Partitioning of Misfolded Membrane Proteins Between Different Degradatory Fates

错误折叠膜蛋白在不同降解命运之间的分配

• 批准号: 8316691
• 负责人: Scott Andrew Houck
• 金额: $ 2.97万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8316691
• 关键词: Affect; Alzheimer' s Disease; Autophagocytosis; Binding; Biogenesis; Biological; Bovine Spongiform Encephalopathy; Cataract; Cell Culture Techniques; Cell membrane; Cell surface; Cells; Clear Cell; Complex; Cytoplasmic Protein; Cytoplasmic Structures; Cytoplasmic Tail; Cytosol; Data; Defect; Deubiquitinating Enzyme; Disease; Endoplasmic Reticulum; Ensure; Extracellular Domain; Failure; G-Protein-Coupled Receptors; Gonadotropin-Releasing Hormone Receptor; Heat-Shock Proteins 70; Homeostasis; Integral Membrane Protein; Klinefelter' s Syndrome; Knowledge; Lead; Literature; Membrane; Membrane Proteins; Modeling; Molecular Chaperones; Mutation; Nerve Degeneration; Parkinson Disease; Pathway interactions; Peripheral; Polyubiquitin; Proteins; Quality Control; Role; Series; Serine; Signal Transduction; Solutions; Surface; System; Testing; Transmembrane Domain; Ubiquitin; Ubiquitin-Conjugating Enzymes; age related; aqueous; base; disease-causing mutation; extracellular; insight; man; multicatalytic endopeptidase complex; mutant; novel; protein aggregate; protein aggregation; protein folding; protein misfolding; repaired; research study; secretory protein; therapeutic development; trafficking; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): The accumulation of misfolded proteins and protein aggregates can perturb protein homeostasis and cause extensive cellular damage. The cell has various quality control (QC) systems to recognize and dispose of misfolded and aggregated proteins. Failure of these QC systems can result in number of diseases, including the age-related diseases Alzheimer's disease, Parkinson's disease, and cataract. Cellular factors, including molecular chaperones and E3 ubiquitin ligases, recognize misfolded proteins and either attempt to refold the proteins or target them for degradation via the proteasome. Additionally, a poorly defined mechanism for selective quality control of proteins and aggregates via autophagy is known to exist. It is important to define the mechanisms for protein QC so that we may gain insight into the cellular basis of protein misfolding diseases. A number of diseases are caused by mutations to membrane proteins that disrupt their transmembrane domains, causing them to misfold, and be degraded by quality control machinery. Gonadotropin releasing hormone receptor (GnRHR), a G protein-coupled receptor (GPCR), contains no cytoplasmic or extracellular domains and is comprised of only a seven-transmembrane span domain. Therefore, study of GnRHR biogenesis provides an opportunity for understanding basic principles for QC of misfolded TM proteins. In addition, there are twenty-three known disease (hypogonadotropic hypogonadism) causing GnRHR mutations and many cause misfolding. Preliminary data in a cell culture model indicates that quality control pathways for various GnRHR mutants are very different. S168R GnRHR undergoes QC via the RMA1 E3 ubiquitin ligase complex and is degraded by the proteasome. In stark contrast, E90K GnRHR is degraded by autophagy. This represents the first example of a plasma membrane protein being selectively partitioned between autophagic and proteasomal quality control. In Aim 1, I will determine how misfolded S168R GnRHR is recognized and targeted for proteasomal degradation. In Aim 2, I will determine why and how E90K GnRHR is selected for autophagy instead of proteasomal quality control. The results obtained here will greatly further our knowledge of how the cell recognizes defects in transmembrane spans and the mechanisms by which those proteins are degraded. PUBLIC HEALTH RELEVANCE: A large number of diseases, such as Alzheimer's disease, Parkinson's disease, cataract, and mad cow disease are caused by the accumulation of toxic proteins. This project will define the mechanisms used by a cell to clear potentially toxic proteins.

描述（由申请人提供）：错误折叠蛋白质和蛋白质聚集体的积累会扰乱蛋白质稳态并导致广泛的细胞损伤。细胞具有各种质量控制 (QC) 系统来识别和处理错误折叠和聚集的蛋白质。这些质量控制系统的故障会导致多种疾病，包括与年龄相关的疾病，阿尔茨海默病、帕金森病和白内障。细胞因子，包括分子伴侣和 E3 泛素连接酶，可识别错误折叠的蛋白质，并尝试重新折叠蛋白质或通过蛋白酶体将其靶向降解。此外，已知存在一种不明确的通过自噬对蛋白质和聚集体进行选择性质量控制的机制。定义蛋白质 QC 的机制非常重要，这样我们就可以深入了解蛋白质错误折叠疾病的细胞基础。许多疾病是由膜蛋白突变引起的，这些突变破坏了膜蛋白的跨膜结构域，导致它们错误折叠，并被质量控制机制降解。促性腺激素释放激素受体 (GnRHR) 是一种 G 蛋白偶联受体 (GPCR)，不包含细胞质或细胞外结构域，仅由七次跨膜结构域组成。因此，GnRHR 生物发生的研究为理解错误折叠 TM 蛋白的 QC 基本原理提供了机会。此外，还有 23 种已知疾病（低促性腺激素性性腺功能减退症）会导致 GnRHR 突变，其中许多疾病会导致错误折叠。细胞培养模型中的初步数据表明，各种 GnRHR 突变体的质量控制途径非常不同。 S168R GnRHR 通过 RMA1 E3 泛素连接酶复合物进行 QC，并被蛋白酶体降解。与此形成鲜明对比的是，E90K GnRHR 会被自噬降解。这是质膜蛋白在自噬和蛋白酶体质量控制之间选择性分配的第一个例子。在目标 1 中，我将确定错误折叠的 S168R GnRHR 如何被识别并靶向蛋白酶体降解。在目标 2 中，我将确定为什么以及如何选择 E90K GnRHR 进行自噬而不是蛋白酶体质量控制。这里获得的结果将极大地加深我们对细胞如何识别跨膜跨度缺陷以及这些蛋白质降解机制的了解。 公共健康相关性：许多疾病，如阿尔茨海默病、帕金森病、白内障和疯牛病是由有毒蛋白质的积累引起的。该项目将定义细胞清除潜在有毒蛋白质的机制。