PDF(Pubmed)
Abstract：
Copper ion dys-homeostasis is linked to neurodegenerative diseases involving amyloid formation. Even if many amyloidogenic proteins can bind copper ions as monomers, little is known about copper interactions with the resulting amyloid fibers. Here, we investigate copper interactions with α-synuclein, the amyloid-forming protein in Parkinson\'s disease. Copper (Cu(II)) binds tightly to monomeric α-synuclein in vitro involving the N-terminal amine and the side chain of His50. Using purified protein and biophysical methods in vitro, we reveal that copper ions are readily incorporated into the formed amyloid fibers when present at the start of aggregation reactions, and the metal ions also bind if added to pre-formed amyloids. Efficient incorporation is observed for α-synuclein variants with perturbation of either one of the high-affinity monomer copper-binding residues (i.e., N-terminus or His50) whereas a variant with both N-terminal acetylation and His50 substituted with Ala does not incorporate any copper into the amyloids. Both the morphology of the resulting α-synuclein amyloids (amyloid fiber pitch, secondary structure, proteinase sensitivity) and the copper chemical properties (redox activity, chemical potential) are altered when copper is incorporated into amyloids. We speculate that copper chelation by α-synuclein amyloids contributes to the observed copper dys-homeostasis (e.g., reduced bioavailable levels) in Parkinson\'s disease patients. At the same time, amyloid-copper interactions may be protective to neuronal cells as they will shield aberrantly free copper ions from promotion of toxic reactive oxygen species.
摘要：
铜离子动态平衡与涉及淀粉样蛋白形成的神经退行性疾病有关。即使许多淀粉样蛋白可以结合铜离子作为单体，对铜与淀粉样蛋白纤维的相互作用知之甚少。这里,我们研究了铜与α-突触核蛋白的相互作用，帕金森病中的淀粉样蛋白。铜（Cu（II））在体外与单体α-突触核蛋白紧密结合，涉及N末端胺和His50的侧链。使用体外纯化的蛋白质和生物物理方法，我们揭示了铜离子在聚集反应开始时很容易掺入形成的淀粉样蛋白纤维中，如果添加到预先形成的淀粉样蛋白中，金属离子也会结合。对于α-突触核蛋白变体，观察到有效的掺入，其中任何一个高亲和力单体铜结合残基（即，N末端或His50），而同时具有N末端乙酰化和用Ala取代的His50的变体不将任何铜掺入淀粉样蛋白中。所得α-突触核蛋白淀粉样蛋白（淀粉样蛋白纤维沥青，二级结构,蛋白酶敏感性)和铜化学性质(氧化还原活性，当将铜掺入淀粉样时，化学势）会发生变化。我们推测，α-突触核蛋白淀粉样蛋白的铜螯合有助于观察到的铜动态平衡（例如，帕金森病患者的生物可利用水平降低)。同时,淀粉样蛋白-铜相互作用可能对神经元细胞具有保护作用，因为它们将保护异常游离的铜离子免受毒性活性氧的促进。
