Pharmacodynamics of Biased G Protein-Coupled Receptor Agonism

虽然G蛋白偶联受体（GPCR）药物开发传统上集中在常规药物上， 激动作用和拮抗作用，“多维功效”和“功能选择性”的新范例 认识到GPCR通过经典G蛋白依赖性和新型G蛋白依赖性介导生物学效应， 不依赖于蛋白质的信号网络，配体结构可以通过稳定活性物质来“偏置”信号传导。 与天然配体不同比例的受体状态。这种“偏向性激动剂”是新的实体， 具有路径选择性功效，实际上产生了具有不同信号传导特征的新受体， 配体结构偏向激动作用的希望在于产生混合激动剂/拮抗剂的能力 在体内起作用，并产生常规激动剂或拮抗剂无法达到的生物学作用。最近 然而，经验表明，体内偏向性激动剂效应通常是不可预测的，这表明， 在我们对偏见激动的理解中存在差距，这是合理设计新型GPCR的障碍 靶向治疗。在过去的五年里，我们实验室的进展提供了一些机制， 深入了解配体偏好的明显特质。我们已经表明，配体结构可以指定 效应器中不同的“激活模式”，导致相同的效应器执行不同的功能，甚至 解离经典连接的效应子功能，例如抑制蛋白依赖性GPCR脱敏和信号传导。 当这些“不平衡”的信号传播时，我们发现偏向的激动剂有时会产生相反的效果 对下游信号网络的影响。因此，体内转录组学 偏向性激动剂和常规激动剂的“指纹”在调节信号传导水平上基本上不重叠 途径和生物过程。幸运的是，在抑制通路选择性偏倚的情况下， 抑制蛋白依赖性信号库受到充分限制， 组织之间的保守性和集中于调控只有几个基本的生物过程。整体 我们未来的研究目标是：1）了解GPCR信号传导的机制， 分子水平，以便更好地预测不同形式的配体偏好将如何改变细胞对 GPCR活化;以及2）确定在工程化的“筛选”细胞系统中测量的功效如何偏倚 与它们在生理相关细胞和组织中产生的生物反应有关。和过去一样， 我们将采用全方位的基于细胞的技术来表征配体结构对受体的影响， 和效应子构象和功能，以及蛋白质组学和 转录组学数据集，以确定特定的功效模式如何影响原代细胞的行为， 细胞背景对反应的影响。该项目的完成将有助于制定一个合理的 将体外配体功效与抑制蛋白途径选择性偏向GPCR的体内作用相关联的框架 配体，提供的信息和工具，是至关重要的发展新的偏见疗法。

While G protein-coupled receptor (GPCR) drug development has traditionally focused on conventional agonism and antagonism, the newer paradigms of `pluridimensional efficacy' and `functional selectivity' recognize that GPCRs mediate biological effects through both classical G protein-dependent and novel G protein-independent signaling networks, and that ligand structure can `bias' signaling by stabilizing active receptor states in different proportions than the native ligand. Such `biased agonists' are novel entities that possess pathway-selective efficacy, in effect creating new receptors with distinct signaling profiles driven by ligand structure. The promise of biased agonism resides with this ability to engender mixed agonist/antagonist effects in vivo and produce biological effects not attainable with conventional agonists or antagonists. Recent experience has shown, however, that biased agonist effects in vivo are often unpredictable, indicating that key gaps exist in our understanding of biased agonism that stand as barriers to the rational design of novel GPCR targeted therapeutics. Progress in our laboratory over the past five years has provided some mechanistic insights into the apparent idiosyncratic nature of ligand bias. We have shown that ligand structure can specify distinct `activation modes' in effectors, causing the same effector to perform different functions and even dissociating classically linked effector functions, e.g. arrestin-dependent GPCR desensitization and signaling. As these `unbalanced' signals propagate, we find that biased agonists can sometimes produce opposite effects on downstream signaling networks than conventional agonists. As a result, the in vivo transcriptomic `fingerprint' of biased and conventional agonists are largely non-overlapping at the level of regulated signaling pathways and biological processes. Fortunately, in the case of arrestin pathway-selective bias it appears that the arrestin-dependent signaling repertoire is sufficiently restricted that the transcriptomic effects are relatively conserved between tissues and focused on regulation only a few basic biological processes. The overall objectives of our future research are: 1) to understand the mechanisms underlying biased GPCR signaling at the molecular level so as to better predict how different forms of ligand bias will change the cellular response to GPCR activation; and, 2) to determine how biased efficacy measured in engineered `screening' cell systems relates to the biological responses they produce in physiologically relevant cells and tissues. As in the past, we will employ a full range of cell-based techniques to characterize the impact of ligand structure on receptor and effector conformation and function, as well as systems level bioinformatics analysis of proteomic and transcriptomic datasets to determine how specific patterns of efficacy impact the behavior of primary cells and the influence of cell background on the response. Completion of this project will help to develop a rational framework for relating in vitro ligand efficacy to the in vivo actions of arrestin pathway-selective biased GPCR ligands, providing information and tools that are critical to the development of novel biased therapeutics.