Reverse Genetics in Candida albicans Predicts ARF Cycling Is Essential for Drug Resistance and Virulence

Epp, Elias; Vanier, Ghyslaine; Harcus, Doreen; Lee, Anna Y.; Jansen, Gregor; Hallett, Michael; Sheppard, Don; Thomas, David Y.; Munro, Carol A.; Mullick, Alaka; Whiteway, Malcolm

doi:10.1371/journal.ppat.1000753

Cited by 54 publications

(54 citation statements)

References 98 publications

(157 reference statements)

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“…Thus, eight TF mutants, the function of which has been fully characterized in C. albicans, were not selected for further analysis. These were mutants for orf19.1358 (GCN4, a bZip TF involved in amino acid response [64]), orf19.3127 (CZF1, a zinc cluster TF involved in regulation of white-opaque switching frequency [6,71]), orf19.3193 (FCR3, a bZip TF involved in iron homeostasis [58,68]), orf19.3683 (AGE3, involved in drug resistance and virulence [21,39]), orf19.3969 (encoding SFL2, a heat shock factor-like TF involved in filamentous growth and virulence [61]), orf19.4318 (MIG1, a transcriptional repressor involved in carbon source utilization [69]), orf19.4961 (STP2, involved in regulation of amino acid permease expression [41]), and orf19.6124 (ACE2, a TF involved in regulation of morphogenesis [36]). …”

Section: Resultsmentioning

confidence: 99%

Identification and Functional Characterization of Rca1, a Transcription Factor Involved in both Antifungal Susceptibility and Host Response in Candida albicans

Vandeputte

Pradervand²,

Ischer

et al. 2012

Eukaryot Cell

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ABSTRACTThe identification of novel transcription factors associated with antifungal response may allow the discovery of fungus-specific targets for new therapeutic strategies. A collection of 241Candida albicanstranscriptional regulator mutants was screened for altered susceptibility to fluconazole, caspofungin, amphotericin B, and 5-fluorocytosine. Thirteen of these mutants not yet identified in terms of their role in antifungal response were further investigated, and the function of one of them, a mutant of orf19.6102 (RCA1), was characterized by transcriptome analysis. Strand-specific RNA sequencing and phenotypic tests assigned Rca1 as the regulator of hyphal formation through the cyclic AMP/protein kinase A (cAMP/PKA) signaling pathway and the transcription factor Efg1, but also probably through its interaction with a transcriptional repressor, most likely Tup1. The mechanisms responsible for the high level of resistance to caspofungin and fluconazole observed resulting fromRCA1deletion were investigated. From our observations, we propose that caspofungin resistance was the consequence of the deregulation of cell wall gene expression and that fluconazole resistance was linked to the modulation of the cAMP/PKA signaling pathway activity. In conclusion, our large-scale screening of aC. albicanstranscription factor mutant collection allowed the identification of new effectors of the response to antifungals. The functional characterization of Rca1 assigned this transcription factor and its downstream targets as promising candidates for the development of new therapeutic strategies, as Rca1 influences host sensing, hyphal development, and antifungal response.

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Section: Resultsmentioning

confidence: 99%

Identification and Functional Characterization of Rca1, a Transcription Factor Involved in both Antifungal Susceptibility and Host Response in Candida albicans

Vandeputte

Pradervand²,

Ischer

et al. 2012

Eukaryot Cell

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“…Recently, studies have identified a critical role for Age3, an ADP ribosylation factor (ARF) GTPase-activating effector protein, in fluconazole resistance, morphogenesis, and virulence of C. albicans (170,321). The deletion of age3 abrogates resistance to a variety of azole drugs, and the pharmacological inhibition of ARF cycling with brefeldin A renders fluconazole fungicidal against a variety of azole-resistant mutants (170).…”

Section: Cellular Stress Responsesmentioning

confidence: 99%

Section: Cellular Stress Responsesmentioning

confidence: 99%

“…The deletion of age3 abrogates resistance to a variety of azole drugs, and the pharmacological inhibition of ARF cycling with brefeldin A renders fluconazole fungicidal against a variety of azole-resistant mutants (170). The constitutive activation of calcineurin signaling renders wild-type cells resistant to the azoles; however, this effect is blocked in age3 mutants (170). age3 mutants abolish the resistance of C. albicans clinical isolates that constitutively overexpress Mdr1 and Erg11, suggesting that the effects of ARF signaling on azole resistance are distinct from the Hsp90-calcineurin stress response pathway (170).…”

Section: Cellular Stress Responsesmentioning

confidence: 99%

“…The constitutive activation of calcineurin signaling renders wild-type cells resistant to the azoles; however, this effect is blocked in age3 mutants (170). age3 mutants abolish the resistance of C. albicans clinical isolates that constitutively overexpress Mdr1 and Erg11, suggesting that the effects of ARF signaling on azole resistance are distinct from the Hsp90-calcineurin stress response pathway (170). Furthermore, age3 mutants have attenuated virulence in a wild-type mouse model of disseminated disease and an improved response to fluconazole in an immunocompromised mouse model (170), providing a genetic proof of principle for a new combinatorial therapy for C. albicans infections.…”

Section: Cellular Stress Responsesmentioning

confidence: 99%

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Regulatory Circuitry Governing Fungal Development, Drug Resistance, and Disease

Shapiro

Robbins

Cowen

2011

Microbiol Mol Biol Rev

499

547

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SUMMARY Pathogenic fungi have become a leading cause of human mortality due to the increasing frequency of fungal infections in immunocompromised populations and the limited armamentarium of clinically useful antifungal drugs. Candida albicans , Cryptococcus neoformans , and Aspergillus fumigatus are the leading causes of opportunistic fungal infections. In these diverse pathogenic fungi, complex signal transduction cascades are critical for sensing environmental changes and mediating appropriate cellular responses. For C. albicans , several environmental cues regulate a morphogenetic switch from yeast to filamentous growth, a reversible transition important for virulence. Many of the signaling cascades regulating morphogenesis are also required for cells to adapt and survive the cellular stresses imposed by antifungal drugs. Many of these signaling networks are conserved in C. neoformans and A. fumigatus , which undergo distinct morphogenetic programs during specific phases of their life cycles. Furthermore, the key mechanisms of fungal drug resistance, including alterations of the drug target, overexpression of drug efflux transporters, and alteration of cellular stress responses, are conserved between these species. This review focuses on the circuitry regulating fungal morphogenesis and drug resistance and the impact of these pathways on virulence. Although the three human-pathogenic fungi highlighted in this review are those most frequently encountered in the clinic, they represent a minute fraction of fungal diversity. Exploration of the conservation and divergence of core signal transduction pathways across C. albicans , C. neoformans , and A. fumigatus provides a foundation for the study of a broader diversity of pathogenic fungi and a platform for the development of new therapeutic strategies for fungal disease.

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