Aggregation of the beta-amyloid peptide (Abeta) to amyloid plaques is a key event in Alzheimer's disease. According to the amyloid-cascade hypothesis, Abeta aggregates are toxic to neurons through the production of reactive oxygen species (ROS). Copper ions play an important role, because they are able to bind to Abeta and influence its aggregation properties. Moreover, Cu-Abeta is supposed to be directly involved in ROS production. To get a better understanding of these reactions, we measured the production of HO(.) and the redox potential of Cu-Abeta. The results were compared to other biological copper-peptide complexes in order to get an insight into the biological relevance. Cu-Abeta produced more HO(.) than the complex of copper with Asp-Ala-His-Lys (Cu-DAHK), but less than with Gly-His-Lys (Cu-GHK). Cyclic voltammetry revealed that the order for reduction potential is Cu-GHK>Cu-Abeta>Cu-DAHK, but for the oxidation potential the order is reversed. Thus, easier copper redox cycling correlated to higher HO(.) production. The copper complex of the form Abeta1-42 showed a HO(.) production five-times higher than that of the form Abeta1-40. Time-dependence and aggregation studies suggest that an aggregation intermediate is responsible for this increased HO(.) production.

Metal swap between Zn7metallothionein-3 and amyloid-β-Cu protects against amyloid-β toxicity Meloni, G; Sonois, V; Delaine, T; Guilloreau , L; Gillet, A; Teissie, J; Faller, P; Vasak, M Meloni, G; Sonois, V; Delaine, T; Guilloreau , L; Gillet, A; Teissie, J; Faller, P; Vasak, M (2008). Metal swap between Zn7metallothionein-3 and amyloid-β-Cu protects against amyloid-β toxicity. Nature Chemical Biology, 4 Metal swap between Zn7metallothionein-3 and amyloid-β-Cu protects against amyloid-β toxicity Abstract Aberrant interactions of copper and zinc ions with the amyloid-β peptide (Aβ) potentiate Alzheimer disease (AD) by participating in the aggregation process of Aβ and in thegeneration of reactive oxygen species (ROS). The ROS production and the neurotoxicity of Aβ are associated with copper binding. Metallothionein-3 (Zn7MT-3), an intra-andextracellularly occurring metalloprotein, is highly expressed in the brain and down-regulated in AD. This protein protects, by an unknown mechanism, cultured neurons from the toxicity of Aβ. Herein, we show that a metal swap between Zn7MT-3 and soluble and aggregated Aβ1-40-Cu(II) abolishes the ROS production and the related cellular toxicity. In this process, copper is reduced by the protein thiolates forming Cu(I)4Zn4MT-3 in which an air stable Cu(I)4-thiolate cluster and two disulfide bonds are present. The discovered protective effect of Zn7MT-3 from the copper-mediated Aβ1-40 toxicity may lead to newtherapeutic strategies in treating AD.Metal swap between Zn 7 metallothionein-3 and amyloid-β-Cu protects against amyloid-β toxicity residue Aβ peptide, a proteolytic fragment generated from the amyloid precursor protein (APP)by β-and γ-secretases 1 . There is significant evidence indicating that the Aβ peptides can interact with metal ions such as Zn(II) and Cu(II), thereby participating in their aggregation and in the production of ROS 1, 2 . Whereas the copper-induced Aβ aggregation is related to the ROS production and neurotoxicity 3 , the zinc-induced Aβ aggregation is considered to be neuroprotective 4 . The ROS are generated by Aβ-Cu(II) through the redox cycling of copper which requires its reduction by biological components such as ascorbate (1), glutathione (2), dopamine (3), and cholesterol (4) 5,6 . A dysregulation of metal ion homeostasis, as occurs in AD, may foster an environment that promotes such degenerative conditions. The modulation of brain metal ion homeostasis, the reduction of aberrant metal-protein interactions by MPAC (metal-

The aggregation of the peptide amyloid-beta (Abeta) to form amyloid plaques is a key event in Alzheimer's disease. It has been shown that CuII can bind to soluble Abeta and influence its aggregation properties. Three histidines and the N-terminal amine have been proposed to be involved in its coordination. Here, for the first time, we show isothermal titration calorimetry (ITC) measurements of the CuII binding to Abeta16 and Abeta28, models of the soluble Abeta. Moreover, different spectroscopic methods were applied. The studies revealed new insights into these CuII-Abeta complexes: (1) ITC showed two CuII binding sites, with an apparent Kd of 10(-7) and 10(-5) M, respectively; (2) the high-affinity site has a smaller enthalpic contribution but a larger entropic contribution than the low-affinity binding site; (3) azide did not bind to CuII in the higher-affinity binding site, suggesting the absence of a weak, labile ligand; (4) azide could bind to the CuII in the low-affinity binding site in Abeta28 but not in Abeta16; (5) 1H-NMR suggests that the carboxylate of aspartic acid in position 1 is involved in the ligation to CuII in the high-affinity binding site; (6) the pKa of 11.3 of tyrosine in position 10 was not influenced by the binding of 2 equivalents of CuII.