Types of cell death and methods of their detection in yeast Saccharomyces cerevisiae

Reduction of ovarian reserves and activation of necroptosis to in vivo air pollution exposures

We investigated the association between air pollution and changes in ovarian follicles, anti-mullerian hormone (AMH) levels, the occurrence of necroptosis cell death by activation of receptor-interacting protein kinase 3 (RIPK3) and, the activation of mixed lineage kinase domain-like (MLKL) proteins. Forty-two female Wistar rats were divided into three groups of 14 each, which were exposed to real-ambient air, filtered air and purified air (control) in two periods of 3 and 5 months. The results showed that the number of ovarian follicles decreased in the group exposed to real-ambient air versus the control group (P < 0.0001). The trend of age-related AMH changes with respect to exposure to air pollutants was affected and its levels decreased after 3 months of exposure. The MLKL increased in the group exposed to the real-ambient air compared to the control group (P = 0.033). Apparently long-term exposure to air pollution can reduce ovarian reserves.

Specifically Targeting Metacaspases of Candida: A New Therapeutic Opportunity

The World Health Organization (WHO) recently published a list of fungal priority pathogens, including Candida albicans and C. auris. The increased level of resistance of Candida is raising concern, considering the availability of only four classes of medicine. The WHO is seeking novel agent classes with different targets and mechanisms of action. Targeting Candida metacaspases to control intrinsic cell death could provide new therapeutic opportunities for invasive candidiasis. In this review, we provide the available evidence for Candida cell death, describe Candida metacaspases, and discuss the potential of Candida metacaspases to offer a new specific target. Targeting Candida cell death has good scientific rationale given that the fungicidal activity of many marketed antifungals is mediated, among others, by cell death triggering. But none of the available antifungals are specifically activating Candida metacaspases, making this target a new therapeutic opportunity for non-susceptible isolates. It is expected that antifungals based on the activation of fungi metacaspases will have a broad spectrum of action, as metacaspases have been described in many fungi, including filamentous fungi. Considering this original mechanism of action, it could be of great interest to combine these new antifungal candidates with existing antifungals. This approach would help to avoid the development of antifungal resistance, which is especially increasing in Candida.

Monitoring yeast regulated cell death: trespassing the point of no return to loss of plasma membrane integrity

Acetic acid and hydrogen peroxide are the most common stimuli to induce apoptosis in yeast. The initial phase of this cell death process is characterized by the maintenance of plasma membrane integrity in cells that had already lost their viability. As loss of plasma membrane integrity is typically assessed by staining with propidium iodide (PI) after exposure of cells to a stimulus and cell viability is determined 48 h after plating, the percentage of cells with compromised plasma membrane integrity and c.f.u. counts often do not correlate. Herein, we developed a simple method to explore at what point after an apoptotic stimulus and plating cells do non-viable cells die as result of plasma membrane disruption, i.e., when cells surpass the point-of-no-return and undergo a secondary necrosis. The method consisted in washing cells and re-suspending them in stimulus-free medium after acetic acid and hydrogen peroxide treatments, to mimic transfer to plating, and then assessing plasma membrane integrity through PI staining. We show that, after the stimuli are removed, cells that had lost proliferative capacity but still maintained plasma membrane integrity continue the cell death process and later lose plasma membrane integrity when progressing to secondary necrosis. After exposure to hydrogen peroxide, cells undergo secondary necrosis preceded by Nhp6Ap-GFP cytosolic localization, in contrast to acetic acid exposure, where Nhp6Ap-GFP cytosolic localization mainly occurs simultaneously with an earlier emergence of secondary necrosis. In conclusion, the developed method allows monitoring the irreversible loss of plasma membrane integrity of dying apoptotic cells after the point-of-no-return is trespassed, and better characterize the process of secondary necrosis after apoptosis.

