過多摺疊不正確的蛋白質累積在內質網時會造成內質網壓力，而在此情況下會促使細胞產生不完全摺疊蛋白反應以幫助細胞紓解內質網壓力，此反應會令細胞內質網壓力感應者PERK活化以抑制新蛋白質合成，而且也可經由IRE1活化一些下游基因如伴隨蛋白幫助蛋白質摺疊。在本實驗室先前研究指出內質網壓力會刺激NFκB活化藉由p38MAPK蛋白這條路徑。另外也有人提到ASK1/MAPKKK5這個p38上游基因在內質網壓力下會與IRE1和TRAF2結合使其可以活化同樣是MAPK成員的JNK蛋白，這告訴我們ASK1在內質網壓力刺激p38表現這條路徑扮演相當重要的角色。為了分析ASK1在內質網壓力下的調控機制，我們利用ASK1 shRNA來抑制Huh7細胞中ASK1表現以觀察其對內質網壓力活化路徑及造成脂肪累積的影響，首先我們建立了持續表現ASK1 shRNA的Huh7細胞，而且也發現到內質網壓力訊息分子GRP78、XBP-1在Huh7 ASK1 shRNA stable細胞中有被抑制的情形，而且脂質累積情形也有降低，然而詳細機制仍需進一步探討。

Accumulation of unfolded and/or misfolded proteins in the endoplasmic reticulum (ER) lumen induces ER stress. ER stress triggers the unfolded protein response (UPR), which includes the attenuation of general protein synthesis and the transcriptional activation of the downstream genes. Initial mediators of ER stress responses are ER-resident type I transmembrane serine/threonine protein kinase, PERK and IRE1. ER stress stimulates the expression of COX-2 through the NF-kappaB subunit p65 Ser276 activation and p38MAPK pathways. Apoptosis signal-regulating kinase 1 (ASK1)/MAPKKK5 is a ubiquitously expressed MAPKKK that activates the JNK and p38 pathways. Since activate IRE1 on ER membrane recruits TRAF2 and ASK-1, we hypothesis that IRE1-TRAF2-ASK-1 axis is a pivotal signaling component for responses to ER stress. In order to analyze the role of ASK1 in ER stress regulating pathway, we employ ASK shRNA to down regulate ASK1 in Huh7 cell, and investigate how it affect the ER stress activated pathway and lipid accumulation. First, we establish the ASK-1 shRNA stably express in Huh7 cells. The activation of ER stress signal molecule, like GRP78、XBP-1 was attenuated in ASK1 shRNA stable cells. We also found that the lipid accumulation were significantly repress in ASK1 knockdown cell, the clear mechanism of ASK1 regulation require further study.

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