1
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Calmodulin-Dependent Regulation of Overexpressed but Not Endogenous TMEM16A Expressed in Airway Epithelial Cells. MEMBRANES 2021; 11:membranes11090723. [PMID: 34564540 PMCID: PMC8471323 DOI: 10.3390/membranes11090723] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 09/16/2021] [Accepted: 09/20/2021] [Indexed: 11/30/2022]
Abstract
Regulation of the Ca2+-activated Cl− channel TMEM16A by Ca2+/calmodulin (CAM) is discussed controversially. In the present study, we compared regulation of TMEM16A by Ca2+/calmodulin (holo-CAM), CAM-dependent kinase (CAMKII), and CAM-dependent phosphatase calcineurin in TMEM16A-overexpressing HEK293 cells and TMEM16A expressed endogenously in airway and colonic epithelial cells. The activator of the Ca2+/CAM-regulated K+ channel KCNN4, 1-EBIO, activated TMEM16A in overexpressing cells, but not in cells with endogenous expression of TMEM16A. Evidence is provided that CAM-interaction with TMEM16A modulates the Ca2+ sensitivity of the Cl− channel. Enhanced Ca2+ sensitivity of overexpressed TMEM16A explains its activity at basal (non-elevated) intracellular Ca2+ levels. The present results correspond well to a recent report that demonstrates a Ca2+-unbound form of CAM (apo-CAM) that is pre-associated with TMEM16A and mediates a Ca2+-dependent sensitization of activation (and inactivation). However, when using activators or inhibitors for holo-CAM, CAMKII, or calcineurin, we were unable to detect a significant impact of CAM, and limit evidence for regulation by CAM-dependent regulatory proteins on receptor-mediated activation of endogenous TMEM16A in airway or colonic epithelial cells. We propose that regulatory properties of TMEM16A and and other members of the TMEM16 family as detected in overexpression studies, should be validated for endogenous TMEM16A and physiological stimuli such as activation of phospholipase C (PLC)-coupled receptors.
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2
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Keating N, Dev K, Hynes AC, Quinlan LR. Mechanism of luminal ATP activated chloride secretion in a polarized epithelium. J Physiol Sci 2019; 69:85-95. [PMID: 29949063 PMCID: PMC10717936 DOI: 10.1007/s12576-018-0623-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 06/06/2018] [Indexed: 10/14/2022]
Abstract
There are both secretory and absorptive pathways working in tandem to support ionic movement driving fluid secretion across epithelia. The mechanisms exerting control of fluid secretion in the oviduct is yet to be fully determined. This study explored the role of apical or luminal extracellular ATP (ATPe)-stimulated ion transport in an oviduct epithelium model, using the Ussing chamber short-circuit current (Isc) technique. Basal Isc in oviduct epithelium in response to apical ATPe comprises both chloride secretion and sodium absorption and has distinct temporal phases. A rapid transient peak followed by a sustained small increase above baseline. Both phases of the apical ATPe Isc response are sensitive to anion (HCO3-, Cl-) and cation (Na+) replacement. Additionally, the role of apical chloride channels, basolateral potassium channels and intracellular calcium in supporting the peak Isc current was confirmed. The role of ATP breakdown to adenosine resulting in the activation of P2 receptors was supported by examining the effects of non-hydrolyzable forms of ATP. A P2YR2 potency profile of ATP = UTP > ADP was generated for the apical membrane, suggesting the involvement of the P2YR2 subtype of purinoceptor. A P2X potency profile of ATP = 2MeSATP > alpha,beta-meATP > BzATP was also generated for the apical membrane. In conclusion, these results provide strong evidence that purinergic activation of apical P2YR2 promotes chloride secretion and is thus an important factor in fluid formation by the oviduct.
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Affiliation(s)
- N Keating
- Physiology, School of Medicine, National University of Ireland, Galway, University Road, Galway, Ireland
| | - K Dev
- Physiology, School of Medicine, National University of Ireland, Galway, University Road, Galway, Ireland
| | - A C Hynes
- Physiology, School of Medicine, National University of Ireland, Galway, University Road, Galway, Ireland
| | - L R Quinlan
- Physiology, School of Medicine, National University of Ireland, Galway, University Road, Galway, Ireland.
- CÚRAM, Centre for Research in Medical Devices, NUI Galway, University Road, Galway, Ireland.
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3
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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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Abstract
Ca(2+)-activated Cl(-) channels (CaCCs) are plasma membrane proteins involved in various important physiological processes. In epithelial cells, CaCC activity mediates the secretion of Cl(-) and of other anions, such as bicarbonate and thiocyanate. In smooth muscle and excitable cells of the nervous system, CaCCs have an excitatory role coupling intracellular Ca(2+) elevation to membrane depolarization. Recent studies indicate that TMEM16A (transmembrane protein 16 A or anoctamin 1) and TMEM16B (transmembrane protein 16 B or anoctamin 2) are CaCC-forming proteins. Induced expression of TMEM16A and B in null cells by transfection causes the appearance of Ca(2+)-activated Cl(-) currents similar to those described in native tissues. Furthermore, silencing of TMEM16A by RNAi causes disappearance of CaCC activity in cells from airway epithelium, biliary ducts, salivary glands, and blood vessel smooth muscle. Mice devoid of TMEM16A expression have impaired Ca(2+)-dependent Cl(-) secretion in the epithelial cells of the airways, intestine, and salivary glands. These animals also show a loss of gastrointestinal motility, a finding consistent with an important function of TMEM16A in the electrical activity of gut pacemaker cells, that is, the interstitial cells of Cajal. Identification of TMEM16 proteins will help to elucidate the molecular basis of Cl(-) transport.
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Affiliation(s)
- Loretta Ferrera
- Laboratory of Molecular Genetics, Istituto Giannina Gaslini, Genova, Italy
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Satoh H, Qu L, Suzuki H, Saitow F. Depolarization-induced depression of inhibitory transmission in cerebellar Purkinje cells. Physiol Rep 2013; 1:e00061. [PMID: 24303140 PMCID: PMC3835016 DOI: 10.1002/phy2.61] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 07/24/2013] [Accepted: 07/25/2013] [Indexed: 11/07/2022] Open
Abstract
Several forms of depolarization-induced plasticity in inhibitory transmission have been reported to occur in cerebellar Purkinje cells (PCs), namely depolarization-induced suppression of inhibition (DSI), depolarization-induced potentiation of inhibition (DPI), and rebound potentiation (RP). Here, we describe another form of synaptic plasticity for gamma-amino butyric acid (GABA)ergic transmission in PCs. Immediately following depolarization trains in a PC, evoked inhibitory postsynaptic currents (eIPSCs) changed their direction from outward to inward currents under a recording condition in which eIPSCs were elicited as an outward current. Subsequently, the eIPSC amplitude remained depressed (depolarization-induced depression of inhibition [DDI]) for more than 20 min under the blockade of cannabinoid and N-methyl-D-aspartic acid (NMDA) receptor-mediated DSI and DPI, respectively. This DDI was completely abolished by intracellular infusion of the fast Ca(2+)-chelating agent BAPTA and by inhibition of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). Furthermore, DDI was strongly suppressed by calcium-activated chloride channel (CaCC) blockers, while an inhibitor of cation-chloride cotransporters (CCCs) partially blocked DDI during the early phase. Exogenous GABA-induced inhibition of spontaneous spike activity was attenuated in ∼50% of the PCs by climbing fiber stimulation-induced depolarization. These results suggest that activation of both CaCCs and CCCs was necessary for alteration of [Cl(-)]i after activation of CaMKII following elevation of [Ca(2+)]i in PCs. DDI may provide another mechanism for regulation of inhibitory inputs to PCs within the neuronal networks of the cerebellar cortex.
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Affiliation(s)
- Hiromasa Satoh
- Department of Pharmacology, Nippon Medical School Tokyo, 113-8602, Japan
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Tian Y, Schreiber R, Wanitchakool P, Kongsuphol P, Sousa M, Uliyakina I, Palma M, Faria D, Traynor-Kaplan AE, Fragata JI, Amaral MD, Kunzelmann K. Control of TMEM16A by INO-4995 and other inositolphosphates. Br J Pharmacol 2013; 168:253-65. [PMID: 22946960 PMCID: PMC3570019 DOI: 10.1111/j.1476-5381.2012.02193.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 07/06/2012] [Accepted: 07/31/2012] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Ca(2+)-dependent Cl(-) secretion (CaCC) in airways and other tissues is due to activation of the Cl(-) channel TMEM16A (anoctamin 1). Earlier studies suggested that Ca(2+) -activated Cl(-) channels are regulated by membrane lipid inositol phosphates, and that 1-O-octyl-2-O-butyryl-myo-inositol 3,4,5,6-tetrakisphosphate octakis(propionoxymethyl) ester (INO-4995) augments CaCC. Here we examined whether TMEM16A is the target for INO-4995 and if the channel is regulated by inositol phosphates. EXPERIMENTAL APPROACH The effects of INO-4995 on CaCC were examined in overexpressing HEK293, colonic and primary airway epithelial cells as well as Xenopus oocytes. We used patch clamping, double electrode voltage clamp and Ussing chamber techniques. KEY RESULTS We found that INO-4995 directly activates a TMEM16A whole cell conductance of 6.1 ± 0.9 nS pF(-1) in overexpressing cells. The tetrakisphosphates Ins(3,4,5,6)P(4) or Ins(1,3,4,5)P(4) and enzymes controlling levels of InsP(4) or PIP(2) and PIP(3) had no effects on the magnitude or kinetics of TMEM16A currents. In contrast in Xenopus oocytes, human airways and colonic cells, which all express TMEM16A endogenously, Cl(-) currents were not acutely activated by INO-4995. However incubation with INO-4995 augmented 1.6- to 4-fold TMEM16A-dependent Cl(-) currents activated by ionomycin or ATP, while intracellular Ca(2+) signals were not affected. The potentiating effect of INO-4995 on transient ATP-activated TMEM16A-currents in cystic fibrosis (CF) airways was twice of that observed in non-CF airways. CONCLUSIONS AND IMPLICATIONS These data indicate that TMEM16A is the target for INO-4995, although the mode of action appears different for overexpressed and endogenous channels. INO-4995 may be useful for the treatment of CF lung disease.
