ROLE OF ORP6 IN INTRACELLULAR CHOLESTEROL TRAFFICKING

ORP6 在细胞内胆固醇贩运中的作用

• 批准号: RGPIN-2020-04851
• 负责人: Ouimet, Mireille
• 金额: $ 2.7万
• 依托单位: University of Ottawa
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=717186
• 关键词: ROLE; ORP6; INTRACELLULAR; CHOLESTEROL; TRAFFICKING

Homeostasis, or the maintenance of a steady-state internal environment by living systems, is a core principal of life. Cholesterol homeostasis is a conserved and essential eukaryotic process. Within mammalian cells, intracellular membrane cholesterol levels are tightly regulated, with complex cellular mechanisms in place to maintain proper cholesterol concentrations at distinct intracellular sites. For this, both vesicular and non-vesicular cholesterol trafficking pathways are required for cholesterol movement between cell compartments. Despite extensive study of these pathways, many questions remain about the mechanisms of cholesterol transfer between different cell compartments and how these processes are regulated. Oxysterol-binding (OSBP)-related proteins (ORPs) are a family of lipid transfer proteins (LTPs) implicated in many cellular processes related with oxysterols, inter-organelle contact, lipid metabolism and non-vesicular sterol transport. The goal of my NSERC research program is to investigate the role of LTPs in the maintenance of cellular and whole-body cholesterol homeostasis. Oxysterol-binding protein-Related Protein 6 (ORP6), a poorly characterized member of the ORP family, has recently emerged as a novel regulator of intracellular cholesterol levels. We previously showed that ORP6 regulates cholesterol trafficking between cell compartments (endosomes and the ER) and the plasma membrane for efflux. Yet, how ORP6 regulates these pathways, and its function in the brain where it is most highly expressed, are unknown. Gene and protein expression data provide evidence that ORP6 expression is enriched in the brain relative to other tissues, and more specifically in astrocytes and neurons relative to other cells of the central nervous system (CNS). To investigate how ORP6 regulates cholesterol transport and to define its physiological role in whole-body cholesterol homeostasis, we propose to: I. Investigate the role of ORP6 in neuronal and glial cholesterol homeostasis. II. Identify mechanisms of ORP6-mediated cholesterol trafficking. III. Determine the physiological role of ORP6 in cholesterol homeostasis. The current proposal combines my unique expertise on oxysterol-binding proteins, cholesterol trafficking, and lipid metabolism. We will employ a combination of techniques established in the lab to test the hypothesis that ORP6 regulates cholesterol homeostasis in the CNS. Because lipoproteins that shuttle lipid to supply tissues of the body cannot cross the blood-brain barrier, the brain constitutes a particularly interesting microenvironment to study lipid homeostasis as it must be more tightly controlled. With functional biological tools in-hand to study ORP6, we are poised to dissect the fundamental mechanisms of action of this unique ORP family member in cellular cholesterol homeostasis and shed light on fundamental mechanisms of lipid transport in the CNS and mammalian cells.

稳态，或维持一个稳定状态的内部环境的生活系统，是一个核心原则的生活。胆固醇稳态是一个保守的和必要的真核生物过程。在哺乳动物细胞内，细胞内膜胆固醇水平受到严格调节，具有复杂的细胞机制以在不同的细胞内位点维持适当的胆固醇浓度。为此，囊泡和非囊泡胆固醇运输途径都需要胆固醇在细胞区室之间移动。尽管对这些途径进行了广泛的研究，但关于胆固醇在不同细胞室之间转移的机制以及这些过程如何调节仍存在许多问题。氧化固醇结合蛋白（OSBP）是一类与氧化固醇、细胞器间接触、脂质代谢和非囊泡固醇转运有关的脂质转运蛋白（LTP）。 我的NSERC研究项目的目标是研究LTP在维持细胞和全身胆固醇稳态中的作用。氧化固醇结合蛋白相关蛋白6（Oxysterol-binding protein-Related Protein 6，ORP 6）是一种新的调节细胞内胆固醇水平的蛋白。我们先前表明，ORP 6调节细胞隔室（内体和ER）和质膜之间的胆固醇运输，用于流出。然而，ORP 6如何调节这些通路，以及它在大脑中表达最高的功能尚不清楚。基因和蛋白质表达数据提供了证据，表明ORP 6表达相对于其他组织在脑中富集，更具体地说，相对于中枢神经系统（CNS）的其他细胞，在星形胶质细胞和神经元中富集。为了研究ORP 6如何调节胆固醇转运并确定其在全身胆固醇稳态中的生理作用，我们建议： I.研究ORP 6在神经元和胶质细胞胆固醇稳态中的作用。 二.确定ORP 6介导的胆固醇运输机制。 三.确定ORP 6在胆固醇稳态中的生理作用。 目前的建议结合了我在氧固醇结合蛋白，胆固醇运输和脂质代谢方面的独特专长。我们将采用实验室建立的技术组合来测试ORP 6调节CNS中胆固醇稳态的假设。由于将脂质运送到身体组织的脂蛋白不能穿过血脑屏障，因此大脑构成了一个特别有趣的微环境来研究脂质稳态，因为它必须受到更严格的控制。有了研究ORP 6的功能生物学工具，我们准备解剖这个独特的ORP家族成员在细胞胆固醇稳态中的基本作用机制，并阐明CNS和哺乳动物细胞中脂质转运的基本机制。