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CRS–MIS in C andida glabrata : sphingolipids modulate echinocandin– Fks interaction
Author(s) -
Healey Kelley R.,
Katiyar Santosh K.,
Raj Shriya,
Edlind Thomas D.
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2012.08194.x
Subject(s) - biology , echinocandin , sphingolipid , mutant , echinocandins , micafungin , candida glabrata , in vitro , yeast , biochemistry , saccharomyces cerevisiae , microbiology and biotechnology , caspofungin , gene , candida albicans , antifungal , fluconazole , amphotericin b
Summary Infections with the azole‐refractory yeast C andida glabrata are now commonly treated with the echinocandins caspofungin ( CSF ) or micafungin ( MCF ). True resistance (> 32‐fold decreased susceptibility) to these lipopeptide inhibitors of cell wall synthesis is rare and strictly associated with mutations in integral membrane proteins F ks1 or F ks2. In contrast, mutants exhibiting 4‐ to 32‐fold CSF reduced susceptibility ( CRS ) were readily selected in vitro , and surprisingly demonstrated 4‐ to 32‐fold MCF increased susceptibility ( MIS ). Sequencing and gene deletion demonstrated that CRS–MIS is F ks‐independent. To explore alternative mechanisms, we initially employed S accharomyces cerevisiae , and observed that CRS was conferred by multiple mutations ( fen1 Δ, sur4 Δ, cka2 Δ and tsc10‐ts ) disrupting sphingolipid biosynthesis. Following this lead, C . glabrata fen1 Δ and cka2 Δ deletants were constructed, and shown to exhibit CRS–MIS . Sphingolipid analysis of CRS–MIS laboratory mutants and clinical isolates demonstrated elevated dihydrosphingosine ( DHS ) and phytosphingosine ( PHS ) levels, and consistent with this sequencing revealed fen1 , sur4 , ifa38 and sur2 mutations. Moreover, exogenous DHS or PHS conferred a CRS–MIS phenotype on wild‐type C . glabrata . Exogenous PHS failed, however, to suppress CRS–MIS in a sur2 mutant blocked in conversion of DHS to PHS , implying that accumulation of these intermediates confers CRS–MIS . We conclude that membrane sphingolipids modulate echinocandin– F ks interaction.