1
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Kunzelmann K, Ousingsawat J, Schreiber R. VSI: The anoctamins: Structure and function: "Intracellular" anoctamins. Cell Calcium 2024; 120:102888. [PMID: 38657371 DOI: 10.1016/j.ceca.2024.102888] [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: 02/20/2024] [Revised: 04/15/2024] [Accepted: 04/16/2024] [Indexed: 04/26/2024]
Abstract
Plasma membrane localized anoctamin 1, 2 and 6 (TMEM16A, B, F) have been examined in great detail with respect to structure and function, but much less is known about the other seven intracellular members of this exciting family of proteins. This is probably due to their limited accessibility in intracellular membranous compartments, such as the endoplasmic reticulum (ER) or endosomes. However, these so-called intracellular anoctamins are also found in the plasma membrane (PM) which adds to the confusion regarding their cellular role. Probably all intracellular anoctamins except of ANO8 operate as intracellular phospholipid (PL) scramblases, allowing for Ca2+-activated, passive transport of phospholipids like phosphatidylserine between both membrane leaflets. Probably all of them also conduct ions, which is probably part of their physiological function. In this brief overview, we summarize key findings on the biological functions of ANO3, 4, 5, 7, 8, 9 and 10 (TMEM16C, D, E, G, H, J, K) that are gradually coming to light. Compartmentalized regulation of intracellular Ca2+ signals, tethering of the ER to specific PM contact sites, and control of intracellular vesicular trafficking appear to be some of the functions of intracellular anoctamins, while loss of function and abnormal expression are the cause for various diseases.
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Affiliation(s)
- Karl Kunzelmann
- 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
| | - Rainer Schreiber
- Physiological Institute, University of Regensburg, University street 31, D-93053, Regensburg, Germany
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2
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Li X, Wang Y, Zhang L, Yao S, Liu Q, Jin H, Tuo B. The role of anoctamin 1 in liver disease. J Cell Mol Med 2024; 28:e18320. [PMID: 38685684 PMCID: PMC11058335 DOI: 10.1111/jcmm.18320] [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: 11/08/2023] [Revised: 03/21/2024] [Accepted: 04/03/2024] [Indexed: 05/02/2024] Open
Abstract
Liver diseases include all types of viral hepatitis, alcoholic liver disease (ALD), nonalcoholic fatty liver disease (NAFLD), cirrhosis, liver failure (LF) and hepatocellular carcinoma (HCC). Liver disease is now one of the leading causes of disease and death worldwide, which compels us to better understand the mechanisms involved in the development of liver diseases. Anoctamin 1 (ANO1), a calcium-activated chloride channel (CaCC), plays an important role in epithelial cell secretion, proliferation and migration. ANO1 plays a key role in transcriptional regulation as well as in many signalling pathways. It is involved in the genesis, development, progression and/or metastasis of several tumours and other diseases including liver diseases. This paper reviews the role and molecular mechanisms of ANO1 in the development of various liver diseases, aiming to provide a reference for further research on the role of ANO1 in liver diseases and to contribute to the improvement of therapeutic strategies for liver diseases by regulating ANO1.
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Affiliation(s)
- Xin Li
- Department of Gastroenterology, Digestive Disease HospitalAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | - Yongfeng Wang
- Department of Gastroenterology, Digestive Disease HospitalAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | - Li Zhang
- Department of Gastroenterology, Digestive Disease HospitalAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | - Shun Yao
- Department of Gastroenterology, Digestive Disease HospitalAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | - Qian Liu
- Department of Gastroenterology, Digestive Disease HospitalAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | - Hai Jin
- Department of Gastroenterology, Digestive Disease HospitalAffiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative Innovation Center of Tissue Damage Repair and Regenerative Medicine of Zunyi Medical UniversityZunyiChina
| | - Biguang Tuo
- Department of Gastroenterology, Digestive Disease HospitalAffiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative Innovation Center of Tissue Damage Repair and Regenerative Medicine of Zunyi Medical UniversityZunyiChina
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3
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Jojoa-Cruz S, Dubin AE, Lee WH, Ward AB. Structure-guided mutagenesis of OSCAs reveals differential activation to mechanical stimuli. eLife 2024; 12:RP93147. [PMID: 38592763 PMCID: PMC11003742 DOI: 10.7554/elife.93147] [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] [Indexed: 04/10/2024] Open
Abstract
The dimeric two-pore OSCA/TMEM63 family has recently been identified as mechanically activated ion channels. Previously, based on the unique features of the structure of OSCA1.2, we postulated the potential involvement of several structural elements in sensing membrane tension (Jojoa-Cruz et al., 2018). Interestingly, while OSCA1, 2, and 3 clades are activated by membrane stretch in cell-attached patches (i.e. they are stretch-activated channels), they differ in their ability to transduce membrane deformation induced by a blunt probe (poking). Here, in an effort to understand the domains contributing to mechanical signal transduction, we used cryo-electron microscopy to solve the structure of Arabidopsis thaliana (At) OSCA3.1, which, unlike AtOSCA1.2, only produced stretch- but not poke-activated currents in our initial characterization (Murthy et al., 2018). Mutagenesis and electrophysiological assessment of conserved and divergent putative mechanosensitive features of OSCA1.2 reveal a selective disruption of the macroscopic currents elicited by poking without considerable effects on stretch-activated currents (SAC). Our results support the involvement of the amphipathic helix and lipid-interacting residues in the membrane fenestration in the response to poking. Our findings position these two structural elements as potential sources of functional diversity within the family.
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Affiliation(s)
- Sebastian Jojoa-Cruz
- Department of Integrative Structural and Computational Biology, Scripps ResearchLa JollaUnited States
| | - Adrienne E Dubin
- Department of Integrative Structural and Computational Biology, Scripps ResearchLa JollaUnited States
- Department of Neuroscience, Scripps ResearchLa JollaUnited States
| | - Wen-Hsin Lee
- Department of Integrative Structural and Computational Biology, Scripps ResearchLa JollaUnited States
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, Scripps ResearchLa JollaUnited States
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4
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Jojoa-Cruz S, Dubin AE, Lee WH, Ward A. Structure-guided mutagenesis of OSCAs reveals differential activation to mechanical stimuli. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.03.560740. [PMID: 37873218 PMCID: PMC10592937 DOI: 10.1101/2023.10.03.560740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The dimeric two-pore OSCA/TMEM63 family has recently been identified as mechanically activated ion channels. Previously, based on the unique features of the structure of OSCA1.2, we postulated the potential involvement of several structural elements in sensing membrane tension1. Interestingly, while OSCA1, 2, and 3 clades are activated by membrane stretch in cell-attached patches (i.e., they are stretch-activated channels), they differ in their ability to transduce membrane deformation induced by a blunt probe (poking). In an effort to understand the domains contributing to mechanical signal transduction, we used cryo-electron microscopy to solve the structure of Arabidopsis thaliana (At) OSCA3.1, which, unlike AtOSCA1.2, only produced stretch- but not poke-activated currents in our initial characterization2. Mutagenesis and electrophysiological assessment of conserved and divergent putative mechanosensitive features of OSCA1.2 reveal a selective disruption of the macroscopic currents elicited by poking without considerable effects on stretch-activated currents (SAC). Our results support the involvement of the amphipathic helix and lipid-interacting residues in the membrane fenestration in the response to poking. Our findings position these two structural elements as potential sources of functional diversity within the family.
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Affiliation(s)
- Sebastian Jojoa-Cruz
- Department of Integrative Structural and Computational Biology, Scripps Research, La Jolla, California 92037, USA
| | - Adrienne E. Dubin
- Department of Neuroscience, Scripps Research, La Jolla, California 92037, USA
| | - Wen-Hsin Lee
- Department of Integrative Structural and Computational Biology, Scripps Research, La Jolla, California 92037, USA
| | - Andrew Ward
- Department of Integrative Structural and Computational Biology, Scripps Research, La Jolla, California 92037, USA
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5
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Lu P, Lifshitz LM, Bellve K, ZhuGe R. TMEM16A in smooth muscle cells acts as a pacemaker channel in the internal anal sphincter. Commun Biol 2024; 7:151. [PMID: 38317010 PMCID: PMC10844222 DOI: 10.1038/s42003-024-05850-1] [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: 12/13/2022] [Accepted: 01/23/2024] [Indexed: 02/07/2024] Open
Abstract
Maintenance of fecal continence requires a continuous or basal tone of the internal anal sphincter (IAS). Paradoxically, the basal tone results largely from high-frequency rhythmic contractions of the IAS smooth muscle. However, the cellular and molecular mechanisms that initiate these contractions remain elusive. Here we show that the IAS contains multiple pacemakers. These pacemakers spontaneously generate propagating calcium waves that drive rhythmic contractions and establish the basal tone. These waves are myogenic and act independently of nerve, paracrine or autocrine signals. Using cell-specific gene knockout mice, we further found that TMEM16A Cl- channels in smooth muscle cells (but not in the interstitial cells of Cajal) are indispensable for pacemaking, rhythmic contractions, and basal tone. Our results identify TMEM16A in smooth muscle cells as a critical pacemaker channel that enables the IAS to contract rhythmically and continuously. This study provides cellular and molecular insights into fecal continence.
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Affiliation(s)
- Ping Lu
- Department of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Lawrence M Lifshitz
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Karl Bellve
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Ronghua ZhuGe
- Department of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, MA, USA.
