A slit-diaphragm-associated protein network for dynamic control of renal filtration
Maciej K. Kocylowski, Hande Aypek, Wolfgang Bildl, Martin Helmstädter, Philipp Trachte, Bernhard Dumoulin, Sina Wittösch, Lukas Kühne, Ute Aukschun, Carolin Teetzen, Oliver Kretz, Botond Gaál, Ákos Kulik, Corinne Antignac, Géraldine Mollet, Anna Köttgen, Burulça Göçmen, Jochen Schwenk, Uwe Schulte, Tobias B. Huber, Bernd Fakler, Florian Grahammer
Abstract
The filtration of blood in the kidney which is crucial for mammalian life is determined by the slit-diaphragm, a cell-cell junction between the foot processes of renal podocytes. The slit-diaphragm is thought to operate as final barrier or as molecular sensor of renal filtration. Using high-resolution proteomic analysis of slit-diaphragms affinity-isolated from rodent kidney, we show that the native slit-diaphragm is built from the junction-forming components Nephrin, Neph1 and Podocin and a co-assembled high-molecular weight network of proteins. The network constituents cover distinct classes of proteins including signaling-receptors, kinases/phosphatases, transporters and scaffolds. Knockout or knock-down of either the core components or the selected network constituents tyrosine kinase MER (MERTK), atrial natriuretic peptide-receptor C (ANPRC), integral membrane protein 2B (ITM2B), membrane-associated guanylate-kinase, WW and PDZ-domain-containing protein1 (MAGI1) and amyloid protein A4 resulted in target-specific impairment or disruption of the filtration process. Our results identify the slit-diaphragm as a multi-component system that is endowed with context-dependent dynamics via a co-assembled protein network.