Estudo da função de tiorredoxina peroxidase citoplasmatica I em Saccharomyces cerevisiae

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Cytosolic thioredoxin peroxidase I (cTPxI) is a Saccharomyces cerevisiae antioxidant enzyme that belongs to peroxiredoxins family, conserved from bacteria to humans, able to reduce hydroperoxides in the presence of a thiol substrate. Our study concerning its role in yeast cells demonstrated that CTPXI is highly expressed in cells exposed to different H2O2 concentrations. Further results revealed that cTPx I is essential for the antioxidant defense of respiratory deficient cells, demonstrated by high sensitivity to H2O2 of ctpxI mutant cells with dysfunctional mitochondria. In addition, we have shown that lack of mitochondrial DNA or COX10 deletion, gene required for cytochrome c oxidase assembly, lead to H2O2 increased generation. Regardless where or how mitochondrial function is perturbed, endogenous ROS production seems to be necessary to increase sensitivity of ctpxI cells to oxidative stress. This phenomenon was demonstrated by viability tests and by sulfhydryl content determinations. Accordingly, C1PX1 expression was high in conditions where the corresponding protein was essential to antioxidant defense. Finally, we have obtained evidences suggesting that cTPxI specifically protects respiratory deficient cells against ROS, since deletion of genes encoding other peroxidases did not alter the sensitivity of cells with mitochondrial dysfunction to HzOz. Therefore, cTPxI seems to be remarkably important in the protection of cells exposed simultaneously to ROS generated by endogenous and exogenous sources. Respiratory deficiencies are frequently associated with cancer, neurodegenerative diseases and aging in human cells. Our results suggest that peroxiredoxins, specially those with high similarity to yeast cTPxI, could exert decisive role in the destiny, survival or death, of cells affected by these disorders

ASSUNTO(S)

mitocondria genetica - expressão stress (fisiologia)

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