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Cara-Fuentes G, Verma R, Venkatareddy M, Bauer C, Piani F, Aksoy ST, Vazzalwar N, Garcia GE, Banks M, Ordoñez FA, de Lucas-Collantes C, Bjornstad P, González Rodríguez JD, Johnson RJ, Garg P. β1-Integrin blockade prevents podocyte injury in experimental models of minimal change disease. Nefrologia 2024; 44:90-99. [PMID: 37150673 DOI: 10.1016/j.nefroe.2023.04.003] [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: 08/03/2022] [Accepted: 11/10/2022] [Indexed: 05/09/2023] Open
Abstract
INTRODUCTION Activation of the focal adhesion kinase (FAK) in podocytes is involved in the pathogenesis of minimal change disease (MCD), but the pathway leading to its activation in this disease is unknown. Here, we tested whether podocyte β1 integrin is the upstream modulator of FAK activation and podocyte injury in experimental models of MCD-like injury. METHODS We used lipopolysaccharide (LPS) and MCD sera to induce MCD-like changes in vivo and in cultured human podocytes, respectively. We performed functional studies using specific β1 integrin inhibitors in vivo and in vitro, and integrated histological analysis, western blotting, and immunofluorescence to assess for morphological and molecular changes in podocytes. By ELISA, we measured serum LPS levels in 35 children with MCD or presumed MCD (idiopathic nephrotic syndrome [INS]) and in 18 healthy controls. RESULTS LPS-injected mice showed morphological (foot process effacement, and normal appearing glomeruli on light microscopy) and molecular features (synaptopodin loss, nephrin mislocalization, FAK phosphorylation) characteristic of human MCD. Administration of a β1 integrin inhibitor to mice abrogated FAK phosphorylation, and ameliorated proteinuria and podocyte injury following LPS. Children with MCD/INS in relapse had higher serum LPS levels than controls. In cultured human podocytes, β1 integrin blockade prevented cytoskeletal rearrangements following exposure to MCD sera in relapse. CONCLUSIONS Podocyte β1 integrin activation is an upstream mediator of FAK phosphorylation and podocyte injury in models of MCD-like injury.
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Messer CL, McDonald JA. Rap1 promotes epithelial integrity and cell viability in a growing tissue. Dev Biol 2023; 501:1-19. [PMID: 37269969 DOI: 10.1016/j.ydbio.2023.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 05/10/2023] [Accepted: 05/24/2023] [Indexed: 06/05/2023]
Abstract
Having intact epithelial tissues is critical for embryonic development and adult homeostasis. How epithelia respond to damaging insults or tissue growth while still maintaining intercellular connections and barrier integrity during development is poorly understood. The conserved small GTPase Rap1 is critical for establishing cell polarity and regulating cadherin-catenin cell junctions. Here, we identified a new role for Rap1 in maintaining epithelial integrity and tissue shape during Drosophila oogenesis. Loss of Rap1 activity disrupted the follicle cell epithelium and the shape of egg chambers during a period of major growth. Rap1 was required for proper E-Cadherin localization in the anterior epithelium and for epithelial cell survival. Both Myo-II and the adherens junction-cytoskeletal linker protein α-Catenin were required for normal egg chamber shape but did not strongly affect cell viability. Blocking the apoptotic cascade failed to rescue the cell shape defects caused by Rap1 inhibition. One consequence of increased cell death caused by Rap1 inhibition was the loss of polar cells and other follicle cells, which later in development led to fewer cells forming a migrating border cell cluster. Our results thus indicate dual roles for Rap1 in maintaining epithelia and cell survival in a growing tissue during development.
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Affiliation(s)
- C Luke Messer
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Jocelyn A McDonald
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA.
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Chen Y, Rui R, Wang L, Wang H, Zhu B, Cao A. Huangqi decoction ameliorates kidney injury in db/db mice by regulating the BMP/Smad signaling pathway. BMC Complement Med Ther 2023; 23:209. [PMID: 37365530 PMCID: PMC10294356 DOI: 10.1186/s12906-023-04029-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 06/08/2023] [Indexed: 06/28/2023] Open
Abstract
PURPOSE This study aims to investigate the mechanism underlying the beneficial effects of Huangqi decoction (HQD) on Diabetic kidney disease (DKD) in diabetic db/db mice. METHODS Eight-week-old male diabetic db/db mice were randomly divided into four groups: Model (1% CMC), HQD-L (0.12 g/kg), HQD-M (0.36 g/kg), and HQD-H (1.08 g/kg) groups. Non-diabetic db/m mice were served as the control group. These mice received HQD treatment for 8 weeks. After treatment, the kidney function, histopathology, micro-assay, and protein expression levels were assessed. RESULTS HQD treatment improved the albumin/creatine ratio (ACR) and 24 h urinary albumin excretion, prevented the pathological phenotypes of increased glomerular volume, widened mesangial areas, the of mesangial matrix proliferation, foot process effacement, decreased nephrin expression and reduced number of podocytes. Expression profiling analysis revealed global transcriptional changes that predicted related functions, diseases and pathways. HQD treatment activated protein expressions of BMP2, BMP7, BMPR2, and active-Rap1, while inhibiting Smad1 and phospho-ERK. In addition, HQD was associated with improvements in lipid deposition in the kidneys of db/db mice. CONCLUSION HQD ameliorated the progression of DKD in db/db mice by regulating BMP transcription and downstream targets, inhibiting the phosphorylation of ERK and the expression of Smad1, promoting Rap1 binding to GTP, and regulating the lipid metabolism. These findings provide a potential therapeutic approach for treating DKD.
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Affiliation(s)
- Ying Chen
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, 164 LanXi Road, Shanghai, 200062, China
| | - Rong Rui
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, 164 LanXi Road, Shanghai, 200062, China
| | - Li Wang
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, 164 LanXi Road, Shanghai, 200062, China
| | - Hao Wang
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, 164 LanXi Road, Shanghai, 200062, China
| | - Bingbing Zhu
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, 164 LanXi Road, Shanghai, 200062, China.
| | - Aili Cao
- Department of Nephrology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, China.
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Boi R, Bergwall L, Ebefors K, Bergö MO, Nyström J, Buvall L. Podocyte Geranylgeranyl Transferase Type-I Is Essential for Maintenance of the Glomerular Filtration Barrier. J Am Soc Nephrol 2023; 34:641-655. [PMID: 36735952 PMCID: PMC10103324 DOI: 10.1681/asn.0000000000000062] [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: 06/20/2022] [Accepted: 11/25/2022] [Indexed: 01/22/2023] Open
Abstract
SIGNIFICANCE STATEMENT A tightly regulated actin cytoskeleton attained through balanced activity of RhoGTPases is crucial to maintaining podocyte function. However, how RhoGTPases are regulated by geranylgeranylation, a post-translational modification, has been unexplored. The authors found that loss of the geranylgeranylation enzyme geranylgeranyl transferase type-I (GGTase-I) in podocytes led to progressive albuminuria and foot process effacement in podocyte-specific GGTase-I knockout mice. In cultured podocytes, the absence of geranylgeranylation resulted in altered activity of its downstream substrates Rac1, RhoA, Cdc42, and Rap1, leading to alterations of β1-integrins and actin cytoskeleton structural changes. These findings highlight the importance of geranylgeranylation in the dynamic management of RhoGTPases and Rap1 to control podocyte function, providing new knowledge about podocyte biology and glomerular filtration barrier function. BACKGROUND Impairment of the glomerular filtration barrier is in part attributed to podocyte foot process effacement (FPE), entailing disruption of the actin cytoskeleton and the slit diaphragm. Maintenance of the actin cytoskeleton, which contains a complex signaling network through its connections to slit diaphragm and focal adhesion proteins, is thus considered crucial to preserving podocyte structure and function. A dynamic yet tightly regulated cytoskeleton is attained through balanced activity of RhoGTPases. Most RhoGTPases are post-translationally modified by the enzyme geranylgeranyl transferase type-I (GGTase-I). Although geranylgeranylation has been shown to regulate activities of RhoGTPases and RasGTPase Rap1, its significance in podocytes is unknown. METHODS We used immunofluorescence to localize GGTase-I, which was expressed mainly by podocytes in the glomeruli. To define geranylgeranylation's role in podocytes, we generated podocyte-specific GGTase-I knockout mice. We used transmission electron microscopy to evaluate FPE and measurements of urinary albumin excretion to analyze filtration barrier function. Geranylgeranylation's effects on RhoGTPases and Rap1 function were studied in vitro by knockdown or inhibition of GGTase-I. We used immunocytochemistry to study structural modifications of the actin cytoskeleton and β1 integrins. RESULTS Depletion of GGTase-I in podocytes in vivo resulted in FPE and concomitant early-onset progressive albuminuria. A reduction of GGTase-I activity in cultured podocytes disrupted RhoGTPase balance by markedly increasing activity of RhoA, Rac1, and Cdc42 together with Rap1, resulting in dysregulation of the actin cytoskeleton and altered distribution of β1 integrins. CONCLUSIONS These findings indicate that geranylgeranylation is of crucial importance for the maintenance of the delicate equilibrium of RhoGTPases and Rap1 in podocytes and consequently for the maintenance of glomerular integrity and function.
