Circadian molecular regulation of the xenobiotic response

描述(申请人提供)：生物钟最近被认为是一系列生理过程的调节器，包括葡萄糖稳态、血压调节、药物新陈代谢和毒性。建议在一天中的特定时间服用几种药物，包括抗高血压药物他汀类药物(如立普妥)和抗糖尿病药物二甲双胍(如葡聚糖)。然而，这些偏好的分子基础还没有被很好地理解。这一提议的基本假设是，治疗药物的细胞运输和代谢可以通过昼夜节律抑制因子在转录水平上进行调节，从而改变核激素受体对异种配体的反应功能。推进我们对这些受体和抑制物相互作用的功能理解可能会突出治疗疾病的新的治疗策略。例如，定义异源生物转录网络的日调节可以预测现有的和新的治疗化合物的最佳治疗时间。此外，更深入地了解核激素受体途径对异源转录反应的调节可能会导致新的策略来调节药物的吸收、代谢和/或毒性。我们以前的研究发现，生物钟成分隐花素(Cry1和Cry2)是营养响应的转录调节因子，因为它们对AMP激活的蛋白激酶(AMPK)磷酸化的敏感性以及它们调控糖皮质激素受体依赖的转录的能力。我们还通过驱动日间表达，确定了肝脏生物钟在葡萄糖动态平衡中的重要作用 肝酶和转运蛋白，包括AMPK。在这些研究过程中，我们产生了独特的工具和专业知识，使我们能够使用生化、遗传学、分子和生理学方法来揭示昼夜节律时钟和昼夜节律抑制因子Cry1和Cry2在控制药物运输和代谢的核激素受体途径中的作用，具体目的如下：1)表征Cry1和Cry2与外源受体PXR和CAR的相互作用(定义隐色素-外源受体相互作用的种类和同工型特异性以及配体和依赖性；2)确定Cry1和Cry2在调节PXR/CAR介导的异种生物代谢中的作用(确定受隐花色素调控的PXR和CAR的特定转录靶点，测量当隐花色素耗尽时药物转运和代谢活动的变化)，3)研究生物钟、PXR和CAR在二甲双胍治疗效果中的作用。

DESCRIPTION (provided by applicant): Circadian clocks have recently become recognized as modulators of a wide array of physiological processes, including glucose homeostasis, blood pressure modulation, and drug metabolism and toxicity. Several drugs, including the anti-hypertensive statins (e.g. Lipitor) and the anti-diabetic drug metformin (e.g. Glucophage), are recommended to be taken at specific times of day. However, the molecular basis for these preferences is not well understood. The underlying hypothesis of this proposal is that the cellular transport and metabolism of therapeutic drugs can be modulated at the transcriptional level by circadian repressors altering the function of nuclear hormone receptors that respond to xenobiotic ligands. Advancing our functional understanding of these receptor and repressor interactions may highlight new therapeutic strategies for treating disease. For example, defining the diurnal regulation of the xenobiotic transcriptional network could enable the prediction of optimal treatment times for existing and novel therapeutic compounds. In addition, a deeper understanding of the diurnal regulation of nuclear hormone receptor pathways that modulate the xenobiotic transcriptional response may lead to new strategies for modulating drug absorption, metabolism and/or toxicities. Our previous studies identified the circadian clock component cryptochromes (Cry1 and Cry2) as nutrient- responsive transcriptional regulators by virtue of their susceptibility to phosphorylation by AMP-activated protein kinase (AMPK) and their ability to modulate glucocorticoid receptor dependent transcription. We have also established an important role for the liver circadian clock in glucose homeostasis, via driving diurnal expression of hepatic enzymes and transporters, including AMPK. In the course of those studies, we have generated unique tools and expertise that enables us to use biochemical, genetic, molecular and physiological approaches to uncover the roles of circadian clocks and of the circadian repressors Cry1 and Cry2 specifically in nuclear hormone receptor pathways governing the control of drug transport and metabolism, in the following specific aims: 1) Characterize the interactions of Cry1 and Cry2 with the xenobiotic receptors PXR and CAR (define the species and isoform specificity and ligand dependence of cryptochrome-xenobiotic receptor interactions; identify domains and sequences required for interaction), 2) Define the role of Cry1 and Cry2 in the regulation of PXR/CAR-mediated xenobiotic metabolism (identify specific transcriptional targets of PXR and CAR that are regulated by cryptochromes, measure changes in drug transport and metabolizing activities upon cryptochrome depletion), 3) Examine the roles of circadian clocks, PXR and CAR in the efficacy of metformin treatment.