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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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Park JS. Effects of ATP on Regulatory Volume Decrease in Mouse Cholangiocytes. KOREAN JOURNAL OF CLINICAL LABORATORY SCIENCE 2016. [DOI: 10.15324/kjcls.2016.48.2.153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Jae Seung Park
- Department of Clinical Pathology, Sohae College, Gunsan 54116, Korea
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3
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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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Dutta AK, Woo K, Khimji AK, Kresge C, Feranchak AP. Mechanosensitive Cl- secretion in biliary epithelium mediated through TMEM16A. Am J Physiol Gastrointest Liver Physiol 2013; 304:G87-98. [PMID: 23104560 PMCID: PMC3543635 DOI: 10.1152/ajpgi.00154.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Bile formation by the liver is initiated by canalicular transport at the hepatocyte membrane, leading to an increase in ductular bile flow. Thus, bile duct epithelial cells (cholangiocytes), which contribute to the volume and dilution of bile through regulated Cl(-) transport, are exposed to changes in flow and shear force at the apical membrane. The aim of the present study was to determine if fluid flow, or shear stress, is a signal regulating cholangiocyte transport. The results demonstrate that, in human and mouse biliary cells, fluid flow, or shear, increases Cl(-) currents and identify TMEM16A, a Ca(2+)-activated Cl(-) channel, as the operative channel. Furthermore, activation of TMEM16A by flow is dependent on PKCα through a process involving extracellular ATP, binding purinergic P2 receptors, and increases in intracellular Ca(2+) concentration. These studies represent the initial characterization of mechanosensitive Cl(-) currents mediated by TMEM16A. Identification of this novel mechanosensitive secretory pathway provides new insight into bile formation 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; and
| | - Kangmee Woo
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Al-karim Khimji
- 2Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Charles Kresge
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Andrew P. Feranchak
- 1Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas; and
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5
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Loganathan A, Linley JE, Rajput I, Hunter M, Lodge JPA, Sandle GI. Basolateral potassium (IKCa) channel inhibition prevents increased colonic permeability induced by chemical hypoxia. Am J Physiol Gastrointest Liver Physiol 2011; 300:G146-53. [PMID: 20966032 PMCID: PMC3025504 DOI: 10.1152/ajpgi.00472.2009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Major liver resection is associated with impaired intestinal perfusion and intestinal ischemia, resulting in decreased mucosal integrity, increased bacterial translocation, and an increased risk of postoperative sepsis. However, the mechanism by which ischemia impairs intestinal mucosal integrity is unclear. We therefore evaluated the role of Ca(2+)-sensitive, intermediate-conductance (IK(Ca)) basolateral potassium channels in enhanced intestinal permeability secondary to chemical hypoxia. The effects of chemical hypoxia induced by 100 μM dinitrophenol (DNP) and 5 mM deoxyglucose (DG) on basolateral IK(Ca) channel activity and whole cell conductance in intact human colonic crypts, and paracellular permeability (G(S)) in isolated colonic sheets, were determined by patch-clamp recording and transepithelial electrical measurements, respectively. DNP and DG rapidly stimulated IK(Ca) channels in cell-attached basolateral membrane patches and elicited a twofold increase (P = 0.004) in whole cell conductance in amphotericin B-permeabilized membrane patches, changes that were inhibited by the specific IK(Ca) channel blockers TRAM-34 (100 nM) and clotrimazole (CLT; 10 μM). In colonic sheets apically permeabilized with nystatin, DNP elicited a twofold increase (P = 0.005) in G(S), which was largely inhibited by the serosal addition of 50 μM CLT. We conclude that, in intestinal epithelia, chemical hypoxia increases G(S) through a mechanism involving basolateral IK(Ca) channel activation. Basolateral IK(Ca) channel inhibition may prevent or limit increased intestinal permeability during liver surgery.
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Affiliation(s)
- A. Loganathan
- 1Leeds Institute of Molecular Medicine and ,2Department of Hepatobiliary Surgery, St. James's University Hospital; and
| | - J. E. Linley
- 3Institute of Membrane and Systems Biology, University of Leeds, Leeds, United Kingdom
| | - I. Rajput
- 1Leeds Institute of Molecular Medicine and ,2Department of Hepatobiliary Surgery, St. James's University Hospital; and
| | - M. Hunter
- 3Institute of Membrane and Systems Biology, University of Leeds, Leeds, United Kingdom
| | - J. P. A. Lodge
- 2Department of Hepatobiliary Surgery, St. James's University Hospital; and
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Dutta AK, Khimji AK, Kresge C, Bugde A, Dougherty M, Esser V, Ueno Y, Glaser SS, Alpini G, Rockey DC, Feranchak AP. Identification and functional characterization of TMEM16A, a Ca2+-activated Cl- channel activated by extracellular nucleotides, in biliary epithelium. J Biol Chem 2010; 286:766-76. [PMID: 21041307 DOI: 10.1074/jbc.m110.164970] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cl(-) channels in the apical membrane of biliary epithelial cells (BECs) provide the driving force for ductular bile formation. Although a cystic fibrosis transmembrane conductance regulator has been identified in BECs and contributes to secretion via secretin binding basolateral receptors and increasing [cAMP](i), an alternate Cl(-) secretory pathway has been identified that is activated via nucleotides (ATP, UTP) binding apical P2 receptors and increasing [Ca(2+)](i). The molecular identity of this Ca(2+)-activated Cl(-) channel is unknown. The present studies in human, mouse, and rat BECs provide evidence that TMEM16A is the operative channel and contributes to Ca(2+)-activated Cl(-) secretion in response to extracellular nucleotides. Furthermore, Cl(-) currents measured from BECs isolated from distinct areas of intrahepatic bile ducts revealed important functional differences. Large BECs, but not small BECs, exhibit cAMP-stimulated Cl(-) currents. However, both large and small BECs express TMEM16A and exhibit Ca(2+)-activated Cl(-) efflux in response to extracellular nucleotides. Incubation of polarized BEC monolayers with IL-4 increased TMEM16A protein expression, membrane localization, and transepithelial secretion (I(sc)). These studies represent the first molecular identification of an alternate, noncystic fibrosis transmembrane conductance regulator, Cl(-) channel in BECs and suggest that TMEM16A may be a potential target to modulate bile formation in the treatment of cholestatic liver disorders.
