Rhodopsins: from biosynthesis and degradation to unconventional functions

视紫红质：从生物合成、降解到非常规功能

基本信息

批准号：
8294154
负责人：
CRAIG MONTELL
金额：
$ 40.5万
依托单位：
JOHNS HOPKINS UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1989
资助国家：
美国
起止时间：
1989-04-01 至 2013-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8294154
关键词：
11 cis Retinal Address Adult Affect Aggressive behavior Anabolism Animal Behavior Animal Model Back Behavior Biochemical Biological Brain Cells Circadian Rhythms Couples Defect Down-Regulation Drosophila genus Drosophila melanogaster Endocytosis Feedback Funding G alpha q Protein G-Protein-Coupled Receptors Genes Genetic Genome Goals Guanosine Triphosphate Phosphohydrolases Heterotrimeric GTP-Binding Proteins Human Hypothalamic structure Image Immune Impairment Insect Repellents Interneurons Invertebrates Larva Lead Light Modeling Molecular Mutation Natural regeneration Neurons Olfactory Receptor Neurons Opsin Pathway interactions Pheromone Phospholipase C Phosphorylation Photons Photoreceptors Phototransduction Protein Kinase C Proteins Research Retina Retinal Retinal Cone Retinal Degeneration Retinal Ganglion Cells Retinal Pigments Retinoids Retinol dehydrogenase Rhodopsin Role Signal Pathway Signal Transduction Structural Genes System Techniques Testing Testis Brain Tissues Vertebrate Photoreceptors Visual system structure Vitamin A Work base chromophore citronellal constriction design fly genetic analysis interdisciplinary approach melanopsin mutant novel therapeutic intervention receptor research study response retinal neuron retinal rods visual cycle

项目摘要

DESCRIPTION (provided by applicant): The goal of the proposed research is to use the fruit fly, Drosophila melanogaster, as an animal model to unravel the molecular mechanisms underlying the biosynthesis, turnover and non-classical functions of rhodopsins. Rhodopsin is comprised of an opsin protein and a vitamin A-derived chromophore, which senses light. Among the most common forms of retinal degeneration are those that result from defects in the visual cycle (retinoid cycle)-an enzymatic pathway required for regeneration of the chromophore. Until recently it was thought that flies do not employ a visual cycle, since the chromophore does not normally release from photoactivated rhodopsin. However, some rhodopsin is internalized and the opsin gets degraded, thereby releasing the chromophore. During the last funding period, we made the discovery that flies use a visual cycle to regenerate the released chromophore. The experiments proposed in aim 1 are designed to differentiate between competing hypotheses to explain the basis for the retinal degeneration that results from defects in this enzymatic pathway. We also propose experiments to test hypotheses predicted by the newly formulated model for the invertebrate cycle. Since the mammalian opsin (melanopsin) that functions in the intrinsically photosensitive retinal ganglion cells appears to be more akin to Drosophila rhodopsins than to rod and cone photopigments, these studies also suggest that a visual cycle might function to regenerate the chromophore used by melanopsin. Although some rhodopsin is normally internalized, excessive internalization and degradation of rhodopsin occurs in a variety of flies with mutations that hyperactivate the phototransduction cascade. This appears to be a feedback mechanism to limit excessive signaling. The second aim addresses a new hypothesis that would explain how uncontrolled activity of the heterotrimeric G-protein leads to excessive turnover of rhodopsin. Although rhodopsins that function in the retina are among the best-characterized receptor proteins, in the past few years it has become clear that some opsins are expressed outside the retina. However, their extra-retinal roles are understood poorly. Aims 3 and 4 of the proposed research will characterize the roles of two opsins that are expressed in neurons in the olfactory system and central brain and that have not been associated with a light response. We propose to test the contributions of these rhodopsins to animal behaviors. The proposed experiments raise intriguing possibilities as to the potential roles for mammalian extra-retinal opsins, such as Opn3 and Opn5, which have not been subjected to genetic analysis. To accomplish our goals, we propose to employ a multidisciplinary approach using a combination of genetic, cell biological, electrophysiological, molecular and biochemical techniques. The long-term goals of these studies are to 1) uncover mechanisms underlying the retinal degenerations that result from defects in the visual cycle with the ultimate goal of discovering new therapeutic approaches, and 2) uncover the roles of the enigmatic extra-retinal opsins. PUBLIC HEALTH RELEVANCE: Rhodopsin is the receptor that is critically important for detecting light, and mutations affecting rhodopsin lead to common forms of retinal degeneration. The focus of the proposed work is to exploit the great technical advantages of the fruit fly as an animal model to uncover mechanisms underlying the retinal degeneration resulting from impairments in rhodopsins, and to identify roles for opsins that are expressed in cells that are not known to function in light reception.

描述（由申请人提供）：拟议的研究的目的是使用果蝇，果蝇Melanogaster作为动物模型，以揭示生物合成，转换和非经典功能的分子机制。 Rhodopsin由Opsin蛋白和维生素A衍生的发色团组成，可感知光。在视网膜变性的最常见形式中，是由于视觉循环（视视视网想周期）中缺陷而导致的 - 发色团再生所需的酶促途径。直到最近，人们认为苍蝇还没有使用视觉周期，因为发色团通常不会从光活化的视紫红质中释放。但是，某些视紫红质被内在化并降解，从而释放了发色团。在最后一个资金期间，我们发现苍蝇使用视觉周期来再生发色团。 AIM 1中提出的实验旨在区分竞争假设，以解释由于该酶途径中缺陷所产生的视网膜变性的基础。我们还提出了实验，以测试由无脊椎动物周期的新配制模型预测的假设。由于在本质上光敏的视网膜神经节细胞中起作用的哺乳动物蛋白（黑色素）似乎比果蝇果蝇和圆锥体的光成像更类似于果蝇，因此这些研究还表明，视觉循环可能起作用可再生于梅拉诺蛋白所使用的千变万化。尽管某些视紫红质通常是内在化的，但是在多种蝇中发生过多的内在化和降解，这些果蝇的突变过度激活了光转导的级联反应。这似乎是限制过度信号传导的反馈机制。第二个目的是解决了一个新的假设，该假设将解释异三聚体G蛋白的不受控制活性如何导致Rhodopsin的过度营业额。尽管在视网膜中发挥作用的动蛋白是特征最佳的受体蛋白之一，但在过去的几年中，很明显，某些Opsins在视网膜之外表达。但是，他们的视网膜外角色的理解很差。拟议的研究的目标3和4将表征两个在嗅觉系统和中央大脑中神经元中表达的Opsin的作用，并且与光反应无关。我们建议测试这些视紫红蛋白对动物行为的贡献。提出的实验引起了关于哺乳动物外视蛋白的潜在作用（例如OPN3和OPN5）的潜在作用，这些可能性尚未经过遗传分析。为了实现我们的目标，我们建议使用遗传，细胞生物学，电生理，分子和生化技术的组合采用多学科方法。这些研究的长期目标是：1）揭示了视觉周期中缺陷导致的视网膜变性的基础机制，其最终目标是发现新的治疗方法，2）揭示了神秘的视网膜外opsins的作用。公共卫生相关性：视紫红质是对检测光非常重要的受体，影响视紫红质的突变会导致视网膜变性的常见形式。拟议工作的重点是利用果蝇作为动物模型的巨大技术优势，以发现视网膜损伤损伤引起的视网膜变性的机制，并识别在未知在光接收中起作用的细胞中表达的Opsins的作用。