The vacuolar V 1 /V 0 ‐ATPase is involved in the release of the HOPS subunit Vps41 from vacuoles, vacuole fragmentation and fusion

At yeast vacuoles, phosphorylation of the HOPS subunit Vps41 depends on the Yck3 kinase. In a screen for mutants that mimic the yck3 Δ phenotype, in which Vps41 accumulates in vacuolar dots, we observed that mutants in the V 0 ‐part of the V 0 /V 1 ‐ATPase, in particular in vma16 Δ, also accumulate Vps41. This accumulation is not due to a phosphorylation defect, but to reduced release of Vps41 from vma16 Δ vacuoles. One reason could be a connection to vacuole fission, which is blocked in V‐ATPase mutants. Vacuole fusion is not impaired between vacuoles lacking the V 0 ‐subunits Vma16 or Vma6 and wild‐type vacuoles, whereas fusion between mutant vacuoles is reduced. Our data suggest a connection between vacuole biogenesis and membrane fusion.