Molecular mechanisms of photoreceptor outer segment morphogenesis

这一建议解决了视觉中最基本的未解决的问题之一：分子和细胞 负责建立和维持脊椎动物感光细胞感光细胞器的机制， 最外层的部分。外段是填充有盘膜堆叠的纤毛结构，该盘膜提供 巨大的表面光捕捉和窝藏蛋白质组成的光转导机制。光盘需要续订 为了抵消光照的不利影响，光盘更新的保真度是至关重要的 用于维持感光器健康和正常视力。以前的研究证实，光感受器盘是 由外节根部质膜连续外翻而成。然而，分子机制 负责执行这些膜转化的人仍然知之甚少。研究策略 本提案中概述的是建立在最近发现的光感受器细胞视盘形成之间的类比基础上 还有许多其他纤毛类型的基本特性--释放纤毛外小泡的能力，称为 胞外体。光感受器纤毛也有一种与生俱来的能力，可以释放大量的胞外体。 然而，在正常的光感受器中，这一过程被光盘特异性蛋白-2抑制，该蛋白 将萌发的膜保留在外部节段的底部，从而使它们能够变形为圆盘。 纤毛外体和感光盘的形成都需要肌动蛋白细胞骨架的作用， 最近的证据表明，胞外体的释放也依赖于ESCRT蛋白复合体。因此，目标是 1将探讨肌动蛋白细胞骨架和ESCRT蛋白之间的类似相互作用是否对 执行光感受器盘形成的第一步骤。目标2将探索通过以下机制 外周蛋白-2使光感受器纤毛的功能状态从释放胞外体变为保留胞外体 在外部节段底部形成薄膜，并将它们转化为圆盘。阐明这些机制是至关重要的。 以增进我们对基本感光细胞生物学和致病生物学机制的了解 光感受器退变常与外节形态发生缺陷有关。

This proposal addresses one of the most fundamental unsolved problems in vision: the molecular and cellular mechanism responsible for building and maintaining the light-sensitive organelle of vertebrate photoreceptor cells, the outer segment. The outer segment is a ciliary structure filled with a stack of disc membranes, which provide vast surfaces for light capture and harbor proteins comprising the phototransduction machinery. Discs are renewed on a daily basis in order to counteract the adverse effects of light exposure, and the fidelity of disc renewal is critical for maintaining photoreceptor health and normal vision. Previous studies established that photoreceptor discs are formed as serial evaginations of the plasma membrane at the outer segment base. Yet, the molecular mechanisms responsible for performing these membrane transformations remain poorly understood. The research strategy outlined in this proposal is built upon the recently uncovered analogy between disc formation in photoreceptor cells and a fundamental property of many other cilia types - the ability to release small extraciliary vesicles, called ectosomes. The photoreceptor cilium also has an innate ability to release massive amounts of ectosomes. However, in normal photoreceptors this process is suppressed by the disc-specific protein, peripherin-2, which retains the budding membranes at the outer segment base, thereby enabling them to be morphed into discs. The formation of both ciliary ectosomes and photoreceptor discs requires the action of the actin cytoskeleton, and recent evidence suggests that ectosome release also relies on the ESCRT protein complex. Therefore, Aim 1 will explore whether a similar interplay between the actin cytoskeleton and ESCRT proteins is responsible for performing the first steps of photoreceptor disc formation. Aim 2 will explore the mechanism by which peripherin-2 transforms the functional state of the photoreceptor cilium from releasing ectosomes to retaining membranes at the outer segment base and transforming them into discs. Elucidating these mechanisms is critical for advancing our understanding of basic photoreceptor cell biology and pathobiological mechanisms underlying photoreceptor degeneration frequently associated with defects in outer segment morphogenesis.