Circadian Photoentrainment in Mammals

描述（由申请人提供）：在哺乳动物中，下丘脑视交叉上核中的主昼夜节律钟控制代谢、心输出量、警觉性和睡眠状态与每日光/暗周期。生物钟的慢性去极化是代谢疾病以及睡眠和情绪障碍的重要因素。即使是生物钟与自然昼夜周期的暂时分离，如时差或轮班工作综合症，也是生产力下降和意外伤害或死亡的主要原因。因此，对生物钟功能的坚定理解，导致相关疾病的治疗，将导致社会的健康和经济效益。 生物钟与外部环境的同步性很大程度上取决于眼睛接受的光线。然而，光携带昼夜节律振荡器的精确机制尚不清楚。昼夜光诱导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。这表明可能涉及新的色素，信号性质和发色团的使用。最近，一种新的视蛋白样色素，黑视蛋白，被发现在视网膜内层，并已被确定为一个主要的调解人的光输入的昼夜节律钟。本计画中提出的实验是为了了解黑视素感光性的一些关键方面。具体来说，我们想了解黑视蛋白的光谱和光化学性质，以及它与抑制蛋白的相互作用如何调节这种功能。我们已经开发了异源表达系统，用于测量活细胞中的黑视蛋白光敏性和用于生物化学分析的视蛋白的高水平表达。使用细胞和生物化学测定，我们将（a）确定黑视素色素是否以两种不同的光谱活性和光可逆状态存在，（B）黑视素是否具有固有的光异构酶活性以再生其自身的发色团，以及（c）与抑制蛋白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视素光转导的关键功能特征，阐明潜在的机制，并提供治疗干预昼夜节律紊乱的潜在切入点。

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.