Small-Molecule Inhibitors of the Budded-to-Hyphal-Form Transition in the Pathogenic Yeast
            <i>Candida albicans</i>

Toenjes, Kurt A.; Munsee, Suzanne M.; Ibrahim, Ashraf S.; Jeffrey, Rachel; Edwards, John E.; Johnson, Douglas I.

doi:10.1128/aac.49.3.963-972.2005

Cited by 64 publications

(90 citation statements)

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“…The following major functional families of miconazole tolerance genes could be distinguished: (i) tryptophan biosynthesis, (ii) membrane trafficking, including endocytosis, (iii) regulation of actin cytoskeleton, and (iv) regulation of gene expression. These genetic data were confirmed by biochemical tests using excess Trp or the endocytosis inhibitor compound 5235236 (C 5235236 ) (5). Regarding miconazole antifungal action, we could demonstrate an antagonism with Trp on one hand and a synergy with C 5235236 on the other hand.…”

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Miconazole Induces Changes in Actin Cytoskeleton prior to Reactive Oxygen Species Induction in Yeast

Thevissen

Ayscough

Aerts

et al. 2007

Journal of Biological Chemistry

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The antifungal compound miconazole inhibits ergosterol biosynthesis and induces reactive oxygen species (ROS) in susceptible yeast species. To further uncover the mechanism of miconazole antifungal action and tolerance mechanisms, we screened the complete set of haploid Saccharomyces cerevisiae gene deletion mutants for mutants with an altered miconazole sensitivity phenotype. We identified 29 S. cerevisiae genes, which when deleted conferred at least 4-fold hypersensitivity to miconazole. Major functional groups encode proteins involved in tryptophan biosynthesis, membrane trafficking including endocytosis, regulation of actin cytoskeleton, and gene expression. With respect to the antifungal activity of miconazole, we demonstrate an antagonism with tryptophan and a synergy with a yeast endocytosis inhibitor. Because actin dynamics and induction of ROS are linked in yeast, we further focused on miconazole-mediated changes in actin cytoskeleton organization. In this respect, we demonstrate that miconazole induces changes in the actin cytoskeleton, indicative of increased filament stability, prior to ROS induction. These data provide novel mechanistic insights in the mode of action of a ROS-inducing azole.Miconazole belongs to the azole antifungals, which are currently the most widely used antimycotics. Azoles inhibit ergosterol biosynthesis, resulting in accumulation of toxic methylated sterol intermediates and, subsequently, fungal cell growth arrest (1). Recently, an additional mode of antifungal action was uncovered for miconazole. Apart from inhibition of ergosterol biosynthesis, miconazole induces reactive oxygen species (ROS) 6 in susceptible fungi, leading to fungal cell death (2, 3).The aim of the present study was to further unravel the mode of antifungal action of miconazole and tolerance mechanisms against miconazole in yeast. Information regarding drug tolerance mechanisms is invaluable for antifungal therapy: theoretically, miconazole action can be increased by using inhibitors of identified yeast tolerance mechanisms. To our knowledge, this study is the first report on yeast tolerance mechanisms against imidazoles, such as miconazole, and their mode of action using a genome-wide screening approach in yeast. In this study, we screened the haploid set of Saccharomyces cerevisiae deletion mutants in non-essential genes for both hypersensitivity and resistance to miconazole by determining the minimal inhibitory miconazole concentration (MIC) for all individual yeast knock-out mutants using 2-fold dilution series of miconazole in liquid YPD medium. In this way, no miconazole-resistant yeast mutants could be identified. However, we could identify 29 S. cerevisiae genes or open reading frames that upon deletion result in at least 4-fold hypersensitivity to miconazole and hence are involved in miconazole tolerance. The following major functional families of miconazole tolerance genes could be distinguished: (i) tryptophan biosynthesis, (ii) membrane trafficking, including endocytosis, (iii) regulation of ac...

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“…: 32-16-32-96-82; Fax: 32-16-32-19-66; E-mail: bruno.cammue@biw.kuleuven.be. 5 Supported by a postdoctoral fellowship from IWT-Vlaanderen (OZM/030508). 6 The abbreviations used are: ROS, reactive oxygen species; MIC, minimal inhibitory concentration of miconazole; MM, minimal medium.…”

Section: Methodsmentioning

confidence: 99%

Miconazole Induces Changes in Actin Cytoskeleton prior to Reactive Oxygen Species Induction in Yeast

Thevissen

Ayscough

Aerts

et al. 2007

Journal of Biological Chemistry

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“…The ability of IFF4 overexpression/suppression to modulate C. albicans-induced endothelial cell injury was determined with the chromium ( 51 Cr) release assay in 96-well tissue culture plates as described previously (52).…”

Section: Methodsmentioning

confidence: 99%

Gene Overexpression/Suppression Analysis of Candidate Virulence Factors of Candida albicans

