Zyrina AN, Smirnova EA, Markova OV, Severin FF, Knorre DA

There are two superoxide dismutases in yeast: cytoplasmic and mitochondrial enzymes. Inactivation of the cytoplasmic enzyme, Sod1p, renders the cells sensitive to a variety of stresses while inactivation of the mitochondrial isoform, Sod2p, typically has a weaker effect. One exception is ethanol-induced stress. Here we studied the role of Sod2p ...

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in yeast ethanol tolerance. First, we found that repression of SOD2 prevents ethanol-induced relocalization of yeast hydrogen peroxide-sensing transcription factor Yap1p - one of the key stress-resistance proteins. In agreement with this, the levels of Trx2p and Gsh1p, proteins encoded by Yap1-target genes, were decreased in the absence of Sod2p. The analysis of the ethanol sensitivities of the cells lacking Sod2p, Yap1p, or both indicated that the two proteins act in the same pathway. Moreover, preconditioning with hydrogen peroxide restored ethanol resistance of yeast cells with repressed SOD2. Interestingly, we found that mitochondria-to-nucleus signaling by Rtg-proteins antagonizes Yap1p activation. Together, our data suggest that hydrogen peroxide produced by Sod2p activates Yap1p and thus plays a signaling role in ethanol tolerance.Bakers yeast harbor multiple systems that ensure tolerance to high concentrations of ethanol. Still, a role of mitochondria under severe ethanol stress in yeast is not completely clear. Our study revealed a signaling function of mitochondria which contributes significantly to ethanol tolerance of yeast cells. We found that mitochondrial superoxide dismutase Sod2p and cytoplasmic hydrogen peroxide sensor Yap1p act together as a module of mitochondria-to-nucleus signaling pathway. We also report a crosstalk between this pathway and the conventional retrograde signaling cascade activated by dysfunctional mitochondria.

Date: Nov. 18, 2016

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