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6
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Shcheynikov N, Boggs K, Green A, Feranchak AP. Identification of the chloride channel, leucine-rich repeat-containing protein 8, subfamily a (LRRC8A), in mouse cholangiocytes. Hepatology 2022; 76:1248-1258. [PMID: 35445421 PMCID: PMC10126881 DOI: 10.1002/hep.32536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 04/18/2022] [Accepted: 04/19/2022] [Indexed: 12/08/2022]
Abstract
BACKGROUND AND AIMS Chloride (Cl- ) channels in the apical membrane of biliary epithelial cells (BECs), also known as cholangiocytes, provide the driving force for biliary secretion. Although two Cl- channels have been identified on a molecular basis, the Cystic Fibrosis Transmembrane Conductance Regulator and Transmembrane Member 16A, a third Cl- channel with unique biophysical properties has been described. Leucine-Rich Repeat-Containing Protein 8, subfamily A (LRRC8A) is a newly identified protein capable of transporting Cl- in other epithelium in response to cell swelling. The aim of the present study was to determine if LRRC8A represents the volume-regulated anion channel in mouse BECs. APPROACH AND RESULTS Studies were performed in mouse small (MSC) and large (MLC) cholangiocytes. Membrane Cl- currents were measured by whole-cell patch-clamp techniques and cell volume measurements were performed by calcein-AM fluorescence. Exposure of either MSC or MLC to hypotonicity (190 mOsm) rapidly increased cell volume and activated Cl- currents. Currents exhibited outward rectification, time-dependent inactivation at positive membrane potentials, and reversal potential at 0 mV (ECl ). Removal of extracellular Cl- or specific pharmacological inhibition of LRRC8A abolished currents. LRRC8A was detected in both MSC and MLC by reverse transcription polymerase chain reaction and confirmed by western blot. Transfection with LRRC8A small interfering RNA decreased protein levels by >70% and abolished volume-stimulated Cl- currents. CONCLUSION These results demonstrate that LRRC8A is functionally present in mouse BECs, contributes to volume-activated Cl- secretion, and, therefore, may be a target to modulate bile formation in the treatment of cholestatic liver disorders.
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Affiliation(s)
- Nikolay Shcheynikov
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kristy Boggs
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Anthony Green
- Tissue and Research Pathology Core, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Andrew P Feranchak
- Department of Pediatrics, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Pittsburgh Liver Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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7
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Florentino RM, Li Q, Coard MC, Haep N, Motomura T, Diaz-Aragon R, Faccioli LAP, Amirneni S, Kocas-Kilicarslan ZN, Ostrowska A, Squires JE, Feranchak AP, Soto-Gutierrez A. Transmembrane channel activity in human hepatocytes and cholangiocytes derived from induced pluripotent stem cells. Hepatol Commun 2022; 6:1561-1573. [PMID: 35289126 PMCID: PMC9234678 DOI: 10.1002/hep4.1920] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 01/06/2022] [Accepted: 01/22/2022] [Indexed: 11/10/2022] Open
Abstract
The initial creation of human-induced pluripotent stem cells (iPSCs) set the foundation for the future of regenerative medicine. Human iPSCs can be differentiated into a variety of cell types in order to study normal and pathological molecular mechanisms. Currently, there are well-defined protocols for the differentiation, characterization, and establishment of functionality in human iPSC-derived hepatocytes (iHep) and iPSC-derived cholangiocytes (iCho). Electrophysiological study on chloride ion efflux channel activity in iHep and iCho cells has not been previously reported. We generated iHep and iCho cells and characterized them based on hepatocyte-specific and cholangiocyte-specific markers. The relevant transmembrane channels were selected: cystic fibrosis transmembrane conductance regulator, leucine rich repeat-containing 8 subunit A, and transmembrane member 16 subunit A. To measure the activity in these channels, we used whole-cell patch-clamp techniques with a standard intracellular and extracellular solution. Our iHep and iCho cells demonstrated definitive activity in the selected transmembrane channels, and this approach may become an important tool for investigating human liver biology of cholestatic diseases.
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Affiliation(s)
- Rodrigo M Florentino
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA.,Pittsburgh Liver Research CenterUniversity of PittsburghPittsburghPennsylvaniaUSA
| | - Qin Li
- Department of PediatricsUniversity of Pittsburgh Medical CenterPittsburghPennsylvaniaUSA
| | - Michael C Coard
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Nils Haep
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Takashi Motomura
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Ricardo Diaz-Aragon
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Lanuza A P Faccioli
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Sriram Amirneni
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | | | - Alina Ostrowska
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA.,Pittsburgh Liver Research CenterUniversity of PittsburghPittsburghPennsylvaniaUSA
| | - James E Squires
- Pittsburgh Liver Research CenterUniversity of PittsburghPittsburghPennsylvaniaUSA.,Division of Gastroenterology, Hepatology, and NutritionUniversity of Pittsburgh Medical CenterPittsburghPennsylvaniaUSA
| | - Andrew P Feranchak
- Pittsburgh Liver Research CenterUniversity of PittsburghPittsburghPennsylvaniaUSA.,Department of PediatricsUniversity of Pittsburgh Medical CenterPittsburghPennsylvaniaUSA
| | - Alejandro Soto-Gutierrez
- Department of PathologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA.,Pittsburgh Liver Research CenterUniversity of PittsburghPittsburghPennsylvaniaUSA.,McGowan Institute for Regenerative MedicinePittsburghPennsylvaniaUSA
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8
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Maul A, Huebner AK, Strenzke N, Moser T, Rübsamen R, Jovanovic S, Hübner CA. The Cl--channel TMEM16A is involved in the generation of cochlear Ca2+ waves and promotes the refinement of auditory brainstem networks in mice. eLife 2022; 11:72251. [PMID: 35129434 PMCID: PMC8871368 DOI: 10.7554/elife.72251] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 02/06/2022] [Indexed: 11/17/2022] Open
Abstract
Before hearing onset (postnatal day 12 in mice), inner hair cells (IHCs) spontaneously fire action potentials, thereby driving pre-sensory activity in the ascending auditory pathway. The rate of IHC action potential bursts is modulated by inner supporting cells (ISCs) of Kölliker’s organ through the activity of the Ca2+-activated Cl--channel TMEM16A (ANO1). Here, we show that conditional deletion of Ano1 (Tmem16a) in mice disrupts Ca2+ waves within Kölliker’s organ, reduces the burst-firing activity and the frequency selectivity of auditory brainstem neurons in the medial nucleus of the trapezoid body (MNTB), and also impairs the functional refinement of MNTB projections to the lateral superior olive. These results reveal the importance of the activity of Kölliker’s organ for the refinement of central auditory connectivity. In addition, our study suggests the involvement of TMEM16A in the propagation of Ca2+ waves, which may also apply to other tissues expressing TMEM16A.
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Affiliation(s)
- Alena Maul
- Neuroscience Department, Max Delbrück Center for Molecular Medicine
| | | | - Nicola Strenzke
- Institute for Auditory Neuroscience, Department of Otolaryngology, University of Göttingen
| | - Tobias Moser
- Institute for Auditory Neuroscience, Department of Otolaryngology, University of Göttingen
| | - Rudolf Rübsamen
- Faculty of Bioscience, Pharmacy and Psychology, University of Leipzig
| | - Saša Jovanovic
- Faculty of Bioscience, Pharmacy and Psychology, University of Leipzig
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9
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Herta T, Kersten R, Chang JC, Hubers L, Go S, Tolenaars D, Paulusma CC, Nathanson MH, Elferink RO, van de Graaf SFJ, Beuers U. Role of the IgG4-related cholangitis autoantigen annexin A11 in cholangiocyte protection. J Hepatol 2022; 76:319-331. [PMID: 34718050 PMCID: PMC10804347 DOI: 10.1016/j.jhep.2021.10.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 09/20/2021] [Accepted: 10/11/2021] [Indexed: 01/01/2023]
Abstract
BACKGROUND & AIMS Annexin A11 was identified as autoantigen in IgG4-related cholangitis (IRC), a B-cell driven disease. Annexin A11 modulates calcium-dependent exocytosis, a crucial mechanism for insertion of proteins into their target membranes. Human cholangiocytes form an apical 'biliary bicarbonate umbrella' regarded as defense against harmful hydrophobic bile acid influx. The bicarbonate secretory machinery comprises the chloride/bicarbonate exchanger AE2 and the chloride channel ANO1. We aimed to investigate the expression and function of annexin A11 in human cholangiocytes and a potential role of IgG1/IgG4-mediated autoreactivity against annexin A11 in the pathogenesis of IRC. METHODS Expression of annexin A11 in human liver was studied by immunohistochemistry and immunofluorescence. In human control and ANXA11 knockdown H69 cholangiocytes, intracellular pH, AE2 and ANO1 surface expression, and bile acid influx were examined using ratio microspectrofluorometry, cell surface biotinylation, and 22,23-3H-glycochenodeoxycholic acid permeation, respectively. The localization of annexin A11-mEmerald and ANO1-mCherry was investigated by live-cell microscopy in H69 cholangiocytes after incubation with IRC patient serum containing anti-annexin A11 IgG1/IgG4-autoantibodies or disease control serum. RESULTS Annexin A11 was strongly expressed in human cholangiocytes, but not hepatocytes. Knockdown of ANXA11 led to reduced plasma membrane expression of ANO1, but not AE2, alkalization of intracellular pH and uncontrolled bile acid influx. High intracellular calcium conditions led to annexin A11 membrane shift and colocalization with ANO1. Incubation with IRC patient serum inhibited annexin A11 membrane shift and reduced ANO1 surface expression. CONCLUSION Cholangiocellular annexin A11 mediates apical membrane abundance of the chloride channel ANO1, thereby supporting biliary bicarbonate secretion. Insertion is inhibited by IRC patient serum containing anti-annexin A11 IgG1/IgG4-autoantibodies. Anti-annexin A11 autoantibodies may contribute to the pathogenesis of IRC by weakening the 'biliary bicarbonate umbrella'. LAY SUMMARY We previously identified annexin A11 as a specific autoantigen in immunoglobulin G4-related cholangitis (IRC), a B-cell driven disease affecting the bile ducts. Human cholangiocytes are protected against harmful hydrophobic bile acid influx by a defense mechanism referred to as the 'biliary bicarbonate umbrella'. We found that annexin A11 is required for the formation of a robust bicarbonate umbrella. Binding of patient-derived annexin A11 autoantibodies inhibits annexin A11 function, possibly contributing to bile duct damage by weakening the biliary bicarbonate umbrella in patients with IRC.
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Affiliation(s)
- Toni Herta
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Remco Kersten
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands; Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, USA
| | - Jung-Chin Chang
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Lowiek Hubers
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Simei Go
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Dagmar Tolenaars
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Coen C Paulusma
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Michael H Nathanson
- Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, USA
| | - Ronald Oude Elferink
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Stan F J van de Graaf
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Ulrich Beuers
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands.
