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Dithmer S, Blasig IE, Fraser PA, Qin Z, Haseloff RF. The Basic Requirement of Tight Junction Proteins in Blood-Brain Barrier Function and Their Role in Pathologies. Int J Mol Sci 2024; 25:5601. [PMID: 38891789 PMCID: PMC11172262 DOI: 10.3390/ijms25115601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 03/10/2024] [Accepted: 03/28/2024] [Indexed: 06/21/2024] Open
Abstract
This review addresses the role of tight junction proteins at the blood-brain barrier (BBB). Their expression is described, and their role in physiological and pathological processes at the BBB is discussed. Based on this, new approaches are depicted for paracellular drug delivery and diagnostics in the treatment of cerebral diseases. Recent data provide convincing evidence that, in addition to its impairment in the course of diseases, the BBB could be involved in the aetiology of CNS disorders. Further progress will be expected based on new insights in tight junction protein structure and in their involvement in signalling pathways.
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Affiliation(s)
- Sophie Dithmer
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125 Berlin, Germany (I.E.B.)
| | - Ingolf E. Blasig
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125 Berlin, Germany (I.E.B.)
| | | | - Zhihai Qin
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100049, China
| | - Reiner F. Haseloff
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125 Berlin, Germany (I.E.B.)
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2
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Dong Y, Jin Q, Sun M, Qi D, Qu H, Wang X, Quan C. CLDN6 inhibits breast cancer metastasis through WIP-dependent actin cytoskeleton-mediated autophagy. J Exp Clin Cancer Res 2023; 42:68. [PMID: 36935496 PMCID: PMC10026481 DOI: 10.1186/s13046-023-02644-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 03/11/2023] [Indexed: 03/21/2023] Open
Abstract
BACKGROUND As a breast cancer suppressor gene, CLDN6 overexpression was found to inhibit breast cancer metastasis in our previous studies, but the specific mechanism remains unclear. This study aimed to clarify the role and mechanism of CLDN6 in inhibiting breast cancer metastasis. METHODS Western blot, immunofluorescence and transmission electron microscopy were performed to detect autophagy. Wound healing, transwell assays and lung metastasis mouse models were used to examine breast cancer metastasis. Phalloidin staining and immunofluorescent staining were used to observe actin cytoskeleton. mRNA seq, RT-PCR, western blot, chromatin immunoprecipitation, dual luciferase reporter assay, co-immunoprecipitation and immunofluorescence were performed to define the molecular mechanism. The expression levels and clinical implication of CLDN6, WIP and LC3 in breast cancer tissues were evaluated using immunohistochemistry. RESULTS We demonstrated that CLDN6 inhibited breast cancer metastasis through autophagy in vitro and vivo. We unraveled a novel mechanism that CLDN6 regulated autophagy via WIP-dependent actin cytoskeleton assembly. Through its PDZ-binding motif, overexpressed CLDN6 interacted with JNK and upregulated JNK/c-Jun pathway. C-Jun promoted WIP expression at the transcriptional level. Notably, we observed c-Jun transcriptionally upregulated CLDN6 expression, and there was a positive feedback loop between CLDN6 and JNK/c-Jun. Finally, we found that CLDN6, WIP and LC3 expression correlated with each other, and WIP expression was significantly associated with lymph node metastasis of breast cancer patients. CONCLUSIONS The data provide a new insight into the inhibitory effects of CLDN6-mediated autophagy on breast cancer metastasis, and revealed the new mechanism of CLDN6 regulating autophagy through WIP-dependent actin cytoskeleton. Our findings enrich the theoretical basis for CLDN6 as a potential biomarker for breast cancer diagnosis and therapy.
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Affiliation(s)
- Yuan Dong
- The Key Laboratory of Pathobiology, Ministry of Education, College of Basic Medical Sciences, Jilin University, 126 Xinmin Avenue, Changchun, 130021, Jilin, China
| | - Qiu Jin
- The Key Laboratory of Pathobiology, Ministry of Education, College of Basic Medical Sciences, Jilin University, 126 Xinmin Avenue, Changchun, 130021, Jilin, China
| | - Minghao Sun
- The Key Laboratory of Pathobiology, Ministry of Education, College of Basic Medical Sciences, Jilin University, 126 Xinmin Avenue, Changchun, 130021, Jilin, China
| | - Da Qi
- The Key Laboratory of Pathobiology, Ministry of Education, College of Basic Medical Sciences, Jilin University, 126 Xinmin Avenue, Changchun, 130021, Jilin, China
| | - Huinan Qu
- The Key Laboratory of Pathobiology, Ministry of Education, College of Basic Medical Sciences, Jilin University, 126 Xinmin Avenue, Changchun, 130021, Jilin, China
| | - Xinqi Wang
- The Key Laboratory of Pathobiology, Ministry of Education, College of Basic Medical Sciences, Jilin University, 126 Xinmin Avenue, Changchun, 130021, Jilin, China
| | - Chengshi Quan
- The Key Laboratory of Pathobiology, Ministry of Education, College of Basic Medical Sciences, Jilin University, 126 Xinmin Avenue, Changchun, 130021, Jilin, China.
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3
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Alexander RT, Dimke H. Molecular mechanisms underlying paracellular calcium and magnesium reabsorption in the proximal tubule and thick ascending limb. Ann N Y Acad Sci 2022; 1518:69-83. [PMID: 36200584 DOI: 10.1111/nyas.14909] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Calcium and magnesium are the most abundant divalent cations in the body. The plasma level is controlled by coordinated interaction between intestinal absorption, reabsorption in the kidney, and, for calcium at least, bone storage and exchange. The kidney adjusts urinary excretion of these ions in response to alterations in their systemic concentration. Free ionized and anion-complexed calcium and magnesium are filtered at the glomerulus. The majority (i.e., >85%) of filtered divalent cations are reabsorbed via paracellular pathways from the proximal tubule and thick ascending limb (TAL) of the loop of Henle. Interestingly, the largest fraction of filtered calcium is reabsorbed from the proximal tubule (65%), while the largest fraction of filtered magnesium is reclaimed from the TAL (60%). The paracellular pathways mediating these fluxes are composed of tight junctional pores formed by claudins. In the proximal tubule, claudin-2 and claudin-12 confer calcium permeability, while the exact identity of the magnesium pore remains to be determined. Claudin-16 and claudin-19 contribute to the calcium and magnesium permeable pathway in the TAL. In this review, we discuss the data supporting these conclusions and speculate as to why there is greater fractional calcium reabsorption from the proximal tubule and greater fractional magnesium reabsorption from the TAL.
