Abstract
KRAS signaling is spatially organized within the dynamic proteolipid nanoclusters on the plasma membrane (PM) that selectively concentrate anionic phospholipids, yet the molecular determinants governing this lipid sorting remain incompletely defined. Here we identify phospholipid acyl chain composition as a critical regulator of KRAS spatial organization and signal output. Using genetic and pharmacological perturbation of lysophosphatidylcholine acyltransferase 3 (LPCAT3), a key enzyme that incorporates polyunsaturated fatty acids into phospholipids, we demonstrate that remodeling of membrane acyl chain unsaturation alters the phosphatidylserine (PS) lipidome without changing total PS abundance. Loss of LPCAT3 depletes polyunsaturated PS species, disrupts KRAS PM association and nanoclustering, and attenuates downstream MAPK signaling and oncogenic activity across multiple KRAS mutant contexts. Acute restoration of polyunsaturated, but not saturated, lipids rescue KRAS nanoclustering, establishing a direct requirement for lipid unsaturation in sustaining signaling-competent assemblies. Mechanistically, these findings define membrane acyl chain composition as a determinant of proteolipid organization that encodes KRAS signaling capacity. Consistent with this model, LPCAT3 inhibition selectively impairs KRAS-dependent proliferation and sensitizes tumor cells to direct KRAS inhibition. Together, this work uncovers lipid acyl chain remodeling as a fundamental regulator of membrane-associated signaling and identifies membrane composition as an exploitable vulnerability in oncogenic KRAS systems.