N
            -Acetylglucosamine (GlcNAc)-Inducible Gene
            GIG2
            Is a Novel Component of GlcNAc Metabolism in Candida albicans

ABSTRACT Candida albicans is an opportunistic fungal pathogen that resides in the human body as a commensal and can turn pathogenic when the host is immunocompromised. Adaptation of C. albicans to host niche-specific conditions is important for the establishment of pathogenicity, where the ability of C. albicans to utilize multiple carbon sources provides additional flexibility. One alternative sugar is N -acetylglucosamine (GlcNAc), which is now established as an important carbon source for many pathogens and can also act as a signaling molecule. Although GlcNAc catabolism has been well studied in many pathogens, the importance of several enzymes involved in the formation of metabolic intermediates still remains elusive. In this context, microarray analysis was carried out to investigate the transcriptional responses induced by GlcNAc under different conditions. A novel gene that was highly upregulated immediately following the GlcNAc catabolic genes was identified and was named GIG2 (GlcNAc-induced gene 2). This gene is regulated in a manner distinct from that of the GlcNAc-induced genes described previously in that GlcNAc metabolism is essential for its induction. Furthermore, this gene is involved in the metabolism of N -acetylneuraminate (sialic acid), a molecule equally important for initial host-pathogen recognition. Mutant cells showed a considerable decrease in fungal burden in mouse kidneys and were hypersensitive to oxidative stress conditions. Since GIG2 is also present in many other fungal and enterobacterial genomes, targeted inhibition of its activity would offer insight into the treatment of candidiasis and other fungal or enterobacterial infections.

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Normal Adaptation of Candida albicans to the Murine Gastrointestinal Tract Requires Efg1p-Dependent Regulation of Metabolic and Host Defense Genes

Eukaryotic Cell ◽

10.1128/ec.00236-12 ◽

2012 ◽

Vol 12 (1) ◽

pp. 37-49 ◽

Cited By ~ 56

Author(s):

Jessica V. Pierce ◽

Daniel Dignard ◽

Malcolm Whiteway ◽

Carol A. Kumamoto

Keyword(s):

Gene Expression ◽

Candida Albicans ◽

Ectopic Expression ◽

Dependent Manner ◽

Null Mutant ◽

Gi Tract ◽

Transcriptional Responses ◽

Content Type ◽

Opportunistic Fungal Pathogen ◽

Mutant Cells

ABSTRACTAlthough gastrointestinal colonization by the opportunistic fungal pathogenCandida albicansis generally benign, severe systemic infections are thought to arise due to escape of commensalC. albicansfrom the gastrointestinal (GI) tract. TheC. albicanstranscription factor Efg1p is a major regulator of GI colonization, hyphal morphogenesis, and virulence. The goals of this study were to identify the Efg1p regulon during GI tract colonization and to compareC. albicansgene expression during colonization of different organs of the GI tract. Our results identified significant differences in gene expression between cells colonizing the cecum and ileum. During colonization,efg1−null mutant cells expressed higher levels of genes involved in lipid catabolism, carnitine biosynthesis, and carnitine utilization than did colonizing wild-type (WT) cells. In addition, during laboratory growth,efg1−null mutant cells grew to a higher density than WT cells. Theefg1−null mutant grew in depleted medium, while WT cells could grow only if the depleted medium was supplemented with carnitine, a compound that promotes the metabolism of fatty acids. Altered gene expression and altered growth capability support the ability ofefg1−cells to hypercolonize naïve mice. Also, Efg1p was shown to be important for transcriptional responses to the stresses present in the cecum environment. For example, during colonization,SOD5, encoding a superoxide dismutase, was highly upregulated in an Efg1p-dependent manner. Ectopic expression ofSOD5in anefg1−null mutant increased the fitness of theefg1−null mutant cells during colonization. These data show thatEFG1is an important regulator of GI colonization.

