P23H rhodopsin aggregation in the ER causes synaptic protein imbalance in rod photoreceptors.

Samantha L Thompson, Sophie M Crowder, Maryam Hekmatara, Emily R Sechrest, Wen-Tao Deng, Michael A Robichaux
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Abstract

Rod photoreceptor neurons in the retina detect scotopic light through the visual pigment rhodopsin (Rho) in their outer segments (OS). Efficient Rho trafficking to the OS through the inner rod compartments is critical for long-term rod health. Given the importance of protein trafficking to the OS, less is known about the trafficking of rod synaptic proteins. Furthermore, the subcellular impact of Rho mislocalization on rod synapses (i.e., "spherules") has not been investigated. In this study we used super-resolution and electron microscopies, along with proteomics, to perform a subcellular analysis of Rho synaptic mislocalization in P23H-Rho-RFP mutant mice. We discovered that mutant P23H-Rho-RFP protein mislocalized in distinct ER aggregations within the spherule cytoplasm, which we confirmed with AAV overexpression. Additionally, we found synaptic protein abundance differences in P23H-Rho-RFP mice. By comparison, Rho mislocalized along the spherule plasma membrane in WT and rd10 mutant rods, in which there was no synaptic protein disruption. Throughout the study, we also identified a network of ER membranes within WT rod presynaptic spherules. Together, our findings indicate that photoreceptor synaptic proteins are sensitive to ER dysregulation.

ER聚集导致视网膜色素变性突变体感光神经元突触蛋白失衡
视网膜上的杆状感光神经元通过将大量视觉色素蛋白罗多司蛋白(Rho)包装到外节(OS)内的叠层膜盘上来检测散射光。由于视网膜色素变性(RP)等疾病会导致 Rho 在这些内部区段(包括视杆细胞突触前终端(即 "球粒"))错位,因此通过视杆细胞内部区段将 Rho 有效地转运到 OS 对于视杆细胞的长期健康至关重要。鉴于蛋白质迁移对操作系统的重要性,人们对维持视杆细胞和视网膜内神经元之间关键突触的视杆细胞突触蛋白的迁移知之甚少。此外,Rho 错定位对杆状球蛋白的亚细胞影响也尚未得到研究。在这项研究中,我们利用超分辨率和电子显微镜以及视杆细胞突触蛋白的蛋白质组学测量,对 P23H-Rho-RFP RP 雌雄突变小鼠的 Rho 突触错定位进行了深入的亚细胞分析。我们发现突变体 P23H-Rho-RFP 蛋白错定位在球状体细胞质内不同的 ER 聚集中,这在过表达 P23H-Rho-RFP 的野生型(WT)杆状病毒中得到了证实。此外,我们还发现在 P23H-Rho-RFP 小鼠中,Dystrophin、BASSOON、ELFN1 和其他突触蛋白的蛋白质丰度存在显著差异。相比之下,在 WT 视杆细胞和 rd10 RP 突变视杆细胞中,Rho 沿球粒质膜错误定位,而在这些视杆细胞中,突触蛋白没有中断。在整个研究过程中,我们还发现了 WT 视杆细胞突触前球粒内的 ER 膜网络。总之,我们的研究结果建立了一个以前未曾描述过的基于ER的分泌系统,该系统介导了小鼠视杆细胞突触的正常贩运和周转:在视网膜中,将蛋白质贩运到杆状感光神经元的外节对视觉至关重要;然而,人们对杆状感光神经元与下游视网膜神经元形成的突触的蛋白质贩运却知之甚少。视网膜色素变性(RP)和其他遗传性视网膜疾病等应激因素会导致视杆细胞中广泛的Rhodopsin(Rho)蛋白错定位,包括突触前终端。本研究探讨了 P23H-Rho RP 突变及其他情况下 Rho 错定位对突触前区域的亚细胞影响。突变型 P23H-Rho-RFP 融合内质网(ER)聚集破坏了杆状突触特异性蛋白质水平,结合检测到的杆状突触前内源性 ER 网络,本研究支持了杆状突触上与疾病相关的基于 ER 的蛋白质贩运和周转机制。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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