Exchangeable zinc ions transiently accumulate in a vesicular compartment in the yeast Saccharomyces cerevisiae

The baker's yeast Saccharomyces cerevisiae was used as a model to visualize intracellular labile zinc under conditions of nutritional zinc imbalance. Zinc-specific staining was performed in yeast cells using both Zinquin fluorescence and zinc-selenium autometallography. Both techniques resulted in specific labeling of an intracellular vesicular compartment that was present in wild type cells as well as in the vacuolar Zn transporter mutants Δzrc1 and Δcot1. This compartment, that closely resembles mammalian zincosomes, appeared rapidly under conditions of zinc availability and was independent of endocytosis. However, persistence of the zinc loaded vesicles in nutritional zinc deficiency was dependent on the presence of functional Zrc1 and Cot1 vacuolar transporters. Overall our findings indicate that labile zinc in yeast cells enters a dynamic vesicular compartment which could represent an extremely important defence to buffer both zinc excess and deficiency.