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Control of Candida albicans Metabolism and Biofilm Formation by Pseudomonas aeruginosa Phenazines

mBio ◽

10.1128/mbio.00526-12 ◽

2013 ◽

Vol 4 (1) ◽

Cited By ~ 128

Author(s):

Diana K. Morales ◽

Nora Grahl ◽

Chinweike Okegbe ◽

Lars E. P. Dietrich ◽

Nicholas J. Jacobs ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Candida Albicans ◽

Biofilm Formation ◽

Carbon Sources ◽

Metabolic Effects ◽

Respiratory Metabolism ◽

Fermentation Products ◽

Content Type ◽

Opportunistic Fungal Pathogen ◽

Biofilm Development

ABSTRACTCandida albicanshas developmental programs that govern transitions between yeast and filamentous morphologies and between unattached and biofilm lifestyles. Here, we report that filamentation, intercellular adherence, and biofilm development were inhibited during interactions betweenCandida albicansandPseudomonas aeruginosathrough the action ofP. aeruginosa-produced phenazines. While phenazines are toxic toC. albicansat millimolar concentrations, we found that lower concentrations of any of three different phenazines (pyocyanin, phenazine methosulfate, and phenazine-1-carboxylate) allowed growth but affected the development ofC. albicanswrinkled colony biofilms and inhibited the fungal yeast-to-filament transition. Phenazines impairedC. albicansgrowth on nonfermentable carbon sources and led to increased production of fermentation products (ethanol, glycerol, and acetate) in glucose-containing medium, leading us to propose that phenazines specifically inhibited respiration. Methylene blue, another inhibitor of respiration, also prevented the formation of structured colony biofilms. The inhibition of filamentation and colony wrinkling was not solely due to lowered extracellular pH induced by fermentation. Compared to smooth, unstructured colonies, wrinkled colony biofilms had higher oxygen concentrations within the colony, and wrinkled regions of these colonies had higher levels of respiration. Together, our data suggest that the structure of the fungal biofilm promotes access to oxygen and enhances respiratory metabolism and that the perturbation of respiration by bacterial molecules such as phenazines or compounds with similar activities disrupts these pathways. These findings may suggest new ways to limit fungal biofilms in the context of disease.IMPORTANCEMany of the infections caused byCandida albicans, a major human opportunistic fungal pathogen, involve both morphological transitions and the formation of surface-associated biofilms. Through the study ofC. albicansinteractions with the bacteriumPseudomonas aeruginosa, which often coinfects withC. albicans, we have found thatP. aeruginosa-produced phenazines modulateC. albicansmetabolism and, through these metabolic effects, impact cellular morphology, cell-cell interactions, and biofilm formation. We suggest that the structure ofC. albicansbiofilms promotes access to oxygen and enhances respiratory metabolism and that the perturbation of respiration by phenazines inhibits biofilm development. Our findings not only provide insight into interactions between these species but also provide valuable insights into novel pathways that could lead to the development of new therapies to treatC. albicansinfections.

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Aspergillus fumigatus Acetate Utilization Impacts Virulence Traits and Pathogenicity

mBio ◽

10.1128/mbio.01682-21 ◽

2021 ◽

Author(s):

Laure Nicolas Annick Ries ◽

Patricia Alves de Castro ◽

Lilian Pereira Silva ◽

Clara Valero ◽

Thaila Fernanda dos Reis ◽

...

Keyword(s):

Aspergillus Fumigatus ◽

Fungal Pathogen ◽

Carbon Sources ◽

Body Fluids ◽

Peripheral Tissues ◽

Content Type ◽

Virulence Traits ◽

Acetate Utilization ◽

Opportunistic Fungal Pathogen

Aspergillus fumigatus is an opportunistic fungal pathogen in humans. During infection, A. fumigatus is predicted to use host carbon sources, such as acetate, present in body fluids and peripheral tissues, to sustain growth and promote colonization and invasion.

