Biasing Mu Opioid Receptor Signaling in vivo

描述（由申请人提供）：处方阿片类麻醉剂，如吗啡、羟考酮和芬太尼，通过激活μ阿片受体（莫尔）（一种G蛋白偶联受体（GPCR））产生镇痛和副作用。我们的长期目标是了解莫尔信号如何产生独特的生物学效应，并最终为开发利用“好”受体信号（缓解疼痛）并避免“坏”受体信号的治疗方法提供信息。 受体信号传导（耐受性、依赖性、便秘和其他副作用）。越来越明显的是，不同的药物结构可能通过改变与细胞内结合配偶体缔合的亲和力，在单个受体上引发不同的受体信号级联。此外，细胞内结合伴侣的分布在神经元群体之间不同。因此，药物反应的性质不仅可以通过药物的化学性质来确定，还可以通过与受体一起存在的信号蛋白的补充来确定;这使得研究生理相关系统中的受体信号至关重要。影响莫尔功能的一种特定细胞内蛋白是β抑制蛋白2。β Arrestin 2是一种支架蛋白，可以作为脱敏元件或作为信号转导促进剂。我们的研究表明，吗啡诱导的镇痛作用增强，而缺乏β-arrestin 2的小鼠的耐受性减弱，这意味着β-arrestin 2作为疼痛调节脑区的脱敏因子。我们的集体工作表明，某些副作用的严重程度，包括身体依赖和便秘，在缺乏β抑制蛋白2的小鼠中显著降低，这表明在某些器官系统和大脑区域中，β抑制蛋白2促进了莫尔信号传导。由于受体在体内对药物的反应性最终取决于包含受体的细胞环境，我们假设β-arrestin 2在镇痛途径中抑制吗啡反应性，同时介导吗啡相关的副作用，如身体依赖和便秘。为此，我们建议阐明β抑制蛋白调节莫尔在脑区域和组织介导吗啡诱导的抗伤害感受和耐受性（脑干），身体依赖（纹状体）和便秘（结肠）的机制。我们将利用新的莫尔激动剂，其在功能上选择性激活G蛋白信号通路（我们假设这将促进抗伤害感受）和抑制招募β抑制蛋白2（我们假设招募β抑制蛋白2导致耐受性、依赖性和便秘）。已发表的和初步的证据表明，G蛋白偏向激动剂促进抗伤害感受，副作用较少。我们将使用这些工具，以获得更好的了解莫尔的调控在内源性设置，因为它涉及到在体内的生理。这些研究应该为开发优先增强预期效果的治疗方法提供指导，例如改善疼痛治疗，同时防止不良反应。

DESCRIPTION (provided by applicant): Prescription opioid narcotics, such as morphine, oxycodone, and fentanyl, produce analgesia and side effects through activation of the mu opioid receptor (MOR), a G protein coupled receptor (GPCR). Our long-standing goal is to understand how MOR signals to produce distinct biological effects and to ultimately inform the development of therapeutics that will take advantage of "good" receptor signaling (pain relief) and avoid "bad" receptor signaling (tolerance, dependence, constipation and other side effects). It has become increasingly evident that different drug structures can elicit different receptor signaling cascade at a single receptor, likely by changing the affinities for association with intracellular binding partners. Further, the intracellular binding partner profile differs between neuronal populations. Therefore, the nature of a drug response can be determined not only by the chemical properties of the drug, but also by the complement of signaling proteins found in residence with the receptor; making it critical to study receptor signaling in physiologically relevant systems. One particular intracellular protein that influences MOR function is betaarrestin2. betaArrestin2 is a scaffolding protein that can act as desensitizing element or as a signal transduction facilitator. Our studies have shown that morphine-induced analgesia is enhanced while tolerance is attenuated in mice lacking betaarrestin2, which implicates betaarrestin2 as a desensitizing factor in pain regulating brain regions. Our collective body of work shows that the severity of certain side effects, including physical dependence and constipation, are significantly reduced in mice lacking betaarrestin2 suggesting that in some organ systems and brain regions, betaarrestin2 facilitates MOR signaling. Since receptor responsiveness to a drug in vivo is ultimately dependent upon the cellular environment that encompasses the receptor, we hypothesize that betaarrestin2 dampens morphine responsiveness in analgesia pathways while it mediates morphine-associated side effects such as physical dependence and constipation. To this end, we propose to elucidate the mechanisms by which betaarrestins regulate MOR in brain regions and tissues that mediate morphine-induced antinociception and tolerance (brainstem), physical dependence (striatum) and constipation (colon). We will utilize new MOR agonists that are functionally selective for activating G protein signaling pathways (we hypothesize this will promote antinociception) and against recruiting betaarrestin2 (we hypothesize that recruiting betaarrestin2 leads to tolerance, dependence and constipation). Published and preliminary evidence suggests that the G protein biased agonists promote antinociception with fewer side effects. We will use these tools to gain a greater understanding of MOR regulation in the endogenous setting as it pertains to in vivo physiologies. These studies should provide guidance for developing therapeutics that preferentially enhance desired effects such as improving pain therapy while preventing adverse reactions.