Low Temperature Heating-Induced Death and Vacuole Injury in Cladosporium sphaerospermum Conidia

The mechanism of thermal death of mold conidia has not been understood in detail. The purpose of this study is to analyze the death kinetics of heated conidia of Cladosporium sphaerospermum and to ascertain the expectant cell injury responsible for the death. The death of the dormant (resting) conidia of Cladosporium sphaerospermum was examined at temperatures of between 43 and 54℃ with the conventional colony count method. The death reaction apparently followed the first order kinetics, but the Arrhenius plot of the death rate constant demonstrated seemingly a break. The linearity at temperatures higher than that at the break was lost at lower temperatures, suggesting the involvement of an unusual mechanism in the latter temperatures. In the cell morphology, we observed with quinacrine staining the vacuole rupture at a lower temperature but not at a high temperature. Interestingly, the vacuole rupture by low-temperature heating was found to correlate with the viability loss. Furthermore, active protease originally locating in vacuoles was detected in the cytoplasm of the conidia after heated at a low temperature. The results obtained suggest the involvement of potent autophagic cell death induced by low temperature heating of C. sphaerospermum conidia.

Development of a method for heat shock stress assessment in yeast based on transcription of specific genes

All living cells, including yeast cells, are challenged by different types of stresses in their environments and must cope with challenges such as heat, chemical stress, or oxidative damage. By reversibly adjusting the physiology while maintaining structural and genetic integrity, cells can achieve a competitive advantage and adapt environmental fluctuations. The yeast Saccharomyces cerevisiae has been extensively used as a model for study of stress responses due to the strong conservation of many essential cellular processes between yeast and human cells. We focused here on developing a tool to detect and quantify early responses using specific transcriptional responses. We analyzed the published transcriptional data on S. cerevisiae DBY strain responses to 10 different stresses in different time points. The principal component analysis (PCA) and the Pearson analysis were used to assess the stress response genes that are highly expressed in each individual stress condition. Except for these stress response genes, we also identified the reference genes in each stress condition, which would not be induced under stress condition and show stable transcriptional expression over time. We then tested our candidates experimentally in the CEN.PK strain. After data analysis, we identified two stress response genes (UBI4 and RRP) and two reference genes (MEX67 and SSY1) under heat shock (HS) condition. These genes were further verified by real-time PCR at mild (42°C), severe (46°C), to lethal temperature (50°C), respectively.

Identifying Genes Devoted to the Cell Death Process in the Gene Regulatory Network of Ustilago maydis

Cell death is a process that can be divided into three morphological patterns: apoptosis, autophagy and necrosis. In fungi, cell death is induced in response to intracellular and extracellular perturbations, such as plant defense molecules, toxins and fungicides, among others. Ustilago maydis is a dimorphic fungus used as a model for pathogenic fungi of animals, including humans, and plants. Here, we reconstructed the transcriptional regulatory network of U. maydis, through homology inferences by using as templates the well-known gene regulatory networks (GRNs) of Saccharomyces cerevisiae, Aspergillus nidulans and Neurospora crassa. Based on this GRN, we identified transcription factors (TFs) as hubs and functional modules and calculated diverse topological metrics. In addition, we analyzed exhaustively the module related to cell death, with 60 TFs and 108 genes, where diverse cell proliferation, mating-type switching and meiosis, among other functions, were identified. To determine the role of some of these genes, we selected a set of 11 genes for expression analysis by qRT-PCR (sin3, rlm1, aif1, tdh3 [isoform A], tdh3 [isoform B], ald4, mca1, nuc1, tor1, ras1, and atg8) whose homologues in other fungi have been described as central in cell death. These genes were identified as downregulated at 72 h, in agreement with the beginning of the cell death process. Our results can serve as the basis for the study of transcriptional regulation, not only of the cell death process but also of all the cellular processes of U. maydis.

Do Somatic Cells Really Sacrifice Themselves? Why an Appeal to Coercion May be a Helpful Strategy in Explaining the Evolution of Multicellularity

An understanding of the factors behind the evolution of multicellularity is one of today’s frontiers in evolutionary biology. This is because multicellular organisms are made of one subset of cells with the capacity to transmit genes to the next generation (germline cells) and another subset responsible for maintaining the functionality of the organism, but incapable of transmitting genes to the next generation (somatic cells). The question arises: why do somatic cells sacrifice their lives for the sake of germline cells? How is germ/soma separation maintained? One conventional answer refers to inclusive fitness theory, according to which somatic cells sacrifice themselves altruistically, because in so doing they enhance the transmission of their genes by virtue of their genetic relatedness to germline cells. In the present article we will argue that this explanation ignores the key role of policing mechanisms in maintaining the germ/soma divide. Based on the pervasiveness of the latter, we argue that the role of altruistic mechanisms in the evolution of multicellularity is limited and that our understanding of this evolution must be enriched through the consideration of coercion mechanisms.

