PAR1 cleavage and signaling in response to activated protein C and thrombin
PAR1 cleavage and signaling in response to activated protein C and thrombin
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DOI：
10.1074/jbc.m410381200
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发表时间：
2005-04-01
影响因子：
4.8
通讯作者：
Coughlin, SR
中科院分区：
文献类型：
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作者：
Ludeman, MJ;Kataoka, H;Coughlin, SR
活化蛋白C（APC）是一种天然的抗凝蛋白酶，可以通过蛋白酶活化受体1（PAR 1）触发细胞反应，PAR 1是凝血酶的G蛋白偶联受体。这种现象是否有助于APC的生理效应尚不清楚。为了回答这个问题，我们比较了APC与凝血酶对内皮细胞上PAR 1切割的动力学。APC确实切割内皮表面上的PAR 1，并且针对内皮蛋白C受体的抗体抑制这种切割。然而，重要的是，在这种情况下，APC的效力比凝血酶低10（4）倍。APC和凝血酶都触发了内皮细胞中PAR 1介导的反应，包括抗凋亡（肿瘤坏死因子-α诱导的α 20和iap-1）和趋化因子（白细胞介素-8（il-8）和cxcl 3）基因的表达，但同样，APC的效力比凝血酶低10（4）倍。向内皮细胞培养物中加入酶原蛋白C并没有改变在低或高浓度凝血酶下PAR 1裂解的速率，并且在凝血酶浓度太低而不能触发蛋白C向APC的可检测转化时PAR 1裂解是实质性的。因此，本地产生的APC没有贡献PAR 1裂解超出凝血酶在这个系统中的影响。尽管与足够高浓度的APC可以在培养物中切割和激活PAR 1的报道一致，但我们的数据表明APC对PAR 1激活的重要生理作用是不可能的。
Activated protein C (APC), a natural anticoagulant protease, can trigger cellular responses via protease-activated receptor-1 (PAR1), a G protein-coupled receptor for thrombin. Whether this phenomenon contributes to the physiological effects of APC is unknown. Toward answering this question, we compared the kinetics of PAR1 cleavage on endothelial cells by APC versus thrombin. APC did cleave PAR1 on the endothelial surface, and antibodies to the endothelial protein C receptor inhibited such cleavage. Importantly, however, APC was similar to 10(4)-fold less potent than thrombin in this setting. APC and thrombin both triggered PAR1-mediated responses in endothelial cells including expression of antiapoptotic ( tumor necrosis factor-alpha-induced a20 and iap-1) and chemokine (interleukin-8 (il-8) and cxcl3) genes, but again, APC was similar to 10(4)-fold less potent than thrombin. The addition of zymogen protein C to endothelial cultures did not alter the rate of PAR1 cleavage at low or high concentrations of thrombin, and PAR1 cleavage was substantial at thrombin concentrations too low to trigger detectable conversion of protein C to APC. Thus, locally generated APC did not contribute to PAR1 cleavage beyond that effected by thrombin in this system. Although consistent with reports that sufficiently high concentrations of APC can cleave and activate PAR1 in culture, our data suggest that a significant physiological role for PAR1 activation by APC is unlikely.