Abstract: Objective The purpose of this experiment was to preliminarily explore the effects of small ubiquitin-like modifier specific protease 3 (SENP3) on lipid droplet regulation and hepatitis C virus (HCV) replication in HepG2 cells in vitro. Methods Human HepG2 cells were infected with infectious HCV particles, and SENP3 protein expression were detected by Western blot. The HepG2 cells were transfected by SENP3-siRNA and infected by HCV particles, then the HCV RNA level was detected by quantitative real-time PCR (qRT-PCR). The lipid droplets were observed by Oil red O staining. After SENP3 knocked down, the HepG2 cells were treated with free fatty acids, and the HCV RNA level was detected by qRT-PCR after HCV infection. Results The relative expression levels of HCV core protein were 0.01±0.00, 0.17±0.02 and 0.43±0.04 on the first, third and sixth days after HCV infection in HepG2 cells, and the relative expression levels of SENP3 protein were 0.23±0.04, 0.42±0.03 and 0.46±0.04, respectively, significantly different among them (P<0.05); the transfection of SENP3-siRNA in the cells effectively reduced the expression of SENP3 and HCV core protein after HCV infection; the relative level of HCV RNA in SENP3 knockdown cells was 54.2±11.4%, significantly lower than that in non-specific siRNA transfection cells (P<0.01); after SENP3 knockdown, the number of lipid droplets decreased significantly; the HCV RNA relative level in SENP3 knockdown HepG2 cells infected with HCV particles was 58.2±5.2%, significantly lower than that in non-specific siRNA transfection cells (P<0.01); the relative level of HCV RNA in HepG2 cells with SENP3 knockdown and co-cultured with palmitic acid was 74.6±6.4%, significantly higher than that in HepG2 cells with SENP3 knockdown (P<0.01). Conclusion The SENP3 could promote HCV replication by participating in regulation of lipid droplet metabolism in HCV-infected hepatocytes.

Key words: HepG2 cells, Hepatitis C virus, Small ubiquitin-like modifier specific protease 3, Lipid droplets