Knockdown of autophagy-related gene decreases the production of infectious hepatitis C virus particles

Hepatitis C virus (HCV) is a positive-strand RNA virus, and classified within the Flaviridae family. Atg7-knockdown decreases the amount of HCV replicon RNA, when HCV JFH1 RNA and HCV subgenomic replicon are transfected into Huh7.5 cells. However, when infectious naive HCV particles are directly infected into Huh7.5.1 cells, it is still unclear whether Atg7-knockdown decreases the production of intracellular HCV-related proteins, HCV mRNA and infectious HCV particles. When Atg7 protein in HCV-infected Huh7.5.1 cells was knocked down by RNA-interference, the levels of intracellular HCV core, NS3, NS5A proteins, HCV mRNA and secreted albumin remained unchanged compared with those in the control HCV-infected cells. However, the level of infectious HCV particles released in the medium was decreased by the Atg7-knockdown. Similar results were obtained when Beclin I was knocked down by RNA-interference. The colocalization of endogenous LC3-puncta with HCV core, HS5A proteins and lipid droplets was also investigated. However, little endogenous LC3-puncta colocalized with HCV core, NS5A proteins or lipid droplets. These results suggested that autophagy contributed to the effective production of HCV particles, but little to the intracellular production of HCV-related proteins, HCV mRNA and the secretory pathway, in a naive HCV particles-infection system.