Citral and geraniol induce necrotic and apoptotic cell death on Saccharomyces cerevisiae

Essential oils and their main components, monoterpenes, have been proven to be important alternatives for the control of pathogenic and spoiling microorganisms, but the mode of action of these compounds is poorly understood. This work aimed to determine the mode of action of citral and geraniol on the model yeast Saccharomyces cerevisiae using a flow cytometry approach. Exponentially growing yeast cells were treated with different concentrations of citral and geraniol for 3 h, and evaluated for cell wall susceptibility to glucanase, membrane integrity, reactive oxygen species (ROS) accumulation, mitochondrial membrane potential, and metacaspase activity. Results provide strong evidence that citral and geraniol acute fungicidal activity against Saccharomyces cells involves the loss of membrane and cell wall integrity resulting in a dose-dependent apoptotic/necrotic cell death. However, yeast cells that escape this first cell membrane disruption, particularly evident on sub-lethal concentration, die by metacaspase-mediated apoptosis induced by the accumulation of intracellular ROS. The deleted mutant on the yca1 gene showed high tolerance to citral and geraniol.

A Quantitative Imaging-Based Protocol for Yeast Growth and Survival on Agar Plates

We present a detailed protocol that describes the evaluation of the growth and survival of yeast cells by quantitatively analyzing spotting assays. This simple method reproducibly detects and quantifies subtle differences in growth by measuring the density of cells within a single spot of defined size on an image of a spotting assay. Our protocol is tailored specifically for low-throughput applications, can be easily adapted for specific experimental conditions, and is accessible to yeast experts and non-experts alike.

For an example of the execution of this protocol, please refer to DiGregorio et al. (Di Gregorio et al., 2020).

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Experimental considerations for enabling spotting assay quantification

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A step-by-step procedure for spotting yeast cultures on agar plates

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Quantification and statistical analysis of spotting assay data

Aspects of Multicellularity in Saccharomyces cerevisiae Yeast: A Review of Evolutionary and Physiological Mechanisms

The evolutionary transition from single-celled to multicellular growth is a classic and intriguing problem in biology. Saccharomyces cerevisiae is a useful model to study questions regarding cell aggregation, heterogeneity and cooperation. In this review, we discuss scenarios of group formation and how this promotes facultative multicellularity in S. cerevisiae. We first describe proximate mechanisms leading to aggregation. These mechanisms include staying together and coming together, and can lead to group heterogeneity. Heterogeneity is promoted by nutrient limitation, structured environments and aging. We then characterize the evolutionary benefits and costs of facultative multicellularity in yeast. We summarize current knowledge and focus on the newest state-of-the-art discoveries that will fuel future research programmes aiming to understand facultative microbial multicellularity.

Glucose causes primary necrosis in exponentially grown yeast Saccharomyces cerevisiae

In this paper, we present data on sugar-induced cell death (SICD) in the yeast Saccharomyces cerevisiae in the exponential phase of growth. We suggest that the nature of SICD in exponentially grown yeast is primary necrosis, in contrast to cells in the stationary growth phase, which exhibit apoptotic SICD. The following findings confirm this conclusion: (i) the process rate; (ii) the impairments of plasma membrane integrity; (iii) the drastic morphological changes in the intracellular content; (iv) the absence of chromatin condensation; (v) the absence of externalization of phosphotidylserine (PS) on the outer leaflet of plasma membrane and (vi) the insensitivity of the SICD process to cycloheximide (CHX). Research shows that SICD occurs in a subpopulation of cells in the S-phase.

Ptychographic imaging of NaD1 induced yeast cell death

Characterising and understanding the mechanisms involved in cell death are especially important to combating threats to human health, particularly for the study of antimicrobial peptides and their effectiveness against pathogenic fungi. However, imaging these processes often relies on the use of synthetic molecules which bind to specific cellular targets to produce contrast. Here we study yeast cell death, induced by the anti-fungal peptide, NaD1. By treating yeast as a model organism we aim to understand anti-fungal cell death processes without relying on sample modification. Using a quantitative phase imaging technique, ptychography, we were able to produce label free images of yeast cells during death and use them to investigate the mode of action of NaD1. Using this technique we were able to identify a significant phase shift which provided a clear signature of yeast cell death. Additionally, ptychography identifies cell death much earlier than a comparative fluorescence study, providing new insights into the cellular changes that occur during cell death. The results indicate ptychography has great potential as a means of providing additional information about cellular processes which otherwise may be masked by indirect labelling approaches.

