Strategies to Maintain Redox Homeostasis in Yeast Cells with Impaired Fermentation-Dependent NADPH Generation.

Redox homeostasis is the balance between oxidation and reduction reactions. Its maintenance depends on glutathione, including its reduced and oxidized form, GSH/GSSG, which is the main intracellular redox buffer, but also on the nicotinamide adenine dinucleotide phosphate, including its reduced and oxidized form, NADPH/NADP. Under conditions that enable yeast cells to undergo fermentative metabolism, the main source of NADPH is the pentose phosphate pathway.

Redox perturbations in yeast cells lacking glutathione reductase.

Cellular redox homeostasis has a major effect on cell functions and its maintenance is supported by glutathione and protein thiols which serve as redox buffers in cells. The regulation of the glutathione biosynthetic pathway is a focus of a lot of scientific research. However, still little is known about how complex cellular networks influence glutathione homeostasis.

Changes in a Protein Profile Can Account for the Altered Phenotype of the Yeast Mutant Lacking the Copper-Zinc Superoxide Dismutase.

Copper-zinc superoxide dismutase (SOD1) is an antioxidant enzyme that catalyzes the disproportionation of superoxide anion to hydrogen peroxide and molecular oxygen (dioxygen). The yeast lacking (Δ) is hypersensitive to the superoxide anion and displays a number of oxidative stress-related alterations in its phenotype. We compared proteomes of the wild-type strain and the Δ mutant employing two-dimensional gel electrophoresis and detected eighteen spots representing differentially expressed proteins, of which fourteen were downregulated and four upregulated.

Unbalance between Pyridine Nucleotide Cofactors in The SOD1 Deficient Yeast Causes Hypersensitivity to Alcohols and Aldehydes.

Alcohol and aldehyde dehydrogenases are especially relevant enzymes involved in metabolic and detoxification reactions that occur in living cells. The comparison between the gene expression, protein content, and enzymatic activities of cytosolic alcohol and aldehyde dehydrogenases of the wild-type strain and the Δ mutant lacking superoxide dismutase 1, which is hypersensitive to alcohols and aldehydes, shows that the activity of these enzymes is significantly higher in the Δ mutant, but this is not a mere consequence of differences in the enzymatic protein content nor in the expression levels of genes. The analysis of the NAD(H) and NADP(H) content showed that the higher activity of alcohol and aldehyde dehydrogenases in the Δ mutant could be a result of the increased availability of pyridine nucleotide cofactors.

Linkage between Carbon Metabolism, Redox Status and Cellular Physiology in the Yeast Devoid of or Gene.

yeast cells may generate energy both by fermentation and aerobic respiration, which are dependent on the type and availability of carbon sources. Cells adapt to changes in nutrient availability, which entails the specific costs and benefits of different types of metabolism but also may cause alteration in redox homeostasis, both by changes in reactive oxygen species (ROS) and in cellular reductant molecules contents. In this study, yeast cells devoid of the or gene and fermentative or respiratory conditions were used to unravel the connection between the type of metabolism and redox status of cells and also how this affects selected parameters of cellular physiology.

Disorders in NADPH generation via pentose phosphate pathway influence the reproductive potential of the Saccharomyces cerevisiae yeast due to changes in redox status.

Intermediary metabolites have a crucial impact on basic cell functions. There is a relationship between cellular metabolism and redox balance. To maintain redox homoeostasis, the cooperation of both glutathione and nicotine adenine dinucleotides is necessary.

Cell Size Influences the Reproductive Potential and Total Lifespan of the Yeast as Revealed by the Analysis of Polyploid Strains.

The total lifespan of the yeast may be divided into two phases: the reproductive phase, during which the cell undergoes mitosis cycles to produce successive buds, and the postreproductive phase, which extends from the last division to cell death. These phases may be regulated by a common mechanism or by distinct ones. In this paper, we proposed a more comprehensive approach to reveal the mechanisms that regulate both reproductive potential and total lifespan in cell size context.

Autofluorescence of yeast Saccharomyces cerevisiae cells caused by glucose metabolism products and its methodological implications.

Autofluorescence is the natural fluorescence emitted by cellular compounds which have light emission properties. The main examples of these compounds, identified as an endogenous fluorophores, include aromatic amino acids, vitamins, coenzymes and electron acceptors. As many of them play a critical role in cell metabolism, changes in their content may provide important information on the physiological status of the cell.

Consequences of calorie restriction and calorie excess for the physiological parameters of the yeast Saccharomyces cerevisiae cells.

Glucose plays an important role in cell metabolism and has an impact on cellular physiology. Changes in glucose availability may strongly influence growth rate of the cell size, cell metabolism and the rate of generation of cellular by-products, such as reactive oxygen species. The positive effect of low glucose concentration conditions-calorie restriction is observed in a wide range of species, including the Saccharomyces cerevisiae yeast, yet little is known about the effect of high glucose concentrations-calorie excess.

L-carnosine enhanced reproductive potential of the Saccharomyces cerevisiae yeast growing on medium containing glucose as a source of carbon.

