Schizosaccharomyces pombe ehs1p is involved in maintaining cell wall integrity and in calcium uptake.
The Schizosaccharomyces pombe mutant ehs1-1 mutant was isolated on the basis of its hypersensitivity to Echinocandin and Calcofluor White, which inhibit cell wall synthesis. The mutant shows a thermosensitive growth phenotype that is suppressed in the presence of an osmotic stabiliser. The mutant also showed other cell wall-associated phenotypes, such ... as enhanced sensitivity to enzymatic cell wall degradation and an imbalance in polysaccharide synthesis. The ehs1 + gene encodes a predicted integral membrane protein that is 30% identical to Saccharomyces cerevisiae Mid1p, a protein that has been proposed to form part of a calcium channel. As expected for such a function, we found that ehs1+ is involved in intracellular Ca2+ accumulation. High external Ca2+ concentrations suppressed all phenotypes associated with the ehs1 null mutation, suggesting that the cell integrity defects of ehs1 mutants result from inadequate levels of calcium in the cell. We observed a genetic relationship between ehs1+ and the protein kinase C homologue pck2+. pck2+ suppressed all phenotypes of ehs1-1 mutant cells. Overproduction of pck2p is deleterious to wild-type cells, increasing 1,3-beta-D-glucan synthase activity and promoting accumulation of extremely high levels of Ca2+. The lethality associated with pck2p, the increase in 1,3-beta-D-glucan synthase production and the strong Ca2+ accumulation are all dependent on the presence of ehs1p. Our results suggest that in fission yeast ehs1p forms part of a calcium channel that is involved in the cell wall integrity pathway that includes the kinase pck2p.
Mesh Terms:
Amino Acid Sequence, Anti-Bacterial Agents, Antifungal Agents, Benzenesulfonates, Calcium, Cell Wall, Cloning, Molecular, Echinocandins, Fungal Proteins, Genes, Lethal, Membrane Glycoproteins, Membrane Proteins, Molecular Sequence Data, Mutation, Peptides, Peptides, Cyclic, Protein Kinase C, Saccharomyces cerevisiae Proteins, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Sequence Homology, Amino Acid
Amino Acid Sequence, Anti-Bacterial Agents, Antifungal Agents, Benzenesulfonates, Calcium, Cell Wall, Cloning, Molecular, Echinocandins, Fungal Proteins, Genes, Lethal, Membrane Glycoproteins, Membrane Proteins, Molecular Sequence Data, Mutation, Peptides, Peptides, Cyclic, Protein Kinase C, Saccharomyces cerevisiae Proteins, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Sequence Homology, Amino Acid
Mol. Gen. Genet.
Date: Sep. 01, 2000
PubMed ID: 11016847
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