Therapeutic Peptide SS-31 Modulates Membrane Binding and Aggregation of α-Synuclein and Restores Impaired Mitochondrial Function.

Membrane binding and aggregation properties of α-synuclein are closely associated with Parkinson's disease and a class of related syndromes named as synucleinopathy. This study explored the potential of SS-31 (Elamipretide), a therapeutic tetrapeptide with alternating cationic and aromatic residues and known properties of mitochondrial inner membrane binding and oxidative stress reduction, in modulating α-synuclein interaction with the lipid membranes and mitigating the impairment of mitochondrial function induced by α-synuclein oligomers. It was demonstrated by both fluorescence correlation spectroscopy and fluorescence anisotropy that SS-31 displaces both wild-type and N-terminal acetylated α-synuclein from negatively charged small unilamellar vesicles in a dose-dependent manner. Thioflavin-T assay and transmission electron microscopy showed that SS-31 inhibits membrane-induced α-synuclein aggregation and alters the morphology of α-synuclein fibrils. Moreover, MTT assay and Seahorse Mito Stress Test indicated that SS-31 enhances cell viability and restores impaired mitochondrial function in α-synuclein oligomer-treated neuroblastoma cells. Finally, confocal imaging revealed that SS-31 hinders cellular uptake of α-synuclein oligomers, possibly by modifying cell membrane electrostatics. These findings suggest that SS-31 potentially attenuates α-synuclein induced mitochondrial impairment via its interaction with the lipid membranes, justifying further development of a peptide-based intervention against α-synuclein mediated pathology.