As the metabolic needs of an organism shift, cellular lipid-storing droplets can grow and shrink rapidly in size and number — but what is the mechanism behind this? Tobias Walther at Yale University in New Haven, Connecticut, and his colleagues have found that an enzyme, CCT, regulates the formation of phosphatidylcholine (PC) during the expansion of lipid droplets. PC acts as a surfactant at the surface of the lipid droplets, preventing them from coalescing.

The authors fluorescently tagged CCT in fruitfly cells and loaded the cells with lipid. They show that CCT binds to the expanding lipid droplets as PC levels run short. This activates the enzyme to stimulate the production of PC. The researchers found a similar mechanism in mouse cells.

Cell Metab. 10.1016/j.cmet.2011.07.013 (2011)