High-speed atomic force microscopy reveals structural dynamics of amyloid β _1–42 aggregates

Abstract

Aggregation of amyloidogenic proteins into insoluble amyloid fibrils is implicated in various neurodegenerative diseases. This process involves protein assembly into oligomeric intermediates and fibrils with highly polymorphic molecular structures. These structural differences may be responsible for different disease presentations. For this reason, elucidation of the structural features and assembly kinetics of amyloidogenic proteins has been an area of intense study. We report here the results of high-speed atomic force microscopy (HS-AFM) studies of fibril formation and elongation by the 42-residue form of the amyloid β-protein (Aβ1–42), a key pathogenetic agent of Alzheimer's disease. Our data demonstrate two different growth modes of Aβ1–42, one producing straight fibrils and the other producing spiral fibrils. Each mode depends on initial fibril nucleus structure, but switching from one growth mode to another was occasionally observed, suggesting that fibril end structure fluctuated between the two growth modes. This switching phenomenon was affected by buffer salt composition. Our findings indicate that polymorphism in fibril structure can occur after fibril nucleation and is affected by relatively modest changes in environmental conditions.

Self-assembly of the full-length amyloid Aβ42 protein in dimers

“…This asymmetry of the dimer structure may play a role in the next stages of the self-assembly process and create the directionality of aggregate growth, as observed in experiments. 52 Indeed, the substitutions at C termini alter dramatically the Aβ42 monomer-monomer interaction. 51 For instance, (Val36/D-Pro)-(Gly37/L-Pro) replacement destabilize the destabilized the C terminal-turn structure on Aβ42, leading to “Aβ40-like” interaction.…”

Direct Observation and Manipulation of Supramolecular Polymerization by High‐Speed Atomic Force Microscopy

“…Thes eed-induced transformation kinetics,w hich we probed using absorption spectroscopy,w as af irst-order function of the concentration of the seed, thus demonstrating the controlled growth of 1NF.T his process is controllable in am anner analogous to living polymerization in polymer chemistry,a si tc an be initiated and hence is not spontaneous;assuch, it can be termed "living supramolecular polymerization". [23][24][25] Them echanistic similarity across these different disciplines suggests that molecular self-assembly under kinetic control is ap romising tool in bottom-up nanotechnology. [21,22] Moreover,t he seeded growth mechanism is reminiscent of some biomolecular phenomena, such as amyloid fibrillization.…”

Effects of Physical Damage in the Intermediate Phase on the Progression of Amyloid β Fibrillization

“…High‐speed atomic force microscopy (HS‐AFM) is used in the analysis of dynamic behavior, such as fluctuation, association, and dissociation, which occur on the time scale of seconds . Instead of using HS‐AFM as originally developed, we used this method in regional scratching experiments with Aβ1‐42 aggregates.…”