HCV-induced oxidative stress by inhibition of Nrf2 triggers autophagy and favors release of viral particles

Viruses are known to exploit the autophagic machinery for their own benefit. In case of the hepatitis C virus autophagy is induced. As autophagy serves as a degradation pathway to maintain cellular homeostasis, it is activated in response to cellular stress such as elevated levels of reactive oxygen species (ROS). Elevated levels of ROS trigger phosphorylation of the autophagic adaptor protein p62 on Ser349 (pS[349] p62) that is involved in the induction of autophagy. Consequently, pS[349] p62 binds with a higher affinity to Keap1 thereby releasing Nrf2 from the complex with Keap1. Although the released Nrf2 should induce as a heterodimer with the sMaf proteins the expression of Nrf2/ARE-dependent genes, in HCV-positive cells no activation of cytoprotective genes occurs even though elevated amounts of pS[349] p62 are present. In HCV-positive cells, free Nrf2 is trapped via delocalized sMaf proteins at the replicon complexes on the cytoplasmic face of the ER and is therefore prevented from its entry into the nucleus. Scavenging of ROS leads to decreased levels of pS[349] p62 and impaired induction of autophagy. Both, inhibition of autophagy and scavenging of ROS result in decreased amounts of released viral particles. Taken together, these data identify an intricate mechanism of HCV-dependent inhibition of Nrf2/ARE-mediated gene expression which counteracts pS[349] p62-induced activation of Nrf2. Thereby elevated ROS-levels are preserved that in turn activate autophagy to favor HCV particle release. [Display omitted] •HCV impairs activation of Nrf2/ARE-dependent genes by a so far unprecedented mechanism.•The impaired Nrf2/ARE signaling leads to elevated ROS levels.•ROS induce by phosphorylation of p62 autophagy that is required for the release of HCV.•p-p62-dependently released Nrf2 is prevented from nuclear translocation by HCV.•Identification of a central target relevant for HCV life cycle and pathogenesis.