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Schreiber R, Ousingsawat J, Kunzelmann K. The anoctamins: Structure and function. Cell Calcium 2024; 120:102885. [PMID: 38642428 DOI: 10.1016/j.ceca.2024.102885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 04/03/2024] [Accepted: 04/04/2024] [Indexed: 04/22/2024]
Abstract
When activated by increase in intracellular Ca2+, anoctamins (TMEM16 proteins) operate as phospholipid scramblases and as ion channels. Anoctamin 1 (ANO1) is the Ca2+-activated epithelial anion-selective channel that is coexpressed together with the abundant scramblase ANO6 and additional intracellular anoctamins. In salivary and pancreatic glands, ANO1 is tightly packed in the apical membrane and secretes Cl-. Epithelia of airways and gut use cystic fibrosis transmembrane conductance regulator (CFTR) as an apical Cl- exit pathway while ANO1 supports Cl- secretion mainly by facilitating activation of luminal CFTR and basolateral K+ channels. Under healthy conditions ANO1 modulates intracellular Ca2+ signals by tethering the endoplasmic reticulum, and except of glands its direct secretory contribution as Cl- channel might be small, compared to CFTR. In the kidneys ANO1 supports proximal tubular acid secretion and protein reabsorption and probably helps to excrete HCO3-in the collecting duct epithelium. However, under pathological conditions as in polycystic kidney disease, ANO1 is strongly upregulated and may cause enhanced proliferation and cyst growth. Under pathological condition, ANO1 and ANO6 are upregulated and operate as secretory channel/phospholipid scramblases, partly by supporting Ca2+-dependent processes. Much less is known about the role of other epithelial anoctamins whose potential functions are discussed in this review.
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Affiliation(s)
- Rainer Schreiber
- Physiological Institute, University of Regensburg, University street 31, D-93053 Regensburg, Germany
| | - Jiraporn Ousingsawat
- Physiological Institute, University of Regensburg, University street 31, D-93053 Regensburg, Germany
| | - Karl Kunzelmann
- Physiological Institute, University of Regensburg, University street 31, D-93053 Regensburg, Germany.
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2
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Aubin Vega M, Girault A, Meunier É, Chebli J, Privé A, Robichaud A, Adam D, Brochiero E. Function of KvLQT1 potassium channels in a mouse model of bleomycin-induced acute lung injury. Front Physiol 2024; 15:1345488. [PMID: 38444763 PMCID: PMC10912346 DOI: 10.3389/fphys.2024.1345488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 01/30/2024] [Indexed: 03/07/2024] Open
Abstract
Acute respiratory distress syndrome (ARDS) is characterized by an exacerbated inflammatory response, severe damage to the alveolar-capillary barrier and a secondary infiltration of protein-rich fluid into the airspaces, ultimately leading to respiratory failure. Resolution of ARDS depends on the ability of the alveolar epithelium to reabsorb lung fluid through active transepithelial ion transport, to control the inflammatory response, and to restore a cohesive and functional epithelium through effective repair processes. Interestingly, several lines of evidence have demonstrated the important role of potassium (K+) channels in the regulation of epithelial repair processes. Furthermore, these channels have previously been shown to be involved in sodium/fluid absorption across alveolar epithelial cells, and we have recently demonstrated the contribution of KvLQT1 channels to the resolution of thiourea-induced pulmonary edema in vivo. The aim of our study was to investigate the role of the KCNQ1 pore-forming subunit of KvLQT1 channels in the outcome of ARDS parameters in a model of acute lung injury (ALI). We used a molecular approach with KvLQT1-KO mice challenged with bleomycin, a well-established ALI model that mimics the key features of the exudative phase of ARDS on day 7. Our data showed that KvLQT1 deletion exacerbated the negative outcome of bleomycin on lung function (resistance, elastance and compliance). An alteration in the profile of infiltrating immune cells was also observed in KvLQT1-KO mice while histological analysis showed less interstitial and/or alveolar inflammatory response induced by bleomycin in KvLQT1-KO mice. Finally, a reduced repair rate of KvLQT1-KO alveolar cells after injury was observed. This work highlights the complex contribution of KvLQT1 in the development and resolution of ARDS parameters in a model of ALI.
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Affiliation(s)
- Mélissa Aubin Vega
- Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
- Département de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Alban Girault
- Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
- Département de Médecine, Université de Montréal, Montréal, QC, Canada
- Laboratoire de Physiologie Cellulaire et Moléculaire (LPCM UR UPJV 4667), Amiens, France
| | - Émilie Meunier
- Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
- Département de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Jasmine Chebli
- Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
- Département de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Anik Privé
- Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
| | | | - Damien Adam
- Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
- Département de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Emmanuelle Brochiero
- Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
- Département de Médecine, Université de Montréal, Montréal, QC, Canada
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3
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Farrell S, Dates J, Ramirez N, Hausknecht-Buss H, Kolosov D. Voltage-gated ion channels are expressed in the Malpighian tubules and anal papillae of the yellow fever mosquito (Aedes aegypti), and may regulate ion transport during salt and water imbalance. J Exp Biol 2024; 227:jeb246486. [PMID: 38197515 PMCID: PMC10912814 DOI: 10.1242/jeb.246486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 12/22/2023] [Indexed: 01/11/2024]
Abstract
Vectors of infectious disease include several species of Aedes mosquitoes. The life cycle of Aedes aegypti, the yellow fever mosquito, consists of a terrestrial adult and an aquatic larval life stage. Developing in coastal waters can expose larvae to fluctuating salinity, causing salt and water imbalance, which is addressed by two prime osmoregulatory organs - the Malpighian tubules (MTs) and anal papillae (AP). Voltage-gated ion channels (VGICs) have recently been implicated in the regulation of ion transport in the osmoregulatory epithelia of insects. In the current study, we: (i) generated MT transcriptomes of freshwater-acclimated and brackish water-exposed larvae of Ae. aegypti, (ii) detected expression of several voltage-gated Ca2+, K+, Na+ and non-ion-selective ion channels in the MTs and AP using transcriptomics, PCR and gel electrophoresis, (iii) demonstrated that mRNA abundance of many altered significantly following brackish water exposure, and (iv) immunolocalized CaV1, NALCN, TRP/Painless and KCNH8 in the MTs and AP of larvae using custom-made antibodies. We found CaV1 to be expressed in the apical membrane of MTs of both larvae and adults, and its inhibition to alter membrane potentials of this osmoregulatory epithelium. Our data demonstrate that multiple VGICs are expressed in osmoregulatory epithelia of Ae. aegypti and may play an important role in the autonomous regulation of ion transport.
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Affiliation(s)
- Serena Farrell
- Department of Biological Sciences, California State University San Marcos, 333 S. Twin Oaks Valley Road, San Marcos, CA 92096, USA
| | - Jocelyne Dates
- Department of Biological Sciences, California State University San Marcos, 333 S. Twin Oaks Valley Road, San Marcos, CA 92096, USA
| | - Nancy Ramirez
- Department of Biological Sciences, California State University San Marcos, 333 S. Twin Oaks Valley Road, San Marcos, CA 92096, USA
| | - Hannah Hausknecht-Buss
- Department of Biological Sciences, California State University San Marcos, 333 S. Twin Oaks Valley Road, San Marcos, CA 92096, USA
| | - Dennis Kolosov
- Department of Biological Sciences, California State University San Marcos, 333 S. Twin Oaks Valley Road, San Marcos, CA 92096, USA
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4
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Scheyer MW, Campbell C, William PL, Hussain M, Begum A, Fonseca SE, Asare IK, Dabney P, Dabney-Smith C, Lorigan GA, Sahu ID. Electron paramagnetic resonance spectroscopic characterization of the human KCNE3 protein in lipodisq nanoparticles for structural dynamics of membrane proteins. Biophys Chem 2023; 301:107080. [PMID: 37531799 DOI: 10.1016/j.bpc.2023.107080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/07/2023] [Accepted: 07/24/2023] [Indexed: 08/04/2023]
Abstract
One of the major challenges in solubilization of membrane proteins is to find the optimal physiological environment for their biophysical studies. EPR spectroscopy is a powerful biophysical technique for studying the structural and dynamic properties of macromolecules. However, the challenges in the membrane protein sample preparation and flexible motion of the spin label limit the utilization of EPR spectroscopy to a majority of membrane protein systems in a physiological membrane-bound state. Recently, lipodisq nanoparticles or styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) have emerged as a membrane mimetic system for investigating the structural studies of membrane proteins. However, its detail characterization for membrane protein studies is still poorly understood. Recently, we characterized the potassium channel membrane protein KCNQ1 voltage sensing domain (KCNQ1-VSD) and KCNE1 reconstituted into lipodisq nanoparticles using EPR spectroscopy. In this study, the potassium channel accessory protein KCNE3 containing flexible N- and C-termini was encapsulated into proteoliposomes and lipodisq nanoparticles and characterized for studying its structural and dynamic properties using nitroxide based site-directed spin labeling EPR spectroscopy. CW-EPR lineshape analysis data indicated an increase in spectral line broadenings with the addition of the styrene-maleic acid (SMA) polymer which approaches close to the rigid limit providing a homogeneous stabilization of the protein-lipid complex. Similarly, EPR DEER measurements indicated an enhanced quality of distance measurements with an increase in the phase memory time (Tm) values upon incorporation of the sample into lipodisq nanoparticles, when compared to proteoliposomes. These results agree with the solution NMR structural structure of the KCNE3 and EPR studies of other membrane proteins in lipodisq nanoparticles. This study along with our earlier studies will provide the reference characterization data that will provide benefit to the membrane protein researchers for studying structural dynamics of challenging membrane proteins.
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Affiliation(s)
- Matthew W Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Conner Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Patrick L William
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Mustakim Hussain
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Afsana Begum
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | | | - Isaac K Asare
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Peyton Dabney
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Indra D Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
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5
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Talbi K, Ousingsawat J, Centeio R, Schreiber R, Kunzelmann K. KCNE1 does not shift TMEM16A from a Ca 2+ dependent to a voltage dependent Cl - channel and is not expressed in renal proximal tubule. Pflugers Arch 2023:10.1007/s00424-023-02829-5. [PMID: 37442855 PMCID: PMC10359377 DOI: 10.1007/s00424-023-02829-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 05/02/2023] [Accepted: 06/08/2023] [Indexed: 07/15/2023]
Abstract
The TMEM16A (ANO1) Cl- channel is activated by Ca2+ in a voltage-dependent manner. It is broadly expressed and was shown to be also present in renal proximal tubule (RPT). KCNQ1 is an entirely different K+ selective channel that forms the cardiac IKS potassium channel together with its ß-subunit KCNE1. Surprisingly, KCNE1 has been claimed to interact with TMEM16A, and to be required for activation of TMEM16A in mouse RPT. Interaction with KCNE1 was reported to switch TMEM16A from a Ca22+-dependent to a voltage-dependent ion channel. Here we demonstrate that KCNE1 is not expressed in mouse RPT. TMEM16A expressed in RPT is activated by angiotensin II and ATP in a KCNE1-independent manner. Coexpression of KCNE1 does not change TMEM16A to a voltage gated Cl- channel and Ca2+-dependent regulation of TMEM16A is fully maintained in the presence of KCNE1. While overexpressed KCNE1 slightly affects Ca2+-dependent regulation of TMEM16A, the data provide no evidence for KCNE1 being an auxiliary functional subunit for TMEM16A.
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Affiliation(s)
- Khaoula Talbi
- Physiological Institute, University of Regensburg, University street 31, D-93053, Regensburg, Germany
| | - Jiraporn Ousingsawat
- Physiological Institute, University of Regensburg, University street 31, D-93053, Regensburg, Germany
| | - Raquel Centeio
- Physiological Institute, University of Regensburg, University street 31, D-93053, Regensburg, Germany
| | - Rainer Schreiber
- Physiological Institute, University of Regensburg, University street 31, D-93053, Regensburg, Germany
| | - Karl Kunzelmann
- Physiological Institute, University of Regensburg, University street 31, D-93053, Regensburg, Germany.
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6
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Abrahamyan A, Eldstrom J, Sahakyan H, Karagulyan N, Mkrtchyan L, Karapetyan T, Sargsyan E, Kneussel M, Nazaryan K, Schwarz JR, Fedida D, Vardanyan V. Mechanism of external K+ sensitivity of KCNQ1 channels. J Gen Physiol 2023; 155:213880. [PMID: 36809486 PMCID: PMC9960071 DOI: 10.1085/jgp.202213205] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/20/2022] [Accepted: 01/31/2023] [Indexed: 02/23/2023] Open
Abstract
KCNQ1 voltage-gated K+ channels are involved in a wide variety of fundamental physiological processes and exhibit the unique feature of being markedly inhibited by external K+. Despite the potential role of this regulatory mechanism in distinct physiological and pathological processes, its exact underpinnings are not well understood. In this study, using extensive mutagenesis, molecular dynamics simulations, and single-channel recordings, we delineate the molecular mechanism of KCNQ1 modulation by external K+. First, we demonstrate the involvement of the selectivity filter in the external K+ sensitivity of the channel. Then, we show that external K+ binds to the vacant outermost ion coordination site of the selectivity filter inducing a diminution in the unitary conductance of the channel. The larger reduction in the unitary conductance compared to whole-cell currents suggests an additional modulatory effect of external K+ on the channel. Further, we show that the external K+ sensitivity of the heteromeric KCNQ1/KCNE complexes depends on the type of associated KCNE subunits.