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Affiliation(s)
- Roberto Boi
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lovisa Bergwall
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Kerstin Ebefors
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Martin O. Bergö
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Institute of Biosciences and Nutrition, Karolinska Institute, Solna, Sweden
| | - Jenny Nyström
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lisa Buvall
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Bioscience Renal, Research and Early Development, Cardiovascular, Renal and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
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Zhang L, Cai J, Xiao J, Ye Z. Identification of core genes and pathways between geriatric multimorbidity and renal insufficiency: potential therapeutic agents discovered using bioinformatics analysis. BMC Med Genomics 2022; 15:212. [PMID: 36209090 PMCID: PMC9548100 DOI: 10.1186/s12920-022-01370-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 09/21/2022] [Indexed: 12/03/2022] Open
Abstract
Background Geriatric people are prone to suffer from multiple chronic diseases, which can directly or indirectly affect renal function. Through bioinformatics analysis, this study aimed to identify key genes and pathways associated with renal insufficiency in patients with geriatric multimorbidity and explore potential drugs against renal insufficiency. Methods The text mining tool Pubmed2Ensembl was used to detect genes associated with the keywords including "Geriatric", "Multimorbidity" and "Renal insufficiency". The GeneCodis program was used to specify Gene Ontology (GO) biological process terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Protein–protein interaction (PPI) networks were constructed using STRING and visualized in Cytoscape. Module analysis was performed using CytoHubba and Molecular Complex Detection (MCODE) plugins. GO and KEGG analysis of gene modules was performed using the Database for Annotation, Visualization and Integrated Discover (DAVID) platform database. Genes clustered in salient modules were selected as core genes. Then, the functions and pathways of core genes were visualized using ClueGO and CluePedia. Finally, the drug-gene interaction database was used to explore drug-gene interactions of the core genes to identify drug candidates for renal insufficiency in patients with geriatric multimorbidity. Results Through text mining, 351 genes associated with "Geriatric", "Multimorbidity" and "Renal insufficiency" were identified. A PPI network consisting of 216 nodes and 1087 edges was constructed and CytoHubba was used to sequence the genes. Five gene modules were obtained by MCODE analysis. The 26 genes clustered in module1 were selected as core candidate genes primarily associated with renal insufficiency in patients with geriatric multimorbidity. The HIF-1, PI3K-Akt, MAPK, Rap1, and FoxO signaling pathways were enriched. We found that 21 of the 26 selected genes could be targeted by 34 existing drugs. Conclusion This study indicated that CST3, SERPINA1, FN1, PF4, IGF1, KNG1, IL6, VEGFA, ALB, TIMP1, TGFB1, HGF, SERPINE1, APOA1, APOB, FGF23, EGF, APOE, VWF, TF, CP, GAS6, APP, IGFBP3, P4HB, and SPP1 were key genes potentially involved with renal insufficiency in patients with geriatric multimorbidity. In addition, 34 drugs were identified as potential agents for the treatment and management of renal insufficiency.
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Affiliation(s)
- Lingyun Zhang
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, No. 221 West Yan'an Road, Shanghai, 200040, People's Republic of China
| | - Jiasheng Cai
- Department of Cardiology, Huadong Hospital Affiliated to Fudan University, No. 221 West Yan'an Road, Shanghai, 200040, People's Republic of China
| | - Jing Xiao
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, No. 221 West Yan'an Road, Shanghai, 200040, People's Republic of China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, No. 221 West Yan'an Road, Shanghai, 200040, People's Republic of China
| | - Zhibin Ye
- Department of Nephrology, Huadong Hospital Affiliated to Fudan University, No. 221 West Yan'an Road, Shanghai, 200040, People's Republic of China. .,Shanghai Key Laboratory of Clinical Geriatric Medicine, No. 221 West Yan'an Road, Shanghai, 200040, People's Republic of China.
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Maywald ML, Picciotto C, Lepa C, Bertgen L, Yousaf FS, Ricker A, Klingauf J, Krahn MP, Pavenstädt H, George B. Rap1 Activity Is Essential for Focal Adhesion and Slit Diaphragm Integrity. Front Cell Dev Biol 2022; 10:790365. [PMID: 35372328 PMCID: PMC8972170 DOI: 10.3389/fcell.2022.790365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 02/24/2022] [Indexed: 11/24/2022] Open
Abstract
Glomerular podocytes build, with their intercellular junctions, part of the kidney filter. The podocyte cell adhesion protein, nephrin, is essential for developing and maintaining slit diaphragms as functional loss in humans results in heavy proteinuria. Nephrin expression and function are also altered in many adult-onset glomerulopathies. Nephrin signals from the slit diaphragm to the actin cytoskeleton and integrin β1 at focal adhesions by recruiting Crk family proteins, which can interact with the Rap guanine nucleotide exchange factor 1 C3G. As Rap1 activity affects focal adhesion formation, we hypothesize that nephrin signals via Rap1 to integrin β. To address this issue, we combined Drosophila in vivo and mammalian cell culture experiments. We find that Rap1 is necessary for correct targeting of integrin β to focal adhesions in Drosophila nephrocytes, which also form slit diaphragm-like structures. In the fly, the Rap1 activity is important for signaling of the nephrin ortholog to integrin β, as well as for nephrin-dependent slit diaphragm integrity. We show by genetic interaction experiments that Rap1 functions downstream of nephrin signaling to integrin β and downstream of nephrin signaling necessary for slit diaphragm integrity. Similarly, in human podocyte culture, nephrin activation results in increased activation of Rap1. Thus, Rap1 is necessary for downstream signal transduction of nephrin to integrin β.
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Affiliation(s)
- Mee-Ling Maywald
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Cara Picciotto
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Carolin Lepa
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | - Luisa Bertgen
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
| | | | - Andrea Ricker
- Institute of Medical Physics and Biophysics, Westfälische Wilhelms-University Münster, Münster, Germany
| | - Jürgen Klingauf
- Institute of Medical Physics and Biophysics, Westfälische Wilhelms-University Münster, Münster, Germany
| | - Michael P. Krahn
- Medizinische Klinik D, Medical Cell Biology, University Hospital Münster, Münster, Germany
| | | | - Britta George
- Medizinische Klinik D, University Hospital Münster, Münster, Germany
- *Correspondence: Britta George,
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Merscher S, Faul C. DACH1 as a multifaceted and potentially druggable susceptibility factor for kidney disease. J Clin Invest 2021; 131:149043. [PMID: 33998596 PMCID: PMC8121511 DOI: 10.1172/jci149043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Kidney diseases affect more than 15% of adults in the US, yet drug development in the kidney field, when compared with that for other common diseases, has been lagging behind. Modifiers that increase the susceptibility to injury and contribute to the pathogenesis and progression of kidney disease include genetic and environmental factors and epigenetic mechanisms. In this issue of the JCI, Cao et al. and Doke et al. independently report the identification of a susceptibility factor called Dachshund homolog 1 (DACH1). Both groups identify an association of reduced DACH1 expression with kidney disease, using different screening approaches, studying different types of human kidney diseases, and using different experimental models, making the fact that both stumbled over the same protein very compelling. Combined, these studies highlight DACH1 as a key safeguard in the kidney, granting various cell types proper function by modulating several molecular pathways.
