title: A Sulfated Glycosaminoglycan Linkage Region is a Novel Type of Human Natural Killer-1 (HNK-1) Epitope Expressed on Aggrecan in Perineuronal Nets.
abstract: Human natural killer-1 (HNK-1) carbohydrate (HSO3-3GlcAβ1-3Galβ1-4GlcNAc-R) is highly expressed in the brain and required for learning and neural plasticity. We previously demonstrated that expression of the HNK-1 epitope is mostly abolished in knockout mice for GlcAT-P (B3gat1), a major glucuronyltransferase required for HNK-1 biosynthesis, but remained in specific regions such as perineuronal nets (PNNs) in these mutant mice. Considering PNNs are mainly composed of chondroitin sulfate proteoglycans (CSPGs) and regulate neural plasticity, GlcAT-P-independent expression of HNK-1 in PNNs is suggested to play a role in neural plasticity. However, the function, structure, carrier glycoprotein and biosynthetic pathway for GlcAT-P-irrelevant HNK-1 epitope remain unclear. In this study, we identified a unique HNK-1 structure on aggrecan in PNNs. To determine the biosynthetic pathway for the novel HNK-1, we generated knockout mice for GlcAT-S (B3gat2), the other glucuronyltransferase required for HNK-1 biosynthesis. However, GlcAT-P and GlcAT-S double-knockout mice did not exhibit reduced HNK-1 expression compared with single GlcAT-P-knockout mice, indicating an unusual biosynthetic pathway for the HNK-1 epitope in PNNs. Aggrecan was purified from cultured cells in which GlcAT-P and -S are not expressed and we determined the structure of the novel HNK-1 epitope using liquid chromatography/mass spectrometry (LC/MS) as a sulfated linkage region of glycosaminoglycans (GAGs), HSO3-GlcA-Gal-Gal-Xyl-R. Taken together, we propose a hypothetical model where GlcAT-I, the sole glucuronyltransferase required for synthesis of the GAG linkage, is also responsible for biosynthesis of the novel HNK-1 on aggrecan. These results could lead to discovery of new roles of the HNK-1 epitope in neural plasticity.
authors.affiliation: Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Yabuno
authors.affiliation: Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
authors.forename: Jyoji
authors.initials: J
authors.lastname: Morise
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kizuka
authors.affiliation: Division of Biological Chemistry and Biologicals, National Institute of Health Sciences, Tokyo, 158-8501, Japan.
authors.forename: Noritaka
authors.initials: N
authors.lastname: Hashii
authors.affiliation: Division of Biological Chemistry and Biologicals, National Institute of Health Sciences, Tokyo, 158-8501, Japan.
authors.forename: Nana
authors.initials: N
authors.lastname: Kawasaki
authors.affiliation: Department of Anatomy and Embryology Faculty of Medicine University of Tsukuba, Tsukuba, 305-8575, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Department of Biochemistry, Kobe Pharmaceutical University, Kobe, 658-8558, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Miyata
authors.affiliation: Department of Biochemistry, Kobe Pharmaceutical University, Kobe, 658-8558, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Izumikawa
authors.affiliation: Department of Biochemistry, Kobe Pharmaceutical University, Kobe, 658-8558, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitagawa
authors.affiliation: Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
authors.forename: Hiromu
authors.initials: H
authors.lastname: Takematsu
authors.affiliation: Department of Biological Chemistry, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Oka
mesh_terms: D053674:Aggrecans / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D018959:CD57 Antigens / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism; D002853:Chromatography, Liquid; D000939:Epitopes / Q000235:genetics / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism*; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009415:Nerve Net / Q000378:metabolism*; D009473:Neuronal Plasticity
chemical_list: D053674:Aggrecans; D018959:CD57 Antigens; D011508:Chondroitin Sulfate Proteoglycans; D000939:Epitopes; D006025:Glycosaminoglycans; C013786:A73025; C513580:B3glct protein, mouse; D016695:Glycosyltransferases