scholarly journals Efg1 Controls Caspofungin-Induced Cell Aggregation of Candida albicans through the Adhesin Als1

2011 ◽  
Vol 10 (12) ◽  
pp. 1694-1704 ◽  
Author(s):  
Christa Gregori ◽  
Walter Glaser ◽  
Ingrid E. Frohner ◽  
Cristina Reinoso-Martín ◽  
Steffen Rupp ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Cell Aggregation ◽  
Large Cell ◽  
Fungal Species ◽  
Invasive Growth ◽  
Cell Integrity ◽  
Fungal Cell ◽  
Content Type ◽  
Cell Wall Remodeling

ABSTRACTEchinocandin drugs such as caspofungin (CASP), micafungin, and anidulafungin inhibit fungal cell wall biogenesis by blocking Fks1-mediated β-glucan deposition into the cell surface. Candins have become suitable drugs to treat life-threatening diseases caused by several fungal species, includingCandida albicans, that are pathogenic for humans.Here, we present the discovery of a novel CASP-induced flocculation phenotype ofC. albicans, which formed large cell aggregates in the presence of CASP. High concentrations of sugars such as mannose or glucose inhibit CASP-induced flocculation and improve survival ofC. albicanscells exposed to CASP. Notably, exposure ofC. albicanscells to CASP triggers Efg1-dependent expression of the adhesinALS1and induces invasive growth on agar plates. Indeed, cells lacking either Efg1 or Als1 show strongly diminished CASP-induced flocculation, and the absence of Efg1 leads to marked CASP hypersensitivity. On the other hand, CASP-induced invasive growth is enhanced in cells lacking Efg1. Hence, CASP stress drives an Efg1-dependent response, indicating that this multifunctional transcriptional regulator, which is otherwise involved in filamentation, white-to-opaque switching, and virulence, also modulates cell wall remodeling upon CASP challenge. Taken together, our data suggest that CASP-induced cell wall damage activates Efg1 in parallel with the known cell integrity stress signaling pathway to coordinate cell wall remodeling.

scholarly journals High-Throughput Screening Identifies Genes Required forCandida albicansInduction of Macrophage Pyroptosis

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Teresa R. O’Meara ◽  
Kwamaa Duah ◽  
Cynthia X. Guo ◽  
Michelle E. Maxson ◽  
Ryan G. Gaudet ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Immune Cells ◽  
High Throughput Screening ◽  
Immune Cell ◽  
Fungal Infections ◽  
Innate Immune ◽  
Fungal Cell ◽  
Content Type ◽  
Cell Wall Remodeling

ABSTRACTThe innate immune system is the first line of defense against invasive fungal infections. As a consequence, many successful fungal pathogens have evolved elegant strategies to interact with host immune cells. For example,Candida albicansundergoes a morphogenetic switch coupled to cell wall remodeling upon phagocytosis by macrophages and then induces macrophage pyroptosis, an inflammatory cell death program. To elucidate the genetic circuitry through whichC. albicansorchestrates this host response, we performed the first large-scale analysis ofC. albicansinteractions with mammalian immune cells. We identified 98C. albicansgenes that enable macrophage pyroptosis without influencing fungal cell morphology in the macrophage, including specific determinants of cell wall biogenesis and the Hog1 signaling cascade. Using these mutated genes, we discovered that defects in the activation of pyroptosis affect immune cell recruitment during infection. Examining host circuitry required for pyroptosis in response toC. albicansinfection, we discovered that inflammasome priming and activation can be decoupled. Finally, we observed thatapoptosis-associatedspeck-like protein containing aCARD (ASC) oligomerization can occur prior to phagolysosomal rupture byC. albicanshyphae, demonstrating that phagolysosomal rupture is not the inflammasome activating signal. Taking the data together, this work defines genes that enable fungal cell wall remodeling and activation of macrophage pyroptosis independently of effects on morphogenesis and identifies macrophage signaling components that are required for pyroptosis in response toC. albicansinfection.IMPORTANCECandida albicansis a natural member of the human mucosal microbiota that can also cause superficial infections and life-threatening systemic infections, both of which are characterized by inflammation. Host defense relies mainly on the ingestion and destruction ofC. albicansby innate immune cells, such as macrophages and neutrophils. Although someC. albicanscells are killed by macrophages, most undergo a morphological change and escape by inducing macrophage pyroptosis. Here, we investigated theC. albicansgenes and host factors that promote macrophage pyroptosis in response to intracellular fungi. This work provides a foundation for understanding how host immune cells interact withC. albicansand may lead to effective strategies to modulate inflammation induced by fungal infections.

