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Albalawy WN, Youm EB, Shipman KE, Trull KJ, Baty CJ, Long KR, Rbaibi Y, Wang XP, Fagunloye OG, White KA, Jurczak MJ, Kashlan OB, Weisz OA. SGLT2-independent effects of canagliflozin on NHE3 and mitochondrial complex I activity inhibit proximal tubule fluid transport and albumin uptake. Am J Physiol Renal Physiol 2024; 326:F1041-F1053. [PMID: 38660713 DOI: 10.1152/ajprenal.00005.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 04/03/2024] [Accepted: 04/18/2024] [Indexed: 04/26/2024] Open
Abstract
Beyond glycemic control, SGLT2 inhibitors (SGLT2is) have protective effects on cardiorenal function. Renoprotection has been suggested to involve inhibition of NHE3 leading to reduced ATP-dependent tubular workload and mitochondrial oxygen consumption. NHE3 activity is also important for regulation of endosomal pH, but the effects of SGLT2i on endocytosis are unknown. We used a highly differentiated cell culture model of proximal tubule (PT) cells to determine the direct effects of SGLT2i on Na+-dependent fluid transport and endocytic uptake in this nephron segment. Strikingly, canagliflozin but not empagliflozin reduced fluid transport across cell monolayers and dramatically inhibited endocytic uptake of albumin. These effects were independent of glucose and occurred at clinically relevant concentrations of drug. Canagliflozin acutely inhibited surface NHE3 activity, consistent with a direct effect, but did not affect endosomal pH or NHE3 phosphorylation. In addition, canagliflozin rapidly and selectively inhibited mitochondrial complex I activity. Inhibition of mitochondrial complex I by metformin recapitulated the effects of canagliflozin on endocytosis and fluid transport, whereas modulation of downstream effectors AMPK and mTOR did not. Mice given a single dose of canagliflozin excreted twice as much urine over 24 h compared with empagliflozin-treated mice despite similar water intake. We conclude that canagliflozin selectively suppresses Na+-dependent fluid transport and albumin uptake in PT cells via direct inhibition of NHE3 and of mitochondrial function upstream of the AMPK/mTOR axis. These additional targets of canagliflozin contribute significantly to reduced PT Na+-dependent fluid transport in vivo.NEW & NOTEWORTHY Reduced NHE3-mediated Na+ transport has been suggested to underlie the cardiorenal protection provided by SGLT2 inhibitors. We found that canagliflozin, but not empagliflozin, reduced NHE3-dependent fluid transport and endocytic uptake in cultured proximal tubule cells. These effects were independent of SGLT2 activity and resulted from inhibition of mitochondrial complex I and NHE3. Studies in mice are consistent with greater effects of canagliflozin versus empagliflozin on fluid transport. Our data suggest that these selective effects of canagliflozin contribute to reduced Na+-dependent transport in proximal tubule cells.
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Affiliation(s)
- Wafaa N Albalawy
- Department of Human Genetics, Pitt Public Health, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Elynna B Youm
- Department of Human Genetics, Pitt Public Health, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Katherine E Shipman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Keelan J Trull
- Department of Chemistry and Biochemistry, University of Notre Dame, South Bend, Indiana, United States
| | - Catherine J Baty
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Kimberly R Long
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Youssef Rbaibi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Xue-Ping Wang
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Olayemi G Fagunloye
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Katharine A White
- Department of Chemistry and Biochemistry, University of Notre Dame, South Bend, Indiana, United States
| | - Michael J Jurczak
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Ossama B Kashlan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
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2
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Wang Y, Xu L, Zhang Y, Fu H, Gao L, Guan Y, Gu W, Sun J, Chen X, Yang F, Lai E, Wang J, Jin Y, Kou Z, Qiu X, Mao J, Hu L. Dent disease 1-linked novel CLCN5 mutations result in aberrant location and reduced ion currents. Int J Biol Macromol 2024; 257:128564. [PMID: 38061527 DOI: 10.1016/j.ijbiomac.2023.128564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 11/12/2023] [Accepted: 11/30/2023] [Indexed: 12/17/2023]
Abstract
Dent disease is a rare renal tubular disease with X-linked recessive inheritance characterized by low molecular weight proteinuria (LMWP), hypercalciuria, and nephrocalcinosis. Mutations disrupting the 2Cl-/1H+ exchange activity of chloride voltage-gated channel 5 (CLCN5) have been causally linked to the most common form, Dent disease 1 (DD1), although the pathophysiological mechanisms remain unclear. Here, we conducted the whole exome capture sequencing and bioinformatics analysis within our DD1 cohort to identify two novel causal mutations in CLCN5 (c.749 G > A, p. G250D, c.829 A > C, p. T277P). Molecular dynamics simulations of ClC-5 homology model suggested that these mutations potentially may induce structural changes, destabilizing ClC-5. Overexpression of variants in vitro revealed aberrant subcellular localization in the endoplasmic reticulum (ER), significant accumulation of insoluble aggregates, and disrupted ion transport function in voltage clamp recordings. Moreover, human kidney-2 (HK-2) cells overexpressing either G250D or T277P displayed higher cell-substrate adhesion, migration capability but reduced endocytic function, as well as substantially altered transcriptomic profiles with G250D resulting in stronger deleterious effects. These cumulative findings supported pathogenic role of these ClC-5 mutations in DD1 and suggested a cellular mechanism for disrupted renal function in Dent disease patients, as well as a potential target for diagnostic biomarker or therapeutic strategy development.
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Affiliation(s)
- Yan Wang
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Lizhen Xu
- Department of Biophysics, and Kidney Disease Center of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Ying Zhang
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, China
| | - Haidong Fu
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Langping Gao
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Yuelin Guan
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Weizhong Gu
- Department of Pathology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Jingmiao Sun
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Xiangjun Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, China; Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou 310020, China
| | - Fan Yang
- Department of Biophysics, and Kidney Disease Center of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - EnYin Lai
- Department of Physiology School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China
| | - Jingjing Wang
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Yanyan Jin
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China
| | - Ziqi Kou
- Institute for Brain Research and Rehabilitation, and Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou 510631, China
| | - Xingyu Qiu
- Department of Physiology School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China
| | - Jianhua Mao
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China.
| | - Lidan Hu
- Department of Nephrology, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China.
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3
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Chen Q, Li Y, Wu X. Dent disease manifesting as nephrotic syndrome. Intractable Rare Dis Res 2023; 12:67-70. [PMID: 36873671 PMCID: PMC9976091 DOI: 10.5582/irdr.2022.01125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 02/05/2023] [Accepted: 02/19/2023] [Indexed: 02/25/2023] Open
Abstract
Dent disease is an X-linked recessive renal tubular disorder, which is mainly caused by mutations of the CLCN5 gene and OCRL gene. It is characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis or nephrolithiasis, and progressive renal failure. Nephrotic syndrome is a glomerular disorder characterized by massive proteinuria, hypoalbuminemia, edema, and hyperlipidemia. In this study, we report two cases of Dent disease manifesting as nephrotic syndrome. Two patients were initially diagnosed with nephrotic syndrome due to edema, nephrotic range proteinuria, hypoalbuminemia, and hyperlipidemia, and responded to prednisone and tacrolimus therapy. Genetic testing revealed mutations in the OCRL and CLCN5 genes. They were eventually diagnosed with Dent disease. Nephrotic syndrome is a rare and insidious phenotype of Dent disease, and its pathogenesis is not fully understood. Patients with nephrotic syndrome are recommended to routinely undergo urinary protein classification and urinary calcium testing, especially those with frequently recurrent nephrotic syndrome and poor response to steroid and immunosuppressive therapy. To date, there is no effective drug treatment for Dent disease. About 30% to 80% of patients progress to end-stage renal disease at the age of 30-50.
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Affiliation(s)
| | | | - Xiaochuan Wu
- Address correspondence to:Xiaochuan Wu, Department of Pediatrics, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan, China. E-mail:
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4
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Lai W, Liau W, Yang L. Preparation of porous biodegradable
PLLA
with tunable pore size through simple variation of
PEG
/
PLLA‐blend
crystallization conditions. POLYM ADVAN TECHNOL 2022. [DOI: 10.1002/pat.5898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Wei‐Chi Lai
- Department of Chemical and Materials Engineering Tamkang University New Taipei City Taiwan
| | - Wen‐Bin Liau
- Department of Materials Science and Engineering National Taiwan University Taipei Taiwan
| | - Ling‐Yueh Yang
- Department of Materials Science and Engineering National Taiwan University Taipei Taiwan
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5
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Zhai P, Lv W, Yang X, Huang Y, Zhai W, Ren X, Zhang X, Yang M, Zhang J, Guo T, Bai M, Yang Y, Ding Y, Huang Y. Renal Expression of CLC-5 and Megalin/Cubilin in Dent-1 Disease With Nonsense Mutations of CLCN5 Gene. Pediatr Dev Pathol 2022; 25:397-403. [PMID: 35100899 DOI: 10.1177/10935266211065554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The study aims to explore the clinicopathological features and whether the nonsense mutations of CLCN5 gene have effect on the renal expression of CLC-5 protein and megalin/cubilin complex in children with Dent-1 disease. The clinicopathological features and genetic examination of three patients with Dent-1 disease were investigated. The expression of CLC-5 and megalin/cubilin complex in renal tissues was detected by using immunohistochemistry method. Urinary albumin, α1-microglobulin, β2-microglobulin, retinol binding protein, and calcium levels were measured by immunonephelometry. Urinary calcium and low molecular weight proteinuria (LMWP) were enhanced in three patients, and two presented with nephrotic range proteinuria. Focal glomerular obsolescence, minor tubulointerstitial injury, and focal calcification in corticomedullary junction were found in one patient. Nonsense mutations of CLCN5 gene from their mothers were identified in all three patients with Dent-1 disease; however, the expression of CLC-5 protein was not decreased in renal tubular cells. As the receptor complex of albumin and LMWP reabsorption, the expression of megalin/cubilin in the brush border of proximal tubules was decreased in Dent-1 patients. Even if the renal CLC-5 protein is expressed normally, the reduced expression of megalin/cubilin in the brush border of renal proximal tubules may be helpful to understand the physiopathology of Dent-1 disease with nonsense mutations of CLCN5 gene.
