p53 increases phospholipid headgroup scavenging in senescence

Changes in cell state are often accompanied by altered metabolic demands, and homeostasis depends on cells adapting to their changing needs. One major cell state change is senescence, which is associated with dramatic changes in cell metabolism, including increases in lipid metabolism, but how cells accommodate such alterations is poorly understood. Here we show that the transcription factor p53 increases recycling of the lipid headgroups required to meet the increased demand for membrane phospholipids during senescence. p53 activation increases the supply of phosphoethanolamine, an intermediate in the Kennedy pathway for de novo synthesis of phosphatidylethanolamine, in part by increasing lipid turnover and transactivating genes involved in autophagy and lysosomal catabolism that enable membrane turnover. Disruption of phosphoethanolamine conversion to phosphatidylethanolamine is well tolerated in the absence of p53 but results in dramatic organelle remodelling and perturbs growth and gene expression following p53 activation. Consistently, CRISPR-Cas9-based genetic screens reveal that p53-activated cells preferentially depend on genes involved in lipid metabolism and lysosomal function. Together, these results reveal lipid headgroup recycling to be a homeostatic function of p53 that confers a cell-state-specific metabolic vulnerability.