Title : Discovery of
O-GlcNAc-6-phosphate modified proteins in large-scale phosphoproteomics data
Abstract :
- 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
- 2011, 10, 2725-2733)
- 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.
- 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
- 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.
- 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
- 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.
- 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.
- 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