Binding of Abeta to alpha- and beta-synucleins: identification of segments in alpha-synuclein/NAC precursor that bind Abeta and NAC.
NAC, a 35-residue peptide derived from the neuronal protein alpha-synuclein/NAC precursor, is tightly associated with Abeta fibrils in Alzheimer's disease amyloid, and alpha-synuclein has recently been shown to bind Abeta in vitro. We have studied the interaction between Abeta and synucleins, aiming at determining segments in alpha-synuclein that can account for the binding, as well as identifying a possible interaction between Abeta and the beta-type synuclein. We report that Abeta binds to native and recombinant alpha-synuclein, and to beta-synuclein in an SDS-sensitive interaction (IC50 approx. 20 microM), as determined by chemical cross-linking and solid-phase binding assays. alpha-Synuclein and beta-synuclein were found to stimulate Abeta-aggregation in vitro to the same extent. The synucleins also displayed Abeta-inhibitable binding of NAC and they were capable of forming dimers. Using proteolytic fragmentation of alpha-synuclein and cross-linking to 125I-Abeta, we identified two consecutive binding domains (residues 1-56 and 57-97) by Edman degradation and mass spectrometric analysis, and a synthetic peptide comprising residues 32-57 possessed Abeta-binding activity. To test further the possible significance in pathology, alpha-synuclein was biotinylated and shown to bind specifically to amyloid plaques in a brain with Alzheimer's disease. It is proposed that the multiple Abeta-binding sites in alpha-synuclein are involved in the development of amyloid plaques.
Jensen
P H
PH
Department of Medical Biochemistry, University of Aarhus, Ole Worms Allé, Building 170, DK-8000 Aarhus C, Denmark.
Hojrup
P
P
Hager
H
H
Nielsen
M S
MS
Jacobsen
L
L
Olesen
O F
OF
Gliemann
J
J
Jakes
R
R
D000682:Amyloid / Q000378:metabolism*; D001665:Binding Sites; D001710:Biotin; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D051843:Synucleins; D051844:alpha-Synuclein; D051846:beta-Synuclein
D000682:Amyloid; D009419:Nerve Tissue Proteins; D011498:Protein Precursors; C497604:SNCA protein, human; C497607:SNCB protein, human; D051843:Synucleins; D051844:alpha-Synuclein; D051846:beta-Synuclein; D001710:Biotin