Zhao L-J, Zhao P, Chen Q-L, Ren H, Pan W, Qi Z-T
Department of Microbiology, State Key Laboratory of Medical Immunology, Second Military Medical University, Shanghai, China.
Cell Prolif. 2007 Aug;40(4):508-21. doi: 10.1111/j.1365-2184.2007.00453.x.
Hepatitis C virus (HCV) is a major pathogenic factor of liver diseases. During HCV infection, interaction of the envelope protein E2 of the virion, with target cells, is a crucial process for viral penetration into the cell and its propagation. We speculate that such interaction may trigger early signalling events required for HCV infection.
Human liver cell line L-02 was treated with HCV E2. The kinase phosphorylation levels of mitogen-activated protein kinase (MAPK) signalling pathways in the treated cells were analyzed by Western blotting. The proliferation of the E2-treated cells was evaluated by MTT assay.
HCV E2 was shown to be an efficient activator for MAPK pathways. Levels of phosphorylation of upstream kinases Raf-1 and MEK1/2 were seen to be elevated following E2 treatment and similarly, phosphorylation levels of downstream kinases MAPK/ERK and p38 MAPK also increased in response to E2 treatment, and specificity of kinase activation by E2 was confirmed. E2-induced MAPK/ERK activation was inhibited by the MEK1/2 inhibitor U0126 in a concentration-dependent manner. Blockage of relevant cellular receptors reduced activation of Raf-1, MEK1/2, MAPK/ERK and p38 MAPK by E2, indicating efflux of the E2 signal from extracellular to the intracellular spaces. Thus, kinase cascades of MAPK pathways were continuously affected by E2 presence. Moreover, enhancement of cell proliferation by E2 appeared to be associated with the dynamic phosphorylation of MAPK/ERK and p38 MAPK.
These results suggest that MAPK signalling pathways triggered by E2 may be a potential target for prevention of HCV infection.
丙型肝炎病毒（HCV）是肝脏疾病的主要致病因素。在HCV感染过程中，病毒粒子包膜蛋白E2与靶细胞的相互作用是病毒侵入细胞及其传播的关键过程。我们推测这种相互作用可能触发HCV感染所需的早期信号事件。
用人肝细胞系L-02进行HCV E2处理。通过蛋白质印迹法分析处理后细胞中丝裂原活化蛋白激酶（MAPK）信号通路的激酶磷酸化水平。通过MTT法评估E2处理细胞的增殖情况。
HCV E2被证明是MAPK通路的有效激活剂。E2处理后，上游激酶Raf-1和MEK1/2的磷酸化水平升高，同样，下游激酶MAPK/ERK和p38 MAPK的磷酸化水平也因E2处理而增加，证实了E2激活激酶的特异性。MEK1/2抑制剂U0126以浓度依赖性方式抑制E2诱导的MAPK/ERK激活。阻断相关细胞受体可降低E2对Raf-1、MEK1/2、MAPK/ERK和p38 MAPK的激活，表明E2信号从细胞外流入细胞内空间。因此，E2的存在持续影响MAPK通路的激酶级联反应。此外，E2对细胞增殖的增强作用似乎与MAPK/ERK和p38 MAPK的动态磷酸化有关。
这些结果表明，E2触发的MAPK信号通路可能是预防HCV感染的潜在靶点。
