Gene-dependent yeast cell death pathway requires AP-3 vesicle trafficking leading to vacuole membrane permeabilization

Abstract

Unicellular eukaryotes are suggested to undergo self-inflicted destruction. However, molecular details are sparse by comparison to the mechanisms of cell death known for human cells and animal models. Here we report a molecular pathway in Saccharomyces cerevisiae leading to vacuole/lysosome membrane permeabilization and cell death. Following exposure to heat-ramp conditions, a model of environmental stress, we observed that yeast cell death occurs over several hours, suggesting an ongoing molecular dying process. A genome-wide screen for death-promoting factors identified all subunits of the AP-3 adaptor complex. AP-3 promotes stress-induced cell death through its Arf1-GTPase-dependent vesicle trafficking function, which is required to transport and install proteins on the vacuole/lysosome membrane, including a death-promoting protein kinase Yck3. Time-lapse microscopy revealed a sequence of events where AP-3-dependent vacuole permeability occurs hours before the loss of plasma membrane integrity. An AP-3-dependent cell death pathway appears to be conserved in the human pathogen Cryptococcus neoformans.

Saccharomyces cerevisiae Cells Lacking the Zinc Vacuolar Transporter Zrt3 Display Improved Ethanol Productivity in Lignocellulosic Hydrolysates

“…A recent study identified that the AP-3 adaptor complex is a death-promoting factor during heat-induced cell death and is also involved in vacuole permeabilization. A recent study uncovered that disruption of the AP-3 adaptor complex, which promotes stress-induced cell death by transporting and installing proteins on the vacuolar membrane, confers resistance to AA and hydrogen peroxide [52]. Since Zrt3 is a candidate cargo protein for the AP-3 adaptor complex, those results are consistent with the data obtained in this study linking absence of Zrt3 from the vacuole with a cell death resistance phenotype.…”

Human and murine Cryptococcus neoformans infection selects for common genomic changes in an environmental isolate

“…Heat tolerance. To determine if resistance to cell death may be related to virulence in these strains, we compared the mouse passaged isolates to the patient strain in a cell death assay that has been previously demonstrated to induce gene-dependent cell death in S. cerevisiae, and more recently in C. neoformans (39,40). To assess cell death susceptibility, a transient sublethal heat-ramp (not heat shock) was applied to all isolates and survival was determined by CFUs when plated at 30°C.…”