Involvement of ERK pathway in interferon alpha-mediated antiviral activity against hepatitis C virus

•HCV impairs ERK signaling triggered by IFN alpha.•Impairment of ERK pathway potentiates HCV inhibition by IFN alpha.•Impairment of ERK pathway enhances antiviral gene induction by IFN alpha.

Interferon alpha (IFN-α) is the key component of the therapy for hepatitis C virus (HCV) infection. IFN-α exerts anti-HCV activity by targeting certain signaling pathways. Using infectious HCV culture system in human hepatoma Huh7.5.1 cells, we analyzed functional relevance of extracellular signal-regulated kinase (ERK) pathway for IFN-α-mediated anti-HCV activity. IFN-α treatment resulted in activation of ERK pathway by increasing phosphorylation of c-Raf, MEK, and ERK1/2 in Huh7.5.1 cells, whereas HCV impaired such activation. IFN-α-dependent ERK1/2 phosphorylation was blocked by MEK inhibitor U0126. Pharmacological inhibition of ERK1/2 by U0126 or siRNA-mediated knockdown of ERK1/2 resulted in suppressive effects on HCV RNA levels and expression of HCV nonstructural protein 3 and envelope protein 2, establishing an important role for ERK pathway in HCV replication. Moreover, induction of a set of antiviral genes by IFN-α was enhanced in HCV-infected Huh7.5.1 cells due to the ERK1/2 knockdown, suggesting that impairment of ERK signaling may potentiate HCV inhibition by IFN-α. These results demonstrate that ERK pathway is involved in IFN-α-mediated antiviral activity against HCV.