Drosophila nephrocyte proteome

Podocyte injury is a major cause of chronic kidney disease, but the involved signaling pathways are largely unknown. Here, we used ultrasensitive proteomics to investigate the response of the native renal podocyte to injury and prioritized candidates by aligning proteinuria in individual mice with protein expression data. The analysis revealed large perturbations of signaling pathways known to associate with FSGS, but also showed perturbation in metabolism and proteins responding to mechanical stress. We employed Drosophila nephrocytes for further functional analysis of selected candidates and studied filtration function and endocytosis. Among the candidates identified was the mechanosensor protein Filamin-B which is a central component of a conserved cellular response to mechanical stress in podocytes in vitro. Loss of Cher, the orthologue of Filamin-B, led to an increased endocytosis in nephrocytes. Of note, Filamin-B expression was only elevated in the Doxorubicin-induced proteome of podocytes but not after LPS induced injury despite the regulation of multiple similar pathways on the systems level. The Filamin-B amount in glomeruli of proteinuric PAN rats correlated with the amount of albumin . In conclusion, this study identified conserved mechanisms of podocyte stress response employing state of the art ultrasensitive proteomics in isolated mouse podocytes and Drosophila nephrocytes.