title: Copper mediates dityrosine cross-linking of Alzheimer's amyloid-beta.
abstract: We have previously reported that amyloid Abeta, the major component of senile plaques in Alzheimer's disease (AD), binds Cu with high affinity via histidine and tyrosine residues [Atwood, C. S., et al. (1998) J. Biol. Chem. 273, 12817-12826; Atwood, C. S., et al. (2000) J. Neurochem. 75, 1219-1233] and produces H(2)O(2) by catalyzing the reduction of Cu(II) or Fe(III) [Huang, X., et al. (1999) Biochemistry 38, 7609-7616; Huang, X., et al. (1999) J. Biol. Chem. 274, 37111-37116]. Incubation with Cu induces the SDS-resistant oligomerization of Abeta [Atwood, C. S., et al. (2000) J. Neurochem. 75, 1219-1233], a feature characteristic of neurotoxic soluble Abeta extracted from the AD brain. Since residues coordinating Cu are most vulnerable to oxidation, we investigated whether modifications of these residues were responsible for Abeta cross-linking. SDS-resistant oligomerization of Abeta caused by incubation with Cu was found to induce a fluorescence signal characteristic of tyrosine cross-linking. Using ESI-MS and a dityrosine specific antibody, we confirmed that Cu(II) (at concentrations lower than that associated with amyloid plaques) induces the generation of dityrosine-cross-linked, SDS-resistant oligomers of human, but not rat, Abeta peptides. The addition of H2O2 strongly promoted Cu-induced dityrosine cross-linking of Abeta1-28, Abeta1-40, and Abeta1-42, suggesting that the oxidative coupling is initiated by interaction of H2O2 with a Cu(II) tyrosinate. The dityrosine modification is significant since it is highly resistant to proteolysis and is known to play a role in increasing structural strength. Given the elevated concentration of Cu in senile plaques, our results suggest that Cu interactions with Abeta could be responsible for causing the covalent cross-linking of Abeta in these structures.
authors.affiliation: Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA. csa@medicine.wisc.edu
authors.forename: Craig S
authors.initials: CS
authors.lastname: Atwood
authors.forename: George
authors.initials: G
authors.lastname: Perry
authors.forename: Hong
authors.initials: H
authors.lastname: Zeng
authors.forename: Yoji
authors.initials: Y
authors.lastname: Kato
authors.forename: Walton D
authors.initials: WD
authors.lastname: Jones
authors.forename: Ke-Qing
authors.initials: KQ
authors.lastname: Ling
authors.forename: Xudong
authors.initials: X
authors.lastname: Huang
authors.forename: Robert D
authors.initials: RD
authors.lastname: Moir
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Sayre
authors.forename: Mark A
authors.initials: MA
authors.lastname: Smith
authors.forename: Shu G
authors.initials: SG
authors.lastname: Chen
authors.forename: Ashley I
authors.initials: AI
authors.lastname: Bush
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D003300:Copper / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D003432:Cross-Linking Reagents; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D012967:Sodium Dodecyl Sulfate; D014443:Tyrosine; D003300:Copper; C007543:dityrosine