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Affiliation(s)
- Amal K Dutta
- Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9063, USA
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7
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Dutta AK, Khimji AK, Sathe M, Kresge C, Parameswara V, Esser V, Rockey DC, Feranchak AP. Identification and functional characterization of the intermediate-conductance Ca(2+)-activated K(+) channel (IK-1) in biliary epithelium. Am J Physiol Gastrointest Liver Physiol 2009; 297:G1009-18. [PMID: 20501432 PMCID: PMC2777461 DOI: 10.1152/ajpgi.00223.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In the liver, adenosine triphosphate (ATP) is an extracellular signaling molecule that is released into bile and stimulates a biliary epithelial cell secretory response via engagement of apical P2 receptors. The molecular identities of the ion channels involved in ATP-mediated secretory responses have not been fully identified. Intermediate-conductance Ca(2+)-activated K(+) channels (IK) have been identified in biliary epithelium, but functional data are lacking. The aim of these studies therefore was to determine the location, function, and regulation of IK channels in biliary epithelial cells and to determine their potential contribution to ATP-stimulated secretion. Expression of IK-1 mRNA was found in both human Mz-Cha-1 biliary cells and polarized normal rat cholangiocyte (NRC) monolayers, and immunostaining revealed membrane localization with a predominant basolateral signal. In single Mz-Cha-1 cells, exposure to ATP activated K(+) currents, increasing current density from 1.6 +/- 0.1 to 7.6 +/- 0.8 pA/pF. Currents were dependent on intracellular Ca(2+) and sensitive to clotrimazole and TRAM-34 (specific IK channel inhibitors). Single-channel recording demonstrated that clotrimazole-sensitive K(+) currents had a unitary conductance of 46.2 +/- 1.5 pS, consistent with IK channels. In separate studies, 1-EBIO (an IK activator) stimulated K(+) currents in single cells that were inhibited by clotrimazole. In polarized NRC monolayers, ATP significantly increased transepithelial secretion which was inhibited by clotrimazole. Lastly, ATP-stimulated K(+) currents were inhibited by the P2Y receptor antagonist suramin and by the inositol 1,4,5-triphosphate (IP3) receptor inhibitor 2-APB. Together these studies demonstrate that IK channels are present in biliary epithelial cells and contribute to ATP-stimulated secretion through a P2Y-IP3 receptor pathway.
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Affiliation(s)
| | - Al-karim Khimji
- 2Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | | | | | - Vinay Parameswara
- 2Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Victoria Esser
- 2Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Don C. Rockey
- 2Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
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8
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Woodberry MW, Aguilera-Aguirre L, Bacsi A, Chopra AK, Kurosky A, Peterson JW, Boldogh I. ATP Depletion Via Mitochondrial F1F0 Complex by Lethal Factor is an Early Event in B. Anthracis-Induced Sudden Cell Death. J Cell Death 2009; 2:25-39. [PMID: 26124678 PMCID: PMC4474334 DOI: 10.4137/jcd.s2811] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bacillus anthracis’ primary virulence factor is a tripartite anthrax toxin consisting of edema factor (EF), lethal factor (LF) and protective antigen (PA). In complex with PA, EF and LF are internalized via receptor-mediated endocytosis. EF is a calmodulin-dependent adenylate cyclase that induces tissue edema. LF is a zinc-metalloprotease that cleaves members of mitogen-activated protein kinase kinases. Lethal toxin (LT: PA plus LF)-induced death of macrophages is primarily attributed to expression of the sensitive Nalp1b allele, inflammasome formation and activation of caspase-1, but early events that initiate these processes are unknown. Here we provide evidence that an early essential event in pyroptosis of alveolar macrophages is LF-mediated depletion of cellular ATP. The underlying mechanism involves interaction of LF with F1F0-complex gamma and beta subunits leading to increased ATPase activity in mitochondria. In support, mitochondrial DNA-depleted MH-S cells have decreased F1F0 ATPase activity due to the lack of F06 and F08 polypeptides and show increased resistance to LT. We conclude that ATP depletion is an important early event in LT-induced sudden cell death and its prevention increases survival of toxin-sensitive cells.
