Mechanisms of programd cell death and morphogenesis in cranio-facial development.

本研究通过分析凋亡信号调节激酶1（Apoptosis Signal-regulating Kinase 1，ASK 1）在颅面发育过程中的信号转导机制，探讨颅面发育过程中细胞程序性死亡和形态发生的机制。我们获得了几条证据表明ASK 1活性受不同衔接子分子的调节。1）硫氧还蛋白（Trx）作为ASK 1抑制剂的鉴定：通过对ASK 1结合蛋白的遗传筛选，Trx（一种涉及抗凋亡功能的氧化还原蛋白）被鉴定为ASK 1的相互作用伴侣。Trx与ASK 1的N-末端部分结合，从而抑制ASK 1活性。Trx作为ASK 1的负调节剂的暗示暗示了细胞凋亡信号转导途径的氧化还原调节的可能机制。2）TRAF 2作为TNF信号传导中ASK 1的激活剂的鉴定：TNF诱导的JNK激活需要TRAF 2。ASK 1被TNF激活并刺激JNK激活。基于这些先前的结果，我们研究了TRAF 2和ASK 1之间可能的联系。ASK 1与TRAF 2过表达相互作用并被其激活。在未转染的哺乳动物细胞中，ASK 1以TNF依赖性方式快速与TRAF 2结合。因此，ASK 1被证明是TRAF 2诱导的JNK激活的介导剂。3）Daxx作为Fas信号传导中ASK 1的激活剂的鉴定：与TRAF 2类似，发现称为Daxx的Fas特异性衔接分子与ASK 1相互作用并激活ASK 1。Daxx-ASK 1轴可能为Fas诱导的细胞凋亡提供了另一条信号通路。

The aim of this study is to understand the mechanisms of programmed cell death and morphogenesis in the process of cranio-facial development by analyzing the signal transduction mechanisms through ASK1 (Apoptosis signal-regulating kinase 1). We obtained several lines of evidence that ASK1 activity is regulated by different adaptor molecules.1) Identification of thioredoxin (Trx) as an ASK1 inhibitor : Through a genetic screen for ASK 1-binding proteins, Trx, a redox protein implicated in anti-apoptotic function, was identified as an interacting partner of ASK 1. Trx associated with the N-terminal part of ASK1 and thereby inhibited ASK1 activity. The implication of Trx as a negative regulator of ASK1 suggests possible mechanisms for the redox regulation of apoptosis signal transduction pathway.2) Identification of TRAF2 as an activator of ASK1 in TNF signaling : TNF-induced activation of the JNK requires TRAF2. ASK1 is activated by TNF and stimulates JNK activation. Based on these previous results, we investigated the possible connection between TRAF2 and ASK1. ASK1 interacts with and is-activated by TRAF2 overexpression. In untransfected mammalian cells ASK1 rapidly associates with TRAF2 in a TNF-dependent manner. Thus, ASK 1 turned out to be a mediator of TRAF2-induced JNK activation.3) Identification of Daxx as an activator of ASK1 in Fas signaling : Similar to TRAF2, Fas-specific adaptor molecule called Daxx was found to interact with and activate ASK1. Daxx-ASK1 axis may provide another signaling pathway to Fas-induced apoptosis.