Function and regulation of lipid metabolism in C. elegans

背景：在真核生物中，脂质具有基本的生物学功能，包括储存能量、传递信号和通过细胞膜划分细胞。然而，由于脂质组的巨大尺寸和多样性，我们对脂质和脂质代谢的功能和调节的了解仍然有限。我的研究计划的长期目标是利用秀丽隐杆线虫强大的遗传工具来解剖脂质和脂质代谢基因如何影响细胞器的功能，反之亦然。***目前，我们主要研究内质网（ER）。内质网合成、加工和分泌蛋白质。受干扰的蛋白质静止激活保守内质网未折叠蛋白反应（UPR-ER），感知并缓解蛋白质错误折叠。内质网也合成和重塑脂质，但脂质失衡是否以及如何影响内质网尚不清楚。重要的是，我们和其他人最近的工作表明，异常的膜脂组成也会打开uper - er，但与蛋白质错误折叠无关。因此，UPR-ER能感知蛋白质和脂质稳态的紊乱。此外，在秀丽隐杆线虫的整个动物环境中，需要UPR-ER来分解脂质以减轻短期禁食。因此，我们假设UPR-ER是脂质稳态的中心传感器和介质，具有不完全表征的输入和输出。为了研究这些，我们的发现基金有两个短期目标：******目标1：定义影响内质网完整性和激活UPR-ER（输入）的代谢改变：内质网完整性可能受到影响脂质组成的代谢途径的影响。为了找到这样的信号，我们将使用反向遗传筛选系统地鉴定代谢基因，其失活诱导UPR-ER标记（伴侣：：GFP）。通过额外的UPR-ER读数和代谢组学验证的候选人将揭示代谢途径和内质网稳态之间的新联系。******目的2：定义UPR-ER依赖和独立的脂肪酶基因表达（输出）的机制：脂质分解是禁食生存所必需的，在禁食的蠕虫中，UPR-ER激活相关基因（脂肪酶）。反之亦然，在被喂食的蠕虫中，脂肪酶被抑制。然而，在这两种状态下，人们对潜在的分子机制知之甚少。我们将通过(a)测试候选转录因子是否在禁食中调节标记脂肪酶来描述脂肪酶基因调控的机制；(b)确定在喂养良好的动物中抑制这种脂肪酶的基因和染色质变化。******这项工作的新颖性和影响是从根本上对脂质、代谢基因、转录途径和细胞器功能之间的相互作用及其在动物体内生理中的作用有了新的认识。对加拿大的好处包括在功能基因组学、遗传学和分子生物学方面公平招聘和培训HQP（2名博士和2名学士学生）。

Background: In eukaryotes, lipids perform fundamental biological functions, including storing energy, transducing signals, and compartmentalizing the cell via membranes. However, due to the lipidome's massive size and diversity, our insight into the function and regulation of lipids and lipid metabolism remains limited. The long-term goal of my research program is to use the powerful genetic tools of the worm Caenorhabditis elegans to dissect how lipids and lipid metabolism genes affect the function of cellular organelles, and vice versa.***Currently, we focus on the endoplasmic reticulum (ER). The ER synthesizes, processes, and secretes proteins. Disturbed proteostasis activates the conserved ER unfolded protein response (UPR-ER), which senses and alleviates protein misfolding. The ER also synthesizes and remodels lipids, but whether and how lipid imbalance impacts the ER is less well understood. Importantly, recent work by us and others showed that abnormal membrane lipid composition also turns on the UPR-ER, but independent of protein misfolding. Thus, the UPR-ER senses disturbances in both protein and lipid homeostasis. Moreover, in the whole animal context of C. elegans, the UPR-ER is required to break down lipids to mitigate short-term fasting. Thus, we hypothesize that the UPR-ER is a central sensor and mediator of lipid homeostasis, with incompletely characterized inputs and outputs. To study these, our Discovery Grant has two short-term objectives:******Aim 1: To define metabolic alterations that impact ER integrity and activate the UPR-ER (inputs): ER integrity may be affected by metabolic pathways impacting lipid composition. To find such signals, we will use a reverse genetic screen to systematically identify metabolic genes whose inactivation induces a UPR-ER marker (chaperone::GFP). Candidates, validated by additional UPR-ER readouts and metabolomics, will reveal novel links between metabolic pathways and ER homeostasis.******Aim 2: To define the mechanism of UPR-ERdependent and independent lipase gene expression (outputs): Lipid breakdown is essential to survive fasting, and the UPR-ER activates pertinent genes (lipases) in fasting worms. Vice versa, lipases are repressed in fed worms. Yet, in both states, the underlying molecular mechanisms are poorly understood. We will delineate mechanisms of lipase gene regulation by (a) testing whether candidate transcription factors regulate a marker lipase in fasting; and (b) defining the genes and chromatin changes that repress this lipase in well-fed animals.******The novelty and impact of this work are fundamentally new insights into the interplays between lipids, metabolic genes, transcriptional pathways, and organelle function, and their role in animal physiology in vivo. Benefits to Canada include equitable recruitment and training of HQP (2 PhD and 2 BSc student) in functional genomics, genetics, and molecular biology.