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Affiliation(s)
- Panpan Zhai
- Department of Pediatrics, 232830Henan University of Chinese Medicine, Henan, China
| | - Weigang Lv
- Department of Pediatrics, 232830Henan University of Chinese Medicine, Henan, China
| | - Xiaoqing Yang
- Department of Pediatrics, 232830The First Affiliated Hospital of Henan University of Chinese Medicine, Henan, China
| | - Yanjie Huang
- Department of Pediatrics, 232830Henan University of Chinese Medicine, Henan, China.,Department of Pediatrics, 232830The First Affiliated Hospital of Henan University of Chinese Medicine, Henan, China
| | - Wensheng Zhai
- Department of Pediatrics, 232830Henan University of Chinese Medicine, Henan, China
| | - Xianqing Ren
- Department of Pediatrics, 232830Henan University of Chinese Medicine, Henan, China
| | - Xia Zhang
- Department of Pediatrics, 232830The First Affiliated Hospital of Henan University of Chinese Medicine, Henan, China
| | - Meng Yang
- Department of Pediatrics, 232830The First Affiliated Hospital of Henan University of Chinese Medicine, Henan, China
| | - Jian Zhang
- Department of Pediatrics, 232830Henan University of Chinese Medicine, Henan, China
| | - Ting Guo
- Department of Pediatrics, 232830The First Affiliated Hospital of Henan University of Chinese Medicine, Henan, China
| | - Minghui Bai
- Department of Pediatrics, 232830The First Affiliated Hospital of Henan University of Chinese Medicine, Henan, China
| | - Yueli Yang
- Department of Pediatrics, 232830The First Affiliated Hospital of Henan University of Chinese Medicine, Henan, China
| | - Ying Ding
- Department of Pediatrics, 232830Henan University of Chinese Medicine, Henan, China
| | - Yanshi Huang
- Pain Medicine, Nanyang Second General Hospital, Henan, China
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6
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Sakhi I, Bignon Y, Frachon N, Hureaux M, Arévalo B, González W, Vargas-Poussou R, Lourdel S. Diversity of functional alterations of the ClC-5 exchanger in the region of the proton glutamate in patients with Dent disease 1. Hum Mutat 2021; 42:537-550. [PMID: 33600050 DOI: 10.1002/humu.24184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 02/04/2021] [Accepted: 02/14/2021] [Indexed: 01/21/2023]
Abstract
Mutations in the CLCN5 gene encoding the 2Cl- /1H+ exchanger ClC-5 are associated with Dent disease 1, an inherited renal disorder characterized by low-molecular-weight (LMW) proteinuria and hypercalciuria. In the kidney, ClC-5 is mostly localized in proximal tubule cells, where it is thought to play a key role in the endocytosis of LMW proteins. Here, we investigated the consequences of eight previously reported pathogenic missense mutations of ClC-5 surrounding the "proton glutamate" that serves as a crucial H+ -binding site for the exchanger. A complete loss of function was observed for a group of mutants that were either retained in the endoplasmic reticulum of HEK293T cells or unstainable at plasma membrane due to proteasomal degradation. In contrast, the currents measured for the second group of mutations in Xenopus laevis oocytes were reduced. Molecular dynamics simulations performed on a ClC-5 homology model demonstrated that such mutations might alter ClC-5 protonation by interfering with the water pathway. Analysis of clinical data from patients harboring these mutations demonstrated no phenotype/genotype correlation. This study reveals that mutations clustered in a crucial region of ClC-5 have diverse molecular consequences in patients with Dent disease 1, ranging from altered expression to defects in transport.
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Affiliation(s)
- Imène Sakhi
- Laboratoire Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Paris, France.,CNRS ERL 8228, Paris, France
| | - Yohan Bignon
- Centre Universitaire des Saints Pères, INSERM, Université Paris Descartes, Paris, France
| | - Nadia Frachon
- Laboratoire Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Paris, France.,CNRS ERL 8228, Paris, France
| | - Marguerite Hureaux
- Département de génétique, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France
| | - Bárbara Arévalo
- Center for Bioinformatics and Molecular Simulations (CBSM), Universidad de Talca, Talca, Chile
| | - Wendy González
- Center for Bioinformatics and Molecular Simulations (CBSM), Universidad de Talca, Talca, Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, Talca, Chile
| | - Rosa Vargas-Poussou
- Laboratoire Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Paris, France.,CNRS ERL 8228, Paris, France.,Département de génétique, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France
| | - Stéphane Lourdel
- Laboratoire Physiologie Rénale et Tubulopathies, Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Paris, France.,CNRS ERL 8228, Paris, France
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7
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Peng F, Cai W, Li J, Li H. ClC-5 Downregulation Induces Osteosarcoma Cell Apoptosis by Promoting Bax and tBid Complex Formation. Front Oncol 2021; 10:556908. [PMID: 33614474 PMCID: PMC7892965 DOI: 10.3389/fonc.2020.556908] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 12/14/2020] [Indexed: 11/13/2022] Open
Abstract
Osteosarcoma is the most common malignant bone tumor. Chloride (Cl-) channels-mediated Cl- movement plays an important role in regulating the functions of various cancer cells, but its role in osteosarcoma remains unclear. In this study, we found that ClC-5 was increased in osteosarcoma tissues compared with normal bone tissues. Patients with high ClC-5 expression showed poor overall survival relative to those patients with low ClC-5 expression. Higher ClC-5 expression and lower intracellular Cl- concentration ([Cl-]i) were observed in osteosarcoma cells compared with normal osteoblasts. Lowering [Cl-]i increased the viability of osteosarcoma cells, which was markedly blocked by ClC-5 downregulation. Knockdown of ClC-5 significantly induced osteosarcoma cell apoptosis and increased the release of cytochrome c from mitochondria to cytosol, concomitantly with cleavage of caspase-9, caspase-3, and PARP. The effect of ClC-5 downregulation on osteosarcoma cell apoptosis and viability was abolished by caspase-3 and caspase-9 inhibitors, but not caspase-8 inhibitor. Furthermore, ClC-5 inhibition promoted Bax translocation from cytosol to mitochondria. Immunoprecipitation showed that ClC-5 interacted with Bax and ClC-5 downregulation enhanced Bax and tBid complex formation. Collectively, we demonstrate that ClC-5 downregulation induces osteosarcoma cell apoptosis via mitochondria-dependent apoptotic pathway activation by promoting Bax and tBid association and subsequent Bax translocation.
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Affiliation(s)
- Fei Peng
- Department of Orthopedics, Renmin Hospital of Wuhan University, Wuhan, China
| | - Weisong Cai
- Department of Orthopedics, Renmin Hospital of Wuhan University, Wuhan, China
| | - Jianping Li
- Department of Orthopedics, Renmin Hospital of Wuhan University, Wuhan, China
| | - Haohuan Li
- Department of Orthopedics, Renmin Hospital of Wuhan University, Wuhan, China
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8
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Gianesello L, Ceol M, Bertoldi L, Terrin L, Priante G, Murer L, Peruzzi L, Giordano M, Paglialonga F, Cantaluppi V, Musetti C, Valle G, Del Prete D, Anglani F. Genetic Analyses in Dent Disease and Characterization of CLCN5 Mutations in Kidney Biopsies. Int J Mol Sci 2020; 21:ijms21020516. [PMID: 31947599 PMCID: PMC7014080 DOI: 10.3390/ijms21020516] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 01/08/2020] [Accepted: 01/10/2020] [Indexed: 11/16/2022] Open
Abstract
Dent disease (DD), an X-linked renal tubulopathy, is mainly caused by loss-of-function mutations in CLCN5 (DD1) and OCRL genes. CLCN5 encodes the ClC-5 antiporter that in proximal tubules (PT) participates in the receptor-mediated endocytosis of low molecular weight proteins. Few studies have analyzed the PT expression of ClC-5 and of megalin and cubilin receptors in DD1 kidney biopsies. About 25% of DD cases lack mutations in either CLCN5 or OCRL genes (DD3), and no other disease genes have been discovered so far. Sanger sequencing was used for CLCN5 gene analysis in 158 unrelated males clinically suspected of having DD. The tubular expression of ClC-5, megalin, and cubilin was assessed by immunolabeling in 10 DD1 kidney biopsies. Whole exome sequencing (WES) was performed in eight DD3 patients. Twenty-three novel CLCN5 mutations were identified. ClC-5, megalin, and cubilin were significantly lower in DD1 than in control biopsies. The tubular expression of ClC-5 when detected was irrespective of the type of mutation. In four DD3 patients, WES revealed 12 potentially pathogenic variants in three novel genes (SLC17A1, SLC9A3, and PDZK1), and in three genes known to be associated with monogenic forms of renal proximal tubulopathies (SLC3A, LRP2, and CUBN). The supposed third Dent disease-causing gene was not discovered.
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Affiliation(s)
- Lisa Gianesello
- Laboratory of Histomorphology and Molecular Biology of the Kidney, Clinical Nephrology, Department of Medicine—DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (M.C.); (L.T.); (G.P.); (D.D.P.)
| | - Monica Ceol
- Laboratory of Histomorphology and Molecular Biology of the Kidney, Clinical Nephrology, Department of Medicine—DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (M.C.); (L.T.); (G.P.); (D.D.P.)
| | - Loris Bertoldi
- CRIBI Biotechnology Centre, University of Padua, 35131 Padua, Italy; (L.B.); (G.V.)
| | - Liliana Terrin
- Laboratory of Histomorphology and Molecular Biology of the Kidney, Clinical Nephrology, Department of Medicine—DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (M.C.); (L.T.); (G.P.); (D.D.P.)
| | - Giovanna Priante
- Laboratory of Histomorphology and Molecular Biology of the Kidney, Clinical Nephrology, Department of Medicine—DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (M.C.); (L.T.); (G.P.); (D.D.P.)
| | - Luisa Murer
- Pediatric Nephrology, Dialysis and Transplant Unit, Department of Women’s and Children’s Health, Padua University Hospital, 35128 Padua, Italy;
| | - Licia Peruzzi
- Pediatric Nephrology Unit, Regina Margherita Children’s Hospital, 10126 CDSS Turin, Italy;
| | - Mario Giordano
- Pediatric Nephrology Unit, University Hospital, P.O. Giovanni XXIII, 70126 Bari, Italy;
| | - Fabio Paglialonga
- Pediatric Nephrology, Dialysis and Transplant Unit, Fondazione IRCCS, Ca’ Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy;
| | - Vincenzo Cantaluppi
- Nephrology and Kidney Transplantation Unit, Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (V.C.); (C.M.)
| | - Claudio Musetti
- Nephrology and Kidney Transplantation Unit, Department of Translational Medicine, University of Piemonte Orientale (UPO), 28100 Novara, Italy; (V.C.); (C.M.)
| | - Giorgio Valle
- CRIBI Biotechnology Centre, University of Padua, 35131 Padua, Italy; (L.B.); (G.V.)
| | - Dorella Del Prete
- Laboratory of Histomorphology and Molecular Biology of the Kidney, Clinical Nephrology, Department of Medicine—DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (M.C.); (L.T.); (G.P.); (D.D.P.)
| | - Franca Anglani
- Laboratory of Histomorphology and Molecular Biology of the Kidney, Clinical Nephrology, Department of Medicine—DIMED, University of Padua, 35128 Padua, Italy; (L.G.); (M.C.); (L.T.); (G.P.); (D.D.P.)
- CRIBI Biotechnology Centre, University of Padua, 35131 Padua, Italy; (L.B.); (G.V.)
- Correspondence: ; Tel.: +39-049-8212-155
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9
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Anglani F, Gianesello L, Beara-Lasic L, Lieske J. Dent disease: A window into calcium and phosphate transport. J Cell Mol Med 2019; 23:7132-7142. [PMID: 31472005 PMCID: PMC6815805 DOI: 10.1111/jcmm.14590] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 07/22/2019] [Accepted: 07/24/2019] [Indexed: 12/19/2022] Open
Abstract
This review examines calcium and phosphate transport in the kidney through the lens of the rare X-linked genetic disorder Dent disease. Dent disease type 1 (DD1) is caused by mutations in the CLCN5 gene encoding ClC-5, a Cl- /H+ antiporter localized to early endosomes of the proximal tubule (PT). Phenotypic features commonly include low molecular weight proteinuria (LMWP), hypercalciuria, focal global sclerosis and chronic kidney disease; calcium nephrolithiasis, nephrocalcinosis and hypophosphatemic rickets are less commonly observed. Although it is not surprising that abnormal endosomal function and recycling in the PT could result in LMWP, it is less clear how ClC-5 dysfunction disturbs calcium and phosphate metabolism. It is known that the majority of calcium and phosphate transport occurs in PT cells, and PT endocytosis is essential for calcium and phosphorus reabsorption in this nephron segment. Evidence from ClC-5 KO models suggests that ClC-5 mediates parathormone endocytosis from tubular fluid. In addition, ClC-5 dysfunction alters expression of the sodium/proton exchanger NHE3 on the PT apical surface thus altering transcellular sodium movement and hence paracellular calcium reabsorption. A potential role for NHE3 dysfunction in the DD1 phenotype has never been investigated, either in DD models or in patients with DD1, even though patients with DD1 exhibit renal sodium and potassium wasting, especially when exposed to even a low dose of thiazide diuretic. Thus, insights from the rare disease DD1 may inform possible underlying mechanisms for the phenotype of hypercalciuria and idiopathic calcium stones.
