Molecular Characterization of Mouse Melanopsin, Circadian Photopigment

小鼠黑视蛋白、昼夜节律感光色素的分子表征

• 批准号: 0615569
• 负责人: Phyllis Robinson
• 金额: --
• 依托单位: University of Maryland Baltimore County
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0615569&HistoricalAwards=false
• 关键词: Molecular; Characterization; Mouse; Melanopsin; Circadian

Many aspects of mammalian physiology and behavior exhibit a daily 24 hour rhythm. These daily oscillations are circadian rhythms and are controlled by a brain structure known as the suprachiasmatic nucleus (SCN). The mammalian circadian clock is constantly being reset by the onset of environmental light. Light entrainment of the clock requires input from the retina, which communicates with the SCN via the axonal projections of a small subset of retinal ganglion cells (RGCs). Surprisingly, rod and cone photoreceptors are not required; instead, RGCs that project to the SCN appear to function as autonomous circadian photoreceptors as they exhibit light responses independent of rod- and cone-driven synaptic input. Interestingly, the action spectrum of the light-evoked depolarization of these photosensitive retinal ganglion cells is described by a photopigment with a wavelength of maximum absorbance of 484 nm.Melanopsin, a novel opsin-like protein expressed in some of the retinal ganglion cells that project to the SCN, appears to be the elusive circadian photopigment based on several lines of evidence. Melanopsin is expressed in the light-sensitive RGCs and disruption of the melanopsin gene in mice abolishes the intrinsic light response of the SCN-projecting RGCs and impairs circadian entrainment. However, these elegant experiments do not address the question of whether melanopsin is a photopigment directly responsible for generating the light response, or simply an isomerase required for chromophore regeneration on a separate photopigment. Data from the Robinson laboratory was the first to demonstrate that melanopsin does indeed form a functional photopigment. This led to the hypothesis that melanopsin has a unique role in mammalian RGCs involved in circadian photoentrainment and the light-activated melanopsin triggers a G-protein cascade that underlies the photic response generated by these melanopsin-containing RGCs. Based on its homology with invertebrate opsins, the prediction is that melanopsin activates a Gq-based signaling pathway. This grant proposes to use molecular and biochemical approaches to further characterize melanopsin.The proposed research is significant because melanopsin is a novel and newly discovered mammalian retinal visual pigment involved in circadian photoentrainment. It appears to have many properties similar to visual pigments that have been characterized in rhabdomeric invertebrate eyes. This makes this pigment unique among mammalian visual pigments and fascinating to study. The approaches proposed in this grant are novel. The Robinson lab is the only laboratory that has taken a decidedly molecular and biochemical approach to study this visual pigment, and is poised to make significant progress on understanding this visual pigment within the next two years. Broader Impacts: The P.I of this grant is acutely aware of NSF's commitment to education and the development of underrepresented groups in the United States' Scientific workforce in the 21 st century. The P.I is currently a co-P.I. on a NSF institutional ADVANCE award to UMBC which as an institution is committed to the inclusion of both women and minorities in science. The P.I. has established an inclusive laboratory environment where underrepresented students, both graduate and undergraduate, have a positive research experience. Part of research described in this grant will be conducted by an African-American male. When possible, these undergraduates will include talented minority and women undergraduates identified form the nationally recognized Meyerhoff Scholars Program. The P.I. will also continue the practice of disseminating research results to the public through public lectures and visits to local high schools.

哺乳动物生理和行为的许多方面表现出每天24小时的节律。这些每日的振荡是昼夜节律，由被称为视交叉上核(SCN)的大脑结构控制。哺乳动物的生物钟随着环境光的到来而不断地被重置。时钟的光携带需要来自视网膜的输入，视网膜通过一小部分视网膜神经节细胞(RGC)的轴突投射与SCN通信。令人惊讶的是，视杆和视锥感受器并不是必需的；相反，投射到SCN的视网膜节细胞似乎作为自主的昼夜节光感受器发挥作用，因为它们表现出独立于视杆和视锥驱动的突触输入的光反应。有趣的是，这些光敏性视网膜神经节细胞的光诱导去极化的作用光谱由最大吸收波长为484 nm的光色素来描述。黑色素是一种新的视蛋白样蛋白，在投射到SCN的一些视网膜神经节细胞中表达，根据几条证据似乎是难以捉摸的昼夜光色。黑素在对光敏感的视网膜节细胞中表达，小鼠黑素视黄素基因的破坏取消了投射SCN的视网膜节细胞的内在光反应，并损害了昼夜节律的携带。然而，这些优雅的实验并没有解决黑色素是一种直接负责产生光反应的光色素，还是仅仅是一种在单独的光色素上再生生色团所需的异构酶的问题。来自罗宾逊实验室的数据第一次证明了黑色素确实形成了一种功能性感光色素。这导致了一个假设，即黑素在哺乳动物视网膜节细胞中具有独特的作用，参与昼夜节律的光包裹，光激活的黑色素素触发G蛋白级联反应，这是这些含有黑素的视网膜节细胞所产生的光反应的基础。根据其与无脊椎动物视蛋白的同源性，预测黑素激活了一条基于GQ的信号通路。这项拨款建议使用分子和生化方法来进一步表征黑色素。拟议的研究具有重要意义，因为黑色素是一种新发现的哺乳动物视网膜视觉色素，参与昼夜光携带。它似乎具有许多类似于横纹肌肉无脊椎动物眼睛所特有的视觉色素的特性。这使得这种色素在哺乳动物的视觉色素中是独一无二的，研究起来很吸引人。这笔赠款中提出的方法是新颖的。罗宾逊实验室是唯一采用明确的分子和生物化学方法来研究这种视觉色素的实验室，并准备在未来两年内在理解这种视觉色素方面取得重大进展。更广泛的影响：这笔拨款的P.I敏锐地意识到NSF对教育的承诺，以及在21世纪美国科学劳动力中代表不足的群体的发展。P.I目前是NSF向UMBC颁发的机构预付款的联合P.I.，作为一个机构，该机构致力于将女性和少数族裔纳入科学领域。P.I.建立了一个包容的实验室环境，在这个环境中，无论是研究生还是本科生，代表性不足的学生都有积极的研究经验。这项拨款中描述的部分研究将由一名非裔美国男性进行。如果可能，这些本科生将包括从全国公认的迈耶霍夫学者计划中挑选出来的有才华的少数族裔和女性本科生。公安部还将继续通过公开讲座和访问当地高中的方式向公众传播研究成果。