Biology subjects

Curk, S.

Publications and source records attributed to Curk, S..

4 recordsLinked to original sources

bioRxiv2025

Structural defects in amyloid-β fibrils drive secondary nucleation

The nucleation of amyloid fibrils from monomeric protein, catalyzed by the surface of existing fibrils, is an important driver of many disorders such as Alzheimers and Parkinsons diseases. The structural basis of this secondary nucleation process, however, is poorly understood. Here, we ask whether secondary nucleation sites are found predominantly at rare growth defects: defects in the fibril core structure generated during their original assembly. We first demonstrate using the specific inhibitor of secondary nucleation, Brichos, that secondary nucleation sites on Alzheimers disease-associated fibrils composed of A{beta}40 and A{beta}42 peptides are rare compared to the number of protein molecules they contain. We then grow A{beta}40 fibrils under conditions designed to eliminate most growth defects while leaving the regular fibril morphology unchanged, and confirm the latter using cryo-electron microscopy. We measure both the ability of these annealed fibrils to promote secondary nucleation and the stoichiometry of their secondary nucleation sites, finding that both are greatly reduced as predicted. Re-analysis of published data for other proteins suggests that fibril growth defects that expose monomer planes or other structural units may also drive secondary nucleation generally, across most or all amyloids. These findings could unlock structure-based drug design of therapeutics that aim to halt amyloid disorders by inhibiting secondary nucleation sites.

biophysics↗

bioRxiv2023

Self-replication of Abeta42 aggregates occurs on small and isolated fibril sites

Self-replication of amyloid fibrils via secondary nucleation is an intriguing physicochemical phenomenon in which existing fibrils catalyse the formation of their own copies. The molecular events behind this fibril surface-mediated process remain largely inaccessible to current structural and imaging techniques. Using statistical mechanics, computer modelling, and chemical kinetics, we show that the catalytic structure of the fibril surface can be inferred from the aggregation behaviour in the presence and absence of a fibril-binding inhibitor. We apply our approach to the case of Alzheimers A{beta}42 amyloid fibrils formed in the presence of proSP-C Brichos inhibitors. We find that self-replication of A{beta}42 fibrils occurs on small catalytic sites on the fibril surface, which are far apart from each other, and each of which can be covered by a single Brichos inhibitor.

biophysics↗

bioRxiv2020

Thermodynamic and kinetic design principles for protein aggregation inhibitors

Understanding the mechanism of action of compounds capable of inhibiting protein aggregation is critical to the development of potential ther-apeutics against protein misfolding diseases. A fundamental challenge for progress is the range of possible target species and the disparate timescales involved, since the aggregating proteins are simultaneously the reactants, products, intermediates and catalysts of the reaction. It is a complex problem, therefore, to choose the states of the aggregating proteins that should be bound by the compounds to achieve the most potent inhibition. We present here a comprehensive kinetic theory of protein aggregation inhibition which reveals the fundamental thermodynamic and kinetic signatures characterising effective inhibitors by identifying quantitative relationships between the aggregation and binding rate constants. These results provide general physical laws to guide the design and optimisation of protein aggregation inhibitors.

biophysics↗

bioRxiv2020

Dynamics of oligomer populations formed during the aggregation of Alzheimer's Aβ42 peptide

Oligomeric aggregates populated during the aggregation of the A{beta}42 peptide have been identified as potent cytotoxins linked to Alzheimers disease, but the fundamental molecular pathways that control their dynamics have yet to be elucidated. By developing a general approach combining theory, experiment, and simulation, we reveal in molecular detail the mechanisms of A{beta}42 oligomer dynamics during amyloid fibril formation. Even though all mature amyloid fibrils must originate as oligomers, we find that most A{beta}42 oligomers dissociate to their monomeric precursors without forming new fibrils. Only a minority of oligomers converts into fibrillar species. Moreover, the heterogeneous ensemble of oligomeric species interconverts on timescales comparable to aggregation. Our results identify fundamentally new steps that could be targeted by therapeutic interventions designed to combat protein misfolding diseases.

biophysics↗