McCullock Tyler W, Cardani Loren P, Kammermeier Paul J
Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642.
bioRxiv. 2023 Jul 28:2023.07.24.550373. doi: 10.1101/2023.07.24.550373.
Metabotropic glutamate receptors (mGluRs) are obligate dimer G protein coupled receptors that can all function as homodimers. Here, each mGluR homodimer was examined for its G protein coupling profile using a BRET based assay that detects the interaction between a split YFP-tagged Gβ and a Nanoluc tagged free Gβ sensor, MAS-GRK3-ct-NLuc with 14 specific G proteins heterologously expressed, representing each family. Canonically, the group II and III mGluRs (2&3, and 4, 6, 7&8, respectively) are thought to couple to G exclusively. In addition, the group I mGluRs (1&5) are known to couple to the G family, and generally thought to also couple to the PTX-sensitive G family; some reports have suggested G coupling is possible as cAMP elevations have been noted. In this study, coupling was observed with all 8 mGluRs through the G proteins, and only mGluR1&5 through G, and perhaps surprisingly, not G. None activated any Gs protein. Interestingly, coupling was seen with the group I and II, but not the group III mGluRs to G. Slow but significant coupling to G was also seen with the group II receptors.
代谢型谷氨酸受体（mGluRs）是 obligate 二聚体 G 蛋白偶联受体，均可作为同型二聚体发挥作用。在此，使用基于生物发光共振能量转移（BRET）的检测方法，检测了每个 mGluR 同型二聚体的 G 蛋白偶联情况，该方法可检测分裂型黄色荧光蛋白（YFP）标记的 Gβ与纳米荧光素酶（Nanoluc）标记的游离 Gβ传感器 MAS-GRK3-ct-NLuc 之间的相互作用，其中异源表达了 14 种特定的 G 蛋白，代表每个家族。通常认为，II 组和 III 组 mGluRs（分别为 2 和 3，以及 4、6、7 和 8）仅与 G 蛋白偶联。此外，I 组 mGluRs（1 和 5）已知与 G 蛋白家族偶联，并且通常认为也与百日咳毒素（PTX）敏感的 G 蛋白家族偶联；一些报告表明可能存在 G 蛋白偶联，因为已观察到 cAMP 升高。在本研究中，通过 G 蛋白观察到所有 8 种 mGluRs 均有偶联，仅 mGluR1 和 5 通过 G 蛋白偶联，也许令人惊讶的是，未通过 G 蛋白偶联。没有一种激活任何 Gs 蛋白。有趣的是，I 组和 II 组 mGluRs 与 G 蛋白偶联，但 III 组 mGluRs 未与 G 蛋白偶联。II 组受体也观察到与 G 蛋白的缓慢但显著的偶联。
