Selimović Denis, Hassan Mohamed
Dental Faculty, Louis Pasteur Unversity, 1,Place de l'Hopital, 67000 Strasbourg, INSERM Institute, U595, Strasbourg, France.
Bosn J Basic Med Sci. 2008 Feb;8(1):4-11. doi: 10.17305/bjbms.2008.2988.
Hepatitis C virus (HCV) is a significant health problem facing the world. More than 170 million people are infected with HCV worldwide. HCV encodes a large polyprotein precursor that is processed into at least 10 distinct products including structural (core, E1 and E2) and non-structural (NS2, NS3, NS4A, NS4B, NS5A and NS5B). Besides its importance in virus replication, NS4A functions as a cofactor for NS3 and contributes to viral pathogenesis by influencing cellular functions. Here, we investigated the effect of NS4A protein on the growth rate induced by core protein in liver cells. Using our established tetracycline inducible system, we demonstrated the ability of NS4A protein to inhibit core protein-induced cell growth in Hepatoma cell line, HepG2. Induction of both core and NS4A proteins in HepG2-core/NS4A transfectants inhibited core-induced growth advantage in HepG2-core transfectants and blocked NS4A protein-induced cell growth inhibition in HepG2-NS4A transfectants. Using both immune fluorescence staining and Western blot analysis, we confirmed the localization of NS4A protein to the mitochondria in HepG2-NS4A transfectants expressing NS4A protein. Data obtained from flow cytometry analysis, using JC-1 demonstrated the loss of mitochondrial membrane potential (DeltaPsim) by the expression of NS4A protein in HepG2-NS4A transfectants, but not by the expression of core protein in HepG2-core transfectants. Whereas, the induction of the expression of both core and NS4A proteins in HepG2-core/NS4A transfectants blocked NS4A-induced loss of DeltaPsim in HepG2 cells. Taken together, our data suggest an important role for mitochondria in the modulation HCV NS4A-induced inhibition of HCV core-mediated cell growth.
丙型肝炎病毒（HCV）是全球面临的一个重大健康问题。全球有超过1.7亿人感染了HCV。HCV编码一种大的多蛋白前体，该前体被加工成至少10种不同的产物，包括结构蛋白（核心蛋白、E1和E2）和非结构蛋白（NS2、NS3、NS4A、NS4B、NS5A和NS5B）。除了在病毒复制中具有重要作用外，NS4A还作为NS3的辅因子发挥作用，并通过影响细胞功能促进病毒发病机制。在此，我们研究了NS4A蛋白对肝细胞中核心蛋白诱导的生长速率的影响。利用我们建立的四环素诱导系统，我们证明了NS4A蛋白在肝癌细胞系HepG2中抑制核心蛋白诱导的细胞生长的能力。在HepG2-core/NS4A转染子中同时诱导核心蛋白和NS4A蛋白，抑制了HepG2-core转染子中核心蛋白诱导的生长优势，并阻断了HepG2-NS4A转染子中NS4A蛋白诱导的细胞生长抑制。通过免疫荧光染色和蛋白质印迹分析，我们证实了在表达NS4A蛋白的HepG2-NS4A转染子中，NS4A蛋白定位于线粒体。使用JC-1从流式细胞术分析获得的数据表明，在HepG2-NS4A转染子中，NS4A蛋白的表达导致线粒体膜电位（ΔΨm）丧失，但在HepG2-core转染子中核心蛋白的表达未导致此现象。然而，在HepG2-core/NS4A转染子中同时诱导核心蛋白和NS4A蛋白的表达，阻断了HepG2细胞中NS4A诱导的ΔΨm丧失。综上所述，我们的数据表明线粒体在调节HCV NS4A诱导的HCV核心介导的细胞生长抑制中起重要作用。
