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Guo C, Ding Y, Yang A, Geng Y, Liu C, Zhou L, Ma L, Yang Z, Hu F, Jiang K, Cai R, Bai P, Quan M, Deng Y, Wu C, Sun Y. CHILKBP protects against podocyte injury by preserving ZO-1 expression. Cell Mol Life Sci 2022; 80:18. [PMID: 36564652 PMCID: PMC11072396 DOI: 10.1007/s00018-022-04661-z] [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: 09/28/2022] [Revised: 11/30/2022] [Accepted: 12/02/2022] [Indexed: 12/25/2022]
Abstract
Glomerular diseases afflict millions of people and impose an enormous burden on public healthcare costs worldwide. Identification of potential therapeutic targets for preventing glomerular diseases is of considerable clinical importance. CHILKBP is a focal adhesion protein and modulates a wide array of biological functions. However, little is known about the role of CHILKBP in glomerular diseases. To investigate the function of CHILKBP in maintaining the structure and function of podocytes in a physiologic setting, a mouse model (CHILKBP cKO) was generated in which CHILKBP gene was conditionally deleted in podocytes using the Cre-LoxP system. Ablation of CHILKBP in podocytes resulted in massive proteinuria and kidney failure in mice. Histologically, typical podocyte injury including podocyte loss, foot process effacement, and glomerulosclerosis was observed in CHILKBP cKO mice. Mechanistically, we identified ZO-1 as a key junctional protein that interacted with CHILKBP. Loss of CHILKBP in podocytes exhibited a significant reduction of ZO-1 expression, leading to abnormal actin organization, aberrant slit diaphragm protein expression and compromised podocyte filtration capacity. Restoration of CHILKBP or ZO-1 in CHILKBP-deficient podocytes effectively alleviated podocyte injury induced by the loss of CHILKBP in vitro and in vivo. Finally, we showed the glomerular expression of CHILKBP and ZO-1 was decreased in patients with proteinuric kidney diseases. Our findings reveal a novel signaling pathway consisting of CHILKBP and ZO-1 that plays an essential role in maintaining podocyte homeostasis and suggest novel therapeutic approaches to alleviate glomerular diseases.
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Affiliation(s)
- Chen Guo
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
- Greater Bay Biomedical InnoCenter, Shenzhen Bay Laboratory, Shenzhen, 518055, China
| | - Yanyan Ding
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Aihua Yang
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Yiqing Geng
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Chengmin Liu
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Li Zhou
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Luyao Ma
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Zhe Yang
- Department of Pathology, The First Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Feng Hu
- National Clinical Research Center for Infectious Diseases, Shenzhen Third People's Hospital, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Ke Jiang
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Renwei Cai
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Panzhu Bai
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Meiling Quan
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Yi Deng
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Chuanyue Wu
- Department of Pathology, School of Medicine, University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
| | - Ying Sun
- Department of Biology, School of Life Sciences, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Southern University of Science and Technology, Shenzhen, 518055, China.
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PI(4,5)P2 controls slit diaphragm formation and endocytosis in Drosophila nephrocytes. Cell Mol Life Sci 2022; 79:248. [PMID: 35437696 PMCID: PMC9016003 DOI: 10.1007/s00018-022-04273-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 03/01/2022] [Accepted: 03/24/2022] [Indexed: 12/03/2022]
Abstract
Drosophila nephrocytes are an emerging model system for mammalian podocytes and proximal tubules as well as for the investigation of kidney diseases. Like podocytes, nephrocytes exhibit characteristics of epithelial cells, but the role of phospholipids in polarization of these cells is yet unclear. In epithelia, phosphatidylinositol(4,5)bisphosphate (PI(4,5)P2) and phosphatidylinositol(3,4,5)-trisphosphate (PI(3,4,5)P3) are asymmetrically distributed in the plasma membrane and determine apical–basal polarity. Here, we demonstrate that both phospholipids are present in the plasma membrane of nephrocytes, but only PI(4,5)P2 accumulates at slit diaphragms. Knockdown of Skittles, a phosphatidylinositol(4)phosphate 5-kinase, which produces PI(4,5)P2, abolished slit diaphragm formation and led to strongly reduced endocytosis. Notably, reduction in PI(3,4,5)P3 by overexpression of PTEN or expression of a dominant-negative phosphatidylinositol-3-kinase did not affect nephrocyte function, whereas enhanced formation of PI(3,4,5)P3 by constitutively active phosphatidylinositol-3-kinase resulted in strong slit diaphragm and endocytosis defects by ectopic activation of the Akt/mTOR pathway. Thus, PI(4,5)P2 but not PI(3,4,5)P3 is essential for slit diaphragm formation and nephrocyte function. However, PI(3,4,5)P3 has to be tightly controlled to ensure nephrocyte development.
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Chen J, Wang X, He Q, Harris RC. TAZ is important for maintenance of the integrity of podocytes. Am J Physiol Renal Physiol 2022; 322:F419-F428. [PMID: 35157550 PMCID: PMC8934679 DOI: 10.1152/ajprenal.00426.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 02/01/2022] [Accepted: 02/07/2022] [Indexed: 11/22/2022] Open
Abstract
The podocyte is an important component of the glomerular filtration barrier, and maintenance of the integrity of its highly specified structure and function is critical for normal kidney function. Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) are two crucial effectors of the Hippo signaling pathway, and recent studies have shown that podocyte-specific YAP deletion causes podocyte apoptosis and the development of focal segmental glomerulosclerosis followed by progressive renal failure. In the present study, we investigated a potential role of the YAP paralog TAZ in podocytes. TAZ was found to be constitutively active in podocytes, and mice with podocyte-specific deletion of TAZ (TazpodKO) developed proteinuria starting at 4 wk of age and had increased podocyte apoptosis. Using primary cultured podocytes or immortalized mouse podocytes from Tazflox/flox mice, we found that TAZ is a transcriptional activator for TEAD-dependent expression of synaptopodin, zonula occludens-1, and zonula occludens-2. This is the first study to determine that TAZ plays an important role in the maintenance of the structure and function of podocytes.NEW & NOTEWORTHY Podocytes play an important role in maintaining the integrity of the structure and function of the kidney. We observed that mice with selective deletion of transcriptional coactivator with PDZ-binding motif (TAZ) in podocytes developed proteinuria. TAZ is constitutively active and critical for expression of synaptopodin, zonula occludens-1, and zonula occludens-2 in podocytes. The findings of this study implicate TAZ as an important mediator of podocyte structural integrity and provide further insights into the role of Hippo-Yes-associated protein/TAZ in podocyte biology.
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Affiliation(s)
- Jianchun Chen
- United States Department of Veterans Affairs, Nashville, Tennessee
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Xiaoyong Wang
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Qian He
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Raymond C Harris
- United States Department of Veterans Affairs, Nashville, Tennessee
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
- Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee
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Dong QQ, Li ZF, Zhang H, Shu HP, Tu YC, Liao QQ, Yao LJ. Serum and Glucocorticoid-Inducible Kinase 3/Nedd4-2 Signaling Pathway Participates in Podocyte Injury by Regulating the Stability of Nephrin. Front Physiol 2022; 12:810473. [PMID: 35126185 PMCID: PMC8811367 DOI: 10.3389/fphys.2021.810473] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 12/13/2021] [Indexed: 11/26/2022] Open
Abstract
Serum and glucocorticoid-inducible kinase 3 (SGK3) is involved in maintaining podocyte function by regulating the protein levels of podocin and CD2-associated protein. Nephrin is also one of the slit diaphragm proteins of podocytes, but whether SGK3 participates in podocyte injury by regulating the levels of nephrin remains unclear. In this study, we focused on whether SGK3 affects nephrin levels and the mechanisms involved in the same. In the kidneys of adriamycin (ADR)-induced podocyte injury mouse model, the protein levels of SGK3 and nephrin were significantly decreased. Furthermore, the expression of SGK3 was negatively correlated with the output of proteinuria, and positively correlated with the levels of nephrin. In ADR-treated conditionally immortalized mouse podocyte cells (MPCs), the protein levels of nephrin and SGK3 were inhibited, while the constitutive expression of SGK3 reversed the ADR-induced decline in nephrin protein levels. Furthermore, ADR treatment or SGK3 inactivation enhanced the ubiquitin-proteasome degradation of nephrin in MPCs, and dramatically activated downstream effector proteins of SGK3, neural precursor cells expressing developmentally downregulated protein 4 subtype 2 (Nedd4-2) and glycogen synthase kinase-3 β (GSK3β). Similarly, Nedd4-2 or GSK3β overexpression resulted in increased activity of Nedd4-2 or GSK3β, and significantly downregulated nephrin levels. Interestingly, ubiquitin-mediated protein degradation of nephrin was regulated by Nedd4-2, rather than by GSK3β. In summary, SGK3 inactivation downregulated the levels of nephrin by increasing Nedd4-2 and GSK3β activity in ADR-induced podocyte injury model; in particular, the SGK3/Nedd4-2 signaling pathway was found to be involved in ubiquitin-mediated proteasome degradation of nephrin.
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Affiliation(s)
- Qing-Qing Dong
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zi-Fang Li
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- Blood Purification Center, Hubei No. 3 People’ Hospital of Jianghan University, Wuhan, China
| | - Hui Zhang
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hua-Pan Shu
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yu-Chi Tu
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qian-Qian Liao
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Li-Jun Yao
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- *Correspondence: Li-Jun Yao,
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5
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Wang J, Vaddadi N, Pak JS, Park Y, Quilez S, Roman CA, Dumontier E, Thornton JW, Cloutier JF, Özkan E. Molecular and structural basis of olfactory sensory neuron axon coalescence by Kirrel receptors. Cell Rep 2021; 37:109940. [PMID: 34731636 PMCID: PMC8628261 DOI: 10.1016/j.celrep.2021.109940] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 07/30/2021] [Accepted: 10/13/2021] [Indexed: 01/21/2023] Open
Abstract
Projections from sensory neurons of olfactory systems coalesce into glomeruli in the brain. The Kirrel receptors are believed to homodimerize via their ectodomains and help separate sensory neuron axons into Kirrel2- or Kirrel3-expressing glomeruli. Here, we present the crystal structures of homodimeric Kirrel receptors and show that the closely related Kirrel2 and Kirrel3 have evolved specific sets of polar and hydrophobic interactions, respectively, disallowing heterodimerization while preserving homodimerization, likely resulting in proper segregation and coalescence of Kirrel-expressing axons into glomeruli. We show that the dimerization interface at the N-terminal immunoglobulin (IG) domains is necessary and sufficient to create homodimers and fail to find evidence for a secondary interaction site in Kirrel ectodomains. Furthermore, we show that abolishing dimerization of Kirrel3 in vivo leads to improper formation of glomeruli in the mouse accessory olfactory bulb as observed in Kirrel3-/- animals. Our results provide evidence for Kirrel3 homodimerization controlling axonal coalescence.
