Peroxiredoxin mediated redox regulation of gluconeogenesis and oxidative stress in yeast

抄録

We have found that a yeast major peroxiredoxin Tsa1 forms transient disulfide bond with pyruvate kinase (Pyk1), and regulates Pyk1 enzyme activity in redox-dependent manner. Because Pyk1 catalyzes a rate-limiting step in glycolysis, we thought metabolic changes might affect cellular redox status.
Here, we investigated contributions of Tsa1-dependent redox regulation of Pyk1 on cellular antioxidant response. We generated a PYK1 mutant yeast strain carrying mutations in cysteine residues responsible for interaction with Tsa1 (PYK1C/A). Wild Type (WT) and PYK1C/A cells were cultured in a glucose medium from a log phase to a stationary phase and spotted on the ager medium containing hydrogen peroxide (H₂O₂). H₂O₂ sensitivity of PYK1C/A was equivalent to WT at the log phase. In contrast, PYK1C/A was more sensitive to H₂O₂ than WT at the stationary phase. Since glucose was depleted from the medium at the stationary phase, NADPH might be supplied from a gluconeogenesis-induced pentose phosphate pathway. NADPH is required for detoxification of H₂O₂. Therefore, we examined requirement of fuructose-1,6-bisphosphatase (fbp1Δ), a key enzyme on gluconeogenesis for the phenotype. As we anticipated, the H₂O₂ sensitivity of PYK1C/A was equivalent to that of WT in fbp1Δ genetic background. Furthermore, TSA1 was also required for the difference of the H₂O₂ sensitivity. Taken together, these results suggested that Tsa1-mediated Pyk1 downregulation might upregulate gluconeogenesis to enhance resistance to H₂O₂ after depletion of glucose at the stationary phase. Our results suggest a novel mechanism on controlling metabolism in response to oxidative stress.