The life cycle of lipid droplets

Abstract

Proteomic studies have revealed many potential functions of cytoplasmic lipid droplets, and recent activity has confirmed that these bona fide organelles are central not only for lipid storage and metabolism, but for development, immunity, and pathogenesis by several microbes. There has been a burst of recent activity on the assembly, maintenance and turnover of lipid droplets that reveals fresh insights. This review summarizes several novel findings in initiation of lipid droplet assembly, protein targeting, droplet fusion, and turnover of droplets through lipophagy.

Figure 1. The life cycle of a lipid droplet

Important events in the lipid droplet life cycle are shown. Recent advances include a pre-droplet organelle and associated ACSL3, a possible cycling of droplets associated and released from the ER mediated by COP1, the dual role of Fsp27 in lipolysis and droplet fusion, and two specific pathways of lipophagy, one common in mammals, the other in yeast. ALR, autophagic lysosome reformation. Although droplets may exist that are disconnected from the ER, the figure is not meant to imply that droplet expansion, fusion, or autophagy is limited to ER-connected or -dissociated droplets.