Taxonomic group: fungi / Basidiomycota
(Phylum: Basidiomycota)
Organ / tissue: capsuleAssociated disease: infection due to Cryptococcus neoformans [ICD11:
XN3EH 
]
NCBI PubMed ID: 32005661Publication DOI: 10.1074/jbc.RA119.012251Journal NLM ID: 2985121RPublisher: Baltimore, MD: American Society for Biochemistry and Molecular Biology
Correspondence: Oscarson S <stefan.oscarson
ucd.ie>; Casadevall A <acasade1
jhu.edu>
Institutions: Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, USA, Centre for Synthesis and Chemical Biology, University College Dublin, Ireland
Chemical biology is an emerging field that enables the study and manipulation of biological systems with probes whose reactivities provide structural insights. The opportunistic fungal pathogen Cryptococcus neoformans possesses a polysaccharide capsule that is a major virulence factor, but is challenging to study. We report here the synthesis of a hydroxylamine-armed fluorescent probe that reacts with reducing glycans and its application to study the architecture of the C. neoformans capsule under a variety of conditions. The probe signal localized intracellularly and at the cell wall-membrane interface, implying the presence of reducing-end glycans at this location where the capsule is attached to the cell body. In contrast, no fluorescence signal was detected in the capsule body. We observed vesicle-like structures containing the reducing-end probe, both intra- and extracellularly, consistent with the importance of vesicles in capsular assembly. Disrupting the capsule with DMSO, ultrasound, or mechanical shear stress resulted in capsule alterations that affected the binding of the probe, as reducing ends were exposed and cell membrane integrity was compromised. Unlike the polysaccharides in the assembled capsule, isolated exopolysaccharides contained reducing ends. The reactivity of the hydroxylamine-armed fluorescent probe suggests a model for capsule assembly whereby reducing ends localize to the cell wall surface, supporting previous findings suggesting that this is an initiation point for capsular assembly. We propose that chemical biology is a promising approach for studying the C. neoformans capsule and its associated polysaccharides to unravel their roles in fungal virulence.
biosynthesis, polysaccharide, capsule, virulence factor, glycobiology, chemical biology, fungi, Glucuronoxylomannan, fungal pathogen, vesicles, extracellular vesicles, aminooxy fluorescent probes, reducing glycans
Structure type: suggested polymer biological repeating unit
Location inside paper: Fig. 8
Trivial name: glucuronoxylomannan (GXM)
Compound class: CPS, EPS, O-polysaccharide, O-antigen, cell wall polysaccharide, polysaccharide, glucuronoxylomannan, capsule polysaccharide
Contained glycoepitopes: IEDB_114701,IEDB_115136,IEDB_115576,IEDB_130701,IEDB_140116,IEDB_140630,IEDB_144983,IEDB_145668,IEDB_152206,IEDB_164174,IEDB_167188,IEDB_174332,IEDB_423153,IEDB_76933,IEDB_983930,SB_197,SB_44,SB_67,SB_72
Methods: 13C NMR, 1H NMR, NMR-2D, TLC, biological assays, cell growth, LC-MS/MS, fluorescence microscopy, HR-ESI-MS, fluorescence labeling, spectrophotometry, evaporation, centrifugation, flash chromatography, filtration
Related record ID(s): 178, 9356, 40552, 40728, 40734, 41250, 42132, 43806, 43814, 43913, 44119, 44282, 110711, 130362, 130611, 136943, 143856, 148625
NCBI Taxonomy refs (TaxIDs): 40410Reference(s) to other database(s): GTC:G53406VG
Show glycosyltransferases
NMR conditions: at 298(H) K
[as TSV]
1H NMR data: present in publication
|
There is only one chemically distinct structure:
Found 
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(later renamed to: Cryptococcus neoformans var. neoformans ATCC 24067)