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Affiliation(s)
- R Todd Alexander
- Departments of Physiology & Pediatrics, University of Alberta, Edmonton, Alberta, Canada.,Women's and Children's Health Institute, Edmonton, Alberta, Canada
| | - Henrik Dimke
- Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Demark.,Department of Nephrology, Odense University Hospital, Odense, Denmark
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4
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Jo CH, Kim S, Kim GH. Claudins in kidney health and disease. Kidney Res Clin Pract 2022; 41:275-287. [PMID: 35354245 PMCID: PMC9184838 DOI: 10.23876/j.krcp.21.279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 12/29/2021] [Indexed: 11/04/2022] Open
Abstract
Claudins are strategically located to exert their physiologic actions along with the nephron segments from the glomerulus. Claudin-1 is normally located in the Bowman’s capsule, but its overexpression can reach the podocytes and lead to albuminuria. In the proximal tubule (PT), claudin-2 forms paracellular channels selective for water, Na+, K+, and Ca2+. Claudin-2 gene mutations are associated with hypercalciuria and kidney stones. Claudin-10 has two splice variants, -10a and -10b; Claudin-10a acts as an anion-selective channel in the PT, and claudin-10b functions as a cation-selective pore in the thick ascending limb (TAL). Claudin-16 and claudin-19 mediate paracellular transport of Na+, Ca2+, and Mg2+ in the TAL, where the expression of claudin-3/16/19 and claudin-10b are mutually exclusive. The claudin-16 or -19 mutation causes familial hypomagnesemia with hypercalciuria and nephrocalcinosis. Claudin-14 polymorphisms have been linked to increased risk of hypercalciuria. Claudin-10b mutations produce HELIX syndrome, which encompasses hypohidrosis, electrolyte imbalance, lacrimal gland dysfunction, ichthyosis, and xerostomia. Hypercalciuria and magnesuria in metabolic acidosis are related to downregulation of PT and TAL claudins. In the TAL, stimulation of calcium-sensing receptors upregulates claudin-14 and negatively acts on the claudin-16/19 complex. Claudin-3 acts as a general barrier to ions in the collecting duct. If this barrier is disturbed, urine acidification might be impaired. Claudin-7 forms a nonselective paracellular channel facilitating Cl– and Na+ reabsorption in the collecting ducts. Claudin-4 and -8 serve as anion channels and mediate paracellular Cl– transport; their upregulation may contribute to pseudohypoaldosteronism II and salt-sensitive hypertension.
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Affiliation(s)
- Chor ho Jo
- Hanyang Biomedical Research Institute, Hanyang University College of Medicine, Seoul, Republic of Korea
| | - Sua Kim
- Hanyang Biomedical Research Institute, Hanyang University College of Medicine, Seoul, Republic of Korea
| | - Gheun-Ho Kim
- Hanyang Biomedical Research Institute, Hanyang University College of Medicine, Seoul, Republic of Korea
- Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Republic of Korea
- Correspondence: Gheun-Ho Kim Department of Internal Medicine, Hanyang University College of Medicine, 222-1 Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea. E-mail:
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5
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Disruption of Claudin-Made Tight Junction Barriers by Clostridium perfringens Enterotoxin: Insights from Structural Biology. Cells 2022; 11:cells11050903. [PMID: 35269525 PMCID: PMC8909277 DOI: 10.3390/cells11050903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 02/26/2022] [Accepted: 03/02/2022] [Indexed: 02/01/2023] Open
Abstract
Claudins are a family of integral membrane proteins that enable epithelial cell/cell interactions by localizing to and driving the formation of tight junctions. Via claudin self-assembly within the membranes of adjoining cells, their extracellular domains interact, forming barriers to the paracellular transport of small molecules and ions. The bacterium Clostridium perfringens causes prevalent gastrointestinal disorders in mammals by employing an enterotoxin (CpE) that targets claudins. CpE binds to claudins at or near tight junctions in the gut and disrupts their barrier function, potentially by disabling their assembly or via cell signaling means—the mechanism(s) remain unclear. CpE ultimately destroys claudin-expressing cells through the formation of a cytotoxic membrane-penetrating β-barrel pore. Structures obtained by X-ray crystallography of CpE, claudins, and claudins in complex with CpE fragments have provided the structural bases of claudin and CpE functions, revealing potential mechanisms for the CpE-mediated disruption of claudin-made tight junctions. This review highlights current progress in this space—what has been discovered and what remains unknown—toward efforts to elucidate the molecular mechanism of CpE disruption of tight junction barriers. It further underscores the key insights obtained through structure that are being applied to develop CpE-based therapeutics that combat claudin-overexpressing cancers or modulate tight junction barriers.
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6
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Qu H, Jin Q, Quan C. CLDN6: From Traditional Barrier Function to Emerging Roles in Cancers. Int J Mol Sci 2021; 22:ijms222413416. [PMID: 34948213 PMCID: PMC8705207 DOI: 10.3390/ijms222413416] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/06/2021] [Accepted: 12/12/2021] [Indexed: 02/07/2023] Open
Abstract
Claudins (CLDNs) are the most important tight junction proteins, which are mainly expressed in endothelial cells or epithelial cells in a tissue-specific manner. As a member of the CLDNs family, CLDN6 is highly expressed in fetal tissues such as the stomach, pancreas, lung, and kidney, but is not expressed in corresponding adult tissues. The expression of CLDN6 is regulated by a variety of factors, including but not limited to stimuli and transcription factors, DNA methylation, and post-translational modifications. CLDN6 has been found to have a key role in the formation of barriers, especially the lung epithelial barrier and the epidermal permeability barrier (EPB). Importantly, the roles of CLDN6 in cancers have gained focus and are being investigated in recent years. Strong evidence indicates that the altered expression of CLDN6 is linked to the development of various cancers. Malignant phenotypes of tumors affected by CLDN6 include proliferation and apoptosis, migration and invasion, and drug resistance, which are regulated by CLDN6-mediated key signaling pathways. Given the important role in tumors and its low or no expression in normal tissues, CLDN6 is an ideal target for tumor therapy. This review aims to provide an overview of the structure and regulation of CLDN6, and its traditional barrier function, with a special emphasis on its emerging roles in cancers, including its impact on the malignant phenotypes, signal-modulating effects, the prognosis of tumor patients, and clinical applications in cancers.