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Affiliation(s)
- Mitchell W Woodberry
- Medical Service Corps, Diagnostic System Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland 21702
| | - Leopoldo Aguilera-Aguirre
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, 77555
| | - Attila Bacsi
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, 77555
| | - Ashok K Chopra
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, 77555
| | - Alexander Kurosky
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, 77555
| | - Johnny W Peterson
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, 77555
| | - Istvan Boldogh
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, 77555
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9
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Dutta AK, Woo K, Doctor RB, Fitz JG, Feranchak AP. Extracellular nucleotides stimulate Cl- currents in biliary epithelia through receptor-mediated IP3 and Ca2+ release. Am J Physiol Gastrointest Liver Physiol 2008; 295:G1004-15. [PMID: 18787062 PMCID: PMC2584822 DOI: 10.1152/ajpgi.90382.2008] [Citation(s) in RCA: 36] [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
Extracellular ATP regulates bile formation by binding to P2 receptors on cholangiocytes and stimulating transepithelial Cl(-) secretion. However, the specific signaling pathways linking receptor binding to Cl(-) channel activation are not known. Consequently, the aim of these studies in human Mz-Cha-1 biliary cells and normal rat cholangiocyte monolayers was to assess the intracellular pathways responsible for ATP-stimulated increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) and membrane Cl(-) permeability. Exposure of cells to ATP resulted in a rapid increase in [Ca(2+)](i) and activation of membrane Cl(-) currents; both responses were abolished by prior depletion of intracellular Ca(2+). ATP-stimulated Cl(-) currents demonstrated mild outward rectification, reversal at E(Cl(-)), and a single-channel conductance of approximately 17 pS, where E is the equilibrium potential. The conductance response to ATP was inhibited by the Cl(-) channel inhibitors NPPB and DIDS but not the CFTR inhibitor CFTR(inh)-172. Both ATP-stimulated increases in [Ca(2+)](i) and Cl(-) channel activity were inhibited by the P2Y receptor antagonist suramin. The PLC inhibitor U73122 and the inositol 1,4,5-triphosphate (IP3) receptor inhibitor 2-APB both blocked the ATP-stimulated increase in [Ca(2+)](i) and membrane Cl(-) currents. Intracellular dialysis with purified IP3 activated Cl(-) currents with identical properties to those activated by ATP. Exposure of normal rat cholangiocyte monolayers to ATP increased short-circuit currents (I(sc)), reflecting transepithelial secretion. The I(sc) was unaffected by CFTR(inh)-172 but was significantly inhibited by U73122 or 2-APB. In summary, these findings indicate that the apical P2Y-IP3 receptor signaling complex is a dominant pathway mediating biliary epithelial Cl(-) transport and, therefore, may represent a potential target for increasing secretion in the treatment of cholestatic liver disease.
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Affiliation(s)
- Amal K. Dutta
- Department of Pediatrics, and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and University of Colorado Health Sciences Center, Denver, Colorado
| | - Kangmee Woo
- Department of Pediatrics, and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and University of Colorado Health Sciences Center, Denver, Colorado
| | - R. Brian Doctor
- Department of Pediatrics, and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and University of Colorado Health Sciences Center, Denver, Colorado
| | - J. Gregory Fitz
- Department of Pediatrics, and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and University of Colorado Health Sciences Center, Denver, Colorado
| | - Andrew P. Feranchak
- Department of Pediatrics, and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; and University of Colorado Health Sciences Center, Denver, Colorado
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Woo K, Dutta AK, Patel V, Kresge C, Feranchak AP. Fluid flow induces mechanosensitive ATP release, calcium signalling and Cl- transport in biliary epithelial cells through a PKCzeta-dependent pathway. J Physiol 2008; 586:2779-98. [PMID: 18388137 DOI: 10.1113/jphysiol.2008.153015] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
ATP in bile is a potent secretogogue, stimulating cholangiocyte Cl- and fluid secretion via binding to membrane P2 receptors, though the physiological stimuli involved in biliary ATP release are unknown. The goal of the present studies was to determine the potential role of fluid flow in biliary ATP release and secretion. In both human Mz-Cha-1 biliary cells and normal rat cholangiocyte monolayers, exposure to flow increased relative ATP release which was proportional to the shear stress. In parallel studies, shear was associated with an increase in [Ca2+]i and membrane Cl- permeability, which were both dependent on extracellular ATP and P2 receptor stimulation. Flow-stimulated ATP release was dependent on [Ca2+]i, exhibited desensitization with repetitive stimulation, and was regulated by PKCzeta. In conclusion, both human and rat biliary cells exhibit flow-stimulated, PKCzeta-dependent, ATP release, increases in [Ca2+]i and Cl- secretion. The finding that fluid flow can regulate membrane transport suggests that mechanosensitive ATP release may be a key regulator of biliary secretion and an important target to modulate bile flow in the treatment of cholestatic liver diseases.
