Spartin-mediated lipid transfer facilitates lipid droplet turnover.

The Troyer syndrome protein spartin was proposed to function as a lipophagy receptor that delivers lipid droplets, organelles key for energy storage and membrane lipid homeostasis, to autophagosomes for degradation. We identify an additional function for spartin as a lipid transfer protein and show its transfer ability is required for lipid droplet degradation, including by lipophagy. Our data support that protein-mediated lipid transfer plays a role in lipid droplet turnover. Moreover, in spartin's senescence domain we have discovered a new lipid transport module that likely also features in still undiscovered aspects of lipid droplet biology and membrane homeostasis.