Periplanetasin-4, a novel antimicrobial peptide from the cockroach, inhibits communications between mitochondria and vacuoles

Communications between various organelle–organelles play an essential role in cell survival. The cross-talk between mitochondria and vacuoles comes up with the vital roles of the intercompartmental process. In this study, we found a couple of cell death features, membrane damage, and apoptosis using antimicrobial peptide from American Cockroach. Periplanetasin-4 (LRHKVYGYCVLGP-NH2) is a 13-mer peptide derived from Periplaneta americana and exhibits phosphatidylserine exposure and caspase activation without DNA fragmentation. Apoptotic features without DNA damage provide evidence that this peptide did not interact with DNA directly and exhibited dysfunction of mitochondria and vacuoles. Superoxide radicals were generated from mitochondria and converted to hydrogen peroxide. Despite the enhancement of catalase and total glutathione contents, oxidative damage disrupted intracellular contents. Periplanetasin-4 induced cell death associated with the production of superoxide radicals, calcium uptake in mitochondria and disorder of vacuoles, such as increased permeability and alkalization. While calcium movement from vacuoles to the mitochondria occurred, the cross-talk with these organelles proceeded and the inherent functionality was impaired. To sum up, periplanetasin-4 stimulates superoxide signal along with undermining the mitochondrial functions and interfering in communication with vacuoles.

PMAP-23 triggers cell death by nitric oxide-induced redox imbalance in Escherichia coli

BACKGROUND

Antibiotic resistance is a global problem and there is an urgent need to augment the arsenal against pathogenic bacteria. The emergence of different drug resistant bacteria is threatening human lives to be pushed toward the pre-antibiotic era. Antimicrobial peptides (AMPs) are a host defense component against infectious pathogens in response to innate immunity. PMAP-23, an AMP derived from porcine myeloid, possesses antibacterial activity. It is currently not clear how the antibacterial activity of PMAP-23 is manifested.

METHODS

The disruptive effect of nitric oxide (NO) on the catalase activity, reactive oxygen species (ROS) production, DNA oxidation and apoptosis-like death were evaluated using the NO generation inhibitor.

RESULTS

In this investigation, PMAP-23 generates NO in a dose dependent manner. NO deactivated catalase and this antioxidant could not protect Escherichia coli against ROS, especially hydroxyl radical. This redox imbalance was shown to induce oxidative stress, thus leading to DNA strand break. Consequently, PMAP-23 treated E. coli cells resulted in apoptosis-like death. These physiological changes were inhibited when NO generation was inhibited. In the ΔdinF mutant, the levels of DNA strand break sharply increased and the cells were more sensitive to PMAP-23 than wild type.

CONCLUSION

Our data strongly indicates that PMAP-23 mediates apoptosis-like cell death through affecting intracellular NO homeostasis. Furthermore, our results demonstrate that DinF functioned in protection from oxidative DNA damage.

GENERAL SIGNIFICANCE

The identification of PMAP-23 antibacterial activity and mechanism provides a promising antibacterial agent, supporting the role of NO in cell death regulation.

Nickel Oxide Nanoparticles Trigger Caspase- and Mitochondria-Dependent Apoptosis in the Yeast Saccharomyces cerevisiae

The expansion of the industrial use of nickel oxide (NiO) nanoparticles (NPs) raises concerns about their potential adverse effects. Our work aimed to investigate the mechanisms of toxicity induced by NiO NPs, using the yeast Saccharomyces cerevisiae as a cell model. Yeast cells exposed to NiO NPs exhibited typical hallmarks of regulated cell death (RCD) by apoptosis [loss of cell proliferation capacity (cell viability), exposure of phosphatidylserine at the outer cytoplasmic membrane leaflet, nuclear chromatin condensation, and DNA damage] in a process that required de novo protein synthesis. The execution of yeast cell death induced by NiO NPs is Yca1p metacaspase-dependent. NiO NPs also induced a decrease in the mitochondrial membrane potential and an increase in the frequency of respiratory-deficient mutants, which supports the involvement of mitochondria in the cell death process. Cells deficient in the apoptosis-inducing factor ( aif1Δ) displayed higher tolerance to NiO NPs, which reinforces the involvement of mitochondria in RCD by apoptosis. In summary, this study shows that NiO NPs induce caspase- and mitochondria-dependent apoptosis in yeast. Our results warn about the possible harmful effects associated with the use of NiO NPs.

