1
|
Schnipper J, Dhennin-Duthille I, Ahidouch A, Ouadid-Ahidouch H. Ion Channel Signature in Healthy Pancreas and Pancreatic Ductal Adenocarcinoma. Front Pharmacol 2020; 11:568993. [PMID: 33178018 PMCID: PMC7596276 DOI: 10.3389/fphar.2020.568993] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/16/2020] [Indexed: 12/11/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is the fourth most common cause of cancer-related deaths in United States and Europe. It is predicted that PDAC will become the second leading cause of cancer-related deaths during the next decades. The development of PDAC is not well understood, however, studies have shown that dysregulated exocrine pancreatic fluid secretion can contribute to pathologies of exocrine pancreas, including PDAC. The major roles of healthy exocrine pancreatic tissue are secretion of enzymes and bicarbonate rich fluid, where ion channels participate to fine-tune these biological processes. It is well known that ion channels located in the plasma membrane regulate multiple cellular functions and are involved in the communication between extracellular events and intracellular signaling pathways and can function as signal transducers themselves. Hereby, they contribute to maintain resting membrane potential, electrical signaling in excitable cells, and ion homeostasis. Despite their contribution to basic cellular processes, ion channels are also involved in the malignant transformation from a normal to a malignant phenotype. Aberrant expression and activity of ion channels have an impact on essentially all hallmarks of cancer defined as; uncontrolled proliferation, evasion of apoptosis, sustained angiogenesis and promotion of invasion and migration. Research indicates that certain ion channels are involved in the aberrant tumor growth and metastatic processes of PDAC. The purpose of this review is to summarize the important expression, localization, and function of ion channels in normal exocrine pancreatic tissue and how they are involved in PDAC progression and development. As ion channels are suggested to be potential targets of treatment they are furthermore suggested to be biomarkers of different cancers. Therefore, we describe the importance of ion channels in PDAC as markers of diagnosis and clinical factors.
Collapse
Affiliation(s)
- Julie Schnipper
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France
| | - Isabelle Dhennin-Duthille
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France
| | - Ahmed Ahidouch
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France.,Department of Biology, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco
| | - Halima Ouadid-Ahidouch
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France
| |
Collapse
|
2
|
Berg P, Svendsen SL, Sorensen MV, Larsen CK, Andersen JF, Jensen-Fangel S, Jeppesen M, Schreiber R, Cabrita I, Kunzelmann K, Leipziger J. Impaired Renal HCO 3 - Excretion in Cystic Fibrosis. J Am Soc Nephrol 2020; 31:1711-1727. [PMID: 32703846 DOI: 10.1681/asn.2020010053] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 04/13/2020] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Patients with cystic fibrosis (CF) do not respond with increased urinary HCO3 - excretion after stimulation with secretin and often present with metabolic alkalosis. METHODS By combining RT-PCR, immunohistochemistry, isolated tubule perfusion, in vitro cell studies, and in vivo studies in different mouse models, we elucidated the mechanism of secretin-induced urinary HCO3 - excretion. For CF patients and CF mice, we developed a HCO3 - drinking test to assess the role of the cystic fibrosis transmembrane conductance regulator (CFTR) in urinary HCO3 -excretion and applied it in the patients before and after treatment with the novel CFTR modulator drug, lumacaftor-ivacaftor. RESULTS β-Intercalated cells express basolateral secretin receptors and apical CFTR and pendrin. In vivo application of secretin induced a marked urinary alkalization, an effect absent in mice lacking pendrin or CFTR. In perfused cortical collecting ducts, secretin stimulated pendrin-dependent Cl-/HCO3 - exchange. In collecting ducts in CFTR knockout mice, baseline pendrin activity was significantly lower and not responsive to secretin. Notably, patients with CF (F508del/F508del) and CF mice showed a greatly attenuated or absent urinary HCO3 --excreting ability. In patients, treatment with the CFTR modulator drug lumacaftor-ivacaftor increased the renal ability to excrete HCO3 -. CONCLUSIONS These results define the mechanism of secretin-induced urinary HCO3 - excretion, explain metabolic alkalosis in patients with CF, and suggest feasibility of an in vivo human CF urine test to validate drug efficacy.
Collapse
Affiliation(s)
- Peder Berg
- Department of Biomedicine, Physiology and Biophysics, Aarhus University, Aarhus, Denmark
| | - Samuel L Svendsen
- Department of Biomedicine, Physiology and Biophysics, Aarhus University, Aarhus, Denmark
| | - Mads V Sorensen
- Department of Biomedicine, Physiology and Biophysics, Aarhus University, Aarhus, Denmark
| | - Casper K Larsen
- Department of Biomedicine, Physiology and Biophysics, Aarhus University, Aarhus, Denmark
| | - Jesper Frank Andersen
- Department of Biomedicine, Physiology and Biophysics, Aarhus University, Aarhus, Denmark
| | - Søren Jensen-Fangel
- Department of Infectious Diseases, Aarhus University Hospital, Aarhus, Denmark
| | - Majbritt Jeppesen
- Department of Infectious Diseases, Aarhus University Hospital, Aarhus, Denmark
| | - Rainer Schreiber
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Ines Cabrita
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, Regensburg, Germany
| | - Jens Leipziger
- Department of Biomedicine, Physiology and Biophysics, Aarhus University, Aarhus, Denmark
| |
Collapse
|
3
|
Webster MJ, Tarran R. Slippery When Wet: Airway Surface Liquid Homeostasis and Mucus Hydration. CURRENT TOPICS IN MEMBRANES 2018; 81:293-335. [PMID: 30243435 DOI: 10.1016/bs.ctm.2018.08.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The ability to regulate cell volume is crucial for normal physiology; equally the regulation of extracellular fluid homeostasis is of great importance. Alteration of normal extracellular fluid homeostasis contributes to the development of several diseases including cystic fibrosis. With regard to the airway surface liquid (ASL), which lies apically on top of airway epithelia, ion content, pH, mucin and protein abundance must be tightly regulated. Furthermore, airway epithelia must be able to switch from an absorptive to a secretory state as required. A heterogeneous population of airway epithelial cells regulate ASL solute and solvent composition, and directly secrete large mucin molecules, antimicrobials, proteases and soluble mediators into the airway lumen. This review focuses on how epithelial ion transport influences ASL hydration and ASL pH, with a specific focus on the roles of anion and cation channels and exchangers. The role of ions and pH in mucin expansion is also addressed. With regard to fluid volume regulation, we discuss the roles of nucleotides, adenosine and the short palate lung and nasal epithelial clone 1 (SPLUNC1) as soluble ASL mediators. Together, these mechanisms directly influence ciliary beating and in turn mucociliary clearance to maintain sterility and to detoxify the airways. Whilst all of these components are regulated in normal airways, defective ion transport and/or mucin secretion proves detrimental to lung homeostasis as such we address how defective ion and fluid transport, and a loss of homeostatic mechanisms, contributes to the development of pathophysiologies associated with cystic fibrosis.
Collapse
Affiliation(s)
- Megan J Webster
- Marsico Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Robert Tarran
- Marsico Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States; Department of Cell Biology & Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| |
Collapse
|
4
|
Cho DY, Zhang S, Lazrak A, Grayson JW, Peña Garcia JA, Skinner DF, Lim DJ, Mackey C, Banks C, Matalon S, Woodworth BA. Resveratrol and ivacaftor are additive G551D CFTR-channel potentiators: therapeutic implications for cystic fibrosis sinus disease. Int Forum Allergy Rhinol 2018; 9:100-105. [PMID: 30152192 DOI: 10.1002/alr.22202] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 06/19/2018] [Accepted: 07/15/2018] [Indexed: 01/04/2023]
Abstract
BACKGROUND Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene result in defective Cl- transport and cause chronic bacterial infections in the upper and lower airways of cystic fibrosis (CF) patients. Ivacaftor is a CFTR potentiator that improves Cl- transport in CF patients with at least 1 copy of the G551D mutation. Resveratrol is also a potent CFTR potentiator that increases determinants of mucociliary transport. The objective of this study is to determine whether resveratrol and ivacaftor improve Cl- secretion in G551D CFTR over either agent alone. METHODS Fisher rat thyroid cells (FRT) transfected with G551D CFTR and human sinonasal epithelial cells (HSNE) containing the CFTR G551D mutation were subjected to pharmacologic manipulation of transepithelial ion transport in Ussing chambers. Activity was further evaluated using whole-cell patch clamp methods in G551D FRT cells. RESULTS In G551D FRT cells, resveratrol (100 μM) and ivacaftor (10 μM) significantly increased Cl- transport (change in short-circuit current, δISC = μA/cm2 ) compared with single-agent and dimethylsulfoxide vehicle controls (resveratrol + ivacaftor 4.97 ± 0.57 vs ivacaftor 0.74 ± 0.12 vs resveratrol 2.96 ± 0.52 vs control 0.74 ± 0.12; p < 0.001). Maximal Cl- secretion (20 μM forskolin) was also significantly enhanced (p < 0.0001). Activity was confirmed in G551D HSNE (resveratrol + ivacaftor 4.48 ± 0.39 vs ivacaftor 1.05 ± 0.11 vs. resveratrol 0.84 ± 0.3 vs control, 0.0 ± 0.02; p < 0.001), and whole-cell patch clamp analysis in G551D FRT cells (resveratrol + ivacaftor -2535 ± 179.3 pA vs ivacaftor -1408.9 ± 101.3 pA vs resveratrol; -766.2 ± 71.2 pA; p < 0.0001). CONCLUSION Additive improvement in G551D CFTR-mediated Cl- secretion suggests that resveratrol could enhance ivacaftor therapy in these patients and improve CF-related rhinosinusitis.
Collapse
Affiliation(s)
- Do-Yeon Cho
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Shaoyan Zhang
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Ahmed Lazrak
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL.,Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Jessica W Grayson
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL
| | - Jaime A Peña Garcia
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL
| | - Daniel F Skinner
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Dong Jin Lim
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Calvin Mackey
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Catherine Banks
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL
| | - Sadis Matalon
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL.,Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Bradford A Woodworth
- Department of Otolaryngology, University of Alabama at Birmingham, Birmingham, AL.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| |
Collapse
|
5
|
Bliss ES, Whiteside E. The Gut-Brain Axis, the Human Gut Microbiota and Their Integration in the Development of Obesity. Front Physiol 2018; 9:900. [PMID: 30050464 PMCID: PMC6052131 DOI: 10.3389/fphys.2018.00900] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 06/21/2018] [Indexed: 12/17/2022] Open
Abstract
Obesity is a global epidemic, placing socioeconomic strain on public healthcare systems, especially within the so-called Western countries, such as Australia, United States, United Kingdom, and Canada. Obesity results from an imbalance between energy intake and energy expenditure, where energy intake exceeds expenditure. Current non-invasive treatments lack efficacy in combating obesity, suggesting that obesity is a multi-faceted and more complex disease than previously thought. This has led to an increase in research exploring energy homeostasis and the discovery of a complex bidirectional communication axis referred to as the gut-brain axis. The gut-brain axis is comprised of various neurohumoral components that allow the gut and brain to communicate with each other. Communication occurs within the axis via local, paracrine and/or endocrine mechanisms involving a variety of gut-derived peptides produced from enteroendocrine cells (EECs), including glucagon-like peptide 1 (GLP1), cholecystokinin (CCK), peptide YY3-36 (PYY), pancreatic polypeptide (PP), and oxyntomodulin. Neural networks, such as the enteric nervous system (ENS) and vagus nerve also convey information within the gut-brain axis. Emerging evidence suggests the human gut microbiota, a complex ecosystem residing in the gastrointestinal tract (GIT), may influence weight-gain through several inter-dependent pathways including energy harvesting, short-chain fatty-acids (SCFA) signalling, behaviour modifications, controlling satiety and modulating inflammatory responses within the host. Hence, the gut-brain axis, the microbiota and the link between these elements and the role each plays in either promoting or regulating energy and thereby contributing to obesity will be explored in this review.
