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Zheng X, Ren B, Gao Y. Tight junction proteins related to blood-brain barrier and their regulatory signaling pathways in ischemic stroke. Biomed Pharmacother 2023; 165:115272. [PMID: 37544283 DOI: 10.1016/j.biopha.2023.115272] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/29/2023] [Accepted: 07/31/2023] [Indexed: 08/08/2023] Open
Abstract
Tight junctions (TJs) are crucial for intercellular connections. The abnormal expression of proteins related to TJs can result in TJ destruction, structural damage, and endothelial and epithelial cell dysfunction. These factors are associated with the occurrence and progression of several diseases. Studies have shown that blood-brain barrier (BBB) damage and dysfunction are the prominent pathological features of stroke. TJs are directly associated with the BBB integrity. In this article, we first discuss the structure and function of BBB TJ-related proteins before focusing on the crucial events that cause TJ dysfunction and BBB damage, as well as the regulatory mechanisms that affect the qualitative and quantitative expression of TJ proteins during ischemic stroke. Multiple regulatory mechanisms, including phosphorylation, matrix metalloproteinases (MMPs), and microRNAs, regulate TJ-related proteins and affect BBB permeability. Some signaling pathways and mechanisms have been demonstrated to have dual functions. Hopefully, our understanding of the regulation of BBB TJs in ischemic stroke will be applied to the development of targeted medications and therapeutic therapies.
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Affiliation(s)
- Xiangyi Zheng
- Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Beida Ren
- Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China; Institute for Brain Disorders, Beijing University of Chinese Medicine, Beijing, China.
| | - Ying Gao
- Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China; Institute for Brain Disorders, Beijing University of Chinese Medicine, Beijing, China.
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2
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Lavie M, Linna L, Moustafa RI, Belouzard S, Fukasawa M, Dubuisson J. Role of the cytosolic domain of occludin in trafficking and hepatitis C virus infection. Traffic 2019; 20:753-773. [PMID: 31328852 DOI: 10.1111/tra.12680] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 07/17/2019] [Accepted: 07/17/2019] [Indexed: 12/12/2022]
Abstract
The role of the tight-junction (TJ) protein occludin (OCLN) in hepatitis C virus (HCV) entry remains elusive. Here, we investigated the OCLN C-terminal cytosolic domain in HCV infection. We expressed a series of C-terminal deletion mutants in Huh-7 cells KO for OCLN and characterized their functionality in HCV infection and trafficking. Deleting the OCLN cytosolic domain led to protein instability and intracellular retention. The first 15 residues (OCLN-C15 mutant) of the cytosolic domain were sufficient for OCLN stability, but led to its accumulation in the trans-Golgi network (TGN) due to a deficient cell surface export after synthesis. In contrast, the OCLN-C18 mutant, containing the first 18 residues of the cytosolic domain, was expressed at the cell surface and could mediate HCV infection. Point mutations in the context of C18 showed that I279 and W281 are crucial residues for cell surface expression of OCLN-C18. However, in the context of full-length OCLN, mutation of these residues only partially affected infection and cell surface localization. Importantly, the characterization of OCLN-C18 in human-polarized hepatocytes revealed a defect in its TJ localization without affecting HCV infection. These data suggest that TJ localization of OCLN is not a prerequisite for HCV infection in polarized hepatocytes.
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Affiliation(s)
- Muriel Lavie
- Universite de Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Lydia Linna
- Universite de Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Rehab I Moustafa
- Universite de Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-CIIL-Center for Infection and Immunity of Lille, Lille, France.,Department of Microbial Biotechnology, Genetic Engineering and Biotechnology Division, National Research Center, Cairo, Egypt
| | - Sandrine Belouzard
- Universite de Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Masayoshi Fukasawa
- Department of Biochemistry & Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Jean Dubuisson
- Universite de Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
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3
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Zeisel MB, Dhawan P, Baumert TF. Tight junction proteins in gastrointestinal and liver disease. Gut 2019; 68:547-561. [PMID: 30297438 PMCID: PMC6453741 DOI: 10.1136/gutjnl-2018-316906] [Citation(s) in RCA: 175] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/16/2018] [Accepted: 08/19/2018] [Indexed: 12/11/2022]
Abstract
Over the past two decades a growing body of evidence has demonstrated an important role of tight junction (TJ) proteins in the physiology and disease biology of GI and liver disease. On one side, TJ proteins exert their functional role as integral proteins of TJs in forming barriers in the gut and the liver. Furthermore, TJ proteins can also be expressed outside TJs where they play important functional roles in signalling, trafficking and regulation of gene expression. A hallmark of TJ proteins in disease biology is their functional role in epithelial-to-mesenchymal transition. A causative role of TJ proteins has been established in the pathogenesis of colorectal cancer and gastric cancer. Among the best characterised roles of TJ proteins in liver disease biology is their function as cell entry receptors for HCV-one of the most common causes of hepatocellular carcinoma. At the same time TJ proteins are emerging as targets for novel therapeutic approaches for GI and liver disease. Here we review our current knowledge of the role of TJ proteins in the pathogenesis of GI and liver disease biology and discuss their potential as therapeutic targets.
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Affiliation(s)
- Mirjam B. Zeisel
- Inserm U1052, CNRS UMR 5286, Cancer Research Center of Lyon (CRCL), Université de Lyon (UCBL), Lyon, France
- Inserm, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
| | - Punita Dhawan
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE
- Buffet Cancer Center, University of Nebraska Medical Center, Omaha, NE
- VA Nebraska-Western Iowa Health Care System, Omaha, NE
| | - Thomas F. Baumert
- Inserm, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
- Institut Hospitalo-Universitaire, Pôle hépato-digestif, Nouvel Hôpital Civil, Strasbourg, France
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4
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Allam AH, Charnley M, Russell SM. Context-Specific Mechanisms of Cell Polarity Regulation. J Mol Biol 2018; 430:3457-3471. [PMID: 29886017 DOI: 10.1016/j.jmb.2018.06.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 06/04/2018] [Accepted: 06/04/2018] [Indexed: 12/31/2022]
Abstract
Cell polarity is an essential process shared by almost all animal tissues. Moreover, cell polarity enables cells to sense and respond to the cues provided by the neighboring cells and the surrounding microenvironment. These responses play a critical role in regulating key physiological processes, including cell migration, proliferation, differentiation, vesicle trafficking and immune responses. The polarity protein complexes regulating these interactions are highly evolutionarily conserved between vertebrates and invertebrates. Interestingly, these polarity complexes interact with each other and key signaling pathways in a cell-polarity context-dependent manner. However, the exact mechanisms by which these interactions take place are poorly understood. In this review, we will focus on the roles of the key polarity complexes SCRIB, PAR and Crumbs in regulating different forms of cell polarity, including epithelial cell polarity, cell migration, asymmetric cell division and the T-cell immunological synapse assembly and signaling.
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Affiliation(s)
- Amr H Allam
- Centre for Micro-Photonics, Faculty of Science, Engineering & Technology, Swinburne University of Technology, Hawthorn, Australia; Immune Signalling Laboratory, Peter MacCallum Cancer Centre, Parkville, Australia.
| | - Mirren Charnley
- Centre for Micro-Photonics, Faculty of Science, Engineering & Technology, Swinburne University of Technology, Hawthorn, Australia; Immune Signalling Laboratory, Peter MacCallum Cancer Centre, Parkville, Australia; Biointerface Engineering Group, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, VIC, Australia.
| | - Sarah M Russell
- Centre for Micro-Photonics, Faculty of Science, Engineering & Technology, Swinburne University of Technology, Hawthorn, Australia; Immune Signalling Laboratory, Peter MacCallum Cancer Centre, Parkville, Australia; Department of Pathology, The University of Melbourne, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Australia.
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5
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Rodriguez-Boulan E, Macara IG. Organization and execution of the epithelial polarity programme. Nat Rev Mol Cell Biol 2014; 15:225-42. [PMID: 24651541 DOI: 10.1038/nrm3775] [Citation(s) in RCA: 504] [Impact Index Per Article: 50.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Epithelial cells require apical-basal plasma membrane polarity to carry out crucial vectorial transport functions and cytoplasmic polarity to generate different cell progenies for tissue morphogenesis. The establishment and maintenance of a polarized epithelial cell with apical, basolateral and ciliary surface domains is guided by an epithelial polarity programme (EPP) that is controlled by a network of protein and lipid regulators. The EPP is organized in response to extracellular cues and is executed through the establishment of an apical-basal axis, intercellular junctions, epithelial-specific cytoskeletal rearrangements and a polarized trafficking machinery. Recent studies have provided insight into the interactions of the EPP with the polarized trafficking machinery and how these regulate epithelial polarization and depolarization.