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7
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Claudin-9 structures reveal mechanism for toxin-induced gut barrier breakdown. Proc Natl Acad Sci U S A 2019; 116:17817-17824. [PMID: 31434788 DOI: 10.1073/pnas.1908929116] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The human pathogenic bacterium Clostridium perfringens secretes an enterotoxin (CpE) that targets claudins through its C-terminal receptor-binding domain (cCpE). Isoform-specific binding by CpE causes dissociation of claudins and tight junctions (TJs), resulting in cytotoxicity and breakdown of the gut epithelial barrier. Here, we present crystal structures of human claudin-9 (hCLDN-9) in complex with cCpE at 3.2 and 3.3 Å. We show that hCLDN-9 is a high-affinity CpE receptor and that hCLDN-9-expressing cells undergo cell death when treated with CpE but not cCpE, which lacks its cytotoxic domain. Structures reveal cCpE-induced alterations to 2 epitopes known to enable claudin self-assembly and expose high-affinity interactions between hCLDN-9 and cCpE that explain isoform-specific recognition. These findings elucidate the molecular bases for hCLDN-9 selective ion permeability and binding by CpE, and provide mechanisms for how CpE disrupts gut homeostasis by dissociating claudins and TJs to affect epithelial adhesion and intercellular transport.
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8
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Nakayama H, Kitagawa N, Otani T, Iida H, Anan H, Inai T. Ochratoxin A, citrinin and deoxynivalenol decrease claudin-2 expression in mouse rectum CMT93-II cells. Microscopy (Oxf) 2018; 67:99-111. [PMID: 29474583 DOI: 10.1093/jmicro/dfy005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 01/16/2018] [Indexed: 01/01/2023] Open
Abstract
Intestinal epithelial cells are the first targets of ingested mycotoxins, such as ochratoxin A, citrinin and deoxynivalenol. It has been reported that paracellular permeability regulated by tight junctions is modulated by several mycotoxins by reducing the expression of specific claudins and integral membrane proteins in cell-cell contacts, accompanied by increase in phosphorylation of mitogen-activated protein kinases, including extracellular signal-related kinase (ERK) 1/2, p38 and c-Jun NH2-terminal protein kinase. Claudin-2 is expressed in the deep crypt cells, but not in the villus/surface cells in vivo. While Caco-2, T84 and IPEC-J2 cells, which are widely used intestinal epithelial cell lines to assess the influence of mycotoxins, do not express claudin-2, CMT93-II cells express claudin-2. We previously reported that inhibition of the ERK pathway reduced claudin-2 levels in cell-cell contacts in CMT93-II cells. In this study, we examined whether ochratoxin A, citrinin and deoxynivalenol affect claudin-2 expression and ERK1/2 phosphorylation in CMT93-II cells. We found that all mycotoxins reduced claudin-2 expression in cell-cell contacts, with reduction (by citrinin and deoxynivalenol) or no change (by ochratoxin A) in phosphorylated ERK1/2. All mycotoxins increased transepithelial electrical resistance, but did not affect flux of fluorescein. While ochratoxin A and citrinin are known to be nephrotoxic, only deoxynivalenol reduced claudin-2 expression in MDCK II cells derived from the renal tubule. These results suggest that claudin-2 expression is regulated not only by the ERK pathway, but also by other pathways in an organ-specific manner.
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Affiliation(s)
- Hideaki Nakayama
- Department of Odontology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan
| | - Norio Kitagawa
- Department of Morphological Biology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan
| | - Takahito Otani
- Department of Morphological Biology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan
| | - Hiroshi Iida
- Laboratory of Zoology, Graduate School of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Hisashi Anan
- Department of Odontology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan
| | - Tetsuichiro Inai
- Department of Morphological Biology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-ku, Fukuoka 814-0193, Japan
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9
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Curry JN, Yu AS. Magnesium Handling in the Kidney. Adv Chronic Kidney Dis 2018; 25:236-243. [PMID: 29793662 DOI: 10.1053/j.ackd.2018.01.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 12/26/2017] [Accepted: 01/02/2018] [Indexed: 02/07/2023]
Abstract
Magnesium is a divalent cation that fills essential roles as regulator and cofactor in a variety of biological pathways, and maintenance of magnesium balance is vital to human health. The kidney, in concert with the intestine, has an important role in maintaining magnesium homeostasis. Although micropuncture and microperfusion studies in the mammalian nephron have shone a light on magnesium handling in the various nephron segments, much of what we know about the protein mediators of magnesium handling in the kidney have come from more recent genetic studies. In the proximal tubule and thick ascending limb, magnesium reabsorption is believed to occur primarily through the paracellular shunt pathway, which ultimately depends on the electrochemical gradient setup by active sodium reabsorption. In the distal convoluted tubule, magnesium transport is transcellular, although magnesium reabsorption also appears to be related to active sodium reabsorption in this segment. In addition, evidence suggests that magnesium transport is highly regulated, although a specific hormonal regulator of extracellular magnesium has yet to be identified.
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10
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Lewis JB, Jimenez FR, Merrell BJ, Kimbler B, Arroyo JA, Reynolds PR. The expression profile of Claudin family members in the developing mouse lung and expression alterations resulting from exposure to secondhand smoke (SHS). Exp Lung Res 2018; 44:13-24. [DOI: 10.1080/01902148.2017.1409846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Joshua B. Lewis
- Department of Physiology and Developmental Biology, Lung and Placenta Research Laboratory, Brigham Young University, Provo, Utah, USA
| | - Felix R. Jimenez
- Department of Physiology and Developmental Biology, Lung and Placenta Research Laboratory, Brigham Young University, Provo, Utah, USA
| | - Brigham J. Merrell
- Department of Physiology and Developmental Biology, Lung and Placenta Research Laboratory, Brigham Young University, Provo, Utah, USA
| | - Brent Kimbler
- Department of Physiology and Developmental Biology, Lung and Placenta Research Laboratory, Brigham Young University, Provo, Utah, USA
| | - Juan A. Arroyo
- Department of Physiology and Developmental Biology, Lung and Placenta Research Laboratory, Brigham Young University, Provo, Utah, USA
| | - Paul R. Reynolds
- Department of Physiology and Developmental Biology, Lung and Placenta Research Laboratory, Brigham Young University, Provo, Utah, USA
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11
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Beggs MR, Alexander RT. Intestinal absorption and renal reabsorption of calcium throughout postnatal development. Exp Biol Med (Maywood) 2017; 242:840-849. [PMID: 28346014 DOI: 10.1177/1535370217699536] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Calcium is vital for many physiological functions including bone mineralization. Postnatal deposition of calcium into bone is greatest in infancy and continues through childhood and adolescence until peek mineral density is reached in early adulthood. Thereafter, bone mineral density remains static until it eventually declines in later life. A positive calcium balance, i.e. more calcium absorbed than excreted, is crucial to bone deposition during growth and thus to peek bone mineral density. Dietary calcium is absorbed from the intestine into the blood. It is then filtered by the renal glomerulus and either reabsorbed by the tubule or excreted in the urine. Calcium can be (re)absorbed across intestinal and renal epithelia via both transcellular and paracellular pathways. Current evidence suggests that significant intestinal and renal calcium transport changes occur throughout development. However, the molecular details of these alterations are incompletely delineated. Here we first briefly review the current model of calcium transport in the intestine and renal tubule in the adult. Then, we describe what is known with regard to calcium handling through postnatal development, and how alterations may aid in mediating a positive calcium balance. The role of transcellular and paracellular calcium transport pathways and the contribution of specific intestinal and tubular segments vary with age. However, the current literature highlights knowledge gaps in how specifically intestinal and renal calcium (re)absorption occurs early in postnatal development. Future research should clarify the specific changes in calcium transport throughout early postnatal development including mediators of these alterations enabling appropriate bone mineralization. Impact statement This mini review outlines the current state of knowledge pertaining to the molecules and mechanisms maintaining a positive calcium balance throughout postnatal development. This process is essential to achieving optimal bone mineral density in early adulthood, thereby lowering the lifetime risk of osteoporosis.
