Calcineurin controls drug tolerance, hyphal growth, and virulence in Candida dubliniensis.

Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
Eukaryotic Cell (Impact Factor: 3.18). 06/2011; 10(6):803-19. DOI: 10.1128/EC.00310-10
Source: PubMed

ABSTRACT Candida dubliniensis is an emerging pathogenic yeast species closely related to Candida albicans and frequently found colonizing or infecting the oral cavities of HIV/AIDS patients. Drug resistance during C. dubliniensis infection is common and constitutes a significant therapeutic challenge. The calcineurin inhibitor FK506 exhibits synergistic fungicidal activity with azoles or echinocandins in the fungal pathogens C. albicans, Cryptococcus neoformans, and Aspergillus fumigatus. In this study, we show that calcineurin is required for cell wall integrity and wild-type tolerance of C. dubliniensis to azoles and echinocandins; hence, these drugs are candidates for combination therapy with calcineurin inhibitors. In contrast to C. albicans, in which the roles of calcineurin and Crz1 in hyphal growth are unclear, here we show that calcineurin and Crz1 play a clearly demonstrable role in hyphal growth in response to nutrient limitation in C. dubliniensis. We further demonstrate that thigmotropism is controlled by Crz1, but not calcineurin, in C. dubliniensis. Similar to C. albicans, C. dubliniensis calcineurin enhances survival in serum. C. dubliniensis calcineurin and crz1/crz1 mutants exhibit attenuated virulence in a murine systemic infection model, likely attributable to defects in cell wall integrity, hyphal growth, and serum survival. Furthermore, we show that C. dubliniensis calcineurin mutants are unable to establish murine ocular infection or form biofilms in a rat denture model. That calcineurin is required for drug tolerance and virulence makes fungus-specific calcineurin inhibitors attractive candidates for combination therapy with azoles or echinocandins against emerging C. dubliniensis infections.


Available from: Scott G Filler, Jun 11, 2015
1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Calcineurin plays essential roles in virulence and growth of pathogenic fungi and is a target of the natural products FK506 and Cyclosporine A. In the pathogenic mucoralean fungus Mucor circinelloides, calcineurin mutation or inhibition confers a yeast-locked phenotype indicating that calcineurin governs the dimorphic transition. Genetic analysis in this study reveals that two calcineurin A catalytic subunits (out of three) are functionally diverged. Homology modeling illustrates modes of resistance resulting from amino substitutions in the interface between each calcineurin subunit and the inhibitory drugs. In addition, we show how the dimorphic transition orchestrated by calcineurin programs different outcomes during host-pathogen interactions. For example, when macrophages phagocytose Mucor yeast, subsequent phagosomal maturation occurs, indicating host cells respond appropriately to control the pathogen. On the other hand, upon phagocytosis of spores, macrophages fail to form mature phagosomes. Cytokine production from immune cells differs following exposure to yeast vs. spores (which germinate into hyphae). Thus, the morphogenic transition can be targeted as an efficient treatment option against Mucor infection. In addition, genetic analysis (including gene disruption and mutational studies) further strengthens the understanding of calcineurin and provides a foundation to develop antifungal agents targeting calcineurin to deploy against Mucor and other pathogenic fungi. This article is protected by copyright. All rights reserved.
    Molecular Microbiology 05/2015; DOI:10.1111/mmi.13071 · 5.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In recent years, the emergence of fungal resistance has become frequent partly due to the widespread clinical use of fluconazole, which is minimally toxic and effective in prevention and treatment of Candida albicans infections. The limited selection of antifungal drugs for clinical fungal infection therapy has prompted us to search for new antifungal targets that can be targeted by new antifungal drugs. Calcium, which acts as the second messenger in both mammals and fungi, plays a direct role in controlling the expression patterns of its signaling systems and important roles in cell survival. In addition, calcium and some of the components, mainly calcineurin, in the fungal calcium signaling pathway mediate fungal resistance to antifungal drugs. Therefore, an overview of the components of the fungal calcium-calcineurin signaling network, and their potential roles as antifungal targets is urgently needed. The calcium-calcineurin signaling pathway consists of various channels, transporters, pumps and other proteins or enzymes. Many transcriptional profiles have indicated that mutant strains that lack some of these components are sensitized to fluconazole or other antifungal drugs. In addition, many researchers have identified efficient compounds that exhibit antifungal activity by themselves or in combination with antifungal drugs by targeting some of the components in the fungal calcium-calcineurin signaling pathway. This targeting disrupts Ca(2+) homeostasis, which suggests that this pathway contains potential antifungal targets for the development of new antifungal drugs. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015; 14(4). DOI:10.1128/EC.00271-14 · 3.18 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Indwelling urinary catheters are commonly used in the management of hospitalized patients. Candida can adhere to the device surface and propagate as a biofilm. These communities differ from free-floating Candida, exhibiting high tolerance to antifungal therapy. The significance of catheter-associated candiduria is often unclear and treatment may be problematic considering the biofilm drug resistant phenotype. Here we describe a rodent model for study of urinary catheter-associated Candida albicans biofilm infection that mimics this common process in patients. In the setting of a functioning, indwelling urinary catheter in a rat, Candida proliferated as a biofilm on the device surface. Characteristic biofilm architecture was observed, including adherent, filamentous cells embedded in an extracelluar matrix. Similar to patients, animals with this infection developed candiduria and pyuria. Infection progressed to cystitis and a biofilm-like covering was observed over the bladder surface. Furthermore, large numbers of C. albicans were dispersed into the urine from either the catheter or bladder wall biofilm over the infection period. We successfully utilized the model to test the efficacy of antifungals, analyze transcriptional patterns, and examine the phenotype of a genetic mutant. The model should be useful for future investigations involving the pathogenesis, diagnosis, therapy, prevention, and drug resistance of Candida biofilms in the urinary tract.
    Infection and Immunity 09/2014; DOI:10.1128/IAI.02284-14 · 4.16 Impact Factor