ER Membrane Phospholipids and Surface Tension Control Cellular Lipid Droplet Formation

Publication date: Available online 1 June 2017
Source:Developmental Cell
Author(s): Kalthoum Ben M'barek, Dalila Ajjaji, Aymeric Chorlay, Stefano Vanni, Lionel Forêt, Abdou Rachid Thiam
Cells convert excess energy into neutral lipids that are made in the endoplasmic reticulum (ER) bilayer. The lipids are then packaged into spherical or budded lipid droplets (LDs) covered by a phospholipid monolayer containing proteins. LDs play a key role in cellular energy metabolism and homeostasis. A key unanswered question in the life of LDs is how they bud off from the ER. Here, we tackle this question by studying the budding of artificial LDs from model membranes. We find that the bilayer phospholipid composition and surface tension are key parameters of LD budding. Phospholipids have differential LD budding aptitudes, and those inducing budding decrease the bilayer tension. We observe that decreasing tension favors the egress of neutral lipids from the bilayer and LD budding. In cells, budding conditions favor the formation of small LDs. Our discovery reveals the importance of altering ER physical chemistry for controlled cellular LD formation.

Graphical abstract

Teaser

Lipid droplets (LDs) are intracellular emulsion droplets that regulate cellular energy metabolism. How LDs physically bud from the endoplasmic reticulum (ER) is still unknown. Ben M'barek et al. reconstituted LD formation topology and find that ER bilayer surface tension, modulated by the bilayer phospholipid composition, determines LD formation and size.


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