Objective: To explore the effects of hepatitis C virus (HCV) core protein on the activity of double-stranded RNA-dependent protein kinase (PKR).
Methods: The human hepatoma cell line BEL-7402 was transfected with the HCV core gene-containing eukaryotic expression vector pCMH6K-Core (at various concentrations), or empty vector, or no vector; a group of cells was co-transfected with the luciferase reporter plasmid pGL3-promoter. The cells were treated with interferon (IFN) a-2b to induce the expression and activation of endogenous PKR, or left untreated to serve as controls. The effect of core protein on PKR phosphorylation was detected by western blotting. Luciferase activity was detected to reflect effects of the core protein on the synthesis of cellular proteins. The t-test and F test were used for statistical analyses.
Results: In the case of IFNa stimulation, PKR phosphorylation levels were significantly lower in the HCV core protein expressing cells than in the cells transfected with empty plasmid or with no vector, but the total PKR expression level was not significantly different among these three groups of cells. Cells co-transfected with luciferase plasmid and the core protein expressing vector showed significantly higher levels of luciferase expression than the cells co-transfected with the empty vector. Moreover, the luciferase activity and core protein expression levels increased in a dose-dependent manner, with the luciferase activity of the cells treated with 0.5 mug, 1.0 mug and 1.5 mug pCMH6K-Core being 1.941 ± 0.199 times, 2.868 ± 0.275 times and 3.839 ± 0.338 times higher than that of the empty vector group (all P < 0.05).
Conclusion: In the human hepatoma cell line BEL-7402, the HCV core protein can inhibit the activity of endogenous PKR, thereby promoting cell protein synthesis.