scholarly journals Remasking of Candida albicans β-Glucan in Response to Environmental pH Is Regulated by Quorum Sensing

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Fabien Cottier ◽  
Sarah Sherrington ◽  
Sarah Cockerill ◽  
Valentina del Olmo Toledo ◽  
Stephen Kissane ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Quorum Sensing ◽  
Immune Responses ◽  
Female Reproductive Tract ◽  
Innate Immune ◽  
Immune Recognition ◽  
Innate Immune Responses ◽  
Content Type ◽  
Cell Wall Remodeling

ABSTRACT Candida albicans is a commensal yeast of the human gut which is tolerated by the immune system but has the potential to become an opportunistic pathogen. One way in which C. albicans achieves this duality is through concealing or exposing cell wall pathogen-associated molecular patterns (PAMPs) in response to host-derived environment cues (pH, hypoxia, and lactate). This cell wall remodeling allows C. albicans to evade or hyperactivate the host’s innate immune responses, leading to disease. Previously, we showed that adaptation of C. albicans to acidic environments, conditions encountered during colonization of the female reproductive tract, induces significant cell wall remodeling resulting in the exposure of two key fungal PAMPs (β-glucan and chitin). Here, we report that this pH-dependent cell wall remodeling is time dependent, with the initial change in pH driving cell wall unmasking, which is then remasked at later time points. Remasking of β-glucan was mediated via the cell density-dependent fungal quorum sensing molecule farnesol, while chitin remasking was mediated via a small, heat-stable, nonproteinaceous secreted molecule(s). Transcript profiling identified a core set of 42 genes significantly regulated by pH over time and identified the transcription factor Efg1 as a regulator of chitin exposure through regulation of CHT2. This dynamic cell wall remodeling influenced innate immune recognition of C. albicans, suggesting that during infection, C. albicans can manipulate the host innate immune responses. IMPORTANCE Candida albicans is part of the microbiota of the skin and gastrointestinal and reproductive tracts of humans and has coevolved with us for millennia. During that period, C. albicans has developed strategies to modulate the host’s innate immune responses, by regulating the exposure of key epitopes on the fungal cell surface. Here, we report that exposing C. albicans to an acidic environment, similar to the one of the stomach or vagina, increases the detection of the yeast by macrophages. However, this effect is transitory, as C. albicans is able to remask these epitopes (glucan and chitin). We found that glucan remasking is controlled by the production of farnesol, a molecule secreted by C. albicans in response to high cell densities. However, chitin-remasking mechanisms remain to be identified. By understanding the relationship between environmental sensing and modulation of the host-pathogen interaction, new opportunities for the development of innovative antifungal strategies are possible.

scholarly journals Aspergillus fumigatus Transcription Factors Involved in the Caspofungin Paradoxical Effect

mBio ◽  
2020 ◽  
Vol 11 (3) ◽  
Author(s):  
Clara Valero ◽  
Ana Cristina Colabardini ◽  
Jéssica Chiaratto ◽  
Lakhansing Pardeshi ◽  
Patrícia Alves de Castro ◽  
...  
Keyword(s):  
Cell Wall ◽  
Transcription Factors ◽  
Invasive Aspergillosis ◽  
Aspergillus Fumigatus ◽  
Rna Polymerase Ii ◽  
Respiratory Function ◽  
Antifungal Agents ◽  
Fungal Species ◽  
Content Type ◽  
Cell Wall Remodeling

