Pathophysiologic Role of ADAM10-mediated Podocyte Membrane Protein Proteolysis

• Applicants: Professorin Dr. Catherine Meyer-Schwesinger; Professor Dr. Paul Saftig
• Subject Area: Nephrology
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 417738345

In the first funding period we identified the membrane-anchored protease A Disintegrin And Metalloproteinase (ADAM) 10 to be expressed at podocyte foot processes and to be dispensable for normal podocyte development. ADAM10 proteolytic activity results in the shedding of numerous membrane-bound substrates and thereby regulates important biological processes such as cell migration and proliferation, neurite, and axon guidance. Some known ADAM10 targets are relevant for podocyte survival, adhesion and signaling, therefore favoring an important role for ADAM10 in podocytes. In line we could demonstrate that podocyte ADAM10 deficiency attenuates the clinical course of anti-podocyte nephritis (immune-complex glomerulonephritis following the injection of sheep anti-podocyte antibodies in C57BL/6 mice.) and preserves the morphological integrity of podocytes despite subepithelial immune deposit formation. Mechanistically, ADAM10-related ectodomain shedding results in cleavage of the cell-cell adhesion proteins N- and P-cadherin, thus decreasing their injury-related surface levels. This favors podocyte loss and the activation of downstream signaling events through the Wnt-signaling pathway in an ADAM10-dependent manner. We hence conclude that ADAM10-mediated ectodomain shedding of injury-related cadherins drives podocyte injury downstream of antibody binding to podocyte antigens. We could additionally establish a significant regulation of ADAM10 at the glomerular filtration barrier of patients with diabetic nephropathy, minimal change disease and membranous nephropathy. Within this proposal prolongation, we want to continue to establish ADAM10 as a master regulator of podocyte foot process membrane protein proteolysis together with AG Saftig, focussing on by us identified new ADAM10 substrates (i.e., among others the membranous nephropathy antigens THSD7A and PLA2R1, -dystroglycan, and the mannose C-type receptor 2 of the same protein family as PLA2R1). Using simple to complex cellular systems, established and unique antigen-specific disease models of membranous nephropathy in transgenic mice with podocyte-specific knockout of ADAM10 and in isolated pig glomeruli, the suggested experiments aim to increase our knowledge on (1) the plethora of podocyte-specific ADAM10 substrates, (2) the podocyte-specific principles of triggering ADAM10-mediated shedding, (3) the functional consequences of ADAM10-mediated podocyte substrate cleavage in (patho)physiology, and on (4) the therapeutic benefit of ADAM10 modulation by drug treatment in nephrotic syndrome. These investigations will clarify that ADAM10 is centrally and differentially involved in the pathogenesis of podocyte injury, suggesting ADAM10 as a novel druggable target.

• DFG Programme: Research Grants