Mechanisms of lipophagy, the selective autophagy of lipid droplets

项目概要/摘要 脂自噬是脂滴 (LD) 的选择性自噬，是调节脂滴 (LD) 的重要机制。 大多数真核细胞的细胞内脂质代谢。脂肪自噬是通过从 LD 传递来完成的。 细胞质到裂解室（哺乳动物中的溶酶体或酵母中的液泡）。与其他自噬一样 途径中，核心自噬机制形成隔离 LD 的自噬隔离膜 来自细胞质。然而，当诱导脂肪自噬时，这种自噬膜如何识别 LD 是未知的。 未知。此外，尚不清楚在其余时间如何控制自噬。因此，自噬 选择性和调节是我们对这种自噬途径理解的主要差距。机械论 对这些领域的了解对于精确控制人类的脂肪自噬以预防和预防至关重要。 治疗多种脂质蓄积性疾病，包括脂肪肝、衰老代谢综合征、 肥胖和动脉粥样硬化。最近，我们发现了一种新型的脂噬负调节因子 1 (Nrl1)， 特异性抑制酵母中的脂肪自噬，但不抑制非选择性自噬。我们的初步数据表明 Nrl1 的功能从酵母到哺乳动物细胞都是保守的，并且它促进 LD 的积累 在小鼠巨噬细胞中。由于脂肪吞噬的特异性抑制剂将是一个很好的治疗靶点 在许多疾病状态下该途径的上调，我们研究计划的第一个项目将是 致力于 Nrl1 的脂噬调节。我们将研究脂肪吞噬的分子机制 Nrl1 的抑制、其对脂噬途径的特异性以及 Nrl1 对脂质代谢的影响 细胞（酵母和巨噬细胞）和有机体（斑马鱼）水平。我们的第二个项目 研究计划将集中于脂肪吞噬的选择性机制。通过追踪监管 Nrl1 的影响，我们将确定其效应子，即脂噬特异性选择性因子。我们还将延长 对 LD 蛋白质组的选择性研究，并确定可能在 Nrl1- 中调节的选择性因素 独立时尚。对脂肪吞噬特异性因素的综合分析是一个重要的挑战 由于这些因素定义了脂肪吞噬途径，因此可以用来控制它，并且预计将被解决 新的自噬蛋白。进化保守的噬脂因子将在两个方面进一步研究 细胞（酵母和巨噬细胞）和有机体（斑马鱼）水平。我们将产生自噬缺陷 斑马鱼模型与组成性脂肪自噬的 nrl1 模型一起将构成新的有价值的工具 解决脂肪吞噬对各种脂质积累疾病的具体贡献。

Project Summary/Abstract Lipophagy, the selective autophagy of lipid droplets (LDs), is an essential mechanism that regulates the intracellular lipid metabolism in most eukaryotic cells. Lipophagy is accomplished by the delivery of LDs from the cytosol to the lytic compartment (lysosome in mammals or vacuole in yeast). As in other autophagic pathways, the core autophagic machinery forms the autophagic isolation membrane that sequesters the LD from the cytosol. However, how this autophagic membrane recognizes the LD when lipophagy is induced is unknown. Also, it is not clear how lipophagy is kept in check the rest of the time. Therefore, lipophagy selectivity and regulation are the key gaps in our understanding of this autophagic pathway. The mechanistic understanding in these areas is critical for the precise control of lipophagy in humans for the prevention and treatment of a whole plethora of lipid accumulation diseases, including fatty liver, metabolic syndrome of aging, obesity and atherosclerosis. Recently, we discovered a novel negative regulator of lipophagy 1 (Nrl1) that specifically represses lipophagy but not non-selective autophagy in yeast. Our preliminary data suggest that the function of Nrl1 is conserved from yeast to mammalian cells and that it promotes the accumulation of LDs in murine macrophages. Since a specific suppressor of lipophagy would be such a good therapeutic target for upregulation of the pathway in so many disease states, the first project of our research program will be dedicated to the regulation of lipophagy by Nrl1. We will study the molecular mechanism of lipophagy repression by Nrl1, how specific it is for the lipophagy pathway and the impact of Nrl1 on lipid metabolism at both the cellular (yeast and macrophages) and organismal (zebrafish) levels. The second project of our research program will be focused on the selectivity mechanisms of lipophagy. By tracking down the regulatory effects of Nrl1, we will identify its effectors, the lipophagy-specific selectivity factors. We will also extend the selectivity studies to the LD proteome and identify the selectivity factors that might be regulated in an Nrl1- independent fashion. Comprehensive analyses of the lipophagy-specific factors is an important challenge to be addressed, since such factors define the lipophagy pathway, can be used to control it and are expected to be the new autophagic proteins. The evolutionary conserved lipophagy factors will be studied further at both the cellular (yeast and macrophages) and organismal (zebrafish) levels. We will generate lipophagy-deficient zebrafish models that together with the nrl1 model of constitutive lipophagy will constitute new valuable tools to address the specific contribution of lipophagy to various lipid accumulation diseases.