Project description:Proteinuria is a cardinal feature of glomerular diseases and an important risk factor for tubulo-interstitial damage, progressive decline in kidney function, and cardiovascular complications, but the precise effects of proteinuria on tubules were previously unclear. Here, using an established mouse model of glomerulopathy, single cell sequencing, in vivo imaging and other complementary methods, we investigate in detail the spatiotemporal landscape of genetic responses to increased protein filtration along the nephron. We show that proteinuria is a potent modulator of cell signaling in tubules, and triggers extensive genetic reprogramming in distal segments, with activation of numerous developmental pathways, and a generalized convergence and loss of differentiation markers. Meanwhile, in the proximal tubule - where filtered proteins are normally endocytosed and degraded - we find that encroachment of protein uptake from early (S1) into later (S2) segments causes substantial remodeling of the latter, with dramatic downregulation of canonical processes such as organic anion/uremic toxin secretion and lipid metabolism, and a concomitant increase in reabsorptive markers. Thus, we demonstrate that the tubular effects of proteinuria are extensive, pleotropic and segment specific. Moreover, we identify protein exposure as an important environmental cue that shapes the axial topography of the nephron. Taken together, these findings could explain some well recognized phenomena in humans with chronic kidney disease (CKD).
Project description:Glomerular-tubular crosstalk within the kidney has been proposed, but the paracrine signals enabling this remain largely unknown. The cold-shock protein Y-box binding protein 1 (YBX1) is known to regulate inflammation and kidney diseases but its role in podocytes remains undetermined. Therefore, we analyzed mice with podocyte specific Ybx1 deletion (Ybx1ΔPod). Albuminuria was increased in unchallenged Ybx1ΔPod mice, which surprisingly was associated with reduced glomerular, but enhanced tubular damage. Tubular toll-like receptor 4 (TLR4) expression, node-like receptor protein 3 (NLRP3) inflammasome activation and kidney inflammatory cell infiltrates were all increased in Ybx1ΔPod mice. In vitro, extracellular YBX1 inhibited NLRP3 inflammasome activation in tubular cells. Co-immunoprecipitation, immunohistochemical analyses, microscale cell-free thermophoresis assays, and blunting of the YBX1-mediated TLR4-inhibition by a unique YBX1-derived decapeptide suggests a direct interaction of YBX1 and TLR4. Since YBX1 can be secreted upon post-translational acetylation, we hypothesized that YBX1 secreted from podocytes can inhibit TLR4 signaling in tubular cells. Indeed, mice expressing a non-secreted YBX1 variant specifically in podocytes (Ybx1PodK2A mice) phenocopied Ybx1ΔPod mice, demonstrating a tubular-protective effect of YBX1 secreted from podocytes. Lipopolysaccharide-induced tubular injury was aggravated in Ybx1ΔPod and Ybx1PodK2A mice, indicating a pathophysiological relevance of this glomerular-tubular crosstalk. Thus, our data show that YBX1 is physiologically secreted from podocytes, thereby negatively modulating sterile inflammation in the tubular compartment, apparently by binding to and inhibiting tubular TLR4 signaling. Hence, we have uncovered an YBX1-dependent molecular mechanism of glomerular-tubular crosstalk.
Project description:Multipotent progenitor cells (MPs) have been observed in human kidneys and particularly in Bowman's capsule and proximal tubules. The kidney owns the ability to repair local damage and renal MPs may play a role in the regenerative processes. Microarray technology was applied to identify differentially expressed genes among resident MPs isolated from glomeruli and tubules of normal renal tissue, renal proximal tubular epithelial cells (RPTECs) and mesenchymal stem cells (MSCs). The results of our analysis represent a starting point for further functional studies. Experiment Overall Design: This study includes three renal tissue samples which were processed to obtain 3 glomerular progenitor populations and 3 tubular ones. Three subcoltures of MSCs and RPTECs were included as well. The differences in gene expression patterns of the 4 cell types were found out.
Project description:Genome-wide chromatin accessibility profiling of primary human glomerular and kidney cortex tubular outgrowth cultures For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODE_Data_Use_Policy_for_External_Users_03-07-14.pdf
Project description:Glomerular and tubulointerstitial fractions were enriched from human kidneys samples. Ages of human kidney samples: 15, 29, 37, 61, 67 and 69 years of age. The glomerular and tubulointerstitial samples were processed to enrich for extracellular matrix components and the fractions analysed by mass spectrometry.
Project description:kidney samples: 15, 29, 37, 61, 67 and 69 years of age. The glomerular and tubulointerstitial samples were processed to enrich for extracellular matrix components and the fractions analysed by mass spectrometry.
Project description:Obesity can initiate and accelerate the progression of kidney diseases. However, it remains unclear how obesity affects renal dysfunction. Here, we show that a newly generated podocyte-specific tubular sclerosis complex 2 (Tsc2) knockout mouse model (Tsc2∆podocyte) develops proteinuria and dies due to end-stage renal dysfunction by 10 weeks of age. Tsc2∆podocyte mice exhibit an increased glomerular size and focal segmental glomerulosclerosis, including podocyte foot process effacement, mesangial sclerosis and proteinaceous casts. Podocytes isolated from Tsc2∆podocyte mice show nuclear factor, erythroid derived 2, like 2-mediated increased oxidative stress response on microarray analysis and their autophagic activity is lowered through the mammalian target of rapamycin (mTOR)—unc-51-like kinase 1 pathway. Rapamycin attenuated podocyte dysfunction and extends survival in Tsc2∆podocyte mice. Additionally, mTOR complex 1 (mTORC1) activity is increased in podocytes of renal biopsy specimens obtained from obese patients with chronic kidney disease. Our work shows that mTORC1 hyperactivation in podocytes leads to severe renal dysfunction and that inhibition of mTORC1 activity in podocytes could be a key therapeutic target for obesity-related kidney diseases.
Project description:Evidence for reduced expression of cyclin-G associated kinase (GAK) in glomeruli of chronic kidney disease patients was observed in the Nephroseq human database and was found to be associated with the decline in kidney function. To examine the role of GAK, a protein that functions to uncoat clathrin during endocytosis, we generated podocyte-specific Gak knockout mice (Gak KO) which developed progressive proteinuria and kidney failure with global glomerulosclerosis. We isolated glomeruli from the mutant mice to perform messenger RNA profiling and unearthed evidence for dysregulated podocyte calpain protease activity as an important contributor to this process. Treatment with calpain inhibitor III specifically inhibited calpain-1/-2 activities, mitigated the degree of proteinuria and glomerulosclerosis, and led to a striking increase in survival in the Gak KO mice. Podocyte-specific deletion of Capns1, essential for calpain-1 and calpain-2 activities, also improved proteinuria and glomerulosclerosis in Gak KO mice. Increased podocyte calpain activity mediated proteolysis of IkB resulted in increased NF-kBp65 induced Gadd45b expression in the Gak KO mice. Our results suggest that loss of podocyte associated Gak induces glomerular injury secondary to calcium dysregulation and aberrant calpain activation, which when inhibited, can provide a protective role.