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Affiliation(s)
- Enrique Rodriguez-Boulan
- Margaret Dyson Vision Research Institute, Weill Cornell Medical College, 1300 York Avenue, LC-301 New York City, New York 10065, USA
| | - Ian G Macara
- Department of Cell & Developmental Biology, Vanderbilt University Medical Center, 465 21st Avenue South, U 3209 MRB III, Nashville Tennessee 37232, USA
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Alvi MM, Chatterjee P. A prospective analysis of co-processed non-ionic surfactants in enhancing permeability of a model hydrophilic drug. AAPS PharmSciTech 2014; 15:339-53. [PMID: 24357111 DOI: 10.1208/s12249-013-0065-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 11/20/2013] [Indexed: 11/30/2022] Open
Abstract
Paracellular route is a natural pathway for the transport of many hydrophilic drugs and macromolecules. The purpose of this study was to prospectively evaluate the ability of novel co-processed non-ionic surfactants to enhance the paracellular permeability of a model hydrophilic drug metformin using Caco-2 (human colonic adenocarcinoma) cell model. A three-tier screen was undertaken to evaluate the co-processed blends based on cytotoxicity, cellular integrity, and permeability coefficient. The relative contribution of the paracellular and the transcellular route in overall transport of metformin by co-processed blends was determined. Immunocytochemistry was conducted to determine the distribution of tight-junction protein claudin-1 after incubation with the co-processed blends. It was found that novel blends of Labrasol and Transcutol-P enhanced metformin permeability by approximately twofold with transient reduction in the transepithelia electrical resistance (TEER) and minimal cytotoxicity compared with the control, with the paracellular pathway as the major route of metformin transport. Maximum permeability of metformin (∼10-fold) was mediated by Tween-20 blends along with >75% reduction in the TEER which was irreversible over 24-h period. A shift in metformin transport from the paracellular to the transcellular route was observed with some Tween-20 blends. Immunocytochemical analysis revealed rearrangement of the cellular borders and fragmentation on treatment with Tween-20 blends. In conclusion, cytotoxicity, cellular integrity, and permeability of the hydrophilic drugs can be greatly influenced by the polyoxyethylene residues and medium chain fatty acids in the non-ionic surfactants at clinically relevant concentrations and therefore should be thoroughly investigated prior to their inclusion in formulations.
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7
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Fong D, Spizzo G, Mitterer M, Seeber A, Steurer M, Gastl G, Brosch I, Moser P. Low expression of junctional adhesion molecule A is associated with metastasis and poor survival in pancreatic cancer. Ann Surg Oncol 2012; 19:4330-6. [PMID: 22549289 DOI: 10.1245/s10434-012-2381-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Indexed: 01/07/2023]
Abstract
BACKGROUND Characterized by its highly aggressive tumor biology, pancreatic cancer still remains a fatal diagnosis. The junctional adhesion molecule A (JAM-A) is a type I transmembrane glycoprotein, which recently has been shown to affect the prognosis of several human malignancies. METHODS JAM-A antigen expression was investigated retrospectively by immunohistochemistry in paraffin-embedded primary tumor tissue samples from a series (n = 186) of consecutive patients with pancreatic adenocarcinoma. Survival was calculated by Kaplan-Meier curves. Parameters found to be of prognostic significance in univariate analysis were verified in a multivariate Cox regression model. RESULTS Low expression of JAM-A was observed in 79 (42 %) of 186 pancreatic cancer specimens and was significantly associated with poor overall survival (P < 0.01). By univariate analysis, low expression of JAM-A was found to correlate with positive lymph node status (P = 0.02), the presence of distant metastasis (P = 0.05), and tumor grade (P = 0.04), suggesting it may be an important event involved in cancer progression. Furthermore, in the subgroup of patients with surgically resected pancreatic cancer, low expression of JAM-A significantly correlated with decreased progression-free survival (P < 0.01). Multivariate analysis revealed JAM-A to be an independent predictor of poor outcome. DISCUSSION These findings suggest for the first time that low levels of JAM-A expression in pancreatic cancer are associated with poor clinical outcome. JAM-A may represents a target molecule for functional inactivation and serve as a novel biomarker of adverse prognosis in pancreatic cancer.
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Affiliation(s)
- Dominic Fong
- Division of Hematology & Oncology, Medical University Innsbruck, Innsbruck, Austria.
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8
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Blasig IE, Bellmann C, Cording J, Del Vecchio G, Zwanziger D, Huber O, Haseloff RF. Occludin protein family: oxidative stress and reducing conditions. Antioxid Redox Signal 2011; 15:1195-219. [PMID: 21235353 DOI: 10.1089/ars.2010.3542] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The occludin-like proteins belong to a family of tetraspan transmembrane proteins carrying a marvel domain. The intrinsic function of the occludin family is not yet clear. Occludin is a unique marker of any tight junction and is found in polarized endothelial and epithelial tissue barriers, at least in the adult vertebrate organism. Occludin is able to oligomerize and to form tight junction strands by homologous and heterologous interactions, but has no direct tightening function. Its oligomerization is affected by pro- and antioxidative agents or processes. Phosphorylation of occludin has been described at multiple sites and is proposed to play a regulatory role in tight junction assembly and maintenance and, hence, to influence tissue barrier characteristics. Redox-dependent signal transduction mechanisms are among the pathways modulating occludin phosphorylation and function. This review discusses the novel concept that occludin plays a key role in the redox regulation of tight junctions, which has a major impact in pathologies related to oxidative stress and corresponding pharmacologic interventions.
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Affiliation(s)
- Ingolf E Blasig
- Leibniz-Institut für Molekulare Pharmakologie, Berlin-Buch, Germany.
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9
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Liu S, Kuo W, Yang W, Liu W, Gibson GA, Dorko K, Watkins SC, Strom SC, Wang T. The second extracellular loop dictates Occludin-mediated HCV entry. Virology 2010; 407:160-70. [PMID: 20822789 PMCID: PMC2946412 DOI: 10.1016/j.virol.2010.08.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 07/18/2010] [Accepted: 08/12/2010] [Indexed: 12/20/2022]
Abstract
Recent findings have implicated tight junction (TJ) protein Occludin (OCLN) as an essential factor for hepatitis C virus (HCV) to enter human hepatocytes. To gain insights into OCLN-mediated HCV entry, we created a panel of OCLN deletion mutants and found that without impairing OCLN's cell surface localization, removal of the extracellular loop 2 (EL2) from OCLN abolished both its ability to mediate HIV-HCV pseudotypes' (HCVpp) entry as well as its ability to coprecipitate HCV glycoprotein E2. Recombinant OCLN EL2, however, failed to robustly bind soluble E2 (sE2) in pull-down assays. Subsequent studies revealed that OCLN formed complex with Dynamin II, an important GTPase for endocytosis, in an EL2-dependent fashion. HCVpp, as well as cell culture grown HCV (HCVcc), was sensitive to Dynamin knockdown or inhibition. We conclude that OCLN EL2 dictates the Dynamin-dependent HCV entry. Furthermore, OCLN could function to bridge virions to Dynamin-dependent endocytic machineries.
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Affiliation(s)
- Shufeng Liu
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Wayne Kuo
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Wei Yang
- Institute of Pathogen Biology, Chinese Academy of Medical Sciences, Peking Union Medical College, Tsinghua University, Beijing, China
| | - Weiqun Liu
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Gregory A. Gibson
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Kenneth Dorko
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Simon C. Watkins
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Stephen C. Strom
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Tianyi Wang
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh, PA 15261
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10
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Abstract
A wide variety of different viruses use tight junction (TJ) proteins in the course of infection and different mechanisms of pathogen–TJ interactions have been described; pathogens may induce the reorganization or degradation of distinct TJ proteins, reorganization of the cell cytoskeleton, activation of host-cell signaling pathways and/or use TJ proteins as receptors to enter host cells. Most recently, the TJ proteins claudin-1 and occludin have been identified as essential host factors for HCV entry. Furthermore, TJ protein occludin has been shown to play an important role in the species specificity of HCV infection. Recent data suggest that claudin-1 is a promising target for antiviral strategies. The aim of this article is to elucidate the impact of the interplay between pathogens and TJ proteins for pathogen–host interactions, summarize recent findings regarding the role of TJ proteins in HCV entry and highlight the relevance of TJ proteins for the development of novel antiviral strategies.
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Affiliation(s)
| | - Marine Turek
- Inserm, U748, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
| | - Thomas F Baumert
- Inserm, U748, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
- Pôle Hépato-digestif, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
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11
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The tight junction-associated protein occludin is required for a postbinding step in hepatitis C virus entry and infection. J Virol 2009; 83:8012-20. [PMID: 19515778 DOI: 10.1128/jvi.00038-09] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The precise mechanisms regulating hepatitis C virus (HCV) entry into hepatic cells remain unknown. However, several cell surface proteins have been identified as entry factors for this virus. Of these molecules, claudin-1, a tight junction (TJ) component, is considered a coreceptor required for HCV entry. Recently, we have demonstrated that HCV envelope glycoproteins (HCVgp) promote structural and functional TJ alterations. Additionally, we have shown that the intracellular interaction between viral E2 glycoprotein and occludin, another TJ-associated protein, could be the cause of the mislocalization of TJ proteins. Herein we demonstrated, by using cell culture-derived HCV particles (HCVcc), that interference of occludin expression markedly reduced HCV infection. Furthermore, our results with HCV pseudotyped particles indicated that occludin, but not other TJ-associated proteins, such as junctional adhesion molecule A or zonula occludens protein 1, was required for HCV entry. Using HCVcc, we demonstrated that occludin did not play an essential role in the initial attachment of HCV to target cells. Surface protein labeling experiments showed that both expression levels and cell surface localization of HCV (co)receptors CD81, scavenger receptor class B type I, and claudin-1 were not affected upon occludin knockdown. In addition, immunofluorescence confocal analysis showed that occludin interference did not affect subcellular distribution of the HCV (co)receptors analyzed. However, HCVgp fusion-associated events were altered after occludin silencing. In summary, we propose that occludin plays an essential role in HCV infection and probably affects late entry events. This observation may provide new insights into HCV infection and related pathogenesis.
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12
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Yoon SI, Park CJ, Nah WH, Gye MC. Expression of occludin in testis and epididymis of wild rabbits, Lepus sinensis coreanus. Reprod Domest Anim 2008; 44:745-50. [PMID: 18992101 DOI: 10.1111/j.1439-0531.2008.01064.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tight junctions (TJs) in inter-Sertoli junctional areas and epididymal epithelia build up the blood-testis barrier (BTB) and the blood-epididymal barrier (BEB), respectively. In this study, the expression of occludin, an integral member of the TJs, was examined in testis and different regions of epididymis of Lepus sinensis coreanus, an Korean wild rabbit species. In testis, intense occludin immunoreactivity was found in the basally located inter-Sertoli junctional area together with diffused immunoreactivity of occludin in the cytoplasm of Sertoli cells. It can be suggested that occludin is one of the robust elements of BTB in seminiferous tubules of rabbit testis. In proximal and distal caput epididymis, occludin immunoreactivity was found in the lateral as well as apical contacts of epithelial cells. In corpus epididymis, intense occludin immunoreactivity was found in the basolateral as well as apical contacts of epithelial cells together with cytoplasmic signal. In cauda epididymis, occludin immunoreactivity in luminal epithelia was relatively strong but largely found in the cytoplasm. This suggests that intriguing regulatory mechanisms differentially recruit occludin to the TJ in the different regions of epididymal epithelia. The differences in the subcellular localization as well as expression levels of occludin among the epididymal segments may reflect differential paracellular permeability of epithelia along the epididymal tubules and be correlated with sperm maturation in rabbit. In Western blot, a major form of occludin was MW 62 kDa together with small fragments of MW 34-39 kDa in testis and epididymis, suggesting the peptide cleavage of occludin. This is the first report on the molecular nature of TJs in a wild rabbit testis and epididymis.
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Affiliation(s)
- S I Yoon
- Department of Life Science, College of Natural Sciences, Hanyang University, Seoul, South Korea
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13
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Cereijido M, Contreras RG, Shoshani L, Flores-Benitez D, Larre I. Tight junction and polarity interaction in the transporting epithelial phenotype. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:770-93. [PMID: 18028872 DOI: 10.1016/j.bbamem.2007.09.001] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 08/28/2007] [Accepted: 09/03/2007] [Indexed: 12/21/2022]
Abstract
Development of tight junctions and cell polarity in epithelial cells requires a complex cellular machinery to execute an internal program in response to ambient cues. Tight junctions, a product of this machinery, can act as gates of the paracellular pathway, fences that keep the identity of plasma membrane domains, bridges that communicate neighboring cells. The polarization internal program and machinery are conserved in yeast, worms, flies and mammals, and in cell types as different as epithelia, neurons and lymphocytes. Polarization and tight junctions are dynamic features that change during development, in response to physiological and pharmacological challenges and in pathological situations like infection.
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Affiliation(s)
- Marcelino Cereijido
- Department of Physiology, Biophysics and Neurosciences, CINVESTAV, AP 14-740, México D.F. 07000, México.
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14
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Wang Z, Wade P, Mandell KJ, Akyildiz A, Parkos CA, Mrsny RJ, Nusrat A. Raf 1 represses expression of the tight junction protein occludin via activation of the zinc-finger transcription factor slug. Oncogene 2006; 26:1222-30. [PMID: 16924233 DOI: 10.1038/sj.onc.1209902] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although dysregulation of tight junction (TJ) proteins is observed in epithelial malignancy, their participation in epithelial transformation is poorly understood. Recently we demonstrated that expression of oncogenic Raf 1 in Pa4 epithelial cells disrupts TJs and induces an oncogenic phenotype by downregulating expression of the TJ protein, occludin. Here we report the mechanism by which Raf 1 regulates occludin expression. Raf 1 inhibited occludin transcription by repressing a minimal segment of the occludin promoter in concert with upregulation of the transcriptional repressor, Slug without influencing the well-documented transcriptional repressor, Snail. Overexpression of Slug in Pa4 cells recapitulated the effect of Raf 1 on occludin expression, and depletion of Slug by small interfering RNA abrogated the effect of Raf 1 on occludin. Finally, chromatin immunoprecipitation assays and site-directed mutagenesis demonstrated a direct interaction between Slug and an E-box within the minimal Raf 1-responsive segment of the occludin promoter. These findings support a role of Slug in mediating Raf 1-induced transcriptional repression of occludin and subsequent epithelial to mesenchymal transition.
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Affiliation(s)
- Z Wang
- Epithelial Pathobiology Research Unit, Department of Pathology, Emory University, Atlanta, GA 30322, USA
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15
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Aijaz S, Balda MS, Matter K. Tight junctions: molecular architecture and function. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 248:261-98. [PMID: 16487793 DOI: 10.1016/s0074-7696(06)48005-0] [Citation(s) in RCA: 223] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Tight junctions are the most apical component of the epithelial junctional complex and are crucial for the formation and functioning of epithelial and endothelial barriers. They regulate selective diffusion of ions and solutes along the paracellular pathway and restrict apical/basolateral intramembrane diffusion of lipids. Research over the past years provided much insight into the molecular composition of tight junctions, and we are starting to understand the mechanisms that permit selective paracellular diffusion. Moreover, a complex network of proteins has been identified at tight junctions that is based on cytoskeleton-linked adaptors that recruit and thereby often regulate different types of signaling components that regulate epithelial proliferation, differentiation, and polarization.
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Affiliation(s)
- Saima Aijaz
- Division of Cell Biology, Institute of Ophthalmology, University College London, London, United Kingdom
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16
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Li Y, Fanning AS, Anderson JM, Lavie A. Structure of the conserved cytoplasmic C-terminal domain of occludin: identification of the ZO-1 binding surface. J Mol Biol 2005; 352:151-64. [PMID: 16081103 DOI: 10.1016/j.jmb.2005.07.017] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 07/05/2005] [Accepted: 07/07/2005] [Indexed: 11/26/2022]
Abstract
Occludin is a transmembrane protein localized at tight junctions whose functions are complex yet poorly understood. Current evidence supports a role for occludin in both the formation of the paracellular barrier and in cell signaling. While the N-terminal extracellular domains of occludin mediate homotypic adhesion, the distal C-terminal cytoplasmic domain of occludin controls protein targeting and endocytosis. The C terminus can also bind to the scaffolding proteins ZO-1, ZO-2, ZO-3, cingulin, the membrane trafficking protein VAP33, and the cytoskeletal protein F-actin, suggesting an important role for this domain. This domain is highly homologous to an important functional domain in the C terminus of the ELL family of RNA polymerase II transcription factors. To explore the function of occludin, we determined the high-resolution crystal structure of its C-terminal distal cytoplasmic domain. The structure comprises three helices that form two separate anti-parallel coiled-coils and a loop that packs tightly against one of the coiled-coils. Using in vitro binding studies and site-directed mutagenesis, we have identified a large positively charged surface that contains the binding site for ZO-1, and this surface is required for proper localization of occludin to cell-cell junctions. On the basis of sequence conservation, we predict that occludin domains from different species and the C-terminal domain of the ELL transcription factors share a very similar structure. Our results provide a model to further test the function of occludin and its binding to other proteins.
