Abstract
Major neutral glycosphingolipid components were extracted from Sporothrix schenckii, a dimorphic fungus exhibiting a hyphal saprophytic phase and a yeast parasitic phase responsible for chronic mycotic infections in mammalian hosts. These components, one from the mycelial form and two from the yeast form, were purified and their structures were elucidated by 1H nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and tandem ESI-MS/MS. All three were characterized as cerebrosides (monohexosylceramides) containing (4E, 8E)-9-methyl-4,8-sphingadienine as the long-chain base attached to N-2′-hydroxyoctadecanoate and N-2′-hydroxy-(E)-Δ3-octadecenoate as the fatty acyl components. However, while the mycelial form expressed only β-glucopyranosylceramide, the yeast form expressed both β-gluco- and β-galactopyranosylceramides in approximately equal amounts. In addition, while the glucosylceramides of both mycelial and yeast forms had similar proportions of saturated and (E)-Δ3 unsaturated 2-hydroxy fatty acid, the galactocerebroside of the yeast form had significantly higher levels of (E)-Δ3 unsaturation. The differences in cerebroside hexose structure represent a novel type of glycosphingolipid dimorphism not previously reported in fungi. Possible implications of these findings with respect to regulation of morphological transitions in S. schenckii and other dimorphic fungi are discussed.—Toledo, M. S., S. B. Levery, A. H. Straus, and H. K. Takahashi. Dimorphic expression of cerebrosides in the mycopathogen Sporothrix schenckii. J. Lipid Res. 2000. 41: 797–806.
Highlights
Major neutral glycosphingolipid components were extracted from Sporothrix schenckii, a dimorphic fungus exhibiting a hyphal saprophytic phase and a yeast parasitic phase responsible for chronic mycotic infections in mammalian hosts
1H-nuclear magnetic resonance (NMR) spectroscopic analysis of S. schenckii cerebrosides. Both 1H- and 13C-NMR spectra for several fungal cerebrosides have been previously acquired in DMSO-d6/2% D2O at 35ЊC and all resonances assigned by homonuclear and heteronuclear 2-D correlation methods [33]. It was sufficient for the present work to obtain 1-D 1H-NMR spectra on the three S. schenckii cerebrosides under identical conditions in order to characterize them with respect to monosaccharide identity and key ceramide structural features, including the presence or absence of (E)-⌬3-unsaturation of the 2-hydroxy fatty Nacyl moiety
A careful examination by multiple techniques of cerebrosides from both forms of S. schenckii revealed a dimorphism with respect to hexose composition which correlated with the phenotypic dimorphism exhibited by this fungus
Summary
Major neutral glycosphingolipid components were extracted from Sporothrix schenckii, a dimorphic fungus exhibiting a hyphal saprophytic phase and a yeast parasitic phase responsible for chronic mycotic infections in mammalian hosts. These components, one from the mycelial form and two from the yeast form, were purified and their structures were elucidated by 1H nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and tandem ESI-MS/MS. Sporothrix schenckii, the causative agent of sporotrichosis, is a dimorphic fungus that exhibits a hyphal morphology in its low temperature saprophytic phase, but is found primarily as a budding yeast in host tissues.
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