Rhodopsin-mediated phospholipid flipping

视紫红质介导的磷脂翻转

• 批准号: 8786659
• 负责人: ANANT K MENON
• 金额: $ 25.43万
• 依托单位: WEILL MEDICAL COLL OF CORNELL UNIV
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8786659
• 关键词: Abbreviations; Affect; Affinity Chromatography; Age related macular degeneration; Binding; Biochemical; Biochemistry; Biological Assay; Cholesterol; Cultured Cells; Defect; Disease; Docosahexaenoic Acids; Elements; Engineering; Environment; Ethanolamines; Eye; Face; G-Protein-Coupled Receptors; Goals; Hereditary Disease; Homeostasis; Inherited; Learning; Lecithin; Light; Link; Lipids; Mediating; Membrane; Membrane Lipids; Molecular; Movement; Mutation; Natural regeneration; Phosphatidylethanolamine; Phospholipids; Photoreceptors; Phototransduction; Polyunsaturated Fatty Acids; Population Heterogeneity; Process; Pump; Retina; Retinal; Retinal Degeneration; Retinal Diseases; Retinal Pigments; Retinitis Pigmentosa; Retinoids; Rhodopsin; Signal Transduction; Stargardt' s disease; Structure; Structure of retinal pigment epithelium; System; Testing; Time; Transducin; Transmembrane Domain; Transmembrane Transport; Vesicle; Vision; Visual system structure; adduct; base; crosslink; disease-causing mutation; fluorophore; interest; lipid transport; metarhodopsin; novel; photoactivation; photoreceptor disc; polyunsaturated fat; public health relevance; reconstitution; research study; retinal rods; trafficking; visual cycle

DESCRIPTION (provided by applicant): Lipid trafficking in the retina is crucial for vision. Retinoids must move rapidly between photoreceptor cells and retinal pigment epithelial cells to regenerate the visual pigment rhodopsin after light impinges on the retina. This trafficking-dependent regeneration process is termed the visual cycle and is essential for continuous vision. Defects in lipid trafficking result in retinopathies; for example, Stargardt's macular dystrophy is caused by the inability to translocate a retinoid-phospholipid adduct across photoreceptor discs. We recently discovered a surprising new player in lipid transport within the retina: our biochemical reconstitution studies revealed that rhodopsin is an ATP-independent phospholipid translocator (flippase) capable of moving phospholipids rapidly across a membrane bilayer. This discovery provides the molecular basis for previous enigmatic observations of phospholipid flip-flop in disc membranes, and assigns a novel activity to rhodopsin in addition to its well-known function in phototransduction. Our goal in this application is to decipher the molecular mechanism by which rhodopsin flips lipids across a membrane bilayer. We propose to identify structural and dynamic features of rhodopsin's transmembrane helical bundle that are necessary for its flippase activity and also determine whether it is regulated by its membrane environment, specifically cholesterol and phospholipids with polyunsaturated acyl chains. We believe that rhodopsin's lipid flippase activity is critical for dic membrane homeostasis as it corrects the phospholipid imbalance caused by ATP-driven lipid transporters, including the Stargardt's disease transporter' ABCA4, that pump phospholipids from the lumen to the cytoplasmic face of discs. Our proposal to elucidate rhodopsin's flipping mechanism is highly significant because it will not only establish a new mechanistic paradigm in membrane transport but is also key to understanding lipid homeostasis in the retina, with implications for retinal degeneration. Mutations in rhodopsin are linked to retinitis pigmentosa, but the underlying disease-causing mechanism for many of the rhodopsin mutations is not known. Our proposed studies have the potential to reveal that some of the unexplained mutations affect flippase activity, thus clarifying aspects of this retinal disease that have remained unresolved for decades. Finally, rhodopsin is a prototypical G protein-coupled receptor (GPCR). As other GPCRs have been shown to have phospholipid flippase activity, our discoveries here will have implications beyond the visual system.

描述（由申请人提供）：视网膜中的脂质运输对于视力至关重要。类维生素A必须在感光细胞和视网膜色素上皮细胞之间快速移动，以便在光线照射到视网膜后再生视觉色素视紫红质。这种依赖于运输的再生过程被称为视觉循环，对于连续视觉至关重要。脂质运输缺陷会导致视网膜病变；例如，斯塔加特黄斑营养不良是由于无法在感光盘上转移类维生素A-磷脂加合物而引起的。我们最近在视网膜内的脂质运输中发现了一个令人惊讶的新参与者：我们的生化重建研究表明，视紫红质是一种不依赖于 ATP 的磷脂转运蛋白（翻转酶），能够快速移动磷脂穿过双层膜。这一发现为之前对椎间盘膜中磷脂触发器的神秘观察提供了分子基础，并且除了众所周知的光转导功能之外，还为视紫红质赋予了新的活性。我们在此应用程序中的目标 的目的是破译视紫红质翻转脂质穿过双层膜的分子机制。我们建议确定视紫红质跨膜螺旋束的结构和动态特征，这些特征对于其翻转酶活性是必需的，并确定它是否受到其膜环境的调节，特别是具有多不饱和酰基链的胆固醇和磷脂。我们认为，视紫红质的脂质翻转酶活性对于椎间盘膜稳态至关重要，因为它可以纠正由 ATP 驱动的脂质转运蛋白引起的磷脂失衡，包括斯塔加特病转运蛋白 ABCA4，后者将磷脂从椎间盘的管腔泵送到细胞质面。我们阐明视紫红质翻转机制的建议非常重要，因为它不仅会在膜运输中建立新的机制范式，而且也是了解视网膜脂质稳态的关键，对视网膜变性具有影响。视紫红质突变与色素性视网膜炎有关，但许多视紫红质突变的潜在致病机制尚不清楚。我们提出的研究有可能揭示一些无法解释的突变影响翻转酶活性，从而澄清这种视网膜疾病几十年来仍未解决的问题。最后，视紫红质是一种典型的 G 蛋白偶联受体 (GPCR)。由于其他 GPCR 已被证明具有磷脂翻转酶活性，因此我们的发现将产生超出视觉系统的影响。