[Cross-talk between ERK and NF-kappaB signal transduction pathways in the hepatocytes expressing hepatitis C virus nonstructural protein 3]

Abstract

Objective: To explore the cross-talk between extracellular signal-regulated kinase (ERK) and nuclear factor (NF-kappaB) signal transduction pathways in the hepatocytes expressing hepatitis C virus nonstructural protein 3 (HCV NS3).

Methods: A cell line QSG7701/NS3, which stably expressed HCV NS3 protein, was constructed by transfecting plasmid pcDNA3.1-NS3 into a human immortalized hepatocyte line QSG7701. Before and after QSG7701/NS3 cells were treated by MEK inhibitor PD98059, the phosphorylation level of ERK and the expression of cyclin D1 protein were detected by Western blot; the DNA binding activities of activator protein 1 (AP-1) and NF-kappaB were evaluated with electrophoretic mobility shift assay (EMSA). Cell cycles were measured by flow cytometry (FCM); the effects of PD98059 on the cell proliferation were determined by MTT assay.

Results: HCV NS3 protein could up-regulate the phosphorylation of ERK and the expression level of cyclin D1 in QSG7701 cells. PD98059 could inhibit the cell proliferation mediated by HCV NS3 protein, down-regulate the activities of AP-1 and NF-kappaB, and suppress the expression of cyclin D1.

Conclusion: The inhibition of ERK can suppress the DNA binding activity of NF-kappaB and the cell proliferation mediated by HCV NS3 protein in a dose-dependent manner. There may be a cross-talk between ERK and NF-kappaB signal transduction pathways, which may exert synergistic action on the proliferation and malignant transformation of hepatocytes.