GM1 oligosaccharide (oligoGM1) stimulates α-synuclein fibrillation in vitro.

VASTI C; CRUZ RODRIGUEZ, L; CELEJ, MS; RODRIGUEZ P; FIDELIO G

Jornada; Primeras Jornadas Virtuales SAB 2020; 2020

α-Synuclein (AS) is an abundant, disordered and highly conserved presynaptic protein in dopaminergic neurons which precise function remains elusive. Intraneuronal aggregates mainly formed by cross-β- AS amyloid fibrils, called Lewy bodies and neurites, are pathognomonic of Parkinson?s disease (PD). Initial studies demonstrated that AS fibril formation is inhibited upon binding to lipid vesicles containing phospholipids of varying composition, in an extent that depends on membrane-induced α-helix formation.[1]. This led to the further observation that the interaction between AS and GM1 ganglioside is particularly strong compared with other gangliosides and lipids[2]. In this work we report for the first time the effect of the oligosaccharide portion of GM1 on fibrillation of AS under in vitro conditions. In order to discern the participation of the oligosaccharide portion of GM1 in the interaction with AS, we synthesized new molecules containing only the oligosaccharide headgroup of GM1 ganglioside (named oligoGM1) and we compared its effect against GM1 micelles. Fibril formation was followed by Thio T fluorescence, a widely-use marker of amyloid fibrils. We were able to demonstrate that oligoGM1 stimulates the formation of amyloid fibrils as compared to GM1 which reduces/inhibits AS aggregation depending on the lipid/protein mole ratio. Furthermore, we analyzed the morphology of fibrils obtained in the presence of oligoGM1 and GM1 by means of atomic force microscopy (AFM). We observed that AS fibrils are lower in height in the presence of oligoGM1 compared to AS fibrils and we visualized structures compatible with AS oligomers in the presence of GM1. This morphological difference correlated with a difference in the intensity of steady-state Thio T fluorescence. These findings highlight the importance of the hydrophobic lipid moiety of GM1 in modulating AS aggregation.