Interferon-α-induced mTOR activation is an anti-hepatitis C virus signal via the phosphatidylinositol 3-kinase-Akt-independent pathway
The interferon-induced Jak-STAT signal alone is not sufficient to explain all the biological effects of IFN. The PI3-K pathways have emerged as a critical additional component of IFN-induced signaling. This study attempted to clarify that relationship between IFN-induced PI3-K-Akt-mTOR activity and anti-viral action.
When the human normal hepatocyte derived cell line was treated with rapamycin (rapa) before accretion of IFN-α, tyrosine phosphorylation of STAT-1 was diminished. Pretreatment of rapa had an inhibitory effect on the IFN-α-induced expression of PKR and p48 in a dose dependent manner. Rapa inhibited the IFN-α inducible IFN-stimulated regulatory element luciferase activity in a dose-dependent manner. However, wortmannin, LY294002 and Akt inhibitor did not influence IFN-α inducible luciferase activity. To examine the effect of PI3-K-Akt-mTOR on the anti-HCV action of IFN-α, the full-length HCV replication system, OR6 cells were used. The pretreatment of rapa attenuated its anti-HCV replication effect in comparison to IFN-α alone, whereas the pretreatment with PI3-K inhibitors, wortmannin and LY294002 and Akt inhibitor did not influence IFN-induced anti-HCV replication.
IFN-induced mTOR activity, independent of PI3K and Akt, is the critical factor for its anti-HCV activity. Jak independent mTOR activity involved STAT-1 phosphorylation and nuclear location, and then PKR is expressed in hepatocytes.
KeywordsmTOR STAT-1 Interferon HCV PKR
Hepatitis C virus
Signal transducers and activators of transcription
IFN-stimulated gene factor 3
IFN-stimulated regulatory element
Double-stranded RNA-dependent protein kinase
Mammalian target of rapamycin
Small interfering RNA
- 4.Walsh MJ, Jonsson JR, Richardson MM, Lipka GM, Purdie DM, Clouston AD, et al. Non-response to antiviral therapy is associated with obesity and increased hepatic expression of suppressor of cytokine signaling 3 (SOCS-3) in patients with chronic hepatitis C, viral genotype 1. Gut. 2006;55:529–35.PubMedCrossRefGoogle Scholar