Structure of a Parkinson's Disease-Involved α-Synuclein Peptide Is Modulated by Membrane Composition and Physical...

α-Synuclein (AS), the protein responsible for Parkinson's disease, contains a 12-residue-long sequence, AS_71-82, that is thought to play a crucial role in the α-synuclein aggregation process. Neuronal membranes are direct interacting partners of α-synuclein and play a role in fibrillogenesis by providing a charged catalytic surface, notably from anionic phospholipids. However, details are lacking regarding the impact of membrane composition and the driving forces leading to membrane anchorage and peptide structure conversion. To decipher the interplay of α-synuclein with neuronal membranes, the structure of AS_71-82 was investigated in the presence of anionic model membranes. Infrared (IR) spectroscopy and solid-state nuclear magnetic resonance data show that AS_71-82 adopts a perfectly in-register parallel β-sheet structure with fibrillar morphology upon interactions with anionic model membranes. IR thermotropism experiments conducted with several membrane compositions revealed that the phospholipids' phase transition induces a rearrangement of the AS_71-82 β-sheet structure. In contrast, membranes are not significantly affected by the presence of AS_71-82, which advocates for the amyloid fibrils to lie loosely on the membrane surface. The results bring new arguments for the lipid-sensing capabilities of AS_71-82 and revealed its protofibrillar structure. The striking similarities between AS_71-82 and α-synuclein make it a potential good aggregation inhibitor upon chemical modifications.