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

Abstract

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 1 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.

Changes in Autophagic Response in Patients with Chronic Hepatitis C Virus Infection

“…[5][6][7][8][9][10][11] In vitro, HCV induced autophagosome formation but was not able to enhance autophagic protein degradation suggesting an inefficient fusion between autophagosomes and lysosomes. 2,6 The results of ultrastructural morphometry obtained in the present study could indirectly support this view.…”

“…4 Several recent in vitro studies have suggested that the autophagic pathway is involved in HCV replication in cultured cells. [5][6][7][8][9][10][11] However, the relevance of such findings in vivo remains unknown because autophagy has never been assessed in chronic hepatitis C (CHC) patients. 2,4 The aims of the present study were to evaluate the autophagic response in CHC patients, and to identify factors influencing the autophagy level in such patients.…”

Hepatitis c virus and host cell lipids: An intimate connection

“…For instance, it has been reported that autophagy contributes to RNA translation, 126 RNA replication, [126][127][128] or particle formation. 125 These discrepancies could be due, at least in part, to diversities of employed technical procedures such as cell lines, systems to introduce the viral RNA into cells (infection vs. transfection) or silencing conditions. Further studies are therefore required to define the contribution of autophagy to the HCV replication cycle.…”

“…However, the lack of colocalization between HCV proteins and autophagosomal markers suggests that the viral replication complex does not assemble on autophagosomes. 125,126 Nevertheless, HCV might exploit certain components of the autophagy machinery to generate DMVs with a specific protein composition. In fact, it has been suggested that HCV prevents the degradation of long-lived proteins, by blocking the fusion between autophagosomes and lysosomes, thus leading to the accumulation of DMVs required for HCV RNA replication.…”

Role of autophagy in the pathogenesis of liver diseases

“…A HCV képes elkerülni, hogy az autophagia felismerje és elpusztítsa a vírusfehérjéket. Immunelektromikroszkópos és immunfl uoreszcens vizsgálatok azt mutatják, hogy HCVfehérjék nincsenek vagy csak nagyon ritkán találhatók az autophagosomák közelében [27,28]. HCV-fertő-zésben nő az autophagosomák száma, de a lebontott fehérjék mennyisége nem változik és a lizoszómák kör-nyezetében nincsenek autophagosomák [27].…”