Structure-Activity Investigation of a G Protein-Biased Agonist Reveals Molecular Determinants for Biased Signaling of the D2 Dopamine Receptor
Structure-Activity Investigation of a G Protein-Biased Agonist Reveals Molecular Determinants for Biased Signaling of the D2 Dopamine Receptor
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DOI：
10.3389/fnsyn.2018.00002
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发表时间：
2018-02-21
影响因子：
3.7
通讯作者：
Sibley, David R.
中科院分区：
文献类型：
--
作者：
Chun, Lani S.;Vekariya, Rakesh H.;Sibley, David R.
已知多巴胺D2受体（D2R）通过激活G蛋白（Gi/o）或f)-阻滞蛋白介导的两种主要信号通路来引发效应。然而，每种途径在生理或治疗活动中的具体作用尚不确定。解剖这些通路的一种方法是通过使用药物，通过一种被称为功能选择性或偏倚信号的机制，选择性地调节一种途径与另一种途径。我们的实验室先前已经描述了一种G蛋白信号偏倚激动剂。MLS1547，用于D2R，使用多种体外功能测定。为了进一步评估该化合物的偏倚信号活性，我们研究了其促进D2R内化的能力，这一过程已知是由13-抑制蛋白介导的。通过使用多种细胞系统和技术，我们发现MLS1547很少促进D2R内化，这与它无法招募f)-阻滞一致。重要的是，我们在D2R高度表达的初级纹状体神经元中验证了这些结果，这表明MLS1547在体内会表现出偏倚的信号活性。为了优化和进一步探索该支架的结构活性关系（SAR），我们进行了迭代化学活动来合成和表征新的MLS1547类似物。结果分析证实了先前描述的G蛋白偏倚激动剂活性的SAR要求，重要的是，阐明了对激动剂功效和MLS1547支架信号偏倚至关重要的新结构特征。G蛋白偏向性信号的最重要决定因素之一是化合物的疏水部分与由D2R的跨膜5和胞外环2内残基形成的确定口袋的相互作用。这些结果揭示了D2R偏倚信号传导的机制，并可能导致功能选择性分子的改进。
The dopamine D2 receptor (D2R) is known to elicit effects through activating two major signaling pathways mediated by either G proteins (Gi/o) or f)-arrestins. However, the specific role of each pathway in physiological or therapeutic activities is not known with certainty. One approach to the dissection of these pathways is through the use of drugs that can selectively modulate one pathway vs. the other through a mechanism known as functional selectivity or biased signaling. Our laboratory has previously described a G protein signaling biased agonist. MLS1547, for the D2R using a variety of in vitro functional assays. To further evaluate the biased signaling activity of this compound, we investigated its ability to promote D2R internalization, a process known to be mediated by 13-arrestin. Using multiple cellular systems and techniques, we found that MLS1547 promotes little D2R internalization, which is consistent with its inability to recruit f)-arrestin. Importantly, we validated these results in primary striatal neurons where the D2R is most highly expressed suggesting that MLS1547 will exhibit biased signaling activity in vivo. In an effort to optimize and further explore structure activity relationships (SAR) for this scaffold, we conducted an iterative chemistry campaign to synthesize and characterize novel analogs of MLS1547. The resulting analysis confirmed previously described SAR requirements for G protein-biased agonist activity and, importantly, elucidated new structural features that are critical for agonist efficacy and signaling bias of the MLS1547 scaffold. One of the most important determinants for G protein-biased signaling is the interaction of a hydrophobic moiety of the compound with a defined pocket formed by residues within transmembrane five and extracellular loop two of the D2R. These results shed new light on the mechanism of biased signaling of the D2R and may lead to improved functionally-selective molecules.