Arias Hugo R, Feuerbach Dominik, Ortells Marcelo O
Department of Medical Education, California Northstate University College of Medicine, Elk Grove, CA, USA.
Novartis Institutes for Biomedical Research, Basel, Switzerland.
Neurochem Int. 2016 Nov;100:67-77. doi: 10.1016/j.neuint.2016.08.013. Epub 2016 Sep 6.
The interaction of (±)-bupropion [(±)-BP] with the human (h) α4β2 nicotinic acetylcholine receptor (AChR) was compared to that for its photoreactive analog (±)-2-(N-tert-butylamino)-3'-iodo-4'-azidopropiophenone [(±)-SADU-3-72]. Ca influx results indicated that (±)-SADU-3-72 and (±)-BP inhibit hα4β2 AChRs with practically the same potency. However, (±)-SADU-3-72 binds to the [H]imipramine sites at resting and desensitized hα4β2 AChRs with 3-fold higher affinity compared to that for (±)-BP, which is supported by molecular docking results. The docking results also indicate that each isomer of BP and SADU-3-72, in the protonated state, interacts with luminal and non-luminal sites. In the channel lumen, both ligands bind to two overlapping subsites, one that overlaps the imipramine site, and another much closer to the cytoplasmic side. The results suggest, for the first time, three differentiated non-luminal domains, including the transmembrane (TMD), extracellular (ECD), and ECD-TMD junction. In the ECD-TMD junction, BP and SADU-3-72 bind to overlapping sites. Interestingly, only SADU-3-72 binds to intrasubunit and intersubunit sites in the TMD, and to additional sites in the ECD. Our results are consistent with a model where BP and SADU-3-72 bind to overlapping sites in the luminal and ECD-TMD junctional domains of the hα4β2, whereas only SADU-3-72 binds to additional non-luminal sites. The BP junctional site opens the door for additional inhibitory mechanisms. The pharmacological properties of (±)-SADU-3-72 showed in this work support further photolabeling studies to mapping the BP binding sites in the hα4β2 AChR.
将（±）-安非他酮[（±）-BP]与人（h）α4β2烟碱型乙酰胆碱受体（AChR）的相互作用与其光反应性类似物（±）-2-（N-叔丁基氨基）-3'-碘-4'-叠氮基苯丙酮[（±）-SADU-3-72]进行了比较。钙内流结果表明，（±）-SADU-3-72和（±）-BP对hα4β2 AChRs的抑制效力几乎相同。然而，与（±）-BP相比，（±）-SADU-3-72以高3倍的亲和力结合静息和脱敏hα4β2 AChRs的[H]丙咪嗪位点，分子对接结果支持了这一点。对接结果还表明，质子化状态下的BP和SADU-3-72的每种异构体都与管腔和非管腔位点相互作用。在通道腔内，两种配体都与两个重叠的亚位点结合，一个与丙咪嗪位点重叠，另一个更靠近细胞质侧。结果首次表明了三个不同的非管腔结构域，包括跨膜（TMD）、细胞外（ECD）和ECD-TMD连接区。在ECD-TMD连接区，BP和SADU-3-72结合到重叠位点。有趣的是，只有SADU-3-72结合到TMD中的亚基内和亚基间位点以及ECD中的其他位点。我们的结果与一个模型一致，即BP和SADU-3-72结合到hα4β2的管腔和ECD-TMD连接结构域中的重叠位点，而只有SADU-3-72结合到其他非管腔位点。BP连接位点为其他抑制机制打开了大门。这项工作中显示的（±）-SADU-3-72的药理学特性支持进一步的光标记研究，以绘制hα4β2 AChR中BP的结合位点。
