Role of the podocyte adhesome in the development of FSGS

无论病因如何，在局灶性节段性肾小球硬化(FSGS)的病理条件下，足细胞表现出一致的细胞形态变化。虽然最早可检测到的变化之一是足细胞足突网络显著回缩和简化，但在后期可观察到足细胞从肾小球基底膜上分离增加，最终导致足细胞进行性丢失。在遗传性足细胞病变的背景下，这些形态学观察和对黏附基因(如ITGA3和CD151)致病突变的鉴定证明了足细胞黏附机制的显著相关性。足细胞的微调黏附是由整合素黏附控制的，整合素黏附是一种与细胞骨架直接相连的多蛋白质复合体。尽管取得了重大进展，但对黏附-细胞骨架关系及其在FSGS发病机制中的作用尚缺乏全面的了解。这项建议的首要目标是描述足细胞粘附性的动态变化的特征，并在FSGS的背景下调查它们的影响。具体地说，我们将解决三个目标：(目标1)通过结合高分辨率蛋白质组学和多维成像方法，我们将描述FSGS不同阶段和模型中粘连签名的变化。(目的2)通过采用新的可诱导小鼠模型，我们将研究黏附的中心IPP复合体如何控制足细胞的机械-物理适应，从而防止足细胞脱离。(目的3)最后，我们将使用一种基于体外和体内模型的互补方法来研究足细胞特异性GTP酶调节剂的作用及其对足细胞粘附性的影响。总之，我们的项目不仅将有助于在FSGS的背景下全面了解足细胞黏附机制的病理性变化，而且还将为最终用于分层的足细胞损伤分级系统的生成提供框架。

Regardless of the underlying etiology, podocytes exhibit a uniform alteration in cellular morphology in pathological conditions of focal segmental glomerulosclerosis (FSGS). While one of the earliest detectable changes is characterized as a prominent retraction and simplification of the podocyte foot process network, increasing detachment of podocytes from the glomerular basement membrane is observed at later stages and finally results in progressive podocyte loss. These morphological observations and the identification of disease-causing mutations in adhesion genes such as ITGA3 and CD151 in the context of hereditary podocytopathies have demonstrated the outstanding relevance of the podocyte adhesion machinery. Fine-tuned adhesion of podocytes is controlled by the integrin adhesome, a multi-protein complex that is directly interconnected with the cytoskeleton. Despite significant progress, a comprehensive understanding of the adhesion-cytoskeletal nexus and its dedicated role in the pathogenesis of FSGS is lacking. The overarching goal of this proposal is to characterize dynamic alterations of the podocyte adhesome and to investigate their impact in the context of FSGS. Specifically, we will address 3 aims: (Aim 1) by combining high-resolution proteomics and multidimensional imaging approaches we will describe alterations in adhesome signatures in different stages and models of FSGS. (Aim 2) By employing novel inducible mouse models we will investigate how the central IPP complex of the adhesome controls mechano-physical adaptation of podocytes and thereby prevents podocyte detachment. (Aim 3) Finally, we will use a complementary approach based on in vitro and in vivo models to investigate the role of podocyte-specific GTPase modulators and their influence on the podocyte adhesome. In summary, our project will not only contribute to a comprehensive understanding of pathogenetic changes in the podocyte adhesion machinery in the context of FSGS but will also provide the framework for the generation of grading systems of podocyte damage which could be eventually used for stratification.