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Affiliation(s)
- Jing Wang
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Neelima Vaddadi
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada
| | - Joseph S Pak
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Yeonwoo Park
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Sabrina Quilez
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada
| | - Christina A Roman
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Emilie Dumontier
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Joseph W Thornton
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL 60637, USA; Department of Human Genetics, The University of Chicago, Chicago, IL 60637, USA; Department of Ecology and Evolution, The University of Chicago, Chicago, IL 60637, USA
| | - Jean-François Cloutier
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada; Department of Anatomy and Cell Biology, McGill University, Montréal, QC H3A 0C7, Canada.
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA.
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6
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Heiden S, Siwek R, Lotz ML, Borkowsky S, Schröter R, Nedvetsky P, Rohlmann A, Missler M, Krahn MP. Apical-basal polarity regulators are essential for slit diaphragm assembly and endocytosis in Drosophila nephrocytes. Cell Mol Life Sci 2021; 78:3657-3672. [PMID: 33651172 PMCID: PMC8038974 DOI: 10.1007/s00018-021-03769-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 01/11/2021] [Accepted: 01/16/2021] [Indexed: 12/02/2022]
Abstract
Apical-basal polarity is a key feature of most epithelial cells and it is regulated by highly conserved protein complexes. In mammalian podocytes, which emerge from columnar epithelial cells, this polarity is preserved and the tight junctions are converted to the slit diaphragms, establishing the filtration barrier. In Drosophila, nephrocytes show several structural and functional similarities with mammalian podocytes and proximal tubular cells. However, in contrast to podocytes, little is known about the role of apical-basal polarity regulators in these cells. In this study, we used expansion microscopy and found the apical polarity determinants of the PAR/aPKC and Crb-complexes to be predominantly targeted to the cell cortex in proximity to the nephrocyte diaphragm, whereas basolateral regulators also accumulate intracellularly. Knockdown of PAR-complex proteins results in severe endocytosis and nephrocyte diaphragm defects, which is due to impaired aPKC recruitment to the plasma membrane. Similar, downregulation of most basolateral polarity regulators disrupts Nephrin localization but had surprisingly divergent effects on endocytosis. Our findings suggest that morphology and slit diaphragm assembly/maintenance of nephrocytes is regulated by classical apical-basal polarity regulators, which have distinct functions in endocytosis.
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Affiliation(s)
- Stefanie Heiden
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149, Münster, Germany
| | - Rebecca Siwek
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149, Münster, Germany
| | - Marie-Luise Lotz
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149, Münster, Germany
| | - Sarah Borkowsky
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149, Münster, Germany
| | - Rita Schröter
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149, Münster, Germany
| | - Pavel Nedvetsky
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149, Münster, Germany
| | - Astrid Rohlmann
- Institute of Anatomy and Molecular Neurobiology, University of Münster, Vesaliusweg 2-4, 48149, Münster, Germany
| | - Markus Missler
- Institute of Anatomy and Molecular Neurobiology, University of Münster, Vesaliusweg 2-4, 48149, Münster, Germany
| | - Michael P Krahn
- Medical Cell Biology, Medical Clinic D, University Hospital of Münster, Albert-Schweitzer Campus 1-A14, 48149, Münster, Germany.
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Yamada H, Shirata N, Makino S, Miyake T, Trejo JAO, Yamamoto-Nonaka K, Kikyo M, Empitu MA, Kadariswantiningsih IN, Kimura M, Ichimura K, Yokoi H, Mukoyama M, Hotta A, Nishimori K, Yanagita M, Asanuma K. MAGI-2 orchestrates the localization of backbone proteins in the slit diaphragm of podocytes. Kidney Int 2020; 99:382-395. [PMID: 33144214 DOI: 10.1016/j.kint.2020.09.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 08/22/2020] [Accepted: 09/10/2020] [Indexed: 01/19/2023]
Abstract
Podocytes are highly specialized cells within the glomerulus that are essential for ultrafiltration. The slit diaphragm between the foot processes of podocytes functions as a final filtration barrier to prevent serum protein leakage into urine. The slit-diaphragm consists mainly of Nephrin and Neph1, and localization of these backbone proteins is essential to maintaining the integrity of the glomerular filtration barrier. However, the mechanisms that regulate the localization of these backbone proteins have remained elusive. Here, we focused on the role of membrane-associated guanylate kinase inverted 2 (MAGI-2) in order to investigate mechanisms that orchestrate localization of slit-diaphragm backbone proteins. MAGI-2 downregulation coincided with a reduced expression of slit-diaphragm backbone proteins in human kidneys glomerular disease such as focal segmental glomerulosclerosis or IgA nephropathy. Podocyte-specific deficiency of MAGI-2 in mice abrogated localization of Nephrin and Neph1 independently of other scaffold proteins. Although a deficiency of zonula occuldens-1 downregulated the endogenous Neph1 expression, MAGI-2 recovered Neph1 expression at the cellular edge in cultured podocytes. Additionally, overexpression of MAGI-2 preserved Nephrin localization to intercellular junctions. Co-immunoprecipitation and pull-down assays also revealed the importance of the PDZ domains of MAGI-2 for the interaction between MAGI-2 and slit diaphragm backbone proteins in podocytes. Thus, localization and stabilization of Nephrin and Neph1 in intercellular junctions is regulated mainly via the PDZ domains of MAGI-2 together with other slit-diaphragm scaffold proteins. Hence, these findings may elucidate a mechanism by which the backbone proteins are maintained.
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Affiliation(s)
- Hiroyuki Yamada
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan; Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Naritoshi Shirata
- Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Sohyaku, Innovative Research Division, Mitsubishi Tanabe Pharmaceutical Corporation, Saitama, Japan
| | - Shinichi Makino
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan; Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takafumi Miyake
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | | | - Kanae Yamamoto-Nonaka
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Mitsuhiro Kikyo
- Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Sohyaku, Innovative Research Division, Mitsubishi Tanabe Pharmaceutical Corporation, Saitama, Japan
| | - Maulana A Empitu
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | | | - Maiko Kimura
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Koichiro Ichimura
- Department of Anatomy and Life Structure, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Hideki Yokoi
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Masashi Mukoyama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Akitsu Hotta
- Department of Reprogramming Science, Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto, Japan
| | - Katsuhiko Nishimori
- Department of Obesity and Inflammation Research, Fukushima Medical University, Fukushima, Japan
| | - Motoko Yanagita
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, Japan
| | - Katsuhiko Asanuma
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
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8
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Blaine J, Dylewski J. Regulation of the Actin Cytoskeleton in Podocytes. Cells 2020; 9:cells9071700. [PMID: 32708597 PMCID: PMC7408282 DOI: 10.3390/cells9071700] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 06/30/2020] [Accepted: 07/07/2020] [Indexed: 12/13/2022] Open
Abstract
Podocytes are an integral part of the glomerular filtration barrier, a structure that prevents filtration of large proteins and macromolecules into the urine. Podocyte function is dependent on actin cytoskeleton regulation within the foot processes, structures that link podocytes to the glomerular basement membrane. Actin cytoskeleton dynamics in podocyte foot processes are complex and regulated by multiple proteins and other factors. There are two key signal integration and structural hubs within foot processes that regulate the actin cytoskeleton: the slit diaphragm and focal adhesions. Both modulate actin filament extension as well as foot process mobility. No matter what the initial cause, the final common pathway of podocyte damage is dysregulation of the actin cytoskeleton leading to foot process retraction and proteinuria. Disruption of the actin cytoskeleton can be due to acquired causes or to genetic mutations in key actin regulatory and signaling proteins. Here, we describe the major structural and signaling components that regulate the actin cytoskeleton in podocytes as well as acquired and genetic causes of actin dysregulation.
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Affiliation(s)
- Judith Blaine
- Renal Division, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA;
| | - James Dylewski
- Renal Division, University of Colorado Anschutz Medical Campus and Denver Health Medical Center, Aurora, CO 80045, USA
- Correspondence: ; Tel.: +303-724-4841
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9
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Kirrel3-Mediated Synapse Formation Is Attenuated by Disease-Associated Missense Variants. J Neurosci 2020; 40:5376-5388. [PMID: 32503885 DOI: 10.1523/jneurosci.3058-19.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 05/24/2020] [Accepted: 05/26/2020] [Indexed: 12/12/2022] Open
Abstract
Missense variants in Kirrel3 are repeatedly identified as risk factors for autism spectrum disorder and intellectual disability, but it has not been reported if or how these variants disrupt Kirrel3 function. Previously, we studied Kirrel3 loss of function using KO mice and showed that Kirrel3 is a synaptic adhesion molecule necessary to form one specific type of hippocampal synapse in vivo Here, we developed an in vitro, gain-of-function assay for Kirrel3 using neuron cultures prepared from male and female mice and rats. We find that WT Kirrel3 induces synapse formation selectively between Kirrel3-expressing neurons via homophilic, transcellular binding. We tested six disease-associated Kirrel3 missense variants and found that five attenuate this synaptogenic function. All variants tested traffic to the cell surface and localize to synapses similar to WT Kirrel3. Two tested variants lack homophilic transcellular binding, which likely accounts for their reduced synaptogenic function. Interestingly, we also identified variants that bind in trans but cannot induce synapses, indicating that Kirrel3 transcellular binding is necessary but not sufficient for its synaptogenic function. Collectively, these results suggest Kirrel3 functions as a synaptogenic, cell-recognition molecule, and this function is attenuated by missense variants associated with autism spectrum disorder and intellectual disability. Thus, we provide critical insight to the mechanism of Kirrel3 function and the consequences of missense variants associated with autism and intellectual disability.SIGNIFICANCE STATEMENT Here, we advance our understanding of mechanisms mediating target-specific synapse formation by providing evidence that Kirrel3 transcellular interactions mediate target recognition and signaling to promote synapse development. Moreover, this study tests the effects of disease-associated Kirrel3 missense variants on synapse formation, and thereby, increases understanding of the complex etiology of neurodevelopmental disorders arising from rare missense variants in synaptic genes.
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10
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Kawachi H, Fukusumi Y. New insight into podocyte slit diaphragm, a therapeutic target of proteinuria. Clin Exp Nephrol 2020; 24:193-204. [PMID: 32020343 PMCID: PMC7040068 DOI: 10.1007/s10157-020-01854-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 01/15/2020] [Indexed: 12/26/2022]
Abstract
Dysfunction of slit diaphragm, a cell–cell junction of glomerular podocytes, is involved in the development of proteinuria in several glomerular diseases. Slit diaphragm should be a target of a novel therapy for proteinuria. Nephrin, NEPH1, P-cadherin, FAT, and ephrin-B1 were reported to be extracellular components forming a molecular sieve of the slit diaphragm. Several cytoplasmic proteins such as ZO-1, podocin, CD2AP, MAGI proteins and Par-complex molecules were identified as scaffold proteins linking the slit diaphragm to the cytoskeleton. In this article, new insights into these molecules and the pathogenic roles of the dysfunction of these molecules were introduced. The slit diaphragm functions not only as a barrier but also as a signaling platform transfer the signal to the inside of the cell. For maintaining the slit diaphragm function properly, the phosphorylation level of nephrin is strictly regulated. The recent studies on the signaling pathway from nephrin, NEPH1, and ephrin-B1 were reviewed. Although the mechanism regulating the function of the slit diaphragm had remained unclear, recent studies revealed TRPC6 and angiotensin II-regulating mechanisms play a critical role in regulating the barrier function of the slit diaphragm. In this review, recent investigations on the regulation of the slit diaphragm function were reviewed, and a strategy for the establishment of a novel therapy for proteinuria was proposed.
