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Marsch P, Rajagopal N, Nangia S. Biophysics of claudin proteins in tight junction architecture: Three decades of progress. Biophys J 2024:S0006-3495(24)00393-X. [PMID: 38859584 DOI: 10.1016/j.bpj.2024.06.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 05/19/2024] [Accepted: 06/07/2024] [Indexed: 06/12/2024] Open
Abstract
Tight junctions are cell-cell adhesion complexes that act as gatekeepers of the paracellular space. Formed by several transmembrane proteins, the claudin family performs the primary gate-keeping function. The claudin proteins form charge and size-selective diffusion barriers to maintain homeostasis across endothelial and epithelial tissue. Of the 27 known claudins in mammals, some are known to seal the paracellular space, while others provide selective permeability. The differences in permeability arise due to the varying expression levels of claudins in each tissue. The tight junctions are observed as strands in freeze-fracture electron monographs; however, at the molecular level, tight junction strands form when multiple claudin proteins assemble laterally (cis assembly) within a cell and head-on (trans assembly) with claudins of the adjacent cell in a zipper-like architecture, closing the gap between the neighboring cells. The disruption of tight junctions caused by changing claudin expression levels or mutations can lead to diseases. Therefore, knowledge of the molecular architecture of the tight junctions and how that is tied to tissue-specific function is critical for fighting diseases. Here, we review the current understanding of the tight junctions accrued over the last three decades from experimental and computational biophysics perspectives.
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Affiliation(s)
- Patrick Marsch
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York
| | - Nandhini Rajagopal
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York
| | - Shikha Nangia
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York.
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2
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Cornelius V, Droessler L, Amasheh S. Quercetin Improves Barrier Properties in Porcine Small Intestine but Not in Peyer's Patches. Int J Mol Sci 2024; 25:1530. [PMID: 38338808 PMCID: PMC10855467 DOI: 10.3390/ijms25031530] [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: 12/21/2023] [Revised: 01/18/2024] [Accepted: 01/24/2024] [Indexed: 02/12/2024] Open
Abstract
Peyer's patches (PPs) are part of the gut-associated lymphatic tissue (GALT) and represent the first line of the intestinal immunological defense. They consist of follicles with lymphocytes and an overlying subepithelial dome with dendritic cells and macrophages, and they are covered by the follicle-associated epithelium (FAE). A sealed paracellular pathway in the FAE is crucial for the controlled uptake of luminal antigens. Quercetin is the most abundant plant flavonoid and has a barrier-strengthening effect on tight junctions (TJs), a protein complex that regulates the paracellular pathway. In this study, we aimed to analyze the effect of quercetin on porcine PPs and the surrounding villus epithelium (VE). We incubated both tissue types for 4 h in Ussing chambers, recorded the transepithelial electrical resistance (TEER), and measured the unidirectional tracer flux of [3H]-mannitol. Subsequently, we analyzed the expression, protein amount, and localization of three TJ proteins, claudin 1, claudin 2, and claudin 4. In the PPs, we could not detect an effect of quercetin after 4 h, neither on TEER nor on the [3H]-mannitol flux. In the VE, quercetin led to a higher TEER value, while the [3H]-mannitol flux was unchanged. The pore-forming claudin 2 was decreased while the barrier-forming claudin 4 was increased and the expression was upregulated. Claudin 1 was unchanged and all claudins could be located in the paracellular membrane by immunofluorescence microscopy. Our study shows the barrier-strengthening effect of quercetin in porcine VE by claudin 4 upregulation and a claudin 2 decrease. Moreover, it underlines the different barrier properties of PPs compared to the VE.
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Affiliation(s)
| | | | - Salah Amasheh
- Institute of Veterinary Physiology, School of Veterinary Medicine, Freie Universität Berlin, 14163 Berlin, Germany
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Awad K, Barmeyer C, Bojarski C, Nagel O, Lee IFM, Schweiger MR, Schulzke JD, Bücker R. Epithelial Barrier Dysfunction in Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D) via Downregulation of Claudin-1. Cells 2023; 12:2846. [PMID: 38132165 PMCID: PMC10741936 DOI: 10.3390/cells12242846] [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: 11/20/2023] [Revised: 12/05/2023] [Accepted: 12/07/2023] [Indexed: 12/23/2023] Open
Abstract
BACKGROUND In patients with diarrhea-predominant irritable bowel syndrome (IBS-D), the diarrheal mechanisms are largely unknown, and they were examined in this study on colon biopsies. METHODS Electrophysiological measurements were used for monitoring functional changes in the diarrheic colon specimens. In parallel, tight junction protein expression was analyzed by Western blot and confocal laser-scanning microscopy, and signaling pathway analysis was performed using RNA sequencing and bioinformatics. RESULTS Epithelial resistance was decreased, indicating an epithelial leak flux diarrheal mechanism with a molecular correlate of decreased claudin-1 expression, while induction of active anion secretion and impairment of active sodium absorption via the epithelial sodium channel, ENaC, were not detected. The pathway analysis revealed activation of barrier-affecting cytokines TNF-α, IFN-γ, IL-1β and IL-4. CONCLUSIONS Barrier dysfunction as a result of epithelial tight junction changes plays a role in IBS-D as a pathomechanism inducing a leak flux type of diarrhea.
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Affiliation(s)
- Karem Awad
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Christian Barmeyer
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Christian Bojarski
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Oliver Nagel
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - In-Fah M. Lee
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Michal R. Schweiger
- Institute for Translational Epigenetics, Medical Faculty, University of Cologne, 50931 Cologne, Germany
| | - Jörg-Dieter Schulzke
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Roland Bücker
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
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Nyimanu D, Behm C, Choudhury S, Yu ASL. The role of claudin-2 in kidney function and dysfunction. Biochem Soc Trans 2023; 51:1437-1445. [PMID: 37387353 DOI: 10.1042/bst20220639] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 06/19/2023] [Accepted: 06/22/2023] [Indexed: 07/01/2023]
Abstract
Claudin-2 is a tight junction protein expressed in leaky epithelia where it forms paracellular pores permeable to cations and water. The paracellular pore formed by claudin-2 is important in energy-efficient cation and water transport in the proximal tubules of the kidneys. Mounting evidence now suggests that claudin-2 may modulate cellular processes often altered in disease, including cellular proliferation. Also, dysregulation of claudin-2 expression has been linked to various diseases, including kidney stone disease and renal cell carcinoma. However, the mechanisms linking altered claudin-2 expression and function to disease are poorly understood and require further investigation. The aim of this review is to discuss the current understanding of the role of claudin-2 in kidney function and dysfunction. We provide a general overview of the claudins and their organization in the tight junction, the expression, and function of claudin-2 in the kidney, and the evolving evidence for its role in kidney disease.
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Affiliation(s)
- Duuamene Nyimanu
- The Jared Grantham Kidney Institute, University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160, U.S.A
| | - Christine Behm
- The Jared Grantham Kidney Institute, University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160, U.S.A
| | - Sonali Choudhury
- The Jared Grantham Kidney Institute, University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160, U.S.A
| | - Alan S L Yu
- The Jared Grantham Kidney Institute, University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160, U.S.A
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Alexander RT. Kidney stones, hypercalciuria, and recent insights into proximal tubule calcium reabsorption. Curr Opin Nephrol Hypertens 2023; 32:359-365. [PMID: 37074688 DOI: 10.1097/mnh.0000000000000892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
PURPOSE OF REVIEW Most kidney stones are composed of calcium, and the greatest risk factor for kidney stone formation is hypercalciuria. Patients who form kidney stones often have reduced calcium reabsorption from the proximal tubule, and increasing this reabsorption is a goal of some dietary and pharmacological treatment strategies to prevent kidney stone recurrence. However, until recently, little was known about the molecular mechanism that mediates calcium reabsorption from the proximal tubule. This review summarizes newly uncovered key insights and discusses how they may inform the treatment of kidney stone formers. RECENT FINDINGS Studies examining claudin-2 and claudin-12 single and double knockout mice, combined with cell culture models, support complementary independent roles for these tight junction proteins in contributing paracellular calcium permeability to the proximal tubule. Moreover, a family with a coding variation in claudin-2 causing hypercalciuria and kidney stones have been reported, and reanalysis of Genome Wide Association Study (GWAS) data demonstrates an association between noncoding variations in CLDN2 and kidney stone formation. SUMMARY The current work begins to delineate the molecular mechanisms whereby calcium is reabsorbed from the proximal tubule and suggests a role for altered claudin-2 mediated calcium reabsorption in the pathogenesis of hypercalciuria and kidney stone formation.
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Affiliation(s)
- R Todd Alexander
- Department of Pediatrics
- Department of Physiology, University of Alberta
- The Women's & Children's Health Research Institute, Edmonton, Alberta, Canada
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Du Z, Yan Q, Shen E, Weinstein AM, Wang T. Regulation of glomerulotubular balance. IV. Implication of aquaporin 1 in flow-dependent proximal tubule transport and cell volume. Am J Physiol Renal Physiol 2022; 323:F642-F653. [PMID: 36108052 PMCID: PMC9705020 DOI: 10.1152/ajprenal.00167.2022] [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: 06/14/2022] [Revised: 09/06/2022] [Accepted: 09/14/2022] [Indexed: 12/14/2022] Open
Abstract
The water channel aquaporin-1 (AQP1) is the principal water pathway for isotonic water reabsorption in the kidney proximal tubule (PT). We investigated flow-mediated fluid (Jv) and [Formula: see text] ([Formula: see text]) reabsorption in PTs of the mouse kidney by microperfusion in wild-type (WT) and AQP1 knockout (KO) mice. Experiments were simulated in an adaptation of a mathematical model of the rat PT. An increase in perfusion rate from 5 to 20 nL/min increased Jv and [Formula: see text] in PTs of WT mice. AQP1 KO mice significantly decreased Jv at low and high flow rates compared with control. In contrast, [Formula: see text] was not reduced at either low or high flow rates. Cell volume showed no significant difference between WT and AQP1 KO mice. Renal clearance experiments showed significantly higher urine flow in AQP1 KO mice, but there was no significant difference in either Na+ and K+ or [Formula: see text] excretion. Acid-base parameters of blood pH, Pco2, [Formula: see text], and urine pH were the same in both WT and KO mice. In model calculations, tubules whose tight junction (TJ) water permeability (Pf) was that assigned to the rat TJ, showed no difference in Jv between WT and KO, whereas TJ Pf set to 25% of the rat predicted Jv concordant with our observations from AQP1 KO. These results affirm the dominance of AQP1 in mediating isotonic water reabsorption by the mouse PT and demonstrate that flow-stimulated [Formula: see text] reabsorption is intact and independent of AQP1. With reference to the model, the findings also suggest that TJ water flux in the PT is less prominent in the mouse than in the rat kidney.NEW & NOTEWORTHY We found an absence of flow-dependent modulation of fluid absorption but no effect on either proximal tubule (PT) [Formula: see text] absorption or acid-base parameters in the aquaporin 1 (AQP1) knockout mouse. We affirmed the dominance of the water channel AQP1 in mediating isotonic water reabsorption by the mouse PT and demonstrated that flow-stimulated [Formula: see text] reabsorption is independent of AQP1. With reference to the model, the findings also suggest that tight junctional water flux in the PT is less prominent in the mouse than rat kidney.
