Characterization of sphingolipids from mycopathogens: Factors correlating with expression of 2-hydroxy fatty acyl (E)-Delta(3)-unsaturation in cerebrosides of Paracoccidioides brasiliensis and Aspergillus fumigatus

Significant differences exist between mammals and fungi with respect to gly cosphingolipid (GSL) structure and biosynthesis. Thus, these compounds, as well as the cellular machinery regulating their expression, have considerab le potential as targets for the diagnosis and treatment of fungal diseases. In this study, the major neutral GSL components extracted from both yeast and mycelium forms of the thermally dimorphic mycopathogen Paracoccidioides brasiliensis were purified and characterized by H-1 and C-13 NMR spectrosc opy, ESI-MS and ESI-MS/CID-MS, and GC-MS. The major GSLs of both forms were identified as beta-glucopyranosylceramides (GlcCer) having (4,8E)-9- methy l-4,8-sphingadienine as long chain base in combination with either N-2'-hyd roxyoctadecanoate or N-2'-hydroxy-(E)-3'-octadecenoate. The mycelium form G lcCer had both fatty acids in a similar to 1:1 ratio, while that of the yea st form had on average only similar to 15% of the (E)-Delta(3)-unsaturated fatty acid. Cerebrosides from two strains of Aspergillus fumigatus (237 and ATCC 9197) expressing both GalCer and GlcCer were also purified and charac terized by similar methods. The GalCer fractions were found to have similar to 70% and similar to 90% N-2'-hydroxy-(E)-3'-octadecenoate, respectively, in the two strains. In contrast, the GlcCer fractions had N-2'-hydroxy-(E) 3'-octadecenoate at only similar to 20 and similar to 50%, respectively. Th e remainder in all cases was the saturated 2-OH fatty acid, which has not b een previously reported in cerebrosides from A. fumigatus. The availability of detailed structures of both glycosylinositol phosphorylceramides [Lever y, S. B., Toledo, M. S., Straus, A. H. and Takahashi, H. K. (1998) Biochemi stry 37, 8764-8775] and cerebrosides from P. brasilienisis revealed paralle l quantitative differences in expression between yeast and mycelium forms, as well as a striking general partitioning of ceramide structure between th e two classes of GSLs. These results are discussed with respect to possible functional roles for fungal sphingolipids, particularly as they relate to the morphological transitions exhibited by P. brasiliensis.