Open AccessNew Fks Hot Spot for Acquired Echinocandin Resistance in Saccharomyces cerevisiae and Its Contribution to Intrinsic Resistance of Scedosporium Species
Author(s) -
Michael E. Johnson,
Säntosh K. Katiyar,
Thomas D. Edlind
Publication year - 2011
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.01811-10
Subject(s) - echinocandin , anidulafungin , micafungin , echinocandins , biology , candida glabrata , mutagenesis , mutant , microbiology and biotechnology , caspofungin , saccharomyces cerevisiae , mutation , genetics , candida albicans , gene , antifungal , amphotericin b , fluconazole
Echinocandins represent a new antifungal group with potent activity againstCandida species. These lipopeptides inhibit the synthesis of β-1,3-glucan, the major cell wall polysaccharide. Acquired resistance or reduced echinocandin susceptibility (RES) is rare and associated with mutations in two “hot spot” regions of Fks1 or Fks2, the probable β-1,3-glucan synthases. In contrast, many fungi demonstrate intrinsic RES for reasons that remain unclear. We are usingSaccharomyces cerevisiae to understand the basis for RES by modeling echinocandin-Fks interaction. Previously characterized mutations confer cross-RES; we screened for mutations conferring differential RES, implying direct interaction of that Fks residue with a variable echinocandin side chain. One mutant (in anfks1 Δ background) exhibited ≥16-fold micafungin and anidulafungin versus caspofungin RES. Sequencing identified a novel Fks2 mutation, W714L/Y715N. Equivalent W695L/Y696N and related W695L/F/C mutations in Fks1 generated by site-directed mutagenesis and the isolation of a W695L-equivalent mutation inCandida glabrata confirmed the role of the new “hot spot 3” in RES. Further mutagenesis expanded hot spot 3 to Fks1 residues 690 to 700, yielding phenotypes ranging from cross-RES to differential hypersusceptibility. Fks1 sequences from intrinsically RESScedosporium species revealed W695F-equivalent substitutions; Fks1 hybrids expressingScedosporium prolificans hot spot 3 confirmed that this substitution imparts RES.