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Affiliation(s)
- Zhaopeng Du
- Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut
| | - Qingshang Yan
- Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut
| | - Emma Shen
- Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut
| | - Alan M Weinstein
- Department of Physiology and Biophysics, Weill Medical College, Cornell University, New York, New York
| | - Tong Wang
- Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut
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Berselli A, Benfenati F, Maragliano L, Alberini G. Multiscale modelling of claudin-based assemblies: a magnifying glass for novel structures of biological interfaces. Comput Struct Biotechnol J 2022; 20:5984-6010. [DOI: 10.1016/j.csbj.2022.10.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 10/24/2022] [Accepted: 10/24/2022] [Indexed: 11/03/2022] Open
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Jafari NV, Rohn JL. The urothelium: a multi-faceted barrier against a harsh environment. Mucosal Immunol 2022; 15:1127-1142. [PMID: 36180582 PMCID: PMC9705259 DOI: 10.1038/s41385-022-00565-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/18/2022] [Accepted: 08/28/2022] [Indexed: 02/04/2023]
Abstract
All mucosal surfaces must deal with the challenge of exposure to the outside world. The urothelium is a highly specialized layer of stratified epithelial cells lining the inner surface of the urinary bladder, a gruelling environment involving significant stretch forces, osmotic and hydrostatic pressures, toxic substances, and microbial invasion. The urinary bladder plays an important barrier role and allows the accommodation and expulsion of large volumes of urine without permitting urine components to diffuse across. The urothelium is made up of three cell types, basal, intermediate, and umbrella cells, whose specialized functions aid in the bladder's mission. In this review, we summarize the recent insights into urothelial structure, function, development, regeneration, and in particular the role of umbrella cells in barrier formation and maintenance. We briefly review diseases which involve the bladder and discuss current human urothelial in vitro models as a complement to traditional animal studies.
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Affiliation(s)
- Nazila V Jafari
- Department of Renal Medicine, Division of Medicine, University College London, Royal Free Hospital Campus, London, UK
| | - Jennifer L Rohn
- Department of Renal Medicine, Division of Medicine, University College London, Royal Free Hospital Campus, London, UK.
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9
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Logan M, Rinas K, McConkey B, Aucoin MG. Vero cells gain renal tubule markers in low-calcium and magnesium chemically defined media. Sci Rep 2022; 12:6180. [PMID: 35418617 PMCID: PMC9008052 DOI: 10.1038/s41598-022-10221-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 03/28/2022] [Indexed: 11/17/2022] Open
Abstract
In this study, a chemically defined, animal component-free media was developed to promote Vero growth in suspension. Key media compounds were screened using Plackett–Burman styled experiments to create a media formulation to support suspension growth. Vero cells remained viable in suspension, but their growth rate was extremely low, conversely, other cell types such as CHO-K1, MDCK and HEK293T were able to grow in single cell suspension in the same media. To investigate the slow growth of Vero cells, RNA-seq analysis was conducted. Vero cells were cultured in three different conditions: adherently in serum-containing medium, adherently in in-house medium, and in suspension in low calcium and magnesium in-house medium. This study illustrates that adherent cells maintain similar gene expression, while the suspension phenotype tends to overexpress genes related to renal tubules.
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Affiliation(s)
- Megan Logan
- Department of Chemical Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Karsten Rinas
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Brendan McConkey
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Marc G Aucoin
- Department of Chemical Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
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Uc PY, Miranda J, Raya-Sandino A, Alarcón L, Roldán ML, Ocadiz-Delgado R, Cortés-Malagón EM, Chávez-Munguía B, Ramírez G, Asomoza R, Shoshani L, Gariglio P, González-Mariscal L. E7 oncoprotein from human papillomavirus 16 alters claudins expression and the sealing of epithelial tight junctions. Int J Oncol 2020; 57:905-924. [PMID: 32945372 PMCID: PMC7473757 DOI: 10.3892/ijo.2020.5105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Accepted: 04/16/2020] [Indexed: 11/24/2022] Open
Abstract
Tight junctions (TJs) are cell-cell adhesion structures frequently altered by oncogenic transformation. In the present study the role of human papillomavirus (HPV) 16 E7 oncoprotein on the sealing of TJs was investigated and also the expression level of claudins in mouse cervix and in epithelial Madin-Darby Canine Kidney (MDCK) cells. It was found that there was reduced expression of claudins -1 and -10 in the cervix of 7-month-old transgenic K14E7 mice treated with 17β-estradiol (E2), with invasive cancer. In addition, there was also a transient increase in claudin-1 expression in the cervix of 2-month-old K14E7 mice, and claudin-10 accumulated at the border of cells in the upper layer of the cervix in FvB mice treated with E2, and in K14E7 mice treated with or without E2. These changes were accompanied by an augmented paracellular permeability of the cervix in 2- and 7-monthold FvB mice treated with E2, which became more pronounced in K14E7 mice treated with or without E2. In MDCK cells the stable expression of E7 increased the space between adjacent cells and altered the architecture of the monolayers, induced the development of an acute peak of transepithelial electrical resistance accompanied by a reduced expression of claudins -1, -2 and -10, and an increase in claudin-4. Moreover, E7 enhances the ability of MDCK cells to migrate through a 3D matrix and induces cell stiffening and stress fiber formation. These observations revealed that cell transformation induced by HPV16 E7 oncoprotein was accompanied by changes in the pattern of expression of claudins and the degree of sealing of epithelial TJs.
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Affiliation(s)
- Perla Yaceli Uc
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Jael Miranda
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Arturo Raya-Sandino
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Lourdes Alarcón
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - María Luisa Roldán
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Rodolfo Ocadiz-Delgado
- Department of Genetics and Molecular Biology, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Enoc Mariano Cortés-Malagón
- Research Unit on Genetics and Cancer, Research Division, Hospital Juárez de México, Mexico City 07760, Mexico
| | - Bibiana Chávez-Munguía
- Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Georgina Ramírez
- Department of Electrical Engineering, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - René Asomoza
- Department of Electrical Engineering, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Liora Shoshani
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Patricio Gariglio
- Department of Genetics and Molecular Biology, Center for Research and Advanced Studies, Mexico City 07360, Mexico
| | - Lorenza González-Mariscal
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies, Mexico City 07360, Mexico
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Anwer S, Szaszi K. Immunofluorescent Staining of Claudin-2 in Cultured Kidney Tubular Cells. Bio Protoc 2020; 10:e3678. [PMID: 33659349 DOI: 10.21769/bioprotoc.3678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/31/2020] [Accepted: 05/20/2020] [Indexed: 11/02/2022] Open
Abstract
Members of the claudin family of tight junction proteins regulate paracellular permeability and modulate cell signaling. During junction remodeling, these proteins are selectively inserted into or retrieved from the tight junctions, but the control and coordination of these processes remain incompletely understood. Visualization of claudins allows the assessment of changes in their localization and abundance. We use the described protocol to stain claudin-2, but it can also be adapted to stain any tight junction protein. We found that using methanol for fixing allows the best preservation of claudin-2 both at the membrane and in cytoplasmic vesicles. Staining is done using a claudin-2 specific primary and a fluorescently labelled secondary antibody, along with DAPI to label nuclei. The samples are then imaged using confocal microscopy, and a z-stack is obtained allowing visualization of both junctional and intracellular claudin-2. Total claudin-2 signal can be quantified after 3D reconstruction of the images using the Imaris software.
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Affiliation(s)
- Shaista Anwer
- Keenan Research Centre for Biomedical Science of the St. Michael's Hospital, Toronto, Canada
| | - Katalin Szaszi
- Keenan Research Centre for Biomedical Science of the St. Michael's Hospital, Toronto, Canada.,Dept. of Surgery, University of Toronto, ON, Canada
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12
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Curry JN, Saurette M, Askari M, Pei L, Filla MB, Beggs MR, Rowe PS, Fields T, Sommer AJ, Tanikawa C, Kamatani Y, Evan AP, Totonchi M, Alexander RT, Matsuda K, Yu AS. Claudin-2 deficiency associates with hypercalciuria in mice and human kidney stone disease. J Clin Invest 2020; 130:1948-1960. [PMID: 32149733 PMCID: PMC7108907 DOI: 10.1172/jci127750] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 01/08/2020] [Indexed: 12/29/2022] Open
Abstract
The major risk factor for kidney stone disease is idiopathic hypercalciuria. Recent evidence implicates a role for defective calcium reabsorption in the renal proximal tubule. We hypothesized that claudin-2, a paracellular cation channel protein, mediates proximal tubule calcium reabsorption. We found that claudin-2-null mice have hypercalciuria due to a primary defect in renal tubule calcium transport and papillary nephrocalcinosis that resembles the intratubular plugs in kidney stone formers. Our findings suggest that a proximal tubule defect in calcium reabsorption predisposes to papillary calcification, providing support for the vas washdown hypothesis. Claudin-2-null mice were also found to have increased net intestinal calcium absorption, but reduced paracellular calcium permeability in the colon, suggesting that this was due to reduced intestinal calcium secretion. Common genetic variants in the claudin-2 gene were associated with decreased tissue expression of claudin-2 and increased risk of kidney stones in 2 large population-based studies. Finally, we describe a family in which males with a rare missense variant in claudin-2 have marked hypercalciuria and kidney stone disease. Our findings indicate that claudin-2 is a key regulator of calcium excretion and a potential target for therapies to prevent kidney stones.
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Affiliation(s)
- Joshua N Curry
- Department of Molecular and Integrative Physiology and
- Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Matthew Saurette
- Department of Pediatrics and
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Masomeh Askari
- Department of Genetics, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, Academic Center for Education, Culture and Research (ACECR), Tehran, Iran
| | - Lei Pei
- Division of Nephrology and Hypertension, Department of Internal Medicine, and
| | - Michael B Filla
- Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas, USA
- Division of Nephrology and Hypertension, Department of Internal Medicine, and
| | - Megan R Beggs
- Department of Pediatrics and
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Peter Sn Rowe
- Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas, USA
- Division of Nephrology and Hypertension, Department of Internal Medicine, and
| | - Timothy Fields
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Andre J Sommer
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
| | - Chizu Tanikawa
- Laboratory of Genome Technology, Human Genome Center, Institute of Medical Science, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
| | - Yoichiro Kamatani
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Andrew P Evan
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Mehdi Totonchi
- Department of Genetics, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, Academic Center for Education, Culture and Research (ACECR), Tehran, Iran
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | - R Todd Alexander
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - Koichi Matsuda
- Laboratory of Genome Technology, Human Genome Center, Institute of Medical Science, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
- Laboratory of Clinical Genome Sequencing, Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan
| | - Alan Sl Yu
- Department of Molecular and Integrative Physiology and
- Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas, USA
- Division of Nephrology and Hypertension, Department of Internal Medicine, and
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13
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Plain A, Pan W, O’Neill D, Ure M, Beggs MR, Farhan M, Dimke H, Cordat E, Alexander RT. Claudin-12 Knockout Mice Demonstrate Reduced Proximal Tubule Calcium Permeability. Int J Mol Sci 2020; 21:ijms21062074. [PMID: 32197346 PMCID: PMC7139911 DOI: 10.3390/ijms21062074] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/11/2020] [Accepted: 03/15/2020] [Indexed: 01/13/2023] Open
Abstract
The renal proximal tubule (PT) is responsible for the reabsorption of approximately 65% of filtered calcium, primarily via a paracellular pathway. However, which protein(s) contribute this paracellular calcium pore is not known. The claudin family of tight junction proteins confers permeability properties to an epithelium. Claudin-12 is expressed in the kidney and when overexpressed in cell culture contributes paracellular calcium permeability (PCa). We therefore examined claudin-12 renal localization and its contribution to tubular paracellular calcium permeability. Claudin-12 null mice (KO) were generated by replacing the single coding exon with β-galactosidase from Escherichia coli. X-gal staining revealed that claudin-12 promoter activity colocalized with aquaporin-1, consistent with the expression in the PT. PTs were microperfused ex vivo and PCa was measured. PCa in PTs from KO mice was significantly reduced compared with WT mice. However, urinary calcium excretion was not different between genotypes, including those on different calcium containing diets. To assess downstream compensation, we examined renal mRNA expression. Claudin-14 expression, a blocker of PCa in the thick ascending limb (TAL), was reduced in the kidney of KO animals. Thus, claudin-12 is expressed in the PT, where it confers paracellular calcium permeability. In the absence of claudin-12, reduced claudin-14 expression in the TAL may compensate for reduced PT calcium reabsorption.