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Affiliation(s)
- Franca Anglani
- Division of Nephrology, Department of Medicine, Laboratory of Histomorphology and Molecular Biology of the Kidney, University of Padua, Padua, Italy
| | - Lisa Gianesello
- Division of Nephrology, Department of Medicine, Laboratory of Histomorphology and Molecular Biology of the Kidney, University of Padua, Padua, Italy
| | - Lada Beara-Lasic
- Division of Nephrology, New York University School of Medicine, New York, NY, USA
| | - John Lieske
- Division of Nephrology and Hypertension, Department of Medicine, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
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10
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Jentsch TJ, Pusch M. CLC Chloride Channels and Transporters: Structure, Function, Physiology, and Disease. Physiol Rev 2018; 98:1493-1590. [DOI: 10.1152/physrev.00047.2017] [Citation(s) in RCA: 214] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion translocation parthway, assemble to homo- or heteromeric dimers that sometimes require accessory β-subunits for function. CLC proteins come in two flavors: anion channels and anion/proton exchangers. Structures of these two CLC protein classes are surprisingly similar. Extensive structure-function analysis identified residues involved in ion permeation, anion-proton coupling and gating and led to attractive biophysical models. In mammals, ClC-1, -2, -Ka/-Kb are plasma membrane Cl−channels, whereas ClC-3 through ClC-7 are 2Cl−/H+-exchangers in endolysosomal membranes. Biological roles of CLCs were mostly studied in mammals, but also in plants and model organisms like yeast and Caenorhabditis elegans. CLC Cl−channels have roles in the control of electrical excitability, extra- and intracellular ion homeostasis, and transepithelial transport, whereas anion/proton exchangers influence vesicular ion composition and impinge on endocytosis and lysosomal function. The surprisingly diverse roles of CLCs are highlighted by human and mouse disorders elicited by mutations in their genes. These pathologies include neurodegeneration, leukodystrophy, mental retardation, deafness, blindness, myotonia, hyperaldosteronism, renal salt loss, proteinuria, kidney stones, male infertility, and osteopetrosis. In this review, emphasis is laid on biophysical structure-function analysis and on the cell biological and organismal roles of mammalian CLCs and their role in disease.
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Affiliation(s)
- Thomas J. Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Michael Pusch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
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11
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Solanki AK, Arif E, Morinelli T, Wilson RC, Hardiman G, Deng P, Arthur JM, Velez JC, Nihalani D, Janech MG, Budisavljevic MN. A Novel CLCN5 Mutation Associated With Focal Segmental Glomerulosclerosis and Podocyte Injury. Kidney Int Rep 2018; 3:1443-1453. [PMID: 30426109 PMCID: PMC6224352 DOI: 10.1016/j.ekir.2018.06.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 06/05/2018] [Accepted: 06/09/2018] [Indexed: 12/17/2022] Open
Abstract
Introduction Tubular dysfunction is characteristic of Dent’s disease; however, focal segmental glomerulosclerosis (FSGS) can also be present. Glomerulosclerosis could be secondary to tubular injury, but it remains uncertain whether the CLCN5 gene, which encodes an endosomal chloride and/or hydrogen exchanger, plays a role in podocyte biology. Here, we implicate a role for CLCN5 in podocyte function and pathophysiology. Methods Whole exome capture and sequencing of the proband and 5 maternally-related family members was conducted to identify X-linked mutations associated with biopsy-proven FSGS. Human podocyte cultures were used to characterize the mutant phenotype on podocyte function. Results We identified a novel mutation (L521F) in CLCN5 in 2 members of a Hispanic family who presented with a histologic diagnosis of FSGS and low-molecular-weight proteinuria without hypercalciuria. Presence of CLCN5 was confirmed in cultured human podocytes. Podocytes transfected with the wild-type or the mutant (L521F) CLCN5 constructs showed differential localization. CLCN5 knockdown in podocytes resulted in defective transferrin endocytosis and was associated with decreased cell proliferation and increased cell migration, which are hallmarks of podocyte injury. Conclusions The CLCN5 mutation, which causes Dent’s disease, may be associated with FSGS without hyercalcuria and nepthrolithiasis. The present findings supported the hypothesis that CLCN5 participates in protein trafficking in podocytes and plays a critical role in organizing the components of the podocyte slit diaphragm to help maintain normal cell physiology and a functional filtration barrier. In addition to tubular dysfunction, mutations in CLCN5 may also lead to podocyte dysfunction, which results in a histologic picture of FSGS that may be a primary event and not a consequence of tubular damage.
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Affiliation(s)
- Ashish K Solanki
- Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Ehtesham Arif
- Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Thomas Morinelli
- Division of Transplant Surgery, Department of Surgery, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Robert C Wilson
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Gary Hardiman
- Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA.,MUSC Bioinformatics, Center for Genomics Medicine, Medical University of South Carolina, Charleston, South Carolina, USA.,Department of Public Health Sciences, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Peifeng Deng
- Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA
| | - John M Arthur
- Division of Nephrology, Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Juan Cq Velez
- Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
| | - Deepak Nihalani
- Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Michael G Janech
- Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Milos N Budisavljevic
- Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA.,Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina, USA
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12
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Bignon Y, Alekov A, Frachon N, Lahuna O, Jean-Baptiste Doh-Egueli C, Deschênes G, Vargas-Poussou R, Lourdel S. A novel CLCN5 pathogenic mutation supports Dent disease with normal endosomal acidification. Hum Mutat 2018; 39:1139-1149. [PMID: 29791050 DOI: 10.1002/humu.23556] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 04/23/2018] [Accepted: 05/19/2018] [Indexed: 12/13/2022]
Abstract
Dent disease is an X-linked recessive renal tubular disorder characterized by low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, nephrocalcinosis, and progressive renal failure. Inactivating mutations of CLCN5, the gene encoding the 2Cl- /H+ exchanger ClC-5, have been reported in patients with Dent disease 1. In vivo studies in mice harboring an artificial mutation in the "gating glutamate" of ClC-5 (c.632A > C, p.Glu211Ala) and mathematical modeling suggest that endosomal chloride concentration could be an important parameter in endocytosis, rather than acidification as earlier hypothesized. Here, we described a novel pathogenic mutation affecting the "gating glutamate" of ClC-5 (c.632A>G, p.Glu211Gly) and investigated its molecular consequences. In HEK293T cells, the p.Glu211Gly ClC-5 mutant displayed unaltered N-glycosylation and normal plasma membrane and early endosomes localizations. In Xenopus laevis oocytes and HEK293T cells, we found that contrasting with wild-type ClC-5, the mutation abolished the outward rectification, the sensitivity to extracellular H+ and converted ClC-5 into a Cl- channel. Investigation of endosomal acidification in HEK293T cells using the pH-sensitive pHluorin2 probe showed that the luminal pH of cells expressing a wild-type or p.Glu211Gly ClC-5 was not significantly different. Our study further confirms that impaired acidification of endosomes is not the only parameter leading to defective endocytosis in Dent disease 1.
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Affiliation(s)
- Yohan Bignon
- Sorbonne Université, Université Paris-Descartes, INSERM, CNRS, Paris, France
| | - Alexi Alekov
- Institut für Neurophysiologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Nadia Frachon
- Sorbonne Université, Université Paris-Descartes, INSERM, CNRS, Paris, France
| | | | | | - Georges Deschênes
- Assistance Publique-Hôpitaux de Paris, Hôpital Robert Debré, Service de Néphrologie Pédiatrique, Paris, France.,Centre de Référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte (MARHEA), Paris, France
| | - Rosa Vargas-Poussou
- Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Département de génétique, Paris, France.,Université Paris-Descartes, Faculté de Médecine, Paris, France
| | - Stéphane Lourdel
- Sorbonne Université, Université Paris-Descartes, INSERM, CNRS, Paris, France
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13
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Poroca DR, Pelis RM, Chappe VM. ClC Channels and Transporters: Structure, Physiological Functions, and Implications in Human Chloride Channelopathies. Front Pharmacol 2017; 8:151. [PMID: 28386229 PMCID: PMC5362633 DOI: 10.3389/fphar.2017.00151] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/09/2017] [Indexed: 02/04/2023] Open
Abstract
The discovery of ClC proteins at the beginning of the 1990s was important for the development of the Cl- transport research field. ClCs form a large family of proteins that mediate voltage-dependent transport of Cl- ions across cell membranes. They are expressed in both plasma and intracellular membranes of cells from almost all living organisms. ClC proteins form transmembrane dimers, in which each monomer displays independent ion conductance. Eukaryotic members also possess a large cytoplasmic domain containing two CBS domains, which are involved in transport modulation. ClC proteins function as either Cl- channels or Cl-/H+ exchangers, although all ClC proteins share the same basic architecture. ClC channels have two gating mechanisms: a relatively well-studied fast gating mechanism, and a slow gating mechanism, which is poorly defined. ClCs are involved in a wide range of physiological processes, including regulation of resting membrane potential in skeletal muscle, facilitation of transepithelial Cl- reabsorption in kidneys, and control of pH and Cl- concentration in intracellular compartments through coupled Cl-/H+ exchange mechanisms. Several inherited diseases result from C1C gene mutations, including myotonia congenita, Bartter's syndrome (types 3 and 4), Dent's disease, osteopetrosis, retinal degeneration, and lysosomal storage diseases. This review summarizes general features, known or suspected, of ClC structure, gating and physiological functions. We also discuss biophysical properties of mammalian ClCs that are directly involved in the pathophysiology of several human inherited disorders, or that induce interesting phenotypes in animal models.
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Affiliation(s)
- Diogo R Poroca
- Department of Physiology and Biophysics, Dalhousie University, Halifax NS, Canada
| | - Ryan M Pelis
- Department of Pharmacology, Dalhousie University, Halifax NS, Canada
| | - Valérie M Chappe
- Department of Physiology and Biophysics, Dalhousie University, Halifax NS, Canada
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14
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Homan KA, Kolesky DB, Skylar-Scott MA, Herrmann J, Obuobi H, Moisan A, Lewis JA. Bioprinting of 3D Convoluted Renal Proximal Tubules on Perfusable Chips. Sci Rep 2016; 6:34845. [PMID: 27725720 PMCID: PMC5057112 DOI: 10.1038/srep34845] [Citation(s) in RCA: 380] [Impact Index Per Article: 47.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 09/19/2016] [Indexed: 02/08/2023] Open
Abstract
Three-dimensional models of kidney tissue that recapitulate human responses are needed for drug screening, disease modeling, and, ultimately, kidney organ engineering. Here, we report a bioprinting method for creating 3D human renal proximal tubules in vitro that are fully embedded within an extracellular matrix and housed in perfusable tissue chips, allowing them to be maintained for greater than two months. Their convoluted tubular architecture is circumscribed by proximal tubule epithelial cells and actively perfused through the open lumen. These engineered 3D proximal tubules on chip exhibit significantly enhanced epithelial morphology and functional properties relative to the same cells grown on 2D controls with or without perfusion. Upon introducing the nephrotoxin, Cyclosporine A, the epithelial barrier is disrupted in a dose-dependent manner. Our bioprinting method provides a new route for programmably fabricating advanced human kidney tissue models on demand.
