Defining the cellular role of TMCO1, a glaucoma-linked gene of unknown function

 描述(由申请人提供)：该项目的目标是fine TMCO1的细胞作用，这是一种与青光眼相关的基因，编码一种功能未知的完整膜蛋白。200多万美国人受到青光眼的影响，青光眼是一组神经退行性疾病，涉及视神经损伤，原因是视网膜神经节细胞(RGC)的凋亡死亡。尽管青光眼的发病率很高，但在分子水平上对青光眼的发展和进展知之甚少。最近在不同人群中进行的多项全基因组关联研究发现，原发性开角型青光眼(POAG)--最常见的青光眼形式--与一种名为TMCO1的基因周围的单核苷酸多态(SNPs)之间存在关联。有趣的是，其中一些SNP与TMCO1基因表达水平的变化有关。这些变化参与了青光眼的发病机制，这与之前的研究一致，表明TMCO1是一种凋亡调节因子，在包括视网膜节细胞在内的多个眼组织中表达。然而，TMCO1在青光眼中的作用仍不清楚，因为它的细胞和分子功能完全在fiNed下。作为系统发育分析的结果，我们最近发现了TMCO1的一个可能功能。我们发现TMCO1属于一个以前未被认识的远缘关系蛋白超家族，广泛参与膜蛋白的生物发生。此外，我们还获得了功能数据，表明TMCO1定位于内质网(ER)膜，在那里它与核糖体和已知生物合成机制的其他组件相互作用。基于这些初步数据，我们假设TMCO1在生物合成过程中将某些膜蛋白插入内质网。一个吸引人的模型是，依赖于TMCO1的插入缺陷会导致错误折叠、有毒聚集体积累和诱导细胞凋亡，这些都是许多神经退行性疾病的特征。或者，疾病表型可能与一种特定的fic蛋白的生物发生失败有关(S) 这对研资局的正常生存是至关重要的。我们利用定量蛋白质组学、基于细胞的定位研究和体外生物化学，独特地定位于fiNe TMCO1的细胞作用。在目标1中，我们将鉴定其生物发生依赖于TMCO1的人膜蛋白。在目标2中，我们将建立一种体外插入试验，并证明TMCO1是一种博纳fi去插入酶。这是一个高风险的项目，有望带来高影响的回报。通过揭示TMCO1的功能并确定其作用底物，这些研究将提供一个分子框架来了解TMCO1表达的变化是如何与青光眼的发展联系在一起的。更广泛地说，如果我们的假设是正确的，我们将在内质网中发现一个新的膜蛋白插入系统。这些工作将影响我们对膜蛋白生物发生及其在人类疾病中的作用的理解。

 DESCRIPTION (provided by applicant): The goal of this project is to define the cellular role of TMCO1, a glaucoma-linked gene which encodes an integral membrane protein of unknown function. More than two million Americans are affected by glaucoma, a group of neurodegenerative diseases involving optic nerve damage resulting from the apoptotic death of retinal ganglion cells (RGC). Despite its prevalence, little is known about the development and progression of glaucoma on the molecular level. Multiple genome-wide association studies in different populations have recently identified associations between primary open angle glaucoma (POAG)-the most common form of glaucoma-and single nucleotide polymorphisms (SNPs) around a gene called TMCO1. Intriguingly, some of these SNPs are correlated with changes in expression levels of the TMCO1 gene. That such changes contribute to the pathogenesis of glaucoma is consistent with previous studies suggesting that TMCO1 is an apoptosis regulator expressed in multiple eye tissues, including RGCs. However, the role of TMCO1 in glaucoma remains unknown, because its cellular and molecular functions are completely undefined. We recently uncovered a possible function for TMCO1 as a result of a phylogenetic analysis. We found that TMCO1 belongs to a previously unrecognized superfamily of distantly related proteins that are broadly involved in membrane protein biogenesis. Furthermore, we have obtained functional data showing that TMCO1 localizes to the endoplasmic reticulum (ER) membrane where it interacts with ribosomes and other components of the known biosynthetic machinery. Based on these preliminary data, we hypothesize that TMCO1 functions to insert certain membrane proteins into the ER during their biosynthesis. An attractive model is that defects in TMCO1-dependent insertion lead to misfolding, accumulation of toxic aggregates and induction of apoptosis, hallmarks of many neurodegenerative diseases. Alternatively, the disease phenotype might be linked to failed biogenesis of a specific protein(s) that is essential for normal RGC survival. We are uniquely positioned to define the cellular role of TMCO1 using quantitative proteomics, cell-based localization studies and in vitro biochemistry. In Aim 1 we will identify human membrane proteins whose biogenesis is dependent on TMCO1. In Aim 2 we will develop an in vitro insertion assay and demonstrate that TMCO1 is a bona fide insertase. This is a high-risk project that promises high-impact payoff. By defining the function of TMCO1 and identifying substrates on which it acts, these studies will provide a molecular framework to understand how changes in TMCO1 expression are linked to the development of glaucoma. More broadly, if our hypothesis is correct, we will have discovered a new membrane protein insertion system in the endoplasmic reticulum. Such work would impact our understanding of membrane protein biogenesis and its role in human disease.