Podocytes form the outer part of the glomerular filter, where they have to withstand enormous transcapillary filtration forces driving glomerular filtration. Detachment of podocytes from the glomerular basement membrane precedes most glomerular diseases. However, little is known about the regulation of podocyte adhesion in vivo. Thus, we systematically screened for podocyte-specific focal adhesome (FA) components, using genetic reporter models in combination with iTRAQ-based mass spectrometry. This approach led to the identification of FERM domain protein EPB41L5 as a highly enriched podocyte-specific FA component in vivo. Genetic deletion of Epb41l5 resulted in severe proteinuria, detachment of podocytes, and development of focal segmental glomerulosclerosis. Remarkably, by binding and recruiting the RhoGEF ARGHEF18 to the leading edge, EPB41L5 directly controls actomyosin contractility and subsequent maturation of focal adhesions, cell spreading, and migration. Furthermore, EPB41L5 controls matrixdependent outside-in signaling by regulating the focal adhesome composition. Thus, by linking extracellular matrix sensing and signaling, focal adhesion maturation, and actomyosin activation EPB41L5 ensures the mechanical stability required for podocytes at the kidney filtration barrier. Finally, a diminution of EPB41L5-dependent signaling programs appears to be a common theme of podocyte disease, and therefore offers unexpected interventional therapeutic strategies to prevent podocyte loss and kidney disease progression.
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Early online date||23 May 2017|
|Publication status||Published - 6 Jun 2017|
We thank Charlotte Meyer, Christina Engel, Betina Kiefer, Barbara Joch, Helga Schachner, and Elisabeth Wiesner for expert technical assistance. In addition, we would like to express our gratitude to all members of our laboratories for helpful discussions and support, especially Ketan Patel for carefully reading the manuscript. We would also like to thank Ronald Roepman for generously providing antibodies and serum against EPB41L5. We thank Cristina Has for providing ITGalpha2 antibodies. This study was supported by the German Research Foundation: collaborative research centers (CRC) 1140 (to T.B.H. and F.G.) and CRC 992 (to T.B.H.), Heisenberg program (T.B.H.), HU 1016/5-1 and HU 1016/8-1 (to T.B.H.); by the European Research Council (T.B.H.), and by the H2020-IMI2 consortium Biomarker Enterprise to Attack Diabetic Kidney Disease (BEAt-DKD) (115974 to T.B.H.); by the Bundesministerium für Bildung und Forschung, STOP Fokale Segmentale Glomerulosklerose (BMBF-STOP-FSGS) 01GM1518C (T.B.H.); by the Excellence Initiative of the German Federal and State Governments (GSC-4, Spemann Graduate School, C.S. and T.B.H.; BIOSS, T.B.H.; and the Freiburg Institute for Advanced Studies, T.B.H. and J.D.); by the Else Kröner Fresenius Stiftung, Nierenfunktionsstörungen als Komplikation von Systemerkrankungen (NAKSYS) (C.S., M.R., and T.B.H.) and Molekulare und Translationale Forschung in Freiburg – Verantwortungsvolle Ausbildung Tatkräftige Ermutigung (MOTIVATE) (D.S.); by the German Society of Nephrology (C.S.); and we gratefully acknowledge the financial support from the Ministerium für Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen, the Senatsverwaltung für Wirtschaft, Technologie und Forschung des Landes Berlin, and the Bundesministerium für Bildung und Forschung (to L.K., R.P.Z., and A.S.).
- Focal adhesion