1
|
Su S, Wahl A, Rugis J, Suresh V, Yule DI, Sneyd J. A mathematical model of ENaC and Slc26a6 regulation by CFTR in salivary gland ducts. Am J Physiol Gastrointest Liver Physiol 2024; 326:G555-G566. [PMID: 38349781 DOI: 10.1152/ajpgi.00168.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 01/17/2024] [Accepted: 02/06/2024] [Indexed: 02/15/2024]
Abstract
Cystic fibrosis (CF) is a genetic disease caused by the mutations of cystic fibrosis transmembrane conductance regulator (CFTR), the cystic fibrosis transmembrane conductance regulator gene. Cftr is a critical ion channel expressed in the apical membrane of mouse salivary gland striated duct cells. Although Cftr is primarily a Cl- channel, its knockout leads to higher salivary Cl- and Na+ concentrations and lower pH. Mouse experiments show that the activation of Cftr upregulates epithelial Na+ channel (ENaC) protein expression level and Slc26a6 (a 1Cl-:2[Formula: see text] exchanger of the solute carrier family) activity. Experimentally, it is difficult to predict how much the coregulation effects of CFTR contribute to the abnormal Na+, Cl-, and [Formula: see text] concentrations and pH in CF saliva. To address this question, we construct a wild-type mouse salivary gland model and simulate CFTR knockout by altering the expression levels of CFTR, ENaC, and Slc26a6. By reproducing the in vivo and ex vivo final saliva measurements from wild-type and CFTR knockout animals, we obtain computational evidence that ENaC and Slc26a6 activities are downregulated in CFTR knockout in salivary glands.NEW & NOTEWORTHY This paper describes a salivary gland mathematical model simulating the ion exchange between saliva and the salivary gland duct epithelium. The novelty lies in the implementation of CFTR regulating ENaC and Slc26a6 in a CFTR knockout gland. By reproducing the experimental saliva measurements in wild-type and CFTR knockout glands, the model shows that CFTR regulates ENaC and Slc26a6 anion exchanger in salivary glands. The method could be used to understand the various cystic fibrosis phenotypes.
Collapse
Affiliation(s)
- Shan Su
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| | - Amanda Wahl
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, United States
| | - John Rugis
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| | - Vinod Suresh
- Auckland Biomedical Engineering Institute, University of Auckland, Auckland, New Zealand
- Department of Engineering Science, University of Auckland, Auckland, New Zealand
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, United States
| | - James Sneyd
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| |
Collapse
|
2
|
Wu M, Chen JH. CFTR dysfunction leads to defective bacterial eradication on cystic fibrosis airways. Front Physiol 2024; 15:1385661. [PMID: 38699141 PMCID: PMC11063615 DOI: 10.3389/fphys.2024.1385661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 04/04/2024] [Indexed: 05/05/2024] Open
Abstract
Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel by genetic mutations causes the inherited disease cystic fibrosis (CF). CF lung disease that involves multiple disorders of epithelial function likely results from loss of CFTR function as an anion channel conducting chloride and bicarbonate ions and its function as a cellular regulator modulating the activity of membrane and cytosol proteins. In the absence of CFTR activity, abundant mucus accumulation, bacterial infection and inflammation characterize CF airways, in which inflammation-associated tissue remodeling and damage gradually destroys the lung. Deciphering the link between CFTR dysfunction and bacterial infection in CF airways may reveal the pathogenesis of CF lung disease and guide the development of new treatments. Research efforts towards this goal, including high salt, low volume, airway surface liquid acidosis and abnormal mucus hypotheses are critically reviewed.
Collapse
Affiliation(s)
| | - Jeng-Haur Chen
- College of Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang, China
| |
Collapse
|
3
|
Pereira R, Barbosa T, Cardoso AL, Sá R, Sousa M. Cystic fibrosis and primary ciliary dyskinesia: Similarities and differences. Respir Med 2023; 209:107169. [PMID: 36828173 DOI: 10.1016/j.rmed.2023.107169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 02/06/2023] [Accepted: 02/18/2023] [Indexed: 02/25/2023]
Abstract
Cystic fibrosis (CF) and Primary ciliary dyskinesia (PCD) are both rare chronic diseases, inherited disorders associated with multiple complications, namely respiratory complications, due to impaired mucociliary clearance that affect severely patients' lives. Although both are classified as rare diseases, PCD has a much lower prevalence than CF, particularly among Caucasians. As a result, CF is well studied, better recognized by clinicians, and with some therapeutic approaches already available. Whereas PCD is still largely unknown, and thus the approach is based on consensus guidelines, expert opinion, and extrapolation from the larger evidence base available for patients with CF. Both diseases have some clinical similarities but are very different, necessitating different treatment by specialists who are familiar with the complexities of each disease.This review aims to provide an overview of the knowledge about the two diseases with a focus on the similarities and differences between both in terms of disease mechanisms, common clinical manifestations, genetics and the most relevant therapeutic options. We hoped to raise clinical awareness about PCD, what it is, how it differs from CF, and how much information is still lacking. Furthermore, this review emphasises the fact that both diseases require ongoing research to find better treatments and, in particular for PCD, to fill the medical and scientific gaps.
Collapse
Affiliation(s)
- Rute Pereira
- Laboratory of Cell Biology, Department of Microscopy, ICBAS-School of Medicine and Biomedical Sciences, University of Porto, Porto, Portugal; UMIB-Unit for Multidisciplinary Research in Biomedicine, ICBAS-UP/ ITR-Laboratory for Integrative and Translational Research in Population Health, UP, Porto, Portugal.
| | - Telma Barbosa
- UMIB-Unit for Multidisciplinary Research in Biomedicine, ICBAS-UP/ ITR-Laboratory for Integrative and Translational Research in Population Health, UP, Porto, Portugal; Department of Pediatrics, Maternal Child Centre of the North (CMIN), University Hospital Centre of Porto (CHUP), Largo da Maternidade, 4050-371, Porto, Portugal.
| | - Ana Lúcia Cardoso
- UMIB-Unit for Multidisciplinary Research in Biomedicine, ICBAS-UP/ ITR-Laboratory for Integrative and Translational Research in Population Health, UP, Porto, Portugal; Department of Pediatrics, Maternal Child Centre of the North (CMIN), University Hospital Centre of Porto (CHUP), Largo da Maternidade, 4050-371, Porto, Portugal.
| | - Rosália Sá
- Laboratory of Cell Biology, Department of Microscopy, ICBAS-School of Medicine and Biomedical Sciences, University of Porto, Porto, Portugal; UMIB-Unit for Multidisciplinary Research in Biomedicine, ICBAS-UP/ ITR-Laboratory for Integrative and Translational Research in Population Health, UP, Porto, Portugal.
| | - Mário Sousa
- Laboratory of Cell Biology, Department of Microscopy, ICBAS-School of Medicine and Biomedical Sciences, University of Porto, Porto, Portugal; UMIB-Unit for Multidisciplinary Research in Biomedicine, ICBAS-UP/ ITR-Laboratory for Integrative and Translational Research in Population Health, UP, Porto, Portugal.
| |
Collapse
|
4
|
Expression of phosphate and calcium transporters and their regulators in parotid glands of mice. Pflugers Arch 2023; 475:203-216. [PMID: 36274099 PMCID: PMC9849193 DOI: 10.1007/s00424-022-02764-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 10/07/2022] [Accepted: 10/13/2022] [Indexed: 02/01/2023]
Abstract
The concentration of inorganic phosphate (Pi) in plasma is under hormonal control, with deviations from normal values promptly corrected to avoid hyper- or hypophosphatemia. Major regulators include parathyroid hormone (PTH), fibroblast growth factor 23 (FGF-23), and active vitamin D3 (calcitriol). This control is achieved by mechanisms largely dependent on regulating intestinal absorption and renal excretion, whose combined actions stabilise plasma Pi levels at around 1-2 mM. Instead, Pi concentrations up to 13 and 40 mM have been measured in saliva from humans and ruminants, respectively, suggesting that salivary glands have the capacity to concentrate Pi. Here we analysed the transcriptome of parotid glands, ileum, and kidneys of mice, to investigate their potential differences regarding the expression of genes responsible for epithelial transport of Pi as well as their known regulators. Given that Pi and Ca2+ homeostasis are tightly connected, the expression of genes involved in Ca2+ homeostasis was also included. In addition, we studied the effect of vitamin D3 treatment on the expression of Pi and Ca2+ regulating genes in the three major salivary glands. We found that parotid glands are equipped preferentially with Slc20 rather than with Slc34 Na+/Pi cotransporters, are suited to transport Ca2+ through the transcellular and paracellular route and are potential targets for PTH and vitamin D3 regulation.
Collapse
|
5
|
A Mathematical Model of Salivary Gland Duct Cells. Bull Math Biol 2022; 84:84. [PMID: 35799078 PMCID: PMC9262821 DOI: 10.1007/s11538-022-01041-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 06/14/2022] [Indexed: 11/18/2022]
Abstract
Saliva is produced in two stages in the salivary glands: the secretion of primary saliva by the acinus and the modification of saliva composition to final saliva by the intercalated and striated ducts. In order to understand the saliva modification process, we develop a mathematical model for the salivary gland duct. The model utilises the realistic 3D structure of the duct reconstructed from an image stack of gland tissue. Immunostaining results show that TMEM16A and aquaporin are expressed in the intercalated duct cells and that ENaC is not. Based on this, the model predicts that the intercalated duct does not absorb Na\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^+$$\end{document}+ and Cl\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^-$$\end{document}- like the striated duct but secretes a small amount of water instead. The input to the duct model is the time-dependent primary saliva generated by an acinar cell model. Our duct model produces final saliva output that agrees with the experimental measurements at various stimulation levels. It also shows realistic biological features such as duct cell volume, cellular concentrations and membrane potentials. Simplification of the model by omission of all detailed 3D structures of the duct makes a negligible difference to the final saliva output. This shows that saliva production is not sensitive to structural variation of the duct.
Collapse
|
6
|
Aspatwar A, Tolvanen MEE, Barker H, Syrjänen L, Valanne S, Purmonen S, Waheed A, Sly WS, Parkkila S. Carbonic Anhydrases in Metazoan Model Organisms: Molecules, Mechanisms, and Physiology. Physiol Rev 2022; 102:1327-1383. [PMID: 35166161 DOI: 10.1152/physrev.00018.2021] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
During the past three decades, mice, zebrafish, fruit flies, and Caenorhabditis elegans have been the primary model organisms used for the study of various biological phenomena. These models have also been adopted and developed to investigate the physiological roles of carbonic anhydrases (CAs) and carbonic anhydrase-related proteins (CARPs). These proteins belong to eight CA families and are identified by Greek letters: α, β, γ, δ, ζ, η, θ, and ι. Studies using model organisms have focused on two CA families, α-CAs and β-CAs, which are expressed in both prokaryotic and eukaryotic organisms with species-specific distribution patterns and unique functions. This review covers the biological roles of CAs and CARPs in light of investigations performed in model organisms. Functional studies demonstrate that CAs are not only linked to the regulation of pH homeostasis, the classical role of CAs but also contribute to a plethora of previously undescribed functions.