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Affiliation(s)
- Sandra Merscher
- Katz Family Division of Nephrology and Hypertension, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida, USA
- Peggy and Harold Katz Family Drug Discovery Center, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Christian Faul
- Division of Nephrology, Department of Medicine, The University of Alabama at Birmingham (UAB), Birmingham, Alabama, USA
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Shank2 Binds to aPKC and Controls Tight Junction Formation with Rap1 Signaling during Establishment of Epithelial Cell Polarity. Cell Rep 2020; 31:107407. [DOI: 10.1016/j.celrep.2020.02.088] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 01/22/2020] [Accepted: 02/25/2020] [Indexed: 11/19/2022] Open
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9
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Zheng Y, Cui B, Sun W, Wang S, Huang X, Gao H, Gao F, Cheng Q, Lu L, An Y, Li X, Sun N. Potential Crosstalk between Liver and Extra-liver Organs in Mouse Models of Acute Liver Injury. Int J Biol Sci 2020; 16:1166-1179. [PMID: 32174792 PMCID: PMC7053327 DOI: 10.7150/ijbs.41293] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 01/18/2020] [Indexed: 12/26/2022] Open
Abstract
Carbon tetrachloride (CCl4), Concanavalin A (ConA), bile duct ligation (BDL), and liver resection (LR) are four types of commonly used mouse models of acute liver injury. However, these four models belong to different types of liver cell damage while their application situations are often confounded. In addition, the systematic changes of multiple extra-liver organs after acute liver injury and the crosstalk between liver and extra-liver organs remain unclear. Here, we aim to map the morphological, metabolomic and transcriptomic changes systematically after acute liver injury and search for the potential crosstalk between the liver and the extra-liver organs. Significant changes of transcriptome were observed in multiple extra-liver organs after different types of acute liver injury despite dramatic morphological damage only occurred in lung tissues of the ConA/BDL models and spleen tissues in the ConA model. Liver transcriptomic changes initiated the serum metabolomic alterations which correlated to transcriptomic variation in lung, kidney, and brain tissues of BDL and LR models. The potential crosstalk might lead to pulmonary damage and development of hepatorenal syndrome (HRS) and hepatic encephalopathy (HE) during liver injury. Serum derived from acute liver injury mice damaged alveolar epithelial cells and human podocytes in vitro. Our data indicated that different types of acute liver injury led to different transcriptomic changes within extra-liver organs. Integration of serum metabolomics and transcriptomics from multiple tissues can improve our understanding of acute liver injury and its effect on the other organs.
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Affiliation(s)
- Yufan Zheng
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Baiping Cui
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Wenrui Sun
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Sining Wang
- Department of Pathology, School of Basic Medical Sciences, Shanghai University of Traditional Chinese Medicine, Shanghai 200032, China
| | - Xu Huang
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Han Gao
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Fei Gao
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Qian Cheng
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Limin Lu
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Yanpeng An
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Metabolomics and Systems Biology Laboratory, Human Phenome Institute, Fudan University, Shanghai 200433, China
| | - Xiaobo Li
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Ning Sun
- Department of Physiology and Pathophysiology, State Key Laboratory of Medical Neurobiology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.,Department of Cardiology, Huashan Hospital, Fudan University, Shanghai 200032, China.,Department of Internal Medicine, Huashan Hospital West Campus, Fudan University, Shanghai 200032, China.,Shanghai Key Laboratory of Clinical Geriatric Medicine, Fudan University, Shanghai 200032, China
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10
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Tutunea-Fatan E, Lee JC, Denker BM, Gunaratnam L. Heterotrimeric Gα 12/13 proteins in kidney injury and disease. Am J Physiol Renal Physiol 2020; 318:F660-F672. [PMID: 31984793 DOI: 10.1152/ajprenal.00453.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Gα12 and Gα13 are ubiquitous members of the heterotrimeric guanine nucleotide-binding protein (G protein) family that play central and integrative roles in the regulation of signal transduction cascades within various cell types in the kidney. Gα12/Gα13 proteins enable the kidney to adapt to an ever-changing environment by transducing stimuli from cell surface receptors and accessory proteins to effector systems. Therefore, perturbations in Gα12/Gα13 levels or their activity can contribute to the pathogenesis of various renal diseases, including renal cancer. This review will highlight and discuss the complex and expanding roles of Gα12/Gα13 proteins on distinct renal pathologies, with emphasis on more recently reported findings. Deciphering how the different Gα12/Gα13 interaction networks participate in the onset and development of renal diseases may lead to the discovery of new therapeutic strategies.
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Affiliation(s)
- Elena Tutunea-Fatan
- Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada
| | - Jasper C Lee
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Bradley M Denker
- Beth Israel Deaconess Medical Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Lakshman Gunaratnam
- Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada.,Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.,Division of Nephrology, Department of Medicine, University of Western Ontario, London, Ontario, Canada
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11
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tRNA-derived fragments (tRFs) contribute to podocyte differentiation. Biochem Biophys Res Commun 2019; 521:1-8. [PMID: 31629473 DOI: 10.1016/j.bbrc.2019.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 09/01/2019] [Accepted: 09/04/2019] [Indexed: 11/21/2022]
Abstract
Loss of glomerular podocytes is the crucial event in the progression of chronic kidney disease (CKD). tRNA-derived fragments (tRFs), a newfangled branch of small non-coding RNA (sncRNA), recently reported to play a vital part in several diseases. In present study, we aimed to detect and reveal the role of tRFs in podocyte differentiation. The expression levels of tRFs between undifferentiated and differentiated podocytes were sequenced by illumina nextseq 500, and further verified by quantitative RT-PCR. 69 upregulated and 70 downregulated tRFs in total were singled out (Fold change > 2, P < 0.05). Gene ontology (GO) analysis indicated they are involved in the biological processes of transcription, DNA-templated, positive regulation of transcription from RNA polymerase II promoter, angiogenesis, cell adhesion. Besides, KEGG analysis suggested that these differentially tRFs are associated with PI3K-Akt signaling pathway, Rap1 signaling pathway, Ras signaling pathway, MAPK signaling pathway, and Wnt signaling pathway. Therefore, the differentially tRFs might regulate the differentiation of podocyte and the process of CKD. The functions and mechanisms of tRFs in podocytes are needed to be further explored.
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12
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Zhu B, Cao A, Li J, Young J, Wong J, Ashraf S, Bierzynska A, Menon MC, Hou S, Sawyers C, Campbell KN, Saleem MA, He JC, Hildebrandt F, D'Agati VD, Peng W, Kaufman L. Disruption of MAGI2-RapGEF2-Rap1 signaling contributes to podocyte dysfunction in congenital nephrotic syndrome caused by mutations in MAGI2. Kidney Int 2019; 96:642-655. [PMID: 31171376 PMCID: PMC7259463 DOI: 10.1016/j.kint.2019.03.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Revised: 03/03/2019] [Accepted: 03/14/2019] [Indexed: 11/21/2022]
Abstract
The essential role of membrane associated guanylate kinase 2 (MAGI2) in podocytes is indicated by the phenotypes of severe glomerulosclerosis of both MAGI2 knockout mice and in patients with congenital nephrotic syndrome (CNS) caused by mutations in MAGI2. Here, we show that MAGI2 forms a complex with the Rap1 guanine nucleotide exchange factor, RapGEF2, and that this complex is lost when expressing MAGI2 CNS variants. Co-expression of RapGEF2 with wild-type MAGI2, but not MAGI2 CNS variants, enhanced activation of the small GTPase Rap1, a central signaling node in podocytes. In mice, podocyte-specific RapGEF2 deletion resulted in spontaneous glomerulosclerosis, with qualitative glomerular features comparable to MAGI2 knockout mice. Knockdown of RapGEF2 or MAGI2 in human podocytes caused similar reductions in levels of Rap1 activation and Rap1-mediated downstream signaling. Furthermore, human podocytes expressing MAGI2 CNS variants show severe abnormalities of cellular morphology and dramatic loss of actin cytoskeletal organization, features completely rescued by pharmacological activation of Rap1 via a non-MAGI2 dependent upstream pathway. Finally, immunostaining of kidney sections from patients with congenital nephrotic syndrome and MAGI2 mutations showed reduced podocyte Rap1-mediated signaling. Thus, MAGI2-RapGEF2-Rap1 signaling is essential for normal podocyte function. Hence, disruption of this pathway is an important cause of the renal phenotype induced by MAGI2 CNS mutations.