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Key Words
- ino-4995
- ino4913
- anoctamin 1
- tmem16a
- inositol phosphates
- ins(3,4,5,6)p4
- inositol 3,4,5,6-tetrakisphosphate
- ins(1,3,4,5)p4
- inositol 1,3,4,5-tetrakisphosphate
- ca2+-activated cl− channels
- cacc
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Affiliation(s)
- Yuemin Tian
- Institut für Physiologie, Universität RegensburgRegensburg, Germany
| | - Rainer Schreiber
- Institut für Physiologie, Universität RegensburgRegensburg, Germany
| | | | | | - Marisa Sousa
- Faculty of Sciences, BioFIG – Centre for Biodiversity, Functional and Integrative Genomics, University of LisboaLisboa, Portugal
- Department of Genetics, National Institute of HealthLisboa, Portugal
| | - Inna Uliyakina
- Faculty of Sciences, BioFIG – Centre for Biodiversity, Functional and Integrative Genomics, University of LisboaLisboa, Portugal
- Department of Genetics, National Institute of HealthLisboa, Portugal
| | - Marta Palma
- Faculty of Sciences, BioFIG – Centre for Biodiversity, Functional and Integrative Genomics, University of LisboaLisboa, Portugal
| | - Diana Faria
- Institut für Physiologie, Universität RegensburgRegensburg, Germany
| | - Alexis E Traynor-Kaplan
- ISM TherapeuticsSeattle, WA, USA
- Division of Gastroenterology, Department of Medicine, University of WashingtonSeattle, WA, USA
| | - José I Fragata
- Department Cardio-Thoracic Surgery, Hospital de Santa MartaLisboa, Portugal
| | - Margarida D Amaral
- Faculty of Sciences, BioFIG – Centre for Biodiversity, Functional and Integrative Genomics, University of LisboaLisboa, Portugal
- Department of Genetics, National Institute of HealthLisboa, Portugal
| | - Karl Kunzelmann
- Institut für Physiologie, Universität RegensburgRegensburg, Germany
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Ganapathi SB, Wei SG, Zaremba A, Lamb FS, Shears SB. Functional regulation of ClC-3 in the migration of vascular smooth muscle cells. Hypertension 2013; 61:174-9. [PMID: 23150504 PMCID: PMC3521842 DOI: 10.1161/hypertensionaha.112.194209] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 10/22/2012] [Indexed: 12/17/2022]
Abstract
Migration of vascular smooth muscle cells (VSMCs) into neointima contributes to atherosclerosis and restenosis. This migration requires coordinated plasmalemmal fluxes of water and ions. Here, we show that aortic VSMC migration depends on the regulation of transmembrane Cl(-) flux by ClC-3, a Cl(-) channel/transporter. The contribution of ClC-3 to plasmalemmal Cl(-) current was studied in VSMCs by electrophysiological recordings. Cl(-) current was negligible in cells perfused with 0 [Ca(2+)]. Raising intracellular [Ca(2+)] to 0.5 μM activated a Cl(-) current (I(Cl.Ca)), approximately half of which was eliminated on inhibition by KN-93 of calmodulin-dependent protein kinase II. I(Cl.Ca) was also halved by inositol-3,4,5,6-tetrakisphosphate, a cellular signal with the biological function of specifically preventing calmodulin-dependent protein kinase II from activating I(Cl.Ca). Gene disruption of ClC-3 reduced I(Cl.Ca) by 50%. Moreover, I(Cl.Ca) in the ClC-3 null VSMCs was not affected by either KN-93 or inositol-3,4,5,6-tetrakisphosphate. We conclude that I(Cl.Ca) is composed of 2 components, one is ClC-3 independent whereas the other is ClC-3 dependent, activated by calmodulin-dependent protein kinase II and inhibited by inositol-3,4,5,6-tetrakisphosphate. We also assayed VSMC migration in transwell assays. Migration was halved in ClC-3 null cells versus wild-type cells. In addition, inhibition of ClC-3 by niflumic acid, KN-93, or inositol-3,4,5,6-tetrakisphosphate each reduced cell migration in wild-type cells but not in ClC-3 null cells. These cell-signaling roles of ClC-3 in VSMC migration suggest new therapeutic approaches to vascular remodeling diseases.