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High-Throughput Nano-Biofilm Microarray for Antifungal Drug Discovery

mBio ◽

10.1128/mbio.00331-13 ◽

2013 ◽

Vol 4 (4) ◽

Cited By ~ 29

Author(s):

Anand Srinivasan ◽

Kai P. Leung ◽

Jose L. Lopez-Ribot ◽

Anand K. Ramasubramanian

Keyword(s):

Cell Culture ◽

Candida Albicans ◽

Drug Discovery ◽

High Throughput ◽

Fungal Pathogen ◽

Microarray Platform ◽

Microbial Cell ◽

Content Type ◽

Petri Dishes ◽

Opportunistic Fungal Pathogen

ABSTRACT Micro- and nanoscale technologies have radically transformed biological research from genomics to tissue engineering, with the relative exception of microbial cell culture, which is still largely performed in microtiter plates and petri dishes. Here, we present nanoscale culture of the opportunistic fungal pathogen Candida albicans on a microarray platform. The microarray consists of 1,200 individual cultures of 30 nl of C. albicans biofilms (“nano-biofilms”) encapsulated in an inert alginate matrix. We demonstrate that these nano-biofilms are similar to conventional macroscopic biofilms in their morphological, architectural, growth, and phenotypic characteristics. We also demonstrate that the nano-biofilm microarray is a robust and efficient tool for accelerating the drug discovery process: (i) combinatorial screening against a collection of 28 antifungal compounds in the presence of immunosuppressant FK506 (tacrolimus) identified six drugs that showed synergistic antifungal activity, and (ii) screening against the NCI challenge set small-molecule library identified three heretofore-unknown hits. This cell-based microarray platform allows for miniaturization of microbial cell culture and is fully compatible with other high-throughput screening technologies. IMPORTANCE Microorganisms are typically still grown in petri dishes, test tubes, and Erlenmeyer flasks in spite of the latest advances in miniaturization that have benefitted other allied research fields, including genomics and proteomics. Culturing microorganisms in small scale can be particularly valuable in cutting down time, cost, and reagent usage. This paper describes the development, characterization, and application of nanoscale culture of an opportunistic fungal pathogen, Candida albicans. Despite a more than 2,000-fold reduction in volume, the growth characteristics and drug response profiles obtained from the nanoscale cultures were comparable to the industry standards. The platform also enabled rapid identification of new drug candidates that were effective against C. albicans biofilms, which are a major cause of mortality in hospital-acquired infections.

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Distinct and Redundant Roles of the Two MYST Histone Acetyltransferases Esa1 and Sas2 in Cell Growth and Morphogenesis of Candida albicans

Eukaryotic Cell ◽

10.1128/ec.00275-12 ◽

2013 ◽

Vol 12 (3) ◽

pp. 438-449 ◽

Cited By ~ 20

Author(s):

Xiongjun Wang ◽

Peng Chang ◽

Jianping Ding ◽

Jiangye Chen

Keyword(s):

Candida Albicans ◽

Cell Growth ◽

Histone Acetylation ◽

Synergistic Effects ◽

Histone Acetyltransferases ◽

Content Type ◽

Functional Roles ◽

Oxidative Stresses ◽

Human Body Temperature ◽

Mutant Cells

ABSTRACTCandida albicansis associated with humans, as both a harmless commensal organism and a pathogen. Adaption to human body temperature is extremely important for its growth and morphogenesis.Saccharomyces cerevisiaeEsa1, a member of the MYST family HATs (histone acetyltransferases) and the catalytic subunit of the NuA4 complex, and its homologues in other eukaryotes have been shown to be essential for cell growth. To investigate the functional roles of two MYST family HATs, Esa1 and Sas2 inC. albicans, we deletedESA1andSAS2in theC. albicansgenome and performed cell growth analyses. Our results demonstrated thatC. albicansEsa1 is not essential for general growth but is essential for filamentous growth. Theesa1/esa1mutant cells exhibited sensitivity to thermal, genotoxic, and oxidative stresses but tolerance to cold, osmotic, and cell wall stresses. In contrast, thesas2/sas2mutant adapted to growth at higher temperatures and promoted filament formation at lower temperatures, resembling the phenotype of aC. albicansstrain overexpressingESA1. Cells with deletions of bothESA1andSAS2were inviable, reflecting the functional redundancy in cell growth.C. albicansEsa1 and Sas2 have distinct and synergistic effects on histone acetylation at H4K5, H4K12, and H4K16. Esa1 contributes mainly to acetylation of H4K5 and H4K12, whereas Sas2 contributes to acetylation of H4K16. Our findings suggest thatC. albicansEsa1 and Sas2 play opposite roles in cell growth and morphogenesis and contribute coordinately to histone acetylation and gene regulation.