Programmed cell death in human pathogenic fungi - a possible therapeutic target

INTRODUCTION

Diseases caused by pathogenic fungi are increasing because of antibiotic overuse, the rise of immunosuppressive therapies, and climate change. The limited variety of antimycotics and the rapid adaptation of pathogenic fungi to antifungal agents serve to exacerbate this issue. Unfortunately, about 1.6 million people are killed by fungal infections annually. Areas covered: The discovery of the small antimicrobial proteins produced by microorganisms, animals, humans, and plants will hopefully overcome challenges in the treatment of fungal infections. These small proteins are highly stable and any resistance to them rarely evolves; therefore, they are potentially good candidates for the treatment and prevention of infections caused by pathogenic fungi. Some of these proteins target the programmed cell death machinery of pathogenic fungi; this is potentially a novel approach in antimycotic therapies. In this review, we highlight the elements of apoptosis in human pathogenic fungi and related model organisms and discuss the possible therapeutic potential of the apoptosis-inducing, small, antifungal proteins. Expert opinion: Small antimicrobial proteins may establish a new class of antimycotics in the future. The rarity of resistance and their synergistic effects with other frequently used antifungal agents may help pave the way for their use in the clinic.

Necrotic cell death induced by dithianon on Saccharomyces cerevisiae

Dithianon is a broad-spectrum anthraquinone fungicide used to control several diseases of grapes, apples, and other fruits and vegetables. Its mode of action is described as multi-site and associated to thiol-reactivity. As other fungicides can affect non-phytopathogenic organisms as yeasts and bacteria, with impact on microbial population, diversity, and fermentation processes. In this context, we study the effect of dithianon on the model organism and fermentative yeast Saccharomyces cerevisiae in order to elucidate the mechanisms involved in yeast cell death., and explain its interference on wine fermentation kinetics. Thus for, we analyzed cellular protein and non-protein thiols, membrane and cell wall integrity, reactive oxygen species accumulation, mitochondrial membrane potential, and phosphatidylserine externalization. The results showed that when exponentially aerobic growing cells of S. cerevisiae are submitted to acute dithianon treatment they loss cell wall and membrane integrity, dying by necrosis, and this behavior is associated to a depletion of reduced proteic and non-proteic thiol groups. We also detected an important increase of cellular reactive oxygen species (ROS) associated to mitochondrial membrane potential modifications on dithianon treated cells. ROS accumulation was not associated to apoptotic cell death, but can be responsible for intracellular damages. Moreover, necrotic cell death induced by dithianon explains its effect on the kinetics of wine fermentations.

Acrolein-Induced Oxidative Stress and Cell Death Exhibiting Features of Apoptosis in the Yeast Saccharomyces cerevisiae Deficient in SOD1

The yeast Saccharomyces cerevisiae is a useful eukaryotic model to study the toxicity of acrolein, an important environmental toxin and endogenous product of lipid peroxidation. The study was aimed at elucidation of the cytotoxic effect of acrolein on the yeast deficient in SOD1, Cu, Zn-superoxide dismutase which is hypersensitive to aldehydes. Acrolein generated within the cell from its precursor allyl alcohol caused growth arrest and cell death of the yeast cells. The growth inhibition involved an increase in production of reactive oxygen species and high level of protein carbonylation. DNA condensation and fragmentation, exposition of phosphatidylserine at the cell surface as well as decreased dynamic of actin microfilaments and mitochondria disintegration point to the induction of apoptotic-type cell death besides necrotic cell death.

RETRACTED:A new function for the yeast trehalose-6P synthase (Tps1) protein, as key pro-survival factor during growth, chronological ageing, and apoptotic stress

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of Marie-Ange Teste, Isabelle Léger-Silvestre, Jean M François and Jean-Luc Parrou. Marjorie Petitjean could not be reached. The corresponding author identified major issues and brought them to the attention of the Journal. These issues span from significant errors in the Material and Methods section of the article and major flaws in cytometry data analysis to data fabrication on the part of one of the authors. Given these errors, the retracting authors state that the only responsible course of action would be to retract the article, to respect scientific integrity and maintain the standards and rigor of literature from the retracting authors' group as well as the Journal. The retracting authors sincerely apologize to the readers and editors.

