泛素化特异性蛋白酶USP18在丙肝病毒耐受干扰素中的作用及分子机制研究

Hepatitis C Virus (HCV) infects 150 million people worldwide. Due to the lack of an effective vaccine, HCV infection is getting more serious and has been listed as one of the 12 diseases to be specifically managed in China since 2012. No prognostic tools are available and the molecular mechanisms of the interferon resistance remain illusive. Previous work from our lab identified 18 differentially expressed hepatic genes whose expression levels prior to treatment predict whether a given patient will respond to IFN-based therapy or not (with an accuracy of 96%). Of these 18 genes, 11 are interferon stimulated genes (ISGs) whose expression levels are higher in treatment non-responder livers. We therefore proposed that the pre-activation of the endogenous IFN signaling pathway leading to increased expression of a subset of ISGs in different cell types ( hepatocytes Vs macrophages) in the liver tissues , especially the activation of the ubiquitin-like ISG15/USP18 pathway , plays an important role in interferon resistance and treatment failure. In this research, we propose to use a combination of genomics, bioinformatics as well as molecular virology tools to study the effect of USP18 on HCV replication and Jak/STAT signaling pathway as well as other innate immune response pathways in cultured cells, primary human hepatocytes, aiming to understand how USP18 affects HCV replication and how the virus evades the innate immune attack and counteracts the IFN anti-viral activity leading to treatment failure and viral persistence. This study will shed light on how HCV exploits the host innate immune response to benefit its own replication and to blunt the interferon anti-viral activity.

丙型肝炎是由丙肝病毒（HCV）感染引起的一种严重肝脏疾病。全世界1.5亿人被感染。我国从2012年开始把丙肝列入12个重点疾病之一加以防控。目前缺乏治疗前疗效预测方法,且对丙肝病毒耐受干扰素的分子机理不清楚。我们前期研究在筛选出18个肝脏差异表达基因用于疗效预测（准确率96%）的基础上，发现内源性干扰素信号传导通路的激活导致干扰素刺激基因（ISG）在肝组织不同细胞内表达，特别是ISG15/USP18类泛素化通路的激活与HCV耐受干扰素及持续感染有关。本项目以体外细胞培养、人原代肝细胞为对象，采用基因组学、生物信息学及传统的分子病毒学技术，研究ISG15/USP18信号传导通路中USP18与HCV复制及干扰素抗病毒活性之间的相互作用。阐明USP18如何通过抑制干扰素信号传导通路来拮抗干扰素的抗病毒活性最终导致治疗失败的分子机制，为HCV及其它病毒如HBV耐药提供全新的理论依据。

丙型肝炎是由丙肝病毒（HCV）感染引起的一种严重肝脏疾病。全世界1.5亿人被感染。我国从2012年开始把丙肝列入12个重点疾病之一加以防控。目前缺乏治疗前疗效预测方法,且对丙肝病毒耐受干扰素的分子机理不清楚。我们前期研究在筛选出18个肝脏差异表达基因用于疗效预测（准确率96%）的基础上，发现内源性干扰素信号传导通路的激活导致干扰素刺激基因（ISG）在肝组织不同细胞内表达，特别是ISG15/USP18类泛素化通路的激活与HCV耐受干扰素及持续感染有关。因此，本项目研究ISG15/USP18信号传导通路中USP18与HCV复制及干扰素抗病毒活性之间的相互作用。研究结果显示：1）USP18对HCV的复制具有促进作用，而且不依赖USP18的蛋白酶活性；2）USP18与HCV病毒的特定蛋白具有相互作用（与HCV的core蛋白、E1蛋白、E2蛋白以及NS4A具有相互作用，与HCV的其余蛋白不具有相互作用）；3）USP18与宿主蛋白也具有相互作用，具体为USP18可以与IRS4，HIP14，EEF1α1，NME1L，TUBB4B，NEMO相互作用；4）进一步研究发现：HIP14以及IRS4与USP18相互作用可以影响干扰素介导的JAK-STAT信号通路及干扰素抗病毒活性。而这些结果的发现阐明了USP18如何通过抑制干扰素信号传导通路来拮抗干扰素的抗病毒活性最终导致治疗失败的分子机制，为HCV及其它病毒如HBV耐药提供全新的理论依据。