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Affiliation(s)
- Hiroshi Kawachi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan.
| | - Yoshiyasu Fukusumi
- Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata, 951-8510, Japan
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11
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Empitu MA, Kadariswantiningsih IN, Aizawa M, Asanuma K. MAGI-2 and scaffold proteins in glomerulopathy. Am J Physiol Renal Physiol 2018; 315:F1336-F1344. [PMID: 30110567 DOI: 10.1152/ajprenal.00292.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In many cells and tissues, including the glomerular filtration barrier, scaffold proteins are critical in optimizing signal transduction by enhancing structural stability and functionality of their ligands. Recently, mutations in scaffold protein membrane-associated guanylate kinase inverted 2 (MAGI-2) encoding gene were identified among the etiology of steroid-resistant nephrotic syndrome. MAGI-2 interacts with core proteins of multiple pathways, such as transforming growth factor-β signaling, planar cell polarity pathway, and Wnt/β-catenin signaling in podocyte and slit diaphragm. Through the interaction with its ligand, MAGI-2 modulates the regulation of apoptosis, cytoskeletal reorganization, and glomerular development. This review aims to summarize recent findings on the role of MAGI-2 and some other scaffold proteins, such as nephrin and synaptopodin, in the underlying mechanisms of glomerulopathy.
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Affiliation(s)
- Maulana A Empitu
- Department of Nephrology, Graduate School of Medicine, Chiba University , Chiba , Japan.,Department of Pharmacology and Therapeutics, Faculty of Medicine, Universitas Airlangga , Surabaya , Indonesia
| | - Ika N Kadariswantiningsih
- Department of Nephrology, Graduate School of Medicine, Chiba University , Chiba , Japan.,Department of Medical Microbiology, Faculty of Medicine, Universitas Airlangga , Surabaya , Indonesia
| | - Masashi Aizawa
- Department of Nephrology, Graduate School of Medicine, Chiba University , Chiba , Japan
| | - Katsuhiko Asanuma
- Department of Nephrology, Graduate School of Medicine, Chiba University , Chiba , Japan
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12
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Itoh M, Nakadate K, Matsusaka T, Hunziker W, Sugimoto H. Effects of the differential expression of ZO-1 and ZO-2 on podocyte structure and function. Genes Cells 2018; 23:546-556. [DOI: 10.1111/gtc.12598] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 04/27/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Masahiko Itoh
- Department of Biochemistry; School of Medicine; Dokkyo Medical University; Mibu-machi Japan
| | - Kazuhiko Nakadate
- Department of Basic Biology, Educational and Research Center for Pharmacy; Meiji Pharmaceutical University; Tokyo Japan
| | - Taiji Matsusaka
- Department of Molecular Life Sciences; Tokai University School of Medicine; Isehara Japan
| | - Walter Hunziker
- Epithelial Cell Biology Laboratory; Institute of Molecular and Cell Biology (IMCB); Singapore Singapore
| | - Hiroyuki Sugimoto
- Department of Biochemistry; School of Medicine; Dokkyo Medical University; Mibu-machi Japan
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13
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Zhang MJ, Hong YY, Li N. Overexpression of Kin of IRRE-Like Protein 1 (KIRREL) in Gastric Cancer and Its Clinical Prognostic Significance. Med Sci Monit 2018; 24:2711-2719. [PMID: 29717104 PMCID: PMC5952805 DOI: 10.12659/msm.910386] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Background The aim of this study was to examine the expression level of IRRE-like protein 1 (KIRREL) in gastric cancer (GC) and to explore its prognostic significance. Material/Methods Bioinformatics methods were used to predict the differential expression levels of KIRREL mRNA in GC and normal gastric tissues by mining cancer-related databases (TCGA and Oncomine). Immunohistochemistry was done to verify the KIRREL protein expression levels in 71 cases of GC tissues combined with matched normal tissues. The relationship between clinicopathologic parameters and KIRREL differential expression levels in GC was investigated by the chi-square test. Kaplan-Meier univariate and Cox multivariate survival analyses were performed to explore the prognostic significance of KIRREL expression in GC patients. Results TCGA and GEO data analyses showed that KIRREL mRNA expression level was remarkably higher in GC than that in normal gastric tissues (both P<0.05). KIRREL mRNA levels were dramatically increased from stage I to stage IV (P=0.037). Immunohistochemical results showed that the high positive rate of KIRREL staining in GC was 61.97% (44/71). Moreover, GC patients with KIRREL mRNA or protein high levels had significantly shorter overall survival times than those with KIRREL mRNA or low protein levels (All P<0.05). Additionally, Cox multivariate survival analysis revealed that KIRREL differential expression levels (low vs. high) were the only independent parameter predicting the prognosis of GC patients (P=0.000). Conclusions KIRREL was overexpressed in GC and the overexpression of KIRREL could serve as an independent predictor of poor prognosis in GC patients.
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Affiliation(s)
- Ming-Jun Zhang
- Department of Oncology, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China (mainland)
| | - Yan-Yan Hong
- Department of Oncology, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China (mainland)
| | - Na Li
- Department of Oncology, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China (mainland)
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14
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Hochapfel F, Denk L, Mendl G, Schulze U, Maaßen C, Zaytseva Y, Pavenstädt H, Weide T, Rachel R, Witzgall R, Krahn MP. Distinct functions of Crumbs regulating slit diaphragms and endocytosis in Drosophila nephrocytes. Cell Mol Life Sci 2017; 74:4573-4586. [PMID: 28717874 PMCID: PMC11107785 DOI: 10.1007/s00018-017-2593-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 06/26/2017] [Accepted: 07/13/2017] [Indexed: 10/19/2022]
Abstract
Mammalian podocytes, the key determinants of the kidney's filtration barrier, differentiate from columnar epithelial cells and several key determinants of apical-basal polarity in the conventional epithelia have been shown to regulate podocyte morphogenesis and function. However, little is known about the role of Crumbs, a conserved polarity regulator in many epithelia, for slit-diaphragm formation and podocyte function. In this study, we used Drosophila nephrocytes as model system for mammalian podocytes and identified a conserved function of Crumbs proteins for cellular morphogenesis, nephrocyte diaphragm assembly/maintenance, and endocytosis. Nephrocyte-specific knock-down of Crumbs results in disturbed nephrocyte diaphragm assembly/maintenance and decreased endocytosis, which can be rescued by Drosophila Crumbs as well as human Crumbs2 and Crumbs3, which were both expressed in human podocytes. In contrast to the extracellular domain, which facilitates nephrocyte diaphragm assembly/maintenance, the intracellular FERM-interaction motif of Crumbs is essential for regulating endocytosis. Moreover, Moesin, which binds to the FERM-binding domain of Crumbs, is essential for efficient endocytosis. Thus, we describe here a new mechanism of nephrocyte development and function, which is likely to be conserved in mammalian podocytes.
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Affiliation(s)
- Florian Hochapfel
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Domagkstr. 3a, 48149, Münster, Germany
| | - Lucia Denk
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Gudrun Mendl
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Ulf Schulze
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Domagkstr. 3a, 48149, Münster, Germany
| | - Christine Maaßen
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Yulia Zaytseva
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Hermann Pavenstädt
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Domagkstr. 3a, 48149, Münster, Germany
| | - Thomas Weide
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Domagkstr. 3a, 48149, Münster, Germany
| | - Reinhard Rachel
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Ralph Witzgall
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
| | - Michael P Krahn
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany.
- Medizinische Klinik und Poliklinik D, Universitätsklinikum Münster, Domagkstr. 3a, 48149, Münster, Germany.
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15
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Coyral-Castel S, Ramé C, Cognié J, Lecardonnel J, Marthey S, Esquerré D, Hennequet-Antier C, Elis S, Fritz S, Boussaha M, Jaffrézic F, Dupont J. KIRREL is differentially expressed in adipose tissue from 'fertil+' and 'fertil-' cows: in vitro role in ovary? Reproduction 2017; 155:183-198. [PMID: 29170164 DOI: 10.1530/rep-17-0649] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 11/18/2017] [Accepted: 11/23/2017] [Indexed: 01/10/2023]
Abstract
We have previously shown that dairy cows carrying the 'fertil-' haplotype for one quantitative trait locus affecting female fertility located on the bovine chromosome three (QTL-F-Fert-BTA3) have a significantly lower conception rate and body weight after calving than cows carrying the 'fertil+' haplotype. Here, we compared by Tiling Array the expression of genes included in the QTL-F-Fert-BTA3 in 'fertil+' and 'fertil-' adipose tissue one week after calving when plasma non-esterified fatty acid concentrations were greater in 'fertil-' animals. We observed that thirty-one genes were overexpressed whereas twelve were under-expressed in 'fertil+' as compared to 'fertil-' cows (P < 0.05). By quantitative PCR and immunoblot we confirmed that adipose tissue KIRREL mRNA and protein were significantly greater expressed in 'fertil+' than in 'fertil-'. KIRREL mRNA is abundant in bovine kidney, adipose tissue, pituitary, and ovary and detectable in hypothalamus and mammary gland. Its expression (mRNA and protein) is greater in kidney of 'fertil+' than 'fertil-' cows (P < 0.05). KIRREL (mRNA and protein) is also present in the different ovarian cells with a greater expression in granulosa cells of 'fertil+' than 'fertil-' cows. In cultured granulosa cells, recombinant KIRREL halved steroid secretion in basal state (P < 0.05). It also decreased cell proliferation (P < 0.05) and in vitro oocyte maturation (P < 0.05). These results were associated to a rapid increase in MAPK1/3 and MAPK14 phosphorylation in granulosa cells and to a decrease in MAPK1/3 phosphorylation in oocyte. Thus, KIRREL could be a potential metabolic messenger linking body composition and fertility.
