Characterization of biased airway smooth muscle TAS2R agonists for treating asthma

哮喘仍然是世界范围内的一个主要公共卫生问题，影响到所有年龄和种族，50%的患者 感受到对疾病控制不力。气道平滑肌收缩所致的气道收缩 是导致哮喘气流阻塞、发病率和死亡率的主要原因。尽管这一点对 干预，只有一类直接支气管扩张剂(激动剂)可用于治疗，它们是 对许多患者来说不是最理想的。我们在人的呼吸道上发现了苦味受体(TAS2Rs) 肌肉(HASM)细胞通过一种独特的机制发出信号。当被激活时，TAS2Rs显著放松HASM和 缓解对激动剂有抵抗力的呼吸道阻塞。然而，已知的TAS2R激动剂已经 低亲和力和通过-arrestin引起的随时间的松弛反应的脱敏(快速反应) 机械装置。最重要的假设是，具有新结构的TAS2R激动剂可以非常有效 在哮喘环境中放松呼吸道，但不会引起心动过速。宏大的长期目标是 确定HASM上表达的两个TAS2Rs(R5和R14)的三维结构和结合位点 使用这些结构来执行不可知的超大型化合物库的虚拟对接，以确定潜在的 配基。这些命中结果将在工程模型细胞中进行检查，但将在 哮喘条件下HASM细胞和人类呼吸道的生理学背景，以描绘新的途径 使偏向松弛而不是脱敏的受体参与。目标1将 使用包括13万亿的方法计算确定R5和R14的结构和结合位点 残基的组合以确定非活化态和活化态的有利能量构象。这个 结构将被用来对接来自高度多样化的图书馆的化合物。这些将在目标2中进行研究 确定基因工程模型细胞和非哮喘和非哮喘HASM细胞的效力和疗效 哮喘的肺。在目标3中，将研究最有利的化合物以确定-arrestin结合 以及在哮喘条件下的模型细胞、HASM细胞和人肺中偏向脱敏。 Aims2/3的结果将反馈给Aim1，以进一步提炼这些HASM的偏向激动剂模型 TAS2Rs。根据我们支持这三个目标的初步数据，我们将了解结构 对这些受体的偏置要求。而且，我们预计多种高效的激动剂 意想不到的结构将被识别，它们在哮喘中的支气管扩张特性将代表一种新的 治疗和预防支气管痉挛的一类有效的非脱敏药物。

Asthma remains a major public health issue worldwide, affecting all ages and ethnicities, with 50% of patients experiencing inadequate control of the disease. Constricted airways from contraction of airway smooth muscle is the major cause of airflow obstruction, and morbidity and mortality, in asthma. Despite this key point for intervention, only one class of direct bronchodilators (-agonists) are available for treatment, and they are suboptimal for many patients. We have discovered bitter taste receptors (TAS2Rs) on human airway smooth muscle (HASM) cells which signal by a unique mechanism. When activated, TAS2Rs markedly relax HASM and relieve airway obstruction that is otherwise resistant to -agonists. However, the known TAS2R agonists have low affinity and evoke desensitization (tachyphylaxis) of the relaxation response over time via -arrestin mechanisms. The overarching hypothesis is that TAS2R agonists with novel structures can be highly effective in relaxing airways in an asthmatic milieu and yet not evoke tachyphylaxis. The broad long-term objectives are to determine the 3D structures and binding sites of two TAS2Rs expressed on HASM (R5 and R14) and then use these structures to perform virtual docking of an agnostic ultra-large compound library to identify potential ligands. These hits will be examined in engineered model cells, but will be most intensely studied within the context of the physiology of HASM cells, and human airways, under asthmatic conditions to delineate novel ways to engage the receptor that are biased towards relaxation and away from desensitization. Aim 1 will computationally determine the structures and binding sites for R5 and R14 using methods that include 13 trillion combinations of the residues to determine favorable energy conformations of inactive and active states. The structures will be used to dock compounds from a highly diverse library. These will be studied in Aim 2 to determine potency and efficacy in genetically engineered model cells and in HASM cells from nonasthmatic and asthmatic lungs. In Aim 3, the most favorable compounds will be studied to ascertain -arrestin engagement and biasing away from desensitization in model cells, HASM cells, and human lungs under asthmatic conditions. Results from Aims2/3 will be fed back into Aim1 to further refine a model of biased agonists for these HASM TAS2Rs. Based on our preliminary data that support all three Aims, we will learn about the structural requirements for biasing for these receptors. And, we anticipate that multiple highly effective agonists with unexpected structures will be identified and that their bronchodilating properties in asthma will represent a new class of powerful non-desensitizing agents for treating and preventing bronchospasm.