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Affiliation(s)
- Kimberly A. Homan
- School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States of America
- Pharmaceutical Sciences, Roche Pharma Research and Early Development, Roche Innovation Center, Basel, Switzerland
| | - David B. Kolesky
- School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States of America
| | - Mark A. Skylar-Scott
- School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States of America
| | - Jessica Herrmann
- School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States of America
| | - Humphrey Obuobi
- School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States of America
| | - Annie Moisan
- Pharmaceutical Sciences, Roche Pharma Research and Early Development, Roche Innovation Center, Basel, Switzerland
| | - Jennifer A. Lewis
- School of Engineering and Applied Sciences, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States of America
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15
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Stankewich MC, Moeckel GW, Ji L, Ardito T, Morrow JS. Isoforms of Spectrin and Ankyrin Reflect the Functional Topography of the Mouse Kidney. PLoS One 2016; 11:e0142687. [PMID: 26727517 PMCID: PMC4703142 DOI: 10.1371/journal.pone.0142687] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 10/26/2015] [Indexed: 11/24/2022] Open
Abstract
The kidney displays specialized regions devoted to filtration, selective reabsorption, and electrolyte and metabolite trafficking. The polarized membrane pumps, channels, and transporters responsible for these functions have been exhaustively studied. Less examined are the contributions of spectrin and its adapter ankyrin to this exquisite functional topography, despite their established contributions in other tissues to cellular organization. We have examined in the rodent kidney the expression and distribution of all spectrins and ankyrins by qPCR, Western blotting, immunofluorescent and immuno electron microscopy. Four of the seven spectrins (αΙΙ, βΙ, βΙΙ, and βΙΙΙ) are expressed in the kidney, as are two of the three ankyrins (G and B). The levels and distribution of these proteins vary widely over the nephron. αΙΙ/βΙΙ is the most abundant spectrin, found in glomerular endothelial cells; on the basolateral membrane and cytoplasmic vesicles in proximal tubule cells and in the thick ascending loop of Henle; and less so in the distal nephron. βΙΙΙ spectrin largely replaces βΙΙ spectrin in podocytes, Bowman’s capsule, and throughout the distal tubule and collecting ducts. βΙ spectrin is only marginally expressed; its low abundance hinders a reliable determination of its distribution. Ankyrin G is the most abundant ankyrin, found in capillary endothelial cells and all tubular segments. Ankyrin B populates Bowman’s capsule, podocytes, the ascending thick loop of Henle, and the distal convoluted tubule. Comparison to the distribution of renal protein 4.1 isoforms and various membrane proteins indicates a complex relationship between the spectrin scaffold, its adapters, and various membrane proteins. While some proteins (e.g. ankyrin B, βΙΙΙ spectrin, and aquaporin 2) tend to share a similar distribution, there is no simple mapping of different spectrins or ankyrins to most membrane proteins. The implications of this data are discussed.
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Affiliation(s)
- Michael C. Stankewich
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States of America
- * E-mail:
| | - Gilbert W. Moeckel
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States of America
| | - Lan Ji
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States of America
| | - Thomas Ardito
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States of America
| | - Jon S. Morrow
- Department of Pathology, Yale School of Medicine, New Haven, CT, United States of America
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, United States of America
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16
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Lee A, Slattery C, Nikolic-Paterson DJ, Hryciw DH, Wilk S, Wilk E, Zhang Y, Valova VA, Robinson PJ, Kelly DJ, Poronnik P. Chloride channel ClC-5 binds to aspartyl aminopeptidase to regulate renal albumin endocytosis. Am J Physiol Renal Physiol 2015; 308:F784-92. [DOI: 10.1152/ajprenal.00322.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 01/04/2015] [Indexed: 12/17/2022] Open
Abstract
ClC-5 is a chloride/proton exchanger that plays an obligate role in albumin uptake by the renal proximal tubule. ClC-5 forms an endocytic complex with the albumin receptor megalin/cubilin. We have identified a novel ClC-5 binding partner, cytosolic aspartyl aminopeptidase (DNPEP; EC 3.4.11.21), that catalyzes the release of N-terminal aspartate/glutamate residues. The physiological role of DNPEP remains largely unresolved. Mass spectrometric analysis of proteins binding to the glutathione- S-transferase (GST)-ClC-5 C terminus identified DNPEP as an interacting partner. Coimmunoprecipitation confirmed that DNPEP and ClC-5 also associated in cells. Further experiments using purified GST-ClC-5 and His-DNPEP proteins demonstrated that the two proteins bound directly to each other. In opossum kidney (OK) cells, confocal immunofluorescence studies revealed that DNPEP colocalized with albumin-containing endocytic vesicles. Overexpression of wild-type DNPEP increased cell-surface levels of ClC-5 and albumin uptake. Analysis of DNPEP-immunoprecipitated products from rat kidney lysate identified β-actin and tubulin, suggesting a role for DNPEP in cytoskeletal maintenance. A DNase I inhibition assay showed a significant decrease in the amount of G actin when DNPEP was overexpressed in OK cells, suggesting a role for DNPEP in stabilizing the cytoskeleton. DNPEP was not present in the urine of healthy rats; however, it was readily detected in the urine in rat models of mild and heavy proteinuria (diabetic nephropathy and anti-glomerular basement membrane disease, respectively). Urinary levels of DNPEP were found to correlate with the severity of proteinuria. Therefore, we have identified another key molecular component of the albumin endocytic machinery in the renal proximal tubule and describe a new role for DNPEP in stabilizing the actin cytoskeleton.
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Affiliation(s)
- Aven Lee
- UQ Centre for Clinical Research, The University of Queensland, Herston, Brisbane, Queensland, Australia
| | - Craig Slattery
- School of Biomolecular and Biomedical Sciences, University College Dublin, Belfield, Dublin, Republic. of Ireland
| | - David J. Nikolic-Paterson
- Department of Nephrology, Monash University Department of Medicine, Monash Medical Centre, Clayton, Victoria, Australia
| | - Deanne H. Hryciw
- Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia
| | - Sherwin Wilk
- Department of Pharmacology, Mount Sinai School of Medicine, New York, New York
| | - Elizabeth Wilk
- Department of Pharmacology, Mount Sinai School of Medicine, New York, New York
| | - Yuan Zhang
- Department of Medicine, Saint Vincent's Hospital, Fitzroy, Victoria, Australia
| | - Valentina A. Valova
- Children's Medical Research Institute, The University of Sydney, Westmead New South Wales, Australia; and
| | - Phillip J. Robinson
- Children's Medical Research Institute, The University of Sydney, Westmead New South Wales, Australia; and
| | - Darren J. Kelly
- Department of Medicine, Saint Vincent's Hospital, Fitzroy, Victoria, Australia
| | - Philip Poronnik
- School of Medical Sciences and the Bosch Institute, The University of Sydney, New South Wales, Australia
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17
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Pusch M, Zifarelli G. ClC-5: Physiological role and biophysical mechanisms. Cell Calcium 2014; 58:57-66. [PMID: 25443653 DOI: 10.1016/j.ceca.2014.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/19/2014] [Accepted: 09/20/2014] [Indexed: 01/05/2023]
Abstract
Cl(-) transport in animal cells has fundamental physiological roles and it is mediated by a variety of protein families, one of them being the CLC family of ion channels and transporters. Besides their physiological relevance, CLC proteins show peculiar biophysical properties. This review will focus on a member of the CLC protein family, the endosomal Cl(-)/H(+) antiporter ClC-5. ClC-5 mutations cause Dent's disease, a renal syndrome due to defective protein reabsorption in the proximal tubule. This established the critical function of ClC-5 for endocytosis. However, our understanding of ClC-5's molecular role in endosomes and of its biophysical properties has proved elusive in spite of important progress achieved in the last two decades. Early models in which ClC-5 would provide a shunt conductance to enable efficient endosomal acidification conflicted with the antiport activity of ClC-5 that has more recently emerged. Currently, the physiological role of ClC-5 is hotly debated and its biophysical properties are still not fully understood.
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Affiliation(s)
- Michael Pusch
- Istituto di Biofisica, CNR, Via De Marini 6, 16149 Genoa, Italy
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18
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Takahashi Y, Fujii T, Fujita K, Shimizu T, Higuchi T, Tabuchi Y, Sakamoto H, Naito I, Manabe K, Uchida S, Sasaki S, Ikari A, Tsukada K, Sakai H. Functional coupling of chloride-proton exchanger ClC-5 to gastric H+,K+-ATPase. Biol Open 2014; 3:12-21. [PMID: 24429108 PMCID: PMC3892156 DOI: 10.1242/bio.20136205] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
It has been reported that chloride–proton exchanger ClC-5 and vacuolar-type H+-ATPase are essential for endosomal acidification in the renal proximal cells. Here, we found that ClC-5 is expressed in the gastric parietal cells which secrete actively hydrochloric acid at the luminal region of the gland, and that it is partially localized in the intracellular tubulovesicles in which gastric H+,K+-ATPase is abundantly expressed. ClC-5 was co-immunoprecipitated with H+,K+-ATPase in the lysate of tubulovesicles. The ATP-dependent uptake of 36Cl− into the vesicles was abolished by 2-methyl-8-(phenylmethoxy)imidazo[1,2-a]pyridine-3-acetonitrile (SCH28080), an inhibitor of H+,K+-ATPase, suggesting functional expression of ClC-5. In the tetracycline-regulated expression system of ClC-5 in the HEK293 cells stably expressing gastric H+,K+-ATPase, ClC-5 was co-immunoprecipitated with H+,K+-ATPase, but not with endogenous Na+,K+-ATPase. The SCH28080-sensitive 36Cl− transporting activity was observed in the ClC-5-expressing cells, but not in the ClC-5-non-expressing cells. The mutant (E211A-ClC-5), which has no H+ transport activity, did not show the SCH28080-sensitive 36Cl− transport. On the other hand, both ClC-5 and its mutant (E211A) significantly increased the activity of H+,K+-ATPase. Our results suggest that ClC-5 and H+,K+-ATPase are functionally associated and that they may contribute to gastric acid secretion.
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Affiliation(s)
- Yuji Takahashi
- Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
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Stauber T, Weinert S, Jentsch TJ. Cell biology and physiology of CLC chloride channels and transporters. Compr Physiol 2013; 2:1701-44. [PMID: 23723021 DOI: 10.1002/cphy.c110038] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Proteins of the CLC gene family assemble to homo- or sometimes heterodimers and either function as Cl(-) channels or as Cl(-)/H(+)-exchangers. CLC proteins are present in all phyla. Detailed structural information is available from crystal structures of bacterial and algal CLCs. Mammals express nine CLC genes, four of which encode Cl(-) channels and five 2Cl(-)/H(+)-exchangers. Two accessory β-subunits are known: (1) barttin and (2) Ostm1. ClC-Ka and ClC-Kb Cl(-) channels need barttin, whereas Ostm1 is required for the function of the lysosomal ClC-7 2Cl(-)/H(+)-exchanger. ClC-1, -2, -Ka and -Kb Cl(-) channels reside in the plasma membrane and function in the control of electrical excitability of muscles or neurons, in extra- and intracellular ion homeostasis, and in transepithelial transport. The mainly endosomal/lysosomal Cl(-)/H(+)-exchangers ClC-3 to ClC-7 may facilitate vesicular acidification by shunting currents of proton pumps and increase vesicular Cl(-) concentration. ClC-3 is also present on synaptic vesicles, whereas ClC-4 and -5 can reach the plasma membrane to some extent. ClC-7/Ostm1 is coinserted with the vesicular H(+)-ATPase into the acid-secreting ruffled border membrane of osteoclasts. Mice or humans lacking ClC-7 or Ostm1 display osteopetrosis and lysosomal storage disease. Disruption of the endosomal ClC-5 Cl(-)/H(+)-exchanger leads to proteinuria and Dent's disease. Mouse models in which ClC-5 or ClC-7 is converted to uncoupled Cl(-) conductors suggest an important role of vesicular Cl(-) accumulation in these pathologies. The important functions of CLC Cl(-) channels were also revealed by human diseases and mouse models, with phenotypes including myotonia, renal loss of salt and water, deafness, blindness, leukodystrophy, and male infertility.
