Regulation of Tyrosine Hydroxylase by CLOCK: Potential Mechanisms Underlying the

描述(申请人提供)：药物滥用后神经可塑性的改变被认为是成瘾出现的基础，成瘾是一种影响全球数百万人的毁灭性疾病。尽管对成瘾的潜在机制进行了深入的研究，但成功的治疗方案的开发在很大程度上仍然没有实现。现在很明显，昼夜节律系统的紊乱是精神疾病的潜在诱因，包括严重的抑郁症、双相情感障碍和药物成瘾。昼夜节律系统协调着最佳功能所需的数千个生物节律。事实上，药物敏感性的昼夜节律，药物使用和过量的季节性模式，以及与昼夜节律系统中的遗传破坏相关的对成瘾的易感性，都表明了这些系统之间的联系。然而，目前尚不清楚构成生物钟的分子机制如何影响药物依赖的核心奖赏回路。此外，缺乏可靠地揭示精神疾病复杂性的动物模型，限制了我们对这些疾病潜在机制的理解。我们的实验室已经确定并表征了昼夜节律基因Clock在奖赏回路调节中的作用，并代表了一个有希望的候选靶点，用于改善成瘾和双相情感障碍模型中的关键风险因素。带有该基因显性负点突变的转基因小鼠，表现出多巴胺能神经元的放电增加，VTA中的TH上调，NAcc中的多巴胺能张力增加，以及对这些动物中观察到的奖赏刺激(包括ICSS、吗啡和可卡因)的高度敏感性。确定时钟影响奖励电路的精确调控机制将为这些疾病的治疗发现新的治疗靶点。VTA中Clock的一个可能靶点是磷酸化的CRE元件结合蛋白(PCREB)，它是TH转录的主要驱动因素，广泛参与介导与成瘾相关的神经元可塑性。我们的实验室最近在VTA的TH启动子上发现了CLOCK和pCREB之间的相互作用，提供了一个潜在的分子链接，通过CLOCK调节多巴胺能传递，并在CLOCK？19突变小鼠中对滥用药物的增强的多巴胺能和行为反应奠定基础。这项建议将1)确定CLOCK和pCREB如何在TH启动子上相互作用以驱动有节奏的多巴胺转录；2)揭示CLOCK？19无法调节VTA中多巴胺传递的机制；以及3)确定CREB信号在CLOCK？19小鼠中的作用，这是在这种双相躁狂症模型中导致对可卡因高度敏感的原因。总而言之，这些研究将弥合昼夜节律系统和奖赏回路之间的差距，这些回路与多种精神疾病相关的药物依赖的发展有关。

DESCRIPTION (provided by applicant): The alterations in neuroplasticity following drug abuse are believed to underlie the emergence of addiction, a devastating illness that affects millions worldwide. Despite intensive research into the mechanisms underlying addiction, the development of successful treatment options remains largely unfulfilled. It is now evident that disruptions in the circadian system, which coordinates the thousands of biological rhythms necessary for optimal functioning, is an underlying causative factor for psychiatric disease, including major depressive disorder, bipolar disorder and drug addiction. Indeed, circadian rhythms in drug sensitivity, seasonal patterns of drug use and overdose, and the susceptibility to addiction associated with genetic disruptions in the circadian system suggest a link between these systems. However, it is unclear how the molecular mechanisms that constitute the circadian clock impact reward circuitry central to drug dependence. Additionally, the lack of animal models that reliably capitulate the complexity of psychiatric disorders has limited our understanding of the underlying mechanisms of these illnesses. Our lab has identified and characterized a role for the circadian gene, Clock, in the regulation of reward circuitry and represents a promising candidate target for ameliorating critical risk factors in models of addiction and bipolar disorder. Transgenic mice with a dominant negative point mutation in this gene, Clock¿19, exhibit increased dopaminergic neuronal firing, upregulated TH in the VTA, increased dopaminergic tone in the NAcc and precipitates the heightened sensitivity to rewarding stimuli, including ICSS, morphine and cocaine observed in these animals. Determining the precise regulatory mechanisms by which Clock impacts reward circuitry will uncover novel therapeutic targets for the treatment of these disorders. A likely target of CLOCK in the VTA is the phosphoactive CRE-element binding protein (pCREB), the principle driver of TH transcription and is widely implicated in mediating the neuronal plasticity associated with addiction. Our lab has recently uncovered an interaction between CLOCK and pCREB at the TH promoter in the VTA providing a potential molecular link by which CLOCK regulates dopaminergic transmission and underlies the heightened dopaminergic and behavioral response to drugs of abuse in the Clock¿19mutant mouse. This proposal will 1) determine how CLOCK and pCREB interact at the TH promoter to drive rhythmic dopamine transcription 2) uncover the mechanisms underlying the inability of CLOCK¿19 to regulate dopamine transmission in the VTA and 3) determine the role of CREB signaling in Clock¿19 mice underlying the heightened sensitivity to cocaine in this model of bipolar mania. Together, these studies will bridge the gap between the circadian system and reward circuitry implicated in the development of drug dependence associated with multiple psychiatric diseases.