The Role of Protein Degradation Systems for Glomerular Protein Homeostasis

蛋白质降解系统对肾小球蛋白质稳态的作用

• 批准号: 429327206
• 负责人: Professorin Dr. Catherine Meyer-Schwesinger
• 金额: --
• 依托单位: Institut für Zelluläre und Integrative Physiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/429327206?language=en
• 关键词: Role; Protein; Degradation; Systems; Glomerular

Three types of glomerular cells, which form a functional syncytium, achieve renal filtration. Of these, podocytes and endothelial cells are separated by the glomerular basement membrane and ultimately compose the three-layered glomerular filtration barrier (GFB), which is thought to impart both size-selective and charge-selective properties. Mesangial cells occupy the space inbetween the GFB to provide structural support and to indirectly participate in filtration by reducing the glomerular surface area by contraction. Typical for glomerular injury is the deposition of proteins originating from the plasma in form of subepithelial, subendothelial and mesangial deposits. Under physiologic conditions glomerular deposition of protein is neglectable even though permeability of the GFB to plasma protein is only partial, suggesting that preventive mechanisms must exist. Impairment of these mechanisms could result in pathologic glomerular protein deposition, which in turn would affect glomerular function. The basis of glomerular protein homeostasis is unknown partly due to the complexity of protein degradation systems and due to the complexity of the glomerular syncytium. In this proposal we hypothesize, that protein uptake and intracellular degradation through the two major degradative systems, namely the ubiquitin-proteasomal system (UPS) and the autophagosomal lysosomal system (ALS) interplay in glomerular cells and contribute to maintain the integrity of the glomerular filter in a cell-specific manner. Preliminary investigations demonstrate that intra- and extracellular protein homeostasis of mesangial and endothelial cells predominantly depends on an intact ALS, whereas podocytes in first line depend on the UPS. Thereby, inhibition of the UPS promotes subepithelial IgG deposition and proteinuria whereas ALS inhibition results in mesangial IgG deposition. To dissect the unknown physiologic and pathophysiologic importance of the UPS and ALS for the intra- and extracellular protein homeostasis of glomerular cells we defined three aims which will be addressed with novel techniques of glomerular cell-specific analyses. (1) Define the differential cell-specific basal activity of the UPS and the ALS in glomerular cells. (2) Comparative analyses of the consequence of clinically used proteasomal inhibitors on the protein homeostasis of glomerular cells. (3) Comparative analyses of the consequence of genetic cell-specific proteasomal and lysosomal impairment for the unchallenged glomerular syncytium and after IgG exposition. The results will provide the missing basis for i.e. understanding the mechanisms of glomerular protein deposition, for understanding conflicting data on adverse drug effects of proteasomal inhibitors, and of the different glomerular phenotypes of mutations involving UPS and ALS proteins.

三种类型的肾小球细胞形成功能性合胞体，实现肾滤过。其中，足细胞和内皮细胞被肾小球基底膜分开，最终组成三层肾小球滤过屏障（GFB），这被认为具有尺寸选择性和电荷选择性特性。系膜细胞占据肾小球FB之间的空间，提供结构支撑，并通过收缩减少肾小球表面积来间接参与滤过。肾小球损伤的典型情况是源自血浆的蛋白质以上皮下、内皮下和系膜沉积物的形式沉积。在生理条件下，尽管 GFB 对血浆蛋白的通透性仅为部分，但肾小球的蛋白沉积可以忽略不计，这表明一定存在预防机制。这些机制的损害可能导致病理性肾小球蛋白沉积，进而影响肾小球功能。肾小球蛋白质稳态的基础尚不清楚，部分原因是蛋白质降解系统的复杂性和肾小球合胞体的复杂性。在本提案中，我们假设，通过两个主要降解系统（即泛素蛋白酶体系统（UPS）和自噬体溶酶体系统（ALS））的蛋白质摄取和细胞内降解在肾小球细胞中相互作用，并有助于维持肾小球滤过器的完整性以细胞特异性的方式。初步研究表明，系膜细胞和内皮细胞的细胞内和细胞外蛋白质稳态主要取决于完整的 ALS，而一线足细胞则取决于 UPS。因此，抑制 UPS 会促进上皮下 IgG 沉积和蛋白尿，而抑制 ALS 则会导致系膜 IgG 沉积。为了剖析 UPS 和 ALS 对肾小球细胞胞内和胞外蛋白质稳态的未知生理和病理生理重要性，我们定义了三个目标，这将通过肾小球细胞特异性分析的新技术来解决。 (1) 定义肾小球细胞中 UPS 和 ALS 的差异细胞特异性基础活性。 (2)临床使用的蛋白酶体抑制剂对肾小球细胞蛋白稳态影响的比较分析。 (3) 未受攻击的肾小球合胞体和 IgG 暴露后遗传细胞特异性蛋白酶体和溶酶体损伤后果的比较分析。这些结果将为了解肾小球蛋白沉积机制、了解蛋白酶体抑制剂药物不良反应的相互矛盾的数据以及涉及 UPS 和 ALS 蛋白的突变的不同肾小球表型提供缺失的基础。