Diabetic nephropathy (DN) develops in approximately 30% of diabetic patients, and represents the leading cause of end-stage renal disease worldwide. The factors that induce DN in some but not all diabetics are poorly understood. Identification of novel pathogenic factors that serve as biomarkers for DN is needed. Semaphorin3a (sema3a), a guidance protein secreted by podocytes, is essential for normal glomerular filtration barrier development. Sema3a gain-of-function prevents slit-diaphragm development and leads to proteinuric glomerular disease in adult mice. We identified the signaling pathway that links sema3a signals to nephrin and the podocyte actin cytoskeleton mechanistically. We observed that podocyte sema3a is increased in human advanced DN. Consistently, circulating sema3a and urinary excretion are elevated in diabetic mice, and advanced DN exacerbates this abnormal sema3a excretion. Moreover, Sema3a gain-of- function induced severe DN. Collectively, these findings raise the possibility that elevated sema3a levels drive glomerular damage in the diabetic milieu, or accentuate such damage, making sema3a a suitable DN biomarker and a potential therapeutic target. The goals of this proposal are to investigate whether sema3a is a pathogenic determinant or a biomarker of diabetic nephropathy (or both), and to identify the molecular mechanisms involved, with the ultimate objective of developing a novel approach to treat or prevent DN. We hypothesize that diabetes-induced excess sema3a negatively regulates nephrin signaling and F-actin via a pathway that involves sema3a receptor plexinA1, downstream signaling, thereby disrupting slit-diaphragms, causing foot process effacement and proteinuria.
Aim 1 will investigate whether sema3a is pathogenic in DN using a T1D model in mice with inducible Sema3a gain-of-function or loss-of-function, assess DN phenotype reversibility and whether sema3a inhibition improves DN;to evaluate whether sema3a is a DN biomarker, urine and plasma sema3a levels will be measured in T1D and T2D human cohorts by quantitative enzyme-linked immunoassay.
Aim 2 will examine how the sema3a-plexinA1 pathway regulates podocyte signaling and F-actin dynamics by evaluating sema3a-induced nephrin turnover, plexinA1-MICAL interaction, MICAL requirement, and modulation of RhoA, CRMP and ?3 integrin by sema3a. Results of the proposed experiments have the potential to establish sema3a as a novel biomarker of DN and to identify targets for therapeutic intervention in DN.
Diabetic nephropathy (DN) affects 30% of diabetic patients, representing the leading cause of renal failure worldwide. The factors that cause DN in some but not all diabetics are unclear. We discovered that a protein made by kidney cells called semaphorin3a is increased in human DN biopsies, in kidneys, blood and urine from diabetic mice. The goal of this proposal is to understand if excess semaphorin3a contributes to cause diabetic nephropathy or is a biomarker of DN. We will use genetically engineered mice and blood and urine samples from mice and humans to test this, and potentially identify a novel DN biomarker and therapeutic target in DN.
|Tufro, Alda (2018) Repairing the GBM Step by Step. J Am Soc Nephrol 29:1346-1347|
|Tufro, Alda (2017) Podocyte Shape Regulation by Semaphorin 3A and MICAL-1. Methods Mol Biol 1493:393-399|
|Gee, Heon Yung; Sadowski, Carolin E; Aggarwal, Pardeep K et al. (2016) FAT1 mutations cause a glomerulotubular nephropathy. Nat Commun 7:10822|
|Tufro, Alda (2015) Tubular vascular endothelial growth factor-a, erythropoietin, and medullary vessels: a trio linked by hypoxia. J Am Soc Nephrol 26:997-8|
|Aggarwal, Pardeep K; Veron, Delma; Thomas, David B et al. (2015) Semaphorin3a promotes advanced diabetic nephropathy. Diabetes 64:1743-59|
|Tufro, Alda (2014) Semaphorin3a signaling, podocyte shape, and glomerular disease. Pediatr Nephrol 29:751-5|
|Tufro, Alda (2013) Cholesterol accumulation in podocytes: a potential novel targetable pathway in diabetic nephropathy. Diabetes 62:3661-2|
|Reidy, Kimberly J; Aggarwal, Pardeep K; Jimenez, Juan J et al. (2013) Excess podocyte semaphorin-3A leads to glomerular disease involving plexinA1-nephrin interaction. Am J Pathol 183:1156-1168|
|Tufro, Alda; Veron, Delma (2012) VEGF and podocytes in diabetic nephropathy. Semin Nephrol 32:385-93|