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Affiliation(s)
- Astghik Abrahamyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia , Vancouver, BC, Canada
| | - Harutyun Sahakyan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular Biology of National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Nare Karagulyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Liana Mkrtchyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Tatev Karapetyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Ernest Sargsyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Matthias Kneussel
- Institute for Molecular Neurogenetics, Center for Molecular Neurobiology Hamburg , Hamburg, Germany
| | - Karen Nazaryan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular Biology of National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Jürgen R Schwarz
- Institute for Molecular Neurogenetics, Center for Molecular Neurobiology Hamburg , Hamburg, Germany
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia , Vancouver, BC, Canada
| | - Vitya Vardanyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
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7
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Barro-Soria R. Sensing its own permeant ion: KCNQ1 channel inhibition by external K. J Gen Physiol 2023; 155:e202313337. [PMID: 36961346 PMCID: PMC10072219 DOI: 10.1085/jgp.202313337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023] Open
Abstract
External potassium inhibits KCNQ1 channel through a mechanism involving increased occupancy of the filter S0 site by K+o.
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Affiliation(s)
- Rene Barro-Soria
- Department of Medicine, Miller School of Medicine, University of Miami, Miami, FL, USA
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8
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Aubin Vega M, Girault A, Adam D, Chebli J, Privé A, Maillé É, Robichaud A, Brochiero E. Impact of KvLQT1 potassium channel modulation on alveolar fluid homeostasis in an animal model of thiourea-induced lung edema. Front Physiol 2023; 13:1069466. [PMID: 36699692 PMCID: PMC9868633 DOI: 10.3389/fphys.2022.1069466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 12/19/2022] [Indexed: 01/11/2023] Open
Abstract
Alveolar ion and fluid absorption is essential for lung homeostasis in healthy conditions as well as for the resorption of lung edema, a key feature of acute respiratory distress syndrome. Liquid absorption is driven by active transepithelial sodium transport, through apical ENaC Na+ channels and basolateral Na+/K+-ATPase. Our previous work unveiled that KvLQT1 K+ channels also participate in the control of Na+/liquid absorption in alveolar epithelial cells. Our aim was to further investigate the function of KvLQT1 channels and their interplay with other channels/transporters involved in ion/liquid transport in vivo using adult wild-type (WT) and KvLQT1 knock-out (KO) mice under physiological conditions and after thiourea-induced lung edema. A slight but significant increase in water lung content (WLC) was observed in naïve KvLQT1-KO mice, relative to WT littermates, whereas lung function was generally preserved and histological structure unaltered. Following thiourea-induced lung edema, KvLQT1-KO did not worsen WLC or lung function. Similarly, lung edema was not aggravated by the administration of a KvLQT1 inhibitor (chromanol). However, KvLQT1 activation (R-L3) significantly reduced WLC in thiourea-challenged WT mice. The benefits of R-L3 were prevented in KO or chromanol-treated WT mice. Furthermore, R-L3 treatment had no effect on thiourea-induced endothelial barrier alteration but restored or enhanced the levels of epithelial alveolar AQP5, Na+/K+-ATPase, and ENaC expressions. Altogether, the results indicate the benefits of KvLQT1 activation in the resolution of lung edema, probably through the observed up-regulation of epithelial alveolar channels/transporters involved in ion/water transport.
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Affiliation(s)
- Mélissa Aubin Vega
- Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada,Département de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Alban Girault
- Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada,Département de Médecine, Université de Montréal, Montréal, QC, Canada,Laboratoire de Physiologie Cellulaire et Moléculaire (LPCM), Amiens, France
| | - Damien Adam
- Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada,Département de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Jasmine Chebli
- Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada,Département de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Anik Privé
- Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
| | - Émilie Maillé
- Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada
| | | | - Emmanuelle Brochiero
- Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada,Département de Médecine, Université de Montréal, Montréal, QC, Canada,*Correspondence: Emmanuelle Brochiero,
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9
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Natural statin derivatives as potential therapy to reduce intestinal fluid loss in cholera. PLoS Negl Trop Dis 2022; 16:e0010989. [PMID: 36490300 PMCID: PMC9770395 DOI: 10.1371/journal.pntd.0010989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 12/21/2022] [Accepted: 11/28/2022] [Indexed: 12/14/2022] Open
Abstract
As a leading cause of death in children under 5 years old, secretory diarrheas including cholera are characterized by excessive intestinal fluid secretion driven by enterotoxin-induced cAMP-dependent intestinal chloride transport. This study aimed to identify fungal bioactive metabolites possessing anti-secretory effects against cAMP-dependent chloride secretion in intestinal epithelial cells. Using electrophysiological analyses in human intestinal epithelial (T84) cells, five fungus-derived statin derivatives including α,β-dehydrolovastatin (DHLV), α,β-dehydrodihydromonacolin K, lovastatin, mevastatin and simvastatin were found to inhibit the cAMP-dependent chloride secretion with IC50 values of 1.8, 8.9, 11.9, 11.4 and 5 μM, respectively. Being the most potent statin derivatives, DHLV was evaluated for its pharmacological properties including cellular toxicity, mechanism of action, target specificity and in vivo efficacy. DHLV at concentrations up to 20 μM did not affect cell viability and barrier integrity of T84 cells. Electrophysiological analyses indicated that DHLV inhibited cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-dependent apical chloride channel, via mechanisms not involving alteration of intracellular cAMP levels or its negative regulators including AMP-activated protein kinases and protein phosphatases. DHLV had no effect on Na+-K+ ATPase activities but inhibited Ca2+-dependent chloride secretion without affecting intracellular Ca2+ levels. Importantly, intraperitoneal (2 mg/kg) and intraluminal (20 μM) injections of DHLV reduced cholera toxin-induced intestinal fluid secretion in mice by 59% and 65%, respectively without affecting baseline intestinal fluid transport. This study identifies natural statin derivatives as novel natural product-derived CFTR inhibitors, which may be beneficial in the treatment of enterotoxin-induced secretory diarrheas including cholera.
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10
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Jo S, Centeio R, Park J, Ousingsawat J, Jeon DK, Talbi K, Schreiber R, Ryu K, Kahlenberg K, Somoza V, Delpiano L, Gray MA, Amaral MD, Railean V, Beekman JM, Rodenburg LW, Namkung W, Kunzelmann K. The SLC26A9 inhibitor S9-A13 provides no evidence for a role of SLC26A9 in airway chloride secretion but suggests a contribution to regulation of ASL pH and gastric proton secretion. FASEB J 2022; 36:e22534. [PMID: 36183361 DOI: 10.1096/fj.202200313rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 08/11/2022] [Accepted: 08/24/2022] [Indexed: 11/11/2022]
Abstract
The solute carrier 26 family member A9 (SLC26A9) is an epithelial anion transporter that is assumed to contribute to airway chloride secretion and surface hydration. Whether SLC26A9 or CFTR is responsible for airway Cl- transport under basal conditions is still unclear, due to the lack of a specific inhibitor for SLC26A9. In the present study, we report a novel potent and specific inhibitor for SLC26A9, identified by screening of a drug-like molecule library and subsequent chemical modifications. The most potent compound S9-A13 inhibited SLC26A9 with an IC50 of 90.9 ± 13.4 nM. S9-A13 did not inhibit other members of the SLC26 family and had no effects on Cl- channels such as CFTR, TMEM16A, or VRAC. S9-A13 inhibited SLC26A9 Cl- currents in cells that lack expression of CFTR. It also inhibited proton secretion by HGT-1 human gastric cells. In contrast, S9-A13 had minimal effects on ion transport in human airway epithelia and mouse trachea, despite clear expression of SLC26A9 in the apical membrane of ciliated cells. In both tissues, basal and stimulated Cl- secretion was due to CFTR, while acidification of airway surface liquid by S9-A13 suggests a role of SLC26A9 for airway bicarbonate secretion.
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Affiliation(s)
- Sungwoo Jo
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, South Korea
| | - Raquel Centeio
- Physiological Institute, University of Regensburg, Regensburg, Germany
| | - Jinhong Park
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, South Korea
| | | | - Dong-Kyu Jeon
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, South Korea
| | - Khaoula Talbi
- Leibniz Institute for Food Systems Biology at the Technical University of Munich, Freising, Germany
| | - Rainer Schreiber
- Physiological Institute, University of Regensburg, Regensburg, Germany
| | - Kunhi Ryu
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, South Korea
| | - Kristin Kahlenberg
- Leibniz Institute for Food Systems Biology at the Technical University of Munich, Freising, Germany
| | - Veronika Somoza
- Leibniz Institute for Food Systems Biology at the Technical University of Munich, Freising, Germany
| | - Livia Delpiano
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Michael A Gray
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Margarida D Amaral
- BioISI-Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Lisbon, Portugal
| | - Violeta Railean
- BioISI-Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Lisbon, Portugal
| | - Jeffrey M Beekman
- Regenerative Medicine Utrecht, University Medical Center, Utrecht University, Utrecht, Netherlands
| | - Lisa W Rodenburg
- Regenerative Medicine Utrecht, University Medical Center, Utrecht University, Utrecht, Netherlands
| | - Wan Namkung
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, South Korea
| | - Karl Kunzelmann
- Physiological Institute, University of Regensburg, Regensburg, Germany
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11
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Campbell C, Faleel FDM, Scheyer MW, Haralu S, Williams PL, Carbo WD, Wilson-Taylor AS, Patel NH, Sanders CR, Lorigan GA, Sahu ID. Comparing the structural dynamics of the human KCNE3 in reconstituted micelle and lipid bilayered vesicle environments. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183974. [PMID: 35716725 DOI: 10.1016/j.bbamem.2022.183974] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 05/12/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
KCNE3 is a single transmembrane protein of the KCNE family that modulates the function and trafficking of several voltage-gated potassium channels, including KCNQ1. Structural studies of KCNE3 have been previously conducted in a wide range of model membrane mimics. However, it is important to assess the impact of the membrane mimics used on the observed conformation and dynamics. In this study, we have optimized a method for the reconstitution of the KCNE3 into POPC/POPG lipid bilayer vesicles for electron paramagnetic resonance (EPR) spectroscopy. Our CD spectroscopic data suggested that the degree of regular secondary structure for KCNE3 protein reconstituted into lipid bilayered vesicle is significantly higher than in DPC detergent micelles. Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling (SDSL) was used to probe the structural dynamics of S49C, M59C, L67C, V85C, and S101C mutations of KCNE3 in both DPC micelles and in POPC/POPG lipid bilayered vesicles. Our CW-EPR power saturation data suggested that the site S74C is buried inside the lipid bilayered membrane while the site V85C is located outside the membrane, in contrast to DPC micelle results. These results suggest that the KCNE3 micelle structures need to be refined using data obtained in the lipid bilayered vesicles in order to ascertain the native structure of KCNE3. This work will provide guidelines for detailed structural studies of KCNE3 in a more native membrane environment and comparing the lipid bilayer results to the isotropic bicelle structure and to the KCNQ1-bound cryo-EM structure.
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Affiliation(s)
- Conner Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | | | - Matthew W Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - Samuel Haralu
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - Patrick L Williams
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - William David Carbo
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | | | - Nima H Patel
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - Charles R Sanders
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville, TN, United States of America
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, United States of America
| | - Indra D Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America; Department of Chemistry and Biochemistry, Miami University, Oxford, OH, United States of America.
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12
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Greenwald MA, Wolfgang MC. The changing landscape of the cystic fibrosis lung environment: From the perspective of Pseudomonas aeruginosa. Curr Opin Pharmacol 2022; 65:102262. [DOI: 10.1016/j.coph.2022.102262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 05/20/2022] [Accepted: 05/24/2022] [Indexed: 02/03/2023]
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13
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Asare IK, Galende AP, Garcia AB, Cruz MF, Moura ACM, Campbell CC, Scheyer M, Alao JP, Alston S, Kravats AN, Sanders CR, Lorigan GA, Sahu ID. Investigating Structural Dynamics of KCNE3 in Different Membrane Environments Using Molecular Dynamics Simulations. MEMBRANES 2022; 12:membranes12050469. [PMID: 35629795 PMCID: PMC9147993 DOI: 10.3390/membranes12050469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/21/2022] [Accepted: 04/21/2022] [Indexed: 11/27/2022]
Abstract
KCNE3 is a potassium channel accessory transmembrane protein that regulates the function of various voltage-gated potassium channels such as KCNQ1. KCNE3 plays an important role in the recycling of potassium ion by binding with KCNQ1. KCNE3 can be found in the small intestine, colon, and in the human heart. Despite its biological significance, there is little information on the structural dynamics of KCNE3 in native-like membrane environments. Molecular dynamics (MD) simulations are a widely used as a tool to study the conformational dynamics and interactions of proteins with lipid membranes. In this study, we have utilized all-atom molecular dynamics simulations to characterize the molecular motions and the interactions of KCNE3 in a bilayer composed of: a mixture of POPC and POPG lipids (3:1), POPC alone, and DMPC alone. Our MD simulation results suggested that the transmembrane domain (TMD) of KCNE3 is less flexible and more stable when compared to the N- and C-termini of KCNE3 in all three membrane environments. The conformational flexibility of N- and C-termini varies across these three lipid environments. The MD simulation results further suggested that the TMD of KCNE3 spans the membrane width, having residue A69 close to the center of the lipid bilayers and residues S57 and S82 close to the lipid bilayer membrane surfaces. These results are consistent with previous biophysical studies of KCNE3. The outcomes of these MD simulations will help design biophysical experiments and complement the experimental data obtained on KCNE3 to obtain a more detailed understanding of its structural dynamics in the native membrane environment.
