1
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Hall G. Genetic insights into the mechanisms of proliferative glomerulonephritis. J Clin Invest 2024; 134:e183090. [PMID: 39087471 PMCID: PMC11291265 DOI: 10.1172/jci183090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2024] Open
Abstract
Glomerular visceral epithelial cells (i.e., podocytes) are an essential component of the tripartite glomerular filtration barrier. Healthy podocytes are terminally differentiated cells with limited replicative capacity; however, inappropriate cell cycle reentry can be induced in podocytes by various injurious stimuli. In this issue of the JCI, Yamaguchi et al. report on a somatic mosaic gain-of-function mutation in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic α subunit (p110α, encoded by PIK3CA). The study reveals that activating mutations of p110α can drive podocyte proliferation in PIK3CA-related overgrowth syndrome (PROS). They also showed that selective, small-molecule inhibitors of p110 may be useful for the treatment of proliferative glomerulonephritis.
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2
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Schneider R, Mansour B, Kolvenbach CM, Buerger F, Salmanullah D, Lemberg K, Merz LM, Mertens ND, Saida K, Yousef K, Franken GAC, Bao A, Yu S, Hölzel S, Nicolas-Frank C, Steinsapir A, Goncalves KA, Shril S, Hildebrandt F. Phenotypic quantification of Nphs1-deficient mice. J Nephrol 2024:10.1007/s40620-024-01987-8. [PMID: 39003671 DOI: 10.1007/s40620-024-01987-8] [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: 01/10/2024] [Accepted: 05/06/2024] [Indexed: 07/15/2024]
Abstract
BACKGROUND Steroid-resistant nephrotic syndrome (SRNS) is the second most frequent cause of chronic kidney disease in children and young adults. The most severe form of steroid-resistant nephrotic syndrome is congenital nephrotic syndrome Finnish type (CNSF), caused by biallelic loss-of-function variants in NPHS1, encoding nephrin. Since each of the 68 monogenic causes of steroid-resistant nephrotic syndrome represents a rare cause of the disease, tailoring therapeutic interventions to multiple molecular targets remains challenging, suggesting gene replacement therapy (GRT) as a viable alternative. To set the ground for a gene replacement study in vivo, we established rigorous, quantifiable, and reproducible phenotypic assessment of a conditional Nphs1 knockout mouse model. METHODS By breeding a floxed Nphs1fl/- mouse (Nphs1tm1Afrn/J) previously studied for pancreatic β-cell survival with a podocin promoter-driven Cre recombinase mouse model (Tg(NPHS2-Cre)295Lbh/J), we generated mice with podocyte-specific nephrin deficiency (Nphs1fl/fl NPHS2-Cre +). RESULTS We observed a median survival to postnatal day P5 in nephrin-deficient mice, whereas heterozygous control mice and wild type (WT) control group showed 90% and 100% survival, respectively (at P50 days). Light microscopy analysis showed a significantly higher number of renal-tubular microcysts per kidney section in nephrin-deficient mice compared to the control groups (P < 0.0022). Transmission electron microscopy demonstrated reduced foot process (FP) density in nephrin-deficient mice compared to controls (P < 0.0001). Additionally, proteinuria quantitation using urine albumin-to-creatinine ratio (UACR) was significantly higher in nephrin-deficient mice compared to controls. CONCLUSIONS This study represents the first comprehensive description of the kidney phenotype in a nephrin-deficient mouse model, laying the foundation for future gene replacement therapy endeavors.
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Affiliation(s)
- Ronen Schneider
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Bshara Mansour
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Caroline M Kolvenbach
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
- Institute of Anatomy and Cell Biology, Medical Faculty, University of Bonn, Bonn, Germany
| | - Florian Buerger
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Daanya Salmanullah
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Katharina Lemberg
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Lea M Merz
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
- Department of Pediatrics, University Leipzig, Leipzig, Germany
| | - Nils D Mertens
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Ken Saida
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Kirollos Yousef
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Gijs A C Franken
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Aaron Bao
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Seyoung Yu
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Selina Hölzel
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Camille Nicolas-Frank
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Andrew Steinsapir
- Deerfield Discovery and Development, Deerfield Management Company, L.P. (Series C), New York, USA
| | - Kevin A Goncalves
- Deerfield Discovery and Development, Deerfield Management Company, L.P. (Series C), New York, USA
| | - Shirlee Shril
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, USA.
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3
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Xu H, Yong L, Gao X, Chen Y, Wang Y, Wang F, Hou X. CaMK4: Structure, physiological functions, and therapeutic potential. Biochem Pharmacol 2024; 224:116204. [PMID: 38615920 DOI: 10.1016/j.bcp.2024.116204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 03/22/2024] [Accepted: 04/11/2024] [Indexed: 04/16/2024]
Abstract
Calcium/calmodulin-dependent protein kinase IV (CaMK4) is a versatile serine/threonine kinase involved in various cellular functions. It regulates T-cell differentiation, podocyte function, tumor cell proliferation/apoptosis, β cell mass, and insulin sensitivity. However, the underlying molecular mechanisms are complex and remain incompletely understood. The aims of this review are to highlight the latest advances in the regulatory mechanisms of CaMK4 underlying T-cell imbalance and parenchymal cell mass in multiple diseases. The structural motifs and activation of CaMK4, as well as the potential role of CaMK4 as a novel therapeutic target are also discussed.
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Affiliation(s)
- Hao Xu
- Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, PR China
| | - Liang Yong
- The First Affiliated Hospital of Ningbo University, Ningbo, Zhejiang 315010, PR China
| | - Xianxian Gao
- Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, PR China
| | - Yandong Chen
- Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, PR China
| | - Yixuan Wang
- Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, PR China
| | - Fuyan Wang
- Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, PR China; Clinical Laboratory, Qingdao Hiser Hospital Affiliated of Qingdao University (Qingdao Traditional Chinese Medicine Hospital), Qingdao, Shandong 266033, PR China
| | - Xin Hou
- Health Science Center, Ningbo University, Ningbo, Zhejiang 315211, PR China.
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4
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Pajoumshariati R, Ewart L, Kujala V, Luc R, Peel S, Corrigan A, Weber H, Nugraha B, Hansen PBL, Williams J. Physiological Replication of the Human Glomerulus Using a Triple Culture Microphysiological System. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303131. [PMID: 37867234 PMCID: PMC10667800 DOI: 10.1002/advs.202303131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 09/12/2023] [Indexed: 10/24/2023]
Abstract
The function of the glomerulus depends on the complex cell-cell/matrix interactions and replication of this in vitro would aid biological understanding in both health and disease. Previous models do not fully reflect all cell types and interactions present as they overlook mesangial cells within their 3D matrix. Herein, the development of a microphysiological system that contains all resident renal cell types in an anatomically relevant manner is presented. A detailed transcriptomic analysis of the contributing biology of each cell type, as well as functionally appropriate albumin retention in the system, is demonstrated. The important role of mesangial cells is shown in promoting the health and maturity of the other cell types. Additionally, a comparison of the incremental advances that each individual cell type brings to the phenotype of the others demonstrates that glomerular cells in simple 2D culture exhibit a state more reflective of the dysfunction observed in human disease than previously recognized. This in vitro model will expand the capability to investigate glomerular biology in a more translatable manner by the inclusion of the important mesangial cell compartment.
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Affiliation(s)
- Ramin Pajoumshariati
- Bioscience RenalResearch and Early DevelopmentCardiovascularRenal and Metabolism (CVRM)BioPharmaceuticals R&DAstraZenecaGothenburg431 83Sweden
| | | | | | | | - Samantha Peel
- Functional Genomics, Research and Early DevelopmentDiscovery SciencesBioPharmaceuticals R&DAstraZenecaCambridgeCB21 6GHUK
| | - Adam Corrigan
- Functional Genomics, Research and Early DevelopmentDiscovery SciencesBioPharmaceuticals R&DAstraZenecaCambridgeCB21 6GHUK
| | | | - Bramasta Nugraha
- Bioscience RenalResearch and Early DevelopmentCardiovascularRenal and Metabolism (CVRM)BioPharmaceuticals R&DAstraZenecaGothenburg431 83Sweden
| | - Pernille B. L. Hansen
- Bioscience RenalResearch and Early DevelopmentCardiovascularRenal and Metabolism (CVRM)BioPharmaceuticals R&DAstraZenecaGothenburg431 83Sweden
| | - Julie Williams
- Bioscience RenalResearch and Early DevelopmentCardiovascularRenal and Metabolism (CVRM)BioPharmaceuticals R&DAstraZenecaGothenburg431 83Sweden
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5
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Salfi G, Casiraghi F, Remuzzi G. Current understanding of the molecular mechanisms of circulating permeability factor in focal segmental glomerulosclerosis. Front Immunol 2023; 14:1247606. [PMID: 37795085 PMCID: PMC10546017 DOI: 10.3389/fimmu.2023.1247606] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 09/05/2023] [Indexed: 10/06/2023] Open
Abstract
The pathogenetic mechanisms underlying the onset and the post-transplant recurrence of primary focal segmental glomerulosclerosis (FSGS) are complex and remain yet to be fully elucidated. However, a growing body of evidence emphasizes the pivotal role of the immune system in both initiating and perpetuating the disease. Extensive investigations, encompassing both experimental models and patient studies, have implicated T cells, B cells, and complement as crucial actors in the pathogenesis of primary FSGS, with various molecules being proposed as potential "circulating factors" contributing to the disease and its recurrence post kidney-transplantation. In this review, we critically assessed the existing literature to identify essential pathways for a comprehensive characterization of the pathogenesis of FSGS. Recent discoveries have shed further light on the intricate interplay between these mechanisms. We present an overview of the current understanding of the engagement of distinct molecules and immune cells in FSGS pathogenesis while highlighting critical knowledge gaps that require attention. A thorough characterization of these intricate immune mechanisms holds the potential to identify noninvasive biomarkers that can accurately identify patients at high risk of post-transplant recurrence. Such knowledge can pave the way for the development of targeted and personalized therapeutic approaches in the management of FSGS.
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Affiliation(s)
| | - Federica Casiraghi
- Istituto di Ricerche Farmacologiche Mario Negri Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Bergamo, Italy
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6
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Wang H, Yuan YC, Chang C, Izumi T, Wang HH, Yang JK. The signaling protein GIV/Girdin mediates the Nephrin-dependent insulin secretion of pancreatic islet β cells in response to high glucose. J Biol Chem 2023; 299:103045. [PMID: 36822326 PMCID: PMC10040812 DOI: 10.1016/j.jbc.2023.103045] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 02/10/2023] [Accepted: 02/12/2023] [Indexed: 02/23/2023] Open
Abstract
Glucose-stimulated insulin secretion of pancreatic β cells is essential in maintaining glucose homeostasis. Recent evidence suggests that the Nephrin-mediated intercellular junction between β cells is implicated in the regulation of insulin secretion. However, the underlying mechanisms are only partially characterized. Herein we report that GIV is a signaling mediator coordinating glucose-stimulated Nephrin phosphorylation and endocytosis with insulin secretion. We demonstrate that GIV is expressed in mouse islets and cultured β cells. The loss of function study suggests that GIV is essential for the second phase of glucose-stimulated insulin secretion. Next, we demonstrate that GIV mediates the high glucose-stimulated tyrosine phosphorylation of GIV and Nephrin by recruiting Src kinase, which leads to the endocytosis of Nephrin. Subsequently, the glucose-induced GIV/Nephrin/Src signaling events trigger downstream Akt phosphorylation, which activates Rac1-mediated cytoskeleton reorganization, allowing insulin secretory granules to access the plasma membrane for the second-phase secretion. Finally, we found that GIV is downregulated in the islets isolated from diabetic mice, and rescue of GIV ameliorates the β-cell dysfunction to restore the glucose-stimulated insulin secretion. We conclude that the GIV/Nephrin/Akt signaling axis is vital to regulate glucose-stimulated insulin secretion. This mechanism might be further targeted for therapeutic intervention of diabetic mellitus.
