Exposure to caspofungin activates Cap and Hog pathways in<i>Candida albicans</i>

Kelly, Judy; Rowan, Raymond; McCann, Malachy; Kavanagh, Kevin

doi:10.3109/13693780802552606

Cited by 35 publications

(19 citation statements)

References 30 publications

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“… A. fumigatus activates a compensatory increase in chitin content in response to sub-MIC caspofungin treatment, which highlights the potential of combining chitin synthase inhibitors with the echinocandins for improved and/or broader spectrum therapy. In addition, the PKC, Ca 2+ -calcineurin, and HOG signaling pathways have been shown to be required for the response of C. albicans and A. fumigatus to caspofungin and the in vitro paradoxical growth phenomenon ( 19 – 21 , 55 , 56 ). Consequently, inhibitors of these pathways together with an echinocandin should be explored as possible combination therapies.…”

Section: Discussionmentioning

confidence: 99%

Caspofungin Treatment of Aspergillus fumigatus Results in ChsG-Dependent Upregulation of Chitin Synthesis and the Formation of Chitin-Rich Microcolonies

Walker

Lee

Munro

et al. 2015

Antimicrob Agents Chemother

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Treatment of Aspergillus fumigatus with echinocandins such as caspofungin inhibits the synthesis of cell wall β-1,3-glucan, which triggers a compensatory stimulation of chitin synthesis. Activation of chitin synthesis can occur in response to sub-MICs of caspofungin and to CaCl2 and calcofluor white (CFW), agonists of the protein kinase C (PKC), and Ca2+-calcineurin signaling pathways. A. fumigatus mutants with the chs gene (encoding chitin synthase) deleted (ΔAfchs) were tested for their response to these agonists to determine the chitin synthase enzymes that were required for the compensatory upregulation of chitin synthesis. Only the ΔAfchsG mutant was hypersensitive to caspofungin, and all other ΔAfchs mutants tested remained capable of increasing their chitin content in response to treatment with CaCl2 and CFW and caspofungin. The resulting increase in cell wall chitin content correlated with reduced susceptibility to caspofungin in the wild type and all ΔAfchs mutants tested, with the exception of the ΔAfchsG mutant, which remained sensitive to caspofungin. In vitro exposure to the chitin synthase inhibitor, nikkomycin Z, along with caspofungin demonstrated synergistic efficacy that was again AfChsG dependent. Dynamic imaging using microfluidic perfusion chambers demonstrated that treatment with sub-MIC caspofungin resulted initially in hyphal tip lysis. However, thickened hyphae emerged that formed aberrant microcolonies in the continued presence of caspofungin. In addition, intrahyphal hyphae were formed in response to echinocandin treatment. These in vitro data demonstrate that A. fumigatus has the potential to survive echinocandin treatment in vivo by AfChsG-dependent upregulation of chitin synthesis. Chitin-rich cells may, therefore, persist in human tissues and act as the focus for breakthrough infections.

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Section: Discussionmentioning

confidence: 99%

Caspofungin Treatment of Aspergillus fumigatus Results in ChsG-Dependent Upregulation of Chitin Synthesis and the Formation of Chitin-Rich Microcolonies

Walker

Lee

Munro

et al. 2015

Antimicrob Agents Chemother

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“…To determine if the NIK1 G2048T mutation impairs Hog1 function, we first monitored phosphorylation of Hog1 in response to both caspofungin and the oxidative stress-inducing agent hydrogen peroxide in the laboratory strain. Hog1 is known to be activated in response to both hydrogen peroxide and caspofungin [ 56 , 57 ]. While both stressors cause an increase in Hog1 phosphorylation in the wild-type strain, only hydrogen peroxide induced Hog1 phosphorylation in the NIK1/NIK1 G2048T mutant ( Fig 5A ).…”

Section: Resultsmentioning

confidence: 99%

Metal Chelation as a Powerful Strategy to Probe Cellular Circuitry Governing Fungal Drug Resistance and Morphogenesis

