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Huang Y, Geng J, Wang M, Liu W, Hu H, Shi W, Li M, Huo G, Huang G, Xu A. A simple protocol to establish a conditionally immortalized mouse podocyte cell line. Sci Rep 2024; 14:11591. [PMID: 38773220 PMCID: PMC11109129 DOI: 10.1038/s41598-024-62547-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 05/17/2024] [Indexed: 05/23/2024] Open
Abstract
Podocytes are specialized terminally differentiated cells in the glomerulus that are the primary target cells in many glomerular diseases. However, the current podocyte cell lines suffer from prolonged in vitro differentiation and limited survival time, which impede research progress. Therefore, it is necessary to establish a cell line that exhibits superior performance and characteristics. We propose a simple protocol to obtain an immortalized mouse podocyte cell (MPC) line from suckling mouse kidneys. Primary podocytes were cultured in vitro and infected with the SV40 tsA58 gene to obtain immortalized MPCs. The podocytes were characterized using Western blotting and quantitative real-time PCR. Podocyte injury was examined using the Cell Counting Kit-8 assay and flow cytometry. First, we successfully isolated an MPC line and identified 39 °C as the optimal differentiation temperature. Compared to undifferentiated MPCs, the expression of WT1 and synaptopodin was upregulated in differentiated MPCs. Second, the MPCs ceased proliferating at a nonpermissive temperature after day 4, and podocyte-specific proteins were expressed normally after at least 15 passages. Finally, podocyte injury models were induced to simulate podocyte injury in vitro. In summary, we provide a simple and popularized protocol to establish a conditionally immortalized MPC, which is a powerful tool for the study of podocytes.
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Affiliation(s)
- Yujiao Huang
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Jie Geng
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Mengdan Wang
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Wenbin Liu
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Haikun Hu
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Wei Shi
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Mei Li
- Dongfang Hospital of Beijing University of Chinese Medicine, Beijing, 100078, China
| | - Guiyang Huo
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China
| | - Guangrui Huang
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China.
| | - Anlong Xu
- School of Life Sciences, Beijing University of Chinese Medicine, Beijing, 102488, China.
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Liu PJ, Sayeeda K, Zhuang C, Krendel M. Roles of myosin 1e and the actin cytoskeleton in kidney functions and familial kidney disease. Cytoskeleton (Hoboken) 2024. [PMID: 38708443 DOI: 10.1002/cm.21861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 03/21/2024] [Accepted: 04/04/2024] [Indexed: 05/07/2024]
Abstract
Mammalian kidneys are responsible for removing metabolic waste and maintaining fluid and electrolyte homeostasis via selective filtration. One of the proteins closely linked to selective renal filtration is myosin 1e (Myo1e), an actin-dependent molecular motor found in the specialized kidney epithelial cells involved in the assembly and maintenance of the renal filter. Point mutations in the gene encoding Myo1e, MYO1E, have been linked to familial kidney disease, and Myo1e knockout in mice leads to the disruption of selective filtration. In this review, we discuss the role of the actin cytoskeleton in renal filtration, the known and hypothesized functions of Myo1e, and the possible explanations for the impact of MYO1E mutations on renal function.
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Affiliation(s)
- Pei-Ju Liu
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Kazi Sayeeda
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Cindy Zhuang
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Mira Krendel
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
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Sun H, Weidner J, Allamargot C, Piper RC, Misurac J, Nester C. Dynein-Mediated Trafficking: A New Mechanism of Diabetic Podocytopathy. KIDNEY360 2023; 4:162-176. [PMID: 36821608 PMCID: PMC10103215 DOI: 10.34067/kid.0006852022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 11/21/2022] [Indexed: 12/12/2022]
Abstract
Key Points The expression of dynein is increased in human and rodent models of diabetic nephropathy (DN), eliciting a new dynein-driven pathogenesis. Uncontrolled dynein impairs the molecular sieve of kidney by remodeling the postendocytic triage and homeostasis of nephrin. The delineation of the dynein-driven pathogenesis promises a broad spectrum of new therapeutic targets for human DN. Background Diabetic nephropathy (DN) is characterized by increased endocytosis and degradation of nephrin, a protein that comprises the molecular sieve of the glomerular filtration barrier. While nephrin internalization has been found activated in diabetes-stressed podocytes, the postinternalization trafficking steps that lead to the eventual depletion of nephrin and the development of DN are unclear. Our work on an inherited podocytopathy uncovered that dysregulated dynein could compromise nephrin trafficking, leading us to test whether and how dynein mediates the pathogenesis of DN. Methods We analyzed the transcription of dynein components in public DN databases, using the Nephroseq platform. We verified altered dynein transcription in diabetic podocytopathy by quantitative PCR. Dynein-mediated trafficking and degradation of nephrin was investigated using an in vitro nephrin trafficking model and was demonstrated in a mouse model with streptozotocin (STZ)-induced DN and in human kidney biopsy sections. Results Our transcription analysis revealed increased expression of dynein in human DN and diabetic mouse kidney, correlated significantly with the severity of hyperglycemia and DN. In diabetic podocytopathy, we observed that dynein-mediated postendocytic sorting of nephrin was upregulated, resulting in accelerated nephrin degradation and disrupted nephrin recycling. In hyperglycemia-stressed podocytes, Dynll1 , one of the most upregulated dynein components, is required for the recruitment of dynein complex that mediates the postendocytic sorting of nephrin. This was corroborated by observing enhanced Dynll1-nephrin colocalization in podocytes of diabetic patients, as well as dynein-mediated trafficking and degradation of nephrin in STZ-induced diabetic mice with hyperglycemia. Knockdown of Dynll1 attenuated lysosomal degradation of nephrin and promoted its recycling, suggesting the essential role of Dynll1 in dynein-mediated mistrafficking. Conclusions Our studies show that hyperglycemia stimulates dynein-mediated trafficking of nephrin to lysosomes by inducing its expression. The decoding of dynein-driven pathogenesis of diabetic podocytopathy offers a spectrum of new dynein-related therapeutic targets for DN.
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Affiliation(s)
- Hua Sun
- Division of Nephrology, Stead Family Department of Pediatrics, The University of Iowa, Iowa City, Iowa
- Carver College of Medicine, The University of Iowa, Iowa City, Iowa
| | - Jillian Weidner
- Division of Nephrology, Stead Family Department of Pediatrics, The University of Iowa, Iowa City, Iowa
- Carver College of Medicine, The University of Iowa, Iowa City, Iowa
| | - Chantal Allamargot
- Central Microscopy Research Facility, The University of Iowa, Iowa City, Iowa
| | - Robert C. Piper
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, The University of Iowa, Iowa City, Iowa
| | - Jason Misurac
- Division of Nephrology, Stead Family Department of Pediatrics, The University of Iowa, Iowa City, Iowa
- Carver College of Medicine, The University of Iowa, Iowa City, Iowa
| | - Carla Nester
- Division of Nephrology, Stead Family Department of Pediatrics, The University of Iowa, Iowa City, Iowa
- Carver College of Medicine, The University of Iowa, Iowa City, Iowa
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Lang K, Milosavljevic J, Heinkele H, Chen M, Gerstner L, Spitz D, Kayser S, Helmstädter M, Walz G, Köttgen M, Spracklen A, Poulton J, Hermle T. Selective endocytosis controls slit diaphragm maintenance and dynamics in Drosophila nephrocytes. eLife 2022; 11:79037. [PMID: 35876643 PMCID: PMC9355562 DOI: 10.7554/elife.79037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 07/24/2022] [Indexed: 11/28/2022] Open
Abstract
The kidneys generate about 180 l of primary urine per day by filtration of plasma. An essential part of the filtration barrier is the slit diaphragm, a multiprotein complex containing nephrin as major component. Filter dysfunction typically manifests with proteinuria and mutations in endocytosis regulating genes were discovered as causes of proteinuria. However, it is unclear how endocytosis regulates the slit diaphragm and how the filtration barrier is maintained without either protein leakage or filter clogging. Here, we study nephrin dynamics in podocyte-like nephrocytes of Drosophila and show that selective endocytosis either by dynamin- or flotillin-mediated pathways regulates a stable yet highly dynamic architecture. Short-term manipulation of endocytic functions indicates that dynamin-mediated endocytosis of ectopic nephrin restricts slit diaphragm formation spatially while flotillin-mediated turnover of nephrin within the slit diaphragm is needed to maintain filter permeability by shedding of molecules bound to nephrin in endosomes. Since slit diaphragms cannot be studied in vitro and are poorly accessible in mouse models, this is the first analysis of their dynamics within the slit diaphragm multiprotein complex. Identification of the mechanisms of slit diaphragm maintenance will help to develop novel therapies for proteinuric renal diseases that are frequently limited to symptomatic treatment.
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Affiliation(s)
- Konrad Lang
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Helena Heinkele
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Mengmeng Chen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Lea Gerstner
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Dominik Spitz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Severine Kayser
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Gerd Walz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Köttgen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrew Spracklen
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - John Poulton
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Tobias Hermle
- Department of Medicine, University of Freiburg, Freiburg, Germany
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Wu N, Zhu Y, Jiang W, Song Y, Yin L, Lu Y, Tao D, Liu Y, Ma Y. A novel NPHS2 mutation (c.865A > G) identified in a Chinese family with steroid-resistant nephrotic syndrome alters subcellular localization of nephrin. Genes Genomics 2022; 44:551-559. [PMID: 35099763 DOI: 10.1007/s13258-022-01220-5] [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: 11/01/2021] [Accepted: 01/16/2022] [Indexed: 11/04/2022]
Abstract
BACKGROUND NPHS2 is the causative gene of nephrotic syndrome type 2 (MIM 600995) which often clinically manifests as steroid-resistant nephrotic syndrome (SRNS). The NPHS2 gene encodes a slit diaphragm (SD) associated protein podocin. OBJECTIVE This study reported a novel disease-causing mutation of NPHS2 in a Chinese family with SRNS. We also investigated the pathogenic mechanism of the variants in this family. METHOD A Chinese family with SRNS was recruited. Whole exome sequencing was performed to screen for disease-causing mutation. Sanger sequencing was used to confirm the results. In vitro functional experiments including immunoblotting, co-immunoprecipitation and double immunofluorescence staining were performed to explore the pathogenic mechanisms of mutations. RESULTS In this family, compound heterozygous mutations of NPHS2 (c.467dupT and c.865A > G) were identified and segregated with the disease. The maternal c.865A > G was a novel variant, leading to amino acid substitution (p.K289E). In vitro functional assays indicated that c.467dupT (p.L156FfsX11) mutant lost interaction with nephrin. Both K289E and L156FfsX11 mutants showed sharply diminished plasma membrane localization. Furthermore, abnormal distribution of podocin mutants also altered the cell membrane localization of nephrin. CONCLUSION We reported a family with SRNS caused by compound heterozygous mutations of NPHS2 (c.467dupT and c.865A > G). c.865A > G (p.K289E) in NPHS2 was a novel causative variant associated with SRNS. Both variants in this family not only affected the normal cell membrane localization of podocin, but also altered the cell membrane localization of nephrin which is the major architectural protein of SD.
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Affiliation(s)
- Na Wu
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Yingchuan Zhu
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Wenhao Jiang
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Yue Song
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Lan Yin
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Yilu Lu
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Dachang Tao
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Yunqiang Liu
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China
| | - Yongxin Ma
- Department of Medical Genetics, West China Hospital, Sichuan University, 1st Keyuan 4 Lu, High-Tech Zone, Chengdu, 610041, Sichuan, China.
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An Z, Wang H, Mokadem M. Role of the Autonomic Nervous System in Mechanism of Energy and Glucose Regulation Post Bariatric Surgery. Front Neurosci 2021; 15:770690. [PMID: 34887725 PMCID: PMC8649921 DOI: 10.3389/fnins.2021.770690] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Accepted: 10/15/2021] [Indexed: 01/06/2023] Open
Abstract
Even though lifestyle changes are the mainstay approach to address obesity, Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) are the most effective and durable treatments facing this pandemic and its associated metabolic conditions. The traditional classifications of bariatric surgeries labeled them as “restrictive,” “malabsorptive,” or “mixed” types of procedures depending on the anatomical rearrangement of each one of them. This conventional categorization of bariatric surgeries assumed that the “restrictive” procedures induce their weight loss and metabolic effects by reducing gastric content and therefore having a smaller reservoir. Similarly, the “malabsorptive” procedures were thought to induce their main energy homeostatic effects from fecal calorie loss due to intestinal malabsorption. Observational data from human subjects and several studies from rodent models of bariatric surgery showed that neither of those concepts is completely true, at least in explaining the multiple metabolic changes and the alteration in energy balance that those two surgeries induce. Rather, neuro-hormonal mechanisms have been postulated to underly the physiologic effects of those two most performed bariatric procedures. In this review, we go over the role the autonomic nervous system plays- through its parasympathetic and sympathetic branches- in regulating weight balance and glucose homeostasis after SG and RYGB.
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Affiliation(s)
- Zhibo An
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Carver College of Medicine, The University of Iowa, Iowa City, IA, United States
| | - Haiying Wang
- Department of Physiology, Basic Medical School of Jining Medical University, Jining, China
| | - Mohamad Mokadem
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Carver College of Medicine, The University of Iowa, Iowa City, IA, United States.,Fraternal Order of Eagles Diabetes Research Center, The University of Iowa, Iowa City, IA, United States.,Obesity Research and Education Initiative, The University of Iowa, Iowa City, IA, United States.,Iowa City Veterans Affairs Health Care System, Iowa City, IA, United States
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7
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Morphology expands understanding of lesions. Kidney Int 2021; 97:627-630. [PMID: 32200853 DOI: 10.1016/j.kint.2020.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 01/17/2020] [Indexed: 11/20/2022]
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Affiliation(s)
- Thomas Benzing
- From Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine, and University Hospital Cologne, and the Excellence Cluster CECAD, University of Cologne, Cologne, Germany (T.B.); and the Section of Nephrology, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston (D.S.)
| | - David Salant
- From Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine, and University Hospital Cologne, and the Excellence Cluster CECAD, University of Cologne, Cologne, Germany (T.B.); and the Section of Nephrology, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston (D.S.)
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Sun H, Perez-Gill C, Schlöndorff JS, Subramanian B, Pollak MR. Dysregulated Dynein-Mediated Trafficking of Nephrin Causes INF2-related Podocytopathy. J Am Soc Nephrol 2021; 32:307-322. [PMID: 33443052 PMCID: PMC8054882 DOI: 10.1681/asn.2020081109] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 10/20/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND FSGS caused by mutations in INF2 is characterized by a podocytopathy with mistrafficked nephrin, an essential component of the slit diaphragm. Because INF2 is a formin-type actin nucleator, research has focused on its actin-regulating function, providing an important but incomplete insight into how these mutations lead to podocytopathy. A yeast two-hybridization screen identified the interaction between INF2 and the dynein transport complex, suggesting a newly recognized role of INF2 in regulating dynein-mediated vesicular trafficking in podocytes. METHODS Live cell and quantitative imaging, fluorescent and surface biotinylation-based trafficking assays in cultured podocytes, and a new puromycin aminoglycoside nephropathy model of INF2 transgenic mice were used to demonstrate altered dynein-mediated trafficking of nephrin in INF2 associated podocytopathy. RESULTS Pathogenic INF2 mutations disrupt an interaction of INF2 with dynein light chain 1, a key dynein component. The best-studied mutation, R218Q, diverts dynein-mediated postendocytic sorting of nephrin from recycling endosomes to lysosomes for degradation. Antagonizing dynein-mediated transport can rescue this effect. Augmented dynein-mediated trafficking and degradation of nephrin underlies puromycin aminoglycoside-induced podocytopathy and FSGS in vivo. CONCLUSIONS INF2 mutations enhance dynein-mediated trafficking of nephrin to proteolytic pathways, diminishing its recycling required for maintaining slit diaphragm integrity. The recognition that dysregulated dynein-mediated transport of nephrin in R218Q knockin podocytes opens an avenue for developing targeted therapy for INF2-mediated FSGS.
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Affiliation(s)
- Hua Sun
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts,Renal Division, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts,Stead Family Department of Pediatrics, University of Iowa, Iowa City, Iowa
| | - Chandra Perez-Gill
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Johannes S Schlöndorff
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Balajikarthick Subramanian
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Martin R. Pollak
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
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Mechanism of Albuminuria Reduction by Chymase Inhibition in Diabetic Mice. Int J Mol Sci 2020; 21:ijms21207495. [PMID: 33050674 PMCID: PMC7589797 DOI: 10.3390/ijms21207495] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 10/09/2020] [Accepted: 10/10/2020] [Indexed: 12/29/2022] Open
Abstract
Chymase has several functions, such as angiotensin II formation, which can promote diabetic kidney disease (DKD). In this study, we evaluated the effect of the chymase inhibitor TY-51469 on DKD in diabetic db/db mice. Diabetic mice were administered TY-51469 (10 mg/kg/day) or placebo for 4 weeks. No significant difference was observed in body weight and fasting blood glucose between TY-51469- and placebo-treated groups. However, a significant reduction in urinary albumin/creatinine ratio was observed in the TY-51469-treated group compared with the placebo-treated group. In the renal extract, chymase activity was significantly higher in placebo-treated mice than in non-diabetic db/m mice, but it was reduced by treatment with TY-51469. Both NADPH oxidase 4 expression and the oxidative stress marker malondialdehyde were significantly augmented in the placebo-treated group, but they were attenuated in the TY-51469-treated group. Significant increases of tumor necrosis factor-α and transforming growth factor-β mRNA levels in the placebo-treated group were significantly reduced by treatment with TY-51469. Furthermore, the expression of nephrin, which is a podocyte-specific protein, was significantly reduced in the placebo-treated group, but it was restored in the TY-51469-treated group. These findings demonstrated that chymase inhibition reduced albuminuria via attenuation of podocyte injury by oxidative stress.
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Abstract
The glomerular basement membrane (GBM) is a key component of the glomerular capillary wall and is essential for kidney filtration. The major components of the GBM include laminins, type IV collagen, nidogens and heparan sulfate proteoglycans. In addition, the GBM harbours a number of other structural and regulatory components and provides a reservoir for growth factors. New technologies have improved our ability to study the composition and assembly of basement membranes. We now know that the GBM is a complex macromolecular structure that undergoes key transitions during glomerular development. Defects in GBM components are associated with a range of hereditary human diseases such as Alport syndrome, which is caused by defects in the genes COL4A3, COL4A4 and COL4A5, and Pierson syndrome, which is caused by variants in LAMB2. In addition, the GBM is affected by acquired autoimmune disorders and metabolic diseases such as diabetes mellitus. Current treatments for diseases associated with GBM involvement aim to reduce intraglomerular pressure and to treat the underlying cause where possible. As our understanding about the maintenance and turnover of the GBM improves, therapies to replace GBM components or to stimulate GBM repair could translate into new therapies for patients with GBM-associated disease.
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Uchio-Yamada K, Yasuda K, Monobe Y, Akagi KI, Suzuki O, Manabe N. Tensin2 is important for podocyte-glomerular basement membrane interaction and integrity of the glomerular filtration barrier. Am J Physiol Renal Physiol 2020; 318:F1520-F1530. [PMID: 32390516 DOI: 10.1152/ajprenal.00055.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Tensin2 (Tns2), an integrin-linked protein, is enriched in podocytes within the glomerulus. Previous studies have revealed that Tns2-deficient mice exhibit defects of the glomerular basement membrane (GBM) soon after birth in a strain-dependent manner. However, the mechanisms for the onset of defects caused by Tns2 deficiency remains unidentified. Here, we aimed to determine the role of Tns2 using newborn Tns2-deficient mice and murine primary podocytes. Ultrastructural analysis revealed that developing glomeruli during postnatal nephrogenesis exhibited abnormal GBM processing due to ectopic laminin-α2 accumulation followed by GBM thickening. In addition, analysis of primary podocytes revealed that Tns2 deficiency led to impaired podocyte-GBM interaction and massive expression of laminin-α2 in podocytes. Our study suggests that weakened podocyte-GBM interaction due to Tns2 deficiency causes increased mechanical stress on podocytes by continuous daily filtration after birth, resulting in stressed podocytes ectopically producing laminin-α2, which interrupts GBM processing. We conclude that Tns2 plays important roles in the podocyte-GBM interaction and maintenance of the glomerular filtration barrier.