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Role of Calprotectin in Withholding Zinc and Copper from Candida albicans

Infection and Immunity ◽

10.1128/iai.00779-17 ◽

2017 ◽

Vol 86 (2) ◽

Cited By ~ 36

Author(s):

Angelique N. Besold ◽

Benjamin A. Gilston ◽

Jana N. Radin ◽

Christian Ramsoomair ◽

Edward M. Culbertson ◽

...

Keyword(s):

Candida Albicans ◽

Stress Responses ◽

Metal Binding ◽

Content Type ◽

Nutritional Immunity ◽

Numerous Cell ◽

Transcriptional Changes ◽

Opportunistic Fungal Pathogen ◽

First Time

ABSTRACT The opportunistic fungal pathogen Candida albicans acquires essential metals from the host, yet the host can sequester these micronutrients through a process known as nutritional immunity. How the host withholds metals from C. albicans has been poorly understood; here we examine the role of calprotectin (CP), a transition metal binding protein. When CP depletes bioavailable Zn from the extracellular environment, C. albicans strongly upregulates ZRT1 and PRA1 for Zn import and maintains constant intracellular Zn through numerous cell divisions. We show for the first time that CP can also sequester Cu by binding Cu(II) with subpicomolar affinity. CP blocks fungal acquisition of Cu from serum and induces a Cu starvation stress response involving SOD1 and SOD3 superoxide dismutases. These transcriptional changes are mirrored when C. albicans invades kidneys in a mouse model of disseminated candidiasis, although the responses to Cu and Zn limitations are temporally distinct. The Cu response progresses throughout 72 h, while the Zn response is short-lived. Notably, these stress responses were attenuated in CP null mice, but only at initial stages of infection. Thus, Zn and Cu pools are dynamic at the host-pathogen interface and CP acts early in infection to restrict metal nutrients from C. albicans.

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Ascorbic Acid Inhibition of Candida albicans Hsp90-Mediated Morphogenesis Occurs via the Transcriptional Regulator Upc2

Eukaryotic Cell ◽

10.1128/ec.00096-14 ◽

2014 ◽

Vol 13 (10) ◽

pp. 1278-1289 ◽

Cited By ~ 6

Author(s):

Frédérique Van Hauwenhuyse ◽

Alessandro Fiori ◽

Patrick Van Dijck

Keyword(s):

Ascorbic Acid ◽

Candida Albicans ◽

Fungal Pathogen ◽

Transcriptional Regulator ◽

Hsp90 Inhibitor ◽

Ergosterol Biosynthesis ◽

Content Type ◽

Temperature Changes ◽

Opportunistic Fungal Pathogen ◽

Hsp90 Function

ABSTRACTMorphogenetic transitions of the opportunistic fungal pathogenCandida albicansare influenced by temperature changes, with induction of filamentation upon a shift from 30 to 37°C. Hsp90 was identified as a major repressor of an elongated cell morphology at low temperatures, as treatment with specific inhibitors of Hsp90 results in elongated growth forms at 30°C. Elongated growth resulting from a compromised Hsp90 is considered neither hyphal nor pseudohyphal growth. It has been reported that ascorbic acid (vitamin C) interferes with the yeast-to-hypha transition inC. albicans. In the present study, we show that ascorbic acid also antagonizes the morphogenetic change caused by hampered Hsp90 function. Further analysis revealed that Upc2, a transcriptional regulator of genes involved in ergosterol biosynthesis, and Erg11, the target of azole antifungals, whose expression is in turn regulated by Upc2, are required for this antagonism. Ergosterol levels correlate with elongated growth and are reduced in cells treated with the Hsp90 inhibitor geldanamycin (GdA) and restored by cotreatment with ascorbic acid. In addition, we show that Upc2 appears to be required for ascorbic acid-mediated inhibition of the antifungal activity of fluconazole. These results identify Upc2 as a major regulator of ascorbic acid-induced effects inC. albicansand suggest an association between ergosterol content and elongated growth upon Hsp90 compromise.

