The high prevalence of
fluconazole resistance among clinical isolates of Candida glabrata has greatly hampered the utility of
fluconazole for the treatment of
invasive candidiasis.
Fluconazole resistance in this yeast is almost exclusively due to activating mutations in the
transcription factor Pdr1, which result in upregulation of the
ABC transporter genes CDR1, PDH1, and SNQ2 and therefore increased
fluconazole efflux. However, the regulation of Pdr1 is poorly understood. In order to identify genes that interact with the Pdr1 transcriptional pathway and influence the susceptibility of C. glabrata to
fluconazole, we screened a collection of deletion mutants for those exhibiting increased resistance to
fluconazole. Deletion of the gene coding for a
protein homologous to the Saccharomyces cerevisiae J
protein Jjj1 resulted in decreased
fluconazole susceptibility. We used the SAT1 flipper method to generate independent deletion mutants for JJJ1 in an SDD clinical isolate. Expression of both CDR1 and PDR1 was increased in the absence of JJJ1. In the absence of CDR1 or PDR1, deletion of JJJ1 has only a modest effect on
fluconazole susceptibility. Transcriptional profiling using transcriptome sequencing (
RNA-seq) revealed upregulation of genes of the Pdr1 regulon in the absence of JJJ1. Jjj1 appears to be a negative regulator of
fluconazole resistance in C. glabrata and acts primarily through upregulation of the
ABC transporter gene CDR1 via activation of the Pdr1 transcriptional pathway. IMPORTANCECandida glabrata is the second most common species of Candida recovered from patients with
invasive candidiasis. The increasing number of
infections due to C. glabrata, combined with its high rates of resistance to the commonly used, well-tolerated
azole class of
antifungal agents, has limited the use of this antifungal class. This has led to the preferential use of
echinocandins as empirical treatment for serious
Candida infections. The primary mechanism of resistance found in clinical isolates is the presence of an activating mutation in the gene encoding the
transcription factor Pdr1 that results in upregulation of one or more of the efflux pumps Cdr1, Pdh1, and Snq2. By developing a better understanding of this mechanism of resistance to the
azoles, it will be possible to develop strategies for reclaiming the utility of the
azole antifungals against this important fungal pathogen.