Nanodisc-Forming Scaffold Protein Promoted Retardation of Amyloid-beta Aggregation

摘要

Peptidic-nanodiscs are useful membrane-mimetic tools for structural and functional studies of membrane proteins, and membrane interacting peptides including amyloids. Here, we demonstrate anti-amyloidogenic activities of a nanodisc-forming 18-residue peptide (denoted as 4F), both in lipid-bound and lipid-free states by using Alzheimer’s amyloid-beta (Aβ40) peptide as an example. Fluorescence based amyloid fibrillation kinetic assays showed a significant delay in Aβ40 amyloid aggregation by the 4F peptide. In addition, 4F-encased lipid-nanodiscs, at an optimal concentration of 4F (>20 μM) and nanodisc size (<10 nm), significantly affect amyloid fibrillation. A comparison of experimental results obtained from nanodiscs with that obtained from liposomes revealed a substantial inhibitory efficacy of 4F-lipid-nanodiscs against Aβ40 aggregation and were also found to be suitable to trap Aβ40 intermediates. A combination of atomistic molecular dynamics (MD) simulations with NMR and circular dichroism experimental results exhibited a substantial change in Aβ40 conformation upon 4F binding through electrostatic and π-π interactions. Specifically, the 4F peptide was found to interfere with the central β-sheet-forming residues of Aβ40 through substantial hydrogen, π-π and π-alkyl interactions. Fluorescence experiments and coarse-grained MD simulations showed the formation of a ternary complex, where Aβ40 binds to the proximity of peptidic-belt and membrane surface that deaccelerate amyloid fibrillation. Electron microscopy images revealed short and thick amyloid fibers of Aβ40 formed in presence of 4F or 4F-lipid-nanodsics. These findings could aid in the development of amyloid inhibitors as well as in stabilizing Aβ40 intermediates for high-resolution structural and neurobiological studies.