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Affiliation(s)
- S Coyral-Castel
- INRAUMR85 Physiologie de la Reproduction et des Comportements, Nouzilly, France.,CNRSUMR7247, Nouzilly, France.,Université François Rabelais de ToursTours, France.,IFCENouzilly, France.,Département GIPSIEInstitut de l'Elevage, Paris Cedex 12, France
| | - C Ramé
- INRAUMR85 Physiologie de la Reproduction et des Comportements, Nouzilly, France.,CNRSUMR7247, Nouzilly, France.,Université François Rabelais de ToursTours, France.,IFCENouzilly, France
| | - J Cognié
- INRAUMR85 Physiologie de la Reproduction et des Comportements, Nouzilly, France.,CNRSUMR7247, Nouzilly, France.,Université François Rabelais de ToursTours, France.,IFCENouzilly, France
| | - J Lecardonnel
- INRAUMR1313, Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France.,AgroParisTechUMR1313 Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France
| | - S Marthey
- INRAUMR1313, Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France.,AgroParisTechUMR1313 Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France
| | - D Esquerré
- INRAUMR1313, Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France.,AgroParisTechUMR1313 Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France
| | | | - S Elis
- INRAUMR85 Physiologie de la Reproduction et des Comportements, Nouzilly, France.,CNRSUMR7247, Nouzilly, France.,Université François Rabelais de ToursTours, France.,IFCENouzilly, France
| | - S Fritz
- ALLICEParis Cedex 12, France
| | - M Boussaha
- INRAUMR1313, Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France.,AgroParisTechUMR1313 Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France
| | - F Jaffrézic
- INRAUMR1313, Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France.,AgroParisTechUMR1313 Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France
| | - J Dupont
- INRAUMR85 Physiologie de la Reproduction et des Comportements, Nouzilly, France .,CNRSUMR7247, Nouzilly, France.,Université François Rabelais de ToursTours, France.,IFCENouzilly, France
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16
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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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17
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Swiatecka-Urban A. Endocytic Trafficking at the Mature Podocyte Slit Diaphragm. Front Pediatr 2017; 5:32. [PMID: 28286744 PMCID: PMC5324021 DOI: 10.3389/fped.2017.00032] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 02/03/2017] [Indexed: 12/16/2022] Open
Abstract
Endocytic trafficking couples cell signaling with the cytoskeletal dynamics by organizing a crosstalk between protein networks in different subcellular compartments. Proteins residing in the plasma membrane are internalized and transported as cargo in endocytic vesicles (i.e., endocytosis). Subsequently, cargo proteins can be delivered to lysosomes for degradation or recycled back to the plasma membrane. The slit diaphragm is a modified tight junction connecting foot processes of the glomerular epithelial cells, podocytes. Signaling at the slit diaphragm plays a critical role in the kidney while its dysfunction leads to glomerular protein loss (proteinuria), manifesting as nephrotic syndrome, a rare condition with an estimated incidence of 2-4 new cases per 100,000 each year. Relatively little is known about the role of endocytic trafficking in podocyte signaling and maintenance of the slit diaphragm integrity. This review will focus on the role of endocytic trafficking at the mature podocyte slit diaphragm.
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Affiliation(s)
- Agnieszka Swiatecka-Urban
- Department of Nephrology, Children's Hospital of Pittsburgh, Pittsburgh, PA, USA; Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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18
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Wakamatsu A, Fukusumi Y, Hasegawa E, Tomita M, Watanabe T, Narita I, Kawachi H. Role of calcineurin (CN) in kidney glomerular podocyte: CN inhibitor ameliorated proteinuria by inhibiting the redistribution of CN at the slit diaphragm. Physiol Rep 2016; 4:4/6/e12679. [PMID: 27009276 PMCID: PMC4814882 DOI: 10.14814/phy2.12679] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/14/2015] [Indexed: 12/21/2022] Open
Abstract
Although calcineurin (CN) is distributed in many cell types and functions in regulating cell functions, the precise roles of CN remained in each type of the cells are not well understood yet. A CN inhibitor (CNI) has been used for steroid‐resistant nephrotic syndrome. A CNI is assumed to ameliorate proteinuria by preventing the overproduction of T‐cell cytokines. However, recent reports suggest that CNI has a direct effect on podocyte. It is accepted that a slit diaphragm (SD), a unique cell–cell junction of podocytes, is a critical barrier preventing a leak of plasma protein into urine. Therefore, we hypothesized that CNI has an effect on the SD. In this study, we analyzed the expression of CN in physiological and in the nephrotic model caused by the antibody against nephrin, a critical component of the SD. We observed that CN is expressed at the SD in normal rat and human kidney sections and has an interaction with nephrin. The staining of CN at the SD was reduced in the nephrotic model, while CN activity in glomeruli was increased. We also observed that the treatment with tacrolimus, a CNI, in this nephrotic model suppressed the redistribution of CN, nephrin, and other SD components and ameliorated proteinuria. These observations suggested that the redistribution and the activation of CN may participate in the development of the SD injury.
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Affiliation(s)
- Ayako Wakamatsu
- Department of Cell Biology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Yoshiyasu Fukusumi
- Department of Cell Biology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Eriko Hasegawa
- Department of Cell Biology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Masayuki Tomita
- Department of Cell Biology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Toru Watanabe
- Department of Pediatrics, Niigata City General Hospital, Niigata, Japan
| | - Ichiei Narita
- Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Hiroshi Kawachi
- Department of Cell Biology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
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19
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Structural Analysis of the Myo1c and Neph1 Complex Provides Insight into the Intracellular Movement of Neph1. Mol Cell Biol 2016; 36:1639-54. [PMID: 27044863 DOI: 10.1128/mcb.00020-16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 03/21/2016] [Indexed: 11/20/2022] Open
Abstract
The Myo1c motor functions as a cargo transporter supporting various cellular events, including vesicular trafficking, cell migration, and stereociliary movements of hair cells. Although its partial crystal structures were recently described, the structural details of its interaction with cargo proteins remain unknown. This study presents the first structural demonstration of a cargo protein, Neph1, attached to Myo1c, providing novel insights into the role of Myo1c in intracellular movements of this critical slit diaphragm protein. Using small angle X-ray scattering studies, models of predominant solution conformation of unliganded full-length Myo1c and Myo1c bound to Neph1 were constructed. The resulting structures show an extended S-shaped Myo1c with Neph1 attached to its C-terminal tail. Importantly, binding of Neph1 did not induce a significant shape change in Myo1c, indicating this as a spontaneous process or event. Analysis of interaction surfaces led to the identification of a critical residue in Neph1 involved in binding to Myo1c. Indeed, a point mutant from this site abolished interaction between Neph1 and Myo1c when tested in the in vitro and in live-cell binding assays. Live-cell imaging, including fluorescence recovery after photobleaching, provided further support for the role of Myo1c in intracellular vesicular movement of Neph1 and its turnover at the membrane.
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20
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SV2B is essential for the integrity of the glomerular filtration barrier. J Transl Med 2015; 95:534-45. [PMID: 25730372 DOI: 10.1038/labinvest.2015.39] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/12/2014] [Accepted: 12/17/2014] [Indexed: 11/09/2022] Open
Abstract
The glomerular visceral epithelial cell (podocyte) is characterized as a specialized structure of the interdigitating foot processes, covering the outer side of the glomerular basement membrane (GBM). The neighboring foot processes are connected by a slit diaphragm, which is a key structure regulating the barrier function of the glomerular capillary wall to prevent proteinuria. We have previously reported that synaptic vesicle protein 2 B (SV2B) is expressed in the podocyte and that the expression is clearly decreased in nephrotic models. However, the precise function of SV2B in the podocyte is unclear. To investigate the role of SV2B in maintaining the podocyte function and to better understand the function of the neuron-like vesicle expressing SV2B in the podocyte, we analyzed them with SV2B knockout (KO) mice. An increase in the amount of proteinuria, effacement of the foot process of the podocyte, and alterations of the GBM were detected in SV2B KO mice. It was also found that the expression of CD2AP, nephrin, and NEPH1, the functional molecules of the slit diaphragm, and laminin, a critical component of the GBM, is clearly altered in SV2B KO mice. Synaptotagmin and neurexin, which have a role in the synaptic vesicle docking in neurons, are downregulated in the kidney cortex of SV2B KO mice. We have previously reported that neurexin interacts with CD2AP, and the present study shows that SV2B interacts with CD2AP. These findings suggest that the SV2B-neurexin complex is involved in the formation and maintenance of the slit diaphragm. In addition, SV2B is densely expressed close to the cell surface in the presumptive podocyte in the early stage of glomerulogenesis. These results suggest that SV2B has an essential role in the formation and maintenance of the glomerular capillary wall.
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21
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An update: the role of Nephrin inside and outside the kidney. SCIENCE CHINA-LIFE SCIENCES 2015; 58:649-57. [PMID: 25921941 DOI: 10.1007/s11427-015-4844-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 02/27/2015] [Indexed: 12/18/2022]
Abstract
Nephrin is a key molecule in podocytes to maintain normal slit diaphragm structure. Nephin interacts with many other podocyte and slit diaphragm protein and also mediates important cell signaling pathways in podocytes. Loss of nephrin during the development leads to the congenital nephrotic syndrome in children. Reduction of nephrin expression is often observed in adult kidney diseases including diabetic nephropathy and HIV-associated nephropathy. The critical role of nephrin has been confirmed by different animal models with nephrin knockout and knockdown. Recent studies demonstrate that knockdown of nephrin expression in adult mice aggravates the progression of unilateral nephrectomy and Adriamycin-induced kidney disease. In addition to its critical role in maintaining normal glomerular filtration unit in the kidney, nephrin is also expressed in other organs. However, the exact role of nephrin in kidney and extra-renal organs has not been well characterized. Future studies are required to determine whether nephrin could be developed as a drug target to treat patients with kidney disease.
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Hulkko J, Patrakka J, Lal M, Tryggvason K, Hultenby K, Wernerson A. Neph1 is reduced in primary focal segmental glomerulosclerosis, minimal change nephrotic syndrome, and corresponding experimental animal models of adriamycin-induced nephropathy and puromycin aminonucleoside nephrosis. NEPHRON EXTRA 2014; 4:146-54. [PMID: 25404935 PMCID: PMC4202611 DOI: 10.1159/000365091] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
BACKGROUND/AIMS The transmembrane proteins Neph1 and nephrin form a complex in the slit diaphragm (SD) of podocytes. As recent studies indicate an involvement of this complex in the polymerization of the actin cytoskeleton and proteinuria, we wanted to study the subcellular localization of Neph1 in the normal human kidney and its expression in focal segmental glomerulosclerosis (FSGS), minimal change nephrotic syndrome (MCNS), and the corresponding experimental models of Adriamycin-induced nephropathy (ADR) and puromycin aminonucleoside nephrosis (PAN). All these disorders are characterized by substantial foot process effacement (FPE) and proteinuria. MATERIALS AND METHODS Kidney biopsies from patients with primary FSGS (perihilar type) and MCNS were compared to normal renal tissue. Mouse and rat kidney cortices from days 7 and 14 after Adriamycin injection and days 2 and 4 after puromycin aminonucleoside injection, respectively, were compared to control mouse and rat kidney. Polyclonal antibodies against Neph1 and nephrin were used for immunoelectron microscopy, and semiquantification was performed. RESULTS We localized Neph1 mainly to, and in close proximity to, the SD. Double staining of Neph1 and nephrin showed the proteins to be in close connection in the SD. The total amount of Neph1 in the podocytes was significantly reduced in FSGS, MCNS, ADR, and PAN. The reduction of Neph1 was also seen in areas with and without FPE. Nephrin was reduced in MCNS and PAN but unchanged in FSGS. CONCLUSION With nephrin (but not Neph1) unchanged in FSGS, there might be a disruption of the complex and an involvement of Neph1 in its pathogenesis.
