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Patel VN, Ball JR, Choi SH, Lane ED, Wang Z, Aure MH, Villapudua CU, Zheng C, Bleck C, Mohammed H, Syed Z, Liu J, Hoffman MP. Loss of 3-O-sulfotransferase enzymes, Hs3st3a1 and Hs3st3b1, reduces kidney and glomerular size and disrupts glomerular architecture. Matrix Biol 2024:S0945-053X(24)00090-8. [PMID: 38944161 DOI: 10.1016/j.matbio.2024.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Revised: 06/25/2024] [Accepted: 06/26/2024] [Indexed: 07/01/2024]
Abstract
Heparan sulfate (HS) is an important component of the kidney anionic filtration barrier, the glomerular basement membrane (GBM). HS chains attached to proteoglycan protein cores are modified by sulfotransferases in a highly ordered series of biosynthetic steps resulting in immense structural diversity due to negatively charged sulfate modifications. 3-O-sulfation is the least abundant modification generated by a family of seven isoforms but creates the most highly sulfated HS domains. We analyzed the kidney phenotypes in the Hs3st3a1, Hs3st3b1 and Hs3st6 -knockout (KO) mice, the isoforms enriched in kidney podocytes. Individual KO mice show no overt kidney phenotype, although Hs3st3b1 kidneys were smaller than wildtype (WT). Furthermore, Hs3st3a1-/-; Hs3st3b1-/- double knockout (DKO) kidneys were smaller but also had a reduction in glomerular size relative to wildtype (WT). Mass spectrometry analysis of kidney HS showed reduced 3-O-sulfation in Hs3st3a1-/- and Hs3st3b1-/-, but not in Hs3st6-/- kidneys. Glomerular HS showed reduced HS staining and reduced ligand-and-carbohydrate engagement (LACE) assay, a tool that detects changes in binding of growth factor receptor-ligand complexes to HS. Interestingly, DKO mice have increased levels of blood urea nitrogen, although no differences were detected in urinary levels of albumin, creatinine and nephrin. Finally, transmission electron microscopy showed irregular and thickened GBM and podocyte foot process effacement in the DKO compared to WT. Together, our data suggest that loss of 3-O-HS domains disrupts the kidney glomerular architecture without affecting the glomerular filtration barrier and overall kidney function.
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Affiliation(s)
- Vaishali N Patel
- Matrix and Morphogenesis Section, National Institute for Dental and Craniofacial Research, NIH, DHHS, Bethesda, MD, USA.
| | - James R Ball
- Matrix and Morphogenesis Section, National Institute for Dental and Craniofacial Research, NIH, DHHS, Bethesda, MD, USA
| | - Sophie H Choi
- Matrix and Morphogenesis Section, National Institute for Dental and Craniofacial Research, NIH, DHHS, Bethesda, MD, USA
| | - Ethan D Lane
- Matrix and Morphogenesis Section, National Institute for Dental and Craniofacial Research, NIH, DHHS, Bethesda, MD, USA
| | - Zhangjie Wang
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, USA
| | - Marit H Aure
- Matrix and Morphogenesis Section, National Institute for Dental and Craniofacial Research, NIH, DHHS, Bethesda, MD, USA
| | - Carlos U Villapudua
- Matrix and Morphogenesis Section, National Institute for Dental and Craniofacial Research, NIH, DHHS, Bethesda, MD, USA
| | | | - Christopher Bleck
- NHLBI Electron Microscopy Core Facility, National Heart, Lung and Blood Institute, NIH, DHHS, Bethesda, MD, USA
| | - Heba Mohammed
- NHLBI Electron Microscopy Core Facility, National Heart, Lung and Blood Institute, NIH, DHHS, Bethesda, MD, USA
| | - Zulfeqhar Syed
- NHLBI Electron Microscopy Core Facility, National Heart, Lung and Blood Institute, NIH, DHHS, Bethesda, MD, USA
| | - Jian Liu
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, USA
| | - Matthew P Hoffman
- Matrix and Morphogenesis Section, National Institute for Dental and Craniofacial Research, NIH, DHHS, Bethesda, MD, USA
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Xia X, Li S, Wang Z, Ye S, Fan Y, Peng W, Chen W, Huang F, Tang R, Chen W. Glomerular Exostosin-Positivity is Associated With Disease Activity and Outcomes in Patients With Membranous Lupus Nephritis. Kidney Int Rep 2024; 9:1040-1046. [PMID: 38765564 PMCID: PMC11101748 DOI: 10.1016/j.ekir.2024.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 12/11/2023] [Accepted: 01/02/2024] [Indexed: 05/22/2024] Open
Abstract
Introduction The relationship of exostosin 1 and exostosin 2 (EXT1/EXT2) expression and outcomes in membranous lupus nephritis (MLN) was controversial. Methods EXT1/EXT2 was performed by immunohistochemistry (IHC) in 283 consecutive patients with MLN. Clinicopathological characteristics and outcomes of EXT1/EXT2-positive patients were compared with EXT1/EXT2-negative patients. The primary end points were adverse renal events, including death, dialysis, and renal transplantation. Results Of the patients with MLN, 29.3% were positive for EXT1/EXT2. The prevalence of EXT1/2-positive MLN was significantly higher in pure class V MLN than those for mixed class V MLN (44.2% vs. 19.4%, P < 0.001). For EXT1/EXT2-positive patients, the median time between onset of lupus and renal biopsy, and lupus nephritis and renal biopsy is shorter (6 [interquartile range, IQR: 2-25] months vs. 12 [IQR: 3-49] months, P = 0.008 and 3 [IQR: 2-18] months vs. 6 [IQR: 2-23] months, P = 0.039) and they had significantly lower systemic lupus erythematosus Disease Activity Index (SLEDAI) scores (P = 0.015) and lower serum creatinine levels (P < 0.001), higher hemoglobin (P = 0.006) as well as lower blood pressure. The EXT1/EXT2-positive patients had significantly fewer chronicity features (glomerulosclerosis, P < 0.001; interstitial fibrosis, P = 0.006; and tubular atrophy, P = 0.002) and fewer activity indicators (endocapillary hypercellularity, P = 0.012; cellular crescents, P = 0.007; and fibrocellular crescents, P < 0.001) on renal biopsy. After a median follow-up of 65 (28-126) months, EXT1/EXT2-positive patients were less likely to experience adverse renal events (2.4% vs. 16.0%, P = 0.001). Conclusion Compared with EXT1/EXT2-negative patients, the EXT1/EXT2-positive patients presented with lower disease activity and were less likely to experience adverse renal events in relationship with the chronicity index.
