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

描述(申请人提供)：丙型肝炎病毒(丙型肝炎病毒)感染全球超过1.7亿人，导致急、慢性肝炎和肝细胞癌[1]。值得注意的是，丙型肝炎肝硬变的增加在最近肝癌的上升中发挥了重要作用，占美国病例的50%[2]。由于没有疫苗可用来预防丙型肝炎病毒感染，只有一小部分慢性感染患者对当前的治疗方案有反应[3]，因此显然迫切需要新的有效的丙型肝炎病毒抗病毒药物以及支持这一领域进步的丙型肝炎病毒实验模型系统。特别是，加入丙型肝炎病毒代表了一个有希望的多方面的药物发现机会(在[4]中回顾)，但需要对这一过程有更深入的了解和连贯的描述，以促进这种努力。因此，我们的长期目标是了解介导丙型肝炎病毒进入的细胞和病毒因素，以便识别可用于治疗干预的新的分子靶点，并使允许丙型肝炎病毒进入的转基因小鼠模型的发展成为可能。与这一长期目标相关的是，我们最近发现细胞胆固醇摄取受体Niemann-Pick C1-like 1(NPC1L1)是丙型肝炎病毒进入所必需的。根据NPC1L1在CHO细胞表面的外源表达导致富含胆固醇的丙型肝炎病毒结合的事实，以及NPC1L1在人而不是小鼠肝细胞上表达的事实，我们推测NPC1L1是一种胆固醇依赖的丙型肝炎病毒进入受体，负责限制丙型肝炎病毒进入人-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发挥作用，来表征丙型肝炎病毒和NPC1L1之间的相互作用；以及2)通过确定NPC1L1的表达是否赋予非肝脏和非人类细胞对丙型肝炎病毒的通透性来阐明NPC1L1在丙型肝炎病毒趋向性中的作用。重要的是，这些研究将为更详细、更有针对性的研究奠定基础，旨在彻底了解NPC1L1如何参与进入丙型肝炎病毒，以便这种相互作用可能被用于治疗干预和开发支持丙型肝炎病毒进入的小鼠模型。

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.