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Affiliation(s)
- Kozue Uchio-Yamada
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka, Japan
| | - Keiko Yasuda
- Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Yoko Monobe
- Section of Laboratory Equipment, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka, Japan
| | - Ken-Ichi Akagi
- Section of Laboratory Equipment, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka, Japan
| | - Osamu Suzuki
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka, Japan
| | - Noboru Manabe
- Department of Human Sciences, Osaka International University, Moriguchi, Osaka, Japan
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Zhuo L, Huang L, Yang Z, Li G, Wang L. A comprehensive analysis of NPHS1 gene mutations in patients with sporadic focal segmental glomerulosclerosis. BMC MEDICAL GENETICS 2019; 20:111. [PMID: 31216994 PMCID: PMC6585123 DOI: 10.1186/s12881-019-0845-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Accepted: 06/06/2019] [Indexed: 01/01/2023]
Abstract
BACKGROUND Focal segmental glomerulosclerosis (FSGS) is still one of the common causes of refractory nephrotic syndrome. Nephrin, encoded by podocyte-specific NPHS1 gene, participated in the pathogenesis of FSGS. The sites of NPHS1 mutations in FSGS is not clarified very well. In this study, we investigated the specific mutations of NPHS1 gene in Chinese patients with sporadic FSGS. METHODS A total of 309 patients with sporadic FSGS were collected and screened for NPHS1 mutations by second-generation sequencing. The variants were compared with those extracted from 2504 healthy controls in the 1000 Genomes Project. The possible pathogenic roles of missense variants were predicted by three different software. We also compared these candidate causal mutations with those summarized from the previous studies. RESULTS Thirty-two genetic mutations of NPHS1 gene were identified in FSGS patients, including 12 synonymous mutations, 17 missense mutations, 1 splicing mutation, and 2 intron mutations, of which c.G3315A (p.S1105S) was the most common variant (261/309). A novel missense mutation c.G2638 T (p.V880F) and a novel splicing mutation 35830957 C > T were identified in FSGS patients. The frequencies of the four synonymous mutations (c.C294T [p.I98I], c.C2223T [p.T741 T], c.C2289T [p.V763 V], c.G3315A [p.S1105S]) were much higher in FSGS patients than in controls. The frequencies of the four missense mutations (c.G349A [p.E117K], c.G1339A [p.E447K], c.G1802C [p.G601A], c.C2398T [p.R800C]) were much higher and one (c.A3230G [p.N1077S]) was lower in FSGS patients than in controls. Five missense mutations, c.C616A (p.P206T), c.G1802C (p.G601A), c.C2309T (p.P770L), c.G2869C (p.V957 L), and c.C3274T (p.R1092C), were predicted to be pathogenic mutations by software analysis. CONCLUSIONS NPHS1 gene mutations were quite common in sporadic FSGS patients. We strongly recommend mutation analysis of the NPHS1 gene in the clinical management of FSGS patients.
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Affiliation(s)
- Ling Zhuo
- Renal Department and Institute of Nephrology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, No. 32, West 2nd Duan, 1st Circle Road, Qingyang District, Chengdu, Sichuan, 610072, People's Republic of China
| | - Lulin Huang
- Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, 610072, China
| | - Zhenglin Yang
- Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, 610072, China
| | - Guisen Li
- Renal Department and Institute of Nephrology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, No. 32, West 2nd Duan, 1st Circle Road, Qingyang District, Chengdu, Sichuan, 610072, People's Republic of China.
| | - Li Wang
- Renal Department and Institute of Nephrology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, No. 32, West 2nd Duan, 1st Circle Road, Qingyang District, Chengdu, Sichuan, 610072, People's Republic of China
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Ueda Y, Miwa T, Gullipalli D, Sato S, Ito D, Kim H, Palmer M, Song WC. Blocking Properdin Prevents Complement-Mediated Hemolytic Uremic Syndrome and Systemic Thrombophilia. J Am Soc Nephrol 2018; 29:1928-1937. [PMID: 29858280 DOI: 10.1681/asn.2017121244] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Accepted: 05/11/2018] [Indexed: 12/30/2022] Open
Abstract
Background Properdin (P) is a positive regulator of the alternative pathway of complement activation. Although P inhibition is expected and has been shown to ameliorate the alternative pathway of complement-mediated tissue injury in several disease models, it unexpectedly exacerbated renal injury in a murine model of C3 glomerulopathy. The role of P in atypical hemolytic uremic syndrome (aHUS) is uncertain.Methods We blocked P function by genetic deletion or mAb-mediated inhibition in mice carrying a factor H (FH) point mutation, W1206R (FHR/R), that causes aHUS and systemic thrombophilia with high mortality.Results P deficiency completely rescued FHR/R mice from premature death and prevented thrombocytopenia, hemolytic anemia, and renal disease. It also eliminated macrovessel thrombi that were prevalent in FHR/R mice. All mice that received a function-blocking anti-P mAb for 8 weeks survived the experimental period and appeared grossly healthy. Platelet counts and hemoglobin levels were significantly improved in FHR/R mice after 4 weeks of anti-P mAb treatment. One half of the FHR/R mice treated with an isotype control mAb but none of the anti-P mAb-treated mice developed stroke-related neurologic disease. Anti-P mAb-treated FHR/R mice showed largely normal renal histology, and residual liver thrombi were detected in only three of 15 treated mice.Conclusions These results contrast with the detrimental effect of P inhibition observed in a murine model of C3 glomerulopathy and suggest that P contributes critically to aHUS pathogenesis. Inhibition of P in aHUS may be of therapeutic benefit.
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Affiliation(s)
- Yoshiyasu Ueda
- Departments of Systems Pharmacology and Translational Therapeutics and
| | - Takashi Miwa
- Departments of Systems Pharmacology and Translational Therapeutics and
| | | | - Sayaka Sato
- Departments of Systems Pharmacology and Translational Therapeutics and
| | - Daisuke Ito
- Departments of Systems Pharmacology and Translational Therapeutics and
| | - Hangsoo Kim
- Departments of Systems Pharmacology and Translational Therapeutics and
| | - Matthew Palmer
- Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Wen-Chao Song
- Departments of Systems Pharmacology and Translational Therapeutics and
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The long journey through renal filtration: new pieces in the puzzle of slit diaphragm architecture. Curr Opin Nephrol Hypertens 2018; 26:148-153. [PMID: 28212178 DOI: 10.1097/mnh.0000000000000322] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
PURPOSE OF REVIEW The podocyte slit diaphragm is probably the least understood component of the kidney filtration barrier. In this review, we aim to integrate the most recent findings on the molecular make-up and structural architecture of this specialized cell-cell junction into a current concept of glomerular filtration. RECENT FINDINGS Analysis of cryopreserved mammalian tissue revealed a bipartite composition of the slit diaphragm. Single NEPH1 molecules span the lower part of the slit close to the glomerular basement membrane whereas NEPHRIN molecules are positioned in the apical part toward Bowman's space. This molecular arrangement could lead to heterogeneous ellipsoidal and circular pores, which are mainly located in the central region of the slit diaphragm. SUMMARY Despite having been first identified in the 1970s, the slit diaphragm's structural architecture has not been fully elucidated to date and remains an area of intense research and scientific debate. The slit diaphragm has been initially described as a rigid 'zipper-like' structure in which periodic, rod-like units extend from a podocyte foot processes to a linear central bar, giving rise to homogeneous 4 × 14 nm pores. Several recent findings have challenged these long-held beliefs and instead pointed to an unanticipated complexity of slit diaphragm structure. High-resolution ultrastructural analysis found evidence that the slit diaphragm is a dynamic and adjustable cell-cell junction that forms a nonclogging barrier within the renal filtration system.
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16
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Muraleedharan S, Sam A, Skaer H, Inamdar MS. Networks that link cytoskeletal regulators and diaphragm proteins underpin filtration function in Drosophila nephrocytes. Exp Cell Res 2018; 364:234-242. [PMID: 29458174 PMCID: PMC5883325 DOI: 10.1016/j.yexcr.2018.02.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 02/06/2018] [Accepted: 02/15/2018] [Indexed: 11/25/2022]
Abstract
Insect nephrocytes provide a valuable model for kidney disease, as they are structurally and functionally homologous to mammalian kidney podocytes. They possess an exceptional macromolecular assembly, the nephrocyte diaphragm (ND), which serves as a filtration barrier and helps maintain tissue homeostasis by filtering out wastes and toxic products. However, the elements that maintain nephrocyte architecture and the ND are not understood. We show that Drosophila nephrocytes have a unique cytoplasmic cluster of F-actin, which is maintained by the microtubule cytoskeleton and Rho-GTPases. A balance of Rac1 and Cdc42 activity as well as proper microtubule organization and endoplasmic reticulum structure, are required to position the actin cluster. Further, ND proteins Sns and Duf also localize to this cluster and regulate organization of the actin and microtubule cytoskeleton. Perturbation of any of these inter-dependent components impairs nephrocyte ultrafiltration. Thus cytoskeletal components, Rho-GTPases and ND proteins work in concert to maintain the specialized nephrocyte architecture and function. Drosophila nephrocytes have a unique cytoplasmic cluster of F-actin. Microtubules, Rho-GTPases and endoplasmic reticulum position the actin cluster. Nephrocyte diaphragm proteins localize to and regulate actin cluster organization. Perturbation of any of these inter-dependent components impairs ultrafiltration.
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Affiliation(s)
- Simi Muraleedharan
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Aksah Sam
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Helen Skaer
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Maneesha S Inamdar
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India; Institute for Stem Cell Biology and Regenerative Medicine, GKVK, Bellary Road, Bangalore 560065, India.
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Hayashi D, Ueda S, Yamanoue M, Ashida H, Shirai Y. Amelioration of diabetic nephropathy by oral administration of d-α-tocopherol and its mechanisms. Biosci Biotechnol Biochem 2018; 82:65-73. [DOI: 10.1080/09168451.2017.1411184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Abstract
Diabetic nephropathy (DN) is a diabetic vascular complication, and abnormal protein kinase C (PKC) activation from increased diacylglycerol (DG) production in diabetic hyperglycemia is one of the causes of DN. Diacylglycerol kinase (DGK) converts DG into phosphatidic acid. In other words, DGK can attenuate PKC activity by reducing the amount of DG. Recently, we reported that intraperitoneally administered d-α-tocopherol (vitamin E, αToc) induces an amelioration of DN in vivo through the activation of DGKα and the prevention of podocyte loss. However, the effect of the oral administration of αToc on DN in mice remains unknown. Here, we evaluated the effect of oral administration of αToc on DN and its molecular mechanism using streptozocin-induced diabetic mice. Consequently, the oral administration of αToc significantly ameliorated the symptoms of DN by preventing the loss of podocytes, and it was revealed that the inhibition of PKC activity was involved in this amelioration.
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Affiliation(s)
- Daiki Hayashi
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Shuji Ueda
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Minoru Yamanoue
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Hitoshi Ashida
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
| | - Yasuhito Shirai
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan
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18
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Martin CE, Jones N. Nephrin Signaling in the Podocyte: An Updated View of Signal Regulation at the Slit Diaphragm and Beyond. Front Endocrinol (Lausanne) 2018; 9:302. [PMID: 29922234 PMCID: PMC5996060 DOI: 10.3389/fendo.2018.00302] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 05/22/2018] [Indexed: 12/11/2022] Open
Abstract
Podocytes are a major component of the glomerular blood filtration barrier, and alterations to the morphology of their unique actin-based foot processes (FP) are a common feature of kidney disease. Adjacent FP are connected by a specialized intercellular junction known as the slit diaphragm (SD), which serves as the ultimate barrier to regulate passage of macromolecules from the blood. While the link between SD dysfunction and reduced filtration selectivity has been recognized for nearly 50 years, our understanding of the underlying molecular circuitry began only 20 years ago, sparked by the identification of NPHS1, encoding the transmembrane protein nephrin. Nephrin not only functions as the core component of the extracellular SD filtration network but also as a signaling scaffold via interactions at its short intracellular region. Phospho-regulation of several conserved tyrosine residues in this region influences signal transduction pathways which control podocyte cell adhesion, shape, and survival, and emerging studies highlight roles for nephrin phospho-dynamics in mechanotransduction and endocytosis. The following review aims to summarize the last 5 years of advancement in our knowledge of how signaling centered at nephrin directs SD barrier formation and function. We further provide insight on promising frontiers in podocyte biology, which have implications for SD signaling in the healthy and diseased kidney.
