Understanding mitochondria and lipids droplet interactions in cell biology

线粒体是能量稳态的重要调节器，因为它们为许多生理过程提供能量。在脂质代谢中，线粒体支持脂肪酸的利用和合成。这种相反的功能需要专门的线粒体来完成特定的工作。此外，这些过程需要在储存脂质的储存单元（例如脂滴）附近进行。 以前，我们发现不同的线粒体亚群在棕色脂肪组织中具有不同的作用。我们已经表明，线粒体结合到脂滴，称为peridrolet线粒体（PDM），增强脂质合成。而胞质线粒体（CM，不与脂滴结合）是消耗脂质的线粒体。肝脏也有很高的能力来合成和储存脂质。因此，肝脏在哺乳动物中充当全身脂质代谢的主要调节器。线粒体与脂滴相互作用的作用及其调节在肝脏中仍然未知。我的建议旨在回答这些问题，这将扩大我们对线粒体如何调节肝脏脂质代谢的理解。 首先，我们将通过测量它们利用脂质和葡萄糖的能力来确定CM与PDM在肝脏中的功能。我们还将确定这些线粒体在禁食和进食状态下如何调节脂质代谢。接下来，我们将通过使用病毒基因递送方法来评估PDM在小鼠中的确切作用，以特异性地增强肝脏中的PDM。使用最先进的蛋白质组学方法，我们将定义CM和PDM的蛋白质组，并确定新的监管机构。最后，我们将探讨AMPK和mTOR信号通路，两个众所周知的管理脂质代谢的调节节点，控制CM和PDM。为此，我们将进行信号转导研究，以确定这两种途径如何在肝细胞中调节。这将是第一项研究，以破译它们在肝脏中的确切功能。 总的来说，我们的工作将是探索控制专门线粒体调节脂质代谢机制的首批研究之一。拟议的研究策略将表征这些线粒体群体中的每一个的独特功能以及管理线粒体和脂滴相互作用的信号通路。这项工作不仅代表了对细胞生物学中脂质代谢的理解的突破，而且还将导致识别参与线粒体附着到脂滴的关键因素。 由于线粒体和脂滴存在于大多数细胞中，因此这项研究计划产生的发现不仅对肝脏代谢而且对所有器官都具有重要意义。根据这一初步建议，我们的方法将使我们能够确定关键的潜在调节因子，并追求我们的长期目标，以确定调节脂质和葡萄糖代谢的线粒体机制。

Mitochondria are important regulators of energy homeostasis as they provide energy to many physiological processes. In lipid metabolism, mitochondria support both fatty acid utilization and synthesis. Such opposite functions require specialized mitochondria tuned to perform specific works. Moreover, these processes need to take place close to the storage unit such as the lipid droplets, where the lipids are stored. Previously, we discovered different mitochondrial subpopulations with distinct roles in brown adipose tissue. We have shown that mitochondria bound to lipid droplet, named peridroplet mitochondria (PDM), enhance lipid synthesis. Whereas the cytosolic mitochondria (CM, not bound to lipid droplets) are the mitochondria consuming lipids. The liver has also a high capacity to synthesize and to store lipids. As such, the liver acts as a major regulator of whole-body lipid metabolism in mammals. The role of mitochondria interacting with lipid droplets nor their regulation are still unknown in the liver. My proposal aims to answer these questions which will lead to expanding our understanding of how mitochondria regulate lipid metabolism in the liver. First, we will determine the function of CM vs. PDM in the liver by measuring their capacity to use lipids and glucose. We will also establish how these mitochondria regulate lipid metabolism in fasting and fed states. Next, we will assess the exact role of PDM in mice by using a viral gene delivery method to enhance specifically PDM in the liver. Using state-of-the-art proteomics approaches, we will define the proteome of CM and PDM as well as identify novel regulators. Finally, we will explore how AMPK and mTOR signaling pathways, two well-known regulatory nodes that govern lipid metabolism, control CM, and PDM. To do so, we will perform signaling studies to establish how these two pathways are regulated in hepatocytes. This will represent the first study to decipher their precise functions in the liver. Overall, our work will represent one of the very first studies exploring the mechanisms that control specialized mitochondria regulating lipid metabolism. The proposed research strategy will characterize the unique function of each of these mitochondrial population and the signaling pathways that govern mitochondria and lipid droplet interactions. This work will not only represent a breakthrough in the understanding of lipid metabolism in cell biology but will also lead to the identification of the key factors involved in mitochondria attachment to lipid droplets. As mitochondria and lipid droplets are present in most cells, the discoveries generated by this research program will be significant not only for liver metabolism but also for all organs. Following this initial proposal, our approaches will allow us to identify the key potential regulators and pursue our long-term goal to define the mitochondrial mechanisms regulating lipid and glucose metabolism.