Cholesterol is a strong promoter of an α-Synuclein membrane binding mode that accelerates oligomerization

Abstract

Dysregulation of the biosynthesis of cholesterol and other lipids has been implicated in neurological diseases, including Parkinson's disease, where the misfolding of membraneassociated -Synuclein is a key molecular event. Recent research also suggests that -Synuclein aggregation is influenced by the lipid environment. The exact molecular mechanisms responsible for cholesterols effect on -Synuclein binding to lipids and how this binding may affect -Synuclein oligomerization and fibrillation remain elusive, as does the relative importance of cholesterol versus other lipid factors. We probed the interactions and fibrillation behaviour of -Synuclein using SMA nanodiscs, containing zwitterionic and anionic lipid model systems with and without cholesterol. SPR and ThT fluorescence assays were then employed to monitor -Synuclein binding, as well as fibrillation in the absence and presence of membrane models. 1H-15N correlated NMR was used to monitor the fold of -Synuclein in response to nanodisc binding, and we determined individual residue apparent affinities for the nanodisc-contained bilayers. Cholesterol inhibited -Synuclein interaction with lipid bilayers. We also find that cholesterol significantly promotes -Synuclein fibrillation, with a more than 20-fold reduction of lag-times before fibrillation onset. When -Synuclein-bilayer interactions were analysed for individual residues by solution-state NMR, we observed two different effects of cholesterol. In nanodiscs made of DOPC, cholesterol modulated the NAC part of -Synuclein, leading to stronger interaction of this region with the lipid bilayer. In contrast, in the nanodiscs comprising DOPC, DOPE and DOPG, the NAC part was mostly unaffected by cholesterol, while the binding of the N-terminal and the C-terminal were both inhibited.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=194 HEIGHT=200 SRC=\"FIGDIR/small/725762v3_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (54K):\norg.highwire.dtl.DTLVardef@1c9c126org.highwire.dtl.DTLVardef@a7e026org.highwire.dtl.DTLVardef@16d1a9forg.highwire.dtl.DTLVardef@1eeda2d_HPS_FORMAT_FIGEXP M_FIG C_FIG