title: Site-specific nitration and oxidative dityrosine bridging of the tau protein by peroxynitrite: implications for Alzheimer's disease.
abstract: Alzheimer's disease (AD) is a progressive amnestic disorder typified by the pathological misfolding and deposition of the microtubule-associated tau protein into neurofibrillary tangles (NFTs). While numerous post-translational modifications influence NFT formation, the molecular mechanisms responsible for tau aggregation remain enigmatic. Since nitrative and oxidative injury have previously been shown to play a mechanistic role in neurodegeneration, we examined whether these events influence tau aggregation. In this report, we characterize the effects of peroxynitrite (ONOO-)-mediated nitration and oxidation on tau polymerization in vitro. Treatment of tau with ONOO- results in 3-nitrotyrosine (3-NT) immunoreactivity and the formation of heat-stable, SDS-insoluble oligomers. Using ESI-MS and HPLC with fluorescent detection, we show that these higher-order aggregates contain 3,3'-dityrosine (3,3'-DT). Tyrosine (Tyr) residues are critical for ONOO(-)-mediated oligomerization, as tau proteins lacking all Tyr residues fail to generate oligomers upon ONOO- treatment. Further, tau nitration targets residues Y18, Y29, and to a lesser degree Y197 and Y394, and nitration at these sites inhibits in vitro polymerization. The inhibitory effect of nitration on tau polymerization is specific for the 3-NT modification, as pseudophosphorylation at these same Tyr residues does not inhibit tau assembly. Our results suggest that the nitrative and oxidative roles of ONOO- differentially affect tau polymerization and that ONOO(-)-mediated cross-linking could facilitate tau aggregation in AD.
authors.affiliation: Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA. m-reynolds@md.northwestern.edu
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Reynolds
authors.forename: Robert W
authors.initials: RW
authors.lastname: Berry
authors.forename: Lester I
authors.initials: LI
authors.lastname: Binder
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D008027:Light; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D030421:Peroxynitrous Acid / Q000737:chemistry*; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012542:Scattering, Radiation; D012967:Sodium Dodecyl Sulfate; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016875:tau Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D003432:Cross-Linking Reagents; D009566:Nitrates; D016875:tau Proteins; D030421:Peroxynitrous Acid; D012967:Sodium Dodecyl Sulfate; D014443:Tyrosine; C007543:dityrosine