Polarity-selective Transfer of Lipophilic Cargoes From Lipid Droplets (Oleosomes) to Lipid Bilayers

Abstract

Lipid Droplets (LDs) or as also called oleosomes are lipid storage organelles in eukaryotic cells. Besides storing lipids, LDs can fuse their core into other intracellular organelles, but the mechanism remains unknown. In this work, this is aimed to understand the effect of cargo's polarity on the transportation of the cargo from LDs to lipid bilayers using liposomes. LDs are loaded with curcumin and Nile red, two lipophilic molecules with similar log P values. The loaded LDs are blended with liposomes, while curcumin and Nile red are tracked using confocal microscopy and spectroscopy. LDs remained intact, while curcumin was transferred in 5 min from LDs to liposomes. Nile red remained in LDs. The difference between curcumin and Nile red is attributed to the amphiphilicity of curcumin, which allowed its adsorption in the LD monolayer and the subsequent transportation to the liposome bilayer upon contact. The unique selectivity of LDs is shown as carriers since lipophilic cargo is transferred to the lipid bilayer only when participating in the LD membrane. The understanding of the transportation mechanism of molecules from LDs to bilayers helps the exploitation of LDs as natural lipid carriers.