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Affiliation(s)
- Kangmee Woo
- UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9063, USA
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11
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Klarl BA, Lang PA, Kempe DS, Niemoeller OM, Akel A, Sobiesiak M, Eisele K, Podolski M, Huber SM, Wieder T, Lang F. Protein kinase C mediates erythrocyte "programmed cell death" following glucose depletion. Am J Physiol Cell Physiol 2006; 290:C244-53. [PMID: 16338977 DOI: 10.1152/ajpcell.00283.2005] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Glucose depletion of erythrocytes leads to activation of Ca2+-permeable cation channels, Ca2+ entry, activation of a Ca2+-sensitive erythrocyte scramblase, and subsequent exposure of phosphatidylserine at the erythrocyte surface. Ca2+ entry into erythrocytes was previously shown to be stimulated by phorbol esters and to be inhibited by staurosporine and chelerythrine and is thus thought to be regulated by protein phosphorylation/dephosphorylation, presumably via protein kinase C (PKC) and the corresponding phosphoserine/threonine phosphatases. The present experiments explored whether PKC could contribute to effects of energy depletion on erythrocyte phosphatidylserine exposure and cell volume. Phosphatidylserine exposure was estimated from annexin binding and cell volume from forward scatter in fluorescence-activated cell sorter analysis. Removal of extracellular glucose led to depletion of cellular ATP, stimulated PKC activity, led to translocation of PKCalpha, enhanced serine phosphorylation of membrane proteins, decreased cell volume, and increased annexin binding, the latter effect being blunted but not abolished in the presence of 1 microM staurosporine or 50 nM calphostin C. The PKC stimulator phorbol-12-myristate-13-acetate (3 microM) and the phosphatase inhibitor okadaic acid (1-10 microM) mimicked the effect of glucose depletion and similarly led to translocation of PKCalpha and enhanced serine phosphorylation, increased annexin binding, and decreased forward scatter, the latter effects being abrogated by PKC inhibitor staurosporine (1 microM). Fluo-3 fluorescence measurements revealed that okadaic acid also enhanced erythrocyte Ca2+ activity. The present observations suggest that protein phosphorylation and dephosphorylation via PKC and the corresponding protein phosphatases contribute to phosphatidylserine exposure and cell shrinkage after energy depletion.
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Affiliation(s)
- Barbara A Klarl
- Department of Physiology, University of Tübingen, Tübingen, Germany
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12
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Feranchak AP, Doctor RB, Troetsch M, Brookman K, Johnson SM, Fitz JG. Calcium-dependent regulation of secretion in biliary epithelial cells: the role of apamin-sensitive SK channels. Gastroenterology 2004; 127:903-13. [PMID: 15362045 DOI: 10.1053/j.gastro.2004.06.047] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND & AIMS Increases in intracellular Ca 2+ are thought to complement cAMP in stimulating Cl - secretion in cholangiocytes, although the site(s) of action and channels involved are unknown. We have identified a Ca 2+ -activated K + channel (SK2) in biliary epithelium that is inhibited by apamin. The purpose of the present studies was to define the role of SK channels in Ca 2+ -dependent cholangiocyte secretion. METHODS Studies were performed in human Mz-Cha-1 cells and normal rat cholangiocytes (NRC). Currents were measured by whole-cell patch clamp technique and transepithelial secretion by Ussing chamber. RESULTS Ca 2+ -dependent stimuli, including purinergic receptor stimulation, ionomycin, and increases in cell volume, each activated K + -selective currents with a linear IV relation and time-dependent inactivation. Currents were Ca 2+ dependent and were inhibited by apamin and by Ba 2+. In intact liver, immunoflourescence with an antibody to SK2 showed a prominent signal in cholangiocyte plasma membrane. To evaluate the functional significance, NRC monolayers were mounted in a Ussing chamber, and the short-circuit current ( I sc ) was measured. Exposure to ionomycin caused an increase in I sc 2-fold greater than that induced by cAMP. Both the basal and ionomycin-induced I sc were inhibited by basolateral Ba 2+, and approximately 58% of the basolateral K + current was apamin sensitive. CONCLUSIONS These studies demonstrate that cholangiocytes exhibit robust Ca 2+ -stimulated secretion significantly greater in magnitude than that stimulated by cAMP. SK2 plays an important role in mediating the increase in transepithelial secretion due to increases in intracellular Ca 2+. SK2 channels, therefore, may represent a target for pharmacologic modulation of bile flow.
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Affiliation(s)
- Andrew P Feranchak
- University of Colorado Health Sciences Center, 4200 East 9th Avenue, Denver, Colorado 80262, USA.
