Pharmacodynamics of Biased G protein-Coupled Receptor Agonism

描述(申请人提供)：有偏向的G蛋白偶联受体(GPCR)激动剂是具有路径选择功效的邻位配体，仅激活或抑制其同源受体信号转导系统的一部分。与通过改变受体药效的数量发挥作用的传统激动剂不同，有偏向的激动剂具有定性改变信号的能力，这表明有可能利用配基偏向来开发最大限度地提高临床疗效同时将副作用降至最低的药物。我们的发现是，一种选择性偏向于arrestin途径的1型甲状旁腺激素受体(PTH1R)激动剂可以促进体内合成代谢的骨形成，而不会刺激骨吸收或产生高钙血症，这为有偏向的激动剂可以用来诱导常规激动剂或拮抗剂药物无法达到的生物反应提供了原理证据。利用生物信息学的代谢途径和基因簇分析，我们发现Arrestin选择性PTH1R激动剂在组织水平上产生了独特的基因组足迹，即其作用机制与传统激动剂不同，并且不能根据现有的经典GPCR信号转导知识进行预测。这一关键的观察结果提出了关于有偏见的激动症的本质的根本问题，我们建议在本申请中解决这一问题。我们将使用体外配基效力分析、基于微阵列的功能基因组分析和基于细胞的生物反应分析，以解决三个特定目标。目的1利用来自野生型和阻滞型2-/-小鼠的原代颅骨成骨细胞和PTH1R配体，在同一种细胞类型中确定常规、G蛋白途径选择性和arrestin途径选择性激动剂的功能特征。我们假设G蛋白选择性激动剂和Arrestin选择性偏向激动剂都将产生与传统激动剂本质上不同的基因组足迹。目的2利用原代肾小管上皮细胞和血管紧张素AT1AR、血管加压素V2R和PTH1R选择性偏向的arrestin通路配体，在相同的细胞背景下确定不同GPCRs激活arrestin信号通路的效果。我们假设，对不同的arrestin选择性激动剂的反应将重叠，而对常规激动剂的反应将因不同G蛋白的伴随激活而不同。目的3将利用原代成骨细胞、肾小管上皮细胞和心肌细胞，以及arrestin途径选择性偏向的AT1AR和PTH1R配体来确定在不同细胞类型中通过共同的GPCR激活arrestin信号通路的效果。我们假设arrestin信号的激活在不同的细胞背景下会产生类似的效果，反映了有限的arrestin依赖的信号库。这项工作将确定影响的范围 这可以使用arrestin选择性激动剂来实现，并确定arrestin依赖效应在不同GPCR和靶组织中的保守程度。这些信息将对开发利用配体偏见的新疗法的努力至关重要。

DESCRIPTION (provided by applicant): Biased G protein-coupled receptor (GPCR) agonists are orthosteric ligands that possess pathway-selective efficacy, activating or inhibiting only a subset of the signaling repertoire of their cognate receptors. Unlike conventional agonists that work by changing the quantity of receptor efficacy, biased agonists possess the ability to qualitatively change signaling, suggesting it may be possible to exploit ligand bias to develop drugs that maximize clinical effectiveness while minimizing side effects. Our finding that an arrestin pathway-selective biased agonist for the type 1 parathyroid hormone receptor (PTH1R) promotes anabolic bone formation in vivo without stimulating bone resorption or producing hypercalcemia offers proof of principal that biased agonists can be used to elicit biological responses that cannot be achieved with conventional agonist or antagonist drugs. Using bioinformatic metabolic pathways and gene cluster analysis, we found that the arrestin-selective PTH1R agonist produces a unique genomic 'footprint' at the tissue level, i.e. that its mechanism of action is distinct from that of a conventional agonist and could not have been predicted on the basis of existing knowledge of classical GPCR signaling. This key observation raises fundamental questions about the nature of biased agonism, which we propose to address in this application. We will employ in vitro ligand efficacy profiling, microarray-based functional genomic analyses, and cell-based assays of biological response, to address three Specific Aims. Aim 1 will employ primary calvarial osteoblasts from wild type and ¿-arrestin2-/- mice and PTH1R ligands to determine the functional characteristics of conventional, G protein pathway-selective, and arrestin pathway-selective agonists in a common cell type. We hypothesize that both G protein-selective and arrestin-selective biased agonists will produce genomic footprints that are qualitatively different from a conventional agonist. Aim 2 will employ primary renal tubular epithelial cells and arrestin pathway- selective biased ligands for the angiotensin AT1AR, vasopressin V2R, and PTH1R to determine the effects of activating arrestin signaling pathways via different GPCRs in a common cell background. We hypothesize that the response to different arrestin-selective agonists will overlap, whereas the responses to conventional agonists will diverge due to the concomitant activation of different G proteins. Aim 3 will employ primary osteoblasts, renal tubular epithelial cells and cardiomyocytes, and arrestin pathway-selective biased ligands for the AT1AR and PTH1R to determine the effects of activating arrestin signaling pathways via a common GPCR in different cell types. We hypothesize that activation of arrestin signaling will produce similar effects in different cell backgrounds, reflecive of a limited arrestin-dependent signaling repertoire. This work will establish the range of effects that can be achieved using arrestin-selective agonists, and determine the extent to which arrestin-dependent effects are conserved across different GPCRs and target tissues. This information will be critical to efforts to develop novel therapeutics that exploit ligand bias.