Catalases and thioredoxin peroxidase protect Saccharomyces cerevisiae against Ca2+-induced mitochondrial membrane permeabilization and cell death

The involvement of reactive oxygen species in Ca2+-induced mitochondrial me mbrane permeabilization and cell viability was studied using yeast cells in which the thioredoxin peroxidase (TPx) gene was disrupted and/or catalase was inhibited by 3-amino-1,2,4-triazole (ATZ) treatment. Wild-type Saccharo myces cerevisiae cells were very resistant to Ca2+ and inorganic phosphate or t-butyl hydroperoxide-induced mitochondrial membrane permeabilization, b ut suffered an immediate decrease in mitochondrial membrane potential when treated with Ca2+ and the dithiol binding reagent phenylarsine oxide. In co ntrast, S, cerevisiae spheroblasts lacking the TPx gene and/or treated with ATZ suffered a decrease in mitochondrial membrane potential, generated hig her amounts of hydrogen peroxide and had decreased viability under these co nditions. In all cases, the decrease in mitochondrial membrane potential co uld be inhibited by ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-te traacetic acid, dithiothreitol or ADP, but not by cyclosporin A. We conclud e that TPx and catalase act together, maintaining cell viability and protec ting S, cerevisiae mitochondria against Ca2+-promoted membrane permeabiliza tion, which presents similar characteristics to mammalian permeability tran sition. (C) 2000 Federation of European Biochemical Societies.