Characterization of Endogenous Human Fc?RIII by Mass Spectrometry Reveals Site, Allele and Sequence Specific Glycosylation.

ABSTRACT: The importance of IgG glycosylation, Fc-gamma receptor (Fc?R) single nucleotide polymorphisms and Fc?R copy number variations in fine tuning the immune response has been well established. There is a growing appreciation of the importance of glycosylation of Fc?Rs in modulating the Fc?R-IgG interaction based on the association between the glycosylation of recombinant Fc?Rs and the kinetics and affinity of the Fc?R-IgG interaction. Although glycosylation of recombinant Fc?Rs has been recently characterized, limited knowledge exists on the glycosylation of endogenous human Fc?Rs. In order to improve the structural understanding of Fc?Rs expressed on human cells we characterized the site specific glycosylation of native human Fc?RIII from neutrophils of 50 healthy donors and from matched plasma for 43 of these individuals. Through this analysis we have confirmed site specific glycosylation patterns previously reported for soluble Fc?RIII from a single donor, identified Fc?RIIIb specific Asn45 glycosylation and an allelic effect on glycosylation at Asn162 of Fc?RIIIb. Identification of Fc?RIIIb specific glycosylation allows for assignment of Fc?RIIIb alleles and relative copy number of the two alleles where DNA/RNA is not available. Intriguingly the types of structures found to be elevated at Asn162 in the NA2 allele have been shown to destabilize the Fc:Fc?RIII interaction resulting in a faster dissociation rate. These differences in glycosylation may in part explain the differential activity reported for the two alleles which have similar in vitro affinity for IgG.

SUBMITTER: Washburn N 

PROVIDER: S-EPMC6398215 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature