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-HT₃A 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 EC₅₀ (0.34 μM) than that of the 5-HT₃A receptor. Partial agonists and competitive antagonists of the 5-HT₃A 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-HT₃A 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-HT₃A receptor and the transmembrane domain of ELIC.

中文翻译：

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5-HT3-ELIC 嵌合体的表征揭示了调节剂的作用位点

Cys-环受体是许多重要的治疗活性化合物的主要作用位点，但那些不作用于正构结合位点或孔的作用位点大多知之甚少。为了帮助理解这些，我们在此描述了一种嵌合受体，它由 5-HT ₃ A 受体的细胞外结构域和原核同源物 ELIC 的跨膜结构域组成。偶联界面处的一些残基的改变是功能所必需的，但所得受体表达良好并且对 5-HT 的反应比 5-HT ₃ A 受体的 EC ₅₀ (0.34 μM) 低。_{5-HT 3}的部分激动剂和竞争性拮抗剂正如预期的那样，受体激活和抑制嵌合体。_{对可影响 5-HT 3} A 受体和 ELIC的一系列受体调节剂（包括乙醇、百里酚、5-羟基吲哚和 5-氯吲哚）的检查表明，这些化合物通过跨膜结构域起作用，但 5-羟基吲哚除外，它可以在正构结合位点与 5-HT 竞争。这些数据进一步阐明了耦合界面在 Cys 环受体中的重要性，并为研究在 5-HT ₃ A 受体的细胞外结构域和 ELIC 的跨膜结构域中起作用的化合物的作用机制提供了一个平台。