Recenzováno
Zwitterionic and acidic glycosphingolipids of the Drosophila melanogaster embryo
Defining glycosphingolipid structures in species amenable to genetic manipulation, such as Drosophila melanogaster, provides a foundation for investigating mechanisms that regulate glycolipid expression. Therefore, eight of the 12 major glycosphingolipids, accounting for 64% of lipid-linked carbohydrate in Drosophila embryos, were purified after separation into acidic and zwitterionic pools. The zwitterionic lipids possess phosphoethanolamine (PEtn) linked to one or more GlcNAc residues and comprise a family of serially related structures. The longest characterized glycolipid, an octaosylceramide, designated Nz₂8, has the structure: GalNAcβ,4(PEtn-6)GlcNAcβ,3Galβ,3GalNAcα,4GalNAcβ,4(PEtn-6)GlcNAcβ,3Manβ,4GlcβCer. Heptaosyl (Nz7), hexaosyl (Nz6), pentaosyl (Nz5) and tetraosyl (Nz4) forms of Nz₂8, sequentially truncated from the nonreducing terminus, possess only one PEtn moiety. The major acidic lipid, designated Az₂9, possesses two PEtn moieties and a glucuronic acid linked to a Gal-extended Nz₂8. Two other acidic glycolipids, Az9 and Az6, exhibit one PEtn moiety and the same hexose and N-acetylhexosamine composition as Az₂9 and Nz6, respectively. The fully extended Drosophila core oligosaccharide differs from that of other dipterans in the linkage at a single glycosidic bond, a distinction with significant structural and biosynthetic consequences. Furthermore, acidic species account for a larger proportion of total glycosphingolipid, and PEtn substitution of GlcNAc is more complete in the Drosophila embryo. Divergent characteristics may reflect interspecies variation or stage-specific glycosphingolipid expression in dipterans
Článek, 2000