The role of lysosomes in lipid homeostasis.

Lipids function as the major building blocks of cellular membranes, as signaling molecules and as energy stores for metabolism. These important functions require a precise regulation of lipid biosynthesis, transport, turnover and storage. Lipids are exchanged among organelles through a sophisticated network of vesicular and non-vesicular transport routes. Lysosomes, as the main catabolic organelle, are at the center of this network and have recently evolved as one of the master-regulators of cellular lipid metabolism. Lipids from both endogenous and exogenous sources can be processed, sensed and sorted in and out of the lysosome. In this review, we focus on the role of the lysosome in lipid catabolism, transport and signaling. We highlight recent discoveries on the transport of lipids out of the lysosomal lumen and their exchange with other organelles via membrane contact sites. We also discuss the direct role of lysosomal lipids in the TORC1 signaling pathway, a regulator of cellular metabolism. Finally, we address lysosomal biogenesis, its role in the sorting of lipid metabolic enzymes and the dysregulation of these processes in disease.