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.
authors.affiliation: Unité de Glycobiologie Structurale et Fonctionnelle, CNRS UMR8576, IFR 147, Université de Lille1, 59655 Villeneuve d'Ascq Cedex, France. caroline.smet@univ-lille1.fr
authors.forename: Caroline
authors.initials: C
authors.lastname: Smet-Nocca
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Broncel
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Wieruszeski
authors.forename: Caroline
authors.initials: C
authors.lastname: Tokarski
authors.forename: Xavier
authors.initials: X
authors.lastname: Hanoulle
authors.forename: Arnaud
authors.initials: A
authors.lastname: Leroy
authors.forename: Isabelle
authors.initials: I
authors.lastname: Landrieu
authors.forename: Christian
authors.initials: C
authors.lastname: Rolando
authors.forename: Guy
authors.initials: G
authors.lastname: Lippens
authors.forename: Christian P R
authors.initials: CP
authors.lastname: Hackenberger
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000235:genetics / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006031:Glycosylation; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D016875:tau Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D019925:Cyclin A; D010455:Peptides; D011994:Recombinant Proteins; D016875:tau Proteins; D012694:Serine; D017351:N-Acetylglucosaminyltransferases; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051357:Cyclin-Dependent Kinase 2; D038362:Glycogen Synthase Kinase 3; D000117:Acetylglucosamine