Abstract：
In the last few years, fluorescence resonance energy transfer (FRET) receptor sensors have contributed to the understanding of GPCR ligand binding and functional activation. FRET sensors based on muscarinic acetylcholine receptors (mAChRs) have been employed to study dual-steric ligands, allowing for the detection of different kinetics and distinguishing between partial, full, and super agonism. Herein, we report the synthesis of the two series of bitopic ligands, 12-Cn and 13-Cn, and their pharmacological investigation at the M1, M2, M4, and M5 FRET-based receptor sensors. The hybrids were prepared by merging the pharmacophoric moieties of the M1/M4-preferring orthosteric agonist Xanomeline 10 and the M1-selective positive allosteric modulator 77-LH-28-1 (1-[3-(4-butyl-1-piperidinyl)propyl]-3,4-dihydro-2(1H)-quinolinone) 11. The two pharmacophores were connected through alkylene chains of different lengths (C3, C5, C7, and C9). Analyzing the FRET responses, the tertiary amine compounds 12-C5, 12-C7, and 12-C9 evidenced a selective activation of M1 mAChRs, while the methyl tetrahydropyridinium salts 13-C5, 13-C7, and 13-C9 showed a degree of selectivity for M1 and M4 mAChRs. Moreover, whereas hybrids 12-Cn showed an almost linear response at the M1 subtype, hybrids 13-Cn evidenced a bell-shaped activation response. This different activation pattern suggests that the positive charge anchoring the compound 13-Cn to the orthosteric site ensues a degree of receptor activation depending on the linker length, which induces a graded conformational interference with the binding pocket closure. These bitopic derivatives represent novel pharmacological tools for a better understanding of ligand-receptor interactions at a molecular level.
摘要：
在过去的几年里，荧光共振能量转移（FRET）受体传感器有助于理解GPCR配体结合和功能激活。基于毒蕈碱乙酰胆碱受体（mAChRs）的FRET传感器已用于研究双空间配体，允许检测不同的动力学并区分部分，满,和超级激动。在这里，我们报道了两个系列的双位配体的合成，12-cn和13-cn，以及它们在M1、M2、M4和M5基于FRET的受体传感器上的药理学研究。通过合并M1/M4优选的正构激动剂Xanomeline10和M1选择性正变构调节剂77-LH-28-1（1-[3-（4-丁基-1-哌啶基）丙基]-3,4-二氢-2（1H）-喹啉酮）11的药效部分来制备杂种。两个药效团通过不同长度的亚烷基链(C3、C5、C7和C9)连接。分析FRET的反应，叔胺化合物12-C5，12-C7和12-C9证明了M1mAChRs的选择性活化，而甲基四氢吡啶鎓盐13-C5、13-C7和13-C9对M1和M4mAChRs显示出一定程度的选择性。此外，而杂种12-Cn在M1亚型表现出几乎线性的反应，杂种13-Cn证明了钟形激活反应。这种不同的激活模式表明，将化合物13-Cn锚定到正构位点的正电荷会导致受体激活程度，具体取决于接头长度。这诱导了与结合口袋闭合的分级构象干扰。这些双位衍生物代表了在分子水平上更好地理解配体-受体相互作用的新的药理学工具。
