Hinge-Region O-Glycosylation of Human Immunoglobulin G3 (IgG3)

R. Plomp, G. Dekkers, Y. Rombouts, R. Visser, C.A.M. Koeleman, G.S.M. Kammeijer, B.C. Jansen, T. Rispens, P.J. Hensbergen, G. Vidarsson, M. Wuhrer

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Abstract

Immunoglobulin G (IgG) is one of the most abundant proteins present in human serum and a fundamental component of the immune system. IgG3 represents ∼8% of the total amount of IgG in human serum and stands out from the other IgG subclasses because of its elongated hinge region and enhanced effector functions. This study reports partial O-glycosylation of the IgG3 hinge region, observed with nanoLC-ESI-IT-MS(/MS) analysis after proteolytic digestion. The repeat regions within the IgG3 hinge were found to be in part O-glycosylated at the threonine in the triple repeat motif. Non-, mono- and disialylated core 1-type O-glycans were detected in various IgG3 samples, both poly- and monoclonal. NanoLC-ESI-IT-MS/MS with electron transfer dissociation fragmentation and CE-MS/MS with CID fragmentation were used to determine the site of IgG3 O-glycosylation. The O-glycosylation site was further confirmed by the recombinant production of mutant IgG3 in which potential O-glycosylation sites had been knocked out. For IgG3 samples from six donors we found similar O-glycan structures and site occupancies, whereas for the same samples the conserved N-glycosylation of the Fc CH2 domain showed considerable interindividual variation. The occupancy of each of the three O-glycosylation sites was found to be ∼10% in six serum-derived IgG3 samples and ∼13% in two monoclonal IgG3 allotypes
Original languageEnglish
Pages (from-to)1373-1384
JournalMolecular and Cellular Proteomics
Volume14
Issue number5
DOIs
Publication statusPublished - 2015

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