| Summary: | 碩士 === 國立成功大學 === 醫學檢驗生物技術學系 === 94 === Hepatitis C virus (HCV), a positive-stranded RNA virus in the Flaviviridae family, can cause various liver diseases including acute and chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. HCV genome encodes a polyprotein of about 3,000 amino acids, which are processed into 10 mature viral proteins. Among these, the functions of non-structural protein 2 (NS2) are largely unknown in the HCV life cycle and pathogenesis. Our previous studies with microarray technology resulted in up-regulation of CD9 mRNA expression by the HCV NS2. As we know CD9 and CD81, a putative HCV receptor, belong to tetraspanin superfamily, in which the members are considered to be related to cell mobility, cell growth, adherence, carcinogenesis, and microbial infections. In this study, we aimed to characterize the regulatory pathways and biological relevance of the NS2-mediated tetraspanin up-regulation. First, the results showed that the fluorescence-tag NS2 proteins were localized in the cytoplasm of transfected Huh7 cells and that the HCV NS2 proteins of various genotypes could increase surface CD9 and CD81 expression. Next, we identified the signally mediators in regulation of CD9 and CD81. A rapid and short induction of oxidative stress was detected, but not correlated with tetraspanin modulation. However, suppression of PKC-δ translocation from cytosol to membrane conferred the NS2 modulation of tetraspanin up-regulation. In additional, ERK phosphorylation was also decreased in NS2 expressing cells. Third, we analyzed the effects of NS2-mediated tetraspanin up-regulation on cell susceptibility to poliovirus and dengue virus, with the results showing the NS2 proteins might promote the virus infection. In conclusion, the HCV NS2 protein can upregulate the surface expressions of tetraspanin CD9 and CD81, which is mediated by inhibition of PKC-δ, and facilitate the infection of susceptible viruses.
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