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Hepatocyte Nuclear Factor-4 Alpha (HNF4α) and Downstream Secreted Phospholipase A2 GXIIB (PLA2GXIIB) Regulate Production of Infectious Hepatitis C Virus
Xinlei Li, Hanfang Jiang, Linbing Qu, Wenxia Yao, Hua Cai, Ling Chen and Tao Peng
Hepatitis C virus (HCV) is a major cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma in humans. The life cycle of HCV is closely associated with the metabolism of lipids, especially very-low-density lipoprotein (VLDL) in hepatocytes. Hepatocyte nuclear factor-4α (HNF4α), the most abundant transcription factor in the liver, regulates the VLDL secretory pathway. However, the effects of HNF4α on HCV life cycle are unclear. In this study, we investigated the regulatory effects of HNF4α on HCV assembly and secretion. HCV in HNF4α-deficient hepatocytes showed reduced assembly and secretion but unchanged entry and RNA replication. Bezafibrate, a chemical inhibitor of HNF4α, suppressed HCV assembly and secretion. HNF4α down-regulation resulted in rearrangement of cytosolic lipid droplets (LDs), as evidenced by the aggregation of large LDs and distorted cytosolic distribution. Phospholipase A2 GXIIB (PLA2GXIIB), an HNF4α-regulated factor involved in VLDL secretion, was found to be crucial in HCV secretion. PLA2GXIIB expression was up-regulated in hepatocytes harboring HCV subgenomic replicons or in HCV-infected hepatocytes. This up-regulation was transcriptionally controlled in an HNF4α-dependent manner after HCV infection. Furthermore, PLA2GXIIB combined with microsomal triglyceride transfer protein was found to be responsible for the regulation of HNF4α-induced HCV infectivity. These results suggest that HNF4α and its downstream PLA2GXIIB are important factors affecting the late stage of HCV life cycle, and may serve as potential drug targets for the treatment of HCV infection.
