Caspase-3 feeds back on caspase-8, Bid and XIAP in type I Fas signaling in primary mouse hepatocytes
Caspase-3 feeds back on caspase-8, Bid and XIAP in type I Fas signaling in primary mouse hepatocytes
复制标题
DOI：
10.1007/s10495-011-0691-0
复制
发表时间：
2012-05-01
期刊：
影响因子：
7.2
通讯作者：
Borner, Christoph
中科院分区：
文献类型：
--
作者：
Ferreira, Karine Sa;Kreutz, Clemens;Borner, Christoph
TNF-R1样受体Fas在肝细胞的质膜上高度表达，并且在肝内稳态中起重要作用。我们最近发现，在胶原蛋白培养的原代小鼠肝细胞，Fas刺激触发细胞凋亡通过所谓的I型外源性信号通路。与II型途径相比，该途径的核心是胱天蛋白酶-8介导的胱天蛋白酶-3的直接裂解和活化，II型途径首先需要胱天蛋白酶-8介导的Bid裂解以触发线粒体细胞色素c释放用于胱天蛋白酶-3活化。数学建模可以用来理解复杂的信号系统，如串扰和反馈或前馈回路。先前发表的模型预测，在淋巴细胞和Hela细胞中，分别在I型和II型FasL信号传导中的活性半胱天冬酶-3和-8之间存在正反馈环。在这里，我们通过使用野生型和XIAP缺陷的原代肝细胞和两种最近表征的选择性半胱天冬酶-3/-7抑制剂（AB 06和AB 13），在我们的肝细胞I型Fas信号通路中实验性地测试了这一假设。半胱天冬酶-3/-7活性测定和定量蛋白质印迹法证实，完全加工的，活性p17半胱天冬酶-3通过将其部分加工的p43形式切割成完全加工的p18物质来反馈半胱天冬酶-8。我们的数据不歧视，如果p18积极或消极地影响FasL诱导的细胞凋亡或负责非凋亡方面的FasL信号。然而，我们发现，caspase-3也反馈投标和降解自己的抑制剂XIAP，这两个事件，可能会提高caspase-3的活性和细胞凋亡。因此，有效的，选择性胱天蛋白酶-3抑制剂是有用的工具，以了解复杂的信号通路在细胞凋亡。
The TNF-R1 like receptor Fas is highly expressed on the plasma membrane of hepatocytes and plays an essential role in liver homeostasis. We recently showed that in collagen-cultured primary mouse hepatocytes, Fas stimulation triggers apoptosis via the so-called type I extrinsic signaling pathway. Central to this pathway is the direct caspase-8-mediated cleavage and activation of caspase-3 as compared to the type II pathway which first requires caspase-8-mediated Bid cleavage to trigger mitochondrial cytochrome c release for caspase-3 activation. Mathematical modeling can be used to understand complex signaling systems such as crosstalks and feedback or feedforward loops. A previously published model predicted a positive feedback loop between active caspases-3 and -8 in both type I and type II FasL signaling in lymphocytes and Hela cells, respectively. Here we experimentally tested this hypothesis in our hepatocytic type I Fas signaling pathway by using wild-type and XIAP-deficient primary hepatocytes and two recently characterized, selective caspase-3/-7 inhibitors (AB06 and AB13). Caspase-3/-7 activity assays and quantitative western blotting confirmed that fully processed, active p17 caspase-3 feeds back on caspase-8 by cleaving its partially processed p43 form into the fully processed p18 species. Our data do not discriminate if p18 positively or negatively influences FasL-induced apoptosis or is responsible for non-apoptotic aspects of FasL signaling. However, we found that caspase-3 also feeds back on Bid and degrades its own inhibitor XIAP, both events that may enhance caspase-3 activity and apoptosis. Thus, potent, selective caspase-3 inhibitors are useful tools to understand complex signaling circuitries in apoptosis.