期刊
MEMBRANES
卷 12, 期 10, 页码 -出版社
MDPI
DOI: 10.3390/membranes12100949
关键词
lipid droplets; phospholipid monolayer; protein-membrane interactions; liquid-crystalline phase transformation; smectic phase; lipid droplet properties; membrane packing defects
类别
资金
- National Institute of General Medicine of the National Institutes of Health [R35GM143117]
- National Science Foundation [ACI-1548562, MCB200018]
- Center for High Performance Computing at the University of Utah
Lipid droplets are organelles that store and transport neutral lipids. The core of lipid droplets can undergo a phase transformation from amorphous to liquid-crystalline. This transformation affects the physical properties of lipid droplets and can influence protein association. The ordering in the core permeates into the lipid/phospholipid interface, changing the arrangement of lipids and inducing ordering in the phospholipid monolayer. These findings have implications for the recruitment of proteins to lipid droplets under different metabolic conditions.
Lipid droplets are essential organelles that store and traffic neutral lipids. The phospholipid monolayer surrounding their neutral lipid core engages with a highly dynamic proteome that changes according to cellular and metabolic conditions. Recent work has demonstrated that when the abundance of sterol esters increases above a critical concentration, such as under conditions of starvation or high LDL exposure, the lipid droplet core can undergo an amorphous to liquid-crystalline phase transformation. Herein, we study the consequences of this transformation on the physical properties of lipid droplets that are thought to regulate protein association. Using simulations of different sterol-ester concentrations, we have captured the liquid-crystalline phase transformation at the molecular level, highlighting the alignment of sterol esters in alternating orientations to form concentric layers. We demonstrate how ordering in the core permeates into the neutral lipid/phospholipid interface, changing the magnitude and nature of neutral lipid intercalation and inducing ordering in the phospholipid monolayer. Increased phospholipid packing is concomitant with altered surface properties, including smaller area per phospholipid and substantially reduced packing defects. Additionally, the ordering of sterol esters in the core causes less hydration in more ordered regions. We discuss these findings in the context of their expected consequences for preferential protein recruitment to lipid droplets under different metabolic conditions.
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