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Affiliation(s)
- Bingbing Zhu
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA; Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Aili Cao
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA; Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Jianhua Li
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - James Young
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Jenny Wong
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Shazia Ashraf
- Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Agnieszka Bierzynska
- University of Bristol, Children's Renal Unit and Bristol Renal, Bristol, United Kingdom
| | - Madhav C Menon
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Steven Hou
- National Cancer Institute, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Charles Sawyers
- Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Kirk N Campbell
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Moin A Saleem
- University of Bristol, Children's Renal Unit and Bristol Renal, Bristol, United Kingdom
| | - John C He
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Friedhelm Hildebrandt
- Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Vivette D D'Agati
- Renal Pathology Laboratory, Columbia University Medical Center, New York, New York, USA
| | - Wen Peng
- Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.
| | - Lewis Kaufman
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
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13
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Dlugos CP, Picciotto C, Lepa C, Krakow M, Stöber A, Eddy ML, Weide T, Jeibmann A, P Krahn M, Van Marck V, Klingauf J, Ricker A, Wedlich-Söldner R, Pavenstädt H, Klämbt C, George B. Nephrin Signaling Results in Integrin β1 Activation. J Am Soc Nephrol 2019; 30:1006-1019. [PMID: 31097607 DOI: 10.1681/asn.2018040362] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 03/18/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Patients with certain mutations in the gene encoding the slit diaphragm protein Nephrin fail to develop functional slit diaphragms and display severe proteinuria. Many adult-onset glomerulopathies also feature alterations in Nephrin expression and function. Nephrin signals from the podocyte slit diaphragm to the Actin cytoskeleton by recruiting proteins that can interact with C3G, a guanine nucleotide exchange factor of the small GTPase Rap1. Because Rap activity affects formation of focal adhesions, we hypothesized that Nephrin transmits signals to the Integrin receptor complex, which mediates podocyte adhesion to the extracellular matrix. METHODS To investigate Nephrin's role in transmitting signals to the Integrin receptor complex, we conducted genetic studies in Drosophila nephrocytes and validated findings from Drosophila in a cultured human podocyte model. RESULTS Drosophila nephrocytes form a slit diaphragm-like filtration barrier and express the Nephrin ortholog Sticks and stones (Sns). A genetic screen identified c3g as necessary for nephrocyte function. In vivo, nephrocyte-specific gene silencing of sns or c3g compromised nephrocyte filtration and caused nephrocyte diaphragm defects. Nephrocytes with impaired Sns or C3G expression displayed an altered localization of Integrin and the Integrin-associated protein Talin. Furthermore, gene silencing of c3g partly rescued nephrocyte diaphragm defects of an sns overexpression phenotype, pointing to genetic interaction of sns and c3g in nephrocytes. We also found that activated Nephrin recruited phosphorylated C3G and resulted in activation of Integrin β1 in cultured podocytes. CONCLUSIONS Our findings suggest that Nephrin can mediate a signaling pathway that results in activation of Integrin β1 at focal adhesions, which may affect podocyte attachment to the extracellular matrix.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - Christian Klämbt
- Neurobiology, Westfälische-Wilhelms University Münster, Münster, Germany
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14
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Sieber KB, Batorsky A, Siebenthall K, Hudkins KL, Vierstra JD, Sullivan S, Sur A, McNulty M, Sandstrom R, Reynolds A, Bates D, Diegel M, Dunn D, Nelson J, Buckley M, Kaul R, Sampson MG, Himmelfarb J, Alpers CE, Waterworth D, Akilesh S. Integrated Functional Genomic Analysis Enables Annotation of Kidney Genome-Wide Association Study Loci. J Am Soc Nephrol 2019; 30:421-441. [PMID: 30760496 PMCID: PMC6405142 DOI: 10.1681/asn.2018030309] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 12/26/2018] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Linking genetic risk loci identified by genome-wide association studies (GWAS) to their causal genes remains a major challenge. Disease-associated genetic variants are concentrated in regions containing regulatory DNA elements, such as promoters and enhancers. Although researchers have previously published DNA maps of these regulatory regions for kidney tubule cells and glomerular endothelial cells, maps for podocytes and mesangial cells have not been available. METHODS We generated regulatory DNA maps (DNase-seq) and paired gene expression profiles (RNA-seq) from primary outgrowth cultures of human glomeruli that were composed mainly of podocytes and mesangial cells. We generated similar datasets from renal cortex cultures, to compare with those of the glomerular cultures. Because regulatory DNA elements can act on target genes across large genomic distances, we also generated a chromatin conformation map from freshly isolated human glomeruli. RESULTS We identified thousands of unique regulatory DNA elements, many located close to transcription factor genes, which the glomerular and cortex samples expressed at different levels. We found that genetic variants associated with kidney diseases (GWAS) and kidney expression quantitative trait loci were enriched in regulatory DNA regions. By combining GWAS, epigenomic, and chromatin conformation data, we functionally annotated 46 kidney disease genes. CONCLUSIONS We demonstrate a powerful approach to functionally connect kidney disease-/trait-associated loci to their target genes by leveraging unique regulatory DNA maps and integrated epigenomic and genetic analysis. This process can be applied to other kidney cell types and will enhance our understanding of genome regulation and its effects on gene expression in kidney disease.
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Affiliation(s)
| | - Anna Batorsky
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | | | | | - Jeff D Vierstra
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | | | - Aakash Sur
- Phase Genomics Inc., Seattle, Washington
- Department of Biomedical and Health Informatics, and
| | - Michelle McNulty
- Division of Pediatric Nephrology, Department of Pediatrics, University of Michigan School of Medicine, Ann Arbor, Michigan; and
| | | | - Alex Reynolds
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | - Daniel Bates
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | - Morgan Diegel
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | - Douglass Dunn
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | - Jemma Nelson
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | - Michael Buckley
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | - Rajinder Kaul
- Altius Institute for Biomedical Sciences, Seattle, Washington
| | - Matthew G Sampson
- Division of Pediatric Nephrology, Department of Pediatrics, University of Michigan School of Medicine, Ann Arbor, Michigan; and
| | - Jonathan Himmelfarb
- Division of Nephrology, Department of Medicine, University of Washington, Seattle, Washington
- Kidney Research Institute, Seattle, Washington
| | - Charles E Alpers
- Department of Anatomic Pathology
- Kidney Research Institute, Seattle, Washington
| | | | - Shreeram Akilesh
- Department of Anatomic Pathology,
- Kidney Research Institute, Seattle, Washington
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15
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Methylation level of Rap1GAP and the clinical significance in MDS. Oncol Lett 2018; 16:7287-7294. [PMID: 30546468 DOI: 10.3892/ol.2018.9503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 04/25/2017] [Indexed: 12/21/2022] Open
Abstract
Previous studies on the pathogenesis of myelodysplastic syndrome (MDS) have identified multiple associated gene mutations, including mutations of tetmethylcytosinedioxygenase 2, isocitrate dehydrogenase [NADP(+)] 1 cytosolic, isocitrate dehydrogenase [NADP(+)] 2 mitochondrial and additional sex combs like 1 transcriptional regulator, all of which may be considered epigenetic regulators. Furthermore, mutations of RAS type GTPase family genes have been identified in 10-15% patients with MDS. The authors' previous study on the gene expression profile of cluster of differentiation 34+ cells using microarray analysis identified elevated expression of RAP1GTPase activating protein 1 (Rap1GAP) in patients with MDS compared with that in non-malignant blood diseases (NM) control group. To further investigate the mechanism of increased Rap1GAP expression, the methylation pattern of the promoter of this gene was determined in 86 patients with MDS (n=29), acute myeloid leukemia (AML) (n=31) or NM (n=26) using bisulfite-specific polymerase chain reaction and DNA sequencing. The results demonstrated that the methylation of Rap1GAP occurred in all 29 patients with MDS at multiple CpG sites. The methylation level of Rap1GAP in patients with MDS was decreased compared with that in patients with NM. Significant differences at 4CpG sites (5,7,8 and 12) of Rap1GAP promoter were identified between MDS and NM. Furthermore, based on the present clinical records of the patient cohort, the methylation status of Rap1GAP promoter did not appear to be associated with the clinicopathological characteristics of patients with MDS, including age, gender and International Prognosis Score System. The difference in methylation level at CpG site 8 of Rap1GAP promoter was identified to be significantly increased in patients with MDS-refractory anemia with ring sideroblasts compared with that in the MDS-refractory cytopenia with multilineage dysplasia or MDS-unclassified groups. The results of the present study suggest that patients with MDS exhibit a lower overall methylation level within Rap1GAP promoter compared with patients with NM or AML. In addition, the methylation level at the four identified CpG sites can distinguish between MDS and NM.