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13
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Gatof D, Kilic G, Fitz JG. Vesicular exocytosis contributes to volume-sensitive ATP release in biliary cells. Am J Physiol Gastrointest Liver Physiol 2004; 286:G538-46. [PMID: 14604861 DOI: 10.1152/ajpgi.00355.2003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Extracellular ATP is a potent autocrine/paracrine signal that regulates a broad range of liver functions through activation of purinergic receptors. In biliary epithelium, increases in cell volume stimulate ATP release through a phosphoinositide 3-kinase (PI3-kinase)-dependent mechanism. Because PI3-kinase also regulates vesicular exocytosis, the purpose of these studies was to determine whether volume-stimulated vesicular exocytosis contributes to cellular ATP release. In a human cholangiocarcinoma cell line, exocytosis was measured by using the plasma membrane marker FM1-43, whereas ATP release was assessed by using a luciferase-luciferin assay. Under basal conditions, cholangiocytes exhibited constitutive exocytosis at a rate of 1.6%/min, and low levels of extracellular ATP were detected at 48.2 arbitrary light units. Increases in cholangiocyte cell volume induced by hypotonic exposure resulted in a 10-fold increase in the rate of exocytosis and a robust 35-fold increase in ATP release. Both vesicular exocytosis and ATP release were proportional to cell volume, and both exhibited similar regulatory properties including: 1) dependence on intact PI3-kinase, 2) attenuation by inhibition of PKC, and 3) potentiation by activation of PKC before hypotonic exposure. These findings demonstrate that increases in cholangiocyte cell volume stimulate ATP release and vesicular exocytosis through similar regulatory paradigms. Functional interactions among cell volume, PKC, and PI3-kinase modulate exocytosis, thereby regulating ATP release and purinergic signaling in cholangiocytes. It is hypothesized that PKC is involved in the recruitment of a volume-sensitive vesicular pool to a readily releasable state.
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Affiliation(s)
- David Gatof
- Department of Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
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Roman R, Feranchak AP, Troetsch M, Dunkelberg JC, Kilic G, Schlenker T, Schaack J, Fitz JG. Molecular characterization of volume-sensitive SK(Ca) channels in human liver cell lines. Am J Physiol Gastrointest Liver Physiol 2002; 282:G116-22. [PMID: 11751164 DOI: 10.1152/ajpgi.2002.282.1.g116] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In human liver, Ca(2+)-dependent changes in membrane K(+) permeability play a central role in coordinating functional interactions between membrane transport, metabolism, and cell volume. On the basis of the observation that K(+) conductance is partially sensitive to the bee venom toxin apamin, we aimed to assess whether small-conductance Ca(2+)-sensitive K(+) (SK(Ca)) channels are expressed endogenously and contribute to volume-sensitive K(+) efflux and cell volume regulation. We isolated a full-length 2,140-bp cDNA (hSK2) highly homologous to rat brain rSK2 cDNA, including the putative apamin-sensitive pore domain, from a human liver cDNA library. Identical cDNAs were isolated from primary human hepatocytes, human HuH-7 hepatoma cells, and human Mz-ChA-1 cholangiocarcinoma cells. Transduction of Chinese hamster ovary cells with a recombinant adenovirus encoding the hSK2-green fluorescent protein fusion construct resulted in expression of functional apamin-sensitive K(+) channels. In Mz-ChA-1 cells, hypotonic (15% less sodium glutamate) exposure increased K(+) current density (1.9 +/- 0.2 to 37.5 +/- 7.1 pA/pF; P < 0.001). Apamin (10-100 nM) inhibited K(+) current activation and cell volume recovery from swelling. Apamin-sensitive SK(Ca) channels are functionally expressed in liver and biliary epithelia and likely contribute to volume-sensitive changes in membrane K(+) permeability. Accordingly, the hSK2 protein is a potential target for pharmacological modulation of liver transport and metabolism through effects on membrane K(+) permeability.
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Affiliation(s)
- Richard Roman
- Department of Medicine, School of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Liu ZX, Nickel CH, Cantley LG. HGF promotes adhesion of ATP-depleted renal tubular epithelial cells in a MAPK-dependent manner. Am J Physiol Renal Physiol 2001; 281:F62-70. [PMID: 11399647 DOI: 10.1152/ajprenal.2001.281.1.f62] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hepatocyte growth factor (HGF) has been shown to enhance recovery from renal tubular ischemia. We investigated the possibility that HGF improves recovery by preventing ischemia-induced loss of cell adhesion. Murine inner medullary collecting duct-3 (mIMCD-3) cells subjected to 90% ATP depletion demonstrated a 55% decrease in adhesion, an effect that was completely reversed by the addition of HGF. Assays examining release of adherent cells revealed similar results with 30 min of ATP depletion causing loss of adhesion of 25% of mIMCD-3 cells and HGF completely reversing this effect. In contrast, HGF was unable to reverse the loss of adhesion of cells exposed to 99% ATP depletion. Examination of the mitogen-activated protein kinase (MAPK) signaling pathway revealed that HGF could induce extracellular signal-regulated kinase (ERK) phosphorylation in control and 90% ATP-depleted cells but not in 99% ATP-depleted cells. Inhibition of ERK activation with U0126 completely blocked the HGF-dependent reversal of ATP-depleted cell adhesion. Thus ATP-depleted cells demonstrate a marked decrease in cell adhesion that is reversible by the addition of HGF. This effect of HGF requires activation of the MAPK pathway.