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Affiliation(s)
- Isaac K. Asare
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Alberto Perez Galende
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Andres Bastidas Garcia
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Mateo Fernandez Cruz
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Anna Clara Miranda Moura
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Conner C. Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Matthew Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - John Paul Alao
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
| | - Steve Alston
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Andrea N. Kravats
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
| | - Charles R. Sanders
- Center for Structural Biology, Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA;
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
- Correspondence: (G.A.L.); (I.D.S.); Tel.: +1-(513)-529-2813 (G.A.L.); +1-(270)-789-5597 (I.D.S.)
| | - Indra D. Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
- Correspondence: (G.A.L.); (I.D.S.); Tel.: +1-(513)-529-2813 (G.A.L.); +1-(270)-789-5597 (I.D.S.)
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14
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Sanguinetti MC, Seebohm G. Physiological Functions, Biophysical Properties, and Regulation of KCNQ1 (K V7.1) Potassium Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1349:335-353. [PMID: 35138621 DOI: 10.1007/978-981-16-4254-8_15] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
KCNQ1 (KV7.1) K+ channels are expressed in multiple tissues, including the heart, pancreas, colon, and inner ear. The gene encoding the KCNQ1 protein was discovered by a positional cloning effort to determine the genetic basis of long QT syndrome, an inherited ventricular arrhythmia that can cause sudden death. Mutations in KCNQ1 can also cause other types of arrhythmia (i.e., short QT syndrome, atrial fibrillation) and the gene may also have a role in diabetes and certain cancers. KCNQ1 α-subunits can partner with accessory β-subunits (KCNE1-KCNE5) to form K+-selective channels that have divergent biophysical properties. In the heart, KCNQ1 α-subunits coassemble with KCNE1 β-subunits to form channels that conduct IKs, a very slowly activating delayed rectifier K+ current. KV7.1 channels are highly regulated by PIP2, calmodulin, and phosphorylation, and rich pharmacology includes blockers and gating modulators. Recent biophysical studies and a cryo-EM structure of the KCNQ1-calmodulin complex have provided new insights into KV7.1 channel function, and how interactions between KCNQ1 and KCNE subunits alter the gating properties of heteromultimeric channels.
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Affiliation(s)
| | - Guiscard Seebohm
- Cellular Electrophysiology and Molecular Biology, Institute for Genetics of Heart Diseases, University Hospital Münster, Münster, Germany
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15
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Gao T, Li K, Liang F, Yu J, Liu A, Ni Y, Sun P. KCNQ1 Potassium Channel Expressed in Human Sperm Is Involved in Sperm Motility, Acrosome Reaction, Protein Tyrosine Phosphorylation, and Ion Homeostasis During Capacitation. Front Physiol 2021; 12:761910. [PMID: 34744797 PMCID: PMC8569670 DOI: 10.3389/fphys.2021.761910] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 09/29/2021] [Indexed: 11/16/2022] Open
Abstract
Potassium channels are involved in membrane hyperpolarization and ion homeostasis regulation during human sperm capacitation. However, the types of potassium channels in human sperm remain controversial. The voltage-gated ion channel KCNQ1 is ubiquitously expressed and regulates key physiological processes in the human body. In the present study, we investigated whether KCNQ1 is expressed in human sperm and what role it might have in sperm function. The expression and localization of KCNQ1 in human sperm were evaluated using Western blotting and indirect immunofluorescence. During capacitation incubation, human sperm were treated with KCNQ1- specific inhibitor chromanol 293B. Sperm motility was analyzed using a computer-assisted sperm analyzer. The acrosome reaction was studied using fluorescein isothiocyanate-conjugated Pisum sativum agglutinin staining. Protein tyrosine phosphorylation levels and localization after capacitation were determined using Western blotting and immunofluorescence. Intracellular K+, Ca2+, Cl−, pH, and membrane potential were analyzed using fluorescent probes. The results demonstrate that KCNQ1 is expressed and localized in the head and tail regions of human sperm. KCNQ1 inhibition reduced sperm motility, acrosome reaction rates, and protein tyrosine phosphorylation but had no effect on hyperactivation. KCNQ1 inhibition also increased intracellular K+, membrane potential, and intracellular Cl−, while decreasing intracellular Ca2+ and pH. In conclusion, the KCNQ1 channel plays a crucial role during human sperm capacitation.
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Affiliation(s)
- Tian Gao
- School of Pharmacy, Hangzhou Medical College, Hangzhou, China
| | - Kun Li
- School of Pharmacy, Hangzhou Medical College, Hangzhou, China.,Zhejiang Provincial Laboratory of Experimental Animal's & Nonclinical Laboratory Studies, Hangzhou Medical College, Hangzhou, China
| | - Fei Liang
- School of Pharmacy, Hangzhou Medical College, Hangzhou, China.,Zhejiang Provincial Laboratory of Experimental Animal's & Nonclinical Laboratory Studies, Hangzhou Medical College, Hangzhou, China
| | - Jianmin Yu
- School of Pharmacy, Hangzhou Medical College, Hangzhou, China.,Zhejiang Provincial Laboratory of Experimental Animal's & Nonclinical Laboratory Studies, Hangzhou Medical College, Hangzhou, China
| | - Ajuan Liu
- School of Pharmacy, Hangzhou Medical College, Hangzhou, China
| | - Ya Ni
- School of Pharmacy, Hangzhou Medical College, Hangzhou, China.,Zhejiang Provincial Laboratory of Experimental Animal's & Nonclinical Laboratory Studies, Hangzhou Medical College, Hangzhou, China
| | - Peibei Sun
- School of Pharmacy, Hangzhou Medical College, Hangzhou, China.,Zhejiang Provincial Laboratory of Experimental Animal's & Nonclinical Laboratory Studies, Hangzhou Medical College, Hangzhou, China
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16
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Tharabenjasin P, Ferraris RP, Choowongkomon K, Pongkorpsakol P, Worakajit N, Sawasvirojwong S, Pabalan N, Na-Bangchang K, Muanprasat C. β-eudesmol but not atractylodin exerts an inhibitory effect on CFTR-mediated chloride transport in human intestinal epithelial cells. Biomed Pharmacother 2021; 142:112030. [PMID: 34426253 DOI: 10.1016/j.biopha.2021.112030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 07/13/2021] [Accepted: 08/07/2021] [Indexed: 11/19/2022] Open
Abstract
Oriental herbal medicine with the two bioactive constituents, β-eudesmol (BE) and atractylodin (AT), has been used as a remedy for gastrointestinal disorders. There was no scientific evidence reporting their antidiarrheal effect and underpinning mechanisms. Therefore, we aimed to investigate the anti-secretory activity of these two compounds in vitro. The inhibitory effect of BE and AT on cAMP-induced Cl- secretion was evaluated by Ussing chamber in human intestinal epithelial (T84) cells. Short-circuit current (ISC) and apical Cl- current (ICl-) were measured after adding indirect and direct cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel activator. MTT assay was used to determine cellular cytotoxicity. Protein-ligand interaction was investigated by in silico molecular docking analysis. BE, but not AT concentration-dependently (IC50 of ~1.05 µM) reduced cAMP-mediated, CFTRinh-172 inhibitable Cl- secretion as determined by transepithelial ISC across a monolayer of T84 cells. Potency of CFTR-mediated ICl- inhibition by BE did not change with the use of different CFTR activators suggesting a direct blockage of the channel active site(s). Pretreatment with BE completely prevented cAMP-induced ICl-. Furthermore, BE at concentrations up to 200 µM (24 h) had no effect on T84 cell viability. In silico studies indicated that BE could best dock onto dephosphorylated structure of CFTR at ATP-binding pockets in nucleotide-binding domain (NBD) 2 region. These findings provide the first evidence for the anti-secretory effect of BE involving inhibition of CFTR function. BE represents a promising candidate for the therapeutic or prophylactic intervention of diarrhea resulted from intestinal hypersecretion of Cl.
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Affiliation(s)
- Phuntila Tharabenjasin
- Chulabhorn International College of Medicine, Thammasat University (Rangsit Campus), Klongnung, Klongluang, Pathum Thani 10120, Thailand
| | - Ronaldo P Ferraris
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07946, USA
| | - Kiattawee Choowongkomon
- Department of Biochemistry, Faculty of Science, Kasetsart University, Ngam Wong Wan Rd, Ladyaow, Chatuchak, Bangkok 10900, Thailand
| | - Pawin Pongkorpsakol
- Faculty of Medicine and Public Health, HRH Princess Chulabhorn College of Medical Science, Chulabhorn Royal Academy, Bangkok 10210, Thailand
| | - Nichakorn Worakajit
- Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bang Pla, Bang Phli, Samut Prakan 10540, Thailand
| | - Sutthipong Sawasvirojwong
- Department of Pathology, Faculty of Medicine, Chulalongkorn University, Phayathai Rd, Pathumwan, Bangkok 10330, Thailand
| | - Noel Pabalan
- Chulabhorn International College of Medicine, Thammasat University (Rangsit Campus), Klongnung, Klongluang, Pathum Thani 10120, Thailand
| | - Kesara Na-Bangchang
- Chulabhorn International College of Medicine, Thammasat University (Rangsit Campus), Klongnung, Klongluang, Pathum Thani 10120, Thailand; Center of Excellence in Pharmacology and Molecular Biology of Malaria and Cholangiocarcinoma, Chulabhorn International College of Medicine, Rangsit Center, Thammasat University (Rangsit Campus), Klongnung, Klongluang, Pathum Thani 10120, Thailand
| | - Chatchai Muanprasat
- Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bang Pla, Bang Phli, Samut Prakan 10540, Thailand.
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17
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Goblet cell LRRC26 regulates BK channel activation and protects against colitis in mice. Proc Natl Acad Sci U S A 2021; 118:2019149118. [PMID: 33431687 DOI: 10.1073/pnas.2019149118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Goblet cells (GCs) are specialized cells of the intestinal epithelium contributing critically to mucosal homeostasis. One of the functions of GCs is to produce and secrete MUC2, the mucin that forms the scaffold of the intestinal mucus layer coating the epithelium and separates the luminal pathogens and commensal microbiota from the host tissues. Although a variety of ion channels and transporters are thought to impact on MUC2 secretion, the specific cellular mechanisms that regulate GC function remain incompletely understood. Previously, we demonstrated that leucine-rich repeat-containing protein 26 (LRRC26), a known regulatory subunit of the Ca2+-and voltage-activated K+ channel (BK channel), localizes specifically to secretory cells within the intestinal tract. Here, utilizing a mouse model in which MUC2 is fluorescently tagged, thereby allowing visualization of single GCs in intact colonic crypts, we show that murine colonic GCs have functional LRRC26-associated BK channels. In the absence of LRRC26, BK channels are present in GCs, but are not activated at physiological conditions. In contrast, all tested MUC2- cells completely lacked BK channels. Moreover, LRRC26-associated BK channels underlie the BK channel contribution to the resting transepithelial current across mouse distal colonic mucosa. Genetic ablation of either LRRC26 or BK pore-forming α-subunit in mice results in a dramatically enhanced susceptibility to colitis induced by dextran sodium sulfate. These results demonstrate that normal potassium flux through LRRC26-associated BK channels in GCs has protective effects against colitis in mice.
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18
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Lam GY, Goodwin J, Wilcox PG, Quon BS. Sex disparities in cystic fibrosis: review on the effect of female sex hormones on lung pathophysiology and outcomes. ERJ Open Res 2021; 7:00475-2020. [PMID: 33532475 PMCID: PMC7836644 DOI: 10.1183/23120541.00475-2020] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 10/13/2020] [Indexed: 12/13/2022] Open
Abstract
Sex differences in morbidity and mortality have been reported in the cystic fibrosis (CF) population worldwide. However, it is unclear why CF women have worse clinical outcomes than men. In this review, we focus on the influence of female sex hormones on CF pulmonary outcomes and summarise data from in vitro and in vivo experiments on how oestrogen and progesterone might modify mucociliary clearance, immunity and infection in the CF airways. The potential for novel sex hormone-related therapeutic interventions is also discussed. A disparity in survival has been noted between men and women with cystic fibrosis where female sex hormones may facilitate lung disease progression. There is strong evidence that implicates oestrogen in numerous aspects of CF airway pathophysiology.https://bit.ly/34ef4Cv
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Affiliation(s)
- Grace Y Lam
- Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.,Adult Cystic Fibrosis Program, St Paul's Hospital, Vancouver, BC, Canada
| | - Jodi Goodwin
- Adult Cystic Fibrosis Program, St Paul's Hospital, Vancouver, BC, Canada
| | - Pearce G Wilcox
- Adult Cystic Fibrosis Program, St Paul's Hospital, Vancouver, BC, Canada
| | - Bradley S Quon
- Centre for Heart Lung Innovation, St Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.,Adult Cystic Fibrosis Program, St Paul's Hospital, Vancouver, BC, Canada
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19
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Inhibition of CFTR-mediated intestinal chloride secretion by a fungus-derived arthropsolide A: Mechanism of action and anti-diarrheal efficacy. Eur J Pharmacol 2020; 885:173393. [DOI: 10.1016/j.ejphar.2020.173393] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/10/2020] [Accepted: 07/20/2020] [Indexed: 11/19/2022]
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20
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Rapetti-Mauss R, Berenguier C, Allegrini B, Soriani O. Interplay Between Ion Channels and the Wnt/β-Catenin Signaling Pathway in Cancers. Front Pharmacol 2020; 11:525020. [PMID: 33117152 PMCID: PMC7552962 DOI: 10.3389/fphar.2020.525020] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 08/31/2020] [Indexed: 12/12/2022] Open
Abstract
Increasing evidence point out the important roles of ion channels in the physiopathology of cancers, so that these proteins are now considered as potential new therapeutic targets and biomarkers in this disease. Indeed, ion channels have been largely described to participate in many hallmarks of cancers such as migration, invasion, proliferation, angiogenesis, and resistance to apoptosis. At the molecular level, the development of cancers is characterised by alterations in transduction pathways that control cell behaviors. However, the interactions between ion channels and cancer-related signaling pathways are poorly understood so far. Nevertheless, a limited number of reports have recently addressed this important issue, especially regarding the interaction between ion channels and one of the main driving forces for cancer development: the Wnt/β-catenin signaling pathway. In this review, we propose to explore and discuss the current knowledge regarding the interplay between ion channels and the Wnt/β-catenin signaling pathway in cancers.
