Circadian molecular regulation of the xenobiotic response

描述（由申请人提供）：最近，生物钟被认为是一系列生理过程的调节剂，包括葡萄糖稳态、血压调节、药物代谢和毒性。几种药物，包括抗高血压他汀类药物（如立普妥）和抗糖尿病药物二甲双胍（如Glucophage），建议在一天中的特定时间服用。然而，这些偏好的分子基础尚不清楚。该提议的基本假设是，治疗药物的细胞运输和代谢可以在转录水平上通过昼夜节律抑制因子调节，改变对外源配体作出反应的核激素受体的功能。推进我们对这些受体和抑制因子相互作用的功能理解可能会突出治疗疾病的新治疗策略。例如，定义外源转录网络的昼夜调节可以预测现有和新型治疗化合物的最佳治疗时间。此外，对调节外源转录反应的核激素受体途径的昼夜调节的更深入了解可能会导致调节药物吸收、代谢和/或毒性的新策略。我们之前的研究发现，生物钟成分隐色素（Cry1和Cry2）是营养反应性转录调节剂，因为它们容易被amp激活的蛋白激酶（AMPK）磷酸化，并且能够调节糖皮质激素受体依赖的转录。我们还通过驱动昼夜表达确立了肝脏生物钟在葡萄糖稳态中的重要作用

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.