Collapse
Affiliation(s)
- Ashok Aspatwar
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | | | - Harlan Barker
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.,Fimlab Ltd and TAYS Cancer Centre, Tampere University Hospital, Tampere, Finland
| | - Leo Syrjänen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.,Department of Otorhinolaryngology, Tampere University Hospital, Tampere, Finland
| | - Susanna Valanne
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Sami Purmonen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Abdul Waheed
- Department of Biochemistry and Molecular Biology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, MO, United States
| | - William S Sly
- Department of Biochemistry and Molecular Biology, Edward A. Doisy Research Center, Saint Louis University School of Medicine, St. Louis, MO, United States
| | - Seppo Parkkila
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.,Fimlab Ltd and TAYS Cancer Centre, Tampere University Hospital, Tampere, Finland
| |
Collapse
|
7
|
Iafusco F, Maione G, Rosanio FM, Mozzillo E, Franzese A, Tinto N. Cystic Fibrosis-Related Diabetes (CFRD): Overview of Associated Genetic Factors. Diagnostics (Basel) 2021; 11:diagnostics11030572. [PMID: 33810109 PMCID: PMC8005125 DOI: 10.3390/diagnostics11030572] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 03/19/2021] [Indexed: 12/21/2022] Open
Abstract
Cystic fibrosis (CF) is the most common autosomal recessive disease in the Caucasian population and is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene that encodes for a chloride/bicarbonate channel expressed on the membrane of epithelial cells of the airways and of the intestine, as well as in cells with exocrine and endocrine functions. A common nonpulmonary complication of CF is cystic fibrosis-related diabetes (CFRD), a distinct form of diabetes due to insulin insufficiency or malfunction secondary to destruction/derangement of pancreatic betacells, as well as to other factors that affect their function. The prevalence of CFRD increases with age, and 40–50% of CF adults develop the disease. Several proposed hypotheses on how CFRD develops have emerged, including exocrine-driven fibrosis and destruction of the entire pancreas, as well as contrasting theories on the direct or indirect impact of CFTR mutation on islet function. Among contributors to the development of CFRD, in addition to CFTR genotype, there are other genetic factors related and not related to type 2 diabetes. This review presents an overview of the current understanding on genetic factors associated with glucose metabolism abnormalities in CF.
Collapse
Affiliation(s)
- Fernanda Iafusco
- Department of Molecular Medicine and Medical Biotechnology, University of Naples “Federico II”, 80131 Naples, Italy; (F.I.); (G.M.)
- CEINGE Advanced Biotechnology, 80131 Naples, Italy
| | - Giovanna Maione
- Department of Molecular Medicine and Medical Biotechnology, University of Naples “Federico II”, 80131 Naples, Italy; (F.I.); (G.M.)
- CEINGE Advanced Biotechnology, 80131 Naples, Italy
| | - Francesco Maria Rosanio
- Regional Center of Pediatric Diabetology, Department of Translational Medical Sciences, Section of Pediatrics, University of Naples “Federico II”, 80131 Naples, Italy; (F.M.R.); (E.M.); (A.F.)
| | - Enza Mozzillo
- Regional Center of Pediatric Diabetology, Department of Translational Medical Sciences, Section of Pediatrics, University of Naples “Federico II”, 80131 Naples, Italy; (F.M.R.); (E.M.); (A.F.)
| | - Adriana Franzese
- Regional Center of Pediatric Diabetology, Department of Translational Medical Sciences, Section of Pediatrics, University of Naples “Federico II”, 80131 Naples, Italy; (F.M.R.); (E.M.); (A.F.)
| | - Nadia Tinto
- Department of Molecular Medicine and Medical Biotechnology, University of Naples “Federico II”, 80131 Naples, Italy; (F.I.); (G.M.)
- CEINGE Advanced Biotechnology, 80131 Naples, Italy
- Correspondence:
| |
Collapse
|
8
|
Massey MK, Reiterman MJ, Mourad J, Luckie DB. Is CFTR an exchanger?: Regulation of HCO 3 -Transport and extracellular pH by CFTR. Biochem Biophys Rep 2020; 25:100863. [PMID: 33376814 PMCID: PMC7758359 DOI: 10.1016/j.bbrep.2020.100863] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 11/10/2020] [Accepted: 11/12/2020] [Indexed: 01/06/2023] Open
Abstract
The disease, cystic fibrosis, is caused by the malfunction of the cystic fibrosis transmembrane conductance regulator. Expression of functional CFTR may normally regulate extracellular pH via control of bicarbonate efflux. Reports also suggest that the CFTR may be a Cl-/HCO3- exchanger. If true, this could be very important for treatment of CF given the airway host defense system is quite sensitive to pH, and acidic pH been found to increase mucus viscosity. We compared evidentiary support of four possible models of CFTR's role in the transport of bicarbonate: 1) CFTR as a Cl-channel that permits bicarbonate conductance, 2) CFTR as an anion Cl-/HCO3- exchanger (AE), 3.) CFTR as both a Cl-channel and an AE, and 4.) CFTR as a Cl-channel that allows for transport of bicarbonate and regulates an independent AE. The effect of stimulators and inhibitors of CFTR and AEs were evaluated via iodide efflux and studies of extracellular pH. This data, as well as that published by others, suggest that while CFTR may support and regulate bicarbonate flux it is unlikely it directly performs Cl-/HCO3- anion exchange. Four possible models of CFTR's role in the transport of HC03- were evaluated. Cells exposed to modulators of CFTR/AE activity were studied by efflux and pHo. Efflux: While CFTR inhibition reduced anion efflux, AE inhibition did not. pHo: In Cl-free buffer conditions CFTR activation reduced pHo acidification. CFTR may regulate but unlikely it directly performs Cl-/HCO3- exchange.
Collapse
Affiliation(s)
| | | | | | - Douglas B. Luckie
- Corresponding author. Cystic Fibrosis Research Laboratory, Department of Physiology, Michigan State University, Biomedical Physical Sciences, 567 Wilson Road, Room 2140, East Lansing, MI, 48824, USA.
| |
Collapse
|
9
|
Shin DH, Kim M, Kim Y, Jun I, Jung J, Nam JH, Cheng MH, Lee MG. Bicarbonate permeation through anion channels: its role in health and disease. Pflugers Arch 2020; 472:1003-1018. [PMID: 32621085 DOI: 10.1007/s00424-020-02425-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/19/2020] [Accepted: 06/26/2020] [Indexed: 12/31/2022]
Abstract
Many anion channels, frequently referred as Cl- channels, are permeable to different anions in addition to Cl-. As the second-most abundant anion in the human body, HCO3- permeation via anion channels has many important physiological roles. In addition to its classical role as an intracellular pH regulator, HCO3- also controls the activity and stability of dissolved proteins in bodily fluids such as saliva, pancreatic juice, intestinal fluid, and airway surface liquid. Moreover, HCO3- permeation through these channels affects membrane potentials that are the driving forces for transmembrane transport of solutes and water in epithelia and affect neuronal excitability in nervous tissue. Consequently, aberrant HCO3- transport via anion channels causes a number of human diseases in respiratory, gastrointestinal, genitourinary, and neuronal systems. Notably, recent studies have shown that the HCO3- permeabilities of several anion channels are not fixed and can be altered by cellular stimuli, findings which may have both physiological and pathophysiological significance. In this review, we summarize recent progress in understanding the molecular mechanisms and the physiological roles of HCO3- permeation through anion channels. We hope that the present discussions can stimulate further research into this very important topic, which will provide the basis for human disorders associated with aberrant HCO3- transport.
Collapse
Affiliation(s)
- Dong Hoon Shin
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Minjae Kim
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Yonjung Kim
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Ikhyun Jun
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Jinsei Jung
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
- Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, 123 Dongdae-ro, Kyungju, 780-714, Republic of Korea
| | - Mary Hongying Cheng
- Department of Computational & Systems Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Min Goo Lee
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea.
| |
Collapse
|
10
|
Correctors modify the bicarbonate permeability of F508del-CFTR. Sci Rep 2020; 10:8440. [PMID: 32439937 PMCID: PMC7242338 DOI: 10.1038/s41598-020-65287-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 04/29/2020] [Indexed: 01/17/2023] Open
Abstract
One of the most common mutations in Cystic Fibrosis (CF) patients is the deletion of the amino acid phenylalanine at position 508. This mutation causes both the protein trafficking defect and an early degradation. Over time, small molecules, called correctors, capable of increasing the amount of mutated channel in the plasma membrane and causing an increase in its transport activity have been developed. This study shows that incubating in vitro cells permanently transfected with the mutated channel with the correctors VX809, VX661 and Corr4a, and the combination of VX809 and Corr4a, a recovery of anion transport activity is observed. Interestingly, the permeability of bicarbonate increases in the cells containing corrected p.F508del CFTR channels is greater than the increase of the halide permeability. These different increases of the permeability of bicarbonate and halides are consistent with the concept that the structural conformation of the pore of the corrector-rescued p.F508del channels would be different than the normal wild type CFTR protein.
Collapse
|
11
|
Munemasa T, Mukaibo T, Melvin JE. Slc26a6 is an apical membrane anion exchanger that drives HCO 3--dependent fluid secretion in murine pancreatic acinar cells. Am J Physiol Cell Physiol 2019; 317:C1153-C1160. [PMID: 31532720 PMCID: PMC6957380 DOI: 10.1152/ajpcell.00257.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 09/10/2019] [Accepted: 09/10/2019] [Indexed: 11/22/2022]
Abstract
The nonselective anion exchanger Slc26a6, also known as putative anion transporter 1 and chloride/formate exchanger, is thought to play a major role in HCO 3 - transport in exocrine glands. In this study, Slc26a6 null mice were used to explore the function of Slc26a6 in the exocrine pancreas. Slc26a6 primarily localized to the apical membrane of pancreatic exocrine acinar cells. The volume of stimulated juice secretion by the ex vivo pancreas was significantly reduced ~35% in Slc26a6-/- mice, but no changes occurred in the gross structure or gland weights of Slc26a6 null mice. The secretion of pancreatic juice by Slc26a6+/+ mice was dependent on HCO 3 - while, in contrast, fluid secretion by Slc26a6-/- mice was independent of HCO 3 - , suggesting that Slc26a6 mediates the HCO 3 - -dependent component of fluid secretion. Consistent with these observations, disruption of Slc26a6 also significantly reduced HCO 3 - secretion by the pancreas ~35%. Taken together, these results demonstrate that the apical Slc26a6 anion exchanger in acinar cells is involved in HCO 3 - -dependent fluid secretion but that another major HCO 3 - -independent pathway is the primary driver of the fluid secretion process in the mouse pancreas.
Collapse
Affiliation(s)
- Takashi Munemasa
- Secretory Mechanisms and Dysfunctions Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Japan
| | - Taro Mukaibo
- Secretory Mechanisms and Dysfunctions Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
- Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Japan
| | - James E Melvin
- Secretory Mechanisms and Dysfunctions Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| |
Collapse
|
12
|
Jowett LA, Howe ENW, Wu X, Busschaert N, Gale PA. New Insights into the Anion Transport Selectivity and Mechanism of Tren-based Tris-(thio)ureas. Chemistry 2018; 24:10475-10487. [PMID: 29786913 DOI: 10.1002/chem.201801463] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 05/09/2018] [Indexed: 11/07/2022]
Abstract
The anion transport properties of a series of previously reported tren-based anionophores have been revisited using new assays designed to measure anion uniport. This study provides new insights into the transport mechanism and selectivity of this important class of transporters. Specifically, we report the chloride and nitrate transport selectivity of these systems and quantify sulfate transport to determine EC50 values for sulfate transport for the first time. Two new assays were developed to study bicarbonate transport allowing accurate quantification of chloride/bicarbonate exchange.
Collapse
Affiliation(s)
- Laura A Jowett
- School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Ethan N W Howe
- School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Xin Wu
- School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia
| | | | - Philip A Gale
- School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia
| |
Collapse
|
13
|
Bhattarai KR, Junjappa R, Handigund M, Kim HR, Chae HJ. The imprint of salivary secretion in autoimmune disorders and related pathological conditions. Autoimmun Rev 2018; 17:376-390. [DOI: 10.1016/j.autrev.2017.11.031] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 11/16/2017] [Indexed: 12/11/2022]
|
14
|
Abstract
Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian populations. Individuals with CF have seen significant increases in life expectancy in the last 60 years. As a result, previously rare complications are now coming to light. The most common of these is cystic fibrosis-related diabetes (CFRD), which affects 40-50% of CF adults. CFRD significantly impacts the pulmonary function and longevity of CF patients, yet a lack of consensus on the best methods to diagnose and treat CFRD remains. We begin by reviewing our understanding of the pathogenesis of CFRD, as emerging evidence shows the cystic fibrosis transmembrane conductance regulator (CFTR) also has important roles in the release of insulin and glucagon and in the protection of β cells from oxidative stress. We then discuss how current recommended methods of CFRD diagnosis are not appropriate, as continuous glucose monitoring becomes more effective, practical, and cost-effective. Finally, we evaluate emerging treatments which have narrowed the mortality gap within the CF patient group. In the future, pharmacological potentiators and correctors directly targeting CFTR show huge promise for both CFRD and the wider CF patient groups.