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10
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Ebihara L, Acharya P, Tong JJ. Mechanical Stress Modulates Calcium-Activated-Chloride Currents in Differentiating Lens Cells. Front Physiol 2022; 13:814651. [PMID: 35173630 PMCID: PMC8842795 DOI: 10.3389/fphys.2022.814651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 01/06/2022] [Indexed: 11/13/2022] Open
Abstract
During accommodation, the lens changes focus by altering its shape following contraction and relaxation of the ciliary muscle. At the cellular level, these changes in shape may be accompanied by fluid flow in and out of individual lens cells. We tested the hypothesis that some of this flow might be directly modulated by pressure-activated channels. In particular, we used the whole cell patch clamp technique to test whether calcium-activated-chloride channels (CaCCs) expressed in differentiating lens cells are activated by mechanical stimulation. Our results show that mechanical stress, produced by focally perfusing the lens cell at a constant rate, caused a significant increase in a chloride current that could be fully reversed by stopping perfusion. The time course of activation and recovery from activation of the flow-induced current occurred rapidly over a time frame similar to that of accommodation. The flow-induced current could be inhibited by the TMEM16A specific CaCC blocker, Ani9, suggesting that the affected current was predominantly due to TMEM16A chloride channels. The mechanism of action of mechanical stress did not appear to involve calcium influx through other mechanosensitive ion channels since removal of calcium from the bath solution failed to block the flow-induced chloride current. In conclusion, our results suggest that CaCCs in the lens can be rapidly and reversibly modulated by mechanical stress, consistent with their participation in regulation of volume in this organ.
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Affiliation(s)
- Lisa Ebihara
- Center of Proteomics and Molecular Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
- Discipline of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
- *Correspondence: Lisa Ebihara,
| | - Pooja Acharya
- Center of Proteomics and Molecular Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Jun-Jie Tong
- Center of Proteomics and Molecular Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
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11
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Roy Choudhury A, Großhans J, Kong D. Ion Channels in Epithelial Dynamics and Morphogenesis. Cells 2021; 10:cells10092280. [PMID: 34571929 PMCID: PMC8465836 DOI: 10.3390/cells10092280] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 08/22/2021] [Accepted: 08/30/2021] [Indexed: 01/21/2023] Open
Abstract
Mechanosensitive ion channels mediate the neuronal sensation of mechanical signals such as sound, touch, and pain. Recent studies point to a function of these channel proteins in cell types and tissues in addition to the nervous system, such as epithelia, where they have been little studied, and their role has remained elusive. Dynamic epithelia are intrinsically exposed to mechanical forces. A response to pull and push is assumed to constitute an essential part of morphogenetic movements of epithelial tissues, for example. Mechano-gated channels may participate in sensing and responding to such forces. In this review, focusing on Drosophila, we highlight recent results that will guide further investigations concerned with the mechanistic role of these ion channels in epithelial cells.
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12
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Roos FJM, Bijvelds MJC, Verstegen MMA, Roest HP, Metselaar HJ, Polak WG, Jonge HRD, IJzermans JNM, van der Laan LJW. Impact of hypoxia and AMPK on CFTR-mediated bicarbonate secretion in human cholangiocyte organoids. Am J Physiol Gastrointest Liver Physiol 2021; 320:G741-G752. [PMID: 33655768 DOI: 10.1152/ajpgi.00389.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cholangiocytes express cystic fibrosis transmembrane conductance regulator (CFTR), which is involved in bicarbonate secretion for the protection against bile toxicity. During liver transplantation, prolonged hypoxia of the graft is associated with cholangiocyte loss and biliary complications. Hypoxia is known to diminish CFTR activity in the intestine, but whether it affects CFTR activity in cholangiocytes remains unknown. Thus, the aim of this study is to investigate the effect of hypoxia on CFTR activity in intrahepatic cholangiocyte organoids (ICOs) and test drug interventions to restore bicarbonate secretion. Fifteen different human ICOs were cultured as monolayers and ion channel [CFTR and anoctamin-1 (ANO1)] activity was determined using an Ussing chamber assay with or without AMP kinase (AMPK) inhibitor under hypoxic and oxygenated conditions. Bile toxicity was tested by apical exposure of cells to fresh human bile. Overall gene expression analysis showed a high similarity between ICOs and primary cholangiocytes. Under oxygenated conditions, both CFTR and ANO1 channels were responsible for forskolin and uridine-5'-triphosphate (UTP) UTP-activated anion secretion. Forskolin stimulation in the absence of intracellular chloride showed ion transport, indicating that bicarbonate could be secreted by CFTR. During hypoxia, CFTR activity significantly decreased (P = 0.01). Switching from oxygen to hypoxia during CFTR measurements reduced CFTR activity (P = 0.03). Consequently, cell death increased when ICO monolayers were exposed to bile during hypoxia compared with oxygen (P = 0.04). Importantly, addition of AMPK inhibitor restored CFTR-mediated anion secretion during hypoxia. ICOs provide an excellent model to study cholangiocyte anion channels and drug-related interventions. Here, we demonstrate that hypoxia affects cholangiocyte ion secretion, leaving cholangiocytes vulnerable to bile toxicity. The mechanistic insights from this model maybe relevant for hypoxia-related biliary injury during liver transplantation.NEW & NOTEWORTHY The previously described liver-derived organoids resemble primary cholangiocytes and should be properly named intrahepatic cholangiocyte organoids (ICOs). ICOs have functional cholangiocyte ion channels (CFTR and ANO1). CFTR might be able to secrete bicarbonate directly into the bile duct lumen. Hypoxia inhibits CFTR and ANO1 functionality in ICOs, which can partially be restored by addition of an AMP kinase inhibitor. Hypoxia impairs cholangiocyte resistance against cytotoxic effects of bile, resulting in increased cell death.
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Affiliation(s)
- Floris J M Roos
- Department of Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Marcel J C Bijvelds
- Department of Gastroenterology and Hepatology, Erasmus Medical Center, Rotterdam, The Netherlands
| | | | - Henk P Roest
- Department of Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Herold J Metselaar
- Department of Gastroenterology and Hepatology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Wojciech G Polak
- Division of Hepato-Pancreato-Biliary and Transplant Surgery, Department of Surgery, Erasmus Medical Center, University Medical Center Rotterdam, Transplant Institute, Rotterdam, The Netherlands
| | - Hugo R de Jonge
- Department of Gastroenterology and Hepatology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Jan N M IJzermans
- Department of Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
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13
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The Groovy TMEM16 Family: Molecular Mechanisms of Lipid Scrambling and Ion Conduction. J Mol Biol 2021; 433:166941. [PMID: 33741412 DOI: 10.1016/j.jmb.2021.166941] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/09/2021] [Accepted: 03/09/2021] [Indexed: 12/28/2022]
Abstract
The TMEM16 family of membrane proteins displays a remarkable functional dichotomy - while some family members function as Ca2+-activated anion channels, the majority of characterized TMEM16 homologs are Ca2+-activated lipid scramblases, which catalyze the exchange of phospholipids between the two membrane leaflets. Furthermore, some TMEM16 scramblases can also function as channels. Due to their involvement in important physiological processes, the family has been actively studied ever since their molecular identity was unraveled. In this review, we will summarize the recent advances in the field and how they influenced our view of TMEM16 family function and evolution. Structural, functional and computational studies reveal how relatively small rearrangements in the permeation pathway are responsible for the observed functional duality: while TMEM16 scramblases can adopt both ion- and lipid conductive conformations, TMEM16 channels can only populate the former. Recent data further provides the molecular details of a stepwise activation mechanism, which is initiated by Ca2+ binding and modulated by various cellular factors, including lipids. TMEM16 function and the surrounding membrane properties are inextricably intertwined, with the protein inducing bilayer deformations associated with scrambling, while the surrounding lipids modulate TMEM16 conformation and activity.
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14
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Wang Z, Faria J, Penning LC, Masereeuw R, Spee B. Tissue-Engineered Bile Ducts for Disease Modeling and Therapy. Tissue Eng Part C Methods 2021; 27:59-76. [PMID: 33267737 DOI: 10.1089/ten.tec.2020.0283] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Recent biotechnical advances in the in vitro culture of cholangiocytes and generation of bioengineered biliary tissue have a high potential for creating biliary tissue to be used for disease modeling, drug screening, and transplantation. For the past few decades, scientists have searched for a source of cholangiocytes, focused on primary cholangiocytes or cholangiocytes derived from hepatocytes or stem cells. At the same time, the development of scaffolds for biliary tissue engineering for transplantation and modeling of cholangiopathies has been explored. In this review, we provide an overview on the current understanding of cholangiocytes sources, the effect of signaling molecules, and transcription factors on cell differentiation, along with the effects of extracellular matrix molecules and scaffolds on bioengineered biliary tissues, and their application in disease modeling and drug screening. Impact statement Over the past few decades, biliary tissue engineering has acquired significant attention, but currently a number of factors hinder this field to eventually generate bioengineered bile ducts that mimic in vivo physiology and are suitable for transplantation. In this review, we present the latest advances with respect to cell source selection, influence of growth factors and scaffolds, and functional characterization, as well as applications in cholangiopathy modeling and drug screening. This review is suited for a broad spectrum of readers, including fundamental liver researchers and clinicians with interest in the current state and application of bile duct engineering and disease modeling.
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Affiliation(s)
- Zhenguo Wang
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.,Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - João Faria
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Louis C Penning
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Rosalinde Masereeuw
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Bart Spee
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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15
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Dulin NO. Calcium-Activated Chloride Channel ANO1/TMEM16A: Regulation of Expression and Signaling. Front Physiol 2020; 11:590262. [PMID: 33250781 PMCID: PMC7674831 DOI: 10.3389/fphys.2020.590262] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 10/13/2020] [Indexed: 01/11/2023] Open
Abstract
Anoctamin-1 (ANO1), also known as TMEM16A, is the most studied member of anoctamin family of calcium-activated chloride channels with diverse cellular functions. ANO1 controls multiple cell functions including cell proliferation, survival, migration, contraction, secretion, and neuronal excitation. This review summarizes the current knowledge of the cellular mechanisms governing the regulation of ANO1 expression and of ANO1-mediated intracellular signaling. This includes the stimuli and mechanisms controlling ANO1 expression, agonists and processes that activate ANO1, and signal transduction mediated by ANO1. The major conclusion is that this field is poorly understood, remains highly controversial, and requires extensive and rigorous further investigation.
