Characterization of a fission yeast P(5)-type ATPase homologue that is essential for Ca(2+)/Mn(2+ )homeostasis in the absence of P(2)-type ATPases.

In the fission yeast Schizosaccharomyces pombe, three P-type ATPases, namely Cta4p, Pmr1p, and Pmc1p, have been shown to be essential for Ca(2+) homeostasis and are required for specific cellular functions as well. Here, we show that the simultaneous deletion of pmc1(+) and SPAC29A4.19c, which encodes a putative P(5)-type ATPase, causes a hypersensitive growth to either high concentrations of Ca(2+) in a medium, or the antiarrhythmic drug amiodarone, which has been known to cause a disruption of Ca(2+) homeostasis. On the other hand, simultaneous deletion of pmr1(+) and SPAC29A4.19c causes a hypersensitive growth to Mn(2+) depletion in a medium. The green fluorescent protein-tagged SPAC29A4.19c protein reveals a typical localization pattern of the Golgi proteins, but the SPAC29A4.19c protein is not exchangeable in function with Pmr1p, which is required for Ca(2+)/Mn(2+) homeostasis in secretory pathways. These results suggest that the putative P(5)-type ATPase encoded by SPAC29A4.19c is essential for Ca(2+) and Mn(2+ )homeostasis in the absence of P(2)-type ATPases, Pmc1p or Pmr1p, respectively. According to the precedent nomenclature of calcium/cation transporting ATPase in fission yeast, SPAC29A4.19 was named cta5(+) in this study.