Modulation of Mitochondrial Outer Membrane Permeabilization and Apoptosis by Ceramide Metabolism

Abstract

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.

Proteome and metabolome profiling of wild-type and YCA1 -knock-out yeast cells during acetic acid-induced programmed cell death

“…In agreement with our results, Rego and co-workers have already suggested that ceramide production contributes to AA-PCD, providing indication that ceramide metabolism is involved in cyt c release and mitochondrial fragmentation [54]. Since it has already been shown that, in distinction from WT cells, AA-PCD occurs without cyt c release in yca1 cells [15], we analysed mitochondrial morphology either in WT or yca1 cells before or after AA-PCD in order to gain insights into the role of YCA1 in ceramide-dependent mitochondrial damage.…”

“…7) without cyt c release in the latter case [15]. Our results strongly suggest that ceramides have an active role in cyt c release in yeast AA-PCD, possibly through the formation of ceramide pore as already suggested by Rego et al [54]. Whether the lack in cyt c release observed in yca1 AA-PCD is related to changes in the mitochondrial level of ceramides and with their ability to form ceramide pores needs further investigation.…”

“…Finally, we provided first experimental evidence of a mechanism which suppresses ceramidemediated PCD through YCA1-dependent FAS2 regulation, confirming that activation of phyto-C-16, phyto-C-18, -OH-phyto-C20, dihydro-C-18 and dihydro-C-20 ceramides can trigger PCD in yeast [54]. Ceramides are bioactive sphingolipids that mediate antiproliferative and pro-apoptotic signalling in response to various stress stimuli [78].…”

The plant decapeptide OSIP108 prevents copper-induced apoptosis in yeast and human cells

“…We found that OSIP108 increases tolerance of plant cells to oxidative stress agents like PQ. Moreover, a significantly increased tolerance to H 2 O 2 was also demonstrated in the model yeast Saccharomyces cerevisiae by either heterologous expression of the OSIP108-encoding gene or after exogenous application of OSIP108 to H 2 O 2 -treated yeast [13]. Hence, OSIP108 seems to protect various cell types against oxidative stress inducing agents such as PQ and H 2 O 2 …”

“…Reported mechanisms underlying Cu toxicity are related to mitochondrial dysfunction and damage, since Cu causes (i) a deficiency in the mitochondrial respiratory chain at the level of the Cu-dependent complex IV [7]; (ii) cross-linking of mitochondrial membranous proteins and subsequent contraction of the membrane [7]; (iii) oxidative stress [8–11] and (iv) increased acid sphingomyelinase (aSMase) activity [12]. The latter results in an increased production of ceramide [12], which has been shown to modulate mitochondrial outer membrane permeabilization and induce apoptosis [13, 14]. …”