Structural analyses of O-glycan sugar chains on IgA1 hinge region using SELDI-TOFMS with various lectins.

The aim of the study was to develop a simple and precise method for identifying glycosylation of the IgA hinge region using surface-enhanced laser desorption/ionization (SELDI)-TOFMS with a lectin-coupled ProteinChip array. Serum IgA was isolated using an anti-IgA antibody column. Following reduction, alkylation, and trypsin digestion, the IgA fragments were applied on the ProteinChip coupled with jacalin, peanut agglutinin (PNA), or Vilsa villosa lectin (VVL). The SELDI-TOFMS peaks corresponding to the fragments containing IgA1 hinge glycopeptides trapped by each lectin were compared. The jacalin-, PNA-, and VVL-immobilized ProteinChips detected 13, 4, and 2 peaks, respectively. One major peak was confirmed as a glycopeptide by MS/MS analysis. These results suggest that a lectin-immobilized ProteinChip assay can be used to simplify the procedures for the analyses of the O-glycans in IgA1 hinge. This method potentially makes it possible to identify a disease-specific glycoform by selecting the appropriate ligand-coupled ProteinChip array.