Collapse
Affiliation(s)
- Kayani Kayani
- Faculty of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Raihan Mohammed
- Faculty of Medicine, University of Cambridge, Cambridge, United Kingdom
- *Correspondence: Raihan Mohammed,
| | - Hasan Mohiaddin
- Faculty of Medicine, Imperial College London, London, United Kingdom
| |
Collapse
|
15
|
Bicarbonate in cystic fibrosis. J Cyst Fibros 2017; 16:653-662. [PMID: 28732801 DOI: 10.1016/j.jcf.2017.06.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/22/2017] [Accepted: 06/22/2017] [Indexed: 11/20/2022]
Abstract
BACKGROUND Cystic fibrosis (CF, mucoviscidosis) is caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), which is a chloride and bicarbonate channel necessary for fluid secretion and extracellular alkalization. For a long time, research concentrated on abnormal Cl- and Na+ transport, but neglected bicarbonate as a crucial factor in CF. METHODS The present short review reports early findings as well as recent insights into the role of CFTR for bicarbonate transport and its defects in CF. RESULTS The available data indicate impaired bicarbonate transport not only in pancreas, intestine, airways, and reproductive organs, but also in salivary glands, sweat duct and renal tubular epithelial cells. Defective bicarbonate transport is closely related to the impaired mucus properties and mucus blocking in secretory organs of CF patients, causing the life threatening lung disease. CONCLUSIONS Apart from the devastating lung disease, abrogated bicarbonate transport also leads to many other organ dysfunctions, which are outlined in the present review.
Collapse
|
16
|
Broadbent D, Ahmadzai MM, Kammala AK, Yang C, Occhiuto C, Das R, Subramanian H. Roles of NHERF Family of PDZ-Binding Proteins in Regulating GPCR Functions. Adv Immunol 2017; 136:353-385. [PMID: 28950951 DOI: 10.1016/bs.ai.2017.05.008] [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: 12/15/2022]
Abstract
Multicellular organisms are equipped with an array of G-protein-coupled receptors (GPCRs) that mediate cell-cell signaling allowing them to adapt to environmental cues and ultimately survive. This is mechanistically possible through complex intracellular GPCR machinery that encompasses a vast network of proteins. Within this network, there is a group called scaffolding proteins that facilitate proper localization of signaling proteins for a quick and robust GPCR response. One protein family within this scaffolding group is the PSD-95/Dlg/ZO-1 (PDZ) family which is important for GPCR localization, internalization, recycling, and downstream signaling. Although the PDZ family of proteins regulate the functions of several receptors, this chapter focuses on a subfamily within the PDZ protein family called the Na+/H+ exchanger regulatory factors (NHERFs). Here we extensively review the predominantly characterized roles of NHERFs in renal phosphate absorption, intestinal ion regulation, cancer progression, and immune cell functions. Finally, we discuss the future perspectives and possible clinical application of targeting NHERFs in several disorders.
Collapse
Affiliation(s)
| | | | | | - Canchai Yang
- Michigan State University, East Lansing, MI, United States
| | | | - Rupali Das
- Michigan State University, East Lansing, MI, United States
| | | |
Collapse
|
17
|
Han JM, Tanimura A, Kirk V, Sneyd J. A mathematical model of calcium dynamics in HSY cells. PLoS Comput Biol 2017; 13:e1005275. [PMID: 28199326 PMCID: PMC5310762 DOI: 10.1371/journal.pcbi.1005275] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 11/30/2016] [Indexed: 12/03/2022] Open
Abstract
Saliva is an essential part of activities such as speaking, masticating and swallowing. Enzymes in salivary fluid protect teeth and gums from infectious diseases, and also initiate the digestion process. Intracellular calcium (Ca2+) plays a critical role in saliva secretion and regulation. Experimental measurements of Ca2+ and inositol trisphosphate (IP3) concentrations in HSY cells, a human salivary duct cell line, show that when the cells are stimulated with adenosine triphosphate (ATP) or carbachol (CCh), they exhibit coupled oscillations with Ca2+ spike peaks preceding IP3 spike peaks. Based on these data, we construct a mathematical model of coupled Ca2+ and IP3 oscillations in HSY cells and perform model simulations of three different experimental settings to forecast Ca2+ responses. The model predicts that when Ca2+ influx from the extracellular space is removed, oscillations gradually slow down until they stop. The model simulation of applying a pulse of IP3 predicts that photolysis of caged IP3 causes a transient increase in the frequency of the Ca2+ oscillations. Lastly, when Ca2+-dependent activation of PLC is inhibited, we see an increase in the oscillation frequency and a decrease in the amplitude. These model predictions are confirmed by experimental data. We conclude that, although concentrations of Ca2+ and IP3 oscillate, Ca2+ oscillations in HSY cells are the result of modulation of the IP3 receptor by intracellular Ca2+, and that the period is modulated by the accompanying IP3 oscillations.
Collapse
Affiliation(s)
- Jung Min Han
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Akihiko Tanimura
- Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
| | - Vivien Kirk
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - James Sneyd
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| |
Collapse
|
18
|
Ueno K, Hirono C, Kitagawa M, Shiba Y, Sugita M. Different rate-limiting activities of intracellular pH regulators for HCO 3- secretion stimulated by forskolin and carbachol in rat parotid intralobular ducts. J Physiol Sci 2016; 66:477-490. [PMID: 26969473 PMCID: PMC10717326 DOI: 10.1007/s12576-016-0443-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 02/23/2016] [Indexed: 11/26/2022]
Abstract
Intracellular pH (pHi) regulation fundamentally participates in maintaining HCO3- release from HCO3--secreting epithelia. We used parotid intralobular ducts loaded with BCECF to investigate the contributions of a carbonic anhydrase (CA), anion channels and a Na+-H+ exchanger (NHE) to pHi regulation for HCO3- secretion by cAMP and Ca2+ signals. Resting pHi was dispersed between 7.4 and 7.9. Forskolin consistently decreased pHi showing the dominance of pHi-lowering activities, but carbachol gathered pHi around 7.6. CA inhibition suppressed the forskolin-induced decrease in pHi, while it allowed carbachol to consistently increase pHi by revealing that carbachol prominently activated NHE via Ca2+-calmodulin. Under NHE inhibition, forskolin and carbachol induced the remarkable decreases in pHi, which were slowed predominantly by CA inhibition and by CA or anion channel inhibition, respectively. Our results suggest that forskolin and carbachol primarily activate the pHi-lowering CA and pHi-raising NHE, respectively, to regulate pHi for HCO3- secretion.
Collapse
Affiliation(s)
- Kaori Ueno
- Department of Physiology and Oral Physiology, Institute of Biomedical and Health Sciences, Hiroshima University, 2-3 Kasumi 1-Chome, Minami-ku, Hiroshima, 734-8553, Japan
| | - Chikara Hirono
- Department of Physiology and Oral Physiology, Institute of Biomedical and Health Sciences, Hiroshima University, 2-3 Kasumi 1-Chome, Minami-ku, Hiroshima, 734-8553, Japan.
| | - Michinori Kitagawa
- Department of Physiology and Oral Physiology, Institute of Biomedical and Health Sciences, Hiroshima University, 2-3 Kasumi 1-Chome, Minami-ku, Hiroshima, 734-8553, Japan
| | - Yoshiki Shiba
- Department of Physiology and Oral Physiology, Institute of Biomedical and Health Sciences, Hiroshima University, 2-3 Kasumi 1-Chome, Minami-ku, Hiroshima, 734-8553, Japan
| | - Makoto Sugita
- Department of Physiology and Oral Physiology, Institute of Biomedical and Health Sciences, Hiroshima University, 2-3 Kasumi 1-Chome, Minami-ku, Hiroshima, 734-8553, Japan
| |
Collapse
|
19
|
Park PW, Ahn JY, Yang D. Ahcyl2 upregulates NBCe1-B via multiple serine residues of the PEST domain-mediated association. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 20:433-40. [PMID: 27382360 PMCID: PMC4930912 DOI: 10.4196/kjpp.2016.20.4.433] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 05/31/2016] [Accepted: 05/31/2016] [Indexed: 12/30/2022]
Abstract
Inositol-1,4,5-triphosphate [IP3] receptors binding protein released with IP3 (IRBIT) was previously reported as an activator of NBCe1-B. Recent studies have characterized IRBIT homologue S-Adenosylhomocysteine hydrolase-like 2 (AHCYL2). AHCYL2 is highly homologous to IRBIT (88%) and heteromerizes with IRBIT. The two important domains in the N-terminus of AHCYL2 are a PEST domain and a coiled-coil domain which are highly comparable to those in IRBIT. Therefore, in this study, we tried to identify the role of those domains in mouse AHCYL2 (Ahcyl2), and we succeeded in identifying PEST domain of Ahcyl2 as a regulation region for NBCe1-B activity. Site directed mutagenesis and coimmunoprecipitation assay showed that NBCe1-B binds to the N-terminal Ahcyl2-PEST domain, and its binding is determined by the phosphorylation of 4 critical serine residues (Ser151, Ser154, Ser157, and Ser160) in Ahcyl2 PEST domain. Also we revealed that 4 critical serine residues in Ahcyl2 PEST domain are indispensable for the activation of NBCe1-B using measurement of intracellular pH experiment. Thus, these results suggested that the NBCe1-B is interacted with 4 critical serine residues in Ahcyl2 PEST domain, which play an important role in intracellular pH regulation through NBCe1-B.
Collapse
Affiliation(s)
- Pil Whan Park
- Department of Laboratory Medicine, Gachon University Gil Hospital, Incheon 21565, Korea
| | - Jeong Yeal Ahn
- Department of Laboratory Medicine, Gachon University Gil Hospital, Incheon 21565, Korea
| | - Dongki Yang
- Department of Physiology, College of Medicine, Gachon University, Incheon 21936, Korea
| |
Collapse
|
20
|
Zinn VZ, Khatri A, Mednieks MI, Hand AR. Localization of cystic fibrosis transmembrane conductance regulator signaling complexes in human salivary gland striated duct cells. Eur J Oral Sci 2015; 123:140-8. [PMID: 25903037 DOI: 10.1111/eos.12184] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/11/2015] [Indexed: 02/03/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic AMP-dependent protein kinase (PKA)-regulated Cl(-) channel, crucial for epithelial cell regulation of salt and water transport. Previous studies showed that ezrin, an actin binding and A-kinase anchoring protein (AKAP), facilitates association of PKA with CFTR. We used immunohistochemistry and immunogold transmission electron microscopy to localize CFTR, ezrin, and PKA type II regulatory (RII) and catalytic (C) subunits in striated duct cells of human parotid and submandibular glands. Immunohistochemistry localized the four proteins mainly to the apical membrane and the apical cytoplasm of striated duct cells. In acinar cells, ezrin localized to the luminal membrane, and PKA RII subunits were present in secretory granules, as previously described. Immunogold labeling showed that CFTR and PKA RII and C subunits were localized to the luminal membrane and associated with apical granules and vesicles of striated duct cells. Ezrin was present along the luminal membrane, on microvilli and along the junctional complexes between cells. Double labeling showed specific protein associations with apical granules and vesicles and along the luminal membrane. Ezrin, CFTR, and PKA RII and C subunits are co-localized in striated duct cells, suggesting the presence of signaling complexes that serve to regulate CFTR activity.