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MESH Headings
- Animals
- Aorta/cytology
- Aorta/drug effects
- Aorta/metabolism
- Benzylamines/pharmacology
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/antagonists & inhibitors
- Cell Movement/drug effects
- Cell Movement/physiology
- Cells, Cultured
- Chloride Channels/genetics
- Chloride Channels/metabolism
- Inositol Phosphates/pharmacology
- Mice
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Niflumic Acid/pharmacology
- Protein Kinase Inhibitors/pharmacology
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Sulfonamides/pharmacology
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Affiliation(s)
- Sindura B. Ganapathi
- Inositol Signaling Group, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, PO Box 12233, NC 27709, USA
| | - Shun-Guang Wei
- Inositol Signaling Group, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, PO Box 12233, NC 27709, USA
| | - Angelika Zaremba
- Inositol Signaling Group, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, PO Box 12233, NC 27709, USA
| | - Fred S. Lamb
- Department of Pediatrics, University of Iowa Children’s Hospital, Iowa City, Iowa 52242, USA
| | - Stephen B. Shears
- Inositol Signaling Group, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, PO Box 12233, NC 27709, USA
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8
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He XD, Goyal RK. CaMKII inhibition hyperpolarizes membrane and blocks nitrergic IJP by closing a Cl(-) conductance in intestinal smooth muscle. Am J Physiol Gastrointest Liver Physiol 2012; 303:G240-6. [PMID: 22538403 PMCID: PMC3404568 DOI: 10.1152/ajpgi.00102.2012] [Citation(s) in RCA: 9] [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
The ionic basis of nitrergic "slow'" inhibitory junction potential (sIJP) is not fully understood. The purpose of the present study was to determine the nature and the role of calmodulin-dependent protein kinase II (CaMKII)-dependent ion conductance in nitrergic neurotransmission at the intestinal smooth muscle neuromuscular junction. Studies were performed in guinea pig ileum. The modified Tomita bath technique was used to induce passive hyperpolarizing electrotonic potentials (ETP) and membrane potential change due to sIJP or drug treatment in the same cell. Changes in membrane potential and ETP were recorded in the same smooth muscle cell, using sharp microelectrode. Nitrergic IJP was elicited by electrical field stimulation in nonadrenergic, noncholinergic conditions and chemical block of purinergic IJP. Modification of ETP during hyperpolarization reflected active conductance change in the smooth muscle. Nitrergic IJP was associated with decreased membrane conductance. The CAMKII inhibitor KN93 but not KN92, the Cl(-) channel blocker niflumic acid (NFA), and the K(ATP)-channel opener cromakalim hyperpolarized the membrane. However, KN93 and NFA were associated with decreased and cromakalim was associated with increased membrane conductance. After maximal NFA-induced hyperpolarization, hyperpolarization associated with KN93 or sIJP was not seen, suggesting a saturation block of the Cl(-) channel signaling. These studies suggest that inhibition of CaMKII-dependent Cl(-) conductance mediates nitrergic sIJP by causing maximal closure of the Cl(-) conductance.
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Affiliation(s)
- Xue-Dao He
- Center for Swallowing and Motility Disorders, Veterans Affairs Boston HealthCare System and Harvard Medical School, Boston, Massachusetts
| | - Raj K. Goyal
- Center for Swallowing and Motility Disorders, Veterans Affairs Boston HealthCare System and Harvard Medical School, Boston, Massachusetts
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Lee MG, Ohana E, Park HW, Yang D, Muallem S. Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion. Physiol Rev 2012; 92:39-74. [PMID: 22298651 DOI: 10.1152/physrev.00011.2011] [Citation(s) in RCA: 267] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.
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Affiliation(s)
- Min Goo Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
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10
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Regulation of inositol 1,3,4-trisphosphate 5/6-kinase (ITPK1) by reversible lysine acetylation. Proc Natl Acad Sci U S A 2012; 109:2290-5. [PMID: 22308441 DOI: 10.1073/pnas.1119740109] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The enzyme inositol 1,3,4-trisphosphate 5/6-kinase (ITPK1) catalyzes the rate-limiting step in the formation of higher phosphorylated forms of inositol in mammalian cells. Because it sits at a key regulatory point in the inositol metabolic pathway, its activity is likely to be regulated. We have previously shown that ITPK1 is phosphorylated, a posttranslational modification used by cells to regulate enzyme activity. We show here that ITPK1 is modified by acetylation of internal lysine residues. The acetylation sites, as determined by mass spectrometry, were found to be lysines 340, 383, and 410, which are all located on the surface of this protein. Overexpression of the acetyltransferases CREB-binding protein or p300 resulted in the acetylation of ITPK1, whereas overexpression of mammalian silent information regulator 2 resulted in the deacetylation of ITPK1. Functionally, ITPK1 acetylation regulates its stability. CREB-binding protein dramatically decreased the half-life of ITPK1. We further found that ITPK1 acetylation down-regulated its enzyme activity. HEK293 cells stably expressing acetylated ITPK1 had reduced levels of the higher phosphorylated forms of inositol, compared with the levels seen in cells expressing unacetylated ITPK1. These results demonstrate that lysine acetylation alters both the stability as well as the activity of ITPK1 in cells.
