Functional and Pharmacological Implications of mGluR Heteromerization

描述（由申请人提供）：G蛋白偶联受体（GPCR）是临床治疗中最常靶向的蛋白质家族。GPCR之间的分子相互作用可以对其功能和靶向药物的作用产生深远的影响。我们研究了两种谷氨酸激活的GPCR（称为mGluR 1和mGluR 5）之间相互作用的功能和药理学作用，这两种GPCR已知可形成同源二聚体复合物（mGluR 1-mGluR 1和mGluR 5-mGluR 5二聚体），参与许多病理生理过程，并广泛分布于中枢神经系统。我们的数据表明，这些受体可以在功能上相互作用，这种相互作用改变了它们的功能。 对靶向它们的选择性药理学试剂的敏感性。我们提出了一种新的假说来解释这种相互作用，其中mGluR 1和mGluR 5二聚体联合收割机形成具有反式激活能力的四聚体（或可能更大）复合物，使得配体与一种受体结合可以通过另一种受体激活G蛋白。此外，这些推定的四聚体受体似乎对某些药理学试剂的反应不同于其同型二聚体成分。为了解决这一假设，我们将追求以下具体目标：1）使用大鼠颈上级神经节（SCG）神经元表达系统来表征mGluR 1/5异聚体的独特药理学性质，2）通过在HeLa细胞中表达并使用不同的效应物来测定受体信号传导来确认mGluR 1/5异聚体的药理学和信号传导性质，3）使用光漂白后多光子荧光恢复（FRAP）和荧光相关光谱（FCS）直接评估荧光标记的mGluR 1、mGluR 5和两种受体一起形成二聚体、四聚体或更高阶多聚体受体的能力，以及4）验证在天然表达mGluR 1和mGluR 5两者的神经元中功能性mGluR相互作用的生理相关性。

DESCRIPTION (provided by applicant): G protein coupled receptors (GPCRs) are the most frequently targeted protein family in clinical therapeutics. The molecular interactions between GPCRs can have a profound impact on their function and on the effects of drugs that target them. We examined the functional and pharmacological effects of interactions between two glutamate-activated GPCRs called mGluR1 and mGluR5, which are known to form homodimeric complexes (mGluR1-mGluR1 and mGluR5-mGluR5 dimers), are involved in many patho-physiological processes, and have widespread distribution in the central nervous system. Our data suggest that these receptors can interact functionally, and that this interaction alters their sensitivity to selective pharmacological agents that target them. We suggest a novel hypothesis to explain this interaction in which mGluR1 and mGluR5 dimers combine to form tetrameric (or possibly larger) complexes with the ability to trans-activate, such that ligand binding to one receptor may activate G protein through the other. Further, these putative tetrameric receptors seem to respond to some pharmacological agents differently than their homodimeric constituents. To address this hypothesis, we will pursue the following Specific Aims: 1) To characterize the unique pharmacological properties of mGluR1/5 heteromers using the rat superior cervical ganglion (SCG) neuronal expression system, 2) To confirm the pharmacological and signaling properties of mGluR1/5 heteromers by expression in HeLa cells and using a different effectors to assay receptor signaling, 3) To directly assess the ability of fluorescently-tagged mGluR1, mGluR5 and both receptors together to form dimeric, tetrameric, or higher order multimeric receptors using multi-photon Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Correlation Spectroscopy (FCS), and 4) To verify the physiological relevance of functional mGluR interactions in neurons that natively express both mGluR1 and mGluR5.