Analysis of O-glycan heterogeneity in IgA1 myeloma proteins by Fourier transform ion cyclotron resonance mass spectrometry: implications for IgA nephropathy.
IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis. In IgAN, IgA1 molecules with incompletely galactosylated O-linked glycans in the hinge region (HR) are present in mesangial immunodeposits and in circulating immune complexes. It is not known whether the galactose deficiency in IgA1 proteins occurs randomly or preferentially at specific sites. We have previously demonstrated the first direct localization of multiple O-glycosylation sites on a single IgA1 myeloma protein by use of activated ion-electron capture dissociation (AI-ECD) Fourier transform ion cyclotron resonance (FT-ICR) tandem mass spectrometry. Here, we report the analysis of IgA1 O-glycan heterogeneity by use of FT-ICR MS and liquid chromatography FT-ICR MS to obtain unbiased accurate mass profiles of IgA1 HR glycopeptides from three different IgA1 myeloma proteins. Additionally, we report the first AI-ECD fragmentation on an individual IgA1 O-glycopeptide from an IgA1 HR preparation that is reproducible for each IgA1 myeloma protein. These results suggest that future analysis of IgA1 HR from IgAN patients and normal healthy controls should be feasible.
Renfrow
Matthew B
MB
UAB Biomedical FT-ICR MS Laboratory, Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, MCLM 570 1530 3rd AVE S, Birmingham, AL 35294-0005, USA. renfrow@uab.edu
Mackay
C Logan
CL
Chalmers
Michael J
MJ
Julian
Bruce A
BA
Mestecky
Jiri
J
Kilian
Mogens
M
Poulsen
Knud
K
Emmett
Mark R
MR
Marshall
Alan G
AG
Novak
Jan
J
D017357:Cyclotrons; D005583:Fourier Analysis; D005922:Glomerulonephritis, IGA; D006801:Humans; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D009194:Myeloma Proteins / Q000737:chemistry*; D011134:Polysaccharides / Q000032:analysis*
D009194:Myeloma Proteins; D011134:Polysaccharides