Function and regulation of lipid metabolism in C. elegans

背景：在真核生物中，脂类具有基本的生物学功能，包括储存能量、传递信号以及通过膜将细胞隔开。然而，由于脂质体的巨大尺寸和多样性，我们对脂类和脂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线虫强大的遗传工具来剖析脂类和脂代谢基因如何影响细胞器的功能，反之亦然。目前，我们专注于内质网(ER)。内质网合成、加工和分泌蛋白质。紊乱的蛋白质平衡激活保守的ER未折叠蛋白反应(UPR-ER)，从而感知和减轻蛋白质的错误折叠。内质网也合成和重塑脂类，但脂质失衡是否以及如何影响内质网还不太清楚。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启动UPR-ER，但不依赖于蛋白质的错误折叠。因此，UPR-ER感觉到蛋白质和脂肪动态平衡的紊乱。此外，在线虫的整个动物环境中，UPR-ER需要分解血脂以缓解短期禁食。因此，我们假设UPR-ER是脂质动态平衡的中枢感受器和介体，具有不完全特征化的输入和输出。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)的代谢变化：内质网完整性可能受到影响脂质成分的代谢途径的影响。为了找到这样的信号，我们将使用反向遗传筛选来系统地识别其失活会导致UPR-ER标记(伴侣：：GFP)的代谢基因。通过额外的UPR-ER读数和代谢组学的验证，候选将揭示代谢途径和ER同源稳定之间的新联系。目标2：确定UPR-ER依赖和独立的脂肪酶基因表达(输出)的机制：脂类分解是禁食生存所必需的，UPR-ER激活禁食蠕虫中的相关基因(脂肪酶)。反之亦然，在喂食的虫子中，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调节禁食中的标记脂肪酶；以及(B)定义在喂养良好的动物中抑制该脂肪酶的基因和染色质变化，来描述脂肪酶基因调控的机制。这项工作的新颖性和影响是对脂类、代谢基因、转录途径和细胞器功能之间的相互作用及其在活体动物生理学中的作用的新的见解。对加拿大的好处包括公平招聘和培训HQP(2名博士和2名理科学生)功能基因组学、遗传学和分子生物学。

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.