Lipid-induced Caveolin1-Lipid droplet trafficking is associated with lipid droplet growth

Caveolae are 50-100 nm sized plasma membrane invaginations involved in cellular lipid uptake and lipid accumulation. Several caveolin1 and cavin1 mutations are associated to human lipodystrophy. Interestingly, previous research identified caveolae proteins at lipid droplets although their specific cellular function at lipid droplets and in lipid trafficking is not understood. Here, we show that extracellular dietary lipids like oleic acid and cholesterol shift caveolae at the plasma membrane to highly spherical invaginations. Within 3 hours of lipid treatment caveolin1 accumulates specifically to lipid droplets. Correlative fluorescence FIB-SEM and split-APEX proteomics revealed no caveolar vesicles at the lipid droplet but caveolin1 alone. Mechanistically, caveolin1-lipid droplet trafficking is regulated by EHD2 at the plasma membrane level, followed by caveolin1 localization to EEA1- and Rab5-positive endosomes within 1 hour of oleic acid treatment, and subsequently lipid droplet accumulation. Caveolin1-lipid droplet trafficking does not depend on lysosomal activity. Surprisingly, the deletion of the central caveolin1 {beta}-barrel (Cav1-F160X), a mutation found in lipodystrophy patients, abolished caveolin1-lipid droplet trafficking and lipid droplet growth. Taken together, our results show that dietary lipids induce caveolae uptake, caveolin1 accumulation to lipid droplets and a caveolin1-dependent lipid droplet growth.