Carnosine is an endogenous dipeptide composed of β-alanine and L-histidine, which occurs in vertebrates, including humans. It has a number of favorable properties including buffering, chelating, antioxidant, anti-glycation and anti-aging activities. In our study we used the Saccharomyces cerevisiae yeast as a model organism to examine the impact of L-carnosine on the cell lifespan.

Acrolein-Induced Oxidative Stress and Cell Death Exhibiting Features of Apoptosis in the Yeast Saccharomyces cerevisiae Deficient in SOD1.

The yeast Saccharomyces cerevisiae is a useful eukaryotic model to study the toxicity of acrolein, an important environmental toxin and endogenous product of lipid peroxidation. The study was aimed at elucidation of the cytotoxic effect of acrolein on the yeast deficient in SOD1, Cu, Zn-superoxide dismutase which is hypersensitive to aldehydes. Acrolein generated within the cell from its precursor allyl alcohol caused growth arrest and cell death of the yeast cells.

Comparison of methods used for assessing the viability and vitality of yeast cells.

Determination of cell viability is the most commonly used method for assessing the impact of various types of stressors in toxicity research and in industrial microbiology studies. Viability is defined as a percentage of live cells in a whole population. Although cell death is one of the consequences of toxicity, chemical or physical factors may exert their toxic effects through a number of cellular alterations that may compromise cell ability to divide without necessarily leading to cell death.

Ascorbate and thiol antioxidants abolish sensitivity of yeast Saccharomyces cerevisiae to disulfiram.

Sensitivity of baker's yeast to disulfiram (DSF) and hypersensitivity of a mutant devoid of Cu, Zn-superoxide dismutase to this compound is reported, demonstrating that yeast may be a simple convenient eukaryotic model to study the mechanism of DSF toxicity. DSF was found to induce oxidative stress in yeast cells demonstrated by increased superoxide production and decrease of cellular glutathione content. Anoxic atmosphere and hydrophilic antioxidants (ascorbate, glutathione, dithiothreitol, cysteine, and N-acetylcysteine) ameliorated DSF toxicity to yeast indicating that oxidative stress plays a critical role in the cellular action of DSF.

Sensitivity of antioxidant-deficient yeast to hypochlorite and chlorite.

Sodium hypochlorite and sodium chlorite are commonly used as disinfectants, and understanding the mechanisms of microbial resistance to these compounds is of considerable importance. In this study, the role of oxidative stress and antioxidant enzymes in the sensitivity of the yeast Saccharomyces cerevisiae to hypochlorite and chlorite was studied. Yeast mutants lacking Cu-Zn superoxide dismutase, but not mutants deficient in cytoplasmic and peroxisomal catalase, were hypersensitive to the action of both hypochlorite and chlorite.

Modulation of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase activity and oxidative modification during the development of adjuvant arthritis.

Adjuvant arthritis (AA) was induced by intradermal administration of Mycobacterium butyricum to the tail of Lewis rats. In sarcoplasmic reticulum (SR) of skeletal muscles, we investigated the development of AA. SR Ca(2+)-ATPase (SERCA) activity decreased on day 21, suggesting possible conformational changes in the transmembrane part of the enzyme, especially at the site of the calcium binding transmembrane part.

The hydrolytic activity of esterases in the yeast Saccharomyces cerevisiae is strain dependent.

Ester precursors of fluorogenic or chromogenic probes are often employed in studies of yeast cell biology. This study was aimed at a comparison of the ability of several commonly used laboratory wild-type Saccharomyces cerevisiae strains to hydrolyse the following model esters: fluorescein diacetate, 2-naphthyl acetate, PNPA (p-nitrophenyl acetate) and AMQI (7-acetoxy-1-methylquinolinum iodide). In all the strains, the esterase activity was localized mainly to the cytosol.

Yeast Saccharomyces cerevisiae devoid of Cu,Zn-superoxide dismutase as a cellular model to study acrylamide toxicity.

Acrylamide is known as a cytotoxic and genotoxic component of starch-containing heat-processed food. We demonstrate that yeast Saccharomyces cerevisiae may be used as a cellular model to examine the biochemical mechanisms of acrylamide toxicity. We found that acrylamide causes impairment of growth of the yeast deficient in Cu,Zn-superoxide dismutase (Δsod1) in a concentration-dependent manner.

Cell volume as a factor limiting the replicative lifespan of the yeast Saccharomyces cerevisiae.

The number of cell divisions of the yeast Saccharomyces cerevisiae is limited, referred to as "replicative lifespan" of this organism and believed to be due to aging mechanisms similar to those of mammalian cells. We demonstrate, using three pairs of isogenic yeast strains (standard and a mutant deficient in an antioxidant defense protein) that although the lifespan differs significantly, the final volume attained after the last division is similar within each pair of strains. In a population, cells cease to bud after various number of cell cycles but attaining a similar final volume.

Relationship between the replicative age and cell volume in Saccharomyces cerevisiae.

Reaching the limit of cell divisions, a phenomenon referred to as replicative aging, of the yeast Saccharomyces cerevisiae involves a progressive increase in the cell volume. However, the exact relationship between the number of cell divisions accomplished (replicative age), the potential for further divisions and yeast cell volume has not been investigated thoroughly. In this study an increase of the yeast cell volume was achieved by treatment with pheromone alpha for up to 18 h.