Collapse
Affiliation(s)
- Edward S. Bliss
- School of Health and Wellbeing, University of Southern Queensland, Toowoomba, QLD, Australia
| | | |
Collapse
|
6
|
Andharia N, Hayashi M, Matsuda H. Electrophysiological properties of anion exchangers in the luminal membrane of guinea pig pancreatic duct cells. Pflugers Arch 2018; 470:897-907. [PMID: 29399744 PMCID: PMC5945753 DOI: 10.1007/s00424-018-2116-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 01/10/2018] [Accepted: 01/23/2018] [Indexed: 12/12/2022]
Abstract
The pancreatic duct epithelium secretes the HCO3−-rich pancreatic juice. The HCO3− transport across the luminal membrane has been proposed to be mediated by SLC26A Cl−–HCO3− exchangers. To examine the electrophysiological properties of Cl−–HCO3− exchangers, we directly measured HCO3− conductance in the luminal membrane of the interlobular pancreatic duct cells from guinea pigs using an inside-out patch-clamp technique. Intracellular HCO3− increased the HCO3− conductance with a half-maximal effective concentration value of approximately 30 mM. The selectivity sequence based on permeability ratios was SCN− (1.4) > Cl− (1.2) = gluconate (1.1) = I− (1.1) = HCO3− (1.0) > methanesulfonate (0.6). The sequence of the relative conductance was HCO3− (1.0) > SCN− (0.7) = I− (0.7) > Cl− (0.5) = gluconate (0.4) > methanesulfonate (0.2). The current dependent on intracellular HCO3− was reduced by replacement of extracellular Cl− with gluconate or by H2DIDS, an inhibitor of Cl−–HCO3− exchangers. RT-PCR analysis revealed that the interlobular and main ducts expressed all SLC26A family members except Slc26a5 and Slc26a8. SLC26A1, SLC26A4, SLC26A6, and SLC26A10 were found to be localized to the luminal membrane of the guinea pig pancreatic duct by immunohistochemistry. These results demonstrate that these SLC26A Cl−–HCO3− exchangers may mediate the electrogenic HCO3− transport through the luminal membrane and may be involved in pancreatic secretion in guinea pig ducts.
Collapse
Affiliation(s)
- N Andharia
- Department of Physiology, Kansai Medical University, 2-5-1 Shinmachi, Hirakata, 573-1010, Japan
| | - M Hayashi
- Department of Physiology, Kansai Medical University, 2-5-1 Shinmachi, Hirakata, 573-1010, Japan.
| | - H Matsuda
- Department of Physiology, Kansai Medical University, 2-5-1 Shinmachi, Hirakata, 573-1010, Japan
| |
Collapse
|
7
|
Hohwieler M, Perkhofer L, Liebau S, Seufferlein T, Müller M, Illing A, Kleger A. Stem cell-derived organoids to model gastrointestinal facets of cystic fibrosis. United European Gastroenterol J 2017; 5:609-624. [PMID: 28815024 PMCID: PMC5548342 DOI: 10.1177/2050640616670565] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Accepted: 08/25/2016] [Indexed: 12/16/2022] Open
Abstract
Cystic fibrosis (CF) is one of the most frequently occurring inherited human diseases caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) which lead to ample defects in anion transport and epithelial fluid secretion. Existing models lack both access to early stages of CF development and a coeval focus on the gastrointestinal CF phenotypes, which become increasingly important due increased life span of the affected individuals. Here, we provide a comprehensive overview of gastrointestinal facets of CF and the opportunity to model these in various systems in an attempt to understand and treat CF. A particular focus is given on forward-leading organoid cultures, which may circumvent current limitations of existing models and thereby provide a platform for drug testing and understanding of disease pathophysiology in gastrointestinal organs.
Collapse
Affiliation(s)
- Meike Hohwieler
- Department of Internal Medicine 1, University Medical Centre Ulm, Ulm, Germany
| | - Lukas Perkhofer
- Department of Internal Medicine 1, University Medical Centre Ulm, Ulm, Germany
| | - Stefan Liebau
- Institute of Neuroanatomy, Eberhard Karls University Tuebingen, Oesterbergstr. 3, 72074 Tuebingen, Germany
| | - Thomas Seufferlein
- Department of Internal Medicine 1, University Medical Centre Ulm, Ulm, Germany
| | - Martin Müller
- Department of Internal Medicine 1, University Medical Centre Ulm, Ulm, Germany
| | - Anett Illing
- Department of Internal Medicine 1, University Medical Centre Ulm, Ulm, Germany
| | - Alexander Kleger
- Department of Internal Medicine 1, University Medical Centre Ulm, Ulm, Germany
| |
Collapse
|
8
|
Saint-Criq V, Gray MA. Role of CFTR in epithelial physiology. Cell Mol Life Sci 2016; 74:93-115. [PMID: 27714410 PMCID: PMC5209439 DOI: 10.1007/s00018-016-2391-y] [Citation(s) in RCA: 252] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/20/2022]
Abstract
Salt and fluid absorption and secretion are two processes that are fundamental to epithelial function and whole body fluid homeostasis, and as such are tightly regulated in epithelial tissues. The CFTR anion channel plays a major role in regulating both secretion and absorption in a diverse range of epithelial tissues, including the airways, the GI and reproductive tracts, sweat and salivary glands. It is not surprising then that defects in CFTR function are linked to disease, including life-threatening secretory diarrhoeas, such as cholera, as well as the inherited disease, cystic fibrosis (CF), one of the most common life-limiting genetic diseases in Caucasian populations. More recently, CFTR dysfunction has also been implicated in the pathogenesis of acute pancreatitis, chronic obstructive pulmonary disease (COPD), and the hyper-responsiveness in asthma, underscoring its fundamental role in whole body health and disease. CFTR regulates many mechanisms in epithelial physiology, such as maintaining epithelial surface hydration and regulating luminal pH. Indeed, recent studies have identified luminal pH as an important arbiter of epithelial barrier function and innate defence, particularly in the airways and GI tract. In this chapter, we will illustrate the different operational roles of CFTR in epithelial function by describing its characteristics in three different tissues: the airways, the pancreas, and the sweat gland.
Collapse
Affiliation(s)
- Vinciane Saint-Criq
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, University Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH UK
| | - Michael A. Gray
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, University Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH UK
| |
Collapse
|
9
|
Chen E, Paré JF, Wichmann T, Smith Y. Sub-synaptic localization of Ca v3.1 T-type calcium channels in the thalamus of normal and parkinsonian monkeys. Brain Struct Funct 2016; 222:735-748. [PMID: 27255751 DOI: 10.1007/s00429-016-1242-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 05/20/2016] [Indexed: 11/25/2022]
Abstract
T-type calcium channels (Cav3) are key mediators of thalamic bursting activity, but also regulate single cells excitability, dendritic integration, synaptic strength and transmitter release. These functions are strongly influenced by the subcellular and subsynaptic localization of Cav3 channels along the somatodendritic domain of thalamic cells. In Parkinson's disease, T-type calcium channels dysfunction in the basal ganglia-receiving thalamic nuclei likely contributes to pathological thalamic bursting activity. In this study, we analyzed the cellular, subcellular, and subsynaptic localization of the Cav3.1 channel in the ventral anterior (VA) and centromedian/parafascicular (CM/Pf) thalamic nuclei, the main thalamic targets of basal ganglia output, in normal and parkinsonian monkeys. All thalamic nuclei displayed strong Cav3.1 neuropil immunoreactivity, although the intensity of immunolabeling in CM/Pf was significantly lower than in VA. Ultrastructurally, 70-80 % of the Cav3.1-immunoreactive structures were dendritic shafts. Using immunogold labeling, Cav3.1 was commonly found perisynaptic to asymmetric and symmetric axo-dendritic synapses, suggesting a role of Cav3.1 in regulating excitatory and inhibitory neurotransmission. Significant labeling was also found at non-synaptic sites along the plasma membrane of thalamic neurons. There was no difference in the overall pattern and intensity of immunostaining between normal and parkinsonian monkeys, suggesting that the increased rebound bursting in the parkinsonian state is not driven by changes in Cav3.1 expression. Thus, T-type calcium channels are located to subserve neuronal bursting, but also regulate glutamatergic and non-glutamatergic transmission along the whole somatodendritic domain of basal ganglia-receiving neurons of the primate thalamus.
Collapse
Affiliation(s)
- Erdong Chen
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA, 30329, USA.,Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, GA, 30322, USA
| | - Jean-Francois Paré
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA, 30329, USA.,Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, GA, 30322, USA
| | - Thomas Wichmann
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA, 30329, USA.,Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, GA, 30322, USA.,Department of Neurology, Emory University, Atlanta, GA, 30322, USA
| | - Yoland Smith
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA, 30329, USA. .,Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, GA, 30322, USA. .,Department of Neurology, Emory University, Atlanta, GA, 30322, USA.
| |
Collapse
|
10
|
Melis N, Tauc M, Cougnon M, Bendahhou S, Giuliano S, Rubera I, Duranton C. Revisiting CFTR inhibition: a comparative study of CFTRinh -172 and GlyH-101 inhibitors. Br J Pharmacol 2016; 171:3716-27. [PMID: 24758416 PMCID: PMC4128068 DOI: 10.1111/bph.12726] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 04/04/2014] [Accepted: 04/10/2014] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE For decades, inhibitors of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel have been used as tools to investigate the role and function of CFTR conductance in cystic fibrosis research. In the early 2000s, two new and potent inhibitors of CFTR, CFTRinh-172 and GlyH-101, were described and are now widely used to inhibit specifically CFTR. However, despite some evidence, the effects of both drugs on other types of Cl−-conductance have been overlooked. In this context, we explore the specificity and the cellular toxicity of both inhibitors in CFTR-expressing and non–CFTR-expressing cells. EXPERIMENTAL APPROACH Using patch-clamp technique, we tested the effects of CFTRinh-172 and GlyH-101 inhibitors on three distinct types of Cl− currents: the CFTR-like conductance, the volume-sensitive outwardly rectifying Cl− conductance (VSORC) and finally the Ca2+-dependent Cl− conductance (CaCC). We also explored the effect of both inhibitors on cell viability using live/dead and cell proliferation assays in two different cell lines. KEY RESULTS We confirmed that these two compounds were potent inhibitors of the CFTR-mediated Cl− conductance. However,GlyH-101 also inhibited the VSORC conductance and the CaCC at concentrations used to inhibit CFTR. The CFTRinh-172 did not affect the CaCC but did inhibit the VSORC, at concentrations higher than 5 µM. Neither inhibitor (20 µM; 24 h exposure) affected cell viability, but both were cytotoxic at higher concentrations. CONCLUSIONS AND IMPLICATIONS Both inhibitors affected Cl− conductances apart from CFTR. Our results provided insights into their use in mouse models.