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Lay AC, Coward RJM. The Evolving Importance of Insulin Signaling in Podocyte Health and Disease. Front Endocrinol (Lausanne) 2018; 9:693. [PMID: 30524379 PMCID: PMC6258712 DOI: 10.3389/fendo.2018.00693] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/05/2018] [Indexed: 12/17/2022] Open
Abstract
Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease worldwide, occuring in approximately one-third of diabetic patients. One of the earliest hallmarks of DKD is albuminuria, often occurring following disruptions to the glomerular filtration barrier. Podocytes are highly specialized cells with a central role in filtration barrier maintenance; hence, podocyte dysfunction is a major cause of albuminuria in many settings, including DKD. Numerous studies over the last decade have highlighted the importance of intact podocyte insulin responses in the maintenance of podocyte function. This review summarizes our current perspectives on podocyte insulin signaling, highlighting evidence to support the notion that dysregulated podocyte insulin responses contribute toward podocyte damage, particularly during the pathogenesis of DKD.
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Lee J, Koh A, Jeong H, Kim E, Ha TS, Saleem MA, Ryu SH. C1-Ten is a PTPase of nephrin, regulating podocyte hypertrophy through mTORC1 activation. Sci Rep 2017; 7:12346. [PMID: 28955049 PMCID: PMC5617844 DOI: 10.1038/s41598-017-12382-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 09/07/2017] [Indexed: 02/06/2023] Open
Abstract
Hypertrophy is a prominent feature of damaged podocytes in diabetic kidney disease (DKD). mTORC1 hyperactivation leads to podocyte hypertrophy, but the detailed mechanism of how mTORC1 activation occurs under pathological conditions is not completely known. Moreover, reduced nephrin tyrosine phosphorylation has been observed in podocytes under pathological conditions, but the molecular mechanism linking nephrin phosphorylation and pathology is unclear so far. In this study, we observed a significant increase in C1-Ten level in diabetic kidney and in high glucose-induced damaged podocytes. C1-Ten acts as a protein tyrosine phosphatase (PTPase) at the nephrin-PI3K binding site and renders PI3K for IRS-1, thereby activating mTORC1. Furthermore, C1-Ten causes podocyte hypertrophy and proteinuria by increasing mTORC1 activity in vitro and in vivo. These findings demonstrate the relationship between nephrin dephosphorylation and the mTORC1 pathway, mediated by C1-Ten PTPase activity. We suggest that C1-Ten contributes to the pathogenesis of DKD by inducing podocyte hypertrophy under high glucose conditions.
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Affiliation(s)
- Jiyoun Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Ara Koh
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Heeyoon Jeong
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Eui Kim
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Tae-Sun Ha
- Department of Pediatrics, College of Medicine, Chungbuk National University, Cheongju, 28644, Republic of Korea
| | - Moin A Saleem
- Academic and Children's Renal Unit, University of Bristol, Learning and Research, Southmead Hospital, Bristol, BS10 5NB, UK
| | - Sung Ho Ryu
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea.
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22
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Ito Y, Katayama K, Nishibori Y, Akimoto Y, Kudo A, Kurayama R, Hada I, Takahashi S, Kimura T, Fukutomi T, Katada T, Suehiro J, Beltcheva O, Tryggvason K, Yan K. Wolf-Hirschhorn syndrome candidate 1-like 1 epigenetically regulates nephrin gene expression. Am J Physiol Renal Physiol 2017; 312:F1184-F1199. [PMID: 28228401 DOI: 10.1152/ajprenal.00305.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 02/09/2017] [Accepted: 02/21/2017] [Indexed: 01/13/2023] Open
Abstract
Altered expression of nephrin underlies the pathophysiology of proteinuria in both congenital and acquired nephrotic syndrome. However, the epigenetic mechanisms of nephrin gene regulation remain elusive. Here, we show that Wolf-Hirschhorn syndrome candidate 1-like 1 long form (WHSC1L1-L) is a novel epigenetic modifier of nephrin gene regulation. WHSC1L1-L was associated with histone H3K4 and H3K36 in human embryonic kidney cells. WHSC1L1-L gene was expressed in the podocytes, and functional protein product was detected in these cells. WHSC1L1-L was found to bind nephrin but not other podocyte-specific gene promoters, leading to its inhibition/suppression, abrogating the stimulatory effect of WT1 and NF-κB. Gene knockdown of WHSC1L1-L in primary cultured podocytes accelerated the transcription of nephrin but not CD2AP. An in vivo zebrafish study involving the injection of Whsc1l1 mRNA into embryos demonstrated an apparent reduction of nephrin mRNA but not podocin and CD2AP mRNA. Immunohistochemistry showed that both WHSC1L1-L and nephrin emerged at the S-shaped body stage in glomeruli. Immunofluorescence and confocal microscopy displayed WHSC1L1 to colocalize with trimethylated H3K4 in the glomerular podocytes. Chromatin immunoprecipitation assay revealed the reduction of the association of trimethylated H3K4 at the nephrin promoter regions. Finally, nephrin mRNA was upregulated in the glomerulus at the early proteinuric stage of mouse nephrosis, which was associated with the reduction of WHSC1L1. In conclusion, our results demonstrate that WHSC1L1-L acts as a histone methyltransferase in podocytes and regulates nephrin gene expression, which may in turn contribute to the integrity of the slit diaphragm of the glomerular filtration barrier.
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Affiliation(s)
- Yugo Ito
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Kan Katayama
- Department of Medical Biochemistry and Biophysics, Division of Matrix Biology, Karolinska Institute, Stockholm, Sweden
| | - Yukino Nishibori
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Yoshihiro Akimoto
- Department of Anatomy, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Akihiko Kudo
- Department of Anatomy, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Ryota Kurayama
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Ichiro Hada
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Shohei Takahashi
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Toru Kimura
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan; and
| | - Toshiyuki Fukutomi
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan; and
| | - Tomohisa Katada
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan; and
| | - Junichi Suehiro
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan; and
| | - Olga Beltcheva
- Molecular Medicine Center and Department of Medical Chemistry and Biochemistry, Medical University of Sofia, Sofia, Bulgaria
| | - Karl Tryggvason
- Department of Medical Biochemistry and Biophysics, Division of Matrix Biology, Karolinska Institute, Stockholm, Sweden
| | - Kunimasa Yan
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan;
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Diacylglycerol Kinase alpha is Involved in the Vitamin E-Induced Amelioration of Diabetic Nephropathy in Mice. Sci Rep 2017; 7:2597. [PMID: 28572624 PMCID: PMC5453949 DOI: 10.1038/s41598-017-02354-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 04/10/2017] [Indexed: 02/05/2023] Open
Abstract
Diabetic nephropathy (DN) is one of vascular complications of diabetes and is caused by abnormal protein kinase C activation as a result of increased diacylglycerol (DG) production in diabetic hyperglycaemia. Diacylglycerol kinase (DGK) converts DG into phosphatidic acid. Therefore, it is expected that the activation of DGK would ameliorate DN. Indeed, it has been reported that vitamin E (VtE) ameliorates DN in rat by activating DGK, and we recently reported that VtE specifically activates DGKα isoform in vitro. However, whether DGKα is involved in the VtE-induced amelioration of DN in vivo remains unknown. Therefore, we investigated the VtE-induced amelioration of DN in wild-type (DGKα+/+) and DGKα–deficient (DGKα−/−) mice in which diabetes was induced by streptozocin. Several symptoms of DN were ameliorated by VtE treatment in the DGKα+/+ mice but not in the DGKα−/− mice. Moreover, transmission electron microscopy of glomeruli and immunofluorescent staining of glomerular epithelial cells (podocytes) indicated that VtE ameliorates podocyte pathology and prevents podocyte loss in the DGKα+/+ mice but not in the DGKα−/− mice. We showed that VtE can ameliorate DN in mice and that DGKα is involved in the VtE-induced amelioration of DN in vivo, suggesting that DGKα is an attractive therapeutic target for DN.
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A functional variant in NEPH3 gene confers high risk of renal failure in primary hematuric glomerulopathies. Evidence for predisposition to microalbuminuria in the general population. PLoS One 2017; 12:e0174274. [PMID: 28334007 PMCID: PMC5363870 DOI: 10.1371/journal.pone.0174274] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 03/06/2017] [Indexed: 01/06/2023] Open
Abstract
Background Recent data emphasize that thin basement membrane nephropathy (TBMN) should not be viewed as a form of benign familial hematuria since chronic renal failure (CRF) and even end-stage renal disease (ESRD), is a possible development for a subset of patients on long-term follow-up, through the onset of focal and segmental glomerulosclerosis (FSGS). We hypothesize that genetic modifiers may explain this variability of symptoms. Methods We looked in silico for potentially deleterious functional SNPs, using very strict criteria, in all the genes significantly expressed in the slit diaphragm (SD). Two variants were genotyped in a cohort of well-studied adult TBMN patients from 19 Greek-Cypriot families, with a homogeneous genetic background. Patients were categorized as “Severe” or “Mild”, based on the presence or not of proteinuria, CRF and ESRD. A larger pooled cohort (HEMATURIA) of 524 patients, including IgA nephropathy patients, was used for verification. Additionally, three large general population cohorts [Framingham Heart Study (FHS), KORAF4 and SAPHIR] were used to investigate if the NEPH3-V353M variant has any renal effect in the general population. Results and conclusions Genotyping for two high-scored variants in 103 TBMN adult patients with founder mutations who were classified as mildly or severely affected, pointed to an association with variant NEPH3-V353M (filtrin). This promising result prompted testing in the larger pooled cohort (HEMATURIA), indicating an association of the 353M variant with disease severity under the dominant model (p = 3.0x10-3, OR = 6.64 adjusting for gender/age; allelic association: p = 4.2x10-3 adjusting for patients’ kinships). Subsequently, genotyping 6,531 subjects of the Framingham Heart Study (FHS) revealed an association of the homozygous 353M/M genotype with microalbuminuria (p = 1.0x10-3). Two further general population cohorts, KORAF4 and SAPHIR confirmed the association, and a meta-analysis of all three cohorts (11,258 individuals) was highly significant (p = 1.3x10-5, OR = 7.46). Functional studies showed that Neph3 homodimerization and Neph3-Nephrin heterodimerization are disturbed by variant 353M. Additionally, 353M was associated with differential activation of the unfolded protein response pathway, when overexpressed in stressed cultured undifferentiated podocyte cells, thus attesting to its functional significance. Genetics and functional studies support a “rare variant-strong effect” role for NEPH3-V353M, by exerting a negative modifier effect on primary glomerular hematuria. Additionally, genetics studies provide evidence for a role in predisposing homozygous subjects of the general population to micro-albuminuria.
