A functional role for NS 5 ATP 9 in the induction of HCV NS 5A‐mediated autophagy

Summary Autophagy has been shown to facilitate replication of hepatitis C virus ( HCV ); however, the mechanism by which HCV induces autophagy has not been fully established. NS 5 A , a nonstructural protein expressed by HCV , regulates numerous cellular pathways, including autophagy, by up‐regulating B eclin 1; however, the underlying mechanism remains unclear. To obtain new insights into HCV ‐regulated autophagy, NS 5 ATP 9 was overexpressed in H ep G 2 and L 02 cells, resulting in up‐regulation of endogenous B eclin 1 m RNA and protein levels, respectively. The luciferase‐reporter assay results showed that both NS 5 A and NS 5 ATP 9 could transactivate B eclin 1 promoter activity, but that NS 5 A could not transactivate the B eclin 1 promoter in NS 5 ATP 9‐silenced H ep G 2 and L 02 cells. Up‐regulation of B eclin 1 m RNA and protein expression by NS 5 A could also be attenuated by NS 5 ATP 9 knock‐down. Furthermore, the H ep G 2 and L02 cells that transiently overexpressed NS 5 ATP 9 had enhanced accumulation of vacuoles carrying the autophagy marker LC 3, consistent with the conversion of endogenous LC 3‐ I to LC 3‐ II . In contrast, the conversion of endogenous LC 3‐ I to LC 3‐ II could not be enhanced by NS 5 A in NS 5 ATP 9‐silenced H ep G 2 cells. These results highlight an important potential role for NS 5 ATP 9 in HCV NS 5 A ‐induced hepatocyte autophagy.