Acquisition of ethanol tolerance in Saccharomyces cerevisiae: the key role of the mitochondrial superoxide dismutase.
Saccharomyces cerevisiae aBR10 cells are able to develop resistance to lethal ethanol concentrations (14%, v/v), by preexposure to a sublethal heat shock (37 degrees C) or ethanol stress (8%, v/v). Heat shock and 8% ethanol stress had no effect on the concentrations of glutathione [reduced (GSH) and oxidized (GSSG) forms] and on glutathione reductase and CuZn superoxide dismutase (SOD) activities, suggesting that the development of resistance to lethal ethanol concentrations is independent of these antioxidant defenses. In fact, a S. cerevisiae mutant, deficient in CuZnSOD, had an even higher ethanol tolerance, compared to the wild-type strain, and this mutation did not impair a further acquisition of ethanol tolerance. In contrast to CuZnSOD, the MnSOD activity seems to play a more important role in ethanol resistance. The MnSOD activity of the S. cerevisiae aBR10 cells increased upon exposure to heat shock or 8% ethanol. The higher tolerance to 14% ethanol in CuZnSOD deficient cells was also associated to a higher MnSOD activity, as compared to the aBR10 cells; this activity decreased during both stress pretreatments (while still higher than that observed in the wild-type strain). The results obtained suggest that maximum ethanol tolerance is attained with a MnSOD activity close to 1.0 U/mg protein. On either side of this value, the increased sensitivity of S. cerevisiae cells to 14% ethanol might be due to an inability to prevent either superoxide radical- or hydrogen peroxide-induced damages, respectively. These results are supported by the fact that a MnSOD deficiency renders yeast cells more ethanol sensitive.
Costa
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V
Departamento de Biologia Molecular, Instituto de Ciências Biomédicas de Abel Salazar, Porto, Portugal.
Reis
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E
Quintanilha
A
A
Moradas-Ferreira
P
P
D004352:Drug Resistance, Microbial; D000431:Ethanol / Q000494:pharmacology*; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism*; D019803:Glutathione Disulfide; D005980:Glutathione Reductase / Q000378:metabolism; D006358:Hot Temperature; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D013997:Time Factors
D007527:Isoenzymes; D000431:Ethanol; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005978:Glutathione; D019803:Glutathione Disulfide