Kusay Ali S, Luo Yujia, O'Mara Megan L, Balle Thomas
Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia.
Brain and Mind Centre, The University of Sydney, Sydney, New South Wales, Australia.
J Neurochem. 2025 Feb;169(2):e70000. doi: 10.1111/jnc.70000.
Neuronal nicotinic acetylcholine receptors (nAChRs) have an established role in pain pathways and devastating neurodegenerative diseases; however, few drugs have been successfully developed to target them. The most abundant nAChR in the brain, the α4β2 nAChR, is assembled from five subunits in a 3α:2β stoichiometry-(α4)(β2). This receptor contains a unique agonist-binding site at the α4α4 interface in addition to two classical agonist-binding sites at α4β2 interfaces. Most known agonists target both α4α4 and α4β2 sites, however, a few compounds with selectivity for the α4α4 site have been identified. These α4α4 selective compounds have a modulator-like effect akin to benzodiazepines in the γ-aminobutyric acid type A receptor, which is desirable from a drug development perspective. The two most well characterised α4α4 selective compounds are CMPI and NS9283. Both are structurally very different from classical agonists, and it is puzzling how they occupy the same binding site. In the search for a common pharmacophore, we conducted extensive molecular dynamics simulations with both classical agonists and site-selective non-classical compounds. Analyses of the simulations revealed that the α4α4 binding site contains a unique pocket not found in the α4β2 binding site. CMPI and NS9283 were observed to bind in this pocket, thereby explaining why they are selective for the α4α4 binding site. The proposed binding mode featured a closed-loop C conformation, which is strongly correlated with agonism in nAChRs and explained key site-directed mutagenesis data for both compounds. Based on this binding mode, we proposed a pharmacophore for drugs targeting the α4α4 binding site. The proposed pharmacophore captures the essence of the original model, that is, nicotinic agonists act as a bridge between protein subunits. The pharmacophore model we propose is unique to the α4α4 binding site and provides a template for developing new site-selective therapeutic agents.
神经元烟碱型乙酰胆碱受体（nAChRs）在疼痛通路和毁灭性神经退行性疾病中已确立其作用；然而，针对它们成功开发的药物却很少。大脑中最丰富的nAChR，即α4β2 nAChR，由五个亚基以3α:2β的化学计量比组装而成——(α4)3(β2)2 。该受体除了在α4β2界面有两个经典的激动剂结合位点外，在α4α4界面还含有一个独特的激动剂结合位点。大多数已知的激动剂靶向α4α4和α4β2位点，然而，已鉴定出一些对α4α4位点具有选择性的化合物。这些α4α4选择性化合物具有类似于苯二氮䓬类药物在γ-氨基丁酸A型受体中的调节剂样作用，从药物开发的角度来看这是很理想的。两种最具特征的α4α4选择性化合物是CMPI和NS9283。两者在结构上都与经典激动剂有很大不同，令人困惑的是它们如何占据相同的结合位点。在寻找共同药效团的过程中，我们对经典激动剂和位点选择性非经典化合物都进行了广泛的分子动力学模拟。模拟分析表明，α4α4结合位点包含一个在α4β2结合位点中未发现的独特口袋。观察到CMPI和NS9283结合在这个口袋中，从而解释了它们为何对α4α4结合位点具有选择性。所提出的结合模式具有闭环C构象，这与nAChRs中的激动作用密切相关，并解释了这两种化合物的关键定点诱变数据。基于这种结合模式，我们提出了一种针对α4α4结合位点的药物药效团。所提出的药效团抓住了原始模型的本质，即烟碱激动剂作为蛋白质亚基之间的桥梁。我们提出的药效团模型是α4α4结合位点所特有的，为开发新的位点选择性治疗药物提供了一个模板。