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Affiliation(s)
- Allein Plain
- Department of Physiology, The University of Alberta, Edmonton, AB T6J 2R7, Canada; (A.P.); (W.P.); (D.O.); (M.U.); (M.R.B.); (E.C.)
| | - Wanling Pan
- Department of Physiology, The University of Alberta, Edmonton, AB T6J 2R7, Canada; (A.P.); (W.P.); (D.O.); (M.U.); (M.R.B.); (E.C.)
| | - Deborah O’Neill
- Department of Physiology, The University of Alberta, Edmonton, AB T6J 2R7, Canada; (A.P.); (W.P.); (D.O.); (M.U.); (M.R.B.); (E.C.)
| | - Megan Ure
- Department of Physiology, The University of Alberta, Edmonton, AB T6J 2R7, Canada; (A.P.); (W.P.); (D.O.); (M.U.); (M.R.B.); (E.C.)
| | - Megan R. Beggs
- Department of Physiology, The University of Alberta, Edmonton, AB T6J 2R7, Canada; (A.P.); (W.P.); (D.O.); (M.U.); (M.R.B.); (E.C.)
- The Women’s & Children’s Health Research Institute, 11405-87 Avenue, Edmonton, AB T6G 1C9 Canada;
| | - Maikel Farhan
- The Women’s & Children’s Health Research Institute, 11405-87 Avenue, Edmonton, AB T6G 1C9 Canada;
- Department of Pediatrics, The University of Alberta, Edmonton, AB T6J 2R7, Canada
| | - Henrik Dimke
- Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, 5230 Odense, Denmark;
- Department of Nephrology, Odense University Hospital, 5000 Odense, Denmark
| | - Emmanuelle Cordat
- Department of Physiology, The University of Alberta, Edmonton, AB T6J 2R7, Canada; (A.P.); (W.P.); (D.O.); (M.U.); (M.R.B.); (E.C.)
| | - R. Todd Alexander
- Department of Physiology, The University of Alberta, Edmonton, AB T6J 2R7, Canada; (A.P.); (W.P.); (D.O.); (M.U.); (M.R.B.); (E.C.)
- The Women’s & Children’s Health Research Institute, 11405-87 Avenue, Edmonton, AB T6G 1C9 Canada;
- Department of Pediatrics, The University of Alberta, Edmonton, AB T6J 2R7, Canada
- Correspondence: ; Tel.: +1-(780)-248-5560
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14
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Curry JN, Tokuda S, McAnulty P, Yu ASL. Combinatorial expression of claudins in the proximal renal tubule and its functional consequences. Am J Physiol Renal Physiol 2020; 318:F1138-F1146. [PMID: 32174144 DOI: 10.1152/ajprenal.00057.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The proximal renal tubule (PT) is characterized by a highly conductive paracellular pathway, which contributes to a significant amount of solute and water reabsorption by the kidney. Claudins are tight junction proteins that, in part, determine the paracellular permeability of epithelia. In the present study, we determined the expression pattern of the major PT claudins. We found that claudin-2 and claudin-10 are coexpressed throughout the PT, whereas claudin-3 is coexpressed with claudin-2 predominantly in the proximal straight tubule. Additionally, claudin-2 and claudin-3 are expressed separately within mutually exclusive populations of descending thin limbs. We developed a novel double-inducible Madin-Darby canine kidney I cell model to characterize in vitro the functional effect of coexpression of PT claudins. In keeping with previous studies, we found that claudin-2 alone primarily increased cation (Na+ and Ca2+) permeability, whereas claudin-10a alone increased anion (Cl-) permeability. Coexpression of claudin-2 and claudin-10a together led to a weak physical interaction between the isoforms and the formation of a monolayer with high conductance but neutral charge selectivity. Claudin-3 expression had a negligible effect on all measures of cell permeability, whether expressed alone or together with claudin-2. In cells coexpressing a claudin-2 mutant, S68C, together with claudin-10a, inhibition of cation permeability through the claudin-2 pore with a thiol-reactive pore blocker did not block anion permeation through claudin-10a. We conclude that claudin-2 and claudin-10a form independent paracellular cation- and anion-selective channels that function in parallel.
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Affiliation(s)
- Joshua N Curry
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas.,Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas
| | - Shinsaku Tokuda
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas.,Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas
| | - Patrick McAnulty
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas.,Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas
| | - Alan S L Yu
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas.,Division of Nephrology and Hypertension, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas.,Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas
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15
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Seker M, Fernández-Rodríguez C, Martínez-Cruz LA, Müller D. Mouse Models of Human Claudin-Associated Disorders: Benefits and Limitations. Int J Mol Sci 2019; 20:ijms20215504. [PMID: 31694170 PMCID: PMC6862546 DOI: 10.3390/ijms20215504] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 11/01/2019] [Accepted: 11/02/2019] [Indexed: 12/16/2022] Open
Abstract
In higher organisms, epithelia separate compartments in order to guarantee their proper function. Such structures are able to seal but also to allow substances to pass. Within the paracellular pathway, a supramolecular structure, the tight junction transport is largely controlled by the temporospatial regulation of its major protein family called claudins. Besides the fact that the expression of claudins has been identified in different forms of human diseases like cancer, clearly defined mutations in the corresponding claudin genes have been shown to cause distinct human disorders. Such disorders comprise the skin and its adjacent structures, liver, kidney, the inner ear, and the eye. From the phenotype analysis, it has also become clear that different claudins can cause a complex phenotype when expressed in different organs. To gain deeper insights into the physiology and pathophysiology of claudin-associated disorders, several mouse models have been generated. In order to model human disorders in detail, they have been designed either as full knockouts, knock-downs or knock-ins by a variety of techniques. Here, we review human disorders caused by CLDN mutations and their corresponding mouse models that have been generated thus far and assess their usefulness as a model for the corresponding human disorder.
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Affiliation(s)
- Murat Seker
- Department of Pediatric Gastroenterology, Nephrology and Metabolism, Charité—Universitätsmedizin Berlin, Charité, 13353 Berlin, Germany;
| | | | | | - Dominik Müller
- Department of Pediatric Gastroenterology, Nephrology and Metabolism, Charité—Universitätsmedizin Berlin, Charité, 13353 Berlin, Germany;
- Correspondence:
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16
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Curry JN, Yu ASL. Paracellular calcium transport in the proximal tubule and the formation of kidney stones. Am J Physiol Renal Physiol 2019; 316:F966-F969. [PMID: 30838875 DOI: 10.1152/ajprenal.00519.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The proximal tubule (PT) is responsible for the majority of calcium reabsorption by the kidney. Most PT calcium transport appears to be passive, although the molecular facilitators have not been well established. Emerging evidence supports a major role for PT calcium transport in idiopathic hypercalciuria and the development of kidney stones. This review will cover recent developments in our understanding of PT calcium transport and the role of the PT in kidney stone formation.
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Affiliation(s)
- Joshua N Curry
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center , Kansas City, Kansas
| | - Alan S L Yu
- Jared Grantham Kidney Institute, University of Kansas Medical Center , Kansas City, Kansas
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17
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Curry JN, Yu AS. Magnesium Handling in the Kidney. Adv Chronic Kidney Dis 2018; 25:236-243. [PMID: 29793662 DOI: 10.1053/j.ackd.2018.01.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 12/26/2017] [Accepted: 01/02/2018] [Indexed: 02/07/2023]
Abstract
Magnesium is a divalent cation that fills essential roles as regulator and cofactor in a variety of biological pathways, and maintenance of magnesium balance is vital to human health. The kidney, in concert with the intestine, has an important role in maintaining magnesium homeostasis. Although micropuncture and microperfusion studies in the mammalian nephron have shone a light on magnesium handling in the various nephron segments, much of what we know about the protein mediators of magnesium handling in the kidney have come from more recent genetic studies. In the proximal tubule and thick ascending limb, magnesium reabsorption is believed to occur primarily through the paracellular shunt pathway, which ultimately depends on the electrochemical gradient setup by active sodium reabsorption. In the distal convoluted tubule, magnesium transport is transcellular, although magnesium reabsorption also appears to be related to active sodium reabsorption in this segment. In addition, evidence suggests that magnesium transport is highly regulated, although a specific hormonal regulator of extracellular magnesium has yet to be identified.
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18
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Yu ASL. Paracellular transport as a strategy for energy conservation by multicellular organisms? Tissue Barriers 2017; 5:e1301852. [PMID: 28452575 DOI: 10.1080/21688370.2017.1301852] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Paracellular transport of solutes and water accompanies transcellular transport across epithelial barriers and together they serve to maintain internal body composition. However, whether paracellular transport is necessary and why it evolved is unknown. In this commentary I discuss our recent studies to address this question in the proximal tubule of the kidney. Paracellular reabsorption of sodium occurs in the proximal tubule and is mediated by claudin-2. However, deletion of claudin-2 in mice does not affect whole kidney sodium excretion because it can be completely compensated by downtream transcellular transport mechanisms. This occurs at the expense of increased oxygen consumption, tissue hypoxia and increased susceptibility to ischemic injury. It is concluded that paracellular transport acts as an energy saving mechanism to increase transport without consuming additional oxygen. It is speculated that this might be why paracellular transport evolved in leaky epithelia with high transport needs.
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Affiliation(s)
- Alan S L Yu
- a Division of Nephrology and Hypertension, Department of Internal Medicine , University of Kansas Medical Center , Kansas City , KS , USA.,b Division of Infectious Diseases, Department of Internal Medicine , University of Kansas Medical Center , Kansas City , KS , USA
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19
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Rosenthal R, Günzel D, Krug SM, Schulzke JD, Fromm M, Yu ASL. Claudin-2-mediated cation and water transport share a common pore. Acta Physiol (Oxf) 2017; 219:521-536. [PMID: 27359349 DOI: 10.1111/apha.12742] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 11/19/2015] [Accepted: 06/28/2016] [Indexed: 12/19/2022]
Abstract
AIM Claudin-2 is a tight junction protein typically located in 'leaky' epithelia exhibiting large paracellular permeabilities like small intestine and proximal kidney tubule. Former studies revealed that claudin-2 forms paracellular channels for small cations like sodium and potassium and also paracellular channels for water. This study analyses whether the diffusive transport of sodium and water occurs through a common pore of the claudin-2 channel. METHODS Wild-type claudin-2 and different claudin-2 mutants were expressed in MDCK I kidney tubule cells using an inducible system. Ion and water permeability and the effect of blocking reagents on both were investigated on different clones of the mutants. RESULTS Neutralization of a negatively charged cation interaction site in the pore with the mutation, D65N, decreased both sodium permeability and water permeability. Claudin-2 mutants (I66C and S68C) with substitution of the pore-lining amino acids with cysteine were used to test the effect of steric blocking of the claudin-2 pore by thiol-reactive reagents. Addition of thiol-reactive reagents to these mutants simultaneously decreased conductance and water permeability. Remarkably, all experimental perturbations caused parallel changes in ion conductance and water permeability, disproving different or independent passage pathways. CONCLUSION Our results indicate that claudin-2-mediated cation and water transport are frictionally coupled and share a common pore. This pore is lined and determined in permeability by amino acid residues of the first extracellular loop of claudin-2.
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Affiliation(s)
- R. Rosenthal
- Department of Gastroenterology, Infectious Diseases and Rheumatology; Institute of Clinical Physiology; Campus Benjamin Franklin; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - D. Günzel
- Department of Gastroenterology, Infectious Diseases and Rheumatology; Institute of Clinical Physiology; Campus Benjamin Franklin; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - S. M. Krug
- Department of Gastroenterology, Infectious Diseases and Rheumatology; Institute of Clinical Physiology; Campus Benjamin Franklin; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - J.-D. Schulzke
- Department of Gastroenterology, Infectious Diseases and Rheumatology; Institute of Clinical Physiology; Campus Benjamin Franklin; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - M. Fromm
- Department of Gastroenterology, Infectious Diseases and Rheumatology; Institute of Clinical Physiology; Campus Benjamin Franklin; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - A. S. L. Yu
- Division of Nephrology and Hypertension, and the Kidney Institute; University of Kansas Medical Center; Kansas City KS USA
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20
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Tokuda S, Hirai T, Furuse M. Effects of Osmolality on Paracellular Transport in MDCK II Cells. PLoS One 2016; 11:e0166904. [PMID: 27855213 PMCID: PMC5113991 DOI: 10.1371/journal.pone.0166904] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 11/04/2016] [Indexed: 12/20/2022] Open
Abstract
Epithelia separate apical and basal compartments, and movement of substances via the paracellular pathway is regulated by tight junctions. Claudins are major constituents of tight junctions and involved in the regulation of tight junction permeability. On the other hand, the osmolality in the extracellular environment fluctuates in association with life activity. However, effects of osmotic changes on the permeaibility of claudins are poorly understood. Therefore, we investigated the effects of osmotic changes on the paracellular transport in MDCK II cells. Interestingly, apical hyposmolality decreased cation selectivity in the paracellular pathway gradually with time, and the elimination of the osmotic gradient promptly restored the cation selectivity. Apical hyposmolality also induced bleb formation at cell-cell contacts and changed the shape of cell-cell contacts from a jagged pattern to a slightly linear pattern. In claudin-2 knockout MDCK II cells, the decrease of cation selectivity, the bleb formation, nor the changes in the shape of cell-cell contacts was observed under the apical hyposmolality. Our findings in this study indicate that osmotic gradient between apical and basal sides is involved in the acute regulation of the cation selective property of claudin-2 channels.
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Affiliation(s)
- Shinsaku Tokuda
- Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- * E-mail:
| | - Toyohiro Hirai
- Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Mikio Furuse
- Division of Cell Structure, National Institute for Physiological Sciences, Okazaki, Japan
- Department of Physiological Sciences, SOKENDAI (The Graduate University for Advanced Studies), Okazaki 444–8585, Japan
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21
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Pei L, Solis G, Nguyen MTX, Kamat N, Magenheimer L, Zhuo M, Li J, Curry J, McDonough AA, Fields TA, Welch WJ, Yu ASL. Paracellular epithelial sodium transport maximizes energy efficiency in the kidney. J Clin Invest 2016; 126:2509-18. [PMID: 27214555 DOI: 10.1172/jci83942] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 04/05/2016] [Indexed: 12/12/2022] Open
Abstract
Efficient oxygen utilization in the kidney may be supported by paracellular epithelial transport, a form of passive diffusion that is driven by preexisting transepithelial electrochemical gradients. Claudins are tight-junction transmembrane proteins that act as paracellular ion channels in epithelial cells. In the proximal tubule (PT) of the kidney, claudin-2 mediates paracellular sodium reabsorption. Here, we used murine models to investigate the role of claudin-2 in maintaining energy efficiency in the kidney. We found that claudin-2-null mice conserve sodium to the same extent as WT mice, even during profound dietary sodium depletion, as a result of the upregulation of transcellular Na-K-2Cl transport activity in the thick ascending limb of Henle. We hypothesized that shifting sodium transport to transcellular pathways would lead to increased whole-kidney oxygen consumption. Indeed, compared with control animals, oxygen consumption in the kidneys of claudin-2-null mice was markedly increased, resulting in medullary hypoxia. Furthermore, tubular injury in kidneys subjected to bilateral renal ischemia-reperfusion injury was more severe in the absence of claudin-2. Our results indicate that paracellular transport in the PT is required for efficient utilization of oxygen in the service of sodium transport. We speculate that paracellular permeability may have evolved as a general strategy in epithelial tissues to maximize energy efficiency.
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22
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Baker OJ. Current trends in salivary gland tight junctions. Tissue Barriers 2016; 4:e1162348. [PMID: 27583188 DOI: 10.1080/21688370.2016.1162348] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 02/28/2016] [Accepted: 03/01/2016] [Indexed: 12/21/2022] Open
Abstract
Tight junctions form a continuous intercellular barrier between epithelial cells that is required to separate tissue spaces and regulate selective movement of solutes across the epithelium. They are composed of strands containing integral membrane proteins (e.g., claudins, occludin and tricellulin, junctional adhesion molecules and the coxsackie adenovirus receptor). These proteins are anchored to the cytoskeleton via scaffolding proteins such as ZO-1 and ZO-2. In salivary glands, tight junctions are involved in polarized saliva secretion and barrier maintenance between the extracellular environment and the glandular lumen. This review seeks to provide an overview of what is currently known, as well as the major questions and future research directions, regarding tight junction expression, organization and function within salivary glands.
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Affiliation(s)
- Olga J Baker
- School of Dentistry, University of Utah , Salt Lake City, UT, USA
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23
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Montalbetti N, Rued AC, Clayton DR, Ruiz WG, Bastacky SI, Prakasam HS, Eaton AF, Kullmann FA, Apodaca G, Carattino MD. Increased urothelial paracellular transport promotes cystitis. Am J Physiol Renal Physiol 2015; 309:F1070-81. [PMID: 26423859 DOI: 10.1152/ajprenal.00200.2015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 09/24/2015] [Indexed: 12/11/2022] Open
Abstract
Changes in the urothelial barrier are observed in patients with cystitis, but whether this leads to inflammation or occurs in response to it is currently unknown. To determine whether urothelial barrier dysfunction is sufficient to promote cystitis, we employed in situ adenoviral transduction to selectively overexpress the pore-forming tight junction-associated protein claudin-2 (CLDN-2). As expected, the expression of CLDN-2 in the umbrella cells increased the permeability of the paracellular route toward ions, but not to large organic molecules. In vivo studies of bladder function revealed higher intravesical basal pressures, reduced compliance, and increased voiding frequency in rats transduced with CLDN-2 vs. controls transduced with green fluorescent protein. While the integrity of the urothelial barrier was preserved in the rats transduced with CLDN-2, we found that the expression of this protein in the umbrella cells initiated an inflammatory process in the urinary bladder characterized by edema and the presence of a lymphocytic infiltrate. Taken together, these results are consistent with the notion that urothelial barrier dysfunction may be sufficient to trigger bladder inflammation and to alter bladder function.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Anna C Rued
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Dennis R Clayton
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Wily G Ruiz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Sheldon I Bastacky
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - H Sandeep Prakasam
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Amity F Eaton
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - F Aura Kullmann
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Gerard Apodaca
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
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24
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Amoozadeh Y, Dan Q, Xiao J, Waheed F, Szászi K. Tumor necrosis factor-α induces a biphasic change in claudin-2 expression in tubular epithelial cells: role in barrier functions. Am J Physiol Cell Physiol 2015; 309:C38-50. [PMID: 25948735 DOI: 10.1152/ajpcell.00388.2014] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 05/02/2015] [Indexed: 01/04/2023]
Abstract
The inflammatory cytokine tumor necrosis factor-α (TNF-α) is a pathogenic factor in acute and chronic kidney disease. TNF-α is known to alter expression of epithelial tight junction (TJ) proteins; however, the underlying mechanisms and the impact of this effect on epithelial functions remain poorly defined. Here we describe a novel biphasic effect of TNF-α on TJ protein expression. In LLC-PK1 tubular cells, short-term (1-6 h) TNF-α treatment selectively elevated the expression of the channel-forming TJ protein claudin-2. In contrast, prolonged (>8 h) TNF-α treatment caused a marked downregulation in claudin-2 and an increase in claudin-1, -4, and -7. The early increase and the late decrease in claudin-2 expression involved distinct mechanisms. TNF-α slowed claudin-2 degradation through ERK, causing the early increase. This increase was also mediated by the EGF receptor and RhoA and Rho kinase. In contrast, prolonged TNF-α treatment reduced claudin-2 mRNA levels and promoter activity independent from these signaling pathways. Electric Cell-substrate Impedance Sensing measurements revealed that TNF-α also exerted a biphasic effect on transepithelial resistance (TER) with an initial decrease and a late increase. Thus there was a good temporal correlation between TNF-α-induced claudin-2 protein and TER changes. Indeed, silencing experiments showed that the late TER increase was at least in part caused by reduced claudin-2 expression. Surprisingly, however, claudin-2 silencing did not prevent the early TER drop. Taken together, the TNF-α-induced changes in claudin-2 levels might contribute to TER changes and could also play a role in newly described functions of claudin-2 such as proliferation regulation.
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Affiliation(s)
- Yasaman Amoozadeh
- Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada
| | - Qinghong Dan
- Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada
| | - Jenny Xiao
- Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada
| | - Faiza Waheed
- Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada
| | - Katalin Szászi
- Keenan Research Centre for Biomedical Science of the St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada
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25
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Luettig J, Rosenthal R, Barmeyer C, Schulzke JD. Claudin-2 as a mediator of leaky gut barrier during intestinal inflammation. Tissue Barriers 2015; 3:e977176. [PMID: 25838982 DOI: 10.4161/21688370.2014.977176] [Citation(s) in RCA: 183] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 10/10/2014] [Indexed: 02/07/2023] Open
Abstract
The epithelial tight junction determines the paracellular water and ion movement in the intestine and also prevents uptake of larger molecules, including antigens, in an uncontrolled manner. Claudin-2, one of the 27 mammalian claudins regulating that barrier function, forms a paracellular channel for small cations and water. It is typically expressed in leaky epithelia like proximal nephron and small intestine and provides a major pathway for the paracellular transport of sodium, potassium, and fluid. In intestinal inflammation (Crohn's disease, ulcerative colitis), immune-mediated diseases (celiac disease), and infections (HIV enteropathy), claudin-2 is upregulated in small and large intestine and contributes to diarrhea via a leak flux mechanism. In parallel to that upregulation, other epithelial and tight junctional features are altered and the luminal uptake of antigenic macromolecules is enhanced, for which claudin-2 may be partially responsible through induction of tight junction strand discontinuities.
