Small molecule promoters of endogenous lipid droplet accumulation drive lysophagy

Abstract

Lipid droplets (LDs) play a central role in regulating metabolism in stress-induced conditions, including one triggered by nutrient deprivation. Unravelling the protein networks involved in the biogenesis of LDs and their causative and functional roles in health and disease continue to evolve. To this cause, genetic manipulation of the lipid metabolic network or supplementation of high fat diet/ oleic acid (OA) are the traditional routes for voluntarily triggering LDs formation in cells and animals. We developed a screening platform for the identification of new LDs inducers, and our primary screening of various fatty acids identified linoleic acid (LOA, DUFA) as a better tool than OA (MUFA) in promoting LDs formation. The screening and validation discovered new small molecule-based tools for promoting a rapid organization of endogenous lipids into droplets in multiple cell types. Notably, our mass spectral lipidomics analysis presented the overproduction of phosphatidylcholines and small triglycerides, a hallmark of LDs. Mechanistic investigations of our lead molecules highlighted lipid peroxidation and ATP depletion through mitochondrial impairment in cells, which could serve as chemical cues for driving the fusion of cellular lipids into LDs. Finally, we uncovered the abrupt levels of LDs formation induced by our molecules promoted lysophagy in cancer cells to prevent their proliferation. Collectively, our work introduces new small molecules as powerful tools for reliably promoting LDs accumulation for studying their roles in biology, and we demonstrate the over accumulation of LDs prevent cancer cell proliferation, movement, and colonization.