title: Unraveling the novel structure and biosynthetic pathway of O-linked glycans in the Golgi apparatus of the human pathogenic yeast Cryptococcus neoformans.
abstract: Cryptococcus neoformans is an encapsulated basidiomycete causing cryptococcosis in immunocompromised humans. The cell surface mannoproteins of C. neoformans were reported to stimulate the host T-cell response and to be involved in fungal pathogenicity; however, their O-glycan structure is uncharacterized. In this study, we performed a detailed structural analysis of the O-glycans attached to cryptococcal mannoproteins using HPLC combined with exoglycosidase treatment and showed that the major C. neoformans O-glycans were short manno-oligosaccharides that were connected mostly by α1,2-linkages but connected by an α1,6-linkage at the third mannose residue. Comparison of the O-glycan profiles from wild-type and uxs1Δ mutant strains strongly supports the presence of minor O-glycans carrying a xylose residue. Further analyses of C. neoformans mutant strains identified three mannosyltransferase genes involved in O-glycan extensions in the Golgi. C. neoformans KTR3, the only homolog of the Saccharomyces cerevisiae KRE2/MNT1 family genes, was shown to encode an α1,2-mannosyltransferase responsible for the addition of the second mannose residue via an α1,2-linkage to the major O-glycans. C. neoformans HOC1 and HOC3, homologs of the Saccharomyces cerevisiae OCH1 family genes, were shown to encode α1,6-mannosyltransferases that can transfer the third mannose residue, via an α1,6-linkage, to minor O-glycans containing xylose and to major O-glycans without xylose, respectively. Moreover, the C. neoformans ktr3Δ mutant strain, which displayed increased sensitivity to SDS, high salt, and high temperature, showed attenuated virulence in a mouse model of cryptococcosis, suggesting that the extended structure of O-glycans is required for cell integrity and full pathogenicity of C. neoformans.
authors.affiliation: From the Department of Life Science, Center for Fungal Pathogenesis, and.
authors.forename: Dong-Jik
authors.initials: DJ
authors.lastname: Lee
authors.affiliation: the Department of Biotechnology, Center for Fungal Pathogenesis, Yonsei University, Seoul 120-749, Korea.
authors.forename: Yong-Sun
authors.initials: YS
authors.lastname: Bahn
authors.affiliation: the College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea and.
authors.forename: Hong-Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: From the Department of Life Science, Center for Fungal Pathogenesis, and.
authors.forename: Seung-Yeon
authors.initials: SY
authors.lastname: Chung
authors.affiliation: From the Department of Life Science, Center for Fungal Pathogenesis, and hyunkang@cau.ac.kr.
authors.forename: Hyun Ah
authors.initials: HA
authors.lastname: Kang
mesh_terms: D000818:Animals; D002473:Cell Wall / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003453:Cryptococcosis / Q000378:metabolism / Q000382:microbiology*; D003455:Cryptococcus neoformans / Q000378:metabolism*; D005260:Female; D005656:Fungal Proteins / Q000378:metabolism; D005816:Genetic Complementation Test; D006031:Glycosylation; D016695:Glycosyltransferases / Q000378:metabolism; D008358:Mannose / Q000737:chemistry; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism*; D008543:Melanins / Q000737:chemistry; D051379:Mice; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D011134:Polysaccharides / Q000096:biosynthesis*; D011487:Protein Conformation; D014994:Xylose / Q000737:chemistry
chemical_list: D005656:Fungal Proteins; D008543:Melanins; D011134:Polysaccharides; D014994:Xylose; D016695:Glycosyltransferases; D008364:Mannosyltransferases; D008358:Mannose
keywords: Cell Wall; Cryptococcus neoforman; Fungi; Glycan Analysis; Glycomics; Glycoprotein; Glycosyltransferase; Mannosyltransferases; O-Mannosylation