Significant Structural Differences between Transient Amyloid‐β Oligomers and Less‐Toxic Fibrils in Regions Known To Harbor Familial Alzheimer′s Mutations

Abstract

Small oligomers of the amyloid β (Aβ) peptide, rather than the monomers or the fibrils, are suspected to initiate Alzheimer's disease (AD). However, their low concentration and transient nature under physiological conditions have made structural investigations difficult. A method for addressing such problems has been developed by combining rapid fluorescence techniques with slower two-dimensional solid-state NMR methods. The smallest Aβ40 oligomers that demonstrate a potential sign of toxicity, namely, an enhanced affinity for cell membranes, were thus probed. The two hydrophobic regions (residues 10-21 and 30-40) have already attained the conformation that is observed in the fibrils. However, the turn region (residues 22-29) and the N-terminal tail (residues 1-9) are strikingly different. Notably, ten of eleven known Aβ mutants that are linked to familial AD map to these two regions. Our results provide potential structural cues for AD therapeutics and also suggest a general method for determining transient protein structures.

Successive Stages of Amyloid-β Self-Assembly Characterized by Solid-State Nuclear Magnetic Resonance with Dynamic Nuclear Polarization

“…These include approximately spherical Aβ40 and Aβ42 assemblies that form in aqueous buffers 7c , 7d , 18 , Aβ42 oligomers prepared by dialysis of a detergent solution 7b , Aβ40 protofibrils stabilized by interaction with the B10AP antibody 19 , small disc-like Aβ42 oligomers 20 , and Aβ40 oligomers formed in the presence of epigallocatechin-3-gallate (EGCG) 21 . In addition, oligomers formed by a GroES-ubiquitin-Aβ42 fusion protein have been studied by electron paramagnetic resonance with spin labeling 22 .…”

“…To date, most ssNMR studies of Aβ self-assembly intermediates have been performed on samples that were concentrated by lyophilization after oligomer formation 7b-7d , 17c , 18a , 19-20,23 . Lyophilization has been required because Aβ concentrations in oligomer preparations in vitro are typically on the order of 1 mM or less.…”

“…For certain Aβ oligomers and protofibrils, evidence has been presented that lyophilization also does not perturb molecular structures significantly 7c , 7d , 17c , 18a . However, in the case of smaller Aβ assemblies and assemblies that are not metastable, lyophilization may produce significant changes in molecular conformations, intermolecular interactions, and assembly sizes.…”

Effect of amyloids on the vesicular machinery: implications for somatic neurotransmission

“…There are rather precise fluorescence-based methods to characterize the different oligomers. Forster resonance energy transfer (FRET)-based experiments yield the conformational state of the oligomers, while fluorescence correlation spectroscopy (FCS)-based studies can measure the size of the aggregates [111,[113][114][115]. It is important to compare the effects of amyloid aggregates correctly, after duly considering the type of aggregates used in each of these experiments.…”

Improving spectral resolution in biological solid-state NMR using phase-alternated rCW heteronuclear decoupling

“…Solid-state NMR spectroscopy is becoming an increasingly important tool for the atomic scale investigation of biological macromolecules in complex heterogenous environment, including protein complexes, amyloid fibrils, and membrane proteins [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. The growing capability of the method is ascribed to development of high-field instrumentation, fast sample spinning probes, new isotope-labelling procedures, and design of efficient pulse sequences for manipulating the spins to ensure high resolution and establishment of structural parameters.…”