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The Evolutionary Rewiring of Ubiquitination Targets Has Reprogrammed the Regulation of Carbon Assimilation in the Pathogenic Yeast Candida albicans

mBio ◽

10.1128/mbio.00495-12 ◽

2012 ◽

Vol 3 (6) ◽

Cited By ~ 54

Author(s):

Doblin Sandai ◽

Zhikang Yin ◽

Laura Selway ◽

David Stead ◽

Janet Walker ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Fatty Acids ◽

Candida Albicans ◽

Isocitrate Lyase ◽

Carbon Sources ◽

Carbon Assimilation ◽

Pathogenic Yeast ◽

Content Type ◽

Catabolite Inactivation ◽

Accelerated Degradation

ABSTRACTMicrobes must assimilate carbon to grow and colonize their niches. Transcript profiling has suggested thatCandida albicans, a major pathogen of humans, regulates its carbon assimilation in an analogous fashion to the model yeastSaccharomyces cerevisiae, repressing metabolic pathways required for the use of alterative nonpreferred carbon sources when sugars are available. However, we show that there is significant dislocation between the proteome and transcriptome inC. albicans. Glucose triggers the degradation of theICL1andPCK1transcripts inC. albicans, yet isocitrate lyase (Icl1) and phosphoenolpyruvate carboxykinase (Pck1) are stable and are retained. Indeed, numerous enzymes required for the assimilation of carboxylic and fatty acids are not degraded in response to glucose. However, when expressed inC. albicans,S. cerevisiaeIcl1 (ScIcl1) is subjected to glucose-accelerated degradation, indicating that likeS. cerevisiae, this pathogen has the molecular apparatus required to execute ubiquitin-dependent catabolite inactivation.C. albicansIcl1 (CaIcl1) lacks analogous ubiquitination sites and is stable under these conditions, but the addition of a ubiquitination site programs glucose-accelerated degradation of CaIcl1. Also, catabolite inactivation is slowed inC. albicans ubi4cells. Ubiquitination sites are present in gluconeogenic and glyoxylate cycle enzymes fromS. cerevisiaebut absent from theirC. albicanshomologues. We conclude that evolutionary rewiring of ubiquitination targets has meant that following glucose exposure,C. albicansretains key metabolic functions, allowing it to continue to assimilate alternative carbon sources. This metabolic flexibility may be critical during infection, facilitating the rapid colonization of dynamic host niches containing complex arrays of nutrients.IMPORTANCEPathogenic microbes must assimilate a range of carbon sources to grow and colonize their hosts. Current views about carbon assimilation in the pathogenic yeastCandida albicansare strongly influenced by theSaccharomyces cerevisiaeparadigm in which cells faced with choices of nutrients first use energetically favorable sugars, degrading enzymes required for the assimilation of less favorable alternative carbon sources. We show that this is not the case inC. albicansbecause there has been significant evolutionary rewiring of the molecular signals that promote enzyme degradation in response to glucose. As a result, this major pathogen of humans retains enzymes required for the utilization of physiologically relevant carbon sources such as lactic acid and fatty acids, allowing it to continue to use these host nutrients even when glucose is available. This phenomenon probably enhances efficient colonization of host niches where sugars are only transiently available.

