title: Presence of beta-linked GalNAc residues on N-glycans of human thyroglobulin.
abstract: Hepatic asialoglycoprotein receptor, which may mediate the clearance of circulating thyroglobulin, is known to have a high affinity for GalNAc. Recently, the receptor has been reported to be present also in the thyroid, implicating interaction with thyroglobulin. Here, mammalian thyroglobulins were analyzed for GalNAc termini by Western blotting with GalNAc-recognizing lectins labeled with peroxidase or (125)I. Wistaria floribunda lectin was found to bind human thyroglobulin and, to some extent, bovine, but not porcine thyroglobulin. After desialylation, the lectin bound all of the thyroglobulins tested. The binding was inhibited by competitive inhibitor GalNAc. Peptide N-glycanase treatment of human desialylated thyroglobulin resulted in the complete loss of reactivity with W. floribunda lectin, indicating that the binding sites are exclusively on N-glycans. The binding sites on human desialylated thyroglobulin were partly sensitive to beta-galactosidase, and the remainder was essentially sensitive to beta-N-acetylhexosaminidase. On the other hand, the binding sites of bovine and porcine desialylated thyroglobulins were totally sensitive to beta-galactosidase. Thus the lectin binds beta-Gal termini, as well as beta-GalNAc. GalNAc-specific Dolichos biflorus lectin also bound human thyroglobulin weakly. In contrast to W. floribunda lectin, desialylation diminished binding, suggesting that these two lectins recognize different GalNAc-terminated structures. Again, the binding was inhibited by GalNAc and by treatment with peptide N-glycanase. These results strongly indicate the presence of distinct GalNAc termini of N-glycans on human thyroglobulin.
authors.affiliation: Department of Legal Medicine, St. Marianna University School of Medicine, 1-16-2 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan. a2takeya@marianna-u.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Takeya
authors.forename: Osamu
authors.initials: O
authors.lastname: Hosomi
authors.forename: Hironori
authors.initials: H
authors.lastname: Nishijima
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Ohe
authors.forename: Kunio
authors.initials: K
authors.lastname: Sugahara
authors.forename: Morihisa
authors.initials: M
authors.lastname: Sagi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yamazaki
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Hayakawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takeshita
authors.forename: Chizuko
authors.initials: C
authors.lastname: Sasaki
authors.forename: Tadahisa
authors.initials: T
authors.lastname: Kogure
authors.forename: Toshiji
authors.initials: T
authors.lastname: Mukai
mesh_terms: D000116:Acetylgalactosamine / Q000737:chemistry*; D000818:Animals; D037263:Asialoglycoprotein Receptor / Q000737:chemistry*; D001665:Binding Sites; D015153:Blotting, Western; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007455:Iodine / Q000032:analysis; D037121:Plant Lectins / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry*; D034781:Receptors, N-Acetylglucosamine / Q000737:chemistry*; D013552:Swine; D013954:Thyroglobulin / Q000737:chemistry*
chemical_list: D037263:Asialoglycoprotein Receptor; D037121:Plant Lectins; D011134:Polysaccharides; D034781:Receptors, N-Acetylglucosamine; C036554:dolichos biflorus agglutinin; C040129:wisteria lectin; D013954:Thyroglobulin; D007455:Iodine; D000116:Acetylgalactosamine