1
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Liu PJ, Sayeeda K, Zhuang C, Krendel M. Roles of myosin 1e and the actin cytoskeleton in kidney functions and familial kidney disease. Cytoskeleton (Hoboken) 2024. [PMID: 38708443 DOI: 10.1002/cm.21861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 03/21/2024] [Accepted: 04/04/2024] [Indexed: 05/07/2024]
Abstract
Mammalian kidneys are responsible for removing metabolic waste and maintaining fluid and electrolyte homeostasis via selective filtration. One of the proteins closely linked to selective renal filtration is myosin 1e (Myo1e), an actin-dependent molecular motor found in the specialized kidney epithelial cells involved in the assembly and maintenance of the renal filter. Point mutations in the gene encoding Myo1e, MYO1E, have been linked to familial kidney disease, and Myo1e knockout in mice leads to the disruption of selective filtration. In this review, we discuss the role of the actin cytoskeleton in renal filtration, the known and hypothesized functions of Myo1e, and the possible explanations for the impact of MYO1E mutations on renal function.
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Affiliation(s)
- Pei-Ju Liu
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Kazi Sayeeda
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Cindy Zhuang
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Mira Krendel
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
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2
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Xi G, Lamba SA, Mysh M, Poulton JS. Oxidative Stress Contributes to Slit Diaphragm Defects Caused by Disruption of Endocytosis. Kidney Int Rep 2024; 9:451-463. [PMID: 38344712 PMCID: PMC10851022 DOI: 10.1016/j.ekir.2023.11.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 10/27/2023] [Accepted: 11/20/2023] [Indexed: 03/04/2024] Open
Abstract
Introduction Podocyte slit diaphragms are an important component of the glomerular filtration barrier. Podocyte injury frequently includes defects in slit diaphragms, and various mechanisms for these defects have been described, including altered endocytic trafficking of slit diaphragm proteins or oxidative stress. However, the potential relationship between endocytosis and oxidative stress in the context of slit diaphragm integrity has not been extensively considered. Methods To examine the potential relationships between endocytosis, oxidative stress, and slit diaphragm integrity, we induced genetic or pharmacological disruption of endocytosis in Drosophila nephrocytes (the insect orthologue of podocytes) and cultured human podocytes. We then employed immunofluorescence microscopy to analyze protein localization and levels, and to quantify signal from reactive oxygen species (ROS) dyes. Immunoprecipitation from podocyte cell lysates was used to examine effects on slit diaphragm protein complex formation (i.e., nephrin/podocin and nephrin/ZO-1). Results Disruption of endocytosis in nephrocytes and podocytes led to slit diaphragm defects, elevated levels of ROS (oxidative stress), and activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant pathway. In nephrocytes with defective endocytosis, perturbation of Nrf2 signaling exacerbated slit diaphragm defects. Conversely, overexpression of Nrf2 target genes catalase or glucose-6-phosphate dehydrogenase (G6PD) significantly ameliorated slit diaphragm defects caused by disruption of endocytosis. Conclusion Oxidative stress is an important consequence of defective endocytosis and contributes to the defects in slit diaphragm integrity associated with disruption of endocytic trafficking.
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Affiliation(s)
- Gang Xi
- UNC Kidney Center, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Sajan A. Lamba
- UNC Kidney Center, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Michael Mysh
- UNC Kidney Center, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - John S. Poulton
- UNC Kidney Center, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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3
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Wang J, Casimiro-Garcia A, Johnson BG, Duffen J, Cain M, Savary L, Wang S, Nambiar P, Lech M, Zhao S, Xi L, Zhan Y, Olson J, Stejskal JA, Lin H, Zhang B, Martinez RV, Masek-Hammerman K, Schlerman FJ, Dower K. A protein kinase C α and β inhibitor blunts hyperphagia to halt renal function decline and reduces adiposity in a rat model of obesity-driven type 2 diabetes. Sci Rep 2023; 13:16919. [PMID: 37805649 PMCID: PMC10560236 DOI: 10.1038/s41598-023-43759-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 09/28/2023] [Indexed: 10/09/2023] Open
Abstract
Type 2 diabetes (T2D) and its complications can have debilitating, sometimes fatal consequences for afflicted individuals. The disease can be difficult to control, and therapeutic strategies to prevent T2D-induced tissue and organ damage are needed. Here we describe the results of administering a potent and selective inhibitor of Protein Kinase C (PKC) family members PKCα and PKCβ, Cmpd 1, in the ZSF1 obese rat model of hyperphagia-induced, obesity-driven T2D. Although our initial intent was to evaluate the effect of PKCα/β inhibition on renal damage in this model setting, Cmpd 1 unexpectedly caused a marked reduction in the hyperphagic response of ZSF1 obese animals. This halted renal function decline but did so indirectly and indistinguishably from a pair feeding comparator group. However, above and beyond this food intake effect, Cmpd 1 lowered overall animal body weights, reduced liver vacuolation, and reduced inguinal adipose tissue (iWAT) mass, inflammation, and adipocyte size. Taken together, Cmpd 1 had strong effects on multiple disease parameters in this obesity-driven rodent model of T2D. Further evaluation for potential translation of PKCα/β inhibition to T2D and obesity in humans is warranted.
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Affiliation(s)
- Ju Wang
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA.
| | | | - Bryce G Johnson
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA
| | - Jennifer Duffen
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA
| | - Michael Cain
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Mediar Therapeutics, Boston, MA, USA
| | - Leigh Savary
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Instem Life Science Systems Ltd, Mount Ida College, South Hadley, MA, USA
| | - Stephen Wang
- Pharmacokinetics and Drug Metabolism, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Novartis Gene Therapies, Novartis Institute for Biomedical Research, Cambridge, MA, USA
| | - Prashant Nambiar
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Strand Therapeutics, Cambridge, MA, USA
| | - Matthew Lech
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA
| | - Shanrong Zhao
- Clinical Genetics and Bioinformatics, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Amunix Pharmaceuticals, San Francisco, CA, USA
| | - Li Xi
- Early Clinical Development, Pfizer Worldwide Research and Development, Cambridge, MA, USA
| | - Yutian Zhan
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Cambridge, MA, USA
| | - Jennifer Olson
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, CT, USA
| | - James A Stejskal
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, CT, USA
- Charles River Laboratories, Shrewsbury, MA, USA
| | - Hank Lin
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Sunovion Pharmaceuticals Inc., Marlborough, MA, USA
| | - Baohong Zhang
- Clinical Genetics and Bioinformatics, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Data Sciences, Biogen, Cambridge, MA, USA
| | - Robert V Martinez
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA
- Center for Technological Innovation, Pfizer Worldwide Research and Development, San Francisco, CA, USA
| | | | - Franklin J Schlerman
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA
| | - Ken Dower
- Inflammation and Immunology, Pfizer Worldwide Research and Development, Cambridge, MA, USA.
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4
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Bouslama R, Dumont V, Lindfors S, Paavolainen L, Tienari J, Nisen H, Mirtti T, Saleem MA, Gordin D, Groop PH, Suetsugu S, Lehtonen S. Phosphorylation of PACSIN2 at S313 Regulates Podocyte Architecture in Coordination with N-WASP. Cells 2023; 12:1487. [PMID: 37296607 PMCID: PMC10252800 DOI: 10.3390/cells12111487] [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: 01/06/2023] [Revised: 05/16/2023] [Accepted: 05/23/2023] [Indexed: 06/12/2023] Open
Abstract
Changes in the dynamic architecture of podocytes, the glomerular epithelial cells, lead to kidney dysfunction. Previous studies on protein kinase C and casein kinase 2 substrates in neurons 2 (PACSIN2), a known regulator of endocytosis and cytoskeletal organization, reveal a connection between PACSIN2 and kidney pathogenesis. Here, we show that the phosphorylation of PACSIN2 at serine 313 (S313) is increased in the glomeruli of rats with diabetic kidney disease. We found that phosphorylation at S313 is associated with kidney dysfunction and increased free fatty acids rather than with high glucose and diabetes alone. Phosphorylation of PACSIN2 emerged as a dynamic process that fine-tunes cell morphology and cytoskeletal arrangement, in cooperation with the regulator of the actin cytoskeleton, Neural Wiskott-Aldrich syndrome protein (N-WASP). PACSIN2 phosphorylation decreased N-WASP degradation while N-WASP inhibition triggered PACSIN2 phosphorylation at S313. Functionally, pS313-PACSIN2 regulated actin cytoskeleton rearrangement depending on the type of cell injury and the signaling pathways involved. Collectively, this study indicates that N-WASP induces phosphorylation of PACSIN2 at S313, which serves as a mechanism whereby cells regulate active actin-related processes. The dynamic phosphorylation of S313 is needed to regulate cytoskeletal reorganization.
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Affiliation(s)
- Rim Bouslama
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Vincent Dumont
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Sonja Lindfors
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Lassi Paavolainen
- Institute for Molecular Medicine Finland (FIMM), Helsinki Institute of Life Science (HiLIFE), University of Helsinki, 00290 Helsinki, Finland
| | - Jukka Tienari
- Department of Pathology, University of Helsinki, Helsinki, and Helsinki University Hospital, 05850 Hyvinkää, Finland
| | - Harry Nisen
- Department of Urology, Helsinki University Hospital, 00029 HUS, Finland
| | - Tuomas Mirtti
- Department of Pathology, Helsinki University Hospital, 00290 Helsinki, Finland
- Research Program in Systems Oncology, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
| | - Moin A. Saleem
- Children’s Renal Unit, Bristol Medical School, University of Bristol, Bristol BS8 1TS, UK
| | - Daniel Gordin
- Minerva Foundation Institute for Medical Research, 00290 Helsinki, Finland
- Abdominal Center, Nephrology, University of Helsinki and Helsinki University Hospital, 00290 Helsinki, Finland
- Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
| | - Per-Henrik Groop
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
- Folkhälsan Institute of Genetics, Folkhälsan Research Center, 00290 Helsinki, Finland
- Department of Nephrology, University of Helsinki, Helsinki, and Helsinki University Hospital, 00290 Helsinki, Finland
- Department of Diabetes, Central Clinical School, Monash University, Melbourne, VIC 3800, Australia
| | - Shiro Suetsugu
- Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma 630-0192, Japan
- Data Science Center, Nara Institute of Science and Technology, Ikoma 630-0192, Japan
- Center for Digital Green-Innovation, Nara Institute of Science and Technology, Ikoma 630-0192, Japan
| | - Sanna Lehtonen
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland
- Department of Pathology, University of Helsinki, 00290 Helsinki, Finland
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5
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Imeri F, Stepanovska Tanturovska B, Manaila R, Pavenstädt H, Pfeilschifter J, Huwiler A. Loss of S1P Lyase Expression in Human Podocytes Causes a Reduction in Nephrin Expression That Involves PKCδ Activation. Int J Mol Sci 2023; 24:ijms24043267. [PMID: 36834691 PMCID: PMC9965238 DOI: 10.3390/ijms24043267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/30/2023] [Accepted: 02/02/2023] [Indexed: 02/11/2023] Open
Abstract
Sphingosine 1-phosphate (S1P) lyase (SPL, Sgpl1) is an ER-associated enzyme that irreversibly degrades the bioactive lipid, S1P, and thereby regulates multiple cellular functions attributed to S1P. Biallelic mutations in the human Sglp1 gene lead to a severe form of a particular steroid-resistant nephrotic syndrome, suggesting that the SPL is critically involved in maintaining the glomerular ultrafiltration barrier, which is mainly built by glomerular podocytes. In this study, we have investigated the molecular effects of SPL knockdown (kd) in human podocytes to better understand the mechanism underlying nephrotic syndrome in patients. A stable SPL-kd cell line of human podocytes was generated by the lentiviral shRNA transduction method and was characterized for reduced SPL mRNA and protein levels and increased S1P levels. This cell line was further studied for changes in those podocyte-specific proteins that are known to regulate the ultrafiltration barrier. We show here that SPL-kd leads to the downregulation of the nephrin protein and mRNA expression, as well as the Wilms tumor suppressor gene 1 (WT1), which is a key transcription factor regulating nephrin expression. Mechanistically, SPL-kd resulted in increased total cellular protein kinase C (PKC) activity, while the stable downregulation of PKCδ revealed increased nephrin expression. Furthermore, the pro-inflammatory cytokine, interleukin 6 (IL-6), also reduced WT1 and nephrin expression. In addition, IL-6 caused increased PKCδ Thr505 phosphorylation, suggesting enzyme activation. Altogether, these data demonstrate that nephrin is a critical factor downregulated by the loss of SPL, which may directly cause podocyte foot process effacement as observed in mice and humans, leading to albuminuria, a hallmark of nephrotic syndrome. Furthermore, our in vitro data suggest that PKCδ could represent a new possible pharmacological target for the treatment of a nephrotic syndrome induced by SPL mutations.
