Unfolded Protein Response in Eye Development and Disease

项目摘要 未折叠蛋白反应(UPR)指的是细胞内被激活的信号通路 内质网(ER)应激。高效的UPR信号有助于抑制错误折叠引起的疾病 内质网中的蛋白质，例如那些由视网膜色素变性(RP)背后的突变视紫红质引起的蛋白质。 相反，UPR缺陷会导致正常生理状态下的某些细胞类型的功能障碍 急诊室压力。该项目的长期目标是了解普遍定期审议的确切作用和监管机制。 在眼睛发育和视网膜退化方面。目前对UPR的理解主要集中在内质网应激 包括IRE1(肌醇需要1)的传感器蛋白，它通过管腔检测错误折叠的多肽 多肽结合域并启动UPR信号的一个分支。在这个提案中，我们提出了一些实验， 可能会改变我们对UPR及其在眼睛发育和疾病中的作用的基本理解。具体而言，在目标1中， 我们计划挑战IRE1介导的UPR的主要生理作用是对错误折叠做出反应的观点 内质网中的多肽。IRE1是正常果蝇眼睛发育所必需的，但与广泛的 IRE1在检测和响应错误折叠的多肽中所起的作用，我们的初步研究表明 Ire 1的S的发育作用独立于其感知错误折叠的多肽的腔结构域。基于此，我 提出计划测试IRE1的S在眼睛发育中的主要作用不是帮助细胞响应展开 蛋白质，而不是对其他来源的生理压力做出反应。在目标2和目标3中，我们将描述一个 以前无法识别的UPR信令分支。具体地说，我们将测试维甲酸的假设，这是 结合适当折叠的视紫红质作为发色团，在释放时作为信号分子 从错误折叠的视紫红质到介导视紫红质-1特异的UPR信号。维甲酸活性的可能性 到目前为止，调控果蝇的基因表达在很大程度上被忽视了。我们的假设部分是基于 我们出人意料的初步数据表明，维甲酸可以诱导果蝇的基因表达，以及两种这样的诱导 基因HighRoad和Fabp参与降解突变的果蝇视紫红质-1等位基因 他们的本性与人类视紫红质突变体的RP有关。作为这项努力的一部分，我们在目标2中建议 细胞维甲酸结合蛋白的果蝇同源物FABP在细胞内的作用 视黄醇介导的基因表达调控与视网膜变性。在目标3中，我们建议 鉴定果蝇光感受器中介导视黄醇信号转导的转录因子，并测定其 在突变型视紫红质降解和视网膜变性中的作用。这些计划的成功结果将是 极大地改变了我们目前对UPR生理作用的理解，并可能有助于 制定针对眼科疾病的治疗策略。

Project Summary The Unfolded Protein Response (UPR) refers to intracellular signaling pathways that are activated in response to endoplasmic reticulum (ER) stress. Efficient UPR signaling can help suppress diseases caused by misfolded proteins in the ER, such as those caused by mutant rhodopsins that underlie Retinitis Pigmentosa (RP). Conversely, defective UPR can lead to the dysfunction of certain cell types that are normally under physiological ER stress. The long term goal of this project is to understand the precise role and regulatory mechanisms of UPR in eye development and retinal degeneration. The current understanding of the UPR centers around ER stress sensor proteins that include IRE1 (Inositol Requiring 1), which detects misfolded peptides through a luminal peptide binding domain and initiates a branch of UPR signaling. In this proposal, we propose experiments that may change our basic understandings of UPR and its role in eye development and disease. Specifically in Aim 1, we plan to challenge the idea that IRE1-mediated UPR’s primary physiological role is to respond to misfolded peptides in the ER. IRE1 is required for normal Drosophila eye development, but contradicting the widely accepted role of IRE1 in detecting and responding to misfolded peptides, our preliminary studies indicate that IRE1’s developmental role is independent of its luminal domain that senses misfolded peptides. Based on this, I propose plans to test the idea that IRE1’s main role in the developing eye is not to help cells respond to unfolded proteins, but instead, to respond to other sources of physiological stress. In Aims 2 and 3, we will characterize a previously unrecognized UPR signaling branch. Specifically, we will test the hypothesis that retinoids, which are conjugated to properly folded rhodopsins to serve as chromophores, act as signaling molecules when released from misfolded rhodopsins to mediate Rhodopsin-1-specific UPR signaling. The possibility that retinoids actively regulate gene expression in Drosophila has thus far been largely overlooked. Our hypothesis is based in part on our unexpected preliminary data that retinoids can induce gene expression in Drosophila, and two such inducible genes highroad and fabp are involved in degrading mutant Drosophila Rhodopsin-1 alleles that are similar in their nature with human rhodopsin mutants that underlie RP. As part of this effort, we propose in Aim 2 to characterize the role of FABP, a Drosophila homolog of Cellular Retinoic Acid Binding Proteins, in retinoid-mediated gene expression control and retinal degeneration in the RP model. In Aim 3, we propose to identify the transcription factor that mediates retinoid signaling in Drosophila photoreceptors, and determine its role in mutant rhodopsin degradation and retinal degeneration. A successful outcome of these plans will significantly change our current understanding of UPR’s physiological role, and may contribute to the development of therapeutic strategies against diseases of the eye.