Aggregation of an amyloid protein, α-synuclein (αS), is a critical step in the neurodegenerative pathway of Parkinson's diseases (PD). Specific detection of amyloid conformers (i.e., monomers, oligomers, and fibrils) produced during αS aggregation is critical in better understanding a molecular basis of PD and developing a diagnostic tool. While various molecular probes are available for detection of αS fibrils, which may serve as a reservoir of toxic αS aggregate forms, these probes suffer from limited conformer-specificity and operational flexibility. In the present study, we explored the potential of non-self-aggregating peptides derived from the highly aggregation-prone KLVFFAE region of an amyloid protein, β-amyloid, as molecular probes for αS aggregates. We show that of the four peptides tested (KLVFWAK, ELVFWAE, and their C-terminal capping variants, all of which were attached with fluorescein isothiocyanate at their respective N-termini), KLVFWAK with C-terminal capping was selectively bound to αS fibrils over monomers and oligomers and readily used for monitoring αS fibrilization. Our analyses suggest that binding of the peptide to αS fibrils is mediated by both electrostatic and hydrophobic interactions. We anticipate that our peptide can readily be optimized for conformer-specificity and operational flexibility. Overall, this study presents the creation of a KLVFFAE-based molecular probe for αS fibrils and demonstrates fine-tuning of its conformer-specificity by terminal mutations and capping.
Keywords: Amyloid aggregation; Fibril; Peptide probe; Protein engineering; α-synuclein.