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Affiliation(s)
- Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie FMP and Max-Delbrück-Centrum für Molekulare Medizin MDC, Berlin, Germany
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20
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Christensen EI, Wagner CA, Kaissling B. Uriniferous tubule: structural and functional organization. Compr Physiol 2013; 2:805-61. [PMID: 23961562 DOI: 10.1002/cphy.c100073] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The uriniferous tubule is divided into the proximal tubule, the intermediate (thin) tubule, the distal tubule and the collecting duct. The present chapter is based on the chapters by Maunsbach and Christensen on the proximal tubule, and by Kaissling and Kriz on the distal tubule and collecting duct in the 1992 edition of the Handbook of Physiology, Renal Physiology. It describes the fine structure (light and electron microscopy) of the entire mammalian uriniferous tubule, mainly in rats, mice, and rabbits. The structural data are complemented by recent data on the location of the major transport- and transport-regulating proteins, revealed by morphological means(immunohistochemistry, immunofluorescence, and/or mRNA in situ hybridization). The structural differences along the uriniferous tubule strictly coincide with the distribution of the major luminal and basolateral transport proteins and receptors and both together provide the basis for the subdivision of the uriniferous tubule into functional subunits. Data on structural adaptation to defined functional changes in vivo and to genetical alterations of specified proteins involved in transepithelial transport importantly deepen our comprehension of the correlation of structure and function in the kidney, of the role of each segment or cell type in the overall renal function,and our understanding of renal pathophysiology.
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Receptor-mediated endocytosis and endosomal acidification is impaired in proximal tubule epithelial cells of Dent disease patients. Proc Natl Acad Sci U S A 2013; 110:7014-9. [PMID: 23572577 DOI: 10.1073/pnas.1302063110] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Receptor-mediated endocytosis, involving megalin and cubilin, mediates renal proximal-tubular reabsorption and is decreased in Dent disease because of mutations of the chloride/proton antiporter, chloride channel-5 (CLC-5), resulting in low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, and renal failure. To facilitate studies of receptor-mediated endocytosis and the role of CLC-5, we established conditionally immortalized proximal-tubular epithelial cell lines (ciPTECs) from three patients with CLC-5 mutations (30:insH, R637X, and del132-241) and a normal male. Confocal microscopy using the tight junction marker zona occludens-1 (ZO-1) and end-binding protein-1 (EB-1), which is specific for the plus end of microtubules demonstrated that the ciPTECs polarized. Receptor-mediated endocytic uptake of fluorescent albumin and transferrin in 30:insH and R637X ciPTECs was significantly decreased, compared with normal ciPTECs, and could be further reduced by competition with 10-fold excess of unlabeled albumin and transferrin, whereas in the del132-241 ciPTEC, receptor-mediated endocytic uptake was abolished. Investigation of endosomal acidification by live-cell imaging of pHluorin-VAMP2 (vesicle-associated membrane protein-2), a pH-sensitive-GFP construct, revealed that the endosomal pH in normal and 30:insH ciPTECs was similar, whereas in del132-241 and R637X ciPTECs, it was significantly more alkaline, indicating defective acidification in these ciPTECs. The addition of bafilomycin-A1, a V-ATPase inhibitor, raised the pH significantly in all ciPTECs, demonstrating that the differences in acidification were not due to alterations in the V-ATPase, but instead to abnormalities of CLC-5. Thus, our studies, which have established human Dent disease ciPTECs that will facilitate studies of mechanisms in renal reabsorption, demonstrate that Dent disease-causing CLC-5 mutations have differing effects on endosomal acidification and receptor-mediated endocytosis that may not be coupled.
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22
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Rbaibi Y, Cui S, Mo D, Carattino M, Rohatgi R, Satlin LM, Szalinski CM, Swanhart LM, Fölsch H, Hukriede NA, Weisz OA. OCRL1 modulates cilia length in renal epithelial cells. Traffic 2012; 13:1295-305. [PMID: 22680056 DOI: 10.1111/j.1600-0854.2012.01387.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 06/06/2012] [Accepted: 06/08/2012] [Indexed: 01/18/2023]
Abstract
Lowe syndrome is an X-linked disorder characterized by cataracts at birth, mental retardation and progressive renal malfunction that results from loss of function of the OCRL1 (oculocerebrorenal syndrome of Lowe) protein. OCRL1 is a lipid phosphatase that converts phosphatidylinositol 4,5-bisphosphate to phosphatidylinositol 4-phosphate. The renal pathogenesis of Lowe syndrome patients has been suggested to result from alterations in membrane trafficking, but this cannot fully explain the disease progression. We found that knockdown of OCRL1 in zebrafish caused developmental defects consistent with disruption of ciliary function, including body axis curvature, pericardial edema, hydrocephaly and impaired renal clearance. In addition, cilia in the proximal tubule of the zebrafish pronephric kidney were longer in ocrl morphant embryos. We also found that knockdown of OCRL1 in polarized renal epithelial cells caused elongation of the primary cilium and disrupted formation of cysts in three-dimensional cultures. Calcium release in response to ATP was blunted in OCRL1 knockdown cells, suggesting changes in signaling that could lead to altered cell function. Our results suggest a new role for OCRL1 in renal epithelial cell function that could contribute to the pathogenesis of Lowe syndrome.
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Affiliation(s)
- Youssef Rbaibi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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23
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Sandoval RM, Wagner MC, Patel M, Campos-Bilderback SB, Rhodes GJ, Wang E, Wean SE, Clendenon SS, Molitoris BA. Multiple factors influence glomerular albumin permeability in rats. J Am Soc Nephrol 2012; 23:447-57. [PMID: 22223875 DOI: 10.1681/asn.2011070666] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Different laboratories recently reported incongruous results describing the quantification of albumin filtration using two-photon microscopy. We investigated the factors that influence the glomerular sieving coefficient for albumin (GSC(A)) in an effort to explain these discordant reports and to develop standard operating procedures for determining GSC(A). Multiple factors influenced GSC(A), including the kidney depth of image acquisition (10-20 μm was appropriate), the selection of fluorophore (probes emitting longer wavelengths were superior), the selection of plasma regions for fluorescence measurements, the size and molecular dispersion characteristics of dextran polymers if used, dietary status, and the genetic strain of rat. Fasting reduced the GSC(A) in Simonsen Munich Wistar rats from 0.035±0.005 to 0.016±0.004 (P<0.01). Frömter Munich Wistar rats had a much lower GSC(A) in both the fed and the fasted states. Finally, we documented extensive albumin transcytosis with vesicular and tubular delivery to and fusion with the basolateral membrane in S1 proximal tubule cells. In summary, these results help explain the previously conflicting microscopy and micropuncture data describing albumin filtration and highlight the dynamic nature of glomerular albumin permeability.
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Affiliation(s)
- Ruben M Sandoval
- Division of Nephrology, Department of Medicine, Indiana Center for Biological Microscopy, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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24
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Hryciw DH, Kruger WA, Briffa JF, Slattery C, Bolithon A, Lee A, Poronnik P. Sgk-1 is a Positive Regulator of Constitutive Albumin Uptake in Renal Proximal Tubule Cells. Cell Physiol Biochem 2012; 30:1215-26. [DOI: 10.1159/000343313] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2012] [Indexed: 12/12/2022] Open
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25
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ClC-5 mutations associated with Dent's disease: a major role of the dimer interface. Pflugers Arch 2011; 463:247-56. [PMID: 22083641 DOI: 10.1007/s00424-011-1052-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 10/23/2011] [Accepted: 10/24/2011] [Indexed: 12/30/2022]
Abstract
Dent's disease is an X-linked recessive disorder affecting the proximal tubules. Mutations in the 2Cl(-)/H(+) exchanger ClC-5 gene CLCN5 are frequently associated with Dent's disease. Functional characterization of mutations of CLCN5 have helped to elucidate the physiopathology of Dent's disease and provided evidence that several different mechanisms underlie the ClC-5 dysfunction in Dent's disease. Modeling studies indicate that many CLCN5 mutations are located at the interface between the monomers of ClC-5, demonstrating that this protein region plays an important role in Dent's disease. On the basis of functional data, CLCN5 mutations can be divided into three different classes. Class 1 mutations impair processing and folding, and as a result, the ClC-5 mutants are retained within the endoplasmic reticulum and targeted for degradation by quality control mechanisms. Class 2 mutations induce a delay in protein processing and reduce the stability of ClC-5. As a consequence, the cell surface expression and currents of the ClC-5 mutants are lower. Class 3 mutations do not alter the trafficking of ClC-5 to the cell surface and early endosomes but induce altered electrical activity. Here, we discuss the functional consequences of the three classes of CLCN5 mutations on ClC-5 structure and function.
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26
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Lin Z, Jin S, Duan X, Wang T, Martini S, Hulamm P, Cha B, Hubbard A, Donowitz M, Guggino SE. Chloride channel (Clc)-5 is necessary for exocytic trafficking of Na+/H+ exchanger 3 (NHE3). J Biol Chem 2011; 286:22833-45. [PMID: 21561868 DOI: 10.1074/jbc.m111.224998] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ClC-5, a chloride/proton exchanger, is predominantly expressed and localized in subapical endosomes of the renal proximal tubule. Mutations of the CLCN5 gene cause Dent disease. The symptoms of Dent disease are replicated in Clcn5 knock-out mice. Absence of ClC-5 in mice is associated with reduced surface expression of NHE3 in proximal tubules. The molecular basis for this change is not fully understood. In this study, we investigated the mechanisms by which ClC-5 regulates trafficking of NHE3. Whether ClC-5-dependent endocytosis, exocytosis, or both contributed to the altered distribution of NHE3 was examined. First, NHE3 activity in proximal tubules of wild type (WT) and Clcn5 KO mice was determined by two-photon microscopy. Basal and dexamethasone-stimulated NHE3 activity of Clcn5 KO mice was decreased compared with that seen in WT mice, whereas the degree of inhibition of NHE3 activity by increasing cellular concentration of cAMP (forskolin) or Ca(2+) (A23187) was not different in WT and Clcn5 KO mice. Second, NHE3-dependent absorption of HCO(3)(-), measured by single tubule perfusion, was reduced in proximal tubules of Clcn5 KO mice. Third, by cell surface biotinylation, trafficking of NHE3 was examined in short hairpin RNA (shRNA) plasmid-transfected opossum kidney cells. Surface NHE3 was reduced in opossum kidney cells with reduced expression of ClC-5, whereas the total protein level of NHE3 did not change. Parathyroid hormone decreased NHE3 surface expression, but the extent of decrease and the rate of endocytosis observed in both scrambled and ClC-5 knockdown cells were not significantly different. However, the rates of basal and dexamethasone-stimulated exocytosis of NHE3 were attenuated in ClC-5 knockdown cells. These results show that ClC-5 plays an essential role in exocytosis of NHE3.