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Key Words
- AP, activator protein
- CARD15, caspase recruitment domain-containing protein 15
- Crohn's disease
- DSS, dextran sodium sulfate
- ECL, extracellular loop
- ERK, extracellular-regulated kinase
- HIV
- HIV, human immunodeficiency virus
- HNF, hepatocyte nuclear factor
- IBD, inflammatory bowel disease
- IFN, interferon
- IFNγ
- IL, interleukin
- JAM, junctional adhesion molecule
- JNK, c-jun N-terminal kinase
- LPS, lipopolysaccharides
- MAPK, mitogen-activated protein kinase
- MDCK, Madine Darby canine kidney
- MLC, myosin light chain
- NFκB, nuclear factor kappa B
- NOD2, nucleotide-binding oligomerization domain-containing protein 2
- PI3K, phosphatidyl-inositol-3-kinase
- ROCK, Rho kinase
- Rho, ras homolog
- STAT, signal transducers and activators of transcription
- TEER, transepithelial electrical resistance
- TJ, tight junction
- TNBS, 2,4,6-trinitrobenzene sulfonic acid
- TNF, tumor necrosis factor
- TNFα
- Tat, trans-activator of transcription
- Vpr, viral protein r; ZO, zonula occludens
- celiac disease
- claudin-2
- gp, glycoprotein
- inflammatory bowel disease
- tight junction
- ulcerative colitis
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Affiliation(s)
- J Luettig
- Institute of Clinical Physiology; Department of Gastroenterology; Charité ; Berlin, Germany
| | - R Rosenthal
- Institute of Clinical Physiology; Department of Gastroenterology; Charité ; Berlin, Germany
| | - C Barmeyer
- Institute of Clinical Physiology; Department of Gastroenterology; Charité ; Berlin, Germany
| | - J D Schulzke
- Institute of Clinical Physiology; Department of Gastroenterology; Charité ; Berlin, Germany
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26
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Abstract
Claudins are tight-junction membrane proteins that function as both pores and barriers in the paracellular pathway in epithelial cells. In the kidney, claudins determine the permeability and selectivity of different nephron segments along the renal tubule. In the proximal tubule, claudins have a role in the bulk reabsorption of salt and water. In the thick ascending limb, claudins are important for the reabsorption of calcium and magnesium and are tightly regulated by the calcium-sensing receptor. In the distal nephron, claudins need to form cation barriers and chloride pores to facilitate electrogenic sodium reabsorption and potassium and acid secretion. Aldosterone and the with-no-lysine (WNK) proteins likely regulate claudins to fine-tune distal nephron salt transport. Genetic mutations in claudin-16 and -19 cause familial hypomagnesemic hypercalciuria with nephrocalcinosis, whereas polymorphisms in claudin-14 are associated with kidney stone risk. It is likely that additional roles for claudins in the pathogenesis of other types of kidney diseases have yet to be uncovered.
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Affiliation(s)
- Alan S L Yu
- Division of Nephrology and Hypertension, and the Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas
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27
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Ahmad R, Chaturvedi R, Olivares-Villagómez D, Habib T, Asim M, Shivesh P, Polk BD, Wilson KT, Washington MK, Van Kaer L, Dhawan P, Singh AB. Targeted colonic claudin-2 expression renders resistance to epithelial injury, induces immune suppression, and protects from colitis. Mucosal Immunol 2014; 7:1340-53. [PMID: 24670427 PMCID: PMC4221190 DOI: 10.1038/mi.2014.21] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 02/17/2014] [Indexed: 02/04/2023]
Abstract
Expression of claudin-2, a tight junction protein, is highly upregulated during inflammatory bowel disease (IBD) and, due to its association with epithelial permeability, has been postulated to promote inflammation. Notably, claudin-2 has also been implicated in the regulation of intestinal epithelial proliferation. However, precise role of claudin-2 in regulating colonic homeostasis remains unclear. Here, we demonstrate, using Villin-Claudin-2 transgenic mice, that increased colonic claudin-2 expression augments mucosal permeability as well as colon and crypt length. Most notably, despite leaky colon, Cl-2TG mice were significantly protected against experimental colitis. Importantly, claudin-2 expression increased colonocyte proliferation and provided protection against colitis-induced colonocyte death in a PI-3Kinase/Bcl-2-dependent manner. However, Cl-2TG mice also demonstrated marked suppression of colitis-induced increases in immune activation and associated signaling, suggesting immune tolerance. Accordingly, colons from naive Cl-2TG mice harbored significantly increased numbers of regulatory (CD4(+)Foxp3(+)) T cells than WT littermates. Furthermore, macrophages isolated from Cl-2TG mouse colon exhibited immune anergy. Importantly, these immunosuppressive changes were associated with increased synthesis of the immunoregulatory cytokine TGF-β by colonic epithelial cells in Cl-2TG mice compared with WT littermates. Taken together, our findings reveal a critical albeit complex role of claudin-2 in intestinal homeostasis by regulating epithelial permeability, inflammation and proliferation and suggest novel therapeutic opportunities.
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Affiliation(s)
- Rizwan Ahmad
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, TN
| | - Rupesh Chaturvedi
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
| | | | | | - Mohammad Asim
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
| | - Punit Shivesh
- University of Southern California & Children’s Hospital Los Angeles, CA
| | - Brent D. Polk
- University of Southern California & Children’s Hospital Los Angeles, CA
| | - Keith T. Wilson
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN,Department of Cancer Biology, and Pathology, Vanderbilt University School of Medicine, Nashville, TN,Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN
| | - Mary K. Washington
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN
| | - Luc Van Kaer
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN
| | - Punita Dhawan
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, TN,Department of Cancer Biology, and Pathology, Vanderbilt University School of Medicine, Nashville, TN,The Veterans Affair Medical Center, Nashville, TN
| | - Amar B. Singh
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, TN,Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
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28
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Schnermann J, Huang Y, Mizel D. Fluid reabsorption in proximal convoluted tubules of mice with gene deletions of claudin-2 and/or aquaporin1. Am J Physiol Renal Physiol 2013; 305:F1352-64. [PMID: 24049145 DOI: 10.1152/ajprenal.00342.2013] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Deletions of claudin-2 (Cldn2) and aquaporin1 (AQP1) reduce proximal fluid reabsorption (PFR) by about 30% and 50%, respectively. Experiments were done to replicate these observations and to determine in AQP1/claudin-2 double knockout mice (DKO) if the effects of deletions of these established water pores are additive. PFR was determined in inactin/ketamine-anesthetized mice by free-flow micropuncture using single-nephron I(125)-iothalamate (io) clearance. Animal means of PFR [% of glomerular filtration rate (GFR)] derived from TF/Piothalamate ratios in 12 mice in each of four groups [wild type (WT), Cldn2(-/-), AQP1(-/-), and DKO) were 45.8 ± 0.85 (51 tubules), 35.4 ± 1 (54 tubules; P < 0.01 vs. WT), 36.8 ± 1 (63 tubules; P < 0.05 vs. WT), and 33.9 ± 1.4 (69 tubules; P < 0.01 vs. WT). Kidney and single-nephron GFRs (SNGFR) were significantly reduced in all mutant strains. The direct relationship between PFR and SNGFR was maintained in mutant mice, but the slope of this relationship was reduced in the absence of Cldn2 and/or AQP1. Transtubular osmotic pressure differences were not different between WT and Cldn2(-/-) mice, but markedly increased in DKO. In conclusion, the deletion of Cldn2, AQP1, or of both Cldn2 and AQP1 reduces PFR by 22.7%, 19.6%, and 26%, respectively. Our data are consistent with an up to 25% paracellular contribution to PFR. The reduced osmotic water permeability caused by absence of AQP1 augments luminal hypotonicity. Aided by a fall in filtered load, the capacity of non-AQP1-dependent transcellular reabsorption is sufficient to maintain PFR without AQP1 and claudin-2 at 75% of control.
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Affiliation(s)
- Jurgen Schnermann
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg. 10, Rm. 4D51, 9000 Rockville Pike, Bethesda, MD 20892.
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29
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Abstract
Claudins are tight junction membrane proteins that are expressed in epithelia and endothelia and form paracellular barriers and pores that determine tight junction permeability. This review summarizes our current knowledge of this large protein family and discusses recent advances in our understanding of their structure and physiological functions.
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Affiliation(s)
- Dorothee Günzel
- Department of Clinical Physiology, Charité, Campus Benjamin Franklin, Berlin, Germany
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30
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Borovac J, Barker RS, Rievaj J, Rasmussen A, Pan W, Wevrick R, Alexander RT. Claudin-4 forms a paracellular barrier, revealing the interdependence of claudin expression in the loose epithelial cell culture model opossum kidney cells. Am J Physiol Cell Physiol 2012; 303:C1278-91. [PMID: 23076790 PMCID: PMC3532495 DOI: 10.1152/ajpcell.00434.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 10/09/2012] [Indexed: 02/03/2023]
Abstract
The effect of claudins on paracellular fluxes has been predominantly studied in either Madin-Darby canine kidney (MDCK) or LLCPK cells. Neither model system has a very low transepithelial resistance (TER) as observed in leaky epithelia. Moreover, results from one model system are not always consistent with another. Opossum kidney (OK) cells form tight junctions yet have a very low TER. We therefore set out to characterize the paracellular transport properties of this cell culture model. Ussing chamber dilution potential measurements revealed that OK cells exhibit a very low TER (11.7 ± 1.4 Ω·cm(2)), slight cation selectivity (P(Na)/P(Cl) = 1.10 ± 0.01), and the Eisenman permeability sequence IV; the permeability of monovalent cations ranking K(+) > Cs(+) > Rb(+) > Na(+) > Li(+). Quantitative real-time PCR studies found that OK cells endogenously express claudin-4 > -1 > -6 > -20 > -9 > -12 > -11 > -15. Overexpression of claudin-4 significantly increased TER, decreased Na(+) and Cl(-) permeability, and increased levels of claudin-1, -6, and -9 mRNA. Knockdown of claudin-4 in the overexpressing cells significantly decreased TER without altering claudin expression; thus claudin-4 forms a barrier in OK cells. Knockdown of endogenous claudin-4 decreased claudin-1, -9, and -12 expression without altering TER. Claudin-2 overexpression decreased TER, significantly increased Na(+) and Cl(-) permeability, and decreased claudin-12 and -6 expression. Together these results demonstrate that claudin expression is tightly coupled in OK cells.
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Affiliation(s)
- Jelena Borovac
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
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31
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Yatabe MS, Yatabe J, Takano K, Murakami Y, Sakuta R, Abe S, Sanada H, Kimura J, Watanabe T. Effects of a high-sodium diet on renal tubule Ca2+ transporter and claudin expression in Wistar-Kyoto rats. BMC Nephrol 2012. [PMID: 23199000 PMCID: PMC3538060 DOI: 10.1186/1471-2369-13-160] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Background Urinary Ca2+ excretion increases with dietary NaCl. NaCl-induced calciuria may be associated with hypertension, urinary stone formation and osteoporosis, but its mechanism and long-term effects are not fully understood. This study examined alterations in the expressions of renal Ca2+ transporters, channels and claudins upon salt loading to better understand the mechanism of salt-induced urinary Ca2+ loss. Methods Eight-week old Wistar-Kyoto rats were fed either 0.3% or 8% NaCl diet for 8 weeks. Renal cortical expressions of Na+/Ca2+ exchanger 1 (NCX1), Ca2+ pump (PCMA1b), Ca2+ channel (TRPV5), calbindin-D28k, and claudins (CLDN-2, -7, -8, -16 and −19) were analyzed by quantitative PCR, western blot and/or immunohistochemistry. Results Fractional excretion of Ca2+ increased 6.0 fold with high-salt diet. Renal cortical claudin-2 protein decreased by approximately 20% with decreased immunological staining on tissue sections. Claudin-16 and −19 expressions were not altered. Renal cortical TRPV5, calbindin-D28k and NCX1 expressions increased 1.6, 1.5 and 1.2 fold, respectively. Conclusions Chronic high-salt diet decreased claudin-2 protein and increased renal TRPV5, calbindin-D28k, and NCX1. Salt loading is known to reduce the proximal tubular reabsorption of both Na+ and Ca2+. The reduction in claudin-2 protein expression may be partly responsible for the reduced Ca2+ reabsorption in this segment. The concerted upregulation of more distal Ca2+-transporting molecules may be a physiological response to curtail the loss of Ca2+, although the magnitude of compensation does not seem adequate to bring the urinary Ca2+ excretion down to that of the normal-diet group.
