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Palma AG, Kotsias BA. The Effect of Dynasore Upon the Negative Interaction Between ENaC and CFTR Channels in Xenopus laevis Oocytes. J Membr Biol 2022; 255:61-69. [DOI: 10.1007/s00232-021-00212-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 12/22/2021] [Indexed: 11/29/2022]
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Schwingshackl A, Lopez B, Teng B, Luellen C, Lesage F, Belperio J, Olcese R, Waters CM. Hyperoxia treatment of TREK-1/TREK-2/TRAAK-deficient mice is associated with a reduction in surfactant proteins. Am J Physiol Lung Cell Mol Physiol 2017; 313:L1030-L1046. [PMID: 28839101 DOI: 10.1152/ajplung.00121.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 08/15/2017] [Accepted: 08/16/2017] [Indexed: 12/29/2022] Open
Abstract
We previously proposed a role for the two-pore domain potassium (K2P) channel TREK-1 in hyperoxia (HO)-induced lung injury. To determine whether redundancy among the three TREK isoforms (TREK-1, TREK-2, and TRAAK) could protect from HO-induced injury, we now examined the effect of deletion of all three TREK isoforms in a clinically relevant scenario of prolonged HO exposure and mechanical ventilation (MV). We exposed WT and TREK-1/TREK-2/TRAAK-deficient [triple knockout (KO)] mice to either room air, 72-h HO, MV [high and low tidal volume (TV)], or a combination of HO + MV and measured quasistatic lung compliance, bronchoalveolar lavage (BAL) protein concentration, histologic lung injury scores (LIS), cellular apoptosis, and cytokine levels. We determined surfactant gene and protein expression and attempted to prevent HO-induced lung injury by prophylactically administering an exogenous surfactant (Curosurf). HO treatment increased lung injury in triple KO but not WT mice, including an elevated LIS, BAL protein concentration, and markers of apoptosis, decreased lung compliance, and a more proinflammatory cytokine phenotype. MV alone had no effect on lung injury markers. Exposure to HO + MV (low TV) further decreased lung compliance in triple KO but not WT mice, and HO + MV (high TV) was lethal for triple KO mice. In triple KO mice, the HO-induced lung injury was associated with decreased surfactant protein (SP) A and SPC but not SPB and SPD expression. However, these changes could not be explained by alterations in the transcription factors nuclear factor-1 (NF-1), NKX2.1/thyroid transcription factor-1 (TTF-1) or c-jun, or lamellar body levels. Prophylactic Curosurf administration did not improve lung injury scores or compliance in triple KO mice.
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Affiliation(s)
| | - Benjamin Lopez
- Department of Pediatrics, University of California, Los Angeles, California
| | - Bin Teng
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee; and
| | - Charlean Luellen
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee; and
| | - Florian Lesage
- Université Côte d'Azur, Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Laboratory of Excellence "Ion Channel Science and Therapeutics," Valbonne, France
| | - John Belperio
- Department of Pulmonary and Critical Care, University of California, Los Angeles, California
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, University of California, Los Angeles, California
| | - Christopher M Waters
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee; and
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Farinha CM, Matos P. Repairing the basic defect in cystic fibrosis - one approach is not enough. FEBS J 2015; 283:246-64. [PMID: 26416076 DOI: 10.1111/febs.13531] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 09/21/2015] [Accepted: 09/23/2015] [Indexed: 12/16/2022]
Abstract
Cystic fibrosis has attracted much attention in recent years due to significant advances in the pharmacological targeting of the basic defect underlying this recessive disorder: the deficient functional expression of mutant cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels at the apical membrane of epithelial cells. However, increasing evidence points to the reduced efficacy of single treatments, thus reinforcing the need to combine several therapeutic strategies to effectively target the multiple basic defect(s). Protein-repair therapies that use potentiators (activating membrane-located CFTR) or correctors (promoting the relocation of intracellular-retained trafficking mutants of CFTR) in frequent mutations such as F508del and G551D have been put forward and made their way to the clinic with moderate to good efficiency. However, alternative (or additional) approaches targeting the membrane stability of mutant proteins, or correcting the cellular phenotype through a direct effect upon other ion channels (affecting the overall electrolyte transport or simply promoting alternative chloride transport) or targeting less frequent mutations (splicing variants, for example), have been proposed and tested in the field of cystic fibrosis (CF). Here, we cover the different strategies that rely on novel findings concerning the CFTR interactome and signalosome through which it might be possible to further influence the cellular trafficking and post-translational modification machinery (to increase rescued CFTR abundance and membrane stability). We also highlight the new data on strategies aiming at the regulation of sodium absorption or to increase chloride transport through alternative channels. The development and implementation of these complementary approaches will pave the way to combinatorial therapeutic strategies with increased benefit to CF patients.