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21
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Vega G, Guequén A, Philp AR, Gianotti A, Arzola L, Villalón M, Zegarra-Moran O, Galietta LJ, Mall MA, Flores CA. Lack of Kcnn4 improves mucociliary clearance in muco-obstructive lung disease. JCI Insight 2020; 5:140076. [PMID: 32814712 PMCID: PMC7455130 DOI: 10.1172/jci.insight.140076] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 07/08/2020] [Indexed: 12/11/2022] Open
Abstract
Airway mucociliary clearance (MCC) is the main mechanism of lung defense keeping airways free of infection and mucus obstruction. Airway surface liquid volume, ciliary beating, and mucus are central for proper MCC and critically regulated by sodium absorption and anion secretion. Impaired MCC is a key feature of muco-obstructive diseases. The calcium-activated potassium channel KCa.3.1, encoded by Kcnn4, participates in ion secretion, and studies showed that its activation increases Na+ absorption in airway epithelia, suggesting that KCa3.1-induced hyperpolarization was sufficient to drive Na+ absorption. However, its role in airway epithelium is not fully understood. We aimed to elucidate the role of KCa3.1 in MCC using a genetically engineered mouse. KCa3.1 inhibition reduced Na+ absorption in mouse and human airway epithelium. Furthermore, the genetic deletion of Kcnn4 enhanced cilia beating frequency and MCC ex vivo and in vivo. Kcnn4 silencing in the Scnn1b-transgenic mouse (Scnn1btg/+), a model of muco-obstructive lung disease triggered by increased epithelial Na+ absorption, improved MCC, reduced Na+ absorption, and did not change the amount of mucus but did reduce mucus adhesion, neutrophil infiltration, and emphysema. Our data support that KCa3.1 inhibition attenuated muco-obstructive disease in the Scnn1btg/+ mice. K+ channel modulation may be a therapeutic strategy to treat muco-obstructive lung diseases. Silencing the calcium-activated potassium channel KCa.3.1 improves mucociliary clearance in muco-obstructive lung disease by decreasing sodium absorption in the airways.
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Affiliation(s)
| | - Anita Guequén
- Centro de Estudios Científicos, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | - Amber R Philp
- Centro de Estudios Científicos, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | | | - Llilian Arzola
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Manuel Villalón
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile
| | | | - Luis Jv Galietta
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy.,Department of Translational Medical Sciences, University of Naples Federico II, Naples, Italy
| | - Marcus A Mall
- Department of Pediatric Pulmonology, Immunology and Critical Care Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Berlin Institute of Health, Berlin, Germany.,German Center for Lung Research, Berlin, Germany
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22
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Abstract
Kv7 channels (Kv7.1-7.5) are voltage-gated K+ channels that can be modulated by five β-subunits (KCNE1-5). Kv7.1-KCNE1 channels produce the slow-delayed rectifying K+ current, IKs, which is important during the repolarization phase of the cardiac action potential. Kv7.2-7.5 are predominantly neuronally expressed and constitute the muscarinic M-current and control the resting membrane potential in neurons. Kv7.1 produces drastically different currents as a result of modulation by KCNE subunits. This flexibility allows the Kv7.1 channel to have many roles depending on location and assembly partners. The pharmacological sensitivity of Kv7.1 channels differs from that of Kv7.2-7.5 and is largely dependent upon the number of β-subunits present in the channel complex. As a result, the development of pharmaceuticals targeting Kv7.1 is problematic. This review discusses the roles and the mechanisms by which different signaling pathways affect Kv7.1 and KCNE channels and could potentially provide different ways of targeting the channel.
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Affiliation(s)
- Emely Thompson
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada;
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23
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van der Horst J, Greenwood IA, Jepps TA. Cyclic AMP-Dependent Regulation of Kv7 Voltage-Gated Potassium Channels. Front Physiol 2020; 11:727. [PMID: 32695022 PMCID: PMC7338754 DOI: 10.3389/fphys.2020.00727] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 06/04/2020] [Indexed: 01/08/2023] Open
Abstract
Voltage-gated Kv7 potassium channels, encoded by KCNQ genes, have major physiological impacts cardiac myocytes, neurons, epithelial cells, and smooth muscle cells. Cyclic adenosine monophosphate (cAMP), a well-known intracellular secondary messenger, can activate numerous downstream effector proteins, generating downstream signaling pathways that regulate many functions in cells. A role for cAMP in ion channel regulation has been established, and recent findings show that cAMP signaling plays a role in Kv7 channel regulation. Although cAMP signaling is recognized to regulate Kv7 channels, the precise molecular mechanism behind the cAMP-dependent regulation of Kv7 channels is complex. This review will summarize recent research findings that support the mechanisms of cAMP-dependent regulation of Kv7 channels.
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Affiliation(s)
- Jennifer van der Horst
- Vascular Biology Group, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Iain A Greenwood
- Molecular and Clinical Sciences Institute, St. George's University of London, London, United Kingdom
| | - Thomas A Jepps
- Vascular Biology Group, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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24
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Mondejar-Parreño G, Perez-Vizcaino F, Cogolludo A. Kv7 Channels in Lung Diseases. Front Physiol 2020; 11:634. [PMID: 32676036 PMCID: PMC7333540 DOI: 10.3389/fphys.2020.00634] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/18/2020] [Indexed: 12/23/2022] Open
Abstract
Lung diseases constitute a global health concern causing disability. According to WHO in 2016, respiratory diseases accounted for 24% of world population mortality, the second cause of death after cardiovascular diseases. The Kv7 channels family is a group of voltage-dependent K+ channels (Kv) encoded by KCNQ genes that are involved in various physiological functions in numerous cell types, especially, cardiac myocytes, smooth muscle cells, neurons, and epithelial cells. Kv7 channel α-subunits are regulated by KCNE1–5 ancillary β-subunits, which modulate several characteristics of Kv7 channels such as biophysical properties, cell-location, channel trafficking, and pharmacological sensitivity. Kv7 channels are mainly expressed in two large groups of lung tissues: pulmonary arteries (PAs) and bronchial tubes. In PA, Kv7 channels are expressed in pulmonary artery smooth muscle cells (PASMCs); while in the airway (trachea, bronchus, and bronchioles), Kv7 channels are expressed in airway smooth muscle cells (ASMCs), airway epithelial cells (AEPs), and vagal airway C-fibers (VACFs). The functional role of Kv7 channels may vary depending on the cell type. Several studies have demonstrated that the impairment of Kv7 channel has a strong impact on pulmonary physiology contributing to the pathophysiology of different respiratory diseases such as cystic fibrosis, asthma, chronic obstructive pulmonary disease, chronic coughing, lung cancer, and pulmonary hypertension. Kv7 channels are now recognized as playing relevant physiological roles in many tissues, which have encouraged the search for Kv7 channel modulators with potential therapeutic use in many diseases including those affecting the lung. Modulation of Kv7 channels has been proposed to provide beneficial effects in a number of lung conditions. Therefore, Kv7 channel openers/enhancers or drugs acting partly through these channels have been proposed as bronchodilators, expectorants, antitussives, chemotherapeutics and pulmonary vasodilators.
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Affiliation(s)
- Gema Mondejar-Parreño
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
| | - Francisco Perez-Vizcaino
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
| | - Angel Cogolludo
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
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25
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Park JH, Ousingsawat J, Cabrita I, Bettels RE, Große-Onnebrink J, Schmalstieg C, Biskup S, Reunert J, Rust S, Schreiber R, Kunzelmann K, Marquardt T. TMEM16A deficiency: a potentially fatal neonatal disease resulting from impaired chloride currents. J Med Genet 2020; 58:247-253. [PMID: 32487539 DOI: 10.1136/jmedgenet-2020-106978] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/14/2020] [Accepted: 04/18/2020] [Indexed: 12/13/2022]
Abstract
INTRODUCTION TMEM16A is a calcium-activated chloride channel expressed in various secretory epithelia. Two siblings presented in early infancy with reduced intestinal peristalsis and recurrent episodes of haemorrhagic diarrhoea. In one of them, the episodes were characterised by hepatic pneumatosis with gas bubbles in the portal vein similar to necrotising enterocolitis of the newborn. METHODS Exome sequencing identified a homozygous truncating pathogenic variant in ANO1. Expression analysis was performed using reverse transcription PCR, western blot and immunohistochemistry. Electrophysiological and cell biological studies were employed to characterise the effects on ion transport both in patient respiratory epithelial cells and in transfected HEK293 cells. RESULTS The identified variant led to TMEM16A dysfunction, which resulted in abolished calcium-activated Cl- currents. Secondarily, CFTR function is affected due to the close interplay between both channels without inducing cystic fibrosis (CF). CONCLUSION TMEM16A deficiency is a potentially fatal disorder caused by abolished calcium-activated Cl- currents in secretory epithelia. Secondary impairment of CFTR function did not cause a CF phenotyp, which may have implications for CF treatment.
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Affiliation(s)
- Julien H Park
- Department of Paediatrics, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
| | | | - Inês Cabrita
- Department of Physiology, University of Regensburg, Regensburg, Bayern, Germany
| | - Ruth E Bettels
- Department of Paediatrics, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
| | - Jörg Große-Onnebrink
- Department of Paediatrics, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
| | - Christian Schmalstieg
- Department of Paediatrics, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
| | | | - Janine Reunert
- Department of Paediatrics, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
| | - Stephan Rust
- Department of Paediatrics, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
| | - Rainer Schreiber
- Department of Physiology, University of Regensburg, Regensburg, Bayern, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, Regensburg, Bayern, Germany
| | - Thorsten Marquardt
- Department of Paediatrics, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
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26
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Brewer KR, Kuenze G, Vanoye CG, George AL, Meiler J, Sanders CR. Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome. Front Pharmacol 2020; 11:550. [PMID: 32431610 PMCID: PMC7212895 DOI: 10.3389/fphar.2020.00550] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022] Open
Abstract
The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.
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Affiliation(s)
- Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
| | - Carlos G. Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Alfred L. George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
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27
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Taylor KC, Kang PW, Hou P, Yang ND, Kuenze G, Smith JA, Shi J, Huang H, White KM, Peng D, George AL, Meiler J, McFeeters RL, Cui J, Sanders CR. Structure and physiological function of the human KCNQ1 channel voltage sensor intermediate state. eLife 2020; 9:e53901. [PMID: 32096762 PMCID: PMC7069725 DOI: 10.7554/elife.53901] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 02/24/2020] [Indexed: 12/14/2022] Open
Abstract
Voltage-gated ion channels feature voltage sensor domains (VSDs) that exist in three distinct conformations during activation: resting, intermediate, and activated. Experimental determination of the structure of a potassium channel VSD in the intermediate state has previously proven elusive. Here, we report and validate the experimental three-dimensional structure of the human KCNQ1 voltage-gated potassium channel VSD in the intermediate state. We also used mutagenesis and electrophysiology in Xenopus laevisoocytes to functionally map the determinants of S4 helix motion during voltage-dependent transition from the intermediate to the activated state. Finally, the physiological relevance of the intermediate state KCNQ1 conductance is demonstrated using voltage-clamp fluorometry. This work illuminates the structure of the VSD intermediate state and demonstrates that intermediate state conductivity contributes to the unusual versatility of KCNQ1, which can function either as the slow delayed rectifier current (IKs) of the cardiac action potential or as a constitutively active epithelial leak current.
