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Chandler JC, Jafree DJ, Malik S, Pomeranz G, Ball M, Kolatsi-Joannou M, Piapi A, Mason WJ, Benest AV, Bates DO, Letunovska A, Al-Saadi R, Rabant M, Boyer O, Pritchard-Jones K, Winyard PJ, Mason AS, Woolf AS, Waters AM, Long DA. Single-cell transcriptomics identifies aberrant glomerular angiogenic signalling in the early stages of WT1 kidney disease. J Pathol 2024. [PMID: 39177649 DOI: 10.1002/path.6339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 06/17/2024] [Accepted: 06/28/2024] [Indexed: 08/24/2024]
Abstract
WT1 encodes a podocyte transcription factor whose variants can cause an untreatable glomerular disease in early childhood. Although WT1 regulates many podocyte genes, it is poorly understood which of them are initiators in disease and how they subsequently influence other cell-types in the glomerulus. We hypothesised that this could be resolved using single-cell RNA sequencing (scRNA-seq) and ligand-receptor analysis to profile glomerular cell-cell communication during the early stages of disease in mice harbouring an orthologous human mutation in WT1 (Wt1R394W/+). Podocytes were the most dysregulated cell-type in the early stages of Wt1R394W/+ disease, with disrupted angiogenic signalling between podocytes and the endothelium, including the significant downregulation of transcripts for the vascular factors Vegfa and Nrp1. These signalling changes preceded glomerular endothelial cell loss in advancing disease, a feature also observed in biopsy samples from human WT1 glomerulopathies. Addition of conditioned medium from murine Wt1R394W/+ primary podocytes to wild-type glomerular endothelial cells resulted in impaired endothelial looping and reduced vascular complexity. Despite the loss of key angiogenic molecules in Wt1R394W/+ podocytes, the pro-vascular molecule adrenomedullin was upregulated in Wt1R394W/+ podocytes and plasma and its further administration was able to rescue the impaired looping observed when glomerular endothelium was exposed to Wt1R394W/+ podocyte medium. In comparative analyses, adrenomedullin upregulation was part of a common injury signature across multiple murine and human glomerular disease datasets, whilst other gene changes were unique to WT1 disease. Collectively, our study describes a novel role for altered angiogenic signalling in the initiation of WT1 glomerulopathy. We also identify adrenomedullin as a proangiogenic factor, which despite being upregulated in early injury, offers an insufficient protective response due to the wider milieu of dampened vascular signalling that results in endothelial cell loss in later disease. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.
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Affiliation(s)
- Jennifer C Chandler
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
| | - Daniyal J Jafree
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
- UCL MB/PhD Programme, Faculty of Medical Sciences, University College London, London, UK
| | - Saif Malik
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
| | - Gideon Pomeranz
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
| | - Mary Ball
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
| | - Maria Kolatsi-Joannou
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
| | - Alice Piapi
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
| | - William J Mason
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
| | - Andrew V Benest
- Endothelial Quiescence Group and Tumour and Vascular Biology Laboratories, Division of Cancer and Stem Cells, Centre for Cancer Sciences, School of Medicine, Biodiscovery Institute, University of Nottingham, Nottingham, UK
| | - David O Bates
- Endothelial Quiescence Group and Tumour and Vascular Biology Laboratories, Division of Cancer and Stem Cells, Centre for Cancer Sciences, School of Medicine, Biodiscovery Institute, University of Nottingham, Nottingham, UK
- Pan-African Cancer Research Institute, University of Pretoria, Hatfield, South Africa
| | - Aleksandra Letunovska
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- Department of Histopathology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Reem Al-Saadi
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- Department of Histopathology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Marion Rabant
- Pathology department, Hôpital Universitaire Necker-Enfants Malades, Institut Imagine, Université Paris Cité, Paris, France
| | - Olivia Boyer
- APHP, Service de Néphrologie Pédiatrique, Hôpital Universitaire Necker-Enfants Malades, Institut Imagine, Université Paris Cité, Paris, France
| | - Kathy Pritchard-Jones
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
| | - Paul J Winyard
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
| | - Andrew S Mason
- Department of Biology and York Biomedical Research Institute, University of York, UK
| | - Adrian S Woolf
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
- Royal Manchester Children's Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - Aoife M Waters