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Affiliation(s)
- Midori Sasaki Yatabe
- Department of Pharmacology, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295, Japan.
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32
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Abstract
Claudins are tight junction membrane proteins that regulate paracellular permeability of renal epithelia to small ions, solutes, and water. Claudins interact within the cell membrane and between neighboring cells to form tight junction strands and constitute both the paracellular barrier and the pore. The first extracellular domain of claudins is thought to be the pore-lining domain and contains the determinants of charge selectivity. Multiple claudins are expressed in different nephron segments; such differential expression likely determines the permeability properties of each segment. Recent evidence has identified claudin-2 as constituting the cation-reabsorptive pathway in the proximal tubule; claudin-14, -16, and -19 as forming a complex that regulates calcium transport in the thick ascending limb of the loop of Henle; and claudin-4, -7, and -8 as determinants of collecting duct chloride permeability. Mutations in claudin-16 and -19 cause familial hypercalciuric hypomagnesemia with nephrocalcinosis. The roles of other claudins in kidney diseases remain to be fully elucidated.
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Affiliation(s)
- Jianghui Hou
- Renal Division, Washington University, St. Louis, Missouri 63110, USA
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33
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Kim TI, Poulin EJ, Blask E, Bukhalid R, Whitehead RH, Franklin JL, Coffey RJ. Myofibroblast keratinocyte growth factor reduces tight junctional integrity and increases claudin-2 levels in polarized Caco-2 cells. Growth Factors 2012; 30:320-32. [PMID: 22946653 PMCID: PMC3594790 DOI: 10.3109/08977194.2012.717076] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The colonic epithelium is composed of a polarized monolayer sheathed by a layer of pericryptal myofibroblasts (PCMFs). We mimicked these cellular compartments in vitro to assess the effects of paracrine-acting PCMF-derived factors on tight junction (TJ) integrity, as measured by transepithelial electrical resistance (TER). Coculture with 18Co PCMFs, or basolateral administration of 18Co conditioned medium, significantly reduced TER of polarized Caco-2 cells. Among candidate paracrine factors, only keratinocyte growth factor (KGF) reduced Caco-2 TER; basolateral KGF treatment led to time- and concentration-dependent increases in claudin-2 levels. We also demonstrate that amphiregulin (AREG), produced largely by Caco-2 cells, increased claudin-2 levels, leading to epidermal growth factor receptor-mediated TER reduction. We propose that colonic epithelial TJ integrity can be modulated by paracrine KGF and autocrine AREG through increased claudin-2 levels. KGF-regulated claudin-2 induction may have implications for inflammatory bowel disease, where both KGF and claudin-2 are upregulated.
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Affiliation(s)
- Tae Il Kim
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Emily J. Poulin
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | | | | | - Robert H. Whitehead
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jeffrey L. Franklin
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Robert J. Coffey
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Veterans Affairs Medical Center, Nashville, TN 37232-2279, USA
- Corresponding Author: Robert J. Coffey, M.D., Epithelial Biology Center, 2213 Garland Avenue, 10415 MRB IV -0441, Vanderbilt University, Nashville, TN 37232, Tel: 615-343-6228, Fax: 615-343-1591,
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34
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Zuehlke J, Ebenau A, Krueger B, Goppelt-Struebe M. Vectorial secretion of CTGF as a cell-type specific response to LPA and TGF-β in human tubular epithelial cells. Cell Commun Signal 2012; 10:25. [PMID: 22938209 PMCID: PMC3503564 DOI: 10.1186/1478-811x-10-25] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 08/16/2012] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED BACKGROUND Increased expression of the pro-fibrotic protein connective tissue growth factor (CTGF) has been detected in injured kidneys and elevated urinary levels of CTGF are discussed as prognostic marker of chronic kidney disease. There is evidence that epithelial cells lining the renal tubular system contribute to uptake and secretion of CTGF. However, the role of different types of tubular epithelial cells in these processes so far has not been addressed in primary cultures of human cells. RESULTS Tubular epithelial cells of proximal and distal origin were isolated from human kidneys and cultured as polarized cells in insert wells. The pro-fibrotic stimuli lysophosphatidic acid (LPA) and transforming growth factor β (TGF-β) were used to induce CTGF secretion.LPA activated CTGF secretion in proximal tubular cells when applied from either the apical or the basolateral side as shown by immunocytochemistry. CTGF was secreted exclusively to the apical side. Signaling pathways activated by LPA included MAP kinase and Rho kinase signaling. TGF-β applied from either side also stimulated CTGF secretion primarily to the apical side with little basolateral release.Interestingly, TGF-β activation induced different signaling pathways depending on the side of TGF-β application. Smad signaling was almost exclusively activated from the basolateral side most prominently in cells of distal origin. Only part of these cells also synthesized CTGF indicating that Smad activation alone was not sufficient for CTGF induction. MAP kinases were involved in apical TGF-β-mediated activation of CTGF synthesis in proximal cells and a subset of epithelial cells of distal origin. This subpopulation of distal tubular cells was also able to internalize recombinant apical CTGF, in addition to proximal cells which were the main cells to take up exogenous CTGF. CONCLUSIONS Analysis of polarized human primary renal epithelial cells in a transwell system shows that vectorial secretion of the pro-fibrotic protein CTGF depends on the cell type, the stimulus and the signaling pathway activated. In all conditions, CTGF was secreted mainly to the apical side upon TGF-β and LPA treatment and therefore, likely contributes to increased urinary CTGF levels in vivo. Moreover, CTGF secreted basolaterally may be active as paracrine pro-fibrotic mediator.
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Affiliation(s)
- Jonathan Zuehlke
- Department of Nephrology and Hypertension, Friedrich-Alexander Universität Erlangen-Nürnberg, Loschgestrasse 8, Erlangen 91054, Germany
| | - Astrid Ebenau
- Department of Nephrology and Hypertension, Friedrich-Alexander Universität Erlangen-Nürnberg, Loschgestrasse 8, Erlangen 91054, Germany
| | - Bettina Krueger
- Department of Cellular and Molecular Physiology, Friedrich-Alexander Universität Erlangen-Nürnberg, Waldstrasse 6, Erlangen, 91054, Germany
| | - Margarete Goppelt-Struebe
- Department of Nephrology and Hypertension, Friedrich-Alexander Universität Erlangen-Nürnberg, Loschgestrasse 8, Erlangen 91054, Germany
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35
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Abstract
Claudins are tight junction integral membrane proteins that are key regulators of the paracellular pathway. The paracellular pathways in the inner ear and in the kidney are predominant routes for transepithelial cation transport. Mutations in claudin-14 cause nonsyndromic recessive deafness DFNB29. A recent genome-wide association study has identified claudin-14 as a major risk gene of hypercalciuric nephrolithiasis. In vitro analyses show that claudin-14 functions as a cation barrier in epithelial cells. The barrier function of claudin-14 is crucial for generating the K(+) gradient between perilymph and endolymph in the inner ear. However, neither homozygous individuals with DFNB29 mutations nor claudin-14 knockout mice show any renal dysfunction. In this short review, I discuss several possible mechanisms to integrate the physiological function of claudin-14 in the inner ear and the kidney.
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Affiliation(s)
- Jianghui Hou
- Renal Division, Washington University Medical School, St. Louis, Missouri, USA.
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36
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Van Itallie CM, Tietgens AJ, LoGrande K, Aponte A, Gucek M, Anderson JM. Phosphorylation of claudin-2 on serine 208 promotes membrane retention and reduces trafficking to lysosomes. J Cell Sci 2012; 125:4902-12. [PMID: 22825868 DOI: 10.1242/jcs.111237] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Claudins are critical components of epithelial and endothelial tight junction seals, but their post-transcriptional regulation remains poorly understood. Several studies have implicated phosphorylation in control of claudin localisation and/or function, but these have focused on single sites or pathways with differing results, so that it has been difficult to draw general functional conclusions. In this study, we used mass spectrometry (MS) analysis of purified claudin-2 from MDCK II cells and found that the cytoplasmic tail is multiply phosphorylated on serines, a threonine and tyrosines. Phos-tag SDS PAGE revealed that one site, S208, is heavily constitutively phosphorylated in MDCK II cells and in mouse kidney; this site was targeted for further study. Mutational analysis revealed that the phosphomimetic mutant of claudin-2, S208E, was preferentially localised to the plasma membrane while claudin-2 S208A, which could not be phosphorylated at this site, both immunolocalized and co-fractionated with lysosomal markers. Mutations at sites that were previously reported to interfere with plasma membrane targeting of claudin-2 reduced phosphorylation at S208, suggesting that membrane localisation is required for phosphorylation; however phosphorylation at S208 did not affect binding to ZO-1 or ZO-2 Administration of forskolin or PGE2 resulted in dephosphorylation at S208 and transient small increases in transepithelial electrical resistance (TER). Together these data are consistent with phosphorylation at S208 playing a major role in the retention of claudin-2 at the plasma membrane.
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Affiliation(s)
- Christina M Van Itallie
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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37
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Abstract
The physiology of paracellular permeation of ions and solutes in the kidney is pivotally important but poorly understood. Claudins are the key components of the paracellular pathway. Defects in claudin function result in a broad range of renal diseases, including hypomagnesemia, hypercalciuria and nephrolithiasis. This review describes recent findings on the physiological function of claudins underlying paracellular transport mechanisms with a focus on renal Ca(2+) handling. We have uncovered a molecular mechanism underlying paracellular Ca(2+) transport in the thick ascending limb of Henle (TAL) that involves the functional interplay of three important claudin genes: claudin-14, -16 and -19, all of which are associated with human kidney diseases with hypercalciuria, nephrolithiasis and bone mineral loss. The Ca(2+) sensing receptor (CaSR) signaling in the kidney has long been a mystery. By analyzing small non-coding RNA molecules in the kidney, we have uncovered a novel microRNA based signaling pathway downstream of CaSR that directly regulates claudin-14 gene expression and establishes the claudin-14 molecule as a key regulator for renal Ca(2+) homeostasis. The molecular cascade of CaSR-microRNAs-claudins forms a regulatory loop to maintain proper Ca(2+) homeostasis in the kidney.
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Affiliation(s)
- Jianghui Hou
- Renal Division, Washington University, St. Louis, MO, USA.