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Affiliation(s)
- Faik Imeri
- Institute of Pharmacology, Inselspital, INO-F, University of Bern, CH-3010 Bern, Switzerland
| | | | - Roxana Manaila
- Institute of Pharmacology, Inselspital, INO-F, University of Bern, CH-3010 Bern, Switzerland
| | - Hermann Pavenstädt
- Medizinische Klinik D, University Hospital Münster, D-48149 Münster, Germany
| | - Josef Pfeilschifter
- Pharmazentrum Frankfurt/ZAFES, University Hospital, Goethe University Frankfurt am Main, Theodor-Stern Kai 7, D-60590 Frankfurt am Main, Germany
| | - Andrea Huwiler
- Institute of Pharmacology, Inselspital, INO-F, University of Bern, CH-3010 Bern, Switzerland
- Correspondence: ; Tel.: +41-31-632-32-14
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6
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Lang K, Milosavljevic J, Heinkele H, Chen M, Gerstner L, Spitz D, Kayser S, Helmstädter M, Walz G, Köttgen M, Spracklen A, Poulton J, Hermle T. Selective endocytosis controls slit diaphragm maintenance and dynamics in Drosophila nephrocytes. eLife 2022; 11:79037. [PMID: 35876643 PMCID: PMC9355562 DOI: 10.7554/elife.79037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 07/24/2022] [Indexed: 11/28/2022] Open
Abstract
The kidneys generate about 180 l of primary urine per day by filtration of plasma. An essential part of the filtration barrier is the slit diaphragm, a multiprotein complex containing nephrin as major component. Filter dysfunction typically manifests with proteinuria and mutations in endocytosis regulating genes were discovered as causes of proteinuria. However, it is unclear how endocytosis regulates the slit diaphragm and how the filtration barrier is maintained without either protein leakage or filter clogging. Here, we study nephrin dynamics in podocyte-like nephrocytes of Drosophila and show that selective endocytosis either by dynamin- or flotillin-mediated pathways regulates a stable yet highly dynamic architecture. Short-term manipulation of endocytic functions indicates that dynamin-mediated endocytosis of ectopic nephrin restricts slit diaphragm formation spatially while flotillin-mediated turnover of nephrin within the slit diaphragm is needed to maintain filter permeability by shedding of molecules bound to nephrin in endosomes. Since slit diaphragms cannot be studied in vitro and are poorly accessible in mouse models, this is the first analysis of their dynamics within the slit diaphragm multiprotein complex. Identification of the mechanisms of slit diaphragm maintenance will help to develop novel therapies for proteinuric renal diseases that are frequently limited to symptomatic treatment.
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Affiliation(s)
- Konrad Lang
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Helena Heinkele
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Mengmeng Chen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Lea Gerstner
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Dominik Spitz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Severine Kayser
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Gerd Walz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Köttgen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrew Spracklen
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - John Poulton
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Tobias Hermle
- Department of Medicine, University of Freiburg, Freiburg, Germany
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7
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Tian X, Bunda P, Ishibe S. Podocyte Endocytosis in Regulating the Glomerular Filtration Barrier. Front Med (Lausanne) 2022; 9:801837. [PMID: 35223901 PMCID: PMC8866310 DOI: 10.3389/fmed.2022.801837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 01/06/2022] [Indexed: 12/26/2022] Open
Abstract
Endocytosis is a mechanism that internalizes and recycles plasma membrane components and transmembrane receptors via vesicle formation, which is mediated by clathrin-dependent and clathrin-independent signaling pathways. Podocytes are specialized, terminally differentiated epithelial cells in the kidney, located on the outermost layer of the glomerulus. These cells play an important role in maintaining the integrity of the glomerular filtration barrier in conjunction with the adjacent basement membrane and endothelial cell layers within the glomerulus. An intact podocyte endocytic machinery appears to be necessary for maintaining podocyte function. De novo pathologic human genetic mutations and loss-of-function studies of critical podocyte endocytosis genes in genetically engineered mouse models suggest that this pathway contributes to the pathophysiology of development and progression of proteinuria in chronic kidney disease. Here, we review the mechanism of cellular endocytosis and its regulation in podocyte injury in the context of glomerular diseases. A thorough understanding of podocyte endocytosis may shed novel insights into its biological function in maintaining a functioning filter and offer potential targeted therapeutic strategies for proteinuric glomerular diseases.
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Affiliation(s)
- Xuefei Tian
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, United States
| | - Patricia Bunda
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, United States
| | - Shuta Ishibe
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT, United States
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8
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Modes of podocyte death in diabetic kidney disease: an update. J Nephrol 2022; 35:1571-1584. [PMID: 35201595 DOI: 10.1007/s40620-022-01269-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 02/01/2022] [Indexed: 02/06/2023]
Abstract
Diabetic kidney disease (DKD) accounts for a large proportion of end-stage renal diseases that require renal replacement therapies including dialysis and transplantation. Therefore, it is critical to understand the occurrence and development of DKD. Podocytes are mainly injured during the development of DKD, ultimately leading to their extensive death and loss. In turn, the injury and death of glomerular podocytes are also the main culprits of DKD. This review introduces the characteristics of podocytes and summarizes the modes of their death in DKD, including apoptosis, autophagy, mitotic catastrophe (MC), anoikis, necroptosis, and pyroptosis. Apoptosis is characterized by nuclear condensation and the formation of apoptotic bodies, and it exerts a different effect from autophagy in mediating DKD-induced podocyte loss. MC mediates a faulty mitotic process while anoikis separates podocytes from the basement membrane. Moreover, pyroptosis activates inflammatory factors to aggravate podocyte injuries whilst necroptosis drives signaling cascades, such as receptor-interacting protein kinases 1 and 3 and mixed lineage kinase domain-like, ultimately promoting the death of podocytes. In conclusion, a thorough knowledge of the modes of podocyte death in DKD can help us understand the development of DKD and lay the foundation for strategies in DKD disease therapy.
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9
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Nakamichi R, Hayashi K, Itoh H. Effects of High Glucose and Lipotoxicity on Diabetic Podocytes. Nutrients 2021; 13:nu13010241. [PMID: 33467659 PMCID: PMC7830342 DOI: 10.3390/nu13010241] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 12/11/2020] [Accepted: 01/11/2021] [Indexed: 01/19/2023] Open
Abstract
Glomerular podocytes are highly differentiated cells that cover glomerular capillaries from the outside and have a characteristic morphology with numerous foot processes. The formation of slit membranes between the foot processes serves as a final filtration barrier for urine filtration from the blood. Podocyte damage causes disruption of the slit membrane, subsequent proteinuria and finally glomerulosclerosis, which is a common pathway in various types of chronic kidney disease (CKD). In recent years, there has been an increase in diabetes, due to rapid lifestyle changes, which is the main cause of CKD. Therefore, understanding the effect of diabetic status on podocytes is of great importance to establish a strategy for preventing CKD progression. In this review, we summarize altered glucose and lipid metabolism in diabetic podocytes and also discuss the reversibility of the changes in podocyte phenotype.
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Affiliation(s)
| | - Kaori Hayashi
- Correspondence: ; Tel.: +81-3-5363-3796; Fax: +81-3-3359-2745
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10
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Blaine J, Dylewski J. Regulation of the Actin Cytoskeleton in Podocytes. Cells 2020; 9:cells9071700. [PMID: 32708597 PMCID: PMC7408282 DOI: 10.3390/cells9071700] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 06/30/2020] [Accepted: 07/07/2020] [Indexed: 12/13/2022] Open
Abstract
Podocytes are an integral part of the glomerular filtration barrier, a structure that prevents filtration of large proteins and macromolecules into the urine. Podocyte function is dependent on actin cytoskeleton regulation within the foot processes, structures that link podocytes to the glomerular basement membrane. Actin cytoskeleton dynamics in podocyte foot processes are complex and regulated by multiple proteins and other factors. There are two key signal integration and structural hubs within foot processes that regulate the actin cytoskeleton: the slit diaphragm and focal adhesions. Both modulate actin filament extension as well as foot process mobility. No matter what the initial cause, the final common pathway of podocyte damage is dysregulation of the actin cytoskeleton leading to foot process retraction and proteinuria. Disruption of the actin cytoskeleton can be due to acquired causes or to genetic mutations in key actin regulatory and signaling proteins. Here, we describe the major structural and signaling components that regulate the actin cytoskeleton in podocytes as well as acquired and genetic causes of actin dysregulation.
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Affiliation(s)
- Judith Blaine
- Renal Division, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA;
| | - James Dylewski
- Renal Division, University of Colorado Anschutz Medical Campus and Denver Health Medical Center, Aurora, CO 80045, USA
- Correspondence: ; Tel.: +303-724-4841
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11
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Abstract
The increasing global prevalence of type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) has prompted research efforts to tackle the growing epidemic of diabetic kidney disease (DKD; also known as diabetic nephropathy). The limited success of much of this research might in part be due to the fact that not all patients diagnosed with DKD have renal dysfunction as a consequence of their diabetes mellitus. Patients who present with CKD and diabetes mellitus (type 1 or type 2) can have true DKD (wherein CKD is a direct consequence of their diabetes status), nondiabetic kidney disease (NDKD) coincident with diabetes mellitus, or a combination of both DKD and NDKD. Preclinical studies using models that more accurately mimic these three entities might improve the ability of animal models to predict clinical trial outcomes. Moreover, improved insights into the pathomechanisms that are shared by these entities - including sodium-glucose cotransporter 2 (SGLT2) and renin-angiotensin system-driven glomerular hyperfiltration and tubular hyper-reabsorption - as well as those that are unique to individual entities might lead to the identification of new treatment targets. Acknowledging that the clinical entity of CKD plus diabetes mellitus encompasses NDKD as well as DKD could help solve some of the urgent unmet medical needs of patients affected by these conditions.
