Molecular, Cellular and Integrative Neurosciences Program, Colorado State University, Fort Collins, Colorado, USA; Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
J Biol Chem. 2021 Jan-Jun;296:100402. doi: 10.1016/j.jbc.2021.100402. Epub 2021 Feb 9.
Beta-amyloid (Aβ) has been recognized as an early trigger in the pathogenesis of Alzheimer's disease (AD) leading to synaptic and cognitive impairments. Aβ can alter neuronal signaling through interactions with nicotinic acetylcholine receptors (nAChRs), contributing to synaptic dysfunction in AD. The three major nAChR subtypes in the hippocampus are composed of α7-, α4β2-, and α3β4-nAChRs. Aβ selectively affects α7- and α4β2-nAChRs, but not α3β4-nAChRs in hippocampal neurons, resulting in neuronal hyperexcitation. However, how nAChR subtype selectivity for Aβ affects synaptic function in AD is not completely understood. Here, we showed that Aβ associated with α7- and α4β2-nAChRs but not α3β4-nAChRs. Computational modeling suggested that two amino acids in α7-nAChRs, arginine 208 and glutamate 211, were important for the interaction between Aβ and α7-containing nAChRs. These residues are conserved only in the α7 and α4 subunits. We therefore mutated these amino acids in α7-containing nAChRs to mimic the α3 subunit and found that mutant α7-containing receptors were unable to interact with Aβ. In addition, mutant α3-containing nAChRs mimicking the α7 subunit interact with Aβ. This provides direct molecular evidence for how Aβ selectively interacted with α7- and α4β2-nAChRs, but not α3β4-nAChRs. Selective coactivation of α7- and α4β2-nAChRs also sufficiently reversed Aβ-induced AMPA receptor dysfunction, including Aβ-induced reduction of AMPA receptor phosphorylation and surface expression in hippocampal neurons. Moreover, costimulation of α7- and α4β2-nAChRs reversed the Aβ-induced disruption of long-term potentiation. These findings support a novel mechanism for Aβ's impact on synaptic function in AD, namely, the differential regulation of nAChR subtypes.
β-淀粉样蛋白(Aβ)已被认为是阿尔茨海默病(AD)发病机制中的早期触发因素,导致突触和认知功能障碍。Aβ 通过与烟碱型乙酰胆碱受体(nAChRs)相互作用改变神经元信号转导,导致 AD 中的突触功能障碍。海马体中的三种主要 nAChR 亚型由α7-、α4β2-和α3β4-nAChRs 组成。Aβ 选择性影响海马神经元中的α7-和α4β2-nAChRs,但不影响α3β4-nAChRs,导致神经元过度兴奋。然而,nAChR 亚型对 Aβ 的选择性如何影响 AD 中的突触功能尚不完全清楚。在这里,我们表明 Aβ 与α7-和α4β2-nAChRs 相关,但与α3β4-nAChRs 无关。计算建模表明,α7-nAChRs 中的两个氨基酸,精氨酸 208 和谷氨酸 211,对于 Aβ 与包含α7 的 nAChRs 之间的相互作用很重要。这些残基仅在α7 和α4 亚基中保守。因此,我们在包含α7 的 nAChRs 中突变这些氨基酸以模拟α3 亚基,发现突变的包含α7 的受体无法与 Aβ 相互作用。此外,模拟α7 亚基的突变α3 包含的 nAChRs 与 Aβ 相互作用。这为 Aβ 如何选择性地与α7-和α4β2-nAChRs 相互作用而不是与α3β4-nAChRs 相互作用提供了直接的分子证据。α7-和α4β2-nAChRs 的选择性共激活也足以逆转 Aβ 诱导的 AMPA 受体功能障碍,包括 Aβ 诱导的海马神经元中 AMPA 受体磷酸化和表面表达减少。此外,α7-和α4β2-nAChRs 的共刺激逆转了 Aβ 诱导的长时程增强的破坏。这些发现支持 Aβ 对 AD 中突触功能影响的一种新机制,即 nAChR 亚型的差异调节。
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