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16
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Rednor SJ, Ross MJ. Molecular Mechanisms of Injury in HIV-Associated Nephropathy. Front Med (Lausanne) 2018; 5:177. [PMID: 29930940 PMCID: PMC5999756 DOI: 10.3389/fmed.2018.00177] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 05/22/2018] [Indexed: 11/15/2022] Open
Abstract
HIV-associated nephropathy (HIVAN) is an important cause of secondary focal glomerulosclerosis that occurs primarily in persons of African ancestry with advanced HIV disease. Although HIVAN is characterized by severe proteinuria and rapid progression to end stage renal disease without treatment, the phenotype is markedly attenuated by treatment with antiretroviral medications. HIV infection of glomerular and tubular epithelial cells and subsequent viral gene expression is a key contributor to HIVAN pathogenesis and the kidney can serve as reservoir for HIV strains that differ those in blood. HIV gene expression in renal epithelial cells leads to dysregulation of cellular pathways including cell cycle, inflammation, cell death, and cytoskeletal homeostasis. Polymorphisms in the APOL1 gene explain the marked predilection of HIVAN to occur in persons of African descent and HIVAN. Since HIVAN has the strongest association with APOL1 genotype of any of the APOL1-associated nephropathies, studies to determine the mechanisms by which HIV and APOL1 risk variants together promote kidney injury hold great promise to improve our understanding of the pathogenesis of APOL1-mediated kidney diseases.
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Affiliation(s)
- Samuel J Rednor
- Division of Nephrology, Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, NY, United States
| | - Michael J Ross
- Division of Nephrology, Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, NY, United States.,Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, United States
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17
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Pan Y, Jiang S, Hou Q, Qiu D, Shi J, Wang L, Chen Z, Zhang M, Duan A, Qin W, Zen K, Liu Z. Dissection of Glomerular Transcriptional Profile in Patients With Diabetic Nephropathy: SRGAP2a Protects Podocyte Structure and Function. Diabetes 2018; 67:717-730. [PMID: 29242313 DOI: 10.2337/db17-0755] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 10/26/2017] [Indexed: 01/19/2023]
Abstract
Podocytes play a pivotal role in maintaining glomerular filtration function through their interdigitated foot processes. However, the mechanisms that govern the podocyte cytoskeletal rearrangement remain unclear. Through analyzing the transcriptional profile of renal biopsy specimens from patients with diabetic nephropathy (DN) and control donors, we identify SLIT-ROBO ρGTPase-activating protein 2a (SRGAP2a) as one of the main hub genes strongly associated with proteinuria and glomerular filtration in type 2 DN. Immunofluorescence staining and Western blot analysis revealed that human and mouse SRGAP2a is primarily localized at podocytes and largely colocalized with synaptopodin. Moreover, podocyte SRGAP2a is downregulated in patients with DN and db/db mice at both the mRNA and the protein level. SRGAP2a reduction is observed in cultured podocytes treated with tumor growth factor-β or high concentrations of glucose. Functional and mechanistic studies show that SRGAP2a suppresses podocyte motility through inactivating RhoA/Cdc42 but not Rac1. The protective role of SRGAP2a in podocyte function also is confirmed in zebrafish, in which knockdown of SRGAP2a, a SRGAP2 ortholog in zebrafish, recapitulates podocyte foot process effacement. Finally, increasing podocyte SRGAP2a levels in db/db mice through administration of adenovirus-expressing SRGAP2a significantly mitigates podocyte injury and proteinuria. The results demonstrate that SRGAP2a protects podocytes by suppressing podocyte migration.
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Affiliation(s)
- Yu Pan
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Song Jiang
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Qing Hou
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Dandan Qiu
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Jingsong Shi
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Ling Wang
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Zhaohong Chen
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Mingchao Zhang
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Aiping Duan
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Weisong Qin
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
| | - Ke Zen
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Zhihong Liu
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China
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18
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Liu Y, Li H, Liu J, Han P, Li X, Bai H, Zhang C, Sun X, Teng Y, Zhang Y, Yuan X, Chu Y, Zhao B. Variations in MicroRNA-25 Expression Influence the Severity of Diabetic Kidney Disease. J Am Soc Nephrol 2017; 28:3627-3638. [PMID: 28923913 DOI: 10.1681/asn.2015091017] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 08/16/2017] [Indexed: 01/19/2023] Open
Abstract
Diabetic nephropathy is characterized by persistent albuminuria, progressive decline in GFR, and secondary hypertension. MicroRNAs are dysregulated in diabetic nephropathy, but identification of the specific microRNAs involved remains incomplete. Here, we show that the peripheral blood from patients with diabetes and the kidneys of animals with type 1 or 2 diabetes have low levels of microRNA-25 (miR-25) compared with those of their nondiabetic counterparts. Furthermore, treatment with high glucose decreased the expression of miR-25 in cultured kidney cells. In db/db mice, systemic administration of an miR-25 agomir repressed glomerular fibrosis and reduced high BP. Notably, knockdown of miR-25 in normal mice by systemic administration of an miR-25 antagomir resulted in increased proteinuria, extracellular matrix accumulation, podocyte foot process effacement, and hypertension with renin-angiotensin system activation. However, excessive miR-25 did not cause kidney dysfunction in wild-type mice. RNA sequencing showed the alteration of miR-25 target genes in antagomir-treated mice, including the Ras-related gene CDC42. In vitro, cotransfection with the miR-25 antagomir repressed luciferase activity from a reporter construct containing the CDC42 3' untranslated region. In conclusion, these results reveal a role for miR-25 in diabetic nephropathy and indicate a potential novel therapeutic target for this disease.
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Affiliation(s)
- Yunshuang Liu
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and.,Clinical Laboratory of Hong Qi Hospital, Mudanjiang Medical University, Heilongjiang, People's Republic of China
| | - Hongzhi Li
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Jieting Liu
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Pengfei Han
- Clinical Laboratory of Hong Qi Hospital, Mudanjiang Medical University, Heilongjiang, People's Republic of China
| | - Xuefeng Li
- Clinical Laboratory of Hong Qi Hospital, Mudanjiang Medical University, Heilongjiang, People's Republic of China
| | - He Bai
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Chunlei Zhang
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Xuelian Sun
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Yanjie Teng
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Yufei Zhang
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Xiaohuan Yuan
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Yanhui Chu
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
| | - Binghai Zhao
- Heilongjiang Key Laboratory of Anti-Fibrosis Biotherapy, Medical Research Center, Heilongjiang, People's Republic of China; and
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19
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The FERM protein EPB41L5 regulates actomyosin contractility and focal adhesion formation to maintain the kidney filtration barrier. Proc Natl Acad Sci U S A 2017; 114:E4621-E4630. [PMID: 28536193 DOI: 10.1073/pnas.1617004114] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Podocytes form the outer part of the glomerular filter, where they have to withstand enormous transcapillary filtration forces driving glomerular filtration. Detachment of podocytes from the glomerular basement membrane precedes most glomerular diseases. However, little is known about the regulation of podocyte adhesion in vivo. Thus, we systematically screened for podocyte-specific focal adhesome (FA) components, using genetic reporter models in combination with iTRAQ-based mass spectrometry. This approach led to the identification of FERM domain protein EPB41L5 as a highly enriched podocyte-specific FA component in vivo. Genetic deletion of Epb41l5 resulted in severe proteinuria, detachment of podocytes, and development of focal segmental glomerulosclerosis. Remarkably, by binding and recruiting the RhoGEF ARGHEF18 to the leading edge, EPB41L5 directly controls actomyosin contractility and subsequent maturation of focal adhesions, cell spreading, and migration. Furthermore, EPB41L5 controls matrix-dependent outside-in signaling by regulating the focal adhesome composition. Thus, by linking extracellular matrix sensing and signaling, focal adhesion maturation, and actomyosin activation EPB41L5 ensures the mechanical stability required for podocytes at the kidney filtration barrier. Finally, a diminution of EPB41L5-dependent signaling programs appears to be a common theme of podocyte disease, and therefore offers unexpected interventional therapeutic strategies to prevent podocyte loss and kidney disease progression.