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Affiliation(s)
- Megan R Beggs
- 1 Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2R7, Canada
| | - R Todd Alexander
- 1 Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2R7, Canada.,2 Department of Pediatrics, University of Alberta, Edmonton, Alberta T6G 2R7, Canada
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12
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Muto S. Physiological roles of claudins in kidney tubule paracellular transport. Am J Physiol Renal Physiol 2017; 312:F9-F24. [DOI: 10.1152/ajprenal.00204.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 10/24/2016] [Accepted: 10/25/2016] [Indexed: 12/30/2022] Open
Abstract
The paracellular pathways in renal tubular epithelia such as the proximal tubules, which reabsorb the largest fraction of filtered solutes and water and are leaky epithelia, are important routes for transepithelial transport of solutes and water. Movement occurs passively via an extracellular route through the tight junction between cells. The characteristics of paracellular transport vary among different nephron segments with leaky or tighter epithelia. Claudins expressed at tight junctions form pores and barriers for paracellular transport. Claudins are from a multigene family, comprising at least 27 members in mammals. Multiple claudins are expressed at tight junctions of individual nephron segments in a nephron segment-specific manner. Over the last decade, there have been advances in our understanding of the structure and functions of claudins. This paper is a review of our current knowledge of claudins, with special emphasis on their physiological roles in proximal tubule paracellular solute and water transport.
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Affiliation(s)
- Shigeaki Muto
- Division of Nephrology, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
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13
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Gattineni J, Baum M. Developmental changes in renal tubular transport-an overview. Pediatr Nephrol 2015; 30:2085-98. [PMID: 24253590 PMCID: PMC4028442 DOI: 10.1007/s00467-013-2666-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 10/01/2013] [Accepted: 10/11/2013] [Indexed: 10/26/2022]
Abstract
The adult kidney maintains a constant volume and composition of extracellular fluid despite changes in water and salt intake. The neonate is born with a kidney that has a small fraction of the glomerular filtration rate of the adult and immature tubules that function at a lower capacity than that of the mature animal. Nonetheless, the neonate is also able to maintain a constant extracellular fluid volume and composition. Postnatal renal tubular development was once thought to be due to an increase in the transporter abundance to meet the developmental increase in glomerular filtration rate. However, postnatal renal development of each nephron segment is quite complex. There are isoform changes of several transporters as well as developmental changes in signal transduction that affect the capacity of renal tubules to reabsorb solutes and water. This review will discuss neonatal tubular function with an emphasis on the differences that have been found between the neonate and adult. We will also discuss some of the factors that are responsible for the maturational changes in tubular transport that occur during postnatal renal development.
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Affiliation(s)
- Jyothsna Gattineni
- Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-9061, USA
| | - Michel Baum
- Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-9061, USA.
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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14
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Alexander RT, Rievaj J, Dimke H. Paracellular calcium transport across renal and intestinal epithelia. Biochem Cell Biol 2014; 92:467-80. [PMID: 25386841 DOI: 10.1139/bcb-2014-0061] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Calcium (Ca(2+)) is a key constituent in a myriad of physiological processes from intracellular signalling to the mineralization of bone. As a consequence, Ca(2+) is maintained within narrow limits when circulating in plasma. This is accomplished via regulated interplay between intestinal absorption, renal tubular reabsorption, and exchange with bone. Many studies have focused on the highly regulated active transcellular transport pathways for Ca(2+) from the duodenum of the intestine and the distal nephron of the kidney. However, comparatively little work has examined the molecular constituents creating the paracellular shunt across intestinal and renal epithelium, the transport pathway responsible for the majority of transepithelial Ca(2+) flux. More specifically, passive paracellular Ca(2+) absorption occurs across the majority of the intestine in addition to the renal proximal tubule and thick ascending limb of Henle's loop. Importantly, recent studies demonstrated that Ca(2+) transport through the paracellular shunt is significantly regulated. Therefore, we have summarized the evidence for different modes of paracellular Ca(2+) flux across renal and intestinal epithelia and highlighted recent molecular insights into both the mechanism of secondarily active paracellular Ca(2+) movement and the identity of claudins that permit the passage of Ca(2+) through the tight junction of these epithelia.
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Affiliation(s)
- R Todd Alexander
- a Department of Pediatrics, The University of Alberta, 4-585 Edmonton Clinic Health Academy, 11405 - 87 Ave, Edmonton, AB T6G 2R7, Canada
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15
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Abstract
The imbalance between bone formation and resorption during bone remodeling has been documented to be a major factor in the pathogenesis of osteoporosis. Recent evidence suggests a significant role for the tight junction proteins, Claudins (Cldns), in the regulation of bone remodeling processes. In terms of function, whereas Cldns act "canonically" as key determinants of paracellular permeability, there is considerable recent evidence to suggest that Cldns also participate in cell signaling, ie, a "noncanonical function". To this end, Cldns have been shown to regulate cell proliferation, differentiation, and gene expression in a variety of cell types. The present review will discuss Cldns' structure, their expression profile, regulation of expression, and their canonical and non- canonical functions in general with special emphasis on bone cells. In order to shed light on the noncanonical functions of Cldns in bone, we will highlight the role of Cldn-18 in regulating bone resorption and osteoclast differentiation. Collectively, we hope to provide a framework for guiding future research on understanding how Cldns modulate osteoblast and osteoclast function and overall bone homeostasis. Such studies should provide valuable insights into the pathogenesis of osteoporosis, and may highlight Cldns as novel targets for the diagnosis and therapeutic management of osteoporosis.
