Title : Identification of
O-GlcNAc sites within
peptides of the
Tau protein and their impact on phosphorylation
Abstract :
- Phosphorylation of the microtubule-associated Tau protein plays a major role in the regulation of its activity of tubulin polymerization and/or stabilization of microtubule assembly
- A dysregulation of the phosphorylation/dephosphorylation balance leading to the hyperphosphorylation of Tau proteins in neurons is thought to favor their aggregation into insoluble filaments
- This in turn might underlie neuronal death as encountered in many neurodegenerative disorders, including Alzheimer's disease
- Another post-translational modification, the O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) , controls the phosphorylation state of Tau , although the precise mechanism is not known
- Moreover, analytical difficulties have hampered the precise localization of the O-GlcNAc sites on Tau , except for the S400 site that was very recently identified on the basis of ETD-FT-MS
- Here, we identify three O-GlcNAc sites by screening a library of small peptides sampling the proline-rich, the microtubule-associated repeats and the carboxy-terminal domains of Tau as potential substrates for the O-β- N-acetylglucosaminyltransferase ( OGT )
- The in vitro activity of the nucleocytoplasmic OGT was assessed by tandem mass spectrometry and NMR spectroscopy
- Using phosphorylated peptides , we establish the relationship between phosphate and O-GlcNAc incorporation at these sites
- Phosphorylation of neighboring residues S396 and S404 was found to decrease significantly S400 O-GlcNAcylation
- Reciprocally, S400 O-GlcNAcylation reduces S404 phosphorylation by the CDK2 /cyclinA3 kinase and interrupts the GSK3β-mediated sequential phosphorylation process