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Affiliation(s)
- Nickolai O Dulin
- Department of Medicine, The University of Chicago, Chicago, IL, United States
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16
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Nejak-Bowen K. If It Looks Like a Duct and Acts Like a Duct: On the Role of Reprogrammed Hepatocytes in Cholangiopathies. Gene Expr 2020; 20:19-23. [PMID: 31439080 PMCID: PMC7284107 DOI: 10.3727/105221619x15664105014956] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cholangiopathies are chronic, progressive diseases of the biliary tree, and can be either acquired or genetic. The primary target is the cholangiocyte (CC), the cell type lining the bile duct that is responsible for bile modification and transport. Despite advances in our understanding and diagnosis of these diseases in recent years, there are no proven therapeutic treatments for the majority of the cholangiopathies, and liver transplantation is the only life-extending treatment option for patients with end-stage cholestatic liver disease. One potential therapeutic strategy is to facilitate endogenous repair of the biliary system, which may alleviate intrahepatic cholestasis caused by these diseases. During biliary injury, hepatocytes (HC) are known to alter their phenotype and acquire CC-like features, a process known as cellular reprogramming. This brief review discusses the potential ways in which reprogrammed HC may contribute to biliary repair, thereby restoring bile flow and reducing the severity of cholangiopathies. Some of these include modifying bile to reduce toxicity, serving as a source of de novo CC to repair the biliary epithelium, or creating new channels to facilitate bile flow.
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Affiliation(s)
- Kari Nejak-Bowen
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA, USA
- Pittsburgh Liver Research Center, University of Pittsburgh, Pittsburgh, PA, USA
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17
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Du Y, Khandekar G, Llewellyn J, Polacheck W, Chen CS, Wells RG. A Bile Duct-on-a-Chip With Organ-Level Functions. Hepatology 2020; 71:1350-1363. [PMID: 31465556 PMCID: PMC7048662 DOI: 10.1002/hep.30918] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 08/22/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND AIMS Chronic cholestatic liver diseases, such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are frequently associated with damage to the barrier function of the biliary epithelium. Here, we report on a bile duct-on-a-chip that phenocopies not only the tubular architecture of the bile duct in three dimensions, but also its barrier functions. APPROACH AND RESULTS We showed that mouse cholangiocytes in the channel of the device became polarized and formed mature tight junctions, that the permeability of the cholangiocyte monolayer was comparable to ex vivo measurements, and that cholangiocytes in the device were mechanosensitive (as demonstrated by changes in calcium flux under applied luminal flow). Permeability decreased significantly when cells formed a compact monolayer with cell densities comparable to those observed in vivo. This device enabled independent access to the apical and basolateral surfaces of the cholangiocyte channel, allowing proof-of-concept toxicity studies with the biliary toxin, biliatresone, and the bile acid, glycochenodeoxycholic acid. The cholangiocyte basolateral side was more vulnerable than the apical side to treatment with either agent, suggesting a protective adaptation of the apical surface that is normally exposed to bile. Further studies revealed a protective role of the cholangiocyte apical glycocalyx, wherein disruption of the glycocalyx with neuraminidase increased the permeability of the cholangiocyte monolayer after treatment with glycochenodeoxycholic acid. CONCLUSIONS This bile duct-on-a-chip captured essential features of a simplified bile duct in structure and organ-level functions and represents an in vitro platform to study the pathophysiology of the bile duct using cholangiocytes from a variety of sources.
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Affiliation(s)
- Yu Du
- Division of GastroenterologyDepartment of MedicinePerelman School of Medicine at the University of PennsylvaniaPhiladelphiaPA,Center for Engineering MechanoBiologyThe University of PennsylvaniaPhiladelphiaPA
| | - Gauri Khandekar
- Division of GastroenterologyDepartment of MedicinePerelman School of Medicine at the University of PennsylvaniaPhiladelphiaPA,Center for Engineering MechanoBiologyThe University of PennsylvaniaPhiladelphiaPA
| | - Jessica Llewellyn
- Division of GastroenterologyDepartment of MedicinePerelman School of Medicine at the University of PennsylvaniaPhiladelphiaPA,Center for Engineering MechanoBiologyThe University of PennsylvaniaPhiladelphiaPA
| | - William Polacheck
- The Wyss Institute for Biologically Inspired EngineeringHarvard UniversityBostonMA,The Biological Design Center and Department of Biomedical EngineeringBoston UniversityBostonMA,Joint Department of Biomedical EngineeringUniversity of North Carolina at Chapel Hill and North Carolina State UniversityChapel HillNC
| | - Christopher S. Chen
- The Biological Design Center and Department of Biomedical EngineeringBoston UniversityBostonMA,Tissue Microfabrication LaboratoryDepartment of Biomedical EngineeringBoston UniversityBostonMA,Center for Engineering MechanoBiologyThe University of PennsylvaniaPhiladelphiaPA
| | - Rebecca G. Wells
- Division of GastroenterologyDepartment of MedicinePerelman School of Medicine at the University of PennsylvaniaPhiladelphiaPA,Department of BioengineeringSchool of Engineering and Applied SciencesThe University of PennsylvaniaPhiladelphiaPA,Department of Pathology and Laboratory MedicinePerelman School of Medicine at the University of PennsylvaniaPhiladelphiaPA,Center for Engineering MechanoBiologyThe University of PennsylvaniaPhiladelphiaPA
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18
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Dutta AK, Boggs K, Khimji AK, Getachew Y, Wang Y, Kresge C, Rockey DC, Feranchak AP. Signaling through the interleukin-4 and interleukin-13 receptor complexes regulates cholangiocyte TMEM16A expression and biliary secretion. Am J Physiol Gastrointest Liver Physiol 2020; 318:G763-G771. [PMID: 32090602 PMCID: PMC7191463 DOI: 10.1152/ajpgi.00219.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
TMEM16A is a Ca2+-activated Cl- channel in the apical membrane of biliary epithelial cells, known as cholangiocytes, which contributes importantly to ductular bile formation. Whereas cholangiocyte TMEM16A activity is regulated by extracellular ATP-binding membrane purinergic receptors, channel expression is regulated by interleukin-4 (IL-4) through an unknown mechanism. Therefore, the aim of the present study was to identify the signaling pathways involved in TMEM16A expression and cholangiocyte secretion. Studies were performed in polarized normal rat cholangiocyte monolayers, human Mz-Cha-1 biliary cells, and cholangiocytes isolated from murine liver tissue. The results demonstrate that all the biliary models expressed the IL-4Rα/IL-13Rα1 receptor complex. Incubation of cholangiocytes with either IL-13 or IL-4 increased the expression of TMEM16A protein, which was associated with an increase in the magnitude of Ca2+-activated Cl- currents in response to ATP in single cells and the short-circuit current response in polarized monolayers. The IL-4- and IL-13-mediated increase in TMEM16A expression was also associated with an increase in STAT6 phosphorylation. Specific inhibition of JAK-3 inhibited the increase in TMEM16A expression and the IL-4-mediated increase in ATP-stimulated currents, whereas inhibition of STAT6 inhibited both IL-4- and IL-13-mediated increases in TMEM16A expression and ATP-stimulated secretion. These studies demonstrate that the cytokines IL-13 and IL-4 regulate the expression and function of biliary TMEM16A channels through a signaling pathway involving STAT6. Identification of this regulatory pathway provides new insight into biliary secretion and suggests new targets to enhance bile formation in the treatment of cholestatic liver disorders.NEW & NOTEWORTHY The Ca2+-activated Cl- channel transmembrane member 16A (TMEM16A) has emerged as an important regulator of biliary secretion and hence, ductular bile formation. The present studies represent the initial description of the regulation of TMEM16A expression in biliary epithelium. Identification of this regulatory pathway involving the IL-4 and IL-13 receptor complex and JAK-3 and STAT-6 signaling provides new insight into biliary secretion and suggests new therapeutic targets to enhance bile formation in the treatment of cholestatic liver disorders.
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Affiliation(s)
- Amal K. Dutta
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Kristy Boggs
- 4Department of Pediatrics, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Al-karim Khimji
- 2Department of Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Yonas Getachew
- 2Department of Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Youxue Wang
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Charles Kresge
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Don C. Rockey
- 3Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Andrew P. Feranchak
- 4Department of Pediatrics, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
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19
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Li Q, Kresge C, Boggs K, Scott J, Feranchak A. Mechanosensor transient receptor potential vanilloid member 4 (TRPV4) regulates mouse cholangiocyte secretion and bile formation. Am J Physiol Gastrointest Liver Physiol 2020; 318:G277-G287. [PMID: 31760763 PMCID: PMC7052575 DOI: 10.1152/ajpgi.00176.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mechanosensitive signaling has emerged as a mechanism for the regulation of cholangiocyte transport and bile formation. The mechanical effect of fluid-flow, or shear, at the apical membrane of cholangiocytes regulates secretion through a process involving increases in [Ca2+]i and activation of Ca2+-activated Cl- channels. However, the initiating steps translating shear force to increases in intracellular calcium concentration ([Ca2+]i) are unknown. Transient receptor potential vanilloid member 4 (TRPV4), a nonselective cation channel present in the apical membrane of cholangiocytes, has been proposed as a potential mechanosensor. The aim of the present studies was to determine the potential role of TRPV4 in initiating mechanosensitive signaling in response to fluid-flow in cholangiocytes. TRPV4 expression was confirmed in both small and large mouse cholangiocytes. Exposure of cells to either fluid flow or specific TRPV4 pharmacological agonists rapidly increased both [Ca2+]i and membrane cation currents. Both flow- and agonist-stimulated currents displayed identical biophysical properties and were inhibited in the presence of TRPV4 antagonists or in cells after transfection with TRPV4 small interfering RNA. Transfection of mouse cholangiocytes with a TRPV4-enhanced green fluorescent protein construct increased the expression of TRPV4 and the magnitude of flow-stimulated currents. A specific TRPV4 agonist significantly increased the biliary concentration of ATP and bile flow in live mice when administered intravenously and increased ATP release from cholangiocyte monolayers when applied exogenously. The findings are consistent with a model in which activation of cholangiocyte TRPV4 translates shear force into an acute rise in membrane cation permeability, [Ca2+]i, ATP release, and bile flow. Understanding the role of mechanosensitive transport pathways may provide novel insights to modulate bile flow for the treatment of cholestatic liver disorders.NEW & NOTEWORTHY These studies functionally characterize TRPV4 as a mechanosensitive channel in mouse cholangiocytes. By mediating a rapid rise in intracellular Ca2+, necessary for Ca2+-dependent secretion, TRPV4 represents a mechanosensor responsible for translating fluid flow into intracellular signaling and biliary secretion. Furthermore, intravenous infusion of a specific TRPV4 agonist increases bile flow in live mice. Understanding the role of TRPV4 in mechanosensitive transport pathways may provide novel insights to modulate bile flow during cholestasis.