ABSTRACT Aspergillus fumigatus is the leading cause of pulmonary fungal diseases. Azoles have been used for many years as the main antifungal agents to treat and prevent invasive aspergillosis. However, in the last 10 years there have been several reports of azole resistance in A. fumigatus and new strategies are needed to combat invasive aspergillosis. Caspofungin is effective against other human-pathogenic fungal species, but it is fungistatic only against A. fumigatus. Resistance to caspofungin in A. fumigatus has been linked to mutations in the fksA gene that encodes the target enzyme of the drug β-1,3-glucan synthase. However, tolerance of high caspofungin concentrations, a phenomenon known as the caspofungin paradoxical effect (CPE), is also important for subsequent adaptation and drug resistance evolution. Here, we identified and characterized the transcription factors involved in the response to CPE by screening an A. fumigatus library of 484 null transcription factors (TFs) in CPE drug concentrations. We identified 11 TFs that had reduced CPE and that encoded proteins involved in the basal modulation of the RNA polymerase II initiation sites, calcium metabolism, and cell wall remodeling. One of these TFs, FhdA, was important for mitochondrial respiratory function and iron metabolism. The ΔfhdA mutant showed decreased growth when exposed to Congo red or to high temperature. Transcriptome sequencing (RNA-seq) analysis and further experimental validation indicated that the ΔfhdA mutant showed diminished respiratory capacity, probably affecting several pathways related to the caspofungin tolerance and resistance. Our results provide the foundation to understand signaling pathways that are important for caspofungin tolerance and resistance. IMPORTANCE Aspergillus fumigatus, one of the most important human-pathogenic fungal species, is able to cause aspergillosis, a heterogeneous group of diseases that presents a wide range of clinical manifestations. Invasive pulmonary aspergillosis is the most serious pathology in terms of patient outcome and treatment, with a high mortality rate ranging from 50% to 95% primarily affecting immunocompromised patients. Azoles have been used for many years as the main antifungal agents to treat and prevent invasive aspergillosis. However, there were several reports of evolution of clinical azole resistance in the last decade. Caspofungin, a noncompetitive β-1,3-glucan synthase inhibitor, has been used against A. fumigatus, but it is fungistatic and is recommended as second-line therapy for invasive aspergillosis. More information about caspofungin tolerance and resistance is necessary in order to refine antifungal strategies that target the fungal cell wall. Here, we screened a transcription factor (TF) deletion library for TFs that can mediate caspofungin tolerance and resistance. We have identified 11 TFs that are important for caspofungin sensitivity and/or for the caspofungin paradoxical effect (CPE). These TFs encode proteins involved in the basal modulation of the RNA polymerase II initiation sites, calcium metabolism or cell wall remodeling, and mitochondrial respiratory function. The study of those genes regulated by TFs identified in this work will provide a better understanding of the signaling pathways that are important for caspofungin tolerance and resistance.

scholarly journals The Als3 Cell Wall Adhesin Plays a Critical Role in Human Serum Amyloid A1-Induced Cell Death and Aggregation in Candida albicans

2020 ◽  
Vol 64 (6) ◽  
Author(s):  
Jiao Gong ◽  
Jian Bing ◽  
Guobo Guan ◽  
Clarissa J. Nobile ◽  
Guanghua Huang
Keyword(s):  
Cell Death ◽  
Cell Wall ◽  
Candida Albicans ◽  
Critical Role ◽  
Membrane Integrity ◽  
Cell Aggregation ◽  
Serum Amyloid ◽  
Mouse Serum ◽  
Content Type ◽  
Serum Amyloid A1

