Membrane Remodeling by α-Synuclein and Effects on Amyloid Formation

alpha-Synuclein (alpha-Syn), an intrinsically disordered protein, is associated with Parkinson's disease. Though molecular pathogenic mechanisms are ill-defined, mounting evidence connects its amyloid forming and membrane binding propensities to disease etiology. Contrary to recent data suggesting that membrane remodeling by alpha-syn involves anionic phospholipids and helical structure, we discovered that the protein deforms vesicles with no net surface charge (phosphatidylcholine, PC) into tubules (average diameter similar to 20 nm). No discernible secondary structural changes were detected by circular dichroism spectroscopy upon the addition of vesicles. Notably, membrane remodeling inhibits alpha-syn amyloid formation affecting both lag and growth phases. Using five single tryptophan variants and time-resolved fluorescence anisotropy measurements, we determined that alpha-syn influences bilayer structure with surprisingly weak interaction and no site specificity (partition constant, K-P similar to 300 M-1). Vesicle deformation by alpha-syn under a variety of different lipid/protein conditions is characterized via transmission electron microscopy. As cellular membranes are enriched in PC lipids, these results support possible biological consequences for alpha-syn induced membrane remodeling related to both function and pathogenesis.