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Affiliation(s)
- Fatima Z Alshbool
- Musculoskeletal Disease Center (F.Z.A., S.M.), Jerry L. Pettis VA Medical Center, Loma Linda, CA 92357; Departments of Medicine (S.M.), Biochemistry (S.M.), Physiology (S.M.), and Pharmacology (F.Z.A., S.M.), Loma Linda University, Loma Linda, California 92354
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16
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Psáder R, Jakab C, Máthé Á, Balka G, Pápa K, Sterczer Á. Expression of claudins in the normal canine gastric mucosa. Acta Vet Hung 2014; 62:13-21. [PMID: 24334088 DOI: 10.1556/avet.2013.053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The aim of the present study was to investigate the expression pattern of claudin-1, -2, -3, -4, -5, -7, -8, -10 and -18 in the intact fundic and pyloric gastric mucosa of dogs. Intense, linear, membranous claudin-18 positivity was detected in the surface gastric cells and in the epithelial cells of the gastric glands both in the fundic and pyloric stomach regions. The mucous neck cells in the apical part of the glands, furthermore the parietal cells and chief cells of the basal part of the gland were all positive for claudin-18, in the same way as the enteroendocrine cells. Cells of the basal part of the pyloric glands showed intense, linear, membranous claudin-2 positivity, but cells of the superficial portion of these glands and the surface gastric cells in this region were claudin-2 negative. Fibroblasts, endothelial cells, lymphocytes of the propria layer, smooth muscle cells and vegetative neurons were all negative for claudin-2. All gastric epithelial cells were negative for claudin-1, -3, -4, -5, -6, -7, -8 and -10. The endothelial cells of the propria layer had intense claudin-5 positivity. We assume that claudin-18 forms a paracellular barrier against gastric acid in the healthy canine stomach, in the same way as in mice.
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Affiliation(s)
- Roland Psáder
- 1 Szent István University Department and Clinic of Internal Medicine, Faculty of Veterinary Science István u. 2 Budapest H-1078 Hungary
| | - Csaba Jakab
- 2 Szent István University Department of Pathology and Forensic Veterinary Medicine, Faculty of Veterinary Science Budapest Hungary
| | - Ákos Máthé
- 1 Szent István University Department and Clinic of Internal Medicine, Faculty of Veterinary Science István u. 2 Budapest H-1078 Hungary
| | - Gyula Balka
- 2 Szent István University Department of Pathology and Forensic Veterinary Medicine, Faculty of Veterinary Science Budapest Hungary
| | - Kinga Pápa
- 1 Szent István University Department and Clinic of Internal Medicine, Faculty of Veterinary Science István u. 2 Budapest H-1078 Hungary
| | - Ágnes Sterczer
- 1 Szent István University Department and Clinic of Internal Medicine, Faculty of Veterinary Science István u. 2 Budapest H-1078 Hungary
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17
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Abstract
Epithelial transport relies on the proper function and regulation of the tight junction (TJ), other-wise uncontrolled paracellular leakage of solutes and water would occur. They also act as a fence against mixing of membrane proteins of the apical and basolateral side. The proteins determining paracellular transport consist of four transmembrane regions, intracellular N and C terminals, one intracellular and two extracellular loops (ECLs). The ECLs interact laterally and with counterparts of the neighboring cell and by this achieve a general sealing function. Two TJ protein families can be distinguished, claudins, comprising 27 members in mammals, and TJ-associated MARVEL proteins (TAMP), comprising occludin, tricellulin, and MarvelD3. They are linked to a multitude of TJ-associated regulatory and scaffolding proteins. The major TJ proteins are classified according to the physiological role they play in enabling or preventing paracellular transport. Many TJ proteins have sealing functions (claudins 1, 3, 5, 11, 14, 19, and tricellulin). In contrast, a significant number of claudins form channels across TJs which feature selectivity for cations (claudins 2, 10b, and 15), anions (claudin-10a and -17), or are permeable to water (claudin-2). For several TJ proteins, function is yet unclear as their effects on epithelial barriers are inconsistent (claudins 4, 7, 8, 16, and occludin). TJs undergo physiological and pathophysiological regulation by altering protein composition or abundance. Major pathophysiological conditions which involve changes in TJ protein composition are (1) effects of pathogens binding to TJ proteins, (2) altered TJ protein composition during inflammation and infection, and (3) altered TJ protein expression in cancers.
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Affiliation(s)
- Dorothee Günzel
- Institute of Clinical Physiology, Charité, Universtätsmedizin Berlin, Campus Benjamin Franklin, Freie Universität/Humboldt-Universität, Berlin, Germany
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18
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Abstract
BACKGROUND Bicarbonate loss into the lumen occurs during intestinal inflammation in different species. However, candidate pathways like CFTR or DRA are inhibited in the inflamed gut. This study addressed the question whether and how inflammation-associated increased intestinal permeability may result in epithelial HCO(3)(-) loss. METHODS Murine proximal colon was studied because it does not express functional DRA but is inflamed in the tumor necrosis factor α overexpressing mouse model (TNF(ΔARE)). Luminal alkalization, (3)H-mannitol fluxes, impedance spectroscopy, and dilution potentials were measured in Ussing chambers, whereas expression and localization of tight junction-associated proteins were analyzed by Western blots and immunohistochemistry. RESULTS Luminal alkalization rates and (3)H-mannitol fluxes were increased in TNF(+/ΔARE) proximal colon, whereas forskolin-stimulated I(sc) was not altered. Epithelial resistance was reduced, but subepithelial resistance increased. The epithelial lining was intact, and enterocyte apoptosis rate was not increased despite massively increased Th1 cytokine levels and lymphoplasmacellular infiltration. Measurement of dilution potentials suggested a loss of cation selectivity with increased anion permeability. Western analysis revealed a downregulation of occludin expression and an upregulation of both claudin-2 and claudin-5, with no change in ZO-1, E-cadherin, claudin-4, and claudin-8. Immunohistochemistry suggested correct occludin localization but reduced tight junction density in TNF(+/ΔARE) surface epithelium. CONCLUSIONS Inflammation during TNF-α overexpression leads to increased epithelial permeability in murine proximal colon, decreased tight junctional cation selectivity, and increased HCO(3)(-) loss into the lumen. Inflammation-associated colonic HCO(3)(-) loss may occur through leaky tight junctions rather than through HCO(3)(-) secreting ion transporters.
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19
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Abstract
Claudins are tight junction membrane proteins that are expressed in epithelia and endothelia and form paracellular barriers and pores that determine tight junction permeability. This review summarizes our current knowledge of this large protein family and discusses recent advances in our understanding of their structure and physiological functions.