Collapse
Affiliation(s)
- N Melis
- University of Nice-Sophia Antipolis, LP2M CNRS-UMR7370, Faculté de médecine, Nice, France
| | | | | | | | | | | | | |
Collapse
|
11
|
Ghosh A, Boucher RC, Tarran R. Airway hydration and COPD. Cell Mol Life Sci 2015; 72:3637-52. [PMID: 26068443 PMCID: PMC4567929 DOI: 10.1007/s00018-015-1946-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 05/26/2015] [Accepted: 06/01/2015] [Indexed: 02/07/2023]
Abstract
Chronic obstructive pulmonary disease (COPD) is one of the prevalent causes of worldwide mortality and encompasses two major clinical phenotypes, i.e., chronic bronchitis (CB) and emphysema. The most common cause of COPD is chronic tobacco inhalation. Research focused on the chronic bronchitic phenotype of COPD has identified several pathological processes that drive disease initiation and progression. For example, the lung's mucociliary clearance (MCC) system performs the critical task of clearing inhaled pathogens and toxic materials from the lung. MCC efficiency is dependent on: (1) the ability of apical plasma membrane ion channels such as the cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial Na(+) channel (ENaC) to maintain airway hydration; (2) ciliary beating; and (3) appropriate rates of mucin secretion. Each of these components is impaired in CB and likely contributes to the mucus stasis/accumulation seen in CB patients. This review highlights the cellular components responsible for maintaining MCC and how this process is disrupted following tobacco exposure and with CB. We shall also discuss existing therapeutic strategies for the treatment of chronic bronchitis and how components of the MCC can be used as biomarkers for the evaluation of tobacco or tobacco-like-product exposure.
Collapse
Affiliation(s)
- Arunava Ghosh
- Cystic Fibrosis Center/Marsico Lung Institute and the Department of Cell Biology and Physiology, The University of North Carolina, 7102 Marsico Hall, Chapel Hill, NC, 27599-7248, USA
| | - R C Boucher
- Cystic Fibrosis Center/Marsico Lung Institute and the Department of Cell Biology and Physiology, The University of North Carolina, 7102 Marsico Hall, Chapel Hill, NC, 27599-7248, USA
| | - Robert Tarran
- Cystic Fibrosis Center/Marsico Lung Institute and the Department of Cell Biology and Physiology, The University of North Carolina, 7102 Marsico Hall, Chapel Hill, NC, 27599-7248, USA.
| |
Collapse
|
12
|
Lee LTO, Ng SYL, Chu JYS, Sekar R, Harikumar KG, Miller LJ, Chow BKC. Transmembrane peptides as unique tools to demonstrate the in vivo action of a cross-class GPCR heterocomplex. FASEB J 2014; 28:2632-44. [PMID: 24599969 DOI: 10.1096/fj.13-246868] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Angiotensin (ANGII) and secretin (SCT) share overlapping, interdependent osmoregulatory functions in brain, where SCT peptide/receptor function is required for ANGII action, yet the molecular basis is unknown. Since receptors for these peptides (AT1aR, SCTR) are coexpressed in osmoregulatory centers, a possible mechanism is formation of a cross-class receptor heterocomplex. Here, we demonstrate such a complex and its functional importance to modulate signaling. Association of AT1aR with SCTR reduced ability of SCT to stimulate cyclic adenosine monophosphate (cAMP), with signaling augmented in presence of ANGII or constitutively active AT1aR. Several transmembrane (TM) peptides of these receptors were able to affect their conformation within complexes, reducing receptor BRET signals. AT1aR TM1 affected only formation and activity of the heterocomplex, without effect on homomers of either receptor, and reduced SCT-stimulated cAMP responses in cells expressing both receptors. This peptide was active in vivo by injection into mouse lateral ventricle, thereby suppressing water-drinking behavior after hyperosmotic shock, similar to SCTR knockouts. This supports the interpretation that active conformation of AT1aR is a key modulator of cAMP responses induced by SCT stimulation of SCTR. The SCTR/AT1aR complex is physiologically important, providing differential signaling to SCT in settings of hyperosmolality or food intake, modulated by differences in levels of ANGII.
Collapse
Affiliation(s)
- Leo T O Lee
- School of Biological Sciences, University of Hong Kong, Hong Kong, China; and
| | - Stephanie Y L Ng
- School of Biological Sciences, University of Hong Kong, Hong Kong, China; and
| | - Jessica Y S Chu
- School of Biological Sciences, University of Hong Kong, Hong Kong, China; and
| | - Revathi Sekar
- School of Biological Sciences, University of Hong Kong, Hong Kong, China; and
| | - Kaleeckal G Harikumar
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona, USA
| | - Laurence J Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona, USA
| | - Billy K C Chow
- School of Biological Sciences, University of Hong Kong, Hong Kong, China; and
| |
Collapse
|
13
|
Affiliation(s)
- T Grotmol
- Institute for Experimental Medical Research, University of Oslo, Norway
| | | | | | | |
Collapse
|
14
|
Chu JYS, Cheng CYY, Sekar R, Chow BKC. Vagal afferent mediates the anorectic effect of peripheral secretin. PLoS One 2013; 8:e64859. [PMID: 23738005 PMCID: PMC3667839 DOI: 10.1371/journal.pone.0064859] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 04/23/2013] [Indexed: 02/02/2023] Open
Abstract
Secretin (SCT) is a classical peptide hormone that is synthesized and released from the gastrointestinal tract after a meal. We have previously shown that it acts both as a central and peripheral anorectic peptide, and that its central effect is mediated via melanocortin system. As peripheral satiety signals from the gastrointestinal tract can be sent to the brain via the vagal afferent or by crossing the blood-brain barrier (BBB), we therefore sought to investigate the pathway by which peripheral SCT reduces appetite in this study. It is found that bilateral subdiaphragmatic vagotomy and treatment of capsaicin, an excitotoxin for primary afferent neurons, could both block the anorectic effect of peripherally injected SCT. These treatments are found to be capable of blunting i.p. SCT-induced Fos activation in pro-opiomelanocortin (POMC) neurons within the hypothalamic Arcuate Nucleus (Arc). Moreover, we have also found that bilateral midbrain transaction could block feeding reduction by peripheral SCT. Taken together, we conclude that the satiety signals of peripheral SCT released from the gastrointestinal tract are sent via the vagus nerves to the brainstem and subsequently Arc, where it controls central expression of other regulatory peptides to regulate food intake.
Collapse
Affiliation(s)
- Jessica Y. S. Chu
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Carrie Y. Y. Cheng
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Revathi Sekar
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Billy K. C. Chow
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| |
Collapse
|
15
|
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
|
16
|
Mass Spectrometry-Based (GeLC-MS/MS) Comparative Proteomic Analysis of Endoscopically (ePFT) Collected Pancreatic and Gastroduodenal Fluids. Clin Transl Gastroenterol 2012; 3:e14. [PMID: 23238231 PMCID: PMC3367612 DOI: 10.1038/ctg.2012.7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
OBJECTIVES: The secretin-stimulated endoscopic pancreatic function test (ePFT) allows for the safe collection of gastroduodenal and pancreatic fluid from the duodenum. We test the hypothesis that these endoscopically collected fluids have different proteomes. As such, we aim to show that the ePFT method can be used to collect fluid enriched in pancreatic proteins to test for pancreatic function. METHODS: Gastroduodenal and pancreatic fluid were collected sequentially from chronic pancreatitis patients undergoing an ePFT. Proteins from each fluid type were extracted using previously published optimized methods and subjected to GeLC-MS/MS analysis for protein identification and bioinformatics analysis. RESULTS: Mass spectrometry analysis identified proteins that were exclusive in either gastroduodenal (46) or pancreatic fluid (234). Subsequent quantitative analysis revealed proteins that were differentially abundant with statistical significance. As expected, proteolytic enzymes and protease inhibitors were among the differentially detected proteins. The proteases pepsinogens and gastrin were enriched in gastroduodenal fluid, while common pancreatic enzymes (e.g., aminopeptidase N, chymotrypsin C, elastase-3A, trypsin, and carboxypeptidase A1, and elastase 2B) were found in greater abundance in pancreatic fluid. Similarly for protease inhibitors, members of the cystatin family were exclusive to gastroduodenal fluid, while serpins A11, B4, and D1 were exclusive to pancreatic fluid. CONCLUSIONS: We have shown that ePFT collection coupled with mass spectrometry can be used to identify differentially detected proteins in gastroduodenal and pancreatic fluids. The data obtained using GeLC-MS/MS techniques provide further evidence supporting the feasibility of using ePFT-collected fluid to study specific diseases of the upper gastrointestinal tract, such as chronic pancreatitis.
Collapse
|
17
|
Jih KY, Li M, Hwang TC, Bompadre SG. The most common cystic fibrosis-associated mutation destabilizes the dimeric state of the nucleotide-binding domains of CFTR. J Physiol 2011; 589:2719-31. [PMID: 21486785 DOI: 10.1113/jphysiol.2010.202861] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel that belongs to the ATP binding cassette (ABC) superfamily. The deletion of the phenylalanine 508 (ΔF508-CFTR) is the most common mutation among cystic fibrosis (CF) patients. The mutant channels present a severe trafficking defect, and the few channels that reach the plasma membrane are functionally impaired. Interestingly, an ATP analogue, N6-(2-phenylethyl)-2′-deoxy-ATP (P-dATP), can increase the open probability (Po) to ∼0.7, implying that the gating defect of ΔF508 may involve the ligand binding domains, such as interfering with the formation or separation of the dimeric states of the nucleotide-binding domains (NBDs). To test this hypothesis, we employed two approaches developed for gauging the stability of the NBD dimeric states using the patch-clamp technique. We measured the locked-open time induced by pyrophosphate (PPi), which reflects the stability of the full NBD dimer state, and the ligand exchange time for ATP/N6-(2-phenylethyl)-ATP (P-ATP), which measures the stability of the partial NBD dimer state wherein the head of NBD1 and the tail of NBD2 remain associated. We found that both the PPi-induced locked-open time and the ATP/P-ATP ligand exchange time of ΔF508-CFTR channels are dramatically shortened, suggesting that the ΔF508 mutation destabilizes the full and partial NBD dimer states. We also tested if mutations that have been shown to improve trafficking of ΔF508-CFTR, namely the solubilizing mutation F494N/Q637R and ΔRI (deletion of the regulatory insertion), exert any effects on these newly identified functional defects associated with ΔF508-CFTR. Our results indicate that although these mutations increase the membrane expression and function of ΔF508-CFTR, they have limited impact on the stability of both full and partial NBD dimeric states for ΔF508 channels. The structure-function insights gained from this mechanism may provide clues for future drug design.
