αB-crystallin affects the morphology of Aβ(1-40) aggregates

Abstract

SummaryαB-crystallin (ABC) is a human small heat shock protein that is strongly linked to Alzheimer’s disease (AD). In vitro, it can inhibit the aggregation and amyloid formation of a range of proteins including Aβ(1-40), a primary component of AD amyloid plaques. Despite the strong links, the mechanism by which ABC inhibits amyloid formation has remained elusive, in part due to the notorious irreproducibility of aggregation assays involving preparations of Aβ-peptides of native sequence. Here, we present a recombinant expression protocol to produce native Aβ(1-40), devoid of any modifications or exogenous residues, with yields up to 4 mg/L E. coli. This material provides highly reproducible aggregation kinetics and, by varying the solution conditions, we obtain either highly ordered amyloid fibrils or more disordered aggregates. Addition of ABC slows the aggregation of Aβ(1-40), and interferes specifically with the formation of ordered amyloid fibrils, favouring instead the more disordered aggregates. Solution-state NMR spectroscopy reveals that the interaction of ABC with Aβ(1-40) depends on the specific aggregate morphology. These results provide mechanistic insight into how ABC inhibits the formation of amyloid fibrils.HighlightsProtocol for production of native recombinant Aβ(1-40)Amyloid formation under physiological conditions is highly reproducibleBoth ordered fibrils and disordered aggregates can be reliably formedαB-crystallin specifically inhibits amyloid fibril assembling, favouring disordered aggregateseTOC blurbMüller et al. introduce a protocol for the highly reproducible production of amyloid from native Aβ(1-40) and determine that the human chaperone ABC specifically destabilises them in favour of disordered aggregates. NMR shows that ABC can distinguish between aggregate morphologies.Graphical Abstract