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12
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IQGAP1 mediates podocyte injury in diabetic kidney disease by regulating nephrin endocytosis. Cell Signal 2019; 59:13-23. [DOI: 10.1016/j.cellsig.2019.03.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 03/07/2019] [Accepted: 03/08/2019] [Indexed: 01/02/2023]
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13
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Espiritu EB, Jiang H, Moreau-Marquis S, Sullivan M, Yan K, Beer Stolz D, Sampson MG, Hukriede NA, Swiatecka-Urban A. The human nephrin Y 1139RSL motif is essential for podocyte foot process organization and slit diaphragm formation during glomerular development. J Biol Chem 2019; 294:10773-10788. [PMID: 31152064 DOI: 10.1074/jbc.ra119.008235] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/16/2019] [Indexed: 11/06/2022] Open
Abstract
Nephrin is an immunoglobulin-type cell-adhesion molecule with a key role in the glomerular interpodocyte slit diaphragm. Mutations in the nephrin gene are associated with defects in the slit diaphragm, leading to early-onset nephrotic syndrome, typically resistant to treatment. Although the endocytic trafficking of nephrin is essential for the assembly of the slit diaphragm, nephrin's specific endocytic motifs remain unknown. To search for endocytic motifs, here we performed a multisequence alignment of nephrin and identified a canonical YXXØ-type motif, Y1139RSL, in the nephrin cytoplasmic tail, expressed only in primates. Using site-directed mutagenesis, various biochemical methods, single-plane illumination microscopy, a human podocyte line, and a human nephrin-expressing zebrafish model, we found that Y1139RSL is a novel endocytic motif and a structural element for clathrin-mediated nephrin endocytosis that functions as a phosphorylation-sensitive signal. We observed that Y1139RSL motif-mediated endocytosis helps to localize nephrin to specialized plasma membrane domains in podocytes and is essential for normal foot process organization into a functional slit diaphragm between neighboring foot processes in zebrafish. The importance of nephrin Y1139RSL for healthy podocyte development was supported by population-level analyses of genetic variations at this motif, revealing that such variations are very rare, suggesting that mutations in this motif have autosomal-recessive negative effects on kidney health. These findings expand our understanding of the mechanism underlying nephrin endocytosis and may lead to improved diagnostic tools or therapeutic strategies for managing early-onset, treatment-resistant nephrotic syndrome.
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Affiliation(s)
- Eugenel B Espiritu
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15201
| | - Huajun Jiang
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15224
| | - Sophie Moreau-Marquis
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
| | - Mara Sullivan
- Department of Nephrology, UPMC Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15201
| | - Kunimasa Yan
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo 181-8611, Japan, and
| | - Donna Beer Stolz
- Department of Nephrology, UPMC Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15201
| | - Matthew G Sampson
- Department of Pediatrics-Nephrology University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Neil A Hukriede
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15201
| | - Agnieszka Swiatecka-Urban
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15224,.
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14
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Dorval G, Kuzmuk V, Gribouval O, Welsh GI, Bierzynska A, Schmitt A, Miserey-Lenkei S, Koziell A, Haq S, Benmerah A, Mollet G, Boyer O, Saleem MA, Antignac C. TBC1D8B Loss-of-Function Mutations Lead to X-Linked Nephrotic Syndrome via Defective Trafficking Pathways. Am J Hum Genet 2019; 104:348-355. [PMID: 30661770 DOI: 10.1016/j.ajhg.2018.12.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 12/20/2018] [Indexed: 12/11/2022] Open
Abstract
Steroid-resistant nephrotic syndrome (SRNS) is characterized by high-range proteinuria and most often focal and segmental glomerulosclerosis (FSGS). Identification of mutations in genes causing SRNS has improved our understanding of disease mechanisms and highlighted defects in the podocyte, a highly specialized glomerular epithelial cell, as major factors in disease pathogenesis. By exome sequencing, we identified missense mutations in TBC1D8B in two families with an X-linked early-onset SRNS with FSGS. TBC1D8B is an uncharacterized Rab-GTPase-activating protein likely involved in endocytic and recycling pathways. Immunofluorescence studies revealed TBC1D8B presence in human glomeruli, and affected individual podocytes displayed architectural changes associated with migration defects commonly found in FSGS. In zebrafish we demonstrated that both knockdown and knockout of the unique TBC1D8B ortholog-induced proteinuria and that this phenotype was rescued by human TBC1D8B mRNA injection, but not by either of the two mutated mRNAs. We also showed an interaction between TBC1D8B and Rab11b, a key protein in vesicular recycling in cells. Interestingly, both internalization and recycling processes were dramatically decreased in affected individuals' podocytes and fibroblasts, confirming the crucial role of TBC1D8B in the cellular recycling processes, probably as a Rab11b GTPase-activating protein. Altogether, these results confirmed that pathogenic variations in TBC1D8B are involved in X-linked podocytopathy and points to alterations in recycling processes as a mechanism of SRNS.
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Affiliation(s)
- Guillaume Dorval
- Laboratory of Hereditary Kidney Diseases, Imagine Institute, INSERM U1163, Paris Descartes University, 75015 Paris, France
| | - Valeryia Kuzmuk
- Bristol Renal, University of Bristol and Bristol Royal Hospital for Children, Bristol, UK
| | - Olivier Gribouval
- Laboratory of Hereditary Kidney Diseases, Imagine Institute, INSERM U1163, Paris Descartes University, 75015 Paris, France
| | - Gavin I Welsh
- Bristol Renal, University of Bristol and Bristol Royal Hospital for Children, Bristol, UK
| | - Agnieszka Bierzynska
- Bristol Renal, University of Bristol and Bristol Royal Hospital for Children, Bristol, UK
| | - Alain Schmitt
- Inserm, U1016, Institut Cochin, 75014 Paris, France; Cnrs, UMR8104, 75014 Paris, France; Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France
| | - Stéphanie Miserey-Lenkei
- Institut Curie, PSL Research University, CNRS, UMR 144, Molecular Mechanisms of Intracellular Transport, 75005 Paris, France
| | - Ania Koziell
- Department of Children's Nephrology and Urology, Evelina London, London SE1 7EH, UK
| | - Shuman Haq
- Paediatric Nephrology, University Hospital Southampton NHS Foundation Trust, Southampton SO16 6YD, UK
| | - Alexandre Benmerah
- Laboratory of Hereditary Kidney Diseases, Imagine Institute, INSERM U1163, Paris Descartes University, 75015 Paris, France
| | - Géraldine Mollet
- Laboratory of Hereditary Kidney Diseases, Imagine Institute, INSERM U1163, Paris Descartes University, 75015 Paris, France
| | - Olivia Boyer
- Laboratory of Hereditary Kidney Diseases, Imagine Institute, INSERM U1163, Paris Descartes University, 75015 Paris, France; Department of Pediatric Nephrology, Reference center for Hereditary Kidney Diseases (MARHEA), Necker Hospital, APHP, 75015 Paris, France
| | - Moin A Saleem
- Bristol Renal, University of Bristol and Bristol Royal Hospital for Children, Bristol, UK.
| | - Corinne Antignac
- Laboratory of Hereditary Kidney Diseases, Imagine Institute, INSERM U1163, Paris Descartes University, 75015 Paris, France; Department of Genetics, Reference center for Hereditary Kidney Diseases (MARHEA), Necker Hospital, APHP,75015 Paris, France.
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15
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Yu SMW, Nissaisorakarn P, Husain I, Jim B. Proteinuric Kidney Diseases: A Podocyte's Slit Diaphragm and Cytoskeleton Approach. Front Med (Lausanne) 2018; 5:221. [PMID: 30255020 PMCID: PMC6141722 DOI: 10.3389/fmed.2018.00221] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/18/2018] [Indexed: 01/19/2023] Open
Abstract
Proteinuric kidney diseases are a group of disorders with diverse pathological mechanisms associated with significant losses of protein in the urine. The glomerular filtration barrier (GFB), comprised of the three important layers, the fenestrated glomerular endothelium, the glomerular basement membrane (GBM), and the podocyte, dictates that disruption of any one of these structures should lead to proteinuric disease. Podocytes, in particular, have long been considered as the final gatekeeper of the GFB. This specialized visceral epithelial cell contains a complex framework of cytoskeletons forming foot processes and mediate important cell signaling to maintain podocyte health. In this review, we will focus on slit diaphragm proteins such as nephrin, podocin, TRPC6/5, as well as cytoskeletal proteins Rho/small GTPases and synaptopodin and their respective roles in participating in the pathogenesis of proteinuric kidney diseases. Furthermore, we will summarize the potential therapeutic options targeting the podocyte to treat this group of kidney diseases.
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Affiliation(s)
- Samuel Mon-Wei Yu
- Department of Medicine, Jacobi Medical Center, Bronx, NY, United States
| | | | - Irma Husain
- Department of Medicine, James J. Peters VA Medical Center, Bronx, NY, United States
| | - Belinda Jim
- Department of Medicine, Jacobi Medical Center, Bronx, NY, United States.,Renal Division, Jacobi Medical Center, Bronx, NY, United States
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16
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Hermle T, Schneider R, Schapiro D, Braun DA, van der Ven AT, Warejko JK, Daga A, Widmeier E, Nakayama M, Jobst-Schwan T, Majmundar AJ, Ashraf S, Rao J, Finn LS, Tasic V, Hernandez JD, Bagga A, Jalalah SM, El Desoky S, Kari JA, Laricchia KM, Lek M, Rehm HL, MacArthur DG, Mane S, Lifton RP, Shril S, Hildebrandt F. GAPVD1 and ANKFY1 Mutations Implicate RAB5 Regulation in Nephrotic Syndrome. J Am Soc Nephrol 2018; 29:2123-2138. [PMID: 29959197 PMCID: PMC6065084 DOI: 10.1681/asn.2017121312] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 05/24/2018] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Steroid-resistant nephrotic syndrome (SRNS) is a frequent cause of CKD. The discovery of monogenic causes of SRNS has revealed specific pathogenetic pathways, but these monogenic causes do not explain all cases of SRNS. METHODS To identify novel monogenic causes of SRNS, we screened 665 patients by whole-exome sequencing. We then evaluated the in vitro functional significance of two genes and the mutations therein that we discovered through this sequencing and conducted complementary studies in podocyte-like Drosophila nephrocytes. RESULTS We identified conserved, homozygous missense mutations of GAPVD1 in two families with early-onset NS and a homozygous missense mutation of ANKFY1 in two siblings with SRNS. GAPVD1 and ANKFY1 interact with the endosomal regulator RAB5. Coimmunoprecipitation assays indicated interaction between GAPVD1 and ANKFY1 proteins, which also colocalized when expressed in HEK293T cells. Silencing either protein diminished the podocyte migration rate. Compared with wild-type GAPVD1 and ANKFY1, the mutated proteins produced upon ectopic expression of GAPVD1 or ANKFY1 bearing the patient-derived mutations exhibited altered binding affinity for active RAB5 and reduced ability to rescue the knockout-induced defect in podocyte migration. Coimmunoprecipitation assays further demonstrated a physical interaction between nephrin and GAPVD1, and immunofluorescence revealed partial colocalization of these proteins in rat glomeruli. The patient-derived GAPVD1 mutations reduced nephrin-GAPVD1 binding affinity. In Drosophila, silencing Gapvd1 impaired endocytosis and caused mistrafficking of the nephrin ortholog. CONCLUSIONS Mutations in GAPVD1 and probably in ANKFY1 are novel monogenic causes of NS. The discovery of these genes implicates RAB5 regulation in the pathogenesis of human NS.