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Affiliation(s)
- Yuanhe Li
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA
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17
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Wang Z, Mandell KJ, Parkos CA, Mrsny RJ, Nusrat A. The second loop of occludin is required for suppression of Raf1-induced tumor growth. Oncogene 2005; 24:4412-20. [PMID: 15806147 DOI: 10.1038/sj.onc.1208634] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Tight junctions (TJs) regulate epithelial cell polarity and paracellular permeability. Loss of functional TJs is commonly associated with epithelial cell-derived cancers. Raf1-mediated transformation of rat salivary gland epithelial cells (Pa4-Raf1) induces transcriptional downregulation of the TJ protein occludin and forced re-expression of occludin rescues polarized phenotype of epithelial cells. In the present study, we used this model to examine how specific structural modifications in the occludin protein affect its function in vitro and influence tumor growth in vivo. Our results revealed that neither the C-terminal nor the N-terminal half of occludin alone were sufficient to rescue cells from transformation by Raf1. However, forced expression of an occludin mutant lacking the first extracellular loop was sufficient to rescue cells from Raf1-mediated transformation. Interestingly, forced expression of an occludin mutant lacking the second extracellular loop did not rescue the epithelial phenotype in vitro nor did it prevent tumor growth in vivo. These results demonstrate that the TJ protein occludin has a potent inhibitory effect on the Raf1-mediated tumorigenesis, and the second extracellular loop of occludin appears to be critical for this function.
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Affiliation(s)
- Zili Wang
- Epithelial Pathobiology Research Unit, Department of Pathology, Emory University, 615 Michael Street, Atlanta, GA 30322, USA
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18
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Harhaj NS, Antonetti DA. Regulation of tight junctions and loss of barrier function in pathophysiology. Int J Biochem Cell Biol 2004; 36:1206-37. [PMID: 15109567 DOI: 10.1016/j.biocel.2003.08.007] [Citation(s) in RCA: 404] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2003] [Accepted: 08/21/2003] [Indexed: 12/16/2022]
Abstract
The mechanism by which epithelial and endothelial cells interact to form polarized tissue is of fundamental importance to multicellular organisms. Dysregulation of these barriers occurs in a variety of diseases, destroying the normal cellular environments and leading to organ failure. Increased levels of growth factors are a common characteristic of diseases exhibiting tissue permeability, suggesting that growth factors play a direct role in elevating permeability. Of particular concern for this laboratory, increased expression of vascular endothelial growth factor may enhance vascular permeability in diabetic retinopathy, leading to vision impairment and blindness. However, the mechanism by which growth factors increase permeability is unclear. Polarized cells form strong barriers through the development of tight junctions, which are specialized regions of the junctional complex. Tight junctions are composed of three types of transmembrane proteins, a number of peripheral membrane structural proteins, and are associated with a variety of regulatory proteins. Recent data suggest that growth factor-stimulated alterations in tight junctions contribute to permeability in a variety of disease states. The goal of this review was to elucidate potential mechanisms by which elevated growth factors elicit deregulated paracellular permeability via altered regulation of tight junctions, with particular emphasis on the tight junction proteins occludin and ZO-1, protein kinase C signaling, and endocytosis of junctional proteins. Understanding the molecular mechanisms underlying growth factor-mediated regulation of tight junctions will facilitate the development of novel treatments for diseases such as brain tumors, diabetic retinopathy and other diseases with compromised tight junction barriers.
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Affiliation(s)
- Nicole S Harhaj
- Penn State Retina Research Group, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA
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19
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Matsuda M, Kubo A, Furuse M, Tsukita S. A peculiar internalization of claudins, tight junction-specific adhesion molecules, during the intercellular movement of epithelial cells. J Cell Sci 2004; 117:1247-57. [PMID: 14996944 DOI: 10.1242/jcs.00972] [Citation(s) in RCA: 185] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Tight junctions (TJs) seal the intercellular space of epithelial cells, while individual epithelial cells move against adjacent cells in cellular sheets. To observe TJs in live epithelial cellular sheets, green fluorescent protein (GFP) was fused to the N-terminus of claudin-3 (a major cell adhesion molecule of TJs), which was stably expressed at a level that was approximately 50% of that of endogenous claudin-3 in mouse Eph4 epithelial cells. Under confluent culture conditions, individual cells moved within cellular sheets, which was associated with the remodeling of TJs. However, during this remodeling, GFP-positive TJs did not lose their structural continuity. When TJs between two adjacent cells decreased in length during this remodeling, GFP-claudin-3 was frequently pinched off as a granular structure from GFP-positive TJs together with endogenous claudins. Co-culture experiments, as well as electron microscopy, revealed that the two apposed membranes of TJs were not detached, but co-endocytosed into one of the adjacent cells. Interestingly, other TJ components such as occludin, JAM and ZO-1 appeared to be dissociated from claudins before this endocytosis. The endocytosis of claudins was facilitated when the intercellular motility was upregulated by wounding the cellular sheets. These findings suggest that this peculiar internalization of claudins plays a crucial role in the remodeling of TJs, and that the fine regulation of this endocytosis is important for TJs to seal the intercellular space of epithelial cells that are moving against adjacent cells within cellular sheets.
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Affiliation(s)
- Miho Matsuda
- Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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20
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Dorkoosh FA, Broekhuizen CAN, Borchard G, Rafiee-Tehrani M, Verhoef JC, Junginger HE. Transport of Octreotide and Evaluation of Mechanism of Opening the Paracellular Tight Junctions Using Superporous Hydrogel Polymers In Caco-2 Cell Monolayers. J Pharm Sci 2004; 93:743-52. [PMID: 14762912 DOI: 10.1002/jps.10570] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The purpose of this study was to investigate the mechanism of opening of tight junctions in Caco-2 cell monolayers using superporous hydrogel (SPH) and SPH composite (SPHC) polymers as permeation enhancers for peptide drug delivery. Moreover, the transport of octreotide across Caco-2 cell monolayers was assessed by application of SPH and SPHC polymers on Caco-2 cell monolayers. In these experiments, N,N,N-trimethyl chitosan chloride with 60% quaternization (TMC60) was used as a positive control for opening of tight junctions. Transepithelial electrical resistance (TEER) studies showed that all three polymers (TMC60, SPH, and SPHC) were able to decrease TEER values to approximately 30% of the initial values, indicating the ability of these polymers to open the tight junctions. Recovery TEER studies showed that the effects of the polymers on Caco-2 cell monolayers were reversible, indicating viability of the cells after incubation with polymers. Both SPH and SPHC (compared with TMC60) were able to increase the paracellular transport of octreotide by their mechanical pressures on tight junctions. The mechanistic studies showed that junctional proteins, including actin, occludin, and claudin-1, were influenced by application of SPH and SPHC polymers to the Caco-2 cell monolayers. SPH and SPHC induced clear changes in the staining pattern of all three proteins compared with the control, indicating that the expression of these proteins in the tight junctions was increased, most likely due to the mechanical pressure of the polymers on the junctional proteins.
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Affiliation(s)
- Farid A Dorkoosh
- Department of Pharmaceutical Technology, Leiden/Amsterdam Center for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
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21
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Abstract
Tight junctions (TJ) in inter-Sertoli junctional areas and epididymal epithelia are important for the formation of blood-testis barrier (BTB) and blood-epididymal barrier (BEB). In this study, the expression of occludin, an integral member of the TJ, was verified in canine testis and epididymis. Both low molecular weight (MW) (25-28 kDa) forms as well as high MW (68-72 kDa) forms of occludin were detected in the testis and epididymis using Western blot. The relative amount of the high MW forms of occludin vs low MW forms was higher in the testis than in the epididymis. Some difference in the composition of different MW forms of occludin was found along the segments of epididymis, suggesting the possible correlation between cellular composition of occludin proteins and paracellular permeability of epithelia along the epididymal tubule. In the testis, intense occludin immunoreactivity was found in the basally located inter-Sertoli junctional area. Diffused immunoreactivity of occludin was also found in the cytoplasm of Sertoli cells. A similar pattern of zonula occludens-1 immunoreactivity was found in the cytoplasm of Sertoli cells, suggesting that occludin was not confined to the inter-Sertoli junctional areas and that subcellular localization of occludin in the Sertoli cells was dynamically regulated during spermatogenesis in canine testis. In the epididymis weak immunoreactivity was found in the apical sides and cytoplasm of epithelial cells.
