Structural insights into perilipin 3 membrane association in response to diacylglycerol accumulation

Abstract

Lipid droplets (LDs) are dynamic organelles that contain an oil core mainly composed of 36 triglycerides (TAG) that is surrounded by a phospholipid monolayer and LD-associated proteins 37 called perilipins (PLINs). During LD biogenesis, perilipin 3 (PLIN3) is recruited to nascent LDs as 38 they emerge from the endoplasmic reticulum. Here, we analyzed how lipid composition affects 39 PLIN3 recruitment to membrane bilayers and LDs, and the structural changes that occur upon 40 membrane binding. We found the TAG precursors phosphatidic acid and diacylglycerol (DAG) 41 recruit PLIN3 to membrane bilayers and define an expanded Perilipin-ADRP-Tip47 (PAT) domain 42 that preferentially binds DAG enriched membranes. Membrane binding induces a disorder/order 43 transition of alpha helices within the PAT domain and 11-mer repeats, with intramolecular 44 distance measurements consistent with the expanded PAT domain adopting a folded but dynamic 45 structure upon membrane binding.