Collapse
Affiliation(s)
- Kang-Yang Jih
- Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Drive, Columbia, MO 65211, USA
| | | | | | | |
Collapse
|
18
|
Yu YC, Miki H, Nakamura Y, Hanyuda A, Matsuzaki Y, Abe Y, Yasui M, Tanaka K, Hwang TC, Bompadre SG, Sohma Y. Curcumin and genistein additively potentiate G551D-CFTR. J Cyst Fibros 2011; 10:243-52. [PMID: 21441077 DOI: 10.1016/j.jcf.2011.03.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 02/19/2011] [Accepted: 03/01/2011] [Indexed: 12/20/2022]
Abstract
BACKGROUND The G551D mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) is a common cause of cystic fibrosis (CF). G551D-CFTR is characterized by an extremely low open probability despite its normal trafficking to the plasma membrane. Numerous small molecules have been shown to increase the activity of G551D-CFTR presumably by binding to the CFTR protein. METHODS We investigated the effect of curcumin, genistein and their combined application on G551D-CFTR activity using the patch clamp technique. RESULTS Curcumin increased G551D-CFTR whole-cell and single-channel currents less than genistein did at their maximally effective concentrations. However, curcumin further increased the channel activity of G551D-CFTR that had been already maximally potentiated by genistein, up to ~50% of the WT-CFTR level. In addition, the combined application of genistein and curcumin over a lower concentration range synergistically rescued the gating defect of G551D-CFTR. CONCLUSIONS The additive effects between curcumin and genistein not only support the hypothesis that multiple mechanisms are involved in the action of CFTR potentiators, but also pose pharmaceutical implications in the development of drugs for CF pharmacotherapy.
Collapse
Affiliation(s)
- Ying-Chun Yu
- Department of Pharmacology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Cheng CYY, Chu JYS, Chow BKC. Central and peripheral administration of secretin inhibits food intake in mice through the activation of the melanocortin system. Neuropsychopharmacology 2011; 36:459-71. [PMID: 20927047 PMCID: PMC3055665 DOI: 10.1038/npp.2010.178] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Secretin (Sct) is released into the circulation postprandially from the duodenal S-cells. The major functions of Sct originated from the gastrointestinal system are to delay gastric emptying, stimulate fluid secretion from pancreas and liver, and hence optimize the digestion process. In recent years, Sct and its receptor (Sctr) have been identified in discrete nuclei of the hypothalamus, including the paraventricular nucleus (PVN) and the arcuate nucleus (Arc). These nuclei are the primary brain sites that are engaged in regulating body energy homeostasis, thus providing anatomical evidence to support a functional role of Sct in appetite control. In this study, the effect of Sct on feeding behavior was investigated using wild-type (wt), Sct(-/-), and secretin receptor-deficient (Sctr(-/-)) mice. We found that both central and peripheral administration of Sct could induce Fos expression in the PVN and Arc, suggesting the activation of hypothalamic feeding centers by this peptide. Consistent with this notion, Sct was found to increase thyrotropin-releasing hormone and melanocortin-4 receptor (Mc4r) transcripts in the PVN, and augment proopiomelanocortin, but reduces agouti-related protein mRNA expression in the Arc. Injection of Sct was able to suppress food intake in wt mice, but not in Sctr(-/-) mice, and that this effect was abolished upon pretreatment with SHU9119, an antagonist for Mc4r. In summary, our data suggest for the first time that Sct is an anorectic peptide, and that this function is mediated by the melanocortin system.
Collapse
Affiliation(s)
- Carrie Yuen Yee Cheng
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Jessica Yan Shuen Chu
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Billy Kwok Chong Chow
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong SAR, China,School of Biological Sciences, The University of Hong Kong, 4N01, Kadoorie Biological Sciences Building, Pokfulam, Hong Kong SAR, China, Tel: +852 22990850, Fax: 852 25599114, E-mail:
| |
Collapse
|
20
|
Novak I, Wang J, Henriksen KL, Haanes KA, Krabbe S, Nitschke R, Hede SE. Pancreatic bicarbonate secretion involves two proton pumps. J Biol Chem 2010; 286:280-9. [PMID: 20978133 DOI: 10.1074/jbc.m110.136382] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Pancreas secretes fluid rich in digestive enzymes and bicarbonate. The alkaline secretion is important in buffering of acid chyme entering duodenum and for activation of enzymes. This secretion is formed in pancreatic ducts, and studies to date show that plasma membranes of duct epithelium express H(+)/HCO(3)(-) transporters, which depend on gradients created by the Na(+)/K(+)-ATPase. However, the model cannot fully account for high-bicarbonate concentrations, and other active transporters, i.e. pumps, have not been explored. Here we show that pancreatic ducts express functional gastric and non-gastric H(+)-K(+)-ATPases. We measured intracellular pH and secretion in small ducts isolated from rat pancreas and showed their sensitivity to H(+)-K(+) pump inhibitors and ion substitutions. Gastric and non-gastric H(+)-K(+) pumps were demonstrated on RNA and protein levels, and pumps were localized to the plasma membranes of pancreatic ducts. Quantitative analysis of H(+)/HCO(3)(-) and fluid transport shows that the H(+)-K(+) pumps can contribute to pancreatic secretion in several species. Our results call for revision of the bicarbonate transport physiology in pancreas, and most likely other epithelia. Furthermore, because pancreatic ducts play a central role in several pancreatic diseases, it is of high relevance to understand the role of H(+)-K(+) pumps in pathophysiology.
Collapse
Affiliation(s)
- Ivana Novak
- Department of Biology, August Krogh Building, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark.
| | | | | | | | | | | | | |
Collapse
|
21
|
Miki H, Zhou Z, Li M, Hwang TC, Bompadre SG. Potentiation of disease-associated cystic fibrosis transmembrane conductance regulator mutants by hydrolyzable ATP analogs. J Biol Chem 2010; 285:19967-75. [PMID: 20406820 PMCID: PMC2888408 DOI: 10.1074/jbc.m109.092684] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 03/31/2010] [Indexed: 11/06/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel belonging to the ATP-binding cassette transporter superfamily. CFTR is gated by ATP binding and hydrolysis at its two nucleotide-binding domains (NBDs), which dimerize in the presence of ATP to form two ATP-binding pockets (ABP1 and ABP2). Mutations reducing the activity of CFTR result in the genetic disease cystic fibrosis. Two of the most common mutations causing a severe phenotype are G551D and DeltaF508. Previously we found that the ATP analog N(6)-(2-phenylethyl)-ATP (P-ATP) potentiates the activity of G551D by approximately 7-fold. Here we show that 2'-deoxy-ATP (dATP), but not 3'-deoxy-ATP, increases the activity of G551D-CFTR by approximately 8-fold. We custom synthesized N(6)-(2-phenylethyl)-2'-deoxy-ATP (P-dATP), an analog combining the chemical modifications in dATP and P-ATP. This new analog enhances G551D current by 36.2 +/- 5.4-fold suggesting an independent but energetically additive action of these two different chemical modifications. We show that P-dATP binds to ABP1 to potentiate the activity of G551D, and mutations in both sides of ABP1 (W401G and S1347G) decrease its potentiation effect, suggesting that the action of P-dATP takes place at the interface of both NBDs. Interestingly, P-dATP completely rectified the gating abnormality of DeltaF508-CFTR by increasing its activity by 19.5 +/- 3.8-fold through binding to both ABPs. This result highlights the severity of the gating defect associated with DeltaF508, the most prevalent disease-associated mutation. The new analog P-dATP can be not only an invaluable tool to study CFTR gating, but it can also serve as a proof-of-principle that, by combining elements that potentiate the channel activity independently, the increase in chloride transport necessary to reach a therapeutic target is attainable.
Collapse
Affiliation(s)
- Haruna Miki
- From the Dalton Cardiovascular Research Center and
- the Osaka University of Pharmaceutical Sciences, Takatsuki, Osaka 569-1094, Japan
| | - Zhen Zhou
- From the Dalton Cardiovascular Research Center and
| | - Min Li
- From the Dalton Cardiovascular Research Center and
| | - Tzyh-Chang Hwang
- From the Dalton Cardiovascular Research Center and
- the Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri 65211 and
| | | |
Collapse
|
22
|
Kim D, Steward MC. The role of CFTR in bicarbonate secretion by pancreatic duct and airway epithelia. THE JOURNAL OF MEDICAL INVESTIGATION 2010; 56 Suppl:336-42. [PMID: 20224219 DOI: 10.2152/jmi.56.336] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The secretory epithelia of the pancreatic duct and airway share the ability to generate HCO(3)(-)-rich fluids. They both express CFTR (cystic fibrosis transmembrane conductance regulator) at the apical membrane and both are adversely affected by cystic fibrosis. CFTR is predominantly a Cl(-) channel, and it is widely believed that HCO(3)(-) secretion in the pancreatic duct is mediated mainly by a Cl(-)/HCO(3)(-) exchanger at the apical membrane. Studies on airway epithelia, however, have suggested that CFTR, despite its low permeability to HCO(3)(-), may nonetheless be directly responsible for HCO(3)(-) secretion across the apical membrane. This article reviews recent work that has re-examined both of these hypotheses.
Collapse
Affiliation(s)
- Dusik Kim
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | | |
Collapse
|
23
|
Abstract
Metabolic pathologies such as Type 2 Diabetes have become a major health problem for worldwide populations. Unfortunately, efforts to cure and especially to prevent these significant global problems have so far been met with disappointment. Recently, the involvement of the gut-derived hormonal dysregulation in the development of obesity-related disturbances has been intensively studied. For instance, studies of gut-derived peptides such as peptide YY 3-36, glucagon-like peptide-1, oxyntomodulin and, more recently, ghrelin have significantly improved our understanding of mechanisms underlying weight and metabolic regulation. Even though early reports of the existence of secretin, the first peptide hormone to be described, date back as far as 1825, so much and yet so little is still known about its physiological role in mammals, including humans. However, recent years have provided a better understanding of how the release of secretin is regulated by enteral secretagogues. On the other hand, most basic questions about its role in the post-prandial regulation of metabolic functions in normal and pathophysiological conditions remain to be elucidated. The present work intends to review the physiology of secretin along with its central and peripheral outcomes on metabolic functions.
Collapse
Affiliation(s)
- D H St-Pierre
- Division of Endocrinology, Diabetology and Metabolism, Department of Internal Medicine, Ospedale Molinette, University of Turin, Turin, Italy
| | | |
Collapse
|
24
|
Treharne KJ, Xu Z, Chen JH, Best OG, Cassidy DM, Gruenert DC, Hegyi P, Gray MA, Sheppard DN, Kunzelmann K, Mehta A. Inhibition of protein kinase CK2 closes the CFTR Cl channel, but has no effect on the cystic fibrosis mutant deltaF508-CFTR. Cell Physiol Biochem 2009; 24:347-60. [PMID: 19910675 DOI: 10.1159/000257427] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2009] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Deletion of phenylalanine-508 (DeltaF508) from the first nucleotide-binding domain (NBD1) in the wild-type cystic fibrosis (CF) transmembrane-conductance regulator (wtCFTR) causes CF. However, the mechanistic relationship between DeltaF508-CFTR and the diversity of CF disease is unexplained. The surface location of F508 on NBD1 creates the potential for protein-protein interactions and nearby, lies a consensus sequence (SYDE) reported to control the pleiotropic protein kinase CK2. METHODS Electrophysiology, immunofluorescence and biochemistry applied to CFTR-expressing cells, Xenopus oocytes, pancreatic ducts and patient biopsies. RESULTS Irrespective of PKA activation, CK2 inhibition (ducts, oocytes, cells) attenuates CFTR-dependent Cl(-) transport, closing wtCFTR in cell-attached membrane patches. CK2 and wtCFTR co-precipitate and CK2 co-localized with wtCFTR (but not DeltaF508-CFTR) in apical membranes of human airway biopsies. Comparing wild-type and DeltaF508CFTR expressing oocytes, only DeltaF508-CFTR Cl(-) currents were insensitive to two CK2 inhibitors. Furthermore, wtCFTR was inhibited by injecting a peptide mimicking the F508 region, whereas the DeltaF508-equivalent peptide had no effect. CONCLUSIONS CK2 controls wtCFTR, but not DeltaF508-CFTR. Others find that peptides from the F508 region of NBD1 allosterically control CK2, acting through F508. Hence, disruption of CK2-CFTR interaction by DeltaF508-CFTR might disrupt multiple, membrane-associated, CK2-dependent pathways, creating a new molecular disease paradigm for deleted F508 in CFTR.
