McCullock Tyler W, Couch Tyler, Kammermeier Paul J
Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York.
Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York.
Mol Pharmacol. 2025 Jul 18;107(9):100063. doi: 10.1016/j.molpha.2025.100063.
Metabotropic glutamate receptors (mGlus) are obligate dimer G protein-coupled receptors that can all homodimerize and heterodimerize in select combinations. Responses of mGlu heterodimers to selective ligands, including orthosteric agonists and allosteric modulators, are largely unknown. The pharmacological properties of each group II and III mGlu homodimer (except the exclusively retinally expressed mGlu6) and several heterodimers were examined when stochastically assembled in HEK293T cells, or specifically measured using an improved G protein-mediated bioluminescence resonance energy transfer assay employing complemented fragments of Nanoluciferase. Stochastically assembled receptors adopted unique signaling characteristics. Some favored the potency, efficacy, or signaling kinetics of a dominant subunit, whereas others exhibited blended profiles reflective of a combination of homo- and heterodimers at various ratios of expressed receptor. Finally, group II and III mGlu dimers were examined for responses to selective agonists and allosteric modulators. Effects of glutamate and selective group II and III orthosteric agonists were found to result in unique concentration response profiles when examining each combination of group II and III mGlu. Effects of select allosteric modulators were examined for each mGlu2-containing dimer as well as several group III dimer pairs. Likewise, allosteric modulator effects were often unique across dimers containing the targeted subunit of the ligand being tested. The results demonstrate that mGlu dimers respond uniquely to ligands selective for just one subunit, even when they are ostensibly pharmacologically similar. SIGNIFICANCE STATEMENT: This study demonstrates novel pharmacological responses to ligands acting on metabotropic glutamate receptor heterodimers in isolation. To our knowledge, it also shows for the first time the kinetics and pharmacological properties of group II and III metabotropic glutamate receptors when expressed in pairs and assembled stochastically.
代谢型谷氨酸受体（mGlus）是一种必需的二聚体G蛋白偶联受体，它们都能以特定组合形成同二聚体和异二聚体。mGlu异二聚体对包括正构激动剂和变构调节剂在内的选择性配体的反应在很大程度上尚不清楚。当在HEK293T细胞中随机组装时，或者使用改进的G蛋白介导的生物发光共振能量转移测定法（采用Nanoluciferase的互补片段）进行特异性测量时，研究了每个II组和III组mGlu同二聚体（除了仅在视网膜中表达的mGlu6）和几种异二聚体的药理学特性。随机组装的受体具有独特的信号传导特征。一些受体有利于优势亚基的效力、效能或信号动力学，而另一些则表现出混合特征，反映了不同比例的表达受体的同二聚体和异二聚体的组合。最后，研究了II组和III组mGlu二聚体对选择性激动剂和变构调节剂的反应。在研究II组和III组mGlu的每种组合时，发现谷氨酸以及选择性II组和III组正构激动剂的作用会导致独特的浓度反应曲线。对每种含mGlu2的二聚体以及几对III组二聚体研究了选择性变构调节剂的作用。同样，变构调节剂的作用在含有被测试配体的靶向亚基的二聚体之间通常也是独特的。结果表明，mGlu二聚体对仅对一个亚基具有选择性的配体有独特的反应，即使它们在表面上具有相似的药理学性质。意义声明：本研究证明了对单独作用于代谢型谷氨酸受体异二聚体的配体的新型药理学反应。据我们所知，它还首次展示了II组和III组代谢型谷氨酸受体以成对形式表达并随机组装时的动力学和药理学特性。