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Affiliation(s)
- M C Gye
- Department of Life Science, College of Natural Sciences, Hanyang University, Seoul, Korea.
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22
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González-Mariscal L, Betanzos A, Nava P, Jaramillo BE. Tight junction proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2003; 81:1-44. [PMID: 12475568 DOI: 10.1016/s0079-6107(02)00037-8] [Citation(s) in RCA: 807] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A fundamental function of epithelia and endothelia is to separate different compartments within the organism and to regulate the exchange of substances between them. The tight junction (TJ) constitutes the barrier both to the passage of ions and molecules through the paracellular pathway and to the movement of proteins and lipids between the apical and the basolateral domains of the plasma membrane. In recent years more than 40 different proteins have been discovered to be located at the TJs of epithelia, endothelia and myelinated cells. This unprecedented expansion of information has changed our view of TJs from merely a paracellular barrier to a complex structure involved in signaling cascades that control cell growth and differentiation. Both cortical and transmembrane proteins integrate TJs. Among the former are scaffolding proteins containing PDZ domains, tumor suppressors, transcription factors and proteins involved in vesicle transport. To date two components of the TJ filaments have been identified: occludin and claudin. The latter is a protein family with more than 20 members. Both occludin and claudins are integral proteins capable of interacting adhesively with complementary molecules on adjacent cells and of co-polymerizing laterally. These advancements in the knowledge of the molecular structure of TJ support previous physiological models that exhibited TJ as dynamic structures that present distinct permeability and morphological characteristics in different tissues and in response to changing natural, pathological or experimental conditions.
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Affiliation(s)
- L González-Mariscal
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies (CINVESTAV), Ave. Politécnico Nacional 2508, México DF, 07000, Mexico.
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23
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Harhaj NS, Barber AJ, Antonetti DA. Platelet-derived growth factor mediates tight junction redistribution and increases permeability in MDCK cells. J Cell Physiol 2002; 193:349-64. [PMID: 12384987 DOI: 10.1002/jcp.10183] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Increased tissue permeability is a common characteristic of a number of diseases such as pulmonary edema, inflammatory bowel disease, several kidney diseases, diabetic retinopathy, and tumors. We hypothesized that growth factors increase permeability by redistribution of tight junction proteins away from the cell border. To investigate mechanisms of growth factor-mediated permeability, we examined the effect of platelet derived growth factor (PDGF) on Madin-Darby canine kidney (MDCK) cell tight junction protein distribution and on permeability. PDGF altered the cellular distribution of occludin and ZO-1 from the cell border to the cytoplasm and increased permeability to 70 kDa dextran in a concentration-dependent manner. Treatment of MDCK cells with PDGF prior to fixation allowed binding of the lectin concanavalin A to the basement membrane of fixed cells, while binding was prevented in untreated control monolayers, implying that PDGF induced the formation of a paracellular transport pathway. Cell fractionation experiments with PDGF-treated cells revealed a novel occludin-containing low-density, detergent resistant subcellular structure, which increased in the buoyant fractions relative to occludin in the pellet in a time- and concentration-dependent manner. Immunocytochemistry revealed that a pool of internalized occludin co-labels with the early endosome marker, EEA1, suggesting that PDGF may stimulate occludin to enter an endosomal pathway. PDGF may act as a permeabilizing agent by moving tight junction proteins away from the cell border in discrete microdomains, and the effects of PDGF on permeability and tight junction protein distribution may model the regulation of epithelial and endothelial barrier properties by other peptide growth factors.
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Affiliation(s)
- Nicole S Harhaj
- The Penn State Retina Research Group, Penn State College of Medicine, Hershey, Pennsylvania 17033, USA
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24
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Mankertz J, Waller JS, Hillenbrand B, Tavalali S, Florian P, Schöneberg T, Fromm M, Schulzke JD. Gene expression of the tight junction protein occludin includes differential splicing and alternative promoter usage. Biochem Biophys Res Commun 2002; 298:657-66. [PMID: 12419305 DOI: 10.1016/s0006-291x(02)02487-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Occludin is an integral membrane protein located at the tight junctions of epithelial cells. Multiple domains of occludin are involved in the regulation of paracellular permeability as well as in the targeting of the protein to the tight junction. In this study, different occludin variants were identified on the mRNA level. Four differentially spliced occludin-specific mRNA transcripts were detected. Expression of the resulting proteins revealed an altered subcellular distribution and a loss of co-localization with zonula occludens protein ZO-1 in the tight junction for two of the four splice variants. Our findings demonstrate that the fourth transmembrane domain of occludin is important for targeting occludin to the tight junction. Loss of the fourth transmembrane domain leads to a relocation of the C-terminal domain to the extracellular space. The structural diversity of natural occludin variants is further increased by an additional promoter and transcription start giving rise to an alternative exon 1. Gene expression mediated by this promoter is influenced by the pro-inflammatory cytokine tumor necrosis factor alpha.
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Affiliation(s)
- Joachim Mankertz
- Medizinische Klinik I Gastroenterologie, Infektiologie und Rheumatologie, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Hindenburgdamm 30, 12000 Berlin, Germany.
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25
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Ghassemifar MR, Sheth B, Papenbrock T, Leese HJ, Houghton FD, Fleming TP. Occludin TM4-: an isoform of the tight junction protein present in primates lacking the fourth transmembrane domain. J Cell Sci 2002; 115:3171-80. [PMID: 12118072 DOI: 10.1242/jcs.115.15.3171] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
The tight junction protein occludin possesses four transmembrane domains,two extracellular loops, and cytoplasmic N- and C-termini. Reverse transcription-PCR analysis of human tissues, embryos and cells using primers spanning the fourth transmembrane domain (TM4) and adjacent C-terminal region revealed two products. The larger and predominant product corresponded in sequence to canonical occludin (TM4+), while the smaller product exhibited a 162 bp deletion encoding the entire TM4 and immediate C-terminal flanking region (TM4-). Examination of the genomic occludin sequence identified that the 162 bp sequence deleted in TM4-coincided precisely with occludin exon 4, strongly suggesting that TM4- is an alternative splice isoform generated by skipping of exon 4. Indeed, the reading frame of downstream exons is not affected by exclusion of exon 4. The presence of both TM4+ and TM4- occludin isoforms was also identified in monkey epithelial cells but TM4-was undetected in murine and canine tissue and cells, indicating a late evolutionary origin for this alternative splicing event. Conceptual translation of TM4- isoform predicts extracellular localisation of the C-terminus. Immunocytochemical processing of living human Caco-2 cells using a C-terminal occludin antibody revealed weak, discontinuous staining restricted to the periphery of subconfluent islands of cells, or islands generated by wounding confluent layers. In occludin immunoblots, a weak band at ∼58 kDa, smaller than the predominant band at 65 kDa and corresponding to the predicted mass of TM4- isoform, is evident and upregulated in subconfluent cells. These data suggest that the TM4- isoform may be translated at low levels in specific conditions and may contribute to regulation of occludin function.
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Affiliation(s)
- M Reza Ghassemifar
- Division of Cell Sciences, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK. Department of Biology, University of York, PO Box 373, York YO10 5YW, UK
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26
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Chen YH, Lu Q, Goodenough DA, Jeansonne B. Nonreceptor tyrosine kinase c-Yes interacts with occludin during tight junction formation in canine kidney epithelial cells. Mol Biol Cell 2002; 13:1227-37. [PMID: 11950934 PMCID: PMC102264 DOI: 10.1091/mbc.01-08-0423] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Occludin is an integral membrane protein that is tyrosine phosphorylated when localized at tight junctions. When Ca(2+) was depleted from the culture medium, occludin tyrosine phosphorylation was diminished from Madin-Darby canine kidney epithelial cells in 2 min. This dephosphorylation was correlated with a significant reduction in transepithelial electrical resistance (TER), indicating a global loss of the tight junction barrier function. Reconstitution of Ca(2+) resulted in a robust tyrosine rephosphorylation of occludin that was temporally associated with an increase in TER. Moreover, we demonstrate in this study that occludin was colocalized with the nonreceptor tyrosine kinase c-Yes at cell junction areas and formed an immunoprecipitable complex with c-Yes in vivo. This complex dissociated when the cells were incubated in medium without Ca(2+) or treated with a c-Yes inhibitor, CGP77675. In the presence of CGP77675 after Ca(2+) repletion, occludin tyrosine phosphorylation was completely abolished and both tight junction formation and the increase of the TER were inhibited. Our study thus provides strong evidence that occludin tyrosine phosphorylation is tightly linked to tight junction formation in epithelial cells, and that the nonreceptor tyrosine kinase c-Yes is involved in the regulation of this process.
