title: Unraveling unique structure and biosynthesis pathway of N-linked glycans in human fungal pathogen Cryptococcus neoformans by glycomics analysis.
abstract: The encapsulated fungal pathogen Cryptococcus neoformans causes cryptococcosis in immunocompromised individuals. Although cell surface mannoproteins have been implicated in C. neoformans pathogenicity, the structure of N-linked glycans assembled on mannoproteins has not yet been elucidated. By analyzing oligosaccharide profiles combined with exoglycosidase treatment, we report here that C. neoformans has serotype-specific high mannose-type N-glycans with or without a β1,2-xylose residue, which is attached to the trimannosyl core of N-glycans. Interestingly, the neutral N-glycans of serotypes A and D were shown to contain a xylose residue, whereas those of serotype B appeared to be much shorter and devoid of a xylose residue. Moreover, analysis of the C. neoformans uxs1Δ mutant demonstrated that UDP-xylose is utilized as a donor sugar in N-glycan biosynthesis. We also constructed and analyzed a set of C. neoformans mutant strains lacking genes putatively assigned to the reconstructed N-glycan biosynthesis pathway. It was shown that the outer chain of N-glycan is initiated by CnOch1p with addition of an α1,6-mannose residue and then subsequently extended by CnMnn2p with multiple additions of α1,2-mannose residues. Finally, comparative analysis of acidic N-glycans from wild-type, Cnoch1Δ, Cnmnn2Δ, and Cnuxs1Δ strains strongly indicated the presence of xylose phosphate attached to mannose residues in the core and outer region of N-glycans. Our data present the first report on the unique structure and biosynthesis pathway of N-glycans in C. neoformans.
authors.affiliation: Department of Life Science, Center for Fungal Pathogenesis, Chung-Ang University, Seoul 156-756, South Korea.
authors.forename: Jeong-Nam
authors.initials: JN
authors.lastname: Park
authors.forename: Dong-Jik
authors.initials: DJ
authors.lastname: Lee
authors.forename: Ohsuk
authors.initials: O
authors.lastname: Kwon
authors.forename: Doo-Byoung
authors.initials: DB
authors.lastname: Oh
authors.forename: Yong-Sun
authors.initials: YS
authors.lastname: Bahn
authors.forename: Hyun Ah
authors.initials: HA
authors.lastname: Kang
mesh_terms: D002236:Carbohydrate Conformation; D050260:Carbohydrate Metabolism / Q000502:physiology*; D003453:Cryptococcosis / Q000235:genetics / Q000378:metabolism; D003455:Cryptococcus neoformans / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D054794:Glycomics / Q000379:methods; D006801:Humans; D009154:Mutation; D011134:Polysaccharides / Q000096:biosynthesis* / Q000235:genetics; D014994:Xylose / Q000378:metabolism
chemical_list: D011134:Polysaccharides; D014994:Xylose