Intracellular Screening of a Peptide Library to Derive a Potent Peptide Inhibitor of ?-Synuclein Aggregation

Aggregation of ?-synuclein (?-syn) into toxic fibrils is a pathogenic hallmark of Parkinson disease (PD). Studies have focused largely on residues 71-82, yet most early-onset mutations are located between residues 46 and 53. A semirationally designed 209,952-member library based entirely on this region was constructed, containing all wild-type residues and changes associated with early-onset PD. Intracellular cell survival screening and growth competition isolated a 10-residue peptide antagonist that potently inhibits ?-syn aggregation and associated toxicity at a 1:1 stoichiometry. This was verified using continuous growth measurements and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity studies. Atomic force microscopy and circular dichroism on the same samples showed a random-coil structure and no oligomers. A new region of ?-syn for inhibitor targeting has been highlighted, together with the approach of using a semirational design and intracellular screening. The peptides can then be used as candidates for modification in drugs capable of slowing or even preventing the onset of PD.