The Role of Muller Cells in Visual Pigment Regeneration

Muller 细胞在视觉色素再生中的作用

• 批准号: 8697054
• 负责人: GABRIEL H TRAVIS
• 金额: $ 49.25万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-03-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8697054
• 关键词: A Mouse; All-Trans-Retinol; Animals; Biochemical; Cations; Cells; Cone; Cultured Cells; Electroretinography; Enzymes; Event; Generations; Human; In Vitro; Insecta; Invertebrates; Isomerase; Knockout Mice; Life; Light; Measurement; Muller' s cell; Mus; N-Myristoylation; Natural regeneration; Opsin; Oxidoreductase; Oxygen; Pathway interactions; Perception; Photons; Photophobia; Photoreceptors; Process; Proteins; Reaction; Recovery; Retina; Retinal Cone; Retinal Detachment; Retinal Pigments; Retinaldehyde; Retinoids; Role; Source; Structure of retinal pigment epithelium; Time; Vertebrates; Visible Radiation; Vision; Visual; Vitamin A; absorption; base; chromophore; desaturase; dihydroceramide desaturase; enzyme pathway; in vivo; light effects; melanopsin; nanodisk; novel; public health relevance; retinal rods; visual cycle

DESCRIPTION (provided by applicant): The first event in light perception is absorption of a photon by an opsin visual pigment in a rod or cone photoreceptor cell. This causes isomerization of the 11-cis-retinaldehyde (11-cis-RAL) chromophore to all-trans-retinaldehyde (all-trans-RAL), which decays to yield apo-opsin and free all-trans-RAL. Light sensitivity is regained by apo-opsin when it recombines with another 11-cis-RAL. Synthesis of 11-cis-RAL is carried out by an enzyme pathway called the Visual Cycle in cells of the retinal pigment epithelium (RPE). Accumulating evidence suggests that cones may have access to another source of visual chromophore in M¿ller cells through a second hypothesized pathway called the Alternate Visual Cycle. This pathway is thought to provide visual chromophore specifically to cones under daylight conditions. We identified the critical isomerase of the Alternate Visual Cycle (isomerase-2) as dihydroceramide desaturase-1 (DES1). The rate of retinol isomerization by DES1 is 300-fold faster than the rate of isomerization catalyzed by Rpe65 of the RPE Visual Cycle. Clinically, the Alternate Visual Cycle, which is located entirely within the retina, may protect photoreceptors from rapid degeneration following retinal detachment, where the retina and RPE become physically separated. This proposal is to characterize the visual-retinoid processing activity of DES1, and to study its role in the Alternate Visual cycle. We recently made the important preliminary observation that the isomerase-2 activity of DES1 is potently stimulated by visible light. This result suggests that under daylight conditions, vertebrates (including humans) capture light energy in their retinas to regenerate visual chromophore. It has been known for some time that insects and other invertebrates regenerate their visual pigments using light energy. The observation that light contributes to chromophore regeneration in animals is unprecedented. Further, this process appears to take place through a novel biochemical mechanism: absorption of a 550-nm photon by a radical-cation of vitamin A inside the DES1 protein. Besides in-depth biochemical characterization of DES1, we will study light-stimulated regeneration of visual chromophore in cultured cells and in live, genetically modified mice.

描述（由申请人提供）：光感知中的第一个事件是杆状或锥状感光细胞中的视蛋白视色素吸收光子。这会导致 11-顺式-视黄醛 (11-cis-RAL) 发色团异构化为全反式-视黄醛 (all-trans-RAL)，其衰变产生脱辅基视蛋白和游离的全反式-RAL。当脱辅基视蛋白与另一个 11-cis-RAL 重组时，它会恢复光敏感性。 11-cis-RAL 的合成是通过视网膜色素上皮 (RPE) 细胞中称为视觉循环的酶途径进行的。越来越多的证据表明，视锥细胞可能通过第二种假设的途径（称为交替视觉循环）获得米勒细胞中视觉发色团的另一种来源。该途径被认为在日光条件下专门为视锥细胞提供视觉发色团。我们将交替视觉循环（异构酶-2）的关键异构酶确定为二氢神经酰胺去饱和酶-1（DES1）。 DES1 引起的视黄醇异构化速率比 RPE Visual Cycle 的 Rpe65 催化的异构化速率快 300 倍。临床上，交替视觉周期完全位于视网膜内，可以保护感光器免受视网膜脱离（视网膜和 RPE 物理分离）后的快速退化。该提案旨在表征 DES1 的视觉类视黄醇处理活动，并研究其在交替视觉循环中的作用。我们最近进行了重要的初步观察，即 DES1 的异构酶 2 活性受到可见光的强烈刺激。这一结果表明，在日光条件下，脊椎动物（包括人类）在视网膜中捕获光能以再生视觉生色团。一段时间以来，人们就知道昆虫和其他无脊椎动物利用光能再生视觉色素。光有助于动物发色团再生的观察是前所未有的。此外，这个过程似乎是通过一种新的生化机制发生的：DES1 蛋白内维生素 A 的自由基阳离子吸收 550 nm 光子。除了深入研究 DES1 的生化特征外，我们还将研究培养细胞和活体转基因小鼠中视觉发色团的光刺激再生。