Perez-Medina Luciano, Meloni Gabriele
Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, 75080, USA.
Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX, 75080, USA.
Free Radic Biol Med. 2025 Aug 23;240:472-490. doi: 10.1016/j.freeradbiomed.2025.08.047.
Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β peptide (Aβ) in the central nervous system (CNS). Copper coordination to Aβ triggers Aβ aggregation and promotes the catalytic generation of reactive oxygen species (ROS). Due to its amphiphilic nature, Aβ can interact with cell membranes and compromise their integrity. In this work, we characterized the insertion of Aβ into an artificial lipid bilayer system mimicking cell membranes and demonstrate that the Aβ-lipid interaction does not prevent the Cu coordination to Aβ. We performed a comparative analysis of the redox reactivities of membrane-bound Aβ (memAβ-Cu) with soluble Aβ-Cu establishing that membrane insertion leads to memAβ-Cu complexes featuring an enhanced detrimental catechol oxidase activity towards the neurotransmitter dopamine. Moreover, memAβ-Cu efficiently catalyzes Aβ di-tyrosine crosslinking and hydroxyl radical production in the presence of ascorbate. In addition, we establish that memAβ-Cu redox reactivity catalyzes polyunsaturated fatty acids (PUFAs) lipid peroxidation, leading to the generation of malondialdehyde (MDA) toxic end-product. This reactivity compromises the structural integrity of the lipid bilayers resulting in membrane leakage. Metallothioneins (MTs) are cysteine-rich metalloproteins central to neuronal and astrocytic metal homeostasis. MTs bind d metals (Cu and Zn) forming two metal thiolate clusters in their structure. In the CNS, the metallothionein-3 (MT-3) isoform possess a neuroprotective role, but it is downregulated in AD patients. MT-3 controls aberrant protein-Cu interactions and redox reactivities of amyloidogenic protein-Cu complexes, including soluble Aβ In this work, we unravel that the detrimental memAβ-Cu redox reactivities can also be efficiently silenced by MT-3 via metal swap reactions, by scavenging and reducing Cu to Cu in its β-domain using thiolates as electron source, forming the redox-inert CuZnMT-3 species. Consequently, MT-3 efficiently prevents lipid peroxidation and protects membrane structural integrity. New strategies targeting membrane-bound Aβ-Cu complexes as key players in AD etiology could be envisioned.
阿尔茨海默病（AD）的特征是淀粉样β肽（Aβ）在中枢神经系统（CNS）中积聚。铜与Aβ配位会触发Aβ聚集，并促进活性氧（ROS）的催化生成。由于其两亲性，Aβ可与细胞膜相互作用并损害其完整性。在这项工作中，我们表征了Aβ插入模拟细胞膜的人工脂质双层系统的情况，并证明Aβ与脂质的相互作用不会阻止铜与Aβ的配位。我们对膜结合的Aβ（memAβ-Cu）与可溶性Aβ-Cu的氧化还原反应性进行了比较分析，确定膜插入导致memAβ-Cu复合物对神经递质多巴胺具有增强的有害儿茶酚氧化酶活性。此外，在抗坏血酸存在下，memAβ-Cu能有效催化Aβ二酪氨酸交联和羟基自由基生成。另外，我们确定memAβ-Cu氧化还原反应性催化多不饱和脂肪酸（PUFA）脂质过氧化，导致有毒终产物丙二醛（MDA）的生成。这种反应性损害了脂质双层的结构完整性，导致膜泄漏。金属硫蛋白（MT）是富含半胱氨酸的金属蛋白，对神经元和星形胶质细胞的金属稳态至关重要。MT结合二价金属（铜和锌），在其结构中形成两个金属硫醇盐簇。在中枢神经系统中，金属硫蛋白-3（MT-3）异构体具有神经保护作用，但在AD患者中其表达下调。MT-3控制异常的蛋白质-铜相互作用以及淀粉样蛋白-铜复合物（包括可溶性Aβ）的氧化还原反应性。在这项工作中，我们发现有害的memAβ-Cu氧化还原反应性也可以被MT-3通过金属交换反应有效抑制，MT-3利用硫醇盐作为电子源，在其β结构域将铜清除并还原为铜，形成氧化还原惰性的CuZnMT-3物种。因此，MT-3能有效防止脂质过氧化并保护膜结构完整性。可以设想针对膜结合的Aβ-Cu复合物作为AD病因关键因素的新策略。
