Mechanisms of endosomal trafficking in lipid droplet catabolism

项目总结/摘要 脂质提供了丰富的能量来源，为基本的细胞过程提供燃料，包括迁移， 分化，并通过低养分可用性时期的生存。存储和利用 脂质燃料的产生依赖于脂滴（LD）。这些独特的细胞器被周围的 磷脂单层，其包封含有中性脂质三酰甘油（TAG）的核心 和胆固醇酯（CE）。LD具有独特的衔接子、酶和结构蛋白质组， 直接与LD单层相互作用并调节生物发生运输的蛋白质， 猫然而，关于LD之间关系的详细机械知识 缺乏单层和LD贩运机制。这一知识对于 脂肪吞噬过程，其中LD的亚群被选择性地靶向溶酶体， 降解我们的初步数据表明，LD具有异质性的脂质签名，在 水平的LD单层，这种异质性影响的命运，某些小LD 嗜脂亚群。此外，我们假设LD单层的脂质 包括甘油二酯（DAG）和磷脂酰肌醇（PI）的代谢受LD分解代谢的调节 酶来影响它们的运输。在项目1中，我们将确定脂肪的作用 甘油三酯脂肪酶（ATGL）在通过TAG水解在LD表面上产生DAG中的作用，并探索 DAG对LD表面蛋白激酶C（PKC）的募集和激活的影响。 在项目2中，我们将研究Rab 5在招募PI 3-激酶到LD表面磷酸化中的作用。 PI，定义了ESCRT蛋白在哺乳动物细胞中用于脂肪吞噬的LD运输中的作用。 我们还将探索某些ESCRT在LD生物发生中的意想不到的作用。获得的结果 从拟议的研究将提供一个机制的理解脂滴运输 和LD单层的调制。

Project Summary/Abstract Lipids provide a rich source of energy to fuel fundamental cellular processes including migration, differentiation, and survival through periods of low nutrient availability. The storage and utilization of lipid fuel relies on lipid droplets (LD). These unique organelles are surrounded by peripheral phospholipid monolayer that encapsulate a core containing neutral lipids triacylglycerol (TAG) and cholesterol ester (CE). LDs possess a unique proteome of adapters, enzymes, and structural proteins that interact directly with the LD monolayer and regulate trafficking for biogenesis and catabolism. However, detailed mechanistic knowledge regarding the relationship between the LD monolayer and LD trafficking machinery is lacking. This knowledge is especially critical for the process of lipophagy, whereby subpopulations of LDs are selectively targeted for lysosomal degradation. Our preliminary data suggest that LDs possess heterogenous lipid signatures at the level of the LD monolayer, and this heterogeneity influences the fate of certain small LD subpopulations toward lipophagy. Furthermore, we postulate that lipids of the LD monolayer including diacylglycerol (DAG) and phosphatidtyliositol (PI) are modulated by LD catabolic enzymes to influence their trafficking. In Project 1, we will determine the role of adipose triglyceride lipase (ATGL) in generating DAG on the LD surface via TAG hydrolysis, and explore the impact of DAG on the recruitment and activation of protein kinase C (PKC) on the LD surface. In Project 2, we will investigate Rab5 in recruiting PI 3-Kinases to the LD surface to phosphorylate PI, define the role of ESCRT proteins in the trafficking of LDs for lipophagy in mammalian cells. We will also explore an unexpected role for certain ESCRTs in LD biogenesis. The results gained from the proposed research will provide a mechanistic understanding of lipid droplet trafficking and the modulation of the LD monolayer.