Pln1 Mediates Lipid Droplet-Vacuole Tethering During Microlipophagy in Saccharomyces cerevisiae

Lipid droplets (LDs) are dynamic organelles that undergo growth or degradation depending on the metabolic state of the cell. One form of LD degradation is autophagy-mediated, referred to as lipophagy. Here, we demonstrate that Pln1, a perilipin located on the surface of LDs in Saccharomyces cerevisiae , previously known for its role in LD biogenesis, is essential for lipophagy. Pln1 facilitates the docking of cytosolic LDs to vacuoles, the lysosome-like organelles responsible for LD degradation, under various nutrient conditions. Molecular dissection of Pln1 revealed that the N-terminal PAT (Perilipin (PLN1), Adipophilin (PLN2), and TIP47 (PLN3)) domain and a hydrophobic region are critical for the localization and binding of LDs to vacuoles. Site-specific mutagenesis within the PAT domain identified a semi-hydrophobic LD Interacting Motif (LIM), which is vital for this interaction. Furthermore, an intrinsically disordered region (IDR) near the center of Pln1 is required for efficient LD-vacuole tethering. These findings support a model in which Pln1 bridges LDs and vacuoles by simultaneously interacting with both organelles. Notably, deleting PLN1 did not impair survival during prolonged nitrogen starvation and enhanced viability in autophagy-defective ( atg8 Δ) cells, suggesting that balancing Pln1-mediated LD biogenesis and lipophagy is crucial for yeast survival under starvation conditions.