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Affiliation(s)
- Zhihong Lin
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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27
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Grand T, L'Hoste S, Mordasini D, Defontaine N, Keck M, Pennaforte T, Genete M, Laghmani K, Teulon J, Lourdel S. Heterogeneity in the processing of
CLCN5
mutants related to Dent disease. Hum Mutat 2011; 32:476-83. [PMID: 21305656 DOI: 10.1002/humu.21467] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Teddy Grand
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Sébastien L'Hoste
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - David Mordasini
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Nadia Defontaine
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Mathilde Keck
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Thomas Pennaforte
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Mathieu Genete
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Kamel Laghmani
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Jacques Teulon
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
| | - Stéphane Lourdel
- UPMC Univ Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
- CNRS, ERL 7226, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
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28
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Duan X, Mao Y, Wen X, Yang T, Xue Y. Excess fluoride interferes with chloride-channel-dependent endocytosis in ameloblasts. J Dent Res 2010; 90:175-80. [PMID: 21148016 DOI: 10.1177/0022034510385687] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF). Both CF and dental fluorosis result in protein retention in mature enamel. We hypothesized that excess fluoride might cause protein retention by interfering with CFTR function, resulting in abnormal expression of proteases and pathological endocytosis. Millimolar concentrations of fluoride reduced uptake of Emdogain, an enamel matrix derivative, in ameloblast-like PABSo-E cells, while stimulating an acidic intracellular environment at the same time. When CFTR function was inhibited by either an siRNA or a chloride channel inhibitor, CFTRinh-172, fluoride's effect on Emdogain uptake was partially blocked. Treatment of cells with CFTR siRNA down-regulated expression of proteases MMP20 and KLK4 and increased intracellular pH. We conclude that excess fluoride inhibits endocytic activity of ameloblasts through the CFTR chloride channel or other chloride channels. The intracellular pH might be the key mechanism by which abnormal proteolytic activity and defective endocytosis cause the residual protein observed in enamel of patients with CF and dental fluorosis.
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Affiliation(s)
- X Duan
- Department of Oral Biology, The Fourth Military Medical University, 145 West Changle Road, Xi’an, Shaanxi 710032, PR China.
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29
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Gena P, Calamita G, Guggino WB. Cadmium impairs albumin reabsorption by down-regulating megalin and ClC5 channels in renal proximal tubule cells. ENVIRONMENTAL HEALTH PERSPECTIVES 2010; 118:1551-1556. [PMID: 20576581 PMCID: PMC2974692 DOI: 10.1289/ehp.0901874] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Revised: 05/16/2010] [Accepted: 06/24/2010] [Indexed: 05/29/2023]
Abstract
BACKGROUND Cadmium (Cd) is a potent nephrotoxicant that impairs the reabsorptive and secretory functions of the renal proximal tubule, leading to albuminuria. OBJECTIVES To gain insights into the mechanisms of Cd-induced albuminuria, we investigated effects of Cd on the expression of megalin and chloride channel 5 (ClC5), two key players in albumin-receptor-mediated endocytosis. METHODS We used quantitative polymerase chain reaction, Western blotting, the albumin endocytosis assay, and confocal microscopy to evaluate effects of Cd on the expression and regulation of megalin and ClC5 in cultured LLC-PK1 cells, a pig proximal tubular cell model. RESULTS Ten micromolar cadmium chloride (CdCl2) caused a significant time- and dose-dependent decrease in both mRNA and protein levels of megalin and ClC5, whereas no changes resulted from exposure to other divalent metals (zinc chloride, manganese chloride, magnesium chloride, and nickel chloride). After inhibiting protein synthesis using cycloheximide (CHX), we found that levels of both megalin and ClC5 were lower in Cd-challenged cells than in cells treated with Cd or CHX only, which is consistent with reduced translation and/or posttranslational down-regulation. Moreover, Cd-induced degradation of megalin and ClC5 was abolished by the lysosomal pathway inhibitor bafilomycin A-1 but not by the proteasome system blocker MG-132, suggesting that the enhanced proteolysis was occurring via lysosomes. Using confocal microscopy, we observed a remarkable reduction of fluoroisothiocyanate (FITC)-labeled albumin uptake after Cd exposure. CONCLUSIONS We found that Cd reduced the transcriptional expression of megalin and ClC5 and, at the same time, increased the degradation of megalin and ClC5 proteins via the lysosomal pathway in an in vitro model of renal proximal tubular cells. Overall, these results provide valuable insights into the molecular mechanisms by which Cd impairs luminal protein reabsorption by renal proximal tubules.
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Affiliation(s)
- Patrizia Gena
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of General and Environmental Physiology, University of Bari, Bari, Italy
| | - Giuseppe Calamita
- Department of General and Environmental Physiology, University of Bari, Bari, Italy
| | - William B. Guggino
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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30
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Stauber T, Jentsch TJ. Sorting motifs of the endosomal/lysosomal CLC chloride transporters. J Biol Chem 2010; 285:34537-48. [PMID: 20817731 DOI: 10.1074/jbc.m110.162545] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The CLC protein family contains plasma membrane chloride channels and the intracellular chloride-proton exchangers ClC-3-7. The latter proteins mainly reside on the various compartments of the endosomal-lysosomal system where they are involved in the luminal acidification or chloride accumulation. Although their partially overlapping subcellular distribution has been studied extensively, little is known about their targeting mechanism. In a comprehensive study we now performed pulldown experiments to systematically map the differential binding of adaptor proteins of the endosomal sorting machinery (adaptor proteins and GGAs (Golgi-localized, γ-ear containing, Arf binding)) as well as clathrin to the cytosolic regions of the intracellular CLCs. The resulting interaction pattern fitted well to the known subcellular localizations of the CLCs. By mutating potential sorting motifs, we could locate almost all binding sites, including one already known for ClC-3 and several new motifs for ClC-5, -6, and -7. The impact of the identified binding sites on the subcellular localization of CLC transporters was determined by heterologous expression of mutants. Surprisingly, some vesicular CLCs retained their localization after disruption of interaction sites. However, ClC-7 could be partially shifted from lysosomes to the plasma membrane by combined mutation of N-terminal sorting motifs. The localization of its β-subunit, Ostm1, was determined by that of ClC-7. Ostm1 was not capable of redirecting ClC-7 to lysosomes.
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Affiliation(s)
- Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie and Max-Delbrück-Centrum für Molekulare Medizin, Berlin D-13125, Germany
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31
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Alex P, Ye M, Zachos NC, Sipes J, Nguyen T, Suhodrev M, Gonzales L, Arora Z, Zhang T, Centola M, Guggino SE, Li X. Clcn5 knockout mice exhibit novel immunomodulatory effects and are more susceptible to dextran sulfate sodium-induced colitis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2010; 184:3988-96. [PMID: 20181886 PMCID: PMC4460988 DOI: 10.4049/jimmunol.0901657] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Although the intracellular Cl(-)/H(+) exchanger Clc-5 is expressed in apical intestinal endocytic compartments, its pathophysiological role in the gastrointestinal tract is unknown. In light of recent findings that CLC-5 is downregulated in active ulcerative colitis (UC), we tested the hypothesis that loss of CLC-5 modulates the immune response, thereby inducing susceptibility to UC. Acute dextran sulfate sodium (DSS) colitis was induced in Clcn5 knockout (KO) and wild-type (WT) mice. Colitis, monitored by disease activity index, histological activity index, and myeloperoxidase activity were significantly elevated in DSS-induced Clcn5 KO mice compared with those in WT mice. Comprehensive serum multiplex cytokine profiling demonstrated a heightened Th1-Th17 profile (increased TNF-alpha, IL-6, and IL-17) in DSS-induced Clcn5 KO mice compared with that in WT DSS colitis mice. Interestingly, Clcn5 KO mice maintained on a high vitamin D diet attenuated DSS-induced colitis. Immunofluorescence and Western blot analyses of colonic mucosa validated the systemic cytokine patterns and further revealed enhanced activation of the NF-kappaB pathway in DSS-induced Clcn5 KO mice compared with those in WT mice. Intriguingly, high baseline levels of IL-6 and phospho-IkappaB were observed in Clcn5 KO mice, suggesting a novel immunopathogenic role for the functional defects that result from the loss of Clc-5. Our studies demonstrate that the loss of Clc-5 1) exhibits IL-6-mediated immunopathogenesis, 2) significantly exacerbated DSS-induced colitis, which is influenced by dietary factors, including vitamin D, and 3) portrays distinct NF-kappaB-modulated Th1-Th17 immune dysregulation, implying a role for CLC-5 in the immunopathogenesis of UC.
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Affiliation(s)
- Philip Alex
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Mei Ye
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Department of Internal Medicine and Geriatrics, Zhongnan Hospital, Wuhan University, Wuhan, China
| | - Nicholas C. Zachos
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Jennifer Sipes
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Thuan Nguyen
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Maxim Suhodrev
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Liberty Gonzales
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Zubin Arora
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Ting Zhang
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Michael Centola
- Immunology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Sandra E. Guggino
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Xuhang Li
- Division of Gastroenterology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
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32
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Reed AAC, Loh NY, Terryn S, Lippiat JD, Partridge C, Galvanovskis J, Williams SE, Jouret F, Wu FTF, Courtoy PJ, Nesbit MA, Rorsman P, Devuyst O, Ashcroft FM, Thakker RV. CLC-5 and KIF3B interact to facilitate CLC-5 plasma membrane expression, endocytosis, and microtubular transport: relevance to pathophysiology of Dent's disease. Am J Physiol Renal Physiol 2009; 298:F365-80. [PMID: 19940036 PMCID: PMC2822520 DOI: 10.1152/ajprenal.00038.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal tubular reabsorption is important for extracellular fluid homeostasis and much of this occurs via the receptor-mediated endocytic pathway. This pathway is disrupted in Dent’s disease, an X-linked renal tubular disorder that is characterized by low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, and renal failure. Dent's disease is due to mutations of CLC-5, a chloride/proton antiporter, expressed in endosomes and apical membranes of renal tubules. Loss of CLC-5 function alters receptor-mediated endocytosis and trafficking of megalin and cubilin, although the underlying mechanisms remain to be elucidated. Here, we report that CLC-5 interacts with kinesin family member 3B (KIF3B), a heterotrimeric motor protein that facilitates fast anterograde translocation of membranous organelles. Using yeast two-hybrid, glutathione-S-transferase pull-down and coimmunoprecipitation assays, the COOH terminus of CLC-5 and the coiled-coil and globular domains of KIF3B were shown to interact. This was confirmed in vivo by endogenous coimmunoprecipitation of CLC-5 and KIF3B and codistribution with endosomal markers in mouse kidney fractions. Confocal live cell imaging in kidney cells further demonstrated association of CLC-5 and KIF3B, and transport of CLC-5-containing vesicles along KIF3B microtubules. KIF3B overexpression and underexpression, using siRNA, had reciprocal effects on whole cell chloride current amplitudes, CLC-5 cell surface expression, and endocytosis of albumin and transferrin. Clcn5Y/− mouse kidneys and isolated proximal tubular polarized cells showed increased KIF3B expression, whose effects on albumin endocytosis were dependent on CLC-5 expression. Thus, the CLC-5 and KIF3B interaction is important for CLC-5 plasma membrane expression and for facilitating endocytosis and microtubular transport in the kidney.
