Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia.
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia.
Int J Mol Sci. 2023 Jul 8;24(14):11241. doi: 10.3390/ijms241411241.
Amyloid-β (Aβ) is a peptide formed by 39-43 amino acids, heterogenous by the length of its C-terminus. Aβ constitutes a subnanomolar monomeric component of human biological fluids; however, in sporadic variants of Alzheimer's disease (AD), it forms soluble neurotoxic oligomers and accumulates as insoluble extracellular polymeric aggregates (amyloid plaques) in the brain tissues. The plaque formation is controlled by zinc ions; therefore, abnormal interactions between the ions and Aβ seem to take part in the triggering of sporadic AD. The amyloid plaques contain various Aβ isoforms, among which the most common is Aβ with an isoaspartate in position 7 (isoD7). The spontaneous conversion of D7 to isoD7 is associated with Aβ aging. Aβ molecules with isoD7 (isoD7-Aβ) easily undergo zinc-dependent oligomerization, and upon administration to transgenic animals (mice, nematodes) used for AD modeling, act as zinc-dependent seeds of the pathological aggregation of Aβ. The formation of zinc-bound homo- and hetero-oligomers with the participation of isoD7-Aβ is based on the rigidly structured segment 11-EVHH-14, located in the Aβ metal binding domain (Aβ). Some hereditary variants of AD are associated with familial mutations within the domain. Among these, the most susceptible to zinc-dependent oligomerization is Aβ with Taiwan (D7H) mutation (D7H-Aβ). In this study, the D7H-Aβ metal binding domain (D7H-Aβ) has been used as a model to establish the molecular mechanism of zinc-induced D7H-Aβ oligomerization through turbidimetry, dynamic light scattering, isothermal titration calorimetry, mass spectrometry, and computer modelling. Additionally, the modeling data showed that a molecule of D7H-Aβ, as well as isoD7-Aβ in combination with two Aβ molecules, renders a stable zinc-induced heterotrimer. The trimers are held together by intermolecular interfaces via zinc ions, with the primary interfaces formed by 11-EVHH-14 sites of the interacting trimer subunits. In summary, the obtained results confirm the role of the 11-EVHH-14 region as a structure and function determinant for the zinc-dependent oligomerization of all known Aβ species (including various chemically modified isoforms and AD-associated mutants) and point at this region as a potent target for drugs aimed to stop amyloid plaque formation in both sporadic and hereditary variants of AD.
淀粉样蛋白-β（Aβ）由 39-43 个氨基酸组成，其 C 末端的长度存在异质性。Aβ是人类生物体液中具有亚纳摩尔浓度的单体成分；然而，在散发性阿尔茨海默病（AD）的变体中，它形成可溶性神经毒性寡聚物，并在脑组织中积累为不溶性细胞外聚合物聚集体（淀粉样斑块）。斑块的形成受锌离子控制；因此，离子与 Aβ 的异常相互作用似乎参与了散发性 AD 的触发。淀粉样斑块包含各种 Aβ 异构体，其中最常见的是位置 7 具有异天冬氨酸（isoD7）的 Aβ。D7 自发转化为 isoD7 与 Aβ 老化有关。具有 isoD7（isoD7-Aβ）的 Aβ 分子容易发生锌依赖性寡聚化，并且在用 AD 建模的转基因动物（小鼠、线虫）中给药时，作为 Aβ 病理性聚集的锌依赖性种子起作用。具有 isoD7-Aβ 的锌结合同型和异型寡聚物的形成基于位于 Aβ 金属结合域（Aβ）中的刚性结构片段 11-EVHH-14。AD 的一些遗传性变体与该域内的家族突变有关。其中，最易受锌依赖性寡聚化影响的是具有台湾（D7H）突变（D7H-Aβ）的 Aβ。在这项研究中，D7H-Aβ 金属结合域（D7H-Aβ）已被用作模型，通过浊度法、动态光散射、等温滴定量热法、质谱法和计算机建模来建立锌诱导 D7H-Aβ 寡聚化的分子机制。此外，建模数据表明，D7H-Aβ 分子以及与两个 Aβ 分子结合的 isoD7-Aβ 形成稳定的锌诱导异型三聚体。三聚体通过锌离子通过分子间界面结合在一起，主要界面由相互作用的三聚体亚基的 11-EVHH-14 位点形成。总之，研究结果证实了 11-EVHH-14 区域作为所有已知 Aβ 物种（包括各种化学修饰的异构体和与 AD 相关的突变体）锌依赖性寡聚化的结构和功能决定因素的作用，并指出该区域是针对旨在阻止散发性和遗传性 AD 变体中淀粉样斑块形成的药物的有效靶点。