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Affiliation(s)
- Keenan C Taylor
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Po Wei Kang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Panpan Hou
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Nien-Du Yang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Departments of Chemistry and Pharmacology, Vanderbilt UniversityNashvilleUnited States
| | - Jarrod A Smith
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Jingyi Shi
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Hui Huang
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Kelli McFarland White
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Dungeng Peng
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical CenterNashvilleUnited States
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of MedicineChicagoUnited States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Departments of Chemistry and Pharmacology, Vanderbilt UniversityNashvilleUnited States
- Department of Bioinformatics, Vanderbilt University Medical CenterNashvilleUnited States
| | - Robert L McFeeters
- Department of Chemistry, University of Alabama in HuntsvilleHuntsvilleUnited States
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Department of Medicine, Vanderbilt University Medical CenterNashvilleUnited States
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28
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Sun J, MacKinnon R. Structural Basis of Human KCNQ1 Modulation and Gating. Cell 2019; 180:340-347.e9. [PMID: 31883792 DOI: 10.1016/j.cell.2019.12.003] [Citation(s) in RCA: 154] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/25/2019] [Accepted: 12/04/2019] [Indexed: 01/04/2023]
Abstract
KCNQ1, also known as Kv7.1, is a voltage-dependent K+ channel that regulates gastric acid secretion, salt and glucose homeostasis, and heart rhythm. Its functional properties are regulated in a tissue-specific manner through co-assembly with beta subunits KCNE1-5. In non-excitable cells, KCNQ1 forms a complex with KCNE3, which suppresses channel closure at negative membrane voltages that otherwise would close it. Pore opening is regulated by the signaling lipid PIP2. Using cryoelectron microscopy (cryo-EM), we show that KCNE3 tucks its single-membrane-spanning helix against KCNQ1, at a location that appears to lock the voltage sensor in its depolarized conformation. Without PIP2, the pore remains closed. Upon addition, PIP2 occupies a site on KCNQ1 within the inner membrane leaflet, which triggers a large conformational change that leads to dilation of the pore's gate. It is likely that this mechanism of PIP2 activation is conserved among Kv7 channels.
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Affiliation(s)
- Ji Sun
- Laboratory of Molecular Neurobiology and Biophysics and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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29
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The membrane protein KCNQ1 potassium ion channel: Functional diversity and current structural insights. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183148. [PMID: 31825788 DOI: 10.1016/j.bbamem.2019.183148] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 11/15/2019] [Accepted: 12/04/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Ion channels play crucial roles in cellular biology, physiology, and communication including sensory perception. Voltage-gated potassium (Kv) channels execute their function by sensor activation, pore-coupling, and pore opening leading to K+ conductance. SCOPE OF REVIEW This review focuses on a voltage-gated K+ ion channel KCNQ1 (Kv 7.1). Firstly, discussing its positioning in the human ion chanome, and the role of KCNQ1 in the multitude of cellular processes. Next, we discuss the overall channel architecture and current structural insights on KCNQ1. Finally, the gating mechanism involving members of the KCNE family and its interaction with non-KCNE partners. MAJOR CONCLUSIONS KCNQ1 executes its important physiological functions via interacting with KCNE1 and non-KCNE1 proteins/molecules: calmodulin, PIP2, PKA. Although, KCNQ1 has been studied in great detail, several aspects of the channel structure and function still remain unexplored. This review emphasizes the structural and biophysical studies of KCNQ1, its interaction with KCNE1 and non-KCNE1 proteins and focuses on several seminal findings showing the role of VSD and the pore domain in the channel activation and gating properties. GENERAL SIGNIFICANCE KCNQ1 mutations can result in channel defects and lead to several diseases including atrial fibrillation and long QT syndrome. Therefore, a thorough structure-function understanding of this channel complex is essential to understand its role in both normal and disease biology. Moreover, unraveling the molecular mechanisms underlying the regulation of this channel complex will help to find therapeutic strategies for several diseases.
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30
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Deckelbaum RA, Lobov IB, Cheung E, Halasz G, Rajamani S, Lerner J, Tong C, Li Z, Boland P, Dominguez M, Hughes V, Yancopoulos GD, Murphy AJ, Thurston G, Cao J, Romano C, Gale NW. The potassium channel Kcne3 is a VEGFA-inducible gene selectively expressed by vascular endothelial tip cells. Angiogenesis 2019; 23:179-192. [PMID: 31754927 PMCID: PMC7160073 DOI: 10.1007/s10456-019-09696-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/02/2019] [Indexed: 12/22/2022]
Abstract
Angiogenesis is largely driven by motile endothelial tip-cells capable of invading avascular tissue domains and enabling new vessel formation. Highly responsive to Vascular Endothelial Growth-Factor-A (VEGFA), endothelial tip-cells also suppress angiogenic sprouting in adjacent stalk cells, and thus have been a primary therapeutic focus in addressing neovascular pathologies. Surprisingly, however, there remains a paucity of specific endothelial tip-cell markers. Here, we employ transcriptional profiling and a lacZ reporter allele to identify Kcne3 as an early and selective endothelial tip-cell marker in multiple angiogenic contexts. In development, Kcne3 expression initiates during early phases of angiogenesis (E9) and remains specific to endothelial tip-cells, often adjacent to regions expressing VEGFA. Consistently, Kcne3 activation is highly responsive to exogenous VEGFA but maintains tip-cell specificity throughout normal retinal angiogenesis. We also demonstrate endothelial tip-cell selectivity of Kcne3 in several injury and tumor models. Together, our data show that Kcne3 is a unique marker of sprouting angiogenic tip-cells and offers new opportunities for investigating and targeting this cell type.
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Affiliation(s)
- Ron A Deckelbaum
- Department of Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA.
| | | | - Eunice Cheung
- Department of Ophthalmology, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Gabor Halasz
- Department of Bioinformatics, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Saathyaki Rajamani
- Department of Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Julia Lerner
- Department of Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Chunxiang Tong
- Department of Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Zhe Li
- Department of Oncology & Angiogenesis, Regeneron Pharmaceuticals Inc., Tarrytown, NY, 10591, USA
| | - Patricia Boland
- Department of Oncology & Angiogenesis, Regeneron Pharmaceuticals Inc., Tarrytown, NY, 10591, USA
| | - Melissa Dominguez
- Department of Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Virginia Hughes
- Department of Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - George D Yancopoulos
- Department of Research, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Andrew J Murphy
- Department of Research, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Gavin Thurston
- Department of Oncology & Angiogenesis, Regeneron Pharmaceuticals Inc., Tarrytown, NY, 10591, USA
| | - Jingtai Cao
- Department of Ophthalmology, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Carmelo Romano
- Department of Ophthalmology, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
| | - Nicholas W Gale
- Department of Pre-Therapeutic Target Discovery, Regeneron Pharmaceuticals Inc, Tarrytown, NY, 10591, USA
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Anderson KJ, Cormier RT, Scott PM. Role of ion channels in gastrointestinal cancer. World J Gastroenterol 2019; 25:5732-5772. [PMID: 31636470 PMCID: PMC6801186 DOI: 10.3748/wjg.v25.i38.5732] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 07/26/2019] [Accepted: 09/27/2019] [Indexed: 02/06/2023] Open
Abstract
In their seminal papers Hanahan and Weinberg described oncogenic processes a normal cell undergoes to be transformed into a cancer cell. The functions of ion channels in the gastrointestinal (GI) tract influence a variety of cellular processes, many of which overlap with these hallmarks of cancer. In this review we focus on the roles of the calcium (Ca2+), sodium (Na+), potassium (K+), chloride (Cl-) and zinc (Zn2+) transporters in GI cancer, with a special emphasis on the roles of the KCNQ1 K+ channel and CFTR Cl- channel in colorectal cancer (CRC). Ca2+ is a ubiquitous second messenger, serving as a signaling molecule for a variety of cellular processes such as control of the cell cycle, apoptosis, and migration. Various members of the TRP superfamily, including TRPM8, TRPM7, TRPM6 and TRPM2, have been implicated in GI cancers, especially through overexpression in pancreatic adenocarcinomas and down-regulation in colon cancer. Voltage-gated sodium channels (VGSCs) are classically associated with the initiation and conduction of action potentials in electrically excitable cells such as neurons and muscle cells. The VGSC NaV1.5 is abundantly expressed in human colorectal CRC cell lines as well as being highly expressed in primary CRC samples. Studies have demonstrated that conductance through NaV1.5 contributes significantly to CRC cell invasiveness and cancer progression. Zn2+ transporters of the ZIP/SLC39A and ZnT/SLC30A families are dysregulated in all major GI organ cancers, in particular, ZIP4 up-regulation in pancreatic cancer (PC). More than 70 K+ channel genes, clustered in four families, are found expressed in the GI tract, where they regulate a range of cellular processes, including gastrin secretion in the stomach and anion secretion and fluid balance in the intestinal tract. Several distinct types of K+ channels are found dysregulated in the GI tract. Notable are hERG1 upregulation in PC, gastric cancer (GC) and CRC, leading to enhanced cancer angiogenesis and invasion, and KCNQ1 down-regulation in CRC, where KCNQ1 expression is associated with enhanced disease-free survival in stage II, III, and IV disease. Cl- channels are critical for a range of cellular and tissue processes in the GI tract, especially fluid balance in the colon. Most notable is CFTR, whose deficiency leads to mucus blockage, microbial dysbiosis and inflammation in the intestinal tract. CFTR is a tumor suppressor in several GI cancers. Cystic fibrosis patients are at a significant risk for CRC and low levels of CFTR expression are associated with poor overall disease-free survival in sporadic CRC. Two other classes of chloride channels that are dysregulated in GI cancers are the chloride intracellular channels (CLIC1, 3 & 4) and the chloride channel accessory proteins (CLCA1,2,4). CLIC1 & 4 are upregulated in PC, GC, gallbladder cancer, and CRC, while the CLCA proteins have been reported to be down-regulated in CRC. In summary, it is clear, from the diverse influences of ion channels, that their aberrant expression and/or activity can contribute to malignant transformation and tumor progression. Further, because ion channels are often localized to the plasma membrane and subject to multiple layers of regulation, they represent promising clinical targets for therapeutic intervention including the repurposing of current drugs.
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Affiliation(s)
- Kyle J Anderson
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, United States
| | - Robert T Cormier
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, United States
| | - Patricia M Scott
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, United States
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32
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Kunzelmann K, Centeio R, Wanitchakool P, Cabrita I, Benedetto R, Saha T, Hoque KM, Schreiber R. Control of Ion Transport by Tmem16a Expressed in Murine Intestine. Front Physiol 2019; 10:1262. [PMID: 31680994 PMCID: PMC6797858 DOI: 10.3389/fphys.2019.01262] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 09/17/2019] [Indexed: 12/30/2022] Open
Abstract
Cl– secretion by the human and murine intestinal epithelium occurs through the cystic fibrosis transmembrane conductance regulator (cftr). However, the Ca2+ activated Cl– channel Tmem16a was shown to contribute to Cl– secretion, mainly, but not exclusively, as a basolaterally located Cl– channel that controls basolateral Ca2+ signaling, and thus activation of basolateral Ca2+ dependent Sk4 K+ channels. In intestinal goblet cells, Tmem16a was shown to regulated Ca2+ signals required for exocytosis of mucus. Because a recent report denied the existence and functional role of Tmem16a in murine intestine, we reexamined in detail expression of mRNA and protein for Tmem16a in mouse colon. In experiments using short-circuited Ussing chamber and whole cell patch-clamp techniques, we further compared ion transport in wild type (WT) colon with that in mice with intestinal epithelial specific knockout of Tmem16a. As reported earlier we fully confirm expression of Tmem16a in colonic epithelial cells and the role of Tmem16a for both Ca2+-dependent and cAMP-regulated ion secretion.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | - Raquel Centeio
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | | | - Inês Cabrita
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | - Roberta Benedetto
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | - Tultul Saha
- Division of Pathophysiology, National Institute of Cholera and Enteric Diseases, Kolkata, India
| | - Kazi Mirajul Hoque
- Division of Pathophysiology, National Institute of Cholera and Enteric Diseases, Kolkata, India.,Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Rainer Schreiber
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
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33
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Nakajo K. Gating modulation of the KCNQ1 channel by KCNE proteins studied by voltage-clamp fluorometry. Biophys Physicobiol 2019; 16:121-126. [PMID: 31236320 PMCID: PMC6587909 DOI: 10.2142/biophysico.16.0_121] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/01/2019] [Indexed: 01/22/2023] Open
Abstract
The KCNQ1 channel is a voltage-dependent potassium channel and is ubiquitously expressed throughout the human body including the heart, lung, kidney, pancreas, intestine and inner ear. Gating properties of the KCNQ1 channel are modulated by KCNE auxiliary subunits. For example, the KCNQ1-KCNE1 channel produces a slowly-activating potassium current, while KCNE3 makes KCNQ1 a voltage-independent, constitutively open channel. Thus, physiological functions of KCNQ1 channels are greatly dependent on the type of KCNE protein that is co-expressed in that organ. It has long been debated how the similar single transmembrane KCNE proteins produce quite different gating behaviors. Recent applications of voltage-clamp fluorometry (VCF) for the KCNQ1 channel have shed light on this question. The VCF is a quite sensitive method to detect structural changes of membrane proteins and is especially suitable for tracking the voltage sensor domains of voltage-gated ion channels. In this short review, I will introduce how the VCF technique can be applied to detect structural changes and what have been revealed by the recent VCF applications to the gating modulation of KCNQ1 channels by KCNE proteins.