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Affiliation(s)
- Hao Wang
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
| | - Ying-Chao Yuan
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Cong Chang
- College of Biology, Hunan University, Changsha, Hunan, China; Hunan Food and Drug Vocational College, Changsha, Hunan, China
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma, Japan
| | - Hong-Hui Wang
- College of Biology, Hunan University, Changsha, Hunan, China.
| | - Jin-Kui Yang
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
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7
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Cara-Fuentes G, Andres-Hernando A, Bauer C, Banks M, Garcia GE, Cicerchi C, Kuwabara M, Shimada M, Johnson RJ, Lanaspa MA. Pulmonary surfactants and the respiratory-renal connection in steroid-sensitive nephrotic syndrome of childhood. iScience 2022; 25:104694. [PMID: 35847557 PMCID: PMC9284382 DOI: 10.1016/j.isci.2022.104694] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 05/23/2022] [Accepted: 06/24/2022] [Indexed: 01/21/2023] Open
Abstract
Steroid-sensitive nephrotic syndrome (SSNS) in childhood is usually due to minimal change disease (MCD). Unlike many glomerular conditions, SSNS/MCD is commonly precipitated by respiratory infections. Of interest, pulmonary inflammation releases surfactants in circulation which are soluble agonists of SIRPα, a podocyte receptor that regulates integrin signaling. Here, we characterized this pulmonary-renal connection in MCD and performed studies to determine its importance. Children with SSNS/MCD in relapse but not remission had elevated plasma surfactants and urinary SIRPα. Sera from relapsing subjects triggered podocyte SIRPα signaling via tyrosine phosphatase SHP-2 and nephrin dephosphorylation, a marker of podocyte activation. Further, addition of surfactants to MCD sera from patients in remission replicated these findings. Similarly, nasal instillation of toll-like receptor 3 and 4 agonists in mice resulted in elevated serum surfactants and their binding to glomeruli triggering proteinuria. Together, our data document a critical pulmonary-podocyte signaling pathway involving surfactants and SIRPα signaling in SSNS/MCD.
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Affiliation(s)
| | - Ana Andres-Hernando
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado, Denver, CO, USA,Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, OR, USA
| | - Colin Bauer
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado, Denver, CO, USA
| | - Mindy Banks
- Rocky Mountain Pediatric Kidney Center, Denver, CO, USA
| | - Gabriela E. Garcia
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado, Denver, CO, USA
| | - Christina Cicerchi
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado, Denver, CO, USA
| | - Masanari Kuwabara
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado, Denver, CO, USA
| | - Michiko Shimada
- Department of Cardiology and Nephrology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Richard J. Johnson
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado, Denver, CO, USA
| | - Miguel A. Lanaspa
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado, Denver, CO, USA,Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, OR, USA,Corresponding author
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8
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Kostovska I, Trajkovska KT, Topuzovska S, Cekovska S, Labudovic D, Kostovski O, Spasovski G. Nephrinuria and podocytopathies. Adv Clin Chem 2022; 108:1-36. [PMID: 35659057 DOI: 10.1016/bs.acc.2021.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The discovery of nephrin in 1998 has launched a new era in glomerular diseases research, emphasizing its crucial role in the structure and function of the glomerular filtration barrier. In the past 20 years, substantial advances have been made in understanding podocyte structure and function as well as the discovery of several podocyte-related proteins including nephrin. The glomerular filtration barrier is comprised of podocytes, the glomerular basement membrane and endothelial cells. Podocytes, with their specialized slit diaphragm, form the essential backbone of the glomerular filtration barrier. Nephrin is a crucial structural and functional feature of the slit diaphragm that prevents plasma protein, blood cell and macromolecule leakage into the urine. Podocyte damage results in nephrin release. Podocytopathies are kidney diseases in which podocyte damage drives proteinuria, i.e., nephrotic syndrome. Many kidney diseases involve podocytopathy including congenital nephrotic syndrome of Finnish type, diffuse mesangial sclerosis, minimal change disease, focal segmental glomerulosclerosis, collapsing glomerulonephropathy, diabetic nephropathy, lupus nephropathy, hypertensive nephropathy and preeclampsia. Recently, urinary nephrin measurement has become important in the early detection of podocytopathies. In this chapter, we elaborate the main structural and functional features of nephrin as a podocyte-specific protein, pathomechanisms of podocytopathies which result in nephrinuria, highlight the most commonly used methods for detecting urinary nephrin and investigate the diagnostic, prognostic and potential therapeutic relevance of urinary nephrin in primary and secondary proteinuric kidney diseases.
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Affiliation(s)
- Irena Kostovska
- Department of Medical and Experimental Biochemistry, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, North Macedonia.
| | - Katerina Tosheska Trajkovska
- Department of Medical and Experimental Biochemistry, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, North Macedonia
| | - Sonja Topuzovska
- Department of Medical and Experimental Biochemistry, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, North Macedonia
| | - Svetlana Cekovska
- Department of Medical and Experimental Biochemistry, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, North Macedonia
| | - Danica Labudovic
- Department of Medical and Experimental Biochemistry, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, North Macedonia
| | - Ognen Kostovski
- University Clinic of Abdominal Surgery, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, North Macedonia
| | - Goce Spasovski
- University Clinic of Nephrology, Faculty of Medicine, Ss. Cyril and Methodius University, Skopje, North Macedonia
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9
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PI(4,5)P2 controls slit diaphragm formation and endocytosis in Drosophila nephrocytes. Cell Mol Life Sci 2022; 79:248. [PMID: 35437696 PMCID: PMC9016003 DOI: 10.1007/s00018-022-04273-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 03/01/2022] [Accepted: 03/24/2022] [Indexed: 12/03/2022]
Abstract
Drosophila nephrocytes are an emerging model system for mammalian podocytes and proximal tubules as well as for the investigation of kidney diseases. Like podocytes, nephrocytes exhibit characteristics of epithelial cells, but the role of phospholipids in polarization of these cells is yet unclear. In epithelia, phosphatidylinositol(4,5)bisphosphate (PI(4,5)P2) and phosphatidylinositol(3,4,5)-trisphosphate (PI(3,4,5)P3) are asymmetrically distributed in the plasma membrane and determine apical–basal polarity. Here, we demonstrate that both phospholipids are present in the plasma membrane of nephrocytes, but only PI(4,5)P2 accumulates at slit diaphragms. Knockdown of Skittles, a phosphatidylinositol(4)phosphate 5-kinase, which produces PI(4,5)P2, abolished slit diaphragm formation and led to strongly reduced endocytosis. Notably, reduction in PI(3,4,5)P3 by overexpression of PTEN or expression of a dominant-negative phosphatidylinositol-3-kinase did not affect nephrocyte function, whereas enhanced formation of PI(3,4,5)P3 by constitutively active phosphatidylinositol-3-kinase resulted in strong slit diaphragm and endocytosis defects by ectopic activation of the Akt/mTOR pathway. Thus, PI(4,5)P2 but not PI(3,4,5)P3 is essential for slit diaphragm formation and nephrocyte function. However, PI(3,4,5)P3 has to be tightly controlled to ensure nephrocyte development.
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10
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Mechanisms of podocyte injury and implications for diabetic nephropathy. Clin Sci (Lond) 2022; 136:493-520. [PMID: 35415751 PMCID: PMC9008595 DOI: 10.1042/cs20210625] [Citation(s) in RCA: 47] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 02/25/2022] [Accepted: 03/25/2022] [Indexed: 02/06/2023]
Abstract
Albuminuria is the hallmark of both primary and secondary proteinuric glomerulopathies, including focal segmental glomerulosclerosis (FSGS), obesity-related nephropathy, and diabetic nephropathy (DN). Moreover, albuminuria is an important feature of all chronic kidney diseases (CKDs). Podocytes play a key role in maintaining the permselectivity of the glomerular filtration barrier (GFB) and injury of the podocyte, leading to foot process (FP) effacement and podocyte loss, the unifying underlying mechanism of proteinuric glomerulopathies. The metabolic insult of hyperglycemia is of paramount importance in the pathogenesis of DN, while insults leading to podocyte damage are poorly defined in other proteinuric glomerulopathies. However, shared mechanisms of podocyte damage have been identified. Herein, we will review the role of haemodynamic and oxidative stress, inflammation, lipotoxicity, endocannabinoid (EC) hypertone, and both mitochondrial and autophagic dysfunction in the pathogenesis of the podocyte damage, focussing particularly on their role in the pathogenesis of DN. Gaining a better insight into the mechanisms of podocyte injury may provide novel targets for treatment. Moreover, novel strategies for boosting podocyte repair may open the way to podocyte regenerative medicine.
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11
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Lin DW, Chang CC, Hsu YC, Lin CL. New Insights into the Treatment of Glomerular Diseases: When Mechanisms Become Vivid. Int J Mol Sci 2022; 23:3525. [PMID: 35408886 PMCID: PMC8998908 DOI: 10.3390/ijms23073525] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 03/18/2022] [Accepted: 03/22/2022] [Indexed: 12/23/2022] Open
Abstract
Treatment for glomerular diseases has been extrapolated from the experience of other autoimmune disorders while the underlying pathogenic mechanisms were still not well understood. As the classification of glomerular diseases was based on patterns of juries instead of mechanisms, treatments were typically the art of try and error. With the advancement of molecular biology, the role of the immune agent in glomerular diseases is becoming more evident. The four-hit theory based on the discovery of gd-IgA1 gives a more transparent outline of the pathogenesis of IgA nephropathy (IgAN), and dysregulation of Treg plays a crucial role in the pathogenesis of minimal change disease (MCD). An epoch-making breakthrough is the discovery of PLA2R antibodies in the primary membranous nephropathy (pMN). This is the first biomarker applied for precision medicine in kidney disease. Understanding the immune system's role in glomerular diseases allows the use of various immunosuppressants or other novel treatments, such as complement inhibitors, to treat glomerular diseases more reasonable. In this era of advocating personalized medicine, it is inevitable to develop precision medicine with mechanism-based novel biomarkers and novel therapies in kidney disease.
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Affiliation(s)
- Da-Wei Lin
- Department of Internal Medicine, St. Martin De Porres Hospital, Chiayi 60069, Taiwan;
| | - Cheng-Chih Chang
- Department of Surgery, Chang Gung Memorial Hospital, Chiayi 613016, Taiwan;
| | - Yung-Chien Hsu
- Department of Nephrology, Chang Gung Memorial Hospital, Chiayi 613016, Taiwan
- Kidney and Diabetic Complications Research Team (KDCRT), Chang Gung Memorial Hospital, Chiayi 613016, Taiwan
| | - Chun-Liang Lin
- Department of Nephrology, Chang Gung Memorial Hospital, Chiayi 613016, Taiwan
- Kidney and Diabetic Complications Research Team (KDCRT), Chang Gung Memorial Hospital, Chiayi 613016, Taiwan
- Division of Chinese Materia Medica Development, National Research Institute of Chinese Medicine, Taipei 613016, Taiwan
- Kidney Research Center, Chang Gung Memorial Hospital, Taipei 613016, Taiwan
- Center for Shockwave Medicine and Tissue Engineering, Chang Gung Memorial Hospital, Kaohsiung 833253, Taiwan
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12
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Maywald ML, Picciotto C, Lepa C, Bertgen L, Yousaf FS, Ricker A, Klingauf J, Krahn MP, Pavenstädt H, George B. Rap1 Activity Is Essential for Focal Adhesion and Slit Diaphragm Integrity. Front Cell Dev Biol 2022; 10:790365. [PMID: 35372328 PMCID: PMC8972170 DOI: 10.3389/fcell.2022.790365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 02/24/2022] [Indexed: 11/24/2022] Open
Abstract
Glomerular podocytes build, with their intercellular junctions, part of the kidney filter. The podocyte cell adhesion protein, nephrin, is essential for developing and maintaining slit diaphragms as functional loss in humans results in heavy proteinuria. Nephrin expression and function are also altered in many adult-onset glomerulopathies. Nephrin signals from the slit diaphragm to the actin cytoskeleton and integrin β1 at focal adhesions by recruiting Crk family proteins, which can interact with the Rap guanine nucleotide exchange factor 1 C3G. As Rap1 activity affects focal adhesion formation, we hypothesize that nephrin signals via Rap1 to integrin β. To address this issue, we combined Drosophila in vivo and mammalian cell culture experiments. We find that Rap1 is necessary for correct targeting of integrin β to focal adhesions in Drosophila nephrocytes, which also form slit diaphragm-like structures. In the fly, the Rap1 activity is important for signaling of the nephrin ortholog to integrin β, as well as for nephrin-dependent slit diaphragm integrity. We show by genetic interaction experiments that Rap1 functions downstream of nephrin signaling to integrin β and downstream of nephrin signaling necessary for slit diaphragm integrity. Similarly, in human podocyte culture, nephrin activation results in increased activation of Rap1. Thus, Rap1 is necessary for downstream signal transduction of nephrin to integrin β.