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Affiliation(s)
- Xi Xia
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Suchun Li
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Zhipeng Wang
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Siyang Ye
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Yuting Fan
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Wenxing Peng
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Wenfang Chen
- Department of Pathology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
| | - Fengxian Huang
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Ruihan Tang
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
| | - Wei Chen
- Department of Nephrology, The First Affiliated Hospital of Sun Yat-Sen University, People’s Republic of China
- NHC Key Laboratory of Clinical Nephrology (Sun Yat-Sen University) and Guangdong Provincial Key Laboratory of Nephrology, People’s Republic of China
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Heparanase Increases Podocyte Survival and Autophagic Flux after Adriamycin-Induced Injury. Int J Mol Sci 2022; 23:ijms232012691. [PMID: 36293542 PMCID: PMC9604275 DOI: 10.3390/ijms232012691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Revised: 10/06/2022] [Accepted: 10/19/2022] [Indexed: 11/17/2022] Open
Abstract
The kidney glomerular filtration barrier (GFB) is enriched with heparan sulfate (HS) proteoglycans, which contribute to its permselectivity. The endoglycosidase heparanase cleaves HS and hence appears to be involved in the pathogenesis of kidney injury and glomerulonephritis. We have recently reported, nonetheless, that heparanase overexpression preserved glomerular structure and kidney function in an experimental model of Adriamycin-induced nephropathy. To elucidate mechanisms underlying heparanase function in podocytes-key GFB cells, we utilized a human podocyte cell line and transgenic mice overexpressing heparanase. Notably, podocytes overexpressing heparanase (H) demonstrated significantly higher survival rates and viability after exposure to Adriamycin or hydrogen peroxide, compared with mock-infected (V) podocytes. Immunofluorescence staining of kidney cryo-sections and cultured H and V podocytes as well as immunoblotting of proteins extracted from cultured cells, revealed that exposure to toxic injury resulted in a significant increase in autophagic flux in H podocytes, which was reversed by the heparanase inhibitor, Roneparstat (SST0001). Heparanase overexpression was also associated with substantial transcriptional upregulation of autophagy genes BCN1, ATG5, and ATG12, following Adriamycin treatment. Moreover, cleaved caspase-3 was attenuated in H podocytes exposed to Adriamycin, indicating lower apoptotic cell death in H vs. V podocytes. Collectively, these findings suggest that in podocytes, elevated levels of heparanase promote cytoprotection.
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Ramnath RD, Butler MJ, Newman G, Desideri S, Russell A, Lay AC, Neal CR, Qiu Y, Fawaz S, Onions KL, Gamez M, Crompton M, Michie C, Finch N, Coward RJ, Welsh GI, Foster RR, Satchell SC. Blocking matrix metalloproteinase-mediated syndecan-4 shedding restores the endothelial glycocalyx and glomerular filtration barrier function in early diabetic kidney disease. Kidney Int 2020; 97:951-965. [PMID: 32037077 PMCID: PMC7184681 DOI: 10.1016/j.kint.2019.09.035] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 09/06/2019] [Accepted: 09/27/2019] [Indexed: 12/18/2022]
Abstract
The endothelial glycocalyx is a key component of the glomerular filtration barrier. We have shown that matrix metalloproteinase (MMP)-mediated syndecan 4 shedding is a mechanism of glomerular endothelial glycocalyx damage in vitro, resulting in increased albumin permeability. Here we sought to determine whether this mechanism is important in early diabetic kidney disease, by studying streptozotocin-induced type 1 diabetes in DBA2/J mice. Diabetic mice were albuminuric, had increased glomerular albumin permeability and endothelial glycocalyx damage. Syndecan 4 mRNA expression was found to be upregulated in isolated glomeruli and in flow cytometry-sorted glomerular endothelial cells. In contrast, glomerular endothelial luminal surface syndecan 4 and Marasmium oreades agglutinin lectin labelling measurements were reduced in the diabetic mice. Similarly, syndecan 4 protein expression was significantly decreased in isolated glomeruli but increased in plasma and urine, suggesting syndecan 4 shedding. Mmp-2, 9 and 14 mRNA expression were upregulated in isolated glomeruli, suggesting a possible mechanism of glycocalyx damage and albuminuria. We therefore characterised in detail the activity of MMP-2 and 9 and found significant increases in kidney cortex, plasma and urine. Treatment with MMP-2/9 inhibitor I for 21 days, started six weeks after diabetes induction, restored endothelial glycocalyx depth and coverage and attenuated diabetes-induced albuminuria and reduced glomerular albumin permeability. MMP inhibitor treatment significantly attenuated glomerular endothelial and plasma syndecan 4 shedding and inhibited plasma MMP activity. Thus, our studies confirm the importance of MMPs in endothelial glycocalyx damage and albuminuria in early diabetes and demonstrate that this pathway is amenable to therapeutic intervention. Hence, treatments targeted at glycocalyx protection by MMP inhibition may be of benefit in diabetic kidney disease.
