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Rationally designed turn promoting mutation in the amyloid-? peptide sequence stabilizes oligomers in solution.

ABSTRACT: Enhanced production of a 42-residue beta amyloid peptide (A?(42)) in affected parts of the brain has been suggested to be the main causative factor for the development of Alzheimer's Disease (AD). The severity of the disease depends not only on the amount of the peptide but also its conformational transition leading to the formation of oligomeric amyloid-derived diffusible ligands (ADDLs) in the brain of AD patients. Despite being significant to the understanding of AD mechanism, no atomic-resolution structures are available for these species due to the evanescent nature of ADDLs that hinders most structural biophysical investigations. Based on our molecular modeling and computational studies, we have designed Met35Nle and G37p mutations in the A?(42) peptide (A?(42)Nle35p37) that appear to organize A?(42) into stable oligomers. 2D NMR on the A?(42)Nle35p37 peptide revealed the occurrence of two ?-turns in the V24-N27 and V36-V39 stretches that could be the possible cause for the oligomer stability. We did not observe corresponding NOEs for the V24-N27 turn in the A?(21-43)Nle35p37 fragment suggesting the need for the longer length amyloid peptide to form the stable oligomer promoting conformation. Because of the presence of two turns in the mutant peptide which were absent in solid state NMR structures for the fibrils, we propose, fibril formation might be hindered. The biophysical information obtained in this work could aid in the development of structural models for toxic oligomer formation that could facilitate the development of therapeutic approaches to AD.

SUBMITTER: Rajadas J

PROVIDER: S-EPMC3142112 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Rationally designed turn promoting mutation in the amyloid-β peptide sequence stabilizes oligomers in solution.

Rajadas Jayakumar J Liu Corey W CW Novick Paul P Kelley Nicholas W NW Inayathullah Mohammed M Lemieux Melburne C MC Pande Vijay S VS

PloS one 20110722 7

Enhanced production of a 42-residue beta amyloid peptide (Aβ(42)) in affected parts of the brain has been suggested to be the main causative factor for the development of Alzheimer's Disease (AD). The severity of the disease depends not only on the amount of the peptide but also its conformational transition leading to the formation of oligomeric amyloid-derived diffusible ligands (ADDLs) in the brain of AD patients. Despite being significant to the understanding of AD mechanism, no atomic-resol ...[more]

PMID: 21799748

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Project description:Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the pathological aggregation of the amyloid-? peptide (A?). Monomeric soluble A? can switch from helicoidal to ?-sheet conformation, promoting its assembly into oligomers and subsequently to amyloid fibrils. Oligomers are highly toxic to neurons and have been reported to induce synaptic transmission impairments. The progression from oligomers to fibrils forming senile plaques is currently considered a protective mechanism to avoid the presence of the highly toxic oligomers. Protein nitration is a frequent post-translational modification under AD nitrative stress conditions. A? can be nitrated at tyrosine 10 (Y10) by peroxynitrite. Based on our analysis of ThT binding, Western blot and electron and atomic force microscopy, we report that A? nitration stabilizes soluble, highly toxic oligomers and impairs the formation of fibrils. We propose a mechanism by which fibril elongation is interrupted upon Y10 nitration: Nitration disrupts fibril-forming folds by preventing H14-mediated bridging, as shown with an A? analog containing a single residue (H to E) replacement that mimics the behavior of nitrated A? related to fibril formation and neuronal toxicity. The pathophysiological role of our findings in AD was highlighted by the study of these nitrated oligomers on mouse hippocampal neurons, where an increased NMDAR-dependent toxicity of nitrated A? oligomers was observed. Our results show that A? nitrotyrosination is a post-translational modification that increases A? synaptotoxicity. SIGNIFICANCE STATEMENT:We report that nitration (i.e., the irreversible addition of a nitro group) of the Alzheimer-related peptide amyloid-? (A?) favors the stabilization of highly toxic oligomers and inhibits the formation of A? fibrils. The nitrated A? oligomers are more toxic to neurons due to increased cytosolic calcium levels throughout their action on NMDA receptors. Sustained elevated calcium levels trigger excitotoxicity, a characteristic event in Alzheimer's disease.

Dataset Information

Rationally designed turn promoting mutation in the amyloid-? peptide sequence stabilizes oligomers in solution.

Publications

Rationally designed turn promoting mutation in the amyloid-β peptide sequence stabilizes oligomers in solution.

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