Mitochondrial degradation in acetic acid-induced yeast apoptosis: the role of Pep4 and the ADP/ATP carrier

Abstract

SummaryWe have previously shown that acetic acid activates a mitochondria-dependent death process in Saccharomyces cerevisiae and that the ADP/ATP carrier (AAC) is required for mitochondrial outer membrane permeabilization and cytochrome c release. Mitochondrial fragmentation and degradation have also been shown in response to this death stimulus. Herein, we show that autophagy is not active in cells undergoing acetic acid-induced apoptosis and is therefore not responsible for mitochondrial degradation. Furthermore, we found that the vacuolar protease Pep4p and the AAC proteins have a role in mitochondrial degradation using yeast genetic approaches. Depletion and overexpression of Pep4p, an orthologue of human cathepsin D, delays and enhances mitochondrial degradation respectively. Moreover, Pep4p is released from the vacuole into the cytosol in response to acetic acid treatment. AAC-deleted cells also show a decrease in mitochondrial degradation in response to acetic acid and are not defective in Pep4p release. Therefore, AAC proteins seem to affect mitochondrial degradation at a step subsequent to Pep4p release, possibly triggering degradation through their involvement in mitochondrial permeabilization. The finding that both mitochondrial AAC proteins and the vacuolar Pep4p interfere with mitochondrial degradation suggests a complex regulation and interplay between mitochondria and the vacuole in yeast programmed cell death.

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

“…yca1-mtGFP cells showed a punctuated mitochondrial morphology at both times analysed, indicative of mitochondrial damage [55]. Similarly WT-mtGFP showed mitochondrial fragmentation as already reported [56][57]. Our results shows that, notwithstanding the lack of cyt c release in yca1 cell AA-PCD [16], mitochondrial fission occurs en route to both WT and yca1 cell AA-PCD pathways.…”

Mitochatting – If only we could be a fly on the cell wall

“…Release of lethal factors from mitochondria, such as cytochrome C, contributes to an apoptotic death process [78]. Moreover, following the induction of apoptosis, mitochondria are degraded, either through mitophagy [79] or by proteolysis through the Pep4 peptidase that is released from vacuoles at this stage [78]. Pep4 mediated proteolysis requires the presence of the mitochondrial ADP/ATP carrier (AAC) proteins, potentially to enable mitochondrial permeabilization.…”

“…Upon prolonged growth in acetic acid, alterations in mitochondrial structure and function can occur which include reduction in cristae number, mitochondrial swelling, ROS accumulation, depolarization of the inner membrane and decreased respiration. Release of lethal factors from mitochondria, such as cytochrome C, contributes to an apoptotic death process [78]. Moreover, following the induction of apoptosis, mitochondria are degraded, either through mitophagy [79] or by proteolysis through the Pep4 peptidase that is released from vacuoles at this stage [78].…”

Flow cytometry as a novel tool for structural and functional characterization of isolated yeast vacuoles

“…However, more recent data demonstrated that these compartments are highly regulated and also have important functions in ion homeostasis, response to nutrient deprivation, osmotic and ionic stress, autophagy and even in cell death (Guicciardi et al, 2004;Klionsky et al, 1990;Li & Kane, 2009;Pereira et al, 2010;Schauer et al, 2009), supporting the view that vacuoles/lysosomes are highly sensitive and responsive to different cellular challenges, and not only storage or degradative compartments. Almost all vacuolar functions depend either on the acidic pH of the lumen or on the pH gradient across the membrane.…”