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Affiliation(s)
- Z X Liu
- Section of Nephrology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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Barfod ET, Moore AL, Lidofsky SD. Cloning and functional expression of a liver isoform of the small conductance Ca2+-activated K+ channel SK3. Am J Physiol Cell Physiol 2001; 280:C836-42. [PMID: 11245600 DOI: 10.1152/ajpcell.2001.280.4.c836] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Small conductance Ca2+-activated K+ (SK) channels have been cloned from mammalian brain, but little is known about the molecular characteristics of SK channels in nonexcitable tissues. Here, we report the isolation from rat liver of an isoform of SK3. The sequence of the rat liver isoform differs from rat brain SK3 in five amino acid residues in the NH3 terminus, where it more closely resembles human brain SK3. SK3 immunoreactivity was detectable in hepatocytes in rat liver and in HTC rat hepatoma cells. Human embryonic kidney (HEK-293) cells transfected with liver SK3 expressed 10 pS K+ channels that were Ca2+ dependent (EC(50) 630 nM) and were blocked by the SK channel inhibitor apamin (IC(50) 0.6 nM); whole cell SK3 currents inactivated at membrane potentials more positive than -40 mV. Notably, the Ca2+ dependence, apamin sensitivity, and voltage-dependent inactivation of SK3 are strikingly similar to the properties of hepatocellular and biliary epithelial SK channels evoked by metabolic stress. These observations raise the possibility that SK3 channels influence membrane K+ permeability in hepatobiliary cells during liver injury.
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Affiliation(s)
- E T Barfod
- Department of Medicine, University of Vermont, Burlington, VT 05405, USA
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Abstract
BACKGROUND/AIMS Purinergic signaling potentially contributes to many liver functions. Therefore, the purpose of these studies was to characterize adenosine 5'-triphosphate (ATP) release from human hepatocytes, and to determine the role of extracellular ATP in the autocrine regulation of Cl- permeability and cell volume homeostasis. METHODS Release of ATP (luciferase-luciferin assay), Cl- currents (whole-cell patch clamp), and cell volume (Coulter Multisizer) were measured in human hepatocytes within 12 h of isolation. RESULTS Hepatocyte swelling increased bioluminescence from basal values of 11.21+/-0.45 to 178.29+/-44.49 and 492.15+/-89.41 arbitrary light units following 20 and 40% buffer dilutions, respectively (p<0.001), representing an increase in extracellular ATP from approximately 10 to >300 nM. Whole-cell Cl- currents activated during exposure to hypotonic buffer (15% less mosmol, 126.34+/-36.49 pA/pF) and ATP (10 microM, 71.92+/-15.48 pA/pF) exhibited outward rectification, time-dependent inactivation at depolarizing potentials, and sensitivity to the anion channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). Removal of extracellular ATP (apyrase) prevented volume-sensitive current activation. Exposure to hypotonic buffer (30% less mosmol) increased mean relative volume to 1.092+/-0.004 by 2.5 min, and volume recovery (1.019+/-0.002 by 30 min) was abolished by NPPB, apyrase, and the P2 receptor antagonist suramin. CONCLUSIONS These findings indicate that human hepatocytes exhibit constitutive and volume-dependent ATP release, which is a critical determinant of membrane Cl- permeability and cell volume regulation. ATP release may represent an extracellular signaling pathway that couples the cellular hydration state to important hepatic functions.
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Affiliation(s)
- A P Feranchak
- Department of Medicine, University of Colorado Health Sciences Center, Denver 80262, USA.
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Kawabata A, Kuroda R, Nishikawa H, Kawai K. Modulation by protease-activated receptors of the rat duodenal motility in vitro: possible mechanisms underlying the evoked contraction and relaxation. Br J Pharmacol 1999; 128:865-72. [PMID: 10556920 PMCID: PMC1571701 DOI: 10.1038/sj.bjp.0702755] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/1999] [Revised: 05/24/1999] [Accepted: 06/03/1999] [Indexed: 11/09/2022] Open
Abstract
1 The present study examined effects of agonist enzymes and receptor-activating peptides for protease-activated receptors (PARs) on duodenal motility in the rat, and also investigated possible mechanisms underlying the evoked responses. 2 Thrombin at 0.03-0.1 microM and the PAR-1-activating peptide SFLLR-NH2 at 3-100 microM or TFLLR-NH2 at 10-50 microM produced a dual action, relaxation followed by contraction of the duodenal longitudinal muscle. The PAR-2-activating peptide SLIGRL-NH2 at 10-100 microM elicited only small contraction. Trypsin at 0.08 microM induced small contraction, or relaxation followed by contraction, depending on preparations. The PAR-4-activating peptide GYPGKF-NH2 at 1000 microM exhibited no effect. 3 The contractile responses of the duodenal strips to TFLLR-NH2 and to SLIGRL-NH2 were partially attenuated by the L-type calcium channel blocker nifedipine (1 microM), the protein kinase C inhibitor GF109203X (1 microM) and the tyrosine kinase inhibitor genistein (15 microM), but were resistant to indomethacin (3 microM) and tetrodotoxin (1-10 microM). 4 The relaxation of the preparations exerted by TFLLR-NH2 was unaffected by indomethacin (3 microM), propranolol (5 microM), NG-nitro-L-arginine methyl ester (100 microM) and tetrodotoxin (1-10 microM). This relaxation was resistant to either GF109203X (1 microM) or genistein (15 microM), but was, remarkably, attenuated by combined application of these two kinase inhibitors. 5 Apamin (0.1 microM), an inhibitor of calcium-activated, small-conductance potassium channels, but not charybdotoxin (0.1 microM), completely abolished the PAR-1-mediated duodenal relaxation, and significantly enhanced the PAR-1-mediated contraction. 6 These findings demonstrate that PAR-1 plays a dual role, suppression and facilitation of smooth muscle motility in the rat duodenum, while PAR-2 plays a minor excitatory role in the muscle, and that PAR-4 is not involved in the duodenal tension modulation. The results also suggest that the contractile responses to PAR-1 and PAR-2 activation are mediated, in part, by activation of L-type calcium channels, protein kinase C and tyrosine kinase, and that the relaxation response to PAR-1 activation occurs via activation of apamin-sensitive, but charybdotoxin-insensitive, potassium channels, in which both protein kinase C and tyrosine kinase might be involved synergistically.
