Role of autophagy in hepatitis C virus replication

Hepatitis C virus (HCV) is a major cause of chronic liver diseases, including liver cirrhosis and hepatocellular carcinoma. This virus replicates in the cytoplasm of hepatocytes where it induces the formation of double membrane vesicles (DMVs) that are derived from the ER. These DMVs have striking structural similarity to autophagosomes, arguing for the involvement of autophagy in the remodeling of intracellular membranes in HCV-infected cells. However, the precise mechanism how autophagy might contribute to DMV formation is poorly understood. Autophagy is a multi-step process mediated by several protein complexes. One of them includes ATG14L and the PI3 kinase that needs to be activated prior to the formation of the isolation membrane, which is the precursor of the autophagosome. By using a series of cell lines containing various deletions of components of the autophagy machinery we found that autophagy as such is not required for HCV replication. Ablation of the autophagy elongation complex (ATG5-ATG12) or LC3, which stably associates with autophagosomal membranes, neither impacted viral RNA replication nor DMV formation. In contrast, deletion of ATG14L, a component of the PI3 kinase complex, profoundly reduced HCV replication and impaired DMV formation. These results suggest that autophagy per se is not required for HCV replication, but the virus utilizes individual components of the autophagy machinery such as ATG14L for the formation of DMVs, which constitute the viral replication factory.