Evaluating The Role of Lipid Metabolic Genes in Cd4+ And Cd8+ T Cell Function and Metabolism

Abstract

Imbalanced effector and regulatory CD4+ T cell subsets drive many inflammatory diseases. These T cell subsets rely on distinct metabolic programs, modulation of which differentially affects T cell fate and function. Lipid metabolism is fundamental yet remains poorly understood across CD4+ T cell subsets. Therefore, we performed targeted in vivo CRISPR/Cas9 screens to identify lipid metabolism genes and phosphatidylinositol (PI) genes and pathways essential for T cell functions. These screens established mitochondrial fatty acid synthesis (mtFAS) genes Mecr, Mcat and Oxsm for lipid metabolism, and Pi4kb in PI metabolism as key metabolic regulators. First with the use of Mecrfl/fl; Cd4cre novel mouse line, MECR-deficient CD4+ T cells proliferated, differentiated, and survived less well than control T cells. T cells ultimately showed signs of mitochondrial stress and dysfunction in the absence of MECR. Importantly, MECR-deficient T cells exhibited fitness disadvantages and were less effective at driving disease in an in vivo model of inflammatory bowel disease (IBD). In addition, the treatment of PI4KB with an inhibitor led to decreased proliferation and effector function in proinflammatory T cells and a subsequent increase in anti-inflammatory Treg phenotypes with dysregulated glycolytic and oxidative metabolism. Thus, previously unknown MECR and PI4KB mediated metabolism broadly supports CD4+ and CD8+ T cell proliferation and survival. This study shows that previously unknown immunologic targets for cancer, inflammatory, and autoimmune diseases can be found using CRISPR/Cas9 screens focusing on lipid metabolism pathways and diverse lipid metabolic pathways control CD4+ and CD8+ T cell function in vitro and in vivo.