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20
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Ni J, Bao S, Johnson RI, Zhu B, Li J, Vadaparampil J, Smith CM, Campbell KN, Grahammer F, Huber TB, He JC, D'Agati VD, Chan A, Kaufman L. MAGI-1 Interacts with Nephrin to Maintain Slit Diaphragm Structure through Enhanced Rap1 Activation in Podocytes. J Biol Chem 2016; 291:24406-24417. [PMID: 27707879 PMCID: PMC5114397 DOI: 10.1074/jbc.m116.745026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 10/05/2016] [Indexed: 12/15/2022] Open
Abstract
MAGI-1 is a multidomain cytosolic scaffolding protein that in the kidney is specifically located at the podocyte slit diaphragm, a specialized junction that is universally injured in proteinuric diseases. There it interacts with several essential molecules, including nephrin and neph1, which are required for slit diaphragm formation and as an intracellular signaling hub. Here, we show that diminished MAGI-1 expression in cultured podocytes reduced nephrin and neph1 membrane localization and weakened tight junction integrity. Global magi1 knock-out mice, however, demonstrated normal glomerular histology and function into adulthood. We hypothesized that a second mild but complementary genetic insult might induce glomerular disease susceptibility in these mice. To identify such a gene, we utilized the developing fly eye to test for functional complementation between MAGI and its binding partners. In this way, we identified diminished expression of fly Hibris (nephrin) or Roughest (neph1) as dramatically exacerbating the effects of MAGI depletion. Indeed, when these combinations were studied in mice, the addition of nephrin, but not neph1, heterozygosity to homozygous deletion of MAGI-1 resulted in spontaneous glomerulosclerosis. In cultured podocytes, MAGI-1 depletion reduced intercellular contact-induced Rap1 activation, a pathway critical for proper podocyte function. Similarly, magi1 knock-out mice showed diminished glomerular Rap1 activation, an effect dramatically enhanced by concomitant nephrin haploinsufficiency. Finally, combined overexpression of MAGI-1 and nephrin increased Rap1 activation, but not when substituting a mutant MAGI-1 that cannot bind nephrin. We conclude that the interaction between nephrin and MAGI-1 regulates Rap1 activation in podocytes to maintain long term slit diaphragm structure.
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Affiliation(s)
- Jie Ni
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029,; the Division of Nephrology, First Affiliated Hospital of Harbin Medical University, Harbin, China 150001
| | - Sujin Bao
- the Saint James School of Medicine, Saint Vincent and the Grenadines
| | - Ruth I Johnson
- the Biology Department, Wesleyan University, Middletown, Connecticut, 06459
| | - Bingbing Zhu
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029,; the Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China 200062
| | - Jianhua Li
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Justin Vadaparampil
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Christopher M Smith
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Kirk N Campbell
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Florian Grahammer
- the Department of Medicine IV, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
| | - Tobias B Huber
- the Department of Medicine IV, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany,; the BIOSS Center for Biological Signaling Studies, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany,; FRIAS, Freiburg Institute for Advanced Studies and Center for Systems Biology (ZBSA), Albert-Ludwigs-University, 79104 Freiburg, Germany
| | - John C He
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Vivette D D'Agati
- the Department of Pathology, Columbia University Medical Center, New York, New York 10032, and
| | - Andrew Chan
- the School of Biomedical Sciences, Chinese University of Hong Kong, Hong Kong, China
| | - Lewis Kaufman
- From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029,.
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21
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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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22
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Gu C, Lee HW, Garborcauskas G, Reiser J, Gupta V, Sever S. Dynamin Autonomously Regulates Podocyte Focal Adhesion Maturation. J Am Soc Nephrol 2016; 28:446-451. [PMID: 27432739 DOI: 10.1681/asn.2016010008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 06/01/2016] [Indexed: 12/31/2022] Open
Abstract
Rho family GTPases, the prototypical members of which are Cdc42, Rac1, and RhoA, are molecular switches best known for regulating the actin cytoskeleton. In addition to the canonical small GTPases, the large GTPase dynamin has been implicated in regulating the actin cytoskeleton via direct dynamin-actin interactions. The physiologic role of dynamin in regulating the actin cytoskeleton has been linked to the maintenance of the kidney filtration barrier. Additionally, the small molecule Bis-T-23, which promotes actin-dependent dynamin oligomerization and thus, increases actin polymerization, improved renal health in diverse models of CKD, implicating dynamin as a potential therapeutic target for the treatment of CKD. Here, we show that treating cultured mouse podocytes with Bis-T-23 promoted stress fiber formation and focal adhesion maturation in a dynamin-dependent manner. Furthermore, Bis-T-23 induced the formation of focal adhesions and stress fibers in cells in which the RhoA signaling pathway was downregulated by multiple experimental approaches. Our study suggests that dynamin regulates focal adhesion maturation by a mechanism parallel to and synergistic with the RhoA signaling pathway. Identification of dynamin as one of the essential and autonomous regulators of focal adhesion maturation suggests a molecular mechanism that underlies the beneficial effect of Bis-T-23 on podocyte physiology.
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Affiliation(s)
- Changkyu Gu
- Department of Medicine, Harvard Medical School, Division of Nephrology, Massachusetts General Hospital, Charlestown, Massachusetts; and
| | - Ha Won Lee
- Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois
| | - Garrett Garborcauskas
- Department of Medicine, Harvard Medical School, Division of Nephrology, Massachusetts General Hospital, Charlestown, Massachusetts; and
| | - Jochen Reiser
- Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois
| | - Vineet Gupta
- Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois
| | - Sanja Sever
- Department of Medicine, Harvard Medical School, Division of Nephrology, Massachusetts General Hospital, Charlestown, Massachusetts; and
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23
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Abstract
PURPOSE OF REVIEW Podocytes are the main gatekeeper of protein filtration in the glomerulus. When podocytes work less efficiently, this translates to the appearance of proteins in the urine, a condition that, if not promptly treated, leads to progression of glomerular damage and renal failure. RECENT FINDINGS Novel gene mutations have been uncovered in patients with nephrotic syndrome combined with a better definition of the role of podocin mutations. Although the importance of the inflammasome pathway and of the mechanisms of autophagy in podocyte health and disease have been increasingly recognized, a precise relationship between these processes still needs to be assessed. Numerous potential therapeutic targets have been identified and numerous data support the possibility of boosting podocyte regeneration. However, translation of experimental results into the clinic could largely depend on the avoidance of undesired side-effects; nanomedicine could provide the means to target old and novel drugs specifically to the podocytes. SUMMARY Podocytes are key cells in the glomerulus, and their damage inevitably leads to proteinuria and glomerular dysfunction. The more is known about the causes and mechanisms of podocyte damage, the more it will be possible to find new cures for glomerular diseases of the kidney.
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Abstract
Podocytes are highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule. When it comes to glomerular filtration, podocytes play an active role in preventing plasma proteins from entering the urinary ultrafiltrate by providing a barrier comprising filtration slits between foot processes, which in aggregate represent a dynamic network of cellular extensions. Foot processes interdigitate with foot processes from adjacent podocytes and form a network of narrow and rather uniform gaps. The fenestrated endothelial cells retain blood cells but permit passage of small solutes and an overlying basement membrane less permeable to macromolecules, in particular to albumin. The cytoskeletal dynamics and structural plasticity of podocytes as well as the signaling between each of these distinct layers are essential for an efficient glomerular filtration and thus for proper renal function. The genetic or acquired impairment of podocytes may lead to foot process effacement (podocyte fusion or retraction), a morphological hallmark of proteinuric renal diseases. Here, we briefly discuss aspects of a contemporary view of podocytes in glomerular filtration, the patterns of structural changes in podocytes associated with common glomerular diseases, and the current state of basic and clinical research.
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Affiliation(s)
- Jochen Reiser
- Department of Medicine, Rush University Medical Center, Chicago, IL, USA
| | - Mehmet M Altintas
- Department of Medicine, Rush University Medical Center, Chicago, IL, USA
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25
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Park F. Accessory proteins for heterotrimeric G-proteins in the kidney. Front Physiol 2015; 6:219. [PMID: 26300785 PMCID: PMC4528294 DOI: 10.3389/fphys.2015.00219] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 07/20/2015] [Indexed: 11/17/2022] Open
Abstract
Heterotrimeric G-proteins play a fundamentally important role in regulating signal transduction pathways in the kidney. Accessory proteins are being identified as direct binding partners for heterotrimeric G-protein α or βγ subunits to promote more diverse mechanisms by which G-protein signaling is controlled. In some instances, accessory proteins can modulate the signaling magnitude, localization, and duration following the activation of cell membrane-associated receptors. Alternatively, accessory proteins complexed with their G-protein α or βγ subunits can promote non-canonical models of signaling activity within the cell. In this review, we will highlight the expression profile, localization and functional importance of these newly identified accessory proteins to control the function of select G-protein subunits under normal and various disease conditions observed in the kidney.