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11
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Shears SB, Ganapathi SB, Gokhale NA, Schenk TMH, Wang H, Weaver JD, Zaremba A, Zhou Y. Defining signal transduction by inositol phosphates. Subcell Biochem 2012; 59:389-412. [PMID: 22374098 PMCID: PMC3925325 DOI: 10.1007/978-94-007-3015-1_13] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ins(1,4,5)P(3) is a classical intracellular messenger: stimulus-dependent changes in its levels elicits biological effects through its release of intracellular Ca(2+) stores. The Ins(1,4,5)P(3) response is "switched off" by its metabolism to a range of additional inositol phosphates. These metabolites have themselves come to be collectively described as a signaling "family". The validity of that latter definition is critically examined in this review. That is, we assess the strength of the hypothesis that Ins(1,4,5)P(3) metabolites are themselves "classical" signals. Put another way, what is the evidence that the biological function of a particular inositol phosphate depends upon stimulus dependent changes in its levels? In this assessment, examples of an inositol phosphate acting as a cofactor (i.e. its function is not stimulus-dependent) do not satisfy our signaling criteria. We conclude that Ins(3,4,5,6)P(4) is, to date, the only Ins(1,4,5)P(3) metabolite that has been validated to act as a second messenger.
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Key Words
- adenosine deaminase
- akt
- β-cells
- calcium
- camp
- camkii
- chloride channel
- clc3
- compartmentalization
- dna repair
- endosomes
- erk
- frizzled receptor
- gap1ip4bp
- mrna export
- ins(1,4,5)p3
- ins(1,4,5)p4 receptor
- ins(1,3,4)p3
- ins(1,3,4,5)p4
- ins(1,3,4,5)p4 receptor
- ins(1,4,5,6)p4
- ins(3,4,5,6)p4
- ins(1,3,4,5,6)p5
- insp6
- insulin
- ipmk
- ipk2
- ip5k
- itp
- itpk1
- itpkb
- lymphocytes
- ku
- neutrophils
- protein phosphatase
- ptdins(4,5)p2
- ptdins(3,4,5)p3
- ph domain
- pten
- rasa3
- transcription
- wnt ligand
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Affiliation(s)
- Stephen B Shears
- Inositol Signaling Section, Laboratory of Signal Transduction, NIEHS, NIH, DHHS, Research Triangle Park, 27709, NC, USA, USA,
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12
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Tian Y, Kongsuphol P, Hug M, Ousingsawat J, Witzgall R, Schreiber R, Kunzelmann K. Calmodulin-dependent activation of the epithelial calcium-dependent chloride channel TMEM16A. FASEB J 2010; 25:1058-68. [PMID: 21115851 DOI: 10.1096/fj.10-166884] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
TMEM16A (anoctamin 1, Ano1), a member of a family of 10 homologous proteins, has been shown to form an essential component of Ca(2+)-activated Cl(-) channels. TMEM16A-null mice exhibit severe defects in epithelial transport along with tracheomalacia and death within 1 mo after birth. Despite its outstanding physiological significance, the mechanisms for activation of TMEM16A remain obscure. TMEM16A is activated on increase in intracellular Ca(2+), but it is unclear whether Ca(2+) binds directly to the channel or whether additional components are required. We demonstrate that TMEM16A is strictly membrane localized and requires cytoskeletal interactions to be fully activated. Despite the need for cytosolic ATP for full activation, phosphorylation by protein kinases is not required. In contrast, the Ca(2+) binding protein calmodulin appears indispensable and interacts physically with TMEM16A. Openers of small- and intermediate-conductance Ca(2+)-activated potassium channels known to interact with calmodulin, such as 1-EBIO, DCEBIO, or riluzole, also activated TMEM16A. These results reinforce the use of these compounds for activation of electrolyte secretion in diseases such as cystic fibrosis.
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Affiliation(s)
- Yuemin Tian
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
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13
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Changes in cellular levels of inositol polyphosphates during apoptosis. Mol Cell Biochem 2010; 345:61-8. [PMID: 20725767 DOI: 10.1007/s11010-010-0560-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 07/29/2010] [Indexed: 10/19/2022]
Abstract
Accumulations of higher inositol polyphosphates, diphosphoinositol polyphosphates or pyrophosphates, have been implicated to mediate cellular apoptosis. Whether cellular levels of lower inositol phosphates (lower than inositol hexakisphosphates) change during apoptosis is not known, although these inositol phosphates are known to play crucial roles in a number of cellular signaling processes including calcium mobilization. Therefore, in this study, we have examined changes in cellular levels of inositol phosphates following metabolic labeling of these compounds by [(3)H]myo-inositol and induction of apoptosis. The levels of inositol mono- and bis-phosphates were increased, whereas the levels of inositol tris- and tetrakis-phosphates decreased significantly with an increasing rate of apoptosis induced by etoposide in a dose-dependent manner. NaF treatment, which increased the rate of apoptosis in a time- and dose-dependent manner, also increased the levels of inositol mono- and bis-phosphates and drastically reduced the levels of inositol tris- and tetrakis-phosphates. Prior treatment with antimycin A, a strategy used to reverse the NaF-induced accumulations of higher InsPs, partially reduced the effects of NaF on apoptosis as well as the levels of lower InsPs. Taken together, our results suggest that cellular levels of lower InsPs are altered during apoptosis.
