Potassium deprivation is sufficient to induce a cell death program in Saccharomyces cerevisiae

Abstract

Cell culture in low potassium (K+) media has been associated to programmed cell death (PCD) in metazoans. In this study, deprivation of K + led Saccharomyces cerevisiae cells to a death process that involved phosphatidylserine externalization, changes in chromatin condensation, DNA and vacuole fragmentation as well as enhanced accumulation of reactive oxygen species. During the course of K+ starvation, plasma membrane hyperpolarization and increased accumulation of calcium (Ca2+) took place. The presence of rubidium (Rb+), a K+-analogue element, in the K+-deprived medium was accompanied by Rb+ accumulation but did not fully prevent the appearance of PCD markers. This argues for a specific effect of K+ on the course of cell death. While the absence of the YCA1 metacaspase did not have a major effect, the absence of TRK (transport of K+) K+-transporters led to changes in the pattern of annexin V/propidium iodide labeling. This change paralleled a fast accumulation of Ca2+. Addition of ethylene glycol tetraacetic acid improved growth and reduced cell death in trk1Δtrk2Δ cells. These findings reveal that K+ deprivation is sufficient to induce PCD in a cell-walled eukaryotic organism and suggest that the phenotype attributed to the lack of TRK genes is partially due to the effect of the encoded transporters on Ca2+ homeostasis.