Collapse
Affiliation(s)
- Vina Z Zinn
- University of Connecticut School of Dental Medicine, Farmington, CT, USA
| | | | | | | |
Collapse
|
21
|
da Silva Lima V, Crajoinas RO, Carraro-Lacroix LR, Godinho AN, Dias JLG, Dariolli R, Girardi ACC, Fonteles MC, Malnic G, Lessa LMA. Uroguanylin inhibits H-ATPase activity and surface expression in renal distal tubules by a PKG-dependent pathway. Am J Physiol Cell Physiol 2014; 307:C532-41. [PMID: 25031022 DOI: 10.1152/ajpcell.00392.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cumulative evidence suggests that guanylin peptides play an important role on electrolyte homeostasis. We have previously reported that uroguanylin (UGN) inhibits bicarbonate reabsorption in a renal distal tubule. In the present study, we tested the hypothesis that the bicarbonaturic effect of UGN is at least in part attributable to inhibition of H(+)-ATPase-mediated hydrogen secretion in the distal nephron. By in vivo stationary microperfusion experiments, we were able to show that UGN inhibits H(+)-ATPase activity by a PKG-dependent pathway because KT5823 (PKG inhibitor) abolished the UGN effect on distal bicarbonate reabsorption and H89 (PKA inhibitor) was unable to prevent it. The in vivo results were confirmed by the in vitro experiments, where we used fluorescence microscopy to measure intracellular pH (pHi) recovery after an acid pulse with NH4Cl. By this technique, we observed that UGN and 8 bromoguanosine-cGMP (8Br-cGMP) inhibited H(+)-ATPase-dependent pHi recovery and that the UGN inhibitory effect was abolished in the presence of the PKG inhibitor. In addition, by using RT-PCR technique, we verified that Madin-Darby canine kidney (MDCK)-C11 cells express guanylate cyclase-C. Besides, UGN stimulated an increase of both cGMP content and PKG activity but was unable to increase the production of cellular cAMP content and PKA activity. Furthermore, we found that UGN reduced cell surface abundance of H+-ATPase B1 subunit in MDCK-C11 and that this effect was abolished by the PKG inhibitor. Taken together, our data suggest that UGN inhibits H(+)-ATPase activity and surface expression in renal distal cells by a cGMP/PKG-dependent pathway.
Collapse
Affiliation(s)
- Vanessa da Silva Lima
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil
| | | | - Luciene R Carraro-Lacroix
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, São Paulo, Brazil
| | - Alana N Godinho
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil
| | - João L G Dias
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil
| | | | | | - Manassés C Fonteles
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil; Mackenzie University, São Paulo, São Paulo, Brazil
| | - Gerhard Malnic
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, São Paulo, Brazil
| | - Lucília M A Lessa
- Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Ceará, Brazil;
| |
Collapse
|
22
|
Ando M, Wong MKS, Takei Y. Mechanisms of guanylin action on water and ion absorption at different regions of seawater eel intestine. Am J Physiol Regul Integr Comp Physiol 2014; 307:R653-63. [PMID: 24990857 DOI: 10.1152/ajpregu.00543.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Guanylin (GN) inhibited water absorption and short-circuit current (Isc) in seawater eel intestine. Similar inhibition was observed after bumetanide, and the effect of bumetanide was abolished by GN or vice versa, suggesting that both act on the same target, Na(+)-K(+)-2Cl(-) cotransporter (NKCC), which is a key player for the Na(+)-K(+)-Cl(-) transport system responsible for water absorption in marine teleost intestine. However, effect of GN was always greater than that of bumetanide: 10% greater in middle intestine (MI) and 40% in posterior intestine (PI) for Isc, and 25% greater in MI and 34% in PI for water absorption. After treatment with GN, Isc decreased to zero, but 20-30% water absorption still remained. The remainder may be due to the Cl(-)/HCO3 (-) exchanger and Na(+)-Cl(-) cotransporter (NCC), since inhibitors for these transporters almost nullified the remaining water absorption. Quantitative PCR analysis revealed the presence of major proteins involved in water absorption; the NKCC2β and AQP1 genes whose expression was markedly upregulated after seawater acclimation. The SLC26A6 (anion exchanger) and NCCβ genes were also expressed in small amounts. Consistent with the inhibitors' effect, expression of NKCC2β was MI > PI, and that of NCCβ was MI << PI. The present study showed that GN not only inhibits the bumetanide-sensitive Na(+)-K(+)-Cl(-) transport system governed by NKCC2β, but also regulates unknown ion transporters different from GN-insensitive SLC26A6 and NCC. A candidate is cystic fibrosis transmembrane conductance regulator Cl(-) channel, as demonstrated in mammals, but its expression is low in eel intestine, and its role may be minor, as indicated by the small effect of its inhibitors.
Collapse
Affiliation(s)
- Masaaki Ando
- Laboratory of Physiology, Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Marty K S Wong
- Laboratory of Physiology, Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Yoshio Takei
- Laboratory of Physiology, Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| |
Collapse
|
23
|
Jung J, Lee MG. Role of calcium signaling in epithelial bicarbonate secretion. Cell Calcium 2014; 55:376-84. [PMID: 24598807 DOI: 10.1016/j.ceca.2014.02.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 02/03/2014] [Accepted: 02/04/2014] [Indexed: 12/24/2022]
Abstract
Transepithelial bicarbonate secretion plays a key role in the maintenance of fluid and protein secretion from epithelial cells and the protection of the epithelial cell surface from various pathogens. Epithelial bicarbonate secretion is mainly under the control of cAMP and calcium signaling. While the physiological roles and molecular mechanisms of cAMP-induced bicarbonate secretion are relatively well defined, those induced by calcium signaling remain poorly understood in most epithelia. The present review summarizes the current status of knowledge on the role of calcium signaling in epithelial bicarbonate secretion. Specifically, this review introduces how cytosolic calcium signaling can increase bicarbonate secretion by regulating membrane transport proteins and how it synergizes with cAMP-induced mechanisms in epithelial cells. In addition, tissue-specific variations in the pancreas, salivary glands, intestines, bile ducts, and airways are discussed. We hope that the present report will stimulate further research into this important topic. These studies will provide the basis for future medicines for a wide spectrum of epithelial disorders including cystic fibrosis, Sjögren's syndrome, and chronic pancreatitis.
Collapse
Affiliation(s)
- Jinsei Jung
- Department of Pharmacology and Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea; Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea
| | - Min Goo Lee
- Department of Pharmacology and Brain Korea 21 Plus Project for Medical Sciences, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
| |
Collapse
|
24
|
Anbazhagan AN, Priyamvada S, Kumar A, Maher DB, Borthakur A, Alrefai WA, Malakooti J, Kwon JH, Dudeja PK. Translational repression of SLC26A3 by miR-494 in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 2014; 306:G123-31. [PMID: 24177028 PMCID: PMC3920076 DOI: 10.1152/ajpgi.00222.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
SLC26A3 [downregulated in adenoma (DRA)] is a Cl(-)/HCO3(-) exchanger involved in electroneutral NaCl absorption in the mammalian intestine. Altered DRA expression levels are associated with infectious and inflammatory diarrheal diseases. Therefore, it is critical to understand the regulation of DRA expression. MicroRNAs (miRNAs) are endogenous, small RNAs that regulate protein expression via blocking the translation and/or promoting mRNA degradation. To investigate potential modulation of DRA expression by miRNA, five different in silico algorithms were used to predict the miRNAs that target DRA. Of these miRNAs, miR-494 was shown to have a highly conserved putative binding site in the DRA 3'-untranslated region (3'-UTR) compared with other DRA-targeting miRNAs in vertebrates. Transfection with pmirGLO dual luciferase vector containing DRA 3'-UTR (pmirGLO-3'-UTR DRA) resulted in a significant decrease in relative luciferase activity compared with empty vector. Cotransfection of the DRA 3'-UTR luciferase vector with a miR-494 mimic further decreased luciferase activity compared with cells transfected with negative control. The transfection of a miR-494 mimic into Caco-2 and T-84 cells significantly increased the expression of miR-494 and concomitantly decreased the DRA protein expression. Mutation of the seed sequences for miR-494 in 3'-UTR of DRA abrogated the effect of miR-494 on 3'-UTR. These data demonstrate a novel regulatory mechanism of DRA expression via miR-494 and indicate that targeting this microRNA may serve to be a potential therapeutic strategy for diarrheal diseases.
Collapse
Affiliation(s)
- Arivarasu N. Anbazhagan
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois;
| | - Shubha Priyamvada
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois;
| | - Anoop Kumar
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois;
| | - Daniel B. Maher
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois;
| | - Alip Borthakur
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois;
| | - Waddah A. Alrefai
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois; ,2Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| | - Jaleh Malakooti
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois;
| | - John H. Kwon
- 3Department of Medicine, University of Chicago, Chicago, Illinois
| | - Pradeep K. Dudeja
- 1Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois, Chicago, Illinois; ,2Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and
| |
Collapse
|
25
|
Alper SL, Sharma AK. The SLC26 gene family of anion transporters and channels. Mol Aspects Med 2013; 34:494-515. [PMID: 23506885 DOI: 10.1016/j.mam.2012.07.009] [Citation(s) in RCA: 249] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/21/2012] [Indexed: 02/08/2023]
Abstract
The phylogenetically ancient SLC26 gene family encodes multifunctional anion exchangers and anion channels transporting a broad range of substrates, including Cl(-), HCO3(-), sulfate, oxalate, I(-), and formate. SLC26 polypeptides are characterized by N-terminal cytoplasmic domains, 10-14 hydrophobic transmembrane spans, and C-terminal cytoplasmic STAS domains, and appear to be homo-oligomeric. SLC26-related SulP proteins of marine bacteria likely transport HCO3(-) as part of oceanic carbon fixation. SulP genes present in antibiotic operons may provide sulfate for antibiotic biosynthetic pathways. SLC26-related Sultr proteins transport sulfate in unicellular eukaryotes and in plants. Mutations in three human SLC26 genes are associated with congenital or early onset Mendelian diseases: chondrodysplasias for SLC26A2, chloride diarrhea for SLC26A3, and deafness with enlargement of the vestibular aqueduct for SLC26A4. Additional disease phenotypes evident only in mouse knockout models include oxalate urolithiasis for Slc26a6 and Slc26a1, non-syndromic deafness for Slc26a5, gastric hypochlorhydria for Slc26a7 and Slc26a9, distal renal tubular acidosis for Slc26a7, and male infertility for Slc26a8. STAS domains are required for cell surface expression of SLC26 proteins, and contribute to regulation of the cystic fibrosis transmembrane regulator in complex, cell- and tissue-specific ways. The protein interactomes of SLC26 polypeptides are under active investigation.
Collapse
Affiliation(s)
- Seth L Alper
- Renal Division and Division of Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
| | | |
Collapse
|
26
|
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) protein is highly expressed in the pancreatic duct epithelia and permits anions and water to enter the ductal lumen. This results in an increased volume of alkaline fluid allowing the highly concentrated proteins secreted by the acinar cells to remain in a soluble state. This work will expound on the pathophysiology and pathology caused by the malfunctioning CFTR protein with special reference to ion transport and acid-base abnormalities both in humans and animal models. We will also discuss the relationship between cystic fibrosis (CF) and pancreatitis, and outline present and potential therapeutic approaches in CF treatment relevant to the pancreas.
