UPC2A is required for high-level azole antifungal resistance in Candida glabrata

Antimicrob Agents Chemother. 2014 Aug;58(8):4543-54. doi: 10.1128/AAC.02217-13. Epub 2014 May 27.


Candida glabrata, the second most common cause of Candida infections, is associated with high rates of mortality and often exhibits resistance to the azole class of antifungal agents. Upc2 and Ecm22 in Saccharomyces cerevisiae and Upc2 in Candida albicans are the transcriptional regulators of ERG11, the gene encoding the target of azoles in the ergosterol biosynthesis pathway. Recently two homologs for these transcription factors, UPC2A and UPC2B, were identified in C. glabrata. One of these, UPC2A, was shown to influence azole susceptibility. We hypothesized that due to the global role for Upc2 in sterol biosynthesis in S. cerevisiae and C. albicans, disruption of UPC2A would enhance the activity of fluconazole in both azole-susceptible dose-dependent (SDD) and -resistant C. glabrata clinical isolates. To test this hypothesis, we constructed mutants with disruptions in UPC2A and UPC2B alone and in combination in a matched pair of clinical azole-SDD and -resistant isolates. Disruption of UPC2A in both the SDD and resistant isolates resulted in increased susceptibility to sterol biosynthesis inhibitors, including a reduction in fluconazole MIC and minimum fungicidal concentration, enhanced azole activity by time-kill analysis, a decrease in ergosterol content, and downregulation of baseline and inducible expression of several sterol biosynthesis genes. Our results indicate that Upc2A is a key regulator of ergosterol biosynthesis and is essential for resistance to sterol biosynthesis inhibitors in C. glabrata. Therefore, the UPC2A pathway may represent a potential cotherapeutic target for enhancing azole activity against this organism.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antifungal Agents / pharmacology*
  • Azoles / pharmacology*
  • Candida albicans / drug effects
  • Candida albicans / genetics
  • Candida albicans / metabolism
  • Candida glabrata / drug effects*
  • Candida glabrata / genetics
  • Candida glabrata / metabolism
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism
  • Drug Resistance, Fungal / genetics*
  • Ergosterol / biosynthesis
  • Fluconazole / pharmacology
  • Gene Expression Regulation, Fungal*
  • Microbial Sensitivity Tests
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Trans-Activators / deficiency
  • Trans-Activators / genetics*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription, Genetic


  • Antifungal Agents
  • Azoles
  • ECM22 protein, S cerevisiae
  • Protein Isoforms
  • Saccharomyces cerevisiae Proteins
  • Trans-Activators
  • Transcription Factors
  • UPC2 protein, S cerevisiae
  • Fluconazole
  • Cytochrome P-450 Enzyme System
  • Erg11 protein, S cerevisiae
  • Ergosterol