The Role of TULP1 in Photoreceptor Cells

描述(申请人提供)：视网膜色素变性(RP)合并大量以感光细胞变性为特征的遗传性视网膜疾病。RP在遗传和表型上是不同的，全世界有100多万人受到影响。一种名为TULP1的基因突变是一种早发性和严重的常染色体隐性遗传性RP的基础。Tulp1是一种光感受器细胞独有的蛋白质，尽管Tulp1的功能仍不清楚，但从缺乏Tulp1的小鼠模型中有证据表明，Tulp1在光感受器的多个隔室中的细胞内蛋白质运动中发挥作用。在Tulp1-/-小鼠中，在光感受器退化之前，视杆和视锥视蛋白被错误定位，携带视紫红质的细胞外小泡聚集在内节(IS)周围，表明Tulp1是蛋白质运输到外节(OS)所必需的。这些小鼠也有先于光感受器退化的突触畸形，很可能干扰了受体后神经元的正常发育。Tulp1的缺失会导致影响多个视网膜位置的结构和功能的异常，以及在不同的光感受器隔间引起明显的异常。这表明，它要么在整个感光器中发挥一般作用，要么参与多个不同的途径。根据我们已发表的工作和初步数据，这一提议的中心假设是Tulp1是参与蛋白质在两个感光细胞间的囊泡运动的分子机制的一个组成部分。我们的长期目标是了解TULP1的生理功能以及与TULP1突变相关的视网膜变性的致病机制。在Aim 1中设计的实验将通过蛋白质组学分析来确定Tulp1相互作用的伙伴，比较IS特有的和突触特有的相互作用。在目标2中，将对缺少Tulp1并表达导致RP的TULP1突变形式的IS和突触进行分子解剖，以探测结构或空间干扰。人们的注意力将集中在与Dynamin-1结合的蛋白质上，Dynamin-1是一种神经元特异性蛋白质，对囊泡运输至关重要。我们认为，Tulp1/Dynamin-1/肌动蛋白相互作用是Tulp1功能复合体的核心，阐述Tulp1/Dynamin-1/肌动蛋白的相互作用将揭开Tulp1的作用机制。Aim 3将分析Tulp1-/-光感受器突触中的囊泡循环。这将通过在电子显微镜下进行苯乙烯基染料的光转化来完成。在这项工作成功完成后，我们将在功能上下文中定位Tulp1并定义其作用机制。我们的结果将为深入了解光感受器蛋白运输途径的功能组织以及与TULP1突变相关的视网膜功能扰动提供洞察力。最后，该项目有可能对与人类视网膜疾病相关的光感受器生物学的一个重要方面产生重大影响。 公共卫生相关性：该研究项目的目标是确定Tulp1的功能，Tulp1是一种光感受器特异的蛋白质，被认为参与蛋白质的运动。TULP1的突变会导致早发和严重的视网膜色素变性，这是一种遗传性失明。这些结果将为深入了解导致光感受器退化的病理机制提供帮助，并显著影响与人类视网膜疾病相关的光感受器生物学的一个重要方面。

DESCRIPTION (provided by applicant): Retinitis pigmentosa (RP) incorporates a large number of inherited retinal disorders characterized by photoreceptor degeneration. RP is genetically and phenotypically heterogeneous, affecting over 1 million individuals worldwide. Mutations in a gene called TULP1 underlie an early-onset and severe form of autosomal recessive RP. Tulp1 is a protein exclusive to photoreceptor cells, and although the function of Tulp1 remains elusive, there is evidence from the murine model lacking Tulp1 that it plays a role in intracellular protein movement in multiple compartments of the photoreceptor. In tulp1-/- mice, prior to photoreceptor degeneration, rod and cone opsins are mislocalized, and rhodopsin-bearing extracellular vesicles accumulate around the inner segment (IS), indicating that Tulp1 is necessary for the transport of proteins to the outer segment (OS). These mice also have a synaptic malformation that precedes photoreceptor degeneration and most likely interferes with the proper development of post-receptoral neurons. The absence of Tulp1 results in abnormalities that affect structure and function in multiple retinal sites, as well as causing distinct abnormalities in separate photoreceptor compartments. This suggests that it either performs a general role throughout the photoreceptor or participates in multiple distinct pathways. Based on our published work and preliminary data, the central hypothesis of this proposal is that Tulp1 is a component of the molecular machinery involved in the vesicular movement of proteins in two photoreceptor cell compartments. Our long-term objectives are to understand the physiological function of TULP1 and the pathogenic mechanism responsible for retinal degeneration associated with TULP1 mutations. Experiments designed in Aim 1 will identify Tulp1 interacting partners by proteomic analysis, comparing IS-specific to synaptic-specific interactomes. In Aim 2, molecular dissections of the IS and synapse lacking Tulp1 and expressing mutant forms of TULP1 that cause RP will be conducted to probe for structural or spatial disturbances. Attention will focus on proteins that bind Dynamin-1, a neuronal-specific protein that is essential for vesicular trafficking. Elaborating on the Tulp1/Dynamin-1/Actin interaction, which we believe composes the core of Tulp1 functional complexes, will unlock the mechanism of action of Tulp1. Aim 3 will analyze vesicle cycling in the tulp1-/- photoreceptor synapse. This will be accomplished using styryl dye photoconversion followed by electron microscopy. At the successful completion of this work, we will position Tulp1 in a functional context and define its mechanism of action. Our results will provide insight into the functional organization of photoreceptor protein transport pathways, as well as insight into the perturbation of retinal function associated with TULP1 mutations. Finally, this project has potential for significantly impacting an important aspect of photoreceptor biology relevant to human retinal disease. PUBLIC HEALTH RELEVANCE: The goal of this research project is to identify the function of Tulp1, a photoreceptor-specific protein proposed to be involved in protein movement. Mutations in TULP1 cause an early-onset and severe form of retinitis pigmentosa, an inherited form of blindness. Results will provide insight into the pathological mechanisms causing photoreceptor degeneration and significantly impact an important aspect of photoreceptor biology relevant to human retinal disease.