Department of Biochemistry , University of Cambridge , Cambridge CB2 1QW , U.K.
ACS Chem Neurosci. 2018 Jun 20;9(6):1409-1415. doi: 10.1021/acschemneuro.8b00028. Epub 2018 Mar 6.
Cys-loop receptors are major sites of action for many important therapeutically active compounds, but the sites of action of those that do not act at the orthosteric binding site or at the pore are mostly poorly understood. To help understand these, we here describe a chimeric receptor consisting of the extracellular domain of the 5-HTA receptor and the transmembrane domain of a prokaryotic homologue, ELIC. Alterations of some residues at the coupling interface are required for function, but the resulting receptor expresses well and responds to 5-HT with a lower EC (0.34 μM) than that of the 5-HTA receptor. Partial agonists and competitive antagonists of the 5-HTA receptor activate and inhibit the chimera as expected. Examination of a range of receptor modulators, including ethanol, thymol, 5-hydroxyindole, and 5-chloroindole, which can affect the 5-HTA receptor and ELIC, suggest that these compounds act via the transmembrane domain, except for 5-hydroxyindole, which can compete with 5-HT at the orthosteric binding site. The data throw further light on the importance of coupling interface in Cys-loop receptors and provide a platform for examining the mechanism of action of compounds that act in the extracellular domain of the 5-HTA receptor and the transmembrane domain of ELIC.
Cys 环受体是许多重要治疗活性化合物的主要作用部位，但对于那些不在正位结合位点或孔道作用的化合物的作用部位，大多数情况下了解甚少。为了帮助理解这些，我们在这里描述了一种嵌合受体，它由 5-HTA 受体的细胞外结构域和原核同源物 ELIC 的跨膜结构域组成。在偶联界面处的一些残基的改变是必需的，但产生的受体表达良好，并以低于 5-HTA 受体的 EC（0.34 μM）对 5-HT 产生反应。5-HTA 受体的部分激动剂和竞争性拮抗剂如预期的那样激活和抑制嵌合体。对一系列受体调节剂的检查，包括乙醇、麝香草酚、5-羟吲哚和 5-氯吲哚，这些调节剂可以影响 5-HTA 受体和 ELIC，表明这些化合物通过跨膜结构域起作用，除了 5-羟吲哚，它可以在正位结合位点与 5-HT 竞争。这些数据进一步阐明了 Cys 环受体中偶联界面的重要性，并为研究作用于 5-HTA 受体细胞外结构域和 ELIC 跨膜结构域的化合物作用机制提供了一个平台。
