丙型肝炎病毒E2蛋白对HepG2细胞MAPK／ERK的激活

人CD81是丙型肝炎病毒（hepatitis Cvirus,HCV）的细胞表面特异性受体，HCV包膜蛋白－2（E2）可与其结合。细胞个信号调节激酶（extracellular signal-regulated protein kinase,MAPK/ERK1,2）信号途径主要介导细胞增殖及分化。为探讨HCV E2蛋白与人CD81结合对MAPK／ERK活性变化的影响，以HCV E2蛋白刺激HepG2细胞，采用免疫印迹、免疫组化及免疫荧光等方法动态观察细胞内MAPK／ERK的激活情况，并以流式细胞术检测细胞表面CD81的表达。结果表明：HepG2细胞高表达人CD81；HCV E2蛋白可激活细胞内MAPK／ERK；MAPK／ERK的磷酸化反应与HCV E2蛋白浓度、作用时间呈依赖关系；HCV E2－CD81相互作用引发的细胞异常信号转导可能与HCV致病性相关。

Activation of Intracellular MAPK/ERK Initiated by Hepatitis C Virus Envelope Protein E2 in HepG2 Cells

CD81, widely expressed on the surface of various human cells including hepatocytes, is a protein involved in intracellular signal transduction pathways. Recent studies suggested that human CD81 could specifically interact with hepatitis C virus (HCV) envelope protein E2. Therefore, CD81 has been identified as a putative cellular receptor for HCV. The HCV E2 CD81 interaction was considered a molecular mechanism contributing to HCV infection and pathogenicity. MAPK/ERK is characteristically associated with cell proliferation and hypertrophy. To investigate the effect of HCV on MAPK/ERK, human HepG2 cells were used in this study. CD81 expression on HepG2 cell surface was determined by flow cytometry with method of immunofluorescence. The cells were cultured in DMEM medium without fetal calf serum for 7 h, and then treated with HCV E2 protein at different time courses. Activation of MAPK/ERK in the cells was measured by Western blot, immunohistochemical and immunofluorescent analyses. Phosphorylation of MAPK/ERK was related to the concentration of HCV E2 proteins and to the time length of stimulation. MAPK/ERK in HepG2 cells was activated by HCV E2 protein, suggesting that HCV E2 CD81 interaction might be involved in intracellular signal transduction and might play an active role in HCV pathogenicity.