Zacharopoulou Maria, Seetaloo Neeleema, Ross James, Stephens Amberley D, Fusco Giuliana, McCoy Thomas M, Dai Wenyue, Mela Ioanna, Fernandez-Villegas Ana, Martel Anne, Routh Alexander F, De Simone Alfonso, Phillips Jonathan J, Kaminski Schierle Gabriele S
Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, U.K.
Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K.
J Am Chem Soc. 2025 Apr 23;147(16):13131-13145. doi: 10.1021/jacs.4c13473. Epub 2025 Apr 10.
Parkinson's disease (PD) is linked to the aggregation of the intrinsically disordered protein α-synuclein (aSyn), but the precise triggers and mechanisms driving this process remain unclear. Local environmental factors, such as ion concentrations, can influence aSyn's conformational ensemble and its tendency to aggregate. In this study, we explore how physiologically relevant ions, mainly Ca and Na, affect aSyn aggregation, monomer structural dynamics, and fibril polymorphism. ThT fluorescence assays show that all ions speed up aggregation, with Ca having the strongest effect. Using heteronuclear single quantum correlation nuclear magnetic resonance (H-N HSQC NMR) spectroscopy, we validate that Ca binds at the C-terminus while Na interacts nonspecifically across the sequence. Small-angle neutron scattering (SANS) and hydrogen-deuterium exchange mass spectrometry (HDX-MS) show that Na leads to more extended aSyn structures, while Ca results in moderate extension. Molecular dynamics (MD) simulations support this, showing Na increases extension between the NAC region and C-terminus, whereas Ca biases the ensemble toward a moderately elongated structure. MD also shows that Ca increases water persistence times in the hydration shell, indicating that aSyn aggregation propensity is due to a combination of conformational bias of the monomer and solvent mobility. Atomic force microscopy (AFM) points toward the formation of distinct fibril polymorphs under different ionic conditions, suggesting ion-induced monomer changes contribute to the diversity of fibril structures. These findings underscore the pivotal influence of the local ionic milieu in shaping the structure and aggregation propensity of aSyn, offering insights into the molecular underpinnings of PD and potential therapeutic strategies targeting aSyn dynamics.
帕金森病（PD）与内在无序蛋白α-突触核蛋白（aSyn）的聚集有关，但驱动这一过程的确切触发因素和机制仍不清楚。局部环境因素，如离子浓度，可影响aSyn的构象集及其聚集倾向。在本研究中，我们探讨了生理相关离子，主要是Ca和Na，如何影响aSyn聚集、单体结构动力学和纤维多态性。硫黄素T荧光分析表明，所有离子均加速聚集，其中Ca的作用最强。使用异核单量子相关核磁共振（H-N HSQC NMR）光谱，我们验证了Ca在C末端结合，而Na在整个序列中进行非特异性相互作用。小角中子散射（SANS）和氢-氘交换质谱（HDX-MS）表明，Na导致aSyn结构更伸展，而Ca导致适度伸展。分子动力学（MD）模拟支持这一点，表明Na增加了NAC区域和C末端之间的伸展，而Ca使构象集偏向适度伸长的结构。MD还表明，Ca增加了水合壳层中的水持续时间，表明aSyn聚集倾向是由于单体的构象偏向和溶剂流动性的组合。原子力显微镜（AFM）表明在不同离子条件下形成了不同的纤维多态性，表明离子诱导的单体变化导致了纤维结构的多样性。这些发现强调了局部离子环境对aSyn结构和聚集倾向的关键影响，为PD的分子基础和靶向aSyn动力学的潜在治疗策略提供了见解。
