Institute of Pharmacology and Toxicology, University of Würzburg, 97078 Würzburg, Germany.
Sci Signal. 2012 Aug 14;5(237):ra59. doi: 10.1126/scisignal.2002720.
The metabotropic glutamate receptor 1 (mGluR1), a class C member of the heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor family, is a constitutive dimer that regulates excitatory neurotransmission. We investigated the role of homodimer formation in mGluR1 activation by examining activation-dependent inter- and intrasubunit conformational changes by fluorescence resonance energy transfer (FRET). We inserted yellow and cyan fluorescent proteins in the second intracellular loop and at the carboxyl terminus of mGluR1 to act as FRET sensors and expressed these proteins in human embryonic kidney 293 cells. Agonist-dependent activation of these mGluR1 chimeras rapidly increased the intersubunit FRET, suggesting rapid movement of the subunits relative to each other. After intersubunit movement, the intrasubunit FRET decreased, reflecting conformational changes within a subunit. Cotransfection of chimeric receptor subunits that were capable or incapable of G protein coupling revealed that only a single subunit assumes an active state in an mGluR1 receptor dimer.
代谢型谷氨酸受体 1（mGluR1）是异源三聚体鸟苷酸结合蛋白（G 蛋白）偶联受体家族的 C 类成员，是一种组成型二聚体，调节兴奋性神经递质传递。我们通过荧光共振能量转移（FRET）研究了同二聚体形成在 mGluR1 激活中的作用，检测了激活依赖性的亚基间和亚基内构象变化。我们将黄色和青色荧光蛋白插入 mGluR1 的第二细胞内环和羧基末端，作为 FRET 传感器，并在人胚肾 293 细胞中表达这些蛋白质。激动剂依赖性地激活这些 mGluR1 嵌合体迅速增加了亚基间的 FRET，表明亚基之间的相对运动很快。亚基间运动后，亚基内的 FRET 减少，反映了亚基内的构象变化。能够或不能与 G 蛋白偶联的嵌合受体亚基的共转染表明，mGluR1 受体二聚体中只有一个亚基处于活性状态。