Collapse
Affiliation(s)
- Michael Wilschanski
- Pediatric Gastroenterology, Hadassah University Hospital, Jerusalem 91240, Israel
| | | |
Collapse
|
27
|
Patterson K, Catalán MA, Melvin JE, Yule DI, Crampin EJ, Sneyd J. A quantitative analysis of electrolyte exchange in the salivary duct. Am J Physiol Gastrointest Liver Physiol 2012; 303:G1153-63. [PMID: 22899825 PMCID: PMC3517652 DOI: 10.1152/ajpgi.00364.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A healthy salivary gland secretes saliva in two stages. First, acinar cells generate primary saliva, a plasma-like, isotonic fluid high in Na(+) and Cl(-). In the second stage, the ducts exchange Na(+) and Cl(-) for K(+) and HCO(3)(-), producing a hypotonic final saliva with no apparent loss in volume. We have developed a tool that aims to understand how the ducts achieve this electrolyte exchange while maintaining the same volume. This tool is part of a larger multiscale model of the salivary gland and can be used at the duct or gland level to investigate the effects of genetic and chemical alterations. In this study, we construct a radially symmetric mathematical model of the mouse salivary gland duct, representing the lumen, the cell, and the interstitium. For a given flow and primary saliva composition, we predict the potential differences and the luminal and cytosolic concentrations along a duct. Our model accounts well for experimental data obtained in wild-type animals as well as knockouts and chemical inhibitors. Additionally, the luminal membrane potential of the duct cells is predicted to be very depolarized compared with acinar cells. We investigate the effects of an electrogenic vs. electroneutral anion exchanger in the luminal membrane on concentration and the potential difference across the luminal membrane as well as how impairing the cystic fibrosis transmembrane conductance regulator channel affects other ion transporting mechanisms. Our model suggests the electrogenicity of the anion exchanger has little effect in the submandibular duct.
Collapse
Affiliation(s)
- Kate Patterson
- Dept. of Mathematics, Univ. of Auckland, Auckland, New Zealand.
| | - Marcelo A. Catalán
- 2Secretory Mechanisms and Dysfunction Section, Division of Intramural Research, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland;
| | - James E. Melvin
- 2Secretory Mechanisms and Dysfunction Section, Division of Intramural Research, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland;
| | - David I. Yule
- 3Department of Pharmacology and Physiology and the Center for Oral Biology, University of Rochester Medical Center, Rochester, New York; and
| | - Edmund J. Crampin
- 4Auckland Bioengineering Institute and Department of Engineering Science, University of Auckland, Auckland, New Zealand
| | - James Sneyd
- 1Department of Mathematics, University of Auckland, Auckland, New Zealand;
| |
Collapse
|
28
|
Park HW, Lee MG. Transepithelial bicarbonate secretion: lessons from the pancreas. Cold Spring Harb Perspect Med 2012; 2:2/10/a009571. [PMID: 23028131 DOI: 10.1101/cshperspect.a009571] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Many cystic fibrosis transmembrane conductance regulator (CFTR)-expressing epithelia secrete bicarbonate (HCO(3)(-))-containing fluids. Recent evidence suggests that defects in epithelial bicarbonate secretion are directly involved in the pathogenesis of cystic fibrosis, in particular by building up hyperviscous mucus in the ductal structures of the lung and pancreas. Pancreatic juice is one of the representative fluids that contain a very high concentration of bicarbonate among bodily fluids that are secreted from CFTR-expressing epithelia. We introduce up-to-date knowledge on the basic principles of transepithelial bicarbonate transport by showing the mechanisms involved in pancreatic bicarbonate secretion. The model of pancreatic bicarbonate secretion described herein may also apply to other exocrine epithelia. As a central regulator of bicarbonate transport at the apical membrane, CFTR plays an essential role in both direct and indirect bicarbonate secretion. The major role of CFTR in bicarbonate secretion would be variable depending on the tissue and cell type. For example, in epithelial cells that produce a low concentration of bicarbonate-containing fluid (up to 80 mm), either CFTR-dependent Cl(-)/HCO(3)(-) exchange or CFTR anion channel with low bicarbonate permeability would be sufficient to generate such fluid. However, in cells that secrete high-bicarbonate-containing fluids, a highly selective CFTR bicarbonate channel activity is required. Therefore, understanding the molecular mechanism of transepithelial bicarbonate transport and the role of CFTR in each specific epithelium will provide therapeutic strategies to recover from epithelial defects induced by hyposecretion of bicarbonate in cystic fibrosis.
Collapse
Affiliation(s)
- Hyun Woo Park
- Department of Pharmacology, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea
| | | |
Collapse
|
29
|
Song Y, Yamamoto A, Steward MC, Ko SBH, Stewart AK, Soleimani M, Liu BC, Kondo T, Jin CX, Ishiguro H. Deletion of Slc26a6 alters the stoichiometry of apical Cl-/HCO-3 exchange in mouse pancreatic duct. Am J Physiol Cell Physiol 2012; 303:C815-24. [PMID: 22895259 DOI: 10.1152/ajpcell.00151.2012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
To define the stoichiometry and molecular identity of the Cl(-)/HCO(3)(-) exchanger in the apical membrane of pancreatic duct cells, changes in luminal pH and volume were measured simultaneously in interlobular pancreatic ducts isolated from wild-type and Slc26a6-null mice. Transepithelial fluxes of HCO(3)(-) and Cl(-) were measured in the presence of anion gradients favoring rapid exchange of intracellular HCO(3)(-) with luminal Cl(-) in cAMP-stimulated ducts. The flux ratio of Cl(-) absorption/HCO(3)(-) secretion was ∼0.7 in wild-type ducts and ∼1.4 in Slc26a6(-/-) ducts where a different Cl(-)/HCO(3)(-) exchanger, most likely SLC26A3, was found to be active. Interactions between Cl(-)/HCO(3)(-) exchange and cystic fibrosis transmembrane conductance regulator (CFTR) in cAMP-stimulated ducts were examined by measuring the recovery of intracellular pH after alkali-loading by acetate prepulse. Hyperpolarization induced by luminal application of CFTRinh-172 enhanced HCO(3)(-) efflux across the apical membrane via SLC26A6 in wild-type ducts but significantly reduced HCO(3)(-) efflux in Slc26a6(-/-) ducts. In microperfused wild-type ducts, removal of luminal Cl(-), or luminal application of dihydro-4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid to inhibit SLC26A6, caused membrane hyperpolarization, which was abolished in Slc26a6(-/-) ducts. In conclusion, we have demonstrated that deletion of Slc26a6 alters the apparent stoichiometry of apical Cl(-)/HCO(3)(-) exchange in native pancreatic duct. Our results are consistent with SLC26A6 mediating 1:2 Cl(-)/HCO(3)(-) exchange, and the exchanger upregulated in its absence, most probably SLC26A3, mediating 2:1 exchange.
Collapse
Affiliation(s)
- Ying Song
- Laboratory of Human Nutrition, Nagoya University Graduate School of Medicine, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Huang J, Shan J, Kim D, Liao J, Evagelidis A, Alper SL, Hanrahan JW. Basolateral chloride loading by the anion exchanger type 2: role in fluid secretion by the human airway epithelial cell line Calu-3. J Physiol 2012; 590:5299-316. [PMID: 22802585 DOI: 10.1113/jphysiol.2012.236919] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Anion exchanger type 2 (AE2 or SLC4A2) is an electroneutral Cl(-)/HCO(3)(-) exchanger expressed at the basolateral membrane of many epithelia. It is thought to participate in fluid secretion by airway epithelia. However, the role of AE2 in fluid secretion remains uncertain, due to the lack of specific pharmacological inhibitors, and because it is electrically silent and therefore does not contribute directly to short-circuit current (I(sc)). We have studied the role of AE2 in Cl(-) and fluid secretion by the airway epithelial cell line Calu-3. After confirming expression of its mRNA and protein, a knock-down cell line called AE2-KD was generated by lentivirus-mediated RNA interference in which AE2 mRNA and protein levels were reduced 90%. Suppressing AE2 increased the expression of the cystic fibrosis transmembrane conductance regulator (CFTR) by ∼70% without affecting the levels of NKCC1 (Na(+)-K(+)-2Cl(-) cotransporter) or NBCe1 (Na(+)-nHCO(3)(-) cotransporter). cAMP agonists stimulated fluid secretion by parental Calu-3 and scrambled shRNA cells >6.5-fold. In AE2-KD cells this response was reduced by ∼70%, and the secreted fluid exhibited elevated pH and [HCO(3)(-)] as compared with the control lines. Unstimulated equivalent short-circuit current (I(eq)) was elevated in AE2-KD cells, but the incremental response to forskolin was unaffected. The modest bumetanide-induced reductions in both I(eq) and fluid secretion were more pronounced in AE2-KD cells. Basolateral Cl(-)/HCO(3)(-) exchange measured by basolateral pH-stat in cells with permeabilized apical membranes was abolished in AE2-KD monolayers, and the intracellular alkalinization resulting from basolateral Cl(-) removal was reduced by ∼80% in AE2-KD cells. These results identify AE2 as a major pathway for basolateral Cl(-) loading during cAMP-stimulated secretion of Cl(-) and fluid by Calu-3 cells, and help explain the large bumetanide-insensitive component of fluid secretion reported previously in airway submucosal glands and some other epithelia.
Collapse
Affiliation(s)
- Junwei Huang
- Department of Physiology, McGill University, Montr´eal, QC, Canada
| | | | | | | | | | | | | |
Collapse
|
31
|
Shan J, Liao J, Huang J, Robert R, Palmer ML, Fahrenkrug SC, O'Grady SM, Hanrahan JW. Bicarbonate-dependent chloride transport drives fluid secretion by the human airway epithelial cell line Calu-3. J Physiol 2012; 590:5273-97. [PMID: 22777674 DOI: 10.1113/jphysiol.2012.236893] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Anion and fluid secretion are both defective in cystic fibrosis (CF); however, the transport mechanisms are not well understood. In this study, Cl(-) and HCO(3)(-) secretion was measured using genetically matched CF transmembrane conductance regulator (CFTR)-deficient and CFTR-expressing cell lines derived from the human airway epithelial cell line Calu-3. Forskolin stimulated the short-circuit current (I(sc)) across voltage-clamped monolayers, and also increased the equivalent short-circuit current (I(eq)) calculated under open-circuit conditions. I(sc) was equivalent to the HCO(3)(-) net flux measured using the pH-stat technique, whereas I(eq) was the sum of the Cl(-) and HCO(3)(-) net fluxes. I(eq) and HCO(3)(-) fluxes were increased by bafilomycin and ZnCl(2), suggesting that some secreted HCO(3)(-) is neutralized by parallel electrogenic H(+) secretion. I(eq) and fluid secretion were dependent on the presence of both Na(+) and HCO(3)(-). The carbonic anhydrase inhibitor acetazolamide abolished forskolin stimulation of I(eq) and HCO(3)(-) secretion, suggesting that HCO(3)(-) transport under these conditions requires catalysed synthesis of carbonic acid. Cl(-) was the predominant anion in secretions under all conditions studied and thus drives most of the fluid transport. Nevertheless, 50-70% of Cl(-) and fluid transport was bumetanide-insensitive, suggesting basolateral Cl(-) loading by a sodium-potassium-chloride cotransporter 1 (NKCC1)-independent mechanism. Imposing a transepithelial HCO(3)(-) gradient across basolaterally permeabilized Calu-3 cells sustained a forskolin-stimulated current, which was sensitive to CFTR inhibitors and drastically reduced in CFTR-deficient cells. Net HCO(3)(-) secretion was increased by bilateral Cl(-) removal and therefore did not require apical Cl(-)/HCO(3)(-) exchange. The results suggest a model in which most HCO(3)(-) is recycled basolaterally by exchange with Cl(-), and the resulting HCO(3)(-)-dependent Cl(-) transport provides an osmotic driving force for fluid secretion.