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Affiliation(s)
- Dorothee Günzel
- Department of Clinical Physiology, Charité, Campus Benjamin Franklin, Berlin, Germany
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20
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Dimke H, Desai P, Borovac J, Lau A, Pan W, Alexander RT. Activation of the Ca(2+)-sensing receptor increases renal claudin-14 expression and urinary Ca(2+) excretion. Am J Physiol Renal Physiol 2013; 304:F761-9. [PMID: 23283989 DOI: 10.1152/ajprenal.00263.2012] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Kidney stones are a prevalent clinical condition imposing a large economic burden on the healthcare system. Hypercalciuria remains the major risk factor for development of a Ca(2+)-containing stone. The kidney's ability to alter Ca(2+) excretion in response to changes in serum Ca(2+) is in part mediated by the Ca(2+)-sensing receptor (CaSR). Recent studies revealed renal claudin-14 (Cldn14) expression localized to the thick ascending limb (TAL) and its expression to be regulated via the CaSR. We find that Cldn14 expression is increased by high dietary Ca(2+) intake and by elevated serum Ca(2+) levels induced by prolonged 1,25-dihydroxyvitamin D3 administration. Consistent with this, activation of the CaSR in vivo via administration of the calcimimetic cinacalcet hydrochloride led to a 40-fold increase in Cldn14 mRNA. Moreover, overexpression of Cldn14 in two separate cell culture models decreased paracellular Ca(2+) flux by preferentially decreasing cation permeability, thereby increasing transepithelial resistance. These data support the existence of a mechanism whereby activation of the CaSR in the TAL increases Cldn14 expression, which in turn blocks the paracellular reabsorption of Ca(2+). This molecular mechanism likely facilitates renal Ca(2+) losses in response to elevated serum Ca(2+). Moreover, dysregulation of the newly described CaSR-Cldn14 axis likely contributes to the development of hypercalciuria and kidney stones.
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Affiliation(s)
- Henrik Dimke
- Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
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21
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Borovac J, Barker RS, Rievaj J, Rasmussen A, Pan W, Wevrick R, Alexander RT. Claudin-4 forms a paracellular barrier, revealing the interdependence of claudin expression in the loose epithelial cell culture model opossum kidney cells. Am J Physiol Cell Physiol 2012; 303:C1278-91. [PMID: 23076790 PMCID: PMC3532495 DOI: 10.1152/ajpcell.00434.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 10/09/2012] [Indexed: 02/03/2023]
Abstract
The effect of claudins on paracellular fluxes has been predominantly studied in either Madin-Darby canine kidney (MDCK) or LLCPK cells. Neither model system has a very low transepithelial resistance (TER) as observed in leaky epithelia. Moreover, results from one model system are not always consistent with another. Opossum kidney (OK) cells form tight junctions yet have a very low TER. We therefore set out to characterize the paracellular transport properties of this cell culture model. Ussing chamber dilution potential measurements revealed that OK cells exhibit a very low TER (11.7 ± 1.4 Ω·cm(2)), slight cation selectivity (P(Na)/P(Cl) = 1.10 ± 0.01), and the Eisenman permeability sequence IV; the permeability of monovalent cations ranking K(+) > Cs(+) > Rb(+) > Na(+) > Li(+). Quantitative real-time PCR studies found that OK cells endogenously express claudin-4 > -1 > -6 > -20 > -9 > -12 > -11 > -15. Overexpression of claudin-4 significantly increased TER, decreased Na(+) and Cl(-) permeability, and increased levels of claudin-1, -6, and -9 mRNA. Knockdown of claudin-4 in the overexpressing cells significantly decreased TER without altering claudin expression; thus claudin-4 forms a barrier in OK cells. Knockdown of endogenous claudin-4 decreased claudin-1, -9, and -12 expression without altering TER. Claudin-2 overexpression decreased TER, significantly increased Na(+) and Cl(-) permeability, and decreased claudin-12 and -6 expression. Together these results demonstrate that claudin expression is tightly coupled in OK cells.
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Affiliation(s)
- Jelena Borovac
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
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22
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Chasiotis H, Kolosov D, Bui P, Kelly SP. Tight junctions, tight junction proteins and paracellular permeability across the gill epithelium of fishes: A review. Respir Physiol Neurobiol 2012; 184:269-81. [DOI: 10.1016/j.resp.2012.05.020] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/18/2012] [Accepted: 05/20/2012] [Indexed: 10/28/2022]
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23
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Schulzke JD, Günzel D, John LJ, Fromm M. Perspectives on tight junction research. Ann N Y Acad Sci 2012; 1257:1-19. [PMID: 22671584 DOI: 10.1111/j.1749-6632.2012.06485.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The tight junction connects neighboring epithelial or endothelial cells. As a general function, it seals the paracellular pathway and thus prevents back-leakage of just transported solutes and water. However, not all tight junctions are merely tight: some tight junction proteins build their own transport pathways by forming channels selective for small cations, anions, or water. Two families of tight junction proteins have been identified, claudins (27 members in mammals) and tight junction-associated MARVEL proteins ((TAMPs) occludin, tricellulin, and MarvelD3); an additional, structurally different, junction protein is junction adhesion molecule (JAM). Besides classification by genetic or molecular kinship, classification of tight junction proteins has been suggested according to permeability attributes. Recent studies describe specific cis and trans interactions and manifold physiologic regulations of claudins and TAMPs. In many inflammatory and infectious diseases they are found to be altered, for example, causing adversely increased permeability. Currently, attempts are being made to alter the paracellular barrier for therapeutic interventions or for transiently facilitating drug uptake. This overview concludes with a list of open questions and future topics in tight junction research.
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Affiliation(s)
- Jörg-Dieter Schulzke
- Department of Gastroenterology, Infectious Diseases, and Rheumatology, Division of Nutritional Medicine, Charité, Universitätsmedizin Berlin, Germany.
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24
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Abstract
Claudins are tight junction membrane proteins that regulate paracellular permeability of renal epithelia to small ions, solutes, and water. Claudins interact within the cell membrane and between neighboring cells to form tight junction strands and constitute both the paracellular barrier and the pore. The first extracellular domain of claudins is thought to be the pore-lining domain and contains the determinants of charge selectivity. Multiple claudins are expressed in different nephron segments; such differential expression likely determines the permeability properties of each segment. Recent evidence has identified claudin-2 as constituting the cation-reabsorptive pathway in the proximal tubule; claudin-14, -16, and -19 as forming a complex that regulates calcium transport in the thick ascending limb of the loop of Henle; and claudin-4, -7, and -8 as determinants of collecting duct chloride permeability. Mutations in claudin-16 and -19 cause familial hypercalciuric hypomagnesemia with nephrocalcinosis. The roles of other claudins in kidney diseases remain to be fully elucidated.
