Abstract
The lipid droplet (LD) is a ubiquitous cellular structure that is made of the core of lipid esters covered by a phospholipid monolayer. LDs have been generally assumed to form by accumulation of lipid esters between the two leaflets of the endoplasmic reticulum (ER), but rigorous evidence to support this conjecture has not been presented. PAT proteins are thought to work as a shield against cytosolic lipases, and also to facilitate budding of LD from the ER. LDs are likely to fuse each other and may divide under some circumstances, which may be augmented by the microtubule-based motility. Because of the unique structure, division of LDs should increase the chance that the lipases get access to the stored lipid esters. By this way, motility and fusion/fission of LD can be linked directly to its physiological functions.