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25
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Velez JCQ, Arif E, Rodgers J, Hicks MP, Arthur JM, Nihalani D, Bruner ET, Budisavljevic MN, Atkinson C, Fitzgibbon WR, Janech MG. Deficiency of the Angiotensinase Aminopeptidase A Increases Susceptibility to Glomerular Injury. J Am Soc Nephrol 2017; 28:2119-2132. [PMID: 28202497 DOI: 10.1681/asn.2016111166] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 01/04/2017] [Indexed: 01/13/2023] Open
Abstract
Aminopeptidase A (APA) is expressed in glomerular podocytes and tubular epithelia and metabolizes angiotensin II (AngII), a peptide known to promote glomerulosclerosis. In this study, we tested whether APA expression changes in response to progressive nephron loss or whether APA exerts a protective role against glomerular damage and during AngII-mediated hypertensive kidney injury. At advanced stages of FSGS, fawn-hooded hypertensive rat kidneys exhibited distinctly increased APA staining in areas of intact glomerular capillary loops. Moreover, BALB/c APA-knockout (KO) mice injected with a nephrotoxic serum showed persistent glomerular hyalinosis and albuminuria 96 hours after injection, whereas wild-type controls achieved virtually full recovery. We then tested the effect of 4-week infusion of AngII (400 ng/kg per minute) in APA-KO and wild-type mice. Although we observed no significant difference in achieved systolic BP, AngII-treated APA-KO mice developed a significant rise in albuminuria not observed in AngII-treated wild-type mice along with increased segmental and global sclerosis and/or collapse of juxtamedullary glomeruli, microcystic tubular dilation, and tubulointerstitial fibrosis. In parallel, AngII treatment significantly increased the kidney AngII content and attenuated the expression of podocyte nephrin in APA-KO mice but not in wild-type controls. These data show that deficiency of APA increases susceptibility to glomerular injury in BALB/c mice. The augmented AngII-mediated kidney injury observed in association with increased intrarenal AngII accumulation in the absence of APA suggests a protective metabolizing role of APA in AngII-mediated glomerular diseases.
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Affiliation(s)
- Juan Carlos Q Velez
- Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana;
| | | | | | - Megan P Hicks
- Institute of Public and Preventative Health, Augusta University, Augusta, Georgia; and
| | - John M Arthur
- Division of Nephrology, Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | | | | | | | - Carl Atkinson
- Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina
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Kato T, Mizuno S. Nephron, Wilms' tumor-1 (WT1), and synaptopodin expression in developing podocytes of mice. Exp Anim 2017; 66:183-189. [PMID: 28179596 PMCID: PMC5543238 DOI: 10.1538/expanim.16-0101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Newborn mouse glomeruli are still immature with a morphological feature of an early
capillary loop stage, but infant mice do not manifest proteinuria. Little is known about
the molecular mechanism whereby infant mice are resistant to proteinuria. Nephrin and
synaptopodin are crucial for slit diaphragm and foot process (FP) formation for avoiding
proteinuria. Nephrin tyrosine phosphorylation means a transient biological signaling
required for FP repair or extension during nephrotic disease. Using an immunohistochemical
technique, we examined the natural course of nephrin, Wilms’ tumor-1 (WT1) and
synaptopodin at 16.5 days of embryonic age (E16.5d) and E19.5d, 7 days of post-neonatal
age (P7d) and P42d during renal development of mice. As a result, nephrin and synaptopodin
were detected at E19.5d in S-shaped bodies. WT1, a transcriptional factor for nephrin, was
detected in nucleus in podocyte-like cells in all stages. Nephrin tyrosine phosphorylation
was evident in glomeruli at P7d, and this was associated with an early-stage of FP
extension. Inversely, nephrin phosphorylation became faint at P42d, along with maturated
FP. Based on the present results, we suggest the sequential molecular mechanism to protect
growing mice from proteinuria: (i) WT1-induced nephrin production by podocytes in S-shaped
bodies at E19.5d; (ii) Synchronized induction of synaptopodin at the same period; and
(iii) FP extension is initiated at a milk-suckling stage under a nephrin
tyrosine-phosphorylated condition, while it is arrested at an adult stage, associated with
a loss of nephrin-based signaling.
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Affiliation(s)
- Takashi Kato
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.,Department of Pathology, Faculty of Medicine, Kindai University, 377-2 Ohno-higashi, Osaka-sayama, Osaka 589-8511, Japan
| | - Shinya Mizuno
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.,Department of Microbiology and Immunology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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Kindt F, Hammer E, Kemnitz S, Blumenthal A, Klemm P, Schlüter R, Quaggin SE, van den Brandt J, Fuellen G, Völker U, Endlich K, Endlich N. A novel assay to assess the effect of pharmaceutical compounds on the differentiation of podocytes. Br J Pharmacol 2016; 174:163-176. [PMID: 27858997 DOI: 10.1111/bph.13667] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 10/26/2016] [Accepted: 10/30/2016] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND AND PURPOSE Therapeutic options for treating glomerulopathies, the main cause of chronic kidney disease, are limited. Podocyte dedifferentiation is a major event in the pathogenesis of glomerulopathies. The goal of the present study was, therefore, to develop an assay to monitor podocyte differentiation suitable for compound screening. EXPERIMENTAL APPROACH We isolated and cultured glomeruli from transgenic mice, expressing cyan fluorescent protein (CFP) under the control of the promoter of nephrin, a marker of podocyte differentiation. Mean CFP fluorescence intensity per glomerulus (MFG) was determined by summation of all glomerular voxels from confocal z-stacks in the absence and presence of pharmaceutical compounds. KEY RESULTS In untreated cultured glomeruli, MFG remained fairly stable during the first 5 days, when foot processes were already effaced, and the level of many podocyte-specific proteins was only mildly affected, as revealed by proteomics. Between day 6 and 9, MFG decreased to almost zero. The decrease in MFG was paralleled by a decrease in CFP and nephrin expression, as determined by RT-PCR, western blots and proteomics. Puromycin aminonucleoside (PAN), which damages podocytes, concentration-dependently induced a complete loss of MFG. Dexamethasone (25 μM) and pioglitazone (10 μM) markedly attenuated the effect of 0.6 μg·mL-1 PAN on MFG. CONCLUSION AND IMPLICATIONS In summary, we established a novel assay to assess the effect of pharmaceutical compounds on the differentiation of podocytes in situ. Our assay is suitable for compound screening to identify drugs for the treatment of glomerulopathies.
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Affiliation(s)
- Frances Kindt
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany.,Institute for Biostatistics and Informatics in Medicine and Ageing Research, Rostock University Medical Centre, Rostock, Germany
| | - Elke Hammer
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Stefan Kemnitz
- Computational Science Group, Institute of Physics, Ernst Moritz Arndt University, Greifswald, Germany
| | - Antje Blumenthal
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Paul Klemm
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Rabea Schlüter
- Imaging Centre of the Faculty of Mathematics and Natural Sciences, Ernst Moritz Arndt University, Greifswald, Germany
| | - Susan E Quaggin
- Feinberg Cardiovascular Research Institute and Division of Nephrology and Hypertension, Northwestern University, Chicago, IL, USA
| | - Jens van den Brandt
- Central Core and Research Facility of Laboratory Animals, University Medicine Greifswald, Greifswald, Germany
| | - Georg Fuellen
- Institute for Biostatistics and Informatics in Medicine and Ageing Research, Rostock University Medical Centre, Rostock, Germany
| | - Uwe Völker
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Karlhans Endlich
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Nicole Endlich
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
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GLCCI1 is a novel component associated with the PI3K signaling pathway in podocyte foot processes. Exp Mol Med 2016; 48:e233. [PMID: 27174202 PMCID: PMC4910149 DOI: 10.1038/emm.2016.28] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 12/02/2015] [Accepted: 01/07/2016] [Indexed: 01/18/2023] Open
Abstract
Podocyte foot processes are interdigitated to form the slit diaphragm and are crucial for the glomerular filtration barrier. Glucocorticoid-induced transcript 1 (GLCCI1) is transcriptionally regulated, but its signaling pathway in podocytes is unknown. The main objective of this study was to investigate the regulation of podocyte foot process proteins and to investigate the role of GLCCI1 in the phosphoinositide 3-kinase (PI3K) pathway using high glucose-induced podocytes and streptozotocin-induced diabetic rats. In podocytes and rat kidneys, GLCCI1 was found to be highly specific for the glomerulus and podocyte foot processes similar to other podocyte-specific proteins (nephrin, podocin, synatopodin and podocalyxin) based on reverse transcription-PCR, western blotting, immunofluorescence and immunoelectron microscopy analyses. In addition, the decrease in the GLCCI1 expression level under hyperglycemic conditions was restored by treatment with a PI3K inhibitor (wortmannin). Immunofluorescence analysis confirmed that GLCCI1 colocalized with nephrin and synaptopodin both in vivo and in vitro. Finally, immunoelectron microscopy data from streptozotocin-induced diabetic rats showed that GLCCI1 also localized in podocyte foot processes. Hence, GLCCI1 is a component of podocyte foot processes, and its expression appears to be regulated via the PI3K pathway.