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Affiliation(s)
- Jianghui Hou
- Renal Division, Washington University, St. Louis, Missouri 63110, USA
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25
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The plasma membrane potential and the organization of the actin cytoskeleton of epithelial cells. Int J Cell Biol 2012; 2012:121424. [PMID: 22315611 PMCID: PMC3272338 DOI: 10.1155/2012/121424] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Accepted: 10/08/2011] [Indexed: 12/22/2022] Open
Abstract
The establishment and maintenance of the polarized epithelial phenotype require a characteristic organization of the cytoskeletal components. There are many cellular effectors involved in the regulation of the cytoskeleton of epithelial cells. Recently, modifications in the plasma membrane potential (PMP) have been suggested to participate in the modulation of the cytoskeletal organization of epithelia. Here, we review evidence showing that changes in the PMP of diverse epithelial cells promote characteristic modifications in the cytoskeletal organization, with a focus on the actin cytoskeleton. The molecular paths mediating these effects may include voltage-sensitive integral membrane proteins and/or peripheral proteins sensitive to surface potentials. The voltage dependence of the cytoskeletal organization seems to have implications in several physiological processes, including epithelial wound healing and apoptosis.
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26
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Li J, Ananthapanyasut W, Yu ASL. Claudins in renal physiology and disease. Pediatr Nephrol 2011; 26:2133-42. [PMID: 21365189 PMCID: PMC3203223 DOI: 10.1007/s00467-011-1824-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 01/26/2011] [Accepted: 01/28/2011] [Indexed: 12/19/2022]
Abstract
The tight junction forms the paracellular permeability barrier in all epithelia, including the renal tubule. Claudins are a family of tight junction membrane proteins with four transmembrane domains that form the paracellular pore and barrier. Their first extracellular domain appears to be important for determining selectivity. A number of claudin isoforms have been found to be important in renal tubule function, both in adults and in neonates. Familial hypomagnesemic hypercalciuria with nephrocalcinosis is an autosomal recessive syndrome characterized by impaired reabsorption of Mg and Ca in the thick ascending limb of Henle's loop. Mutations in claudin-16 and 19 can both cause this syndrome, but the pathophysiological mechanism remains controversial.
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Affiliation(s)
- Jiahua Li
- Systems Biology and Disease Program, University of Southern California Keck School of Medicine, Los Angeles, CA 90033 USA
| | - Wanwarat Ananthapanyasut
- Division of Nephrology, Department of Medicine, University of Southern California, 2025 Zonal Avenue, RMR 406, Los Angeles, CA 90089 USA
| | - Alan S. L. Yu
- Division of Nephrology, Department of Medicine, University of Southern California, 2025 Zonal Avenue, RMR 406, Los Angeles, CA 90089 USA ,Systems Biology and Disease Program, University of Southern California Keck School of Medicine, Los Angeles, CA 90033 USA
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27
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Shen L, Weber CR, Raleigh DR, Yu D, Turner JR. Tight junction pore and leak pathways: a dynamic duo. Annu Rev Physiol 2011. [PMID: 20936941 DOI: 10.1146/annurev-physiol- 012110-142150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Tissue barriers that restrict passage of liquids, ions, and larger solutes are essential for the development of multicellular organisms. In simple organisms this allows distinct cell types to interface with the external environment. In more complex species, the diversity of cell types capable of forming barriers increases dramatically. Although the plasma membranes of these barrier-forming cells prevent flux of most hydrophilic solutes, the paracellular, or shunt, pathway between cells must also be sealed. This function is accomplished in vertebrates by the zonula occludens, or tight junction. The tight junction barrier is not absolute but is selectively permeable and is able to discriminate between solutes on the basis of size and charge. Many tight junction components have been identified over the past 20 years, and recent progress has provided new insights into the proteins and interactions that regulate structure and function. This review presents these data in a historical context and proposes an integrated model in which dynamic regulation of tight junction protein interactions determines barrier function.
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Affiliation(s)
- Le Shen
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
| | | | - David R Raleigh
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
| | - Dan Yu
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
| | - Jerrold R Turner
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
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28
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Shen L, Weber CR, Raleigh DR, Yu D, Turner JR. Tight junction pore and leak pathways: a dynamic duo. Annu Rev Physiol 2011; 73:283-309. [PMID: 20936941 DOI: 10.1146/annurev-physiol-012110-142150] [Citation(s) in RCA: 611] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Tissue barriers that restrict passage of liquids, ions, and larger solutes are essential for the development of multicellular organisms. In simple organisms this allows distinct cell types to interface with the external environment. In more complex species, the diversity of cell types capable of forming barriers increases dramatically. Although the plasma membranes of these barrier-forming cells prevent flux of most hydrophilic solutes, the paracellular, or shunt, pathway between cells must also be sealed. This function is accomplished in vertebrates by the zonula occludens, or tight junction. The tight junction barrier is not absolute but is selectively permeable and is able to discriminate between solutes on the basis of size and charge. Many tight junction components have been identified over the past 20 years, and recent progress has provided new insights into the proteins and interactions that regulate structure and function. This review presents these data in a historical context and proposes an integrated model in which dynamic regulation of tight junction protein interactions determines barrier function.
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Affiliation(s)
- Le Shen
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
| | | | - David R Raleigh
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
| | - Dan Yu
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
| | - Jerrold R Turner
- Department of Pathology, The University of Chicago, Chicago, Illinois 60637
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29
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Elkouby-Naor L, Ben-Yosef T. Functions of claudin tight junction proteins and their complex interactions in various physiological systems. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 279:1-32. [PMID: 20797675 DOI: 10.1016/s1937-6448(10)79001-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Members of the claudin family of proteins are the main components of tight junctions (TJs), the major selective barrier of the paracellular pathway between epithelial cells. As such, the claudins have the ability to generate the TJ physiological barrier and to control various physiological processes. Therefore, the importance of this family of proteins is obvious and many efforts were made to reveal different aspects of claudin TJ protein biology. In this review, we discuss recent advances in our understanding of claudin structure and function, as well as their distribution pattern in different organs and tissues. We mainly highlight the complex interactions of claudins in various physiological systems and suggest a possible role for a coregulation mechanism.