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Affiliation(s)
- Raina D Ramnath
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom.
| | - Matthew J Butler
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Georgina Newman
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Sara Desideri
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Amy Russell
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Abigail C Lay
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Chris R Neal
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Yan Qiu
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Sarah Fawaz
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Karen L Onions
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Monica Gamez
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Michael Crompton
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Chris Michie
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Natalie Finch
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Richard J Coward
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Gavin I Welsh
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Rebecca R Foster
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Simon C Satchell
- Bristol Renal, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
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Sethi S, Madden BJ, Debiec H, Charlesworth MC, Gross L, Ravindran A, Hummel AM, Specks U, Fervenza FC, Ronco P. Exostosin 1/Exostosin 2-Associated Membranous Nephropathy. J Am Soc Nephrol 2019; 30:1123-1136. [PMID: 31061139 DOI: 10.1681/asn.2018080852] [Citation(s) in RCA: 178] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 03/24/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND In membranous nephropathy (MN), which is characterized by deposition of immune complexes along the glomerular basement membrane (GBM), phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain-containing 7A are target antigens in approximately 70% and 1%-5% of cases of primary MN, respectively. In other cases of primary MN and in secondary MN, the target antigens are unknown. METHODS We studied 224 cases of biopsy-proven PLA2R-negative MN and 102 controls (including 47 cases of PLA2R-associated MN) in pilot and discovery cohorts. We also evaluated 48 cases of PLA2R-negative presumed primary MN and lupus MN in a validation cohort. We used laser microdissection and mass spectrometry to identify new antigens, which were localized by immunohistochemistry. RESULTS Mass spectrometry detected exostosin 1 (EXT1) and exostosin 2 (EXT2) in 21 cases of PLA2R-negative MN, but not in PLA2R-associated MN and control cases. Immunohistochemistry staining revealed bright granular GBM staining for EXT1 and EXT2. Clinical and biopsy findings showed features of autoimmune disease, including lupus, in 80.7% of the 26 EXT1/EXT2-associated MN cases we identified. In the validation cohort, we confirmed that EXT1/EXT2 staining was detected in pure class 5 lupus nephritis (eight of 18 patients) and in presumed primary MN associated with signs of autoimmunity (three of 16 patients); only one of the 14 cases of mixed class 5 and 3/4 lupus nephritis was positive for EXT1/EXT2. Tests in seven patients with EXT1/EXT2-associated MN found no circulating anti-exostosin antibodies. CONCLUSIONS A subset of MN is associated with accumulation of EXT1 and EXT2 in the GBM. Autoimmune disease is common in this group of patients.
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Affiliation(s)
| | | | - Hanna Debiec
- Sorbonne Université, Université Pierre et Marie Curie Paris 06, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche S1155, Paris, France; and
| | | | | | | | | | - Ulrich Specks
- Divisions of Pulmonary and Critical Care Medicine and
| | | | - Pierre Ronco
- Sorbonne Université, Université Pierre et Marie Curie Paris 06, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche S1155, Paris, France; and.,Department of Nephrology and Dialysis, Assistance Publique-Hôpitaux de Paris, Tenon Hospital, Paris, France
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6
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Glucocorticoid therapy regulates podocyte motility by inhibition of Rac1. Sci Rep 2017; 7:6725. [PMID: 28751734 PMCID: PMC5532274 DOI: 10.1038/s41598-017-06810-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 06/19/2017] [Indexed: 02/03/2023] Open
Abstract
Nephrotic syndrome (NS) occurs when the glomerular filtration barrier becomes excessively permeable leading to massive proteinuria. In childhood NS, immune system dysregulation has been implicated and increasing evidence points to the central role of podocytes in the pathogenesis. Children with NS are typically treated with an empiric course of glucocorticoid (Gc) therapy; a class of steroids that are activating ligands for the glucocorticoid receptor (GR) transcription factor. Although Gc-therapy has been the cornerstone of NS management for decades, the mechanism of action, and target cell, remain poorly understood. We tested the hypothesis that Gc acts directly on the podocyte to produce clinically useful effects without involvement of the immune system. In human podocytes, we demonstrated that the basic GR-signalling mechanism is intact and that Gc induced an increase in podocyte barrier function. Defining the GR-cistrome identified Gc regulation of motility genes. These findings were functionally validated with live-cell imaging. We demonstrated that treatment with Gc reduced the activity of the pro-migratory small GTPase regulator Rac1. Furthermore, Rac1 inhibition had a direct, protective effect on podocyte barrier function. Our studies reveal a new mechanism for Gc action directly on the podocyte, with translational relevance to designing new selective synthetic Gc molecules.
