| Summary: | 碩士 === 中臺科技大學 === 醫學生物科技研究所 === 97 === Cholesterol is essential for regulation of cell membrane structure and function and is believed to be a modulator of membrane protein function. In recent years, increasing evidences have suggested that cholesterol is involved in the various replication steps of enveloped RNA viruses. In flavivirus such as Tick-borne encephalitis virus (TBEV), membrane fusion activity and trimerization of envelope (E) protein of virus have been show to be dependent on the presence of cholesterol in the target membrane in a liposomal model system. The formation of E protein into trimers results in a conformational change in the hinge region of domain II, a key structural element that contains the hydrophobic fusion peptide essential for virus and cell membrane fusion. Collectively, it is tempting to postulate that the resulting cholesterol composition of the viral envelope plays a role in some aspect of the viral life cycle. By using reverse genetic technique, we have previously generated three site-directed E mutants from Japanese encephalitis virus (JEV) infectious clones that amino acid substitutions at position 52 (Gln->Lys), 138 (Glu->Lys) or 275 (Ser->Pro) in the hinge regions of domain II dramatically affected virus infectivity. Thus, the mutants offer an opportunity to identify the molecular determinant(s) involved in the virus cholesterol requirement. Our results suggest that envelope cholesterol plays critical role for JEV infection, and has identified a single-amino acid substitution at position 275 (Ser->Pro) in the hinge regions of domain II that dramatically inhibits virus infection upon treatment with MβCD. MβCD-mediated cholesterol depletion of cell membrane in JEV-infected cells increased the release of virus particles（E138 E->K）. Therefore penetrates this result to let us be possible further to discuss the molecular determinants of the protein E importance of growth cycle in the viral.
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