Ligand Profiling to Characterize Different Polymorphic Forms of α-Synuclein Aggregates

The presence of amyloid fibrils is a characteristic feature of many diseases, most famously neurodegenerative disease. The supramolecular structure of these fibrils appears to be disease-specific. Identifying the unique morphologies of amyloid fibrils could, therefore, form the basis of a diagnostic tool. Here we report a method to characterize the morphology of alpha-synuclein (alpha Syn) fibrils based on profiling multiple different ligand binding sites that are present on the surfaces of fibrils. By employing various competition binding assays, seven different types of binding sites were identified on four different morphologies of alpha Syn fibrils. Similar binding sites on different fibrils were shown to bind ligands with significantly different affinities. We combined this information to construct individual profiles for different alpha Syn fibrils based on the distribution of binding sites and ligand interactions. These results demonstrate that ligand-based profiling can be used as an analytical method to characterize fibril morphologies with operationally simple fluorescence binding assays.

Automated summary

This study reports a method to characterize the morphology of alpha-synuclein fibrils by profiling multiple ligand binding sites on their surfaces. By using various competition binding assays, seven different types of binding sites were identified on four different morphologies of alpha-synuclein fibrils. Similar binding sites on different fibrils showed significantly different affinities for ligands. The information on binding sites and ligand interactions was combined to construct individual profiles for different alpha-synuclein fibrils.