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Affiliation(s)
- Liron Elkouby-Naor
- Department of Genetics, The Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa, Israel
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30
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A claudin-9-based ion permeability barrier is essential for hearing. PLoS Genet 2009; 5:e1000610. [PMID: 19696885 PMCID: PMC2720454 DOI: 10.1371/journal.pgen.1000610] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Accepted: 07/20/2009] [Indexed: 11/28/2022] Open
Abstract
Hereditary hearing loss is one of the most common birth defects, yet the majority of genes required for audition is thought to remain unidentified. Ethylnitrosourea (ENU)–mutagenesis has been a valuable approach for generating new animal models of deafness and discovering previously unrecognized gene functions. Here we report on the characterization of a new ENU–induced mouse mutant (nmf329) that exhibits recessively inherited deafness. We found a widespread loss of sensory hair cells in the hearing organs of nmf329 mice after the second week of life. Positional cloning revealed that the nmf329 strain carries a missense mutation in the claudin-9 gene, which encodes a tight junction protein with unknown biological function. In an epithelial cell line, heterologous expression of wild-type claudin-9 reduced the paracellular permeability to Na+ and K+, and the nmf329 mutation eliminated this ion barrier function without affecting the plasma membrane localization of claudin-9. In the nmf329 mouse line, the perilymphatic K+ concentration was found to be elevated, suggesting that the cochlear tight junctions were dysfunctional. Furthermore, the hair-cell loss in the claudin-9–defective cochlea was rescued in vitro when the explanted hearing organs were cultured in a low-K+ milieu and in vivo when the endocochlear K+-driving force was diminished by deletion of the pou3f4 gene. Overall, our data indicate that claudin-9 is required for the preservation of sensory cells in the hearing organ because claudin-9–defective tight junctions fail to shield the basolateral side of hair cells from the K+-rich endolymph. In the tight-junction complexes of hair cells, claudin-9 is localized specifically to a subdomain that is underneath more apical tight-junction strands formed by other claudins. Thus, the analysis of claudin-9 mutant mice suggests that even the deeper (subapical) tight-junction strands have biologically important ion barrier function. Hereditary deafness is a common birth defect in the human population, yet the majority of genes required for audition is thought to be unidentified. Genetic approaches in the mouse have greatly contributed to our understanding of the molecular mechanisms that underlie hearing. Random mutagenesis of mice, identification of deaf mutants, and subsequent analysis of the deafness-causing gene defects has led to the discovery of several previously unrecognized gene functions. Here, we report on the characterization of a new mutant mouse line (nmf329) that exhibits profound hearing loss and loss of sensory cells in the auditory organ. Genetic analysis reveals that these animals carry a mutation in the claudin-9 gene, which encodes a protein with hitherto unknown biological function. We have found that normal claudin-9—but not a mutant form—inhibits the paracellular movement of certain ions. The lack of the claudin-9 ion barrier in the inner ear leads to changes in ionic conditions that can account for the loss of sensory cells in the mutant mice. Within the cell–cell junctions, the claudin-9 layer is located basal to those of other claudins. Thus, our analysis of claudin-9–deficient animals suggests that even the deeper layers of claudins have important ion barrier function.
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31
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Carrozzino F, Pugnale P, Féraille E, Montesano R. Inhibition of basal p38 or JNK activity enhances epithelial barrier function through differential modulation of claudin expression. Am J Physiol Cell Physiol 2009; 297:C775-87. [PMID: 19605737 DOI: 10.1152/ajpcell.00084.2009] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Tight junctions (TJs) form a barrier to the paracellular diffusion of ions and solutes across epithelia. Although transmembrane proteins of the claudin family have emerged as critical determinants of TJ permeability, little is known about the signaling pathways that control their expression. The aim of this study was to assess the role of three mitogen-activated protein kinases (MAPKs), i.e., extracellular signal-regulated kinase-1/2 (ERK1/2), c-Jun NH(2)-terminal kinases (JNKs), and p38 kinases, in the regulation of epithelial barrier function and claudin expression in mammary epithelial cells. Addition of either PD169316 (a p38 inhibitor) or SP600125 (a JNK inhibitor) induced formation of domes (a phenomenon dependent on TJ barrier function) and enhanced transepithelial electrical resistance, whereas U0126 (an inhibitor of the ERK1/2 activators MEK1/MEK2) had no significant effect. Similar results were obtained using mechanistically unrelated p38 or JNK inhibitors. PD169316 increased the expression of claudin-4 and -8, whereas SP600125 increased claudin-4 and -9 and downregulated claudin-8. Silencing of p38alpha by isoform-specific small interfering RNAs increased claudin-4 and -8 mRNAs, whereas silencing of p38beta only increased claudin-4 mRNA. Silencing of either JNK1 or JNK2 increased claudin-9 mRNA expression while decreasing claudin-8 mRNA. Moreover, selective silencing of JNK2 increased claudin-4 and -7 mRNAs. Finally, both PD169316 and SP600125 inhibited the paracellular diffusion of Na(+) and Cl(-) across epithelial monolayers. Collectively, these results provide evidence that inhibition of either p38 or JNK enhances epithelial barrier function by selectively modulating claudin expression, implying that the basal activity of these MAPKs exerts a tonic effect on TJ ionic permeability.
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Affiliation(s)
- Fabio Carrozzino
- Dept. of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
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32
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Balkovetz DF, Chumley P, Amlal H. Downregulation of claudin-2 expression in renal epithelial cells by metabolic acidosis. Am J Physiol Renal Physiol 2009; 297:F604-11. [PMID: 19587148 DOI: 10.1152/ajprenal.00043.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic metabolic acidosis (CMA) is associated with an inhibition of fluid reabsorption in the renal proximal tubule. The effects of CMA on paracellular transport across the renal epithelial tight junction (TJ) is unknown. Claudin-2 is a transmembrane TJ-associated protein which confers TJ paracellular permeability to Na(+). We examined the effects of CMA on the expression of TJ transport proteins using both in vivo and in vitro models of CMA. The results showed downregulation of claudin-2 mRNA and protein expression in the cortex of rats subjected to the NH(4)Cl loading model of CMA. Madin-Darby canine kidney (MDCK) and HK-2 cells are models of renal epithelial cells and express claudin-2 protein in their TJ. We examined the effects of acidic pH exposure on the expression of claudin-2 in MDCK and HK-2 renal epithelial cells. Exposure of MDCK cells to pH 6.96 medium caused a significant and reversible decrease in claudin-2 protein abundance. A dose-response analysis of acidic medium exposure of MDCK and HK-2 cells demonstrated a downregulation of claudin-2 protein. The downregulation effect of acidic pH is specific to claudin-2 expression as the expression of other TJ-associated proteins (i.e., claudin-1, -3, -4, and -7, occludin, and zonula occludens-1) remained unchanged compared with control pH (7.40). Collectively, these data demonstrate that CMA downregulates the expression of claudin-2 likely through a direct effect of acidic pH. Potential physiological significance of these changes is discussed.
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Affiliation(s)
- Daniel F Balkovetz
- Dept. of Medicine, 1530 3rd. Ave. South, LHRB 642, Univ. of Alabama at Birmingham, Birmingham, AL 35294-0007, USA.
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