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Affiliation(s)
- Jenny Hulkko
- Department of Clinical Science, Intervention and Technology, Stockholm, Sweden
| | - Jaakko Patrakka
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Mark Lal
- Department of Medical Biochemistry and Biophysics, Stockholm, Sweden
| | - Karl Tryggvason
- Department of Medical Biochemistry and Biophysics, Stockholm, Sweden
| | - Kjell Hultenby
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Annika Wernerson
- Department of Clinical Science, Intervention and Technology, Stockholm, Sweden
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Costa MSA, Machado MCR, Vieceli FM, Amistá L, Baroneza JE, Yan CYI, Ramos RGP. The Rst-Neph family of cell adhesion molecules in Gallus gallus. J Neurogenet 2014; 28:270-81. [PMID: 24914768 DOI: 10.3109/01677063.2014.933220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The Rst-Neph family comprises an evolutionarily conserved group of single-pass transmembrane glycoproteins that belong to the immunoglobulin superfamily and participate in a wide range of cell adhesion and recognition events in both vertebrates and invertebrates. In mammals and fish, three Rst-Neph members, named Neph1-3, are present. Besides being widely expressed in the embryo, particularly in the developing nervous system, they also contribute to the formation and integrity of the urine filtration apparatus in the slit diaphragm of kidney glomerular podocytes, where they form homodimers, as well as heterodimers with Nephrin, another immunoglobulin-like cell adhesion molecule. In mice, absence of Neph1 causes severe proteinuria, podocyte effacement and perinatal death, while in humans, a mutated form of Nephrin leads to congenital nephrotic syndrome of the Finnish type. Intriguingly, neither Nephrin nor Neph3 are present in birds, which nevertheless have typical vertebrate kidneys with mammalian-like slit diaphragms. These characteristics make, in principle, avian systems very helpful for understanding the evolution and functional significance of the complex interactions displayed by Rst-Neph proteins. To this end we have started a systematic study of chicken Neph embryonic and post-embryonic expression, both at mRNA and protein level. RT-qPCR mRNA quantification of the two Neph paralogues in adult tissues showed that both are expressed in heart, brain, and retina. Neph1 is additionally present in kidney, liver, pancreas, lungs, and testicles, while Neph2 mRNA is barely detected in kidney, testicles, pancreas and absent in liver and lungs. In embryos, mRNA from both genes can already be detected at as early as stage HH14, and remain expressed until at least HH28. Finally, we used a specific antibody to examine the spatial dynamics and subcellular distribution of ggNeph2 between stages HH20-28, particularly in the mesonephros, dermomyotomes, developing heart, and retina.
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Affiliation(s)
- Mara Silvia A Costa
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo , Ribeirão Preto , Brazil
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Özkan E, Chia PH, Wang RR, Goriatcheva N, Borek D, Otwinowski Z, Walz T, Shen K, Garcia KC. Extracellular architecture of the SYG-1/SYG-2 adhesion complex instructs synaptogenesis. Cell 2014; 156:482-94. [PMID: 24485456 PMCID: PMC3962013 DOI: 10.1016/j.cell.2014.01.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 09/04/2013] [Accepted: 01/06/2014] [Indexed: 01/29/2023]
Abstract
SYG-1 and SYG-2 are multipurpose cell adhesion molecules (CAMs) that have evolved across all major animal taxa to participate in diverse physiological functions, ranging from synapse formation to formation of the kidney filtration barrier. In the crystal structures of several SYG-1 and SYG-2 orthologs and their complexes, we find that SYG-1 orthologs homodimerize through a common, bispecific interface that similarly mediates an unusual orthogonal docking geometry in the heterophilic SYG-1/SYG-2 complex. C. elegans SYG-1's specification of proper synapse formation in vivo closely correlates with the heterophilic complex affinity, which appears to be tuned for optimal function. Furthermore, replacement of the interacting domains of SYG-1 and SYG-2 with those from CAM complexes that assume alternative docking geometries or the introduction of segmental flexibility compromised synaptic function. These results suggest that SYG extracellular complexes do not simply act as "molecular velcro" and that their distinct structural features are important in instructing synaptogenesis. PAPERFLICK:
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Affiliation(s)
- Engin Özkan
- Department of Molecular and Cellular Physiology and Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Poh Hui Chia
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Ruiqi Rachel Wang
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Natalia Goriatcheva
- Department of Molecular and Cellular Physiology and Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Dominika Borek
- Departments of Biochemistry and Biophysics, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | - Zbyszek Otwinowski
- Departments of Biochemistry and Biophysics, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | - Thomas Walz
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Kang Shen
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - K Christopher Garcia
- Department of Molecular and Cellular Physiology and Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.
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25
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Arif E, Rathore YS, Kumari B, Ashish F, Wong HN, Holzman LB, Nihalani D. Slit diaphragm protein Neph1 and its signaling: a novel therapeutic target for protection of podocytes against glomerular injury. J Biol Chem 2014; 289:9502-18. [PMID: 24554715 DOI: 10.1074/jbc.m113.505743] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Podocytes are specialized epithelial cells that are critical components of the glomerular filtration barrier, and their dysfunction leads to proteinuria and renal failure. Therefore, preserving podocyte function is therapeutically significant. In this study, we identified Neph1 signaling as a therapeutic target that upon inhibition prevented podocyte damage from a glomerular injury-inducing agent puromycin aminonucleoside (PAN). To specifically inhibit Neph1 signaling, we used a protein transduction approach, where the cytoplasmic domain of Neph1 (Neph1CD) tagged with a protein transduction domain trans-activator of transcription was transduced in cultured podocytes prior to treatment with PAN. The PAN-induced Neph1 phosphorylation was significantly reduced in Neph1CD-transduced cells; in addition, these cells were resistant to PAN-induced cytoskeletal damage. The biochemical analysis using subfractionation studies showed that unlike control cells Neph1 was retained in the lipid raft fractions in the transduced cells following treatment with PAN, indicating that transduction of Neph1CD in podocytes prevented PAN-induced mislocalization of Neph1. In accordance, the immunofluorescence analysis further suggested that Neph1CD-transduced cells had increased ability to retain endogenous Neph1 at the membrane in response to PAN-induced injury. Similar results were obtained when angiotensin was used as an injury-inducing agent. Consistent with these observations, maintaining high levels of Neph1 at the membrane using a podocyte cell line overexpressing chimeric Neph1 increased the ability of podocytes to resist PAN-induced injury and PAN-induced albumin leakage. Using a zebrafish in vivo PAN and adriamycin injury models, we further demonstrated the ability of transduced Neph1CD to preserve glomerular function. Collectively, these results support the conclusion that inhibiting Neph1 signaling is therapeutically significant in preventing podocyte damage from glomerular injury.
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Affiliation(s)
- Ehtesham Arif
- From the Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
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26
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Functions of the podocyte proteins nephrin and Neph3 and the transcriptional regulation of their genes. Clin Sci (Lond) 2013; 126:315-28. [DOI: 10.1042/cs20130258] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Nephrin and Neph-family proteins [Neph1–3 (nephrin-like 1–3)] belong to the immunoglobulin superfamily of cell-adhesion receptors and are expressed in the glomerular podocytes. Both nephrin and Neph-family members function in cell adhesion and signalling, and thus regulate the structure and function of podocytes and maintain normal glomerular ultrafiltration. The expression of nephrin and Neph3 is altered in human proteinuric diseases emphasizing the importance of studying the transcriptional regulation of the nephrin and Neph3 genes NPHS1 (nephrosis 1, congenital, Finnish type) and KIRREL2 (kin of IRRE-like 2) respectively. The nephrin and Neph3 genes form a bidirectional gene pair, and they share transcriptional regulatory mechanisms. In the present review, we summarize the current knowledge of the functions of nephrin and Neph-family proteins and transcription factors and agents that control nephrin and Neph3 gene expression.
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27
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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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28
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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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29
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Xu J, Lim SBH, Ng MY, Ali SM, Kausalya JP, Limviphuvadh V, Maurer-Stroh S, Hunziker W. ZO-1 regulates Erk, Smad1/5/8, Smad2, and RhoA activities to modulate self-renewal and differentiation of mouse embryonic stem cells. Stem Cells 2013; 30:1885-900. [PMID: 22782886 DOI: 10.1002/stem.1172] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
ZO-1/Tjp1 is a cytosolic adaptor that links tight junction (TJ) transmembrane proteins to the actin cytoskeleton and has also been implicated in regulating cell proliferation and differentiation by interacting with transcriptional regulators and signaling proteins. To explore possible roles for ZO-1 in mouse embryonic stem cells (mESCs), we inactivated the ZO-1 locus by homologous recombination. The lack of ZO-1 was found to affect mESC self-renewal and differentiation in the presence of leukemia-inhibiting factor (LIF) and Bmp4 or following removal of the growth factors. Our data suggest that ZO-1 suppresses Stat3 and Smad1/5/8 activities and sustains extracellular-signal-regulated kinase (Erk) activity to promote mESC differentiation. Interestingly, Smad2, critical for human but not mESC self-renewal, was hyperactivated in ZO-1(-/-) mESCs and RhoA protein levels were concomitantly enhanced, suggesting attenuation of the noncanonical transforming growth factor β (Tgfβ)/Activin/Nodal pathway that mediates ubiquitination and degradation of RhoA via the TJ proteins Occludin, Par6, and Smurf1 and activation of the canonical Smad2-dependent pathway. Furthermore, Bmp4-induced differentiation of mESCs in the absence of LIF was suppressed in ZO-1(-/-) mESCs, but differentiation down the neural or cardiac lineages was not disturbed. These findings reveal novel roles for ZO-1 in mESC self-renewal, pluripotency, and differentiation by influencing several signaling networks that regulate these processes. Possible implications for the differing relevance of Smad2 in mESC and human ESC self-renewal and how ZO-1 may connect to the different pathways are discussed.