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Verma R, Venkatareddy M, Kalinowski A, Patel SR, Garg P. Integrin Ligation Results in Nephrin Tyrosine Phosphorylation In Vitro. PLoS One 2016; 11:e0148906. [PMID: 26848974 PMCID: PMC4743922 DOI: 10.1371/journal.pone.0148906] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 01/24/2016] [Indexed: 11/19/2022] Open
Abstract
Nephrin is expressed at the basolateral aspect of podocytes and is an important signaling protein at the glomerular slit diaphragm. In vitro studies have demonstrated that Nephrin phosphorylation-dependent signaling is able to assemble a protein complex that is able to polymerize actin. However, proximal signaling events that result in nephrin tyrosine phosphorylation are not well understood. Nephrin deletion in mice and human nephrin mutations result in developmental failure of the podocyte intercellular junction resutling in proteinuria. This has been presumed to be due to a failure to respond to an external polarized cue in the absence of nephrin or a failure to transduce an outside-in signal in patients with nephrin mutations. The nephrin extracellular domain binds to itself or neph1 across the foot process intercellular junction. Nephrin is tyrosine phosphorylation-silent in healthy glomeruli when presumably the nephrin extracellular domain is in an engaged state. These observations raise the possibility of an alternate proximal signaling mechanism that might be responsible for nephrin tyrosine phosphorylation. Here we present data showing that integrin engagement at the basal aspect of cultured podocytes results in nephrin tyrosine phosphorylation. This is abrogated by incubating podocytes with an antibody that prevents integrin β1 ligation and activation in response to binding to extracellular matrix. Furthermore, nephrin tyrosine phosphorylation was observed in podocytes expressing a membrane-targeted nephrin construct that lacks the extracellular domain. We propose, integrin-activation based signaling might be responsible for nephrin phosphorylation rather than engagment of the nephrin extracellular domain by a ligand.
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Affiliation(s)
- Rakesh Verma
- Division of Nephroloigy, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan, United States of America
| | - Madhusudan Venkatareddy
- Division of Nephroloigy, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan, United States of America
| | - Anne Kalinowski
- Division of Nephroloigy, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan, United States of America
| | - Sanjeevkumar R. Patel
- Division of Nephroloigy, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan, United States of America
| | - Puneet Garg
- Division of Nephroloigy, Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan, United States of America
- * E-mail:
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Venkatareddy M, Verma R, Kalinowski A, Patel SR, Shisheva A, Garg P. Distinct Requirements for Vacuolar Protein Sorting 34 Downstream Effector Phosphatidylinositol 3-Phosphate 5-Kinase in Podocytes Versus Proximal Tubular Cells. J Am Soc Nephrol 2016; 27:2702-19. [PMID: 26825532 DOI: 10.1681/asn.2015050555] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 12/09/2015] [Indexed: 12/16/2022] Open
Abstract
The mechanisms by which the glomerular filtration barrier prevents the loss of large macromolecules and simultaneously, maintains the filter remain poorly understood. Recent studies proposed that podocytes have an active role in both the endocytosis of filtered macromolecules and the maintenance of the filtration barrier. Deletion of a key endosomal trafficking regulator, the class 3 phosphatidylinositol (PtdIns) 3-kinase vacuolar protein sorting 34 (Vps34), in podocytes results in aberrant endosomal membrane morphology and podocyte dysfunction. We recently showed that the vacuolation phenotype in cultured Vps34-deficient podocytes is caused by the absence of a substrate for the Vps34 downstream effector PtdIns 3-phosphate 5-kinase (PIKfyve), which phosphorylates Vps34-generated PtdIns(3)P to produce PtdIns (3,5)P2. PIKfyve perturbation and PtdIns(3,5)P2 reduction result in massive membrane vacuolation along the endosomal system, but the cell-specific functions of PIKfyve in vivo remain unclear. We show here that the genetic deletion of PIKfyve in endocytically active proximal tubular cells resulted in the development of large cytoplasmic vacuoles caused by arrested endocytic traffic progression at a late-endosome stage. In contrast, deletion of PIKfyve in glomerular podocytes did not significantly alter the endosomal morphology, even in age 18-month-old mice. However, on culturing, the PIKfyve-deleted podocytes developed massive cytoplasmic vacuoles. In summary, these data suggest that glomerular podocytes and proximal tubules have different requirements for PIKfyve function, likely related to distinct in vivo needs for endocytic flux.
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Affiliation(s)
- Madhusudan Venkatareddy
- Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan; and
| | - Rakesh Verma
- Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan; and
| | - Anne Kalinowski
- Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan; and
| | - Sanjeevkumar R Patel
- Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan; and
| | - Assia Shisheva
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Puneet Garg
- Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan; and
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Ensuring the Quality of Stem Cell-Derived In Vitro Models for Toxicity Testing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 856:259-297. [DOI: 10.1007/978-3-319-33826-2_11] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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32
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Chang AS, Hathaway CK, Smithies O, Kakoki M. Transforming growth factor-β1 and diabetic nephropathy. Am J Physiol Renal Physiol 2015; 310:F689-F696. [PMID: 26719364 DOI: 10.1152/ajprenal.00502.2015] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 12/24/2015] [Indexed: 12/19/2022] Open
Abstract
Transforming growth factor-β1 (TGF-β1) is established to be involved in the pathogenesis of diabetic nephropathy. The diabetic milieu enhances oxidative stress and induces the expression of TGF-β1. TGF-β1 promotes cell hypertrophy and extracellular matrix accumulation in the mesangium, which decreases glomerular filtration rate and leads to chronic renal failure. Recently, TGF-β1 has been demonstrated to regulate urinary albumin excretion by both increasing glomerular permeability and decreasing reabsorption in the proximal tubules. TGF-β1 also increases urinary excretion of water, electrolytes and glucose by suppressing tubular reabsorption in both normal and diabetic conditions. Although TGF-β1 exerts hypertrophic and fibrogenic effects in diabetic nephropathy, whether suppression of the function of TGF-β1 can be an option to prevent or treat the complication is still controversial. This is partly because adrenal production of mineralocorticoids could be augmented by the suppression of TGF-β1. However, differentiating the molecular mechanisms for glomerulosclerosis from those for the suppression of the effects of mineralocorticoids by TGF-β1 may assist in developing novel therapeutic strategies for diabetic nephropathy. In this review, we discuss recent findings on the role of TGF-β1 in diabetic nephropathy.
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Affiliation(s)
- Albert S Chang
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Catherine K Hathaway
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Oliver Smithies
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Masao Kakoki
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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33
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Shp2 Associates with and Enhances Nephrin Tyrosine Phosphorylation and Is Necessary for Foot Process Spreading in Mouse Models of Podocyte Injury. Mol Cell Biol 2015; 36:596-614. [PMID: 26644409 DOI: 10.1128/mcb.00956-15] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 11/24/2015] [Indexed: 11/20/2022] Open
Abstract
In most forms of glomerular diseases, loss of size selectivity by the kidney filtration barrier is associated with changes in the morphology of podocytes. The kidney filtration barrier is comprised of the endothelial lining, the glomerular basement membrane, and the podocyte intercellular junction, or slit diaphragm. The cell adhesion proteins nephrin and neph1 localize to the slit diaphragm and transduce signals in a Src family kinase Fyn-mediated tyrosine phosphorylation-dependent manner. Studies in cell culture suggest nephrin phosphorylation-dependent signaling events are primarily involved in regulation of actin dynamics and lamellipodium formation. Nephrin phosphorylation is a proximal event that occurs both during development and following podocyte injury. We hypothesized that abrogation of nephrin phosphorylation following injury would prevent nephrin-dependent actin remodeling and foot process morphological changes. Utilizing a biased screening approach, we found nonreceptor Src homology 2 (sh2) domain-containing phosphatase Shp2 to be associated with phosphorylated nephrin. We observed an increase in nephrin tyrosine phosphorylation in the presence of Shp2 in cell culture studies. In the human glomerulopathies minimal-change nephrosis and membranous nephropathy, there is an increase in Shp2 phosphorylation, a marker of increased Shp2 activity. Mouse podocytes lacking Shp2 do not develop foot process spreading when subjected to podocyte injury in vivo using protamine sulfate or nephrotoxic serum (NTS). In the NTS model, we observed a lack of foot process spreading in mouse podocytes with Shp2 deleted and smaller amounts of proteinuria. Taken together, these results suggest that Shp2-dependent signaling events are necessary for changes in foot process structure and function following injury.
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34
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Abou Msallem J, Chalhoub H, Al-Hariri M, Saad L, Jaffa MA, Ziyadeh FN, Jaffa AA. Mechanisms of bradykinin-induced expression of connective tissue growth factor and nephrin in podocytes. Am J Physiol Renal Physiol 2015; 309:F980-90. [PMID: 26447218 DOI: 10.1152/ajprenal.00233.2015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 09/29/2015] [Indexed: 12/24/2022] Open
Abstract
Diabetic nephropathy (DN) is the main cause of morbidity and mortality in diabetes and is characterized by mesangial matrix deposition and podocytopathy, including podocyte loss. The risk factors and mechanisms involved in the pathogenesis of DN are still not completely defined. In the present study, we aimed to understand the cellular mechanisms through which activation of B2 kinin receptors contribute to the initiation and progression of DN. Stimulation of cultured rat podocytes with bradykinin (BK) resulted in a significant increase in ROS generation, and this was associated with a significant increase in NADPH oxidase (NOX)1 and NOX4 protein and mRNA levels. BK stimulation also resulted in a signicant increase in the phosphorylation of ERK1/2 and Akt, and this effect was inhibited in the presence of NOX1 and Nox4 small interfering (si)RNA. Furthermore, podocytes stimulated with BK resulted in a significant increase in protein and mRNA levels of connective tissue growth factor (CTGF) and, at the same time, a significant decrease in protein and mRNA levels of nephrin. siRNA targeted against NOX1 and NOX4 significantly inhibited the BK-induced increase in CTGF. Nephrin expression was increased in response to BK in the presence of NOX1 and NOX4 siRNA, thus implicating a role for NOXs in modulating the BK response in podocytes. Moreover, nephrin expression in response to BK was also significantly increased in the presence of siRNA targeted against CTGF. These findings provide novel aspects of BK signal transduction pathways in pathogenesis of DN and identify novel targets for interventional strategies.
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Affiliation(s)
- J Abou Msallem
- Biochemistry and Molecular Genetics Department, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - H Chalhoub
- Biochemistry and Molecular Genetics Department, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - M Al-Hariri
- Biochemistry and Molecular Genetics Department, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - L Saad
- Biochemistry and Molecular Genetics Department, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - M A Jaffa
- Epidemiology and Population Health Department, Faculty of Health Sciences, American University of Beirut, Beirut, Lebanon; and
| | - F N Ziyadeh
- Biochemistry and Molecular Genetics Department, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - A A Jaffa
- Biochemistry and Molecular Genetics Department, Faculty of Medicine, American University of Beirut, Beirut, Lebanon; Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
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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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36
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Low TGFβ1 expression prevents and high expression exacerbates diabetic nephropathy in mice. Proc Natl Acad Sci U S A 2015; 112:5815-20. [PMID: 25902541 DOI: 10.1073/pnas.1504777112] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nephropathy develops in many but not all patients with long-standing type 1 diabetes. Substantial efforts to identify genotypic differences explaining this differential susceptibility have been made, with limited success. Here, we show that the expression of the transforming growth factor β1 gene (Tgfb1) affects the development of diabetic nephropathy in mice. To do this we genetically varied Tgfb1 expression in five steps, 10%, 60%, 100%, 150%, and 300% of normal, in mice with type 1 diabetes caused by the Akita mutation in the insulin gene (Ins2(Akita)). Although plasma glucose levels were not affected by Tgfb1 genotype, many features of diabetic nephropathy (mesangial expansion, elevated plasma creatinine and urea, decreased creatinine clearance and albuminuria) were progressively ameliorated as Tgfb1 expression decreased and were progressively exacerbated when expression was increased. The diabetic 10% hypomorphs had comparable creatinine clearance and albumin excretion to wild-type mice and no harmful changes in renal morphology. The diabetic 300% hypermorphs had ∼1/3 the creatinine clearance of wild-type mice, >20× their albumin excretion, ∼3× thicker glomerular basement membranes and severe podocyte effacement, matching human diabetic nephropathy. Switching Tgfb1 expression from low to high in the tubules of the hypomorphs increased their albumin excretion more than 10-fold but creatinine clearance remained high. Switching Tgfb1 expression from low to high in the podocytes markedly decreased creatinine clearance, but minimally increased albumin excretion. Decreasing expression of Tgfb1 could be a promising option for preventing loss of renal function in diabetes.
