Exploring the Release of Toxic Oligomers from α-Synuclein Fibrils with Antibodies and STED Microscopy

alpha-Synuclein (alpha S) is an intrinsically disordered and highly dynamic protein involved in dopamine release at presynaptic terminals. The abnormal aggregation of alpha S as mature fibrils into intraneuronal inclusion bodies is directly linked to Parkinson's disease. Increasing experimental evidence suggests that soluble oligomers formed early during the aggregation process are the most cytotoxic forms of alpha S. This study investigated the uptake by neuronal cells of pathologically relevant alpha S oligomers and fibrils exploiting a range of conformation-sensitive antibodies, and the super-resolution stimulated emission depletion (STED) microscopy. We found that prefibrillar oligomers promptly penetrate neuronal membranes, thus resulting in cell dysfunction. By contrast, fibril docking to the phospholipid bilayer is accompanied by alpha S conformational changes with a progressive release of A11-reactive oligomers, which can enter into the neurons and trigger cell impairment. Our data provide important evidence on the role of alpha S fibrils as a source of harmful oligomers, which resemble the intermediate conformers formed de novo during aggregation, underling the dynamic and reversible nature of protein aggregates responsible for alpha-synucleinopathies.

Automated summary

This study found that prefibrillar oligomers of alpha-synuclein can quickly penetrate neuronal membranes, leading to cell dysfunction; on the other hand, fibril docking to the phospholipid bilayer causes conformational changes in alpha-synuclein, releasing harmful oligomers.