Depletion of the Squalene Synthase (
            <i>ERG9</i>
            ) Gene Does Not Impair Growth of
            <i>Candida glabrata</i>
            in Mice

Nakayama, Hironobu; Izuta, Miho; Nakayama, Noboru; Arisawa, Mikio; Aoki, Yuko

doi:10.1128/aac.44.9.2411-2418.2000

Cited by 53 publications

(43 citation statements)

References 32 publications

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“…Lipids and other hydrophobic molecules typically found in the cell membrane, such as sterols, are abundant in serum (4 to 8 mg/ml). Incorporation of cholesterol (the mammalian equivalent of the fungal sterol ergosterol) by a related species, Candida glabrata, has been observed (35), and thus uptake of sterols and lipids by C. albicans might occur in the lipid-rich environment of serum.…”

Section: Resultsmentioning

confidence: 99%

Calcineurin Is Required forCandida albicansTo Survive Calcium Stress in Serum

Blankenship¹,

Heitman

2005

Infect Immun

100

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The calcium-activated protein phosphatase calcineurin plays a critical role in the virulence of Candida albicans. Previous studies demonstrated that calcineurin is not required for the yeast-hypha dimorphic transition, host cell adherence, or host cell injury, which are all established virulence attributes of this organism. Calcineurin is, however, essential for survival in serum and disseminated infection. Here we identify the component of serum that is toxic to calcineurin mutant cells. Proteins, peptides, lipids, and other hydrophobic components were all excluded as essential toxic elements. Upon testing of small molecules present in serum, we discovered that calcineurin protects cells from stress caused by the endogenous levels of calcium ions present in serum. These studies illustrate how calcineurin functions in a calcium homeostatic pathway that enables a common human commensal to survive passage through the hostile environment of the bloodstream to establish deep-seated infections and cause disease.

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Section: Resultsmentioning

confidence: 99%

Calcineurin Is Required forCandida albicansTo Survive Calcium Stress in Serum

Blankenship¹,

Heitman

2005

Infect Immun

100

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“…Whether this event can occur during treatment of patients with amphotericin B is questionable. Experiments in which ERG11 has been "switched off" have been performed with C. glabrata in animal models and showed that the lack of ERG11 expression has only minor effects in animal models, probably because host sterols can compensate for the absence of C. glabrata sterols (22,23). Therefore, positive selection of erg11 mutants in the context of animal experiments can be envisaged.…”

Section: Discussionmentioning

confidence: 99%

Candida albicans Mutations in the Ergosterol Biosynthetic Pathway and Resistance to Several Antifungal Agents

Sanglard

Ischer

Parkinson

et al. 2003

Antimicrob Agents Chemother

365

257

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The role of sterol mutations in the resistance of Candida albicans to antifungal agents has not been thoroughly investigated. Previous work reported that clinical C. albicans strains resistant to both azole antifungals and amphotericin B were defective in ERG3, a gene encoding sterol ⌬ 5,6 -desaturase. It is also believed that a deletion of the lanosterol 14␣-demethylase gene, ERG11, is possible only under aerobic conditions when ERG3 is not functional. We tested these hypotheses by creating mutants by targeted deletion of the ERG3 and ERG11 genes and subjecting those mutants to antifungal susceptibility testing and sterol analysis. The homozygous erg3/erg3 mutant created, DSY1751, was resistant to azole derivatives, as expected. This mutant was, however, slightly more susceptible to amphotericin B than the parent wild type. It was possible to generate erg11/erg11 mutants in the DSY1751 background but also, surprisingly, in the background of a wild-type isolate with functional ERG3 alleles under aerobic conditions. This mutant (DSY1769) was obtained by exposure of an ERG11/erg11 heterozygous strain in a medium containing 10 g of amphotericin B per ml. Amphotericin B-resistant strains were obtained only from ERG11/erg11 heterozygotes at a frequency of approximately 5 ؋ 10 ؊5 to 7 ؋ 10 ؊5 , which was consistent with mitotic recombination between the first disrupted erg11 allele and the other remaining functional ERG11 allele. DSY1769 was also resistant to azole derivatives. The main sterol fraction in DSY1769 contained lanosterol and eburicol. These studies showed that erg11/erg11 mutants of a C. albicans strain harboring a defective erg11 allele can be obtained in vitro in the presence of amphotericin B. Amphotericin B-resistant strains could therefore be selected by similar mechanisms during antifungal therapy.

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“…Indeed, the therapeutic efficacy of azoles against Candida glabrata is affected by the pathogen's ability to utilize host cholesterol in the absence of ergosterol biosynthesis, and neither ERG11 nor ERG9 is essential in a murine infection model despite both genes being confirmed essential for in vitro growth of this pathogen (30,31). Thus beyond ergosterol (and amino acid biosynthesis), our study includes 17 additional genes reported as auxotrophic mutants under in vitro growth conditions (either in C. albicans or S. cerevisiae orthologs; Tables S1 and S2) and rescued by diverse metabolites.…”

Section: Discussionmentioning

confidence: 99%

Pathway analysis of Candida albicans survival and virulence determinants in a murine infection model

Becker

Kauffman²,

Hauser³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

122

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One potentially rich source of possible targets for antifungal therapy are those Candida albicans genes deemed essential for growth under the standard culture (i.e., in vitro) conditions; however, these genes are largely unexplored as drug targets because essential genes are not experimentally amenable to conventional gene deletion and virulence studies. Using tetracycline-regulatable promoter-based conditional mutants, we investigated a murine model of candidiasis in which repressing essential genes in the host was achieved. By adding doxycycline to the drinking water starting 3 days prior to (dox − 3D) or 2 days post (dox þ 2D) infection, the phenotypic consequences of temporal gene inactivation were assessed by monitoring animal survival and fungal burden in prophylaxis and acute infection settings. Of 177 selected conditional shutoff strains tested, the virulence of 102 was blocked under both repressing conditions, suggesting that the corresponding genes are essential for growth and survival in a murine host across early and established infection periods. Among these genes were those previously identified as antifungal drug targets (i.e., FKS1, ERG1, and ERG11), verifying that this methodology can be used to validate potential new targets. We also identify genes either conditionally essential or dispensable for in vitro growth but required for survival and virulence, including those in late stage ergosterol synthesis, or early steps in fatty acid or riboflavin biosynthesis. This study evaluates the role of essential genes with respect to pathogen virulence in a large-scale, systems biology context, and provides a general method for gene target validation and for uncovering unexpected antimicrobial targets.animal model | antifungal target | conditional expression | systemic candidiasis | virulence factor

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Depletion of the Squalene Synthase ( ERG9 ) Gene Does Not Impair Growth of Candida glabrata in Mice

Cited by 53 publications

References 32 publications

Calcineurin Is Required forCandida albicansTo Survive Calcium Stress in Serum

Calcineurin Is Required forCandida albicansTo Survive Calcium Stress in Serum

Candida albicans Mutations in the Ergosterol Biosynthetic Pathway and Resistance to Several Antifungal Agents

Pathway analysis of Candida albicans survival and virulence determinants in a murine infection model

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