title: The Muscular Dystrophy Gene TMEM5 Encodes a Ribitol β1,4-Xylosyltransferase Required for the Functional Glycosylation of Dystroglycan.
abstract: A defect in O-mannosyl glycan is the cause of α-dystroglycanopathy, a group of congenital muscular dystrophies caused by aberrant α-dystroglycan (α-DG) glycosylation. Recently, the entire structure of O-mannosyl glycan, [3GlcAβ1-3Xylα1]n-3GlcAβ1-4Xyl-Rbo5P-1Rbo5P-3GalNAcβ1-3GlcNAcβ1-4 (phospho-6)Manα1-, which is required for the binding of α-DG to extracellular matrix ligands, has been proposed. However, the linkage of the first Xyl residue to ribitol 5-phosphate (Rbo5P) is not clear. TMEM5 is a gene product responsible for α-dystroglycanopathy and was reported as a potential enzyme involved in this linkage formation, although the experimental evidence is still incomplete. Here, we report that TMEM5 is a xylosyltransferase that forms the Xylβ1-4Rbo5P linkage on O-mannosyl glycan. The anomeric configuration and linkage position of the product (β1,4 linkage) was determined by NMR analysis. The introduction of two missense mutations in TMEM5 found in α-dystroglycanopathy patients impaired xylosyltransferase activity. Furthermore, the disruption of the TMEM5 gene by CRISPR/Cas9 abrogated the elongation of the (-3GlcAβ1-3Xylα1-) unit on O-mannosyl glycan. Based on these results, we concluded that TMEM5 acts as a UDP-d-xylose:ribitol-5-phosphate β1,4-xylosyltransferase in the biosynthetic pathway of O-mannosyl glycan.
authors.affiliation: From the Molecular Glycobiology, Research Team for Mechanism of Aging, Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Tokyo 173-0015, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Manya
authors.affiliation: the Structural Glycobiology Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center for Systems Chemical Biology, RIKEN Global Research Cluster, Wako, Saitama 351-0198, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Yamaguchi
authors.affiliation: the Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan.
authors.forename: Motoi
authors.initials: M
authors.lastname: Kanagawa
authors.affiliation: the Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: the Department of Molecular Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Osaka 594-1101, Japan, and.
authors.forename: Michiko
authors.initials: M
authors.lastname: Tajiri
authors.affiliation: From the Molecular Glycobiology, Research Team for Mechanism of Aging, Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Tokyo 173-0015, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Akasaka-Manya
authors.affiliation: the Laboratory of Glyco-organic Chemistry, The Noguchi Institute, Itabashi, Tokyo 173-0003, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kawakami
authors.affiliation: the Laboratory of Glyco-organic Chemistry, The Noguchi Institute, Itabashi, Tokyo 173-0003, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Mizuno
authors.affiliation: the Department of Molecular Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Osaka 594-1101, Japan, and.
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Wada
authors.affiliation: the Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan.
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Toda
authors.affiliation: From the Molecular Glycobiology, Research Team for Mechanism of Aging, Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, Tokyo 173-0015, Japan,. Electronic address: endo@tmig.or.jp.
authors.forename: Tamao
authors.initials: T
authors.lastname: Endo
mesh_terms: D002460:Cell Line; D049030:Dystroglycans / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009136:Muscular Dystrophies / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D019906:Nuclear Magnetic Resonance, Biomolecular; D010430:Pentosyltransferases; D017855:Transferases (Other Substituted Phosphate Groups) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D049030:Dystroglycans; D010430:Pentosyltransferases; C578283:RXYLT1 protein, human; D017855:Transferases (Other Substituted Phosphate Groups)
keywords: O-mannosyl glycan; TMEM5; dystroglycan; glycoconjugate; glycosylation; glycosyltransferase; muscular dystrophy; xylosyltransferase