Programmed cell death in Saccharomyces cerevisiae

ntroduction:Like multicellular organisms, the yeastSaccharomycescerevisiaecan undergo programmed cell death (PCD) induced by dif-ferent environmental stress. By using an experimental system in whichyeast PCD is induced by acetic acid (AA-PCD), we investigated bothcell survival and a variety of processes occurringen routeto death,including: production of reactive oxygen species (ROS) and its regula-tion, the involvement of proteasome and metacaspase YCA1, cyto-chrome c release.Methods:AA-PCD was induced in exponential yeast cells. Catalase(CAT) or superoxide dismutase (SOD) was over-expressed in yeast cellsand YCA1 gene-knock out strain was constructed. ROS formation,enzyme activities and cytochrome c release were assayed by fluores-cence microscopy, spectrophotometric and immunoblotting analysis.Results:We show thaten routeto AA-PCD:ROS are produced in a CAT and SOD dependent-fashion;proteasome activation is needed for AA-PCD to occur;cytochrome c is released from coupled mitochondria and can work asan electron donor and a ROS scavenger;YCA1 is dispensable for AA-PCD to occur and caspase inhibitorzVAD-fmk does not prevent AA-PCD.Conclusion:The picture emerging from these results is as follows:early H2O2production occurs in AA-PCD in a manner modulated byCAT and SOD. Proteasome is transiently activated starting 60 minutesafter PCD induction. Release of cytochromecoccurs starting at60 minutes of AA-PCD and is complete at 150 minutes. YCA1 partici-pates in AA-PCD also in a manner unrelated to its caspase-like activity.Acknowledgement:This work was financed by MIUR-Contributistraordinari di ricerca/aree obiettivo I and TIORCAS INTERREG/IIIA