Luo

Spellberg

et al. 2008

Eukaryot Cell

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We developed a conditional overexpression/suppression genetic strategy in Candida albicans to enable simultaneous testing of gain or loss of function in order to identify new virulence factors. The strategy involved insertion of a strong, tetracycline-regulated promoter in front of the gene of interest. To validate the strategy, a library of genes encoding glycosylphosphatidylinositol (GPI)-anchored surface proteins was screened for virulence phenotypes in vitro. During the screening, overexpression of IFF4 was found to increase the adherence of C. albicans to plastic and to human epithelial cells, but not endothelial cells. Consistent with the in vitro results, IFF4 overexpression modestly increased the tissue fungal burden during murine vaginal candidiasis. In addition to the in vitro screening tests, IFF4 overexpression was found to increase C. albicans susceptibility to neutrophil-mediated killing. Furthermore, IFF4 overexpression decreased the severity of hematogenously disseminated candidiasis in normal mice, but not in neutropenic mice, again consistent with the in vitro phenotype. Overexpression of 12 other GPI proteins did not affect normal GPI protein cell surface accumulation, demonstrating that the overexpression strategy did not affect the cell capacity for making such proteins. These data indicate that the same gene can increase or decrease candidal virulence in distinct models of infection, emphasizing the importance of studying virulence genes in different anatomical contexts. Finally, these data validate the use of a conditional overexpression/suppression genetic strategy to identify candidal virulence factors.Candida albicans causes hematogenously disseminated and mucosal infections (7, 33). Despite current antifungal therapy, mortality and morbidity are unacceptably high (1,16,34). Therefore, new prophylactic and therapeutic strategies are urgently needed. The identification of virulence genes that can be targeted to alter pathogenicity is a necessary step in devising novel strategies to treat or prevent Candida infections.Virulence factors in C. albicans include proteins that mediate adherence to and invasion of host tissues (43), morphological change from yeast to hyphae (29,30), secretion of lytic enzymes (17,27,41), maintenance of cell wall integrity (55), and avoidance of the host immune response (39). Many of these virulence factors are glycosylphosphatidylinositol (GPI)-anchored proteins, which comprise 88% of all covalently linked cell wall proteins in C. albicans (23). Examples of GPI-anchored virulence factors are Phr1p and Phr2p, which mediate cell wall biogenesis and hyphal formation in response to changes in pH (15); Hwp1p, an epithelial adhesin and biofilm promoter (32) that is required for virulence during murine hematogenously disseminated candidiaisis (48); Als1p and Als3p, adhesins with broad substrate specificity (13,22,43); and Gpi7, an antivirulence factor that reduces candidal resistance to macrophages and virulence in mice (36). Numerous GPI proteins have been identified...

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“…Many other small molecules have been reported to affect morphogenesis in C. albicans (135,136). Propranolol, a calmodulin inhibitor (141), was shown to inhibit serum-induced hypha formation by reducing EFG1 expression levels (10, 138).…”

Section: Other Small Moleculesmentioning

confidence: 99%

Modulation of Morphogenesis in Candida albicans by Various Small Molecules

2011

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The pathogenic yeast Candida albicans, a member of the mucosal microbiota, is responsible for a large spectrum of infections, ranging from benign thrush and vulvovaginitis in both healthy and immunocompromised individuals to severe, life-threatening infections in immunocompromised patients. A striking feature of C. albicans is its ability to grow as budding yeast and as filamentous forms, including hyphae and pseudohyphae. The yeast-to-hypha transition contributes to the overall virulence of C. albicans and may even constitute a target for the development of antifungal drugs. Indeed, impairing morphogenesis in C. albicans has been shown to be a means to treat candidiasis. Additionally, a large number of small molecules such as farnesol, fatty acids, rapamycin, geldanamycin, histone deacetylase inhibitors, and cell cycle inhibitors have been reported to modulate the yeast-to-hypha transition in C. albicans. In this minireview, we take a look at molecules that modulate morphogenesis in this pathogenic yeast. When possible, we address experimental findings regarding their mechanisms of action and their therapeutic potential. We discuss whether or not modulating morphogenesis constitutes a strategy to treat Candida infections.

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Small-Molecule Inhibitors of the Budded-to-Hyphal-Form Transition in the Pathogenic Yeast Candida albicans

Cited by 64 publications

References 50 publications

Miconazole Induces Changes in Actin Cytoskeleton prior to Reactive Oxygen Species Induction in Yeast

Miconazole Induces Changes in Actin Cytoskeleton prior to Reactive Oxygen Species Induction in Yeast

Gene Overexpression/Suppression Analysis of Candidate Virulence Factors of Candida albicans

Modulation of Morphogenesis in Candida albicans by Various Small Molecules

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