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
| | - David A Long
- Developmental Biology and Cancer Research and Teaching Department, University College London Great Ormond Street Institute of Child Health, London, UK
- UCL Centre for Kidney and Bladder Health, London, UK
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Increased circulating galectin-1 levels are associated with the progression of kidney function decline in patients undergoing coronary angiography. Sci Rep 2020; 10:1435. [PMID: 31996694 PMCID: PMC6989666 DOI: 10.1038/s41598-020-58132-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 01/05/2020] [Indexed: 12/20/2022] Open
Abstract
Galectin-1 modulates acute and chronic inflammation, and is associated with glucose homeostasis and chronic renal disease. Whether the serum galectin-1 level can predict short-term and long-term renal outcomes after contrast exposure in patients undergoing coronary angiography (CAG) remains uncertain. This study aimed to evaluate the relationship between the serum galectin-1 level and the incidence of contrast-induced nephropathy (CIN), and to investigate the predictive role of the circulating galectin-1 level for renal function decline in patients undergoing CAG. In total, 798 patients who had undergone CAG were enrolled. Baseline creatinine and serum galectin-1 levels were determined before CAG. CIN was defined as an increase in the serum creatinine level of 0.5 mg/dl or a 25% increase from baseline within 48 h after the procedure, and renal function decline was defined as > 30% reduction of the estimated glomerular filtration rate from baseline. All patients were followed for at least 1 year or until the occurrence of death after CAG. Overall, CIN occurred in 41 (5.1%) patients. During a median follow-up period of 1.4 ± 1.1 years, 80 (10.0%) cases showed subsequent renal function decline. After adjustment for demographic characteristics, kidney function, traditional risk factors, and medications, higher galectin-1 levels were found to be associated independently with a greater risk of renal function decline [tertile 2: hazard ratio (HR) 5.56, 95% confidence interval (CI) 1.79-17.22; tertile 3: HR 5.56, 95% CI 1.97-16.32], but not with CIN, regardless of the presence of diabetes. In conclusion, higher baseline serum galectin-1 levels were associated with a greater risk of renal function decline in patients undergoing CAG, but were not associated independently with CIN.
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Carlos CP, Silva AA, Gil CD, Oliani SM. Pharmacological treatment with galectin-1 protects against renal ischaemia-reperfusion injury. Sci Rep 2018; 8:9568. [PMID: 29934646 PMCID: PMC6015078 DOI: 10.1038/s41598-018-27907-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 06/07/2018] [Indexed: 11/21/2022] Open
Abstract
Galectin-1 protein (GAL-1) has important anti-inflammatory properties, but related pharmacologic approaches to effectively treat or prevent renal ischaemia and reperfusion injury are highly limited. Here, we investigated the effect of GAL-1 in a renal ischaemia-reperfusion injury rat model and an in vitro hypoxia-reoxygenation model with a proximal renal tubular epithelial cell line. In vivo, pretreatment with GAL-1 attenuated the renal parameters changed by ischaemia-reperfusion/hypoxia-reoxygenation, with recovery of renal function, protecting against influx of leukocytes, cell death and oxidative stress. Ischaemia-reperfusion/hypoxia-reoxygenation was also associated with increased renal endogenous expression of GAL-1 and intercellular adhesion molecule 1 (ICAM-1) plus augmented levels of proinflammatory cytokines IL-1β, TNF-α and MCP-1 and decreased anti-inflammatory IL-10 in urine, all of which were abrogated by GAL-1 treatment. In vitro studies demonstrated renal tubular epithelial cells as an important source of GAL-1 during hypoxia-reoxygenation and confirmed the protective effects of exogenous GAL-1 through downregulation of proinflammatory cytokine release by proximal renal tubular epithelial cells. Collectively, our findings confirm the important anti-inflammatory role of GAL-1 in kidney ischaemia and reperfusion injury and indicate its promising use as a therapeutic approach.
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Affiliation(s)
- Carla P Carlos
- Department of Biology, Instituto de Biociências, Letras e Ciências Exatas, Sao Paulo State University, UNESP, São José do Rio Preto, SP, Brazil.,Department of Medicine, FACERES School of Medicine, São José do Rio Preto, SP, Brazil
| | - Analice A Silva
- Department of Biology, Instituto de Biociências, Letras e Ciências Exatas, Sao Paulo State University, UNESP, São José do Rio Preto, SP, Brazil
| | - Cristiane D Gil
- Department of Morphology and Genetics, Federal University of Sao Paulo, UNIFESP, São Paulo, SP, Brazil
| | - Sonia M Oliani
- Department of Biology, Instituto de Biociências, Letras e Ciências Exatas, Sao Paulo State University, UNESP, São José do Rio Preto, SP, Brazil. .,Department of Morphology and Genetics, Federal University of Sao Paulo, UNIFESP, São Paulo, SP, Brazil.
