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Saccharomyces cerevisiae exhibits a yAP-1-mediated adaptive response to malondialdehyde
H E Turton1, I W Dawes, C M Grant
1School of Biochemistry and Molecular Genetics and C.R.C. for Food Industry Innovation, University of New South Wales, Sydney, Australia.
Abstract:
Malondialdehyde (MDA) is a highly reactive aldehyde generally formed as a consequence of lipid peroxidation. MDA has been inferred to have mutagenic and cytotoxic roles and possibly to be a participant in the onset of atherosclerosis. Wild-type Saccharomyces cerevisiae acquires resistance to a lethal dose (5 mM) of MDA following prior exposure to a nonlethal concentration (1 mM). This response was completely inhibited by cycloheximide (50 microg ml(-1)), indicating a requirement for protein synthesis for adaptation. Furthermore, we have examined the roles of glutathione (GSH), mitochondrial function, and yAP-1-mediated transcription in conferring resistance and adaptation to MDA. A yap1 disruption mutant exhibited the greatest sensitivity and was unable to adapt to MDA, implicating yAP-1 in both the adaptive response and constitutive survival. The effect of MDA on GSH mutants indicated a role for GSH in initial resistance, whereas resistance acquired through adaptation was independent of GSH. Likewise, respiratory mutants (petite mutants) were sensitive to MDA but were still able to mount an adaptive response similar to that of the wild type, excluding mitochondria from any role in adaptation. MDA was detected in yeast cells by the thiobarbituric acid test and subsequent high-pressure liquid chromatography separation. Elevated levels were detected following treatment with hydrogen peroxide. However, the MDA-adaptive response was independent of that to H2O2.
Insights
Yeast cells adapt to toxic malondialdehyde (MDA) through a protein synthesis-dependent process. The transcription factor yAP-1 is crucial for this adaptation and survival, while glutathione aids initial resistance but not adaptation.
Area of Science:
- Biochemistry
- Cell Biology
- Genetics
Background:
- Malondialdehyde (MDA) is a reactive aldehyde linked to lipid peroxidation, cytotoxicity, and atherosclerosis.
- Understanding cellular responses to MDA is vital for comprehending oxidative stress and disease pathogenesis.
Purpose of the Study:
- To investigate the molecular mechanisms underlying yeast adaptation and resistance to malondialdehyde (MDA).
- To elucidate the roles of protein synthesis, glutathione (GSH), mitochondrial function, and the transcription factor yAP-1 in MDA resistance.
Main Methods:
- Exposure of wild-type Saccharomyces cerevisiae and various mutants (e.g., yap1, GSH, petite) to nonlethal and lethal doses of MDA.
- Inhibition studies using cycloheximide to assess the role of protein synthesis.
- Measurement of MDA levels using thiobarbituric acid test and HPLC.
- Assessment of adaptation and resistance phenotypes.
Main Results:
- Wild-type yeast acquired MDA resistance via a process dependent on protein synthesis.
- A yap1 disruption mutant showed extreme sensitivity and failed to adapt, highlighting yAP-1's critical role.
- Glutathione (GSH) contributed to initial resistance but not acquired adaptation.
- Mitochondrial function was not required for MDA adaptation, as petite mutants could still adapt.
Conclusions:
- The transcription factor yAP-1 is essential for both constitutive survival and adaptive resistance to MDA in yeast.
- Adaptation to MDA involves de novo protein synthesis and is independent of GSH and mitochondrial respiration.
- This study reveals key molecular players in cellular defense against lipid peroxidation byproducts.