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Li X, Chuang PY, D'Agati VD, Dai Y, Yacoub R, Fu J, Xu J, Taku O, Premsrirut PK, Holzman LB, He JC. Nephrin Preserves Podocyte Viability and Glomerular Structure and Function in Adult Kidneys. J Am Soc Nephrol 2015; 26:2361-77. [PMID: 25644109 DOI: 10.1681/asn.2014040405] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 11/19/2014] [Indexed: 01/12/2023] Open
Abstract
Nephrin is required during kidney development for the maturation of podocytes and formation of the slit diaphragm junctional complex. Because nephrin expression is downregulated in acquired glomerular diseases, nephrin deficiency is considered a pathologic feature of glomerular injury. However, whether nephrin deficiency exacerbates glomerular injury in glomerular diseases has not been experimentally confirmed. Here, we generated mice with inducible RNA interference-mediated nephrin knockdown. Short-term nephrin knockdown (6 weeks), starting after the completion of kidney development at 5 weeks of age, did not affect glomerular structure or function. In contrast, mice with long-term nephrin knockdown (20 weeks) developed mild proteinuria, foot process effacement, filtration slit narrowing, mesangial hypercellularity and sclerosis, glomerular basement membrane thickening, subendothelial zone widening, and podocyte apoptosis. When subjected to an acquired glomerular insult induced by unilateral nephrectomy or doxorubicin, mice with short-term nephrin knockdown developed more severe glomerular injury compared with mice without nephrin knockdown. Additionally, nephrin-knockdown mice developed more exaggerated glomerular enlargement when subjected to unilateral nephrectomy and more podocyte apoptosis and depletion after doxorubicin challenge. AKT phosphorylation, which is a slit diaphragm-mediated and nephrin-dependent pathway in the podocyte, was markedly reduced in mice with long-term or short-term nephrin knockdown challenged with uninephrectomy or doxorubicin. Taken together, our data establish that under the basal condition and in acquired glomerular diseases, nephrin is required to maintain slit diaphragm integrity and slit diaphragm-mediated signaling to preserve glomerular function and podocyte viability in adult mice.
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Affiliation(s)
- Xuezhu Li
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Nephrology; Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Peter Y Chuang
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York;
| | - Vivette D D'Agati
- Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York
| | - Yan Dai
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Nephrology, Shanghai First Municipal Hospital, Shanghai Jiaotao University School of Medicine; Shanghai, China
| | - Rabi Yacoub
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jia Fu
- Research Institute of Nephrology, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Jin Xu
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Oltjon Taku
- State University of New York at University at Binghamton, Binghamton, New York
| | | | - Lawrence B Holzman
- Renal Electrolyte and Hypertension Division, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania; and
| | - John Cijiang He
- Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York; Renal Section, James J Peter Veterans Administration Medical Center, Bronx, New York
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38
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Wilmes A, Jennings P. The Use of Renal Cell Culture for Nephrotoxicity Investigations. METHODS AND PRINCIPLES IN MEDICINAL CHEMISTRY 2014. [DOI: 10.1002/9783527674183.ch10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Glomerular development--shaping the multi-cellular filtration unit. Semin Cell Dev Biol 2014; 36:39-49. [PMID: 25153928 DOI: 10.1016/j.semcdb.2014.07.016] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 07/29/2014] [Accepted: 07/31/2014] [Indexed: 01/09/2023]
Abstract
The glomerulus represents a highly structured filtration unit, composed of glomerular endothelial cells, mesangial cells, podocytes and parietal epithelial cells. During glomerulogenesis an intricate network of signaling pathways involving transcription factors, secreted factors and cell-cell communication is required to guarantee accurate evolvement of a functional, complex 3-dimensional glomerular architecture. Here, we want to provide an overview on the critical steps and relevant signaling cascades of glomerular development.
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40
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Fukusumi Y, Miyauchi N, Hashimoto T, Saito A, Kawachi H. Therapeutic target for nephrotic syndrome: Identification of novel slit diaphragm associated molecules. World J Nephrol 2014; 3:77-84. [PMID: 25332898 PMCID: PMC4202494 DOI: 10.5527/wjn.v3.i3.77] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 05/15/2014] [Accepted: 06/27/2014] [Indexed: 02/06/2023] Open
Abstract
The slit diaphragm bridging the neighboring foot processes functions as a final barrier of glomerular capillary wall for preventing the leak of plasma proteins into primary urine. It is now accepted that the dysfunction of the sit diaphragm contributes to the development of proteinuria in several glomerular diseases. Nephrin, a gene product of NPHS1, a gene for a congenital nephrotic syndrome of Finnish type, constitutes an extracellular domain of the slit diaphragm. Podocin was identified as a gene product of NPHS2, a gene for a familial steroid-resistant nephrotic syndrome of French. Podocin binds the cytoplasmic domain of nephrin. After then, CD2 associated protein, NEPH1 and transient receptor potential-6 were also found as crucial molecules of the slit diaphragm. In order to explore other novel molecules contributing to the development of proteinuria, we performed a subtraction hybridization assay with a normal rat glomerular RNA and a glomerular RNA of rats with a puromycin aminonucleoside nephropathy, a mimic of a human minimal change type nephrotic syndrome. Then we have found that synaptic vesicle protein 2B, ephrin-B1 and neurexin were already downregulated at the early stage of puromycin aminonucleoside nephropathy, and that these molecules were localized close to nephrin. It is conceivable that these molecules are the slit diaphragm associated molecules, which participate in the regulation of the barrier function. These molecules could be targets to establish a novel therapy for nephrotic syndrome.
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41
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Jennings P, Aschauer L, Wilmes A, Gstraunthaler G. Renal Cell Culture. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2014. [DOI: 10.1007/978-1-4939-0521-8_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Fukuyo Y, Nakamura T, Bubenshchikova E, Powell R, Tsuji T, Janknecht R, Obara T. Nephrin and Podocin functions are highly conserved between the zebrafish pronephros and mammalian metanephros. Mol Med Rep 2013; 9:457-65. [PMID: 24337247 PMCID: PMC3896505 DOI: 10.3892/mmr.2013.1844] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Accepted: 11/22/2013] [Indexed: 01/28/2023] Open
Abstract
The slit diaphragm (SD) is a highly specialized intercellular junction between podocyte foot processes and is crucial in the formation of the filtration barrier in the renal glomeruli. Zebrafish Nephrin and Podocin are important in the formation of the podocyte SD and mutations in NEPHRIN and PODOCIN genes cause human nephrotic syndrome. In the present study, the zebrafish Podocin protein was observed to be predominantly localized in the pronephric glomerular podocytes, as previously reported for Nephrin. To understand the function of Podocin and Nephrin in zebrafish, splice-blocking morpholino antisense oligonucleotides were used. Knockdown of Podocin or Nephrin by this method induced pronephric glomerular hypoplasia with pericardial edema. Human NEPHRIN and PODOCIN mRNA rescued this glomerular phenotype, however, the efficacy of the rescues was greatly reduced when mRNA-encoding human disease-causing NEPHRIN-R1109X and PODOCIN-R138Q were used. Furthermore, an association between zebrafish Nephrin and Podocin proteins was observed. Notably, Podocin-R150Q, corresponding to human PODOCIN-R138Q, markedly interacted with NEPHRIN compared with wild-type PODOCIN, suggesting that this strong binding capacity of mutated PODOCIN impairs the transport of NEPHRIN and PODOCIN out of the endoplasmic reticulum. The results suggest that the functions of Nephrin and Podocin are highly conserved between the zebrafish pronephros and mammalian metanephros. Accordingly, the zebrafish pronephros may provide a useful tool for analyzing disease-causing gene mutations in human kidney disorders.
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Affiliation(s)
- Yayoi Fukuyo
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Tomomi Nakamura
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Ekaterina Bubenshchikova
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Rebecca Powell
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Takashi Tsuji
- Department of Biological Science and Technology, Graduate School of Industrial Science and Technology, Tokyo University of Science, Noda, Chiba 278‑8510, Japan
| | - Ralf Janknecht
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Tomoko Obara
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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Constitutional Nephrin Deficiency in Conditionally Immortalized Human Podocytes Induced Epithelial-Mesenchymal Transition, Supported by β-Catenin/NF-kappa B Activation: A Consequence of Cell Junction Impairment? Int J Nephrol 2013; 2013:457490. [PMID: 24392227 PMCID: PMC3874297 DOI: 10.1155/2013/457490] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/11/2013] [Indexed: 01/08/2023] Open
Abstract
The kidney glomerular podocytes are the cellular target of many chronic nephropathies both determined and acquired genetically. Mutations that affected the expression and/or the function of nephrin, a key component of the slit-diaphragm, are often causes of these pathologies. Recent findings showed that murine podocytes could undergo epithelial-mesenchymal transformation (EMT), suggesting new hypotheses about the pathogenesis of glomerular fibrosis. Here, we show that also human podocytes can undergo EMT, but more importantly nephrin ablation itself can trigger this phenotypic transformation. In fact, a model of human podocyte with engineered nephrin deficiency constitutionally expressed high levels of α-SMA, vimentin, fibronectin, and other hallmarks of EMT. Since it is known that cell contact abrogation is one of the triggers of EMT, we reasoned that nephrin loss could account for such cell junction disruption and cause the EMT. Therefore, we demonstrated that also normal podocytes could spontaneously undergo EMT if grown in Ca2+-free medium, which is known to impair cell contacts. The analysis of the main intracellular signal transduction pathways evidenced some major anomalies consequent with the nephrin abrogation. The most intriguing was the activation of β-catenin pathway, which plays a critical role in podocyte ontogenesis as well as in the nephrin expression and EMT regulation. Also other important signaling proteins, like NF-κB, p53, and retinoblastoma protein (RB), showed important activity modifications. Interestingly, most of the above indicated signaling pathway alterations were again reproducible by cell junction rupture, induced by Ca2+ deprivation. Finally, immunofluorescence analysis on kidney sections of patients with NS of Finnish type confirmed the constitutive expression of α-SMA.
