Mechanisms of endosomal trafficking in lipid droplet catabolism

项目摘要/摘要 脂质提供了丰富的能量来源，为包括迁移在内的基本细胞过程提供燃料， 分化，以及通过低养分可获得性时期的生存。存储和利用 脂类燃料的主要来源是脂滴(LD)。这些独特的细胞器周围环绕着 包裹含有中性脂质三酰甘油(TAG)的核心的磷脂单分子层 和胆固醇酯(CE)。LDS具有一种独特的蛋白质组，包括接头、酶和结构 直接与LD单层相互作用并调节生物发生和运输的蛋白质 分解代谢。然而，关于劳工部和劳工部之间关系的详细机械知识 缺乏单层和LD贩运机制。这方面的知识对于 脂噬过程，在此过程中，LDS的亚群选择性地针对溶酶体 退化。我们的初步数据表明，LDS在 LD单层的水平，这种异质性影响着某些小LD的命运 亚群趋向于吞脂性。此外，我们假设LD单层的脂类 包括二酰甘油(DAG)和磷脂酰肌醇(PI)是由LD分解代谢调节的 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)通过TAG水解酶在LD表面生成DAG，并探索 DAG对LD表面蛋白激酶C(PKC)募集和激活的影响。 在项目2中，我们将研究Rab5在将PI3-激酶招募到LD表面以使其磷酸化的过程 PI，确定ESCRT蛋白在哺乳动物细胞中脂类吞噬的LDS运输中的作用。 我们还将探索某些ESCRT在LD生物发生中意想不到的作用。取得了良好的效果 将提供对脂滴运输的机制的理解 以及LD单分子膜的调制。

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.