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Affiliation(s)
- A Kawabata
- Department of Pathophysiology & Therapeutics, Faculty of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan
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Morris AP. The regulation of epithelial cell cAMP- and calcium-dependent chloride channels. ADVANCES IN PHARMACOLOGY 1999; 46:209-51. [PMID: 10332504 DOI: 10.1016/s1054-3589(08)60472-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
This chapter has focused on two types of chloride conductance found in epithelial cells. The leap from the Ussing chamber to patch-clamp studies has identified yet other conductances present which have also been electrophysiologically characterized. In the case of the swelling activated wholecell chloride current, a physiological function is apparent and a single-channel basis found, but its genetic identity remains unknown (see reviews by Frizzell and Morris, 1994; and Strange et al., 1996). The outwardly rectified chloride channel has been the subject of considerable electrophysiological interest over the past 10 years and is well characterized at the single-channel level, but its physiological function remains controversial (reviewed by Frizzell and Morris, 1994; Devidas and Guggino, 1997). Yet other conductances related to the CLC gene family also appear to be present in epithelial cells of the kidney (reviewed by Jentsch, 1996; Jentsch and Gunter, 1997) where physiological functions for some isoforms are emerging. Clearly, there remain many unknowns. Chief among these is the molecular basis of GCa2+Cl and many of other the conductances. As sequences become available it is expected that the wealth of information gained by investigation into CFTR function will provide a conceptual blueprint for similar studies in these later channel clones.
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Affiliation(s)
- A P Morris
- Department of Integrative Biology, University of Texas-Houston Health Science Center 77030, USA
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Hatton JP, Gaubert F, Lewis ML, Darsel Y, Ohlmann P, Cazenave JP, Schmitt D. The kinetics of translocation and cellular quantity of protein kinase C in human leukocytes are modified during spaceflight. FASEB J 1999; 13 Suppl:S23-33. [PMID: 10352142 DOI: 10.1096/fasebj.13.9001.s23] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Protein kinase C (PKC) is a family of serine/threonine kinases that play an important role in mediating intracellular signal transduction in eukaryotes. U937 cells were exposed to microgravity during a space shuttle flight and stimulated with a radiolabeled phorbol ester ([3H]PDBu) to both specifically label and activate translocation of PKC from the cytosol to the particulate fraction of the cell. Although significant translocation of PKC occurred at all g levels, the kinetics of translocation in flight were significantly different from those on the ground. In addition, the total quantity of [3H]PDBu binding PKC was increased in flight compared to cells at 1 g on the ground, whereas the quantity in hypergravity (1.4 g) was decreased with respect to 1 g. Similarly, in purified human peripheral blood T cells the quantity of PKCdelta varied in inverse proportion to the g level for some experimental treatments. In addition to these novel findings, the results confirm earlier studies which showed that PKC is sensitive to changes in gravitational acceleration. The mechanisms of cellular gravisensitivity are poorly understood but the demonstrated sensitivity of PKC to this stimulus provides us with a useful means of measuring the effect of altered gravity levels on early cell activation events.
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Affiliation(s)
- J P Hatton
- INSERM U311, Etablissement de Transfusion Sanguine, 67065 Strasbourg, France.