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Pathogenesis of proteinuria in idiopathic minimal change disease: molecular mechanisms. Pediatr Nephrol 2016; 31:2179-2189. [PMID: 27384691 DOI: 10.1007/s00467-016-3379-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/07/2016] [Accepted: 03/14/2016] [Indexed: 12/13/2022]
Abstract
Minimal change disease (MCD) is the most common type of nephrotic syndrome in children and adolescents. The pathogenesis of proteinuria in this condition is currently being reassessed. Following the Shalhoub hypothesis, most efforts have been placed on identifying the putative circulating factor, but recent advancement in podocyte biology has focused attention on the molecular changes at the glomerular capillary wall, which could explain the mechanism of proteinuria in MCD. This report critically reviews current knowledge on the different postulated mechanisms at the glomerular capillary wall level for increased permeability to plasma proteins in MCD. The report helps describe the rationale behind novel therapies and suggests future targeted therapies for MCD.
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Liu Y, Long L, Yuan F, Liu F, Liu H, Peng Y, Sun L, Chen G. High glucose-induced Galectin-1 in human podocytes implicates the involvement of Galectin-1 in diabetic nephropathy. Cell Biol Int 2014; 39:217-23. [PMID: 25182410 DOI: 10.1002/cbin.10363] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Accepted: 07/31/2014] [Indexed: 01/06/2023]
Affiliation(s)
- Yinghong Liu
- Department of Nephrology; Second Xiangya Hospital; Central South University; Changsha Hunan P. R. China
- Department of Pathology; University of lowa; Iowa City Iowa USA
| | - Luping Long
- Department of Nephrology; Yiyang Central Hospital; Hunan P. R. China
| | - Fang Yuan
- Department of Nephrology; Second Xiangya Hospital; Central South University; Changsha Hunan P. R. China
| | - Fuyou Liu
- Department of Nephrology; Second Xiangya Hospital; Central South University; Changsha Hunan P. R. China
| | - Hong Liu
- Department of Nephrology; Second Xiangya Hospital; Central South University; Changsha Hunan P. R. China
| | - Youming Peng
- Department of Nephrology; Second Xiangya Hospital; Central South University; Changsha Hunan P. R. China
| | - Lin Sun
- Department of Nephrology; Second Xiangya Hospital; Central South University; Changsha Hunan P. R. China
| | - Guochun Chen
- Department of Nephrology; Second Xiangya Hospital; Central South University; Changsha Hunan P. R. China
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Hovakimyan M, Meyer A, Lukas J, Luo J, Gudziol V, Hummel T, Rolfs A, Wree A, Witt M. Olfactory deficits in Niemann-Pick type C1 (NPC1) disease. PLoS One 2013; 8:e82216. [PMID: 24391715 PMCID: PMC3877006 DOI: 10.1371/journal.pone.0082216] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 10/24/2013] [Indexed: 01/22/2023] Open
Abstract
Background Niemann-Pick type C disease (NPC) is a rare autosomal recessive lipid storage disease characterized by progressive neurodegeneration. As only a few studies have been conducted on the impact of NPC on sensory systems, we used a mutant mouse model (NPC1−/−) to examine the effects of this disorder to morphologically distinct regions of the olfactory system, namely the olfactory epithelium (OE) and olfactory bulb (OB). Methodology/Principal findings For structural and functional analysis immunohistochemistry, electron microscopy, western blotting, and electrophysiology have been applied. For histochemistry and western blotting, we used antibodies against a series of neuronal and glia marker proteins, as well as macrophage markers. NPC1−/− animals present myelin-like lysosomal deposits in virtually all types of cells of the peripheral and central olfactory system. Especially supporting cells of the OE and central glia cells are affected, resulting in pronounced astrocytosis and microgliosis in the OB and other olfactory cortices. Up-regulation of Galectin-3, Cathepsin D and GFAP in the cortical layers of the OB underlines the critical role and location of the OB as a possible entrance gate for noxious substances. Unmyelinated olfactory afferents of the lamina propria seem less affected than ensheathing cells. Supporting the structural findings, electro-olfactometry of the olfactory mucosa suggests that NPC1−/− animals exhibit olfactory and trigeminal deficits. Conclusions/Significance Our data demonstrate a pronounced neurodegeneration and glia activation in the olfactory system of NPC1−/−, which is accompanied by sensory deficits.