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Affiliation(s)
- Koichi Nakajo
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
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Kunzelmann K, Ousingsawat J, Cabrita I, Doušová T, Bähr A, Janda M, Schreiber R, Benedetto R. TMEM16A in Cystic Fibrosis: Activating or Inhibiting? Front Pharmacol 2019; 10:3. [PMID: 30761000 PMCID: PMC6362895 DOI: 10.3389/fphar.2019.00003] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 01/04/2019] [Indexed: 12/26/2022] Open
Abstract
The inflammatory airway disease cystic fibrosis (CF) is characterized by airway obstruction due to mucus hypersecretion, airway plugging, and bronchoconstriction. The cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is dysfunctional in CF, leading to defects in epithelial transport. Although CF pathogenesis is still disputed, activation of alternative Cl- channels is assumed to improve lung function in CF. Two suitable non-CFTR Cl- channels are present in the airway epithelium, the Ca2+ activated channel TMEM16A and SLC26A9. Activation of these channels is thought to be feasible to improve hydration of the airway mucus and to increase mucociliary clearance. Interestingly, both channels are upregulated during inflammatory lung disease. They are assumed to support fluid secretion, necessary to hydrate excess mucus and to maintain mucus clearance. During inflammation, however, TMEM16A is upregulated particularly in mucus producing cells, with only little expression in ciliated cells. Recently it was shown that knockout of TMEM16A in ciliated cells strongly compromises Cl- conductance and attenuated mucus secretion, but does not lead to a CF-like lung disease and airway plugging. Along this line, activation of TMEM16A by denufosol, a stable purinergic ligand, failed to demonstrate any benefit to CF patients in earlier studies. It rather induced adverse effects such as cough. A number of studies suggest that TMEM16A is essential for mucus secretion and possibly also for mucus production. Evidence is now provided for a crucial role of TMEM16A in fusion of mucus-filled granules with the apical plasma membrane and cellular exocytosis. This is probably due to local Ca2+ signals facilitated by TMEM16A. Taken together, TMEM16A supports fluid secretion by ciliated airway epithelial cells, but also maintains excessive mucus secretion during inflammatory airway disease. Because TMEM16A also supports airway smooth muscle contraction, inhibition rather than activation of TMEM16A might be the appropriate treatment for CF lung disease, asthma and COPD. As a number of FDA-approved and well-tolerated drugs have been shown to inhibit TMEM16A, evaluation in clinical trials appears timely.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | | | - Inês Cabrita
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | - Tereza Doušová
- Department of Pediatrics, Second Faculty of Medicine, University Hospital Motol, Charles University in Prague, Prague, Czechia
| | - Andrea Bähr
- Institute of Molecular Animal Breeding and Biotechnology, Ludwig-Maximilians-Universität München, Munich, Germany
- Innere Medizin I, Klinikum Rechts der Isar der TU München, München, Germany
| | - Melanie Janda
- Institute of Molecular Animal Breeding and Biotechnology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Rainer Schreiber
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | - Roberta Benedetto
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
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Abstract
Mucociliary clearance is critically important in protecting the airways from infection and from the harmful effects of smoke and various inspired substances known to induce oxidative stress and persistent inflammation. An essential feature of the clearance mechanism involves regulation of the periciliary liquid layer on the surface of the airway epithelium, which is necessary for normal ciliary beating and maintenance of mucus hydration. The underlying ion transport processes associated with airway surface hydration include epithelial Na+ channel-dependent Na+ absorption occurring in parallel with CFTR and Ca2+-activated Cl- channel-dependent anion secretion, which are coordinately regulated to control the depth of the periciliary liquid layer. Oxidative stress is known to cause both acute and chronic effects on airway ion transport function, and an increasing number of studies in the past few years have identified an important role for autophagy as part of the physiological response to the damaging effects of oxidation. In this review, recent studies addressing the influence of oxidative stress and autophagy on airway ion transport pathways, along with results showing the potential of autophagy modulators in restoring the function of ion channels involved in transepithelial electrolyte transport necessary for effective mucociliary clearance, are presented.
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Affiliation(s)
- Scott M O'Grady
- Departments of Animal Science, Integrative Biology and Physiology, University of Minnesota , St. Paul, Minnesota
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Rajendran VM, Sandle GI. Colonic Potassium Absorption and Secretion in Health and Disease. Compr Physiol 2018; 8:1513-1536. [PMID: 30215859 PMCID: PMC9769410 DOI: 10.1002/cphy.c170030] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The colon has large capacities for K+ absorption and K+ secretion, but its role in maintaining K+ homeostasis is often overlooked. For many years, passive diffusion and/or solvent drag were thought to be the primary mechanisms for K+ absorption in human and animal colon. However, it is now clear that apical H+ ,K+ -ATPase, in coordination with basolateral K+ -Cl- cotransport and/or K+ and Cl- channels operating in parallel, mediate electroneutral K+ absorption in animal colon. We now know that K+ absorption in rat colon reflects ouabain-sensitive and ouabain-insensitive apical H+ ,K+ -ATPase activities. Ouabain-insensitive and ouabain-sensitive H+ ,K+ -ATPases are localized in surface and crypt cells, respectively. Colonic H+ ,K+ -ATPase consists of α- (HKCα ) and β- (HKCβ ) subunits which, when coexpressed, exhibit ouabain-insensitive H+ ,K+ -ATPase activity in HEK293 cells, while HKCα coexpressed with the gastric β-subunit exhibits ouabain-sensitive H+ ,K+ -ATPase activity in Xenopus oocytes. Aldosterone enhances apical H+ ,K+ -ATPase activity, HKCα specific mRNA and protein expression, and K+ absorption. Active K+ secretion, on the other hand, is mediated by apical K+ channels operating in a coordinated way with the basolateral Na+ -K+ -2Cl- cotransporter. Both Ca2+ -activated intermediate conductance K+ (IK) and large conductance K+ (BK) channels are located in the apical membrane of colonic epithelia. IK channel-mediated K+ efflux provides the driving force for Cl- secretion, while BK channels mediate active (e.g., cAMP-activated) K+ secretion. BK channel expression and activity are increased in patients with end-stage renal disease and ulcerative colitis. This review summarizes the role of apical H+ ,K+ -ATPase in K+ absorption, and apical BK channel function in K+ secretion in health and disease. © 2018 American Physiological Society. Compr Physiol 8:1513-1536, 2018.
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Affiliation(s)
| | - Geoffrey I. Sandle
- Leeds Institute of Biomedical and Clinical Sciences, St James’s University Hospital, Leeds LS9 7TF, UK
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Lucas ML. Enterocyte K + ion permeability and fluid secretion: missing the correct channel or missing the point? J Physiol 2018; 596:2463-2464. [PMID: 29604065 DOI: 10.1113/jp276102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Michael L Lucas
- School of Life Sciences, University of Glasgow, Room 311, West Medical Building, Glasgow, G12 9PW, UK
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Yin J, Tse CM, Avula LR, Singh V, Foulke-Abel J, de Jonge HR, Donowitz M. Molecular Basis and Differentiation-Associated Alterations of Anion Secretion in Human Duodenal Enteroid Monolayers. Cell Mol Gastroenterol Hepatol 2018; 5:591-609. [PMID: 29930980 PMCID: PMC6009799 DOI: 10.1016/j.jcmgh.2018.02.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 02/05/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS Human enteroids present a novel tool to study human intestinal ion transport physiology and pathophysiology. The present study describes the contributions of Cl- and HCO3- secretion to total cyclic adenosine monophosphate (cAMP)-stimulated electrogenic anion secretion in human duodenal enteroid monolayers and the relevant changes after differentiation. METHODS Human duodenal enteroids derived from 4 donors were grown as monolayers and differentiated by a protocol that includes the removal of Wnt3A, R-spondin1, and SB202190 for 5 days. The messenger RNA level and protein expression of selected ion transporters and carbonic anhydrase isoforms were determined by quantitative real-time polymerase chain reaction and immunoblotting, respectively. Undifferentiated and differentiated enteroid monolayers were mounted in the Ussing chamber/voltage-current clamp apparatus, using solutions that contained as well as lacked Cl- and HCO3-/CO2, to determine the magnitude of forskolin-induced short-circuit current change and its sensitivity to specific inhibitors that target selected ion transporters and carbonic anhydrase(s). RESULTS Differentiation resulted in a significant reduction in the messenger RNA level and protein expression of cystic fibrosis transmembrane conductance regulator, (CFTR) Na+/K+/2Cl- co-transporter 1 (NKCC1), and potassium channel, voltage gated, subfamily E, regulatory subunit 3 (KCNE3); and, conversely, increase of down-regulated-in-adenoma (DRA), electrogenic Na+/HCO3- co-transporter 1 (NBCe1), carbonic anhydrase 2 (CA2), and carbonic anhydrase 4 (CA4). Both undifferentiated and differentiated enteroids showed active cAMP-stimulated anion secretion that included both Cl- and HCO3- secretion as the magnitude of total active anion secretion was reduced after the removal of extracellular Cl- or HCO3-/CO2. The magnitude of total anion secretion in differentiated enteroids was approximately 33% of that in undifferentiated enteroids, primarily owing to the reduction in Cl- secretion with no significant change in HCO3- secretion. Anion secretion was consistently lower but detectable in differentiated enteroids compared with undifferentiated enteroids in the absence of extracellular Cl- or HCO3-/CO2. Inhibiting CFTR, NKCC1, carbonic anhydrase(s), cAMP-activated K+ channel(s), and Na+/K+-adenosine triphosphatase reduced cAMP-stimulated anion secretion in both undifferentiated and differentiated enteroids. CONCLUSIONS Human enteroids recapitulate anion secretion physiology of small intestinal epithelium. Enteroid differentiation is associated with significant alterations in the expression of several ion transporters and carbonic anhydrase isoforms, leading to a reduced but preserved anion secretory phenotype owing to markedly reduced Cl- secretion but no significant change in HCO3- secretion.
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Key Words
- AE2, anion exchanger 2
- Bicarbonate Secretion
- CA, carbonic anhydrase
- CFTR, cystic fibrosis transmembrane conductance regulator
- Chloride Secretion
- DRA
- DRA, down-regulated-in-adenoma
- Ion Transport
- Isc, short-circuit current
- KRB, Krebs–Ringer bicarbonate
- NBC, Na+/HCO3- co-transporter
- NBCe1, electrogenic Na+/HCO3- co-transporter 1
- NHE, Na+/H+ exchanger
- NKCC1, Na+/K+/2Cl- co-transporter 1
- SDS, sodium dodecyl sulfate
- SITS, 4-Acetamido-4′-isothiocyanato-2,2′-stilbenedisulfonic acid disodium salt hydrate
- TER, transepithelial electrical resistance
- cAMP, cyclic adenosine monophosphate
- mRNA, messenger ribonucleic acid
- qRT-PCR, quantitative real-time polymerase chain reaction
- ΔIsc, change in short-circuit current
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Affiliation(s)
- Jianyi Yin
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Chung-Ming Tse
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Leela Rani Avula
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Varsha Singh
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Jennifer Foulke-Abel
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Hugo R. de Jonge
- Department of Gastroenterology and Hepatology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Mark Donowitz
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland,Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland,Correspondence Address correspondence to: Mark Donowitz, MD, Johns Hopkins University School of Medicine, 720 Rutland Avenue, 925 Ross Research Building, Baltimore, Maryland 21205. fax: (410) 955-9677.
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Julio-Kalajzić F, Villanueva S, Burgos J, Ojeda M, Cid LP, Jentsch TJ, Sepúlveda FV. K 2P TASK-2 and KCNQ1-KCNE3 K + channels are major players contributing to intestinal anion and fluid secretion. J Physiol 2017; 596:393-407. [PMID: 29143340 DOI: 10.1113/jp275178] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Accepted: 11/08/2017] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS K+ channels are important in intestinal epithelium as they ensure the ionic homeostasis and electrical potential of epithelial cells during anion and fluid secretion. Intestinal epithelium cAMP-activated anion secretion depends on the activity of the (also cAMP dependent) KCNQ1-KCNE3 K+ channel, but the secretory process survives after genetic inactivation of the K+ channel in the mouse. Here we use double mutant mice to investigate which alternative K+ channels come into action to compensate for the absence of KCNQ1-KCNE3 K+ channels. Our data establish that whilst Ca2+ -activated KCa 3.1 channels are not involved, K2P two-pore domain TASK-2 K+ channels are major players providing an alternative conductance to sustain the intestinal secretory process. Work with double mutant mice lacking both TASK-2 and KCNQ1-KCNE3 channels nevertheless points to yet-unidentified K+ channels that contribute to the robustness of the cAMP-activated anion secretion process. ABSTRACT Anion and fluid secretion across the intestinal epithelium, a process altered in cystic fibrosis and secretory diarrhoea, is mediated by cAMP-activated CFTR Cl- channels and requires the simultaneous activity of basolateral K+ channels to maintain cellular ionic homeostasis and membrane potential. This function is fulfilled by the cAMP-activated K+ channel formed by the association of pore-forming KCNQ1 with its obligatory KCNE3 β-subunit. Studies using mice show sizeable cAMP-activated intestinal anion secretion in the absence of either KCNQ1 or KCNE3 suggesting that an alternative K+ conductance must compensate for the loss of KCNQ1-KCNE3 activity. We used double mutant mouse and pharmacological approaches to identify such a conductance. Ca2+ -dependent anion secretion can also be supported by Ca2+ -dependent KCa 3.1 channels after independent CFTR activation, but cAMP-dependent anion secretion is not further decreased in the combined absence of KCa 3.1 and KCNQ1-KCNE3 K+ channel activity. We show that the K2P K+ channel TASK-2 is expressed in the epithelium of the small and large intestine. Tetrapentylammonium, a TASK-2 inhibitor, abolishes anion secretory current remaining in the absence of KCNQ1-KCNE3 activity. A double mutant mouse lacking both KCNQ1-KCNE3 and TASK-2 showed a much reduced cAMP-mediated anion secretion compared to that observed in the single KCNQ1-KCNE3 deficient mouse. We conclude that KCNQ1-KCNE3 and TASK-2 play major roles in the intestinal anion and fluid secretory phenotype. The persistence of an, admittedly reduced, secretory activity in the absence of these two conductances suggests that further additional K+ channel(s) as yet unidentified contribute to the robustness of the intestinal anion secretory process.
