Binding Interactions of Agents That Alter α-Synuclein Aggregation.

Area of Science:

• Biochemistry
• Neuroscience
• Drug Discovery

Background:

• Alpha-synuclein aggregation into amyloid fibrils is central to Parkinson's disease pathogenesis.
• Developing small peptides to inhibit alpha-synuclein amyloid formation is a key therapeutic strategy.
• Previous inhibitors sometimes promote non-amyloid aggregate formation, necessitating improved designs.

Purpose of the Study:

• To design and identify more potent peptide inhibitors of alpha-synuclein amyloid formation.
• To elucidate the mechanism of inhibition and binding sites of effective peptide inhibitors.
• To investigate the early stages of alpha-synuclein aggregation using biophysical techniques.

Main Methods:

• Synthesis and characterization of novel peptide inhibitors, including backbone cyclized variants.
• Inhibition assays to assess the effect of peptides on alpha-synuclein beta-structure formation.
• Nuclear Magnetic Resonance (NMR) spectroscopy (15N HSQC) to study alpha-synuclein-peptide interactions and aggregation dynamics.

Main Results:

• Several new peptides, particularly those with multiple tyrosine residues and Trp-bearing structures, demonstrated potent inhibition.
• The backbone cyclized peptide cyclo-WW2, featuring a Trp/Trp cluster, completely inhibited beta-structure formation at a 2:1 ratio.
• NMR studies revealed that effective inhibitors bind to the C-terminal segment (Q109-E137) of alpha-synuclein, with cyclo-WW2 also binding to the G41-T54 region.
• NMR data provided mechanistic insights into early aggregation, identifying H50 as a critical residue and a binding site for cyclo-WW2.

Conclusions:

• Peptides incorporating antiparallel beta-strands, especially with Trp residues and specific cyclization strategies, are highly effective inhibitors of alpha-synuclein amyloidogenesis.
• Cyclo-WW2 represents a lead compound for developing small peptide inhibitors that specifically block amyloid formation without promoting alternative aggregation pathways.
• Understanding the binding sites and early aggregation mechanisms via NMR is crucial for designing targeted therapeutic interventions for synucleinopathies.