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Affiliation(s)
- Mee-Ling Maywald
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Cara Picciotto
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Carolin Lepa
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Luisa Bertgen
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | | | - Andrea Ricker
- Institute of Medical Physics and Biophysics, Westfälische Wilhelms-University Münster, Münster, Germany
| | - Jürgen Klingauf
- Institute of Medical Physics and Biophysics, Westfälische Wilhelms-University Münster, Münster, Germany
| | - Michael P. Krahn
- Medizinische Klinik D, Medical Cell Biology, University Hospital Münster, Münster, Germany
| | | | - Britta George
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
- *Correspondence: Britta George,
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13
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Purohit S, Piani F, Ordoñez FA, de Lucas-Collantes C, Bauer C, Cara-Fuentes G. Molecular Mechanisms of Proteinuria in Minimal Change Disease. Front Med (Lausanne) 2022; 8:761600. [PMID: 35004732 PMCID: PMC8733331 DOI: 10.3389/fmed.2021.761600] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/15/2021] [Indexed: 11/13/2022] Open
Abstract
Minimal change disease (MCD) is the most common type of idiopathic nephrotic syndrome in childhood and represents about 15% cases in adults. It is characterized by massive proteinuria, edema, hypoalbuminemia, and podocyte foot process effacement on electron microscopy. Clinical and experimental studies have shown an association between MCD and immune dysregulation. Given the lack of inflammatory changes or immunocomplex deposits in the kidney tissue, MCD has been traditionally thought to be mediated by an unknown circulating factor(s), probably released by T cells that directly target podocytes leading to podocyte ultrastructural changes and proteinuria. Not surprisingly, research efforts have focused on the role of T cells and podocytes in the disease process. Nevertheless, the pathogenesis of the disease remains a mystery. More recently, B cells have been postulated as an important player in the disease either by activating T cells or by releasing circulating autoantibodies against podocyte targets. There are also few reports of endothelial injury in MCD, but whether glomerular endothelial cells play a role in the disease remains unexplored. Genome-wide association studies are providing insights into the genetic susceptibility to develop the disease and found a link between MCD and certain human haplotype antigen variants. Altogether, these findings emphasize the complex interplay between the immune system, glomerular cells, and the genome, raising the possibility of distinct underlying triggers and/or mechanisms of proteinuria among patients with MCD. The heterogeneity of the disease and the lack of good animal models of MCD remain major obstacles in the understanding of MCD. In this study, we will review the most relevant candidate mediators and mechanisms of proteinuria involved in MCD and the current models of MCD-like injury.
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Affiliation(s)
- Shrey Purohit
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.,Department of Pediatrics, Section of Pediatric Nephrology, Children's Hospital Colorado, Aurora, CO, United States
| | - Federica Piani
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.,Department of Medicine and Surgery Sciences, Alma Mater Studiorum University of Bologna, Bologna, Italy
| | - Flor A Ordoñez
- Division of Pediatric Nephrology, Hospital Universitario Central de Asturias, Oviedo, Spain
| | | | - Colin Bauer
- Department of Pediatrics, Section of Pediatric Nephrology, Children's Hospital Colorado, Aurora, CO, United States
| | - Gabriel Cara-Fuentes
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.,Department of Pediatrics, Section of Pediatric Nephrology, Children's Hospital Colorado, Aurora, CO, United States
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14
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Abstract
Rho family GTPases are molecular switches best known for their pivotal role in dynamic regulation of the actin cytoskeleton, but also of cellular morphology, motility, adhesion and proliferation. The prototypic members of this family (RhoA, Rac1 and Cdc42) also contribute to the normal kidney function and play important roles in the structure and function of various kidney cells including tubular epithelial cells, mesangial cells and podocytes. The kidney's vital filtration function depends on the structural integrity of the glomerulus, the proximal portion of the nephron. Within the glomerulus, the architecturally actin-based cytoskeleton podocyte forms the final cellular barrier to filtration. The glomerulus appears as a highly dynamic signalling hub that is capable of integrating intracellular cues from its individual structural components. Dynamic regulation of the podocyte cytoskeleton is required for efficient barrier function of the kidney. As master regulators of actin cytoskeletal dynamics, Rho GTPases are therefore of critical importance for sustained kidney barrier function. Dysregulated activities of the Rho GTPases and of their effectors are implicated in the pathogenesis of both hereditary and idiopathic forms of kidney diseases. Diabetic nephropathy is a progressive kidney disease that is caused by injury to kidney glomeruli. High glucose activates RhoA/Rho-kinase in mesangial cells, leading to excessive extracellular matrix production (glomerulosclerosis). This RhoA/Rho-kinase pathway also seems involved in the post-transplant hypertension frequently observed during treatment with calcineurin inhibitors, whereas Rac1 activation was observed in post-transplant ischaemic acute kidney injury.
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Affiliation(s)
- Clara Steichen
- Inserm UMR-1082 Irtomit, Poitiers, France,Faculté De Médecine Et De Pharmacie, Université De Poitiers, Poitiers, France
| | - Claude Hervé
- Inserm UMR-1082 Irtomit, Poitiers, France,CONTACT Claude HervéInserm UMR-1082 Irtomit, Poitiers, France
| | - Thierry Hauet
- Inserm UMR-1082 Irtomit, Poitiers, France,Faculté De Médecine Et De Pharmacie, Université De Poitiers, Poitiers, France,Department of Medical Biology, Service De Biochimie, CHU De Poitiers, Poitiers, France
| | - Nicolas Bourmeyster
- Faculté De Médecine Et De Pharmacie, Université De Poitiers, Poitiers, France,Department of Medical Biology, Service De Biochimie, CHU De Poitiers, Poitiers, France,Laboratoire STIM CNRS ERL 7003, Université de Poitiers, Poitiers Cédex, France
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15
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Wang X, Dong Y, Bao Z, Lin S. Acidic Stigma maydis polysaccharides protect against podocyte injury in membranous nephropathy by maintenance of glomerular filtration barrier integrity and gut-kidney axis. Food Funct 2022; 13:11794-11810. [DOI: 10.1039/d2fo02652j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
MN mice models were induced by C-BSA, and we found that acidic stigma maydis polysaccharides maintained the integrity of the glomerular filtration barrier by promoting slit diaphragm proteins expression and PI3K/AKT signaling.
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Affiliation(s)
- Xizhu Wang
- National Engineering Research Center of Seafood, School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, Liaoning Province, China
| | - Yifei Dong
- National Engineering Research Center of Seafood, School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, Liaoning Province, China
| | - Zhijie Bao
- National Engineering Research Center of Seafood, School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, Liaoning Province, China
| | - Songyi Lin
- National Engineering Research Center of Seafood, School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, Liaoning Province, China
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16
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Mahesaniya A, Williamson CR, Keyvani Chahi A, Martin CE, Mitro AE, Lu P, New LA, Watson KL, Moorehead RA, Jones N. Sex Differences in Glomerular Protein Expression and Effects of Soy-Based Diet on Podocyte Signaling. Can J Kidney Health Dis 2022; 9:20543581221121636. [PMID: 36199279 PMCID: PMC9528100 DOI: 10.1177/20543581221121636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Indexed: 12/02/2022] Open
Abstract
Background: Kidney disease is a major public health issue arising from loss of glomerular podocyte function, and there are considerable sex differences in its prognosis. Evidence suggests a renoprotective effect of estrogen and soy diet-derived phytoestrogens, although the molecular basis for this is poorly understood. Objective: Here, we aim to assess sex differences in expression of key proteins associated with podocyte survival and determine the effects of dietary soy on glomerular and podocyte signaling. Methods: Male and female FVB mice were fed control, low (1%), and high (20%) doses of isolated soy protein (ISP) in utero and until 100 days of age. Spot urine was collected to measure proteinuria and isolated glomeruli were used to quantify activated and total levels of nephrin, Akt, and ERK1/2. To investigate protective effects of specific soy phytoestrogens, cultured podocytes were treated with or without daidzein and subject to control or high glucose as a model of podocyte injury. Results: Nephrin and Akt were elevated at baseline in glomeruli from females compared to males. Both sexes that were fed 1% and 20% ISP displayed robust increases in total glomerular Akt compared to controls, and these effects were more prominent in females. A similar trend at both doses in both sexes was observed with activated Akt and total nephrin. Notably, males exclusively showed increased phosphorylation of nephrin and extracellular signal-regulated kinase (ERK) at the 1% ISP dose; however, no overt changes in urinary albumin excretion or podocin levels were observed, suggesting that the soy diets did not impair podocyte function. Finally, in cultured male and female podocytes, daidzein treatment suppressed high glucose-induced ERK activation. Conclusions: Together, our findings reveal a putative mechanism to explain the protective influence of sex on kidney disease progression, and they provide further evidence to support a beneficial role for dietary soy in preserving glomerular function.
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Affiliation(s)
- Afreeda Mahesaniya
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
| | - Casey R. Williamson
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
| | - Ava Keyvani Chahi
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
- Present address: Department of Biochemistry & Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Claire E. Martin
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
- Present address: Lunenfeld-Tanenbaum Research Institute, Toronto, ON, Canada
| | - Alexander E. Mitro
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
| | - Peihua Lu
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
| | - Laura A. New
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
| | | | | | - Nina Jones
- Department of Molecular and Cellular Biology, University of Guelph, ON, Canada
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17
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Song H, Zhuang L, Xu X, Shi J, Hu W, Liu Z, Shi S. MCC Regulator of WNT Signaling Pathway (MCC) Is a Podocyte Essential Gene. Front Med (Lausanne) 2021; 8:777563. [PMID: 34926519 PMCID: PMC8674659 DOI: 10.3389/fmed.2021.777563] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 11/11/2021] [Indexed: 12/13/2022] Open
Abstract
Podocytes are an integral part of the glomerular filtration barrier. Many genes are already known to be essential for podocyte survival, structure and function, but there are more podocyte essential genes to be identified. By single-cell RNA-seq of mouse podocytes, we detected the expression of gene encoding MCC regulator of WNT signaling pathway (MCC) in majority of the podocytes and speculated that MCC is essential for podocytes. We confirmed MCC expression in mouse podocytes and further showed its expression in human podocytes. To experimentally prove the essentiality of MCC for podocytes, we knocked down MCC in cultured podocytes and found marked morphological change of cell shape, cytoskeletal F-actin stress fiber disruption, increased apoptosis, and downregulation of podocyte essential genes, CD2AP and WT1, demonstrating that MCC is essential for podocytes. Since MCC has been implicated in cell cycle and β-catenin signaling, we examined the expression of cell cycle related genes and activity of β-catenin in the MCC knockdown podocytes, but did not find significant changes. To further explore the mechanism underlying the role of MCC in podocytes, we performed RNA-sequencing and bioinformatics analysis of MCC knockdown podocytes and found a significant enrichment of the regulated genes in lamellipodia formation. Consistently, we found that MCC is present in lamellipodia and MCC knockdown resulted in loss of lamellipodia in the cells. Lastly, we found that MCC was downregulated in podocytes treated with puromycin aminonucleosides and in glomeruli of diabetic mice and FSGS patients, implicating MCC is involved in the development of podocytopathy and proteinuria. In conclusion, MCC is potentially essential for podocytes and its downregulation may be involved in podocytopathy.
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Affiliation(s)
- Hui Song
- National Clinical Research Center for Kidney Diseases, Affiliated Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Lulu Zhuang
- National Clinical Research Center for Kidney Diseases, Affiliated Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Xiaodong Xu
- National Clinical Research Center for Kidney Diseases, Affiliated Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Jingsong Shi
- National Clinical Research Center for Kidney Diseases, Affiliated Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Weixin Hu
- National Clinical Research Center for Kidney Diseases, Affiliated Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Zhihong Liu
- National Clinical Research Center for Kidney Diseases, Affiliated Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Shaolin Shi
- National Clinical Research Center for Kidney Diseases, Affiliated Jinling Hospital, Medical School of Nanjing University, Nanjing, China
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18
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Afsar B, Afsar RE, Demiray A, Covic A, Kanbay M. Deciphering nutritional interventions for podocyte structure and function. Pharmacol Res 2021; 172:105852. [PMID: 34450318 DOI: 10.1016/j.phrs.2021.105852] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 08/22/2021] [Accepted: 08/22/2021] [Indexed: 12/11/2022]
Abstract
Despite increasing awareness and therapeutic options chronic kidney disease (CKD) is still and important health problem and glomerular diseases constitute and important percentage of CKD. Proteinuria/albuminuria is not just a marker; but it also plays a direct pathogenic role in renal disease progression of CKD. Glomerular filtration barrier (GFB) which consists of fenestrated endothelial cells, fused basal membrane and interdigitating podocyte foot process and filtration slits between foot process is the major barrier for proteinuria/albuminuria. Many glomerular diseases are characterized by disruption of GFB podocytes, foot process and slit diaphragm. Many proteinuric diseases are non-specifically targeted by therapeutic agents such as steroids and calcineurin inhibitors with systemic side effects. Thus, there is unmet need for more efficient and less toxic therapeutic options to treat glomerular diseases. In recent years, modification of dietary intake, has been gained to treat pathologic processes introducing the concept of 'food as a medicine'. The effect of various nutritional products on podocyte function and structure is also trending, especially in recent years. In the current review, we summarized the effect of nutritional interventions on podocyte function and structure.