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Affiliation(s)
- Tobias Hermle
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
- Renal Division, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ronen Schneider
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - David Schapiro
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Daniela A Braun
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Amelie T van der Ven
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Jillian K Warejko
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Ankana Daga
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Eugen Widmeier
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Makiko Nakayama
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Tilman Jobst-Schwan
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Amar J Majmundar
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Shazia Ashraf
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Jia Rao
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Laura S Finn
- Department of Pathology, Seattle Children's Hospital, University of Washington, Seattle, Washington
| | - Velibor Tasic
- Department of Pediatric Nephrology, Medical Faculty Skopje, University Children's Hospital, Skopje, Macedonia
| | - Joel D Hernandez
- Department of Pediatric Nephrology, Providence Sacred Heart Medical Center and Children's Hospital, Spokane, Washington
| | - Arvind Bagga
- Division of Nephrology, All India Institute of Medical Sciences, New Delhi, India
| | | | - Sherif El Desoky
- Pediatric Nephrology Center of Excellence and Pediatric Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Jameela A Kari
- Pediatric Nephrology Center of Excellence and Pediatric Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Kristen M Laricchia
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Monkol Lek
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Heidi L Rehm
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Daniel G MacArthur
- Broad Center for Mendelian Genetics, Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts
| | - Shrikant Mane
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut; and
| | - Richard P Lifton
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut; and
- Laboratory of Human Genetics and Genomics, The Rockefeller University, New York, New York
| | - Shirlee Shril
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Friedhelm Hildebrandt
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts;
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17
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Kvirkvelia N, McMenamin M, Warren M, Jadeja RN, Kodeboyina SK, Sharma A, Zhi W, O'Connor PM, Raju R, Lucas R, Madaio MP. Kidney-targeted inhibition of protein kinase C-α ameliorates nephrotoxic nephritis with restoration of mitochondrial dysfunction. Kidney Int 2018; 94:280-291. [PMID: 29731111 DOI: 10.1016/j.kint.2018.01.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 12/21/2017] [Accepted: 01/18/2018] [Indexed: 01/26/2023]
Abstract
To investigate the role of protein kinase C-α (PKC-α) in glomerulonephritis, the capacity of PKC-α inhibition to reverse the course of established nephrotoxic nephritis (NTN) was evaluated. Nephritis was induced by a single injection of nephrotoxic serum and after its onset, a PKC-α inhibitor was administered either systemically or by targeted glomerular delivery. By day seven, all mice with NTN had severe nephritis, whereas mice that received PKC-α inhibitors in either form had minimal evidence of disease. To further understand the underlying mechanism, label-free shotgun proteomic analysis of the kidney cortexes were performed, using quantitative mass spectrometry. Ingenuity pathway analysis revealed 157 differentially expressed proteins and mitochondrial dysfunction as the most modulated pathway. Functional protein groups most affected by NTN were mitochondrial proteins associated with respiratory processes. These proteins were down-regulated in the mice with NTN, while their expression was restored with PKC-α inhibition. This suggests a role for proteins that regulate oxidative phosphorylation in recovery. In cultured glomerular endothelial cells, nephrotoxic serum caused a decrease in mitochondrial respiration and membrane potential, mitochondrial morphologic changes and an increase in glycolytic lactic acid production; all normalized by PKC-α inhibition. Thus, PKC-α has a critical role in NTN progression, and the results implicate mitochondrial processes through restoring oxidative phosphorylation, as an essential mechanism underlying recovery. Importantly, our study provides additional support for targeted therapy to glomeruli to reverse the course of progressive disease.
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Affiliation(s)
- Nino Kvirkvelia
- Department of Medicine, Augusta University, Augusta, Georgia, USA
| | | | - Marie Warren
- Department of Pharmacology and Toxicology, Augusta University, Augusta, Georgia, USA
| | - Ravirajsinh N Jadeja
- Department of Biochemistry and Molecular Biology, Augusta University, Augusta, Georgia, USA
| | - Sai Karthik Kodeboyina
- Center for Biotechnology and Genomic Medicine, Augusta University, Augusta, Georgia, USA
| | - Ashok Sharma
- Center for Biotechnology and Genomic Medicine, Augusta University, Augusta, Georgia, USA
| | - Wenbo Zhi
- Center for Biotechnology and Genomic Medicine, Augusta University, Augusta, Georgia, USA
| | - Paul M O'Connor
- Department of Physiology and Endocrinology, Augusta University, Augusta, Georgia, USA
| | - Raghavan Raju
- Department of Pharmacology and Toxicology, Augusta University, Augusta, Georgia, USA
| | - Rudolf Lucas
- Vascular Biology Center, Department of Pharmacology and Toxicology, Augusta University, Augusta, Georgia, USA
| | - Michael P Madaio
- Department of Medicine, Augusta University, Augusta, Georgia, USA.
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18
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Hayashi D, Ueda S, Yamanoue M, Ashida H, Shirai Y. Amelioration of diabetic nephropathy by oral administration of d-α-tocopherol and its mechanisms. Biosci Biotechnol Biochem 2018; 82:65-73. [DOI: 10.1080/09168451.2017.1411184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Abstract
Diabetic nephropathy (DN) is a diabetic vascular complication, and abnormal protein kinase C (PKC) activation from increased diacylglycerol (DG) production in diabetic hyperglycemia is one of the causes of DN. Diacylglycerol kinase (DGK) converts DG into phosphatidic acid. In other words, DGK can attenuate PKC activity by reducing the amount of DG. Recently, we reported that intraperitoneally administered d-α-tocopherol (vitamin E, αToc) induces an amelioration of DN in vivo through the activation of DGKα and the prevention of podocyte loss. However, the effect of the oral administration of αToc on DN in mice remains unknown. Here, we evaluated the effect of oral administration of αToc on DN and its molecular mechanism using streptozocin-induced diabetic mice. Consequently, the oral administration of αToc significantly ameliorated the symptoms of DN by preventing the loss of podocytes, and it was revealed that the inhibition of PKC activity was involved in this amelioration.
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Affiliation(s)
- Daiki Hayashi
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Shuji Ueda
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Minoru Yamanoue
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Hitoshi Ashida
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Yasuhito Shirai
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
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19
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Martin CE, Jones N. Nephrin Signaling in the Podocyte: An Updated View of Signal Regulation at the Slit Diaphragm and Beyond. Front Endocrinol (Lausanne) 2018; 9:302. [PMID: 29922234 PMCID: PMC5996060 DOI: 10.3389/fendo.2018.00302] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 05/22/2018] [Indexed: 12/11/2022] Open
Abstract
Podocytes are a major component of the glomerular blood filtration barrier, and alterations to the morphology of their unique actin-based foot processes (FP) are a common feature of kidney disease. Adjacent FP are connected by a specialized intercellular junction known as the slit diaphragm (SD), which serves as the ultimate barrier to regulate passage of macromolecules from the blood. While the link between SD dysfunction and reduced filtration selectivity has been recognized for nearly 50 years, our understanding of the underlying molecular circuitry began only 20 years ago, sparked by the identification of NPHS1, encoding the transmembrane protein nephrin. Nephrin not only functions as the core component of the extracellular SD filtration network but also as a signaling scaffold via interactions at its short intracellular region. Phospho-regulation of several conserved tyrosine residues in this region influences signal transduction pathways which control podocyte cell adhesion, shape, and survival, and emerging studies highlight roles for nephrin phospho-dynamics in mechanotransduction and endocytosis. The following review aims to summarize the last 5 years of advancement in our knowledge of how signaling centered at nephrin directs SD barrier formation and function. We further provide insight on promising frontiers in podocyte biology, which have implications for SD signaling in the healthy and diseased kidney.
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20
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Diacylglycerol Kinase alpha is Involved in the Vitamin E-Induced Amelioration of Diabetic Nephropathy in Mice. Sci Rep 2017; 7:2597. [PMID: 28572624 PMCID: PMC5453949 DOI: 10.1038/s41598-017-02354-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 04/10/2017] [Indexed: 02/05/2023] Open
Abstract
Diabetic nephropathy (DN) is one of vascular complications of diabetes and is caused by abnormal protein kinase C activation as a result of increased diacylglycerol (DG) production in diabetic hyperglycaemia. Diacylglycerol kinase (DGK) converts DG into phosphatidic acid. Therefore, it is expected that the activation of DGK would ameliorate DN. Indeed, it has been reported that vitamin E (VtE) ameliorates DN in rat by activating DGK, and we recently reported that VtE specifically activates DGKα isoform in vitro. However, whether DGKα is involved in the VtE-induced amelioration of DN in vivo remains unknown. Therefore, we investigated the VtE-induced amelioration of DN in wild-type (DGKα+/+) and DGKα–deficient (DGKα−/−) mice in which diabetes was induced by streptozocin. Several symptoms of DN were ameliorated by VtE treatment in the DGKα+/+ mice but not in the DGKα−/− mice. Moreover, transmission electron microscopy of glomeruli and immunofluorescent staining of glomerular epithelial cells (podocytes) indicated that VtE ameliorates podocyte pathology and prevents podocyte loss in the DGKα+/+ mice but not in the DGKα−/− mice. We showed that VtE can ameliorate DN in mice and that DGKα is involved in the VtE-induced amelioration of DN in vivo, suggesting that DGKα is an attractive therapeutic target for DN.
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21
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Dumont V, Tolvanen TA, Kuusela S, Wang H, Nyman TA, Lindfors S, Tienari J, Nisen H, Suetsugu S, Plomann M, Kawachi H, Lehtonen S. PACSIN2 accelerates nephrin trafficking and is up-regulated in diabetic kidney disease. FASEB J 2017; 31:3978-3990. [PMID: 28550045 PMCID: PMC5572687 DOI: 10.1096/fj.201601265r] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 05/01/2017] [Indexed: 01/07/2023]
Abstract
Nephrin is a core component of podocyte (glomerular epithelial cell) slit diaphragm and is required for kidney ultrafiltration. Down-regulation or mislocalization of nephrin has been observed in diabetic kidney disease (DKD), characterized by albuminuria. Here, we investigate the role of protein kinase C and casein kinase 2 substrate in neurons 2 (PACSIN2), a regulator of endocytosis and recycling, in the trafficking of nephrin and development of DKD. We observe that PACSIN2 is up-regulated and nephrin mislocalized in podocytes of obese Zucker diabetic fatty (ZDF) rats that have altered renal function. In cultured podocytes, PACSIN2 and nephrin colocalize and interact. We show that nephrin is endocytosed in PACSIN2-positive membrane regions and that PACSIN2 overexpression increases both nephrin endocytosis and recycling. We identify rabenosyn-5, which is involved in early endosome maturation and endosomal sorting, as a novel interaction partner of PACSIN2. Interestingly, rabenosyn-5 expression is increased in podocytes in obese ZDF rats, and, in vitro, its overexpression enhances the association of PACSIN2 and nephrin. We also show that palmitate, which is elevated in diabetes, enhances this association. Collectively, PACSIN2 is up-regulated and nephrin is abnormally localized in podocytes of diabetic ZDF rats. In vitro, PACSIN2 enhances nephrin turnover apparently via a mechanism involving rabenosyn-5. The data suggest that elevated PACSIN2 expression accelerates nephrin trafficking and associates with albuminuria.—Dumont, V., Tolvanen, T. A., Kuusela, S., Wang, H., Nyman, T. A., Lindfors, S., Tienari, J., Nisen, H., Suetsugu, S., Plomann, M., Kawachi, H., Lehtonen, S. PACSIN2 accelerates nephrin trafficking and is up-regulated in diabetic kidney disease.