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Affiliation(s)
| | - Sandra Villanueva
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | - Johanna Burgos
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | - Margarita Ojeda
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - L Pablo Cid
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
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Pongkorpsakol P, Yimnual C, Chatsudthipong V, Rukachaisirikul V, Muanprasat C. Cellular mechanisms underlying the inhibitory effect of flufenamic acid on chloride secretion in human intestinal epithelial cells. J Pharmacol Sci 2017; 134:93-100. [PMID: 28651800 DOI: 10.1016/j.jphs.2017.05.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 05/09/2017] [Accepted: 05/19/2017] [Indexed: 01/10/2023] Open
Abstract
Intestinal Cl- secretion is involved in the pathogenesis of secretory diarrheas including cholera. We recently demonstrated that flufenamic acid (FFA) suppressed Vibrio cholerae El Tor variant-induced intestinal fluid secretion via mechanisms involving AMPK activation and NF-κB-suppression. The present study aimed to investigate the effect of FFA on transepithelial Cl- secretion in human intestinal epithelial (T84) cells. FFA inhibited cAMP-dependent Cl- secretion in T84 cell monolayers with IC50 of ∼8 μM. Other fenamate drugs including tolfenamic acid, meclofenamic acid and mefenamic acid exhibited the same effect albeit with lower potency. FFA also inhibited activities of CFTR, a cAMP-activated apical Cl- channel, and KCNQ1/KCNE3, a cAMP-activated basolateral K+ channel. Mechanisms of CFTR inhibition by FFA did not involve activation of its negative regulators. Interestingly, FFA inhibited Ca2+-dependent Cl- secretion with IC50 of ∼10 μM. FFA inhibited activities of Ca2+-activated Cl- channels and KCa3.1, a Ca2+-activated basolateral K+ channels, but had no effect on activities of Na+-K+-Cl- cotransporters and Na+-K+ ATPases. These results indicate that FFA inhibits both cAMP and Ca2+-dependent Cl- secretion by suppressing activities of both apical Cl- channels and basolateral K+ channels. FFA and other fenamate drugs may be useful in the treatment of secretory diarrheas.
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Affiliation(s)
- Pawin Pongkorpsakol
- Translational Medicine Graduate Program, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand
| | - Chantapol Yimnual
- Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand
| | - Varanuj Chatsudthipong
- Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand
| | - Vatcharin Rukachaisirikul
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand
| | - Chatchai Muanprasat
- Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand; Excellent Center for Drug Discovery (ECDD), Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand.
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Bidirectional KCNQ1:β-catenin interaction drives colorectal cancer cell differentiation. Proc Natl Acad Sci U S A 2017; 114:4159-4164. [PMID: 28373572 DOI: 10.1073/pnas.1702913114] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The K+ channel KCNQ1 has been proposed as a tumor suppressor in colorectal cancer (CRC). We investigated the molecular mechanisms regulating KCNQ1:β-catenin bidirectional interactions and their effects on CRC differentiation, proliferation, and invasion. Molecular and pharmacologic approaches were used to determine the influence of KCNQ1 expression on the Wnt/β-catenin signaling and epithelial-to-mesenchymal transition (EMT) in human CRC cell lines of varying stages of differentiation. The expression of KCNQ1 was lost with increasing mesenchymal phenotype in poorly differentiated CRC cell lines as a consequence of repression of the KCNQ1 promoter by β-catenin:T-cell factor (TCF)-4. In well-differentiated epithelial CRC cell lines, KCNQ1 was localized to the plasma membrane in a complex with β-catenin and E-cadherin. The colocalization of KCNQ1 with adherens junction proteins was lost with increasing EMT phenotype. ShRNA knock-down of KCNQ1 caused a relocalization of β-catenin from the plasma membrane and a loss of epithelial phenotype in CRC spheroids. Overexpression of KCNQ1 trapped β-catenin at the plasma membrane, induced a patent lumen in CRC spheroids, and slowed CRC cell invasion. The KCNQ1 ion channel inhibitor chromanol 293B caused membrane depolarization, redistribution of β-catenin into the cytosol, and a reduced transepithelial electrical resistance, and stimulated CRC cell proliferation. Analysis of human primary CRC tumor patient databases showed a positive correlation between KCNQ1:KCNE3 channel complex expression and disease-free survival. We conclude that the KCNQ1 ion channel is a target gene and regulator of the Wnt/β-catenin pathway, and its repression leads to CRC cell proliferation, EMT, and tumorigenesis.
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42
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King EC, Patel V, Anand M, Zhao X, Crump SM, Hu Z, Weisleder N, Abbott GW. Targeted deletion of Kcne3 impairs skeletal muscle function in mice. FASEB J 2017; 31:2937-2947. [PMID: 28356343 DOI: 10.1096/fj.201600965rr] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 03/13/2017] [Indexed: 11/11/2022]
Abstract
KCNE3 (MiRP2) forms heteromeric voltage-gated K+ channels with the skeletal muscle-expressed KCNC4 (Kv3.4) α subunit. KCNE3 was the first reported skeletal muscle K+ channel disease gene, but the requirement for KCNE3 in skeletal muscle has been questioned. Here, we confirmed KCNE3 transcript and protein expression in mouse skeletal muscle using Kcne3-/- tissue as a negative control. Whole-transcript microarray analysis (770,317 probes, interrogating 28,853 transcripts) findings were consistent with Kcne3 deletion increasing gastrocnemius oxidative metabolic gene expression and the proportion of type IIa fast-twitch oxidative muscle fibers, which was verified using immunofluorescence. The down-regulated transcript set overlapped with muscle unloading gene expression profiles (≥1.5-fold change; P < 0.05). Gastrocnemius K+ channel α subunit remodeling arising from Kcne3 deletion was highly specific, involving just 3 of 69 α subunit genes probed: known KCNE3 partners KCNC4 and KCNH2 (mERG) were down-regulated, and KCNK4 (TRAAK) was up-regulated (P < 0.05). Functionally, Kcne3-/- mice exhibited abnormal hind-limb clasping upon tail suspension (63% of Kcne3-/- mice ≥10-mo-old vs. 0% age-matched Kcne3+/+ littermates). Whereas 5 of 5 Kcne3+/+ mice exhibited the typical biphasic decline in contractile force with repetitive stimuli of hind-limb muscle, both in vivo and in vitro, this was absent in 6 of 6 Kcne3-/- mice tested. Finally, myoblasts isolated from Kcne3-/- mice exhibit faster-inactivating and smaller sustained outward currents than those from Kcne3+/+ mice. Thus, Kcne3 deletion impairs skeletal muscle function in mice.-King, E. C., Patel, V., Anand, M., Zhao, X., Crump, S. M., Hu, Z., Weisleder, N., Abbott, G. W. Targeted deletion of Kcne3 impairs skeletal muscle function in mice.
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Affiliation(s)
- Elizabeth C King
- Department of Pharmacology, Weill Medical College of Cornell University, New York, New York, USA
| | - Vishal Patel
- Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey, USA
| | - Marie Anand
- Department of Pharmacology, School of Medicine, University of California, Irvine, California, USA.,Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, California, USA
| | - Xiaoli Zhao
- Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey, USA
| | - Shawn M Crump
- Department of Pharmacology, School of Medicine, University of California, Irvine, California, USA.,Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, California, USA
| | - Zhaoyang Hu
- Department of Pharmacology, School of Medicine, University of California, Irvine, California, USA.,Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, California, USA
| | - Noah Weisleder
- Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey, USA;
| | - Geoffrey W Abbott
- Department of Pharmacology, School of Medicine, University of California, Irvine, California, USA; .,Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, California, USA
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Fujii S, Suzuki K, Kawamoto A, Ishibashi F, Nakata T, Murano T, Ito G, Shimizu H, Mizutani T, Oshima S, Tsuchiya K, Nakamura T, Araki A, Ohtsuka K, Okamoto R, Watanabe M. PGE 2 is a direct and robust mediator of anion/fluid secretion by human intestinal epithelial cells. Sci Rep 2016; 6:36795. [PMID: 27827428 PMCID: PMC5101536 DOI: 10.1038/srep36795] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 10/21/2016] [Indexed: 12/13/2022] Open
Abstract
Intestinal epithelial cells (IECs) play an indispensable role in maintaining body fluid balance partly through their ability to regulate anion/fluid secretion. Yet in various inflammatory gastrointestinal diseases, over-secretion of anions results in symptoms such as severe diarrhoea. Endogenous mediators, such as vasoactive intestinal peptide or prostaglandin E2 (PGE2), regulate intestinal anion/fluid secretion, but their direct effect on purified human IECs has never been described in detail. Based on a previously described intestinal organoid swelling model, we established a 3D-scanner-assisted quantification method to evaluate the anion/fluid secretory response of cultured human IECs. Among various endogenous secretagogues, we found that PGE2 had the lowest EC50 value with regard to the induction of swelling of the jejunal and colonic organoids. This PGE2-mediated swelling response was dependent on environmental Cl- concentrations as well as on several channels and transporters as shown by a series of chemical inhibitor studies. The concomitant presence of various inflammatory cytokines with PGE2 failed to modulate the PGE2-mediated organoid swelling response. Therefore, the present study features PGE2 as a direct and robust mediator of anion/fluid secretion by IECs in the human intestine.
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Affiliation(s)
- Satoru Fujii
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kohei Suzuki
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ami Kawamoto
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Fumiaki Ishibashi
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Toru Nakata
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tatsuro Murano
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Go Ito
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.,Institute of Clinical Molecular Biology, Christian-Albrechts-University Kiel, Kiel, Germany
| | - Hiromichi Shimizu
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.,Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Tomohiro Mizutani
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Shigeru Oshima
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kiichiro Tsuchiya
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tetsuya Nakamura
- Department of Advanced Therapeutics in GI Diseases, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Akihiro Araki
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kazuo Ohtsuka
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ryuichi Okamoto
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.,Center for Stem Cell and Regenerative Medicine, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
| | - Mamoru Watanabe
- Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan
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44
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da Cunha MF, Simonin J, Sassi A, Freund R, Hatton A, Cottart CH, Elganfoud N, Zoubairi R, Dragu C, Jais JP, Hinzpeter A, Edelman A, Sermet-Gaudelus I. Analysis of nasal potential in murine cystic fibrosis models. Int J Biochem Cell Biol 2016; 80:87-97. [PMID: 27717840 DOI: 10.1016/j.biocel.2016.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/30/2016] [Accepted: 10/03/2016] [Indexed: 12/27/2022]
Abstract
The nasal epithelium of the mouse closely mimics the bioelectrical phenotype of the human airways. Ion transport across the nasal epithelium induces a nasal transepithelial potential difference. Its measurement by a relatively non-invasive method adapted from humans allows in vivo longitudinal measurements of CFTR-dependent ionic transport in the murine nasal mucosa. This test offers a useful tool to assess CFTR function in preclinical studies for novel therapeutics modulating CFTR activity. Here we extensively review work done to assess transepithelial transport in the murine respiratory epithelium in the basal state and after administration of CFTR modulators. Factors of variability and discriminative threshold between the CF and the WT mice for different readouts are discussed.
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Affiliation(s)
- Mélanie Faria da Cunha
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Juliette Simonin
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Ali Sassi
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Romain Freund
- Unité de Biostatistiques, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Aurélie Hatton
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Charles-Henry Cottart
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Nadia Elganfoud
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Rachid Zoubairi
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Corina Dragu
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Jean Philippe Jais
- Unité de Biostatistiques, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Alexandre Hinzpeter
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
| | - Aleksander Edelman
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Sorbonne, Paris, France
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45
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Kroncke BM, Van Horn WD, Smith J, Kang C, Welch RC, Song Y, Nannemann DP, Taylor KC, Sisco NJ, George AL, Meiler J, Vanoye CG, Sanders CR. Structural basis for KCNE3 modulation of potassium recycling in epithelia. SCIENCE ADVANCES 2016; 2:e1501228. [PMID: 27626070 PMCID: PMC5017827 DOI: 10.1126/sciadv.1501228] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 08/10/2016] [Indexed: 05/25/2023]
Abstract
The single-span membrane protein KCNE3 modulates a variety of voltage-gated ion channels in diverse biological contexts. In epithelial cells, KCNE3 regulates the function of the KCNQ1 potassium ion (K(+)) channel to enable K(+) recycling coupled to transepithelial chloride ion (Cl(-)) secretion, a physiologically critical cellular transport process in various organs and whose malfunction causes diseases, such as cystic fibrosis (CF), cholera, and pulmonary edema. Structural, computational, biochemical, and electrophysiological studies lead to an atomically explicit integrative structural model of the KCNE3-KCNQ1 complex that explains how KCNE3 induces the constitutive activation of KCNQ1 channel activity, a crucial component in K(+) recycling. Central to this mechanism are direct interactions of KCNE3 residues at both ends of its transmembrane domain with residues on the intra- and extracellular ends of the KCNQ1 voltage-sensing domain S4 helix. These interactions appear to stabilize the activated "up" state configuration of S4, a prerequisite for full opening of the KCNQ1 channel gate. In addition, the integrative structural model was used to guide electrophysiological studies that illuminate the molecular basis for how estrogen exacerbates CF lung disease in female patients, a phenomenon known as the "CF gender gap."
