Inhibition of α-Synuclein Amyloid Fibril Elongation by Blocking Fibril Ends

Misfolding of the protein α-synuclein (αSyn) into amyloid fibrils plays a central role in the development of Parkinson's disease. Most approaches for the inhibition of αSyn fibril formation are based on stabilizing the native monomeric form of the protein or destabilizing the fibrillized misfolded form. They require high concentrations of inhibitor and therefore cannot be easily used for therapies. In this work, we designed an inhibitor (Inh-β) that selectively binds the growing ends of αSyn fibrils and creates steric hindrance for the binding of monomeric αSyn. This approach permits the inhibition of fibril formation at Inh-β concentrations (IC₅₀ =850 nm) much lower than the concentration of monomeric αSyn. We studied its kinetic mechanism in vitro and identified the reactions that limit inhibition efficiency. It is shown that blocking of αSyn fibril ends is an effective approach to inhibiting fibril growth and provides insights for the development of effective inhibitors of αSyn aggregation.