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Affiliation(s)
- Anita A C Reed
- Academic Endocrine Unit, Nuffield Department of Medicine, University of Oxford, Oxford Centre for Diabetes, Endocrinology, and Metabolism, Churchill Hospital, Oxford, United Kingdom
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Cui S, Guerriero CJ, Szalinski CM, Kinlough CL, Hughey RP, Weisz OA. OCRL1 function in renal epithelial membrane traffic. Am J Physiol Renal Physiol 2009; 298:F335-45. [PMID: 19940034 DOI: 10.1152/ajprenal.00453.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The X-linked disorder Lowe syndrome arises from mutations in OCRL1, a lipid phosphatase that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP(2)). Most patients with Lowe syndrome develop proteinuria very early in life. PIP(2) dynamics are known to modulate numerous steps in membrane trafficking, and it has been proposed that OCRL1 activity regulates the biogenesis or trafficking of the multiligand receptor megalin. To examine this possibility, we investigated the effects of siRNA-mediated OCRL1 knockdown on biosynthetic and postendocytic membrane traffic in canine and human renal epithelial cells. Cells depleted of OCRL1 did not have significantly elevated levels of cellular PIP(2) but displayed an increase in actin comets, as previously observed in cultured cells derived from Lowe patients. Using assays to independently quantitate the endocytic trafficking of megalin and of megalin ligands, we could observe no defect in the trafficking or function of megalin upon OCRL1 knockdown. Moreover, apical delivery of a newly synthesized marker protein was unaffected. OCRL1 knockdown did result in a significant increase in secretion of the lysosomal hydrolase cathepsin D, consistent with a role for OCRL1 in membrane trafficking between the trans-Golgi network and endosomes. Together, our studies suggest that OCRL1 does not directly modulate endocytosis or postendocytic membrane traffic and that the renal manifestations observed in Lowe syndrome patients are downstream consequences of the loss of OCRL1 function.
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Affiliation(s)
- Shanshan Cui
- Renal Electrolyte Division, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15261, USA
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Selvam S, Chang WV, Nakamura T, Samant DM, Thomas PB, Trousdale MD, Mircheff AK, Schechter JE, Yiu SC. Microporous poly(L-lactic acid) membranes fabricated by polyethylene glycol solvent-cast/particulate leaching technique. Tissue Eng Part C Methods 2009; 15:463-74. [PMID: 19260769 DOI: 10.1089/ten.tec.2008.0431] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
With the eventual goal of developing a tissue-engineered tear secretory system, we found that primary lacrimal gland acinar cells grown on solid poly(L-lactic acid) (PLLA) supports expressed the best histiotypic morphology. However, to be able to perform vectorial transport functions, epithelia must be supported by a permeable substratum. In the present study, we describe the use of a solvent-cast/particulate leaching technique to fabricate microporous PLLA membranes (mpPLLAm) from PLLA/polyethylene glycol blends. Scanning electron microscopy revealed pores on both the air-cured ( approximately 4 microm) and glass-cured sides (<2 microm) of the mpPLLAm. Diffusion studies were performed with mpPLLAm fabricated from 57.1% PLLA/42.9% polyethylene glycol blends to confirm the presence of channelized pores. The data reveal that glucose, L-tryptophan, and dextran (a high molecular weight glucose polymer) readily permeate mpPLLAm. Diffusion of the immunoglobulin G through the mpPLLAm decreased with time, suggesting the possible adsorption and occlusion of the pores. Cells cultured on the mpPLLAm (57.1/42.9 wt%) grew to subconfluent monolayers but retained histiotypic morphological and physiological characteristics of lacrimal acinar cells in vivo. Our results suggest that mpPLLAm fabricated using this technique may be useful as a scaffold for a bioartificial lacrimal gland device.
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Affiliation(s)
- Shivaram Selvam
- Mork Family Department of Chemical Engineering and Materials Science, Viterbi School of Engineering, University of Southern California, Los Angeles, California
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Novel CLCN5 mutations in patients with Dent’s disease result in altered ion currents or impaired exchanger processing. Kidney Int 2009; 76:999-1005. [DOI: 10.1038/ki.2009.305] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
The multiple and complex functions of the renal tubule in regulating water, electrolyte, and mineral homeostasis make it prone to numerous genetic abnormalities resulting in malfunction. The phenotypic expression depends on the mode of interference with the normal physiology of the segment affected, and whether the abnormality is caused by loss of function or, less commonly, gain of function. In this review we address the current knowledge about the association between the genetics and clinical manifestations and treatment of representative disorders affecting the length of the nephron.
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Sullivan S, Alex P, Dassopoulos T, Zachos NC, Iacobuzio-Donahue C, Donowitz M, Brant SR, Cuffari C, Harris ML, Datta LW, Conklin A, Chen Y, Li X. Downregulation of sodium transporters and NHERF proteins in IBD patients and mouse colitis models: potential contributors to IBD-associated diarrhea. Inflamm Bowel Dis 2009; 15:261-74. [PMID: 18942765 PMCID: PMC2627787 DOI: 10.1002/ibd.20743] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND One of the most common symptoms among patients with inflammatory bowel disease (IBD) is diarrhea, which is thought to be contributed by changes in electrolyte transport associated with intestinal inflammation. This study was designed to test the hypothesis that intestinal Na(+)-related transporters/channels and their regulatory proteins may be downregulated as a potential contributor to IBD-associated diarrhea. METHODS SDS-PAGE and Western blotting and/or confocal immunomicroscopy were used to examine the expression of Na(+)/H(+)-exchangers 1-3 (NHE1-3), epithelial Na(+) channel (ENaC), Na(+)/K(+)-ATPase, the intracellular Cl(-) channel 5 (ClC-5), and NHE3 regulatory factors (NHERF1,2) in ileal and colonic pinch biopsies from IBD patients and noninflammatory controls, as well as from colonic mucosa of dextran sodium sulfate (DSS)- and TNBS-induced acute murine IBD models. RESULTS NHE1,3 (but not NHE2), beta-ENaC, Na(+)/K(+)-ATPase-alpha, ClC-5, and NHERF1 were all downregulated in sigmoid mucosal biopsies from most cases of active UC and/or CD compared to controls. NHE3 was also decreased in ileal mucosal biopsies of active CD, as well as in approximately 50% of sigmoid biopsies from inactive UC or CD. Importantly, similar downregulation of NHE1,3, beta-ENaC, and NHERF1,2 was also observed in the mouse colon (but not ileum) of DSS- and TNBS-induced colitis. CONCLUSIONS IBD-associated diarrhea may be due to a coordinated downregulation of multiple Na(+) transporter and related regulatory proteins, including NHE1,3, Na(+)/K(+)-ATPase, and ENaC, as well as NHERF1,2, and ClC-5, all of which are involved directly or indirectly in intestinal Na(+) absorption.
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Affiliation(s)
- Sean Sullivan
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205,Dept of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Philip Alex
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | | | - Nicholas C. Zachos
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | | | - Mark Donowitz
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Steven R. Brant
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Carmen Cuffari
- Dept of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Mary L. Harris
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Lisa Wu Datta
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - aurie Conklin
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205,Dept of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Yueping Chen
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Xuhang Li
- GI Division/Dept of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205,Address correspondence to: Xuhang Li, Ph.D. 720 Rutland Ave, 918 Ross Research Bldg GI Division, Department of Medicine Johns Hopkins University School of Medicine Baltimore, MD 21205 Tel. 443-287-4804 Fax. 410-955-9677 E-mail:
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Smith AJ, Reed AAC, Loh NY, Thakker RV, Lippiat JD. Characterization of Dent's disease mutations of CLC-5 reveals a correlation between functional and cell biological consequences and protein structure. Am J Physiol Renal Physiol 2008; 296:F390-7. [PMID: 19019917 PMCID: PMC2643861 DOI: 10.1152/ajprenal.90526.2008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mutations of the human CLCN5 gene, which encodes the CLC-5 Cl(-)/H(+) exchanger, lead to Dent's disease. Mutations result in functional defects that range from moderate reductions to complete loss of whole cell currents, although the severity of the functional defect rarely correlates with the severity of the disease. To further elucidate the basis of CLC-5 mutations causing Dent's disease, we examined the functional and cell biological consequences of seven previously reported missense mutants, utilizing electrophysiological and cell biological techniques. This revealed three classes of Dent's disease-causing CLC-5 mutations. Class 1 mutations lead to endoplasmic reticulum retention and degradation of CLC-5. Class 2 mutations appear to have little effect on subcellular distribution of CLC-5 but cause defective function resulting in severe defects in endosomal acidification. Class 3 mutations lead to alterations in the endosomal distribution of CLC-5 but are otherwise able to support endosomal acidification. Molecular modeling demonstrates a structural basis that may underlie the nature of the defect resulting from each mutation with each class occupying discrete regions of the protein quaternary structure. Thus these results demonstrate that the cell biological consequences of CLC-5 mutations are heterogeneous and can be classified into three major groups and that a correlation between the nature of the defect and the location of the mutation in the structure may be drawn. This model may prove to be useful as a tool to aid in the diagnosis and future therapeutic intervention of the disease.
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Affiliation(s)
- Andrew J Smith
- Institute of Membrane & Systems Biology, Faculty of Biological Sciences, Univ. of Leeds, Leeds, LS2 9JT, UK
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Physiological roles of CLC Cl−/H+ exchangers in renal proximal tubules. Pflugers Arch 2008; 458:23-37. [DOI: 10.1007/s00424-008-0597-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 09/22/2008] [Accepted: 09/26/2008] [Indexed: 12/19/2022]
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40
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Jouret F, Devuyst O. CFTR and defective endocytosis: new insights in the renal phenotype of cystic fibrosis. Pflugers Arch 2008; 457:1227-36. [PMID: 18839205 DOI: 10.1007/s00424-008-0594-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2008] [Accepted: 09/23/2008] [Indexed: 12/18/2022]
Abstract
Inactivation of the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) causes cystic fibrosis (CF). Although CFTR is expressed in the kidney, no overwhelming renal phenotype is associated with CF. Recent studies have shown that the level of CFTR mRNA in mouse kidney approaches that found in lung. CFTR is particularly abundant in the apical area of proximal tubule cells, where it co-distributes with the Cl(-)/H(+) exchanger ClC-5 and Rab5a in endosomes. The biological relevance of CFTR in proximal tubule endocytosis has been tested in CF mouse models and CF patients. Mice lacking CFTR show a defective receptor-mediated endocytosis, as evidenced by impaired uptake of (125)I-beta(2)-microglobulin, a decreased expression of the cubilin receptor in the kidney, and a significant excretion of cubilin and its low-molecular-weight ligands into the urine. Low-molecular-weight proteinuria (and particularly transferrinuria) is similarly detected in CF patients in comparison with normal controls or patients with chronic lung inflammation. These studies suggest that the functional loss of CFTR impairs the handling of low-molecular-weight proteins by the kidney, supporting a role of CFTR in receptor-mediated endocytosis in proximal tubule cells. The selective proteinuria should be integrated in the pathophysiology of multi-systemic complications increasingly observed in CF patients.
