Turn nucleation perturbs amyloid ? self-assembly and cytotoxicity.

ABSTRACT: The accumulation of senile plaques composed of amyloid ? (A?) fibrils is a hallmark of Alzheimer's disease, although prefibrillar oligomeric species are believed to be the primary neurotoxic congeners in the pathogenesis of Alzheimer's disease. Uncertainty regarding the mechanistic relationship between A? oligomer and fibril formation and the cytotoxicity of these aggregate species persists. ?-Turn formation has been proposed to be a potential rate-limiting step during A? fibrillogenesis. The effect of turn nucleation on A? self-assembly was probed by systematically replacing amino acid pairs in the putative turn region of A? (residues 24-27) with d-ProGly ((D)PG), an effective turn-nucleating motif. The kinetic, thermodynamic, and cytotoxic effects of these mutations were characterized. It was found that turn formation dramatically accelerated A? fibril self-assembly dependent on the site of turn nucleation. The cytotoxicity of the three (D)PG-containing A? variants was significantly lower than that of wild-type A?40, presumably due to decreased oligomer populations as a function of a more rapid progression to mature fibrils; oligomer populations were not eliminated, however, suggesting that turn formation is also a feature of oligomer structures. These results indicate that turn nucleation is a critical step in A?40 fibril formation.

SUBMITTER: Doran TM 

PROVIDER: S-EPMC4654632 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature