Excess Podocyte Semaphorin-3A Leads to Glomerular Disease Involving PlexinA 1 –Nephrin Interaction

Abstract

Semaphorin-3A (Sema3a), a guidance protein secreted by podocytes, is essential for normal kidney patterning and glomerular filtration barrier development. Here, we report that podocyte-specific Sema3a gain-of-function in adult mice leads to proteinuric glomerular disease involving the three layers of the glomerular filtration barrier. Reversibility of the glomerular phenotype upon removal of the transgene induction provided proof-of-principle of the cause-and-effect relationship between podocyte Sema3a excess and glomerular disease. Mechanistically, excess Sema3a induces dysregulation of nephrin, matrix metalloproteinase 9, and αvβ3 integrin in vivo. Sema3a cell-autonomously disrupts podocyte shape. We identified a novel direct interaction between the Sema3a signaling receptor plexinA1 and nephrin, linking extracellular Sema3a signals to the slit-diaphragm signaling complex. We conclude that Sema3a functions as an extracellular negative regulator of the structure and function of the glomerular filtration barrier in the adult kidney. Our findings demonstrate a crosstalk between Sema3a and nephrin signaling pathways that is functionally relevant both in vivo and in vitro.

Semaphorins and Plexins in Kidney Disease

“…Sema3A, a soluble, secreted semaphorin (fig. 1), has been found to be expressed in immortalized murine podocytes in vitro as well as in podocytes of adult humans, mice and rats in vivo [5,6,7,8] (table 1). In a mouse model of diabetes, and in diabetic patients, Sema3A expression levels in podocytes are elevated [8,9].…”

“…2a). Systemic administration of exogenous recombinant Sema3A into mice or doxycycline-inducible, podocyte-specific overexpression of Sema3A in transgenic mice induce marked morphological abnormalities in the renal corpuscle including podocyte damage and glomerular endothelial swelling, which are accompanied by proteinuria [6,10]. Consistent with these effects of Sema3A in normal mice, podocyte-specific overexpression of Sema3A in diabetic mice worsens glomerulosclerosis and kidney function [8].…”

“…Interestingly, treatment of diabetic mice with a Sema3A-inhibitory peptide is effective after the onset of proteinuria, suggesting that approaches targeting Sema3A might hold therapeutic potential [9]. Mechanistically, excessive Sema3A impacts on the integrity of the slit diaphragm by interfering with the nephrin-podocin-CD2-associated protein (CD2AP) junctional complex [5,6,10] (fig. 2a).…”

“…It interacts with podocin, a membrane-associated intracellular scaffold, which controls actin dynamics through several proteins, including the multidomain scaffolding protein CD2AP, thereby maintaining podocyte intercellular junctions and podocyte morphology. In mice with podocyte-specific overexpression of Sema3A, or after administration of exogenous Sema3A, nephrin expression is downregulated [6,10]. Moreover, in immortalized murine podocytes and in isolated glomeruli, Sema3A treatment interferes with the interaction between nephrin and podocin as well as between podocin and CD2AP [5].…”

Podocyte-Specific VEGF-A Gain of Function Induces Nodular Glomerulosclerosis in eNOS Null Mice

“…5,6 Quantitation of immunofluorescent signals was performed in 5-10 glomeruli/ mouse, n=5/experimental group using ImageJ software (National Institutes of Health, Bethesda, MD), as previously described. 59 …”