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Mol Cell Proteomics. 2014 Nov;13(11):3097-113. doi: 10.1074/mcp.M114.039693. Epub 2014 Jul 28.

Identification of distinct glycoforms of IgA1 in plasma from patients with immunoglobulin A (IgA) nephropathy and healthy individuals.

Author information

1
From the Departments of ‡Biochemistry and.
2
§Department of Cellular and Molecular Medicine, Copenhagen Center for Glycomics, Copenhagen, Denmark;
3
¶Department of Molecular Cell Biology & Immunology, VU University Medical Center, Amsterdam, The Netherlands.
4
‖Medicine, Emory University School of Medicine, Atlanta, GA 30322;
5
From the Departments of ‡Biochemistry and tju@emory.edu.

Abstract

Immunoglobulin A nephropathy (IgAN) is the most common form of glomerulonephritis worldwide and is histologically characterized by the deposition of IgA1 and consequent inflammation in the glomerular mesangium. Prior studies suggested that serum IgA1 from IgAN patients contains aberrant, undergalactosylated O-glycans, for example, Tn antigen and its sialylated version, SialylTn (STn), but the mechanisms underlying aberrant O-glycosylation are not well understood. Here we have used serial lectin separation technologies, Western blot, enzymatic modifications, and mass spectrometry to explore whether there are different glycoforms of IgA1 in plasma from patients with IgAN and healthy individuals. Although total plasma IgA in IgAN patients was elevated ∼ 1.6-fold compared with that in healthy donors, IgA1 in all samples was unexpectedly separable into two distinct glycoforms: one with core 1 based O-glycans, and the other exclusively containing Tn/STn structures. Importantly, Tn antigen present on IgA1 from IgAN patients and controls was convertible into the core 1 structure in vitro by recombinant T-synthase. Our results demonstrate that undergalactosylation of O-glycans in IgA1 is not restricted to IgAN and suggest that in vivo inefficiency of T-synthase toward IgA1 in a subpopulation of B or plasma cells, as well as overall elevation of IgA, may contribute to IgAN pathogenesis.

PMID:
25071157
PMCID:
PMC4223494
DOI:
10.1074/mcp.M114.039693
[Indexed for MEDLINE]
Free PMC Article
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