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Affiliation(s)
- Vincent Dumont
- Department of Pathology, University of Helsinki, Helsinki, Finland
| | | | - Sara Kuusela
- Department of Pathology, University of Helsinki, Helsinki, Finland
| | - Hong Wang
- Department of Pathology, University of Helsinki, Helsinki, Finland
| | - Tuula A Nyman
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Sonja Lindfors
- Department of Pathology, University of Helsinki, Helsinki, Finland
| | - Jukka Tienari
- Department of Pathology, Helsinki University Hospital, Hyvinkää, Finland.,Department of Pathology, Helsinki University Hospital, Hyvinkää, Finland
| | - Harry Nisen
- Department of Urology, Helsinki University Hospital, Helsinki, Finland
| | - Shiro Suetsugu
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan
| | | | - Hiroshi Kawachi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Sanna Lehtonen
- Department of Pathology, University of Helsinki, Helsinki, Finland;
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22
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Sorting Nexin 9 facilitates podocin endocytosis in the injured podocyte. Sci Rep 2017; 7:43921. [PMID: 28266622 PMCID: PMC5339724 DOI: 10.1038/srep43921] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 02/01/2017] [Indexed: 12/18/2022] Open
Abstract
The irreversibility of glomerulosclerotic changes depends on the degree of podocyte injury. We have previously demonstrated the endocytic translocation of podocin to the subcellular area in severely injured podocytes and found that this process is the primary disease trigger. Here we identified the protein sorting nexin 9 (SNX9) as a novel facilitator of podocin endocytosis in a yeast two-hybrid analysis. SNX9 is involved in clathrin-mediated endocytosis, actin rearrangement and vesicle transport regulation. Our results revealed and confirmed that SNX9 interacts with podocin exclusively through the Bin–Amphiphysin–Rvs (BAR) domain of SNX9. Immunofluorescence staining revealed the expression of SNX9 in response to podocyte adriamycin-induced injury both in vitro and in vivo. Finally, an analysis of human glomerular disease biopsy samples demonstrated strong SNX9 expression and co-localization with podocin in samples representative of severe podocyte injury, such as IgA nephropathy with poor prognosis, membranous nephropathy and focal segmental glomerulosclerosis. In conclusion, we identified SNX9 as a facilitator of podocin endocytosis in severe podocyte injury and demonstrated the expression of SNX9 in the podocytes of both nephropathy model mice and human patients with irreversible glomerular disease.
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23
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Swiatecka-Urban A. Endocytic Trafficking at the Mature Podocyte Slit Diaphragm. Front Pediatr 2017; 5:32. [PMID: 28286744 PMCID: PMC5324021 DOI: 10.3389/fped.2017.00032] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 02/03/2017] [Indexed: 12/16/2022] Open
Abstract
Endocytic trafficking couples cell signaling with the cytoskeletal dynamics by organizing a crosstalk between protein networks in different subcellular compartments. Proteins residing in the plasma membrane are internalized and transported as cargo in endocytic vesicles (i.e., endocytosis). Subsequently, cargo proteins can be delivered to lysosomes for degradation or recycled back to the plasma membrane. The slit diaphragm is a modified tight junction connecting foot processes of the glomerular epithelial cells, podocytes. Signaling at the slit diaphragm plays a critical role in the kidney while its dysfunction leads to glomerular protein loss (proteinuria), manifesting as nephrotic syndrome, a rare condition with an estimated incidence of 2-4 new cases per 100,000 each year. Relatively little is known about the role of endocytic trafficking in podocyte signaling and maintenance of the slit diaphragm integrity. This review will focus on the role of endocytic trafficking at the mature podocyte slit diaphragm.
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Affiliation(s)
- Agnieszka Swiatecka-Urban
- Department of Nephrology, Children's Hospital of Pittsburgh, Pittsburgh, PA, USA; Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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24
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Teng B, Schroder P, Müller-Deile J, Schenk H, Staggs L, Tossidou I, Dikic I, Haller H, Schiffer M. CIN85 Deficiency Prevents Nephrin Endocytosis and Proteinuria in Diabetes. Diabetes 2016; 65:3667-3679. [PMID: 27531950 PMCID: PMC5314701 DOI: 10.2337/db16-0081] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 07/31/2016] [Indexed: 12/12/2022]
Abstract
Diabetic nephropathy (DN) is the major cause of end-stage renal disease worldwide. Podocytes are important for glomerular filtration barrier function and maintenance of size selectivity in protein filtration in the kidney. Podocyte damage is the basis of many glomerular diseases characterized by loss of interdigitating foot processes and decreased expression of components of the slit diaphragm. Nephrin, a podocyte-specific protein, is the main component of the slit diaphragm. Loss of nephrin is observed in human and rodent models of diabetic kidney disease. The long isoform of CIN85 (RukL) is a binding partner of nephrin that mediates nephrin endocytosis via ubiquitination in podocytes. Here we demonstrate that the loss of nephrin expression and the onset of proteinuria in diabetic mice correlate with an increased accumulation of ubiquitinated proteins and expression of CIN85/RukL in podocytes. CIN85/RukL deficiency preserved nephrin surface expression on the slit diaphragm and reduced proteinuria in diabetic mice, whereas overexpression of CIN85 in zebrafish induced severe edema and disruption of the filtration barrier. Thus, CIN85/RukL is involved in endocytosis of nephrin in podocytes under diabetic conditions, causing podocyte depletion and promoting proteinuria. CIN85/RukL expression therefore shows potential to be a novel target for antiproteinuric therapy in diabetes.
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Affiliation(s)
- Beina Teng
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | | | - Janina Müller-Deile
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Heiko Schenk
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Lynne Staggs
- Mount Desert Island Biological Laboratory, Salisbury Cove, ME
| | - Irini Tossidou
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Ivan Dikic
- Institute of Biochemistry II, Goethe University Frankfurt, Frankfurt, Germany
| | - Hermann Haller
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Mario Schiffer
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
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25
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Abstract
Genetic studies of hereditary forms of nephrotic syndrome have identified several proteins that are involved in regulating the permselective properties of the glomerular filtration system. Further extensive research has elucidated the complex molecular basis of the glomerular filtration barrier and clearly established the pivotal role of podocytes in the pathophysiology of glomerular diseases. Podocyte architecture is centred on focal adhesions and slit diaphragms - multiprotein signalling hubs that regulate cell morphology and function. A highly interconnected actin cytoskeleton enables podocytes to adapt in order to accommodate environmental changes and maintain an intact glomerular filtration barrier. Actin-based endocytosis has now emerged as a regulator of podocyte integrity, providing an impetus for understanding the precise mechanisms that underlie the steady-state control of focal adhesion and slit diaphragm components. This Review outlines the role of actin dynamics and endocytosis in podocyte biology, and discusses how molecular heterogeneity in glomerular disorders could be exploited to deliver more rational therapeutic interventions, paving the way for targeted medicine in nephrology.
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Protein kinase C α inhibition prevents peritoneal damage in a mouse model of chronic peritoneal exposure to high-glucose dialysate. Kidney Int 2016; 89:1253-67. [DOI: 10.1016/j.kint.2016.01.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 12/23/2015] [Accepted: 01/07/2016] [Indexed: 12/27/2022]
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Pullen N, Fornoni A. Drug discovery in focal and segmental glomerulosclerosis. Kidney Int 2016; 89:1211-20. [PMID: 27165834 PMCID: PMC4875964 DOI: 10.1016/j.kint.2015.12.058] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 12/23/2015] [Accepted: 12/29/2015] [Indexed: 11/26/2022]
Abstract
Despite the high medical burden experienced by patients with focal segmental glomerulosclerosis, the etiology of the condition remains largely unknown. Focal segmental glomerulosclerosis is highly heterogeneous in clinical and morphologic manifestations. While this presents challenges for the development of new treatments, research investments over the last 2 decades have yielded a surfeit of potential avenues for therapeutic intervention. The development of many of those ideas and concepts into new therapies, however, has been very disappointing. Here, we describe some of the factors that have potentially contributed to the poor translational performance from this research investment, including the confidence we ascribe to a target, the conduct of experimental studies, and the availability of selective reagents to test hypotheses. We will discuss the significance of genetic and systems traits as well as other methods for reducing bias. We will analyze the limitations of a successful drug development. We will use specific examples hoping that these will guide a consensus for investment and drive greater translational quality. We hope that this substrate will serve to exemplify the tremendous opportunity for intervention as well as facilitate greater collaborative effort between industry, academia, and private foundations in promoting appropriate validation of these targets. Only then will we have achieved our goal for curative therapies for this devastating disease.
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Affiliation(s)
- Nick Pullen
- Pfizer Global Research & Development, Cambridge, Massachusetts, USA.
| | - Alessia Fornoni
- Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida, USA.
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28
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Kataoka H, Ariyama Y, Deushi M, Osaka M, Nitta K, Yoshida M. Inhibitory Effect of Serotonin Antagonist on Leukocyte-Endothelial Interactions In Vivo and In Vitro. PLoS One 2016; 11:e0147929. [PMID: 26824242 PMCID: PMC4732655 DOI: 10.1371/journal.pone.0147929] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 01/11/2016] [Indexed: 11/25/2022] Open
Abstract
Background Although 5-HT2A serotonergic antagonists have been used to treat vascular disease in patients with diabetes mellitus or obesity, their effects on leukocyte-endothelial interactions have not been fully investigated. In this study, we assessed the effects of sarpogrelate hydrochloride (SRPO), a 5-HT2A receptor inverse agonist, on leukocyte-endothelial cell interactions in obesity both in vivo and in vitro. Methods and Findings In the in vivo experiment, C57BL/6 mice were fed a high-fat high-fructose diet (HFFD), comprising 20% fat and 30% fructose, with or without intraperitoneal injection of 5 mg/kg/day SRPO for 4 weeks. The body weight, visceral fat weight, and serum monocyte chemoattractant protein-1 levels in the mice increased significantly with the HFFD, but these effects were prevented by chronic injections of SRPO. Intravital microscopy of the femoral artery detected significant leukocyte-endothelial interactions after treatment with HFFD, but these leukocyte-endothelial interactions were reduced in the mice injected with SRPO. In the in vitro experiment, pre-incubation of activated human umbilical vein endothelial cells (HUVECs) with platelet-rich plasma (PRP) induced THP-1 cell adhesion under physiological flow conditions, but the adhesion was reduced by pretreatment of PRP with SRPO. A fluorescent immunobinding assay showed that PRP induced significant upregulation of E-selectin in HUVECs, but this upregulation was reduced by pretreatment of PRP with SRPO. In other in vitro conditions, pre-incubation of THP-1 cells with phorbol 12-myristate 13-acetate increased the adhesion of THP-1 cells to activated HUVECs under rotational conditions, but this adhesion was reduced by pretreatment with SRPO. Western blotting analysis showed that protein kinase C α activation in THP-1 cells was inhibited by SRPO. Conclusion Our findings indicated that SRPO inhibits vascular inflammation in obesity via inactivation of platelets and leukocytes, and improvement of obese.
