Inorg Chem. 2021 Jun 21;60(12):8958-8972. doi: 10.1021/acs.inorgchem.1c00846. Epub 2021 May 27.
Amyloid β (Aβ) is a Cu-binding peptide that plays a key role in the pathology of Alzheimer's disease. A recent report demonstrated that Aβ disrupts the Cu-dependent interaction between cellular prion protein (PrP) and -methyl-d-aspartate receptor (NMDAR), inducing overactivation of NMDAR and neurotoxicity. In this context, it has been proposed that Aβ competes for Cu with PrP; however, there is no spectroscopic evidence to support this hypothesis. Prion protein (PrP) can bind up to six Cu(II) ions: from one to four at the octarepeat (OR) region, producing low- and high-occupancy modes, and two at the His96 and His111 sites. Additionally, PrP is cleaved by α-secretases at Lys110/His111, yielding a new Cu(II)-binding site at the α-cleaved His111. In this study, the competition for Cu(II) between Aβ(1-16) and peptide models for each Cu-binding site of PrP was evaluated using circular dichroism and electron paramagnetic resonance. Our results show that the impact of Aβ(1-16) on Cu(II) coordination to PrP is highly site-specific: Aβ(1-16) cannot effectively compete with the low-occupancy mode at the OR region, whereas it partially removes the metal ion from the high-occupancy modes and forms a ternary OR-Cu(II)-Aβ(1-16) complex. In contrast, Aβ(1-16) removes all Cu(II) ions from the His96 and His111 sites without formation of ternary species. Finally, at the α-cleaved His111 site, Aβ(1-16) yields at least two different ternary complexes depending on the ratio of PrP/Cu(II)/Aβ. Altogether, our spectroscopic results indicate that only the low-occupancy mode at the OR region resists the effect of Aβ, while Cu(II) coordination to the high-occupancy modes and all other tested sites of PrP is perturbed, by either removal of the metal ion or formation of ternary complexes. These results provide important insights into the intricate effect of Aβ on Cu(II) binding to PrP and the potential neurotoxic mechanisms through which Aβ might affect Cu-dependent functions of PrP, such as NMDAR modulation.
淀粉样蛋白β（Aβ）是一种 Cu 结合肽，在阿尔茨海默病的病理学中起关键作用。最近的一份报告表明，Aβ破坏了细胞朊病毒蛋白（PrP）与 N-甲基-D-天冬氨酸受体（NMDAR）之间的 Cu 依赖性相互作用，导致 NMDAR过度激活和神经毒性。在这种情况下，有人提出 Aβ与 PrP 竞争 Cu；然而，没有光谱证据支持这一假设。朊病毒蛋白（PrP）可以结合多达六个 Cu(II)离子：在八重复（OR）区域有一到四个，产生低和高占有率模式，在 His96 和 His111 位点有两个。此外，PrP 被 α-分泌酶在 Lys110/His111 处切割，在 α-切割 His111 处产生新的 Cu(II)结合位点。在这项研究中，使用圆二色性和电子顺磁共振评估了 Aβ(1-16)与 PrP 每个 Cu 结合位点的肽模型之间对 Cu(II)的竞争。我们的结果表明，Aβ(1-16)对 PrP 中 Cu(II)配位的影响具有高度的位点特异性：Aβ(1-16)不能有效地与 OR 区域的低占有率模式竞争，而它部分地从高占有率模式中去除金属离子并形成三元 OR-Cu(II)-Aβ(1-16)配合物。相比之下，Aβ(1-16)从 His96 和 His111 位点去除所有的 Cu(II)离子而不形成三元物种。最后，在 α-切割 His111 位点，Aβ(1-16)根据 PrP/Cu(II)/Aβ 的比例产生至少两种不同的三元配合物。总之，我们的光谱结果表明，只有 OR 区域的低占有率模式抵抗 Aβ 的影响，而 Cu(II)与 PrP 的高占有率模式和所有其他测试位点的配位受到干扰，要么是金属离子被去除，要么是形成三元配合物。这些结果为 Aβ 对 PrP 中 Cu(II)结合的复杂影响以及 Aβ 可能通过影响 PrP 的 Cu 依赖性功能（如 NMDAR 调节）而产生潜在神经毒性机制提供了重要的见解。