Collapse
Affiliation(s)
- Jiajie Shan
- Department of Physiology, McGill University, Montr´eal, QC H3G 1Y6, Canada
| | | | | | | | | | | | | | | |
Collapse
|
32
|
Lee MG, Ohana E, Park HW, Yang D, Muallem S. Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion. Physiol Rev 2012; 92:39-74. [PMID: 22298651 DOI: 10.1152/physrev.00011.2011] [Citation(s) in RCA: 267] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.
Collapse
Affiliation(s)
- Min Goo Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
| | | | | | | | | |
Collapse
|
33
|
Schwabe K, Cetin Y. Guanylin and functional coupling proteins in the hepatobiliary system of rat and guinea pig. Histochem Cell Biol 2012; 137:589-97. [PMID: 22310983 DOI: 10.1007/s00418-012-0927-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2012] [Indexed: 12/13/2022]
Abstract
Guanylin, a bioactive intestinal peptide, is involved in the cystic fibrosis transmembrane conductance (CFTR)-regulated electrolyte/water secretion in various epithelia. In the present work we report on the expression and cellular localization of guanylin and its affiliated signaling and effector proteins, including guanylate cyclase C (Gucy2c), Proteinkinase GII (Pkrg2), CFTR and the solute carrier family 4, anion exchanger, member 2 (Slc4a2) in the hepatobiliary system of rat and guinea pig. Localization studies in the liver and the gallbladder revealed that guanylin is located in the secretory epithelial cells of bile ducts of the liver and of the gallbladder, while Gucy2c, Pkrg2, CFTR, and Slc4a2 are confined exclusively to the apical membrane of the same epithelial cells. Based on these findings, we assume that guanylin is synthesized as an intrinsic peptide in epithelial cells of the hepatobiliary system and released luminally into the hepatic and cystic bile to regulate electrolyte secretion by a paracrine/luminocrine signaling pathway.
Collapse
Affiliation(s)
- Karen Schwabe
- Department of Molecular Cell Biology, Institute of Anatomy and Cell Biology, Philipps-Universität Marburg, Marburg, Germany
| | | |
Collapse
|
34
|
Stewart AK, Shmukler BE, Vandorpe DH, Reimold F, Heneghan JF, Nakakuki M, Akhavein A, Ko S, Ishiguro H, Alper SL. SLC26 anion exchangers of guinea pig pancreatic duct: molecular cloning and functional characterization. Am J Physiol Cell Physiol 2011; 301:C289-303. [PMID: 21593449 DOI: 10.1152/ajpcell.00089.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The secretin-stimulated human pancreatic duct secretes HCO(3)(-)-rich fluid essential for normal digestion. Optimal stimulation of pancreatic HCO(3)(-) secretion likely requires coupled activities of the cystic fibrosis transmembrane regulator (CFTR) anion channel and apical SLC26 Cl(-)/HCO(3)(-) exchangers. However, whereas stimulated human and guinea pig pancreatic ducts secrete ∼140 mM HCO(3)(-) or more, mouse and rat ducts secrete ∼40-70 mM HCO(3)(-). Moreover, the axial distribution and physiological roles of SLC26 anion exchangers in pancreatic duct secretory processes remain controversial and may vary among mammalian species. Thus the property of high HCO(3)(-) secretion shared by human and guinea pig pancreatic ducts prompted us to clone from guinea pig pancreatic duct cDNAs encoding Slc26a3, Slc26a6, and Slc26a11 polypeptides. We then functionally characterized these anion transporters in Xenopus oocytes and human embryonic kidney (HEK) 293 cells. In Xenopus oocytes, gpSlc26a3 mediated only Cl(-)/Cl(-) exchange and electroneutral Cl(-)/HCO(3)(-) exchange. gpSlc26a6 in Xenopus oocytes mediated Cl(-)/Cl(-) exchange and bidirectional exchange of Cl(-) for oxalate and sulfate, but Cl(-)/HCO(3)(-) exchange was detected only in HEK 293 cells. gpSlc26a11 in Xenopus oocytes exhibited pH-dependent Cl(-), oxalate, and sulfate transport but no detectable Cl(-)/HCO(3)(-) exchange. The three gpSlc26 anion transporters exhibited distinct pharmacological profiles of (36)Cl(-) influx, including partial sensitivity to CFTR inhibitors Inh-172 and GlyH101, but only Slc26a11 was inhibited by PPQ-102. This first molecular and functional assessment of recombinant SLC26 anion transporters from guinea pig pancreatic duct enhances our understanding of pancreatic HCO(3)(-) secretion in species that share a high HCO(3)(-) secretory output.
Collapse
Affiliation(s)
- Andrew K Stewart
- Renal Division and Vascular Biology Center, Beth Israel Deaconess Medical Center, Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Abstract
The pancreas has both endocrine and exocrine functions. As an endocrine organ, stimulation of the pancreatic β-cells results in insulin secretion to control systemic glucose levels. The exocrine function of the pancreas and the need for alkaline pancreatic secretion (pH 8.0-8.5) have been appreciated for more than 40 years. Yet, our knowledge of the cellular mechanisms (signaling, transporters and channels) which accomplish these critical functions has evolved greatly. In the mid-1990s, basolateral Na-bicarbonate (HCO(3)(-)) uptake by NBCe1 (Slc4a4) was shown to be critical for the generation of approximately 75% of stimulated HCO(3)(-) secretion. In the last 10 years, several new HCO(3)(-) transporters in the Slc26 family and their interaction with the cystic fibrosis transmembrane conductance regulator-chloride channel have elucidated the HCO(3)(-) exit step at the ductal lumen. Most recently, both IRBIT (inositol 1,4,5-trisphosphate receptor-binding protein) and WNK [with no lysine (K)] kinase have been implicated as additional HCO(3)(-) secretory controllers. and IAP.
Collapse
Affiliation(s)
- Aleksandra Sinđić
- Department of Physiology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | | | - Michael F. Romero
- Department of Physiology and Biomedical Engineering, Rochester, Minn., USA,Mayo Clinic O'Brien Urology Research Center, Mayo Clinic College of Medicine, Rochester, Minn., USA,*Michael F. Romero, PhD, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905 (USA), Tel. +1 507 284 8127, E-Mail
| |
Collapse
|
36
|
Catalán MA, Scott-Anne K, Klein MI, Koo H, Bowen WH, Melvin JE. Elevated incidence of dental caries in a mouse model of cystic fibrosis. PLoS One 2011; 6:e16549. [PMID: 21304986 PMCID: PMC3031584 DOI: 10.1371/journal.pone.0016549] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Accepted: 12/23/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Dental caries is the single most prevalent and costly infectious disease worldwide, affecting more than 90% of the population in the U.S. The development of dental cavities requires the colonization of the tooth surface by acid-producing bacteria, such as Streptococcus mutans. Saliva bicarbonate constitutes the main buffering system which neutralizes the pH fall generated by the plaque bacteria during sugar metabolism. We found that the saliva pH is severely decreased in a mouse model of cystic fibrosis disease (CF). Given the close relationship between pH and caries development, we hypothesized that caries incidence might be elevated in the mouse CF model. METHODOLOGY/PRINCIPAL FINDINGS We induced carious lesions in CF and wildtype mice by infecting their oral cavity with S. mutans, a well-studied cariogenic bacterium. After infection, the mice were fed a high-sucrose diet for 5 weeks (diet 2000). The mice were then euthanized and their jaws removed for caries scoring and bacterial counting. A dramatic increase in caries and severity of lesions scores were apparent in CF mice compared to their wildtype littermates. The elevated incidence of carious lesions correlated with a striking increase in the S. mutans viable population in dental plaque (20-fold increase in CF vs. wildtype mice; p value < 0.003; t test). We also found that the pilocarpine-stimulated saliva bicarbonate concentration was significantly reduced in CF mice (16 ± 2 mM vs. 31 ± 2 mM, CF and wildtype mice, respectively; p value < 0.01; t test). CONCLUSIONS/SIGNIFICANCE Considering that bicarbonate is the most important pH buffering system in saliva, and the adherence and survival of aciduric bacteria such as S. mutans are enhanced at low pH values, we speculate that the decrease in the bicarbonate content and pH buffering of the saliva is at least partially responsible for the increased severity of lesions observed in the CF mouse.
Collapse
Affiliation(s)
- Marcelo A. Catalán
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Kathleen Scott-Anne
- Center for Oral Biology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Marlise I. Klein
- Center for Oral Biology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Hyun Koo
- Center for Oral Biology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - William H. Bowen
- Center for Oral Biology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - James E. Melvin
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail:
| |
Collapse
|
37
|
Xie C, Tang X, Xu W, Diao R, Cai Z, Chan HC. A host defense mechanism involving CFTR-mediated bicarbonate secretion in bacterial prostatitis. PLoS One 2010; 5:e15255. [PMID: 21151921 PMCID: PMC2998414 DOI: 10.1371/journal.pone.0015255] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 11/02/2010] [Indexed: 11/18/2022] Open
Abstract
Background Prostatitis is associated with a characteristic increase in prostatic fluid pH; however, the underlying mechanism and its physiological significance have not been elucidated. Methodology/Principal Findings In this study a primary culture of rat prostatic epithelial cells and a rat prostatitis model were used. Here we reported the involvement of CFTR, a cAMP-activated anion channel conducting both Cl− and HCO3−, in mediating prostate HCO3− secretion and its possible role in bacterial killing. Upon Escherichia coli (E coli)-LPS challenge, the expression of CFTR and carbonic anhydrase II (CA II), along with several pro-inflammatory cytokines was up-regulated in the primary culture of rat prostate epithelial cells. Inhibiting CFTR function in vitro or in vivo resulted in reduced bacterial killing by prostate epithelial cells or the prostate. High HCO3− content (>50 mM), rather than alkaline pH, was found to be responsible for bacterial killing. The direct action of HCO3− on bacterial killing was confirmed by its ability to increase cAMP production and suppress bacterial initiation factors in E coli. The relevance of the CFTR-mediated HCO3− secretion in humans was demonstrated by the upregulated expression of CFTR and CAII in human prostatitis tissues. Conclusions/Significance The CFTR and its mediated HCO3− secretion may be up-regulated in prostatitis as a host defense mechanism.
Collapse
Affiliation(s)
- Chen Xie
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Xiaoxiao Tang
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Wenming Xu
- The Chinese University of Hong Kong Joint Laboratory of Reproductive Medicine, Sichuan University, West China Second University Hospital, Hong Kong, China
| | - Ruiying Diao
- Guangdong Key Laboratory of Male Reproduction and Genetics, Peking University Shenzhen Hospital, Shenzhen, China
| | - Zhiming Cai
- Guangdong Key Laboratory of Male Reproduction and Genetics, Peking University Shenzhen Hospital, Shenzhen, China
| | - Hsiao Chang Chan
- Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
- The Chinese University of Hong Kong Joint Laboratory of Reproductive Medicine, Sichuan University, West China Second University Hospital, Hong Kong, China
- * E-mail:
| |
Collapse
|
38
|
Roussa E. Channels and transporters in salivary glands. Cell Tissue Res 2010; 343:263-87. [PMID: 21120532 DOI: 10.1007/s00441-010-1089-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 11/03/2010] [Indexed: 01/04/2023]
Abstract
According to the two-stage hypothesis, primary saliva, a NaCl-rich plasma-like isotonic fluid is secreted by salivary acinar cells and its ionic composition becomes modified in the duct system. The ducts secrete K(+) and HCO (3) (-) and reabsorb Na(+) and Cl(-) without any water movement, thus establishing a hypotonic final saliva. Salivary secretion depends on the coordinated action of several channels and transporters localized in the apical and basolateral membrane of acinar and duct cells. Early functional studies in perfused glands, followed by the molecular cloning of several transport proteins and the subsequent analysis of mutant mice, have greatly contributed to our understanding of salivary fluid and the electrolyte secretion process. With a few exceptions, most of the key channels and transporters involved in salivary secretion have now been identified and characterized. However, the picture that has emerged from all these studies is one of a complex molecular network characterized by redundancy for several transport proteins, compensatory mechanisms, and adaptive changes in health and disease. Current research is directed to the molecular interactions between the determinants and the ways in which they are regulated by extracellular signals and intracellular mediators. This review focuses on the functionally and molecularly best-characterized channels and transporters that are considered to be involved in transepithelial fluid and electrolyte transport in salivary glands.
