Circadian Photoentrainment in Mammals

描述(申请人提供)：在哺乳动物中，位于下丘脑视交叉上核的主生物钟将新陈代谢、心输出量、警觉性和睡眠状态与每日的光/暗周期同步。生物钟的慢性不同步是代谢性疾病以及睡眠和情绪障碍的一个重要因素。即使是时钟与自然昼夜周期的暂时不同步，如时差或轮班工作综合症，也是导致生产力损失和意外伤害或死亡的主要原因。因此，对生物钟功能的深入了解将有助于相关疾病的治疗，从而为社会带来健康和经济利益。 时钟与外部环境的同步性在很大程度上取决于眼睛所接受的光线。然而，光进入昼夜节律振荡器的确切机制尚不清楚。昼夜节律光携带的一个有趣的特征是它对几种通常导致失明的生理条件和突变的抵抗力。这可能涉及到新的光色素、信号特性和生色团的用途。最近，在视网膜内部发现了一种新的视蛋白样光色素，黑色素，它已经被确定为昼夜节律时钟光输入的主要中介。这个项目中提出的实验是为了了解黑素的光敏性的一些关键方面。具体地说，我们想要了解黑素的光谱和光化学性质，以及它与arrestin的相互作用是如何调节这种功能的。我们已经开发了异源表达系统，用于测量活细胞中黑色素的光敏性，并用于生化分析的视蛋白的高水平表达。利用细胞和生化分析，我们将(A)确定黑素光色素是否以两种不同的光谱活性和光可逆状态存在，(B)黑素是否具有再生自身发色团的内在光异构酶活性，以及(C)与arrestin的相互作用如何决定其光化学性质。这些目标的成功完成将确定黑素光转导的关键功能特征，阐明其潜在的机制，并为昼夜节律紊乱的治疗干预提供潜在的切入点。

DESCRIPTION (provided by applicant): In mammals, a master circadian clock in the suprachiasmatic nucleus of the hypothalamus synchronizes metabolism, cardiac output, alertness, and sleep state with the daily light/dark cycle. Chronic desynchronization of the circadian clock is a significant contributor to metabolic diseases, as well as sleep and mood disorders. Even temporary desynchronization of the clock with the natural day:night cycle, such as in jet lag or shift work syndrome, is a leading cause of productivity loss and accidental injury or death. Thus, a firm understanding of circadian clock function that leads to treatment of related disorders will lead to health and economic benefits of the society. Synchrony of the clock with the external environment is largely governed by exposure to light received by the eye. However, the precise mechanism by which light entrains the circadian oscillator is not known. An intriguing feature of circadian light entrainment is its resistance to several physiological conditions and mutations that usually causes blindness. This suggested novel photopigment, signaling property and chromophore use may be involved. Recently, a new opsin-like photopigment, melanopsin, was found in the inner retina and has been established as a dominant mediator of light input to the circadian clock. Experiments proposed in this project are to understand some key aspects of melanopsin's photosensitivity. Specifically, we want to understand the spectral and photochemical properties of melanopsin and how its interaction with arrestin modulates such function. We have developed heterologous expression systems for the measurement of melanopsin photosensitivity in living cells and for high level expression of the opsin for biochemical analysis. Using both cellular and biochemical assays we will (a) determine whether melanopsin photopigment exists in two distinct spectrally active and photoreversible states, (b) whether melanopsin has an intrinsic photoisomerase activity to regenerate its own chromophore and (c) how interaction with arrestin determines its photochemical properties. Successful completion of these aims will identify key functional features of melanopsin phototransduction, elucidate the underlying mechanism, and provide potential entry points for therapeutic intervention in circadian disorders.