Affiliation:
1. Department of Molecular Physiology and Biophysics, Carver College of Medicine University of Iowa, Iowa City, Iowa, USA
Abstract
ABSTRACT
Fluconazole is one of the most commonly used antifungals today. A result of this has been the inevitable selection of fluconazole-resistant organisms. This is an especially acute problem in the pathogenic yeast
Candida glabrata
. Elevated minimal inhibitory concentrations for fluconazole in
C. glabrata
are frequently associated with substitution mutations within the Zn2Cys6 zinc cluster-containing transcription factor-encoding gene
PDR1
. These mutant Pdr1 regulators drive constitutively high expression of target genes like
CDR1
that encodes an ATP-binding cassette transporter thought to act as a drug efflux pump. Exposure of
C. glabrata
to fluconazole induced expression of both Pdr1 and
CDR1
, although little is known of the molecular basis underlying the upstream signals that trigger Pdr1 activation. Here, we show that the protein phosphatase calcineurin is required for fluconazole-dependent induction of Pdr1 transcriptional regulation. Calcineurin catalytic activity is required for normal Pdr1 regulation, and a hyperactive form of this phosphatase can decrease susceptibility to the echinocandin caspofungin but does not show a similar change for fluconazole susceptibility. Loss of calcineurin from strains expressing two different gain-of-function forms of Pdr1 also caused a decrease in
CDR1
expression and increased fluconazole susceptibility, demonstrating that even these hyperactive Pdr1 regulatory mutants cannot bypass the requirement for calcineurin. Our data implicate calcineurin activity as a link tying azole and echinocandin susceptibility together via the control of transcription factor activity.
IMPORTANCE
Drug-resistant microorganisms are a problem in the treatment of all infectious diseases; this is an especially acute problem with fungi due to the existence of only three major classes of antifungal drugs, including the azole drug fluconazole. In the pathogenic yeast
Candida glabrata
, mutant forms of a transcription factor called Pdr1 are commonly associated with decreased fluconazole susceptibility and poor clinical outcomes. Here, we identify a protein phosphatase called calcineurin that is required for fluconazole-dependent induction of Pdr1 transcriptional activation and associated drug susceptibility. Gain-of-function mutant forms of Pdr1 still required the presence of calcineurin to confer normally decreased fluconazole susceptibility. Previous studies showed that calcineurin controls susceptibility to the echinocandin class of antifungal drugs, and our data demonstrate that this protein phosphatase is also required for normal azole drug susceptibility. Calcineurin plays a central role in susceptibility to two of the three major classes of antifungal drugs in
C. glabrata
.
Funder
HHS | National Institutes of Health
Publisher
American Society for Microbiology
Cited by
1 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献