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Affiliation(s)
- Qin Li
- 1Department of Physiology, Jianghan University School of Medicine, Wuhan, China,3Department of Pediatrics, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Charles Kresge
- 2Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Kristy Boggs
- 3Department of Pediatrics, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Julie Scott
- 3Department of Pediatrics, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Andrew Feranchak
- 3Department of Pediatrics, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
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20
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Tong JJ, Acharya P, Ebihara L. Calcium-Activated Chloride Channels in Newly Differentiating Mouse Lens Fiber Cells and Their Role in Volume Regulation. Invest Ophthalmol Vis Sci 2019; 60:1621-1629. [PMID: 30995319 PMCID: PMC6736345 DOI: 10.1167/iovs.19-26626] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/14/2019] [Indexed: 11/24/2022] Open
Abstract
Purpose Chloride channels have been proposed to play an important role in the regulation of lens volume. Unfortunately, little information is available about the molecular identity of these channels or how they are regulated in the lens due to the difficulties in isolating mouse fiber cells. Recently, our laboratory has developed a new technique for isolating these cells by using transgenic mouse lenses that lack both Cx50 and Cx46. The purpose of this study was to test the hypothesis that newly differentiating mouse fiber cells express calcium-activated chloride channels (CaCCs) by using this technique. Methods Differentiating fiber cells were isolated from lenses of double knockout mice that lack both Cx50 and Cx46 by using collagenase. Membrane currents were studied using the whole-cell patch clamp technique. The molecular identity and distribution of CaCCs were investigated using RT-PCR and immunofluorescence. Results Our electrophysiologic experiments suggest that peripheral fiber cells express a calcium-activated chloride current. The voltage gating properties, calcium sensitivity, and pharmacologic properties of this current resembled those of TMEM16 CaCCs. RT-PCR analysis demonstrated the presence of TMEM16A and TMEM16B transcripts in wild-type and double knockout mouse lenses. Both TMEM16A and TMEM16B proteins were detected in the differentiating epithelial cells and newly elongating fiber cells near the equator of the lens by immunohistochemistry. Conclusions Our results demonstrate that membrane conductance of peripheral fiber cells contain CaCCs that can be attributed to TMEM16A and TMEM16B. Given their critical role in volume regulation in other tissues, we speculate that these channels play a similar role in the lens.
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Affiliation(s)
- Jun-Jie Tong
- Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, Chicago, Illinois, United States
| | - Pooja Acharya
- Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, Chicago, Illinois, United States
| | - Lisa Ebihara
- Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, Chicago, Illinois, United States
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21
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Pethő Z, Najder K, Bulk E, Schwab A. Mechanosensitive ion channels push cancer progression. Cell Calcium 2019; 80:79-90. [PMID: 30991298 DOI: 10.1016/j.ceca.2019.03.007] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 03/26/2019] [Accepted: 03/26/2019] [Indexed: 02/07/2023]
Abstract
In many cases, the mechanical properties of a tumor are different from those of the host tissue. Mechanical cues regulate cancer development by affecting both tumor cells and their microenvironment, by altering cell migration, proliferation, extracellular matrix remodeling and metastatic spread. Cancer cells sense mechanical stimuli such as tissue stiffness, shear stress, tissue pressure of the extracellular space (outside-in mechanosensation). These mechanical cues are transduced into a cellular response (e. g. cell migration and proliferation; inside-in mechanotransduction) or to a response affecting the microenvironment (e. g. inducing a fibrosis or building up growth-induced pressure; inside-out mechanotransduction). These processes heavily rely on mechanosensitive membrane proteins, prominently ion channels. Mechanosensitive ion channels are involved in the Ca2+-signaling of the tumor and stroma cells, both directly, by mediating Ca2+ influx (e. g. Piezo and TRP channels), or indirectly, by maintaining the electrochemical gradient necessary for Ca2+ influx (e. g. K2P, KCa channels). This review aims to discuss the diverse roles of mechanosenstive ion channels in cancer progression, especially those involved in Ca2+-signaling, by pinpointing their functional relevance in tumor pathophysiology.
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Affiliation(s)
- Zoltán Pethő
- Institut für Physiologie II, Robert-Koch-Str. 27b, 48149 Münster, Germany.
| | - Karolina Najder
- Institut für Physiologie II, Robert-Koch-Str. 27b, 48149 Münster, Germany
| | - Etmar Bulk
- Institut für Physiologie II, Robert-Koch-Str. 27b, 48149 Münster, Germany
| | - Albrecht Schwab
- Institut für Physiologie II, Robert-Koch-Str. 27b, 48149 Münster, Germany
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22
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Rodrigues PM, Perugorria MJ, Santos-Laso A, Bujanda L, Beuers U, Banales JM. Primary biliary cholangitis: A tale of epigenetically-induced secretory failure? J Hepatol 2018; 69:1371-1383. [PMID: 30193962 DOI: 10.1016/j.jhep.2018.08.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 08/14/2018] [Accepted: 08/24/2018] [Indexed: 12/16/2022]
Abstract
Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease associated with autoimmune-related destruction of small to medium size intrahepatic bile ducts. The aetiology of PBC is unknown and its pathogenesis remains obscure. Both genetic variants and environmental factors have been linked to increased PBC susceptibility, with other alterations known to cooperate in disease pathobiology. Increasing evidence indicates the presence of epigenetic abnormalities in PBC, particularly alterations of cholangiocellular microRNAs (miRNAs or miRs). This review highlights and discusses the most relevant epigenetic alterations found in patients with PBC, focusing on the role of miR-506 in the promotion of cholestasis and immune activation.
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Affiliation(s)
- Pedro M Rodrigues
- Department of Liver and Gastrointestinal Diseases, Biodonostia Health Research Institute - Donostia University Hospital, University of the Basque Country (UPV/EHU), San Sebastian, Spain
| | - Maria J Perugorria
- Department of Liver and Gastrointestinal Diseases, Biodonostia Health Research Institute - Donostia University Hospital, University of the Basque Country (UPV/EHU), San Sebastian, Spain; National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd, "Instituto de Salud Carlos III"), Spain; Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Alvaro Santos-Laso
- Department of Liver and Gastrointestinal Diseases, Biodonostia Health Research Institute - Donostia University Hospital, University of the Basque Country (UPV/EHU), San Sebastian, Spain
| | - Luis Bujanda
- Department of Liver and Gastrointestinal Diseases, Biodonostia Health Research Institute - Donostia University Hospital, University of the Basque Country (UPV/EHU), San Sebastian, Spain; National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd, "Instituto de Salud Carlos III"), Spain
| | - Ulrich Beuers
- Tytgat Institute for Liver and Intestinal Research and Department of Gastroenterology & Hepatology, Amsterdam Gastroenterology and Metabolism, AMC, Amsterdam, The Netherlands
| | - Jesus M Banales
- Department of Liver and Gastrointestinal Diseases, Biodonostia Health Research Institute - Donostia University Hospital, University of the Basque Country (UPV/EHU), San Sebastian, Spain; National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd, "Instituto de Salud Carlos III"), Spain; Ikerbasque, Basque Foundation for Science, Bilbao, Spain.
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23
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Wu N, Meng F, Zhou T, Venter J, Giang TK, Kyritsi K, Wu C, Alvaro D, Onori P, Mancinelli R, Gaudio E, Francis H, Alpini G, Glaser S, Franchitto A. The Secretin/Secretin Receptor Axis Modulates Ductular Reaction and Liver Fibrosis through Changes in Transforming Growth Factor-β1-Mediated Biliary Senescence. THE AMERICAN JOURNAL OF PATHOLOGY 2018; 188:2264-2280. [PMID: 30036520 PMCID: PMC6168967 DOI: 10.1016/j.ajpath.2018.06.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/26/2018] [Accepted: 06/19/2018] [Indexed: 12/12/2022]
Abstract
Activation of the secretin (Sct)/secretin receptor (SR) axis stimulates ductular reaction and liver fibrosis, which are hallmarks of cholangiopathies. Our aim was to define the role of Sct-regulated cellular senescence, and we demonstrated that both ductular reaction and liver fibrosis are significantly reduced in Sct-/-, SR-/-, and Sct-/-/SR-/- bile duct ligated (BDL) mice compared with BDL wild-type mice. The reduction in hepatic fibrosis in Sct-/-, SR-/-, and Sct-/-/SR-/- BDL mice was accompanied by reduced transforming growth factor-β1 levels in serum and cholangiocyte supernatant, as well as decreased expression of markers of cellular senescence in cholangiocytes in contrast to enhanced cellular senescence in hepatic stellate cells compared with BDL wild-type mice. Secretin directly stimulated the senescence of cholangiocytes and regulated, by a paracrine mechanism, the senescence of hepatic stellate cells and liver fibrosis via modulation of transforming growth factor-β1 biliary secretion. Targeting senescent cholangiocytes may represent a novel therapeutic approach for ameliorating hepatic fibrosis during cholestatic liver injury.
