PPP2R5D Promotes Hepatitis C Virus Infection Through Binding to NS5B Protein

Background: Hepatitis C virus (HCV) is an important human pathogen causing chronic hepatitis C, end-stage liver diseases, and hepatocellular carcinoma. The development of infectious HCV cell culture systems primarily relied on the replication enhancement effect of adaptive mutations. Although the mode of action may vary, those adaptive mutations could direct the study of virus-host interactions required for efficient virus infection. We previously identified a substitution D559G in NS5B (RNA dependent RNA polymerase) critical for the replication of HCV genomes. In this study, we set out to study whether D559G-NS5B specifically interacted with some host factors crucial for HCV infection.Methods: Through mass spectrometry analysis of immunoprecipitation mixture of ectopically expressed wild-type and D559G-mutated NS5B, we identified candidate factors showing potential interactions with NS5B and D559G-NS5B. The requirement of selected host factor in HCV infection in vitro was demonstrated by gene knockout, overexpression, virus infection, and co-immunoprecipitation approaches.Results: From the results of immunoprecipitation and mass spectrometry analysis, we selected protein phosphatase 2 regulatory subunit B’delta (PPP2R5D) for further characterization. Co-immunoprecipitation confirmed that both wild-type and D559G NS5B proteins interacted with PPP2R5D, but the interaction between D559G-NS5B and PPP2R5D was more efficient. Silencing of PPP2R5D decreased HCV infection, and knockout of PPP2R5D nearly eliminated HCV infection in Huh7.5 cells. Transient and stably overexpression of PPP2R5D in PPP2R5D-knockout cells restored HCV infection to a level close to that seen for wild-type Huh7.5 cells. Conclusions: PPP2R5D is required for HCV infection in cultured hepatoma cells, and PPP2R5D may function through binding to HCV NS5B. The underlying mechanism of PPP2R5D in the complete HCV life cycle requires further investigation.