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Affiliation(s)
- Yan-Hua Chen
- Department of Anatomy and Cell Biology, East Carolina University School of Medicine, Greenville, NC 27858, USA.
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27
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Suzuki T, Fujikura K, Koyama H, Matsuzaki T, Takahashi Y, Takata K. The apical localization of SGLT1 glucose transporter is determined by the short amino acid sequence in its N-terminal domain. Eur J Cell Biol 2001; 80:765-74. [PMID: 11831390 DOI: 10.1078/0171-9335-00204] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
SGLT1, an isoform of Na+-dependent glucose cotransporters, is localized at the apical plasma membrane in the epithelial cells of the small intestine and the kidney, where it plays a pivotal role in the absorption and reabsorption of sugars, respectively. To search the domain responsible for the apical localization of SGLT1, we constructed an N-terminal deletion clone series of rat SGLT1 and analyzed the localization of the respective products in Madin-Darby canine kidney (MDCK) cells. The products of N-terminal deletion clones up to the 19th amino acid were localized at the apical plasma membrane, whereas the products of N-terminal 20- and 23-amino-acid deletion clones were localized along the entire plasma membrane. Since single-amino-acid mutations of either D28N or D28G in the N-terminal domain give rise to glucose/galactose malabsorption disease, we examined the localization of these mutants. The products of D28N and D28G clones were localized in the cytoplasm, showing that the aspartic acid-28 may be essential for the delivery of SGLT1 to the plasma membrane. These results suggest that a short amino acid sequence of the N-terminal domain of SGLT1 plays important roles in plasma membrane targeting and specific apical localization of the protein.
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Affiliation(s)
- T Suzuki
- Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
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28
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Cereijido M, Shoshani L, Contreras RG. Molecular physiology and pathophysiology of tight junctions. I. Biogenesis of tight junctions and epithelial polarity. Am J Physiol Gastrointest Liver Physiol 2000; 279:G477-82. [PMID: 10960345 DOI: 10.1152/ajpgi.2000.279.3.g477] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The tight junction (TJ) was first noticed through its ability to control permeation across the paracellular route, but the homologies of its molecular components with peptides that participate in tumor suppression, nuclear addressing, and cell proliferation indicate that it may be involved in many other fundamental functions. TJs are formed by a dozen molecular species that assemble through PDZ and other protein-protein clustering promoting sequences, in response to the activation of E-cadherin. The TJ occupies a highly specific position between the apical and the basolateral domains. Its first molecular components seem to be delivered to such a position by addressing signals in their molecule and, once anchored, serve as a clustering nucleus for further TJ-associated molecules. Although in mature epithelial cells TJs and E-cadherin do not colocalize, a complex chain of reactions goes from one to the other that involves alpha-, beta-, and gamma-catenins, two different G proteins, phospholipase C, protein kinase C, calmodulin, mitogen-activated protein kinase, and molecules pertaining to the cytoskeleton, which keep the TJ sensitive to physiological requirements and local conditions (notably to Ca(2+)-dependent cell-cell contacts) throughout the life of the epithelium.
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Affiliation(s)
- M Cereijido
- Center for Research and Advanced Studies, 07000 Mexico City, Mexico.
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29
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Fesenko I, Kurth T, Sheth B, Fleming TP, Citi S, Hausen P. Tight junction biogenesis in the early Xenopus embryo. Mech Dev 2000; 96:51-65. [PMID: 10940624 DOI: 10.1016/s0925-4773(00)00368-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tight junctions (TJs) perform a critical role in the transport functions and morphogenetic activity of the primary epithelium formed during Xenopus cleavage. Biogenesis of these junctions was studied by immunolocalization of TJ-associated proteins (cingulin, ZO-1 and occludin) and by an in vivo biotin diffusion assay. Using fertilized eggs synchronized during the first division cycle, we found that membrane assembly of the TJ initiated at the animal pole towards the end of zygote cytokinesis and involved sequential incorporation of components in the order cingulin, ZO-1 and occludin. The three constituents appeared to be recruited from maternal stores and were targeted to the nascent TJ site by different pathways. TJ protein assembly was focused precisely to the border between the oolemma-derived apical membrane and newly-inserted basolateral membrane generated during cytokinesis and culminated in the formation of functional TJs in the two-cell embryo, which maintained a diffusion barrier. New membrane formation and the generation of cell surface polarity therefore precede initiation of TJ formation. Moreover, assembly of TJ marker protein precisely at the apical-basolateral membrane boundary was preserved in the complete absence of intercellular contacts and adhesion. Thus, the mechanism of TJ biogenesis in the Xenopus early embryo relies on intrinsic cues of a cell autonomous mechanism. These data reveal a distinction between Xenopus and mammalian early embryos in the origin and mechanisms of epithelial cell polarization and TJ formation during cleavage of the egg.
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Affiliation(s)
- I Fesenko
- Max-Planck-Institute for Developmental Biology, Spemannstrasse 35, D-72076, Tübingen, Germany
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30
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Abstract
Tight junctions from a morphological and functional boundary between the apical and basolateral cell surface domains of epithelia and endothelia, and regulate selective diffusion along the paracellular space. Two types of four-span transmembrane proteins, occludin and claudins, as well as the single-span protein JAM are associated with tight junctions. The functional analysis of these proteins starts to reveal how they are involved in the functions of tight junctions, which of their domains are important for these functions, and how they interact with each other to form the junctional diffusion barriers.
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Affiliation(s)
- M S Balda
- Département de Biologie Cellulaire, Université de Genève Sciences III, 30, Quai Ernest-Ansermet, 1211 Genève-4, Switzerland.
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31
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Bazzoni G, Martinez-Estrada OM, Orsenigo F, Cordenonsi M, Citi S, Dejana E. Interaction of junctional adhesion molecule with the tight junction components ZO-1, cingulin, and occludin. J Biol Chem 2000; 275:20520-6. [PMID: 10877843 DOI: 10.1074/jbc.m905251199] [Citation(s) in RCA: 323] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Junctional adhesion molecule (JAM) is an integral membrane protein that has been reported to colocalize with the tight junction molecules occludin, ZO-1, and cingulin. However, evidence for the association of JAM with these molecules is missing. Transfection of Chinese hamster ovary cells with JAM (either alone or in combination with occludin) resulted in enhanced junctional localization of both endogenous ZO-1 and cotransfected occludin. Additionally, JAM was coprecipitated with ZO-1 in the detergent-insoluble fraction of Caco-2 epithelial cells. A putative PDZ-binding motif at the cytoplasmic carboxyl terminus of JAM was required for mediating the interaction of JAM with ZO-1, as assessed by in vitro binding and coprecipitation experiments. JAM was also coprecipitated with cingulin, another cytoplasmic component of tight junctions, and this association required the amino-terminal globular head of cingulin. Taken together, these data indicate that JAM is a component of the multiprotein complex of tight junctions, which may facilitate junction assembly.
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Affiliation(s)
- G Bazzoni
- Istituto di Ricerche Farmacologiche Mario Negri, 20157 Milano, Italy.
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32
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Balda MS, Flores-Maldonado C, Cereijido M, Matter K. Multiple domains of occludin are involved in the regulation of paracellular permeability. J Cell Biochem 2000. [DOI: 10.1002/(sici)1097-4644(20000701)78:1<85::aid-jcb8>3.0.co;2-f] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Wu Z, Nybom P, Magnusson KE. Distinct effects of Vibrio cholerae haemagglutinin/protease on the structure and localization of the tight junction-associated proteins occludin and ZO-1. Cell Microbiol 2000; 2:11-7. [PMID: 11207559 DOI: 10.1046/j.1462-5822.2000.00025.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Vibrio cholerae produces a little-studied cytotoxin, haemagglutinin/protease (HA/P), in addition to several better-characterized enterotoxins, i.e. cholera toxin (CT), zonula occludens toxin (ZOT) and accessory cholera enterotoxin (Ace). We have found recently that HA/P perturbs the barrier function of Mardin-Darby canine kidney epithelial cell line I (MDCK-I) by affecting the intercellular tight junctions (TJs) and the F-actin cytoskeleton. In the present study we have assessed more specifically how TJs are affected by HA/P by investigating the cellular localization and biochemical integrity of two well-characterized TJ-associated proteins, occludin and ZO-1. Western blot analysis showed that occludin bands of 66-85 kDa were digested by HA/P to two predominant bands of around 50 kDa and 35 kDa, and that this degradation was greatly attenuated when the specific bacterial metalloproteinase inhibitor Zincov was co-administered. Trypsin, on the other hand, did not degrade occludin when it was applied in the same way, suggesting that the degradation of occludin by HA/P is an early and specific event. The other TJ-associated protein ZO-1 was not degraded by HA/P in parallel experiments, suggesting the selectivity of HA/P-associated protein degradation. Moreover, immunofluorescence labelling and confocal microscopy showed that ZO-1, but not occludin, around cell-cell boundaries was rearranged by HA/P treatment. Since ZO-1 is located on the inside of the plasma membrane and is directly associated with occludin, the results indicate that breakdown of occludin may send signals to ZO-1 that affect its organization and the structure of the F-actin cytoskeleton. Our finding that the zinc-containing metalloprotease of V. cholerae specifically degraded occludin suggests that specific degradation of important host proteins by bacterial zinc-containing metalloproteases may be an important mechanism in microbial pathogenesis.
