Characterization of site-specific O-glycan structures within the mucin-like domain of alpha-dystroglycan from human skeletal muscle

Glycobiology. 2010 Sep;20(9):1160-9. doi: 10.1093/glycob/cwq082. Epub 2010 May 27.

Abstract

The glycosylation of the extracellular protein alpha-dystroglycan is important for its ligand-binding activity, and altered or blocked glycosylation is associated with several forms of congenital muscular dystrophies. By immunoprecipitation and sialic acid capture-and-release enrichment strategies, we isolated tryptic glycopeptides of alpha-dystroglycan from human skeletal muscle. Nano-liquid chromatography tandem mass spectrometry was used to identify both glycopeptides and peptides corresponding to the mucin-like and C-terminal domain of alpha-dystroglycan. The O-glycans found had either Hex-O-Thr or HexNAc-O-Ser/Thr anchored structures, which were often elongated and frequently, but not always, terminated with sialic acid. The HexNAc-O-Ser/Thr, but not Hex-O-Thr glycopeptides, displayed heterogeneity regarding glycan core structures and level of glycosylation site occupancy. We demonstrate for the first time glycan attachment sites of the NeuAcHexHexNAcHex-O structure corresponding to the anticipated Neu5Acalpha3Galbeta4GlcNAcbeta2Man-O-glycan (sLacNAc-Man), within the mucin-like domain of human alpha-dystroglycan from human skeletal muscle. Twenty-five glycopeptides were characterized from human alpha-dystroglycan, which provide insight to the complex in vivo O-glycosylation of alpha-dystroglycan.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Carbohydrate Sequence
  • Catalytic Domain
  • Dystroglycans / analysis
  • Dystroglycans / chemistry*
  • Dystroglycans / metabolism
  • Glycosylation
  • Humans
  • Molecular Sequence Data
  • Mucins / chemistry*
  • Muscle, Skeletal / chemistry
  • Muscle, Skeletal / metabolism*
  • N-Acetylneuraminic Acid / chemistry
  • N-Acetylneuraminic Acid / metabolism
  • Peptide Mapping
  • Polysaccharides / chemistry
  • Polysaccharides / metabolism*
  • Protein Processing, Post-Translational
  • Protein Structure, Tertiary / physiology
  • Structure-Activity Relationship
  • Substrate Specificity

Substances

  • DAG1 protein, human
  • Mucins
  • Polysaccharides
  • Dystroglycans
  • N-Acetylneuraminic Acid