GTDC2 modifies O-mannosylated α-dystroglycan in the endoplasmic reticulum to generate N-acetyl glucosamine epitopes reactive with CTD110.6 antibody

Biochem Biophys Res Commun. 2013 Oct 11;440(1):88-93. doi: 10.1016/j.bbrc.2013.09.022. Epub 2013 Sep 13.

Abstract

Hypoglycosylation is a common characteristic of dystroglycanopathy, which is a group of congenital muscular dystrophies. More than ten genes have been implicated in α-dystroglycanopathies that are associated with the defect in the O-mannosylation pathway. One such gene is GTDC2, which was recently reported to encode O-mannose β-1,4-N-acetylglucosaminyltransferase. Here we show that GTDC2 generates CTD110.6 antibody-reactive N-acetylglucosamine (GlcNAc) epitopes on the O-mannosylated α-dystroglycan (α-DG). Using the antibody, we show that mutations of GTDC2 identified in Walker-Warburg syndrome and alanine-substitution of conserved residues between GTDC2 and EGF domain O-GlcNAc transferase resulted in decreased glycosylation. Moreover, GTDC2-modified GlcNAc epitopes are localized in the endoplasmic reticulum (ER). These data suggested that GTDC2 is a novel glycosyltransferase catalyzing GlcNAcylation of O-mannosylated α-DG in the ER. CTD110.6 antibody may be useful to detect a specific form of GlcNAcylated O-mannose and to analyze defective O-glycosylation in α-dystroglycanopathies.

Keywords: CTD110.6; DG; EGF; EGF domain O-GlcNAc transferase; EOGT; ER; GTDC2; GlcNAc; N-Acetylglucosamine; N-acetylglucosamine; dystroglycan; endoplasmic reticulum; epidermal growth factor; α-Dystroglycan.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylglucosamine / immunology
  • Acetylglucosamine / metabolism*
  • Animals
  • Antibodies / immunology
  • Dystroglycans / chemistry
  • Dystroglycans / immunology
  • Dystroglycans / metabolism*
  • Endoplasmic Reticulum / immunology
  • Endoplasmic Reticulum / metabolism*
  • Epitopes / immunology
  • Epitopes / metabolism*
  • Glycosylation
  • Glycosyltransferases / genetics
  • Glycosyltransferases / immunology
  • Glycosyltransferases / metabolism*
  • HEK293 Cells
  • Humans
  • Mutation
  • Protein Structure, Tertiary
  • Walker-Warburg Syndrome / genetics
  • Walker-Warburg Syndrome / immunology
  • Walker-Warburg Syndrome / metabolism

Substances

  • Antibodies
  • Epitopes
  • Dystroglycans
  • Glycosyltransferases
  • POMGNT2 protein, human
  • Acetylglucosamine