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38
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Assimakopoulos SF, Papageorgiou I, Charonis A. Enterocytes’ tight junctions: From molecules to diseases. World J Gastrointest Pathophysiol 2011; 2:123-37. [PMID: 22184542 PMCID: PMC3241743 DOI: 10.4291/wjgp.v2.i6.123] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 08/26/2011] [Accepted: 10/31/2011] [Indexed: 02/06/2023] Open
Abstract
Tight junctions (TJs) are structures between cells where cells appear in the closest possible contact. They are responsible for sealing compartments when epithelial sheets are generated. They regulate the permeability of ions, (macro) molecules and cells via the paracellular pathway. Their structure at the electron microscopic level has been well known since the 1970s; however, only recently has their macromolecular composition been revealed. This review first examines the major macromolecular components of the TJs (occludin, claudins, junctional adhesion molecule and tricellulin) and then the associated macromolecules at the intracellular plaque [zonula occludens (ZO)-1, ZO-2, ZO-3, AF-6, cingulin, 7H6]. Emphasis is given to their interactions in order to begin to understand the mode of assembly of TJs. The functional significance of TJs is detailed and several mechanisms and factors involved are discussed briefly. Emphasis is given to the role of intestinal TJs and the alterations observed or speculated in diverse disease states. Specifically, intestinal TJs may exert a pathogenetic role in intestinal (inflammatory bowel disease, celiac disease) and extraintestinal diseases (diabetes type 1, food allergies, autoimmune diseases). Additionally, intestinal TJs may be secondarily disrupted during the course of diverse diseases, subsequently allowing the bacterial translocation phenomenon and promoting the systemic inflammatory response, which is often associated with clinical deterioration. The major questions in the field are highlighted.
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39
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Li J, Ananthapanyasut W, Yu ASL. Claudins in renal physiology and disease. Pediatr Nephrol 2011; 26:2133-42. [PMID: 21365189 PMCID: PMC3203223 DOI: 10.1007/s00467-011-1824-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 01/26/2011] [Accepted: 01/28/2011] [Indexed: 12/19/2022]
Abstract
The tight junction forms the paracellular permeability barrier in all epithelia, including the renal tubule. Claudins are a family of tight junction membrane proteins with four transmembrane domains that form the paracellular pore and barrier. Their first extracellular domain appears to be important for determining selectivity. A number of claudin isoforms have been found to be important in renal tubule function, both in adults and in neonates. Familial hypomagnesemic hypercalciuria with nephrocalcinosis is an autosomal recessive syndrome characterized by impaired reabsorption of Mg and Ca in the thick ascending limb of Henle's loop. Mutations in claudin-16 and 19 can both cause this syndrome, but the pathophysiological mechanism remains controversial.
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Affiliation(s)
- Jiahua Li
- Systems Biology and Disease Program, University of Southern California Keck School of Medicine, Los Angeles, CA 90033 USA
| | - Wanwarat Ananthapanyasut
- Division of Nephrology, Department of Medicine, University of Southern California, 2025 Zonal Avenue, RMR 406, Los Angeles, CA 90089 USA
| | - Alan S. L. Yu
- Division of Nephrology, Department of Medicine, University of Southern California, 2025 Zonal Avenue, RMR 406, Los Angeles, CA 90089 USA ,Systems Biology and Disease Program, University of Southern California Keck School of Medicine, Los Angeles, CA 90033 USA
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40
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Muto S, Furuse M, Kusano E. Claudins and renal salt transport. Clin Exp Nephrol 2011; 16:61-7. [PMID: 22038258 DOI: 10.1007/s10157-011-0491-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Accepted: 01/03/2011] [Indexed: 11/25/2022]
Abstract
Tight junctions (TJs) are the most apical component of junctional complexes and regulate the movement of electrolytes and solutes by the paracellular pathway across epithelia. The defining ultrastructural features of TJs are strands of transmembrane protein particles that adhere to similar strands on adjacent cells. These strands are mainly composed of linearly polymerized integral membrane proteins called claudins. Claudins comprise a multigene family consisting of more than 20 members in mammals. Recent work has shown that claudins form barriers, determined by the paracellular electrical resistance and charge selectivity, and pores in the TJ strands. The paracellular pathways in renal tubular epithelia such as the proximal tubule, which reabsorbs the largest fraction of filtered NaCl and water, are important routes for the transport of electrolytes and water. Their transport characteristics vary among different nephron segments. Multiple claudins are expressed at TJs of individual nephron segments in a nephron segment-specific manner. Among them, claudin-2 is highly expressed at TJs of proximal tubules, which are leaky epithelia. Overexpression and knockdown of claudin-2 in epithelial cell lines, and knockout of the claudin-2 gene in mice, have demonstrated that claudin-2 forms high-conductance cation-selective pores in the proximal tubule. Here, we review the renal physiology of paracellular transport and the physiological roles of claudins in kidney function, especially claudin-2 and proximal tubule paracellular NaCl transport.
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Affiliation(s)
- Shigeaki Muto
- Division of Nephrology, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi, 329-0498, Japan.
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Zaarour N, Defontaine N, Demaretz S, Azroyan A, Cheval L, Laghmani K. Secretory carrier membrane protein 2 regulates exocytic insertion of NKCC2 into the cell membrane. J Biol Chem 2011; 286:9489-502. [PMID: 21205824 DOI: 10.1074/jbc.m110.166546] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The renal-specific Na-K-2Cl co-transporter, NKCC2, plays a pivotal role in regulating body salt levels and blood pressure. NKCC2 mutations lead to type I Bartter syndrome, a life-threatening kidney disease. Regulation of NKCC2 trafficking behavior serves as a major mechanism in controlling NKCC2 activity across the plasma membrane. However, the identities of the protein partners involved in cell surface targeting of NKCC2 are largely unknown. To gain insight into these processes, we used a yeast two-hybrid system to screen a kidney cDNA library for proteins that interact with the NKCC2 C terminus. One binding partner we identified was SCAMP2 (secretory carrier membrane protein 2). Microscopic confocal imaging and co-immunoprecipitation assays confirmed NKCC2-SCAMP2 interaction in renal cells. SCAMP2 associated also with the structurally related co-transporter NCC, suggesting that the interaction with SCAMP2 is a common feature of sodium-dependent chloride co-transporters. Heterologous expression of SCAMP2 specifically decreased cell surface abundance as well as transport activity of NKCC2 across the plasma membrane. Co-immunolocalization experiments revealed that intracellularly retained NKCC2 co-localizes with SCAMP2 in recycling endosomes. The rate of NKCC2 endocytic retrieval, assessed by the sodium 2-mercaptoethane sulfonate cleavage assay, was not affected by SCAMP2. The surface-biotinylatable fraction of newly inserted NKCC2 in the plasma membrane was reduced by SCAMP2, demonstrating that SCAMP2-induced decrease in surface NKCC2 is due to decreased exocytotic trafficking. Finally, a single amino acid mutation, cysteine 201 to alanine, within the conserved cytoplasmic E peptide of SCAMP2, which is believed to regulate exocytosis, abolished SCAMP2-mediated down-regulation of the co-transporter. Taken together, these data are consistent with a model whereby SCAMP2 regulates NKCC2 transit through recycling endosomes and limits the cell surface targeting of the co-transporter by interfering with its exocytotic trafficking.
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Affiliation(s)
- Nancy Zaarour
- INSERM, Centre de Recherche des Cordeliers, UMRS 872, CNRS, ERL7226, 75006 Paris, France
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Hong EJ, Sahu B, Jänne OA, Hammond GL. Cytoplasmic accumulation of incompletely glycosylated SHBG enhances androgen action in proximal tubule epithelial cells. Mol Endocrinol 2010; 25:269-81. [PMID: 21193555 DOI: 10.1210/me.2010-0483] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Human sex hormone-binding globulin (SHBG) accumulates within the cytoplasm of epithelial cells lining the proximal convoluted tubules of mice expressing human SHBG transgenes. The main ligands of SHBG, testosterone and its metabolite, 5α-dihydrotestosterone (DHT), alter expression of androgen-responsive genes in the kidney. To determine how intracellular SHBG might influence androgen action, we used a mouse proximal convoluted tubule (PCT) cell line with characteristics of S1/S2 epithelial cells in which human SHBG accumulates. Western blotting revealed that SHBG extracted from PCT cells expressing a human SHBG cDNA (PCT-SHBG) is 5-8 kDa smaller than the SHBG secreted by these cells, due to incomplete N-glycosylation and absence of O-linked oligosaccharides. PCT-SHBG cells sequester [(3)H]DHT more effectively from culture medium than parental PCT cells, and the presence of SHBG accentuates androgen-dependent activation of a luciferase reporter gene, as well as the endogenous kidney androgen-regulated protein (Kap) gene. After androgen withdrawal, androgen-induced Kap mRNA levels in PCT-SHBG cells are maintained for more than 2 wk vs 2 d in parental PCT cells. Transcriptome profiling after testosterone or DHT pretreatments, followed by 3 d of steroid withdrawal, also demonstrated that intracellular SHBG enhances androgen-dependent stimulation (e.g. Adh7, Vcam1, Areg, Tnfaip2) or repression (e.g. Cldn2 and Osr2) of many other genes in PCT cells. In addition, nuclear localization of the androgen receptor is enhanced and retained longer after steroid withdrawal in PCT cells containing functional SHBG. Thus, intracellular SHBG accentuates the uptake of androgens and sustains androgens access to the androgen receptor, especially under conditions of limited androgen supply.
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Affiliation(s)
- Eui-Ju Hong
- Department of Obstetrics and Gynecology, University of British Columbia, Child and Family Research Institute, Vancouver, British Columbia, Canada
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Yu ASL, Cheng MH, Coalson RD. Calcium inhibits paracellular sodium conductance through claudin-2 by competitive binding. J Biol Chem 2010; 285:37060-9. [PMID: 20807759 DOI: 10.1074/jbc.m110.146621] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Claudins form paracellular pores at the tight junction in epithelial cells. Profound depletion of extracellular calcium is well known to cause loosening of the tight junction with loss of transepithelial resistance. However, moderate variations in calcium concentrations within the physiological range can also regulate transepithelial permeability. To investigate the underlying molecular mechanisms, we studied the effects of calcium on the permeability of claudin-2, expressed in an inducible MDCK I cell line. We found that in the physiological range, calcium acts as a reversible inhibitor of the total conductance and Na(+) permeability of claudin-2, without causing changes in tight junction structure. The effect of calcium is enhanced at low Na(+) concentrations, consistent with a competitive effect. Furthermore, mutation of an intrapore negatively charged binding site, Asp-65, to asparagine partially abrogated the inhibitory effect of calcium. This suggests that calcium competes with Na(+) for binding to Asp-65. Other polyvalent cations had similar effects, including La(3+), which caused severe and irreversible inhibition of conductance. Brownian dynamics simulations demonstrated that such inhibition can be explained if Asp-65 has a relatively high charge density, thus favoring binding of Ca(2+) over that of Na(+), reducing Ca(2+) permeation by inhibiting its dissociation from this site, and decreasing Na(+) conductance through repulsive electrostatic interaction with Ca(2+). These findings may explain why hypercalcemia inhibits Na(+) reabsorption in the proximal tubule of the kidney.
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Affiliation(s)
- Alan S L Yu
- Division of Nephrology, Department of Medicine, University of Southern California Keck School of Medicine, Los Angeles, California 90089, USA.