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Affiliation(s)
- Marina Hovakimyan
- Institute of Anatomy, Rostock University Medical Center, Rostock, Germany
| | - Anja Meyer
- Institute of Anatomy, Rostock University Medical Center, Rostock, Germany
| | - Jan Lukas
- Albrecht-Kossel Institute for Neuroregeneration, Rostock University Medical Center, Rostock, Germany
| | - Jiankai Luo
- Albrecht-Kossel Institute for Neuroregeneration, Rostock University Medical Center, Rostock, Germany
| | - Volker Gudziol
- Department of Otorhinolaryngology, University of Dresden Medical School, Dresden, Germany
| | - Thomas Hummel
- Department of Otorhinolaryngology, University of Dresden Medical School, Dresden, Germany
| | - Arndt Rolfs
- Albrecht-Kossel Institute for Neuroregeneration, Rostock University Medical Center, Rostock, Germany
| | - Andreas Wree
- Institute of Anatomy, Rostock University Medical Center, Rostock, Germany
| | - Martin Witt
- Institute of Anatomy, Rostock University Medical Center, Rostock, Germany
- * E-mail:
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Carlsson MC, Bakoush O, Tengroth L, Kilsgård O, Malmström J, Hellmark T, Segelmark M, Leffler H. Galectin-8 in IgA nephritis: decreased binding of IgA by galectin-8 affinity chromatography and associated increased binding in non-IgA serum glycoproteins. J Clin Immunol 2011; 32:246-55. [PMID: 22173878 PMCID: PMC3305883 DOI: 10.1007/s10875-011-9618-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 11/11/2011] [Indexed: 12/18/2022]
Abstract
Background Immunoglobulin A nephritis (IgAN) is the most common primary glomerulonephritis worldwide. It is caused by accumulation of IgA1-containing immune complexes in the kidney resulting in renal failure, which is thought to be due to altered glycosylation of IgA with a decrease of 2–3-sialylated galactosides (NeuAcα2-3Gal). Purpose The purpose of this study was to analyze whether altered glycosylation of IgA would lead to an altered binding to galectin-8, an endogenous lectin with strong affinity for 2–3-sialylated galactosides. Galectins are a family of β-galactoside-binding proteins; by binding various glycoproteins, they play important roles in the regulation of cellular functions in inflammation and immunity. Hence, an altered binding of IgA to galectin-8 could lead to pathologic immune functions, such as glomerulonephritis. Methods Affinity chromatography of serum glycoproteins on the human sialogalactoside-binding lectin galectin-8N permitted quantitation of bound and unbound fractions, including IgA. Results Analysis of ∼100 IgA nephritis sera showed that the galectin-8N unbound fraction of IgA increased compared to ∼100 controls, consistent with the known loss of galactosylation. A subgroup of ∼15% of the IgAN patients had a ratio of galectin-8 bound/unbound IgA <0.09, not found for any of the controls. Unexpectedly, the galectin-8N-binding fraction of serum glycoproteins other than IgA increased in the sera of IgAN patients but not in controls, suggesting a previously unrecognized change in this disease. Conclusion This is the first study that relates a galectin, an endogenous lectin family, to IgA nephritis and thus should stimulate new avenues of research into the pathophysiology of the disease. Electronic supplementary material The online version of this article (doi:10.1007/s10875-011-9618-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Michael C. Carlsson
- Section MIG (Microbiology, Immunology, Glycobiology), Department of Laboratory Medicine, Lund University, Sölvegatan 23, 223 62 Lund, Sweden
| | - Omran Bakoush
- Department of Nephrology, Lund University Hospital, Lund, Sweden
| | - Lotta Tengroth
- Section MIG (Microbiology, Immunology, Glycobiology), Department of Laboratory Medicine, Lund University, Sölvegatan 23, 223 62 Lund, Sweden
| | - Ola Kilsgård
- Department of Immunotechnology, Lund University, Lund, Sweden
| | - Johan Malmström
- Department of Immunotechnology, Lund University, Lund, Sweden
| | - Thomas Hellmark
- Department of Nephrology, Lund University Hospital, Lund, Sweden
| | - Mårten Segelmark
- Department of Nephrology, Lund University Hospital, Lund, Sweden
- Department of Medicine and Health, Linköping University, Linköping, Sweden
| | - Hakon Leffler
- Section MIG (Microbiology, Immunology, Glycobiology), Department of Laboratory Medicine, Lund University, Sölvegatan 23, 223 62 Lund, Sweden
