Biology subjects

Dear, A. J.

Publications and source records attributed to Dear, A. J..

3 recordsLinked to original sources

bioRxiv2024

Global kinetic model of lipid-induced alpha-synuclein aggregation and its inhibition by small molecules

The aggregation of -synuclein into amyloid fibrils is a hallmark of Parkinsons disease. This process has been shown to directly involve interactions between proteins and lipid surfaces when the latter are present. Despite this importance, the molecular mechanisms of lipid-induced amyloid aggregation have remained largely elusive. Here, we present a global kinetic model to describe lipid-induced amyloid aggregation of -synuclein. Using this framework we find that -synuclein fibrils form via a two-step primary nucleation mechanism and that lipid molecules are directly involved in both the nucleation and fibril elongation steps, giving rise to lipid-protein coaggregates. To illustrate the applicability of this kinetic approach to drug discovery, we identify the mechanism of action of squalamine, a known inhibitor of -synuclein aggregation, finding that this small molecule reduces the rate of lipid-dependent primary nucleation. Our work will likely guide the rational design of -synuclein aggregation inhibitors. Significance StatementAmyloid aggregation is a hallmark of a diverse range of diseases including Parkinsons Disease, where the protein -synuclein is a major con-stituent of proteinaceous deposits found in patients. It is well established that interactions between -synuclein and lipids modulate aggregation. However, the molecular mechanisms driving this lipid-induced aggregation have remained largely elusive, which has frustrated so far the discovery of drugs that prevent lipid-induced aggregation. In this work, we present the first global kinetic model describing lipid-induced aggregation and by integrating this theoretical framework with in vitro experimental data of lipid-induced -synuclein aggregation, we reveal the role of lipid membranes in the aggregation process and uncover the mechanism by which small molecule inhibitors interfere with this process.

biophysics↗

bioRxiv2023

Molecular mechanism of α-synuclein aggregation on lipid membranes revealed.

The central hallmark of Parkinsons disease pathology is the aggregation of the -synuclein protein, which, in its healthy form, is associated with lipid membranes. Purified monomeric -synuclein is relatively stable in vitro, but its aggregation can be triggered by the presence of lipid vesicles. Despite this central importance of lipids in the context of -synuclein aggregation, their mechanistic role in this process has not been established to date. Here, we use chemical kinetics to develop a detailed mechanistic model that is able to globally describe the aggregation behaviour of -synuclein in the presence of DMPS lipid vesicles, across a range of lipid and protein concentrations. Through the application of our kinetic model to experimental data, we find that the reaction is a co-aggregation process involving both protein and lipids and that lipids promote aggregation predominantly by enabling the elongation process. Moreover, we find that the initial formation of aggregates, via primary nucleation, takes place not on the surface of lipid vesicles but at the interfaces present in vitro. Our model will enable mechanistic insights, also in other lipid-protein co-aggregation systems, which will be crucial in the rational design of drugs that inhibit aggregate formation and act at the key points in the -synuclein aggregation cascade.

biophysics↗

bioRxiv2023

α-Synuclein oligomers form by secondary nucleation

Oligomeric species arising during aggregation of -synuclein are proposed to be a major source of toxicity in Parkinsons disease, and thus a major potential drug target. However, their mechanism of formation and role in aggregation are largely unresolved. Here we first show that, at physiological pH, -synuclein aggregates by secondary nucleation, rather than fragmentation, and that this process is enhanced by agitation. Moreover, using a combination of single molecule and bulk level techniques, we identify secondary nucleation on the surfaces of existing fibrils, rather than formation directly from monomers, as the dominant source of oligomers. Our results highlight secondary nucleation as not only the key source of oligomers, but also the main mechanism of aggregate formation, and show that these processes take place under physiologically relevant conditions.

biophysics↗