Role of circadian clocks in maintaining a healthy nervous system

描述（由申请人提供）：本研究的长期目标是确定生物钟调节神经元健康的分子途径。昼夜节律钟是产生大脑和各种外周组织每日细胞节律的分子反馈回路。生物钟的破坏与神经系统疾病有关，但将生物钟与神经元健康联系起来的基本机制尚不清楚。我们最近的研究表明，果蝇生物钟的缺失会显著增加氧化损伤蛋白、过氧化物脂质的积累，并导致大脑神经退行性变化。此外，我们确定了活性氧（ROS）水平的每日节律，而在生物钟被打乱的果蝇中，ROS不断升高。分子氧化损伤是与年龄相关的神经系统疾病的重要危险因素，谷胱甘肽（GSH）是保护神经细胞免受氧化应激的关键抗氧化剂。谷胱甘肽水平下降在许多神经系统疾病中都有发现，包括精神分裂症、帕金森氏症和阿尔茨海默病以及正常的衰老。为了对抗神经系统疾病，需要进行基础研究来了解调节谷胱甘肽稳态的机制。我们获得了令人兴奋的初步数据，表明谷胱甘肽的合成可能受到生物钟的控制。我们揭示了谷氨酸半胱氨酸连接酶（GCL）的催化亚基（GCLc）和调节亚基（GCLm）表达的昼夜节律，以及谷氨酸半胱氨酸水平的每日节律变化。GCL是谷胱甘肽生物合成的限速酶。这些节律在生物钟被基因破坏的果蝇和生物钟受损的老年果蝇中被废除。我们假设生物钟调节谷胱甘肽的生物合成，而谷胱甘肽内稳态的时间调节可以有效地预防/修复氧化损伤和保护神经系统。为了验证这一假设，我们提出了一个跨学科合作使用优秀的模型系统果蝇黑腹。在目标1中，我们将确定生物钟在调节大脑中谷胱甘肽生物合成中的作用。然后，我们将在目标2中探索谷胱甘肽生物合成节律和神经元健康之间的功能联系。最后，在目标3中，我们将确定衰老的生物钟对谷胱甘肽系统和神经元健康的影响。公共卫生意义：从这项工作中获得的见解可能会导致新的策略来避免人类衰老的神经变性，这是一个至关重要的医学和社会问题。

DESCRIPTION (provided by applicant): The long term objective of this research is to define molecular pathways by which the circadian clock regulates neuronal health. Circadian clocks are molecular feedback loops that generate daily cellular rhythms in the brain and various peripheral tissues. Disruption of the circadian clock has been implicated in neurological disorders but the underling mechanisms connecting the clock to neuronal health are not understood. We have recently shown that loss of the circadian clock in Drosophila dramatically increased accumulation of oxidatively damaged proteins, lipids peroxides, and caused neurodegenerative changes in the brain. Furthermore, we identified a daily rhythm in levels of reactive oxygen species (ROS), while ROS was constantly elevated in flies with a disrupted circadian clock. Molecular oxidative damage is a significant risk factor for age-related neurological disorders and glutathione (GSH) is a key antioxidant that protects neuronal cells against oxidative stress. Depleted GSH levels are found in a number of neurological disorders including schizophrenia, Parkinson's, and Alzheimer's diseases as well as in normal aging. To counteract neurological diseases, basic research is needed to understand mechanisms regulating GSH homeostasis. We obtained exciting preliminary data suggesting that GSH synthesis may be controlled by the circadian clock. We revealed a circadian rhythm in the expression of the catalytic (GCLc) and modulatory (GCLm) subunits of glutamate cysteine ligase (GCL), which is the rate-limiting enzyme in GSH biosynthesis, as well as daily rhythmic changes in GSH levels. These rhythms were abolished in flies with a genetically disrupted circadian clock and in older flies, whose circadian clock becomes impaired. We hypothesize that the circadian clock modulates GSH biosynthesis, and that temporal regulation of GSH homeostasis results in efficient prevention/repair of oxidative damage and protection of the nervous system. To test this hypothesis, we propose an interdisciplinary collaboration using the excellent model system Drosophila melanogaster. In aim 1, we will determine roles of circadian clocks in the regulation of glutathione biosynthesis in the brain. We will then explore functional links between rhythms in GSH biosynthesis and neuronal health in aim 2. Finally, in aim 3 we will determine the effect of an aging circadian clock on the GSH system and neuronal health. Public health significance: Insights obtained from this work may lead to novel strategies to avert neurodegeneration in aging humans, which is a critically important medical and societal issue.