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Fester L, Zhou L, Ossig C, Labitzke J, Bläute C, Bader M, Vollmer G, Jarry H, Rune GM. Synaptopodin is regulated by aromatase activity. J Neurochem 2016; 140:126-139. [PMID: 27861893 DOI: 10.1111/jnc.13889] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 10/17/2016] [Accepted: 10/28/2016] [Indexed: 01/25/2023]
Abstract
Locally synthesized estradiol plays an important role in synaptic plasticity in the hippocampus. We have previously shown that in hippocampal neurons, activity of the enzyme aromatase, which converts testosterone into estradiol, is reduced via Ca2+ -dependent phosphorylation. Synaptopodin is a highly estrogen responsive protein, and it has been shown that it is an important regulator of synaptic plasticity, mediated by its close association with internal calcium stores. In this study, we show that the expression of synaptopodin is stronger in the hippocampus of female animals than in that of male animals. Phosphorylation of aromatase, using letrozole, however, down-regulates synaptopodin immunohistochemistry in the hippocampus of both male and females. Similarly, in aromatase knock-out mice synaptopodin expression in the hippocampus is reduced sex independently. Using primary-dissociated hippocampal neurons, we found that evoked release of Ca2+ from internal stores down-regulates aromatase activity, which is paralleled by reduced expression of synaptopodin. Opposite effects were achieved after inhibition of the release. Calcium-dependent regulation of synaptopodin expression was abolished when the control of aromatase activity by the Ca2+ transients was disrupted. Our data suggest that the regulation of aromatase activity by Ca2+ transients in neurons contributes to synaptic plasticity in the hippocampus of male and female animals as an on-site regulatory mechanism.
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Affiliation(s)
- Lars Fester
- Institute of Neuroanatomy, University Medical Center, Hamburg, Germany
| | - Lepu Zhou
- Institute of Neuroanatomy, University Medical Center, Hamburg, Germany
| | - Christiana Ossig
- Institute of Neuroanatomy, University Medical Center, Hamburg, Germany
| | - Jan Labitzke
- Institute of Neuroanatomy, University Medical Center, Hamburg, Germany
| | - Corinna Bläute
- Institute of Neuroanatomy, University Medical Center, Hamburg, Germany
| | - Manuela Bader
- Department of Biology, Technische Universität Dresden, Dresden, Germany
| | - Günter Vollmer
- Department of Biology, Technische Universität Dresden, Dresden, Germany
| | - Hubertus Jarry
- Department of Experimental Endocrinology, University of Goettingen, Goettingen, Germany
| | - Gabriele M Rune
- Institute of Neuroanatomy, University Medical Center, Hamburg, Germany
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Herman-Edelstein M, Chagnac A, Nevo Z, Skutelsky E, Evron Y, Hirsch Y, Ben-Dor L, Schwartz I, Schwartz D, Weinstein T. Angiotensin converting-enzyme inhibition restores glomerular glycosaminoglycans in rat puromycin nephrosis. ACTA ACUST UNITED AC 2016; 68:543-552. [DOI: 10.1016/j.etp.2016.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Revised: 08/03/2016] [Accepted: 08/22/2016] [Indexed: 11/25/2022]
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Cathepsin L is crucial for the development of early experimental diabetic nephropathy. Kidney Int 2016; 90:1012-1022. [DOI: 10.1016/j.kint.2016.06.035] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 06/22/2016] [Accepted: 06/30/2016] [Indexed: 11/20/2022]
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10
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Borza DB. Glomerular basement membrane heparan sulfate in health and disease: A regulator of local complement activation. Matrix Biol 2016; 57-58:299-310. [PMID: 27609404 DOI: 10.1016/j.matbio.2016.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 08/30/2016] [Accepted: 09/01/2016] [Indexed: 12/26/2022]
Abstract
The glomerular basement membrane (GBM) is an essential component of the glomerular filtration barrier. Heparan sulfate proteoglycans such as agrin are major components of the GBM, along with α345(IV) collagen, laminin-521 and nidogen. A loss of GBM heparan sulfate chains is associated with proteinuria in several glomerular diseases and may contribute to the underlying pathology. As the major determinants of the anionic charge of the GBM, heparan sulfate chains have been thought to impart charge selectivity to the glomerular filtration, a view challenged by the negligible albuminuria in mice that lack heparan sulfate in the GBM. Recent studies provide increasing evidence that heparan sulfate chains modulate local complement activation by recruiting complement regulatory protein factor H, the major inhibitor of the alternative pathway in plasma. Factor H selectively inactivates C3b bound to surfaces bearing host-specific polyanions such as heparan sulfate, thus limiting complement activation on self surfaces such as the GBM, which are not protected by cell-bound complement regulators. We discuss mechanisms whereby the acquired loss of GBM heparan sulfate can impair the local regulation of the alternative pathway, exacerbating complement activation and glomerular injury in immune-mediated kidney diseases such as membranous nephropathy and lupus nephritis.
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Affiliation(s)
- Dorin-Bogdan Borza
- Department of Microbiology and Immunology, Meharry Medical College, 1005 Dr. D. B. Todd, Jr., Blvd., Nashville, TN 37208, USA.
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Marshall CB. Rethinking glomerular basement membrane thickening in diabetic nephropathy: adaptive or pathogenic? Am J Physiol Renal Physiol 2016; 311:F831-F843. [PMID: 27582102 DOI: 10.1152/ajprenal.00313.2016] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/21/2016] [Indexed: 12/12/2022] Open
Abstract
Diabetic nephropathy (DN) is the leading cause of chronic kidney disease in the United States and is a major cause of cardiovascular disease and death. DN develops insidiously over a span of years before clinical manifestations, including microalbuminuria and declining glomerular filtration rate (GFR), are evident. During the clinically silent period, structural lesions develop, including glomerular basement membrane (GBM) thickening, mesangial expansion, and glomerulosclerosis. Once microalbuminuria is clinically apparent, structural lesions are often considerably advanced, and GFR decline may then proceed rapidly toward end-stage kidney disease. Given the current lack of sensitive biomarkers for detecting early DN, a shift in focus toward examining the cellular and molecular basis for the earliest structural change in DN, i.e., GBM thickening, may be warranted. Observed within one to two years following the onset of diabetes, GBM thickening precedes clinically evident albuminuria. In the mature glomerulus, the podocyte is likely key in modifying the GBM, synthesizing and assembling matrix components, both in physiological and pathological states. Podocytes also secrete matrix metalloproteinases, crucial mediators in extracellular matrix turnover. Studies have shown that the critical podocyte-GBM interface is disrupted in the diabetic milieu. Just as healthy podocytes are essential for maintaining the normal GBM structure and function, injured podocytes likely have a fundamental role in upsetting the balance between the GBM's synthetic and degradative pathways. This article will explore the biological significance of GBM thickening in DN by reviewing what is known about the GBM's formation, its maintenance during health, and its disruption in DN.
