Lipid droplet-sphingolipid crosstalk regulates Doa1 activity and DNA damage response

Neutral lipid droplets (nLDs) are dynamic storage organelles that protect the cells from lipotoxicity. They store excess neutral lipids, sequester heavy metals and serve as membrane reservoirs. However, their role in genome integrity remains unclear. Previous studies have linked the shortened lifespan of LD deficient cells to impaired mitochondrial functions caused by defective sterol metabolism, but the molecular origin of this dysfunction remains elusive. In this study, we demonstrate that lack of nLDs inhibits DNA damage sensing mechanism, causing insensitivity to DNA damaging agents. Despite sustained DNA breaks, LD deficient cells unable to activate the checkpoint kinases or arrest cell cycle progression. Persistent insensitivity to double strand breaks results in accumulation of mutations, loss of nuclear as well as mitochondrial DNA integrity leading to accelerated cellular ageing. Through systematic genetic dissection of nLD synthesis genes, we identify a crucial role of lanosterol esterification in lipid droplet formation and their role in the regulation of DNA damage sensing and repair responses. Our study identifies a key regulatory protein, Doa1 that functionally links lipid droplet biosynthesis to DNA damage repair kinase signalling. Together, these findings establish a previously uncharacterized role of neutral lipid droplets in the maintaining the genome stability by acting not only as metabolic buffers but also as signalling platforms that coordinate DNA damage sensing and repair processes. Our work reveals a new mechanistic connection between cellular lipid homeostasis and genome maintenance, highlighting lipid droplets as critical determinants of healthy cellular aging.