Background: Multi-Drug Resistance pumps contribute to acquired and intrinsic resistance to azoles in species of pathogenic fungi, and their inhibition may significantly enhance the clinical utility of these azoles. We previously reported the identification of Fungal Efflux Pump Inhibitors (FEPIs) of several chemical classes with inhibitory activity against multiple CDR-type pumps from C. albicans and C. glabrata. We sought to investigate whether or not the interactions of various classes of FEPI with both CDR1 and the highly homologous CgCDR1 pump from C. glabrata are similar. Methods: Compounds from each class were used to isolate mutations in cdr1 from C. albicans that resulted in resistance to fluconazole potentiation by various FEPIs (potR). After identifying cdr1 potR mutations, we generated six mutations in cgcdr1 based on alignment between the two genes. Mutant CgCDR1s were shown to be resistant to fluconazole potentiation with at least one FEPI, indicating the relevance of each of the altered amino acids in the interactions with the inhibitor(s). We compared the patterns of responses to individual FEPIs for CDR1 and CgCDR1 potR mutants. Results: We found that mutation of cdr1 Gly521 and cgcdr1 Gly518 to Asp resulted in resistance in all FEPI classes, indicating the importance of this amino acid in the interaction of all FEPIs with both pumps. Conversely, none of the other amino acid changes in CDR1 or CgCDR1 resulted in a similar uniformly resistant profile; the effects were more class- or compound-specific. Conclusions: These data indicate that a FEPI with activity against both C. albicans and C. glabrata may bind to overlapping but not identical sets of amino acids in CDR1 and CgCDR1 efflux pumps, and also are suggestive of similar (but not identical) binding sites for various FEPI classes. Further analysis of the potR mutants may provide insights into the mechanism of binding to various pumps by different classes of inhibitors.
Full conference title:
42nd Interscience Conference on Antimicrobial Agents and Chemotherapy
- ICAAC 42nd