Regulation of Lipid Droplet Biogenesis and Lipophagy

摘要 在美国，代谢性疾病是一个紧迫的公共卫生问题。随着胰岛素的迅速上升 抵抗、肥胖和动脉粥样硬化，对脂代谢的机械理解不可能更多了 势在必行。这些代谢紊乱中的许多都涉及到不适当地将脂肪储存到细胞中 细胞器称为脂滴(LDS)。这些独特的细胞器含有三酰甘油和 胆固醇酯，当饮食中的游离脂肪酸丰富时积聚，反之在 对能源的需求很高。在这种情况下，低密度脂蛋白对细胞和全身都是必不可少的 动态平衡。存在于LDS表面的蛋白质通过以下方式在LDS的动态周转中发挥关键作用 控制体内储存的脂类的摄取和释放。尽管LDS的代谢作用很好 众所周知，用来调节单个LDS生长和分解代谢的机制很差。 明白了。我们已经确定了两种蛋白质，DFCP1和WHAMM，它们将发挥至关重要的作用 腰椎间盘突出症的代谢开关。特别是，我们发现DFCP1定位于参与 LD的生物发生和分解代谢。此外，我们还发现DFCP1具有独特的生化特性 这使得它能够在LDS上形成一层低聚物涂层，这表明它可能在LDS与LDS的连接中发挥作用 急诊室和其他LD。强迫DFCP1从LDS上拆解会导致LD分解代谢的错误调节。因此， 我们推测，DFCP1作为一个分子开关，从内质网中释放出生长的LD，用于 分解代谢。有趣的是，LD的释放与Arp2/3复合体激活剂的积累相耦合， WHAMM和肌动蛋白。我们发现，WHAMM和肌动蛋白在LDS中的积累发生在特定的反应中 到饥饿，在那里它驱动肌动蛋白介导的LDS的动员和收缩。因此，我们的目标是 这项提议是为了定义DFCP1、WHAMM和肌动蛋白所使用的分子机制 驱动LD分解代谢的细胞骨架。为了充分解决这些问题，我们将使用自下而上的方法来 确定DFCP1使低密度脂蛋白从生长转换为分解代谢的机制和分子特性 (目标1)。同时，我们将研究WHAMM和ARP2/3复合体如何与DFCP1协调以驱动LD 动力学和分解代谢(目标2)。通过这些研究获得的机械洞察力将提供新的见解 了解LD代谢如何帮助维持细胞内环境平衡，以及这一过程是如何失调的 在代谢性疾病的发病机制中起重要作用。

ABSTRACT Metabolic diseases are a pressing public health issue in the United States. With the meteoric rise of insulin resistance, obesity, and atherosclerosis, mechanistic understanding of lipid metabolism could not be more imperative. Many of these metabolic disorders involve improper storage of lipids into cellular lipid storage organelles known as lipid droplets (LDs). These unique organelles, which contain a core of triacylglycerols and cholesterol esters, accumulate when dietary free fatty acids are abundant, and conversely get consumed when there is a high demand for energy. In this way, LDs are essential for both cellular and whole-body homeostasis. Proteins that reside on the surface of LDs play critical roles in the dynamic turnover of LDs by controlling the intake and release of the lipids stored within. Although the metabolic roles of LDs are well known, the mechanisms employed to regulate the growth and catabolism of individual LDs are poorly understood. We have identified two proteins, DFCP1 and WHAMM, which are poised to function as crucial metabolic switches for LDs. In particular, we found that DFCP1 localizes to compartments that are involved in both LD biogenesis and catabolism. Moreover, we discovered that DFCP1 has unique biochemical properties that allow it to form an oligomeric coat on LDs, which suggests that it could play a role in the tethering of LDs to the ER and other LDs. Forcing DFCP1 to disassemble from LDs leads to misregulated LD catabolism. Thus, we postulate that DFCP1 functions as a molecular switch that releases growing LDs from the ER for catabolism. Interestingly, LD release is coupled to the accumulation of the activator of the Arp2/3 complex, WHAMM, and actin. We found that accumulation of WHAMM and actin to LDs occurs specifically in response to starvation, where it drives actin-mediated mobilization and constriction of LDs. Consequently, the goals of this proposal are to define the molecular mechanisms employed by DFCP1, WHAMM, and the actin cytoskeleton to drive LD catabolism. To fully address these questions, we will use a bottom-up approach to determine the mechanism and molecular properties that allow DFCP1 to switch LDs from growth to catabolism (Aim 1). In parallel, we will examine how WHAMM and the Arp2/3 complex coordinate with DFCP1 to drive LD dynamics and catabolism (Aim 2). The mechanistic insight obtained by these studies will provide new insights into how LD metabolism helps to maintain cellular homeostasis, but also how misregulation of this process contributes to the pathogenesis of metabolic diseases.