Phospholipids are a major component of cellular membranes that compartmentalize metabolic pathways and separate the cellular environment from the outside environment. Alteration in membrane phospholipid composition has been linked to a variety of diseases, including cancer, liver diseases, cardiovascular diseases, and neurodegenerative disorders. However, mechanisms underlying the role of phospholipids in pathogenesis are poorly understood. In many disease states, metabolism and gene expression are dysregulated in response to a dynamic nutrient environment. An open question remains how membrane lipids, at the interface of extra- and intra- cellular environments, integrate environmental cues for homeostatic regulation. My recent studies demonstrated that methylation of the phospholipid phosphatidylethanolamine (PE) for the synthesis of phosphatidylcholine is the major consumer of the biological methyl donor S-adenosylmethionine (SAM) and required for the efficient synthesis of cysteine and glutathione. Cells lacking phospholipid methylation accumulate SAM, leading to hypermethylation of histones, revealing an unforeseen membrane-to-histone communication that is required for optimal cellular metabolism and transcriptional regulation. As such, an important scientific goal, and that of this NIH Pathway to Independence Award, is to further understand cellular and physiological basis underpinning the crosstalk between membrane phospholipids and the epigenome. I propose an innovative program combing cutting-edge genomics, metabolomics, and lipidomics, as well as classic biochemistry and genetics to understand regulatory mechanisms of phospholipid methylation using yeast, human cell lines, and mouse models. I hypothesize that PE methylation can translate dietary and environmental cues into metabolic and transcriptional signals for controlling cellular homeostasis. I will focus on three specific aims: 1) understanding how epigenetic regulation redirects metabolism in response to PE methylation deficiency; 2) examining how the membrane lipid environment dictates the behavior of the PE methylation enzyme; and 3) elucidating cellular mechanisms and physiological basis linking TORC1 (target of rapamycin complex 1) signaling to PE methylation. Dr. Benjamin Tu?s laboratory and UT Southwestern Medical Center provide an ideal training environment for the proposed research. I will avail an Advisory Committee with a spectrum of expertise in metabolism, epigenetics, membrane biology, lipidomic analysis, and mouse liver physiology. Under their mentorship, I will acquire necessary training, including mass spectrometry-based lipidomic analysis and the use of mouse models for translational research during the mentored K99 phase. The Pathway to Independence Award will enable me to expand my scientific and technical repertoire and develop a hypothesis-driven research program, with which I will build an integrative and translational research platform to perform membrane lipid research independently in my own laboratory.
The synthesis of phospholipids is essential for membrane biogenesis, the regulation of which necessitates coordination with metabolic control of cellular homeostasis. This proposal aims to understand how phospholipid methylation translates environmental cues into regulatory signals for metabolic adaptation. Because many of the metabolic deficiencies studied in the proposal have implications in human cancers, liver diseases, and cardiovascular diseases, this work will provide new insights into disease states.