Vicerrectoría de Investigación y Estudios de Posgrado, Benemérita Universidad Autónoma de Puebla, 72000 Puebla, Pue., Mexico.
Laboratory of Computational Molecular Simulations, Departamento de Farmacia, Benemérita Universidad Autónoma de Puebla, 72410 Puebla, Pue., Mexico.
ACS Chem Neurosci. 2022 Jan 19;13(2):229-244. doi: 10.1021/acschemneuro.1c00639. Epub 2022 Jan 6.
The activation of -methyl-d-aspartate receptor (NMDAR) is triggered by the closure of bilobed (D1 and D2) clamshell-like clefts upon binding glycine (Gly) and glutamate. There is evidence that cholinergic compounds modulate NMDAR-mediated currents via direct receptor-ligand interactions; however, molecular bases are unknown. Here, we first propose a mechanistic structure-based explanation for the observed ACh-induced submaximal potentiation of NMDA-elicited currents in striatal neurons by predicting competitive inhibition with Gly. Then, the model was validated, in principle, by confirming that the coapplication of Gly and ACh significantly reduces these neuronal currents. Finally, we delineate the interplay of ACh with the NMDAR by a combination of computational strategies. Crystallographic ACh-bound complexes were studied, revealing a similar ACh binding environment on the GluN1 subunit of the NMDAR. We illustrate how ACh can occupy X-ray monomeric open, dimeric "semiopen" cleft conformations obtained by molecular dynamics and a full-active cryo-EM NMDAR structure, explaining the suboptimal NMDAR electrophysiological activity under the "Venus Flytrap model". At an evolutionary biology level, the binding mode of ACh coincides with that of the homologous ornithine-bound periplasmic LAO binding protein complex. Our computed results indicate an analogous mechanism of action, inasmuch as ACh may stabilize the GluN1 subunit "semiclosed" conformations by inducing direct and indirect D1-to-D2 interdomain bonds. Additionally, an alternative binding site was detected, shared by the known NMDAR allosteric modulators. Experimental and computed results strongly suggest that ACh acts as a Gly-competitive, submaximal potentiating agent of the NMDAR, possibly constituting a novel chemotype for multitarget-directed drug development, e.g., to treat Alzheimer's, and it may lead to a new understanding of glutamatergic neurotransmission.
N-甲基-D-天冬氨酸受体（NMDAR）的激活是通过结合甘氨酸（Gly）和谷氨酸后二叶瓣（D1 和 D2）蛤壳样裂隙的闭合触发的。有证据表明，胆碱能化合物通过直接受体-配体相互作用调节 NMDAR 介导的电流；然而，分子基础尚不清楚。在这里，我们首先通过预测与 Gly 的竞争性抑制作用，提出了一种基于机制的结构解释，说明观察到的 ACh 诱导纹状体神经元中 NMDA 诱发电流的亚最大增强作用。然后，通过确认 Gly 和 ACh 的共同应用显著降低这些神经元电流，从原则上验证了该模型。最后，我们通过组合计算策略描绘了 ACh 与 NMDAR 的相互作用。研究了晶体学 ACh 结合复合物，揭示了 NMDAR 的 GluN1 亚基上类似的 ACh 结合环境。我们说明了 ACh 如何占据 X 射线单体开放、二聚体“半开放”裂隙构象，这些构象是通过分子动力学和全活性冷冻电镜 NMDAR 结构获得的，解释了“维纳斯捕蝇草模型”下 NMDAR 电生理活性的次优性。在进化生物学水平上，ACh 的结合模式与同源鸟氨酸结合周质 LAO 结合蛋白复合物的结合模式一致。我们的计算结果表明了类似的作用机制，因为 ACh 可以通过诱导直接和间接的 D1-D2 结构域间键来稳定 GluN1 亚基“半封闭”构象。此外，还检测到了一个替代结合位点，该结合位点与已知的 NMDAR 变构调节剂共享。实验和计算结果强烈表明，ACh 是 NMDAR 的甘氨酸竞争性、亚最大增强剂，可能构成多靶标药物开发的新型化学型，例如治疗阿尔茨海默病，并且可能导致对谷氨酸能神经传递的新理解。