Collapse
Affiliation(s)
- Kate J Treharne
- Centre for Cardiovascular and Lung Biology, University of Dundee, Ninewells Hospital, UK
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Ducts isolated from the pancreas of CFTR-null mice secrete fluid. Pflugers Arch 2009; 459:203-14. [PMID: 19655163 DOI: 10.1007/s00424-009-0704-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 07/21/2009] [Indexed: 01/01/2023]
Abstract
The pancreatic pathology in cystic fibrosis (CF) is normally attributed to the failure of ductal fluid secretion resulting from the lack of functional CF transmembrane conductance regulator (CFTR). However, murine models of CF show little or no pancreatic pathology. To resolve this dichotomy we analysed the transport mechanisms involved in fluid and electrolyte secretion by pancreatic ducts isolated from CFTR-null mice. Experiments were performed on cultured interlobular duct segments isolated from the pancreas of the Cftr(tm1Cam) strain of CFTR-null mouse. Fluid secretion to the closed luminal space was measured by video microscopy. The secretory response of ducts isolated from CF mice to cAMP-elevating agonists forskolin and secretin was significantly reduced compared with wild type but not abolished. The Cl(-)- and HCO(3) (-) -dependent components of the ductal secretion were affected equally by the absence of CFTR. The secretory response to carbachol stimulation was unaltered in CF ducts. Loading the ductal cells with the Ca2+ chelator BAPTA completely abolished carbachol-evoked secretion, but did not affect forskolin-evoked secretion in CF or wild-type ducts. We conclude that pancreatic duct cells from CF mice can secrete a significant amount of water and electrolytes by a cAMP-stimulated mechanism that is independent of CFTR and cannot be ascribed to the activation of calcium-activated chloride channels.
Collapse
|
26
|
Lam IPY, Siu FKY, Chu JYS, Chow BKC. Multiple actions of secretin in the human body. INTERNATIONAL REVIEW OF CYTOLOGY 2008; 265:159-90. [PMID: 18275888 DOI: 10.1016/s0074-7696(07)65004-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The discovery of secretin initiated the field of endocrinology. Over the past century, multiple gastrointestinal functions of secretin have been extensively studied, and it was discovered that the principal function of this peptide in the gastrointestinal system is to facilitate digestion and to provide protection. In view of the late identification of secretin and the secretin receptor in various tissues, including the central nervous system, the pleiotropic functions of secretin have more recently been an area of intense focus. Secretin is a classical hormone, and recent studies clearly showed secretin's involvement in neural and neuroendocrine pathways, although the neuroactivity and neural regulation of its release are yet to be elucidated. This chapter reviews our current understanding of the pleiotropic actions of secretin with a special focus on the hormonal and neural interdependent pathways that mediate these actions.
Collapse
Affiliation(s)
- Ian P Y Lam
- Department of Zoology, University of Hong Kong, Hong Kong, China
| | | | | | | |
Collapse
|
27
|
Novak I, Hede SE, Hansen MR. Adenosine receptors in rat and human pancreatic ducts stimulate chloride transport. Pflugers Arch 2007; 456:437-47. [PMID: 18057956 DOI: 10.1007/s00424-007-0403-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Accepted: 11/15/2007] [Indexed: 11/26/2022]
Abstract
Previously, we have shown that pancreatic acini release adenosine triphosphate (ATP) and ATP-handling enzymes, and pancreatic ducts express various purinergic P2 receptors. The aim of the present study was to establish whether pancreatic ducts also express adenosine receptors and whether these could be involved in secretory processes, which involve cystic fibrosis transmembrane regulator (CFTR) Cl- channels or Ca2+-activated Cl- channels and H(+)/HCO(-)(3) transporters. Reverse transcriptase polymerase chain reaction analysis on rat pancreatic ducts and human duct cell adenocarcinoma lines showed that they express A1, A2A, A2B, and A3 receptors. Real-time PCR revealed relatively low messenger RNA levels of adenosine receptors compared to beta-actin; the rank order for the receptors was A2A>A2B>or=A3>>A1 for rat pancreas and A2B>A2A>>A3>or=A1 for duct cell lines. Whole-cell patch-clamp recordings on rat pancreatic ducts showed that, in about half of the recordings, adenosine depolarized the membrane voltage, and this was because of the opening of Cl- channels. Using a Cl--sensitive fluorophore and single-cell imaging on duct cell lines, it was found that 58% of PANC-1 cells responded to adenosine, whereas only 9% of CFPAC-1 cells responded. Adenosine elicited Ca2+ signals only in a few rat and human duct cells, which did not seem to correlate with Cl- signals. A2A receptors were localized in the luminal membranes of rat pancreatic ducts, plasma membrane of many PANC-1 cells, but only a few CFPAC-1 cells. Taken together, our data indicate that A2A receptors open Cl- channels in pancreatic ducts cells with functional CFTR. We propose that adenosine can stimulate pancreatic secretion and, thereby, is an active player in the acini-to-duct signaling.
Collapse
Affiliation(s)
- Ivana Novak
- Department of Biosciences, August Krogh Building, University of Copenhagen, Universitetsparken 13, 2100 Copenhagen, Denmark.
| | | | | |
Collapse
|
28
|
Siu FKY, Lam IPY, Chu JYS, Chow BKC. Signaling mechanisms of secretin receptor. ACTA ACUST UNITED AC 2006; 137:95-104. [PMID: 16930743 DOI: 10.1016/j.regpep.2006.02.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 02/14/2006] [Accepted: 02/27/2006] [Indexed: 10/24/2022]
Abstract
Secretin, a 27-amino acid gastrointestinal peptide, was initially discovered based on its activities in stimulating pancreatic juice. In the past 20 years, secretin was demonstrated to exhibit pleiotropic functions in many different tissues and more importantly, its role as a neuropeptide was substantiated. To carry out its activities in the central nervous system and in peripheral organs, secretin interacts specifically with one known receptor. Secretin receptor, a member of guanine nucleotide-binding protein (G protein)-coupled receptor (GPCR) in the secretin/VIP/glucagon subfamily, possesses the characteristics of GPCR with seven conserved transmembrane domains, a relatively large amino-terminal extracellular domain and an intracellular carboxyl terminus. The structural features and signal transduction pathways of the secretin receptor in various tissues are reviewed in this article.
Collapse
Affiliation(s)
- Francis K Y Siu
- Department of Zoology, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, PR China
| | | | | | | |
Collapse
|
29
|
Burghardt B, Nielsen S, Steward MC. The Role of Aquaporin Water Channels in Fluid Secretion by the Exocrine Pancreas. J Membr Biol 2006; 210:143-53. [PMID: 16868672 DOI: 10.1007/s00232-005-0852-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Indexed: 01/04/2023]
Abstract
The mammalian exocrine pancreas secretes a near-isosmotic fluid over a wide osmolarity range. The role of aquaporin (AQP) water channels in this process is now becoming clearer. AQP8 water channels, which were initially cloned from rat pancreas, are expressed at the apical membrane of pancreatic acinar cells and contribute to their osmotic permeability. However, the acinar cells secrete relatively little fluid and there is no obvious defect in pancreatic function in AQP8 knockout mice. Most of the fluid secreted by the pancreas is generated by ductal epithelial cells, which comprise only a small fraction of the gland mass. In the human pancreas, secretion occurs mainly in the intercalated ducts, where the epithelial cells express abundant AQP1 and AQP5 at the apical membrane and AQP1 alone at the basolateral membrane. In the rat and mouse, fluid secretion occurs mainly in the interlobular ducts where AQP1 and AQP5 are again co-localized at the apical membrane but appear to be expressed at relatively low levels. Nonetheless, the transepithelial osmotic permeability of rat interlobular ducts is sufficient to support near-isosmotic fluid secretion at observed rates. Furthermore, apical, but not basolateral, application of Hg(2+) significantly reduces the transepithelial osmotic permeability, suggesting that apical AQP1 and AQP5 may contribute significantly to fluid secretion. The apparently normal fluid output of the pancreas in AQP1 knockout mice may reflect the presence of AQP5 at the apical membrane.
Collapse
Affiliation(s)
- B Burghardt
- Molecular Oral Biology Research Group, Department of Oral Biology, Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary
| | | | | |
Collapse
|
30
|
Noel S, Faveau C, Norez C, Rogier C, Mettey Y, Becq F. Discovery of pyrrolo[2,3-b]pyrazines derivatives as submicromolar affinity activators of wild type, G551D, and F508del cystic fibrosis transmembrane conductance regulator chloride channels. J Pharmacol Exp Ther 2006; 319:349-59. [PMID: 16829626 DOI: 10.1124/jpet.106.104521] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) represents the main Cl(-) channel in the apical membrane of epithelial cells for cAMP-dependent Cl(-) secretion. Here we report on the synthesis and screening of a small library of 6-phenylpyrrolo[2,3-b]pyrazines (named RP derivatives) evaluated as activators of wild-type CFTR, G551D-CFTR, and F508del-CFTR Cl(-) channels. Iodide efflux and whole-cell patch-clamp recordings analysis identified RP107 [7-n-butyl-6-(4-hydroxyphenyl)[5H]-pyrrolo[2,3-b]pyrazine] as a submicromolar activator of wild-type (WT)-CFTR [human airway epithelial Calu-3 and WT-CFTR-Chinese hamster ovary (CHO) cells], G551D-CFTR (G551D-CFTR-CHO cells), and F508del-CFTR (in temperature-corrected human airway epithelial F508del/F508del CF15 cells). The structural analog RP108 [7-n-butyl-6-(4-chlorophenyl)[5H]pyrrolo[2,3-b]pyrazine], contrary to RP107, was a less potent activator only at micromolar concentrations. RP107 and RP108 did not have any effect on the cellular cAMP level. Activation was potentiated by low concentration of forskolin and inhibited by glibenclamide and CFTR(inh)-172 [3-[(3-trifluoromethyl)phenyl]-5-[(4-carboxyphenyl-)methylene]-2-thioxo-4-thiazolidinone]but not by calixarene or DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid). Finally, we found significant stimulation of short circuit current (I(sc)) by RP107 (EC(50) = 89 nM) and RP108 (EC(50) = 103 microM) on colon of Cftr(+)(/)(+) but not of Cftr(-/-) mice mounted in Ussing chamber. Stimulation of I(sc) was inhibited by glibenclamide but not affected by DIDS. These results show that RP107 stimulates wild-type CFTR and mutated CFTR, with submicromolar affinity by a cAMP-independent mechanism. Our preliminary structure-activity relationship study identified 4-hydroxyphenyl and 7-n-butyl as determinants required for activation of CFTR. The potency of these agents indicates that compounds in this class may be of therapeutic benefit in CFTR-related diseases, including cystic fibrosis.
