Paper ID: 364
Department of Biology, University of Fribourg, Fribourg (Switzerland)
Lipid droplets serve to store metabolic energy in form of neutral lipids, particularly triacylglycerol and steryl ester. These neutral lipids are formed by integral membrane enzymes of the endoplasmatic reticulum and are then deposited in lipid droplets from where they can be released again by the action of lipases. While there is growing evidence that early steps of lipid droplet formation occur at or within the ER membrane, later stages of droplet biogenesis are less well understood. We discuss different models of droplet formation and provide experimental evidence that lipid droplets stay closely associated with the ER membrane, possibly throughout their life cycle. Such a close, but topologically still ill-defined association between the ER membrane and lipid droplets is likely to allow for a continuous exchange of membrane anchored proteins as well as lipids between the two compartments.