An adaptive organelle triad houses lipid droplets for dynamic regulation

Cell organelles compartmentalize metabolic reactions and require inter-organelle communications to coordinate metabolic activities in fluctuating nutrient environments. While membrane contacts enable this communication by facilitating metabolite exchange, the functional organization of organelles through these contacts remains underexplored. Here, we show that excess lactate induces severe metabolic stress under nutrient deprivation in the budding yeast Saccharomyces cerevisiae, necessitating a rapid life cycle of lipid droplets (LDs) for cellular adaptation. This process uncovers a previously uncharacterized subcellular architecture-an organelle triad-comprising the vacuole, LDs, and the nuclear endoplasmic reticulum (ER). The vacuole undergoes expansion and deformation, enveloping the entire nucleus that is encircled by an orbit of LDs. Formation of this organelle triad depends on the timely and abundant expression of membrane-tethering proteins that mediate vacuole-LD contact sites and nuclear ER-vacuole junctions. This dynamic and reversible subcellular organization ensures efficient LD metabolism to support cell survival under nutrient stress.