Collapse
Affiliation(s)
- Sabrina Noel
- IPBC CNRS UMR 6187, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
| | | | | | | | | | | |
Collapse
|
31
|
Abstract
In many species the pancreatic duct epithelium secretes HCO3- ions at a concentration of around 140 mM by a mechanism that is only partially understood. We know that HCO3- uptake at the basolateral membrane is achieved by Na+-HCO3- cotransport and also by a H+-ATPase and Na+/H+ exchanger operating together with carbonic anhydrase. At the apical membrane, the secretion of moderate concentrations of HCO3- can be explained by the parallel activity of a Cl-/HCO3- exchanger and a Cl- conductance, either the cystic fibrosis transmembrane conductance regulator (CFTR) or a Ca2+-activated Cl- channel (CaCC). However, the sustained secretion of HCO3- into a HCO- -rich luminal fluid cannot be explained by conventional Cl-/HCO3- exchange. HCO3- efflux across the apical membrane is an electrogenic process that is facilitated by the depletion of intracellular Cl-, but it remains to be seen whether it is mediated predominantly by CFTR or by an electrogenic SLC26 anion exchanger.
Collapse
Affiliation(s)
- Martin C Steward
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
| | | | | |
Collapse
|
32
|
Dérand R, Montoni A, Bulteau-Pignoux L, Janet T, Moreau B, Muller JM, Becq F. Activation of VPAC1 receptors by VIP and PACAP-27 in human bronchial epithelial cells induces CFTR-dependent chloride secretion. Br J Pharmacol 2004; 141:698-708. [PMID: 14744818 PMCID: PMC1574226 DOI: 10.1038/sj.bjp.0705597] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
1. In the human airway epithelium, VIP/PACAP receptors are distributed in nerve fibers and in epithelial cells but their role in transepithelial ion transport have not been reported. Here, we show that human bronchial epithelial Calu-3 cells expressed the VPAC(1) receptor subtype which shares similar high affinity for VIP and PACAP-27. 2. The stoichiometric binding parameters characterizing the (125)I-VIP and (125)I-PACAP-27 binding to these receptors were determined. 3. We found that VIP (EC(50) approximately 7.6 nM) and PACAP-27 (EC(50) approximately 10 nM) stimulated glibenclamide-sensitive and DIDS-insensitive iodide efflux in Calu-3 cells. 4. The protein kinase A (PKA) inhibitor, H-89 and the protein kinase C (PKC) inhibitor, chelerythrine chloride prevented activation by both peptides demonstrating that PKA and PKC are part of the signaling pathway. This profile corresponds to the pharmacological signature of CFTR. 5. In the cystic fibrosis airway epithelial IB3-1 cell lacking functional CFTR but expressing VPAC(1) receptors, neither VIP, PACAP-27 nor forskolin stimulated chloride transport. 6. Ussing chamber experiments demonstrated stimulation of CFTR-dependent short-circuit currents by VIP or PACAP-27 applied to the basolateral but not to the apical side of Calu-3 cells monolayers. 7. This study shows the stimulation in human bronchial epithelial cells of CFTR-dependent chloride secretion following activation by VIP and PACAP-27 of basolateral VPAC(1) receptors.
Collapse
Affiliation(s)
- Renaud Dérand
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR 6558 CNRS, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
| | - Alicia Montoni
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR 6558 CNRS, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
| | - Laurence Bulteau-Pignoux
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR 6558 CNRS, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
| | - Thierry Janet
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR 6558 CNRS, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
| | - Bertrand Moreau
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR 6558 CNRS, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
| | - Jean-Marc Muller
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR 6558 CNRS, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
| | - Frédéric Becq
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR 6558 CNRS, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
- Author for correspondence:
| |
Collapse
|
33
|
Gross E, Kurtz I. Structural determinants and significance of regulation of electrogenic Na(+)-HCO(3)(-) cotransporter stoichiometry. Am J Physiol Renal Physiol 2002; 283:F876-87. [PMID: 12372762 DOI: 10.1152/ajprenal.00148.2002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Na(+)-HCO(3)(-) cotransporters play an important role in intracellular pH regulation and transepithelial HCO(3)(-) transport in various tissues. Of the characterized members of the HCO(3)(-) transporter superfamily, NBC1 and NBC4 proteins are known to be electrogenic. An important functional property of electrogenic Na(+)-HCO(3)(-) cotransporters is their HCO(3)(-):Na(+) coupling ratio, which sets the transporter reversal potential and determines the direction of Na(+)-HCO(3)(-) flux. Recent studies have shown that the HCO(3)(-):Na(+) transport stoichiometry of NBC1 proteins is either 2:1 or 3:1 depending on the cell type in which the transporters are expressed, indicating that the HCO(3)(-):Na(+) coupling ratio can be regulated. Mutational analysis has been very helpful in revealing the molecular mechanisms and signaling pathways that modulate the coupling ratio. These studies have demonstrated that PKA-dependent phosphorylation of the COOH terminus of NBC1 proteins alters the transport stoichiometry. This cAMP-dependent signaling pathway provides HCO(3)(-) -transporting epithelia with an efficient mechanism for modulating the direction of Na(+)-HCO(3)(-) flux through the cotransporter.
Collapse
Affiliation(s)
- Eitan Gross
- Departments of Urology and Physiology and Biophysics, Case Western Reserve University, and Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
| | | |
Collapse
|
34
|
Ishiguro H, Steward MC, Sohma Y, Kubota T, Kitagawa M, Kondo T, Case RM, Hayakawa T, Naruse S. Membrane potential and bicarbonate secretion in isolated interlobular ducts from guinea-pig pancreas. J Gen Physiol 2002; 120:617-28. [PMID: 12407075 PMCID: PMC2229553 DOI: 10.1085/jgp.20028631] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The interlobular duct cells of the guinea-pig pancreas secrete HCO(3)(-) across their luminal membrane into a HCO(3)(-)-rich (125 mM) luminal fluid against a sixfold concentration gradient. Since HCO(3)(-) transport cannot be achieved by luminal Cl-/HCO(3)(-) exchange under these conditions, we have investigated the possibility that it is mediated by an anion conductance. To determine whether the electrochemical potential gradient across the luminal membrane would favor HCO(3)(-) efflux, we have measured the intracellular potential (V(m)) in microperfused, interlobular duct segments under various physiological conditions. When the lumen was perfused with a 124 mM Cl- -25 mM HCO(3)(-) solution, a condition similar to the basal state, the resting potential was approximately -60 mV. Stimulation with dbcAMP or secretin caused a transient hyperpolarization (approximately 5 mV) due to activation of electrogenic Na+-HCO(3)(-) cotransport at the basolateral membrane. This was followed by depolarization to a steady-state value of approximately -50 mV as a result of anion efflux across the luminal membrane. Raising the luminal HCO(3)(-) concentration to 125 mM caused a hyperpolarization (approximately 10 mV) in both stimulated and unstimulated ducts. These results can be explained by a model in which the depolarizing effect of Cl- efflux across the luminal membrane is minimized by the depletion of intracellular Cl- and offset by the hyperpolarizing effects of Na+-HCO(3)(-) cotransport at the basolateral membrane. The net effect is a luminally directed electrochemical potential gradient for HCO(3)(-) that is sustained during maximal stimulation. Our calculations indicate that the electrodiffusive efflux of HCO(3)(-) to the lumen via CFTR, driven by this gradient, would be sufficient to fully account for the observed secretory flux of HCO(3)(-).
Collapse
Affiliation(s)
- H Ishiguro
- Internal Medicine II, Nagoya University School of Medicine, Showa-ku, Nagoya 466-8550, Japan.
| | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Ishiguro H, Naruse S, Kitagawa M, Mabuchi T, Kondo T, Hayakawa T, Case RM, Steward MC. Chloride transport in microperfused interlobular ducts isolated from guinea-pig pancreas. J Physiol 2002; 539:175-89. [PMID: 11850511 PMCID: PMC2290131 DOI: 10.1113/jphysiol.2001.012490] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2001] [Accepted: 11/12/2001] [Indexed: 11/08/2022] Open
Abstract
Isolated interlobular ducts from the guinea-pig pancreas secrete a HCO3--rich fluid in response to secretin. To determine the role of Cl- transporters in this process, intracellular Cl- concentration ([Cl-]i) was measured in ducts loaded with the Cl--sensitive fluoroprobe, 6-methoxy-N-ethylquinolinium chloride (MEQ). [Cl-]i decreased when the luminal Cl- concentration was reduced. This effect was stimulated by forskolin, was not dependent on HCO3- and was not inhibited by application of the anion channel/transporter inhibitor H2DIDS to the luminal membrane. It is therefore attributed to a cAMP-stimulated Cl- conductance, probably the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel. [Cl-]i also decreased when the basolateral Cl- concentration was reduced. This effect was not stimulated by forskolin, was largely dependent on HCO3- and was inhibited by basolateral H2DIDS. It is therefore mediated mainly by Cl-/HCO3- exchange. With high Cl- and low HCO3- concentrations in the lumen, steady-state [Cl-]i was 25-35 mM in unstimulated cells. Stimulation with forskolin caused [Cl-]i to increase by approximately 4 mM due to activation of the luminal anion exchanger. With low Cl- and high HCO3- concentrations in the lumen to simulate physiological conditions, steady-state [Cl-]i was 10-15 mM in unstimulated cells. Upon stimulation with forskolin, [Cl-]i fell to approximately 7 mM due to increased Cl- efflux via the luminal conductance. We conclude that, during stimulation under physiological conditions, [Cl-]i decreases to very low levels in guinea-pig pancreatic duct cells, largely as a result of the limited capacity of the basolateral transporters for Cl- uptake. The resulting lack of competition from intracellular Cl- may therefore favour HCO3- secretion via anion conductances in the luminal membrane, possibly CFTR.