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Affiliation(s)
- Jianliang Xu
- Epithelial Cell Biology Laboratory, Institute of Molecular and Cell Biology, Singapore
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30
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Mallik L, Arif E, Sharma P, Rathore YS, Wong HN, Holzman LB, Ashish, Nihalani D. Solution structure analysis of cytoplasmic domain of podocyte protein Neph1 using small/wide angle x-ray scattering (SWAXS). J Biol Chem 2012; 287:9441-53. [PMID: 22262837 PMCID: PMC3308819 DOI: 10.1074/jbc.m111.284927] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 01/16/2012] [Indexed: 12/27/2022] Open
Abstract
Neph1 is present in podocytes, where it plays a critical role in maintaining the filtration function of the glomerulus, in part through signaling events mediated by its cytoplasmic domain that are involved in actin cytoskeleton organization. To understand the function of this protein, a detailed knowledge of the structure of the Neph1 cytoplasmic domain (Neph1-CD) is required. In this study, the solution structure of this domain was determined by small/wide angle x-ray scattering (SWAXS). Analysis of Neph1-CD by SWAXS suggested that this protein adopts a global shape with a radius of gyration and a maximum linear dimension of 21.3 and 70 Å, respectively. These parameters and the data from circular dichroism experiments were used to construct a structural model of this protein. The His-ZO-1-PDZ1 (first PDZ domain of zonula occludens) domain that binds Neph1-CD was also analyzed by SWAXS, to confirm that it adopts a global structure similar to its crystal structure. We used the SWAXS intensity profile, the structural model of Neph1-CD, and the crystal structure of ZO-1-PDZ1 to construct a structural model of the Neph1-CD·ZO-1-PDZ1 complex. Mapping of the intermolecular interactions suggested that in addition to the C-terminal residues Thr-His-Val, residues Lys-761 and Tyr-762 in Neph1 are also critical for stabilizing the complex. Estimated intensity values from the SWAXS data and in vivo and in vitro pull-down experiments demonstrated loss of binding to ZO-1 when these residues were individually mutated to alanines. Our findings present a structural model that provides novel insights into the molecular structure and function of Neph1-CD.
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Affiliation(s)
- Leena Mallik
- From the CSIR-Institute of Microbial Technology, Chandigarh 160036, India and
| | - Ehtesham Arif
- the Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Pankaj Sharma
- From the CSIR-Institute of Microbial Technology, Chandigarh 160036, India and
| | - Yogendra S. Rathore
- From the CSIR-Institute of Microbial Technology, Chandigarh 160036, India and
| | - Hetty N. Wong
- the Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Lawrence B. Holzman
- the Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Ashish
- From the CSIR-Institute of Microbial Technology, Chandigarh 160036, India and
| | - Deepak Nihalani
- the Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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31
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González-Mariscal L, Quirós M, Díaz-Coránguez M. ZO proteins and redox-dependent processes. Antioxid Redox Signal 2011; 15:1235-53. [PMID: 21294657 DOI: 10.1089/ars.2011.3913] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
SIGNIFICANCE ZO-1, ZO-2, and ZO-3 are scaffold proteins of the tight junction (TJ) that belong to the MAGUK protein family characterized for exhibiting PDZ, SH3, and GuK domains. ZO proteins are present only in multicellular organisms, being the placozoa the first to have them. ZO proteins associate among themselves and with other integral and adaptor proteins of the TJ, of the ZA and of gap junctions, as with numerous signaling proteins and the actin cytoskeleton. ZO proteins are also present at the nucleus of proliferating cells. RECENT ADVANCES Oxidative stress disassembles the TJs of endothelial and epithelial cells. CRITICAL ISSUES Oxidative stress alters ZO proteins expression and localization, in conditions like hypoxia, bacterial and viral infections, vitamin deficiencies, age-related diseases, diabetes and inflammation, alcohol and tobacco consumption. FUTURE DIRECTIONS Molecules present in the signaling pathways triggered by oxidative stress can be targets for therapeutic intervention.
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Affiliation(s)
- Lorenza González-Mariscal
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies (Cinvestav), Mexico DF, México.
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Relevance of VEGF and nephrin expression in glomerular diseases. JOURNAL OF SIGNAL TRANSDUCTION 2011; 2011:718609. [PMID: 21808734 PMCID: PMC3144718 DOI: 10.1155/2011/718609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 05/25/2011] [Indexed: 12/23/2022]
Abstract
The glomerular filtration barrier is affected in a large number of acquired and inherited diseases resulting in extensive leakage of plasma albumin and larger proteins, leading to nephrotic syndrome and end-stage renal disease. Unfortunately, the molecular mechanisms governing the development of the nephrotic syndrome remain poorly understood. Here, I give an overview of recent investigations that have focused on characterizing the interrelationships between the slit diaphragm components and podocytes-secreted VEGF, which have a significant role for maintaining the normal podocyte structure and the integrity of the filtering barrier.
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The BAR domain protein PICK1 regulates cell recognition and morphogenesis by interacting with Neph proteins. Mol Cell Biol 2011; 31:3241-51. [PMID: 21690291 DOI: 10.1128/mcb.05286-11] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neph proteins are evolutionarily conserved membrane proteins of the immunoglobulin superfamily that control the formation of specific intercellular contacts. Cell recognition through these proteins is essential in diverse cellular contexts such as patterning of the compound eye in Drosophila melanogaster, neuronal connectivity in Caenorhabditis elegans, and the formation of the kidney filtration barrier in mammals. Here we identify the PDZ and BAR domain protein PICK1 (protein interacting with C-kinase 1) as a Neph-interacting protein. Binding required dimerization of PICK1, was dependent on PDZ domain protein interactions, and mediated stabilization of Neph1 at the plasma membrane. Moreover, protein kinase C (PKCα) activity facilitated the interaction through releasing Neph proteins from their binding to the multidomain scaffolding protein zonula occludens 1 (ZO-1), another PDZ domain protein. In Drosophila, the Neph homologue Roughest is essential for sorting of interommatidial precursor cells and patterning of the compound eye. RNA interference-mediated knockdown of PICK1 in the Drosophila eye imaginal disc caused a Roughest destabilization at the plasma membrane and a phenotype that resembled rst mutation. These data indicate that Neph proteins and PICK1 synergistically regulate cell recognition and contact formation.
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Tyrosine kinase signaling in kidney glomerular podocytes. JOURNAL OF SIGNAL TRANSDUCTION 2011; 2011:317852. [PMID: 21776384 PMCID: PMC3135133 DOI: 10.1155/2011/317852] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 03/17/2011] [Accepted: 03/30/2011] [Indexed: 01/27/2023]
Abstract
During the last decade, several key molecules have been identified as essential components for the filtration barrier function of kidney glomerular podocytes. Mutations in genes encoding these molecules severely impair the podocyte architecture in the affected patients, leading to the development of proteinuria. Extensive investigations have been performed on the function of these molecules, which highlights the importance of tyrosine kinase signaling in the podocytes. An Src family tyrosine kinase, Fyn, plays a major role in this signaling pathway. Here, we review the current understanding of this important signal transduction system and its role in the development and the maintenance of podocytes.
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Motor protein Myo1c is a podocyte protein that facilitates the transport of slit diaphragm protein Neph1 to the podocyte membrane. Mol Cell Biol 2011; 31:2134-50. [PMID: 21402783 DOI: 10.1128/mcb.05051-11] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The podocyte proteins Neph1 and nephrin organize a signaling complex at the podocyte cell membrane that forms the structural framework for a functional glomerular filtration barrier. Mechanisms regulating the movement of these proteins to and from the membrane are currently unknown. This study identifies a novel interaction between Neph1 and the motor protein Myo1c, where Myo1c plays an active role in targeting Neph1 to the podocyte cell membrane. Using in vivo and in vitro experiments, we provide data supporting a direct interaction between Neph1 and Myo1c which is dynamic and actin dependent. Unlike wild-type Myo1c, the membrane localization of Neph1 was significantly reduced in podocytes expressing dominant negative Myo1c. In addition, Neph1 failed to localize at the podocyte cell membrane and cell junctions in Myo1c-depleted podocytes. We further demonstrate that similarly to Neph1, Myo1c also binds nephrin and reduces its localization at the podocyte cell membrane. A functional analysis of Myo1c knockdown cells showed defects in cell migration, as determined by a wound assay. In addition, the ability to form tight junctions was impaired in Myo1c knockdown cells, as determined by transepithelial electric resistance (TER) and bovine serum albumin (BSA) permeability assays. These results identify a novel Myo1c-dependent molecular mechanism that mediates the dynamic organization of Neph1 and nephrin at the slit diaphragm and is critical for podocyte function.
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Kurihara H, Harita Y, Ichimura K, Hattori S, Sakai T. SIRP-alpha-CD47 system functions as an intercellular signal in the renal glomerulus. Am J Physiol Renal Physiol 2010; 299:F517-27. [PMID: 20554646 DOI: 10.1152/ajprenal.00571.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The renal glomerulus consists of endothelial cells, podocytes, and mesangial cells. These cells cooperate with each other for glomerular filtration; however, the intercellular signaling molecules between glomerular cells are not fully determined. Tyrosine phosphorylation of slit diaphragm molecules is a key to the detection of the signal to podocytes from other cells. Although src kinase is involved in this event, the molecules working for dephosphorylation remain unclear. We demonstrate that signal-inhibitory regulatory protein (SIRP)-alpha, which recruits a broadly distributed tyrosine dephosphorylase SHP-2 to the plasma membrane, is located in podocytes. SIRP-alpha is a type I transmembrane glycoprotein, which has three immunoglobulin-like domains in the extracellular region and two SH2 binding motifs in the cytoplasm. This molecule functions as a scaffold for many proteins, especially the SHP-2 molecule. SIRP-alpha is concentrated in the slit diaphragm region of normal podocytes. CD47, a ligand for SIRP-alpha, is also expressed in the glomerulus. CD47 is located along the plasma membrane of mesangial cells, but not on podocytes. CD47 is markedly decreased during mesangiolysis, but increased in mesangial cells in the restoration stage. SIRP-alpha is heavily tyrosine phosphorylated under normal conditions; however, tyrosine phosphorylation of SIRP-alpha was markedly decreased during mesangiolysis induced by Thy1.1 monoclonal antibody injection. It is known that the cytoplasmic domain of SIPR-alpha is dephosphorylated when CD47 binds to the extracellular domain of SIRP-alpha. The data suggest that the CD47-SIRP-alpha interaction may be functionally important in cell-cell communication in the diseased glomerulus.
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Affiliation(s)
- Hidetake Kurihara
- Department of Anatomy, Juntendo University School of Medicine, Tokyo, Japan.
