Methodological approaches to the analysis of IgA1 O-glycosylation in IgA nephropathy.
IgA nephropathy (IgAN) is a common form of glomerulonephritis in which IgA1 molecules deposit in the renal mesangium, leading to progressive glomerular inflammatory injury in a significant proportion of patients. The mechanisms underlying the pathogenesis of IgAN remain poorly understood, but altered O-glycosylation, a physicochemical abnormality of IgA1 observed in these patients, may be a contributory factor. Although many studies have reported aberrant IgA1 O-glycosylation in IgAN, the precise structural nature of the defect remains to be fully characterised, and analysis of IgA1 O-glycans has proved technically challenging. Three main strategies have been employed: lectin binding to the O-glycans in situ on the whole IgA1 molecule; mass spectroscopy of isolated O-glycosylated glycopeptides; and size/charge separation of free O-glycans released from IgA1. In this review, the basic principles, strengths and weaknesses of each of these methodological approaches are considered, together with a summary of the data obtained from their use. One of the common criticisms of many studies of IgA1 O-glycosylation is the method of IgA1 purification employed, and therefore, this issue is also critically discussed.
Allen
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AC
Department of Nephrology, Leicester General Hospital, UK. aa50@le.ac.uk
D002846:Chromatography, Affinity; D004586:Electrophoresis; D005922:Glomerulonephritis, IGA / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D007070:Immunoglobulin A / Q000302:isolation & purification / Q000378:metabolism*; D013058:Mass Spectrometry
D007070:Immunoglobulin A