Disruption of the Transcriptional Regulator Cas5 Results in Enhanced Killing of Candida albicans by Fluconazole

Abstract

One of these genes, UPC2, was previously characterized with regard to its role in azole susceptibility. Of mutants representing the three remaining TF genes of interest, one (CAS5) was unable to recover from fluconazole exposure at concentrations as low as 2 g/ml after 72 h in YPD medium. This mutant also showed reduced susceptibility and a clear zone of inhibition by Etest, was unable to grow on solid medium containing 10 g/ml fluconazole, and exhibited increased susceptibility by time-kill analysis. CAS5 disruption in highly azole-resistant clinical isolates exhibiting multiple resistance mechanisms did not alter susceptibility. However, CAS5 disruption in strains with specific resistance mutations resulted in moderate reductions in MICs and MFCs. Genome-wide transcriptional analysis was performed in the presence of fluconazole and was consistent with the suggested role of CAS5 in cell wall organization while also suggesting a role in iron transport and homeostasis. These findings suggest that Cas5 regulates a transcriptional network that influences the response of C. albicans to fluconazole. Further delineation of this transcriptional network may identify targets for potential cotherapeutic strategies to enhance the activity of the azole class of antifungals.

The Candida albicans transcription factor Cas5 couples stress responses, drug resistance and cell cycle regulation

“…This highlights a divergence in signal transduction cascades required to respond to environmental stressors, and suggests that Cas5 may be the central downstream effector of Glc7 that modulates stress responses in C. albicans . Consistent with this possibility, Cas5 controls responses not only to cell wall stress, but also to cell membrane stress exerted by the azole antifungal drugs 52 .…”

Kinase Inhibitors that Increase the Sensitivity of Methicillin Resistant Staphylococcus aureus to β-Lactam Antibiotics

“…To confirm that the decrease in optical density observed on treatment of MRSA with kinase inhibitor and NAF correlated with decreased bacterial CFU, we performed a time-to-kill analysis, as described [ 11 , 12 ]. Briefly, 10 4 CFU of WT MRSA (LAC) was grown for 24 h in either media alone, antibiotic NAF alone (4 µg/mL), kinase inhibitor alone (40 µg/mL), or kinase inhibitor containing NAF.…”

Cell wall integrity signalling in human pathogenic fungi

“…cerevisiae that can be identified by homology search (Bruno et al ., ). The ∆Ca cas5 /∆Ca cas5 mutant suffers from several CWI‐related phenotypes, including hypersensitivity to CR, caspofungin and fluconazole and also reduced virulence (Bruno et al ., ; Chamilos et al ., ; Vasicek et al ., ). However, experimental data that proof a direct activation route from the CWI MAPK to CaCas5 (but also to CaRlm1) is still missing.…”