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Affiliation(s)
- Nan Wu
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Fanyin Meng
- Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas
| | - Tianhao Zhou
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Julie Venter
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Thao K Giang
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Konstantina Kyritsi
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas
| | - Chaodong Wu
- Department of Nutrition and Food Science, Texas A&M University, College Station, Texas
| | | | - Paolo Onori
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy
| | - Romina Mancinelli
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy
| | - Eugenio Gaudio
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy
| | - Heather Francis
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas; Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas
| | - Gianfranco Alpini
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas; Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas.
| | - Shannon Glaser
- Department of Medical Physiology, Department of Research, Texas A&M University College of Medicine, Temple, Texas; Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Baylor Scott & White Health Care, Temple, Texas
| | - Antonio Franchitto
- Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Sapienza, Rome, Italy; Department of Medicine, Sapienza, Rome, Italy; Eleonora Lorillard Spencer Cenci Foundation, Rome, Italy
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24
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Oliva-Vilarnau N, Hankeova S, Vorrink SU, Mkrtchian S, Andersson ER, Lauschke VM. Calcium Signaling in Liver Injury and Regeneration. Front Med (Lausanne) 2018; 5:192. [PMID: 30023358 PMCID: PMC6039545 DOI: 10.3389/fmed.2018.00192] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 06/11/2018] [Indexed: 12/12/2022] Open
Abstract
The liver fulfills central roles in metabolic control and detoxification and, as such, is continuously exposed to a plethora of insults. Importantly, the liver has a unique ability to regenerate and can completely recoup from most acute, non-iterative insults. However, multiple conditions, including viral hepatitis, non-alcoholic fatty liver disease (NAFLD), long-term alcohol abuse and chronic use of certain medications, can cause persistent injury in which the regenerative capacity eventually becomes dysfunctional, resulting in hepatic scaring and cirrhosis. Calcium is a versatile secondary messenger that regulates multiple hepatic functions, including lipid and carbohydrate metabolism, as well as bile secretion and choleresis. Accordingly, dysregulation of calcium signaling is a hallmark of both acute and chronic liver diseases. In addition, recent research implicates calcium transients as essential components of liver regeneration. In this review, we provide a comprehensive overview of the role of calcium signaling in liver health and disease and discuss the importance of calcium in the orchestration of the ensuing regenerative response. Furthermore, we highlight similarities and differences in spatiotemporal calcium regulation between liver insults of different etiologies. Finally, we discuss intracellular calcium control as an emerging therapeutic target for liver injury and summarize recent clinical findings of calcium modulation for the treatment of ischemic-reperfusion injury, cholestasis and NAFLD.
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Affiliation(s)
- Nuria Oliva-Vilarnau
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Simona Hankeova
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.,Faculty of Science, Institute of Experimental Biology, Masaryk University, Brno, Czechia
| | - Sabine U Vorrink
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Souren Mkrtchian
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Emma R Andersson
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.,Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Volker M Lauschke
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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25
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Hall C, Sato K, Wu N, Zhou T, Kyritsi K, Meng F, Glaser S, Alpini G. Regulators of Cholangiocyte Proliferation. Gene Expr 2017; 17:155-171. [PMID: 27412505 PMCID: PMC5494439 DOI: 10.3727/105221616x692568] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cholangiocytes, a small population of cells within the normal liver, have been the focus of a significant amount of research over the past two decades because of their involvement in cholangiopathies such as primary sclerosing cholangitis and primary biliary cholangitis. This article summarizes landmark studies in the field of cholangiocyte physiology and aims to provide an updated review of biliary pathogenesis. The historical approach of rodent extrahepatic bile duct ligation and the relatively recent utilization of transgenic mice have led to significant discoveries in cholangiocyte pathophysiology. Cholangiocyte physiology is a complex system based on heterogeneity within the biliary tree and a number of signaling pathways that serve to regulate bile composition. Studies have expanded the list of neuropeptides, neurotransmitters, and hormones that have been shown to be key regulators of proliferation and biliary damage. The peptide histamine and hormones, such as melatonin and angiotensin, angiotensin, as well as numerous sex hormones, have been implicated in cholangiocyte proliferation during cholestasis. Numerous pathways promote cholangiocyte proliferation during cholestasis, and there is growing evidence to suggest that cholangiocyte proliferation may promote hepatic fibrosis. These pathways may represent significant therapeutic potential for a subset of cholestatic liver diseases that currently lack effective therapies.
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Affiliation(s)
- Chad Hall
- *Research, Central Texas Veterans Health Care System, Temple, TX, USA
- †Baylor Scott & White Digestive Disease Research Center, Temple, TX, USA
- ‡Department of Surgery, Baylor Scott & White and Texas A&M Health Science Center, Temple, TX, USA
| | - Keisaku Sato
- §Operational Funds, Baylor Scott & White, Temple, TX, USA
| | - Nan Wu
- §Operational Funds, Baylor Scott & White, Temple, TX, USA
| | - Tianhao Zhou
- §Operational Funds, Baylor Scott & White, Temple, TX, USA
| | | | - Fanyin Meng
- *Research, Central Texas Veterans Health Care System, Temple, TX, USA
- §Operational Funds, Baylor Scott & White, Temple, TX, USA
- ¶Department of Medicine, Baylor Scott & White and Texas A&M Health Science Center, Temple, TX, USA
| | - Shannon Glaser
- *Research, Central Texas Veterans Health Care System, Temple, TX, USA
- §Operational Funds, Baylor Scott & White, Temple, TX, USA
- ¶Department of Medicine, Baylor Scott & White and Texas A&M Health Science Center, Temple, TX, USA
| | - Gianfranco Alpini
- ‡Department of Surgery, Baylor Scott & White and Texas A&M Health Science Center, Temple, TX, USA
- §Operational Funds, Baylor Scott & White, Temple, TX, USA
- ¶Department of Medicine, Baylor Scott & White and Texas A&M Health Science Center, Temple, TX, USA
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26
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Ma K, Wang H, Yu J, Wei M, Xiao Q. New Insights on the Regulation of Ca 2+ -Activated Chloride Channel TMEM16A. J Cell Physiol 2016; 232:707-716. [PMID: 27682822 DOI: 10.1002/jcp.25621] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 09/27/2016] [Indexed: 12/16/2022]
Abstract
TMEM16A, also known as anoctamin 1, is a recently identified Ca2+ -activated chloride channel and the first member of a 10-member TMEM16 family. TMEM16A dysfunction is implicated in many diseases such as cancer, hypertension, and cystic fibrosis. TMEM16A channels are well known to be dually regulated by voltage and Ca2+ . In addition, recent studies have revealed that TMEM16A channels are regulated by many molecules such as calmodulin, protons, cholesterol, and phosphoinositides, and a diverse range of stimuli such as thermal and mechanical stimuli. A better understanding of the regulatory mechanisms of TMEM16A is important to understand its physiological and pathological role. Recently, the crystal structure of a TMEM16 family member from the fungus Nectria haematococcaten (nhTMEM16) is discovered, and provides valuable information for studying the structure and function of TMEM16A. In this review, we discuss the structure and function of TMEM16A channels based on the crystal structure of nhTMEM16A and focus on the regulatory mechanisms of TMEM16A channels. J. Cell. Physiol. 232: 707-716, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Ke Ma
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Hui Wang
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Jiankun Yu
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Minjie Wei
- Department of Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Qinghuan Xiao
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
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27
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Liu LI, Cai S, Qiu G, Lin J. Fluid shear stress enhances the cell volume decrease of osteoblast cells by increasing the expression of the ClC-3 chloride channel. Biomed Rep 2016; 4:408-412. [PMID: 27073622 DOI: 10.3892/br.2016.595] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 09/08/2015] [Indexed: 12/18/2022] Open
Abstract
ClC-3 is a volume-sensitive chloride channel that is responsible for cell volume adjustment and regulatory cell volume decrease (RVD). In order to evaluate the effects of fluid shear stress (FSS) stimulation on the osteoblast ClC-3 chloride channel, MC3T3-E1 cells were stimulated by FSS in the experimental group. Fluorescence quantitative polymerase chain reaction was used to detect changes in ClC-3 mRNA expression, the chloride ion fluorescent probe N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE) was used to detect the chloride channel activity, and whole-cell patch clamping was used to monitor the changes in the volume-sensitive chloride current activated by a hypotonic environment following mechanical stimulation. The results show that the expression of the osteoblast chloride channel ClC-3 was significantly higher in the FSS group compared with the control group. MQAE fluorescence intensity was significantly reduced in the FSS group compared to the control group, suggesting that mechanical stimulation increased chloride channel activity and increased the efflux of intracellular chloride ions. Image analysis of osteoblast volume changes showed that osteoblast RVD was enhanced by mechanical stimulation. Whole-cell patch clamping showed that the osteoblast volume-sensitive chloride current was larger in the stimulated group compared to the control group, suggesting that elevated ClC-3 chloride channel expression results in an increased volume-sensitive chloride current. In conclusion, FSS stimulation enhances the RVD of osteoblast cell by increasing the expression of the ClC-3 and enhancing the chloride channel activity.
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Affiliation(s)
- L I Liu
- Department of Medical Oncology, Affiliated Tumor Hospital of Xinjiang Medical University, Urumqi, Xinjiang 830011, P.R. China
| | - Siyi Cai
- Department of Orthopedics, Peking Union Medical College Hospital, Beijing 100730, P.R. China
| | - Guixing Qiu
- Department of Orthopedics, Peking Union Medical College Hospital, Beijing 100730, P.R. China
| | - Jin Lin
- Department of Orthopedics, Peking Union Medical College Hospital, Beijing 100730, P.R. China
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28
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Li Q, Kresge C, Bugde A, Lamphere M, Park JY, Feranchak AP. Regulation of mechanosensitive biliary epithelial transport by the epithelial Na(+) channel. Hepatology 2016; 63:538-49. [PMID: 26475057 PMCID: PMC4780683 DOI: 10.1002/hep.28301] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 10/14/2015] [Indexed: 12/07/2022]
Abstract
UNLABELLED Intrahepatic biliary epithelial cells (BECs), also known as cholangiocytes, modulate the volume and composition of bile through the regulation of secretion and absorption. While mechanosensitive Cl(-) efflux has been identified as an important secretory pathway, the counterabsorptive pathways have not been identified. In other epithelial cells, the epithelial Na(+) channel (ENaC) has been identified as an important contributor to fluid absorption; however, its expression and function in BECs have not been previously studied. Our studies revealed the presence of α, β, and γ ENaC subunits in human BECs and α and γ subunits in mouse BECs. In studies of confluent mouse BEC monolayers, the ENaC contributes to the volume of surface fluid at the apical membrane during constitutive conditions. Further, functional studies using whole-cell patch clamp of single BECs demonstrated small constitutive Na(+) currents, which increased significantly in response to fluid-flow or shear. The magnitude of Na(+) currents was proportional to the shear force, displayed inward rectification and a reversal potential of +40 mV (ENa+ = +60 mV), and were abolished with removal of extracellular Na(+) (N-methyl-d-glucamine) or in the presence of amiloride. Transfection with ENaCα small interfering RNA significantly inhibited flow-stimulated Na(+) currents, while overexpression of the α subunit significantly increased currents. ENaC-mediated currents were positively regulated by proteases and negatively regulated by extracellular adenosine triphosphate. CONCLUSION These studies represent the initial characterization of mechanosensitive Na(+) currents activated by flow in biliary epithelium; understanding the role of mechanosensitive transport pathways may provide strategies to modulate the volume and composition of bile during cholestatic conditions. (Hepatology 2016;63:538-549).