ABSTRACT Antimicrobial peptides and proteins play critical roles in the host defense against invading pathogens. We recently discovered that recombinantly expressed human and mouse serum amyloid A1 (rhSAA1 and rmSAA1, respectively) proteins have potent antifungal activities against the major human fungal pathogen Candida albicans. At high concentrations, rhSAA1 disrupts C. albicans membrane integrity and induces rapid fungal cell death. In the present study, we find that rhSAA1 promotes cell aggregation and targets the C. albicans cell wall adhesin Als3. Inactivation of ALS3 in C. albicans leads to a striking decrease in cell aggregation and cell death upon rhSAA1 treatment, suggesting that Als3 plays a critical role in SAA1 sensing. We further demonstrate that deletion of the transcriptional regulators controlling the expression of ALS3, such as AHR1, BCR1, and EFG1, in C. albicans results in similar effects to that of the als3/als3 mutant upon rhSAA1 treatment. Global gene expression profiling indicates that rhSAA1 has a discernible impact on the expression of cell wall- and metabolism-related genes, suggesting that rhSAA1 treatment could lead to a nutrient starvation effect on C. albicans cells.

scholarly journals Aggregate Filamentous Growth Responses in Yeast

mSphere ◽  
2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Jacky Chow ◽  
Heather M. Dionne ◽  
Aditi Prabhakar ◽  
Amit Mehrotra ◽  
Jenn Somboonthum ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Candida Albicans ◽  
Signaling Pathways ◽  
Budding Yeast ◽  
Filamentous Growth ◽  
Fungal Species ◽  
Fungal Pathogenesis ◽  
Invasive Growth ◽  
Content Type ◽  
Secreted Enzymes

ABSTRACTMany fungal species, including pathogens, undergo a morphogenetic response called filamentous growth, where cells differentiate into a specialized cell type to promote nutrient foraging and surface colonization. Despite the fact that filamentous growth is required for virulence in some plant and animal pathogens, certain aspects of this behavior remain poorly understood. By examining filamentous growth in the budding yeastSaccharomyces cerevisiaeand the opportunistic pathogenCandida albicans, we identify responses where cells undergo filamentous growth in groups of cells or aggregates. InS. cerevisiae, aggregate invasive growth was regulated by signaling pathways that control normal filamentous growth. These pathways promoted aggregation in part by fostering aspects of microbial cooperation. For example, aggregate invasive growth required cellular contacts mediated by the flocculin Flo11p, which was produced at higher levels in aggregates than cells undergoing regular invasive growth. Aggregate invasive growth was also stimulated by secreted enzymes, like invertase, which produce metabolites that are shared among cells. Aggregate invasive growth was also induced by alcohols that promote density-dependent filamentous growth in yeast. Aggregate invasive growth also required highly polarized cell morphologies, which may affect the packing or organization of cells. A directed selection experiment for aggregating phenotypes uncovered roles for the fMAPK and RAS pathways, which indicates that these pathways play a general role in regulating aggregate-based responses in yeast. Our study extends the range of responses controlled by filamentation regulatory pathways and has implications in understanding aspects of fungal biology that may be relevant to fungal pathogenesis.IMPORTANCEFilamentous growth is a fungal morphogenetic response that is critical for virulence in some fungal species. Many aspects of filamentous growth remain poorly understood. We have identified an aspect of filamentous growth in the budding yeastSaccharomyces cerevisiaeand the human pathogenCandida albicanswhere cells behave collectively to invade surfaces in aggregates. These responses may reflect an extension of normal filamentous growth, as they share the same signaling pathways and effector processes. Aggregate responses may involve cooperation among individual cells, because aggregation was stimulated by cell adhesion molecules, secreted enzymes, and diffusible molecules that promote quorum sensing. Our study may provide insights into the genetic basis of collective cellular responses in fungi. The study may have ramifications in fungal pathogenesis, in situations where collective responses occur to promote virulence.

scholarly journals Cell Wall Remodeling Enzymes Modulate Fungal Cell Wall Elasticity and Osmotic Stress Resistance

mBio ◽  
2015 ◽  
Vol 6 (4) ◽  
Author(s):  
Iuliana V. Ene ◽  
Louise A. Walker ◽  
Marion Schiavone ◽  
Keunsook K. Lee ◽  
Hélène Martin-Yken ◽  
...  
Keyword(s):  
Gene Expression ◽  
Tensile Strength ◽  
Cell Wall ◽  
Stress Resistance ◽  
Osmotic Shock ◽  
Fungal Cell ◽  
Content Type ◽  
Hyperosmotic Shock ◽  
Cell Wall Elasticity ◽  
Cell Wall Remodeling