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Affiliation(s)
- Hiroshi Kataoka
- Department of Medicine, Kidney Center, Tokyo Women’s Medical University, Tokyo, Japan
| | - Yuno Ariyama
- Department of Life Sciences and Bioethics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Michiyo Deushi
- Department of Life Sciences and Bioethics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Mizuko Osaka
- Department of Life Sciences and Bioethics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kosaku Nitta
- Department of Medicine, Kidney Center, Tokyo Women’s Medical University, Tokyo, Japan
| | - Masayuki Yoshida
- Department of Life Sciences and Bioethics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
- * E-mail:
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29
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Conserva F, Gesualdo L, Papale M. A Systems Biology Overview on Human Diabetic Nephropathy: From Genetic Susceptibility to Post-Transcriptional and Post-Translational Modifications. J Diabetes Res 2016; 2016:7934504. [PMID: 26798653 PMCID: PMC4698547 DOI: 10.1155/2016/7934504] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 08/16/2015] [Accepted: 09/10/2015] [Indexed: 12/19/2022] Open
Abstract
Diabetic nephropathy (DN), a microvascular complication occurring in approximately 20-40% of patients with type 2 diabetes mellitus (T2DM), is characterized by the progressive impairment of glomerular filtration and the development of Kimmelstiel-Wilson lesions leading to end-stage renal failure (ESRD). The causes and molecular mechanisms mediating the onset of T2DM chronic complications are yet sketchy and it is not clear why disease progression occurs only in some patients. We performed a systematic analysis of the most relevant studies investigating genetic susceptibility and specific transcriptomic, epigenetic, proteomic, and metabolomic patterns in order to summarize the most significant traits associated with the disease onset and progression. The picture that emerges is complex and fascinating as it includes the regulation/dysregulation of numerous biological processes, converging toward the activation of inflammatory processes, oxidative stress, remodeling of cellular function and morphology, and disturbance of metabolic pathways. The growing interest in the characterization of protein post-translational modifications and the importance of handling large datasets using a systems biology approach are also discussed.
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Affiliation(s)
- Francesca Conserva
- Division of Nephrology, Department of Emergency and Organ Transplantation, University of Bari, 70124 Bari, Italy
- Division of Cardiology and Cardiac Rehabilitation, “S. Maugeri” Foundation, IRCCS, Institute of Cassano Murge, 70020 Cassano delle Murge, Italy
| | - Loreto Gesualdo
- Division of Nephrology, Department of Emergency and Organ Transplantation, University of Bari, 70124 Bari, Italy
- *Loreto Gesualdo:
| | - Massimo Papale
- Molecular Medicine Center, Section of Nephrology, Department of Medical and Surgical Sciences, University of Foggia, 71122 Foggia, Italy
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30
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Inoue K, Ishibe S. Podocyte endocytosis in the regulation of the glomerular filtration barrier. Am J Physiol Renal Physiol 2015; 309:F398-405. [PMID: 26084928 DOI: 10.1152/ajprenal.00136.2015] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 06/15/2015] [Indexed: 02/06/2023] Open
Abstract
Severe defects in the glomerular filtration barrier result in nephrotic syndrome, which is characterized by massive proteinuria. The podocyte, a specialized epithelial cell with interdigitating foot processes separated by a slit diaphragm, plays a vital role in regulating the passage of proteins from the capillary lumen to Bowman's space. Recent findings suggest a critical role for endocytosis in podocyte biology as highlighted by genetic mouse models of disease and human genetic mutations that result in the loss of the integrity of the glomerular filtration barrier. In vitro podocyte studies have also unraveled a plethora of constituents that are differentially internalized to maintain homeostasis. These observations provide a framework and impetus for understanding the precise regulation of podocyte endocytic machinery in both health and disease.
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Affiliation(s)
- Kazunori Inoue
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Shuta Ishibe
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
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31
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An update: the role of Nephrin inside and outside the kidney. SCIENCE CHINA-LIFE SCIENCES 2015; 58:649-57. [PMID: 25921941 DOI: 10.1007/s11427-015-4844-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 02/27/2015] [Indexed: 12/18/2022]
Abstract
Nephrin is a key molecule in podocytes to maintain normal slit diaphragm structure. Nephin interacts with many other podocyte and slit diaphragm protein and also mediates important cell signaling pathways in podocytes. Loss of nephrin during the development leads to the congenital nephrotic syndrome in children. Reduction of nephrin expression is often observed in adult kidney diseases including diabetic nephropathy and HIV-associated nephropathy. The critical role of nephrin has been confirmed by different animal models with nephrin knockout and knockdown. Recent studies demonstrate that knockdown of nephrin expression in adult mice aggravates the progression of unilateral nephrectomy and Adriamycin-induced kidney disease. In addition to its critical role in maintaining normal glomerular filtration unit in the kidney, nephrin is also expressed in other organs. However, the exact role of nephrin in kidney and extra-renal organs has not been well characterized. Future studies are required to determine whether nephrin could be developed as a drug target to treat patients with kidney disease.
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32
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Li X, Yang B, Chen M, Klein JD, Sands JM, Chen G. Activation of protein kinase C-α and Src kinase increases urea transporter A1 α-2, 6 sialylation. J Am Soc Nephrol 2015; 26:926-34. [PMID: 25300290 PMCID: PMC4378103 DOI: 10.1681/asn.2014010026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 07/18/2014] [Indexed: 11/03/2022] Open
Abstract
The urea transporter A1 (UT-A1) is a glycosylated protein with two glycoforms: 117 and 97 kD. In diabetes, the increased abundance of the heavily glycosylated 117-kD UT-A1 corresponds to an increase of kidney tubule urea permeability. We previously reported that diabetes not only causes an increase of UT-A1 protein abundance but also, results in UT-A1 glycan changes, including an increase of sialic acid content. Because activation of the diacylglycerol (DAG)-protein kinase C (PKC) pathway is elevated in diabetes and PKC-α regulates UT-A1 urea transport activity, we explored the role of PKC in UT-A1 glycan sialylation. We found that activation of PKC specifically promotes UT-A1 glycan sialylation in both UT-A1-MDCK cells and rat kidney inner medullary collecting duct suspensions, and inhibition of PKC activity blocks high glucose-induced UT-A1 sialylation. Overexpression of PKC-α promoted UT-A1 sialylation and membrane surface expression. Conversely, PKC-α-deficient mice had significantly less sialylated UT-A1 compared with wild-type mice. Furthermore, the effect of PKC-α-induced UT-A1 sialylation was mainly mediated by Src kinase but not Raf-1 kinase. Functionally, increased UT-A1 sialylation corresponded with enhanced urea transport activity. Thus, our results reveal a novel mechanism by which PKC regulates UT-A1 function by increasing glycan sialylation through Src kinase pathways, which may have an important role in preventing the osmotic diuresis caused by glucosuria under diabetic conditions.
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Affiliation(s)
- Xuechen Li
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China; and
- Department of Physiology and
| | - Baoxue Yang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China; and
| | | | - Janet D. Klein
- Department of Physiology and
- Renal Division, Department of Medicine, Emory University, Atlanta, Georgia
| | - Jeff M. Sands
- Department of Physiology and
- Renal Division, Department of Medicine, Emory University, Atlanta, Georgia
| | - Guangping Chen
- Department of Physiology and
- Renal Division, Department of Medicine, Emory University, Atlanta, Georgia
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33
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Podocin is translocated to cytoplasm in puromycin aminonucleoside nephrosis rats and in poor-prognosis patients with IgA nephropathy. Cell Tissue Res 2015; 360:391-400. [PMID: 25676004 PMCID: PMC4544490 DOI: 10.1007/s00441-014-2100-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 12/18/2014] [Indexed: 11/02/2022]
Abstract
Podocytes serve as the final barrier to urinary protein loss through a highly specialized structure called a slit membrane and maintain foot process and glomerular basement membranes. Podocyte injury results in progressive glomerular damage and accelerates sclerotic changes, although the exact mechanism of podocyte injury is still obscure. We focus on the staining gap (podocin gap) defined as the staining difference between podocin and synaptopodin, which are normally located in the foot process. In puromycin aminonucleoside nephrosis rats, the podocin gap is significantly increased (p < 0.05) and podocin is translocated to the cytoplasm on days 7 and 14 but not on day 28. Surprisingly, the gap is also significantly increased (p < 0.05) in human kidney biopsy specimens of poor-prognosis IgA nephropathy patients. This suggests that the podocin gap could be a useful marker for classifying the prognosis of IgA nephropathy and indicating the translocation of podocin to the cytoplasm. Next, we find more evidence of podocin trafficking in podocytes where podocin merges with Rab5 in puromycin aminonucleoside nephrosis rats at day 14. In immunoelectron microscopy, the podocin positive area was significantly translocated from the foot process areas to the cytoplasm (p< 0.05) on days 7 and 14 in puromycin aminonucleoside nephrosis rats. Interestingly, podocin is also translocated to the cytoplasm in poor-prognosis human IgA nephropathy. In this paper, we demonstrate that the translocation of podocin by endocytosis could be a key traffic event of critical podocyte injury and that the podocin gap could indicate the prognosis of IgA nephropathy.
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34
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Kapodistria K, Tsilibary EP, Politis P, Moustardas P, Charonis A, Kitsiou P. Nephrin, a transmembrane protein, is involved in pancreatic beta-cell survival signaling. Mol Cell Endocrinol 2015; 400:112-28. [PMID: 25448064 DOI: 10.1016/j.mce.2014.11.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 10/15/2014] [Accepted: 11/03/2014] [Indexed: 01/15/2023]
Abstract
Nephrin, a cell surface signaling receptor, regulates podocyte function in health and disease. We study the role of nephrin in β-cell survival signaling. We report that in mouse islet β-cells and the mouse pancreatic beta-cell line (βTC-6 cells) nephrin is associated and partly co-localized with PI3-kinase. Incubation of cells with functional anti-nephrin antibodies induced nephrin clustering at the plasma membrane, nephrin phosphorylation and recruitment of PI3-kinase to nephrin thus resulting in increased PI3K-dependent Akt phosphorylation and augmented phosphorylation/inhibition of pro-apoptotic Bad and FoxO. Nephrin silencing abolished Akt activation and increased susceptibility of cells to apoptosis. High glucose impaired nephrin signaling, increased nephrin internalization and up-regulated PKCα expression. Interestingly, a marked decrease in nephrin expression and phosphorylated Akt was observed in pancreatic islets of db/db lepr-/- diabetic mice. Our findings revealed that nephrin is involved in β-cell survival and suggest that glucose-induced changes in nephrin signaling may contribute to gradual pancreatic β-cell loss in type 2 diabetes.