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Hempel A, Lindschau C, Maasch C, Mahn M, Bychkov R, Noll T, Luft FC, Haller H. Calcium antagonists ameliorate ischemia-induced endothelial cell permeability by inhibiting protein kinase C. Circulation 1999; 99:2523-9. [PMID: 10330383 DOI: 10.1161/01.cir.99.19.2523] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Dihydropyridines block calcium channels; however, they also influence endothelial cells, which do not express calcium channels. We tested the hypothesis that nifedipine can prevent ischemia-induced endothelial permeability increases by inhibiting protein kinase C (PKC) in cultured porcine endothelial cells. METHODS AND RESULTS Ischemia was induced by potassium cyanide/deoxyglucose, and permeability was measured by albumin flux. Ion channels were characterized by patch clamp. [Ca2+]i was measured by fura 2. PKC activity was measured by substrate phosphorylation after cell fractionation. PKC isoforms were assessed by Western blot and confocal microscopy. Nifedipine prevented the ischemia-induced increase in permeability in a dose-dependent manner. Ischemia increased [Ca2+]i, which was not affected by nifedipine. Instead, ischemia-induced PKC translocation was prevented by nifedipine. Phorbol ester also increased endothelial cell permeability, which was dose dependently inhibited by nifedipine. The effects of non-calcium-channel-binding dihydropyridine derivatives were similar. Analysis of the PKC isoforms showed that nifedipine prevented ischemia-induced translocation of PKC-alpha and PKC-zeta. Specific inhibition of PKC isoforms with antisense oligodeoxynucleotides demonstrated a major role for PKC-alpha. CONCLUSIONS Nifedipine exerts a direct effect on endothelial cell permeability that is independent of calcium channels. The inhibition of ischemia-induced permeability by nifedipine seems to be mediated primarily by PKC-alpha inhibition. Anti-ischemic effects of dihydropyridine calcium antagonists could be due in part to their effects on endothelial cell permeability.
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Affiliation(s)
- A Hempel
- Franz Volhard Clinic, Humboldt University of Berlin, Germany
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Roman RM, Bodily KO, Wang Y, Raymond JR, Fitz JG. Activation of protein kinase Calpha couples cell volume to membrane Cl- permeability in HTC hepatoma and Mz-ChA-1 cholangiocarcinoma cells. Hepatology 1998; 28:1073-80. [PMID: 9755245 DOI: 10.1002/hep.510280423] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Physiological increases in liver cell volume lead to an adaptive response that includes opening of membrane Cl- channels, which is critical for volume recovery. The purpose of these studies was to assess the potential role for protein kinase C (PKC) as a signal involved in cell volume homeostasis. Studies were performed in HTC rat hepatoma and Mz-ChA-1 human cholangiocarcinoma cells, which were used as model hepatocytes and cholangiocytes, respectively. In each cell type, cell volume increases were followed by: 1) translocation of PKC from cytosolic to particulate (membrane) fractions; 2) a 10- to 40-fold increase in whole-cell membrane Cl- current density; and 3) partial recovery of cell volume. In HTC cells, the volume-dependent Cl- current response (-46 +/- 5 pA/pF) was inhibited by down-regulation of PKC (100 nmol/L phorbol 12-myristate 13-acetate for 18 hours [PMA]; -1.97 +/- 1.5 pA/pF), chelation of cytosolic Ca2+ (2 mmol/L EGTA; -5.3 +/- 4.0 pA/pF), depletion of cytosolic adenosine triphosphate (ATP) (3 U/mL apyrase; -12.58 +/- 1. 45 pA/pF), and by the putative PKC inhibitor, chelerythrine (25 micromol/L; -7 +/- 3 pA/pF). In addition, PKC inhibition by chelerythrine and calphostin C (500 nmol/L) prevented cell volume recovery from swelling. Similar results were obtained in Mz-ChA-1 biliary cells. These findings indicate that swelling-induced activation of PKC represents an important signal coupling cell volume to membrane Cl- permeability in both hepatic and biliary cell models.
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Affiliation(s)
- R M Roman
- University of Colorado Health Sciences Center, Denver, CO 80262, USA
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St Pierre MV, Schlenker T, Dufour JF, Jefferson DM, Fitz JG, Arias IM. Stimulation of cyclic guanosine monophosphate production by natriuretic peptide in human biliary cells. Gastroenterology 1998; 114:782-90. [PMID: 9516399 DOI: 10.1016/s0016-5085(98)70592-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND & AIMS Guanosine 3',5'-cyclic monophosphate (cGMP), whose production is stimulated by the interaction of nitric oxide, natriuretic peptides, and guanylin with their respective guanylate cyclases, activates secretion through ion channels in several epithelia. Cl- channels have been identified in the apical membrane of biliary epithelial cells. The aim of this study was to investigate the production of cGMP and its effects on Cl- permeability in biliary epithelial cells. METHODS Halide efflux measurement, whole-cell patch clamp recording, radioimmunoassay, and reverse-transcription polymerase chain reaction using two human biliary cell lines (H69 and Mz-ChA-1) were performed. RESULTS In cells equilibrated with 125I, bromo-cGMP stimulated halide efflux by 22%. In whole-cell patch clamp recordings, the addition of cGMP intracellularly, or of atrial natriuretic peptide extracellularly, stimulated inward currents at negative membrane potentials, consistent with Cl- efflux through open channels. In H69 cells, atrial and C-type natriuretic peptides stimulated production of cGMP. Mz-ChA-1 responded only to atrial natriuretic peptide. Both cell lines expressed messenger RNA for the guanylate cyclase type A receptor and the guanylate cyclase free-clearance receptor. CONCLUSIONS These data suggest that natriuretic peptide stimulates cGMP production in human biliary epithelial cells, which in turn may regulate ductular bile formation through the opening of Cl- channels.
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Affiliation(s)
- M V St Pierre
- Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts, USA
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