The Pzh1 protein phosphatase and the Spm1 protein kinase are involved in the regulation of the plasma membrane H⁺‐ATPase in fission yeast

Abstract

We have previously shown that the mutation of the Schizosaccharomyces pombe PPZ-like protein phosphatase encoded by the gene pzh1 + results in increased tolerance to sodium and in hypersensitivity to potassium ions. A similar phenotype has also been reported for deletants in the spm1/pmk1 gene, encoding a mitogen-activated protein (MAP) kinase. We have found that the sodium tolerance phenotype of pzh1 deletants is stronger than that of spm1 mutants, and both effects are additive. Therefore, most probably both gene products mediate different pathways on sodium tolerance. In our hands, mutation of the kinase does not alter the tolerance to potassium, but it yields cells more tolerant to magnesium ions. While in budding yeast the mutations are synthetically lethal, fission yeast cells lacking both the phosphatase and the kinase genes are viable. Interestingly, their ability to export H + to the medium is greatly impaired (although not that of pzh1 or spm1 single mutants). We have observed that, although the amount of the H + -ATPase in the plasma membrane is not altered, the activity of the enzyme is lower than normal and cannot be induced by glucose. These observations suggest that the activity of the H + -ATPase in fission yeast might be regulated by phospho-dephosphorylation mechanisms that might involve the pzh1 + and spm1 + gene products.z 1998 Federation of European Biochemical Societies.

The Schizosaccharomyces pombe fusion gene hal3 encodes three distinct activities

“…While it could be argued that S. pombe Hal3 might have little or no relevance in the control of Pzh1 activity in fission yeast, it is known that, similarly to S. cerevisiae Ppz1, Pzh1 is involved in the maintenance of saline homeostasis in S. pombe. However, the precise targets for the fission yeast phosphatase may differ from those found in budding yeast (Balcells et al ., 1997; 1998; 1999). In any case, it seems unlikely that, while the phosphatase perfectly retains all structural requirements for inhibition, its associated inhibitory component would be no longer functional.…”

Regulation of Yeast H+-ATPase by Protein Kinases Belonging to a Family Dedicated to Activation of Plasma Membrane Transporters

“…However, mutational analysis has indicated that the mechanism of V max regulation is more complex than simple phosphorylation (12) and involves the membrane protein YOR137c (9) and the small heat shock protein Hsp30 (4). Other pieces of the puzzle of ion homeostasis in yeast include the calcium-regulated protein phosphatase calcineurin, which regulates both Trk1,2 and the ATPase (62), and, as demonstrated in fission yeast, some type I protein phosphatases and mitogen-activated protein kinases (2).…”

Carbohydrate and energy-yielding metabolism in non-conventional yeasts

“…This activation is likely due to a phosphorylation and could implicate the MAP kinase encoded by the spm1 /pmk1 and the protein phosphatase encoded by the pzh1 gene. This is suggested by the fact that an spm1 3 pzh1 3 mutant exhibits a lower level of H -ATPase activity that cannot be activated by glucose [268].…”