Collapse
Affiliation(s)
- Eleni Roussa
- Anatomy and Cell Biology II, Department of Molecular Embryology, Albert Ludwigs University Freiburg, 79104, Freiburg i. Br., Germany.
| |
Collapse
|
39
|
Park HW, Nam JH, Kim JY, Namkung W, Yoon JS, Lee JS, Kim KS, Venglovecz V, Gray MA, Kim KH, Lee MG. Dynamic regulation of CFTR bicarbonate permeability by [Cl-]i and its role in pancreatic bicarbonate secretion. Gastroenterology 2010; 139:620-31. [PMID: 20398666 DOI: 10.1053/j.gastro.2010.04.004] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2009] [Revised: 02/05/2010] [Accepted: 04/08/2010] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Pancreatic bicarbonate (HCO3-) secretion is important for a healthy pancreas as well as digestive physiology. However, how human pancreatic duct cells secrete copious amounts of HCO3- has long been a puzzle. Here, we report that a dynamic increase in the cystic fibrosis transmembrane conductance regulator (CFTR) HCO3- permeability by intracellular Cl- concentration ([Cl-]i)-sensitive mechanisms plays a pivotal role in pancreatic HCO3- secretion. METHODS The role of [Cl-]i-sensitive kinases in CFTR-mediated HCO3- transport was examined in heterologous expression systems, PANC1 human pancreatic duct cells, and human and guinea pig pancreatic tissues using an integrated molecular and physiologic approach. RESULTS In human pancreatic tissues, CFTR-positive duct cells abundantly expressed with-no-lysine (WNK1) kinase, oxidative stress-responsive kinase 1 (OSR1), and sterile 20/SPS1-related proline/alanine-rich kinase (SPAK), which are known to be activated by low [Cl-]i. Interestingly, CFTR activation rapidly decreased [Cl-]i in response to luminal Cl- depletion in polarized PANC1 human pancreatic duct cells. Notably, the WNK1-mediated OSR1 and SPAK activation by low [Cl-]i strongly increased CFTR HCO3- permeability in CFTR-transfected HEK 293T, PANC1, and guinea pig pancreatic duct cells, making CFTR primarily an HCO3- channel, which is essential for the secretion of pancreatic juice containing HCO3- at a concentration greater than 140 mmol/L. In contrast, OSR1 and SPAK activation inhibited CFTR-dependent Cl-/HCO3- exchange activity that may reabsorb HCO3- from the high HCO3--containing pancreatic juice. CONCLUSIONS These results indicate that the [Cl-]i-sensitive activation of the WNK1-OSR1/SPAK pathway is the molecular switch to generate HCO3--rich fluid in the human pancreatic duct.
Collapse
Affiliation(s)
- Hyun Woo Park
- Department of Pharmacology, Institute of Gastroenterology, Brain Korea 21 Project for Medical Science, Seoul, Korea
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Catalán MA, Nakamoto T, Melvin JE. The salivary gland fluid secretion mechanism. THE JOURNAL OF MEDICAL INVESTIGATION 2010; 56 Suppl:192-6. [PMID: 20224180 DOI: 10.2152/jmi.56.192] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Fluid secretion by exocrine glands requires the coordinated activity of multiple water and ion transporter and channel proteins. The molecular cloning of many of the transporter molecules involved in fluid secretion has yielded a better understanding of the fluid secretion process. Mouse salivary glands are easily accessible model systems for the study of exocrine gland secretion at the cellular and organ level. Indeed, the characterization of mice with null mutations in many of the water and ion transporter and channel genes has demonstrated the physiological roles of individual proteins. This overview will focus on recent developments in determining the molecular identification of the proteins that are involved in the fluid secretion process.
Collapse
Affiliation(s)
- Marcelo A Catalán
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York, NY 14642, USA
| | | | | |
Collapse
|
41
|
Song Y, Ishiguro H, Yamamoto A, Jin CX, Kondo T. Effects of Slc26a6 deletion and CFTR inhibition on HCO3- secretion by mouse pancreatic duct. THE JOURNAL OF MEDICAL INVESTIGATION 2010; 56 Suppl:332-5. [PMID: 20224218 DOI: 10.2152/jmi.56.332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Pancreatic duct epithelium secretes HCO(3)(-)-rich fluid, which is dependent on cystic fibrosis transmembrane conductance regulator (CFTR). HCO(3)(-) transport across the apical membrane is thought to be mediated by both SLC26A6 Cl(-)-HCO(3)(-) exchange and CFTR HCO(3)(-) conductance. In this study we examined the relative contribution and interaction of SLC26A6 and CFTR in apical HCO(3)(-) transport. Interlobular pancreatic ducts were isolated from slc26a6 null mice. Intracellular pH (pH(i)) was measured by BCECF microfluorometry. Duct cells were stimulated with forskolin and alkalinized by acetate pre-pulse in the presence of HCO(3)(-)-CO(2). Apical HCO(3)(-) secretion was estimated from the recovery rate of pH(i) from alkaline load. When the lumen was perfused with high-Cl(-) solution, the rate of apical HCO(3)(-) secretion was increased by luminal application of CFTRinh-172 in ducts from wild-type mice but it was decreased in ducts from slc26a6 -/- mice. This suggests that slc26a6 and CFTR compensate/compete with each other for apical HCO(3)(-) secretion with high Cl(-) in the lumen. With high HCO(3)(-) in the lumen, luminal CFTRinh-172 reduced the rate of apical HCO(3)(-) secretion in both wild-type and slc26a6 -/- ducts. This suggests that HCO(3)(-) conductance of CFTR mediates a significant portion of apical HCO(3)(-) secretion with high HCO(3)(-) in the lumen.
Collapse
Affiliation(s)
- Ying Song
- Second Clinical College of Norman Bethune Medical Division, Jilin University, Changchun, China
| | | | | | | | | |
Collapse
|
42
|
Li C, Naren AP. CFTR chloride channel in the apical compartments: spatiotemporal coupling to its interacting partners. Integr Biol (Camb) 2010; 2:161-77. [PMID: 20473396 DOI: 10.1039/b924455g] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-regulated chloride channel located primarily at the apical or luminal surfaces of epithelial cells in the airway, intestine, pancreas, kidney, sweat gland, as well as male reproductive tract, where it plays a crucial role in transepithelial fluid homeostasis. CFTR dysfunction can be detrimental and may result in life-threatening disorders. CFTR hypofunctioning because of genetic defects leads to cystic fibrosis, the most common lethal genetic disease in Caucasians, whereas CFTR hyperfunctioning resulting from various infections evokes secretory diarrhea, the leading cause of mortality in early childhood. Therefore, maintaining a dynamic balance between CFTR up-regulating processes and CFTR down-regulating processes is essential for maintaining fluid and body homeostasis. Accumulating evidence suggests that protein-protein interactions play a critical role in the fine-tuned regulation of CFTR function. A growing number of proteins have been reported to interact directly or indirectly with CFTR chloride channel, suggesting that CFTR might be coupled spatially and temporally to a wide variety of interacting partners including ion channels, receptors, transporters, scaffolding proteins, enzyme molecules, signaling molecules, and effectors. Most interactions occur primarily between the opposing terminal tails (amino or carboxyl) of CFTR protein and its binding partners, either directly or mediated through various PDZ scaffolding proteins. These dynamic interactions impact the channel function, as well as localization and processing of CFTR protein within cells. This article reviews the most recent progress and findings about the interactions between CFTR and its binding partners through PDZ scaffolding proteins, as well as the spatiotemporal regulation of CFTR-containing macromolecular signaling complexes in the apical compartments of polarized cells lining the secretory epithelia.
Collapse
Affiliation(s)
- Chunying Li
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, 540 E. Canfield Avenue, 5312 Scott Hall, Detroit, Michigan 48201, USA
| | | |
Collapse
|
43
|
Romanenko VG, Catalán MA, Brown DA, Putzier I, Hartzell HC, Marmorstein AD, Gonzalez-Begne M, Rock JR, Harfe BD, Melvin JE. Tmem16A encodes the Ca2+-activated Cl- channel in mouse submandibular salivary gland acinar cells. J Biol Chem 2010; 285:12990-3001. [PMID: 20177062 DOI: 10.1074/jbc.m109.068544] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Activation of an apical Ca(2+)-dependent Cl(-) channel (CaCC) is the rate-limiting step for fluid secretion in many exocrine tissues. Here, we compared the properties of native CaCC in mouse submandibular salivary gland acinar cells to the Ca(2+)-gated Cl(-) currents generated by Tmem16A and Best2, members from two distinct families of Ca(2+)-activated Cl(-) channels found in salivary glands. Heterologous expression of Tmem16A and Best2 transcripts in HEK293 cells produced Ca(2+)-activated Cl(-) currents with time and voltage dependence and inhibitor sensitivity that resembled the Ca(2+)-activated Cl(-) current found in native salivary acinar cells. Best2(-/-) and Tmem16A(-/-) mice were used to further characterize the role of these channels in the exocrine salivary gland. The amplitude and the biophysical footprint of the Ca(2+)-activated Cl(-) current in submandibular gland acinar cells from Best2-deficient mice were the same as in wild type cells. Consistent with this observation, the fluid secretion rate in Best2 null mice was comparable with that in wild type mice. In contrast, submandibular gland acinar cells from Tmem16A(-/-) mice lacked a Ca(2+)-activated Cl(-) current and a Ca(2+)-mobilizing agonist failed to stimulate Cl(-) efflux, requirements for fluid secretion. Furthermore, saliva secretion was abolished by the CaCC inhibitor niflumic acid in wild type and Best2(-/-) mice. Our results demonstrate that both Tmem16A and Best2 generate Ca(2+)-activated Cl(-) current in vitro with similar properties to those expressed in native cells, yet only Tmem16A appears to be a critical component of the acinar Ca(2+)-activated Cl(-) channel complex that is essential for saliva production by the submandibular gland.
Collapse
Affiliation(s)
- Victor G Romanenko
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Newport S, Amin N, Dozor AJ. Exhaled breath condensate pH and ammonia in cystic fibrosis and response to treatment of acute pulmonary exacerbations. Pediatr Pulmonol 2009; 44:866-72. [PMID: 19670404 DOI: 10.1002/ppul.21078] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Exhaled breath condensate (EBC) pH reflects the acid-base homeostasis of the airway lining fluid and is up to 3 log order lower in various inflammatory lung diseases including asthma, COPD, bronchiectasis, and cystic fibrosis (CF) than in normal controls. The aim of this study was to confirm this finding in CF and determine if there was a significant change in EBC pH after treatment of an acute pulmonary exacerbation. Ten subjects with CF and a pulmonary exacerbation, and 10 healthy age-matched control subjects were studied. EBC was collected at the onset of an acute pulmonary exacerbation and after treatment with intravenous antibiotics (median duration: 14 days (interquartile range, IQR): 12-14) when the exacerbation was considered resolved. The median age for CF patients was 15.9 years (IQR: 13-18.8), compared to 18 years (IQR: 15-24.8) for the control group, P = 0.242. All CF subjects had severe lung disease, median FEV(1) = 41.5% of predicted (IQR: 30.8-46.5%). Median EBC pH in CF subjects at the onset of a pulmonary exacerbation was 6.61 (IQR: 6.17-7.91) compared to median EBC pH of 8.14 (IQR: 7.45-9.08) in the control group, P < 0.02. Median EBC pH after resolution of an exacerbation was 7.02 (IQR: 5.8-8.64), not significantly different (P = 0.667) than during the acute exacerbation. EBC pH decreased in five subjects, increased in three subjects and there was no change in two subjects. There was no correlation between EBC pH and FEV(1) either before or after intravenous antibiotics. EBC ammonia, an important buffer of ASL, was also measured and similarly found to be lower than in normal controls. EBC pH is lower in CF than age-matched controls, and did not change consistently in response to treatment of an acute pulmonary exacerbation.
