Membrane Remodeling by α-Synuclein and Effects on Amyloid Formation

Abstract

α-Synuclein (α-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 α-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 ∼20 nm). No discernible secondary structural changes were detected by circular dichroism spectroscopy upon the addition of vesicles. Notably, membrane remodeling inhibits α-syn amyloid formation affecting both lag and growth phases. Using five single tryptophan variants and time-resolved fluorescence anisotropy measurements, we determined that α-syn influences bilayer structure with surprisingly weak interaction and no site specificity (partition constant, Kp ∼ 300 M(-1)). Vesicle deformation by α-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 α-syn induced membrane remodeling related to both function and pathogenesis.