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14
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Zonia L. Spatial and temporal integration of signalling networks regulating pollen tube growth. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:1939-57. [PMID: 20378665 DOI: 10.1093/jxb/erq073] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The overall function of a cell is determined by its contingent of active signal transduction cascades interacting on multiple levels with metabolic pathways, cytoskeletal organization, and regulation of gene expression. Much work has been devoted to analysis of individual signalling cascades interacting with unique cellular targets. However, little is known about how cells integrate information across hierarchical signalling networks. Recent work on pollen tube growth indicates that several key signalling cascades respond to changes in cell hydrodynamics and apical volume. Combined with known effects on cytoarchitecture and signalling from other cell systems, hydrodynamics has the potential to integrate and synchronize the function of the broader signalling network in pollen tubes. This review will explore recent work on cell hydrodynamics in a variety of systems including pollen, and discuss hydrodynamic regulation of cell signalling and function including exocytosis and endocytosis, actin cytoskeleton reorganization, cell wall deposition and assembly, phospholipid and inositol polyphosphate signalling, ion flux, small G-proteins, fertilization, and self-incompatibility. The combined data support a newly emerging model of pollen tube growth.
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Affiliation(s)
- Laura Zonia
- University of Amsterdam, Swammerdam Institute for Life Sciences, Section of Plant Physiology, Kruislaan 904, 1098 XH Amsterdam, The Netherlands.
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15
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Galietta LJV. The TMEM16 protein family: a new class of chloride channels? Biophys J 2010; 97:3047-53. [PMID: 20006941 DOI: 10.1016/j.bpj.2009.09.024] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 09/14/2009] [Accepted: 09/16/2009] [Indexed: 01/12/2023] Open
Abstract
Cl(-) channels play important roles in many physiological processes, including transepithelial ion absorption and secretion, smooth and skeletal muscle contraction, neuronal excitability, sensory perception, and cell volume regulation. The molecular identity of many types of Cl(-) channels is still unknown. Recently, three research groups have arrived independently at the identification of TMEM16A (also known as anoctamin-1) as a membrane protein strongly related to the activity of Ca(2+)-activated Cl(-) channels (CaCCs). Site-specific mutagenesis of TMEM16A alters the properties of the channels, thus suggesting that TMEM16A forms, at least in part, the CaCC. TMEM16A is a member of a family that includes nine other membrane proteins. All TMEM16 proteins have a similar structure, with eight putative transmembrane domains and cytosolic amino- and carboxy-termini. TMEM16B expression also evokes the appearance of CaCCs, but with biophysical characteristics (voltage dependence, unitary conductance) different from those associated to TMEM16A. The roles of the other TMEM16 proteins are still unknown. The study of TMEM16 proteins may lead to identification of novel molecular mechanisms underlying ion transport and channel gating by voltage and Ca(2+).
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Affiliation(s)
- Luis J V Galietta
- Laboratory of Molecular Genetics, Istituto Giannina Gaslini, Genoa, Italy.
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16
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Ferrera L, Caputo A, Ubby I, Bussani E, Zegarra-Moran O, Ravazzolo R, Pagani F, Galietta LJV. Regulation of TMEM16A chloride channel properties by alternative splicing. J Biol Chem 2009; 284:33360-8. [PMID: 19819874 DOI: 10.1074/jbc.m109.046607] [Citation(s) in RCA: 176] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression of TMEM16A protein is associated with the activity of Ca(2+)-activated Cl(-) channels. TMEM16A primary transcript undergoes alternative splicing. thus resulting in the generation of multiple isoforms. We have determined the pattern of splicing and assessed the functional properties of the corresponding TMEM16A variants. We found three alternative exons, 6b, 13, and 15, coding for segments of 22, 4, and 26 amino acids, respectively, which are differently spliced in human organs. By patch clamp experiments on transfected cells, we found that skipping of exon 6b changes the Ca(2+) sensitivity by nearly 4-fold, resulting in Cl(-) currents requiring lower Ca(2+) concentrations to be activated. At the membrane potential of 80 mV, the apparent half-effective concentration decreases from 350 to 90 nm when the segment corresponding to exon 6b is excluded. Skipping of exon 13 instead strongly reduces the characteristic time-dependent activation observed for Ca(2+)-activated Cl(-) channels at positive membrane potentials. This effect was also obtained by deleting only the second pair of amino acids corresponding to exon 13. Alternative splicing appears as an important mechanism to regulate the voltage and Ca(2+) dependence of the TMEM16A-dependent Cl(-) channels in a tissue-specific manner.