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Neumann-Haefelin E, Kramer-Zucker A, Slanchev K, Hartleben B, Noutsou F, Martin K, Wanner N, Ritter A, Gödel M, Pagel P, Fu X, Müller A, Baumeister R, Walz G, Huber TB. A model organism approach: defining the role of Neph proteins as regulators of neuron and kidney morphogenesis. Hum Mol Genet 2010; 19:2347-59. [PMID: 20233749 DOI: 10.1093/hmg/ddq108] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mutations of the immunoglobulin superfamily proteins nephrin and Neph1 lead to congenital nephrotic syndrome in humans or mice. Neph proteins are three closely related molecules that are evolutionarily conserved and mediate cell recognition. Their importance for morphogenetic processes including the formation of the kidney filtration barrier in vertebrates and synaptogenesis in Caenorhabditis elegans has recently been uncovered. However, the individual morphogenetic function of mammalian Neph1-3 isoforms remained elusive. We demonstrate now that the Neph/nephrin family proteins can form cell-cell adhesion modules across species. Expression of all three mammalian Neph isoforms partially rescued mutant C. elegans lacking their Neph homolog syg-1 and restored synapse formation, suggesting a functional redundancy between the three isoforms. Strikingly, the rescue of defective synaptic connectivity was prevented by deletion of the highly conserved cytoplasmic PSD95/Dlg/ZO-1-binding motif of SYG-1/Neph proteins, indicating the critical role of this intracellular signaling motif for SYG-1/Neph-dependent morphogenetic events. To determine the significance of Neph isoform redundancy for vertebrate kidney development, we analyzed the expression pattern and the functional role of Neph proteins in zebrafish. In situ hybridizations identified zNeph1 and zNeph2 as glomerular proteins. Morpholino knockdown of either zNeph1 or zNeph2 resulted in loss of slit diaphragms and leakiness of the glomerular filtration barrier. This is the first report utilizing C. elegans to study mammalian Neph/nephrin protein function and to demonstrate a functional overlap of Neph1-3 proteins. Furthermore, we identify Neph2 as a novel critical regulator of glomerular function, indicating that both Neph1 and Neph2 are required for glomerular maintenance and development.
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Nishida K, Hoshino M, Kawaguchi Y, Murakami F. Ptf1a directly controls expression of immunoglobulin superfamily molecules Nephrin and Neph3 in the developing central nervous system. J Biol Chem 2009; 285:373-80. [PMID: 19887377 DOI: 10.1074/jbc.m109.060657] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ptf1a, a basic helix-loop-helix transcription factor, plays an indispensable role for cell fate specification of subsets of neurons in the developing central nervous system. However, downstream molecules induced by Ptf1a during neural development have not been well characterized. In the present study, we identified immunoglobulin superfamily molecules, Nephrin and Neph3, as direct downstream targets of Ptf1a. First, the expression domains of Nephrin and Neph3 closely resembled those of Ptf1a in the developing retina, hypothalamus, cerebellum, hindbrain, and spinal cord. Second, Ptf1a bound directly to a PTF-binding motif in the 5'-flanking region of Nephrin and Neph3 genes. Third, Ptf1a activated transcription driven by the 5'-flanking region of these genes. Finally, the expression of Nephrin and Neph3 was lost in Ptf1a-null mice, whereas ectopic expression of Nephrin and Neph3 was induced by forced expression of Ptf1a. We provided further evidence that Nephrin and Neph3 could interact homophilically and heterophilically, suggesting that Nephrin and Neph3 might regulate certain developmental aspects of Ptf1a-positive neurons as homo- or heterooligomers.
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Affiliation(s)
- Kazuhiko Nishida
- Graduate School of Frontier Biosciences, Osaka University, Yamadaoka 1-3, Suita, Osaka 565-0871, Japan.
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Bringing together components of the fly renal system. Curr Opin Genet Dev 2009; 19:526-32. [PMID: 19783135 PMCID: PMC2789252 DOI: 10.1016/j.gde.2009.08.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Revised: 07/31/2009] [Accepted: 08/28/2009] [Indexed: 12/02/2022]
Abstract
The function of all animal excretory systems is to rid the body of toxins and to maintain homeostatic balance. Although excretory organs in diverse animal species appear superficially different they are often built on two common principals: filtration and tubular secretion/reabsorbtion. The Drosophila excretory system is composed of filtration nephrocytes and Malpighian (renal) tubules. Here we review recent molecular genetic data on the development and differentiation of nephrocytes and renal tubules. We focus in particular on the molecular mechanisms that underpin key cell and tissue behaviours during morphogenesis, drawing parallels with other species where they exist. Finally we assess the implications of patterned tissue differentiation for the subsequent regulation of renal function. These studies highlight the continuing usefulness of the fly to provide fundamental insights into the complexities of organ formation.
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Liu S, Ding J, Fan Q, Zhang H. The activation of extracellular signal-regulated kinase is responsible for podocyte injury. Mol Biol Rep 2009; 37:2477-84. [PMID: 19728154 DOI: 10.1007/s11033-009-9761-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Accepted: 08/11/2009] [Indexed: 01/02/2023]
Abstract
Podocyte and its slit diaphragm play an important role in maintaining normal glomerular filtration barrier function and structure. Podocyte apoptosis and slit diaphragm injury leads to proteinuria and glomerulosclerosis. However, the molecular mechanism of podocyte injury remains poorly understood. The family of mitogen-activated protein kinases including extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase, and p38 signal pathways, are implicated in the progression of various glomerulopathies. However, the role of the activated signal pathway(s) in podocyte injury is elusive. This study examined phosphorylation of ERK in rat puromycin aminonucleoside (PAN) nephropathy as well as conditionally immortalized mouse podocyte treated with PAN in vitro. The effect of treatment with U0126, an inhibitor of ERK, was also investigated. In PAN nephropathy, the phosphorylation of ERK was marked. In podocyte injury, the marked and sustained activation of ERK pathway was also observed before the appearance of significant podocyte apoptosis. Pretreatment with U0126 to podocyte completely inhibited ERK activation, with complete suppression podocyte apoptosis and ameliorated nephrin protein expression along with the phosphorylation of nephrin in podocyte injury. In cultured podocyte, PAN induced actin recorganition, and U0126 inhibited such change. However, U0126 did not recovery the phosphorylation change of neph1 in podocyte injury. We concluded that the sustained activation of ERK along with the phosphorylation of neph1 might be necessary for podocyte injury. The study here suggested that ERK might become a potential target for therapeutic intervention to prevent podocytes from injury which will result in proteinuria.
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Affiliation(s)
- Shufang Liu
- Department of Pediatrics, Peking University First Hospital, No.1, Xi An Men Da Jie, 100034, Beijing, People's Republic of China.
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Miao J, Fan Q, Cui Q, Zhang H, Chen L, Wang S, Guan N, Guan Y, Ding J. Newly identified cytoskeletal components are associated with dynamic changes of podocyte foot processes. Nephrol Dial Transplant 2009; 24:3297-305. [PMID: 19617259 DOI: 10.1093/ndt/gfp338] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Proteinuria, one of the main manifestations of nephrotic syndrome, is an important risk factor for the progression of renal diseases. Podocyte foot processes (FPs) injury induces proteinuria in most renal diseases. The podocyte cytoskeleton plays important roles in maintaining the normal morphology of FPs. However, the underlying cytoskeletal component that initiates and regulates the dynamic changes of FPs is still unclear. Here, the involved podocyte cytoskeletal molecules were explored on different days in puromycin aminonucleoside nephropathy rats. METHODS Microarray analysis of isolated glomeruli was performed at Day 2, Day 10 and Day 15 in puromycin aminonucleoside nephropathy rats. Cytoskeletal genebank was established by sorting with the keyword 'cytoskeleton' from PUBMED genebank to identify the differential cytoskeleton genes. Microarray results were further confirmed by real-time PCR, western blot and double immunolabelling to validate their localizations. RESULTS Nine different cytoskeletal genes were found to be involved in the dynamic changes of FPs in puromycin aminonucleoside nephropathy rats, including six up-regulated (Tagln, Actr2, Dnm3, Arc, Vcl and Birc5) and three down-regulated (Krt2-7, Nebl and Tnnc1). The differential expression of transgelin, survivin, arp2, cytokeratin7 and vinculin was verified by real-time PCR and western blot. Double immunolabelling revealed that five cytoskeletal proteins indeed colocalized with podocyte specific markers synaptopodin or alpha-actinin-4. In addition, similar expression and distribution changes were detected in patients with proteinuric renal diseases and puromycin aminonucleoside-treated podocytes. CONCLUSIONS We identified five novel podocyte cytoskeletal proteins and found that they were associated with the dynamic changes of FPs in podocyte injury.
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Affiliation(s)
- Jing Miao
- 1Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
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Zhuang S, Shao H, Guo F, Trimble R, Pearce E, Abmayr SM. Sns and Kirre, the Drosophila orthologs of Nephrin and Neph1, direct adhesion, fusion and formation of a slit diaphragm-like structure in insect nephrocytes. Development 2009; 136:2335-44. [PMID: 19515699 DOI: 10.1242/dev.031609] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The Immunoglobulin superfamily (IgSF) proteins Neph1 and Nephrin are co-expressed within podocytes in the kidney glomerulus, where they localize to the slit diaphragm (SD) and contribute to filtration between blood and urine. Herein, we demonstrate that their Drosophila orthologs Kirre (Duf) and Sns are co-expressed within binucleate garland cell nephrocytes (GCNs) that contribute to detoxification of the insect hemolymph by uptake of molecules through an SD-like nephrocyte diaphragm (ND) into labyrinthine channels that are active sites of endocytosis. The functions of Kirre and Sns in the embryonic musculature, to mediate adhesion and fusion between myoblasts to form multinucleate muscle fibers, have been conserved in the GCNs, where they contribute to adhesion of GCNs in the ;garland' and to their fusion into binucleate cells. Sns and Kirre proteins localize to the ND at the entry point into the labyrinthine channels and, like their vertebrate counterparts, are essential for its formation. Knockdown of Kirre or Sns drastically reduces the number of NDs at the cell surface. These defects are associated with a decrease in uptake of large proteins, suggesting that the ND distinguishes molecules of different sizes and controls access to the channels. Moreover, mutations in the Sns fibronectin-binding or immunoglobulin domains lead to morphologically abnormal NDs and to reduced passage of proteins into the labyrinthine channels for uptake by endocytosis, suggesting a crucial and direct role for Sns in ND formation and function. These data reveal significant similarities between the insect ND and the SD in mammalian podocytes at the level of structure and function.
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Affiliation(s)
- Shufei Zhuang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
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Fukasawa H, Bornheimer S, Kudlicka K, Farquhar MG. Slit diaphragms contain tight junction proteins. J Am Soc Nephrol 2009; 20:1491-503. [PMID: 19478094 DOI: 10.1681/asn.2008101117] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Slit diaphragms are essential components of the glomerular filtration apparatus, as changes in these junctions are the hallmark of proteinuric diseases. Slit diaphragms, considered specialized adherens junctions, contain both unique membrane proteins (e.g., nephrin, podocin, and Neph1) and typical adherens junction proteins (e.g., P-cadherin, FAT, and catenins). Whether slit diaphragms also contain tight junction proteins is unknown. Here, immunofluorescence, immunogold labeling, and cell fractionation demonstrated that rat slit diaphragms contain the tight junction proteins JAM-A (junctional adhesion molecule A), occludin, and cingulin. We found these proteins in the same protein complexes as nephrin, podocin, CD2AP, ZO-1, and Neph1 by cosedimentation, coimmunoprecipitation, and pull-down assays. PAN nephrosis increased the protein levels of JAM-A, occludin, cingulin, and ZO-1 several-fold in glomeruli and loosened their attachment to the actin cytoskeleton. These data extend current information about the molecular composition of slit diaphragms by demonstrating the presence of tight junction proteins, although slit diaphragms lack the characteristic morphologic features of tight junctions. The contribution of these proteins to the assembly of slit diaphragms and potential signaling cascades requires further investigation.
