alpha-Synuclein Association with Lipids Modulate Its Conformation And Aggregation Process

FALOMIR LOCKHART LJ; SHVADCHAK VV; JOVIN TM

Maastricht

Congreso; 9th ISSFAL Meeting - Maastricht 2010; 2010

ISSFAL - University of Maastricht

Background: Parkinson’s Disease is a progressive neurodegenerative pathology present in more than 1% of the population older than 65 years. This disease is characterized by amyloid aggregates of proteins known as Lewy bodies, alpha-Synuclein (AS) being the most abundant component. AS is also of particular interest because it belongs to the group of natively unfolded proteins. Objective: To investigate the role of the lipids representative of neuronal tissue on the putative conformational changes that may trigger the pathological aggregation of AS we conducted experiments evaluating the interactions of monomeric and different stages of aggregated AS with fatty acids (FA) as well as with phospholipidic membranes. Procedure: We employed AS labeled at positions 18, 90 or 140 with a solvatochromic fluorescent dye of 3-hydroxyflavone family (which reports local environmental polarity and H-bonding) to characterize the binding of monomeric AS to membranes. The aggregation process of AS was followed in parallel by standard ThioflavinT assay, vesicle leakage of ANTS/DPX complexes, Static and Dynamic Light Scattering and Atomic Force Microscopy in the presence of saturated (SFA), monounsaturated (MUFA) and polyunsaturated FA (PUFA). Results: Membrane charge and curvature, phospholipid phase and the degree of unsaturation of the FA are important factors that modulate AS conformation and binding to lipids. In particular, AS seems to preferentially bind to negatively charged membranes or neutral phospholipids in the gel phase, and its conformation in the interface depends on the properties of the membrane and the protein/lipid ratio. Conclusions: The fluorescent probes employed can clearly discriminate monomeric AS bound to membranes of different composition, and the labels at different positions also allowed us to estimate the relative immersion of different regions of the protein into the membranes. The presence of FA have different effects on the aggregation kinetics of AS.