Pdr1 regulates multidrug resistance in Candida glabrata: gene disruption and genome‐wide expression studies

Abstract

SummaryCandida glabrata emerged in the last decade as a common cause of mucosal and invasive fungal infection, in large part due to its intrinsic or acquired resistance to azole antifungals such as fluconazole. In C. glabrata clinical isolates, the predominant mechanism behind azole resistance is upregulated expression of multidrug transporter genes CDR1 and PDH1. We previously reported that azole-resistant mutants (MIC Ն 64 mg ml ) to both F15 and 66032 and eliminated both constitutive and fluconazole-induced CDR1-PDH1 expression. Reintroduction of wild-type or F15 PDR1 fully reversed these effects; together these results demonstrate a role for this gene in both acquired and intrinsic azole resistance. CDR1 disruption had a partial effect, reducing fluconazole trailing in both strains while restoring wild-type susceptibility (MIC = 16 mg ml -1 ) to F15. In an azole-resistant clinical isolate, PDR1 disruption reduced azole MICs eight-to 64-fold with no effect on sensitivity to other antifungals. To extend this analysis, C. glabrata microarrays were generated and used to analyse genome-wide expression in F15 relative to its parent. Homologues of 10 S. cerevisiae genes previously shown to be Pdr1-Pdr3 targets were upregulated (YOR1, RTA1, RSB1, RPN4, YLR346c and YMR102c along with CDR1, PDH1 and PDR1 itself) or downregulated (PDR12); roles for these genes include small molecule transport and transcriptional regulation. However, expression of 99 additional genes was specifically altered in C. glabrata F15; their roles include transport (e.g. QDR2, YBT1), lipid metabolism (ATF2, ARE1), cell stress (HSP12, CTA1), DNA repair (YIM1, MEC3) and cell wall function (MKC7, MNT3). These azole resistance-associated changes could affect C. glabrata tissue-specific virulence; in support of this, we detected differences in F15 oxidant, alcohol and weak acid sensitivities. C. glabrata provides a promising model for studying the genetic basis of multidrug resistance and its impact on virulence.

Gain-of-Function Mutations in PDR1 , a Regulator of Antifungal Drug Resistance in Candida glabrata, Control Adherence to Host Cells

“…This mechanism is mediated by upregulation of a single or a combination of a few ATP-binding cassette (ABC) transporters, among which are at least CgCDR1, CgCDR2, and CgSNQ2 (5)(6)(7)(8)(9). Upregulation of ABC transporters occurs following alterations in their major regulator, the zinc cluster transcription factor CgPDR1 (10,11). CgPDR1 combines functional attributes of transcription factors PDR1 and PDR3 from the nonpathogenic baker's yeast Saccharomyces cerevisiae (12).…”

Genomewide Expression Profile Analysis of the Candida glabrata Pdr1 Regulon

“…These transporters are regulated by the zinc binuclear cluster transcription factor CgPdr1, a single-gene homolog of Saccharomyces cerevisiae Pdr1 (ScPdrl) and ScPdr3 transcription factors (35,36). CgPDR1, CgCDR1, CgPDH1, and CgSNQ2 all contain at least one pleiotropic drug response element sequence (PDRE) in their promoters, suggesting that CgPdr1 may regulate its own expression, as well as that of the transporters, through binding these regulatory elements (32, 35).…”

The Rho1 GTPase-activating Protein CgBem2 Is Required for Survival of Azole Stress in Candida glabrata

“…CgCDR1, CgCDR2, and CgSNQ2 are under the transcriptional regulation of a Zn 2 Cys 6 zinc cluster-containing transcription factor, CgPdr1 (12,13). CgPdr1 can directly bind to drugs and xenobiotics and stimulates drug efflux (14).…”