Activation of the Ras/Raf/MEK pathway facilitates hepatitis C virus replication via attenuation of the interferon-JAK-STAT pathway

J Virol. 2012 Feb;86(3):1544-54. doi: 10.1128/JVI.00688-11. Epub 2011 Nov 23.

Abstract

Hepatitis C virus (HCV) is a major cause of chronic liver diseases worldwide, often leading to the development of hepatocellular carcinoma (HCC). Constitutive activation of the Ras/Raf/MEK pathway is responsible for approximately 30% of cancers. Here we attempted to address the correlation between activation of this pathway and HCV replication. We showed that knockdown of Raf1 inhibits HCV replication, while activation of the Ras/Raf/MEK pathway by V12, a constitutively active form of Ras, stimulates HCV replication. We further demonstrated that this effect is regulated through attenuation of the interferon (IFN)-JAK-STAT pathway. Activation of the Ras/Raf/MEK pathway downregulates the expression of IFN-stimulated genes (ISGs), attenuates the phosphorylation of STAT1/2, and inhibits the expression of interferon (alpha, beta, and omega) receptors 1 and 2 (IFNAR1/2). Furthermore, we observed that HCV infection activates the Ras/Raf/MEK pathway. Thus, we propose that during HCV infection, the Ras/Raf/MEK pathway is activated, which in turn attenuates the IFN-JAK-STAT pathway, resulting in stimulation of HCV replication.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Cell Line
  • DNA Primers
  • Enzyme Activation
  • Gene Knockdown Techniques
  • Hepacivirus / physiology*
  • Humans
  • Interferons / metabolism*
  • Janus Kinases / metabolism*
  • Phosphorylation
  • Protein Kinases / metabolism*
  • Real-Time Polymerase Chain Reaction
  • STAT Transcription Factors / metabolism*
  • Virus Replication*

Substances

  • DNA Primers
  • STAT Transcription Factors
  • Interferons
  • Protein Kinases
  • Janus Kinases