Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

The Amyloid beta peptide (Abeta) of Alzheimer's diseases (AD) is closely linked to the progressive cognitive decline associated with the disease. Cu2+ ions can induce the de novo aggregation of the Abeta peptide into non-amyloidogenic aggregates and the production of a toxic species. The mechanism by which Cu2+ mediates the change from amyloid material toward Cu2+ induced aggregates is poorly defined. Here we demonstrate that the aggregation state of Abeta1-42 at neutral pH is governed by the Cu2+:peptide molar ratio. By probing amyloid content and total aggregation, we observed a distinct Cu2+ switching effect centered at equimolar Cu2+:peptide ratios. At sub-equimolar Cu2+:peptide molar ratios, Abeta1-42 forms thioflavin-T reactive amyloid; conversely, at supra-equimolar Cu2+:peptide molar ratios, Abeta1-42 forms both small spherical oligomers approximately 10-20 nm in size and large amorphous aggregates. We demonstrate that these insoluble aggregates form spontaneously via a soluble species without the presence of an observable lag phase. In seeding experiments, the Cu2+ induced aggregates were unable to influence fibril formation or convert into fibrillar material. Aged Cu2+ induced aggregates are toxic when compared to Abeta1-42 aged in the absence of Cu2+. Importantly, the formation of dityrosine crosslinked Abeta, by the oxidative modification of the peptide, only occurs at equimolar molar ratios and above. The formation of dityrosine adducts occurs following the initiation of aggregation and hence does not drive the formation of the Cu2+ induced aggregates. These results define the role Cu2+ plays in modulating the aggregation state and toxicity of Abeta1-42.

Original publication

DOI

10.1021/bi0620961

Type

Journal article

Journal

Biochemistry

Publication Date

13/03/2007

Volume

46

Pages

2881 - 2891

Keywords

Alzheimer Disease, Amyloid beta-Peptides, Copper, Humans, Solubility, Tyrosine