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Affiliation(s)
- Qin Li
- Department of Physiology, Jianhan University School of Medicine, Wuhan, China,Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Charles Kresge
- Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX
| | - Abhijit Bugde
- Departments of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Michelle Lamphere
- Department of Pathology and Laboratory Medicine, Children’s Health, Children’s Medical Center, University of Texas Southwestern Medical Center, Dallas, TX
| | - Jason Y. Park
- Department of Pathology and Laboratory Medicine, Children’s Health, Children’s Medical Center, University of Texas Southwestern Medical Center, Dallas, TX,Pathology, University of Texas Southwestern Medical Center, Dallas, TX,Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX
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29
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Abstract
Ca2+-activated Cl− channels (CaCCs) are a class of Cl− channels activated by intracellular Ca2+ that are known to mediate numerous physiological functions. In 2008, the molecular identity of CaCCs was found to be anoctamin 1 (ANO1/TMEM16A). Its roles have been studied in electrophysiological, histological, and genetic aspects. ANO1 is known to mediate Cl− secretion in secretory epithelia such as airways, salivary glands, intestines, renal tubules, and sweat glands. ANO1 is a heat sensor activated by noxious heat in somatosensory neurons and mediates acute pain sensation as well as chronic pain. ANO1 is also observed in vascular as well as airway smooth muscles, controlling vascular tone as well as airway hypersensitivity. ANO1 is upregulated in numerous types of cancers and thus thought to be involved in tumorigenesis. ANO1 is also found in proliferating cells. In addition to ANO1, involvement of its paralogs in pathophysiological conditions was also reported. ANO2 is involved in olfaction, whereas ANO6 works as a scramblase whose mutation causes a rare bleeding disorder, the Scott syndrome. ANO5 is associated with muscle and bone diseases. Recently, an X-ray crystal structure of a fungal TMEM16 was reported, which explains a precise molecular gating mechanism as well as ion conduction or phospholipid transport across the plasma membrane.
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30
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Dutta AK, Khimji AK, Liu S, Karamysheva Z, Fujita A, Kresge C, Rockey DC, Feranchak AP. PKCα regulates TMEM16A-mediated Cl⁻ secretion in human biliary cells. Am J Physiol Gastrointest Liver Physiol 2016; 310:G34-42. [PMID: 26542395 PMCID: PMC4698437 DOI: 10.1152/ajpgi.00146.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 10/31/2015] [Indexed: 02/07/2023]
Abstract
TMEM16A is a newly identified Ca(2+)-activated Cl(-) channel in biliary epithelial cells (BECs) that is important in biliary secretion. While extracellular ATP stimulates TMEM16A via binding P2 receptors and increasing intracellular Ca(2+) concentration ([Ca(2+)]i), the regulatory pathways have not been elucidated. Protein kinase C (PKC) contributes to ATP-mediated secretion in BECs, although its potential role in TMEM16A regulation is unknown. To determine whether PKCα regulates the TMEM16A-dependent membrane Cl(-) transport in BECs, studies were performed in human biliary Mz-cha-1 cells. Addition of extracellular ATP induced a rapid translocation of PKCα from the cytosol to the plasma membrane and activation of whole cell Ca(2+)-activated Cl(-) currents. Currents demonstrated outward rectification and reversal at 0 mV (properties consistent with TMEM16A) and were inhibited by either molecular (siRNA) or pharmacologic (PMA or Gö6976) inhibition of PKCα. Intracellular dialysis with recombinant PKCα activated Cl(-) currents with biophysical properties identical to TMEM16A in control cells but not in cells after transfection with TMEM16A siRNA. In conclusion, our studies demonstrate that PKCα is coupled to ATP-stimulated TMEM16A activation in BECs. Targeting this ATP-Ca(2+)-PKCα signaling pathway may represent a therapeutic strategy to increase biliary secretion and promote bile formation.
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Affiliation(s)
- Amal K. Dutta
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas;
| | | | - Songling Liu
- 4Department of Internal Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Zemfira Karamysheva
- 3Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Akiko Fujita
- 2Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas;
| | - Charles Kresge
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas;
| | - Don C. Rockey
- 4Department of Internal Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Andrew P. Feranchak
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas;
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31
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Modulating Ca²⁺ signals: a common theme for TMEM16, Ist2, and TMC. Pflugers Arch 2015; 468:475-90. [PMID: 26700940 DOI: 10.1007/s00424-015-1767-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/24/2015] [Accepted: 11/26/2015] [Indexed: 12/21/2022]
Abstract
Since the discovery of TMEM16A (anoctamin 1, ANO1) as Ca(2+)-activated Cl(-) channel, the protein was found to serve different physiological functions, depending on the type of tissue. Subsequent reports on other members of the anoctamin family demonstrated a broad range of yet poorly understood properties. Compromised anoctamin function is causing a wide range of diseases, such as hearing loss (ANO2), bleeding disorder (ANO6), ataxia and dystonia (ANO3, 10), persistent borrelia and mycobacteria infection (ANO10), skeletal syndromes like gnathodiaphyseal dysplasia and limb girdle muscle dystrophy (ANO5), and cancer (ANO1, 6, 7). Animal models demonstrate CF-like airway disease, asthma, and intestinal hyposecretion (ANO1). Although present data indicate that ANO1 is a Ca(2+)-activated Cl(-) channel, it remains unclear whether all anoctamins form plasma membrane-localized or intracellular chloride channels. We find Ca(2+)-activated Cl(-) currents appearing by expression of most anoctamin paralogs, including the Nectria haematococca homologue nhTMEM16 and the yeast homologue Ist2. As recent studies show a role of anoctamins, Ist2, and the related transmembrane channel-like (TMC) proteins for intracellular Ca(2+) signaling, we will discuss the role of these proteins in generating compartmentalized Ca(2+) signals, which may give a hint as to the broad range of cellular functions of anoctamins.
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32
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Godoy V, Banales JM, Medina JF, Pastor-Anglada M. Functional crosstalk between the adenosine transporter CNT3 and purinergic receptors in the biliary epithelia. J Hepatol 2014; 61:1337-43. [PMID: 25034758 DOI: 10.1016/j.jhep.2014.06.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 06/17/2014] [Accepted: 06/27/2014] [Indexed: 12/14/2022]
Abstract
BACKGROUND & AIMS Both hepatocytes and cholangiocytes release ATP into the bile, where it acts as a potent autocrine/paracrine stimulus that activates biliary secretory mechanisms. ATP is known to be metabolized into multiple breakdown products, ultimately yielding adenosine. However, the elements implicated in the adenosine-dependent purinergic regulation of cholangiocytes are not known. METHODS Normal rat cholangiocytes (NRCs) were used to study the expression of adenosine receptors and transporters and their functional interactions at the apical and basolateral membrane domains of polarized cholangiocytes. RESULTS We found that: (1) cholangiocytes exclusively express two concentrative nucleoside transporters (CNT) known to be efficient adenosine carriers: CNT3, located at the apical membrane, and CNT2, located at apical and basolateral membrane domains; (2) in both domains, NRCs also express the high affinity adenosine receptor A2A, which modulated the activity of apical CNT3 in a domain-specific manner; (3) the regulation exerted by A2A on CNT3 was dependent upon the cAMP/PKA/ERK/CREB axis, intracellular trafficking mechanisms and AMPK phosphorylation; (4) secretin increased the activity of the apically-located CNT3, and promoted additional basolateral CNT3-related activity; and (5) extracellular ATP (a precursor of adenosine) was able to exert an inhibitory effect on the apical activity of both CNT3 and CNT2. CONCLUSIONS This study uncovered the functional expression of nucleoside transporters in cholangiocytes and provides evidence for direct crosstalks between adenosine transporters and receptors for adenosine and its natural extracellular precursor, ATP. Our data anticipate the possibility of adenosine playing a major role in the physiopathology of the biliary epithelia.
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Affiliation(s)
- Valeria Godoy
- Molecular Pharmacology and Experimental Therapeutics, Department of Biochemistry and Molecular Biology, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain; National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd), Spain
| | - Jesús M Banales
- Department of Liver Diseases, Biodonostia Research Institute (Donostia University Hospital), IKERBASQUE (Basque Foundation for Science), University of Basque Country (UPV/EHU), San Sebastian, Spain; National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd), Spain
| | - Juan F Medina
- Molecular Genetics, Division of Gene Therapy and Hepatology, School of Medicine and CIMA of the University of Navarra, Pamplona, Spain; National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd), Spain
| | - Marçal Pastor-Anglada
- Molecular Pharmacology and Experimental Therapeutics, Department of Biochemistry and Molecular Biology, Institute of Biomedicine (IBUB), University of Barcelona, Barcelona, Spain; National Institute for the Study of Liver and Gastrointestinal Diseases (CIBERehd), Spain.
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33
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Abstract
Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by selective destruction of intrahepatic cholangiocytes. Mechanisms underlying the development and progression of the disease are still controversial and largely undefined. Evidence suggests that PBC results from an articulated immunologic response against an immunodominant mitochondrial autoantigen, the E2 component of the pyruvate dehydrogenase complex (PDC-E2); characteristics of the disease are also the presence of disease-specific antimitochondrial autoantibodies (AMAs) and autoreactive CD4 and CD8 T cells. Recent evidence suggests that cholangiocytes show specific immunobiological features that are responsible for the selective targeting of those cells by the immune system. The immune reaction in PBC selectively targets small sized, intrahepatic bile ducts; although a specific reason for that has not been defined yet, it has been established that the biliary epithelium displays a unique heterogeneity, for which the physiological and pathophysiological features of small and large cholangiocytes significantly differ. In this review article, the authors provide a critical overview of the current evidence on the role of cholangiocytes in the immune-mediated destruction of the biliary tree that characterizes PBC.
