and regulate vacuolar size and function in .

The yeast vacuole plays key roles in cellular stress responses. Here, we show that deletion of , the fission yeast homolog of the Chediak-Higashi Syndrome / gene, increases vacuolar size, similar to deletion of the Rab4 homolog . Overexpression of lvs1-YFP rescued vacuolar size in cells, but ypt4-YFP did not rescue , suggesting that may act downstream of . Vacuoles were capable of hypotonic shock-induced fusion and recovery in both and cells, although recovery may be slightly delayed in . Endocytic and secretory trafficking were not affected, but and strains were sensitive to neutral pH and CaCl, consistent with vacuolar dysfunction. In addition to changes in vacuolar size, deletion of also dramatically increased cell size, similar to mutants. These results implicate and in maintenance of vacuolar size and suggest that may link vacuolar homeostasis to cell cycle progression.