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Claudin-2-deficient mice are defective in the leaky and cation-selective paracellular permeability properties of renal proximal tubules. Proc Natl Acad Sci U S A 2010; 107:8011-6. [PMID: 20385797 DOI: 10.1073/pnas.0912901107] [Citation(s) in RCA: 219] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Claudin-2 is highly expressed in tight junctions of mouse renal proximal tubules, which possess a leaky epithelium whose unique permeability properties underlie their high rate of NaCl reabsorption. To investigate the role of claudin-2 in paracellular NaCl transport in this nephron segment, we generated knockout mice lacking claudin-2 (Cldn2(-/-)). The Cldn2(-/-) mice displayed normal appearance, activity, growth, and behavior. Light microscopy revealed no gross histological abnormalities in the Cldn2(-/-) kidney. Ultrathin section and freeze-fracture replica electron microscopy revealed that, similar to those of wild types, the proximal tubules of Cldn2(-/-) mice were characterized by poorly developed tight junctions with one or two continuous tight junction strands. In contrast, studies in isolated, perfused S2 segments of proximal tubules showed that net transepithelial reabsorption of Na(+), Cl(-), and water was significantly decreased in Cldn2(-/-) mice and that there was an increase in paracellular shunt resistance without affecting the apical or basolateral membrane resistances. Moreover, deletion of claudin-2 caused a loss of cation (Na(+)) selectivity and therefore relative anion (Cl(-)) selectivity in the proximal tubule paracellular pathway. With free access to water and food, fractional Na(+) and Cl(-) excretions in Cldn2(-/-) mice were similar to those in wild types, but both were greater in Cldn2(-/-) mice after i.v. administration of 2% NaCl. We conclude that claudin-2 constitutes leaky and cation (Na(+))-selective paracellular channels within tight junctions of mouse proximal tubules.
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Tight junctions in salivary epithelium. J Biomed Biotechnol 2010; 2010:278948. [PMID: 20182541 PMCID: PMC2825559 DOI: 10.1155/2010/278948] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Revised: 11/12/2009] [Accepted: 11/27/2009] [Indexed: 12/13/2022] Open
Abstract
Epithelial cell tight junctions (TJs) consist of a narrow belt-like structure in the apical region of the lateral plasma membrane that circumferentially binds each cell to its neighbor. TJs are found in tissues that are involved in polarized secretions, absorption functions, and maintaining barriers between blood and interstitial fluids. The morphology, permeability, and ion selectivity of TJ vary among different types of tissues and species. TJs are very dynamic structures that assemble, grow, reorganize, and disassemble during physiological or pathological events. Several studies have indicated the active role of TJ in intestinal, renal, and airway epithelial function; however, the functional significance of TJ in salivary gland epithelium is poorly understood. Interactions between different combinations of the TJ family (each with their own unique regulatory proteins) define tissue specificity and functions during physiopathological processes; however, these interaction patterns have not been studied in salivary glands. The purpose of this review is to analyze some of the current data regarding the regulatory components of the TJ that could potentially affect cellular functions of the salivary epithelium.
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Kirk A, Campbell S, Bass P, Mason J, Collins J. Differential expression of claudin tight junction proteins in the human cortical nephron. Nephrol Dial Transplant 2010; 25:2107-19. [PMID: 20124215 PMCID: PMC2891746 DOI: 10.1093/ndt/gfq006] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Background. In renal tubules, paracellular permeability is tightly controlled to facilitate solute absorption and urinary concentration and is regulated by tight junctions, which incorporate claudin proteins. There is very limited information confirming the localization of these proteins in the human renal cortex. Most data is inferred from mouse, bovine and rabbit studies and differences exist between mouse and other species. Methods. A survey of claudin staining was performed on human kidney cortex embedded in glycolmethacrylate resin to enhance tissue morphology and facilitate the cutting of 2 µm serial sections. Results. Claudin-2, -10 and -11 antibodies labelled renal tubular epithelial cells, correlating with Lotus tetragonolobus and N-cadherin positive proximal tubules. Claudin-3, -10, -11 and -16 antibodies strongly stained a population of tubules that were positive for Tamm Horsfall protein on adjacent sections, confirming expression in the thick ascending limb of the Loop of Henle. Claudin-3, -4 and -8 antibodies reacted with tubules that correlated with the distal nephron markers, E-cadherin, epithelial membrane antigen and Dolichos biflorus and claudin-3, -4, -7 and -8 with the distal tubule marker, calbindin, and the collecting duct marker, aquaporin-2. Claudin-14 was localized in distal convoluted tubules, correlating positively with calbindin but negatively with aquaporin-2, whereas claudin-1 staining was identified in the parietal epithelium of Bowman's capsule, distal convoluted tubule and collecting duct. Cellular and tight junction localization of claudin staining in renal tubules was heterogeneous and is discussed. Conclusions. Complex variation in the expression of human claudins likely determines paracellular permeability in the kidney. Altered claudin expression may influence pathologies involving abnormalities of absorption.
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Affiliation(s)
- Adam Kirk
- 1Division of Infection, Inflammation and Immunity, Mailpoint 813, University of Southampton Medical School, Sir Henry Wellcome Laboratories, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, UK
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Angelow S, Yu ASL. Structure-function studies of claudin extracellular domains by cysteine-scanning mutagenesis. J Biol Chem 2009; 284:29205-17. [PMID: 19690347 DOI: 10.1074/jbc.m109.043752] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Claudins form size- and charge-selective pores in the tight junction that control the paracellular flux of inorganic ions and small molecules. However, the structural basis for ion selectivity of paracellular pores is poorly understood. Here we applied cysteine scanning to map the paracellular pathway of ion permeation across claudin-2-transfected Madin-Darby canine kidney type I cells. Four potential pore-lining amino acid residues in the first extracellular loop were mutated to cysteine and screened for their accessibility to thiol-reactive reagents. All mutants were functional except D65C, which formed dimers by intermolecular disulfide bonding, leading to a loss of charge and size selectivity. This suggests that claudin-2 pores are multimeric and that Asp(65) lies close to a protein-protein interface. Methanethiosulfonate reagents of different size and charge and the organic mercury derivate, p-(chloromercuri)benzenesulfonic acid, significantly decreased paracellular ion permeation across I66C-transfected cells by a mechanism that suggests steric blocking of the pore. The conductance of wild-type claudin-2 and the other cysteine mutants was only weakly affected. The rate of reaction with I66C decreased dramatically with increasing size of the reagent, suggesting that Ile(66) is buried deep within a narrow segment of the pore with its side group facing into the lumen. Furthermore, labeling with N-biotinoylaminoethyl methanethiosulfonate showed that I66C was weakly reactive, whereas Y35C was strongly reactive, suggesting that Tyr(35) is located at the protein surface outside of the pore.
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Affiliation(s)
- Susanne Angelow
- Division of Nephrology, Department of Medicine, University of Southern California Keck School of Medicine, Los Angeles, California 90089, USA
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Bagherie-Lachidan M, Wright SI, Kelly SP. Claudin-8 and -27 tight junction proteins in puffer fish Tetraodon nigroviridis acclimated to freshwater and seawater. J Comp Physiol B 2008; 179:419-31. [PMID: 19112569 DOI: 10.1007/s00360-008-0326-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 11/07/2008] [Accepted: 12/01/2008] [Indexed: 01/03/2023]
Abstract
Genes encoding for claudin-8 and -27 tight junction proteins in the euryhaline puffer fish (Tetraodon nigroviridis) were identified using its recently sequenced genome. Phylogenetic analysis indicated that multiple genes encoding for claudin-8 proteins (designated Tncldn8a, Tncldn8b, Tncldn8c and Tncldn8d) arose by tandem gene duplication. In contrast, both tandem and whole genome duplication events appear to have generated genes encoding for claudin-27 proteins (designated Tncldn27a, Tncldn27b, Tncldn27c and Tncldn27d). Tncldn8 and Tncldn27 mRNA were widely distributed in Tetraodon, suggesting involvement in various physiological processes. All Tncldn8 and Tncldn27 genes were expressed in gill and skin tissue (i.e., epithelia exposed directly to the external environment). A potential role for claudin-8 and -27 proteins in the regulation of hydromineral balance in Tetraodon was investigated by examining alterations in mRNA abundance in select ionoregulatory tissue of fish acclimated to freshwater (FW) and seawater (SW). In FW or SW, Tetraodon exhibited alterations in Na(+)-K(+)-ATPase activity (a correlate of transcellular transport) typical of a euryhaline teleost fish. Simultaneously, tissue and gene specific alterations in Tncldn8 and Tncldn27 transcript abundance occurred. These data provide some insight into the duplication history of cldn8 and cldn27 genes in fishes and suggest a possible role for claudin-8 and -27 proteins in the osmoregulatory strategies of euryhaline teleosts.
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Yu ASL, Kanzawa SA, Usorov A, Lantinga-van Leeuwen IS, Peters DJM. Tight junction composition is altered in the epithelium of polycystic kidneys. J Pathol 2008; 216:120-8. [PMID: 18666097 DOI: 10.1002/path.2392] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Kidney cysts in autosomal dominant polycystic kidney disease (ADPKD) undergo progressive enlargement together with luminal fluid secretion. This involves active, uphill transcellular Cl(-) transport which drives passive Na(+) and water secretion. Implicit in this mechanism is the assumption that the paracellular permeability of the cyst epithelium to Cl(-) must be very low. Claudins are tight junction (TJ) transmembrane proteins that determine the ion selectivity of paracellular barriers. The aim of this study was to determine the expression and localization of claudins within renal cysts in a mouse hypomorphic model of ADPKD and in human patients. We found that the majority of cysts were of collecting duct origin. Claudins normally expressed in collecting duct (3, 4, 7, 8, and 10) were found in small cysts. However, only claudin-7 persisted at substantive levels in the dedifferentiated epithelium of large, presumably late-stage cysts, where it was localized both at the TJ and basolaterally. The constitutively expressed TJ proteins, ZO-1 and occludin, were also abundantly expressed and correctly localized, suggesting that the basic infrastructure of the TJ is preserved. A previous study suggested that claudin-7 may function as a paracellular Cl(-) barrier. We postulate that the role of claudin-7 in ADPKD is to seal the paracellular route in Cl(-)-secreting cyst epithelium, preventing backleak of Cl(-), and that it thereby plays a permissive role in fluid secretion and cyst growth.
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Affiliation(s)
- A S L Yu
- Division of Nephrology, Department of Medicine, University of Southern California Keck School of Medicine, Los Angeles, California 90089, USA.
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Hypertonic stress increases claudin-4 expression and tight junction integrity in association with MUPP1 in IMCD3 cells. Proc Natl Acad Sci U S A 2008; 105:15797-802. [PMID: 18840681 DOI: 10.1073/pnas.0805761105] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We reported that the multiple PDZ protein 1 (MUPP1) is an osmotic response protein in kidney cells. This up-regulation was found to be necessary for the maintenance of tight epithelial properties in these cells. We investigated whether an interaction with one or more members of the claudin family is responsible for this observation. In response to hypertonicity, the up-regulation of claudin-4 (Cldn4) expression, and not other claudins, was initially identified in inner medullary collecting duct (IMCD3) cells by gene array and further verified by quantitative PCR and Western blotting. In kidney tissues, Cldn4 expression was substantial in the papilla and absent in the cortex. Furthermore, Cldn4 expression significantly increased in the papilla of mice after 36 h of thirsting. Cldn4 immunofluorescence in hypertonically stressed cells revealed colocalization with MUPP1 at the tight junctions. Interaction between Cldn4 and MUPP1 was also demonstrated by coimmunoprecipitation of both proteins from IMCD3 cells chronically adapted to hypertonicity. In IMCD3 cells stably silenced for MUPP1 expression under hypertonic conditions, a significant decrement in Cldn4 expression was observed that was restored after inhibition of lysosome activity. Immunofluorescence detection identified that in these MUPP1-silenced cells Cldn4 was mistargeted to the lysosomes. Functionally, silencing Cldn4 expression in IMCD3 cells resulted in a decrease in the transepithelial resistance to the same degree as observed when MUPP1 expression was silenced, suggesting that MUPP1 contributes to the maintenance of a tight epithelium in the medulla of the kidney under hypertonic stress by correctly localizing Cldn4 to the tight junctions.
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