Interactions of α-synuclein with membranes.

SHVADCHAK VV; FALOMIR LOCKHART LJ; YUSHCHENKO DA; JOVIN TM

Strassburg

Congreso; MAF-12; 2011

MAF

α-synuclein (AS) is the main constituent of pathological deposits in the midbrain of individuals affected by Parkinson’s disease. Evidence suggests that neurotoxicity may originate from the binding of oligomeric AS to cellular membranes, resulting in disruption and cell leakage. Defining the interactions of AS with membranes is thus essential for understanding its physiological and pathological functions. We performed a systematic in vitro study of the effects of membrane charge, phase, curvature, defects and lipid unsaturation on AS binding using model vesicles and AS labeled with a new solvatochromic fluorescent probe MFE. This dye senses protein microenvironment via the ratio of two emission bands resulting from Excited State Intramolecular Proton Transfer (ESIPT). The emission spectrum of MFE strongly depends on the membrane properties, allowing clear discrimination of the protein bound to vesicles of different composition and corresponding affinities by competition experiment without performing titrations. The two-band ratiometric response of the MFE label also enables stopped-flow measurements of the kinetics of AS migration between membranes of different compositions [1], that are hardly accessible by conventional methods. The interaction of AS with vesicular membranes is fast and reversible. The protein dissociates from neutral membranes upon thermal transition to the Ld phase and transfers to vesicles with higher affinity, e.g. those that are negatively charged.