Similar environments but diverse fates: Responses of budding yeast to nutrient deprivation

Diploid budding yeast (Saccharomyces cerevisiae) can adopt one of several alternative differentiation fates in response to nutrient limitation, and each of these fates provides distinct biological functions. When different strain backgrounds are taken into account, these various fates occur in response to similar environmental cues, are regulated by the same signal transduction pathways, and share many of the same master regulators. I propose that the relationships between fate choice, environmental cues and signaling pathways are not Boolean, but involve graded levels of signals, pathway activation and master-regulator activity. In the absence of large differences between environmental cues, small differences in the concentration of cues may be reinforced by cell-to-cell signals. These signals are particularly essential for fate determination within communities, such as colonies and biofilms, where fate choice varies dramatically from one region of the community to another. The lack of Boolean relationships between cues, signaling pathways, master regulators and cell fates may allow yeast communities to respond appropriately to the wide range of environments they encounter in nature.

Identification of human ferritin, heavy polypeptide 1 (FTH1) and yeast RGI1 (YER067W) as pro-survival sequences that counteract the effects of Bax and copper in Saccharomyces cerevisiae

Ferritin is a sub-family of iron binding proteins that form multi-subunit nanotype iron storage structures and prevent oxidative stress induced apoptosis. Here we describe the identification and characterization of human ferritin, heavy polypeptide 1 (FTH1) as a suppressor of the pro-apoptotic murine Bax sequence in yeast. In addition we demonstrate that FTH1 is a general pro-survival sequence since it also prevents the cell death inducing effects of copper when heterologously expressed in yeast. Although ferritins are phylogenetically widely distributed and are present in most species of Bacteria, Archaea and Eukarya, ferritin is conspicuously absent in most fungal species including Saccharomyces cerevisiae. An in silico analysis of the yeast proteome lead to the identification of the 161 residue RGI1 (YER067W) encoded protein as a candidate for being a yeast ferritin. In addition to sharing 20% sequence identity with the 183 residue FTH1, RGI1 also has similar pro-survival properties as ferritin when overexpressed in yeast. Analysis of recombinant protein by SDS-PAGE and by electron microscopy revealed the expected formation of higher-order structures for FTH1 that was not observed with Rgi1p. Further analysis revealed that cells overexpressing RGI1 do not show increased resistance to iron toxicity and do not have enhanced capacity to store iron. In contrast, cells lacking RGI1 were found to be hypersensitive to the toxic effects of iron. Overall, our results suggest that Rgi1p is a novel pro-survival protein whose function is not related to ferritin but nevertheless it may have a role in regulating yeast sensitivity to iron stress.

A Single-Amino-Acid Substitution in Obg Activates a New Programmed Cell Death Pathway in Escherichia coli

Programmed cell death (PCD) is an important hallmark of multicellular organisms. Cells self-destruct through a regulated series of events for the benefit of the organism as a whole. The existence of PCD in bacteria has long been controversial due to the widely held belief that only multicellular organisms would profit from this kind of altruistic behavior at the cellular level. However, over the past decade, compelling experimental evidence has established the existence of such pathways in bacteria. Here, we report that expression of a mutant isoform of the essential GTPase ObgE causes rapid loss of viability in Escherichia coli. The physiological changes that occur upon expression of this mutant protein—including loss of membrane potential, chromosome condensation and fragmentation, exposure of phosphatidylserine on the cell surface, and membrane blebbing—point to a PCD mechanism. Importantly, key regulators and executioners of known bacterial PCD pathways were shown not to influence this cell death program. Collectively, our results suggest that the cell death pathway described in this work constitutes a new mode of bacterial PCD.

Programmed cell death (PCD) is a well-known phenomenon in higher eukaryotes. In these organisms, PCD is essential for embryonic development—for example, the disappearance of the interdigital web—and also functions in tissue homeostasis and elimination of pathogen-invaded cells. The existence of PCD mechanisms in unicellular organisms like bacteria, on the other hand, has only recently begun to be recognized. We here demonstrate the existence of a bacterial PCD pathway that induces characteristics that are strikingly reminiscent of eukaryotic apoptosis, such as fragmentation of DNA, exposure of phosphatidylserine on the cell surface, and membrane blebbing. Our results can provide more insight into the mechanism and evolution of PCD pathways in higher eukaryotes. More importantly, especially in the light of the looming antibiotic crisis, they may point to a bacterial Achilles’ heel and can inspire innovative ways of combating bacterial infections, directed at the targeted activation of PCD pathways.