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Affiliation(s)
- Carlos M Farinha
- BioISI - Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Portugal
| | - Paulo Matos
- BioISI - Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Portugal.,Department of Human Genetics, National Health Institute 'Dr. Ricardo Jorge', Lisboa, Portugal
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Deficiency of the two-pore-domain potassium channel TREK-1 promotes hyperoxia-induced lung injury. Crit Care Med 2014; 42:e692-701. [PMID: 25126877 DOI: 10.1097/ccm.0000000000000603] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES We previously reported the expression of the two-pore-domain K channel TREK-1 in lung epithelial cells and proposed a role for this channel in the regulation of alveolar epithelial cytokine secretion. In this study, we focused on investigating the role of TREK-1 in vivo in the development of hyperoxia-induced lung injury. DESIGN Laboratory animal experiments. SETTING University research laboratory. SUBJECTS Wild-type and TREK-1-deficient mice. INTERVENTIONS Mice were anesthetized and exposed to 1) room air, no mechanical ventilation, 2) 95% hyperoxia for 24 hours, and 3) 95% hyperoxia for 24 hours followed by mechanical ventilation for 4 hours. MEASUREMENTS AND MAIN RESULTS Hyperoxia exposure accentuated lung injury in TREK-1-deficient mice but not controls, resulting in increase in lung injury scores, bronchoalveolar lavage fluid cell numbers, and cellular apoptosis and a decrease in quasi-static lung compliance. Exposure to a combination of hyperoxia and injurious mechanical ventilation resulted in further morphological lung damage and increased lung injury scores and bronchoalveolar lavage fluid cell numbers in control but not TREK-1-deficient mice. At baseline and after hyperoxia exposure, bronchoalveolar lavage cytokine levels were unchanged in TREK-1-deficient mice compared with controls. Exposure to hyperoxia and mechanical ventilation resulted in an increase in bronchoalveolar lavage interleukin-6, monocyte chemotactic protein-1, and tumor necrosis factor-α levels in both mouse types, but the increase in interleukin-6 and monocyte chemotactic protein-1 levels was less prominent in TREK-1-deficient mice than in controls. Lung tissue macrophage inflammatory protein-2, keratinocyte-derived cytokine, and interleukin-1β gene expression was not altered by hyperoxia in TREK-1-deficient mice compared with controls. Furthermore, we show for the first time TREK-1 expression on alveolar macrophages and unimpaired tumor necrosis factor-α secretion from TREK-1-deficient macrophages. CONCLUSIONS TREK-1 deficiency resulted in increased sensitivity of lungs to hyperoxia, but this effect is less prominent if overwhelming injury is induced by the combination of hyperoxia and injurious mechanical ventilation. TREK-1 may constitute a new potential target for the development of novel treatment strategies against hyperoxia-induced lung injury.
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Hobbs CA, Da Tan C, Tarran R. Does epithelial sodium channel hyperactivity contribute to cystic fibrosis lung disease? J Physiol 2013; 591:4377-87. [PMID: 23878362 DOI: 10.1113/jphysiol.2012.240861] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Airway epithelia absorb Na+ through the epithelial Na+ channel (ENaC) and secrete Cl- through the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel. This balance maintains sufficient airway surface liquid hydration to permit efficient mucus clearance, which is needed to maintain sterility of the lung. Cystic fibrosis (CF) is a common autosomal recessive inherited disease caused by mutations in the CFTR gene that lead to the reduction or elimination of the CFTR protein. CF is a multi-organ disease that affects epithelia lining the intestines, lungs, pancreas, sweat ducts and vas deferens, among others. CF lungs are characterized by viscous, dehydrated mucus, persistent neutrophilia and chronic infections. ENaC is negatively regulated by CFTR and, in patients with CF, the absence of CFTR results in a double hit of reduced Cl-/HCO3- and H2O secretion as well as ENaC hyperactivity and increased Na+ and H2O absorption. Together, these effects are hypothesized to trigger mucus dehydration, resulting in a failure to clear mucus. Rehydrating CF mucus has become a recent clinical focus and yields important end-points for clinical trials. However, while ENaC hyperactivity in CF airways has been detected in vivo and in vitro, recent data have brought the role of ENaC in CF lung disease pathogenesis into question. This review will focus on our current understanding of the contribution of ENaC to CF pathogenesis.