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Affiliation(s)
- Frank Park
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center Memphis, TN, USA
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26
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Maddala R, Nagendran T, Lang RA, Morozov A, Rao PV. Rap1 GTPase is required for mouse lens epithelial maintenance and morphogenesis. Dev Biol 2015. [PMID: 26212757 DOI: 10.1016/j.ydbio.2015.06.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Rap1, a Ras-like small GTPase, plays a crucial role in cell-matrix adhesive interactions, cell-cell junction formation, cell polarity and migration. The role of Rap1 in vertebrate organ development and tissue architecture, however, remains elusive. We addressed this question in a mouse lens model system using a conditional gene targeting approach. While individual germline deficiency of either Rap1a or Rap1b did not cause overt defects in mouse lens, conditional double deficiency (Rap1 cKO) prior to lens placode formation led to an ocular phenotype including microphthalmia and lens opacification in embryonic mice. The embryonic Rap1 cKO mouse lens exhibited striking defects including loss of E-cadherin- and ZO-1-based cell-cell junctions, disruption of paxillin and β1-integrin-based cell adhesive interactions along with abnormalities in cell shape and apical-basal polarity of epithelium. These epithelial changes were accompanied by increased levels of α-smooth muscle actin, vimentin and N-cadherin, and expression of transcriptional suppressors of E-cadherin (Snai1, Slug and Zeb2), and a mesenchymal metabolic protein (Dihydropyrimidine dehydrogenase). Additionally, while lens differentiation was not overtly affected, increased apoptosis and dysregulated cell cycle progression were noted in epithelium and fibers in Rap1 cKO mice. Collectively these observations uncover a requirement for Rap1 in maintenance of lens epithelial phenotype and morphogenesis.
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Affiliation(s)
- Rupalatha Maddala
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Tharkika Nagendran
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Richard A Lang
- The Visual System Group, Division of Pediatric Ophthalmology and Developmental Biology, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Alexei Morozov
- Virginia Tech Carilion Research Institute, Roanoke, VA 24016, USA
| | - Ponugoti V Rao
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA; Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA.
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27
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Abstract
The function of the kidney, filtering blood and concentrating metabolic waste into urine, takes place in an intricate and functionally elegant structure called the renal glomerulus. Normal glomerular function retains circulating cells and valuable macromolecular components of plasma in blood, resulting in urine with just trace amounts of proteins. Endothelial cells of glomerular capillaries, the podocytes wrapped around them, and the fused extracellular matrix these cells form altogether comprise the glomerular filtration barrier, a dynamic and highly selective filter that sieves on the basis of molecular size and electrical charge. Current understanding of the structural organization and the cellular and molecular basis of renal filtration draws from studies of human glomerular diseases and animal models of glomerular dysfunction.
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Affiliation(s)
- Rizaldy P Scott
- Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Susan E Quaggin
- Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
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28
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Chen YM, Liapis H. Focal segmental glomerulosclerosis: molecular genetics and targeted therapies. BMC Nephrol 2015; 16:101. [PMID: 26156092 PMCID: PMC4496884 DOI: 10.1186/s12882-015-0090-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 06/16/2015] [Indexed: 12/18/2022] Open
Abstract
Recent advances show that human focal segmental glomerulosclerosis (FSGS) is a primary podocytopathy caused by podocyte-specific gene mutations including NPHS1, NPHS2, WT-1, LAMB2, CD2AP, TRPC6, ACTN4 and INF2. This review focuses on genes discovered in the investigation of complex FSGS pathomechanisms that may have implications for the current FSGS classification scheme. It also recounts recent recommendations for clinical management of FSGS based on translational studies and clinical trials. The advent of next-generation sequencing promises to provide nephrologists with rapid and novel approaches for the diagnosis and treatment of FSGS. A stratified and targeted approach based on the underlying molecular defects is evolving.
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Affiliation(s)
- Ying Maggie Chen
- Renal Division, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO, 63110, USA.
| | - Helen Liapis
- , Nephropath, Little Rock, Arkansas
- Pathology & Immunology, Washington University School of Medicine, St. Louis, MO, USA
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29
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Schwartzman M, Reginensi A, Wong JS, Basgen JM, Meliambro K, Nicholas SB, D'Agati V, McNeill H, Campbell KN. Podocyte-Specific Deletion of Yes-Associated Protein Causes FSGS and Progressive Renal Failure. J Am Soc Nephrol 2015; 27:216-26. [PMID: 26015453 DOI: 10.1681/asn.2014090916] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 04/02/2015] [Indexed: 11/03/2022] Open
Abstract
FSGS is the most common primary glomerular disease underlying ESRD in the United States and is increasing in incidence globally. FSGS results from podocyte injury, yet the mechanistic details of disease pathogenesis remain unclear. This has resulted in an unmet clinical need for cell-specific therapy in the treatment of FSGS and other proteinuric kidney diseases. We previously identified Yes-associated protein (YAP) as a prosurvival signaling molecule, the in vitro silencing of which increases podocyte susceptibility to apoptotic stimulus. YAP is a potent oncogene that is a prominent target for chemotherapeutic drug development. In this study, we tested the hypothesis that podocyte-specific deletion of Yap leads to proteinuric kidney disease through increased podocyte apoptosis. Yap was selectively silenced in podocytes using Cre-mediated recombination controlled by the podocin promoter. Yap silencing in podocytes resulted in podocyte apoptosis, podocyte depletion, proteinuria, and an increase in serum creatinine. Histologically, features characteristic of FSGS, including mesangial sclerosis, podocyte foot process effacement, tubular atrophy, interstitial fibrosis, and casts, were observed. In human primary FSGS, we noted reduced glomerular expression of YAP. Taken together, these results suggest a role for YAP as a physiologic antagonist of podocyte apoptosis, the signaling of which is essential for maintaining the integrity of the glomerular filtration barrier. These data suggest potential nephrotoxicity with strategies directed toward inhibition of YAP function. Further studies should evaluate the role of YAP in proteinuric glomerular disease pathogenesis and its potential utility as a therapeutic target.
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Affiliation(s)
- Monica Schwartzman
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Antoine Reginensi
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Jenny S Wong
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - John M Basgen
- Department of Research, Morphometry and Stereology Laboratory, Charles R. Drew University of Medicine and Science, Los Angeles, California
| | - Kristin Meliambro
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Susanne B Nicholas
- Department of Research, Morphometry and Stereology Laboratory, Charles R. Drew University of Medicine and Science, Los Angeles, California; Department of Medicine, Division of Nephrology, University of California Los Angeles, Los Angeles, California; and
| | - Vivette D'Agati
- Department of Pathology, Columbia University College of Physicians and Surgeons, New York, New York
| | - Helen McNeill
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Kirk N Campbell
- Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York;
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30
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Lee HW, Khan SQ, Faridi MH, Wei C, Tardi NJ, Altintas MM, Elshabrawy HA, Mangos S, Quick KL, Sever S, Reiser J, Gupta V. A Podocyte-Based Automated Screening Assay Identifies Protective Small Molecules. J Am Soc Nephrol 2015; 26:2741-52. [PMID: 25858967 DOI: 10.1681/asn.2014090859] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 01/08/2015] [Indexed: 12/30/2022] Open
Abstract
Podocyte injury and loss mark an early step in the pathogenesis of various glomerular diseases, making these cells excellent targets for therapeutics. However, cell-based high-throughput screening assays for the rational development of podocyte-directed therapeutics are currently lacking. Here, we describe a novel high-content screening-based phenotypic assay that analyzes thousands of podocytes per assay condition in 96-well plates to quantitatively measure dose-dependent changes in multiple cellular features. Our assay consistently produced a Z' value >0.44, making it suitable for compound screening. On screening with >2100 pharmacologically active agents, we identified 24 small molecules that protected podocytes against injury in vitro (1% hit rate). Among the identified hits, we confirmed an β1-integrin agonist, pyrintegrin, as a podocyte-protective agent. Treatment with pyrintegrin prevented damage-induced decreases in F-actin stress fibers, focal adhesions, and active β1-integrin levels in cultured cells. In vivo, administration of pyrintegrin protected mice from LPS-induced podocyte foot process effacement and proteinuria. Analysis of the murine glomeruli showed that LPS administration reduced the levels of active β1 integrin in the podocytes, which was prevented by cotreatment with pyrintegrin. In rats, pyrintegrin reduced peak proteinuria caused by puromycin aminonucleoside-induced nephropathy. Our findings identify pyrintegrin as a potential therapeutic candidate and show the use of podocyte-based screening assays for identifying novel therapeutics for proteinuric kidney diseases.