Human Thyroid Cancer-1 (TC-1) is a vertebrate specific oncogenic protein that protects against copper and pro-apoptotic genes in yeast

The human Thyroid Cancer-1 (hTC-1) protein, also known as C8orf4 was initially identified as a gene that was up-regulated in human thyroid cancer. Here we show that hTC-1 is a peptide that prevents the effects of over-expressing Bax in yeast. Analysis of the 106 residues of hTC-1 in available protein databases revealed direct orthologues in jawed-vertebrates, including mammals, frogs, fish and sharks. No TC-1 orthologue was detected in lower organisms, including yeast. Here we show that TC-1 is a general pro-survival peptide since it prevents the growth- and cell death-inducing effects of copper in yeast. Human TC-1 also prevented the deleterious effects that occur due to the over-expression of a number of key pro-apoptotic peptides, including YCA1, YBH3, NUC1, and AIF1. Even though the protective effects were more pronounced with the over-expression of YBH3 and YCA1, hTC-1 could still protect yeast mutants lacking YBH3 and YCA1 from the effects of copper sulfate. This suggests that the protective effects of TC-1 are not limited to specific pathways or processes. Taken together, our results indicate that hTC-1 is a pro-survival protein that retains its function when heterologously expressed in yeast. Thus yeast is a useful model to characterize the potential roles in cell death and survival of cancer related genes.

Multiparameter analysis of apoptosis in puromycin-treated Saccharomyces cerevisiae

In Saccharomyces cerevisiae, a typical apoptotic phenotype is induced by some stress factors such as sugars, acetic acid, hydrogen peroxide, aspirin and age. Nevertheless, no data have been reported for apoptosis induced by puromycin, a damaging agent known to induce apoptosis in mammalian cells. We treated S. cerevisiae with puromycin to induce apoptosis and evaluated the percentage of dead cells by using Hoechst 33342 staining, transmission electron microscopy (TEM) and Annexin V flow cytometry (FC) analysis. Hoechst 33342 fluorescence images were processed to acquire parameters to use for multiparameter analysis [and perform a principal component analysis, (PCA)]. Cell viability was evaluated by Rhodamine 123 (Rh 123) and Acridine Orange microscope fluorescence staining. The results show puromycin-induced apoptosis in S. cerevisiae, and the PCA analysis indicated that the increasing percentage of apoptotic cells delineated a well-defined graph profile. The results were supported by TEM and FC. This study gives new insights into yeast apoptosis using puromycin as inducer agent, and PCA analysis may complement molecular analysis facilitating further studies to its detection.

Response of Saccharomyces cerevisiae to the stimulation of lipopolysaccharide

Lipopolysaccharide, known as endotoxin, can stimulate potent host immune responses through the complex of Toll-like-receptor 4 and myeloid differentiation protein 2; but its influence on Saccharomyces cerevisiae, a model organism for studying eukaryotes, is not clear. In this study, we found that lipopolysaccharide-treated S. cerevisiae cells could be stained by methylene blue, but did not die. Transcriptional profiling of the lipopolysaccharide-treated S. cerevisiae cells showed that 5745 genes were modulated: 2491 genes up-regulated and 3254 genes down-regulated. Significantly regulated genes (460 up-regulated genes and 135 down-regulated genes) in lipopolysaccharide-treated S. cerevisiae cells were analyzed on Gene Ontology, and used to establish physical protein-protein interaction network and protein phosphorylation network. Based on these analyses, most of the regulated genes in lipopolysaccharide-treated S. cerevisiae cells were related to cell wall, membrane, peroxisome and mitochondrion. Further experiments demonstrated that lipopolysaccharide stimulation caused the exposure of phosphatidylserine and the increase of mitochondrial membrane potential in S. cerevisiae cells, but levels of intracellular reactive oxygen species and metacaspase activation were not increased. This study demonstrated that lipopolysaccharide stimulation causes significant changes in S. cerevisiae cells, and the results would contribute to understand the response of eukaryotic cells to lipopolysaccharide stimulation.