Lipid transport at the endoplasmic reticulum -lipid droplet interface – LipDropER

Lipid droplets (LDs) are ubiquitous organelles with a unique structure that consists of a neutral lipid oil core surrounded by a monolayer of phospholipids associated with peripheral proteins. LDs are not uniform mere energy stores, they have a dynamic life cycle and adapt their composition, size, number, localization, and mobility in response to cellular needs. LDs interact dynamically with other organelles notably with the endoplasmic reticulum (ER), its mother organelle. LDs establish transient physical contacts with the ER in structures termed membrane contact sites (MCS). However, very little is known on the identity of the machineries that build and control these ER-LD contacts. Actually, the role of these structures in the complex biology of LD remains largely enigmatic. LipDropER will unveil the functions of a so far unknown type of ER-LD contacts whose formation is mediated by a receptor present at the surface of the ER which combines several assets including the ability to tether membranes and capture lipids. Thereby, LipDropER will address the hypothesis that ER-LD contacts are active cellular subdomains that funnel lipid exchange and regulate the lipid composition of LDs, and thus play a major role in their biology. This project will bring novel insights on the way the ER orchestrates energy storage and utilization in the cell.