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.

形成功能性合胞体的三种类型的肾小球细胞可实现肾脏过滤。其中，足细胞和内皮细胞通过肾小球基底膜分离，最终组成了三层肾小球滤过屏障（GFB），该层层肾上腺滤波器（GFB）被认为赋予尺寸选择性和电荷性特性。肾小球细胞占据GFB之间的空间，以提供结构支撑，并通过收缩减少肾小球表面积来间接参与过滤。肾小球损伤的典型是蛋白质的沉积，该蛋白质是从血浆，下皮下皮和膜膜片的形式形式的。在生理条件下，蛋白质的肾小球沉积是可以忽略的，即使GFB对血浆蛋白的渗透性仅部分，这表明必须存在预防机制。这些机制的损害可能导致病理肾小球蛋白沉积，从而影响肾小球功能。肾小球蛋白稳态的基础是未知的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。在这一提案中，我们假设，通过两个主要降解系统的蛋白质摄取和细胞内降解，即泛素 - 蛋白酶体系统（UPS）和自噬体溶酶体系统（ALS）在肾小球中的互联网中的互联网效果并有助于维持肾小球的完整性。初步研究表明，肾小球和内皮细胞的细胞内和细胞外蛋白稳态主要取决于完整的ALS，而第一线的足细胞取决于UPS。因此，对UPS的抑制会促进上皮下IgG沉积和蛋白尿，而ALS抑制作用导致肾小球IgG沉积。为了剖析UPS和ALS对肾小球细胞的细胞内和细胞外蛋白稳态的未知生理和病理生理的重要性，我们定义了三个目标，这些目标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的差分细胞特异性基础活性。 （2）对肾小球细胞蛋白稳态上临床使用的蛋白酶体抑制剂的后果的比较分析。 （3）对遗传细胞特异性蛋白酶体和溶酶体损伤的后果进行比较分析，用于无挑战的肾小球合胞体和IgG爆炸后。结果将为理解肾小球蛋白沉积的机制提供缺失的基础，以了解蛋白酶体抑制剂的不良药物影响以及涉及UPS和ALS蛋白质的突变的不同肾小球表型。