- Department of Clinical Immunology and Transfusion Medicine, Skåne University Hospital SUS., Lund, Sweden
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Okano K, Tsuruta Y, Yamashita T, Takano M, Echida Y, Nitta K. Suppression of renal fibrosis by galectin-1 in high glucose-treated renal epithelial cells. Exp Cell Res 2010; 316:3282-91. [PMID: 20828557 DOI: 10.1016/j.yexcr.2010.08.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 08/24/2010] [Accepted: 08/29/2010] [Indexed: 12/27/2022]
Abstract
Diabetic nephropathy is the most common cause of chronic kidney disease. We investigated the ability of intracellular galectin-1 (Gal-1), a prototype of endogenous lectin, to prevent renal fibrosis by regulating cell signaling under a high glucose (HG) condition. We demonstrated that overexpression of Gal-1 reduces type I collagen (COL1) expression and transcription in human renal epithelial cells under HG conditions and transforming growth factor-β1 (TGF-β1) stimulation. Matrix metalloproteinase 1 (MMP1) is stimulated by Gal-1. HG conditions and TGF-β1 treatment augment expression and nuclear translocation of Gal-1. In contrast, targeted inhibition of Gal-1 expression reduces COL1 expression and increases MMP1 expression. The Smad3 signaling pathway is inhibited, whereas two mitogen-activated protein kinase (MAPK) pathways, p38 and extracellular signal-regulated kinase (ERK), are activated by Gal-1, indicating that Gal-1 regulates these signaling pathways in COL1 production. Using specific inhibitors of Smad3, ERK, and p38 MAPK, we showed that ERK MAPK activated by Gal-1 plays an inhibitory role in COL1 transcription and that activation of the p38 MAPK pathway by Gal-1 plays a negative role in MMP1 production. Taken together, two MAPK pathways are stimulated by increasing levels of Gal-1 in the HG condition, leading to suppression of COL1 expression and increase of MMP1 expression.
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Affiliation(s)
- Kazuhiro Okano
- Department of Medicine, Kidney Center, Tokyo Women's Medical University, Tokyo 162-8666, Japan.
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Expression of galectin-3 in nephrotic syndrome glomerulopaties in children. Folia Histochem Cytobiol 2009; 47:315-22. [DOI: 10.2478/v10042-009-0069-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Expression of galectin-1, a new component of slit diaphragm, is altered in minimal change nephrotic syndrome. J Transl Med 2009; 89:178-95. [PMID: 19079321 DOI: 10.1038/labinvest.2008.125] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Nephrin is an essential structural component of the glomerular slit diaphragm (SD), a highly organized intercellular junction that constitutes the ultrafiltration barrier of the kidney. Recent studies have identified two additional nephrin-interacting SD proteins (NEPH1 and NEPH2), suggesting that the zipper-like pattern of the SD is formed through complex intra- and intermolecular interactions of these proteins. However, the complexity of the SD structure suggests that additional SD components remain to be discovered. In this study, we identified galectin-1 (Gal-1) as a new component of the SD, binding to the ectodomain of nephrin. Using dual-immunofluorescence and confocal microscopy and dual-immunoelectron microscopy, we found Gal-1 co-localizing with the ectodomain of nephrin at the SD in normal human kidney. By immunoprecipitation and surface plasmon resonance, we confirmed a direct molecular interaction between Gal-1 and nephrin. Moreover, recombinant Gal-1 induced tyrosine phosphorylation of the cytoplasmic domain of nephrin and activation of the extracellular signal-regulated kinase 1/2 in podocytes. We also showed that podocytes are a major site of biosynthesis of Gal-1 in the glomerulus and that the normal expression patterns and levels of Gal-1 are altered in patients with minimal change nephrotic syndrome. Finally, in puromycin aminonucleoside-induced rat nephrosis, an apparent reduction in the levels of Gal-1 and nephrin around the onset of heavy proteinuria was also revealed. Our data present Gal-1 as a new extracellular ligand of nephrin localized at the glomerular SD, and provide further insight into the complex molecular organization, interaction, and structure of the SD, which is an active site of intracellular signaling necessary for podocyte function.
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