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Affiliation(s)
- Hirotaka Fukasawa
- Department of Cellular and Molecular Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0651, USA
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Schermer B, Benzing T. Lipid-protein interactions along the slit diaphragm of podocytes. J Am Soc Nephrol 2009; 20:473-8. [PMID: 19244577 DOI: 10.1681/asn.2008070694] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Podocytes are visceral epithelial cells supporting the function of the glomerular filter. Interdigitating foot processes of podocytes enwrap the glomerular capillaries and are connected by a highly specialized cell junction, the slit diaphragm. Signal transduction at the slit diaphragm is essential for the proper function of the kidney filtration barrier. The slit diaphragm constitutes a dynamic multiprotein signaling complex that contains structural proteins, receptors, signaling adaptors, ion channels, and scaffolding proteins. Function of some of these proteins requires cholesterol attached to the multiprotein complex. Recruitment of cholesterol is achieved through the PHB domain protein podocin, a member of a novel family of lipid-binding proteins that are conserved through evolution. The finding that cholesterol interaction regulates the activity of ion channels at the glomerular filtration barrier has important implications for renal physiology and pathophysiology.
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Affiliation(s)
- Bernhard Schermer
- Department of Medicine and Centre for Molecular Medicine, University of Cologne, Cologne, Germany
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45
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Fischbach KF, Linneweber GA, Andlauer TFM, Hertenstein A, Bonengel B, Chaudhary K. The irre cell recognition module (IRM) proteins. J Neurogenet 2009; 23:48-67. [PMID: 19132596 DOI: 10.1080/01677060802471668] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
One of the most challenging problems in developmental neurosciences is to understand the establishment and maintenance of specific membrane contacts between axonal, dendritic, and glial processes in the neuropils, which eventually secure neuronal connectivity. However, underlying cell recognition events are pivotal in other tissues as well. This brief review focuses on the pleiotropic functions of a small, evolutionarily conserved group of proteins of the immunoglobulin superfamily involved in cell recognition. In Drosophila, this protein family comprises Irregular chiasm C/Roughest (IrreC/Rst), Kin of irre (Kirre), and their interacting protein partners, Sticks and stones (SNS) and Hibris (Hbs). For simplicity, we propose to name this ensemble of proteins the irre cell recognition module (IRM) after the first identified member of this family. Here, we summarize evidence that the IRM proteins function together in various cellular interactions, including myoblast fusion, cell sorting, axonal pathfinding, and target recognition in the optic neuropils of Drosophila. Understanding IRM protein function will help to unravel the epigenetic rules by which the intricate neurite networks in sensory neuropils are formed.
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Affiliation(s)
- Karl-Friedrich Fischbach
- Department of Neurobiology, Institute for Biology III, Faculty of Biology, Albert-Ludwigs-University Freiburg, Germany.
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The insect nephrocyte is a podocyte-like cell with a filtration slit diaphragm. Nature 2008; 457:322-6. [PMID: 18971929 PMCID: PMC2687078 DOI: 10.1038/nature07526] [Citation(s) in RCA: 222] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Accepted: 10/08/2008] [Indexed: 11/26/2022]
Abstract
The nephron is the basic structural and functional unit of the vertebrate kidney. It is composed of a glomerulus, the site of ultrafiltration, and a renal tubule, along which the filtrate is modified. Although widely regarded as a vertebrate adaptation1 ‘nephron-like’ features can be found in the excretory systems of many invertebrates, raising the possibility that components of the vertebrate excretory system were inherited from their invertebrate ancestors2. Here we show that the insect nephrocyte has remarkable anatomical, molecular and functional similarity with the glomerular podocyte, a cell in the vertebrate kidney that forms the main size-selective barrier as blood is ultrafiltered to make urine. In particular, both cell types possess a specialised filtration diaphragm, known as the slit diaphragm in podocytes or the nephrocyte diaphragm in nephrocytes. We find that fly orthologues of the major constituents of the slit diaphragm, including nephrin, neph1, CD2AP, ZO-1 and podocin are expressed in the nephrocyte and form a complex of interacting proteins that closely mirrors the vertebrate slit diaphragm complex. Furthermore, we find the nephrocyte diaphragm is completely lost in flies mutant for nephrin or neph1 orthologues, a phenotype resembling loss of the slit diaphragm in the absence of either nephrin (as in the human kidney disease NPHS1) or neph1. These changes drastically impair filtration function in the nephrocyte. The similarities we describe between invertebrate nephrocytes and vertebrate podocytes provide evidence suggesting the two cell types are evolutionarily related and establish the nephrocyte as a simple model in which to study podocyte biology and podocyte-associated diseases.
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Wagner MC, Rhodes G, Wang E, Pruthi V, Arif E, Saleem MA, Wean SE, Garg P, Verma R, Holzman LB, Gattone V, Molitoris BA, Nihalani D. Ischemic injury to kidney induces glomerular podocyte effacement and dissociation of slit diaphragm proteins Neph1 and ZO-1. J Biol Chem 2008; 283:35579-89. [PMID: 18922801 DOI: 10.1074/jbc.m805507200] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Glomerular injury is often characterized by the effacement of podocytes, loss of slit diaphragms, and proteinuria. Renal ischemia or the loss of blood flow to the kidneys has been widely associated with tubular and endothelial injury but rarely has been shown to induce podocyte damage and disruption of the slit diaphragm. In this study, we have used an in vivo rat ischemic model to demonstrate that renal ischemia induces podocyte effacement with loss of slit diaphragm and proteinuria. Biochemical analysis of the ischemic glomerulus shows that ischemia induces rapid loss of interaction between slit diaphragm junctional proteins Neph1 and ZO-1. To further understand the effect of ischemia on molecular interactions between slit diaphragm proteins, a cell culture model was employed to study the binding between Neph1 and ZO-1. Under physiologic conditions, Neph1 co-localized with ZO-1 at cell-cell contacts in cultured human podocytes. Induction of injury by ATP depletion resulted in rapid loss of Neph1 and ZO-1 binding and redistribution of Neph1 and ZO-1 proteins from cell membrane to the cytoplasm. Recovery resulted in increased Neph1 tyrosine phosphorylation, restoring Neph1 and ZO-1 binding and their localization at the cell membrane. We further demonstrate that tyrosine phosphorylation of Neph1 mediated by Fyn results in significantly increased Neph1 and ZO-1 binding, suggesting a critical role for Neph1 tyrosine phosphorylation in reorganizing the Neph1-ZO-1 complex. This study documents that renal ischemia induces dynamic changes in the molecular interactions between slit diaphragm proteins, leading to podocyte damage and proteinuria.
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Affiliation(s)
- Mark C Wagner
- Department of Medicine, Division of Nephrology, Indiana University, Indianapolis, Indiana 46202, USA
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48
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Tesař V, Zima T. Recent Progress in the Pathogenesis of Nephrotic Proteinuria. Crit Rev Clin Lab Sci 2008; 45:139-220. [DOI: 10.1080/10408360801934865] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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49
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Otaki Y, Miyauchi N, Higa M, Takada A, Kuroda T, Gejyo F, Shimizu F, Kawachi H. Dissociation of NEPH1 from nephrin is involved in development of a rat model of focal segmental glomerulosclerosis. Am J Physiol Renal Physiol 2008; 295:F1376-87. [PMID: 18715943 DOI: 10.1152/ajprenal.00075.2008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Focal segmental glomerulosclerosis (FSGS) is a disease showing severe proteinuria, and the disease progresses to end-stage kidney failure in many cases. However, the pathogenic mechanism of FSGS is not well understood. The slit diaphragm (SD), which bridges the neighboring foot processes of glomerular epithelial cells, is understood to function as a barrier of the glomerular capillary wall. To investigate the role of SD dysfunction in the development of FSGS, we analyzed the expression of SD-associated molecules in rat adriamycin-induced nephropathy, a mimic of FSGS. The staining of the SD molecules nephrin, podocin, and NEPH1 had already shifted to a discontinuous dotlike pattern at the initiation phase of the disease, when neither proteinuria nor any morphological alterations were detected yet. The alteration of NEPH1 expression was the most evident among the molecules examined, and NEPH1 was dissociated from nephrin at the initiation phase. On day 28, when severe proteinuria was detected and sclerotic changes were already observed, alteration of the expressions of nephrin, podocin, and NEPH1 worsened, but no alteration in the expression of other SD-associated molecules or other podocyte molecules was detected. It is postulated that the dissociation of NEPH1 from nephrin initiates proteinuria and that the SD alteration restricted in these molecules plays a critical role in the development of sclerotic changes in FSGS.
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Affiliation(s)
- Yasuhiro Otaki
- Department of Cell Biology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Niigata, 951-8510, Japan
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Chao DL, Shen K. Functional dissection of SYG-1 and SYG-2, cell adhesion molecules required for selective synaptogenesis in C. elegans. Mol Cell Neurosci 2008; 39:248-57. [PMID: 18675916 DOI: 10.1016/j.mcn.2008.07.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 05/20/2008] [Accepted: 07/01/2008] [Indexed: 01/17/2023] Open
Abstract
Cell adhesion molecules of the Immunoglobulin superfamily (IgCAMs) play diverse functions during neural development. Previously, we have identified SYG-1/Neph1 and SYG-2/Nephrin, IgCAMs necessary for synaptic specificity in Caenorhabditis elegans. Here, we conduct an in vivo structure-function analysis of SYG-1 and SYG-2 to identify domains of SYG-1 and SYG-2 necessary for heterophilic binding as well as synaptic specificity. We find the first Ig domain of SYG-1 and the first 5 Ig domains of SYG-2 are necessary and sufficient for their binding in vivo, as well as for synapse formation. We also find the SYG-2 cytoplasmic domain is required for SYG-2 subcellular trafficking, while the intracellular region of SYG-1 is required for synaptic function at earlier developmental stages, but is dispensable for later stages. This study defines the domain requirements for SYG-1/SYG-2 heterophilic binding and suggests that unknown SYG-1 extracellular interactors may play a role in SYG-1-mediated synaptic specificity.
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Affiliation(s)
- Daniel L Chao
- Department of Biology and Neurosciences Program, Stanford University, Stanford, CA 94305, USA
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