title: Carbohydrate-binding domain of the POMGnT1 stem region modulates O-mannosylation sites of α-dystroglycan.
abstract: The dystrophin glycoprotein complex, which connects the cell membrane to the basement membrane, is essential for a variety of biological events, including maintenance of muscle integrity. An O-mannose-type GalNAc-β1,3-GlcNAc-β1,4-(phosphate-6)-Man structure of α-dystroglycan (α-DG), a subunit of the complex that is anchored to the cell membrane, interacts directly with laminin in the basement membrane. Reduced glycosylation of α-DG is linked to some types of inherited muscular dystrophy; consistent with this relationship, many disease-related mutations have been detected in genes involved in O-mannosyl glycan synthesis. Defects in protein O-linked mannose β1,2-N-acetylglucosaminyltransferase 1 (POMGnT1), a glycosyltransferase that participates in the formation of GlcNAc-β1,2-Man glycan, are causally related to muscle-eye-brain disease (MEB), a congenital muscular dystrophy, although the role of POMGnT1 in postphosphoryl modification of GalNAc-β1,3-GlcNAc-β1,4-(phosphate-6)-Man glycan remains elusive. Our crystal structures of POMGnT1 agreed with our previous results showing that the catalytic domain recognizes substrate O-mannosylated proteins via hydrophobic interactions with little sequence specificity. Unexpectedly, we found that the stem domain recognizes the β-linked GlcNAc of O-mannosyl glycan, an enzymatic product of POMGnT1. This interaction may recruit POMGnT1 to a specific site of α-DG to promote GlcNAc-β1,2-Man clustering and also may recruit other enzymes that interact with POMGnT1, e.g., fukutin, which is required for further modification of the GalNAc-β1,3-GlcNAc-β1,4-(phosphate-6)-Man glycan. On the basis of our findings, we propose a mechanism for the deficiency in postphosphoryl modification of the glycan observed in POMGnT1-KO mice and MEB patients.
authors: Photon Factory, Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan;
authors: Naoyuki
authors: N
authors: Kuwabara
authors: Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Itabashi-ku, Tokyo 173-0015, Japan;
authors: Hiroshi
authors: H
authors: Manya
authors: Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Itabashi-ku, Tokyo 173-0015, Japan;
authors: Takeyuki
authors: T
authors: Yamada
authors: Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan;
authors: Hiroaki
authors: H
authors: Tateno
authors: Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan;
authors: Motoi
authors: M
authors: Kanagawa
authors: Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan;
authors: Kazuhiro
authors: K
authors: Kobayashi
authors: Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Itabashi-ku, Tokyo 173-0015, Japan;
authors: Keiko
authors: K
authors: Akasaka-Manya
authors: Laboratory of Glyco-organic Chemistry, The Noguchi Institute, Itabashi-ku, Tokyo 173-0003, Japan;
authors: Yuriko
authors: Y
authors: Hirose
authors: Laboratory of Glyco-organic Chemistry, The Noguchi Institute, Itabashi-ku, Tokyo 173-0003, Japan;
authors: Mamoru
authors: M
authors: Mizuno
authors: Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa 230-0045, Japan;
authors: Mitsunori
authors: M
authors: Ikeguchi
authors: Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan;
authors: Tatsushi
authors: T
authors: Toda
authors: Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan;
authors: Jun
authors: J
authors: Hirabayashi
authors: Photon Factory, Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan; School of High Energy Accelerator Science, SOKENDAI University, Tsukuba, Ibaraki 305-0801, Japan.
authors: Toshiya
authors: T
authors: Senda
authors: Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Itabashi-ku, Tokyo 173-0015, Japan; ryuichi.kato@kek.jp endo@tmig.or.jp.
authors: Tamao
authors: T
authors: Endo
authors: Photon Factory, Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan; School of High Energy Accelerator Science, SOKENDAI University, Tsukuba, Ibaraki 305-0801, Japan ryuichi.kato@kek.jp endo@tmig.or.jp.
authors: Ryuichi
authors: R
authors: Kato
mesh_terms: D001665:Binding Sites; D003460:Crystallization; D049030:Dystroglycans / Q000737:chemistry*; D006031:Glycosylation; D006801:Humans; D008358:Mannose / Q000737:chemistry; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry*
chemical_list: C483081:DAG1 protein, human; D049030:Dystroglycans; D017351:N-Acetylglucosaminyltransferases; C443106:protein O-mannose beta-1,2-N-acetylglucosaminyltransferase; D008358:Mannose
keywords: O-mannosyl glycan; glycosyltransferase; lectin; muscular dystrophy; α-dystroglycanopathy