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Affiliation(s)
- Carey A Hobbs
- R. Tarran: 7125 Thurston Bowles Building, UNC, Chapel Hill, NC 27599-7248, USA.
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Bakouh N, Chérif-Zahar B, Hulin P, Prié D, Friedlander G, Edelman A, Planelles G. Functional interaction between CFTR and the sodium-phosphate co-transport type 2a in Xenopus laevis oocytes. PLoS One 2012; 7:e34879. [PMID: 22514683 PMCID: PMC3325942 DOI: 10.1371/journal.pone.0034879] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 03/09/2012] [Indexed: 11/25/2022] Open
Abstract
Background A growing number of proteins, including ion transporters, have been shown to interact with Cystic Fibrosis Transmembrane conductance Regulator (CFTR). CFTR is an epithelial chloride channel that is involved in Cystic Fibrosis (CF) when mutated; thus a better knowledge of its functional interactome may help to understand the pathophysiology of this complex disease. In the present study, we investigated if CFTR and the sodium-phosphate co-transporter type 2a (NPT2a) functionally interact after heterologous expression of both proteins in Xenopus laevis oocytes. Methodology/Findings NPT2a was expressed alone or in combination with CFTR in X. laevis oocytes. Using the two-electrode voltage-clamp technique, the inorganic phosphate-induced current (IPi) was measured and taken as an index of NPT2a activity. The maximal IPi for NPT2a substrates was reduced when CFTR was co-expressed with NPT2a, suggesting a decrease in its expression at the oolemna. This was consistent with Western blot analysis showing reduced NPT2a plasma membrane expression in oocytes co-expressing both proteins, whereas NPT2a protein level in total cell lysate was the same in NPT2a- and NPT2a+CFTR-oocytes. In NPT2a+CFTR- but not in NPT2a-oocytes, IPi and NPT2a surface expression were increased upon PKA stimulation, whereas stimulation of Exchange Protein directly Activated by cAMP (EPAC) had no effect. When NPT2a-oocytes were injected with NEG2, a short amino-acid sequence from the CFTR regulatory domain that regulates PKA-dependent CFTR trafficking to the plasma membrane, IPi values and NPT2a membrane expression were diminished, and could be enhanced by PKA stimulation, thereby mimicking the effects of CFTR co-expression. Conclusion/Perspectives We conclude that when both CFTR and NPT2a are expressed in X. laevis oocytes, CFTR confers to NPT2a a cAMPi-dependent trafficking to the membrane. This functional interaction raises the hypothesis that CFTR may play a role in phosphate homeostasis.
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Affiliation(s)
- Naziha Bakouh
- Inserm UMRS-845, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine Paris Descartes, Paris, France
| | - Baya Chérif-Zahar
- Inserm UMRS-845, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine Paris Descartes, Paris, France
| | - Philippe Hulin
- Inserm UMRS-845, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine Paris Descartes, Paris, France
| | - Dominique Prié
- Inserm UMRS-845, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine Paris Descartes, Paris, France
| | - Gérard Friedlander
- Inserm UMRS-845, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine Paris Descartes, Paris, France
| | - Aleksander Edelman
- Inserm UMRS-845, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine Paris Descartes, Paris, France
| | - Gabrielle Planelles
- Inserm UMRS-845, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine Paris Descartes, Paris, France
- * E-mail:
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Abstract
A thin layer of airway surface liquid (ASL) lines the entire surface of the lung and is the first point of contact between the lung and the environment. Surfactants contained within this layer are secreted in the alveolar region and are required to maintain a low surface tension and to prevent alveolar collapse. Mucins are secreted into the ASL throughout the respiratory tract and serve to intercept inhaled pathogens, allergens and toxins. Their removal by mucociliary clearance (MCC) is facilitated by cilia beating and hydration of the ASL by active ion transport. Throughout the lung, secretion, ion transport and cilia beating are under purinergic control. Pulmonary epithelia release ATP into the ASL which acts in an autocrine fashion on P2Y(2) (ATP) receptors. The enzymatic network describes in Chap. 2 then mounts a secondary wave of signaling by surface conversion of ATP into adenosine (ADO), which induces A(2B) (ADO) receptor-mediated responses. This chapter offers a comprehensive description of MCC and the extensive ramifications of the purinergic signaling network on pulmonary surfaces.
