Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
J Phys Chem B. 2010 Jan 14;114(1):626-32. doi: 10.1021/jp908944e.
The neuronal alpha4beta2 nicotinic acetylcholine receptor (nAChR) is a potential molecular target for general anesthetics. It is unclear, however, whether anesthetic action produces the same effect on the open and closed channels. Computations parallel to our previous open channel study (J. Phys. Chem. B 2009, 113, 12581) were performed on the closed-channel alpha4beta2 nAChR to investigate the conformation-dependent anesthetic effects on channel structures and dynamics. Flexible ligand docking and over 20 ns molecular dynamics simulations revealed similar halothane-binding sites in the closed and open channels. The sites with relatively high binding affinities (approximately -6.0 kcal/mol) were identified at the interface of extracellular (EC) and transmembrane (TM) domains or at the interface between alpha4 and beta2 subunits. Despite similar sites for halothane binding, the closed-channel conformation showed much less sensitivity than the open channel to the structural and dynamical perturbations from halothane. Compared to the systems without anesthetics, the amount of water inside the pore decreased by 22% in the presence of halothane in the open channel but only by 6% in the closed channel. Comparison of the nonbonded interactions at the EC/TM interfaces suggested that the beta2 subunits were more prone than the alpha4 subunits to halothane binding. In addition, our data support the notion that halothane exerts its effect by disturbing the quaternary structure and dynamics of the channel. The study concludes that sensitivity and global dynamics responsiveness of alpha4beta2 nAChR to halothane are conformation dependent. The effect of halothane on the global dynamics of the open-channel conformation might also account for the action of other inhaled general anesthetics.
神经元α4β2 烟碱型乙酰胆碱受体 (nAChR) 是全身麻醉剂的潜在分子靶标。然而，尚不清楚麻醉作用是否对开放和关闭通道产生相同的效果。与我们之前的开放通道研究（J. Phys. Chem. B 2009, 113, 12581）平行的计算在封闭通道α4β2 nAChR 上进行，以研究构象依赖性麻醉效应对通道结构和动力学的影响。灵活的配体对接和超过 20 ns 的分子动力学模拟揭示了在封闭和开放通道中存在相似的氟烷结合位点。具有相对较高结合亲和力（约-6.0 kcal/mol）的位点被鉴定为在细胞外（EC）和跨膜（TM）域之间的界面或在α4 和β2 亚基之间的界面上。尽管氟烷结合的位点相似，但与开放通道相比，封闭通道构象对氟烷的结构和动力学干扰的敏感性要低得多。与没有麻醉剂的系统相比，在开放通道中存在氟烷时，孔内的水量减少了 22%，而在封闭通道中仅减少了 6%。比较 EC/TM 界面处的非键相互作用表明，β2 亚基比α4 亚基更容易与氟烷结合。此外，我们的数据支持这样的观点，即氟烷通过干扰通道的四级结构和动力学来发挥其作用。该研究得出结论，α4β2 nAChR 对氟烷的敏感性和整体动力学响应取决于构象。氟烷对开放通道构象整体动力学的影响也可能解释其他吸入性全身麻醉剂的作用。
