Molecular basis of G protein-coupled receptor function

激动剂与GPCRs结合可通过GPCRK使激活的受体快速磷酸化。这个过程促进arrestin蛋白家族的成员(-arrestin-1和-2)被激活的受体重新招募，破坏受体/G蛋白偶联，并通过将受体靶向笼状蛋白包裹的凹坑来促进GPCR内化。然而，在过去的10-15年中，许多研究表明，逮捕蛋白本身也可以作为信号分子。这一观察结果不仅具有理论意义，而且具有潜在的临床意义。 在过去的几年里，DREADDS(由设计药物独有地激活的设计受体)已经成为研究不同功能类别的GPCRs激活的信号通路的生理相关性的强有力的新的化学发生工具。从结构上讲，DREADDS代表突变的毒碱受体，可以被氯氮平-N-氧化物(CNO)激活，CNO是一种药理上的惰性试剂，具有高效力和有效性。重要的是，这些新设计的受体不能被内源性M受体激动剂乙酰胆碱激活。 与DREADD的GPCR样特性一致，我们最近证明了基于M3R的DREADD不仅可以激活GQ家族的G蛋白，还可以与β-arrestin-1和-2相互作用，触发依赖于β-arrestin的下游信号。综上所述，这些发现支持这样一个概念，即在特定组织或细胞类型中激活特定GPCR(或DREADD)的生理结果代表了G蛋白和β-arrestin依赖的信号通路激活所引起的综合反应。为了深入了解这两个不同的GPCR信号分支的生理相关性，重要的是评估G蛋白和β-arrestin依赖的信号对特定组织反应的相对贡献。为了阐明这个问题，我们最近生成了一个基于M3R的偏向于arrestin的DREADD(Nakajima等人，2015年)以及一个基于M3R的GQ/11偏向DREADD，它缺乏与β-抑制素相互作用的能力(Hu等人，2016)。我们发现后者DREADD在体内是活跃的，并且新的设计者受体的细胞类型选择性表达可以导致对G蛋白与β-arrestin依赖的信号的生理作用的新的见解。这些功能偏向的DREADD是研究不同组织和细胞类型中GQ/11-与β-arrestin依赖的信号级联的生理学相关性的强大新工具。重要的是，这些信息可以被用于开发临床上有用的新型药物，包括G蛋白或β-arrestin偏向激动剂。 (胡杰、斯特恩·M、吉梅内兹·勒、万卡·L、朱·L、罗西·M、梅斯特·J、井上A、贝克-西金格、古里维奇·V、韦斯·J)。基于G蛋白的设计者G蛋白偶联受体有助于研究GQ/11依赖的信号通路的生理相关性。J Biol Chem 291,7809-20,2016；本周论文)。 回顾： 王建国，李美华，王建国，等.芳香素偏向DREADD的设计与分析.摘自：《由设计者药物独有地激活设计者受体》，《神经方法系列》，第108册，编辑。G.泰尔，施普林格科学+商业媒体，纽约，NY，第29-48页，2015年。 ===

Agonist binding to GPCRs causes rapid phosphorylation of the activated receptors by GPCR kinases. This process promotes the recruitment of members of the arrestin protein family (-arrestin-1 and -2) to the activated receptors, disrupting receptor/G protein coupling and promoting GPCR internalization by targeting the receptors to clathrin-coated pits. However, during the past 10-15 years, many studies have demonstrated that -arrestins can also act as signaling molecules in their own right. This observation is not only of theoretical interest but also of potential clinical relevance. During the past few years, DREADDs (designer receptors exclusively activated by designer drug) have emerged as powerful novel chemogenetic tools to study the physiological relevance of signaling pathways activated by different functional classes of GPCRs. Structurally, DREADDs represent mutant muscarinic receptors that can be activated by clozapine-N-oxide (CNO), an otherwise pharmacologically inert agent, with high potency and efficacy. Importantly, these new designer receptors cannot be activated by acetylcholine, the endogenous muscarinic receptor agonist. Consistent with the GPCR-like properties of DREADDs, we recently demonstrated that an M3 muscarinic receptor (M3R)-based DREADD does not only activate G proteins of the Gq family but can also interact with beta-arrestin-1 and -2 and trigger beta-arrestin-dependent downstream signaling. Taken together, these findings support the concept that the physiological outcome of activating a specific GPCR (or DREADD) in a particular tissue or cell type represents an integrated response caused by the activation of both G protein- and beta-arrestin-dependent signaling pathways. To gain insight into the physiological relevance of these two distinct GPCR signaling branches, it is important to assess the relative contribution of G protein- and beta-arrestin-dependent signaling to a particular tissue response. To shed light on this issue, we recently generated an M3R-based -arrestin-biased DREADD (Nakajima et al., 2015) as well as an M3R-based Gq/11-biased DREADD that lacks the ability to interact with beta-arrestins (Hu et al., 2016). We showed that this latter DREADD is active in vivo and that cell type-selective expression of the new designer receptors can lead to novel insights into the physiological roles of G protein- vs. beta-arrestin-dependent signaling. These functionally biased DREADDs represent powerful new tools to study the physiological relevance of Gq/11- vs. beta-arrestin-dependent signaling cascades in distinct tissues and cell types. Importantly, such information could be exploited for developing novel classes of clinically useful drugs, including G protein- or beta-arrestin-biased agonists. (Hu J, Stern M, Gimenez LE, Wanka L, Zhu L, Rossi M, Meister J, Inoue A, Beck-Sickinger AG, Gurevich VV, Wess J. A G protein-biased designer G protein-coupled receptor useful for studying the physiological relevance of Gq/11-dependent signaling pathways. J Biol Chem 291, 7809-20, 2016;paper of the week). Review: Nakajima K, Gimenea LE, Gurevich VV, Wess J. Design and analysis of an arrestin-biased DREADD. In: "Designer Receptors Exclusively Activated by Designer Drugs", Neuromethods Series, Book 108, ed. G. Thiel, Springer Science + Business Media, New York, NY, pp. 29-48, 2015. ==