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Affiliation(s)
- François Jouret
- Division of Nephrology, Université catholique de Louvain Medical School, Avenue Hippocrate, 10, 1200 Brussels, Belgium
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41
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Jentsch TJ. CLC chloride channels and transporters: from genes to protein structure, pathology and physiology. Crit Rev Biochem Mol Biol 2008; 43:3-36. [PMID: 18307107 DOI: 10.1080/10409230701829110] [Citation(s) in RCA: 277] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
CLC genes are expressed in species from bacteria to human and encode Cl(-)-channels or Cl(-)/H(+)-exchangers. CLC proteins assemble to dimers, with each monomer containing an ion translocation pathway. Some mammalian isoforms need essential beta -subunits (barttin and Ostm1). Crystal structures of bacterial CLC Cl(-)/H(+)-exchangers, combined with transport analysis of mammalian and bacterial CLCs, yielded surprising insights into their structure and function. The large cytosolic carboxy-termini of eukaryotic CLCs contain CBS domains, which may modulate transport activity. Some of these have been crystallized. Mammals express nine CLC isoforms that differ in tissue distribution and subcellular localization. Some of these are plasma membrane Cl(-) channels, which play important roles in transepithelial transport and in dampening muscle excitability. Other CLC proteins localize mainly to the endosomal-lysosomal system where they may facilitate luminal acidification or regulate luminal chloride concentration. All vesicular CLCs may be Cl(-)/H(+)-exchangers, as shown for the endosomal ClC-4 and -5 proteins. Human diseases and knockout mouse models have yielded important insights into their physiology and pathology. Phenotypes and diseases include myotonia, renal salt wasting, kidney stones, deafness, blindness, male infertility, leukodystrophy, osteopetrosis, lysosomal storage disease and defective endocytosis, demonstrating the broad physiological role of CLC-mediated anion transport.
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Affiliation(s)
- Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany.
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42
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Cunningham R, Esmaili A, Brown E, Biswas RS, Murtazina R, Donowitz M, Dijkman HB, van der Vlag J, Hogema BM, De Jonge HR, Shenolikar S, Wade JB, Weinman EJ. Urine electrolyte, mineral, and protein excretion in NHERF-2 and NHERF-1 null mice. Am J Physiol Renal Physiol 2008; 294:F1001-7. [PMID: 18256311 DOI: 10.1152/ajprenal.00504.2007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The adaptor proteins sodium/hydrogen exchanger regulatory factor (NHERF)-1 and NHERF-2 have overlapping tissue distribution in renal cells and overlapping specificity in their binding to renal transporters and other proteins. To compare the kidney-specific differences in the function of these adaptor proteins, NHERF-1 and NHERF-2 null mice were compared with wild-type control mice. In NHERF-2 null mice, the renal proximal tubule abundance and distribution of NHERF-1 and NHERF-3 were not different from those in wild-type animals. The glomerular expression of podocalyxin and ZO-1 also did not differ. NHERF-1 null mice had increased urinary excretion of phosphate, calcium, and uric acid compared with wild-type control and NHERF-2 null mice. Because of the association between NHERF-2 and podocalyxin in glomeruli and ClC-5 in the renal proximal tubule, the urinary excretion of protein was determined. There were no differences in the urinary excretion of protein or low-molecular-weight proteins between wild-type control, NHERF-1(-/-), and NHERF-2(-/-) mice. These studies indicate that the increased urinary excretion of phosphate and uric acid are specific to NHERF-1 null mice and highlight the fact that predictions about the role of adaptor proteins such as the NHERF proteins obtained from studies of model cell systems must be confirmed in whole animals.
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Affiliation(s)
- Rochelle Cunningham
- Univ. of Maryland School of Medicine, 22 S. Greene St., N3W143, Baltimore, MD 21201, USA.
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Abstract
NHE3 is the brush-border (BB) Na+/H+exchanger of small intestine, colon, and renal proximal tubule which is involved in large amounts of neutral Na+absorption. NHE3 is a highly regulated transporter, being both stimulated and inhibited by signaling that mimics the postprandial state. It also undergoes downregulation in diarrheal diseases as well as changes in renal disorders. For this regulation, NHE3 exists in large, multiprotein complexes in which it associates with at least nine other proteins. This review deals with short-term regulation of NHE3 and the identity and function of its recognized interacting partners and the multiprotein complexes in which NHE3 functions.
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Affiliation(s)
- Mark Donowitz
- Department of Medicine, GI Division, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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44
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Schmieder S, Bogliolo S, Ehrenfeld J. N-glycosylation of the Xenopus laevis ClC-5 protein plays a role in cell surface expression, affecting transport activity at the plasma membrane. J Cell Physiol 2007; 210:479-88. [PMID: 17111367 DOI: 10.1002/jcp.20882] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Mutations in the gene encoding ClC-5 lead to X-linked hypercalciuric nephrolithiasis (XLHN), characterized by proteinuria, hypercalciuria, and phosphaturia. In renal proximal tubule cells, ClC-5 was identified as an important player in endocytosis, which ensures reabsorption of filtered protein. However, the recent finding that ClC-5 is a Cl(-)/H(+) antiporter and not a Cl(-) channel as long thought points to the lack of understanding of its functional role. Also, little biochemical data are available about ClC-5 and its post-translational modifications have not been investigated. Here, we examined the role of N-glycosylation of xClC-5 in the Xenopus oocyte expression system by comparing wild-type (WT) xClC-5 and N-glycosylation site mutants. We found that xClC-5 is N-glycosylated on asparagines 169 and 470, which are the only N-glycosylated sites. xClC-5 mutants have an increased susceptibility to polyubiquitination and proteasomal degradation; however, without a notable impact on the expression level. Using a cross-linking reagent, we showed that xClC-5 assembles into protein complexes, independent of its N-glycosylation. Voltage-clamp measurements showed a reduced conductance in the presence of tunicamycin and with xClC-5 N-glycosylation site mutants. Using immunocytochemistry, we localized xClC-5 mainly in intracellular compartments, and found that its cell surface pool is reduced in the absence of N-glycans. We further examined the plasma membrane retrieval of WT and mutant xClC-5 in the presence of Brefeldin A (BFA), and found that the non-glycosylated mutant was retrieved more than five times faster than the WT protein. We conclude that N-glycosylation enhances cell surface expression of xClC-5, increasing its plasma membrane transport activity.
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Affiliation(s)
- Sandra Schmieder
- Laboratoire de Physiologie Cellulaire et Moléculaire Des Systèmes Intégrés, Université de Nice-Sophia Antipolis/CNRS, UMR 6548, Nice, France
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Zifarelli G, Pusch M. CLC chloride channels and transporters: a biophysical and physiological perspective. Rev Physiol Biochem Pharmacol 2007; 158:23-76. [PMID: 17729441 DOI: 10.1007/112_2006_0605] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chloride-transporting proteins play fundamental roles in many tissues in the plasma membrane as well as in intracellular membranes. They have received increasing attention in the last years because crucial, and often unexpected and novel, physiological functions have been disclosed with gene-targeting approaches, X-ray crystallography, and biophysical analysis. CLC proteins form a gene family that comprises nine members in mammals, at least four of which are involved in human genetic diseases. The X-ray structure of the bacterial CLC homolog, ClC-ec1, revealed a complex fold and confirmed the anticipated homodimeric double-barreled architecture of CLC-proteins with two separate Cl-ion transport pathways, one in each subunit. Four of the mammalian CLC proteins, ClC-1, ClC-2, ClC-Ka, and ClC-Kb, are chloride ion channels that fulfill their functional roles-stabilization of the membrane potential, transepithelial salt transport, and ion homeostasisin the plasma membrane. The other five CLC proteins are predominantly expressed in intracellular organelles like endosomes and lysosomes, where they are probably important for a proper luminal acidification, in concert with the V-type H+-ATPase. Surprisingly, ClC-4, ClC-5, and probably also ClC-3, are not Cl- ion channels but exhibit significant Cl-/H+ antiporter activity, as does the bacterial homolog ClC-ec1 and the plant homolog AtCLCa. The physiological significance of the Cl-/H+ antiport activity remains to be established.
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Affiliation(s)
- G Zifarelli
- CNR, Istituto di Biofisica, Via De Marini 6, 16149 Genova, Italy
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Ludwig M, Utsch B, Monnens LAH. Recent advances in understanding the clinical and genetic heterogeneity of Dent's disease. Nephrol Dial Transplant 2006; 21:2708-17. [PMID: 16861240 DOI: 10.1093/ndt/gfl346] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- Michael Ludwig
- Department of Clinical Biochemistry, University of Bonn, Sigmund-Freud-Strasse 25, D-53105 Bonn, Germany.
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Caruso-Neves C, Kwon SH, Guggino WB. Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT2 receptor-mediated protein kinase B activation. Proc Natl Acad Sci U S A 2005; 102:17513-8. [PMID: 16293694 PMCID: PMC1297674 DOI: 10.1073/pnas.0507255102] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Albumin endocytosis in renal proximal tubule cells is a clathrin- and receptor-mediated mechanism that, in several pathophysiological conditions, is involved in initiating or promoting tubule-interstitial disease. Although much work has been done on this pathway, the regulation of albumin endocytosis in proximal tubule cells is not well understood. Here, we study the modulation by angiotensin II (Ang II) of albumin endocytosis in LLC-PK1, a model of proximal tubule cells. We observed that Ang II increases albumin endocytosis by approximately 100% at 10(-9) M. This effect is completely reversed by 10(-9) M PD123319, a specific AT(2) receptor antagonist, but not by losartan, a specific AT(1) receptor antagonist, at concentrations up to 10(-7) M. The Ang II effect on albumin endocytosis is also reversed by: phosphoinositide 3-kinase inhibitors LY294002 (2.5 x 10(-6) M) or wortmannin (10(-7) M), the protein kinase B inhibitor (2 x 10(-5) M), and staurosporine (2 x 10(-6) M), an inhibitor of 3'-phosphoinositide-dependent kinase 1. Ang II induced the selective phosphorylation of protein kinase B (PKB) at the Thr-308 residue without a change in Ser-473 phosphorylation, a combination that leads to an increase in PKB activity. These effects were completely abolished by 3 x 10(-6) M staurosporine or 10(-8) M PD123319. Our experiments also showed that PKB is present in the membrane fraction in overnight-starved LLC-PK1 cells. Taken together, these data show that Ang II increases albumin endocytosis through an AT(2) receptor mediated by activation of PKB in the plasma membrane, which depends on the basal activity of the phosphatidyl-inositol 3-kinase.
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Affiliation(s)
- Celso Caruso-Neves
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil
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48
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Hryciw DH, Ekberg J, Pollock CA, Poronnik P. ClC-5: a chloride channel with multiple roles in renal tubular albumin uptake. Int J Biochem Cell Biol 2005; 38:1036-42. [PMID: 16226913 DOI: 10.1016/j.biocel.2005.09.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 09/05/2005] [Accepted: 09/08/2005] [Indexed: 11/15/2022]
Abstract
ClC-5 is a chloride (Cl(-)) channel expressed in renal tubules and is critical for normal tubular function. Loss of function nonsense or missense mutations in ClC-5 are associated with Dent's disease, a condition in which patients present with low molecular weight (LMW) proteinuria (including albuminuria), hypercalciuria and nephrolithiasis. Several key studies in ClC-5 knockout mice have shown that the proteinuria results from defective tubular reabsorption of proteins. ClC-5 is typically regarded as an intracellular Cl(-) channel and thus the defect in this receptor-mediated uptake pathway was initially attributed to the failure of the early endosomes to acidify correctly. ClC-5 was postulated to play a key role in transporting the Cl(-) ions required to compensate for the movement of H(+) during endosomal acidification. However, more recent studies suggest additional roles for ClC-5 in the endocytosis of albumin. ClC-5 is now known to be expressed at low levels at the cell surface and appears to be a key component in the assembly of the macromolecular complex involved in protein endocytosis. Furthermore, mutations in ClC-5 affect the trafficking of v-H(+)-ATPase and result in decreased expression of the albumin receptor megalin/cubulin. Thus, the expression of ClC-5 at the cell surface as well as its presence in endosomes appears to be essential for normal protein uptake by the renal proximal tubule.
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Affiliation(s)
- Deanne H Hryciw
- School of Biomedical Sciences, The University of Queensland, Brisbane, Qld 4072, Australia
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