PMID: 22826440

 

    Legend: Sugar

Title : Discovery of O-GlcNAc-6-phosphate modified proteins in large-scale phosphoproteomics data

Abstract :
  1. Phosphorylated O-GlcNAc is a novel post-translational modification that has so far only been found on the neuronal protein AP180 from the rat (Graham et al., J. Proteome Res
  2. 2011, 10, 2725-2733)
  3. Upon collision induced dissociation, the modification generates a highly mass deficient fragment ion (m/z 284.0530) that can be used as a reporter for the identification of phosphorylated O-GlcNAc.
  4. Using a publically available mouse brain phosphoproteome data set, we employed our recently developed Oscore software to re-evaluate high resolution/high accuracy tandem mass spectra and discovered the modification on 23 peptides corresponding to 11 mouse proteins
  5. The systematic analysis of 220 candidate phosphoGlcNAc tandem mass spectra as well as a synthetic standard enabled the dissection of the major phosphoGlcNAc fragmentation pathways, suggesting that the modification is O-GlcNAc-6-phosphate.
  6. We find that the classical O-GlcNAc modification often exists on the same peptides indicating that O-GlcNAc-6-phosphate may biosynthetically arise in two steps involving the O-GlcNAc transferase and a currently unknown kinase
  7. Many of the identified proteins are involved in synaptic transmission and for Ca(2 +) /calmodulin kinase IV , the O-GlcNAc-6-phosphate modification was found in the vicinity of two autophosphorylation sites required for full activation of the kinase suggesting a potential regulatory role for O-GlcNAc-6-phosphate.
  8. By re-analyzing mass spectrometric data from human embryonic and induced pluripotent stem cells, our study also identified Zinc finger protein 462 ( ZNF462 ) as the first human O-GlcNAc-6-phosphate modified protein.
  9. Collectively, the data suggests that O-GlcNAc-6-phosphate is a general post-translation modification of mammalian proteins with a variety of possible cellular functions