Analysis of glycosylinositol phosphorylceramides expressed by the opportunistic mycopathogen Aspergillus fumigatus.

Acidic glycosphingolipid components were ex- tracted from the opportunistic mycopathogen Aspergillus fumigatus and identified as inositol phosphorylceramide and glycosylinositol phosphorylceramides (GIPCs). Using nuclear magnetic resonance sppectroscopy, mass spec- trometry, and other techniques, the structures of six major components were elucidated as Ins-P-Cer (Af-0), Manp (a1Y3)Manp(a1Y2)Ins-P-Cer (Af-2), Manp(a1Y2)Manp (a1Y3)Manp(a1Y2)Ins-P-Cer (Af-3a), Manp (a1Y3) (Galf(b1Y6))Manp(a1Y2)-Ins-P-Cer (Af-3b), Manp (a1Y2)-Manp(a1Y3)(Galf(b1Y6))Manp(a1Y2)Ins-P-Cer (Af-4), and Manp(a1Y3)Manp(a1Y6)GlcpN(a1Y2)Ins-P- Cer (Af-3c) (where Ins 5 myo-inositol and P 5 phosphodi- ester). A minor A. fumigatus GIPC was also identified as the N-acetylated version of Af-3c (Af-3c*), which suggests that formation of the GlcNa1Y2Ins linkage may proceed by a two-step process, similar to the GlcNa1Y6Ins linkage in glycosylphosphatidylinositol (GPI) anchors (transfer of GlcNAc, followed by enzymatic de-N-acetylation). The glycosylinositol of Af-3b, which bears a distinctive branch- ing Galf (b1Y6) residue, is identical to that of a GIPC isolated previously from the dimorphic mycopathogen Paracoccidioides brasiliensis (designated Pb-3), but com- ponents Af-3a and Af-4 have novel structures. Overlay immunostaining of A. fumigatus GIPCs separated on thin- layer chromatograms was used to assess their reactivity against sera from a patient with aspergillosis and against a murine monoclonal antibody (MEST-1) shown previously to react with the Galf (b1Y6) residue in Pb-3. These results are discussed in relation to pathogenicity and potential approaches to the immunodiagnosis of A. fumi- gatus.— Toledo, M. S., S. B. Levery, B. Bennion, L. L. Guimaraes, S. A. Castle, R. Lindsey, M. Momany, C. Park, A. H. Straus, and H. K. Takahashi. Analysis of glycosyl- inositol phosphorylceramides expressed by the opportu- nistic mycopathogen Aspergillus fumigatus. J. Lipid Res. 2007. 48: 1801-1824.