Jjj1 Is a Negative Regulator of Pdr1-Mediated Fluconazole Resistance in Candida glabrata

The high prevalence of fluconazole resistance among clinical isolates of 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 , , and 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 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 J protein Jjj1 resulted in decreased fluconazole susceptibility. We used the flipper method to generate independent deletion mutants for in an SDD clinical isolate. Expression of both and was increased in the absence of . In the absence of or , deletion of 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 appears to be a negative regulator of fluconazole resistance in and acts primarily through upregulation of the ABC transporter gene via activation of the Pdr1 transcriptional pathway. is the second most common species of recovered from patients with invasive candidiasis. The increasing number of infections due to , 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 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.