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Lv W, Zhang Y, Guan G, Li P, Wang J, Qi D. Mycophenolate mofetil and valsartan inhibit podocyte apoptosis in streptozotocin-induced diabetic rats. Pharmacology 2013; 92:227-34. [PMID: 24158161 DOI: 10.1159/000354600] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/22/2013] [Indexed: 01/24/2023]
Abstract
AIM To investigate the effects of mycophenolate mofetil on apoptosis and the expression of Bax and Bcl-2 of podocytes in rats with diabetic nephropathy. METHODS A total of 40 male rats were randomly divided into two groups: healthy control group (NC, n = 8) and diabetic nephropathy group (DN, n = 32). The diabetic rat models were induced by streptozotocin, which was injected intraperitoneally. After the DN model was established successfully, the DN group was subdivided into four groups: (1) group treated with the dissolvent (DN), (2) group treated with mycophenolate mofetil (DN + M), (3) group treated with valsartan (DN + V) and (4) group treated with mycophenolate mofetil and valsartan (DN + MV). After 16 weeks of treatment, kidney and body weight, urinary protein level and serum glucose were measured. Histomorphology of renal tissue was observed by an optical microscope. Apoptosis of podocytes was determined by transferase-mediated dUTP nick-end labeling (TUNEL) test. The expression of nephrin and Wilms' tumor suppressor gene (WT1) were detected by immunohistochemistry and real-time PCR, and the protein expression of Bax and Bcl-2 were examined by Western blot. RESULTS The mRNA and protein expression of nephrin and WT1 were both downregulated. The apoptosis rate, the expression of Bax, caspase-3 activity and cleavage increased, while the expression of Bcl-2 decreased in the DN group compared with the NC group. However, they were all improved in the groups treated with either mycophenolate mofetil or valsartan. CONCLUSION Mycophenolate mofetil can protect renal function by increasing Bcl-2 expression and decreasing Bax expression and podocyte apoptosis rate, thereby reducing proteinuria.
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Affiliation(s)
- Wei Lv
- Department of Nephrology, the Second Hospital of Shandong University, Jinan, PR China
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45
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Ichimura K, Powell R, Nakamura T, Kurihara H, Sakai T, Obara T. Podocalyxin regulates pronephric glomerular development in zebrafish. Physiol Rep 2013; 1. [PMID: 24224085 PMCID: PMC3819108 DOI: 10.1002/phy2.74] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Vertebrate glomerular podocytes possess a highly sialylated transmembrane glycoprotein, Podocalyxin. In mammals, the sialic acid of Podocalyxin plays a crucial role in the formation of the characteristic podocyte architecture required for glomerular filtration. We examined the function of Podocalyxin in the developing zebrafish pronephros by disrupting the expression of podocalyxin through the use of morpholino antisense oligonucleotides. Podocalyxin was localized at the apical membrane of podocytes throughout pronephric glomerular development in zebrafish. Translational blocking of podocalyxin expression resulted in pericardial edema and a hypoplastic glomerulus. Whereas regular foot processes with a slit diaphragm covered 66.7 ± 7.8% of the urinary surface of glomerular basement membrane in control fish, only 14.4 ± 7.5% of this area was covered with regular foot processes in the translationally blocked morphants. Splice blocking of podocalyxin exon 2, which partially encodes the bulky mucin domain with extensive sialic acid-containing sugar chains, resulted in the deletion of 53% of mucin domain-coding sequence from podocalyxin mRNA. Approximately 40% of these splice-blocked morphants had mild pericardial edema. Although the pronephric glomerulus in the splice-blocked morphants exhibited almost normal appearance with developed glomerular capillaries and mesangium, they had only 36.3 ± 6.9% of the area covered with regular foot processes. In conclusion, Podocalyxin is predominantly expressed in the podocytes and plays a distinct role in the formation of the podocyte foot processes with a slit diaphragm during zebrafish pronephric development.
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Affiliation(s)
- Koichiro Ichimura
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA ; Department of Anatomy and Life Structure, Juntendo University School of Medicine, Tokyo, Japan
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Burghardt T, Kastner J, Suleiman H, Rivera-Milla E, Stepanova N, Lottaz C, Kubitza M, Böger CA, Schmidt S, Gorski M, de Vries U, Schmidt H, Hertting I, Kopp J, Rascle A, Moser M, Heid IM, Warth R, Spang R, Wegener J, Mierke CT, Englert C, Witzgall R. LMX1B is essential for the maintenance of differentiated podocytes in adult kidneys. J Am Soc Nephrol 2013; 24:1830-48. [PMID: 23990680 DOI: 10.1681/asn.2012080788] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Mutations of the LMX1B gene cause nail-patella syndrome, a rare autosomal-dominant disorder affecting the development of the limbs, eyes, brain, and kidneys. The characterization of conventional Lmx1b knockout mice has shown that LMX1B regulates the development of podocyte foot processes and slit diaphragms, but studies using podocyte-specific Lmx1b knockout mice have yielded conflicting results regarding the importance of LMX1B for maintaining podocyte structures. In order to address this question, we generated inducible podocyte-specific Lmx1b knockout mice. One week of Lmx1b inactivation in adult mice resulted in proteinuria with only minimal foot process effacement. Notably, expression levels of slit diaphragm and basement membrane proteins remained stable at this time point, and basement membrane charge properties also did not change, suggesting that alternative mechanisms mediate the development of proteinuria in these mice. Cell biological and biophysical experiments with primary podocytes isolated after 1 week of Lmx1b inactivation indicated dysregulation of actin cytoskeleton organization, and time-resolved DNA microarray analysis identified the genes encoding actin cytoskeleton-associated proteins, including Abra and Arl4c, as putative LMX1B targets. Chromatin immunoprecipitation experiments in conditionally immortalized human podocytes and gel shift assays showed that LMX1B recognizes AT-rich binding sites (FLAT elements) in the promoter regions of ABRA and ARL4C, and knockdown experiments in zebrafish support a model in which LMX1B and ABRA act in a common pathway during pronephros development. Our report establishes the importance of LMX1B in fully differentiated podocytes and argues that LMX1B is essential for the maintenance of an appropriately structured actin cytoskeleton in podocytes.
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Simske JS. Claudins reign: The claudin/EMP/PMP22/γ channel protein family in C. elegans. Tissue Barriers 2013; 1:e25502. [PMID: 24665403 PMCID: PMC3879130 DOI: 10.4161/tisb.25502] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 06/19/2013] [Accepted: 06/21/2013] [Indexed: 01/06/2023] Open
Abstract
The claudin family of integral membrane proteins was identified as the major protein component of the tight junctions in all vertebrates. Since their identification, claudins, and their associated pfam00822 superfamily of proteins have been implicated in a wide variety of cellular processes. Claudin homologs have been identified in invertebrates as well, including Drosophila and C. elegans. Recent studies demonstrate that the C. elegans claudins, clc-1-clc- 5, and similar proteins in the greater PMP22/EMP/claudin/voltage-gated calcium channel γ subunit family, including nsy-4, and vab-9, while highly divergent at a sequence level from each other and from the vertebrate claudins, in many cases play roles similar to those traditionally assigned to their vertebrate homologs. These include regulating cell adhesion and passage of small molecules through the paracellular space, channel activity, protein aggregation, sensitivity to pore-forming toxins, intercellular signaling, cell fate specification and dynamic changes in cell morphology. Study of claudin superfamily proteins in C. elegans should continue to provide clues as to how claudin family protein function has been adapted to perform diverse functions at specialized cell-cell contacts in metazoans.
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Abstract
In the past decade, our understanding of the role of podocytes in the function of the glomerular filtration barrier, and of the role of podocyte injury in the pathogenesis of proteinuric kidney disease, has substantially increased. Landmark genetic studies identified mutations in genes expressed by podocytes as a cause of albuminuria and nephrotic syndrome, leading to breakthrough discoveries from many laboratories. These discoveries contributed to a dramatic change in our view of the glomerular filtration barrier of the kidney and of the role of podocyte injury in the development of albuminuria and progressive kidney disease. In the past several years, studies have demonstrated that podocyte injury is a major cause of marked albuminuria and nephrotic syndrome, and have confirmed that podocytes are important for the maintenance of an intact glomerular filtration barrier. An essential role of loss of these cells in the pathogenesis of glomerulosclerosis and progressive proteinuric kidney disease has also been identified. In this Review, we discuss the importance of podocytes for the maintenance of an intact glomerular filtration barrier and their role in albumin handling.
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Affiliation(s)
- Paul Thomas Brinkkoetter
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Kerpener Strasse 62, 50937 Cologne, Germany
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Abstract
Observations of hereditary glomerular disease support the contention that podocyte intercellular junction proteins are essential for junction formation and maintenance. Genetic deletion of most of these podocyte intercellular junction proteins results in foot process effacement and proteinuria. This review focuses on the current understanding of molecular mechanisms by which podocyte intercellular junction proteins such as the nephrin-neph1-podocin-receptor complex coordinate cytoskeletal dynamics and thus intercellular junction formation, maintenance, and injury-dependent remodeling.
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Ichimura K, Fukuyo Y, Nakamura T, Powell R, Sakai T, Janknecht R, Obara T. Developmental localization of nephrin in zebrafish and medaka pronephric glomerulus. J Histochem Cytochem 2013; 61:313-24. [PMID: 23324868 DOI: 10.1369/0022155413477115] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Slit diaphragm (SD) is a highly specialized intercellular junction between podocyte foot processes and plays a crucial role in the formation of the filtration barrier. In this study, we examined the developmental localization of Nephrin, an essential component of SD, in the pronephric glomerulus of zebrafish and medaka. In the mature glomerulus of both fish, Nephrin is localized along the glomerular basement membrane as seen in mammals, indicating that Nephrin is localized at the SD. Interestingly, Nephrin was detected already in immature podocytes before the SD and foot processes started to form in both fish. Nephrin was localized along the cell surface of immature podocytes but as different localization patterns. In zebrafish, Nephrin signal bordered the lateral membrane of podocytes, which were columnar in shape, as in rat immature podocytes. However, in medaka immature podocytes, Nephrin was localized in a punctate pattern among podocyte cell bodies. These findings suggest that Nephrin needs to be integrated to the membrane before the formation of the SD and then moves to the proper site to form the SD. Furthermore, a podocyte-specific marker, such as Nephrin, should be a useful tool for the future analysis of pronephric glomerular development in fish mutants and morphants.
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Affiliation(s)
- Koichiro Ichimura
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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