Collapse
Affiliation(s)
- H Ishiguro
- Internal Medicine II and Human Nutrition, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466 8550, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Affiliation(s)
- I Novak
- August Krogh Institute, Copenhagen University, DK-2100 Copenhagen, Denmark
| |
Collapse
|
37
|
Ishiguro H, Naruse S, Kitagawa M, Suzuki A, Yamamoto A, Hayakawa T, Case RM, Steward MC. CO2 permeability and bicarbonate transport in microperfused interlobular ducts isolated from guinea-pig pancreas. J Physiol 2000; 528 Pt 2:305-15. [PMID: 11034620 PMCID: PMC2270129 DOI: 10.1111/j.1469-7793.2000.00305.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Permeabilities of the luminal and basolateral membranes of pancreatic duct cells to CO2 and HCO3- were examined in interlobular duct segments isolated from guinea-pig pancreas. Intracellular pH (pHi) was measured by microfluorometry in unstimulated, microperfused ducts loaded with the pH-sensitive fluoroprobe 2'7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). When HCO3-/CO2 was admitted to the bath, pHi decreased transiently as a result of CO2 diffusion and then increased to a higher value as a result of HCO3- uptake across the basolateral membrane by Na+-HCO3- cotransport. When HCO3-/CO2 was admitted to the lumen, pHi again decreased but no subsequent increase was observed, indicating that the luminal membrane was permeable to CO2 but did not allow HCO3- entry to the cells from the lumen. Only when the luminal HCO3- concentration was raised above 125 mM was HCO3- entry detected. The same was true of duct cells stimulated with forskolin. Recovery of pHi from an acid load, induced by exposure to an NH4+ pulse, was dependent on basolateral but not luminal Na+ and could be blocked by basolateral application of methylisobutylamiloride and H2DIDS. This indicates that the Na+-H+ exchangers and Na+-HCO3- cotransporters are located exclusively at the basolateral membrane. In the presence of HCO3-/CO2, substitution of basolateral Cl- with glucuronate caused larger increases in pHi than substitution of luminal Cl-. This suggests that the anion exchanger activity in the basolateral membrane is greater than that in the luminal membrane. We conclude that the luminal and basolateral membranes are both freely permeable to CO2, but while the basolateral membrane has both uptake and efflux pathways for HCO3-, the luminal membrane presents a significant barrier to the re-entry of secreted HCO3-, largely through the inhibition of the luminal anion exchanger by high luminal HCO3- concentrations.
Collapse
Affiliation(s)
- H Ishiguro
- Internal Medicine II, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
38
|
O'Reilly CM, Winpenny JP, Argent BE, Gray MA. Cystic fibrosis transmembrane conductance regulator currents in guinea pig pancreatic duct cells: inhibition by bicarbonate ions. Gastroenterology 2000; 118:1187-96. [PMID: 10833494 DOI: 10.1016/s0016-5085(00)70372-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND & AIMS Cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channels play an important role in HCO(3)(-) secretion by pancreatic duct cells (PDCs). Our aims were to characterize the CFTR conductance of guinea pig PDCs and to establish whether CFTR is regulated by HCO(3)(-). METHODS PDCs were isolated from small intralobular and interlobular ducts, and their Cl(- )conductance was studied using the whole-cell patch clamp technique. RESULTS Activation of a typical CFTR conductance by adenosine 3',5'-cyclic monophosphate (cAMP) was observed in 114 of 204 cells (56%). A larger (10-fold), time- and voltage-dependent Cl(-) conductance was activated in 39 of 204 cells (19%). Secretin had a similar effect. Coexpression of both conductances in the same cell was observed, and both conductances had similar anion selectivity and pharmacology. Extracellular HCO(3)(-) caused a dose-dependent inhibition of both currents (K(i), approximately 7 mmol/L), which was independent of intracellular and extracellular pH, and the PCO(2) and CO(3)(2-) content of the bathing solutions. CONCLUSIONS Two kinetically distinct Cl(-) conductances are activated by cAMP in guinea pig PDCs. Because these conductances are coexpressed and exhibit similar characteristics (anion selectivity, pharmacology, and HCO(3)(-) inhibition), we conclude that CFTR underlies them both. The inhibition of CFTR by HCO(3)(-) has implications for the current model of pancreatic ductal HCO(3)(-) secretion.
Collapse
Affiliation(s)
- C M O'Reilly
- Department of Physiological Sciences, University Medical School, Newcastle upon Tyne, England
| | | | | | | |
Collapse
|
39
|
Abstract
Pancreatic bicarbonate secretion is impaired in patients with cystic fibrosis. This article reviews recent advances in bicarbonate dependent transporters in pancreatic duct cells and discusses their regulation in cystic fibrosis.
Collapse
Affiliation(s)
- M Soleimani
- Department of Medicine, University of Cincinnati, Ohio, USA.
| | | |
Collapse
|
40
|
Fukuda M, Ohara A, Bamba T, Saek Y. Activation of transepithelial ion transport by secretin in human intestinal Caco-2 cells. THE JAPANESE JOURNAL OF PHYSIOLOGY 2000; 50:215-25. [PMID: 10880878 DOI: 10.2170/jjphysiol.50.215] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Secretin stimulates bicarbonate secretion from pancreatic duct cells, but what influence secretin exerts on intestinal tissues remains to be clarified. The aim of this study is to examine effects of secretin on ion transport in intestinal epithelial Caco-2 cells. We mounted monolayers of Caco-2 cells grown on permeable supports for 21-28 d in a Ussing chamber and measured short-circuit currents (I(sc)). Addition of secretin (5-100 nM) to the basolateral solution dose-dependently induced biphasic increases of I(sc) (transient and sustained phase). Dibutyryl cyclic AMP (200 microM), forskolin (10 microM), and 3-isobutyl-1-methylxanthine (IBMX, 1 mM) also induced I(sc) responses similar to the administration of secretin. Addition of 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB, 100 microM) or benzamil (100 microM) to the apical solution markedly reduced the secretin-induced I(sc) increase in the transient phase. A selective antagonist of cAMP-dependent protein kinase (PKA), N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89, 1 microM), and a membrane permeable Ca(2+) chelator, 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA/AM, 10 microM) reduced the secretin-induced I(sc). Basolateral addition of 4, 4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, 1 mM) suppressed the sustained phase I(sc) increase. Secretin also induced alkalinization of the apical solution (DeltapH, 0.053 +/- 0.013). The alkalinization did not occur when DIDS (1 mM) was added to the basolateral solution or Na(+) was removed from the solutions. Taken together, our observations suggest: (1) secretin stimulates a benzamil-sensitive Na(+) influx and an NPPB-sensitive Cl(-) efflux across the apical membrane through PKA-dependent and Ca(2+)-sensitive pathways; and (2) secretin also induces alkalinization of the apical solution through the activation of a DIDS-sensitive Na(+)-HCO(3)(-) cotransport in the basolateral membrane of Caco-2 cells.
Collapse
Affiliation(s)
- M Fukuda
- 2nd Department of Internal Medicine, Shiga University of Medical Science, Ohtsu, 520-2192 Japan
| | | | | | | |
Collapse
|
41
|
Schwiehert EM, Rozmahel R. Chapter 6 The cystic fibrosis transmembrane conductance regulator in the gastrointestinal system. CURRENT TOPICS IN MEMBRANES 2000. [DOI: 10.1016/s1063-5823(00)50008-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
42
|
Nagel G. Differential function of the two nucleotide binding domains on cystic fibrosis transmembrane conductance regulator. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1461:263-74. [PMID: 10581360 DOI: 10.1016/s0005-2736(99)00162-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The genetic disease cystic fibrosis is caused by defects in the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR). CFTR belongs to the family of ABC transporters. In contrast to most other members of this family which transport substrates actively across a membrane, the main function of CFTR is to regulate passive flux of substrates across the plasma membrane. Chloride channel activity of CFTR is dependent on protein phosphorylation and presence of nucleoside triphosphates. From electrophysiological studies of CFTR detailed models of its regulation by phosphorylation and nucleotide interaction have evolved. These investigations provide ample evidence that ATP hydrolysis is crucial for CFTR gating. It becomes apparent that the two nucleotide binding domains on CFTR not only diverge strongly in sequence, but also in function. Based on previous models and taking into account new data from pre-steady-state experiments, a refined model for the action of nucleotides at two nucleotide binding domains was recently proposed.
Collapse
Affiliation(s)
- G Nagel
- Max-Planck-Institut für Biophysik, Kennedyallee 70, 60596, Frankfurt/M., Germany
| |
Collapse
|
43
|
Hede SE, Amstrup J, Christoffersen BC, Novak I. Purinoceptors evoke different electrophysiological responses in pancreatic ducts. P2Y inhibits K(+) conductance, and P2X stimulates cation conductance. J Biol Chem 1999; 274:31784-91. [PMID: 10542200 DOI: 10.1074/jbc.274.45.31784] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In epithelia, extracellular nucleotides are often associated with regulation of ion transporters, especially Cl(-) channels. In this study, we investigated which purinoceptors are present in native pancreatic ducts and how they regulate ion transport. We applied whole-cell patch-clamp recordings, intracellular Ca(2+) and pH measurements, and reverse transcription-polymerase chain reaction (RT-PCR) analysis. The data show two types of purinoceptors and cellular responses. UTP and ATP produced large Ca(2+) transients, a decrease in intracellular pH, 8-10-mV depolarization of the membrane voltage, and a decrease in the whole-cell conductance. The membrane effects were due to closure of K(+) channels, as confirmed by dependence on extracellular K(+). UTP/ATP effects could be associated with P2Y(2) purinoceptors, and RT-PCR revealed mRNAs for P2Y(2) and P2Y(4) receptors. On the other hand, 2', 3'-O-4-benzoylbenzoyl-ATP induced Ca(2+) influx and approximately 20-mV depolarization of the membrane voltage with a concomitant increase in the whole-cell conductance. These effects were dependent on extracellular Na(+), not Cl(-), indicating opening of cation channels associated with P2X(7) purinoceptors. RT-PCR showed mRNAs for P2X(7) and P2X(4) receptors. In microperfused ducts, luminal (but not basolateral) ATP caused large depolarizations of membrane voltages recorded with microelectrodes, consistent with luminal localization of P2X(7) receptors. Thus, P2Y(2) (and possibly P2Y(4)) purinoceptors inhibit K(+) channels and may not support secretion in native ducts. P2X(7) (and possibly P2X(4)) receptors are associated with cation channels and may contribute to regulation of secretion.
Collapse
Affiliation(s)
- S E Hede
- August Krogh Institute, Copenhagen University, Universitetsparken 13, DK-2100 Copenhagen O, Denmark
| | | | | | | |
Collapse
|
44
|
Zhu T, Dahan D, Evagelidis A, Zheng S, Luo J, Hanrahan JW. Association of cystic fibrosis transmembrane conductance regulator and protein phosphatase 2C. J Biol Chem 1999; 274:29102-7. [PMID: 10506164 DOI: 10.1074/jbc.274.41.29102] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels are rapidly deactivated by a membrane-bound phosphatase activity. The efficiency of this regulation suggests CFTR and protein phosphatases may be associated within a regulatory complex. In this paper we test that possibility using co-immunoprecipitation and cross-linking experiments. A monoclonal anti-CFTR antibody co-precipitated type 2C protein phosphatase (PP2C) from baby hamster kidney cells stably expressing CFTR but did not co-precipitate PP1, PP2A, or PP2B. Conversely, a polyclonal anti-PP2C antibody co-precipitated CFTR from baby hamster kidney membrane extracts. Exposing baby hamster kidney cell lysates to dithiobis (sulfosuccinimidyl propionate) caused the cross-linking of histidine-tagged CFTR (CFTR(His10)) and PP2C into high molecular weight complexes that were isolated by chromatography on Ni(2+)-nitrilotriacetic acid-agarose. Chemical cross-linking was specific for PP2C, because PP1, PP2A, and PP2B did not co-purify with CFTR(His10) after dithiobis (sulfosuccinimidyl propionate) exposure. These results suggest CFTR and PP2C exist in a stable complex that facilitates regulation of the channel.