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Rubenstein RC, Lockwood SR, Lide E, Bauer R, Suaud L, Grumbach Y. Regulation of endogenous ENaC functional expression by CFTR and ΔF508-CFTR in airway epithelial cells. Am J Physiol Lung Cell Mol Physiol 2010; 300:L88-L101. [PMID: 20935229 DOI: 10.1152/ajplung.00142.2010] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The functional expression of the epithelial sodium channel (ENaC) appears elevated in cystic fibrosis (CF) airway epithelia, but the mechanism by which this occurs is not clear. We tested the hypothesis that the cystic fibrosis transmembrane conductance regulator (CFTR) alters the trafficking of endogenously expressed human ENaC in the CFBE41o⁻ model of CF bronchial epithelia. Functional expression of ENaC, as defined by amiloride-inhibited short-circuit current (I(sc)) in Ussing chambers, was absent under control conditions but present in CFBE41o⁻ parental and ΔF508-CFTR-overexpressing cells after treatment with 1 μM dexamethasone (Dex) for 24 h. The effect of Dex was mimicked by incubation with the glucocorticoid hydrocortisone but not with the mineralocorticoid aldosterone. Application of trypsin to the apical surface to activate uncleaved, "near-silent" ENaC caused an additional increase in amiloride-sensitive I(sc) in the Dex-treated cells and was without effect in the control cells, suggesting that Dex increased ENaC cell surface expression. In contrast, Dex treatment did not stimulate amiloride-sensitive I(sc) in CFBE41o⁻ cells that stably express wild-type (wt) CFTR. CFBE41o⁻ wt cells also had reduced expression of α- and γ-ENaC compared with parental and ΔF508-CFTR-overexpressing cells. Furthermore, application of trypsin to the apical surface of Dex-treated CFBE41o⁻ wt cells did not stimulate amiloride-sensitive I(sc), suggesting that ENaC remained absent from the surface of these cells even after Dex treatment. We also tested the effect of trafficking-corrected ΔF508-CFTR on ENaC functional expression. Incubation with 1 mM 4-phenylbutyrate synergistically increased Dex-induced ENaC functional expression in ΔF508-CFTR-overexpressing cells. These data support the hypothesis that wt CFTR can regulate the whole cell, functional, and surface expression of endogenous ENaC in airway epithelial cells and that absence of this regulation may foster ENaC hyperactivity in CF airway epithelia.
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Affiliation(s)
- Ronald C Rubenstein
- The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, USA.
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Regulation of the epithelial Na+ channel and airway surface liquid volume by serine proteases. Pflugers Arch 2010; 460:1-17. [PMID: 20401730 DOI: 10.1007/s00424-010-0827-z] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 03/10/2010] [Accepted: 03/12/2010] [Indexed: 01/11/2023]
Abstract
Mammalian airways are protected from infection by a thin film of airway surface liquid (ASL) which covers airway epithelial surfaces and acts as a lubricant to keep mucus from adhering to the epithelial surface. Precise regulation of ASL volume is essential for efficient mucus clearance and too great a reduction in ASL volume causes mucus dehydration and mucus stasis which contributes to chronic airway infection. The epithelial Na(+) channel (ENaC) is the rate-limiting step that governs Na(+) absorption in the airways. Recent in vitro and in vivo data have demonstrated that ENaC is a critical determinant of ASL volume and hence mucus clearance. ENaC must be cleaved by either intracellular furin-type proteases or extracellular serine proteases to be active and conduct Na(+), and this process can be inhibited by protease inhibitors. ENaC can be regulated by multiple pathways, and once proteolytically cleaved ENaC may then be inhibited by intracellular second messengers such as cAMP and PIP(2). In the airways, however, regulation of ENaC by proteases seems to be the predominant mode of regulation since knockdown of either endogenous serine proteases such as prostasin, or inhibitors of ENaC proteolysis such as SPLUNC1, has large effects on ENaC activity in airway epithelia. In this review, we shall discuss how ENaC is proteolytically cleaved, how this process can regulate ASL volume, and how its failure to operate correctly may contribute to chronic airway disease.
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Abstract
The epithelial sodium channel (ENaC) represents the rate-limiting step of sodium absorption across airway epithelia and thereby constitutes the major pathway for volume absorption from the airway surface liquid compartment. ENaC dysregulation leads to dehydration of airway surfaces in patients with cystic fibrosis, which in turn disrupts the primary innate lung defense mechanism, mucus clearance. The development of treatment strategies that address this defect is a logical and promising means of preventing or delaying the onset of this lethal lung disease.
