TRP channel expression and function in ON-bipolar cells

ON-双极细胞中 TRP 通道的表达和功能

• 批准号: 8007358
• 负责人: RONALD Lane BROWN
• 金额: $ 44.44万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8007358
• 关键词: Affect; Apical; Biochemical; Blindness; Cations; Cells; Complex; Coupled; Darkness; Data; Defect; Dendrites; Disease; Electrophysiology (science); Electroretinography; Equus caballus; Eye; Eye Movements; Eye diseases; Family; GRM6 gene; Gated Ion Channel; Gene Expression Profiling; Genes; Genetic; Glutamate Receptor; Glutamates; Go Alpha Subunit; Goals; Hyperopia; Immunohistochemistry; In Situ Hybridization; In Vitro; Inherited; Ion Channel; Light; Lighting; Macaca; Measures; Mediating; Metabotropic Glutamate Receptors; Molecular; Molecular Genetics; Mus; Mutation; Myopia; Night Blindness; Pathologic Nystagmus; Pathology; Pathway interactions; Pharmacology; Phenotype; Photoreceptors; Physiological; Physiology; Property; RNA Splicing; Reporting; Research; Rest; Retina; Retinal; Retinal Cone; Retinal Diseases; Reverse Transcriptase Polymerase Chain Reaction; Shapes; Signal Pathway; Signal Transduction; Staging; Symptoms; Synapses; Synaptic Transmission; Testing; Variant; Vision; Visual; Visual Acuity; Visual Pathways; Visual system structure; Work; base; gene function; image processing; in vivo; insight; light intensity; member; mouse model; mutant; null mutation; patch clamp; postsynaptic; public health relevance; receptor; response; retinal rods; visual information; visual process; visual processing

DESCRIPTION (provided by applicant): Congenital stationary night blindness (CSNB) is a group of non-progressive retinal diseases characterized by impaired scotopic vision. Mutations in a number of genes have been shown to be associated with CSNB. They generally affect synaptic transmission between photoreceptors and the second order bipolar cells. When the mutant gene is expressed only in rods, or rod bipolar cells, the phenotype is limited to night blindness. However, when the mutant gene function is also required for synaptic transmission between cones and cone bipolar cells, further visual symptoms are apparent such as myopia, hyperopia, nystagmus, and reduced visual acuity. One such example are mutations in GRM6, the gene encoding mGluR6, which cause an autosomal recessive form of CSNB. In the retina, visual information is segregated into pathways that respond to increases and decreases in light intensity. At the first retinal synapse, the tonic release of glutamate from photoreceptor terminals maintains a high synaptic concentration in darkness that decreases in response to light. Two types of postsynaptic cells, the ON- and OFF-bipolar cells, respond with opposite polarity to glutamate released by photoreceptors, thus establishing the opposing visual pathways. The basis of signaling in OFF-bipolar cells, which relies on the activation of ionotropic glutamate receptors, is well understood. The signaling pathway that generates the light response in ON-bipolar cells, however, is more complex, and the molecular mechanisms remain to be elucidated. The ON-bipolar cell signaling pathway originates with a unique metabotropic glutamate receptor, mGluR6, which is found on the dendrites of ON-bipolar cells. mGluR6 acts via a G-protein, Go, to regulate the activity of an unidentified cation channel such that the light-induced decrease in synaptic glutamate opens the channel and depolarizes the cell. Recently, it has been reported that CSNB in Appaloosa horses is associated with a mutation causing a reduced expression of the TRPM1 cation channel. We hypothesize that TRPM1, and possibly other related TRP channels, are the cation channels coupled to mGluR6 that mediate the depolarizing light response of ON-bipolar cells. We further suggest that mutations in TRP channels will cause CSNB. Using a combination of biochemical, immunohistochemical, and electrophysiological approaches, we will test this hypothesis by answering the following questions: 1. Which TRP channel variants are expressed in ON-bipolar cells? 2. Do mice that carry null mutations in TRP channels expressed in bipolar cells have CSNB? 3. Can the physiological and pharmacological properties of retinal ON bipolar cell responses be reproduced in transfected HEK cells expressing the proper combination of TRP channel variants? The data from this study will contribute to the elucidation of the signaling pathway in the ON-bipolar cell, a fundamental, yet poorly understood, step in visual processing. PUBLIC HEALTH RELEVANCE: Congenital stationary night blindness (CSNB) is an inherited eye disorder causing night blindness, and also often shortsightedness, nystagmus (involuntary eye movement), and reduced visual acuity, even under normal lighting conditions. The proposed research will determine if abnormal ion channel function in the eye can be a cause of CSNB.

描述（由申请人提供）：先天性静止性夜盲症（CSNB）是一组以暗视觉受损为特征的非进行性视网膜疾病。许多基因突变已被证明与 CSNB 相关。它们通常影响光感受器和二阶双极细胞之间的突触传递。当突变基因仅在视杆细胞或视杆细胞双极细胞中表达时，表型仅限于夜盲症。然而，当视锥细胞和视锥双极细胞之间的突触传递也需要突变基因功能时，进一步的视觉症状就会明显，例如近视、远视、眼球震颤和视力下降。其中一个例子是 GRM6（编码 mGluR6 的基因）的突变，它会导致常染色体隐性遗传形式的 CSNB。 在视网膜中，视觉信息被分成对光强度的增加和减少做出反应的通路。在第一个视网膜突触处，光感受器末梢释放的谷氨酸盐在黑暗中维持高突触浓度，但随着光的反应而降低。两种类型的突触后细胞，即开双极细胞和关双极细胞，对光感受器释放的谷氨酸以相反的极性做出反应，从而建立相反的视觉通路。 OFF-双极细胞中的信号传导基础依赖于离子型谷氨酸受体的激活，这是众所周知的。然而，ON-双极细胞中产生光响应的信号通路更为复杂，其分子机制仍有待阐明。 ON-双极细胞信号通路起源于一种独特的代谢型谷氨酸受体 mGluR6，该受体存在于 ON-双极细胞的树突上。 mGluR6 通过 G 蛋白 Go 发挥作用，调节未识别的阳离子通道的活性，从而使光诱导的突触谷氨酸减少打开通道并使细胞去极化。 最近，有报道称阿帕卢萨马的 CSNB 与导致 TRPM1 阳离子通道表达减少的突变有关。我们假设 TRPM1 以及可能其他相关的 TRP 通道是与 mGluR6 偶联的阳离子通道，介导 ON-双极细胞的去偏振光响应。我们进一步认为 TRP 通道的突变会导致 CSNB。我们将结合使用生化、免疫组织化学和电生理学方法，通过回答以下问题来检验这一假设： 1. ON-双极细胞中表达哪些 TRP 通道变体？ 2. 双极细胞中表达的 TRP 通道携带无效突变的小鼠是否患有 CSNB？ 3. 视网膜 ON 双极细胞反应的生理学和药理学特性能否在表达正确的 TRP 通道变体组合的转染 HEK 细胞中重现？这项研究的数据将有助于阐明 ON-双极细胞中的信号传导途径，这是视觉处理中的一个基本但仍知之甚少的步骤。 公共健康相关性：先天性静止性夜盲症 (CSNB) 是一种遗传性眼部疾病，导致夜盲症，并且经常导致近视、眼球震颤（不自主眼球运动）和视力下降，即使在正常照明条件下也是如此。拟议的研究将确定眼睛中离子通道功能异常是否可能是 CSNB 的原因。