Pharmacodynamics of Biased G Protein-Coupled Receptor Agonism

而G蛋白偶联受体(GPCR)药物的开发传统上集中在传统的 激励性与拮抗性--“多维效能”与“功能选择性”的新范式 认识到GPCRs通过经典的G蛋白依赖和新的G蛋白依赖来调节生物效应 蛋白质不依赖的信号网络，这种配基结构可以通过稳定活性来对信号进行“偏向” 受体状态与天然配基的比例不同。这种有偏见的激动剂是一种新的实体， 具有路径选择功效，有效地创造了具有不同信号特征的新受体，其驱动因素 配基结构。有偏见的激动剂的前景在于产生混合激动剂/拮抗剂的能力。 在体内产生作用，并产生常规激动剂或拮抗剂无法达到的生物效应。近期 然而，经验表明，体内偏向的激动剂效应往往是不可预测的，这表明关键 我们对有偏见的激动主义的理解存在差距，这些障碍阻碍了新型gpr的合理设计。 靶向治疗。在过去的五年里，我们实验室的进步提供了一些机制 对配基偏向的明显特质的洞察。我们已经证明了配体结构可以指定 效应器中不同的“激活模式”，导致同一效应器执行不同的功能，甚至 解离经典关联的效应器功能，例如依赖arrestin的GPCR脱敏和信号转导。 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。 在下游信号网络上比传统的激动剂更有效。结果，体内转录切分 偏向激动剂和常规激动剂的“指纹”在调控信号水平上基本上是不重叠的 途径和生物过程。幸运的是，在arrestin途径选择性偏见的情况下，似乎 依赖arrestin的信号库受到充分的限制，以至于转录效应相对 在组织间保守，只专注于调节几个基本的生物过程。整体而言 我们未来研究的目标是：1)了解存在偏见的gpr信号转导机制。 分子水平，以便更好地预测不同形式的配体偏向将如何改变细胞对 以及，2)确定如何在工程“筛选”细胞系统中测量有偏的疗效 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， 我们将使用一系列基于细胞的技术来表征配体结构对受体的影响 和效应器的构象和功能，以及蛋白质组和系统水平的生物信息学分析 转录数据集，以确定特定的药效模式如何影响原代细胞和 细胞背景对反应的影响。该项目的完成将有助于开发一个合理的 体外配基效应与Arrestin途径选择性偏向GPCR体内作用相关的框架 配体，提供对开发新的偏向疗法至关重要的信息和工具。

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.