How do keratins protect hepatocytes against toxic stress

中间丝具有微管和肌动蛋白微丝，它们是大多数哺乳动物细胞的主要细胞骨架成分。在许多人类慢性肝病中，如酒精性肝炎、肝豆状核变性、印度儿童期肝硬变和肥胖所致的肝脏脂肪变性，K8/18IF结构的改变和含有角蛋白的聚集体Mallory小体(MBS)的形成是常见的。最近我们和其他人的研究表明，K8/18在保护肝细胞免受慢性应激诱导的肝损伤中发挥着重要作用。我们项目的长期目标是确定K8/18在肝细胞中发挥保护作用的分子机制。更具体地说，我们想要1)研究特定位点(K8S73、K8S431和K18S52)上的角蛋白磷酸化在肝细胞凋亡信号通路中的作用。在这方面，我们将验证这样的假设，即角蛋白通过直接与促(FasR)和抗(PACT)凋亡分子相互作用，在维持促凋亡和抗凋亡信号分子之间的微妙平衡方面发挥关键调节作用。2)越来越多的证据表明，角蛋白的位点和模式特异性磷酸化在保护肝细胞免受应激中起着关键作用。因此，我们想要研究K8/18在对照组和GF处理的肝细胞中的磷酸化模式，并对K8/18磷酸化进行功能分析。确定在肝细胞对应激反应中影响角蛋白的修饰(翻译后修饰，与其他蛋白质结合)，并研究它们与肝细胞功能的关系，将是我们理解角蛋白实现其功能的分子机制的重要一步。这将直接引导我们进一步研究角蛋白与细胞信号之间的相互作用，以及角蛋白如何影响疾病的发病机制。

Intermediate filaments (IFs) are with microtubules and actin microfilaments the major cytoskeletal components of most mammalian cells. Modifications in K8/18 IFs organisation and formation of keratin containing aggregates called Mallory bodies (MBs) are common to many human chronic liver diseases such as alcoholic hepatitis, Wilson's disease, Indian childhood cirrhosis and liver steatosis in obesity. Recent studies realised by us and others have shown evidences that K8/18 play an important role in the protection of hepatocytes against chronic stress-induced liver injuries.The long-term objective of our project is to determine the molecular mechanism by which K8/18 accomplish their protective role in hepatocytes. More specifically we want to 1) study the role of keratin phosphorylation on specific sites (K8 S73, K8S431 and K18 S52) in the apoptotic signalling pathway in hepatocytes. In this regard we will test the hypothesis that keratins act as a key regulator in maintaining the delicate balance between pro and anti-apoptotic signals molecules by directly interacting with pro (FASr) and anti (pAKT) apoptotic molecules. 2) There is accumulating evidence that sites and pattern- specific phosphorylation of keratin play a key role in the protection of hepatocytes against stress. Thus, we want to characterize K8/18 phosphorylation paterns in control and GF treated hepatocytes and perform functional analysis of K8/18 phosphorylation.The characterization of the modifications that affect keratins (post-translational modification, association with other proteins) during the response of hepatocytes to stress and the study of their relation with hepatocytes functions will constitutes an important step in our understanding of the molecular mechanisms used by keratins to accomplish their functions. This will directly lead us to further research on the cross-talk between keratins and cell signalling, and on how keratins affect disease pathogenesis.