ABSTRACTThe fungal cell wall confers cell morphology and protection against environmental insults. For fungal pathogens, the cell wall is a key immunological modulator and an ideal therapeutic target. Yeast cell walls possess an inner matrix of interlinked β-glucan and chitin that is thought to provide tensile strength and rigidity. Yeast cells remodel their walls over time in response to environmental change, a process controlled by evolutionarily conserved stress (Hog1) and cell integrity (Mkc1, Cek1) signaling pathways. These mitogen-activated protein kinase (MAPK) pathways modulate cell wall gene expression, leading to the construction of a new, modified cell wall. We show that the cell wall is not rigid but elastic, displaying rapid structural realignments that impact survival following osmotic shock. Lactate-grownCandida albicanscells are more resistant to hyperosmotic shock than glucose-grown cells. We show that this elevated resistance is not dependent on Hog1 or Mkc1 signaling and that most cell death occurs within 10 min of osmotic shock. Sudden decreases in cell volume drive rapid increases in cell wall thickness. The elevated stress resistance of lactate-grown cells correlates with reduced cell wall elasticity, reflected in slower changes in cell volume following hyperosmotic shock. The cell wall elasticity of lactate-grown cells is increased by a triple mutation that inactivates the Crh family of cell wall cross-linking enzymes, leading to increased sensitivity to hyperosmotic shock. Overexpressing Crh family members in glucose-grown cells reduces cell wall elasticity, providing partial protection against hyperosmotic shock. These changes correlate with structural realignment of the cell wall and with the ability of cells to withstand osmotic shock.IMPORTANCETheC. albicanscell wall is the first line of defense against external insults, the site of immune recognition by the host, and an attractive target for antifungal therapy. Its tensile strength is conferred by a network of cell wall polysaccharides, which are remodeled in response to growth conditions and environmental stress. However, little is known about how cell wall elasticity is regulated and how it affects adaptation to stresses such as sudden changes in osmolarity. We show that elasticity is critical for survival under conditions of osmotic shock, before stress signaling pathways have time to induce gene expression and drive glycerol accumulation. Critical cell wall remodeling enzymes control cell wall flexibility, and its regulation is strongly dependent on host nutritional inputs. We also demonstrate an entirely new level of cell wall dynamism, where significant architectural changes and structural realignment occur within seconds of an osmotic shock.

scholarly journals Micafungin Enhances the Human Macrophage Response to Candida albicans through β-Glucan Exposure

2018 ◽  
Vol 62 (5) ◽  
Author(s):  
José Pedro Guirao-Abad ◽  
Ruth Sánchez-Fresneda ◽  
Francisco Machado ◽  
Juan Carlos Argüelles ◽  
María Martínez-Esparza
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Human Tissue ◽  
Pathogenic Fungus ◽  
Human Macrophage ◽  
Fungal Cell ◽  
Necrosis Factor Alpha ◽  
Content Type ◽  
Macrophage Response ◽  
Blowing Up

ABSTRACT Micafungin belongs to the antifungal family of echinocandins, which act as noncompetitive inhibitors of the fungal cell wall β-1,3- d -glucan synthase. Since Candida albicans is the most prevalent pathogenic fungus in humans, we study the involvement of micafungin in the modulation of the inflammatory response developed by human tissue macrophages against C. albicans . The MIC for micafungin was 0.016 μg/ml on the C. albicans SC5314 standard strain. Micafungin induced a drastic reduction in the number of exponential SC5314 viable cells, with the fungicidal effect being dependent on the cellular metabolic activity. Notably, micafungin also caused a structural remodelling of the cell wall, leading to exposure of the β-glucan and chitin content on the external surface. At the higher doses used (0.05 μg/ml), the antifungal also induced the blowing up of budding yeasts. In addition, preincubation with micafungin before exposure to human tissue macrophages enhanced the secretion of tumor necrosis factor alpha (TNF-α), interleukin-17A (IL-17A), and IL-10 cytokines. Our results strongly suggest that in C. albicans treatment with micafungin, in addition to having the expected toxic antifungal effect, it potentiates the immune response, improving the interaction and activation of human macrophages, probably through the unmasking of β-glucans on the cell wall surface.