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Affiliation(s)
- Caroline B Marshall
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and Department of Veterans Affairs Medical Center, Birmingham, Alabama
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Abstract
Genetic studies of hereditary forms of nephrotic syndrome have identified several proteins that are involved in regulating the permselective properties of the glomerular filtration system. Further extensive research has elucidated the complex molecular basis of the glomerular filtration barrier and clearly established the pivotal role of podocytes in the pathophysiology of glomerular diseases. Podocyte architecture is centred on focal adhesions and slit diaphragms - multiprotein signalling hubs that regulate cell morphology and function. A highly interconnected actin cytoskeleton enables podocytes to adapt in order to accommodate environmental changes and maintain an intact glomerular filtration barrier. Actin-based endocytosis has now emerged as a regulator of podocyte integrity, providing an impetus for understanding the precise mechanisms that underlie the steady-state control of focal adhesion and slit diaphragm components. This Review outlines the role of actin dynamics and endocytosis in podocyte biology, and discusses how molecular heterogeneity in glomerular disorders could be exploited to deliver more rational therapeutic interventions, paving the way for targeted medicine in nephrology.
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Kasinath BS. The podocyte and the proteoglycan. Am J Physiol Renal Physiol 2016; 311:F310-1. [PMID: 27226109 DOI: 10.1152/ajprenal.00295.2016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 05/18/2016] [Indexed: 11/22/2022] Open
Affiliation(s)
- Balakuntalam S Kasinath
- University of Texas Health Science Center, South Texas Veterans Health Care System, San Antonio, Texas
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Sugar T, Wassenhove-McCarthy DJ, Orr AW, Green J, van Kuppevelt TH, McCarthy KJ. N-sulfation of heparan sulfate is critical for syndecan-4-mediated podocyte cell-matrix interactions. Am J Physiol Renal Physiol 2016; 310:F1123-35. [PMID: 26936875 PMCID: PMC5002056 DOI: 10.1152/ajprenal.00603.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 02/26/2016] [Indexed: 12/23/2022] Open
Abstract
Previous research has shown that podocytes unable to assemble heparan sulfate on cell surface proteoglycan core proteins have compromised cell-matrix interactions. This report further explores the role of N-sulfation of intact heparan chains in podocyte-matrix interactions. For the purposes of this study, a murine model in which the enzyme N-deacetylase/N-sulfotransferase 1 (NDST1) was specifically deleted in podocytes and immortalized podocyte cell lines lacking NDST1 were developed and used to explore the effects of such a mutation on podocyte behavior in vitro. NDST1 is a bifunctional enzyme, ultimately responsible for N-sulfation of heparan glycosaminoglycans produced by cells. Immunostaining of glomeruli from mice whose podocytes were null for Ndst1 (Ndst1(-/-)) showed a disrupted pattern of localization for the cell surface proteoglycan, syndecan-4, and for α-actinin-4 compared with controls. The pattern of immunostaining for synaptopodin and nephrin did not show as significant alterations. In vitro studies showed that Ndst1(-/-) podocytes attached, spread, and migrated less efficiently than Ndst1(+/+) podocytes. Immunostaining in vitro for several markers for molecules involved in cell-matrix interactions showed that Ndst1(-/-) cells had decreased clustering of syndecan-4 and decreased recruitment of protein kinase-Cα, α-actinin-4, vinculin, and phospho-focal adhesion kinase to focal adhesions. Total intracellular phospho-focal adhesion kinase was decreased in Ndst1(-/-) compared with Ndst1(+/+) cells. A significant decrease in the abundance of activated integrin α5β1 on the cell surface of Ndst1(-/-) cells compared with Ndst1(+/+) cells was observed. These results serve to highlight the critical role of heparan sulfate N-sulfation in facilitating normal podocyte-matrix interactions.
