Rationally Designed Protein-Based Inhibitor of -Synuclein Fibrillization in Cells

Misfolding of the neuronal protein alpha-synuclein (alpha Syn) into amyloid fibrils is involved in the development of Parkinson's disease (PD), and inhibition of this process is considered to be a promising therapeutic approach. In this work, we engineered protein inhibitors that bind to fibrils with higher affinity than the monomeric alpha Syn. They were developed based on the recent structural data of the alpha Syn fibrils and were shown to prevent fibril elongation upon binding to fibril ends. These inhibitors are highly selective to the misfolded alpha Syn, nontoxic, and active in cytosol in small concentrations. The best-performing inhibitor shows IC50 similar to 10 nM in a cell-based assay, which corresponds to the similar to 1:60 molar ratio to alpha Syn. It can suppress the formation of alpha Syn aggregates in cells that can be potentially used to slow down the spreading of the pathological aggregates from cell to cell during the course of the PD.