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Affiliation(s)
- Katerina Kapodistria
- Institute of Biosciences and Applications, National Centre for Scientific Research, N.C.S.R. "Demokritos", Terma Patriarchou Grigoriou & Neapoleos, 15310 Agia Paraskevi, Attiki, Greece
| | - Effie-Photini Tsilibary
- Institute of Biosciences and Applications, National Centre for Scientific Research, N.C.S.R. "Demokritos", Terma Patriarchou Grigoriou & Neapoleos, 15310 Agia Paraskevi, Attiki, Greece
| | - Panagiotis Politis
- Center for Basic Research, Biomedical Research Foundation Academy of Athens (BRFAA), 4 Soranou Ephessiou, Athens 115 27, Greece
| | - Petros Moustardas
- Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation Academy of Athens (BRFAA), 4 Soranou Ephessiou, Athens 115 27, Greece
| | - Aristidis Charonis
- Center for Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation Academy of Athens (BRFAA), 4 Soranou Ephessiou, Athens 115 27, Greece
| | - Paraskevi Kitsiou
- Institute of Biosciences and Applications, National Centre for Scientific Research, N.C.S.R. "Demokritos", Terma Patriarchou Grigoriou & Neapoleos, 15310 Agia Paraskevi, Attiki, Greece.
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35
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Muthenna P, Raghu G, Kumar PA, Surekha M, Reddy GB. Effect of cinnamon and its procyanidin-B2 enriched fraction on diabetic nephropathy in rats. Chem Biol Interact 2014; 222:68-76. [DOI: 10.1016/j.cbi.2014.08.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 08/23/2014] [Accepted: 08/27/2014] [Indexed: 01/17/2023]
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36
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Tossidou I, Himmelseher E, Teng B, Haller H, Schiffer M. SUMOylation determines turnover and localization of nephrin at the plasma membrane. Kidney Int 2014; 86:1161-73. [PMID: 24940800 DOI: 10.1038/ki.2014.198] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 04/15/2014] [Accepted: 04/17/2014] [Indexed: 01/01/2023]
Abstract
Podocyte effacement and the reformation of foot processes and slit diaphragms can be induced within minutes experimentally. Therefore, it seems likely that the slit diaphragm proteins underlie orchestrated recycling mechanisms under the control of posttranslational modifiers. One of these modifiers, SUMO (small ubiquitin-like modifier), is an ubiquitin-like protein with a 20% corresponding identity to ubiquitin. Modification by SUMOs to proteins on lysine residues can block the ubiquitination of the same site leading to the stabilization of the target protein. Here we found in vitro and in vivo that nephrin is a substrate modified by SUMO proteins thereby increasing its steady-state level and expression at the plasma membrane. A conversion of lysines to arginines at positions 1114 and 1224 of the intracellular tail of murine nephrin led to decreased stability of nephrin, decreased expression at the plasma membrane, and decreased PI3K/AKT signaling. Furthermore, treatment of podocytes with the SUMOylation inhibitor ginkgolic acid led to reduced membrane expression of nephrin. Similarly, the conversion of lysine to arginine at position 1100 of human nephrin caused decreased stability and expression at the plasma membrane. As SUMOylation is a reversible process, our results suggest that SUMOylation participates in the tight orchestration of nephrin turnover at the slit diaphragm.
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Affiliation(s)
- Irini Tossidou
- Hannover Medical School, Division of Nephrology, Hannover, Germany
| | - Erik Himmelseher
- Hannover Medical School, Division of Nephrology, Hannover, Germany
| | - Beina Teng
- Hannover Medical School, Division of Nephrology, Hannover, Germany
| | - Hermann Haller
- Hannover Medical School, Division of Nephrology, Hannover, Germany
| | - Mario Schiffer
- Hannover Medical School, Division of Nephrology, Hannover, Germany
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37
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Satoh D, Hirose T, Harita Y, Daimon C, Harada T, Kurihara H, Yamashita A, Ohno S. aPKCλ maintains the integrity of the glomerular slit diaphragm through trafficking of nephrin to the cell surface. J Biochem 2014; 156:115-28. [PMID: 24700503 PMCID: PMC4112437 DOI: 10.1093/jb/mvu022] [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] [Indexed: 12/21/2022] Open
Abstract
The slit diaphragm (SD), the specialized intercellular junction between renal glomerular epithelial cells (podocytes), provides a selective-filtration barrier in renal glomeruli. Dysfunction of the SD results in glomerular diseases that are characterized by disappearance of SD components, such as nephrin, from the cell surface. Although the importance of endocytosis and degradation of SD components for the maintenance of SD integrity has been suggested, the dynamic nature of the turnover of intact cell-surface SD components remained unclear. Using isolated rat glomeruli we show that the turnover rates of cell-surface SD components are relatively high; they almost completely disappear from the cell surface within minutes. The exocytosis, but not endocytosis, of heterologously expressed nephrin requires the kinase activity of the cell polarity regulator atypical protein kinase C (aPKC). Consistently, we demonstrate that podocyte-specific deletion of aPKCλ resulted in a decrease of cell-surface localization of SD components, causing massive proteinuria. In conclusion, the regulation of SD turnover by aPKC is crucial for the maintenance of SD integrity and defects in aPKC signalling can lead to proteinuria. These findings not only reveal the pivotal importance of the dynamic turnover of cell-surface SD components but also suggest a novel pathophysiological basis in glomerular disease.
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Affiliation(s)
- Daisuke Satoh
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Tomonori Hirose
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Yutaka Harita
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, JapanDepartment of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Chikara Daimon
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Tomonori Harada
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Hidetake Kurihara
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Akio Yamashita
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Shigeo Ohno
- Department of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, JapanDepartment of Molecular Biology, Graduate School of Medical Science, Yokohama City University, Yokohama; Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo; Department of Pediatrics, Yokohama City University, Yokohama; Department of Anatomy, Juntendo University, School of Medicine, Bunkyo, Tokyo; and Advanced Medical Research Center, Yokohama City University, Yokohama, Kanagawa, Japan
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Teng B, Duong M, Tossidou I, Yu X, Schiffer M. Role of protein kinase C in podocytes and development of glomerular damage in diabetic nephropathy. Front Endocrinol (Lausanne) 2014; 5:179. [PMID: 25414693 PMCID: PMC4220730 DOI: 10.3389/fendo.2014.00179] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/06/2014] [Indexed: 12/13/2022] Open
Abstract
The early glomerular changes in diabetes include a podocyte phenotype with loss of slit diaphragm proteins, changes in the actin cytoskeleton and foot process architecture. This review focuses on the role of the protein kinase C (PKC) family in podocytes and points out the differential roles of classical, novel, and atypical PKCs in podocytes. Some PKC isoforms are indispensable for proper glomerular development and slit diaphragm maintenance, whereas others might be harmful when activated in the diabetic milieu. Therefore, some might be interesting treatment targets in the early phase of diabetes.
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Affiliation(s)
- Beina Teng
- Department of Medicine/Nephrology, Hannover Medical School, Hannover, Germany
| | - Michelle Duong
- Department of Medicine/Nephrology, Hannover Medical School, Hannover, Germany
| | - Irini Tossidou
- Department of Medicine/Nephrology, Hannover Medical School, Hannover, Germany
| | - Xuejiao Yu
- Department of Medicine/Nephrology, Hannover Medical School, Hannover, Germany
| | - Mario Schiffer
- Department of Medicine/Nephrology, Hannover Medical School, Hannover, Germany
- *Correspondence: Mario Schiffer, Department of Medicine/Nephrology, Hannover Medical School, Carl Neuberg Street 1-OE6840, Hannover 30625, Germany e-mail:
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Worthmann K, Leitges M, Teng B, Sestu M, Tossidou I, Samson T, Haller H, Huber TB, Schiffer M. Def-6, a novel regulator of small GTPases in podocytes, acts downstream of atypical protein kinase C (aPKC) λ/ι. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 183:1945-1959. [PMID: 24096077 PMCID: PMC5707189 DOI: 10.1016/j.ajpath.2013.08.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 08/21/2013] [Accepted: 08/26/2013] [Indexed: 11/23/2022]
Abstract
The atypical protein kinase C (aPKC) isotypes PKCλ/ι and PKCζ are both expressed in podocytes; however, little is known about differences in their function. Previous studies in mice have demonstrated that podocyte-specific loss of PKCλ/ι leads to a severe glomerular phenotype, whereas mice deficient in PKCζ develop no renal phenotype. We analyzed various effects caused by PKCλ/ι and PKCζ deficiency in cultured murine podocytes. In contrast to PKCζ-deficient podocytes, PKCλ/ι-deficient podocytes exhibited a severe actin cytoskeletal phenotype, reduced cell size, decreased number of focal adhesions, and increased activation of small GTPases. Comparative microarray analysis revealed that the guanine nucleotide exchange factor Def-6 was specifically up-regulated in PKCλ/ι-deficient podocytes. In vivo Def-6 expression is significantly increased in podocytes of PKCλ/ι-deficient mice. Cultured PKCλ/ι-deficient podocytes exhibited an enhanced membrane association of Def-6, indicating enhanced activation. Overexpression of aPKCλ/ι in PKCλ/ι-deficient podocytes could reduce the membrane-associated expression of Def-6 and rescue the actin phenotype. In the present study, PKCλ/ι was identified as an important factor for actin cytoskeletal regulation in podocytes and Def-6 as a specific downstream target of PKCλ/ι that regulates the activity of small GTPases and subsequently the actin cytoskeleton of podocytes.
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Affiliation(s)
- Kirstin Worthmann
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Michael Leitges
- Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
| | - Beina Teng
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Marcello Sestu
- Faculty of Medicine, Interdisciplinary Centre for Clinical Research (IZKF) Leipzig, University of Leipzig, Leipzig, Germany
| | - Irini Tossidou
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Thomas Samson
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina
| | - Hermann Haller
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Tobias B Huber
- Renal Division, University Hospital Freiburg, Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University, Freiburg, Germany
| | - Mario Schiffer
- Division of Nephrology, Department of Medicine, Hannover Medical School, Hannover, Germany.
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Hagiwara S, Jha JC, Cooper ME. Identifying and interpreting novel targets that address more than one diabetic complication: a strategy for optimal end organ protection in diabetes. Diabetol Int 2013. [DOI: 10.1007/s13340-013-0148-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Abstract
PURPOSE OF REVIEW In this review, we discuss the role of endocytosis, a fundamental process internalizing molecules from the plasma membrane, and its critical importance in podocyte biology. RECENT FINDINGS Endocytic clathrin and nonclathrin-coated pits have been visualized in podocytes using electron microscopy, but the functional biological relevance has not been well defined. Recent evidence suggests that loss of key clathrin endocytic regulatory apparatus, such as dynamin, synaptojanin 1 or endophilin, in genetic mouse models of disease results in severe proteinuria and foot process effacement. In addition, several genes implicated in human nephrotic syndrome directly or indirectly associate with these endocytic proteins, thus creating a protein network that is linked in actin dynamics, signalling and endocytosis. SUMMARY This review summarizes our current understanding of membrane trafficking specifically in podocytes, thus giving further novel insights into the molecular mechanisms and pathogenesis of nephrotic syndrome.