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Affiliation(s)
- Ana Lleo
- Liver Unit and Center for Autoimmune Liver Diseases, Humanitas Clinical and Research Center, Rozzano (MI), Italy
| | - Luca Maroni
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy
| | - Shannon Glaser
- Research, Central Texas Veterans Health Care System, S and W and Texas A and M System Health Science Center, College of Medicine, Temple, Texas,Scott & White Digestive Disease Research Center, S and W and Texas A and M System Health Science Center, College of Medicine, Temple, Texas,Department of Medicine, Division Gastroenterology, S and W and Texas A and M System Health Science Center, College of Medicine, Temple, Texas
| | - Gianfranco Alpini
- Research, Central Texas Veterans Health Care System, S and W and Texas A and M System Health Science Center, College of Medicine, Temple, Texas,Scott & White Digestive Disease Research Center, S and W and Texas A and M System Health Science Center, College of Medicine, Temple, Texas,Department of Medicine, Division Gastroenterology, S and W and Texas A and M System Health Science Center, College of Medicine, Temple, Texas
| | - Marco Marzioni
- Clinic of Gastroenterology and Hepatology, Università Politecnica delle Marche, Ancona, Italy
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34
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Abstract
TMEM16 proteins, also known as anoctamins, are involved in a variety of functions that include ion transport, phospholipid scrambling, and regulation of other membrane proteins. The first two members of the family, TMEM16A (anoctamin-1, ANO1) and TMEM16B (anoctamin-2, ANO2), function as Ca2+-activated Cl- channels (CaCCs), a type of ion channel that plays important functions such as transepithelial ion transport, smooth muscle contraction, olfaction, phototransduction, nociception, and control of neuronal excitability. Genetic ablation of TMEM16A in mice causes impairment of epithelial Cl- secretion, tracheal abnormalities, and block of gastrointestinal peristalsis. TMEM16A is directly regulated by cytosolic Ca2+ as well as indirectly by its interaction with calmodulin. Other members of the anoctamin family, such as TMEM16C, TMEM16D, TMEM16F, TMEM16G, and TMEM16J, may work as phospholipid scramblases and/or ion channels. In particular, TMEM16F (ANO6) is a major contributor to the process of phosphatidylserine translocation from the inner to the outer leaflet of the plasma membrane. Intriguingly, TMEM16F is also associated with the appearance of anion/cation channels activated by very high Ca2+ concentrations. Furthermore, a TMEM16 protein expressed in Aspergillus fumigatus displays both ion channel and lipid scramblase activity. This finding suggests that dual function is an ancestral characteristic of TMEM16 proteins and that some members, such as TMEM16A and TMEM16B, have evolved to a pure channel function. Mutations in anoctamin genes (ANO3, ANO5, ANO6, and ANO10) cause various genetic diseases. These diseases suggest the involvement of anoctamins in a variety of cell functions whose link with ion transport and/or lipid scrambling needs to be clarified.
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Salzer I, Gafar H, Gindl V, Mahlknecht P, Drobny H, Boehm S. Excitation of rat sympathetic neurons via M1 muscarinic receptors independently of Kv7 channels. Pflugers Arch 2014; 466:2289-303. [PMID: 24668449 PMCID: PMC4233321 DOI: 10.1007/s00424-014-1487-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 02/13/2014] [Accepted: 02/14/2014] [Indexed: 01/14/2023]
Abstract
The slow cholinergic transmission in autonomic ganglia is known to be mediated by an inhibition of Kv7 channels via M1 muscarinic acetylcholine receptors. However, in the present experiments using primary cultures of rat superior cervical ganglion neurons, the extent of depolarisation caused by the M1 receptor agonist oxotremorine M did not correlate with the extent of Kv7 channel inhibition in the very same neuron. This observation triggered a search for additional mechanisms. As the activation of M1 receptors leads to a boost in protein kinase C (PKC) activity in sympathetic neurons, various PKC enzymes were inhibited by different means. Interference with classical PKC isoforms led to reductions in depolarisations and in noradrenaline release elicited by oxotremorine M, but left the Kv7 channel inhibition by the muscarinic agonist unchanged. M1 receptor-induced depolarisations were also altered when extra- or intracellular Cl− concentrations were changed, as were depolarising responses to γ-aminobutyric acid. Depolarisations and noradrenaline release triggered by oxotremorine M were reduced by the non-selective Cl− channel blockers 4-acetamido-4′-isothiocyanato-stilbene-2,2′-disulfonic acid and niflumic acid. Oxotremorine M induced slowly rising inward currents at negative membrane potentials that were blocked by inhibitors of Ca2+-activated Cl− and TMEM16A channels and attenuated by PKC inhibitors. These channel blockers also reduced oxotremorine M-evoked noradrenaline release. Together, these results reveal that slow cholinergic excitation of sympathetic neurons involves the activation of classical PKCs and of Ca2+-activated Cl− channels in addition to the well-known inhibition of Kv7 channels.
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Affiliation(s)
- Isabella Salzer
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Waehringerstrasse 13a, 1090, Vienna, Austria
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Kunzelmann K, Nilius B, Owsianik G, Schreiber R, Ousingsawat J, Sirianant L, Wanitchakool P, Bevers EM, Heemskerk JWM. Molecular functions of anoctamin 6 (TMEM16F): a chloride channel, cation channel, or phospholipid scramblase? Pflugers Arch 2014; 466:407-14. [PMID: 23748496 DOI: 10.1007/s00424-013-1305-1] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 05/27/2013] [Accepted: 05/28/2013] [Indexed: 10/26/2022]
Abstract
Anoctamin 6 (Ano6; TMEM16F gene) is a ubiquitous protein; the expression of which is defective in patients with Scott syndrome, an inherited bleeding disorder based on defective scrambling of plasma membrane phospholipids. For Ano6, quite diverse functions have been described: (1) it can form an outwardly rectifying, Ca(2+)-dependent and a volume-regulated Cl(-) channel; (2) it was claimed to be a Ca(2+)-regulated nonselective cation channel permeable for Ca(2+); (3) it was shown to be essential for Ca(2+)-mediated scrambling of membrane phospholipids; and (4) it can regulate cell blebbing and microparticle shedding. Deficiency of Ano6 in blood cells from Scott patients or Ano6 null mice appears to affect all of these cell responses. Furthermore, Ano6 deficiency in mice impairs the mineralization of osteoblasts, resulting in reduced skeletal development. These diverse results have been obtained under different experimental conditions, which may explain some of the contradictions. This review therefore aims to summarize the currently available information on the diverse roles of Ano6 and tries to clear up some of the existing controversies.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany,
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The calcium-activated chloride channel Anoctamin 1 contributes to the regulation of renal function. Kidney Int 2014; 85:1369-81. [PMID: 24476694 DOI: 10.1038/ki.2013.535] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 10/16/2013] [Accepted: 11/14/2013] [Indexed: 01/14/2023]
Abstract
The role of calcium-activated chloride channels for renal function is unknown. By immunohistochemistry we demonstrate dominant expression of the recently identified calcium-activated chloride channels, Anoctamin 1 (Ano1, TMEM16A) in human and mouse proximal tubular epithelial (PTE) cells, with some expression in podocytes and other tubular segments. Ano1-null mice had proteinuria and numerous large reabsorption vesicles in PTE cells. Selective knockout of Ano1 in podocytes (Ano1-/-/Nphs2-Cre) did not impair renal function, whereas tubular knockout in Ano1-/-/Ksp-Cre mice increased urine protein excretion and decreased urine electrolyte concentrations. Purinergic stimulation activated calcium-dependent chloride currents in isolated proximal tubule epithelial cells from wild-type but not from Ano1-/-/Ksp-Cre mice. Ano1 currents were activated by acidic pH, suggesting parallel stimulation of Ano1 chloride secretion with activation of the proton-ATPase. Lack of calcium-dependent chloride secretion in cells from Ano1-/-/Ksp-Cre mice was paralleled by attenuated proton secretion and reduced endosomal acidification, which compromised proximal tubular albumin uptake. Tubular knockout of Ano1 enhanced serum renin and aldosterone concentrations, probably leading to enhanced compensatory distal tubular reabsorption, thus maintaining normal blood pressure levels. Thus, Ano1 has a role in proximal tubular proton secretion and protein reabsorption. The results correspond to regulation of the proton-ATPase by the Ano1-homolog Ist2 in yeast.
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Concepcion AR, Lopez M, Ardura-Fabregat A, Medina JF. Role of AE2 for pHi regulation in biliary epithelial cells. Front Physiol 2014; 4:413. [PMID: 24478713 PMCID: PMC3894451 DOI: 10.3389/fphys.2013.00413] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 12/27/2013] [Indexed: 12/31/2022] Open
Abstract
The Cl−/HCO−3anion exchanger 2 (AE2) is known to be involved in intracellular pH (pHi) regulation and transepithelial acid-base transport. Early studies showed that AE2 gene expression is reduced in liver biopsies and blood mononuclear cells from patients with primary biliary cirrhosis (PBC), a disease characterized by chronic non-suppurative cholangitis associated with antimitochondrial antibodies (AMA) and other autoimmune phenomena. Microfluorimetric analysis of the Cl−/HCO−3 anion exchange (AE) in isolated cholangiocytes showed that the cAMP-stimulated AE activity is diminished in PBC compared to both healthy and diseased controls. More recently, it was found that miR-506 is upregulated in cholangiocytes of PBC patients and that AE2 may be a target of miR-506. Additional evidence for a pathogenic role of AE2 dysregulation in PBC was obtained with Ae2−/−a,b mice, which develop biochemical, histological, and immunologic alterations that resemble PBC (including development of serum AMA). Analysis of HCO−3 transport systems and pHi regulation in cholangiocytes from normal and Ae2−/−a,b mice confirmed that AE2 is the transporter responsible for the Cl−/HCO−3exchange in these cells. On the other hand, both Ae2+/+a,b and Ae2−/−a,b mouse cholangiocytes exhibited a Cl−-independent bicarbonate transport system, essentially a Na+-bicarbonate cotransport (NBC) system, which could contribute to pHi regulation in the absence of AE2.
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Affiliation(s)
- Axel R Concepcion
- Division of Gene Therapy and Hepatology, Center for Applied Medical Research (CIMA), School of Medicine, University of Navarra, and Ciberehd Pamplona, Spain
| | - María Lopez
- Division of Gene Therapy and Hepatology, Center for Applied Medical Research (CIMA), School of Medicine, University of Navarra, and Ciberehd Pamplona, Spain
| | - Alberto Ardura-Fabregat
- Division of Gene Therapy and Hepatology, Center for Applied Medical Research (CIMA), School of Medicine, University of Navarra, and Ciberehd Pamplona, Spain
| | - Juan F Medina
- Division of Gene Therapy and Hepatology, Center for Applied Medical Research (CIMA), School of Medicine, University of Navarra, and Ciberehd Pamplona, Spain
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