Martinez Pomier Karla, Ahmed Rashik, Huang Jinfeng, Melacini Giuseppe
Department of Chemistry and Chemical Biology, McMaster University ON L8S 4M1 Canada
Department of Biochemistry and Biomedical Sciences, McMaster University Hamilton ON L8S 4M1 Canada.
Chem Sci. 2024 Jan 31;15(10):3502-3515. doi: 10.1039/d3sc06285f. eCollection 2024 Mar 6.
Human serum albumin (HSA), the most abundant protein in plasma and cerebrospinal fluid, not only serves as a crucial carrier of various exogenous and endogenous ligands but also modulates the aggregation of amyloidogenic proteins, including alpha synuclein (αSyn), which is associated with Parkinson's disease and other α-synucleinopathies. HSA decreases αSyn toxicity through the direct binding to monomeric and oligomeric αSyn species. However, it is possible that HSA also sequesters metal ions that otherwise promote aggregation. Cu(ii) ions, for example, enhance αSyn fibrillization , while also leading to neurotoxicity by generating reactive oxygen species (ROS). However, it is currently unclear if and how HSA affects Cu(ii)-binding to αSyn. Using an integrated set of NMR experiments, we show that HSA is able to chelate Cu(ii) ions from αSyn more efficiently than standard chelators such as EDTA, revealing an unexpected cooperativity between the HSA metal-binding sites. Notably, fatty acid binding to HSA perturbs this cooperativity, thus interfering with the sequestration of Cu(ii) ions from αSyn. We also observed that glycation of HSA diminished Cu(ii)-binding affinity, while largely preserving the degree of cooperativity between the HSA metal-binding sites. Additionally, our results show that Cu(ii)-binding to HSA stabilizes the interactions of HSA with αSyn primarily at two different regions, the N-terminus, Tyr 39 and the majority of the C-terminus. Our study not only unveils the effect of fatty acid binding and age-related posttranslational modifications, such as glycation, on the neuroprotective mechanisms of HSA, but also highlights the potential of αSyn as a viable NMR-based sensor to investigate HSA-metal interactions.
人血清白蛋白（HSA）是血浆和脑脊液中含量最丰富的蛋白质，它不仅是各种外源性和内源性配体的重要载体，还能调节包括α-突触核蛋白（αSyn）在内的淀粉样蛋白的聚集，α-突触核蛋白与帕金森病和其他α-突触核蛋白病有关。HSA通过直接结合单体和寡聚αSyn物种来降低αSyn毒性。然而，HSA也可能螯合原本会促进聚集的金属离子。例如，铜（II）离子会增强αSyn的纤维化，同时通过产生活性氧（ROS）导致神经毒性。然而，目前尚不清楚HSA是否以及如何影响铜（II）与αSyn的结合。通过一组综合的核磁共振实验，我们表明HSA比标准螯合剂（如EDTA）更有效地从αSyn中螯合铜（II）离子，揭示了HSA金属结合位点之间意想不到的协同作用。值得注意的是，脂肪酸与HSA的结合扰乱了这种协同作用，从而干扰了从αSyn中螯合铜（II）离子。我们还观察到HSA的糖基化降低了铜（II）的结合亲和力，同时在很大程度上保留了HSA金属结合位点之间的协同程度。此外，我们的结果表明，铜（II）与HSA的结合主要在两个不同区域稳定了HSA与αSyn的相互作用，即N端的Tyr 39和大部分C端。我们的研究不仅揭示了脂肪酸结合和与年龄相关的翻译后修饰（如糖基化）对HSA神经保护机制的影响，还强调了αSyn作为一种可行的基于核磁共振的传感器来研究HSA-金属相互作用的潜力。
