Identification of O-linked N-acetylglucosamine (O-GlcNAc)-modified osteoblast proteins by electron transfer dissociation tandem mass spectrometry reveals proteins critical for bone formation

Mol Cell Proteomics. 2013 Apr;12(4):945-55. doi: 10.1074/mcp.M112.026633. Epub 2013 Feb 26.


The nutrient-responsive β-O-linked N-acetylglucosamine (O-GlcNAc) modification of critical effector proteins modulates signaling and transcriptional pathways contributing to cellular development and survival. An elevation in global protein O-GlcNAc modification occurs during the early stages of osteoblast differentiation and correlates with enhanced transcriptional activity of RUNX2, a key regulator of osteogenesis. To identify other substrates of O-GlcNAc transferase in differentiating MC3T3E1 osteoblasts, O-GlcNAc-modified peptides were enriched by wheat germ agglutinin lectin weak affinity chromatography and identified by tandem mass spectrometry using electron transfer dissociation. This peptide fragmentation approach leaves the labile O-linkage intact permitting direct identification of O-GlcNAc-modified peptides. O-GlcNAc modification was observed on enzymes involved in post-translational regulation, including MAST4 and WNK1 kinases, a ubiquitin-associated protein (UBAP2l), and the histone acetyltransferase CREB-binding protein. CREB-binding protein, a transcriptional co-activator that associates with CREB and RUNX2, is O-GlcNAcylated at Ser-147 and Ser-2360, the latter of which is a known site of phosphorylation. Additionally, O-GlcNAcylation of components of the TGFβ-activated kinase 1 (TAK1) signaling complex, TAB1 and TAB2, occurred in close proximity to known sites of Ser/Thr phosphorylation and a putative nuclear localization sequence within TAB2. These findings demonstrate the presence of O-GlcNAc modification on proteins critical to bone formation, remodeling, and fracture healing and will enable evaluation of this modification on protein function and regulation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acetylgalactosamine / chemistry
  • Acetylgalactosamine / metabolism*
  • Amino Acid Sequence
  • Animals
  • Carbohydrate Conformation
  • Cells, Cultured
  • Chromatography, Affinity
  • Glycoproteins / chemistry
  • Glycoproteins / isolation & purification
  • Glycoproteins / metabolism*
  • Glycosylation
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Osteoblasts / metabolism*
  • Osteogenesis
  • Peptide Fragments / chemistry
  • Peptide Fragments / isolation & purification
  • Protein Processing, Post-Translational*
  • Proteome / chemistry
  • Proteome / isolation & purification
  • Proteome / metabolism
  • Tandem Mass Spectrometry / methods*


  • Glycoproteins
  • Peptide Fragments
  • Proteome
  • Acetylgalactosamine