Hepatitis C Virus NS5a Protein and Oxidative Stress

描述（由申请人提供）：丙型肝炎病毒（HCV）是慢性肝炎和肝硬化的主要病原体之一。HCV感染与肝细胞癌的发生有关。据估计，美国约有400万人感染HCV。该病毒的RNA基因组编码3010个氨基酸的多聚蛋白。HCV RNA基因组5'端和3'端具有独特的序列和结构，是病毒翻译和复制所必需的基本特征。RNA基因组编码三种结构蛋白和至少六种非结构蛋白。NS 5A是一种非结构蛋白，由于其在干扰素抗性中的作用而引起了人们的极大兴趣。在本申请中，我们建议研究与HCV NS 5A相关的功能。HCV RNA基因组的翻译和复制功能与ER膜相关。ER中的这些活性诱导ER应激和ER过载反应。ER应激导致未折叠蛋白反应（UPR），其导致整个宿主的ER伴侣蛋白的激活。ER超载反应似乎涉及两个第二信使，钙和活性氧。它们的活性最终导致转录因子的活化和易位到细胞核，在那里它们结合同源DNA序列并调节基因表达。NF-kappaB和STAT-3是两种这样的转录因子，其通过磷酸化激活并被转运到细胞核。在此，我们拟探讨HCV NS 5A激活ER-核信号转导通路的机制。这些研究有可能提供与慢性肝病发病机制直接相关的信息，包括其进展为与HCV感染相关的肝细胞癌。

DESCRIPTION (provided by applicant): Hepatitis C virus (HCV) is one of the leading causative agents of chronic hepatitis and cirrhosis. HCV infection of liver is associated with the development of hepatocellular carcinoma. It is estimated that about 4 million people in the US are infected with HCV. The RNA genome of this virus encodes a polyprotein of 3010 amino acids. HCV RNA genome consists of unique sequences and structures at its 5' and 3' termini, which are essential features required for viral translation and replication. The RNA genome codes for three structural proteins and at least six nonstructural proteins. One of the nonstructural proteins, NS5A has generated significant levels of interest due largely to its suggested role in interferon-resistance. In this application, we propose to investigate the functions associated with the HCV NS5A. Translation and replication functions of the HCV RNA genome are associated with the ER membrane. These activities in the ER induce ER stress and ER overload responses. ER stress leads to unfolded protein response (UPR), which leads to activation of whole host of ER chaperone proteins. The ER overload response appears to involve two second messengers, calcium and reactive oxygen species. Their activities ultimately lead to the activation and translocation of transcription factors to the nucleus whereupon they bind cognate DNA sequences and regulate gene expression. NF-kappaB and STAT-3 are two such transcription factors which are activated by phosphorylation and are transported to nucleus. Herein, we propose to investigate the mechanism of activation of ER-nucleus signal transduction pathway by the HCV NS5A. These studies have the potential to provide information of direct relevance to the chronic liver disease pathogenesis including its progression to hepatocellular carcinoma associated with the HCV infection.