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

• 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
• 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

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）：拟议研究的目标是使用果蝇（Drosophila melanogaster）作为动物模型，以阐明视紫红质生物合成、周转和非经典功能的分子机制。视紫红质由视蛋白和维生素A衍生的发色团组成，其感测光。最常见的视网膜变性形式是由视觉周期（类维生素A周期）缺陷引起的，这是一种生色团再生所需的酶途径。直到最近，人们还认为苍蝇不使用视觉周期，因为发色团通常不会从光敏视紫红质中释放出来。然而，一些视紫红质被内化，视蛋白被降解，从而释放发色团。在上一个资助期间，我们发现苍蝇使用视觉周期来再生释放的生色团。目的1中提出的实验旨在区分竞争性假设，以解释该酶途径缺陷导致的视网膜变性的基础。我们还提出了实验来测试新制定的无脊椎动物周期模型预测的假设。由于在固有光敏视网膜神经节细胞中发挥作用的哺乳动物视蛋白（黑视蛋白）似乎更类似于果蝇视紫红质，而不是视杆细胞和视锥细胞的感光色素，因此这些研究还表明视觉周期可能具有再生黑视蛋白使用的发色团的功能。虽然一些视紫红质是正常的内化，过度内化和降解的视紫红质发生在各种果蝇与突变，过度激活光转导级联。这似乎是一种反馈机制，以限制过度的信号。第二个目标解决了一个新的假设，这将解释如何不受控制的活动的异源三聚体G蛋白导致过度营业额的视紫红质。虽然在视网膜中起作用的视紫红质是最具特征的受体蛋白质之一，但在过去的几年中，已经清楚的是，一些视蛋白在视网膜外表达。然而，其视网膜外的作用知之甚少。拟议研究的目标3和4将描述两种视蛋白的作用，这两种视蛋白在嗅觉系统和中枢脑的神经元中表达，并且与光反应无关。我们建议测试这些视紫红质对动物行为的贡献。拟议的实验提出了关于哺乳动物视网膜外视蛋白（如Opn3和Opn5）潜在作用的有趣可能性，这些视蛋白尚未进行遗传分析。为了实现我们的目标，我们建议采用多学科的方法，使用遗传学，细胞生物学，电生理学，分子和生物化学技术的组合。这些研究的长期目标是1）揭示由视觉周期缺陷导致的视网膜变性的机制，最终目标是发现新的治疗方法，以及2）揭示神秘的视网膜外视蛋白的作用。 公共卫生关系：视紫红质是对检测光至关重要的受体，并且影响视紫红质的突变导致常见形式的视网膜变性。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，以揭示由视紫红质损伤引起的视网膜变性的机制，并确定视蛋白在细胞中表达的作用，这些细胞不知道在光接收中起作用。