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Affiliation(s)
- Scott H Donaldson
- Cystic Fibrosis Research and Treatment Center, 6007B Thurston Bowles Building, CB# 7248, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Dobbs LG, Johnson MD. Alveolar epithelial transport in the adult lung. Respir Physiol Neurobiol 2007; 159:283-300. [PMID: 17689299 DOI: 10.1016/j.resp.2007.06.011] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 05/31/2007] [Accepted: 06/18/2007] [Indexed: 01/11/2023]
Abstract
The alveolar surface comprises >99% of the internal surface area of the lungs. At birth, the fetal lung rapidly converts from a state of net fluid secretion, which is necessary for normal fetal lung development, to a state in which there is a minimal amount of alveolar liquid. The alveolar surface epithelium facing the air compartment is composed of TI and TII cells. The morphometric characteristics of both cell types are fairly constant over a range of mammalian species varying in body weight by a factor of approximately 50,000. From the conservation of size and shape across species, one may infer that both TI and TII cells also have important conserved functions. The regulation of alveolar ion and liquid transport has been extensively investigated using a variety of experimental models, including whole animal, isolated lung, isolated cell, and cultured cell model systems, each with their inherent strengths and weaknesses. The results obtained with different model systems and a variety of different species point to both interesting parallels and some surprising differences. Sometimes it has been difficult to reconcile results obtained with different model systems. In this section, the primary focus will be on aspects of alveolar ion and liquid transport under normal physiologic conditions, emphasizing newer data and describing evolving paradigms of lung ion and fluid transport. We will highlight some of the unanswered questions, outline the similarities and differences in results obtained with different model systems, and describe some of the complex and interweaving regulatory networks.
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Affiliation(s)
- Leland G Dobbs
- Department of Medicine, University of California San Francisco, San Francisco, CA 94118, USA.
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Chambers LA, Rollins BM, Tarran R. Liquid movement across the surface epithelium of large airways. Respir Physiol Neurobiol 2007; 159:256-70. [PMID: 17692578 PMCID: PMC2696130 DOI: 10.1016/j.resp.2007.06.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 06/08/2007] [Accepted: 06/08/2007] [Indexed: 01/25/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator CFTR gene is found on chromosome 7 [Kerem, B., Rommens, J.M., Buchanan, J.A., Markiewicz, D., Cox, T.K., Chakravarti, A., Buchwald, M., Tsui, L.C., 1989. Identification of the cystic fibrosis gene: genetic analysis. Science 245, 1073-1080; Riordan, J.R., Rommens, J.M., Kerem, B., Alon, N., Rozmahel, R., Grzelczak, Z., Zielenski, J., Lok, S., Plavsic, N., Chou, J.L., et al., 1989. Identification of the cystic fibrosis gene: cloning and characterization of complementary DNA. Science 245, 1066-1073] and encodes for a 1480 amino acid protein which is present in the plasma membrane of epithelial cells [Anderson, M.P., Sheppard, D.N., Berger, H.A., Welsh, M.J., 1992. Chloride channels in the apical membrane of normal and cystic fibrosis airway and intestinal epithelia. Am. J. Physiol. 263, L1-L14]. This protein appears to have many functions, but a unifying theme is that it acts as a protein kinase C- and cyclic AMP-regulated Cl(-) channel [Winpenny, J.P., McAlroy, H.L., Gray, M.A., Argent, B.E., 1995. Protein kinase C regulates the magnitude and stability of CFTR currents in pancreatic duct cells. Am. J. Physiol. 268, C823-C828; Jia, Y., Mathews, C.J., Hanrahan, J.W., 1997. Phosphorylation by protein kinase C is required for acute activation of cystic fibrosis transmembrane conductance regulator by protein kinase A. J. Biol. Chem. 272, 4978-4984]. In the superficial epithelium of the conducting airways, CFTR is involved in Cl(-) secretion [Boucher, R.C., 2003. Regulation of airway surface liquid volume by human airway epithelia. Pflugers Arch. 445, 495-498] and also acts as a regulator of the epithelial Na(+) channel (ENaC) and hence Na(+) absorption [Boucher, R.C., Stutts, M.J., Knowles, M.R., Cantley, L., Gatzy, J.T., 1986. Na(+) transport in cystic fibrosis respiratory epithelia. Abnormal basal rate and response to adenylate cyclase activation. J. Clin. Invest. 78, 1245-1252; Stutts, M.J., Canessa, C.M., Olsen, J.C., Hamrick, M., Cohn, J.A., Rossier, B.C., Boucher, R.C., 1995. CFTR as a cAMP-dependent regulator of sodium channels. Science 269, 847-850]. In this chapter, we will discuss the regulation of these two ion channels, and how they can influence liquid movement across the superficial airway epithelium.
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Affiliation(s)
- Lucy A Chambers
- Cystic Fibrosis/Pulmonary Research & Treatment Center, University of North Carolina, Chapel Hill, NC 27599-7248, USA
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