The heat shock protein 70 family members HSC70 and HSP70 play distinct roles in the hepatitis C viral life cycle (144.1)

Abstract

We have previously identified HSC70 in complex with viral NS5A along with other heat shock proteins. HSC70 has been reported to modulate HCV infectivity. Here, we further analyze the NS5A/HSC70 interaction biochemically and investigate the role of HSC70 in viral life cycle. We demonstrate that HSC70 knockdown significantly affects virus production with no cytotoxicity. We observed that HSC70 knockdown did not affect viral RNA replication and protein production. In fact, we found a slight, but statistically significant increase in viral RNA and protein levels likely caused by compensatory upregulation of HSP70, which we have previously shown to be required for viral protein production. NS5A‐augmented IRES‐mediated translation was also not inhibited by HSC70 knockdown and, rather, slightly increased. In contrast, we discovered that intracellular infectious virion assembly was significantly impaired by HSC70 knockdown. We also discovered that both HSC70 nucleotide binding and substrate binding domains directly bind NS5A. Thus, HSC70 and HSP70 play discrete roles in HCV viral life cycle which is further validated by our finding that knockdown of both HSC70 and HSP70 displays synergistic and dramatic reductions in virus production compared with knockdown of each alone. Investigation of these different functions may facilitate developing of novel strategies that target host proteins to treat HCV infection.Grant Funding Source: NIH R01DK090794, SWF; NIH AI084090, AD