scholarly journals The MARVEL Domain Protein Nce102 Regulates Actin Organization and Invasive Growth of Candida albicans

mBio ◽  
2013 ◽  
Vol 4 (6) ◽  
Author(s):  
Lois M. Douglas ◽  
Hong X. Wang ◽  
James B. Konopka
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Plasma Membrane ◽  
Virulence Factors ◽  
Fungal Pathogen ◽  
Invasive Growth ◽  
Cell Wall Synthesis ◽  
Content Type ◽  
Actin Organization ◽  
Domain Protein

ABSTRACTInvasive growth of the fungal pathogenCandida albicansinto tissues promotes disseminated infections in humans. The plasma membrane is essential for pathogenesis because this important barrier mediates morphogenesis and invasive growth, as well as secretion of virulence factors, cell wall synthesis, nutrient import, and other processes. Previous studies showed that the Sur7 tetraspan protein that localizes to MCC (membrane compartment occupied by Can1)/eisosome subdomains of the plasma membrane regulates a broad range of key functions, including cell wall synthesis, morphogenesis, and resistance to copper. Therefore, a distinct tetraspan protein found in MCC/eisosomes, Nce102, was investigated. Nce102 belongs to the MARVEL domain protein family, which is implicated in regulating membrane structure and function. Deletion ofNCE102did not cause the broad defects seen insur7Δcells. Instead, thence102Δmutant displayed a unique phenotype in that it was defective in forming hyphae and invading low concentrations of agar but could invade well in higher agar concentrations. This phenotype was likely due to a defect in actin organization that was observed by phalloidin staining. In support of this, the invasive growth defect of abni1Δmutant that mislocalizes actin due to lack of the Bni1 formin was also reversed at high agar concentrations. This suggests that a denser matrix provides a signal that compensates for the actin defects. Thence102Δmutant displayed decreased virulence and formed abnormal hyphae in mice. These studies identify novel ways that Nce102 and the physical environment surroundingC. albicansregulate morphogenesis and pathogenesis.IMPORTANCEThe plasma membrane promotes virulence of the human fungal pathogenCandida albicansby acting as a protective barrier around the cell and mediating dynamic activities, such as morphogenesis, cell wall synthesis, secretion of virulence factors, and nutrient uptake. To better understand how the plasma membrane contributes to virulence, we analyzed a set of eight genes encoding MARVEL family proteins that are predicted to function in membrane organization. Interestingly, deletion of one gene,NCE102, caused a strong defect in formation of invasive hyphal growthin vitroand decreased virulence in mice. Thence102Δmutant cells showed defects in actin organization that underlie the morphogenesis defect, since mutation of a known regulator of actin organization caused a similar defect. These studies identify a novel way in which the plasma membrane regulates the actin cytoskeleton and contributes to pathogenesis.

scholarly journals Inhibition of Classical and Alternative Modes of Respiration in Candida albicans Leads to Cell Wall Remodeling and Increased Macrophage Recognition

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. e02535-18 ◽  
Author(s):  
Lucian Duvenage ◽  
Louise A. Walker ◽  
Aleksandra Bojarczuk ◽  
Simon A. Johnston ◽  
Donna M. MacCallum ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Electron Transport ◽  
Fungal Pathogen ◽  
Fungal Infections ◽  
Nitric Oxide Donor ◽  
Mammalian Host ◽  
Content Type ◽  
Human Fungal Pathogen ◽  
Cell Wall Remodeling

