title: Mechanisms for the inhibition of amyloid aggregation by small ligands.
abstract: The formation of amyloid aggregates is the hallmark of systemic and neurodegenerative disorders, also known as amyloidoses. Many proteins have been found to aggregate into amyloid-like fibrils and this process is recognized as a general tendency of polypeptides. Lysozyme, an antibacterial protein, is a well-studied model since it is associated in human with systemic amyloidosis and that is widely available from chicken eggs (HEWL, hen egg white lysozyme). In the present study we investigated the mechanism of interaction of aggregating HEWL with rosmarinic acid and resveratrol, that we verified to be effective and ineffective, respectively, in inhibiting aggregate formation. We used a multidisciplinary strategy to characterize such effects, combining biochemical and biophysical methods with molecular dynamics (MD) simulations on the HEWL peptide 49-64 to gain insights into the mechanisms and energy variations associated to amyloid formation and inhibition. MD revealed that neither resveratrol nor rosmarinic acid were able to compete with the initial formation of the β-sheet structure. We then tested the association of two β-sheets, representing the model of an amyloid core structure. MD showed that rosmarinic acid displayed an interaction energy and a contact map comparable to that of sheet pairings. On the contrary, resveratrol association energy was found to be much lower and its contact map largely different than that of sheet pairings. The overall characterization elucidated a possible mechanism explaining why, in this model, resveratrol is inactive in blocking fibril formation, whereas rosmarinic acid is instead a powerful inhibitor.
authors: Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi di Firenze, viale Morgangi 50, 50134 Firenze, Italy matteo.ramazzotti@unifi.it.
authors: Matteo
authors: M
authors: Ramazzotti
authors: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e Salute del Bambino, Università degli Studi di Firenze, Viale Pieraccini 6, 50139 Firenze, Italy.
authors: Fabrizio
authors: F
authors: Melani
authors: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e Salute del Bambino, Università degli Studi di Firenze, Viale Pieraccini 6, 50139 Firenze, Italy.
authors: Laura
authors: L
authors: Marchi
authors: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e Salute del Bambino, Università degli Studi di Firenze, Viale Pieraccini 6, 50139 Firenze, Italy.
authors: Nadia
authors: N
authors: Mulinacci
authors: Liceo Scientifico Statale N. Copernico, via Borgovalsugana 63, 59100 Prato, Italy.
authors: Stefano
authors: S
authors: Gestri
authors: ISC-CNR-Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche Sede di Firenze, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy.
authors: Bruno
authors: B
authors: Tiribilli
authors: Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi di Firenze, viale Morgangi 50, 50134 Firenze, Italy.
authors: Donatella
authors: D
authors: Degl'Innocenti
keywords: HEWL; MD; contact map; energy; molecular modelling; polyphenols