Molecular recycling within amyloid fibrils

Abstract

Amyloid fibrils are thread-like protein aggregates with a core region formed from repetitive arrays of beta-sheets oriented parallel to the fibril axis. Such structures were first recognized in clinical disorders, but more recently have also been linked to a variety of non-pathogenic phenomena ranging from the transfer of genetic information to synaptic changes associated with memory. The observation that many proteins can convert into similar structures in vitro has suggested that this ability is a generic feature of polypeptide chains. Here we have probed the nature of the amyloid structure by monitoring hydrogen/deuterium exchange in fibrils formed from an SH3 domain using a combination of nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry. The results reveal that under the conditions used in this study, exchange is dominated by a mechanism of dissociation and re-association that results in the recycling of molecules within the fibril population. This insight into the dynamic nature of amyloid fibrils, and the ability to determine the parameters that define this behaviour, have important implications for the design of therapeutic strategies directed against amyloid disease.

Disruption of Amyloid‐Derived Peptide Assemblies through the Controlled Induction of a β‐Sheet to α‐Helix Transformation: Application of the Switch Concept

“…The experimental data offer new insights into the stability and structural properties of amyloid fibrils. Our studies support the hypothesis of a dynamic structure for amyloid [5] and demonstrate that significant structural rearrangements can take place within the b-sheet structure of amyloid fibrils.…”

The NatA Acetyltransferase Couples Sup35 Prion Complexes to the [PSI+] Phenotype

“…First, reducing the stability of prion complexes could allow enhanced exchange of Sup35 between the inactive, aggregated form and the functional, soluble form, thereby rescuing the translation termination defect in these strains by continually creating an active but transient pool. Consistent with this idea, dynamic exchange of subunits has been detected for self-replicating complexes of various proteins in vitro (Carulla et al, 2005;Maji et al, 2008). Second, the reduced stability of prion complexes in NatA mutant strains could reflect a partial or complete loss of factors other than Sup35 from these aggregates.…”

Mass spectrometry and the amyloid problem—How far can we go in the gas phase?

“…The amyloid-forming properties of the SH3 domain of bovine phosphatidylinositol-3-kinase (PI3-SH3), an 86-residue protein, have been interrogated in vitro [12,73]. Under acidic pH conditions, P13-SH3 adopts a compact denatured state which slowly forms a gel that consists of typical amyloid fibrils [74].…”

“…Under acidic pH conditions, P13-SH3 adopts a compact denatured state which slowly forms a gel that consists of typical amyloid fibrils [74]. During an HDX-ESI-MS study to probe the nature of this amyloid structure, the fibrils were exposed to deuterated buffer for varying lengths of time and then solubilized into monomers using dimethylsulphoxide before analysis [73]. ESI-MS, with its ability to detect coexisting populations of molecules with different degrees of exchange, showed two well-resolved peaks on HDX exposure, indicating that two distinct isotopically labeled populations are present within the amyloid fibrils: one representing an exchange of ϳ50% of the labile hydrogen atoms, the other almost complete exchange.…”