et al. 2016

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Fungal pathogens have evolved diverse strategies to sense host-relevant cues and coordinate cellular responses, which enable virulence and drug resistance. Defining circuitry controlling these traits opens new opportunities for chemical diversity in therapeutics, as the cognate inhibitors are rarely explored by conventional screening approaches. This has great potential to address the pressing need for new therapeutic strategies for invasive fungal infections, which have a staggering impact on human health. To explore this approach, we focused on a leading human fungal pathogen, Candida albicans, and screened 1,280 pharmacologically active compounds to identify those that potentiate the activity of echinocandins, which are front-line therapeutics that target fungal cell wall synthesis. We identified 19 compounds that enhance activity of the echinocandin caspofungin against an echinocandin-resistant clinical isolate, with the broad-spectrum chelator DTPA demonstrating the greatest synergistic activity. We found that DTPA increases susceptibility to echinocandins via chelation of magnesium. Whole genome sequencing of mutants resistant to the combination of DTPA and caspofungin identified mutations in the histidine kinase gene NIK1 that confer resistance to the combination. Functional analyses demonstrated that DTPA activates the mitogen-activated protein kinase Hog1, and that NIK1 mutations block Hog1 activation in response to both caspofungin and DTPA. The combination has therapeutic relevance as DTPA enhanced the efficacy of caspofungin in a mouse model of echinocandin-resistant candidiasis. We found that DTPA not only reduces drug resistance but also modulates morphogenesis, a key virulence trait that is normally regulated by environmental cues. DTPA induced filamentation via depletion of zinc, in a manner that is contingent upon Ras1-PKA signaling, as well as the transcription factors Brg1 and Rob1. Thus, we establish a new mechanism by which metal chelation modulates morphogenetic circuitry and echinocandin resistance, and illuminate a novel facet to metal homeostasis at the host-pathogen interface, with broad therapeutic potential.

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“…Nuclear translocation of Cap1 in response to the echinocandin caspofungin has been reported along with the induction of two Cap1-regulated genes, GLR1 and SOD2 [44]. However, transcript profiling of caspofungin-treated C. albicans demonstrated repression of CAP1 and no up-regulation of oxidative stress genes [42], suggesting that very high concentrations of caspofungin, as those used by Kelly et al [44], are required to observe oxidative stress. Finally, exposure to ketoconazole does not trigger overexpression of stress genes [42] while fluconazole can induce 2 Cap1-dependent oxidative stress genes, TRR1 and GRE2 [45].…”

Section: Discussionmentioning

confidence: 99%

“…In S. cerevisiae, YAP1 does not influence the susceptibility to amphotericin B [43]. Nuclear translocation of Cap1 in response to the echinocandin caspofungin has been reported along with the induction of two Cap1-regulated genes, GLR1 and SOD2 [44]. However, transcript profiling of caspofungin-treated C. albicans demonstrated repression of CAP1 and no up-regulation of oxidative stress genes [42], suggesting that very high concentrations of caspofungin, as those used by Kelly et al [44], are required to observe oxidative stress.…”

Section: Discussionmentioning

confidence: 99%

Antifungal Activity of Fused Mannich Ketones Triggers an Oxidative Stress Response and Is Cap1-Dependent in Candida albicans

et al. 2013

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We investigated the antifungal activity of fused Mannich ketone (FMK) congeners and two of their aminoalcohol derivatives. In particular, FMKs with five-membered saturated rings were shown to have minimum inhibitory concentration (MIC90s) ranging from 0.8 to 6 µg/mL toward C. albicans and the closely related C. parapsilosis and C. krusei while having reduced efficacy toward C. glabrata and almost no efficacy against Aspergillus sp. Transcript profiling of C. albicans cells exposed for 30 or 60 min to 2-(morpholinomethyl)-1-indanone, a representative FMK with a five-membered saturated ring, revealed a transcriptional response typical of oxidative stress and similar to that of a C. albicans Cap1 transcriptional activator. Consistently, C. albicans lacking the CAP1 gene was hypersensitive to this FMK, while C. albicans strains overexpressing CAP1 had decreased sensitivity to 2-(morpholinomethyl)-1-indanone. Quantitative structure–activity relationship studies revealed a correlation of antifungal potency and the energy of the lowest unoccupied molecular orbital of FMKs and unsaturated Mannich ketones thereby implicating redox cycling-mediated oxidative stress as a mechanism of action. This conclusion was further supported by the loss of antifungal activity upon conversion of representative FMKs to aminoalcohols that were unable to participate in redox cycles.

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Exposure to caspofungin activates Cap and Hog pathways inCandida albicans

Cited by 35 publications

References 30 publications

Caspofungin Treatment of Aspergillus fumigatus Results in ChsG-Dependent Upregulation of Chitin Synthesis and the Formation of Chitin-Rich Microcolonies

Caspofungin Treatment of Aspergillus fumigatus Results in ChsG-Dependent Upregulation of Chitin Synthesis and the Formation of Chitin-Rich Microcolonies

Metal Chelation as a Powerful Strategy to Probe Cellular Circuitry Governing Fungal Drug Resistance and Morphogenesis

Antifungal Activity of Fused Mannich Ketones Triggers an Oxidative Stress Response and Is Cap1-Dependent in Candida albicans

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