Cross-talk between the circadian clock and the cAMP signaling pathway

描述（由申请人提供）：哺乳动物的摄食行为是间歇性和昼夜节律性的。因此，哺乳动物已经开发出暂时调节肝脏再生以维持葡萄糖稳态的机制。CREB/CRTC2途径通过顺式作用的cAMP反应元件（CREs）调节糖异生基因的转录，以响应禁食和进食。同时，自我维持的肝脏昼夜节律钟介导代谢基因表达的昼夜节律-其中一些由CREB和CRTC2调节-峰值水平与一天中的适当时间一致。虽然生物钟和CREB/CRTC2通路之间的分子相互作用被认为是塑造对喂养方案的整体适应，但这些相互作用尚未得到很好的定义。核心生物钟基于转录反馈环，其中Clock/Bamal 1转录激活因子与Per和Cry基因启动子中的顺式作用E-box结合，其蛋白质产物反过来抑制Clock/Bmal 1功能，从而在Per和Cry蛋白中产生昼夜节律。本申请测试了生物钟和CREB途径通过Per/CRY抑制剂和CREB/CRTC2激活剂之间的相互调节相互作用促进代谢适应环境变化的假设。目的1至3解决Cry蛋白在响应于间歇性进食的肝CREB和CRTC 2活性的昼夜节律调节中的作用。特别是，我们将评估Crys在减弱cAMP产生的胰高血糖素依赖性增加中的拟议作用。胞质Cry干扰G蛋白偶联受体信号传导吗？ 目的4 - 6解决CREB/CRTC2途径对时钟活性的反调节作用。特别是，我们将研究CREB结合位点对Per基因的调节重要性，这提供了一个节点，用于同步Per转录，从而使昼夜节律与每日摄食节律同步。最后，我们将测试这些相互作用如何塑造生物体对摄食方案的长期适应。 公共卫生相关性：生物钟被认为通过调节代谢活性组织中禁食和进食程序的表达来促进能量稳态。生物钟功能紊乱与胰岛素抵抗和代谢综合征的风险增加有关，尤其是在轮班工人中。本申请测试了新鉴定的生物钟和细胞表面受体信号传导途径之间的相互作用在维持葡萄糖稳态中的重要性。

DESCRIPTION (provided by applicant): Feeding behavior in mammals is both episodic and circadian. Accordingly, mammals have developed mechanisms to temporally regulate liver gluconeogenesis to maintain glucose homeostasis. The CREB/CRTC2 pathway regulates transcription of gluconeogenic genes via cis-acting cAMP Response Elements (CREs) in response to fasting and feeding bouts. In parallel, the self sustaining hepatic circadian clock mediates circadian rhythm in expression of metabolic genes- a number of which are regulated by CREB and CRTC2- with peak levels aligned to appropriate time of the day. Although molecular interactions between the circadian clock and the CREB/CRTC2 pathway are thought to shape the overall adaptation to feeding regimen, these interactions are not well defined. The core circadian clock is based on a transcriptional feedback loop in which Clock/Bamal1 transcriptional activators bind to cis acting E-box in the promoters of Per and Cry genes, whose protein products in turn inhibit Clock/Bmal1 function, thus producing circadian rhythms in Per and Cry proteins. The current application tests the hypothesis that the circadian clock and CREB pathway promote metabolic adaptation to environmental changes through reciprocal regulatory interactions between the Per/CRY inhibitors and CREB/CRTC2 activators. Aims 1 to 3 address the role of Cry proteins in the circadian modulation of hepatic CREB and CRTC2 activities in response to episodic feeding. In particular, we will evaluate the proposed role of Crys in attenuating glucagon-dependent increases in cAMP production. Does cytoplasmic Cry interfere with G protein coupled receptor signaling? Aims 4-6 address counter-regulatory effects of the CREB/CRTC2 pathway on clock activity. In particular, we will examine the regulatory importance of CREB binding sites on Per genes, which offer a node for synchronizing Per transcription and consequently the circadian clock with the daily feeding rhythms. Finally, we will test how these interactions shape long term adaptation of the organism to feeding regimens. PUBLIC HEALTH RELEVANCE: The circadian clock is thought to promote energy homeostasis by modulating the expression of fasting and feeding programs in metabolically active tissues. Disturbances in clock function have been associated with an increased risk of insulin resistance and the metabolic syndrome, most notably in shift workers. The current application tests the importance of a newly identified interaction between the circadian clock and a cell surface receptor signaling pathway in maintaining glucose homeostasis.