Cholesterol is a strong promotor 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 α-Synuclein is a key molecular event. Recent research also suggests that α-Synuclein aggregation is influenced by the lipid environment. The exact molecular mechanisms responsible for cholesterol’s effect on α-Synuclein binding to lipids and how this binding may affect α-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 α-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 α-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 α-Synuclein in response to nanodisc binding, and we determined individual residue apparent affinities for the nanodisc-contained bilayers. Cholesterol inhibited α-Synuclein interaction with lipid bilayers. We also find that cholesterol significantly promotes α-Synuclein fibrillation, with a more than 20-fold reduction of lag-times before fibrillation onset. When α-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 α-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.

Potential Crosstalk Between Parkinson's Disease and Energy Metabolism

“…A recent study reported that cholesterol modulates the conformational state of α-Syn and accelerates its oligomerization [ 99 ]. The treatment of neuronal culture with cholesterol results in excessive α-Syn aggregation.…”

α-Synuclein: An All-Inclusive Trip Around its Structure, Influencing Factors and Applied Techniques

“…Recently, surface plasmon resonance (SPR) was employed to measure the binding of αSyn monomers to lipid vesicles and this resulted decreased with the addition of cholesterol molecules to the membrane composition. The effect was detected also in the presence of negatively charged vesicles ( Jakubec et al, 2019 ). A very recent publication from Fusco and coworkers confirmed these results showing by CD experiments that αSyn binding is reduced in the presence of cholesterol.…”

“…At the same time, Jakubec et al questioned whether cholesterol could influence αSyn fibrillation and they observed that the aggregation was effectively promoted by analyzing ThT (thioflavin T) and TPE-TPP (bis(triphenylphosphonium) tetraphenylethene) fluorescence assays. This outcome could be explained taking into consideration that cholesterol could act as a nucleation site ( Jakubec et al, 2019 ).…”

Current Developments in Native Nanometric Discoidal Membrane Bilayer Formed by Amphipathic Polymers

“…As new developments in this field continues to emerge, the need for The SMALP platform enables us to obtain equally informative snapshots from surroundings of membrane proteins; however, it requires more improvement to a need for engineering the amphipathic polymers for formation of larger nanodiscs. Other analytical approaches such as EPR [ 92 ], Fluorescence-based methods (FRET/BRET) [ 93 ], surface plasmon resonance (SPR) [ 94 ], SAXS, and NMR have been utilized to shed light on lipid dependent protein-protein interaction in the lipid bilayer, receptor oligomerizations/regulation and lipid-dependent oligomerization of essential peripheral membrane proteins (such as α-synuclein and Amyloid precursor protein (APP) peptides) [ 72 , 88 ], in polymer-based nanodiscs. The size and lipid composition of nanodiscs are well-controlled during the preparation of LUV vesicles.…”