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Affiliation(s)
- Terrel Sugar
- Department of Cell Biology and Anatomy, LSU Health Sciences Center, Shreveport, Louisiana
| | | | - A Wayne Orr
- Department of Pathology, LSU Health Sciences Center, Shreveport, Louisiana; and
| | - Jonette Green
- Department of Pathology, LSU Health Sciences Center, Shreveport, Louisiana; and
| | - Toin H van Kuppevelt
- Department of Biochemistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Kevin J McCarthy
- Department of Cell Biology and Anatomy, LSU Health Sciences Center, Shreveport, Louisiana; Department of Pathology, LSU Health Sciences Center, Shreveport, Louisiana; and
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15
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Ramnath R, Foster RR, Qiu Y, Cope G, Butler MJ, Salmon AH, Mathieson PW, Coward RJ, Welsh GI, Satchell SC. Matrix metalloproteinase 9-mediated shedding of syndecan 4 in response to tumor necrosis factor α: a contributor to endothelial cell glycocalyx dysfunction. FASEB J 2014; 28:4686-99. [PMID: 25122554 DOI: 10.1096/fj.14-252221] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
The endothelial surface glycocalyx is a hydrated mesh in which proteoglycans are prominent. It is damaged in diseases associated with elevated levels of tumor necrosis factor α (TNF-α). We investigated the mechanism of TNF-α-induced disruption of the glomerular endothelial glycocalyx. We used conditionally immortalized human glomerular endothelial cells (GEnCs), quantitative PCR arrays, Western blotting, immunoprecipitation, immunofluorescence, and dot blots to examine the effects of TNF-α. TNF-α induced syndecan 4 (SDC4) mRNA up-regulation by 2.5-fold, whereas cell surface SDC4 and heparan sulfate (HS) were reduced by 36 and 30%, respectively, and SDC4 and sulfated glycosaminoglycan in the culture medium were increased by 52 and 65%, respectively, indicating TNF-α-induced shedding. Small interfering (siRNA) knockdown of SDC4 (by 52%) caused a corresponding loss of cell surface HS of similar magnitude (38%), and immunoprecipitation demonstrated that SDC4 and HS are shed as intact proteoglycan ectodomains. All of the effects of TNF-α on SDC4 and HS were abrogated by the metalloproteinase (MMP) inhibitor batimastat. Also abrogated was the associated 37% increase in albumin passage across GEnC monolayers. Specific MMP9 knockdown by siRNA similarly blocked TNF-α effects. SDC4 is the predominant HS proteoglycan in the GEnC glycocalyx. TNF-α-induced MMP9-mediated shedding of SDC4 is likely to contribute to the endothelial glycocalyx disruption observed in diabetes and inflammatory states.
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Affiliation(s)
- Raina Ramnath
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Rebecca R Foster
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Yan Qiu
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - George Cope
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Matthew J Butler
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Andrew H Salmon
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Peter W Mathieson
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Richard J Coward
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Gavin I Welsh
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Simon C Satchell
- Academic Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
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16
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Škoberne A, Behnert A, Teng B, Fritzler MJ, Schiffer L, Pajek J, Lindič J, Haller H, Schiffer M. Serum with phospholipase A2 receptor autoantibodies interferes with podocyte adhesion to collagen. Eur J Clin Invest 2014; 44:753-65. [PMID: 24942189 DOI: 10.1111/eci.12292] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 06/12/2014] [Indexed: 12/16/2022]
Abstract
BACKGROUND The majority of sera from patients with primary membranous nephropathy have autoantibodies against the M-type phospholipase A2 receptor (PLA2R) which is expressed on human podocytes. The rabbit variant of PLA2R attaches to collagen type IV via the fibronectin type II domain, which is also present in the human variant of PLA2R. DESIGN To assess whether the human PLA2R variant is also involved in attachment to collagen type IV, we conducted a cell adhesion assay on a collagen-coated surface using PLA2R-transfected and mock-transfected human embryonic kidney (HEK) cells. To test the hypothesis that sera from patients containing anti-PLA2R antibodies interfere with the adhesion of podocytes to collagen, we performed cell adhesion assays on a collagen type IV-coated surface using positive and negative serum samples from patients and cultured human podocytes in vitro expressing PLA2R. RESULTS The HEK cell adhesion assay confirmed an enhanced attachment of PLA2R-transfected cells to collagen type IV. We confirmed diminished podocyte adhesion in the presence of serum with anti-PLA2R antibodies. The concentration of anti-PLA2R antibodies correlated with proteinuria and to the degree of diminished adhesion of podocytes. CONCLUSIONS We demonstrated that serum of patients containing autoantibodies directed to PLA2R interferes with the ability of podocytes to attach to collagen type IV in vitro, providing evidence of a serum soluble pathogenic factor interfering with podocyte adhesion in membranous nephropathy.
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Affiliation(s)
- Andrej Škoberne
- Division of Nephrology, Hannover Medical School, Hannover, Germany; Department of Nephrology, University Medical Centre Ljubljana, Ljubljana, Slovenia
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17
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Thilo F, Lee M, Xia S, Zakrzewicz A, Tepel M. High glucose modifies transient receptor potential canonical type 6 channels via increased oxidative stress and syndecan-4 in human podocytes. Biochem Biophys Res Commun 2014; 450:312-7. [DOI: 10.1016/j.bbrc.2014.05.116] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 05/24/2014] [Indexed: 12/31/2022]
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Lennon R, Randles MJ, Humphries MJ. The importance of podocyte adhesion for a healthy glomerulus. Front Endocrinol (Lausanne) 2014; 5:160. [PMID: 25352829 PMCID: PMC4196579 DOI: 10.3389/fendo.2014.00160] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 09/21/2014] [Indexed: 12/23/2022] Open
Abstract
Podocytes are specialized epithelial cells that cover the outer surfaces of glomerular capillaries. Unique cell junctions, known as slit diaphragms, which feature nephrin and Neph family proteins in addition to components of adherens, tight, and gap junctions, connect adjacent podocyte foot processes. Single gene disorders affecting the slit diaphragm result in nephrotic syndrome in humans, characterized by massive loss of protein across the capillary wall. In addition to specialized cell junctions, interconnecting podocytes also adhere to the glomerular basement membrane (GBM) of the capillary wall. The GBM is a dense network of secreted, extracellular matrix (ECM) components and contains tissue-restricted isoforms of collagen IV and laminin in addition to other structural proteins and ECM regulators such as proteases and growth factors. The specialized niche of the GBM provides a scaffold for endothelial cells and podocytes to support their unique functions and human genetic mutations in GBM components lead to renal failure, thus highlighting the importance of cell-matrix interactions in the glomerulus. Cells adhere to ECM via adhesion receptors, including integrins, syndecans, and dystroglycan and in particular the integrin heterodimer α3β1 is required to maintain barrier integrity. Therefore, the sophisticated function of glomerular filtration relies on podocyte adhesion both at cell junctions and at the interface with the ECM. In health, the podocyte coordinates signals from cell junctions and cell-matrix interactions, in response to environmental cues in order to regulate filtration and as our understanding of mechanisms that control cell adhesion in the glomerulus develops, then insight into the effects of disease will improve. The ultimate goal will be to develop targeted therapies to prevent or repair defects in the filtration barrier and to restore glomerular function.