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Affiliation(s)
- Baris Afsar
- Division of Nephrology, Department of Nephrology, Suleyman Demirel University School of Medicine, Isparta, Turkey.
| | - Rengin Elsurer Afsar
- Division of Nephrology, Department of Nephrology, Suleyman Demirel University School of Medicine, Isparta, Turkey
| | - Atalay Demiray
- Department of Medicine, Koc University School of Medicine, Istanbul, Turkey
| | - Adrian Covic
- Department of Nephrology, Grigore T. Popa' University of Medicine, Iasi, Romania
| | - Mehmet Kanbay
- Division of Nephrology, Department of Medicine, Koc University School of Medicine, Istanbul, Turkey
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19
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Bhargava R, Lehoux S, Maeda K, Tsokos MG, Krishfield S, Ellezian L, Pollak M, Stillman IE, Cummings RD, Tsokos GC. Aberrantly glycosylated IgG elicits pathogenic signaling in podocytes and signifies lupus nephritis. JCI Insight 2021; 6:147789. [PMID: 33784256 PMCID: PMC8262331 DOI: 10.1172/jci.insight.147789] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 03/25/2021] [Indexed: 12/27/2022] Open
Abstract
Lupus nephritis (LN) is a serious complication occurring in 50% of patients with systemic lupus erythematosus (SLE) for which there is a lack of biomarkers, a lack of specific medications, and a lack of a clear understanding of its pathogenesis. The expression of calcium/calmodulin kinase IV (CaMK4) is increased in podocytes of patients with LN and lupus-prone mice, and its podocyte-targeted inhibition averts the development of nephritis in mice. Nephrin is a key podocyte molecule essential for the maintenance of the glomerular slit diaphragm. Here, we show that the presence of fucose on N-glycans of IgG induces, whereas the presence of galactose ameliorates, podocyte injury through CaMK4 expression. Mechanistically, CaMK4 phosphorylates NF-κB, upregulates the transcriptional repressor SNAIL, and limits the expression of nephrin. In addition, we demonstrate that increased expression of CaMK4 in biopsy specimens and in urine podocytes from people with LN is linked to active kidney disease. Our data shed light on the role of IgG glycosylation in the development of podocyte injury and propose the development of “liquid kidney biopsy” approaches to diagnose LN.
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Affiliation(s)
| | - Sylvain Lehoux
- Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.,Beth Israel Deaconess Medical Center Glycomics Core, Boston, Massachusetts, USA
| | | | | | | | | | | | - Isaac E Stillman
- Department of Pathology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Richard D Cummings
- Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.,Beth Israel Deaconess Medical Center Glycomics Core, Boston, Massachusetts, USA
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20
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Role of Rho GTPase Interacting Proteins in Subcellular Compartments of Podocytes. Int J Mol Sci 2021; 22:ijms22073656. [PMID: 33915776 PMCID: PMC8037304 DOI: 10.3390/ijms22073656] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 03/22/2021] [Accepted: 03/26/2021] [Indexed: 01/15/2023] Open
Abstract
The first step of urine formation is the selective filtration of the plasma into the urinary space at the kidney structure called the glomerulus. The filtration barrier of the glomerulus allows blood cells and large proteins such as albumin to be retained while eliminating the waste products of the body. The filtration barrier consists of three layers: fenestrated endothelial cells, glomerular basement membrane, and podocytes. Podocytes are specialized epithelial cells featured by numerous, actin-based projections called foot processes. Proteins on the foot process membrane are connected to the well-organized intracellular actin network. The Rho family of small GTPases (Rho GTPases) act as intracellular molecular switches. They tightly regulate actin dynamics and subsequent diverse cellular functions such as adhesion, migration, and spreading. Previous studies using podocyte-specific transgenic or knockout animal models have established that Rho GTPases are crucial for the podocyte health and barrier function. However, little attention has been paid regarding subcellular locations where distinct Rho GTPases contribute to specific functions. In the current review, we discuss cellular events involving the prototypical Rho GTPases (RhoA, Rac1, and Cdc42) in podocytes, with particular focus on the subcellular compartments where the signaling events occur. We also provide our synthesized views of the current understanding and propose future research directions.
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21
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Papakrivopoulou E, Jafree DJ, Dean CH, Long DA. The Biological Significance and Implications of Planar Cell Polarity for Nephrology. Front Physiol 2021; 12:599529. [PMID: 33716764 PMCID: PMC7952641 DOI: 10.3389/fphys.2021.599529] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 02/01/2021] [Indexed: 11/13/2022] Open
Abstract
The orientation of cells in two-dimensional and three-dimensional space underpins how the kidney develops and responds to disease. The process by which cells orientate themselves within the plane of a tissue is termed planar cell polarity. In this Review, we discuss how planar cell polarity and the proteins that underpin it govern kidney organogenesis and pathology. The importance of planar cell polarity and its constituent proteins in multiple facets of kidney development is emphasised, including ureteric bud branching, tubular morphogenesis and nephron maturation. An overview is given of the relevance of planar cell polarity and its proteins for inherited human renal diseases, including congenital malformations with unknown aetiology and polycystic kidney disease. Finally, recent work is described outlining the influence of planar cell polarity proteins on glomerular diseases and highlight how this fundamental pathway could yield a new treatment paradigm for nephrology.
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Affiliation(s)
- Eugenia Papakrivopoulou
- Developmental Biology and Cancer Programme, UCL Great Ormond Street Institute of Child Health, London, United Kingdom.,Department of Internal Medicine and Nephrology, Clinique Saint Jean, Brussels, Belgium
| | - Daniyal J Jafree
- Developmental Biology and Cancer Programme, UCL Great Ormond Street Institute of Child Health, London, United Kingdom.,UCL MB/Ph.D. Programme, Faculty of Medical Science, University College London, London, United Kingdom
| | - Charlotte H Dean
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - David A Long
- Developmental Biology and Cancer Programme, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
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22
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Elekofehinti OO, Oyedokun VO, Iwaloye O, Lawal AO, Ejelonu OC. Momordica charantia silver nanoparticles modulate S OCS/JAK/STAT and P13K/Akt/PTEN signalling pathways in the kidney of streptozotocin-induced diabetic rats. J Diabetes Metab Disord 2021; 20:245-260. [PMID: 34178835 DOI: 10.1007/s40200-021-00739-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 01/10/2021] [Indexed: 12/23/2022]
Abstract
Objectives Diabetes nephropathy (DN) is one of the complications of diabetes mellitus (DM) marked by gradual progressive loss of renal function. SOCS/JAK/STAT and PI3K/Akt/PTEN signalling pathways are among the chain of interactions implicated in the onset, progression and pathology of DN. Momordica charantia (bitter melon) is often used in folk medicine as therapy for DM due to its hypoglycemic properties. This study was designed to evaluate M. charantia silver nanoparticles' therapeutic effect on DN-induced by streptozotocin (STZ) in Wistar rats. Methods The M. charantia nanoparticles used was synthesized using the filtrate from the plant methanolic extract added to 1 mM concentration of aqueous silver nitrate. DM was induced in Wistar rats by intraperitoneal injection of STZ (65 mg/kg). The animals' treatment groups were divided into; Diabetic control (65 mg/kg STZ), Control, and groups treated with silver nitrate (10 mg/kg), M. charantia nanoparticles (50 mg/kg), metformin (100 mg/kg), and plant extract (100 mg/kg). Treatment was terminated after 11 days. RT-PCR determined renal mRNA expression of Akt, PI3k, PTEN, TGF-β, JAK2, STAT3, STAT5, SOCS3, SOCS4 and glucokinase (GCK). Consequently, characterized compounds from M. charantia identified from literatures were docked with PI3K, JAK2 and TGF-β and STAT3 to retrieve potential hits. Results Oral administration of M. charantia nanoparticles (50 mg/kg) to STZ-induced diabetic untreated rats significantly ((p < 0.05) down-regulated the mRNA expression of Akt, PI3k, TGF-β, JAK2, STAT3 and upregulated the mRNA expression of PTEN, SOCS3 and SOCS4, thus establishing the role of M. charantia nanoparticles in alleviating DN in diabetic rats. Additionally, there was a significant up-regulation of glucose metabolizing gene (glucokinase) upon administering M. charantia nanoparticles. Molecular docking results showed 12 compounds from bitter melon with docking score ranging from -6.114 kcal/mol to -8.221 kcal/mol that are likely to exert anti-diabetic properties. Conclusion Observation drawn from this study suggests that M. charantia nanoparticles ameliorate DN through regulation of SOCS/JAK/STAT and PI3K/Akt/PTEN signalling pathways.
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Affiliation(s)
- Olusola Olalekan Elekofehinti
- Bioinformatics and Molecular Biology Unit, Department of Biochemistry, Federal University of Technology Akure, Akure, Ondo State Nigeria
| | - Victor Oluwatoyin Oyedokun
- Bioinformatics and Molecular Biology Unit, Department of Biochemistry, Federal University of Technology Akure, Akure, Ondo State Nigeria
| | - Opeyemi Iwaloye
- Bioinformatics and Molecular Biology Unit, Department of Biochemistry, Federal University of Technology Akure, Akure, Ondo State Nigeria
| | - Akeem Olalekan Lawal
- Bioinformatics and Molecular Biology Unit, Department of Biochemistry, Federal University of Technology Akure, Akure, Ondo State Nigeria
| | - Oluwamodupe Cecilia Ejelonu
- Biochemistry Programme, Department of Chemical Sciences, School of Sciences, Olusegun Agagu University of Science and Technology, Okitipupa, Ondo State Nigeria
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23
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Nakamichi R, Hayashi K, Itoh H. Effects of High Glucose and Lipotoxicity on Diabetic Podocytes. Nutrients 2021; 13:nu13010241. [PMID: 33467659 PMCID: PMC7830342 DOI: 10.3390/nu13010241] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 12/11/2020] [Accepted: 01/11/2021] [Indexed: 01/19/2023] Open
Abstract
Glomerular podocytes are highly differentiated cells that cover glomerular capillaries from the outside and have a characteristic morphology with numerous foot processes. The formation of slit membranes between the foot processes serves as a final filtration barrier for urine filtration from the blood. Podocyte damage causes disruption of the slit membrane, subsequent proteinuria and finally glomerulosclerosis, which is a common pathway in various types of chronic kidney disease (CKD). In recent years, there has been an increase in diabetes, due to rapid lifestyle changes, which is the main cause of CKD. Therefore, understanding the effect of diabetic status on podocytes is of great importance to establish a strategy for preventing CKD progression. In this review, we summarize altered glucose and lipid metabolism in diabetic podocytes and also discuss the reversibility of the changes in podocyte phenotype.
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Affiliation(s)
| | - Kaori Hayashi
- Correspondence: ; Tel.: +81-3-5363-3796; Fax: +81-3-3359-2745
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24
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Zhang Z, Liang W, Luo Q, Hu H, Yang K, Hu J, Chen Z, Zhu J, Feng J, Zhu Z, Chi Q, Ding G. PFKP Activation Ameliorates Foot Process Fusion in Podocytes in Diabetic Kidney Disease. Front Endocrinol (Lausanne) 2021; 12:797025. [PMID: 35095764 PMCID: PMC8794994 DOI: 10.3389/fendo.2021.797025] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 12/20/2021] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Glycolysis dysfunction is an important pathogenesis of podocyte injury in diabetic kidney disease (DKD). Foot process fusion of podocytes and increased albuminuria are markers of early DKD. Moreover, cytoskeletal remodeling has been found to be involved in the foot process fusion of podocytes. However, the connections between cytoskeletal remodeling and alterations of glycolysis in podocytes in DKD have not been clarified. METHODS mRNA sequencing of glomeruli obtained from db/db and db/m mice with albuminuria was performed to analyze the expression profiling of genes in glucose metabolism. Expressions of phosphofructokinase platelet type (PFKP) in the glomeruli of DKD patients were detected. Clotrimazole (CTZ) was used to explore the renal effects of PFKP inhibition in diabetic mice. Using Pfkp siRNA or recombinant plasmid to manipulate PFKP expression, the effects of PFKP on high glucose (HG) induced podocyte damage were assessed in vitro. The levels of fructose-1,6-bisphosphate (FBP) were measured. Targeted metabolomics was performed to observe the alterations of the metabolites in glucose metabolism after HG stimulation. Furthermore, aldolase type b (Aldob) siRNA or recombinant plasmid were applied to evaluate the influence of FBP level alteration on podocytes. FBP was directly added to podocyte culture media. Db/db mice were treated with FBP to investigate its effects on their kidney. RESULTS mRNA sequencing showed that glycolysis enzyme genes were altered, characterized by upregulation of upstream genes (Hk1, and Pfkp) and down-regulation of downstream genes of glycolysis (Pkm, and Ldha). Moreover, the expression of PFKP was increased in glomeruli of DKD patients. The CTZ group presented more severe renal damage. In vitro, the Pfkp siRNA group and ALDOB overexpression group showed much more induced cytoskeletal remodeling in podocytes, while overexpression of PFKP and suppression of ALDOB in vitro rescued podocytes from cytoskeletal remodeling through regulation of FBP levels and inhibition of the RhoA/ROCK1 pathway. Furthermore, targeted metabolomics showed FBP level was significantly increased in HG group compared with the control group. Exogenous FBP addition reduced podocyte cytoskeletal remodeling and renal damage of db/db mice. CONCLUSIONS These findings provide evidence that PFKP may be a potential target for podocyte injury in DN and provide a rationale for applying podocyte glycolysis enhancing agents in patients with DKD.
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Affiliation(s)
- Zongwei Zhang
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Wei Liang
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
- *Correspondence: Wei Liang, ; Guohua Ding,
| | - Qiang Luo
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Hongtu Hu
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Keju Yang
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
- The First College of Clinical Medical Science, China Three Gorges University, Yichang, China
| | - Jijia Hu
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Zhaowei Chen
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Jili Zhu
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Jun Feng
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Zijing Zhu
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
| | - Qingjia Chi
- Department of Mechanics and Engineering Structure, Wuhan University of Technology, Wuhan, China
| | - Guohua Ding
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
- Nephrology and Urology Research Institute of Wuhan University, Wuhan, China
- *Correspondence: Wei Liang, ; Guohua Ding,
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25
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Lehtonen S. Metformin Protects against Podocyte Injury in Diabetic Kidney Disease. Pharmaceuticals (Basel) 2020; 13:ph13120452. [PMID: 33321755 PMCID: PMC7764076 DOI: 10.3390/ph13120452] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 12/06/2020] [Accepted: 12/08/2020] [Indexed: 02/07/2023] Open
Abstract
Metformin is the most commonly prescribed drug for treating type 2 diabetes mellitus (T2D). Its mechanisms of action have been under extensive investigation, revealing that it has multiple cellular targets, either direct or indirect ones, via which it regulates numerous cellular pathways. Diabetic kidney disease (DKD), the serious complication of T2D, develops in up to 50% of the individuals with T2D. Various mechanisms contribute to the development of DKD, including hyperglycaemia, dyslipidemia, oxidative stress, chronic low-grade inflammation, altered autophagic activity and insulin resistance, among others. Metformin has been shown to affect these pathways, and thus, it could slow down or prevent the progression of DKD. Despite several animal studies demonstrating the renoprotective effects of metformin, there is no concrete evidence in clinical settings. This review summarizes the renoprotective effects of metformin in experimental settings. Special emphasis is on the effects of metformin on podocytes, the glomerular epithelial cells that are central in maintaining the glomerular ultrafiltration function.
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Affiliation(s)
- Sanna Lehtonen
- Research Program for Clinical and Molecular Metabolism and Department of Pathology, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
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26
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Matsuda J, Asano-Matsuda K, Kitzler TM, Takano T. Rho GTPase regulatory proteins in podocytes. Kidney Int 2020; 99:336-345. [PMID: 33122025 DOI: 10.1016/j.kint.2020.08.035] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 08/21/2020] [Accepted: 08/25/2020] [Indexed: 12/14/2022]
Abstract
The Rho family of small GTPases (Rho GTPases) are the master regulators of the actin cytoskeleton and consist of 22 members. Previous studies implicated dysregulation of Rho GTPases in podocytes in the pathogenesis of proteinuric glomerular diseases. Rho GTPases are primarily regulated by the three families of proteins; guanine nucleotide exchange factors (GEFs; 82 members), GTPase-activating proteins (GAPs; 69 members), and GDP dissociation inhibitors (GDIs; 3 members). Since the regulatory proteins far outnumber their substrate Rho GTPases and act in concert in a cell/context-dependent manner, the upstream regulatory mechanism directing Rho GTPases in podocytes is largely unknown. In this review, we summarize recent advances in the understanding of the role of Rho GTPase regulatory proteins in podocytes, including the known mutations of these proteins that cause proteinuria in humans. We also provide critical appraisal of the in vivo and in vitro studies and identify the knowledge gap in the field that will require further studies.
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Affiliation(s)
- Jun Matsuda
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada; Research Institute, McGill University Health Centre, Montreal, Quebec, Canada
| | - Kana Asano-Matsuda
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada; Research Institute, McGill University Health Centre, Montreal, Quebec, Canada
| | - Thomas M Kitzler
- Research Institute, McGill University Health Centre, Montreal, Quebec, Canada; Division of Medical Genetics, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada; Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Tomoko Takano
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada; Research Institute, McGill University Health Centre, Montreal, Quebec, Canada.
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27
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Feng D. Phosphorylation of key podocyte proteins and the association with proteinuric kidney disease. Am J Physiol Renal Physiol 2020; 319:F284-F291. [PMID: 32686524 DOI: 10.1152/ajprenal.00002.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Podocyte dysfunction contributes to proteinuric chronic kidney disease. A number of key proteins are essential for podocyte function, including nephrin, podocin, CD2-associated protein (CD2AP), synaptopodin, and α-actinin-4 (ACTN4). Although most of these proteins were first identified through genetic studies associated with human kidney disease, subsequent studies have identified phosphorylation of these proteins as an important posttranslational event that regulates their function. In this review, a brief overview of the function of these key podocyte proteins is provided. Second, the role of phosphorylation in regulating the function of these proteins is described. Third, the association between these phosphorylation pathways and kidney disease is reviewed. Finally, challenges and future directions in studying phosphorylation are discussed. Better characterization of these phosphorylation pathways and others yet to be discovered holds promise for translating this knowledge into new therapies for patients with proteinuric chronic kidney disease.
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Affiliation(s)
- Di Feng
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
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28
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Blaine J, Dylewski J. Regulation of the Actin Cytoskeleton in Podocytes. Cells 2020; 9:cells9071700. [PMID: 32708597 PMCID: PMC7408282 DOI: 10.3390/cells9071700] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 06/30/2020] [Accepted: 07/07/2020] [Indexed: 12/13/2022] Open
Abstract
Podocytes are an integral part of the glomerular filtration barrier, a structure that prevents filtration of large proteins and macromolecules into the urine. Podocyte function is dependent on actin cytoskeleton regulation within the foot processes, structures that link podocytes to the glomerular basement membrane. Actin cytoskeleton dynamics in podocyte foot processes are complex and regulated by multiple proteins and other factors. There are two key signal integration and structural hubs within foot processes that regulate the actin cytoskeleton: the slit diaphragm and focal adhesions. Both modulate actin filament extension as well as foot process mobility. No matter what the initial cause, the final common pathway of podocyte damage is dysregulation of the actin cytoskeleton leading to foot process retraction and proteinuria. Disruption of the actin cytoskeleton can be due to acquired causes or to genetic mutations in key actin regulatory and signaling proteins. Here, we describe the major structural and signaling components that regulate the actin cytoskeleton in podocytes as well as acquired and genetic causes of actin dysregulation.
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Affiliation(s)
- Judith Blaine
- Renal Division, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA;
| | - James Dylewski
- Renal Division, University of Colorado Anschutz Medical Campus and Denver Health Medical Center, Aurora, CO 80045, USA
- Correspondence: ; Tel.: +303-724-4841
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29
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Khokhar M, Roy D, Modi A, Agarwal R, Yadav D, Purohit P, Sharma P. Perspectives on the role of PTEN in diabetic nephropathy: an update. Crit Rev Clin Lab Sci 2020; 57:470-483. [PMID: 32306805 DOI: 10.1080/10408363.2020.1746735] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Phosphatase and tensin homolog (PTEN) is a potent tumor suppressor gene that antagonizes the proto-oncogenic phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) signaling pathway and governs basic cellular metabolic processes. Recently, its role in cell growth, metabolism, architecture, and motility as an intramolecular and regulatory mediator has gained widespread research interest as it applies to non-tumorous diseases, such as insulin resistance (IR) and diabetic nephropathy (DN). DN is characterized by renal tubulointerstitial fibrosis (TIF) and epithelial-mesenchymal transition (EMT), and PTEN plays a significant role in the regulation of both. Epigenetics and microRNAs (miRNAs) are novel players in post-transcriptional regulation and research evidence demonstrates that they reduce the expression of PTEN by acting as key regulators of autophagy and TIF through activation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway. These regulatory processes might play an important role in solving the complexities of DN pathogenesis and IR, as well as the therapeutic management of DN with the help of PTEN K27-linked polyubiquitination. Currently, there are no comprehensive reviews citing the role PTEN plays in the development of DN and its regulation via miRNA and epigenetic modifications. The present review explores these facets of PTEN in the pathogenesis of IR and DN.
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Affiliation(s)
- Manoj Khokhar
- Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, India
| | - Dipayan Roy
- Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, India
| | - Anupama Modi
- Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, India
| | - Riddhi Agarwal
- Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, India
| | - Dharmveer Yadav
- Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, India
| | - Purvi Purohit
- Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, India
| | - Praveen Sharma
- Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, India
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30
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Kravets I, Mallipattu SK. The Role of Podocytes and Podocyte-Associated Biomarkers in Diagnosis and Treatment of Diabetic Kidney Disease. J Endocr Soc 2020; 4:bvaa029. [PMID: 32232184 PMCID: PMC7093089 DOI: 10.1210/jendso/bvaa029] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 02/27/2020] [Indexed: 12/23/2022] Open
Abstract
Diabetic kidney disease (DKD) is an important public health problem. Podocyte injury is a central event in the mechanism of DKD development. Podocytes are terminally differentiated, highly specialized glomerular visceral epithelial cells critical for the maintenance of the glomerular filtration barrier. Although potential mechanisms by which diabetic milieu contributes to irreversible loss of podocytes have been described, identification of markers that prognosticate either the development of DKD or the progression to end-stage kidney disease (ESKD) have only recently made it to the forefront. Currently, the most common marker of early DKD is microalbuminuria; however, this marker has significant limitations: not all diabetic patients with microalbuminuria will progress to ESKD and as many as 30% of patients with DKD have normal urine albumin levels. Several novel biomarkers indicating glomerular or tubular damage precede microalbuminuria, suggesting that the latter develops when significant kidney injury has already occurred. Because podocyte injury plays a key role in DKD pathogenesis, identification of markers of early podocyte injury or loss may play an important role in the early diagnosis of DKD. Such biomarkers in the urine include podocyte-released microparticles as well as expression of podocyte-specific markers. Here, we review the mechanisms by which podocyte injury contributes to DKD as well as key markers that have been recently implicated in the development and/or progression of DKD and might serve to identify individuals that require earlier preventative care and treatment in order to slow the progression to ESKD.
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Affiliation(s)
- Igor Kravets
- Division of Endocrinology, Department of Medicine, Stony Brook University, Stony Brook, NY
| | - Sandeep K Mallipattu
- Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, NY
- Renal Section, Northport VA Medical Center, Northport, NY
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31
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Kawachi H, Fukusumi Y. New insight into podocyte slit diaphragm, a therapeutic target of proteinuria. Clin Exp Nephrol 2020; 24:193-204. [PMID: 32020343 PMCID: PMC7040068 DOI: 10.1007/s10157-020-01854-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 01/15/2020] [Indexed: 12/26/2022]
Abstract
Dysfunction of slit diaphragm, a cell–cell junction of glomerular podocytes, is involved in the development of proteinuria in several glomerular diseases. Slit diaphragm should be a target of a novel therapy for proteinuria. Nephrin, NEPH1, P-cadherin, FAT, and ephrin-B1 were reported to be extracellular components forming a molecular sieve of the slit diaphragm. Several cytoplasmic proteins such as ZO-1, podocin, CD2AP, MAGI proteins and Par-complex molecules were identified as scaffold proteins linking the slit diaphragm to the cytoskeleton. In this article, new insights into these molecules and the pathogenic roles of the dysfunction of these molecules were introduced. The slit diaphragm functions not only as a barrier but also as a signaling platform transfer the signal to the inside of the cell. For maintaining the slit diaphragm function properly, the phosphorylation level of nephrin is strictly regulated. The recent studies on the signaling pathway from nephrin, NEPH1, and ephrin-B1 were reviewed. Although the mechanism regulating the function of the slit diaphragm had remained unclear, recent studies revealed TRPC6 and angiotensin II-regulating mechanisms play a critical role in regulating the barrier function of the slit diaphragm. In this review, recent investigations on the regulation of the slit diaphragm function were reviewed, and a strategy for the establishment of a novel therapy for proteinuria was proposed.
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Affiliation(s)
- Hiroshi Kawachi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan.
| | - Yoshiyasu Fukusumi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan
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32
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VEGFR2 Blockade Improves Renal Damage in an Experimental Model of Type 2 Diabetic Nephropathy. J Clin Med 2020; 9:jcm9020302. [PMID: 31973092 PMCID: PMC7074274 DOI: 10.3390/jcm9020302] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 01/14/2020] [Accepted: 01/16/2020] [Indexed: 12/29/2022] Open
Abstract
The absence of optimal treatments for Diabetic Nephropathy (DN) highlights the importance of the search for novel therapeutic targets. The vascular endothelial growth factor receptor 2 (VEGFR2) pathway is activated in experimental and human DN, but the effects of its blockade in experimental models of DN is still controversial. Here, we test the effects of a therapeutic anti-VEGFR2 treatment, using a VEGFR2 kinase inhibitor, on the progression of renal damage in the BTBR ob/ob (leptin deficiency mutation) mice. This experimental diabetic model develops histological characteristics mimicking the key features of advanced human DN. A VEGFR2 pathway-activation blockade using the VEGFR2 kinase inhibitor SU5416, starting after kidney disease development, improves renal function, glomerular damage (mesangial matrix expansion and basement membrane thickening), tubulointerstitial inflammation and tubular atrophy, compared to untreated diabetic mice. The downstream mechanisms involved in these beneficial effects of VEGFR2 blockade include gene expression restoration of podocyte markers and downregulation of renal injury biomarkers and pro-inflammatory mediators. Several ligands can activate VEGFR2, including the canonical ligands VEGFs and GREMLIN. Activation of a GREMLIN/VEGFR2 pathway, but not other ligands, is correlated with renal damage progression in BTBR ob/ob diabetic mice. RNA sequencing analysis of GREMLIN-regulated genes confirm the modulation of proinflammatory genes and related-molecular pathways. Overall, these data show that a GREMLIN/VEGFR2 pathway activation is involved in diabetic kidney disease and could potentially be a novel therapeutic target in this clinical condition.
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Song Y, Liu W, Tang K, Zang J, Li D, Gao H. Mangiferin Alleviates Renal Interstitial Fibrosis in Streptozotocin-Induced Diabetic Mice through Regulating the PTEN/PI3K/Akt Signaling Pathway. J Diabetes Res 2020; 2020:9481720. [PMID: 32076626 PMCID: PMC7016412 DOI: 10.1155/2020/9481720] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/12/2019] [Accepted: 12/31/2019] [Indexed: 12/11/2022] Open
Abstract
Renal interstitial fibrosis is considered to be the typical manifestation of diabetic nephropathy (DN). Mangiferin has shown positive effect on the prevention or treatment of diabetes and its complications. The aim of this study was to explore the inhibitive effect and mechanism of mangiferin on renal interstitial fibrosis in diabetic mice. Streptozotocin- (STZ-) induced diabetic mice were treated with mangiferin (15, 30, and 60 mg/kg/d) for 4 weeks. The morphology of kidneys was observed by Masson's trichrome staining, and the biochemical parameters (fasting blood glucose (FBG), triglyceride (TG), total cholesterol (TC), blood urea nitrogen (BUN), serum creatinine (SCr), and urine protein) were determined by kits. In addition, the levels of inflammatory cytokines (tumor necrosis factor-α (TNF-α), interleukin- (IL-) 6, and IL-1β), antioxidant enzymes (SOD, CAT, and GSH-Px), MDA, and ROS were assessed. Furthermore, the expressions of fibronectin (FN), collagen I (Col I), and α-SMA were measured by immunohistochemistry. Regulations of TGF-β1 and the PTEN/PI3K/Akt pathway were detected by Western blotting. Treatment with mangiferin significantly ameliorated renal dysfunction in diabetic mice, as evidenced by the increase in body weight and decreases in FBG, TG, TC, BUN, SCr, urine protein, and the kidney to body weight ratio (KW/BW). Furthermore, mangiferin treatment prevented renal interstitial fibrosis evidenced by decreases in the positive expression of FN, Col I, and α-SMA, in comparison with morphological changes in the renal tissue. Meanwhile, mangiferin increased antioxidant enzymes, reduced the TNF-α, IL-6, and IL-1β, as well as MDA and ROS. Additionally, mangiferin administration also downregulated TGF-β1, upregulated PTEN, and decreased the phosphorylation of both PI3K and Akt. These findings demonstrate that mangiferin may reduce inflammation and oxidative stress in DN, thereby inhibiting the renal interstitial fibrosis by reducing the TGF-β1-mediated elevation of Col I, FN, and α-SMA through the PTEN/PI3K/Akt pathway.
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Affiliation(s)
- Yanyan Song
- Department of Nephrology, The Second Hospital of Jilin University, No. 218 Ziqiang Street, Changchun 130021, China
| | - Wei Liu
- Department of Spinal Surgery, The First Hospital of Jilin University, No. 71 Xinmin Street, Changchun, Jilin 130021, China
| | - Ke Tang
- Department of Electrical Diagnosis, The Second Hospital of Jilin University, No. 218 Ziqiang Street, Changchun 130021, China
| | - Junting Zang
- Department of Bone and Joint Surgery, The First Hospital of Jilin University, No. 71 Xinmin Street, Changchun 130021, China
| | - Dong Li
- Department of Immunology, College of Basic Medical Sciences, Jilin University, No. 126 Xinmin Avenue, Changchun, Jilin Province 130021, China
| | - Hang Gao
- Department of Bone and Joint Surgery, The First Hospital of Jilin University, No. 71 Xinmin Street, Changchun 130021, China
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Wang J, Fu D, Senouthai S, You Y. Critical roles of PI3K/Akt/NF‑κB survival axis in angiotensin II‑induced podocyte injury. Mol Med Rep 2019; 20:5134-5144. [PMID: 31638199 PMCID: PMC6854545 DOI: 10.3892/mmr.2019.10733] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 08/30/2019] [Indexed: 12/12/2022] Open
Abstract
Numerous studies have reported that angiotensin (Ang) II, nephrin, and podocin serve pivotal roles in podocyte injury, and thus can lead to the occurrence of proteinuria and the progression of kidney diseases. This study aimed to investigate the effects of Ang II on the production of nephrin and podocin, and their relationship with podocyte injury. We also aimed to determine whether nephrin, podocin and caspase-9 production depends on the PI3K/Akt/nuclear factor (NF)-κB signaling pathway in cultured mouse podocytes. We treated mouse podocytes with different doses of Ang II (10−9, 10−8, 10−7 and 10−6 mol/l) for 12, 24, and 48 h to analyse cell viability, and at 10−6 mol/l Ang II for 12, 24, and 48 h to evaluate cell apoptosis. Cells were treated with 10−6 mol/l of Ang II and/or LY294002 (inhibitor of Akt) or 740Y-P (activator of PI3K) for 48 h to detect Akt, phosphorylated (phospho)-Akt, p65 NF-κB, and phospho-p65 NF-κB, nephrin, podocin and caspase-9 expression, and podocyte apoptosis. Treatment with Ang II suppressed the viability and promoted the apoptosis of podocytes in a dose- and time-dependent manner. Ang II decreased phospho-Akt, phospho-p65 NF-κB, nephrin, and podocin and increased caspase-9 expression, while podocyte apoptosis was promoted. LY294002 further enhanced Ang II-induced downregulation of Akt and p65 NF-κB activation, as well as upregulation of caspase-9 mRNA and protein, and promoted the apoptosis of podocytes. Of note, 740Y-P restored Ang II-induced downregulation of Akt and p65 NF-κB activation, and upregulation of caspase-9, and decreased podocyte apoptosis. Interestingly, LY294002 and 740Y-P were determined to have no notable effects on the expression of nephrin and podocin. The data suggested that Ang II could regulate the expression of nephrin, podocin and caspase-9. Collectively, our findings suggested that the PI3K/Akt/NF-κB survival axis may serve a pivotal role in podocyte injury.
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Affiliation(s)
- Junjie Wang
- Department of Nephrology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, Guangxi Zhuang Autonomous Region 533000, P.R. China
| | - Dongdong Fu
- Department of Nephrology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, Guangxi Zhuang Autonomous Region 533000, P.R. China
| | - Soulixay Senouthai
- Department of Nephrology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, Guangxi Zhuang Autonomous Region 533000, P.R. China
| | - Yanwu You
- Department of Nephrology, The Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, Guangxi Zhuang Autonomous Region 533000, P.R. China
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Huang QY, Lai XN, Qian XL, Lv LC, Li J, Duan J, Xiao XH, Xiong LX. Cdc42: A Novel Regulator of Insulin Secretion and Diabetes-Associated Diseases. Int J Mol Sci 2019; 20:ijms20010179. [PMID: 30621321 PMCID: PMC6337499 DOI: 10.3390/ijms20010179] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 12/26/2018] [Accepted: 12/29/2018] [Indexed: 02/07/2023] Open
Abstract
Cdc42, a member of the Rho GTPases family, is involved in the regulation of several cellular functions including cell cycle progression, survival, transcription, actin cytoskeleton organization and membrane trafficking. Diabetes is a chronic and metabolic disease, characterized as glycometabolism disorder induced by insulin deficiency related to β cell dysfunction and peripheral insulin resistance (IR). Diabetes could cause many complications including diabetic nephropathy (DN), diabetic retinopathy and diabetic foot. Furthermore, hyperglycemia can promote tumor progression and increase the risk of malignant cancers. In this review, we summarized the regulation of Cdc42 in insulin secretion and diabetes-associated diseases. Organized researches indicate that Cdc42 is a crucial member during the progression of diabetes, and Cdc42 not only participates in the process of insulin synthesis but also regulates the insulin granule mobilization and cell membrane exocytosis via activating a series of downstream factors. Besides, several studies have demonstrated Cdc42 as participating in the pathogenesis of IR and DN and even contributing to promote cancer cell proliferation, survival, invasion, migration, and metastasis under hyperglycemia. Through the current review, we hope to cast light on the mechanism of Cdc42 in diabetes and associated diseases and provide new ideas for clinical diagnosis, treatment, and prevention.
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Affiliation(s)
- Qi-Yuan Huang
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
| | - Xing-Ning Lai
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
| | - Xian-Ling Qian
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
| | - Lin-Chen Lv
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
| | - Jun Li
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
| | - Jing Duan
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
| | - Xing-Hua Xiao
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
| | - Li-Xia Xiong
- Department of Pathophysiology, Medical College, Nanchang University, Jiangxi Province Key Laboratory of Tumor Pathogenesis and Molecular Pathology, 461 Bayi Road, Nanchang 330006, China.
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Ha TS, Ha DS. Ginseng Total Saponin Attenuates Podocyte Apoptosis Induced by Diabetic Conditions Through the Recovery of CD2-Associated Protein. J Med Food 2019; 22:170-177. [PMID: 30601089 DOI: 10.1089/jmf.2017.4139] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
CD2-associated protein (CD2AP), an adaptor protein, plays several important roles in podocyte function, linking slit diaphragms to actin-based cytoskeleton and sending survival signals. Here, we investigated whether ginseng total saponin (GTS) had a protective role in the changes of podocyte CD2AP protein and podocyte apoptosis under in vitro diabetic conditions. Conditionally immortalized mouse podocytes cultured with normal glucose (5 mM) or high glucose (30 mM) and with or without advanced glycosylation end products were treated with GTS. We found that CD2AP co-localized with the F-actin fibers in podocyte cytoplasm using confocal imaging; however, diabetic conditions caused the podocytes to diminish and conglomerate CD2AP stainings in the peripheral cytoplasm, which were recovered by GTS. Diabetic conditions also suppressed CD2AP protein levels at 6 and 24 h in western blotting. These phenotypical changes of CD2AP protein were mitigated by GTS. Diabetic conditions also induced podocyte apoptosis at 24 h, which were attenuated by GTS. These findings provide a novel mechanism that diabetic conditions induce quantitative and qualitative changes of podocyte CD2AP protein and apoptosis, which would be restored by GTS.
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Affiliation(s)
- Tae-Sun Ha
- 1 Department of Pediatrics, College of Medicine, Chungbuk National University, Cheongju, Korea.,2 Department of Pediatrics, Chungbuk National University Hospital, Cheongju, Korea
| | - Dong-Soo Ha
- 3 Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
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Abstract
Phosphoinositides (PIs) play pivotal roles in the regulation of many biological processes. The quality and quantity of PIs is regulated in time and space by the activity of PI kinases and PI phosphatases. The number of PI-metabolizing enzymes exceeds the number of PIs with, in many cases, more than one enzyme controlling the same biochemical step. This would suggest that the PI system has an intrinsic ability to buffer and compensate for the absence of a specific enzymatic activity. However, there are several examples of severe inherited human diseases caused by mutations in one of the PI enzymes, although other enzymes with the same activity are fully functional. The kidney depends strictly on PIs for physiological processes, such as cell polarization, filtration, solute reabsorption, and signal transduction. Indeed, alteration of the PI system in the kidney very often results in pathological conditions, both inherited and acquired. Most of the knowledge of the roles that PIs play in the kidney comes from the study of KO animal models for genes encoding PI enzymes and from the study of human genetic diseases, such as Lowe syndrome/Dent disease 2 and Joubert syndrome, caused by mutations in the genes encoding the PI phosphatases, OCRL and INPP5E, respectively.
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Affiliation(s)
- Leopoldo Staiano
- Telethon Institute of Genetics and Medicine, 80078 Pozzuoli, Italy
| | - Maria Antonietta De Matteis
- Telethon Institute of Genetics and Medicine, 80078 Pozzuoli, Italy .,University of Naples Federico II, 80131 Naples, Italy
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Min SY, Ha DS, Ha TS. Puromycin aminonucleoside triggers apoptosis in podocytes by inducing endoplasmic reticulum stress. Kidney Res Clin Pract 2018; 37:210-221. [PMID: 30254845 PMCID: PMC6147198 DOI: 10.23876/j.krcp.2018.37.3.210] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 05/14/2018] [Accepted: 06/26/2018] [Indexed: 01/13/2023] Open
Abstract
Background Puromycin aminonucleoside (PAN) is a known podocytotoxin. PAN-induced nephrosis is a widely used animal model for studying human idiopathic nephrotic syndrome. Abnormal protein accumulation associated with podocyte-specific endoplasmic reticulum (ER) stress damages cells structurally and functionally, which in turn induces apoptosis and severe proteinuria. In the present study, we investigated the effect of PAN on ER stress and apoptosis in podocytes in vitro. Methods Mouse podocytes were cultured and treated with various concentrations of PAN. ER stress markers were then evaluated by western blotting, and apoptosis was evaluated by fluorescence-activated cell sorting (FACS) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays. Results PAN treatment increased ER stress markers such as activating transcription factor (ATF) 6α and caspase-12 in a dose-dependent manner at 12 and 24 hours, respectively. These markers were reduced by chemical chaperones, such as sodium 4-phenylbutyric acid and tauroursodeoxycholic acid. PAN treatment also increased 78 kD glucose-regulated protein (GRP78)/binding immunoglobulin protein (BiP) at the earlier stage of 12 hours. PAN significantly induced podocyte apoptosis in concentration- and time-dependent manners, as seen using FACS and TUNEL assays. This result was improved by Nox4 siRNA, ATF6 siRNA, and chemical chaperones. LY294002, a PI3-kinase inhibitor, significantly boosted ER stress and apoptosis. PAN-induced ER stress increased oxidative stress and subsequently induced apoptosis, and could be mitigated by inhibition of PI3-kinase signaling. Conclusion Our findings suggest that PAN induces ER stress in podocytes mainly through the GRP78/BiP, ATF6α, and caspase-12 pathways, which trigger apoptosis via induction of oxidative stress. This stress is mitigated by inhibiting PI3-kinase signaling.
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Affiliation(s)
- Seo-Yun Min
- Department of Pediatrics, Chungbuk National University College of Medicine, Cheongju, Korea
| | - Dong-Soo Ha
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Tae-Sun Ha
- Department of Pediatrics, Chungbuk National University College of Medicine, Cheongju, Korea
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Yu SMW, Nissaisorakarn P, Husain I, Jim B. Proteinuric Kidney Diseases: A Podocyte's Slit Diaphragm and Cytoskeleton Approach. Front Med (Lausanne) 2018; 5:221. [PMID: 30255020 PMCID: PMC6141722 DOI: 10.3389/fmed.2018.00221] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/18/2018] [Indexed: 01/19/2023] Open
Abstract
Proteinuric kidney diseases are a group of disorders with diverse pathological mechanisms associated with significant losses of protein in the urine. The glomerular filtration barrier (GFB), comprised of the three important layers, the fenestrated glomerular endothelium, the glomerular basement membrane (GBM), and the podocyte, dictates that disruption of any one of these structures should lead to proteinuric disease. Podocytes, in particular, have long been considered as the final gatekeeper of the GFB. This specialized visceral epithelial cell contains a complex framework of cytoskeletons forming foot processes and mediate important cell signaling to maintain podocyte health. In this review, we will focus on slit diaphragm proteins such as nephrin, podocin, TRPC6/5, as well as cytoskeletal proteins Rho/small GTPases and synaptopodin and their respective roles in participating in the pathogenesis of proteinuric kidney diseases. Furthermore, we will summarize the potential therapeutic options targeting the podocyte to treat this group of kidney diseases.
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Affiliation(s)
- Samuel Mon-Wei Yu
- Department of Medicine, Jacobi Medical Center, Bronx, NY, United States
| | | | - Irma Husain
- Department of Medicine, James J. Peters VA Medical Center, Bronx, NY, United States
| | - Belinda Jim
- Department of Medicine, Jacobi Medical Center, Bronx, NY, United States.,Renal Division, Jacobi Medical Center, Bronx, NY, United States
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The protective effect of the EP2 receptor on TGF-β1 induced podocyte injury via the PI3K / Akt signaling pathway. PLoS One 2018; 13:e0197158. [PMID: 29746568 PMCID: PMC5945042 DOI: 10.1371/journal.pone.0197158] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 04/27/2018] [Indexed: 12/17/2022] Open
Abstract
Transforming growth factor β1 (TGF-β1) plays a central role in chronic kidney diseases. TGF-β1 induction causes podocyte injury, which results in proteinuria and renal failure. However, the effect of the prostaglandin E2 /E-prostanoid receptor (EP2) on TGF-β1-induced podocyte injury remains unknown. Previous studies have shown that phosphoinositide 3-OH kinase (PI3K)/Akt is widespread in cells, and is vital for the regulation of cell proliferation, differentiation, apoptosis and metabolism. In this study, we cultured immortalized mouse podocytes in vitro in different groups: control group; TGF-β1 (5ng/ml) group; EP2 agonist Butaprost treatment (10−7, 10−6, or 10-5mol/L) +TGF-β1 group; EP2 antagonist AH6809 treatment (10−7, 10−6, or 10-5mol / L) + TGF-β1 group. We found that compared with the control group, proliferation of podocytes in the TGF-β1 group significantly decreased and apoptosis increased. Expression of cAMP decreased, whereas PGE2 increased. Meanwhile, expressions of nephrin, podocin and CD2AP mRNA and protein were dramatically downregulated, activated caspase-3 was increased, and activated PI3K/Akt activity were depressed. Butaprost intervention promoted podocyte proliferation with reduced apoptosis. Conversely, AH6809 intervention led to opposite results (P<0.05). Our findings suggested that EP2 agonist protects podocytes by increasing expression of cAMP, which creates feedback of inhibiting PGE2 expression. This causes the interaction of nephrin, podocin and CD2AP resulting the inhibition of apoptosis induced by activation of the PI3K / Akt signaling pathway.
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Fukusumi Y, Zhang Y, Yamagishi R, Oda K, Watanabe T, Matsui K, Kawachi H. Nephrin-Binding Ephrin-B1 at the Slit Diaphragm Controls Podocyte Function through the JNK Pathway. J Am Soc Nephrol 2018; 29:1462-1474. [PMID: 29602834 DOI: 10.1681/asn.2017090993] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 02/13/2018] [Indexed: 11/03/2022] Open
Abstract
Background B-type ephrins are membrane-bound proteins that maintain tissue function in several organs. We previously reported that ephrin-B1 is localized at the slit diaphragm of glomerular podocytes. However, the function of ephrin-B1 at this location is unclear.Methods We analyzed the phenotype of podocyte-specific ephrin-B1 knockout mice and assessed the molecular association of ephrin-B1 and nephrin, a key molecule of the slit diaphragm, in HEK293 cells and rats with anti-nephrin antibody-induced nephropathy.Results Compared with controls, ephrin-B1 conditional knockout mice displayed altered podocyte morphology, disarrangement of the slit diaphragm molecules, and proteinuria. Ephrin-B1 expressed in HEK293 cells immunoprecipitated with nephrin, which required the basal regions of the extracellular domains of both proteins. Treatment of cells with an anti-nephrin antibody promoted the phosphorylation of nephrin and ephrin-B1. However, phosphorylation of ephrin-B1 did not occur in cells expressing a mutant nephrin lacking the ephrin-B1 binding site or in cells treated with an Src kinase inhibitor. The phosphorylation of ephrin-B1 enhanced the phosphorylation of nephrin and promoted the phosphorylation of c-Jun N-terminal kinase (JNK), which was required for ephrin-B1-promoted cell motility in wound-healing assays. Notably, phosphorylated JNK was detected in the glomeruli of control mice but not ephrin-B1 conditional knockout mice. In rats, the phosphorylation of ephrin-B1, JNK, and nephrin occurred in the early phase (24 hours) of anti-nephrin antibody-induced nephropathy.Conclusions Through interactions with nephrin, ephrin-B1 maintains the structure and barrier function of the slit diaphragm. Moreover, phosphorylation of ephrin-B1 and, consequently, JNK are involved in the development of podocyte injury.
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Affiliation(s)
- Yoshiyasu Fukusumi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Ying Zhang
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Ryohei Yamagishi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Kanako Oda
- Department of Comparative and Experimental Medicine, Brain Research Institute, Niigata University, Niigata, Japan
| | - Toru Watanabe
- Department of Pediatrics, Niigata City General Hospital, Niigata, Japan; and
| | - Katsuyuki Matsui
- Department of Internal Medicine IV, Teikyo University School of Medicine, Kawasaki, Japan
| | - Hiroshi Kawachi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan;
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Yu SMW, Bonventre JV. Acute Kidney Injury and Progression of Diabetic Kidney Disease. Adv Chronic Kidney Dis 2018; 25:166-180. [PMID: 29580581 DOI: 10.1053/j.ackd.2017.12.005] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 12/15/2017] [Accepted: 12/22/2017] [Indexed: 12/23/2022]
Abstract
Diabetic kidney disease, commonly termed diabetic nephropathy (DN), is the most common cause of end-stage kidney disease (ESKD) worldwide. The characteristic histopathology of DN includes glomerular basement membrane thickening, mesangial expansion, nodular glomerular sclerosis, and tubulointerstitial fibrosis. Diabetes is associated with a number of metabolic derangements, such as reactive oxygen species overproduction, hypoxic state, mitochondrial dysfunction, and inflammation. In the past few decades, our knowledge of DN has advanced considerably although much needs to be learned. The traditional paradigm of glomerulus-centered pathophysiology has expanded to the tubule-interstitium, the immune response and inflammation. Biomarkers of proximal tubule injury have been shown to correlate with DN progression, independent of traditional glomerular injury biomarkers such as albuminuria. In this review, we summarize mechanisms of increased susceptibility to acute kidney injury in diabetes mellitus and the roles played by many kidney cell types to facilitate maladaptive responses leading to chronic and end-stage kidney disease.
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Sagoo MK, Gnudi L. Diabetic nephropathy: Is there a role for oxidative stress? Free Radic Biol Med 2018; 116:50-63. [PMID: 29305106 DOI: 10.1016/j.freeradbiomed.2017.12.040] [Citation(s) in RCA: 130] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/27/2017] [Accepted: 12/31/2017] [Indexed: 01/06/2023]
Abstract
Oxidative stress has been implicated in the pathophysiology of diabetic nephropathy. Studies in experimental animal models of diabetes strongly implicate oxidant species as a major determinant in the pathophysiology of diabetic kidney disease. The translation, in the clinical setting, of these concepts have been quite disappointing, and new theories have challenged the concepts that oxidative stress per se plays a role in the pathophysiology of diabetic kidney disease. The concept of mitochondrial hormesis has been introduced to explain this apparent disconnect. Hormesis is intended as any cellular process that exhibits a biphasic response to exposure to increasing amounts of a substance or condition: specifically, in diabetic kidney disease, oxidant species may represent, at determined concentration, an essential and potentially protective factor. It could be postulated that excessive production or inhibition of oxidant species formation might result in an adverse phenotype. This review discusses the evidence underlying these two apparent contradicting concepts, with the aim to propose and speculate on potential mechanisms underlying the role of oxidant species in the pathophysiology of diabetic nephropathy and possibly open future more efficient therapies to be tested in the clinical settings.
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Affiliation(s)
- Manpreet K Sagoo
- School of Cardiovascular Medicine & Sciences, British Heart Foundation Centre of Research Excellence, Faculty of Life Sciences & Medicine, King's College London, 150 Stamford Street, London SE1 9NH, UK
| | - Luigi Gnudi
- School of Cardiovascular Medicine & Sciences, British Heart Foundation Centre of Research Excellence, Faculty of Life Sciences & Medicine, King's College London, 150 Stamford Street, London SE1 9NH, UK.
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Wasik AA, Lehtonen S. Glucose Transporters in Diabetic Kidney Disease-Friends or Foes? Front Endocrinol (Lausanne) 2018; 9:155. [PMID: 29686650 PMCID: PMC5900043 DOI: 10.3389/fendo.2018.00155] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 03/22/2018] [Indexed: 12/16/2022] Open
Abstract
Diabetic kidney disease (DKD) is a major microvascular complication of diabetes and a common cause of end-stage renal disease worldwide. DKD manifests as an increased urinary protein excretion (albuminuria). Multiple studies have shown that insulin resistance correlates with the development of albuminuria in non-diabetic and diabetic patients. There is also accumulating evidence that glomerular epithelial cells or podocytes are insulin sensitive and that insulin signaling in podocytes is essential for maintaining normal kidney function. At the cellular level, the mechanisms leading to the development of insulin resistance include mutations in the insulin receptor gene, impairments in the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway, or perturbations in the trafficking of glucose transporters (GLUTs), which mediate the uptake of glucose into cells. Podocytes express several GLUTs, including GLUT1, GLUT2, GLUT3, GLUT4, and GLUT8. Of these, the most studied ones are GLUT1 and GLUT4, both shown to be insulin responsive in podocytes. In the basal state, GLUT4 is preferentially located in perinuclear and cytosolic vesicular structures and to a lesser extent at the plasma membrane. After insulin stimulation, GLUT4 is sorted into GLUT4-containing vesicles (GCVs) that translocate to the plasma membrane. GCV trafficking consists of several steps, including approaching of the GCVs to the plasma membrane, tethering, and docking, after which the lipid bilayers of the GCVs and the plasma membrane fuse, delivering GLUT4 to the cell surface for glucose uptake into the cell. Studies have revealed novel molecular regulators of the GLUT trafficking in podocytes and unraveled unexpected roles for GLUT1 and GLUT4 in the development of DKD, summarized in this review. These findings pave the way for better understanding of the mechanistic pathways associated with the development and progression of DKD and aid in the development of new treatments for this devastating disease.
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Martin CE, Jones N. Nephrin Signaling in the Podocyte: An Updated View of Signal Regulation at the Slit Diaphragm and Beyond. Front Endocrinol (Lausanne) 2018; 9:302. [PMID: 29922234 PMCID: PMC5996060 DOI: 10.3389/fendo.2018.00302] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 05/22/2018] [Indexed: 12/11/2022] Open
Abstract
Podocytes are a major component of the glomerular blood filtration barrier, and alterations to the morphology of their unique actin-based foot processes (FP) are a common feature of kidney disease. Adjacent FP are connected by a specialized intercellular junction known as the slit diaphragm (SD), which serves as the ultimate barrier to regulate passage of macromolecules from the blood. While the link between SD dysfunction and reduced filtration selectivity has been recognized for nearly 50 years, our understanding of the underlying molecular circuitry began only 20 years ago, sparked by the identification of NPHS1, encoding the transmembrane protein nephrin. Nephrin not only functions as the core component of the extracellular SD filtration network but also as a signaling scaffold via interactions at its short intracellular region. Phospho-regulation of several conserved tyrosine residues in this region influences signal transduction pathways which control podocyte cell adhesion, shape, and survival, and emerging studies highlight roles for nephrin phospho-dynamics in mechanotransduction and endocytosis. The following review aims to summarize the last 5 years of advancement in our knowledge of how signaling centered at nephrin directs SD barrier formation and function. We further provide insight on promising frontiers in podocyte biology, which have implications for SD signaling in the healthy and diseased kidney.
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MicroRNA-25 inhibits high glucose-induced apoptosis in renal tubular epithelial cells via PTEN/AKT pathway. Biomed Pharmacother 2017; 96:471-479. [PMID: 29031207 DOI: 10.1016/j.biopha.2017.10.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 09/17/2017] [Accepted: 10/02/2017] [Indexed: 01/08/2023] Open
Abstract
Diabetic nephropathy (DN) has become the major cause of end-stage renal disease (ESRD). It has been demonstrated that apoptosis of renal tubular epithelial cells induced by hyperglycemia contributes to the pathogenesis of DN. Recent researches have corroborated the critical roles of microRNAs (miRNAs) in the apoptosis of various types of cells including renal tubular epithelial cells. However, the eff ; ;ect of miRNAs on the hyperglycemia-induced apoptosis of renal tubular epithelial cells remains unclear. The aim of this study is to explore the eff ; ;ect of miRNAs on the hyperglycemia-induced apoptosis of renal tubular epithelial cells and its molecular mechanism. Using a miRNA microarray, miRNAs putatively associated with DN were examined in renal biopsy tissue samples from DN patients and healthy controls. Validation analysis of miR-25 level in serum samples and renal biopsy tissue samples was performed using quantitative reverse transcription PCR (qRT-PCR). Then, gain- and loss- of function experiments were performed to determine the protective roles of miR-25 in high glucose-induced damage to renal tubular epithelial cells. Furthermore, the target gene of miR-25 and the downstream signaling pathway were also investigated. Microarray analysis and qRT-PCR revealed that miR-25 was significantly downregulated in renal biopsy tissue and serum samples from DN patients. We also observed that an inverse relationship between serum miR-25 level and proteinuria in DN patients. Meanwhile, miR-25 was decreased in human kidney (HK-2) cells subjected to HG treatment in a time dependent manner. Its overexpression reduced production of reactive oxygen species (ROS), suppressed cell apoptosis in HG-induced cell damage model, which was coupled with the decreased expression of cleaved caspase-3 and activity of caspase-3. Subsequent analyses demonstrated that phosphatase and tensin homolog deleted on chromosome ten (PTEN) was a direct and functional target of miR-25, which was validated by the dual luciferase reporter assay. Most importantly, the overexpression of PTEN effectively reversed the protective effects of miR-25 mimics on renal tubular epithelial cell injury. We also found that the anti-apoptotic effects of miR-25 are dependent on the activation of PTEN/Akt pathway. In addition, we observed that PTEN was upregulated in renal biopsy tissue samples from patients with DN, and an inverse relationship was found between PTEN and miR-25 expression, suggesting that miR-25 may exert its function through regulation of PTEN in DN. Taken together, our study proved that overexpression of miR-25 could ameliorate HG-induced oxidative stress and apoptosis in renal tubular epithelial cells through activation of PTEN/AKT pathway, suggesting that overexpression of miR-25 might provide a potential therapeutic approach for DN.
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Martin CE, Petersen KA, Aoudjit L, Tilak M, Eremina V, Hardy WR, Quaggin SE, Takano T, Jones N. ShcA Adaptor Protein Promotes Nephrin Endocytosis and Is Upregulated in Proteinuric Nephropathies. J Am Soc Nephrol 2017; 29:92-103. [PMID: 29018139 DOI: 10.1681/asn.2017030285] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 07/23/2017] [Indexed: 11/03/2022] Open
Abstract
Nephrin is a key structural component of the podocyte slit diaphragm, and proper expression of nephrin on the cell surface is critical to ensure integrity of the blood filtration barrier. Maintenance of nephrin within this unique cell junction has been proposed to require dynamic phosphorylation events and endocytic recycling, although the molecular mechanisms that control this interplay are poorly understood. Here, we investigated the possibility that the phosphotyrosine adaptor protein ShcA regulates nephrin turnover. Western blotting and immunostaining analysis confirmed that ShcA is expressed in podocytes. In immunoprecipitation and pulldown assays, ShcA, via its SH2 domain, was associated with several phosphorylated tyrosine residues on nephrin. Overexpression of ShcA promoted nephrin tyrosine phosphorylation and reduced nephrin signaling and cell surface expression in vitro In a rat model of reversible podocyte injury and proteinuria, phosphorylated nephrin temporally colocalized with endocytic structures coincident with upregulation of ShcA expression. In vivo biotinylation assays confirmed that nephrin expression decreased at the cell surface and correspondingly increased in the cytosol during the injury time course. Finally, immunostaining in kidney biopsy specimens demonstrated overexpression of ShcA in several human proteinuric kidney diseases compared with normal conditions. Our results suggest that increases in ShcA perturb nephrin phosphosignaling dynamics, leading to aberrant nephrin turnover and slit diaphragm disassembly.
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Affiliation(s)
- Claire E Martin
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Kelly A Petersen
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Lamine Aoudjit
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
| | - Manali Tilak
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Vera Eremina
- The Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada; and
| | - W Rod Hardy
- The Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada; and
| | - Susan E Quaggin
- The Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada; and.,Feinberg Cardiovascular Research Institute and Division of Nephrology and Hypertension, Northwestern University of Chicago, Illinois
| | - Tomoko Takano
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada
| | - Nina Jones
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada;
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Lee J, Koh A, Jeong H, Kim E, Ha TS, Saleem MA, Ryu SH. C1-Ten is a PTPase of nephrin, regulating podocyte hypertrophy through mTORC1 activation. Sci Rep 2017; 7:12346. [PMID: 28955049 PMCID: PMC5617844 DOI: 10.1038/s41598-017-12382-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 09/07/2017] [Indexed: 02/06/2023] Open
Abstract
Hypertrophy is a prominent feature of damaged podocytes in diabetic kidney disease (DKD). mTORC1 hyperactivation leads to podocyte hypertrophy, but the detailed mechanism of how mTORC1 activation occurs under pathological conditions is not completely known. Moreover, reduced nephrin tyrosine phosphorylation has been observed in podocytes under pathological conditions, but the molecular mechanism linking nephrin phosphorylation and pathology is unclear so far. In this study, we observed a significant increase in C1-Ten level in diabetic kidney and in high glucose-induced damaged podocytes. C1-Ten acts as a protein tyrosine phosphatase (PTPase) at the nephrin-PI3K binding site and renders PI3K for IRS-1, thereby activating mTORC1. Furthermore, C1-Ten causes podocyte hypertrophy and proteinuria by increasing mTORC1 activity in vitro and in vivo. These findings demonstrate the relationship between nephrin dephosphorylation and the mTORC1 pathway, mediated by C1-Ten PTPase activity. We suggest that C1-Ten contributes to the pathogenesis of DKD by inducing podocyte hypertrophy under high glucose conditions.
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Affiliation(s)
- Jiyoun Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Ara Koh
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Heeyoon Jeong
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Eui Kim
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Tae-Sun Ha
- Department of Pediatrics, College of Medicine, Chungbuk National University, Cheongju, 28644, Republic of Korea
| | - Moin A Saleem
- Academic and Children's Renal Unit, University of Bristol, Learning and Research, Southmead Hospital, Bristol, BS10 5NB, UK
| | - Sung Ho Ryu
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea.
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ARF6 mediates nephrin tyrosine phosphorylation-induced podocyte cellular dynamics. PLoS One 2017; 12:e0184575. [PMID: 28880939 PMCID: PMC5589247 DOI: 10.1371/journal.pone.0184575] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 08/26/2017] [Indexed: 01/10/2023] Open
Abstract
ADP-ribosylation factor 6 (ARF6) is a small GTPase necessary for regulating cellular structure, motility, and vesicle trafficking. In several cellular systems, ARF6 was shown to regulate actin dynamics in coordination with Rac1, a Rho small GTPase. We examined the function of ARF6 in the kidney podocyte because Rac1 was implicated in kidney diseases involving this cell. We found that ARF6 expression was enriched in human podocytes and that it modulated podocyte cytoskeletal dynamics through a functional interaction with nephrin, an intercellular junction protein necessary for podocyte injury-induced signaling requiring activation by tyrosine phosphorylation of its cytoplasmic domain. ARF6 was necessary for nephrin activation-induced ruffling and focal adhesion turnover, possibly by altering Rac1 activity. In podocyte-specific Arf6 (ARF6_PodKO) knockout mice, ARF6 deficiency did not result in a spontaneous kidney developmental phenotype or proteinuria after aging. However, ARF6_PodKO mice exhibited distinct phenotypes in two in vivo glomerular injury models. In the protamine sulfate perfusion model, which induced acute podocyte effacement, ARF6_PodKO mice were protected from podocyte effacement. In the nephrotoxic serum nephritis model, which induced immune-complex mediated injury, ARF6_PodKO mice exhibited aggravated proteinuria. Together, these observations suggest that while ARF6 is necessary for nephrin tyrosine phosphorylation-induced cytoskeletal dynamics in cultured podocytes, ARF6 has pleotropic podocyte roles in vivo, where glomerular injury-specific mechanisms might activate distinct signaling pathways that dictate whether ARF6 activity is beneficial or deleterious for maintaining the integrity of the glomerular filtration barrier.
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