Moving the fat: Emerging roles of rab GTPases in the regulation of lipid droplet contact sites.

Lipid droplets (LDs) play crucial roles in lipid metabolism, energy homeostasis, and cellular stress. Throughout their lifecycle, LDs establish membrane contact sites (MCSs) with the endoplasmic reticulum, mitochondria, peroxisomes, endosomes, lysosomes, and phagosomes. LD MCSs are dynamically generated in response to metabolic or immune cues to ensure that LD lipids (and proteins) are timely delivered to optimize valuable substrates and avoid lipotoxicity. It is increasingly evident that many Rab GTPases are involved in LD dynamics. Here, we summarize our current understanding of how and when Rab proteins dynamically drive the generation of LD MCSs and regulate a variety of LD functions.