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Affiliation(s)
- Z Wu
- Department of Health and Environmental, Linköping University, Sweden
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Inai T, Kobayashi J, Shibata Y. Claudin-1 contributes to the epithelial barrier function in MDCK cells. Eur J Cell Biol 1999; 78:849-55. [PMID: 10669103 DOI: 10.1016/s0171-9335(99)80086-7] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Tight junctions (TJs) create a paracellular permeability barrier and also act as a fence preventing intermixing of proteins and lipids between the apical and basolateral plasma membranes. Recently, claudin-1 has been identified as an integral membrane protein localizing at TJs, and introduced claudin-1 can form TJ-like networks in fibroblasts. To investigate the function of claudin-1, MDCK cells were transfected with a mammalian expression vector containing myc-tagged mouse claudin-1, and four stable clones were obtained. The myc-tagged claudin-1 precisely colocalized with both occludin and ZO-1 at cell-cell contact sites, indicating that exogenous claudin-1 was properly targeted to the TJs. Immunoblot analysis revealed that overexpression of claudin-1 increased expression of ZO-1 but not of occludin or ZO-2. The barrier functions of these cells were evaluated by transepithelial electrical resistance (TER) and paracellular flux. Claudin-1-expressing cells exhibited about four times higher TER than wild-type MDCK cells. Consistent with the increase of TER, the cells overexpressing claudin-1 showed reduced paracellular flux, estimated at 4 and 40 kD FITC-dextrans. These results suggest that claudin-1 is involved in the barrier function at TJs.
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Affiliation(s)
- T Inai
- Department of Developmental Molecular Anatomy, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.
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Sonoda N, Furuse M, Sasaki H, Yonemura S, Katahira J, Horiguchi Y, Tsukita S. Clostridium perfringens enterotoxin fragment removes specific claudins from tight junction strands: Evidence for direct involvement of claudins in tight junction barrier. J Cell Biol 1999; 147:195-204. [PMID: 10508866 PMCID: PMC2164970 DOI: 10.1083/jcb.147.1.195] [Citation(s) in RCA: 465] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Claudins, comprising a multigene family, constitute tight junction (TJ) strands. Clostridium perfringens enterotoxin (CPE), a single approximately 35-kD polypeptide, was reported to specifically bind to claudin-3/RVP1 and claudin-4/CPE-R at its COOH-terminal half. We examined the effects of the COOH-terminal half fragment of CPE (C-CPE) on TJs in L transfectants expressing claudin-1 to -4 (C1L to C4L, respectively), and in MDCK I cells expressing claudin-1 and -4. C-CPE bound to claudin-3 and -4 with high affinity, but not to claudin-1 or -2. In the presence of C-CPE, reconstituted TJ strands in C3L cells gradually disintegrated and disappeared from their cell surface. In MDCK I cells incubated with C-CPE, claudin-4 was selectively removed from TJs with its concomitant degradation. At 4 h after incubation with C-CPE, TJ strands were disintegrated, and the number of TJ strands and the complexity of their network were markedly decreased. In good agreement with the time course of these morphological changes, the TJ barrier (TER and paracellular flux) of MDCK I cells was downregulated by C-CPE in a dose-dependent manner. These findings provided evidence for the direct involvement of claudins in the barrier functions of TJs.
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Affiliation(s)
- Noriyuki Sonoda
- Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Mikio Furuse
- Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hiroyuki Sasaki
- Laboratory of Cell Biology, KAN Research Institute Inc., Kyoto Research Park, Chudoji, Shimogyo-ku, Kyoto 600-8317, Japan
- Department of Molecular Cell Biology, Institute of DNA Medicine, The Jikei University School of Medicine, Nishi-Shinbashi, Minato-ku, Tokyo 105-8461, Japan
| | - Shigenobu Yonemura
- Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Jun Katahira
- Project Research for Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yasuhiko Horiguchi
- Project Research for Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Shoichiro Tsukita
- Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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36
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Cordenonsi M, Turco F, D'atri F, Hammar E, Martinucci G, Meggio F, Citi S. Xenopus laevis occludin. Identification of in vitro phosphorylation sites by protein kinase CK2 and association with cingulin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 264:374-84. [PMID: 10491082 DOI: 10.1046/j.1432-1327.1999.00616.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Occludin is a protein component of the membrane domain of tight junctions, and has been shown to be phosphorylated in vivo in cultured cells and Xenopus laevis embryos. However, nothing is known about the identity of specific occludin kinase(s) and occludin phosphorylation site(s). Furthermore, nothing is known about the interaction of occludin with cingulin, a cytoplasmic plaque component of tight junctions. Here we report the isolation and sequencing of a complete X. laevis occludin cDNA, and experiments aimed at mapping X. laevis occludin in vitro phosphorylation site(s) and characterizing occludin interaction with cingulin. The sequence of Xenopus occludin is homologous to that of occludins from other species, with identities ranging from 41% to 58%. Bacterially expressed domain E of Xenopus occludin (amino acids 247-493) was a good substrate for protein kinase CK2 (stoichiometry 10.8%, Km 8.4 microM) but not for CK1 kinase, protein kinase A, cdc2 kinase, MAP kinase or syk kinase. Residues Thr375 and Ser379 were identified as potential CK2 phosphorylation sites in this region based on sequence analysis. Mutation of Ser379 to aspartic acid or alanine reduced phosphorylation by CK2 by approximately 50%, and double mutation of Ser379 into aspartic acid and Thr375 into aspartic acid essentially abolished phosphorylation. Glutathione S-transferase (GST) pull-down experiments using extracts of Xenopus A6 epithelial cells showed that constructs of GST fused to wild-type and mutant forms of the C-terminal region of X. laevis occludin associate with several polypeptides, and immunoblot analysis showed that one of these polypeptides is cingulin. GST pull-down experiments using in vitro translated, full-length Xenopus cingulin indicated that cingulin interacts directly with the C-terminal region of occludin.
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Affiliation(s)
- M Cordenonsi
- Department of Biology, University of Padova, Italy
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Mitic LL, Schneeberger EE, Fanning AS, Anderson JM. Connexin-occludin chimeras containing the ZO-binding domain of occludin localize at MDCK tight junctions and NRK cell contacts. J Cell Biol 1999; 146:683-93. [PMID: 10444075 PMCID: PMC2150551 DOI: 10.1083/jcb.146.3.683] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/1999] [Accepted: 06/25/1999] [Indexed: 12/27/2022] Open
Abstract
Occludin is a transmembrane protein of the tight junction that functions in creating both an intercellular permeability barrier and an intramembrane diffusion barrier. Creation of the barrier requires the precise localization of occludin, and a distinct family of transmembrane proteins called claudins, into continuous linear fibrils visible by freeze-fracture microscopy. Conflicting evidence exists regarding the relative importance of the transmembrane and extracellular versus the cytoplasmic domains in localizing occludin in fibrils. To specifically address whether occludin's COOH-terminal cytoplasmic domain is sufficient to target it into tight junction fibrils, we created chimeras with the transmembrane portions of connexin 32. Despite the gap junction targeting information present in their transmembrane and extracellular domains, these connexin-occludin chimeras localized within fibrils when expressed in MDCK cells, as assessed by immunofluorescence and immunogold freeze-fracture imaging. Localization of chimeras at tight junctions depends on the COOH-terminal ZO-binding domain and not on the membrane proximal domain of occludin. Furthermore, neither endogenous occludin nor claudin is required for targeting to ZO-1-containing cell-cell contacts, since in normal rat kidney fibroblasts targeting of chimeras again required only the ZO-binding domain. These results suggest an important role for cytoplasmic proteins, presumably ZO-1, ZO-2, and ZO-3, in localizing occludin in tight junction fibrils. Such a scaffolding and cytoskeletal coupling function for ZO MAGUKs is analogous to that of other members of the MAGUK family.