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Affiliation(s)
- Brett M. Kroncke
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Wade D. Van Horn
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
- Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
- Center for Personalized Diagnostics, Arizona State University, Tempe, AZ 85287, USA
| | - Jarrod Smith
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - CongBao Kang
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Experimental Therapeutics Centre, Agency for Science Technology and Research, Singapore, Singapore
| | - Richard C. Welch
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Yuanli Song
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - David P. Nannemann
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Keenan C. Taylor
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Nicholas J. Sisco
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
- Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
- Center for Personalized Diagnostics, Arizona State University, Tempe, AZ 85287, USA
| | - Alfred L. George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Carlos G. Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Charles R. Sanders
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37240, USA
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46
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Abbott GW. Novel exon 1 protein-coding regions N-terminally extend human KCNE3 and KCNE4. FASEB J 2016; 30:2959-69. [PMID: 27162025 DOI: 10.1096/fj.201600467r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 04/26/2016] [Indexed: 01/02/2023]
Abstract
The 5 human (h)KCNE β subunits each regulate various cation channels and are linked to inherited cardiac arrhythmias. Reported here are previously undiscovered protein-coding regions in exon 1 of hKCNE3 and hKCNE4 that extend their encoded extracellular domains by 44 and 51 residues, which yields full-length proteins of 147 and 221 residues, respectively. Full-length hKCNE3 and hKCNE4 transcript and protein are expressed in multiple human tissues; for hKCNE4, only the longer protein isoform is detectable. Two-electrode voltage-clamp electrophysiology revealed that, when coexpressed in Xenopus laevis oocytes with various potassium channels, the newly discovered segment preserved conversion of KCNQ1 by hKCNE3 to a constitutively open channel, but prevented its inhibition of Kv4.2 and KCNQ4. hKCNE4 slowing of Kv4.2 inactivation and positive-shifted steady-state inactivation were also preserved in the longer form. In contrast, full-length hKCNE4 inhibition of KCNQ1 was limited to 40% at +40 mV vs. 80% inhibition by the shorter form, and augmentation of KCNQ4 activity by hKCNE4 was entirely abolished by the additional segment. Among the genome databases analyzed, the longer KCNE3 is confined to primates; full-length KCNE4 is widespread in vertebrates but is notably absent from Mus musculus Findings highlight unexpected KCNE gene diversity, raise the possibility of dynamic regulation of KCNE partner modulation via splice variation, and suggest that the longer hKCNE3 and hKCNE4 proteins should be adopted in future mechanistic and genetic screening studies.-Abbott, G. W. Novel exon 1 protein-coding regions N-terminally extend human KCNE3 and KCNE4.
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Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Pharmacology and Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, California, USA
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47
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Ao M, Domingue JC, Khan N, Javed F, Osmani K, Sarathy J, Rao MC. Lithocholic acid attenuates cAMP-dependent Cl- secretion in human colonic epithelial T84 cells. Am J Physiol Cell Physiol 2016; 310:C1010-23. [PMID: 27076617 DOI: 10.1152/ajpcell.00350.2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 04/12/2016] [Indexed: 01/14/2023]
Abstract
Bile acids (BAs) play a complex role in colonic fluid secretion. We showed that dihydroxy BAs, but not the monohydroxy BA lithocholic acid (LCA), stimulate Cl(-) secretion in human colonic T84 cells (Ao M, Sarathy J, Domingue J, Alrefai WA, Rao MC. Am J Physiol Cell Physiol 305: C447-C456, 2013). In this study, we explored the effect of LCA on the action of other secretagogues in T84 cells. While LCA (50 μM, 15 min) drastically (>90%) inhibited FSK-stimulated short-circuit current (Isc), it did not alter carbachol-stimulated Isc LCA did not alter basal Isc, transepithelial resistance, cell viability, or cytotoxicity. LCA's inhibitory effect was dose dependent, acted faster from the apical membrane, rapid, and not immediately reversible. LCA also prevented the Isc stimulated by the cAMP-dependent secretagogues 8-bromo-cAMP, lubiprostone, or chenodeoxycholic acid (CDCA). The LCA inhibitory effect was BA specific, since CDCA, cholic acid, or taurodeoxycholic acid did not alter FSK or carbachol action. While LCA alone had no effect on intracellular cAMP concentration ([cAMP]i), it decreased FSK-stimulated [cAMP]i by 90%. Although LCA caused a small increase in intracellular Ca(2+) concentration ([Ca(2+)]i), chelation by BAPTA-AM did not reverse LCA's effect on Isc LCA action does not appear to involve known BA receptors, farnesoid X receptor, vitamin D receptor, muscarinic acetylcholine receptor M3, or bile acid-specific transmembrane G protein-coupled receptor 5. LCA significantly increased ERK1/2 phosphorylation, which was completely abolished by the MEK inhibitor PD-98059. Surprisingly PD-98059 did not reverse LCA's effect on Isc Finally, although LCA had no effect on basal Isc, nystatin permeabilization studies showed that LCA both stimulates an apical cystic fibrosis transmembrane conductance regulator Cl(-) current and inhibits a basolateral K(+) current. In summary, 50 μM LCA greatly inhibits cAMP-stimulated Cl(-) secretion, making low doses of LCA of potential therapeutic interest for diarrheal diseases.
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Affiliation(s)
- Mei Ao
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois
| | - Jada C Domingue
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois
| | - Nabihah Khan
- Department of Biology, Benedictine University, Lisle, Illinois
| | - Fatima Javed
- Department of Biology, Benedictine University, Lisle, Illinois
| | - Kashif Osmani
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois
| | - Jayashree Sarathy
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois; Department of Biology, Benedictine University, Lisle, Illinois
| | - Mrinalini C Rao
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois; Department of Medicine, University of Illinois at Chicago, Chicago, Illinois; and
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48
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Lisewski U, Koehncke C, Wilck N, Buschmeyer B, Pieske B, Roepke TK. Increased aldosterone-dependent Kv1.5 recycling predisposes to pacing-induced atrial fibrillation in Kcne3-/- mice. FASEB J 2016; 30:2476-89. [PMID: 26985008 DOI: 10.1096/fj.201600317r] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/02/2016] [Indexed: 01/11/2023]
Abstract
Hyperaldosteronism is associated with an increased prevalence of atrial fibrillation (AF). Mutations in KCNE3 have been associated with AF, and Kcne3(-/-) mice exhibit hyperaldosteronism. In this study, we used recently developed Kcne3(-/-) mice to study atrial electrophysiology with respect to development of aldosterone-dependent AF. In invasive electrophysiology studies, Kcne3(-/-) mice displayed a reduced atrial effective refractory period (AERP) and inducible episodes of paroxysmal AF. The cellular arrhythmogenic correlate for AF predisposition was a significant increase in atrial Kv currents generated by the micromolar 4-aminopyridine-sensitive Kv current encoded by Kv1.5. Electrophysiological alterations in Kcne3(-/-) mice were aldosterone dependent and were associated with increased Rab4, -5, and -9-dependent recycling of Kv1.5 channels to the Z-disc/T-tubulus region and lateral membrane via activation of the Akt/AS160 pathway. Treatment with spironolactone inhibited Akt/AS160 phosphorylation, reduced Rab-dependent Kv1.5 recycling, normalized AERP and atrial Kv currents to the wild-type level, and reduced arrhythmia induction in Kcne3(-/-) mice. Kcne3 deletion in mice predisposes to AF by a heretofore unrecognized mechanism-namely, increased aldosterone-dependent Kv1.5 recycling via Rab GTPases. The findings uncover detailed molecular mechanisms underpinning a channelopathy-linked form of AF and emphasize the inevitability of considering extracardiac mechanisms in genetic arrhythmia syndromes.-Lisewski, U., Koehncke, C., Wilck, N., Buschmeyer, B., Pieske, B., Roepke, T. K. Increased aldosterone-dependent Kv1.5 recycling predisposes to pacing-induced atrial fibrillation in Kcne3(-/-) mice.
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Affiliation(s)
| | - Clemens Koehncke
- Experimental and Clinical Research Center, Berlin, Germany; Department of Cardiology, Campus Virchow, Universitätsmedizin Berlin, Berlin, Germany; and
| | - Nicola Wilck
- Experimental and Clinical Research Center, Berlin, Germany
| | | | - Burkert Pieske
- Department of Cardiology, Campus Virchow, Universitätsmedizin Berlin, Berlin, Germany; and
| | - Torsten K Roepke
- Experimental and Clinical Research Center, Berlin, Germany; Department of Cardiology and Angiology, Campus Mitte, Charité, Universitätsmedizin Berlin, Berlin, Germany
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49
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Chen L, Tuo B, Dong H. Regulation of Intestinal Glucose Absorption by Ion Channels and Transporters. Nutrients 2016; 8:nu8010043. [PMID: 26784222 PMCID: PMC4728656 DOI: 10.3390/nu8010043] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 12/18/2015] [Accepted: 01/06/2016] [Indexed: 12/14/2022] Open
Abstract
The absorption of glucose is electrogenic in the small intestinal epithelium. The major route for the transport of dietary glucose from intestinal lumen into enterocytes is the Na+/glucose cotransporter (SGLT1), although glucose transporter type 2 (GLUT2) may also play a role. The membrane potential of small intestinal epithelial cells (IEC) is important to regulate the activity of SGLT1. The maintenance of membrane potential mainly depends on the activities of cation channels and transporters. While the importance of SGLT1 in glucose absorption has been systemically studied in detail, little is currently known about the regulation of SGLT1 activity by cation channels and transporters. A growing line of evidence suggests that cytosolic calcium ([Ca2+]cyt) can regulate the absorption of glucose by adjusting GLUT2 and SGLT1. Moreover, the absorption of glucose and homeostasis of Ca2+ in IEC are regulated by cation channels and transporters, such as Ca2+ channels, K+ channels, Na+/Ca2+ exchangers, and Na+/H+ exchangers. In this review, we consider the involvement of these cation channels and transporters in the regulation of glucose uptake in the small intestine. Modulation of them may be a potential strategy for the management of obesity and diabetes.
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Affiliation(s)
- Lihong Chen
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, and Digestive Disease Institute of Guizhou Province, Zunyi 563003, China.
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, and Digestive Disease Institute of Guizhou Province, Zunyi 563003, China.
| | - Hui Dong
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, and Digestive Disease Institute of Guizhou Province, Zunyi 563003, China.
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China.
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50
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Al-Hazza A, Linley J, Aziz Q, Hunter M, Sandle G. Upregulation of basolateral small conductance potassium channels (KCNQ1/KCNE3) in ulcerative colitis. Biochem Biophys Res Commun 2015; 470:473-478. [PMID: 26718405 PMCID: PMC4748010 DOI: 10.1016/j.bbrc.2015.12.086] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 12/20/2015] [Indexed: 12/04/2022]
Abstract
Background Basolateral K+ channels hyperpolarize colonocytes to ensure Na+ (and thus water) absorption. Small conductance basolateral (KCNQ1/KCNE3) K+ channels have never been evaluated in human colon. We therefore evaluated KCNQ1/KCNE3 channels in distal colonic crypts obtained from normal and active ulcerative colitis (UC) patients. Methods KCNQ1 and KCNE3 mRNA levels were determined by qPCR, and KCNQ1/KCNE3 channel activity in normal and UC crypts, and the effects of forskolin (activator of adenylate cyclase) and UC-related proinflammatory cytokines on normal crypts, studied by patch clamp recording. Results Whereas KCNQ1 and KCNE3 mRNA expression was similar in normal and UC crypts, single 6.8 pS channels were seen in 36% of basolateral patches in normal crypts, and to an even greater extent (74% of patches, P < 0.001) in UC crypts, with two or more channels per patch. Channel activity was 10-fold higher (P < 0.001) in UC crypts, with a greater contribution to basolateral conductance (5.85 ± 0.62 mS cm−2) than in controls (0.28 ± 0.04 mS cm−2, P < 0.001). In control crypts, forskolin and thromboxane A2 stimulated channel activity 30-fold and 10-fold respectively, while PGE2, IL-1β, and LTD4 had no effect. Conclusions KCNQ1/KCNE3 channels make only a small contribution to basolateral conductance in normal colonic crypts, with increased channel activity in UC appearing insufficient to prevent colonic cell depolarization in this disease. This supports the proposal that defective Na+ absorption rather than enhanced Cl− secretion, is the dominant pathophysiological mechanism of diarrhea in UC.
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Affiliation(s)
- Adel Al-Hazza
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - John Linley
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - Qadeer Aziz
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - Malcolm Hunter
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - Geoffrey Sandle
- Leeds Institute of Biomedical and Clinical Sciences, St. James's University Hospital, Leeds, UK.
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