Collapse
Affiliation(s)
- T Zhu
- Department of Physiology, McGill University, Montréal, Québec H3G 1Y6, Canada
| | | | | | | | | | | |
Collapse
|
45
|
Becq F, Mettey Y, Gray MA, Galietta LJ, Dormer RL, Merten M, Métayé T, Chappe V, Marvingt-Mounir C, Zegarra-Moran O, Tarran R, Bulteau L, Dérand R, Pereira MM, McPherson MA, Rogier C, Joffre M, Argent BE, Sarrouilhe D, Kammouni W, Figarella C, Verrier B, Gola M, Vierfond JM. Development of substituted Benzo[c]quinolizinium compounds as novel activators of the cystic fibrosis chloride channel. J Biol Chem 1999; 274:27415-25. [PMID: 10488073 DOI: 10.1074/jbc.274.39.27415] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chloride channels play an important role in the physiology and pathophysiology of epithelia, but their pharmacology is still poorly developed. We have chemically synthesized a series of substituted benzo[c]quinolizinium (MPB) compounds. Among them, 6-hydroxy-7-chlorobenzo[c]quinolizinium (MPB-27) and 6-hydroxy-10-chlorobenzo[c]quinolizinium (MPB-07), which we show to be potent and selective activators of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. We examined the effect of MPB compounds on the activity of CFTR channels in a variety of established epithelial and nonepithelial cell systems. Using the iodide efflux technique, we show that MPB compounds activate CFTR chloride channels in Chinese hamster ovary (CHO) cells stably expressing CFTR but not in CHO cells lacking CFTR. Single and whole cell patch clamp recordings from CHO cells confirm that CFTR is the only channel activated by the drugs. Ussing chamber experiments reveal that the apical addition of MPB to human nasal epithelial cells produces a large increase of the short circuit current. This current can be totally inhibited by glibenclamide. Whole cell experiments performed on native respiratory cells isolated from wild type and CF null mice also show that MPB compounds specifically activate CFTR channels. The activation of CFTR by MPB compounds was glibenclamide-sensitive and 4, 4'-diisothiocyanostilbene-2,2'-disulfonic acid-insensitive. In the human tracheal gland cell line MM39, MPB drugs activate CFTR channels and stimulate the secretion of the antibacterial secretory leukoproteinase inhibitor. In submandibular acinar cells, MPB compounds slightly stimulate CFTR-mediated submandibular mucin secretion without changing intracellular cAMP and ATP levels. Similarly, in CHO cells MPB compounds have no effect on the intracellular levels of cAMP and ATP or on the activity of various protein phosphatases (PP1, PP2A, PP2C, or alkaline phosphatase). Our results provide evidence that substituted benzo[c]quinolizinium compounds are a novel family of activators of CFTR and of CFTR-mediated protein secretion and therefore represent a new tool to study CFTR-mediated chloride and secretory functions in epithelial tissues.
Collapse
Affiliation(s)
- F Becq
- Laboratoire de neurobiologie UPR-9024 CNRS, 31 ch. J. Aiguier F-13402 Marseille cedex 20, France.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Hyde K, Harrison D, Hollingsworth MA, Harris A. Chloride-bicarbonate exchangers in the human fetal pancreas. Biochem Biophys Res Commun 1999; 263:315-21. [PMID: 10491290 DOI: 10.1006/bbrc.1999.1367] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes a small conductance cAMP-activated chloride ion channel. In the CF pancreatic duct, mutations in CFTR cause a reduction in bicarbonate secretion. This is thought to result from CFTR operating in parallel with a chloride-bicarbonate (Cl(-)/HCO(-)(3)) exchanger, located in the apical membrane of pancreatic duct cells. The molecular basis of this Cl(-)/HCO(-)(3) exchanger has not been identified. A combination of screening cDNA libraries, RNase protection, and 5' RACE analysis was used to identify Cl(-)/HCO(-)(3) exchangers in human fetal pancreas. An AE2 Cl(-)/HCO(-)(3) exchanger was shown to be expressed in human fetal pancreas from the midtrimester of gestation, at a time when CF-associated pathology commences. In addition, an AE1 Cl(-)/HCO(3) was identified in fetal pancreas but was absent from the adult pancreas and cultured ductal epithelial cells from fetal and adult pancreas.
Collapse
Affiliation(s)
- K Hyde
- Institute of Molecular Medicine, Oxford University, John Radcliffe Hospital, Oxford, OX3 9DS, United Kingdom
| | | | | | | |
Collapse
|
47
|
Luo X, Zheng W, Yan M, Lee MG, Muallem S. Multiple functional P2X and P2Y receptors in the luminal and basolateral membranes of pancreatic duct cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:C205-15. [PMID: 10444396 DOI: 10.1152/ajpcell.1999.277.2.c205] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Purinergic receptors in the basolateral and luminal membranes of the pancreatic duct can act by a feedback mechanism to coordinate transport activity in the two membranes during ductal secretion. The goal of the present work was to identify and localize the functional P2 receptors (P2R) in the rat pancreatic duct. The lack of selective agonists and/or antagonists for any of the cloned P2R dictated the use of molecular and functional approaches to the characterization of ductal P2R. For the molecular studies, RNA was prepared from microdissected pancreatic intralobular ducts and was shown to be free of mRNA for amylase and endothelial nitric oxide synthase (markers for acinar and endothelial cells, respectively). A new procedure is described to obtain an enriched preparation of single duct cells suitable for electrophysiological studies. Localization of P2R was achieved by testing the effect of various P2R agonists on intracellular Ca(2+) concentration ([Ca(2+)](i)) of microperfused intralobular ducts. RT-PCR analysis suggested the expression of six subtypes of P2R in the pancreatic duct: three P2YR and three P2XR. Activation of Cl(-) current by various nucleotides and coupling of the receptors activated by these nucleotides to G proteins confirmed the expression of multiple P2R in duct cells. Measurement of [Ca(2+)](i) in microperfused intralobular ducts suggested the expression of P2X(1)R, P2X(4)R, probably P2X(7)R, and as yet unidentified P2YR, possibly P2Y(1)R, in the basolateral membrane. Expression of P2Y(2)R, P2Y(4)R, and P2X(7)R was found in the luminal membrane. The unprecedented expression of such a variety of P2R in one cell type, many capable of activating Cl(-) channels, suggests that these receptors may have an important role in pancreatic duct cell function.
Collapse
Affiliation(s)
- X Luo
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA
| | | | | | | | | |
Collapse
|
48
|
Marino CR, Jeanes V, Boron WF, Schmitt BM. Expression and distribution of the Na(+)-HCO(-)(3) cotransporter in human pancreas. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:G487-94. [PMID: 10444464 DOI: 10.1152/ajpgi.1999.277.2.g487] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
The cellular mechanisms of HCO(-)(3) secretion in the human pancreas are unclear. Expression of a Na(+)-HCO(-)(3) cotransporter (NBC) mRNA has been observed recently, but the distribution and physiological role of the NBC protein are not known. Here we examined the expression and localization of NBC in human pancreas by Northern blot, immunoblot, and immunofluorescence microscopy. Rat kidney NBC probes detected a single 9.5-kb band by Northern blot. On immunoblots, two polyclonal antisera directed against different epitopes of rat kidney NBC identified a single approximately 130-kDa protein. In cryosections of normal human pancreas, both antisera labeled basolateral membranes of large, morphologically identifiable ducts and produced a distinct labeling pattern in the remainder of the parenchyma. In double-labeling experiments, NBC immunoreactivity in the parenchyma colocalized with the Na(+)-K(+) pump, a basolateral marker. In contrast, NBC and cystic fibrosis transmembrane conductance regulator, an apical membrane marker, were detected within the same histological structures but at different subcellular localizations. The NBC antisera did not label acinar or islet cells. Our observations suggest that secretion of HCO(-)(3) by human pancreatic duct cells involves the basolateral uptake of Na(+) and HCO(-)(3) via NBC, an electrogenic Na(+)-HCO(-)(3) cotransporter.
Collapse
Affiliation(s)
- C R Marino
- Veterans Affairs Medical Center, University of Tennessee, Memphis, Tennessee 68163, USA
| | | | | | | |
Collapse
|
49
|
Morris AP. The regulation of epithelial cell cAMP- and calcium-dependent chloride channels. ADVANCES IN PHARMACOLOGY 1999; 46:209-51. [PMID: 10332504 DOI: 10.1016/s1054-3589(08)60472-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
This chapter has focused on two types of chloride conductance found in epithelial cells. The leap from the Ussing chamber to patch-clamp studies has identified yet other conductances present which have also been electrophysiologically characterized. In the case of the swelling activated wholecell chloride current, a physiological function is apparent and a single-channel basis found, but its genetic identity remains unknown (see reviews by Frizzell and Morris, 1994; and Strange et al., 1996). The outwardly rectified chloride channel has been the subject of considerable electrophysiological interest over the past 10 years and is well characterized at the single-channel level, but its physiological function remains controversial (reviewed by Frizzell and Morris, 1994; Devidas and Guggino, 1997). Yet other conductances related to the CLC gene family also appear to be present in epithelial cells of the kidney (reviewed by Jentsch, 1996; Jentsch and Gunter, 1997) where physiological functions for some isoforms are emerging. Clearly, there remain many unknowns. Chief among these is the molecular basis of GCa2+Cl and many of other the conductances. As sequences become available it is expected that the wealth of information gained by investigation into CFTR function will provide a conceptual blueprint for similar studies in these later channel clones.
Collapse
Affiliation(s)
- A P Morris
- Department of Integrative Biology, University of Texas-Houston Health Science Center 77030, USA
| |
Collapse
|
50
|
Cho WK, Boyer JL. Characterization of ion transport mechanisms involved in bombesin-stimulated biliary secretion in rat cholangiocytes. J Hepatol 1999; 30:1045-51. [PMID: 10406182 DOI: 10.1016/s0168-8278(99)80258-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND/AIMS Bombesin is a neuropeptide which stimulates fluid and bicarbonate secretion from cholangiocytes by stimulating Cl-/HCO3- exchange. However, the underlying regulation and interactions of ion transporters and channels mediating this bombesin-stimulated biliary secretion are not well characterized. The aim of the study was to characterize the ion transport processes involved in bombesin-stimulated secretion in polarized cholangiocytes in comparison with those of secretin. METHODS Isolated bile duct units (IBDU) were prepared from normal rat liver. Biliary secretion induced by bombesin was measured by quantitative video-microscopy in the presence and absence of inhibitors. RESULTS Bombesin-stimulated secretion was inhibited by H2-DIDS, NPPB, BaCl2, TEA, and acetazolamide. However, in contrast to secretin, bombesin-stimulated secretion was not inhibited by disruption of microtubules. CONCLUSIONS Bombesin-stimulated biliary secretion is dependent on anion exchangers, Cl- and K+ channels, and carbonic anhydrase but not on microtubules. Bombesin regulates secretion in cholangiocytes by different mechanisms from those established for secretin.
Collapse
Affiliation(s)
- W K Cho
- Division of Gastroenterology/Hepatology, Indiana University School of Medicine, Indianapolis 46202, USA.
| | | |
Collapse
|