Function and regulation of lipid metabolism in C. elegans

点击翻译按钮获取中文摘要

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-ER–dependent 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.