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A Suppressor Mutation in the β-Subunit Kis1 Restores Functionality of the SNF1 Complex in Candida albicans snf4 Δ Mutants

mSphere ◽

10.1128/msphere.00929-21 ◽

2021 ◽

Author(s):

Bernardo Ramírez-Zavala ◽

Austin Mottola ◽

Ines Krüger ◽

Joachim Morschhäuser

Keyword(s):

Candida Albicans ◽

Protein Kinase ◽

Carbon Sources ◽

Metabolic Adaptation ◽

Β Subunit ◽

Wild Type ◽

Pathogenic Yeast ◽

Α Subunit ◽

Content Type ◽

Repressor Proteins

The highly conserved protein kinase SNF1 plays a key role in the metabolic adaptation of the pathogenic yeast Candida albicans , but it is not clear how it regulates its downstream targets in this fungus. We show that the repressor proteins Mig1 and Mig2 are phosphorylated also in cells lacking the catalytic α-subunit Snf1 of the SNF1 complex, but the amounts of both proteins were reduced in wild-type cells when glucose was replaced by alternative carbon sources, pointing to an indirect mechanism of regulation.

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Multiple Alternative Carbon Pathways Combine To Promote Candida albicans Stress Resistance, Immune Interactions, and Virulence

mBio ◽

10.1128/mbio.03070-19 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 10

Author(s):

Robert B. Williams ◽

Michael C. Lorenz

Keyword(s):

Amino Acids ◽

Cell Wall ◽

Candida Albicans ◽

Stress Resistance ◽

Innate Immune System ◽

Carbon Sources ◽

Innate Immune ◽

Content Type ◽

Multiple Alternative ◽

Carbon Pathways

ABSTRACT The phagocytic cells of the innate immune system are an essential first line of antimicrobial defense, and yet Candida albicans, one of the most problematic fungal pathogens, is capable of resisting the stresses imposed by the macrophage phagosome, eventually resulting in the destruction of the phagocyte. C. albicans rapidly adapts to the phagosome by upregulating multiple alternative carbon utilization pathways, particularly those for amino acids, carboxylic acids, and N-acetylglucosamine (GlcNAc). Here, we report that C. albicans recognizes these carbon sources both as crucial nutrients and as independent signals in its environment. Even in the presence of glucose, each carbon source promotes increased resistance to a unique profile of stressors; lactate promotes increased resistance to osmotic and cell wall stresses, amino acids increased resistance to oxidative and nitrosative stresses, and GlcNAc increased resistance to oxidative stress and caspofungin, while all three alternative carbon sources have been shown to induce resistance to fluconazole. Moreover, we show mutants incapable of utilizing these carbon sources, in particular, strains engineered to be defective in all three pathways, are significantly attenuated in both macrophage and mouse models, with additive effects observed as multiple carbon pathways are eliminated, suggesting that C. albicans simultaneously utilizes multiple carbon sources within the macrophage phagosome and during disseminated candidiasis. Taking the data together, we propose that, in addition to providing energy to the pathogen within host environments, alternative carbon sources serve as niche-specific priming signals that allow C. albicans to recognize microenvironments within the host and to prepare for stresses associated with that niche, thus promoting host adaptation and virulence. IMPORTANCE Candida albicans is a fungal pathogen and a significant cause of morbidity and mortality, particularly in people with defects, sometimes minor ones, in innate immunity. The phagocytes of the innate immune system, particularly macrophages and neutrophils, generally restrict this organism to its normal commensal niches, but C. albicans shows a robust and multifaceted response to these cell types. Inside macrophages, a key component of this response is the activation of multiple pathways for the utilization of alternative carbon sources, particularly amino acids, carboxylic acids, and N-acetylglucosamine. These carbon sources are key sources of energy and biomass but also independently promote stress resistance, induce cell wall alterations, and affect C. albicans interactions with macrophages. Engineered strains incapable of utilizing these alternative carbon pathways are attenuated in infection models. These data suggest that C. albicans recognizes nutrient composition as an indicator of specific host environments and tailors its responses accordingly.

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