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Affiliation(s)
- Ha Won Lee
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Samia Q Khan
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Mohd Hafeez Faridi
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Changli Wei
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Nicholas J Tardi
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Mehmet M Altintas
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Hatem A Elshabrawy
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Steve Mangos
- Department of Medicine, Rush University Medical Center, Chicago, Illinois
| | - Kevin L Quick
- Cellular Imaging and Analysis, PerkinElmer Life Sciences, Waltham, Massachusetts; and
| | - Sanja Sever
- Department of Medicine, Harvard Medical School, Division of Nephrology, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Jochen Reiser
- Department of Medicine, Rush University Medical Center, Chicago, Illinois;
| | - Vineet Gupta
- Department of Medicine, Rush University Medical Center, Chicago, Illinois;
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31
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Boor P, Floege J. Renal allograft fibrosis: biology and therapeutic targets. Am J Transplant 2015; 15:863-86. [PMID: 25691290 DOI: 10.1111/ajt.13180] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 11/30/2014] [Accepted: 12/19/2014] [Indexed: 01/25/2023]
Abstract
Renal tubulointerstitial fibrosis is the final common pathway of progressive renal diseases. In allografts, it is assessed with tubular atrophy as interstitial fibrosis/tubular atrophy (IF/TA). IF/TA occurs in about 40% of kidney allografts at 3-6 months after transplantation, increasing to 65% at 2 years. The origin of renal fibrosis in the allograft is complex and includes donor-related factors, in particular in case of expanded criteria donors, ischemia-reperfusion injury, immune-mediated damage, recurrence of underlying diseases, hypertensive damage, nephrotoxicity of immunosuppressants, recurrent graft infections, postrenal obstruction, etc. Based largely on studies in the non-transplant setting, there is a large body of literature on the role of different cell types, be it intrinsic to the kidney or bone marrow derived, in mediating renal fibrosis, and the number of mediator systems contributing to fibrotic changes is growing steadily. Here we review the most important cellular processes and mediators involved in the progress of renal fibrosis, with a focus on the allograft situation, and discuss some of the challenges in translating experimental insights into clinical trials, in particular fibrosis biomarkers or imaging modalities.
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Affiliation(s)
- P Boor
- Division of Nephrology and Clinical Immunology, RWTH University of Aachen, Aachen, Germany; Department of Pathology, RWTH University of Aachen, Aachen, Germany; Institute of Molecular Biomedicine, Bratislava, Slovakia
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32
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Saleem MA. One hundred ways to kill a podocyte. Nephrol Dial Transplant 2015; 30:1266-71. [PMID: 25637640 DOI: 10.1093/ndt/gfu363] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 10/27/2014] [Indexed: 12/30/2022] Open
Abstract
The podocyte is a highly specialized cell, forming within the developing glomerulus from a mesenchymal origin, acquiring some but not complete features of an epithelial cell as it matures. Once mature, this cell has the potential to receive signals from several different directions and sits within a dynamic microenvironment. By taking an overview of many lines of evidence, it is clear that we already know many signals that are tightly controlled in keeping the podocyte healthy. For example, vascular endothelial growth factor, insulin and integrins are all known to have bidirectional effects on podocyte functionality, depending on whether there is too much or too little. It is of little surprise therefore that disrupting this delicate balance can result in a dramatic loss of function, and manifestation of glomerular disease originating from many different primary insults. The cues directing podocyte phenotype and functionality for the purpose of this review will be divided into four main sources: (i) genetic, (ii) paracrine signals from endothelial and mesangial cells, (iii) direct contact signals to/from the glomerular basement membrane and (iv) signals from circulating plasma. Of course there are other influences, which we still know little about, such as flow and shear stresses, signals from the urinary space that should all be considered in the overall healthy environment.
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Affiliation(s)
- Moin A Saleem
- Bristol Children's Hospital, University of Bristol, Bristol, UK
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33
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Abstract
Heterotrimeric G proteins play a crucial role in regulating signal processing to maintain normal cellular homeostasis, and subtle perturbations in its activity can potentially lead to the pathogenesis of renal disorders or diseases. Cell-surface receptors and accessory proteins, which normally modify and organize the coupling of individual G protein subunits, contribute to the regulation of heterotrimeric G protein activity and their convergence and/or divergence of downstream signaling initiated by effector systems. Activators of G protein signaling (AGS) are a family of accessory proteins that intervene at multiple distinct points during the activation-inactivation cycle of G proteins, even in the absence of receptor stimulation. Perturbations in the expression of individual AGS proteins have been reported to modulate signal transduction pathways in a wide array of diseases and disorders within the brain, heart, immune system, and more recently, the kidney. This review will provide an overview of the expression profile, localization, and putative biologic role of the AGS family in the context of normal and diseased states of the kidney.
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Affiliation(s)
- Frank Park
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee
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34
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Bai X, Geng J, Li X, Yang F, Tian J. VEGF-A inhibition ameliorates podocyte apoptosis via repression of activating protein 1 in diabetes. Am J Nephrol 2015; 40:523-34. [PMID: 25572464 DOI: 10.1159/000369942] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 11/12/2014] [Indexed: 12/14/2022]
Abstract
BACKGROUND/AIMS Vascular endothelial growth factor-A (VEGF-A) upregulation and podocyte apoptosis have been documented in diabetes. This study was designed to investigate whether inhibiting VEGF-A could ameliorate podocyte apoptosis in diabetes and the underlying mechanisms. METHODS In vitro, small interfering RNAs (siRNAs) of VEGF-A and activator protein 1 (AP-1, c-fos and c-jun), bevacizumab (VEGF-A inhibitor) and SP600125 (AP-1 inhibitor) were added to high glucose (30 mM) induced podocytes. Luciferase reporter assay was used to investigate whether AP-1 was a direct target of VEGF-A. In vivo, bevacizumab and SP600125 were administered to 12-week-old streptozotocin-induced male Sprague Dawley rats. The level of VEGF-A, c-fos, c-jun and bcl-2 were examined using immunostaining and Western blot analysis. Podocyte apoptosis was detected using the terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) assay, electron microscopy and flow cytometry. RESULTS Silencing VEGF-A or AP-1 upregulated bcl-2 and ameliorated podocyte apoptosis. Silencing VEGF-A decreased the level of c-fos and c-jun and bevacizumab and SP600125 treatment attenuated podocyte apoptosis. Luciferase reporter activity of VEGF-A-3'-UTR constructs was significantly provoked when stimulated with TGF-β1. In diabetic rat kidneys, VEGF-A co-localized with bcl-2 in podocytes. With bevacizumab and SP600125 treatment, the level of VEGF-A and AP-1 decreased while bcl-2 increased. Podocyte apoptotic rate was reduced with condensed podocyte nuclei less frequently observed. The urine albumin excretion rate (UAER) and albumin/creatinine were improved. CONCLUSION This study demonstrates VEGF-A inhibition ameliorates podocyte apoptosis by regulating AP-1 and bcl-2 signaling. AP-1 is a direct target of VEGF-A and a novel player in podocyte apoptosis.
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Affiliation(s)
- Xiaoyan Bai
- Division of Nephrology, Nanfang Hospital, Southern Medical University, National Clinical Medical Research Center for Kidney Disease, National Key Lab for Organ Failure Research, Guangdong Provincial Institute of Nephrology, Guangzhou, Guangdong, PR China
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35
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Localization and expression profile of Group I and II Activators of G-protein Signaling in the kidney. J Mol Histol 2014; 46:123-36. [PMID: 25533045 DOI: 10.1007/s10735-014-9605-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/15/2014] [Indexed: 10/24/2022]
Abstract
Activators of G-protein Signaling (AGS) are a family of accessory proteins that were discovered as modulators of heterotrimeric G-protein subunits. The primary aim of the present study was to localize Group I and II AGS proteins and determine the renal expression profile using immunohistochemistry and quantitative RT-PCR, respectively, during normal and injured states of the kidney. Group I AGS1 was found to be predominantly localized to the proximal tubule, Group II AGS3 and AGS5 were exclusively localized to the distal tubular segments, and Group II AGS6 was ubiquitously expressed in every nephron segment of the rodent kidney. In rat kidneys following ischemia-reperfusion injury (IRI), Group I AGS1 mRNA was dramatically increased after 24 h by fivefold (P < 0.05), whereas Group II AGS3 and AGS4 mRNA was significantly decreased at the same time point (P < 0.05). No significant change in the transcript levels were detected at other time points for any of the AGS genes between control and IRI groups. In polycystic diseased kidneys, mRNA levels for AGS3, AGS4 and AGS6 was significantly increased (P < 0.05) by 75-80 % in PCK rat kidneys. The identification of Group I and II AGS mRNA and protein in the kidney may provide insight into the potential mechanism of action during normal and varying states of renal disease or injury.
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36
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Schlondorff J. How many Achilles' heels does a podocyte have? An update on podocyte biology: Table 1. Nephrol Dial Transplant 2014; 30:1091-7. [DOI: 10.1093/ndt/gfu214] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 05/07/2014] [Indexed: 11/15/2022] Open
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