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Affiliation(s)
- Rachel Lennon
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
- Institute of Human Development, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, UK
- Department of Paediatric Nephrology, Manchester Academic Health Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
- *Correspondence: Rachel Lennon, Wellcome Trust Centre for Cell-Matrix Research, The University of Manchester, Michael Smith Building, Manchester M13 9PT, UK e-mail:
| | - Michael J. Randles
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
- Institute of Human Development, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, UK
| | - Martin J. Humphries
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
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Sugar T, Wassenhove-McCarthy DJ, Esko JD, van Kuppevelt TH, Holzman L, McCarthy KJ. Podocyte-specific deletion of NDST1, a key enzyme in the sulfation of heparan sulfate glycosaminoglycans, leads to abnormalities in podocyte organization in vivo. Kidney Int 2013; 85:307-18. [PMID: 23924956 PMCID: PMC4624314 DOI: 10.1038/ki.2013.281] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Revised: 05/03/2013] [Accepted: 05/23/2013] [Indexed: 01/18/2023]
Abstract
Heparan sulfate proteoglycans have been shown to modulate podocyte adhesion to- and pedicel organization on- the glomerular basement membrane. Recent studies showed that foot process effacement developed in a mutant mouse model whose podocytes were unable to assemble heparan sulfate glycosaminoglycan chains. This study, a further refinement, explored the role of heparan N-sulfation on podocyte behavior. A novel mutant mouse (Ndst1-/-) was developed, having podocyte-specific deletion of NDST1, the enzyme responsible for N-sulfation of heparan sulfate chains. Podocytes having this mutation had foot process effacement and abnormal adhesion to Bowman's capsule. Although glomerular hypertrophy did develop in the kidneys of mutant animals, mesangial expansion was not seen. The lack of heparan N-sulfation did not affect the expression of agrin or perlecan proteoglycan core proteins. Loss of N-sulfation did not result in significant proteinuria, but the increase in the albumin/creatinine ratio was coincident with the development of the enlarged lysosomes in the proximal tubules. Thus, although the renal phenotype of the Ndst1-/- mouse is mild, the data show that heparan chain N-sulfation plays a key role in podocyte organization.
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Affiliation(s)
- Terrel Sugar
- Department of Cell Biology and Anatomy, LSU Health Sciences Center, Shreveport, Louisiana, USA
| | | | - Jeffrey D Esko
- Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, San Diego, California, USA
| | - Toin H van Kuppevelt
- Department of Biochemistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Lawrence Holzman
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Kevin J McCarthy
- 1] Department of Cell Biology and Anatomy, LSU Health Sciences Center, Shreveport, Louisiana, USA [2] Department of Pathology, LSU Health Sciences Center, Shreveport, Louisiana, USA
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20
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Sachs N, Sonnenberg A. Cell-matrix adhesion of podocytes in physiology and disease. Nat Rev Nephrol 2013; 9:200-10. [PMID: 23338211 DOI: 10.1038/nrneph.2012.291] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cell-matrix adhesion is crucial for maintaining the mechanical integrity of epithelial tissues. Podocytes--a key component of the glomerular filtration barrier--are exposed to permanent transcapillary filtration pressure and must therefore adhere tightly to the underlying glomerular basement membrane (GBM). The major cell-matrix adhesion receptor in podocytes is the integrin α3β1, which connects laminin 521 in the GBM through various adaptor proteins to the intracellular actin cytoskeleton. Other cell-matrix adhesion receptors expressed by podocytes include the integrins α2β1 and αvβ3, α-dystroglycan, syndecan-4 and type XVII collagen. Mutations in genes encoding any of the components critical for podocyte adhesion cause glomerular disease. This Review highlights recent advances in our understanding of the cell biology and genetics of podocyte adhesion with special emphasis on glomerular disease.
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Affiliation(s)
- Norman Sachs
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
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21
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Tan R, Patni H, Tandon P, Luan L, Sharma B, Salhan D, Saleem MA, Mathieson PW, Malhotra A, Husain M, Upadhya P, Singhal PC. Nef interaction with actin compromises human podocyte actin cytoskeletal integrity. Exp Mol Pathol 2012; 94:51-7. [PMID: 22721673 DOI: 10.1016/j.yexmp.2012.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 06/07/2012] [Indexed: 10/28/2022]
Abstract
The HIV-1 accessory protein Nef is considered to play an important role in the development of a podocyte phenotype in HIV-1 associated nephropathy. We hypothesized that Nef may be altering the podocyte phenotype both structurally and functionally. To elucidate the involved mechanisms, podocyte proteins interacting with Nef were identified using GST pull down assay and yeast two hybrid assay. The GST pull down assay on protein extracts made from stable colonies of conditionally immortalized human podocytes expressing Nef (Nef/CIHP) displayed a band at 45 kD, which was identified as actin by mass spectrometry. Yeast two hybrid assay identified the following Nef-interacting proteins: syntrophin, filamin B, syntaxin, translational elongation factor 1, and zyxin. The Nef-actin and Nef-zyxin interactions were confirmed by co-localization studies on Nef/CIHP stable cell lines. The co-localization studies also showed that Nef/CIHP stable cell lines had a decreased number of actin filaments (stress fibers), displayed formation of lamellipodia, and increased number of podocyte projections (filopodia). Nef/CIHP displayed an enhanced cortical F-actin score index (P<0.001) and thus indicated a reorganization of F-actin in the cortical regions. Microarray analysis showed that Nef enhanced the expression of Rac1, syndecan-4, Rif, and CDC42 and attenuated the expression of syndecan-3 and syntenin. In addition, Nef/CIHPs displayed a diminished sphingomyelinase (ASMase) activity. Functionally, Nef/CIHPs displayed diminished attachment and enhanced detachment to their substrate. These findings indicate that Nef interaction with actin compromises the podocyte cytoskeleton integrity.
