Bax‐induced cell death in Candida albicans

Abstract

Bax is a pro-apoptotic member of the Bcl-2 family of proteins involved in the regulation of genetically programmed cell death in mammalian cells. It has been shown that heterologous expression of Bax in several yeast species, such as Saccharomyces cerevisiae, Schizosaccharomyces pombe and Pichia pastoris, also induces cell death. In this study we investigated the effects of Bax expression in the pathogenic yeast Candida albicans. Cell death inducing expression of Bax required a synthetic BAX gene that was codon-optimized for expression in Candida albicans. Expression of this BAX gene resulted in growth inhibition and cell death. By fusing Bax with the yeast enhanced green fluorescent protein of Aequoria victoria, the cell death-inducing effect of Bax was increased due to reduced proteolytic degradation of Bax. Using this fusion protein we showed that, upon expression in C. albicans, Bax co-localizes with the mitochondria. Furthermore, we showed for the first time that expression of Bax in yeast causes the mitochondria, which are normally distributed throughout the cell, to cluster in the perinuclear region.

Bcl-2 proteins link programmed cell death with growth and morphogenetic adaptations in the fungal plant pathogen Colletotrichum gloeosporioides

“…These results are similar to results that were previously reported in S. cerevisiae, suggesting a common mechanism in C. gloeosporioides (De Smet, 2004;Ligr et al, 1998;Madeo et al, 2004). We also showed that Bcl-2 expression delayed natural fungal death due to aging and reduced the sensitivity of the fungus to moderate environmental stresses including UV, temperature, and oxidative stress.…”

“…We also showed that Bcl-2 expression delayed natural fungal death due to aging and reduced the sensitivity of the fungus to moderate environmental stresses including UV, temperature, and oxidative stress. Similar results have been reported in budding yeast and plants where Bcl-2 expression promoted longevity and provided protection from biotic (including pathogenic fungi) and abiotic stresses (Borner, 2003;De Smet et al, 2004;Igaki and Miura, 2004;Madeo et al, 2004). Notably, Chen and Dickman (Chen and Dickman, 2005;Dickman et al, 2001) recently reported that elevated endogenous levels of reactive oxygen species (ROS) lead to apoptotic cell death in a related Colletotrichum species.…”

“…Until recently, no other homologues of apoptosis-related genes have been identiWed in S. cerevisiae, and therefore it has been considered to represent "apoptosis" null background (Frohlich and Madeo, 2000). Nonetheless, expression of mammalian Bcl-2 proteins in several yeast species showed functional conservation in which expression of pro-apoptotic Bcl-2 species lead to cell death, while expression of anti-apoptotic members of the group inhibited this eVect (De Smet et al, 2004;Madeo et al, 2004;Polcic and Forte, 2003;Priault et al, 2003;Rodriguez-Menocal and D'Urso, 2004). Moreover, expression of the anti-apoptotic protein Bcl-2 in S. cerevisiae lead to enhanced resistance of cells to H 2 O 2 and heat stresses, and increased longterm survival of yeast colonies (Chen et al, 2003a,b;Longo et al, 1997).…”

TmpL, a Transmembrane Protein Required for Intracellular Redox Homeostasis and Virulence in a Plant and an Animal Fungal Pathogen

“…Ultrastructural analysis revealed more frequent cell necrosis-like phenotypes in cells of the Ab ΔtmpL conidia compared with seemingly intact wild-type conidia (Figure 5C, TEM). In order to clarify the TEM observation, we determined the percentage of old conidia that stained positive with annexin V-FITC, a compound that specifically stains apoptotic or dead cells by binding to phosphatidylserine present on the outer leaflet [58],[59]. The annexin V-stained conidia from 21-day-old Ab ΔtmpL strain were increased significantly to 30%, whereas the annexin V-positive wild-type conidia had increased less than 10% after 21 days of growth on CM (Figure S6).…”

The mitochondrial pathway in yeast apoptosis

“…Heterologous expression of the human key apoptotic inducer Bax causes rapid cell death in the yeast Saccharomyces cerevisiae [51,52] and Candida albicans [53]. Manon and colleagues demonstrated that Bax expression induces the release of cytochrome c from mitochondria-a hallmark of mammalian Bax action [25].…”