BPS2026 – Impact of membrane phase and charge on α synuclein binding

⍺-Synuclein (⍺Syn) is an intrinsically disordered protein (IDP) implicated in neurodegenerative disorders such as Parkinson’s disease and Lewy body dementia. Prevalent in neurons, healthy ⍺Syn plays a role in the docking and fusion of synaptic vesicles, indicating its importance in synaptic transmission. Therefore, the interaction of ⍺Syn with cellular membranes is crucial for proper neuronal function. However, the impact of membrane properties in driving αSyn adsorption is not well understood. Our work aims to characterize the binding of N-terminally acetylated-αSyn (NTA-αSyn) to small unilamellar vesicles (SUVs) as a function of membrane charge and membrane phase. We modulated membrane charge by varying the composition of phospholipids with either zwitterionic or anionic headgroups. To assess the role of membrane phase, we compared NTA-αSyn binding to membranes in the gel phase versus in the liquid phase. Through fluorescence microscopy and circular dichroism spectroscopy coupled with Martini 3 coarse-grained molecular dynamics simulations, we demonstrate that αSyn shows stronger baseline binding to gel-phase membranes. However, the introduction of charge produces a more pronounced increase in binding to vesicles in the liquid state, suggesting that the effect of electrostatics is strongly phase-dependent. Interestingly, our results further demonstrate that binding of αSyn is more dynamic on membranes in the gel state and become less dynamic as it transitions into the liquid state. Altogether, our results provide new insight into how membrane physicochemical properties work synergistically to regulate αSyn binding.