Collapse
Affiliation(s)
- Sharon Newport
- Division of Pediatric Pulmonology, Maria Fareri Children's Hospital at Westchester Medical Center and New York Medical College, Valhalla, New York, USA.
| | | | | |
Collapse
|
45
|
Gee HY, Kim YW, Jo MJ, Namkung W, Kim JY, Park HW, Kim KS, Kim H, Baba A, Yang J, Kim E, Kim KH, Lee MG. Synaptic scaffolding molecule binds to and regulates vasoactive intestinal polypeptide type-1 receptor in epithelial cells. Gastroenterology 2009; 137:607-17, 617.e1-4. [PMID: 19642226 DOI: 10.1053/j.gastro.2009.01.065] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Vasoactive intestinal polypeptide (VIP) is a principal regulator of fluid and electrolyte secretion in the gastrointestinal system. The VIP type-1 receptor (VPAC1), a class II G-protein-coupled receptor, contains a putative C-terminal PDZ-binding motif. A yeast 2-hybrid screen indicated that the C-terminus of VPAC1 bound to the PDZ domain of synaptic scaffolding molecule (S-SCAM, also known as membrane-associated guanylate kinase inverted-2 [MAGI-2]). We analyzed the association between S-SCAM and VPAC1. METHODS The biochemical properties and physiologic significance of the interaction between VPAC1 and S-SCAM were examined in heterologous expression systems, T84 colonic epithelial cells, and human pancreas and colon tissues using an integrated molecular and physiologic approach. RESULTS The physical interaction between VPAC1 and S-SCAM was confirmed by immunoprecipitation in HEK 293 mammalian cells and human pancreatic and colonic tissues. Immunocytochemical analysis indicated that S-SCAM recruited VPAC1 to the junctional area near the apical end of the lateral membrane in T84 cells. Several lines of evidence revealed that S-SCAM inhibits VPAC1 activation. Overexpression of S-SCAM inhibited VPAC1-mediated cAMP production and agonist-induced VPAC1 internalization in HEK 293 and HeLa cells. In addition, S-SCAM decreased the VPAC1-mediated current through the cystic fibrosis transmembrane conductance regulator in Xenopus oocytes, especially at low concentrations of VIP. Importantly, loss of S-SCAM increased VIP-induced short-circuit currents in T84 monolayers, which endogenously express VPAC1 and S-SCAM. CONCLUSIONS S-SCAM/MAGI-2 interacts with and regulates VPAC1 intracellular localization in epithelial cells and inhibits VPAC1 agonist-induced activation and internalization.
Collapse
Affiliation(s)
- Heon Yung Gee
- Department of Pharmacology and Brain Korea 21 Project for Medical Science, Institute of Gastroenterology, Yonsei University College of Medicine, Seoul, Korea
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Stewart AK, Yamamoto A, Nakakuki M, Kondo T, Alper SL, Ishiguro H. Functional coupling of apical Cl-/HCO3- exchange with CFTR in stimulated HCO3- secretion by guinea pig interlobular pancreatic duct. Am J Physiol Gastrointest Liver Physiol 2009; 296:G1307-17. [PMID: 19342507 PMCID: PMC2697944 DOI: 10.1152/ajpgi.90697.2008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Pancreatic ductal epithelium produces a HCO(3)(-)-rich fluid. HCO(3)(-) transport across ductal apical membranes has been proposed to be mediated by both SLC26-mediated Cl(-)/HCO(3)(-) exchange and CFTR-mediated HCO(3)(-) conductance, with proportional contributions determined in part by axial changes in gene expression and luminal anion composition. In this study we investigated the characteristics of apical Cl(-)/HCO(3)(-) exchange and its functional interaction with Cftr activity in isolated interlobular ducts of guinea pig pancreas. BCECF-loaded epithelial cells of luminally microperfused ducts were alkalinized by acetate prepulse or by luminal Cl(-) removal in the presence of HCO(3)(-)-CO(2). Intracellular pH recovery upon luminal Cl(-) restoration (nominal Cl(-)/HCO(3)(-) exchange) in cAMP-stimulated ducts was largely inhibited by luminal dihydro-DIDS (H(2)DIDS), accelerated by luminal CFTR inhibitor inh-172 (CFTRinh-172), and was insensitive to elevated bath K(+) concentration. Luminal introduction of CFTRinh-172 into sealed duct lumens containing BCECF-dextran in HCO(3)(-)-free, Cl(-)-rich solution enhanced cAMP-stimulated HCO(3)(-) secretion, as calculated from changes in luminal pH and volume. Luminal Cl(-) removal produced, after a transient small depolarization, sustained cell hyperpolarization of approximately 15 mV consistent with electrogenic Cl(-)/HCO(3)(-) exchange. The hyperpolarization was inhibited by H(2)DIDS and potentiated by CFTRinh-172. Interlobular ducts expressed mRNAs encoding CFTR, Slc26a6, and Slc26a3, as detected by RT-PCR. Thus Cl(-)-dependent apical HCO(3)(-) secretion in pancreatic duct is mediated predominantly by an Slc26a6-like Cl(-)/HCO(3)(-) exchanger and is accelerated by inhibition of CFTR. This study demonstrates functional coupling between Cftr and Slc26a6-like Cl(-)/HCO(3)(-) exchange activity in apical membrane of guinea pig pancreatic interlobular duct.
Collapse
Affiliation(s)
- A. K. Stewart
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, Massachusetts; and Human Nutrition, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - A. Yamamoto
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, Massachusetts; and Human Nutrition, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - M. Nakakuki
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, Massachusetts; and Human Nutrition, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - T. Kondo
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, Massachusetts; and Human Nutrition, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - S. L. Alper
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, Massachusetts; and Human Nutrition, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| | - H. Ishiguro
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, Massachusetts; and Human Nutrition, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Japan
| |
Collapse
|
47
|
Hille C, Lahn M, Löhmannsröben HG, Dosche C. Two-photon fluorescence lifetime imaging of intracellular chloride in cockroach salivary glands. Photochem Photobiol Sci 2009; 8:319-27. [DOI: 10.1039/b813797h] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
48
|
Yang D, Shcheynikov N, Zeng W, Ohana E, So I, Ando H, Mizutani A, Mikoshiba K, Muallem S. IRBIT coordinates epithelial fluid and HCO3- secretion by stimulating the transporters pNBC1 and CFTR in the murine pancreatic duct. J Clin Invest 2008; 119:193-202. [PMID: 19033647 DOI: 10.1172/jci36983] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 10/15/2008] [Indexed: 01/01/2023] Open
Abstract
Fluid and HCO3- secretion are vital functions of secretory epithelia. In most epithelia, this entails HCO3- entry at the basolateral membrane, mediated by the Na+-HCO3- cotransporter, pNBC1, and exit at the luminal membrane, mediated by a CFTR-SLC26 transporters complex. Here we report that the protein IRBIT (inositol-1,4,5-trisphosphate [IP3] receptors binding protein released with IP3), a previously identified activator of pNBC1, activates both the basolateral pNBC1 and the luminal CFTR to coordinate fluid and HCO3- secretion by the pancreatic duct. We used video microscopy and ion selective microelectrodes to measure fluid secretion and Cl- and HCO3- concentrations in cultured murine sealed intralobular pancreatic ducts. Short interference RNA-mediated knockdown of IRBIT markedly inhibited ductal pNBC1 and CFTR activities, luminal Cl- absorption and HCO3- secretion, and the associated fluid secretion. Single-channel measurements suggested that IRBIT regulated CFTR by reducing channel mean close time. Furthermore, expression of IRBIT constructs in HEK cells revealed that activation of pNBC1 required only the IRBIT PEST domain, while activation of CFTR required multiple IRBIT domains, suggesting that IRBIT activates these transporters by different mechanisms. These findings define IRBIT as a key coordinator of epithelial fluid and HCO3- secretion and may have implications to all CFTR-expressing epithelia and to cystic fibrosis.
Collapse
Affiliation(s)
- Dongki Yang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Abstract
Disruption of normal gastrointestinal function as a result of infection, hereditary or acquired diseases, or complications of surgical procedures uncovers its important role in acid-base homeostasis. Metabolic acidosis or alkalosis may occur, depending on the nature and volume of the unregulated losses that occur. Investigation into the specific pathophysiology of gastrointestinal disorders has provided important new insights into the normal physiology of ion transport along the gut and has also provided new avenues for treatment. This review provides a brief overview of normal ion transport along the gut and then discusses the pathophysiology and treatment of the metabolic acid-base disorders that occur when normal gut function is disrupted.
Collapse
Affiliation(s)
- F John Gennari
- Department of Medicine, University of Vermont College of Medicine, Burlington, Vermont, USA.
| | | |
Collapse
|
50
|
Lee RJ, Harlow JM, Limberis MP, Wilson JM, Foskett JK. HCO3(-) secretion by murine nasal submucosal gland serous acinar cells during Ca2+-stimulated fluid secretion. ACTA ACUST UNITED AC 2008; 132:161-83. [PMID: 18591422 PMCID: PMC2442172 DOI: 10.1085/jgp.200810017] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Airway submucosal glands contribute to airway surface liquid (ASL) composition and volume, both important for lung mucociliary clearance. Serous acini generate most of the fluid secreted by glands, but the molecular mechanisms remain poorly characterized. We previously described cholinergic-regulated fluid secretion driven by Ca2+-activated Cl− secretion in primary murine serous acinar cells revealed by simultaneous differential interference contrast (DIC) and fluorescence microscopy. Here, we evaluated whether Ca2+-activated Cl− secretion was accompanied by secretion of HCO3−, possibly a critical ASL component, by simultaneous measurements of intracellular pH (pHi) and cell volume. Resting pHi was 7.17 ± 0.01 in physiological medium (5% CO2–25 mM HCO3−). During carbachol (CCh) stimulation, pHi fell transiently by 0.08 ± 0.01 U concomitantly with a fall in Cl− content revealed by cell shrinkage, reflecting Cl− secretion. A subsequent alkalinization elevated pHi to above resting levels until agonist removal, whereupon it returned to prestimulation values. In nominally CO2–HCO3−-free media, the CCh-induced acidification was reduced, whereas the alkalinization remained intact. Elimination of driving forces for conductive HCO3− efflux by ion substitution or exposure to the Cl− channel inhibitor niflumic acid (100 μM) strongly inhibited agonist-induced acidification by >80% and >70%, respectively. The Na+/H+ exchanger (NHE) inhibitor dimethylamiloride (DMA) increased the magnitude (greater than twofold) and duration of the CCh-induced acidification. Gene expression profiling suggested that serous cells express NHE isoforms 1–4 and 6–9, but pharmacological sensitivities demonstrated that alkalinization observed during both CCh stimulation and pHi recovery from agonist-induced acidification was primarily due to NHE1, localized to the basolateral membrane. These results suggest that serous acinar cells secrete HCO3− during Ca2+-evoked fluid secretion by a mechanism that involves the apical membrane secretory Cl− channel, with HCO3− secretion sustained by activation of NHE1 in the basolateral membrane. In addition, other Na+-dependent pHi regulatory mechanisms exist, as evidenced by stronger inhibition of alkalinization in Na+-free media.
Collapse
Affiliation(s)
- Robert J Lee
- Department of Physiology, Division of Medical Genetics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | | | | | | |
Collapse
|