Unique Asn-linked oligosaccharides of the human pathogen Entamoeba histolytica
Magnelli, Paula ; Cipollo, John F. ; Ratner, Daniel M. ; Cui, Jike ; Kelleher, Daniel J. ; Gilmore, Reid ; Costello, Catherine E. ; Robbins, Phillips W. ; Samuelson, John
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Keywords
Asparagine
Concanavalin A
Endoplasmic Reticulum
Entamoeba histolytica
*Gene Expression Regulation
Glycosylation
Lectins
Mass Spectrometry
Models, Chemical
Molecular Conformation
Oligosaccharides
Polysaccharides
Protein Folding
alpha-Mannosidase
Biochemistry
Biochemistry, Biophysics, and Structural Biology
Molecular Biology
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Abstract
N-Glycans of Entamoeba histolytica, the protist that causes amebic dysentery and liver abscess, are of great interest for multiple reasons. E. histolytica makes an unusual truncated N-glycan precursor (Man(5)GlcNAc(2)), has few nucleotide sugar transporters, and has a surface that is capped by the lectin concanavalin A. Here, biochemical and mass spectrometric methods were used to examine N-glycan biosynthesis and the final N-glycans of E. histolytica with the following conclusions. Unprocessed Man(5)GlcNAc(2), which is the most abundant E. histolytica N-glycan, is aggregated into caps on the surface of E. histolytica by the N-glycan-specific, anti-retroviral lectin cyanovirin-N. Glc(1)Man(5)GlcNAc(2), which is made by a UDP-Glc: glycoprotein glucosyltransferase that is part of a conserved N-glycan-dependent endoplasmic reticulum quality control system for protein folding, is also present in mature N-glycans. A swainsonine-sensitive alpha-mannosidase trims some N-glycans to biantennary Man(3)GlcNAc(2). Complex N-glycans of E. histolytica are made by the addition of alpha1,2-linked Gal to both arms of small oligomannose glycans, and Gal residues are capped by one or more Glc. In summary, E. histolytica N-glycans include unprocessed Man(5)GlcNAc(2), which is a target for cyanovirin-N, as well as unique, complex N-glycans containing Gal and Glc.
Source
J Biol Chem. 2008 Jun 27;283(26):18355-64. doi: 10.1074/jbc.M800725200. Epub 2008 Apr 16.Link to article on publisher's site