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Affiliation(s)
- L L Mitic
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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Bauer H, Stelzhammer W, Fuchs R, Weiger TM, Danninger C, Probst G, Krizbai IA. Astrocytes and neurons express the tight junction-specific protein occludin in vitro. Exp Cell Res 1999; 250:434-8. [PMID: 10413597 DOI: 10.1006/excr.1999.4558] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression of occludin, an integral plasma membrane protein specifically located at tight junctions, was studied in various epithelial and nonepithelial tissues by means of RT-PCR, Western blotting, and immunofluorescent staining. Besides detection in epithelial and endothelial tissue, expression of occludin was found in primary and secondary cultures of neurons and astrocytes. Differentiation of astrocytes in vitro led to a marked decrease in occludin expression. Extractability of occludin from plasma membranes differed considerably between epithelial and nonepithelial cells. Following treatment with Triton X-100, occludin was completely extracted from astrocytic membranes but not from membranes derived from MDCK cells, suggesting a difference in the cytoplasmic and/or plasma membrane anchoring of occludin between these cell types.
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Affiliation(s)
- H Bauer
- Institute of Molecular Biology, Austrian Academy of Sciences, Salzburg, 5020, Austria.
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Bamforth SD, Kniesel U, Wolburg H, Engelhardt B, Risau W. A dominant mutant of occludin disrupts tight junction structure and function. J Cell Sci 1999; 112 ( Pt 12):1879-88. [PMID: 10341207 DOI: 10.1242/jcs.112.12.1879] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The tight junction is the most apical intercellular junction of epithelial cells and forms a diffusion barrier between individual cells. Occludin is an integral membrane protein specifically associated with the tight junction which may contribute to the function or regulation of this intercellular seal. In order to elucidate the role of occludin at the tight junction, a full length and an N-terminally truncated murine occludin construct, both FLAG-tagged at the N terminus, were stably introduced into the murine epithelial cell line CSG 120/7. Both constructs were correctly targeted to the tight junction, as defined by colocalization with another tight junction protein, ZO-1. The construct lacking the N terminus and extracellular domains of occludin was found to exert a dramatic effect on tight junction integrity. Cell monolayers failed to develop an efficient permeability barrier, as demonstrated by low transcellular electrical resistance values and an increased paracellular flux to small molecular mass tracers. Furthermore, gaps were found to have been induced in the P-face associated tight junction strands, as visualized by freeze-fracture electron microscopy. These findings demonstrate an important role for the N-terminal half of occludin in tight junction assembly and maintaining the barrier function of the tight junction.
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Affiliation(s)
- S D Bamforth
- Max Planck Institute for Physiological and Clinical Research, Department of Molecular Cell Biology, Germany
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Lechner J, Krall M, Netzer A, Radmayr C, Ryan MP, Pfaller W. Effects of interferon alpha-2b on barrier function and junctional complexes of renal proximal tubular LLC-PK1 cells. Kidney Int 1999; 55:2178-91. [PMID: 10354267 DOI: 10.1046/j.1523-1755.1999.00487.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Interferon alpha-2b (IFNalpha) treatment of diseases can be accompanied by impaired renal function and capillary leak syndrome. To explore potential mechanisms of IFNalpha-induced renal dysfunction, an in vitro cell culture model system was established to investigate the effects of IFNalpha on barrier function and junctional complexes. METHODS LLC-PK1 cells were cultured on microporous membranes. Transepithelial resistance (TER) was measured, and the dose- and time-dependent effects of IFNalpha were assessed. The expression patterns of junctional proteins were examined by Western blot analysis and by confocal immunofluorescence microscopy. RESULTS IFNalpha produced a dose- and time-dependent decrease in TER. The effect was reversible on removal of IFNalpha at doses up to 5 x 103 U/ml. Tyrphostin, an inhibitor of phosphotyrosine kinases, ameliorated the IFNalpha-induced decrease in TER. Increased expression of occludin and E-cadherin was detected by Western blot analysis after IFNalpha treatment. Immunofluorescence confocal microscopy revealed a broader staining of occludin and E-cadherin following IFNalpha treatment, with prominent staining at the basal cell pole in addition to localization at the junctional region. A marked increase in phosphotyrosine staining along the apico-lateral cell border was detected after IFNalpha treatment. CONCLUSIONS These findings provide evidence that IFNalpha can directly affect barrier function in renal epithelial cells. The mechanisms involve enhanced tyrosine phosphorylation and overexpression and possibly displacement or missorting of the junctional proteins occludin and E-cadherin.
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Affiliation(s)
- J Lechner
- Institute of Physiology, University of Innsburck, Austria
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41
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Affiliation(s)
- S Citi
- Department of Molecular Biology, University of Geneva, Geneva, Switzerland.
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42
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Gut A, Balda MS, Matter K. The cytoplasmic domains of a beta1 integrin mediate polarization in Madin-Darby canine kidney cells by selective basolateral stabilization. J Biol Chem 1998; 273:29381-8. [PMID: 9792639 DOI: 10.1074/jbc.273.45.29381] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
In Madin-Darby canine kidney cells, newly synthesized apical and basolateral membrane proteins are generally transported directly to their respective cell surface domain due to targeting determinants that mediate sorting in the Golgi complex. In several basolateral membrane proteins, these targeting determinants reside in the cytoplasmic domains. We show here that basolateral expression of the human alpha5beta1 integrin in stably transfected Madin-Darby canine kidney cells is also mediated by the cytoplasmic domains. Distinct regions in both cytoplasmic domains were found to be sufficient to mediate basolateral expression independently from one another. Unexpectedly, newly synthesized wild-type alpha5beta1 and basolaterally expressed chimeras containing the cytoplasmic domain of either alpha5 or beta1 were integrated into both cell surface domains, preferentially apically, during biosynthesis. The apical pools of wild-type integrin and chimeric subunits were found to become quickly degraded, whereas the basolateral pools were stabilized. Thus, the cytoplasmic domains of the alpha5beta1 integrin are independently sufficient to mediate sorting by selective basolateral stabilization.
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Affiliation(s)
- A Gut
- Department of Cell Biology, University of Geneva, 1211 Geneva, Switzerland
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Nussenzveig DR, Matos MD, Thaw CN. Human calcitonin receptor is directly targeted to and retained in the basolateral surface of MDCK cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:C1264-76. [PMID: 9814975 DOI: 10.1152/ajpcell.1998.275.5.c1264] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human calcitonin receptor (hCTR) is expressed in polarized cells of the kidney, bone, and nervous system. In the kidney, hCTRs are found in cells of the distal nephron to which blood-borne calcitonin has access only at the basolateral surface. We expressed hCTR subtypes 1 and 2 in Madin-Darby canine kidney (MDCK) cells to establish a cell model useful for delineating the molecular mechanisms underlying hCTR polarity. Selective cell surface incubation demonstrated functional polarity of hCTRs by equilibrium binding or cross-linking of radioiodinated salmon calcitonin (125I-sCT) and cAMP accumulation stimulated by sCT. We estimated that at the steady state there are 40-fold more hCTRs on the basolateral than on the apical side. Domain-selective cell surface biotinylation followed by immunoblotting of streptavidin-agarose-fractionated biotinylated glycoproteins independently confirmed the polarized distribution of FLAG epitope-tagged hCTR-2 in the basolateral domain. Confocal microscopy of immunostained receptors revealed that hCTRs are concentrated on a lateral subdomain of the basolateral membrane. Cell surface arrival assay of newly formed receptors demonstrated that direct delivery to the basolateral domain is the mechanism by which hCTRs become polarized. Measurement of receptor turnover on the basolateral surface showed that retention contributes to hCTR distribution at the steady state.
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Affiliation(s)
- D R Nussenzveig
- Division of Molecular Medicine, Department of Medicine, Cornell University Medical College, New York, New York 10021, USA
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Matter K, Balda MS. Occludin and the functions of tight junctions. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 186:117-46. [PMID: 9770298 DOI: 10.1016/s0074-7696(08)61052-9] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The tight junction or zonula occludens is the most apical structure of the epithelial junctional complex. Tight junctions from semipermeable intercellular diffusion barriers that control paracellular diffusion in a regulated manner. This intercellular junction also acts as an intramembrane fence that prevents the intermixing of apical and basolateral lipids in the exocytoplasmic leaflet of the plasma membrane. Moreover, evidence suggests that tight junction components participate in the regulation of cell growth and differentiation. Occludin was the first identified transmembrane protein of this intercellular junction and received much attention since its molecular characterization. This review discusses experiments that were done with occludin and how they influenced our current thinking of the molecular functioning of tight junctions.
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Affiliation(s)
- K Matter
- Department of Cell Biology, University of Geneva, Switzerland
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