Elucidating the role of the NPC1L1 cholesterol uptake receptor in HCV infection

描述（由申请人提供）：全球有超过1.7亿人感染丙型肝炎病毒（HCV），引起急性和慢性肝炎和肝细胞癌（HCC）。值得注意的是，HCV肝硬化的增加在最近HCC的上升中起了主要作用，在美国HCC病例中占50%。由于没有可用的预防丙型肝炎病毒感染的疫苗，而且只有一小部分慢性感染患者对目前的治疗方案有反应，因此迫切需要新的有效的丙型肝炎病毒抗病毒药物以及支持该领域进展的丙型肝炎病毒实验模型系统。特别是，HCV的进入代表了一个有希望的药物发现的多方面机会（[4]综述），但需要对这一过程进行更深入的理解和连贯的描述，以促进这一努力。因此，我们的长期目标是了解介导HCV进入的细胞和病毒因素，以确定可修改治疗干预的新分子靶点，并使开发允许HCV进入的转基因小鼠模型成为可能。与这一长期目标相关，我们最近发现细胞胆固醇摄取受体尼曼-匹克c1样1 （NPC1L1）是HCV进入所必需的。基于观察到外源性NPC1L1在CHO细胞表面的表达会导致富含胆固醇的HCV病毒粒子的结合，以及NPC1L1表现出有限的组织分布，并且在人而不是小鼠肝细胞上表达，我们假设NPC1L1是一种胆固醇依赖性的HCV进入受体，负责限制HCV进入人肝细胞的趋向性。因此，我们建议：1)通过确定相互作用的决定因素和评估NPC1L1在病毒进入过程中如何以及何时起作用，来表征HCV与NPC1L1在HCV进入过程中的相互作用；2)通过确定NPC1L1的表达是否使HCV对非肝细胞和非人细胞具有亲和性，阐明NPC1L1在HCV趋向性中的作用。重要的是，这些研究将奠定基础，使更详细和更有针对性的研究能够彻底了解NPC1L1如何参与HCV进入，以便这种相互作用可以潜在地用于治疗干预和开发支持HCV进入的小鼠模型。

DESCRIPTION (provided by applicant): Hepatitis C virus (HCV) infects more than 170 million people worldwide, causing acute and chronic hepatitis and hepatocellular carcinoma (HCC)[1]. Notably, increases in HCV cirrhosis have played a major role in the recent rise in HCC, accounting for up to 50% of cases in the United States[2]. With no vaccine available to protect against HCV infection and only a subset of chronically infected patients responding to current treatment options[3], there is an obvious and immediate need for new effective HCV antivirals as well as the HCV experimental model systems that would support advancement in this area. In particular, HCV entry represents a promising multi-faceted opportunity for drug discovery (reviewed in[4]), but a deeper understanding and coherent description of the process is needed to facilitate such endeavors. Thus, our long term goal is to understand the cellular and viral factors that mediate HCV entry in order to identify novel molecular targets amendable to therapeutic intervention and enable the development of transgenic mouse models permissive for HCV entry. Relevant to this long term goal, we recently discovered that the cellular cholesterol uptake receptor Niemann-Pick C1-like 1 (NPC1L1) is required for HCV entry. Based on the observation that exogenous expression of NPC1L1 on the surface of CHO cells results in binding of the cholesterol-enriched HCV virion and the fact that NPC1L1 exhibits restricted tissue distribution and is expressed on human but not mouse hepatocytes, we hypothesize that NPC1L1 is a cholesterol-dependent HCV entry receptor responsible for the restricted human-hepatocyte tropism of HCV entry. As such, we propose to 1) Characterize the interaction between HCV and NPC1L1 during HCV entry by identifying the determinants of the interaction and assessing how and when NPC1L1 functions during the viral entry process; and 2) Elucidate the role of NPC1L1 in HCV tropism by determining if NPC1L1 expression confers HCV permissiveness to non-hepatic and non-human cells. Importantly, these studies will lay the groundwork that will enable a more detailed and specifically focused studies aimed at thoroughly understanding how NPC1L1 participates in HCV entry so that such interactions can be potentially exploited for therapeutic intervention and the development of a mouse model that supports HCV entry.