ABSTRACT The human fungal pathogen Candida albicans requires respiratory function for normal growth, morphogenesis, and virulence. Mitochondria therefore represent an enticing target for the development of new antifungal strategies. This possibility is bolstered by the presence of characteristics specific to fungi. However, respiration in C. albicans, as in many fungal organisms, is facilitated by redundant electron transport mechanisms, making direct inhibition a challenge. In addition, many chemicals known to target the electron transport chain are highly toxic. Here we made use of chemicals with low toxicity to efficiently inhibit respiration in C. albicans. We found that use of the nitric oxide donor sodium nitroprusside (SNP) and of the alternative oxidase inhibitor salicylhydroxamic acid (SHAM) prevents respiration and leads to a loss of viability and to cell wall rearrangements that increase the rate of uptake by macrophages in vitro and in vivo. We propose that treatment with SNP plus SHAM (SNP+SHAM) leads to transcriptional changes that drive cell wall rearrangement but which also prime cells to activate the transition to hyphal growth. In line with this, we found that pretreatment of C. albicans with SNP+SHAM led to an increase in virulence. Our data reveal strong links between respiration, cell wall remodeling, and activation of virulence factors. Our findings demonstrate that respiration in C. albicans can be efficiently inhibited with chemicals that are not damaging to the mammalian host but that we need to develop a deeper understanding of the roles of mitochondria in cellular signaling if they are to be developed successfully as a target for new antifungals. IMPORTANCE Current approaches to tackling fungal infections are limited, and new targets must be identified to protect against the emergence of resistant strains. We investigated the potential of targeting mitochondria, which are organelles required for energy production, growth, and virulence, in the human fungal pathogen Candida albicans. Our findings suggest that mitochondria can be targeted using drugs that can be tolerated by humans and that this treatment enhances their recognition by immune cells. However, release of C. albicans cells from respiratory inhibition appears to activate a stress response that increases the levels of traits associated with virulence. Our results make it clear that mitochondria represent a valid target for the development of antifungal strategies but that we must determine the mechanisms by which they regulate stress signaling and virulence ahead of successful therapeutic advance.

scholarly journals Proteolytic Cleavage of Covalently Linked Cell Wall Proteins by Candida albicans Sap9 and Sap10

2010 ◽  
Vol 10 (1) ◽  
pp. 98-109 ◽  
Author(s):  
Lydia Schild ◽  
Antje Heyken ◽  
Piet W. J. de Groot ◽  
Ekkehard Hiller ◽  
Marlen Mock ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Cell Surface ◽  
Pathogenic Fungus ◽  
Proteolytic Cleavage ◽  
Cell Wall Proteins ◽  
Ph Optimum ◽  
Fungal Cell ◽  
Content Type ◽  
Covalently Linked

ABSTRACT The cell wall of the human-pathogenic fungus Candida albicans is a robust but also dynamic structure which mediates adaptation to changing environmental conditions during infection. Sap9 and Sap10 are cell surface-associated proteases which function in C. albicans cell wall integrity and interaction with human epithelial cells and neutrophils. In this study, we have analyzed the enzymatic properties of Sap9 and Sap10 and investigated whether these proteases cleave proteins on the fungal cell surface. We show that Sap9 and Sap10, in contrast to other aspartic proteases, exhibit a near-neutral pH optimum of proteolytic activity and prefer the processing of peptides containing basic or dibasic residues. However, both proteases also cleaved at nonbasic sites, and not all tested peptides with dibasic residues were processed. By digesting isolated cell walls with Sap9 or Sap10, we identified the covalently linked cell wall proteins (CWPs) Cht2, Ywp1, Als2, Rhd3, Rbt5, Ecm33, and Pga4 as in vitro protease substrates. Proteolytic cleavage of the chitinase Cht2 and the glucan-cross-linking protein Pir1 by Sap9 was verified using hemagglutinin (HA) epitope-tagged versions of both proteins. Deletion of the SAP9 and SAP10 genes resulted in a reduction of cell-associated chitinase activity similar to that upon deletion of CHT2 , suggesting a direct influence of Sap9 and Sap10 on Cht2 function. In contrast, cell surface changes elicited by SAP9 and SAP10 deletion had no major impact on the phagocytosis and killing of C. albicans by human macrophages. We propose that Sap9 and Sap10 influence distinct cell wall functions by proteolytic cleavage of covalently linked cell wall proteins.

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