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.
Carnero
E
E
Departamento de Microbiología y Genética, Instituto de Microbiología Bioquímica, CSIC and Universidad de Salamanca, Spain.
Ribas
J C
JC
García
B
B
Durán
A
A
Sánchez
Y
Y
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology; D001557:Benzenesulfonates / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D054714:Echinocandins; D005656:Fungal Proteins / Q000235:genetics; D005804:Genes, Lethal; D008562:Membrane Glycoproteins / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides; D010456:Peptides, Cyclic; D011493:Protein Kinase C / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid
D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D001557:Benzenesulfonates; D054714:Echinocandins; D005656:Fungal Proteins; C090463:MID1 protein, S cerevisiae; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010455:Peptides; D010456:Peptides, Cyclic; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C405644:YAM8 protein, S pombe; C007061:C.I. Fluorescent Brightening Agent 28; C007572:echinocandin B; D011493:Protein Kinase C; D002118:Calcium