fibroblasts, glial, and neuronal cells are involved in extravascular prothrombin activation
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DOI：
10.1093/oxfordjournals.jbchem.a022499
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发表时间：
1999-10-01
影响因子：
2.7
通讯作者：
Morita, T
中科院分区：
文献类型：
--
作者：
Yamazaki, Y;Shikamoto, Y;Morita, T
在来源于非造血细胞的各种培养细胞上发现了膜相关凝血酶原激活物（MAPA）[Sekiya，F，et al，（1994）J，Biol，Chem，269，32441-32445]。在这项研究中，我们使用蛋白酶抑制剂研究了这种酶的酶性质。金属蛋白酶抑制剂邻菲咯啉对MAPA活性无影响，而某些Kunitz型丝氨酸蛋白酶抑制剂可减弱MAPA活性，重组组织因子途径抑制剂（rTFPI）也可显著降低MAPA活性（IC 50，1.3+/-0.6 × 10（-10）M），因此，MAPA活性最可能是由于Xa因子。我们评估了外源性Xa因子对MAPA活性的影响，在成纤维细胞上观察到因子Xa依赖性凝血酶原活化（表观K-d，1.47+/-0.72 nM）。在表达MAPA活性的神经胶质细胞和神经元细胞上也观察到活化。这些结果表明，膜结合因子Xa的结果在这些细胞上的MAPA活性。因此，我们认为参与因子Va，凝血酶原酶的一个组成部分，在这种活动。我们检查了凝血酶原酶复合物是否在这些细胞上组装。凝血酶原以依赖于外源性因子Xa和因子Va的方式活化（因子Va的表观Kd为0.51-1.81 nM）。这些结果表明凝血酶原酶复合物特异性地在各种血管外细胞上形成。虽然凝血酶原酶复合物可以在单核细胞和淋巴细胞上组装，但不知道为什么这些细胞可以特异性地激活凝血酶原。具有凝血酶原激活剂活性的这些细胞也可以激活因子X;即具有因子X激活活性的细胞能够转化凝血酶原。这些观察结果表明，凝血酶是通过两种促凝血活性产生的;因子X活化和随后在这些细胞表面上凝血酶原酶复合物的形成，这种机制可以解释各种病理状态涉及或导致血管外凝血酶和纤维蛋白的形成。
A membrane-associated prothrombin activator (MAPA) was found on various cultured cells derived from non-hematopoietic cells [Sekiya, F, et al, (1994) J, Biol, Chem, 269, 32441-32445], In this study, we investigated the enzymatic properties of this enzyme using protease inhibitors. While the metalloproteinase inhibitor, o-phenanthroline, had no effect, some Kunitz type serine protease inhibitors attenuated MAPA activity, Recombinant tissue factor pathway inhibitor (rTFPI) also markedly reduced the activity (IC50, 1.3+/-0.6 X 10(-10) M), MAPA activity is, therefore, most likely to be due to factor Xa, We evaluated the effect of exogenous factor Xa on MAPA activity, Factor Xa-dependent prothrombin activation was observed on fibroblast cells (apparent K-d, 1.47+/-0.72 nM). Activation was also observed on glial and neuronal cells, which expressed MAPA activity. These results imply that membrane-bound factor Xa results in MAPA activity on these cells. Therefore, we considered the involvement of factor Va, a component of prothrombinase, in this activity. We examined whether or not the prothrombinase complex is assembled on these cells. Prothrombin was activated in a manner dependent on both exogenous factor Xa and factor Va (apparent K-d of 0.51-1.81 nM for factor Va). These results indicate that the prothrombinase complex forms specifically on various extravascular cells. Although the prothrombinase complex can be assembled on monocytes and lymphocytes, it is not known why these cells can activate prothrombin specifically. These cells which have the capacity for prothrombin activator activity could also activate factor X; i.e. cells with factor X activation activity were able to convert prothrombin, These observations suggest that thrombin was generated via two procoagulant activities; factor X activation and subsequent prothrombinase complex formation on the surface of these cells, This mechanism may explain the various pathological states involving or resulting from extravascular thrombin and fibrin formation.