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Affiliation(s)
- Keita Soda
- Department of Internal Medicine, Section of Nephrology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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Soetikno V, Suzuki K, Veeraveedu PT, Arumugam S, Lakshmanan AP, Sone H, Watanabe K. Molecular understanding of curcumin in diabetic nephropathy. Drug Discov Today 2013; 18:756-63. [PMID: 23651956 DOI: 10.1016/j.drudis.2013.04.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/29/2013] [Accepted: 04/26/2013] [Indexed: 01/12/2023]
Abstract
Diabetic nephropathy is characterized by a plethora of signaling abnormalities. Recent trials have suggested that intensive glucose-lowering treatment leads to hypoglycemic events, which can be dangerous. Curcumin is the active ingredient of turmeric, which has been widely used in many countries for centuries to treat numerous diseases. The preventive and therapeutic properties of curcumin are associated with its antioxidant and anti-inflammatory properties. Here, we highlight the renoprotective role of curcumin in diabetes mellitus (DM) with an emphasis on the molecular basis of this effect. We also briefly discuss the numerous approaches that have been undertaken to improve the pharmacokinetics of curcumin.
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Affiliation(s)
- Vivian Soetikno
- Department of Clinical Pharmacology, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, Niigata City 956-8603, Japan.
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Abstract
Vascular endothelial growth factor-A (VEGF-A) is a protein secreted by podocytes that is necessary for survival of endothelial cells, podocytes, and mesangial cells. VEGF-A regulates slit-diaphragm signaling and podocyte shape via VEGF-receptor 2-nephrin-nck-actin interactions. Chronic hyperglycemia-induced excess podocyte VEGF-A and low endothelial nitric oxide drive the development and the progression of diabetic nephropathy. The abnormal cross-talk between VEGF-A and nitric oxide pathways is fueled by the diabetic milieu, resulting in increased oxidative stress. Recent findings on these pathogenic molecular mechanisms provide new potential targets for therapy for diabetic renal disease.
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Affiliation(s)
- Alda Tufro
- Department of Pediatrics, Section of Nephrology, Yale University School of Medicine, New Haven, CT 06520-8064, USA.
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Menne J, Shushakova N, Bartels J, Kiyan Y, Laudeley R, Haller H, Park JK, Meier M. Dual inhibition of classical protein kinase C-α and protein kinase C-β isoforms protects against experimental murine diabetic nephropathy. Diabetes 2013; 62:1167-74. [PMID: 23434935 PMCID: PMC3609593 DOI: 10.2337/db12-0534] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy with proteinuria and peritubular extracellular matrix production. We have previously shown that the PKC isoforms α and β mediate different cellular effects. PKC-β contributes to hyperglycemia-induced renal matrix production, whereby PKC-α is involved in the development of albuminuria. We further tested this hypothesis by deletion of both isoforms and used a PKC inhibitor. We analyzed the phenotype of nondiabetic and streptozotocin (STZ)-induced diabetic homozygous PKC-α/β double-knockout mice (PKC-α/β(-/-)). After 8 weeks of diabetes mellitus, the high-glucose-induced renal and glomerular hypertrophy as well as transforming growth factor-β1) and extracellular matrix production were diminished in the PKC-α/β(-/-) mice compared with wild-type controls. Urinary albumin/creatinine ratio also was significantly reduced, however, it was not completely abolished in diabetic PKC-α/β(-/-) mice. Treatment with CGP41252, which inhibits PKC-α and PKC-β, is able to prevent the development of albuminuria and to reduce existing albuminuria in type 1 (STZ model) or type 2 (db/db model) diabetic mice. These results support our hypothesis that PKC-α and PKC-β contribute to the pathogenesis of diabetic nephropathy, and that dual inhibition of the classical PKC isoforms is a suitable therapeutic strategy in the prevention and treatment of diabetic nephropathy.
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Affiliation(s)
- Jan Menne
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
- Phenos GmbH, Hannover, Germany
- Corresponding authors: Jan Menne, , and Hermann Haller,
| | - Nelli Shushakova
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
- Phenos GmbH, Hannover, Germany
| | - Janina Bartels
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
| | - Yulia Kiyan
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
| | - Robert Laudeley
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
| | - Hermann Haller
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
- Corresponding authors: Jan Menne, , and Hermann Haller,
| | - Joon-Keun Park
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
| | - Matthias Meier
- Clinic for Nephrology and Hypertension, Hannover Medical School, Hannover, Germany
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Abstract
It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.
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Affiliation(s)
- Josephine M Forbes
- Diabetes Division, Baker IDI Heart and Diabetes Institute, Melbourne, Australia
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A novel domain regulating degradation of the glomerular slit diaphragm protein podocin in cell culture systems. PLoS One 2013; 8:e57078. [PMID: 23437316 PMCID: PMC3577791 DOI: 10.1371/journal.pone.0057078] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Accepted: 01/17/2013] [Indexed: 11/19/2022] Open
Abstract
Mutations in the gene NPHS2 are the most common cause of hereditary steroid-resistant nephrotic syndrome. Its gene product, the stomatin family member protein podocin represents a core component of the slit diaphragm, a unique structure that bridges the space between adjacent podocyte foot processes in the kidney glomerulus. Dislocation and misexpression of slit diaphragm components have been described in the pathogenesis of acquired and hereditary nephrotic syndrome. However, little is known about mechanisms regulating cellular trafficking and turnover of podocin. Here, we discover a three amino acids-comprising motif regulating intracellular localization of podocin in cell culture systems. Mutations of this motif led to markedly reduced degradation of podocin. These findings give novel insight into the molecular biology of the slit diaphragm protein podocin, enabling future research to establish the biological relevance of podocin turnover and localization.
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Swiatecka-Urban A. Membrane trafficking in podocyte health and disease. Pediatr Nephrol 2013; 28:1723-37. [PMID: 22932996 PMCID: PMC3578983 DOI: 10.1007/s00467-012-2281-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 07/19/2012] [Accepted: 07/20/2012] [Indexed: 12/21/2022]
Abstract
Podocytes are highly specialized epithelial cells localized in the kidney glomerulus. The distinct cell signaling events and unique cytoskeletal architecture tailor podocytes to withstand changes in hydrostatic pressure during glomerular filtration. Alteration of glomerular filtration leads to kidney disease and frequently manifests with proteinuria. It has been increasingly recognized that cell signaling and cytoskeletal dynamics are coupled more tightly to membrane trafficking than previously thought. Membrane trafficking coordinates the cross-talk between protein networks and signaling cascades in a spatially and temporally organized fashion and may be viewed as a communication highway between the cell exterior and interior. Membrane trafficking involves transport of cargo from the plasma membrane to the cell interior (i.e., endocytosis) followed by cargo trafficking to lysosomes for degradation or to the plasma membrane for recycling. Yet, recent studies indicate that the conventional classification does not fully reflect the complex and versatile nature of membrane trafficking. While the increasing complexity of elaborate protein scaffolds and signaling cascades is being recognized in podocytes, the role of membrane trafficking is less well understood. This review will focus on the role of membrane trafficking in podocyte health and disease.
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Osmolarity and glucose differentially regulate aldose reductase activity in cultured mouse podocytes. EXPERIMENTAL DIABETES RESEARCH 2011; 2011:278963. [PMID: 22253613 PMCID: PMC3255165 DOI: 10.1155/2011/278963] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 09/05/2011] [Accepted: 09/23/2011] [Indexed: 12/04/2022]
Abstract
Podocyte injury is associated with progression of many renal diseases, including diabetic nephropathy. In this study we examined whether aldose reductase (AR), the enzyme implicated in diabetic complications in different tissues, is modulated by high glucose and osmolarity in podocyte cells. AR mRNA, protein expression, and activity were measured in mouse podocytes cultured in both normal and high glucose and osmolarity for 6 hours to 5 days. Hyperosmolarity acutely stimulated AR expression and activity, with subsequent increase of AR expression but decrease of activity. High glucose also elevated AR protein level; however, this was not accompanied by respective enzyme activation. Furthermore, high glucose appeared to counteract the osmolarity-dependent activation of AR. In conclusion, in podocytes AR is modulated by high glucose and increased osmolarity in a different manner. Posttranslational events may affect AR activity independent of enzyme protein amount. Activation of AR in podocytes may be implicated in diabetic podocytopathy.
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49
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Bertuccio C, Veron D, Aggarwal PK, Holzman L, Tufro A. Vascular endothelial growth factor receptor 2 direct interaction with nephrin links VEGF-A signals to actin in kidney podocytes. J Biol Chem 2011; 286:39933-44. [PMID: 21937443 DOI: 10.1074/jbc.m111.241620] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transmembrane protein nephrin is an essential component of slit diaphragms, the specialized cell junctions that link podocyte foot processes. Podocytes are epithelial cells that surround the glomerular capillaries in the kidney and are necessary for the organ-filtering function. Nephrin signaling complex transduces extracellular cues to the podocyte cytoskeleton and regulates podocyte shape and function. Vascular endothelial growth factor A (VEGF-A) is a required growth factor produced and secreted by podocytes. Accumulating evidence suggests a cross-talk between VEGF-A and nephrin signaling pathways. We previously showed that in vivo nephrin associates with VEGF receptor-2 (VEGFR2), the signaling receptor for VEGF-A. In the present work, we characterized the interaction between nephrin and VEGFR2 in cultured cells and in vitro. We demonstrate that nephrin-VEGFR2 interaction is direct using mass spectrometry, immunoprecipitation, GST-binding assays, and blot overlay experiments. This interaction occurs through VEGFR2 and nephrin cytoplasmic domains. Nephrin-VEGFR2 interaction is modulated by tyrosine phosphorylation of both cytoplasmic domains. Furthermore, the nephrin-VEGFR2 complex involves Nck and actin. VEGF-A signaling via this complex results in decreased cell size. We provide evidence that this multiprotein interaction occurs in cultured podocytes. We propose that the nephrin-VEGFR2 complex acts as a key mediator to transduce local VEGF-A signals to the podocyte actin cytoskeleton, regulating the foot process structure and glomerular filter integrity.
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Affiliation(s)
- Claudia Bertuccio
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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Kim EY, Dryer SE. Effects of insulin and high glucose on mobilization of slo1 BKCa channels in podocytes. J Cell Physiol 2011; 226:2307-15. [PMID: 21660954 DOI: 10.1002/jcp.22567] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Podocytes are dynamic polarized cells that lie on the surface of glomerular capillaries and comprise an essential component of the glomerular filtration barrier. Podocytes are affected in the earliest stages of diabetic nephropathy and insulin signaling to podocytes is essential for normal glomerular function. Large-conductance Ca(2+)-activated K(+) channels (BK(Ca) channels) encoded by the Slo1 gene are expressed in podocytes in a complex with multiple glomerular slit diaphragm proteins including nephrin, TRPC6 channels, and several different actin-binding proteins. Here we show that insulin increases cell surface expression of podocyte BK(Ca) channels, which is accompanied by a corresponding increase in the density of current flowing through these channels. Insulin stimulation of BK(Ca) channels was detectable in 15 min and required activation of both Erk and Akt signaling cascades. Exposure to high glucose (36.1 mM) for 24 h caused a marked reduction in the steady-state surface expression of BK(Ca) channels as well as of the slit diaphragm signaling molecule nephrin. High glucose treatment also abolished the stimulatory effects of insulin on BK(Ca) current density, although insulin continued to increase phosphorylation of Erk and Akt under those conditions. Therefore, in contrast to most other cell types, high glucose abrogates the effects of insulin in podocytes at relatively distal steps in its signaling pathway. Insulin stimulation of BK(Ca) channels in podocytes may prepare podocytes to adapt to changes in pressure gradients that occur during postprandial hyperfiltration.
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Affiliation(s)
- Eun Young Kim
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001, USA
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