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Affiliation(s)
- Loretta Ferrera
- Laboratory of Molecular Genetics, Istituto Giannina Gaslini, Largo G. Gaslini 5, 16147 Genova
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17
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Yoo B, Lemaire A, Mangmool S, Wolf MJ, Curcio A, Mao L, Rockman HA. Beta1-adrenergic receptors stimulate cardiac contractility and CaMKII activation in vivo and enhance cardiac dysfunction following myocardial infarction. Am J Physiol Heart Circ Physiol 2009; 297:H1377-86. [PMID: 19633206 DOI: 10.1152/ajpheart.00504.2009] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The beta-adrenergic receptor (betaAR) signaling system is one of the most powerful regulators of cardiac function and a key regulator of Ca(2+) homeostasis. We investigated the role of betaAR stimulation in augmenting cardiac function and its role in the activation of Ca(2+)/calmodulin-dependent kinase II (CaMKII) using various betaAR knockouts (KO) including beta(1)ARKO, beta(2)ARKO, and beta(1)/beta(2)AR double-KO (DKO) mice. We employed a murine model of left anterior descending coronary artery ligation to examine the differential contributions of specific betaAR subtypes in the activation of CaMKII in vivo in failing myocardium. Cardiac inotropy, chronotropy, and CaMKII activity following short-term isoproterenol stimulation were significantly attenuated in beta(1)ARKO and DKO compared with either the beta(2)ARKO or wild-type (WT) mice, indicating that beta(1)ARs are required for catecholamine-induced increases in contractility and CaMKII activity. Eight weeks after myocardial infarction (MI), beta(1)ARKO and DKO mice showed a significant attenuation in fractional shortening compared with either the beta(2)ARKO or WT mice. CaMKII activity after MI was significantly increased only in the beta(2)ARKO and WT hearts and not in the beta(1)ARKO and DKO hearts. The border zone of the infarct in the beta(2)ARKO and WT hearts demonstrated significantly increased apoptosis by TUNEL staining compared with the beta(1)ARKO and DKO hearts. Taken together, these data show that cardiac function and CaMKII activity are mediated almost exclusively by the beta(1)AR. Moreover, it appears that beta(1)AR signaling is detrimental to cardiac function following MI, possibly through activation of CaMKII.
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Affiliation(s)
- ByungSu Yoo
- Departments of Medicine, Cell Biology and Molecular Genetics, Duke University Medical Center, Durham, North Carolina 27710, USA
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18
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Shears SB. Molecular basis for the integration of inositol phosphate signaling pathways via human ITPK1. ACTA ACUST UNITED AC 2009; 49:87-96. [PMID: 19200440 DOI: 10.1016/j.advenzreg.2008.12.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Stephen B Shears
- Inositol Signaling Section, Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, NC 27709, USA.
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19
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Mitchell J, Wang X, Zhang G, Gentzsch M, Nelson DJ, Shears SB. An expanded biological repertoire for Ins(3,4,5,6)P4 through its modulation of ClC-3 function. Curr Biol 2008; 18:1600-5. [PMID: 18951024 DOI: 10.1016/j.cub.2008.08.073] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 08/08/2008] [Accepted: 08/28/2008] [Indexed: 01/01/2023]
Abstract
Ins(3,4,5,6)P(4) inhibits plasma membrane Cl(-) flux in secretory epithelia [1]. However, in most other mammalian cells, receptor-dependent elevation of Ins(3,4,5,6)P(4) levels is an "orphan" response that lacks biological significance [2]. We set out to identify Cl(-) channel(s) and/or transporter(s) that are regulated by Ins(3,4,5,6)P4 in vivo. Several candidates [3-5] were excluded through biophysical criteria, electrophysiological analysis, and confocal immunofluorescence microscopy. Then, we heterologously expressed ClC-3 in the plasma membrane of HEK293-tsA201 cells; whole-cell patch-clamp analysis showed Ins(3,4,5,6)P4 to inhibit Cl(-) conductance through ClC-3. Next, we heterologously expressed ClC-3 in the early endosomal compartment of BHK cells; by fluorescence ratio imaging of endocytosed FITC-transferrin, we recorded intra-endosomal pH, an in situ biosensor for Cl(-) flux across endosomal membranes [6]. A cell-permeant, bioactivatable Ins(3,4,5,6)P4 analog elevated endosomal pH from 6.1 to 6.6, reflecting inhibition of ClC-3. Finally, Ins(3,4,5,6)P(4) inhibited endogenous ClC-3 conductance in postsynaptic membranes of neonatal hippocampal neurones. Among other ClC-3 functions that could be regulated by Ins(3,4,5,6)P4 are tumor cell migration [7], apoptosis [8], and inflammatory responses [9]. Ins(3,4,5,6)P4 is a ubiquitous cellular signal with diverse biological actions.
