SRGAP1 Controls Small Rho GTPases To Regulate Podocyte Foot Process Maintenance

• Published in: Journal of the American Society of Nephrology 2021-03, Vol.32 (3), p.563-579
• Main Authors: Rogg, Manuel, Maier, Jasmin I, Dotzauer, Robert, Artelt, Nadine, Kretz, Oliver, Helmstädter, Martin, Abed, Ahmed, Sammarco, Alena, Sigle, August, Sellung, Dominik, Dinse, Patrick, Reiche, Karoline, Yasuda-Yamahara, Mako, Biniossek, Martin L, Walz, Gerd, Werner, Martin, Endlich, Nicole, Schilling, Oliver, Huber, Tobias B, Schell, Christoph
• Format: Article
• Language: English
• Subjects: Actomyosin - metabolism; Animals; Basic Research; Cell Surface Extensions - metabolism; Cell Surface Extensions - ultrastructure; Cells, Cultured; Disease Models, Animal; Female; Glomerulosclerosis, Focal Segmental - etiology; Glomerulosclerosis, Focal Segmental - metabolism; Glomerulosclerosis, Focal Segmental - pathology; GTPase-Activating Proteins - deficiency; GTPase-Activating Proteins - genetics; GTPase-Activating Proteins - metabolism; Humans; Integrins - metabolism; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Biological; Nephrotic Syndrome - etiology; Nephrotic Syndrome - metabolism; Nephrotic Syndrome - pathology; Podocytes - metabolism; Podocytes - ultrastructure; Protein Interaction Mapping; Proteome; Pseudopodia - metabolism; Pseudopodia - ultrastructure; rho GTP-Binding Proteins - metabolism; Transcriptome
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/asn.2020081126

Previous research demonstrated that small Rho GTPases, modulators of the actin cytoskeleton, are drivers of podocyte foot-process effacement in glomerular diseases, such as FSGS. However, a comprehensive understanding of the regulatory networks of small Rho GTPases in podocytes is lacking. We conducted an analysis of podocyte transcriptome and proteome datasets for Rho GTPases; mapped , podocyte-specific Rho GTPase affinity networks; and examined conditional knockout mice and murine disease models targeting . To evaluate podocyte foot-process morphology, we used super-resolution microscopy and electron microscopy; proximity ligation assays were used to determine the subcellular localization of the small GTPase-activating protein SRGAP1. We performed functional analysis of CRISPR/Cas9-generated knockout podocytes in two-dimensional and three-dimensional cultures and quantitative interaction proteomics. We demonstrated SRGAP1 localization to podocyte foot processes and to cellular protrusions . but not knockout mice developed an FSGS-like phenotype at adulthood. Podocyte-specific deletion of by resulted in increased susceptibility to doxorubicin-induced nephropathy. Detailed analysis demonstrated significant effacement of podocyte foot processes. Furthermore, -knockout podocytes showed excessive protrusion formation and disinhibition of the small Rho GTPase machinery . Evaluation of a SRGAP1-dependent interactome revealed the involvement of SRGAP1 with protrusive and contractile actin networks. Analysis of glomerular biopsy specimens translated these findings toward human disease by displaying a pronounced redistribution of SRGAP1 in FSGS. SRGAP1, a podocyte-specific RhoGAP, controls podocyte foot-process architecture by limiting the activity of protrusive, branched actin networks. Therefore, elucidating the complex regulatory small Rho GTPase affinity network points to novel targets for potentially precise intervention in glomerular diseases.