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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cu and Zn have been shown to accumulate in the brains of Alzheimer's disease patients. We have previously reported that Cu2+ and Zn2+ bind amyloid β (Aβ), explaining their enrichment in plaque pathology. Here we detail the stoichiometries and binding affinities of multiple cooperative Cu2+-binding sites on synthetic Aβ1-40 and Aβ1-42. We have developed a ligand displacement technique (competitive metal capture analysis) that uses metal-chelator complexes to evaluate metal ion binding to Aβ, a notoriously self-aggregating peptide. This analysis indicated that there is a very-high-affinity Cu2+-binding site on Aβ1-42 (log Kapp = 17.2) that mediates peptide precipitation and that the tendency of this peptide to self-aggregate in aqueous solutions is due to the presence of trace Cu2+ contamination (customarily ∼0.1 μM). In contrast, Aβ1-40 has much lower affinity for Cu2+ at this site (estimated log Kapp = 10.3), explaining why this peptide is less self-aggregating. The greater Cu2+-binding affinity of Aβ1-42 compared with Aβ1-40 is associated with significantly diminished negative cooperativity. The role of trace metal contamination in inducing Aβ precipitation was confirmed by the demonstration that Aβ peptide (10 μM) remained soluble for 5 days only in the presence of high-affinity Cu2+-selective chelators.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It has previously been reported that amyloid-β (Aβ) peptide is neurotrophic to undifferentiated but neurotoxic to differentiated primary neurons. The underlying reasons for this differential effect is not understood. Recently, the toxicity of Aβ to neurons was shown to be dependent upon the activation of cyclin-dependent kinase 5 (Cdk5), thought to promote tau phosphorylation that leads to cytoskeletal disruption, morphological degeneration and apoptosis. Here we report that Cdk5, tau, and phosphorylated-tau (P-tau) are expressed at very low levels in undifferentiated primary neurons, but that the expression of Cdk5 and tau and the phosphorylation of tau increase markedly between 4 and 8 days of differentiation in vitro. Tau expression decreased after this time, as did the level of P-tau, to low levels by 17 days. Aβ induced tau phosphorylation of neurons only after ≥ 4 days of differentiation, a time that coincides with the onset of Aβ toxicity. Blocking tau expression (and therefore tau phosphorylation) with an antisense oligonucleotide completely blocked Aβ toxicity of differentiated primary neurons, thereby confirming that tau was essential for mediating Aβ toxicity. Our results demonstrate that differentiation-associated changes in tau and Cdk-5 modulate the toxicity of Aβ and explain the opposite responses of differentiated and undifferentiated neurons to Aβ. Our results predict that only cells containing appreciable levels of tau are susceptible to Aβ-induced toxicity and may explain why Aβ is more toxic to neurons compared with other cell types.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: While there is a host of pro-apoptotic stimuli that target neurons in Alzheimer disease (AD), given the chronicity of the disease and the survival of many neurons, those neurons must either avoid or, at minimum, delay apoptotic death signaling. In this study, we investigated Bcl-w, a novel member of the Bcl-2 family that promotes cell survival. In AD, we found increased levels of Bcl-w associated with neurofibrillary pathology and punctate intracytoplasmic structures whereas, in marked contrast, there are only low diffuse levels of Bcl-w in the neuronal cytoplasm of age-matched control cases. Immunoblot analysis confirmed that Bcl-w levels were significantly increased in AD. By electron microscopy, we determined that the increased Bcl-w expression in AD was ultrastructurally localized to mitochondria and neurofibrillary pathology. To investigate the cause and consequence of Bcl-w up-regulation in neurons, we found that fibrillized amyloid-β led to increased Bcl-w protein levels in M17 human neuroblastoma cells, and that overexpression of Bcl-w significantly protected neurons against staurosporine- and amyloid-β-induced apoptosis. Taken together, these series of results suggest that Bcl-w may play an important protective role in neurons in the diseased brain and that this aspect could be therapeutically harnessed to afford neuroprotection.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 416 (2002), S. 677-677 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sir One potential route for therapy for Alzheimer's disease involves the immunization of patients against the amyloid-β peptide, the major proteinaceous component that characterizes plaques in the brains of patients with this disease. Resulting from earlier research on ...
    Type of Medium: Electronic Resource
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