Aβ-affected pathogenic induction of S-nitrosylation of OGT and identification of Cys-NO linkage triplet

Biochim Biophys Acta. 2016 May;1864(5):609-21. doi: 10.1016/j.bbapap.2016.02.003. Epub 2016 Feb 5.

Abstract

Mechanistic link of protein hypo-O-GlcNAcylation to the pathogenesis of Alzheimer's disease (AD) remains unclear. Here, we found that S-nitrosylation of O-linked N-acetylglucosaminyltransferase (SNO-OGT) was induced by β-amyloid peptide (Aβ) exposure to SK-N-MC and SK-N-SH human neuroblastoma cells. Subsequently, Aβ-induced SNO-OGT led to protein hypo-O-GlcNAcylation globally including tau hypo-O-GlcNAcylation. Our results support that underlying mechanism for induction of SNO-OGT comprises the concerted action of Aβ-triggered Ca2+ entry into cells and nNOS-catalyzed NO production. Intriguingly, OGT was found to be associated with nNOS and its association was enhanced during Aβ treatment. In parallel with SNO-OGT-mediated tau hypo-O-GlcNAcylation, Aβ led to SNO-Akt-mediated GSK3β activation for tau phosphorylation, suggesting that tau hyperphosphorylation is established by synergistic connection between SNO-OGT and GSK3β activation. We also observed that Aβ-neurotoxicity including both reactive oxygen species (ROS) production and cell death was amplified with DON treatment, whereas it was restored by PUGNAc treatment, GlcNH2 treatment or OGT overexpression. Early time-course Aβ-monitoring assay revealed that premaintained hyper-O-GlcNAcylation inside cells blocked not only Aβ-triggered Ca2+ entry into cells but also induction of SNO-OGT and SNO-Akt. Together, these findings suggest that induction of SNO-OGT by Aβ exposure is a pathogenic mechanism to cause cellular hypo-O-GlcNAcylation by which Aβ neurotoxicity is executed, and conversely, hyper-O-GlcNAcylation within cells can defend against Aβ neurotoxicity. Furthermore, our Cys mapping demonstrates that cysteine-nitric oxide (Cys-NO) linkages in SNO-OGT occur at triple Cys845, Cys921, and Cys965 residues in C-terminal catalytic domain (C-CAT), suggesting that Cys-NO linkage triplet in SNO-OGT is associated with null OGT activity.

Keywords: Aβ neurotoxicity; Cys-NO linkages; Hypo-O-GlcNAcylation; O-GlcNAc; OGT; SNO-OGT.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acylation
  • Alzheimer Disease / metabolism*
  • Alzheimer Disease / pathology
  • Amyloid beta-Peptides / chemistry
  • Amyloid beta-Peptides / metabolism*
  • Calcium / metabolism
  • Cell Line
  • Cysteine / chemistry
  • Glycogen Synthase Kinase 3 / chemistry
  • Glycogen Synthase Kinase 3 / metabolism
  • Glycogen Synthase Kinase 3 beta
  • Humans
  • N-Acetylglucosaminyltransferases / chemistry*
  • N-Acetylglucosaminyltransferases / metabolism
  • Nitric Oxide / chemistry
  • Phosphorylation
  • Protein Processing, Post-Translational / genetics*
  • Reactive Oxygen Species
  • Signal Transduction / genetics

Substances

  • Amyloid beta-Peptides
  • Reactive Oxygen Species
  • Nitric Oxide
  • N-Acetylglucosaminyltransferases
  • UDP-N-acetylglucosamine-peptide beta-N-acetylglucosaminyltransferase
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Glycogen Synthase Kinase 3
  • Cysteine
  • Calcium