The interplay between the UPR and protein biogenesis at the ER

UPR 和 ER 蛋白质生物发生之间的相互作用

基本信息

批准号：
10614583
负责人：
MALAIYALAM MARIAPPAN
金额：
$ 34.51万
依托单位：
YALE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2016
资助国家：
美国
起止时间：
2016-06-01 至 2025-04-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10614583
关键词：
ATP phosphohydrolase Address Antibodies Apoptotic Architecture Attenuated Beta Cell Biochemical Biogenesis CRISPR/Cas technology Carrier Proteins Cell Death Cell Death Induction Cells Cessation of life Chronic Complex Data Defect Degradation Pathway Development Diabetes Mellitus Disease Dominant-Negative Mutation Endoplasmic Reticulum Enzymes Funding Genes Homeostasis Hormones Human Knowledge Lead Life Link Malignant Neoplasms Mediating Membrane Membrane Proteins Messenger RNA Molecular Molecular Chaperones Monitor Mutation Non-Insulin-Dependent Diabetes Mellitus Pathway interactions Phosphorylation Phosphotransferases Physiological Play Protein translocation Proteins Quality Control RNA Splicing Ribonucleases Ribosomes Role Signal Transduction Structure Testing Ubiquitination Work XBP1 gene endoplasmic reticulum stress human disease insight misfolded protein novel polycystic liver disease polypeptide prevent protein folding reconstitution recruit response secretory protein sensor transcription factor

项目摘要

Project Summary/Abstract: Secretory and membrane proteins, which account for ~30% of all human proteins, are co-translationally translocated across or inserted into the endoplasmic reticulum (ER). These nascent polypeptides are folded into functional proteins with the help of chaperones and folding enzymes in the ER. Defects in protein folding lead to the accumulation of misfolded proteins and the triggering of ER stress, which activates the unfolded protein response (UPR). Of the three major UPR sensors, IRE1α is the most conserved ER-localized transmembrane kinase/RNase that is activated through oligomerization/phosphorylation upon ER stress. Once activated, IRE1α mediates the splicing of XBP1u mRNA to produce an active transcription factor, XBP1s, which drives expression of UPR target genes to mitigate ER stress. Also, IRE1α promiscuously cleaves ER- localized mRNAs through the regulated Ire1-dependent decay (RIDD) pathway to reduce the burden of the incoming protein load. Under chronic ER stress conditions, however, IRE1α switches from the pro-survival mode to pro-apoptotic mode, resulting in cell death, which is associated with human diseases including, type 2 diabetes and cancer. Despite the physiological importance, the factors that control activation and inactivation of IRE1α/XBP1 signaling remain unclear. We have recently discovered that IRE1α forms a complex with the Sec61/Sec63 translocon complex to access its mRNA substrates. In the current funding period, we have shown that the Sec61 translocon bridges IRE1α with the Sec63/BiP complex to turnoff IRE1α signaling during persistent ER stress. Our studies discovered that the Sec63/BiP complex is also responsible for freeing clogged Sec61 translocons as well as promoting protein folding in the ER. These new findings raise the hypothesis that the IRE1α/Sec61/Sec63 complex plays a central role in the activation and inactivation of IRE1α/XBP1 signaling to maintain ER homeostasis in cells. In the next funding period, we will test this hypothesis by (i) determining the role of this complex in making life-or-death decisions during ER stress; (ii) determining the architecture of the IRE1α/Sec61/Sec63/BiP complex; (iii) determining the role of this complex in sensing/responding to protein translocation defects in the ER. In an independent aim, we will establish a novel functional link between a cytosolic quality control and IRE1α/XBP1 signaling. We plan to use a combined approach of CRISPR/Cas9 edited cells, biochemical reconstitution, and structural approaches to address these problems. Overall, we expect these studies will provide a mechanistic insight into how the UPR and protein translocation/quality control pathways work together to maintain ER homeostasis. The knowledge gained from these studies will inform the development of possible treatments for several human diseases including diabetes, cancer, and polycystic liver diseases.

项目摘要/摘要：分泌蛋白和膜蛋白约占所有人类蛋白质的 30%，是共翻译的这些新生多肽被折叠穿过或插入内质网 (ER)。在内质网中的分子伴侣和折叠酶的帮助下转化为功能性蛋白质。导致错误折叠蛋白质的积累并触发内质网应激，从而激活未折叠的蛋白质蛋白质反应 (UPR) 在三种主要的 UPR 传感器中，IRE1α 是内质网定位最保守的。跨膜激酶/RNase 在 ER 应激时通过寡聚/磷酸化被激活。 IRE1α 激活后，介导 XBP1u mRNA 的剪接，产生活性转录因子 XBP1s， IRE1α 会驱动 UPR 靶基因的表达来减轻 ER 应激。通过调节 Ire1 依赖性衰变 (RIDD) 途径定位 mRNA，以减轻然而，在慢性 ER 应激条件下，IRE1α 从促生存转变。模式转变为促凋亡模式，导致细胞死亡，这与人类疾病（包括 2 型）相关尽管具有生理重要性，但控制激活和失活的因素。 IRE1α/XBP1 信号传导的机制仍不清楚。我们最近发现IRE1α与Sec61/Sec63易位子复合物形成复合物在当前资助期间，我们已经证明了 Sec61 易位子桥。 IRE1α 与 Sec63/BiP 复合物在持续 ER 应激期间关闭 IRE1α 信号传导。发现 Sec63/BiP 复合体还负责释放堵塞的 Sec61 易位子以及这些新发现提出了 IRE1α/Sec61/Sec63 的假设。复合物在 IRE1α/XBP1 信号传导的激活和失活中发挥核心作用，以维持 ER 在下一个资助期内，我们将通过（i）确定其作用来检验这一假设。在 ER 压力下做出生死攸关的决定很复杂；(ii) 确定结构 IRE1α/Sec61/Sec63/BiP 复合物；(iii) 确定该复合物在感知/响应蛋白质中的作用 ER 中的易位缺陷在一个独立的目标中，我们将在 ER 之间建立一种新颖的功能联系。我们计划使用 CRISPR/Cas9 的组合方法进行胞质质量控制和 IRE1α/XBP1 信号传导。总的来说，我们通过编辑细胞、生化重建和结构方法来解决这些问题。希望这些研究能够提供有关 UPR 和蛋白质易位/质量如何变化的机制见解从这些研究中获得的知识将共同维持内质网稳态。为多种人类疾病的可能治疗方法的开发提供信息，包括糖尿病、癌症和多囊肝病。