title: Reactivities of N-acetylgalactosamine-specific lectins with human IgA1 proteins.
abstract: Lectins are proteins with specificity of binding to certain monosaccharides or oligosaccharides. They can detect abnormal glycosylation patterns on immunoglobulins in patients with various chronic inflammatory diseases, including rheumatoid arthritis and IgA nephropathy (IgAN). However, lectins exhibit binding heterogeneity, depending on their source and methods of isolation. To characterize potential differences in recognition of terminal N-acetylgalactosamine (GalNAc) on IgA1, we evaluated the binding characteristics of several commercial preparations of GalNAc-specific lectins using a panel of IgA1 and, as controls, IgA2 and IgG myeloma proteins. These lectins originated from snails Helix aspersa (HAA) and Helix pomatia (HPA), and the plant Vicia villosa (VV). Only HAA and HPA bound exclusively to IgA1, with its O-linked glycans composed of GalNAc, galactose, and sialic acid. In contrast, VV reacted with sugars of both IgA subclasses and IgG, indicating that it also recognized N-linked glycans without GalNAc. Furthermore, HAA and HPA from several manufacturers differed in their ability to bind various IgA1 myeloma proteins and other GalNAc-containing glycoproteins in ELISA and Western blot. For serum samples from IgAN patients, HAA was the optimal lectin to study IgA1 glycosylation in ELISA and Western blot assays, including identification of the sites of attachment of the aberrant glycans. The galactose-deficient glycans were site-specific, localized mostly at Thr228 and/or Ser230. Because of the heterogeneity of GalNAc-specific lectins, they should be carefully characterized with appropriate substrates before undertaking any study.
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Moore
authors.forename: Rose
authors.initials: R
authors.lastname: Kulhavy
authors.forename: Milan
authors.initials: M
authors.lastname: Tomana
authors.forename: Zina
authors.initials: Z
authors.lastname: Moldoveanu
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Rhubell
authors.initials: R
authors.lastname: Brown
authors.forename: Stacy
authors.initials: S
authors.lastname: Hall
authors.forename: Mogens
authors.initials: M
authors.lastname: Kilian
authors.forename: Knud
authors.initials: K
authors.lastname: Poulsen
authors.forename: Jiri
authors.initials: J
authors.lastname: Mestecky
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Julian
authors.forename: Jan
authors.initials: J
authors.lastname: Novak
mesh_terms: D000116:Acetylgalactosamine / Q000032:analysis*; D000595:Amino Acid Sequence; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D005922:Glomerulonephritis, IGA / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood / Q000737:chemistry* / Q000378:metabolism; D037102:Lectins / Q000378:metabolism*; D008969:Molecular Sequence Data; D037121:Plant Lectins / Q000378:metabolism*
chemical_list: C038095:Helix lectin; D007070:Immunoglobulin A; D037102:Lectins; D037121:Plant Lectins; C042242:Vicia lectins; D000116:Acetylgalactosamine