Mitochondrial ABC Transporter Atm1p Is Required for Protection against Oxidative Stress and Vacuolar Functions in Schizosaccharomyces pombe

A potential correlation between mitochondrial and vacuolar functions is known to exit in yeast. Fission yeast atm1+, SPAC15A10.01, encodes a putative half-type ABC transporter with an N-terminal mitochondrial-targeting signal. In an attempt to evaluate the possible involvement of mitochondrion in vacuole function, a functional analysis of atm1+was performed by gene disruption. Growth of the atm1mutant was inhibited in the presence of oxidizing agents, and S. cerevisiaeAtm1p was found to complement this growth defect. atm1Δ cells exhibited defects in fluid-phase endocytosis and vacuolar fusion under hypotonic stress. GFP-tagged Atm1p was observed to be localized in the mitochondria. These data strongly suggest that fission yeast Atm1p was not only involved in protection against oxidative stress, but also played a role in vacuolar functions.