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 triglycerides (TAG) that is surrounded by a phospholipid monolayer and LD-associated proteins called perilipins (PLINs). During LD biogenesis, perilipin 3 (PLIN3) is recruited to nascent LDs as they emerge from the endoplasmic reticulum. Here, we analyze how lipid composition affects PLIN3 recruitment to membrane bilayers and LDs, and the structural changes that occur upon membrane binding. We find that the TAG precursors phosphatidic acid and diacylglycerol (DAG) recruit PLIN3 to membrane bilayers and define an expanded Perilipin-ADRP-Tip47 (PAT) domain that preferentially binds DAG-enriched membranes. Membrane binding induces a disorder to order transition of alpha helices within the PAT domain and 11-mer repeats, with intramolecular distance measurements consistent with the expanded PAT domain adopting a folded but dynamic structure upon membrane binding. In cells, PLIN3 is recruited to DAG-enriched ER membranes, and this requires both the PAT domain and 11-mer repeats. This provides molecular details of PLIN3 recruitment to nascent LDs and identifies a function of the PAT domain of PLIN3 in DAG binding.

Surface tension-driven sorting of human perilipins on lipid droplets

“…Finally, we tested the effect of 1,2 dioleoyl-glycerol (DOG) on PLIN3 binding properties. Diacylglycerols are intermediates in LD metabolism and have been shown to promote the binding of PLIN3 to lipid bilayers (15, 37–39). To quantify the effect of DOG on PLIN3 binding to bilayers, we used the membrane environment-sensitive fluorescent probe NBD (19).…”

“…We first performed experiments with full-length PLIN3 and with phosphatidylcholine (PC)-covered LDs ( Figure 1B ). PLIN3 is intrinsically soluble and its purification does not require any detergent or chaotropic agent (15, 29, 34). PC is the most abundant phospholipid found on LDs in cells (3, 4).…”

“…This uneven distribution might result from differences in protein turnover during cell differentiation and/or from intrinsic differences in the physicochemical properties of PLINs. These include the amino-acid composition of their AH regions, the presence of additional hydrophobic regions, or the ability of the PAT region or the 4-helix bundle to undergo conformational changes (14, 15, 20, 27).…”

“…In humans, the PLIN family contains 5 members (PLIN1-5), which show notable differences in their tissue and subcellular distribution, mode of regulation, and protein interactions (12–14). PLINs contain three main regions: (i) an N-terminal PAT domain, the structure of which is not known but which might contain three helices (15), (ii) a central disordered region, which has been shown to target lipid droplets by providing 3-11 amphipathic helices (AH) that bind to the LD interface (16–20), and (iii) a C-terminal domain, whose structure has been solved in the case of PLIN3 as forming a 4-helix bundle (21). However, PLINs show variations around this canonical scheme.…”

Crystal structures of human and mouse ketohexokinase provide a structural basis for species- and isoform-selective inhibitor design

“…Here, isothermal titration calorimetry would possibly shed light on differences in the thermodynamic profiles of ligand binding. Alternatively, hydrogen-deuterium exchange mass spectrometry (Renaud et al, 2016), spin labeling (Choi et al, 2023) or molecular-dynamics simulations on long timescales might offer experimental strategies to study protein dynamics.…”