Stabilizing a Native Fold of Alpha-Synuclein with Short Helix-Constrained Peptides

Area of Science:

• Neuroscience
• Biochemistry
• Drug Discovery

Background:

• Alpha-synuclein (αS) aggregation into toxic species is central to Parkinson's disease and Lewy body dementia.
• Targeting intracellular αS aggregation is challenging due to large protein interfaces and poor cell permeability of conventional therapeutics.
• Peptides offer a promising therapeutic modality due to their intermediate size and potential for cell penetration.

Purpose of the Study:

• To identify the smallest functional peptide capable of inhibiting αS aggregation and toxicity.
• To systematically truncate and constrain peptides derived from the αS N-terminal region (αS_1-25) to optimize therapeutic properties.
• To evaluate the impact of helix constraints on peptide efficacy, stability, and cellular activity.

Main Methods:

• Systematic N- and C-terminal truncation of αS_1-25 to reduce peptide size.
• Introduction of i → i + 4 helix constraints to stabilize α-helical structure.
• Assessment of peptide binding to αS, inhibition of αS aggregation, serum stability, neuronal uptake, and phenotypic rescue in cellular models.

Main Results:

• Peptide downsizing achieved a 56% reduction in length while retaining αS binding and aggregation inhibition.
• Helix constraints significantly improved α-helicity, aggregation inhibition, serum stability, and neuronal uptake.
• The optimized peptide, αS_2-12(L6), demonstrated potent inhibition of αS aggregation and toxicity, with enhanced therapeutic characteristics.

Conclusions:

• Key amphipathic features and critical residues for αS engagement and inhibition were identified.
• The helix-constrained peptide αS_2-12(L6) represents a highly effective and promising therapeutic candidate for αS-related neurodegenerative diseases.
• This study provides a roadmap for designing potent peptide-based therapeutics targeting protein aggregation.