BPS2026 – Lipid droplet binding proteins at the oil-aqueous interface

Lipid droplets (LDs) are neutral lipid agglomerations found in all cell types throughout a wide diversity of species. The primary function of LDs is lipid storage. In plants they show potential for biofuels and other biotechnological applications, while in animals they play an integral role in several metabolic processes. LDs consist of a neutral lipid core, surrounded by a phospholipid monolayer with LD binding proteins attached at the aqueous-oil interface. For this work, we use a range of LD binding proteins from both animals and plants. These proteins include fibrillins, which are proteins involved in plastoglobule structural development in plants; perilipin 3, found in all human cell types and play a role in the biogenesis of LDs; and apolipoprotein A1 (APOA1), a major structural protein of high-density lipoprotein (HDL) that contribute to reverse cholesterol transport and cellular cholesterol homeostasis. All these proteins contain an amphipathic region in their secondary structures that is assumed to be involved in LD binding. We use pendant drop tensiometry to measure the oil-aqueous interfacial tension and dilatational rheology upon protein binding. The surface tension values reflect the binding affinity of different proteins, including mutants with specific parts of the proteins removed. Dilatational rheology complements the interfacial tension results, helping to gain a better understanding of the targeting and binding of proteins at the triolein-buffer interface. Interfacial tension is determined using axisymmetric drop shape analysis (ADSA) and corroborated by Neumann number analysis.