Reyes-Alcaraz Arfaxad, Lee Yoo-Na, Yun Seongsik, Hwang Jong-Ik, Seong Jae Young
Graduate School of Medicine, Korea University, Seoul, 02841, Republic of Korea.
Commun Biol. 2018 Sep 3;1:128. doi: 10.1038/s42003-018-0134-3. eCollection 2018.
Discovery of biased ligands and receptor mutants allows characterization of G-protein- and β-arrestin-mediated signaling mechanisms of G-protein-coupled receptors (GPCRs). However, the structural mechanisms underlying biased agonism remain unclear for many GPCRs. We show that while Galanin induces the activation of the galanin receptor 2 (Galr2) that leads to a robust stimulation toward Gαq-protein and β-arrestin1/2, an alternative ligand Spexin and its analog have biased agonism toward G-protein signaling relative to Galanin. We used intramolecular fluorescein arsenical hairpin bioluminescence resonance energy transfer-based biosensors of β-arrestin2 combined with NanoBit technology to measure β-arrestin2-Galr2 interactions in real-time living systems. We found that Spexin and Galanin induce specific active conformations of Galr2, which may lead to different internalization rates of the receptor as well as different signaling outputs. This work represents an additional pharmacological evidence of endogenous G-protein-biased agonism at a GPCR.
偏向性配体和受体突变体的发现有助于表征G蛋白偶联受体（GPCR）的G蛋白介导和β-抑制蛋白介导的信号传导机制。然而，许多GPCR的偏向性激动作用背后的结构机制仍不清楚。我们发现，虽然甘丙肽可诱导甘丙肽受体2（Galr2）激活，从而强烈刺激Gαq蛋白和β-抑制蛋白1/2，但另一种配体Spexin及其类似物相对于甘丙肽对G蛋白信号传导具有偏向性激动作用。我们使用基于分子内荧光素砷发夹生物发光共振能量转移的β-抑制蛋白2生物传感器结合NanoBit技术，在实时活体系统中测量β-抑制蛋白2与Galr2的相互作用。我们发现Spexin和甘丙肽可诱导Galr2的特定活性构象，这可能导致受体的内化速率不同以及信号输出不同。这项工作为GPCR上内源性G蛋白偏向性激动作用提供了额外的药理学证据。
