Modulation of mitochondrial outer membrane permeabilization and apoptosis by ceramide metabolism

The yeast Saccharomyces cerevisiae undergoes a mitochondrial-dependent programmed cell death in response to different stimuli, such as acetic acid, with features similar to those of mammalian apoptosis. However, the upstream signaling events in this process, including those leading to mitochondrial membrane permeabilization, are still poorly characterized. Changes in sphingolipid metabolism have been linked to modulation of apoptosis in both yeast and mammalian cells, and ceramides have been detected in mitochondria upon apoptotic stimuli. In this study, we aimed to characterize the contribution of enzymes involved in ceramide metabolism to apoptotic cell death induced by acetic acid. We show that isc1Δ and lag1Δ mutants, lacking inositol phosphosphingolipid phospholipase C and ceramide synthase, respectively, exhibited a higher resistance to acetic acid that was associated with lower levels of some phytoceramide species. Consistently, these mutant cells displayed lower levels of ROS production and reduced mitochondrial alterations, such as mitochondrial fragmentation and degradation, and decreased translocation of cytochrome c into the cytosol in response to acetic acid. These results suggest that ceramide production contributes to cell death induced by acetic acid, especially through hydrolysis of complex sphingolipids catalyzed by Isc1p and de novo synthesis catalyzed by Lag1p, and provide the first in vivo indication of its involvement in mitochondrial outer membrane permeabilization in yeast.This project was financially supported by FEDER (Fundo Europeu de Desenvolvimento Regional) through the program “Programa Operacional Factores de Competitividade-COMPETE” and FCT (Fundação para a Ciência e Tecnologia), through the projects Pest-C/BIA/UI4050/2011, Pest-C/SAU/LA0002/2011, FCOMP-01-0124-FEDER-022718 and FCOMP-01-0124-FEDER-007047. Research was supported in part by Grant GM 063265, the Lipidomics Shared Resource, Hollings Cancer Center, Medical University of South Carolina (P30 CA138313) and the Lipidomics Core in the SC Lipidomics and Pathobiology COBRE, Department Biochemistry, MUSC (P20 RR017677). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript