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Gujarati NA, Chow AK, Mallipattu SK. Central role of podocytes in mediating cellular cross talk in glomerular health and disease. Am J Physiol Renal Physiol 2024; 326:F313-F325. [PMID: 38205544 PMCID: PMC11207540 DOI: 10.1152/ajprenal.00328.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/20/2023] [Accepted: 12/20/2023] [Indexed: 01/12/2024] Open
Abstract
Podocytes are highly specialized epithelial cells that surround the capillaries of the glomeruli in the kidney. Together with the glomerular endothelial cells, these postmitotic cells are responsible for regulating filtrate from the circulating blood with their organized network of interdigitating foot processes that wrap around the glomerular basement membrane. Although podocyte injury and subsequent loss is the hallmark of many glomerular diseases, recent evidence suggests that the cell-cell communication between podocytes and other glomerular and nonglomerular cells is critical for the development and progression of kidney disease. In this review, we highlight these key cellular pathways of communication and how they might be a potential target for therapy in glomerular disease. We also postulate that podocytes might serve as a central hub for communication in the kidney under basal conditions and in response to cellular stress, which may have implications for the development and progression of glomerular diseases.
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Affiliation(s)
- Nehaben A Gujarati
- Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, New York, United States
| | - Andrew K Chow
- Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, New York, United States
| | - Sandeep K Mallipattu
- Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, New York, United States
- Renal Section, Northport Veterans Affairs Medical Center, Northport, New York, United States
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2
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Lizotte F, Rousseau M, Denhez B, Lévesque D, Guay A, Liu H, Moreau J, Higgins S, Sabbagh R, Susztak K, Boisvert FM, Côté AM, Geraldes P. Deletion of protein tyrosine phosphatase SHP-1 restores SUMOylation of podocin and reverses the progression of diabetic kidney disease. Kidney Int 2023; 104:787-802. [PMID: 37507049 DOI: 10.1016/j.kint.2023.06.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 06/03/2023] [Accepted: 06/29/2023] [Indexed: 07/30/2023]
Abstract
Both clinical and experimental data suggest that podocyte injury is involved in the onset and progression of diabetic kidney disease (DKD). Although the mechanisms underlying the development of podocyte loss are not completely understood, critical structural proteins such as podocin play a major role in podocyte survival and function. We have reported that the protein tyrosine phosphatase SHP-1 expression increased in podocytes of diabetic mice and glomeruli of patients with diabetes. However, the in vivo contribution of SHP-1 in podocytes is unknown. Conditional podocyte-specific SHP-1-deficient mice (Podo-SHP-1-/-) were generated to evaluate the impact of SHP-1 deletion at four weeks of age (early) prior to the onset of diabetes and after 20 weeks (late) of diabetes (DM; Ins2+/C96Y) on kidney function (albuminuria and glomerular filtration rate) and kidney pathology. Ablation of the SHP-1 gene specifically in podocytes prevented and even reversed the elevated albumin/creatinine ratio, glomerular filtration rate progression, mesangial cell expansion, glomerular hypertrophy, glomerular basement membrane thickening and podocyte foot process effacement induced by diabetes. Moreover, podocyte-specific deletion of SHP-1 at an early and late stage prevented diabetes-induced expression of collagen IV, fibronectin, transforming growth factor-β, transforming protein RhoA, and serine/threonine kinase ROCK1, whereas it restored nephrin, podocin and cation channel TRPC6 expression. Mass spectrometry analysis revealed that SHP-1 reduced SUMO2 post-translational modification of podocin while podocyte-specific deletion of SHP-1 preserved slit diaphragm protein complexes in the diabetic context. Thus, our data uncovered a new role of SHP-1 in the regulation of cytoskeleton dynamics and slit diaphragm protein expression/stability, and its inhibition preserved podocyte function preventing DKD progression.
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Affiliation(s)
- Farah Lizotte
- Research Center of the Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Marina Rousseau
- Research Center of the Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Benoit Denhez
- Research Center of the Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Dominique Lévesque
- Department of Immunology and Cell Biology, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Andréanne Guay
- Research Center of the Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - HongBo Liu
- Renal, Electrolyte, and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Penn/CHOP Kidney Innovation Center, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Genetics Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Julie Moreau
- Research Center of the Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Sarah Higgins
- Division of Nephrology, Department of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Robert Sabbagh
- Department of Surgery, Université de Sherbrooke, Québec, Canada
| | - Katalin Susztak
- Renal, Electrolyte, and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Penn/CHOP Kidney Innovation Center, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Genetics Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | - Anne Marie Côté
- Research Center of the Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Division of Nephrology, Department of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Pedro Geraldes
- Research Center of the Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Division of Endocrinology, Department of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada.
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3
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Ye Q, Lan B, Liu H, Persson PB, Lai EY, Mao J. A critical role of the podocyte cytoskeleton in the pathogenesis of glomerular proteinuria and autoimmune podocytopathies. Acta Physiol (Oxf) 2022; 235:e13850. [PMID: 35716094 DOI: 10.1111/apha.13850] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 04/23/2022] [Accepted: 06/13/2022] [Indexed: 01/19/2023]
Abstract
Selective glomerular filtration relies on the membrane separating the glomerular arterioles from the Bowman space. As a major component of the glomerular filtration barrier, podocytes form foot processes by the actin cytoskeleton, which dynamically adjusts in response to environmental changes to maintain filtration barrier integrity. The slit diaphragms bridge the filtration slits between neighboring foot processes and act as signaling hubs interacting with the actin cytoskeleton. Focal adhesions relay signals to regulate actin dynamics while allowing podocyte adherence to the basement membrane. Mutations in actin regulatory and signaling proteins may disrupt the actin cytoskeleton, resulting in foot process retraction, effacement, and proteinuria. Large-scale gene expression profiling platforms, transgenic animal models, and other in vivo gene delivery methods now enhance our understanding of the interactions among podocyte focal adhesions, slit diaphragms, and actin dynamics. In addition, our team found that at least 66% of idiopathic nephrotic syndrome (INS) children have podocyte autoantibodies, which was defined as a new disease subgroup-, autoimmune podocytopathies. This review outlines the pathophysiological mechanisms of podocyte cytoskeleton protein interactions in proteinuria and glomerular podocytopathy.
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Affiliation(s)
- Qing Ye
- Department of Clinical Laboratory, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, National Children's Regional Medical Center, Hangzhou, China
| | - Bing Lan
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, National Children's Regional Medical Center, Hangzhou, China
| | - Huihui Liu
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, National Children's Regional Medical Center, Hangzhou, China
| | - Pontus B Persson
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Translational Physiology, Berlin, Germany
| | - En Yin Lai
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Translational Physiology, Berlin, Germany.,Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China
| | - Jianhua Mao
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, National Children's Regional Medical Center, Hangzhou, China
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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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5
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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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6
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Lepa C, Möller-Kerutt A, Stölting M, Picciotto C, Eddy ML, Butt E, Kerjaschki D, Korb-Pap A, Vollenbröker B, Weide T, George B, Kremerskothen J, Pavenstädt H. LIM and SH3 protein 1 (LASP-1): A novel link between the slit membrane and actin cytoskeleton dynamics in podocytes. FASEB J 2020; 34:5453-5464. [PMID: 32086849 DOI: 10.1096/fj.201901443r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 01/27/2020] [Accepted: 02/11/2020] [Indexed: 02/03/2023]
Abstract
The foot processes of podocytes exhibit a dynamic actin cytoskeleton, which maintains their complex cell structure and antagonizes the elastic forces of the glomerular capillary. Interdigitating secondary foot processes form a highly selective filter for proteins in the kidney, the slit membrane. Knockdown of slit membrane components such as Nephrin or Neph1 and cytoskeletal adaptor proteins such as CD2AP in mice leads to breakdown of the filtration barrier with foot process effacement, proteinuria, and early death of the mice. Less is known about the crosstalk between the slit membrane-associated proteins and cytoskeletal components inside the podocyte foot processes. Our study shows that LASP-1, an actin-binding protein, is highly expressed in podocytes. Electron microscopy studies demonstrate that LASP-1 is found at the slit membrane suggesting a role in anchoring slit membrane components to the actin cytoskeleton. Live cell imaging experiments with transfected podocytes reveal that LASP-1 is either part of a highly dynamic granular complex or a static, actin cytoskeleton-bound protein. We identify CD2AP as a novel LASP-1 binding partner that regulates its association with the actin cytoskeleton. Activation of the renin-angiotensin-aldosterone system, which is crucial for podocyte function, leads to phosphorylation and altered localization of LASP-1. In vivo studies using the Drosophila nephrocyte model indicate that Lasp is necessary for the slit membrane integrity and functional filtration.
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Affiliation(s)
- Carolin Lepa
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Annika Möller-Kerutt
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Miriam Stölting
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Cara Picciotto
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Mee-Ling Eddy
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Elke Butt
- Institutfür Experimentelle Biomedizin II, Klinikum der Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Dontscho Kerjaschki
- Klinisches Institut für Pathologie, Medizinische Universität Wien, Wien, Austria
| | - Adelheid Korb-Pap
- Institut für Experimentelle Muskuloskelettale Medizin, Universitätsklinikum Münster, Münster, Germany
| | - Beate Vollenbröker
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Thomas Weide
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Britta George
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Joachim Kremerskothen
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
| | - Hermann Pavenstädt
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Münster, Germany
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Rachubik P, Piwkowska A. The role of vasodilator‐stimulated phosphoprotein in podocyte functioning. Cell Biol Int 2019; 43:1092-1101. [DOI: 10.1002/cbin.11149] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 04/06/2019] [Indexed: 12/20/2022]
Affiliation(s)
- Patrycja Rachubik
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research CentrePolish Academy of Sciences Wita Stwosza 63, 80‐308 Gdańsk Poland
| | - Agnieszka Piwkowska
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research CentrePolish Academy of Sciences Wita Stwosza 63, 80‐308 Gdańsk Poland
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8
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Nihalani D, Solanki AK, Arif E, Srivastava P, Rahman B, Zuo X, Dang Y, Fogelgren B, Fermin D, Gillies CE, Sampson MG, Lipschutz JH. Disruption of the exocyst induces podocyte loss and dysfunction. J Biol Chem 2019; 294:10104-10119. [PMID: 31073028 PMCID: PMC6664173 DOI: 10.1074/jbc.ra119.008362] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/06/2019] [Indexed: 11/06/2022] Open
Abstract
Although the slit diaphragm proteins in podocytes are uniquely organized to maintain glomerular filtration assembly and function, little is known about the underlying mechanisms that participate in trafficking these proteins to the correct location for development and homeostasis. Identifying these mechanisms will likely provide novel targets for therapeutic intervention to preserve podocyte function following glomerular injury. Analysis of structural variation in cases of human nephrotic syndrome identified rare heterozygous deletions of EXOC4 in two patients. This suggested that disruption of the highly-conserved eight-protein exocyst trafficking complex could have a role in podocyte dysfunction. Indeed, mRNA profiling of injured podocytes identified significant exocyst down-regulation. To test the hypothesis that the exocyst is centrally involved in podocyte development/function, we generated homozygous podocyte-specific Exoc5 (a central exocyst component that interacts with Exoc4) knockout mice that showed massive proteinuria and died within 4 weeks of birth. Histological and ultrastructural analysis of these mice showed severe glomerular defects with increased fibrosis, proteinaceous casts, effaced podocytes, and loss of the slit diaphragm. Immunofluorescence analysis revealed that Neph1 and Nephrin, major slit diaphragm constituents, were mislocalized and/or lost. mRNA profiling of Exoc5 knockdown podocytes showed that vesicular trafficking was the most affected cellular event. Mapping of signaling pathways and Western blot analysis revealed significant up-regulation of the mitogen-activated protein kinase and transforming growth factor-β pathways in Exoc5 knockdown podocytes and in the glomeruli of podocyte-specific Exoc5 KO mice. Based on these data, we propose that exocyst-based mechanisms regulate Neph1 and Nephrin signaling and trafficking, and thus podocyte development and function.
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Affiliation(s)
- Deepak Nihalani
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425,
| | - Ashish K Solanki
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ehtesham Arif
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Pankaj Srivastava
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Bushra Rahman
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Xiaofeng Zuo
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Yujing Dang
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ben Fogelgren
- the Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | | | | | - Matthew G Sampson
- the Department of Pediatrics-Nephrology and.,Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Joshua H Lipschutz
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425.,the Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401
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9
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Dlugos CP, Picciotto C, Lepa C, Krakow M, Stöber A, Eddy ML, Weide T, Jeibmann A, P Krahn M, Van Marck V, Klingauf J, Ricker A, Wedlich-Söldner R, Pavenstädt H, Klämbt C, George B. Nephrin Signaling Results in Integrin β1 Activation. J Am Soc Nephrol 2019; 30:1006-1019. [PMID: 31097607 DOI: 10.1681/asn.2018040362] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 03/18/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Patients with certain mutations in the gene encoding the slit diaphragm protein Nephrin fail to develop functional slit diaphragms and display severe proteinuria. Many adult-onset glomerulopathies also feature alterations in Nephrin expression and function. Nephrin signals from the podocyte slit diaphragm to the Actin cytoskeleton by recruiting proteins that can interact with C3G, a guanine nucleotide exchange factor of the small GTPase Rap1. Because Rap activity affects formation of focal adhesions, we hypothesized that Nephrin transmits signals to the Integrin receptor complex, which mediates podocyte adhesion to the extracellular matrix. METHODS To investigate Nephrin's role in transmitting signals to the Integrin receptor complex, we conducted genetic studies in Drosophila nephrocytes and validated findings from Drosophila in a cultured human podocyte model. RESULTS Drosophila nephrocytes form a slit diaphragm-like filtration barrier and express the Nephrin ortholog Sticks and stones (Sns). A genetic screen identified c3g as necessary for nephrocyte function. In vivo, nephrocyte-specific gene silencing of sns or c3g compromised nephrocyte filtration and caused nephrocyte diaphragm defects. Nephrocytes with impaired Sns or C3G expression displayed an altered localization of Integrin and the Integrin-associated protein Talin. Furthermore, gene silencing of c3g partly rescued nephrocyte diaphragm defects of an sns overexpression phenotype, pointing to genetic interaction of sns and c3g in nephrocytes. We also found that activated Nephrin recruited phosphorylated C3G and resulted in activation of Integrin β1 in cultured podocytes. CONCLUSIONS Our findings suggest that Nephrin can mediate a signaling pathway that results in activation of Integrin β1 at focal adhesions, which may affect podocyte attachment to the extracellular matrix.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - Christian Klämbt
- Neurobiology, Westfälische-Wilhelms University Münster, Münster, Germany
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10
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Kim DY, Kang MK, Lee EJ, Kim YH, Oh H, Kang YH. Eucalyptol Inhibits Advanced Glycation End Products-Induced Disruption of Podocyte Slit Junctions by Suppressing Rage-Erk-C-Myc Signaling Pathway. Mol Nutr Food Res 2018; 62:e1800302. [PMID: 29987888 DOI: 10.1002/mnfr.201800302] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 05/28/2018] [Indexed: 02/06/2023]
Abstract
SCOPE The maintenance of interpodocyte slit diaphragm is critical in the sieving function of glomerular filtration barrier. Eucalyptol is a natural constituent in aromatic plants with antioxidant properties. This study investigates whether and how eucalyptol inhibits podocyte slit diaphragm malfunction in glucose-exposed podocytes and diabetic mouse kidneys. METHODS AND RESULTS Podocytes were incubated in media containing 33 mm glucose with 1-20 μm eucalyptol. The in vivo model employed db/db mice orally administrated with 10 mg kg-1 eucalyptol. Nontoxic eucalyptol enhanced podocyte expression of nephrin, podocin, FAT-1, CD2AP, and α-actinin-4 diminished by glucose. Oral administration of eucalyptol augmented the induction of the slit diaphragm proteins, α-actinin-4, and integrin β1 in diabetic kidneys, and ameliorated glomerular fibrosis and foot process effacement. Eucalyptol counteracted the receptor of advanced glycation end products (RAGE) induction in podocytes with glucose or AGE-BSA, and elevated the reduction of the slit diaphragm proteins by AGE-BSA. Eucalyptol attenuated the RAGE induction and AGE accumulation in diabetic kidneys. The blockade of ERK-c-Myc signaling enhanced the nephrin and CD2AP expression downregulated in AGE-exposed podocytes. These results indicate that eucalyptol blocked glucose-induced AGE-RAGE axis and podocyte injury through disturbing RAGE-ERK-c-Myc signaling. CONCLUSION Eucalyptol may be a potent agent antagonizing diabetes-associated malformation of interpodocyte slit junction and podocyte actin cytoskeleton.
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Affiliation(s)
- Dong Yeon Kim
- Department of Food Science and Nutrition, Hallym University, Chuncheon, Kangwon-do, 24252, Korea
| | - Min-Kyung Kang
- Department of Food Science and Nutrition, Hallym University, Chuncheon, Kangwon-do, 24252, Korea
| | - Eun-Jung Lee
- Department of Food Science and Nutrition, Hallym University, Chuncheon, Kangwon-do, 24252, Korea
| | - Yun-Ho Kim
- Department of Food Science and Nutrition, Hallym University, Chuncheon, Kangwon-do, 24252, Korea
| | - Hyeongjoo Oh
- Department of Food Science and Nutrition, Hallym University, Chuncheon, Kangwon-do, 24252, Korea
| | - Young-Hee Kang
- Department of Food Science and Nutrition, Hallym University, Chuncheon, Kangwon-do, 24252, Korea
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11
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Wu Z, Blessing NA, Simske JS, Bruggeman LA. Fyn-binding protein ADAP supports actin organization in podocytes. Physiol Rep 2018; 5. [PMID: 29192064 PMCID: PMC5727265 DOI: 10.14814/phy2.13483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 09/29/2017] [Indexed: 01/19/2023] Open
Abstract
The renal podocyte is central to the filtration function of the kidney that is dependent on maintaining both highly organized, branched cell structures forming foot processes, and a unique cell-cell junction, the slit diaphragm. Our recent studies investigating the developmental formation of the slit diaphragm identified a novel claudin family tetraspannin, TM4SF10, which is a binding partner for ADAP (also known as Fyn binding protein Fyb). To investigate the role of ADAP in podocyte function in relation to Fyn and TM4SF10, we examined ADAP knockout (KO) mice and podocytes. ADAP KO mice developed glomerular pathology that began as hyalinosis and progressed to glomerulosclerosis, with aged male animals developing low levels of albuminuria. Podocyte cell lines established from the KO mice had slower attachment kinetics compared to wild-type cells, although this did not affect the total number of attached cells nor the ability to form focal contacts. After attachment, the ADAP KO cells did not attain typical podocyte morphology, lacking the elaborate cell protrusions typical of wild-type podocytes, with the actin cytoskeleton forming circumferential stress fibers. The absence of ADAP did not alter Fyn levels nor were there differences between KO and wild-type podocytes in the reduction of Fyn activating phosphorylation events with puromycin aminonucleoside treatment. In the setting of endogenous TM4SF10 overexpression, the absence of ADAP altered the formation of cell-cell contacts containing TM4SF10. These studies suggest ADAP does not alter Fyn activity in podocytes, but appears to mediate downstream effects of Fyn controlled by TM4SF10 involving actin cytoskeleton organization.
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Affiliation(s)
- Zhenzhen Wu
- Department of Medicine and Rammelkamp Center for Education and Research, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Natalya A Blessing
- Department of Medicine and Rammelkamp Center for Education and Research, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Jeffrey S Simske
- Department of Medicine and Rammelkamp Center for Education and Research, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Leslie A Bruggeman
- Department of Medicine and Rammelkamp Center for Education and Research, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio
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12
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Gromnitza S, Lepa C, Weide T, Schwab A, Pavenstädt H, George B. Tropomyosin-related kinase C (TrkC) enhances podocyte migration by ERK-mediated WAVE2 activation. FASEB J 2018; 32:1665-1676. [PMID: 29162704 DOI: 10.1096/fj.201700703r] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Podocyte malfunction is central to glomerular diseases and is marked by defective podocyte intercellular junctions and actin cytoskeletal dynamics. Podocytes share many morphologic features with neurons, so that similar sets of proteins appear to regulate cell process formation. One such protein is the tropomyosin-related kinase C (TrkC). TrkC deficiency in mice leads to proteinuria as a surrogate of defective kidney filter function. Activation of endogenous TrkC by its ligand neurotrophin-3 resulted in increased podocyte migration-a surrogate of podocyte actin dynamics in vivo. Employing a mutagenesis approach, we found that the Src homologous and collagen-like (Shc) binding site Tyr516 within the TrkC cytoplasmic domain was necessary for TrkC-induced migration of podocytes. TrkC activation led to a mobility shift of Wiskott-Aldrich syndrome family verprolin-homologous protein (WAVE)-2 which is known to orchestrate Arp2/3 activation and actin polymerization. Chemical inactivation of Erk or mutagenesis of 2 of 4 known Erk target sites within WAVE2, Thr346 and Ser351, abolished the TrkC-induced WAVE2 mobility shift. Knockdown of WAVE2 by shRNA abolished TrkC-induced podocyte migration. In summary, TrkC signals to the podocyte actin cytoskeleton to induce migration by phosphorylating WAVE2 Erk dependently. This signaling mechanism may be important for TrkC-mediated cytoskeletal dynamics in podocyte disease.-Gromnitza, S., Lepa, C., Weide, T., Schwab, A., Pavenstädt, H., George, B. Tropomyosin-related kinase C (TrkC) enhances podocyte migration by ERK-mediated WAVE2 activation.
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Affiliation(s)
- Sascha Gromnitza
- Medizinische Klinik D, Universitätsklinikum Münster, Muenster, Germany
| | - Carolin Lepa
- Medizinische Klinik D, Universitätsklinikum Münster, Muenster, Germany
| | - Thomas Weide
- Medizinische Klinik D, Universitätsklinikum Münster, Muenster, Germany
| | - Albrecht Schwab
- Institut für Physiologie II, Westfälische-Wilhelms-Universität Münster, Muenster, Germany
| | | | - Britta George
- Medizinische Klinik D, Universitätsklinikum Münster, Muenster, Germany
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13
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Ha TS, Nam JA, Seong SB, Saleem MA, Park SJ, Shin JI. Montelukast improves the changes of cytoskeletal and adaptor proteins of human podocytes by interleukin-13. Inflamm Res 2017; 66:793-802. [PMID: 28608180 DOI: 10.1007/s00011-017-1058-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 05/10/2017] [Accepted: 05/23/2017] [Indexed: 01/04/2023] Open
Abstract
OBJECTIVE AND DESIGN Interleukin-13 (IL-13) has recently been reported to be a potential cytokine in the pathogenesis of minimal-change nephrotic syndrome (MCNS). However, the mechanistic insights associated with podocyte dysfunction mediated by IL-13-induced changes in various slit diaphragm (SD) and cytoskeletal molecules have not yet been shown in cultured human podocytes in vitro. MATERIALS Human conditionally immortalized podocytes were used. TREATMENT Podocytes were incubated with various concentrations of IL-13 during the indicated time periods (6, 12, and 24 h) and montelukast was administered with the dose of 0.1 μg. RESULTS Treatment of IL-13 resulted in a progressive decrease in distinct processes or projections of the human podocytes and high dose of IL-13 increased podocyte permeability in vitro at 6 h. IL-13 had a substantial impact on the redistribution and rearrangement of zonula occludens (ZO)-1, synaptopodin, α-actinin, CD2-associated protein (CD2AP) in podocytes and disrupted the cytoskeletal connections in a concentration-dependent manner on confocal microscopy. IL-13 also down-modulated ZO-1, synaptopodin, α-actinin, CD2AP, and p130Cas at protein levels and upregulated β-catenin and B7-1 in podocytes. Furthermore, we demonstrated that down-modulated changes in various SD and cytoskeletal structures of human podocytes induced by IL-13 was significantly restored after treatment with montelukast with upregulation of B7-1. CONCLUSION Our results suggest that targeting IL-13 may be one of the important cytokines in the pathogenesis of MCNS and targeting IL-13 could be one of the potential therapeutic strategies in MCNS.
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Affiliation(s)
- Tae-Sun Ha
- Department of Pediatrics, College of Medicine, Chungbuk National University, Cheongju, Korea.,Department of Pediatrics, Chungbuk National University Hospital, Cheongju, Korea
| | - Ja Ae Nam
- Department of Pediatrics, College of Medicine, Chungbuk National University, Cheongju, Korea
| | - Su-Bin Seong
- Department of Pediatrics, College of Medicine, Chungbuk National University, Cheongju, Korea
| | - Moin A Saleem
- Children's and Academic Renal Unit, Southmead Hospital, University of Bristol, Bristol, UK
| | - Se Jin Park
- Department of Pediatrics, Daewoo General Hospital, Ajou University School of Medicine, Geoje, Korea
| | - Jae Il Shin
- Department of Pediatrics, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, C.P.O. Box 8044, Seoul, 120-752, Republic of Korea. .,Department of Pediatric Nephrology, Severance Children's Hospital, Seoul, Korea. .,Institute of Kidney Disease Research, Yonsei University College of Medicine, Seoul, Korea.
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14
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Ni J, Bao S, Johnson RI, Zhu B, Li J, Vadaparampil J, Smith CM, Campbell KN, Grahammer F, Huber TB, He JC, D'Agati VD, Chan A, Kaufman L. MAGI-1 Interacts with Nephrin to Maintain Slit Diaphragm Structure through Enhanced Rap1 Activation in Podocytes. J Biol Chem 2016; 291:24406-24417. [PMID: 27707879 PMCID: PMC5114397 DOI: 10.1074/jbc.m116.745026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 10/05/2016] [Indexed: 12/15/2022] Open
Abstract
MAGI-1 is a multidomain cytosolic scaffolding protein that in the kidney is specifically located at the podocyte slit diaphragm, a specialized junction that is universally injured in proteinuric diseases. There it interacts with several essential molecules, including nephrin and neph1, which are required for slit diaphragm formation and as an intracellular signaling hub. Here, we show that diminished MAGI-1 expression in cultured podocytes reduced nephrin and neph1 membrane localization and weakened tight junction integrity. Global magi1 knock-out mice, however, demonstrated normal glomerular histology and function into adulthood. We hypothesized that a second mild but complementary genetic insult might induce glomerular disease susceptibility in these mice. To identify such a gene, we utilized the developing fly eye to test for functional complementation between MAGI and its binding partners. In this way, we identified diminished expression of fly Hibris (nephrin) or Roughest (neph1) as dramatically exacerbating the effects of MAGI depletion. Indeed, when these combinations were studied in mice, the addition of nephrin, but not neph1, heterozygosity to homozygous deletion of MAGI-1 resulted in spontaneous glomerulosclerosis. In cultured podocytes, MAGI-1 depletion reduced intercellular contact-induced Rap1 activation, a pathway critical for proper podocyte function. Similarly, magi1 knock-out mice showed diminished glomerular Rap1 activation, an effect dramatically enhanced by concomitant nephrin haploinsufficiency. Finally, combined overexpression of MAGI-1 and nephrin increased Rap1 activation, but not when substituting a mutant MAGI-1 that cannot bind nephrin. We conclude that the interaction between nephrin and MAGI-1 regulates Rap1 activation in podocytes to maintain long term slit diaphragm structure.
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Affiliation(s)
- Jie Ni
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029,; the Division of Nephrology, First Affiliated Hospital of Harbin Medical University, Harbin, China 150001
| | - Sujin Bao
- the Saint James School of Medicine, Saint Vincent and the Grenadines
| | - Ruth I Johnson
- the Biology Department, Wesleyan University, Middletown, Connecticut, 06459
| | - Bingbing Zhu
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029,; the Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China 200062
| | - Jianhua Li
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Justin Vadaparampil
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Christopher M Smith
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Kirk N Campbell
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Florian Grahammer
- the Department of Medicine IV, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
| | - Tobias B Huber
- the Department of Medicine IV, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany,; the BIOSS Center for Biological Signaling Studies, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany,; FRIAS, Freiburg Institute for Advanced Studies and Center for Systems Biology (ZBSA), Albert-Ludwigs-University, 79104 Freiburg, Germany
| | - John C He
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Vivette D D'Agati
- the Department of Pathology, Columbia University Medical Center, New York, New York 10032, and
| | - Andrew Chan
- the School of Biomedical Sciences, Chinese University of Hong Kong, Hong Kong, China
| | - Lewis Kaufman
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029,.
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15
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Abstract
Podocytes are highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule. When it comes to glomerular filtration, podocytes play an active role in preventing plasma proteins from entering the urinary ultrafiltrate by providing a barrier comprising filtration slits between foot processes, which in aggregate represent a dynamic network of cellular extensions. Foot processes interdigitate with foot processes from adjacent podocytes and form a network of narrow and rather uniform gaps. The fenestrated endothelial cells retain blood cells but permit passage of small solutes and an overlying basement membrane less permeable to macromolecules, in particular to albumin. The cytoskeletal dynamics and structural plasticity of podocytes as well as the signaling between each of these distinct layers are essential for an efficient glomerular filtration and thus for proper renal function. The genetic or acquired impairment of podocytes may lead to foot process effacement (podocyte fusion or retraction), a morphological hallmark of proteinuric renal diseases. Here, we briefly discuss aspects of a contemporary view of podocytes in glomerular filtration, the patterns of structural changes in podocytes associated with common glomerular diseases, and the current state of basic and clinical research.
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Affiliation(s)
- Jochen Reiser
- Department of Medicine, Rush University Medical Center, Chicago, IL, USA
| | - Mehmet M Altintas
- Department of Medicine, Rush University Medical Center, Chicago, IL, USA
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16
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Katsura M, Cyou-Nakamine H, Zen Q, Zen Y, Nansai H, Amagasa S, Kanki Y, Inoue T, Kaneki K, Taguchi A, Kobayashi M, Kaji T, Kodama T, Miyagawa K, Wada Y, Akimitsu N, Sone H. Effects of Chronic Low-Dose Radiation on Human Neural Progenitor Cells. Sci Rep 2016; 6:20027. [PMID: 26795421 PMCID: PMC4726121 DOI: 10.1038/srep20027] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 10/19/2015] [Indexed: 12/24/2022] Open
Abstract
The effects of chronic low-dose radiation on human health have not been well established. Recent studies have revealed that neural progenitor cells are present not only in the fetal brain but also in the adult brain. Since immature cells are generally more radiosensitive, here we investigated the effects of chronic low-dose radiation on cultured human neural progenitor cells (hNPCs) derived from embryonic stem cells. Radiation at low doses of 31, 124 and 496 mGy per 72 h was administered to hNPCs. The effects were estimated by gene expression profiling with microarray analysis as well as morphological analysis. Gene expression was dose-dependently changed by radiation. By thirty-one mGy of radiation, inflammatory pathways involving interferon signaling and cell junctions were altered. DNA repair and cell adhesion molecules were affected by 124 mGy of radiation while DNA synthesis, apoptosis, metabolism, and neural differentiation were all affected by 496 mGy of radiation. These in vitro results suggest that 496 mGy radiation affects the development of neuronal progenitor cells while altered gene expression was observed at a radiation dose lower than 100 mGy. This study would contribute to the elucidation of the clinical and subclinical phenotypes of impaired neuronal development induced by chronic low-dose radiation.
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Affiliation(s)
- Mari Katsura
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
| | - Hiromasa Cyou-Nakamine
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
- Faculty of Pharmaceutical Sciences, Department of Pharmacy, Tokyo University of Science, Noda, Japan
| | - Qin Zen
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
| | - Yang Zen
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
| | - Hiroko Nansai
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
| | - Shota Amagasa
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
| | - Yasuharu Kanki
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
| | - Tsuyoshi Inoue
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
- Division of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kiyomi Kaneki
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Akashi Taguchi
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Mika Kobayashi
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Toshiyuki Kaji
- Faculty of Pharmaceutical Sciences, Department of Pharmacy, Tokyo University of Science, Noda, Japan
| | - Tatsuhiko Kodama
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Kiyoshi Miyagawa
- Laboratory of Molecular Radiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Japan
| | - Youichiro Wada
- Isotope Science Center, The University of Tokyo, Tokyo, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | | | - Hideko Sone
- Center for Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Japan
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17
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Auguste D, Maier M, Baldwin C, Aoudjit L, Robins R, Gupta IR, Takano T. Disease-causing mutations of RhoGDIα induce Rac1 hyperactivation in podocytes. Small GTPases 2016; 7:107-21. [PMID: 26726844 DOI: 10.1080/21541248.2015.1113353] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Nephrotic syndrome (NS) describes a group of kidney disorders in which there is injury to podocyte cells, specialized cells within the kidney's glomerular filtration barrier, allowing proteins to leak into the urine. Three mutations in ARHGDIA, which encodes Rho GDP dissociation inhibitor α (GDIα), have been reported in patients with heritable NS and encode the following amino acid changes: ΔD185, R120X, and G173V. To investigate the impact of these mutations on podocyte function, endogenous GDIα was knocked-down in cultured podocytes by shRNA and then the cells were re-transfected with wild-type or mutant GDIα constructs. Among the 3 prototypical Rho-GTPases, Rac1 was markedly hyperactivated in podocytes with any of the 3 mutant forms of GDIα while the activation of RhoA and Cdc42 was modest and variable. All three mutant GDIα proteins resulted in slow podocyte motility, suggesting that podocytes are sensitive to the relative balance of Rho-GTPase activity. In ΔD185 podocytes, both random and directional movements were impaired and kymograph analysis of the leading edge showed increased protrusion and retraction of leading edge (phase switching). The mutant podocytes also showed impaired actin polymerization, smaller cell size, and increased cellular projections. In the developing kidney, GDIα expression increased as podocytes matured. Conversely, active Rac1 was detected only in immature, but not in mature, podocytes. The results indicate that GDIα has a critical role in suppressing Rac1 activity in mature podocytes, to prevent podocyte injury and nephrotic syndrome.
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Affiliation(s)
- David Auguste
- a Division of Nephrology, McGill University Health Centre , Montreal , Quebec , Canada
| | - Mirela Maier
- a Division of Nephrology, McGill University Health Centre , Montreal , Quebec , Canada
| | - Cindy Baldwin
- a Division of Nephrology, McGill University Health Centre , Montreal , Quebec , Canada
| | - Lamine Aoudjit
- a Division of Nephrology, McGill University Health Centre , Montreal , Quebec , Canada
| | - Richard Robins
- a Division of Nephrology, McGill University Health Centre , Montreal , Quebec , Canada
| | - Indra R Gupta
- a Division of Nephrology, McGill University Health Centre , Montreal , Quebec , Canada
| | - Tomoko Takano
- a Division of Nephrology, McGill University Health Centre , Montreal , Quebec , Canada
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18
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Martin EA, Muralidhar S, Wang Z, Cervantes DC, Basu R, Taylor MR, Hunter J, Cutforth T, Wilke SA, Ghosh A, Williams ME. The intellectual disability gene Kirrel3 regulates target-specific mossy fiber synapse development in the hippocampus. eLife 2015; 4:e09395. [PMID: 26575286 PMCID: PMC4642954 DOI: 10.7554/elife.09395] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 10/13/2015] [Indexed: 12/14/2022] Open
Abstract
Synaptic target specificity, whereby neurons make distinct types of synapses with different target cells, is critical for brain function, yet the mechanisms driving it are poorly understood. In this study, we demonstrate Kirrel3 regulates target-specific synapse formation at hippocampal mossy fiber (MF) synapses, which connect dentate granule (DG) neurons to both CA3 and GABAergic neurons. Here, we show Kirrel3 is required for formation of MF filopodia; the structures that give rise to DG-GABA synapses and that regulate feed-forward inhibition of CA3 neurons. Consequently, loss of Kirrel3 robustly increases CA3 neuron activity in developing mice. Alterations in the Kirrel3 gene are repeatedly associated with intellectual disabilities, but the role of Kirrel3 at synapses remained largely unknown. Our findings demonstrate that subtle synaptic changes during development impact circuit function and provide the first insight toward understanding the cellular basis of Kirrel3-dependent neurodevelopmental disorders. DOI:http://dx.doi.org/10.7554/eLife.09395.001 Nerve cells in the brain connect to each other via junctions called synapses to form vast networks that process information. Much like streets can be joined with stop signs, traffic lights, or exit ramps depending on the flow of traffic, different types of synapses control the flow of information along nerves in distinct ways. In a region of the brain called the hippocampus, nerve cells called DG neurons are connected to other neurons by two different types of synapses. One type of synapse allows the DG neurons to activate CA3 neurons, while the second type allows the DG neurons to activate GABAergic neurons. These same GABAergic neurons can then inhibit the activity of the CA3 neurons. Therefore, through these two different types of synapses, DG neurons can both increase and decrease the activity of the CA3 neurons. This delicate balance of activity across the two types of DG synapses is very important for the hippocampus to work properly, which is critical for our ability to learn and remember. Mutations in the gene that encodes a protein called Kirrel3 are associated with autism, Jacobsen's syndrome, and other disorders that affect intellectual ability in humans. Kirrel3 is similar to a protein found in roundworms that regulates the formation of synapses, but it is not known if it plays the same role in humans and other mammals. Now, Martin, Muralidhar et al. studied the role of Kirrel3 in mice. The experiments show that Kirrel3 is produced in both the DG neurons and the GABAergic neurons, but not the CA3 neurons. Young mutant mice that lacked Kirrel3 made fewer synapse-forming structures between DG neurons and GABAergic neurons than normal mice, but the synapses that connect DG neurons to CA3 neurons formed normally. This disrupted the balance of activity across the two types of DG synapses and the CA3 neurons in the mutant mice were over-active. Together, Martin, Muralidhar et al.'s findings show that altering the levels of Kirrel3 can alter the balance of synapses in the hippocampus. This may explain how even very small changes in synapse formation during brain development can have a big impact on nerve cell activity. The next challenge is to understand exactly how Kirrel3 helps build synapses, which may lead to the development of new drugs that help to rebalance brain activity in people that lack Kirrel3. DOI:http://dx.doi.org/10.7554/eLife.09395.002
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Affiliation(s)
- E Anne Martin
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Shruti Muralidhar
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Zhirong Wang
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Diégo Cordero Cervantes
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Raunak Basu
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Matthew R Taylor
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Jennifer Hunter
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Tyler Cutforth
- Department of Neurology, Columbia University, New York City, United States
| | - Scott A Wilke
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, San Diego, United States
| | - Anirvan Ghosh
- Neuroscience Discovery, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Megan E Williams
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
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19
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Bi J, Carroll RT, James ML, Ouderkirk JL, Krendel M, Sirotkin V. Effects of FSGS-associated mutations on the stability and function of myosin-1 in fission yeast. Dis Model Mech 2015; 8:891-902. [PMID: 26092123 PMCID: PMC4527290 DOI: 10.1242/dmm.020214] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 06/09/2015] [Indexed: 12/26/2022] Open
Abstract
Point mutations in the human MYO1E gene, encoding class I myosin Myo1e, are associated with focal segmental glomerulosclerosis (FSGS), a primary kidney disorder that leads to end-stage kidney disease. In this study, we used a simple model organism, fission yeast Schizosaccharomyces pombe, to test the effects of FSGS-associated mutations on myosin activity. Fission yeast has only one class I myosin, Myo1, which is involved in actin patch assembly at the sites of endocytosis. The amino acid residues mutated in individuals with FSGS are conserved between human Myo1e and yeast Myo1, which allowed us to introduce equivalent mutations into yeast myosin and use the resulting mutant strains for functional analysis. Yeast strains expressing mutant Myo1 exhibited defects in growth and endocytosis similar to those observed in the myo1 deletion strain. These mutations also disrupted Myo1 localization to endocytic actin patches and resulted in mis-localization of Myo1 to eisosomes, linear membrane microdomains found in yeast cells. Although both mutants examined in this study exhibited loss of function, one of these mutants was also characterized by the decreased protein stability. Thus, using the yeast model system, we were able to determine that the kidney-disease-associated mutations impair myosin functional activity and have differential effects on protein stability. Summary: In the fission yeast S. pombe, kidney disease-associated mutations in Myo1, a homolog of human Myo1e, disrupt myosin localization and function.
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Affiliation(s)
- Jing Bi
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
| | - Robert T Carroll
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
| | - Michael L James
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
| | - Jessica L Ouderkirk
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
| | - Mira Krendel
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
| | - Vladimir Sirotkin
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
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20
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Li X, Chuang PY, D'Agati VD, Dai Y, Yacoub R, Fu J, Xu J, Taku O, Premsrirut PK, Holzman LB, He JC. Nephrin Preserves Podocyte Viability and Glomerular Structure and Function in Adult Kidneys. J Am Soc Nephrol 2015; 26:2361-77. [PMID: 25644109 DOI: 10.1681/asn.2014040405] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 11/19/2014] [Indexed: 01/12/2023] Open
Abstract
Nephrin is required during kidney development for the maturation of podocytes and formation of the slit diaphragm junctional complex. Because nephrin expression is downregulated in acquired glomerular diseases, nephrin deficiency is considered a pathologic feature of glomerular injury. However, whether nephrin deficiency exacerbates glomerular injury in glomerular diseases has not been experimentally confirmed. Here, we generated mice with inducible RNA interference-mediated nephrin knockdown. Short-term nephrin knockdown (6 weeks), starting after the completion of kidney development at 5 weeks of age, did not affect glomerular structure or function. In contrast, mice with long-term nephrin knockdown (20 weeks) developed mild proteinuria, foot process effacement, filtration slit narrowing, mesangial hypercellularity and sclerosis, glomerular basement membrane thickening, subendothelial zone widening, and podocyte apoptosis. When subjected to an acquired glomerular insult induced by unilateral nephrectomy or doxorubicin, mice with short-term nephrin knockdown developed more severe glomerular injury compared with mice without nephrin knockdown. Additionally, nephrin-knockdown mice developed more exaggerated glomerular enlargement when subjected to unilateral nephrectomy and more podocyte apoptosis and depletion after doxorubicin challenge. AKT phosphorylation, which is a slit diaphragm-mediated and nephrin-dependent pathway in the podocyte, was markedly reduced in mice with long-term or short-term nephrin knockdown challenged with uninephrectomy or doxorubicin. Taken together, our data establish that under the basal condition and in acquired glomerular diseases, nephrin is required to maintain slit diaphragm integrity and slit diaphragm-mediated signaling to preserve glomerular function and podocyte viability in adult mice.
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Affiliation(s)
- Xuezhu Li
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Nephrology; Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Peter Y Chuang
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York;
| | - Vivette D D'Agati
- Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York
| | - Yan Dai
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Nephrology, Shanghai First Municipal Hospital, Shanghai Jiaotao University School of Medicine; Shanghai, China
| | - Rabi Yacoub
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jia Fu
- Research Institute of Nephrology, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Jin Xu
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Oltjon Taku
- State University of New York at University at Binghamton, Binghamton, New York
| | | | - Lawrence B Holzman
- Renal Electrolyte and Hypertension Division, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania; and
| | - John Cijiang He
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York; Renal Section, James J Peter Veterans Administration Medical Center, Bronx, New York
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21
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Hiltunen TP, Donner KM, Sarin A, Saarela J, Ripatti S, Chapman AB, Gums JG, Gong Y, Cooper‐DeHoff RM, Frau F, Glorioso V, Zaninello R, Salvi E, Glorioso N, Boerwinkle E, Turner ST, Johnson JA, Kontula KK. Pharmacogenomics of hypertension: a genome‐wide, placebo‐controlled cross‐over study, using four classes of antihypertensive drugs. J Am Heart Assoc 2015. [PMID: 25622599 PMCID: PMC4330076 DOI: 10.1161/jaha.114.001521] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND Identification of genetic markers of antihypertensive drug responses could assist in individualization of hypertension treatment. METHODS AND RESULTS We conducted a genome-wide association study to identify gene loci influencing the responsiveness of 228 male patients to 4 classes of antihypertensive drugs. The Genetics of Drug Responsiveness in Essential Hypertension (GENRES) study is a double-blind, placebo-controlled cross-over study where each subject received amlodipine, bisoprolol,hydrochlorothiazide, and losartan, each as a monotherapy, in a randomized order. Replication analyses were performed in 4 studies with patients of European ancestry (PEAR Study, N=386; GERA I and II Studies, N=196 and N=198; SOPHIA Study, N=372). We identified 3 single-nucleotide polymorphisms within the ACY3 gene that showed associations with bisoprolol response reaching genome-wide significance (P<5x10(-8))however, this could not be replicated in the PEAR Study using atenolol. In addition, 39 single-nucleotide polymorphisms showed P values of 10(-5) to 10(-7). The 20 top-associated single-nucleotide polymorphisms were different for each antihypertensive drug. None of these top single-nucleotide polymorphisms co-localized with the panel of >40 genes identified in genome-wide association studies of hypertension. Replication analyses of GENRES results provided suggestive evidence for a missense variant (rs3814995) in the NPHS1 (nephrin) gene influencing losartan response, and for 2 variants influencing hydrochlorothiazide response, located within or close to the ALDH1A3 (rs3825926) and CLIC5 (rs321329) genes. CONCLUSIONS These data provide some evidence for a link between biology of the glomerular protein nephrin and antihypertensive action of angiotensin receptor antagonists and encourage additional studies on aldehyde dehydrogenase–mediated reactions in antihypertensive drug action.
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Affiliation(s)
- Timo P. Hiltunen
- Department of Medicine, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland (T.P.H., K.K.K.)
| | - Kati M. Donner
- Institute for Molecular Medicine Finland FIMM, University of Helsinki, Helsinki, Finland (K.M.D., A.P.S., J.S., S.R.)
| | - Antti‐Pekka Sarin
- Institute for Molecular Medicine Finland FIMM, University of Helsinki, Helsinki, Finland (K.M.D., A.P.S., J.S., S.R.)
- Public Health Genomics Unit, National Institute for Health and Welfare, University of Helsinki, Helsinki, Finland (A.P.S.)
| | - Janna Saarela
- Institute for Molecular Medicine Finland FIMM, University of Helsinki, Helsinki, Finland (K.M.D., A.P.S., J.S., S.R.)
| | - Samuli Ripatti
- Institute for Molecular Medicine Finland FIMM, University of Helsinki, Helsinki, Finland (K.M.D., A.P.S., J.S., S.R.)
- Department of Public Health, Hjelt Institute, University of Helsinki, Helsinki, Finland (S.R.)
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom (S.R.)
| | - Arlene B. Chapman
- Mayo Clinic, Rochester, MN (A.B.C.)
- Department of Medicine, Renal Division, Emory University School of Medicine, Atlanta, GA (A.B.C.)
| | - John G. Gums
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, University of Florida, Gainesville, FL (J.G.G., Y.G., R.M.C.D.H., J.A.J.)
- Department of Community Health and Family Medicine, Gainesville, FL (J.G.G.)
| | - Yan Gong
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, University of Florida, Gainesville, FL (J.G.G., Y.G., R.M.C.D.H., J.A.J.)
| | - Rhonda M. Cooper‐DeHoff
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, University of Florida, Gainesville, FL (J.G.G., Y.G., R.M.C.D.H., J.A.J.)
- Department of Medicine, Gainesville, FL (R.M.C.D.H.)
| | - Francesca Frau
- Department of Health Sciences, Genomics and Bioinformatics Unit, University of Milan and Filarete Foundation, Milan, Italy (F.F., E.S.)
| | - Valeria Glorioso
- Hypertension and Related Disease Centre, AOU‐University of Sassari, Sassari, Italy (V.G., R.Z., N.G.)
| | - Roberta Zaninello
- Hypertension and Related Disease Centre, AOU‐University of Sassari, Sassari, Italy (V.G., R.Z., N.G.)
| | - Erika Salvi
- Department of Health Sciences, Genomics and Bioinformatics Unit, University of Milan and Filarete Foundation, Milan, Italy (F.F., E.S.)
| | - Nicola Glorioso
- Hypertension and Related Disease Centre, AOU‐University of Sassari, Sassari, Italy (V.G., R.Z., N.G.)
| | - Eric Boerwinkle
- University of Florida, Gainesville, FL (E.B.)
- Human Genetics and Institute of Molecular Medicine, University of Texas Health Science Center, Houston, TX (E.B.)
| | - Stephen T. Turner
- Division of Nephrology and Hypertension, Department of Internal Medicine, Mayo Clinic, Rochester, MN (S.T.T.)
| | - Julie A. Johnson
- Department of Pharmacotherapy and Translational Research, Center for Pharmacogenomics, University of Florida, Gainesville, FL (J.G.G., Y.G., R.M.C.D.H., J.A.J.)
| | - Kimmo K. Kontula
- Department of Medicine, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland (T.P.H., K.K.K.)
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22
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Keaney JF, Loscalzo J. Pharmacogenomics of hypertension: a genome‐wide, placebo‐controlled cross‐over study, using four classes of antihypertensive drugs. J Am Heart Assoc 2015; 4:e001778. [PMID: 25628411 PMCID: PMC4330084 DOI: 10.1161/jaha.115.001778] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Identification of genetic markers of antihypertensive drug responses could assist in individualization of hypertension treatment. METHODS AND RESULTS We conducted a genome-wide association study to identify gene loci influencing the responsiveness of 228 male patients to 4 classes of antihypertensive drugs. The Genetics of Drug Responsiveness in Essential Hypertension (GENRES) study is a double-blind, placebo-controlled cross-over study where each subject received amlodipine, bisoprolol,hydrochlorothiazide, and losartan, each as a monotherapy, in a randomized order. Replication analyses were performed in 4 studies with patients of European ancestry (PEAR Study, N=386; GERA I and II Studies, N=196 and N=198; SOPHIA Study, N=372). We identified 3 single-nucleotide polymorphisms within the ACY3 gene that showed associations with bisoprolol response reaching genome-wide significance (P<5x10(-8))however, this could not be replicated in the PEAR Study using atenolol. In addition, 39 single-nucleotide polymorphisms showed P values of 10(-5) to 10(-7). The 20 top-associated single-nucleotide polymorphisms were different for each antihypertensive drug. None of these top single-nucleotide polymorphisms co-localized with the panel of >40 genes identified in genome-wide association studies of hypertension. Replication analyses of GENRES results provided suggestive evidence for a missense variant (rs3814995) in the NPHS1 (nephrin) gene influencing losartan response, and for 2 variants influencing hydrochlorothiazide response, located within or close to the ALDH1A3 (rs3825926) and CLIC5 (rs321329) genes. CONCLUSIONS These data provide some evidence for a link between biology of the glomerular protein nephrin and antihypertensive action of angiotensin receptor antagonists and encourage additional studies on aldehyde dehydrogenase–mediated reactions in antihypertensive drug action.
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Affiliation(s)
- John F. Keaney
- UMass Medical School and UMass Memorial Medical Center, Worcester, MA (J.F.K.)
| | - Joseph Loscalzo
- Harvard Medical School and Brigham and Women's Hospital, Boston, MA (J.L.)
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23
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Small molecule membrane transporters in the mammalian podocyte: a pathogenic and therapeutic target. Int J Mol Sci 2014; 15:21366-80. [PMID: 25411800 PMCID: PMC4264230 DOI: 10.3390/ijms151121366] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/06/2014] [Accepted: 11/13/2014] [Indexed: 01/10/2023] Open
Abstract
The intriguingly complex glomerular podocyte has been a recent object of intense study. Researchers have sought to understand its role in the pathogenesis of common proteinuric diseases such as minimal change disease and focal segmental glomerular sclerosis. In particular, considerable effort has been directed towards the anatomic and functional barrier to macromolecular filtration provided by the secondary foot processes, but little attention has been paid to the potential of podocytes to handle plasma proteins beyond the specialization of the slit diaphragm. Renal membrane transporters in the proximal tubule have been extensively studied for decades, particularly in relation to drug metabolism and elimination. Recently, uptake and efflux transporters for small organic molecules have also been found in the glomerular podocyte, and we and others have found that these transporters can engage not only common pharmaceuticals but also injurious endogenous and exogenous agents. We have also found that the activity of podocyte transporters can be manipulated to inhibit pathogen uptake and efflux. It is conceivable that podocyte transporters may play a role in disease pathogenesis and may be a target for future drug development.
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24
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Sun H, Al-Romaih KI, MacRae CA, Pollak MR. Human Kidney Disease-causing INF2 Mutations Perturb Rho/Dia Signaling in the Glomerulus. EBioMedicine 2014; 1:107-15. [PMID: 26086034 PMCID: PMC4457406 DOI: 10.1016/j.ebiom.2014.11.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 11/08/2014] [Accepted: 11/11/2014] [Indexed: 01/10/2023] Open
Abstract
Mutations in Inverted Formin 2 (INF2), a diaphanous formin family protein that regulates actin cytoskeleton dynamics, cause focal segmental glomerulosclerosis (FSGS) and Charcot-Marie-Tooth Disease (CMT) in humans. In addition to directly remodeling actin filaments in vitro, we have shown that INF2 regulates intracellular actin dynamics and actin dependent cellular behavior by opposing Rhoa/Dia signaling. As a step towards a better understanding of the human kidney disease, we wanted to explore the relevance of these findings to the in vivo situation. We used dose dependent knockdown of INF2 to first define an in vivo model and establish an overt glomerular phenotype in zebrafish. This simple assay was validated by rescue with wild type INF2 confirming the specificity of the findings. The edema, podocyte dysfunction, and an altered glomerular filtration barrier observed in the zebrafish pronephros correlate with mistrafficking of glomerular slit diaphragm proteins, defective slit-diaphragm signaling, and disinhibited diaphanous formin (mDia) activity. In contrast to wild-type human INF2, INF2 mutants associated with kidney disease fail to rescue the zINF2 morphant phenotype. Of particular interest, this INF2 knockdown phenotype is also rescued by loss of either RhoA or Dia2. This simple assay allows the demonstration that INF2 functions, at least in part, to modulate Dia-mediated Rho signaling, and that disease causing mutations specifically impair this regulatory function. These data support a model in which disease-associated diaphanous inhibitory domain (DID) mutants in INF2 interfere with its binding to and inhibition of Dia, leading to uncontrolled Rho/Dia signaling and perturbed actin dynamics. Methods to fine tune Rho signaling in the glomerulus may lead to new approaches to therapy in humans.
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Affiliation(s)
- Hua Sun
- Nephrology Division, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, United States ; Harvard Medical School, Boston, MA 02215, United States ; Iowa University Children's Hospital, Iowa City, IA 52242, United States
| | - Khaldoun I Al-Romaih
- Nephrology Division, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, United States ; Harvard Medical School, Boston, MA 02215, United States
| | - Calum A MacRae
- Harvard Medical School, Boston, MA 02215, United States ; Cardiology Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, United States ; Broad Institute of Harvard and MIT, Cambridge, MA, United States
| | - Martin R Pollak
- Nephrology Division, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, United States ; Harvard Medical School, Boston, MA 02215, United States ; Broad Institute of Harvard and MIT, Cambridge, MA, United States
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25
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Ichii O, Otsuka-Kanazawa S, Nakamura T, Ueno M, Kon Y, Chen W, Rosenberg AZ, Kopp JB. Podocyte injury caused by indoxyl sulfate, a uremic toxin and aryl-hydrocarbon receptor ligand. PLoS One 2014; 9:e108448. [PMID: 25244654 PMCID: PMC4171541 DOI: 10.1371/journal.pone.0108448] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 08/21/2014] [Indexed: 02/07/2023] Open
Abstract
Indoxyl sulfate is a uremic toxin and a ligand of the aryl-hydrocarbon receptor (AhR), a transcriptional regulator. Elevated serum indoxyl sulfate levels may contribute to progressive kidney disease and associated vascular disease. We asked whether indoxyl sulfate injures podocytes in vivo and in vitro. Mice exposed to indoxyl sulfate for 8 w exhibited prominent tubulointerstitial lesions with vascular damage. Indoxyl sulfate-exposed mice with microalbuminuria showed ischemic changes, while more severely affected mice showed increased mesangial matrix, segmental solidification, and mesangiolysis. In normal mouse kidneys, AhR was predominantly localized to the podocyte nuclei. In mice exposed to indoxyl sulfate for 2 h, isolated glomeruli manifested increased Cyp1a1 expression, indicating AhR activation. After 8 w of indoxyl sulfate, podocytes showed foot process effacement, cytoplasmic vacuoles, and a focal granular and wrinkled pattern of podocin and synaptopodin expression. Furthermore, vimentin and AhR expression in the glomerulus was increased in the indoxyl sulfate-exposed glomeruli compared to controls. Glomerular expression of characteristic podocyte mRNAs was decreased, including Actn4, Cd2ap, Myh9, Nphs1, Nphs2, Podxl, Synpo, and Wt1. In vitro, immortalized-mouse podocytes exhibited AhR nuclear translocation beginning 30 min after 1 mM indoxyl sulfate exposure, and there was increased phospho-Rac1/Cdc42 at 2 h. After exposure to indoxyl sulfate for 24 h, mouse podocytes exhibited a pro-inflammatory phenotype, perturbed actin cytoskeleton, decreased expression of podocyte-specific genes, and decreased cell viability. In immortalized human podocytes, indoxyl sulfate treatment caused cell injury, decreased mRNA expression of podocyte-specific proteins, as well as integrins, collagens, cytoskeletal proteins, and bone morphogenetic proteins, and increased cytokine and chemokine expression. We propose that basal levels of AhR activity regulate podocyte function under normal conditions, and that increased activation of podocyte AhR by indoxyl sulfate contributes to progressive glomerular injury.
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Affiliation(s)
- Osamu Ichii
- Laboratory of Anatomy, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Hokkaido, Japan
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| | - Saori Otsuka-Kanazawa
- Laboratory of Anatomy, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Hokkaido, Japan
| | - Teppei Nakamura
- Laboratory of Anatomy, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Hokkaido, Japan
- Section of Biological Safety Research, Chitose Laboratory, Japan Food Research Laboratories, Chitose, Japan
| | - Masaaki Ueno
- Section of Biological Safety Research, Chitose Laboratory, Japan Food Research Laboratories, Chitose, Japan
| | - Yasuhiro Kon
- Laboratory of Anatomy, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Hokkaido, Japan
| | - Weiping Chen
- Microarray Core Facility, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Avi Z. Rosenberg
- Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jeffrey B. Kopp
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
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26
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Smad3/Nox4-mediated mitochondrial dysfunction plays a crucial role in puromycin aminonucleoside-induced podocyte damage. Cell Signal 2014; 26:2979-91. [PMID: 25229402 DOI: 10.1016/j.cellsig.2014.08.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 08/17/2014] [Indexed: 11/20/2022]
Abstract
Podocyte depletion due to apoptosis is the key hallmark of proteinuric kidney disease progression. Recently, several studies reported that mitochondrial (mt) dysfunction is involved in podocyte injury, while the underlying molecular mechanisms remain elusive. This study investigated the potential proximal signaling related to in vitro and in vivo mitochondrial dysfunction in a puromycin aminonucleoside (PA)-induced podocyte injury model. PA time- and dose-dependently resulted in cultured mouse podocyte damage, presenting with an increase of apoptotic cells and induction of activated caspase3/9. PA also caused mitochondrial damage and dysfunction based on the downregulation of the mtDNA level, decrease of transcriptional factors mtTfa and Nrf-1, decrease of CoxI, II and IV, and reduction of the oxygen consumption level and mitochondrial membrane potential level as well as excessive production of cellular ROS. Additionally, antioxidant MnSOD and catalase levels were decreased in mitochondrial fractions, and reduction of complex I and IV activity was also observed in PA-stimulated podocytes. Furthermore, an obvious translocation of p-Smad3 from the cytosol to nuclei and induction of mitochondrial Nox4 were detected following PA application. The PA-induced shift of cytochrome c was observed from mitochondria to the cytoplasm. Induction of Nox4 by PA administration was significantly repressed by Smad3-shRNA, while Nox4-shRNA showed no effect on PA-induced p-Smad3 activation. Notably, both Smad3 and Nox4 silencing significantly prevented the reduction of the mtDNA level, restored mitochondrial function, and decreased cellular apoptosis in PA-stimulated podocytes. A similar mitochondrial dysfunction was obtained in a PA-injected nephropathy rat, which was effectively inhibited by treatment with the antiproteinuric drug prednisone. In addition, Dab2 knockdown decreased albumin uptake and influx whereas it showed no effect on cellular apoptosis in PA-stimulated podocytes. In conclusion, our findings demonstrated that Smad3-Nox4 axis-mediated mitochondrial dysfunction is involved in PA-induced podocyte damage likely via increasing ROS generation and activating the cytochrome c-caspase9-caspase3 apoptotic signaling pathway. Dab2 may be required for the increased permeability of podocytes following injury.
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27
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Itoh M, Nakadate K, Horibata Y, Matsusaka T, Xu J, Hunziker W, Sugimoto H. The structural and functional organization of the podocyte filtration slits is regulated by Tjp1/ZO-1. PLoS One 2014; 9:e106621. [PMID: 25184792 PMCID: PMC4153657 DOI: 10.1371/journal.pone.0106621] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 07/30/2014] [Indexed: 01/16/2023] Open
Abstract
Blood filtration in the kidney glomerulus is essential for physiological homeostasis. The filtration apparatus of the kidney glomerulus is composed of three distinct components: the fenestrated endothelial cells, the glomerular basement membrane, and interdigitating foot processes of podocytes that form the slit diaphragm. Recent studies have demonstrated that podocytes play a crucial role in blood filtration and in the pathogenesis of proteinuria and glomerular sclerosis; however, the molecular mechanisms that organize the podocyte filtration barrier are not fully understood. In this study, we suggest that tight junction protein 1 (Tjp1 or ZO-1), which is encoded by Tjp1 gene, plays an essential role in establishing the podocyte filtration barrier. The podocyte-specific deletion of Tjp1 down-regulated the expression of podocyte membrane proteins, impaired the interdigitation of the foot processes and the formation of the slit diaphragm, resulting in glomerular dysfunction. We found the possibility that podocyte filtration barrier requires the integration of two independent units, the pre-existing epithelial junction components and the newly synthesized podocyte-specific components, at the final stage in glomerular morphogenesis, for which Tjp1 is indispensable. Together with previous findings that Tjp1 expression was decreased in glomerular diseases in human and animal models, our results indicate that the suppression of Tjp1 could directly aggravate glomerular disorders, highlights Tjp1 as a potential therapeutic target.
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Affiliation(s)
- Masahiko Itoh
- Department of Biochemistry, School of Medicine, Dokkyo Medical University, Mibu-machi, Shimotsuga-gun, Tochigi, Japan
- * E-mail: (MI); (WH)
| | - Kazuhiko Nakadate
- Department of Basic Biology, Educational and Research Center for Pharmacy, Meiji Pharmaceutical University, Kiyose, Tokyo, Japan
| | - Yasuhiro Horibata
- Department of Biochemistry, School of Medicine, Dokkyo Medical University, Mibu-machi, Shimotsuga-gun, Tochigi, Japan
| | - Taiji Matsusaka
- Department of Internal Medicine, Tokai University School of Medicine, Isehara, Kanagawa, Japan
| | - Jianliang Xu
- Epithelial Cell Biology Laboratory, Institute of Molecular and Cell Biology (IMCB), Singapore, Singapore
| | - Walter Hunziker
- Epithelial Cell Biology Laboratory, Institute of Molecular and Cell Biology (IMCB), Singapore, Singapore
- * E-mail: (MI); (WH)
| | - Hiroyuki Sugimoto
- Department of Biochemistry, School of Medicine, Dokkyo Medical University, Mibu-machi, Shimotsuga-gun, Tochigi, Japan
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28
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Costa MSA, Machado MCR, Vieceli FM, Amistá L, Baroneza JE, Yan CYI, Ramos RGP. The Rst-Neph family of cell adhesion molecules in Gallus gallus. J Neurogenet 2014; 28:270-81. [PMID: 24914768 DOI: 10.3109/01677063.2014.933220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The Rst-Neph family comprises an evolutionarily conserved group of single-pass transmembrane glycoproteins that belong to the immunoglobulin superfamily and participate in a wide range of cell adhesion and recognition events in both vertebrates and invertebrates. In mammals and fish, three Rst-Neph members, named Neph1-3, are present. Besides being widely expressed in the embryo, particularly in the developing nervous system, they also contribute to the formation and integrity of the urine filtration apparatus in the slit diaphragm of kidney glomerular podocytes, where they form homodimers, as well as heterodimers with Nephrin, another immunoglobulin-like cell adhesion molecule. In mice, absence of Neph1 causes severe proteinuria, podocyte effacement and perinatal death, while in humans, a mutated form of Nephrin leads to congenital nephrotic syndrome of the Finnish type. Intriguingly, neither Nephrin nor Neph3 are present in birds, which nevertheless have typical vertebrate kidneys with mammalian-like slit diaphragms. These characteristics make, in principle, avian systems very helpful for understanding the evolution and functional significance of the complex interactions displayed by Rst-Neph proteins. To this end we have started a systematic study of chicken Neph embryonic and post-embryonic expression, both at mRNA and protein level. RT-qPCR mRNA quantification of the two Neph paralogues in adult tissues showed that both are expressed in heart, brain, and retina. Neph1 is additionally present in kidney, liver, pancreas, lungs, and testicles, while Neph2 mRNA is barely detected in kidney, testicles, pancreas and absent in liver and lungs. In embryos, mRNA from both genes can already be detected at as early as stage HH14, and remain expressed until at least HH28. Finally, we used a specific antibody to examine the spatial dynamics and subcellular distribution of ggNeph2 between stages HH20-28, particularly in the mesonephros, dermomyotomes, developing heart, and retina.
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Affiliation(s)
- Mara Silvia A Costa
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo , Ribeirão Preto , Brazil
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29
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30
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Pollak MR, Quaggin SE, Hoenig MP, Dworkin LD. The glomerulus: the sphere of influence. Clin J Am Soc Nephrol 2014; 9:1461-9. [PMID: 24875196 DOI: 10.2215/cjn.09400913] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The glomerulus, the filtering unit of the kidney, is a unique bundle of capillaries lined by delicate fenestrated endothelia, a complex mesh of proteins that serve as the glomerular basement membrane and specialized visceral epithelial cells that form the slit diaphragms between interdigitating foot processes. Taken together, this arrangement allows continuous filtration of the plasma volume. The dynamic physical forces that determine the single nephron glomerular filtration are considered. In addition, new insights into the cellular and molecular components of the glomerular tuft and their contribution to glomerular disorders are explored.
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Affiliation(s)
- Martin R Pollak
- Beth Israel Deaconess Medical Center, Boston, Massachusetts;
| | - Susan E Quaggin
- Feinberg School of Medicine, Northwestern University, Chicago, Illinois; and
| | | | - Lance D Dworkin
- Brown Medical School, Brown University, Providence, Rhode Island
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31
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Chen XP, Lei FY, Qin YH, Zhou TB, Jiang L, Zhao YJ, Huang WF, Peng QL. The role of retinoic acid receptors in the signal pathway of all-trans retinoic acid-induced differentiation in adriamycin-induced podocyte injury. J Recept Signal Transduct Res 2014; 34:484-92. [PMID: 24846581 DOI: 10.3109/10799893.2014.920394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Sun Y, Zhang H, Hu R, Sun J, Mao X, Zhao Z, Chen Q, Zhang Z. The expression and significance of neuronal iconic proteins in podocytes. PLoS One 2014; 9:e93999. [PMID: 24699703 PMCID: PMC3974844 DOI: 10.1371/journal.pone.0093999] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 03/10/2014] [Indexed: 11/18/2022] Open
Abstract
Growing evidence suggests that there are many common cell biological features shared by neurons and podocytes; however, the mechanism of podocyte foot process formation remains unclear. Comparing the mechanisms of process formation between two cell types should provide useful guidance from the progress of neuron research. Studies have shown that some mature proteins of podocytes, such as podocin, nephrin, and synaptopodin, were also expressed in neurons. In this study, using cell biological experiments and immunohistochemical techniques, we showed that some neuronal iconic molecules, such as Neuron-specific enolase, nestin and Neuron-specific nuclear protein, were also expressed in podocytes. We further inhibited the expression of Neuron-specific enolase, nestin, synaptopodin and Ubiquitin carboxy terminal hydrolase-1 by Small interfering RNA in cultured mouse podocytes and observed the significant morphological changes in treated podocytes. When podocytes were treated with Adriamycin, the protein expression of Neuron-specific enolase, nestin, synaptopodin and Ubiquitin carboxy terminal hydrolase-1 decreased over time. Meanwhile, the morphological changes in the podocytes were consistent with results of the Small interfering RNA treatment of these proteins. The data demonstrated that neuronal iconic proteins play important roles in maintaining and regulating the formation and function of podocyte processes.
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Affiliation(s)
- Yu Sun
- Department of Pathology, Key Laboratory of Molecular Medicine, Chinese Ministry of Education, Shanghai Medical College, School of Basic Medical Science, Fudan University, Shanghai, P.R. China
| | - Hongxia Zhang
- Department of Pathology, Weifang Medical University, Weifang, Shandong, P.R. China
| | - Ruimin Hu
- Department of Pathology, Key Laboratory of Molecular Medicine, Chinese Ministry of Education, Shanghai Medical College, School of Basic Medical Science, Fudan University, Shanghai, P.R. China
| | - Jianyong Sun
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, P.R. China
| | - Xing Mao
- Department of Pathology, Key Laboratory of Molecular Medicine, Chinese Ministry of Education, Shanghai Medical College, School of Basic Medical Science, Fudan University, Shanghai, P.R. China
| | - Zhonghua Zhao
- Department of Pathology, Key Laboratory of Molecular Medicine, Chinese Ministry of Education, Shanghai Medical College, School of Basic Medical Science, Fudan University, Shanghai, P.R. China
| | - Qi Chen
- Department of Pathology, Key Laboratory of Molecular Medicine, Chinese Ministry of Education, Shanghai Medical College, School of Basic Medical Science, Fudan University, Shanghai, P.R. China
| | - Zhigang Zhang
- Department of Pathology, Key Laboratory of Molecular Medicine, Chinese Ministry of Education, Shanghai Medical College, School of Basic Medical Science, Fudan University, Shanghai, P.R. China
- * E-mail:
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Tufro A. Semaphorin3a signaling, podocyte shape, and glomerular disease. Pediatr Nephrol 2014; 29:751-5. [PMID: 24464477 PMCID: PMC3992269 DOI: 10.1007/s00467-013-2743-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 12/17/2013] [Accepted: 12/18/2013] [Indexed: 12/21/2022]
Abstract
Semaphorin3a (sema3a), a member of class 3 semaphorins, is a guidance protein that regulates angiogenesis, branching morphogenesis, axon growth, and cell migration, and has pleiotropic roles on organogenesis, immune response, and cancer. Sema3a is secreted by podocytes and is required for normal kidney patterning and glomerular filtration barrier development. We recently discovered that after completion of kidney development, Sema3a gain-of-function in podocytes leads to proteinuric glomerular disease in mice. Excess sema3a causes foot process effacement, glomerular basement lamination, and endothelial damage in vivo, and disrupts cell autonomously podocyte shape by down-regulating nephrin and inhibiting αvβ3 integrin. We identified a novel direct interaction between nephrin and plexinA1, the sema3a signaling receptor. Nephrin-plexinA1 interaction links the slit-diaphragm signaling complex to extracellular sema3a signals. Hence, sema3a functions as an extracellular negative regulator of the structure and function of the glomerular filtration barrier.
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Affiliation(s)
- Alda Tufro
- Department of Pediatrics, Yale University School of Medicine, 333 Cedar Street, PO Box 208064, New Haven, CT, 06520-8064, USA,
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34
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Rinschen MM, Wu X, König T, Pisitkun T, Hagmann H, Pahmeyer C, Lamkemeyer T, Kohli P, Schnell N, Schermer B, Dryer S, Brooks BR, Beltrao P, Krueger M, Brinkkoetter PT, Benzing T. Phosphoproteomic analysis reveals regulatory mechanisms at the kidney filtration barrier. J Am Soc Nephrol 2014; 25:1509-22. [PMID: 24511133 DOI: 10.1681/asn.2013070760] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Diseases of the kidney filtration barrier are a leading cause of ESRD. Most disorders affect the podocytes, polarized cells with a limited capacity for self-renewal that require tightly controlled signaling to maintain their integrity, viability, and function. Here, we provide an atlas of in vivo phosphorylated, glomerulus-expressed proteins, including podocyte-specific gene products, identified in an unbiased tandem mass spectrometry-based approach. We discovered 2449 phosphorylated proteins corresponding to 4079 identified high-confidence phosphorylated residues and performed a systematic bioinformatics analysis of this dataset. We discovered 146 phosphorylation sites on proteins abundantly expressed in podocytes. The prohibitin homology domain of the slit diaphragm protein podocin contained one such site, threonine 234 (T234), located within a phosphorylation motif that is mutated in human genetic forms of proteinuria. The T234 site resides at the interface of podocin dimers. Free energy calculation through molecular dynamic simulations revealed a role for T234 in regulating podocin dimerization. We show that phosphorylation critically regulates formation of high molecular weight complexes and that this may represent a general principle for the assembly of proteins containing prohibitin homology domains.
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Affiliation(s)
- Markus M Rinschen
- Department of Internal Medicine II, Center for Molecular Medicine, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, Systems Biology of Ageing Cologne
| | - Xiongwu Wu
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Tim König
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases,Institute for Genetics, University of Cologne, Cologne, Germany
| | - Trairak Pisitkun
- Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Henning Hagmann
- Department of Internal Medicine II, Center for Molecular Medicine
| | | | - Tobias Lamkemeyer
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases
| | - Priyanka Kohli
- Department of Internal Medicine II, Center for Molecular Medicine, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases
| | - Nicole Schnell
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases
| | - Bernhard Schermer
- Department of Internal Medicine II, Center for Molecular Medicine, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, Systems Biology of Ageing Cologne
| | - Stuart Dryer
- Department of Biology and Biochemistry, University of Houston, Houston, Texas; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases
| | - Bernard R Brooks
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Pedro Beltrao
- European Molecular Biology Laboratory-European Bioinformatics Institute, Hinxton, Cambridge, United Kingdom; and
| | - Marcus Krueger
- Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | | | - Thomas Benzing
- Department of Internal Medicine II, Center for Molecular Medicine, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, Systems Biology of Ageing Cologne,
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Crk1/2 and CrkL form a hetero-oligomer and functionally complement each other during podocyte morphogenesis. Kidney Int 2014; 85:1382-1394. [PMID: 24499776 PMCID: PMC4040156 DOI: 10.1038/ki.2013.556] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 10/29/2013] [Accepted: 11/21/2013] [Indexed: 01/19/2023]
Abstract
Activation of the slit diaphragm protein nephrin induces actin cytoskeletal remodeling, resulting in lamellipodia formation in podocytes in vitro in a phosphatidylinositol-3 kinase-, focal adhesion kinase-, Cas-, and Crk1/2-dependent fashion. In mice, podocyte-specific deletion of Crk1/2 prevents or attenuates foot process effacement in two models of podocyte injury. This suggests that cellular mechanisms governing lamellipodial protrusion in vitro are similar to those in vivo during foot process effacement. As Crk1/2-null mice developed and aged normally, we tested whether the Crk1/2 paralog, CrkL, functionally complements Crk1/2 in a podocyte-specific context. Podocyte-specific CrkL-null mice, like podocyte-specific Crk1/2-null mice, developed and aged normally but were protected from protamine sulfate-induced foot process effacement. Simultaneous podocyte-specific deletion of Crk1/2 and CrkL resulted in albuminuria detected by 6 weeks postpartum and associated with altered podocyte process architecture. Nephrin-induced lamellipodia formation in podocytes in vitro was CrkL-dependent. CrkL formed a hetero-oligomer with Crk2 and, like Crk2, was recruited to tyrosine phosphorylated nephrin. Thus, Crk1/2 and CrkL are physically linked, functionally complement each other during podocyte foot process spreading, and together are required for developing typical foot process architecture.
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Zhang YJ, Tian ZL, Yu XY, Zhao XX, Yao L. Activation of integrin β1-focal adhesion kinase-RasGTP pathway plays a critical role in TGF beta1-induced podocyte injury. Cell Signal 2013; 25:2769-79. [DOI: 10.1016/j.cellsig.2013.08.044] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 08/31/2013] [Indexed: 12/22/2022]
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Abstract
Steroid-resistant nephrotic syndrome has a poor prognosis and often leads to end-stage renal disease development. In this issue of the JCI, Ashraf and colleagues used exome sequencing to identify mutations in the aarF domain containing kinase 4 (ADCK4) gene that cause steroid-resistant nephrotic syndrome. Patients with ADCK4 mutations had lower coenzyme Q10 levels, and coenzyme Q10 supplementation ameliorated renal disease in a patient with this particular mutation, suggesting a potential therapy for patients with steroid-resistant nephrotic syndrome with ADCK4 mutations.
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38
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Grahammer F, Schell C, Huber TB. The podocyte slit diaphragm--from a thin grey line to a complex signalling hub. Nat Rev Nephrol 2013; 9:587-98. [PMID: 23999399 DOI: 10.1038/nrneph.2013.169] [Citation(s) in RCA: 173] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The architectural design of our kidneys is amazingly complex, and culminates in the 3D structure of the glomerular filter. During filtration, plasma passes through a sieve consisting of a fenestrated endothelium and a broad basement membrane before it reaches the most unique part, the slit diaphragm, a specialized type of intercellular junction that connects neighbouring podocyte foot processes. When podocytes become stressed, irrespective of the causative stimulus, they undergo foot process effacement and loss of slit diaphragms--two key steps leading to proteinuria. Thus, proteinuria is the unifying denominator of a broad spectrum of podocytopathies. With the rising prevalence of chronic kidney disease and the fact that glomerular diseases account for the majority of patients with end-stage renal disease, further investigation and elucidation of this unique structure is of paramount importance. This Review recounts how perception of the slit diaphragm has changed over time as a result of intense research, from its first anatomical description as a thin intercellular connection, to an appreciation of its role as a dynamic signalling hub. These observations led to the introduction of novel concepts in podocyte biology, which could pave the way to development of highly desired, specific therapeutic strategies for glomerular diseases.
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Affiliation(s)
- Florian Grahammer
- Renal Division, University Hospital Freiburg, Hugstetter Strasse 55, Freiburg 79106, Germany
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Bi J, Chase SE, Pellenz CD, Kurihara H, Fanning AS, Krendel M. Myosin 1e is a component of the glomerular slit diaphragm complex that regulates actin reorganization during cell-cell contact formation in podocytes. Am J Physiol Renal Physiol 2013; 305:F532-44. [PMID: 23761676 DOI: 10.1152/ajprenal.00223.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glomerular visceral epithelial cells, also known as podocytes, are critical to both normal kidney function and the development of kidney disease. Podocyte actin cytoskeleton and their highly specialized cell-cell junctions (also called slit diaphragm complexes) play key roles in controlling glomerular filtration. Myosin 1e (myo1e) is an actin-based molecular motor that is expressed in renal glomeruli. Disruption of the Myo1e gene in mice and humans promotes podocyte injury and results in the loss of the integrity of the glomerular filtration barrier. Here, we have used biochemical and microscopic approaches to determine whether myo1e is associated with the slit diaphragm complexes in glomerular podocytes. Myo1e was consistently enriched in the slit diaphragm fraction during subcellular fractionation of renal glomeruli and colocalized with the slit diaphragm markers in mouse kidney. Live cell imaging studies showed that myo1e was recruited to the newly formed cell-cell junctions in cultured podocytes, where it colocalized with the actin filament cables aligned with the nascent contacts. Myo1e-null podocytes expressing FSGS-associated myo1e mutant (A159P) did not efficiently assemble actin cables along new cell-cell junctions. We have mapped domains in myo1e that were critical for its localization to cell-cell junctions and determined that the SH3 domain of myo1e tail interacts with ZO-1, a component of the slit diaphragm complex and tight junctions. These findings suggest that myo1e represents a component of the slit diaphragm complex and may contribute to regulating junctional integrity in kidney podocytes.
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Affiliation(s)
- J Bi
- Dept. of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210.
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40
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Höhne M, Ising C, Hagmann H, Völker LA, Brähler S, Schermer B, Brinkkoetter PT, Benzing T. Light microscopic visualization of podocyte ultrastructure demonstrates oscillating glomerular contractions. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 182:332-8. [PMID: 23246153 DOI: 10.1016/j.ajpath.2012.11.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 10/17/2012] [Accepted: 11/01/2012] [Indexed: 12/23/2022]
Abstract
Podocytes, the visceral epithelial cells of the kidney glomerulus, elaborate primary and interdigitating secondary extensions to enwrap the glomerular capillaries. A hallmark of podocyte injury is the loss of unique ultrastructure and simplification of the cell shape, called foot process effacement, which is a classic feature of proteinuric kidney disease. Although several key pathways have been identified that control cytoskeletal regulation, actin dynamics, and polarity signaling, studies into the dynamic regulation of the podocyte structure have been hampered by the fact that ultrastructural analyses require electron microscopic imaging of fixed tissue. We developed a new technique that allows for visualization of podocyte foot processes using confocal laser scanning microscopy. The combination of inducible and mosaic expression of membrane-tagged fluorescent proteins in a small subset of podocytes enabled us to acquire light microscopic images of podocyte foot processes in unprecedented detail, even in living podocytes of freshly isolated glomeruli. Moreover, this technique visualized oscillatory glomerular contractions and confirmed the morphometric evaluations obtained in static electron microscopic images of podocyte processes. These data suggest that the new technique will provide an extremely powerful tool for studying the dynamics of podocyte ultrastructure.
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Affiliation(s)
- Martin Höhne
- Department II of Internal Medicine and the Center for Molecular Medicine Cologne, University of Cologne, 50937 Cologne, Germany
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