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Affiliation(s)
- Raymond Tan
- Department of Immunology, Feinstein Institute for Medical Research, North Shore LIJ Health System, NY, USA
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22
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McCarthy KJ, Wassenhove-McCarthy DJ. The glomerular basement membrane as a model system to study the bioactivity of heparan sulfate glycosaminoglycans. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2012; 18:3-21. [PMID: 22258721 PMCID: PMC3351113 DOI: 10.1017/s1431927611012682] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The glomerular basement membrane and its associated cells are critical elements in the renal ultrafiltration process. Traditionally the anionic charge associated with several carbohydrate moieties in the glomerular basement membrane are thought to form a charge selective barrier that restricts the transmembrane flux of anionic proteins across the glomerular basement membrane into the urinary space. The charge selective function, along with the size selective component of the basement membrane, serves to limit the efflux of plasma proteins from the capillary lumen. Heparan sulfate glycosaminoglycans are anionically charged carbohydrate structures attached to proteoglycan core proteins and have a role in establishing the charge selective function of the glomerular basement membrane. Although there are a large number of studies in the literature that support this concept, the results of several recent studies using molecular genetic approaches to minimize the anionic charge of the glomerular basement membrane would suggest that the role of heparan sulfate glycosaminoglycans in the glomerular capillary wall are still not yet entirely resolved, suggesting that this research area still requires new and novel exploration.
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Affiliation(s)
- Kevin J McCarthy
- Department of Pathology, LSU Health Sciences Center-Shreveport, 1501 Kings Highway, Shreveport, LA 71130-3932, USA.
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Abstract
Proteoglycans (PGs) impact many aspects of kidney health and disease. Models that permit genetic dissection of PG core protein and glycosaminoglycan (GAG) function have been instrumental to understanding their roles in the kidney. Matrix-associated PGs do not serve critical structural roles in the organ, nor do they contribute significantly to the glomerular barrier under normal conditions, but their abnormal expression influences fibrosis, inflammation, and progression of kidney disease. Most core proteins are dispensable for nephrogenesis (glypican-3 being an exception) and for maintenance of function in adult life, but their loss alters susceptibility to experimental kidney injury. In contrast, kidney development is exquisitely sensitive to GAG expression and fine structure as evidenced by the severe phenotypes of mutants for genes involved in GAG biosynthesis. This article reviews PG expression in normal kidney and the abnormalities caused by their disruption in mice and man.
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Affiliation(s)
- Scott J Harvey
- INSERM Avenir U983, Hôpital Necker-Enfants Malades, Paris, France
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24
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Liu Y, Echtermeyer F, Thilo F, Theilmeier G, Schmidt A, Schülein R, Jensen BL, Loddenkemper C, Jankowski V, Marcussen N, Gollasch M, Arendshorst WJ, Tepel M. The proteoglycan syndecan 4 regulates transient receptor potential canonical 6 channels via RhoA/Rho-associated protein kinase signaling. Arterioscler Thromb Vasc Biol 2011; 32:378-85. [PMID: 22155451 DOI: 10.1161/atvbaha.111.241018] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Syndecan 4 (Sdc4) modulates signal transduction and regulates activity of protein channels. Sdc4 is essential for the regulation of cellular permeability. We hypothesized that Sdc4 may regulate transient receptor potential canonical 6 (TRPC6) channels, a determinant of glomerular permeability, in a RhoA/Rho-associated protein kinase-dependent manner. METHODS AND RESULTS Sdc4 knockout (Sdc4(-/-)) mice showed increased glomerular filtration rate and ameliorated albuminuria under baseline conditions and after bovine serum albumin overload (each P<0.05). Using reverse transcription-polymerase chain reaction and immunoblotting, Sdc4(-/-) mice showed reduced TRPC6 mRNA by 79% and TRPC6 protein by 82% (each P<0.05). Sdc4(-/-) mice showed an increased RhoA activity by 87% and increased phosphorylation of ezrin in glomeruli by 48% (each P<0.05). Sdc4 knockdown in cultured podocytes reduced TRPC6 gene expression and reduced the association of TRPC6 with plasma membrane and TRPC6-mediated calcium influx and currents. Sdc4 knockdown inactivated negative regulatory protein Rho GTPase activating protein by 33%, accompanied by a 41% increase in RhoA activity and increased phosphorylation of ezrin (P<0.05). Conversely, overexpression of Sdc4 reduced RhoA activity and increased TRPC6 protein and TRPC6-mediated calcium influx and currents. CONCLUSIONS Our results establish a previously unknown function of Sdc4 for regulation of TRPC6 channels and support the role of Sdc4 for the regulation of glomerular permeability.
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Affiliation(s)
- Ying Liu
- Odense University Hospital and University of Southern Denmark, Institute for Molecular Medicine, Cardiovascular and Renal Research, Institute of Clinical Research, Winsløwparken 21.3, DK-5000 Odense C, Denmark
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