Oxygen Stress: A Regulator of Apoptosis in Yeast

Abstract

Oxygen radicals are important components of metazoan apoptosis. We have found that apoptosis can be induced in the yeast Saccharomyces cerevisiae by depletion of glutathione or by low external doses of H2O2. Cycloheximide prevents apoptotic death revealing active participation of the cell. Yeast can also be triggered into apoptosis by a mutation in CDC48 or by expression of mammalian bax. In both cases, we show oxygen radicals to accumulate in the cell, whereas radical depletion or hypoxia prevents apoptosis. These results suggest that the generation of oxygen radicals is a key event in the ancestral apoptotic pathway and offer an explanation for the mechanism of bax-induced apoptosis in the absence of any established apoptotic gene in yeast.

Selective activation of protein kinase C-δ and -ɛ by 6,11,12,14-tetrahydroxy-abieta-5,8,11,13-tetraene-7-one (coleon U)

“…ROS production was monitored by flow cytometry using dihydroethidium (DHE) from Molecular Probes (Alfagene, Carcavelos, Portugal) as described [25]. About 10 6 cells, incubated in galactose selective medium with 1 M coleon U or DMSO only, were collected and incubated with 5 g/ml DHE for 30 min at 30 ºC.…”

Mitochondrial factors with dual roles in death and survival

“…Evidence for genetic cell suicide mechanisms in yeast was based in part on morphological characteristics of yeast treated with various insults (Madeo et al, 1999). Yeast were reported to exhibit characteristics of apoptotic mammalian cells, including externalized phosphatidylserine on the outer leaflet of the plasma membrane, DNA degradation and chromatin condensation (Madeo et al, 1997(Madeo et al, , 2002a.…”

Bcl-2 family members inhibit oxidative stress-induced programmed cell death in Saccharomyces cerevisiae

“…When considering experimental systems for evaluating ROS-mediated toxicities, the yeast Saccharomyces cerevisiae is an excellent organism to study the regulation of heterologous gene expression in response to oxidative stress [7,8]. S. cerevisiae is sensitive both to H 2 O 2 and to superoxide-generating agents [9][10][11].…”

“…Yeasts have recently been used to study apoptosis, and a number of reports have provided evidence that S. cerevisiae (and fission yeast Schizosaccharomyces pombe) display several of the hallmark features associated with apoptosis, including chromatin condensation, DNA fragmentation, and external membrane exposure of phosphatidylserine [7,14]. Upon examination of the completed genomic sequence of S. cerevisiae, yeast have no apparent homologues of major apoptotic regulators (e.g., Bax/Bcl-2 family, caspases, Apaf-1/CED-4, etc.)…”

“…Following treatment with H 2 O 2 or depletion of glutathione, yeast exhibits apoptotic-like features prior to death [7]. Yeast cells can also be induced to die in an apoptotic-like manner by expression of Bax or treatment with cycloheximide, implying that yeast cell death is an active process, as it is in a number of cases in mammalian cells.…”