ABSTRACT
Calorie restriction increases longevity of mammals and yeasts but this mechanism remains unclear. In this study, the role of glutathione on lifespan extension induced by calorie restriction was investigated by using a Saccharomyces cerevisiae strain deficient in glutathione synthesis (gsh1). We observed an increase in chronological lifespan of calorie-restricted gsh1 mutant cells, compared to WT (wild type) strain, which was associated with a reduction in the levels of oxidative stress biomarkers. The gsh1 strain showed an increase in cell yield under calorie restriction that was associated with a higher pyruvate kinase activity and a reduction in oxygen consumption and aconitase activity. This indicates that the respiratory metabolism is decreased in gsh1 mutant cells. The lifespan extension of gsh1 mutant cells did not represent an advantage at long term, since old cells of gsh1 strain showed a higher frequency of petite mutants. In addition, aged WT cells outlast aged gsh1 mutant cells in direct competition assays in a fresh medium. These results suggest that glutathione is required for the beneficial effects of calorie restriction on cellular longevity.
Subject(s)
Glutathione/metabolism , Saccharomyces cerevisiae/metabolism , Aconitate Hydratase/metabolism , Antioxidants/metabolism , Culture Media , Genes, Fungal , Glucosephosphate Dehydrogenase/metabolism , Glutamate-Cysteine Ligase/genetics , Glutamate-Cysteine Ligase/metabolism , Glutathione Reductase/metabolism , Models, Biological , Mutation , Oxidative Stress , Oxygen Consumption , Protein Carbonylation , Pyruvate Kinase/metabolism , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/growth & development , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/metabolismABSTRACT
The inositolphosphosphingolipid phospholipase C (Isc1p) of Saccharomyces cerevisiae belongs to the family of neutral sphingomyelinases that generates the bioactive sphingolipid ceramide. In this work the role of Isc1p in oxidative stress resistance and chronological lifespan was investigated. Loss of Isc1p resulted in a higher sensitivity to hydrogen peroxide that was associated with an increase in oxidative stress markers, namely intracellular oxidation, protein carbonylation, and lipid peroxidation. Microarray analysis showed that Isc1p deficiency up-regulated the iron regulon leading to increased levels of iron, which is known to catalyze the production of the highly reactive hydroxyl radicals via the Fenton reaction. In agreement, iron chelation suppressed hydrogen peroxide sensitivity of isc1Delta mutants. Cells lacking Isc1p also displayed a shortened chronological lifespan associated with oxidative stress markers and aging of parental cells was correlated with a decrease in Isc1p activity. The analysis of DNA fragmentation and caspase-like activity showed that Isc1p deficiency increased apoptotic cell death associated with oxidative stress and aging. Furthermore, deletion of Yca1p metacaspase suppressed the oxidative stress sensitivity and premature aging phenotypes of isc1Delta mutants. These results indicate that Isc1p plays an important role in the regulation of cellular redox homeostasis, through modulation of iron levels, and of apoptosis.
Subject(s)
Apoptosis/drug effects , Hydrogen Peroxide/pharmacology , Iron/metabolism , Saccharomyces cerevisiae Proteins/metabolism , Saccharomyces cerevisiae/cytology , Saccharomyces cerevisiae/metabolism , Type C Phospholipases/metabolism , Antioxidants/metabolism , Biomarkers/metabolism , Caspases/metabolism , Gene Expression Profiling , Gene Expression Regulation, Fungal/drug effects , Intracellular Space/drug effects , Intracellular Space/metabolism , Models, Biological , Mutation , Oligonucleotide Array Sequence Analysis , Oxidation-Reduction/drug effects , Oxidative Stress/drug effects , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/genetics , Time Factors , Type C Phospholipases/deficiencyABSTRACT
Turnover of damaged molecules is considered to play a key role in housekeeping of cells exposed to oxidative stress, and during the progress of ageing. In this work, global changes in the transcriptome were analysed during recovery of yeast cells after H(2)O(2) stress. Regarding induced genes, those associated with protein fate were the most significantly over-represented. In addition to genes encoding subunits of the 20S proteasome, genes related to vacuolar proteolysis (PEP4 and LAP4), protein sorting into the vacuole, and vacuolar fusion were found to be induced. The upregulation of PEP4 gene expression was associated with an increase in Pep4p activity. The induction of genes related to proteolysis was correlated with an increased protein turnover after H(2)O(2)-induced oxidation. Furthermore, protein degradation and the removal of oxidized proteins decreased in Pep4p-deficient cells. Pep4p activity also increased during chronological ageing, and cells lacking Pep4p displayed a shortened lifespan associated with higher levels of carbonylated proteins. PEP4 overexpression prevented the accumulation of oxidized proteins, but did not increase lifespan. These results indicate that Pep4p is important for protein turnover after oxidative damage; however, increased removal of oxidized proteins is not sufficient to enhance lifespan.
