Beta-Arrestin-Biased Agonism at the D1 Receptor as a Novel Approach to Levodopa-Induced Dyskinesias in Advanced Parkinson's Disease

项目总结 帕金森病(PD)是世界上第二常见的神经退行性疾病，具有 据估计，60岁以上人群的患病率约为1%，这使得它变得越来越重要 我们老龄化人口中的医疗问题。左旋多巴是目前治疗帕金森病的标准，其功能是 在多巴胺耗竭的黑质纹状体通路中，多巴胺水平集中增加。然而，左旋多巴是 由于不良副作用，特别是运动波动，不适合长期治疗使用 左旋多巴诱发的运动障碍(LIDs)是常见的报道。据估计，超过50%的人会出现眼睑 帕金森病患者经过5至10年的治疗，对老年帕金森病患者的影响不成比例 通过大幅限制这一人群的治疗选择，达到晚期疾病阶段。 最近的研究表明，除了G蛋白信号外，多巴胺受体还可以 信号通过一条不同的依赖于b-arr2的途径。这一途径在调节 多巴胺1受体(D1R)的下游反应，在多巴胺转化过程中起重要作用 发出信号进入运动功能。以往的研究表明，在D1R的b-arr2信号的遗传调制 啮齿动物和非人类灵长类PD模型改善了运动功能，同时防止了眼睑。差异化 配体激活这些不同的下游信号通路被称为功能选择性或 到目前为止，D1R的𝛽-ARR2信号通路还没有被药理学靶向 以一种功能选择性的方式潜在地减少与左旋多巴相关的不良反应。 为了实现这一点，目标1建议合成和表征新的D1R配体 系统地修饰先前确定的D1R选择性的非儿茶酚先导化合物。配体 将使用三种检测它们在激活G时的相对势能的方法来分析功能选择性 D1R的蛋白质和b-arr2信号转导。每种配体的血脑屏障通透性将用 一种经过验证的人工膜检测方法。在目标2中，在电子对接研究中，基于分子动力学的自由- 利用先前合成的类似物进行能量计算和模型验证实验 将执行不同的功能选择性配置文件，以确定D1R结构元素 对𝜷-ARR2偏置很重要。这些结果将提供关键的结构信息，以帮助推断结构 𝛽-Arr2在D1R的招募机制和结构-功能选择性关系 将进一步的支架优化转化为有效的𝛽-Arr2偏向化合物。 该项目的发现将通过提供化学工具来极大地促进该领域的知识 将有助于研究D1R如何产生偏向信号，以及D1R下游的分子通路如何 受体参与PD和LID的病理生理过程。从这些研究中获得的见解将提供 指导新的治疗方法的重要线索，以解决这一具有挑战性的、尚未解决的医学问题。 好了！

PROJECT SUMMARY Parkinson’s Disease (PD) is the second most common neurodegenerative disease in the world with a prevalence estimated to be approximately 1% in people over age 60, making it an increasingly important medical problem in our aging population. Levodopa is the current standard of care for PD and functions by increasing levels of dopamine centrally in the dopamine-depleted nigrostriatal pathway. Levodopa, however, is not a viable agent for long-term therapeutic use as undesirable side effects, notably motor fluctuations termed Levodopa-induced dyskinesias (LIDs), are commonly reported. LIDs are estimated to occur in over 50% of PD patients after 5 to 10 years of treatment and disproportionately impact older PD patients at more advanced disease stages by substantially limiting the therapeutic options for this population subset. Recent research has elucidated that, in addition to G protein signaling, dopamine receptors can also signal through a distinct b-arrestin2 (b-arr2)-dependent pathway. This pathway is important in regulating downstream responses at the Dopamine 1 Receptor (D1R) and plays a significant role in converting dopamine signaling into motor function. Previous studies showed that genetic modulation of b-arr2 signaling at D1R in rodent and non-human primate PD models improved motor functioning, while preventing LIDs. The differential activation of these distinct downstream signaling pathways by a ligand is termed “functional selectivity” or “biased agonism”, and to date, the 𝛽-arr2 signaling pathway at D1R has not been pharmacologically targeted in a functionally selective manner to potentially reduce the adverse effects associated with Levodopa. To accomplish this, Aim 1 proposes the synthesis and characterization of new D1R ligands by systematically modifying a previously identified D1R-selective, non-catechol lead compound. Ligands will be profiled for functional selectivity using three assays that detect their relative potencies at activating G protein and b-arr2 signaling at D1R. The blood-brain barrier permeability of each ligand will be assessed using a validated artificial membrane assay. In Aim 2, in silico docking studies, molecular dynamics-based free- energy calculations, and model validation experiments utilizing previously synthesized analogues with diverse functional selectivity profiles will be performed to identify D1R structural elements that are important for 𝜷-arr2 bias. These results will provide critical structural information to help deduce a structural mechanism for 𝛽-arr2 recruitment at D1R and a structure-functional selectivity relationship (SFSR) that will inform further scaffold optimization into a potent, 𝛽-arr2-biased compound. Findings from this project will greatly advance knowledge in the field by providing chemical tools that will enable the study of how biased signaling occurs at D1R and how molecular pathways downstream of this receptor contribute to PD and LID pathophysiologies. The insights gained from such studies will provide important clues guiding novel therapeutic approaches to this challenging, unsolved medical problem. !