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Affiliation(s)
- Jennifer Mitchell
- Inositol Signaling Group, National Institute of Environmental Health Sciences, National Institutes of Health, U.S. Department of Health and Human Services, P.O. Box 12233, Research Triangle Park, North Carolina 27709, USA
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20
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Is Intervention in Inositol Phosphate Signaling a Useful Therapeutic Option for Cystic Fibrosis? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007. [DOI: 10.1007/0-387-23250-8_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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21
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Kunzelmann K, Milenkovic VM, Spitzner M, Soria RB, Schreiber R. Calcium-dependent chloride conductance in epithelia: is there a contribution by Bestrophin? Pflugers Arch 2007; 454:879-89. [PMID: 17361457 DOI: 10.1007/s00424-007-0245-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Accepted: 02/26/2007] [Indexed: 01/09/2023]
Abstract
Although known for more than 20 years, the molecular identity of epithelial Ca(2+)-activated Cl(-) channels remains obscure. Previous candidate proteins did not hold initial promises, and thus, new hope is put into the recently identified family of bestrophin proteins, as they reflect many of the properties found for native channels. Mutations in the bestrophin gene cause an autosomal form of macular dystrophy of the retina. Bestrophin 1 is assumed to form the basolateral Ca(2+)-activated Cl(-) channel in the retinal pigment epithelium of the eye. Other data suggest that bestrophin is a regulator of voltage gated Ca(2+) channels. Structural information on bestrophins is available and a Cl(-) selective filter has been localized to the second transmembrane domain of bestrophin. It is possible that bestrophins function as physiologically regulated Cl(-) channels only in association with additional subunits and auxiliary proteins. Little is known about expression of bestrophin in gland acinar cells, which show a pronounced Ca(2+)-activated Cl(-) secretion. In airways and intestinal epithelia, bestrophins could be particularly important in diseases such as cystic fibrosis and secretory diarrhea.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstrasse 31, 93053, Regensburg, Germany.
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22
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Chien LT, Zhang ZR, Hartzell HC. Single Cl- channels activated by Ca2+ in Drosophila S2 cells are mediated by bestrophins. ACTA ACUST UNITED AC 2006; 128:247-59. [PMID: 16940553 PMCID: PMC2151570 DOI: 10.1085/jgp.200609581] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mutations in human bestrophin-1 (VMD2) are genetically linked to several forms of retinal degeneration but the underlying mechanisms are unknown. Bestrophin-1 (hBest1) has been proposed to be a Cl− channel involved in ion and fluid transport by the retinal pigment epithelium (RPE). To date, however, bestrophin currents have only been described in overexpression systems and not in any native cells. To test whether bestrophins function as Ca2+-activated Cl− (CaC) channels physiologically, we used interfering RNA (RNAi) in the Drosophila S2 cell line. S2 cells express four bestrophins (dbest1–4) and have an endogenous CaC current. The CaC current is abolished by several RNAi constructs to dbest1 and dbest2, but not dbest3 or dbest4. The endogenous CaC current was mimicked by expression of dbest1 in HEK cells, and the rectification and relative permeability of the current were altered by replacing F81 with cysteine. Single channel analysis of the S2 bestrophin currents revealed an ∼2-pS single channel with fast gating kinetics and linear current–voltage relationship. A similar channel was observed in CHO cells transfected with dbest1, but no such channel was seen in S2 cells treated with RNAi to dbest1. This provides definitive evidence that bestrophins are components of native CaC channels at the plasma membrane.
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Affiliation(s)
- Li-Ting Chien
- Department of Cell Biology and Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322, USA
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23
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Zonia L, Munnik T. Cracking the green paradigm: functional coding of phosphoinositide signals in plant stress responses. Subcell Biochem 2006; 39:207-37. [PMID: 17121277 DOI: 10.1007/0-387-27600-9_9] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Laura Zonia
- Section of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 318, NL-1098 SM, Amsterdam, The Netherlands
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24
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Barro Soria R, Spitzner M, Schreiber R, Kunzelmann K. Bestrophin-1 enables Ca2+-activated Cl- conductance in epithelia. J Biol Chem 2006; 284:29405-12. [PMID: 17003041 PMCID: PMC2785573 DOI: 10.1074/jbc.m605716200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epithelial cells express calcium-activated Cl(-) channels of unknown molecular identity. These Cl(-) channels play a central role in diseases such as secretory diarrhea, polycystic kidney disease, and cystic fibrosis. The family of bestrophins has been suggested to form calcium-activated Cl(-) channels. Here, we demonstrate molecular and functional expression of bestrophin-1 (BEST1) in mouse and human airways, colon, and kidney. Endogenous calcium-activated whole cell Cl(-) currents coincide with endogenous expression of the Vmd2 gene product BEST1 in murine and human epithelial cells, whereas calcium-activated Cl(-) currents are absent in epithelial tissues lacking BEST1 expression. Blocking expression of BEST1 with short interfering RNA or applying an anti-BEST1 antibody to a patch pipette suppressed ATP-induced whole cell Cl(-) currents. Calcium-dependent Cl(-) currents were activated by ATP in HEK293 cells expressing BEST1. Thus, BEST1 may form the Ca2+-activated Cl(-) current, or it may be a component of a Cl(-) channel complex in epithelial tissues.
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Affiliation(s)
- René Barro Soria
- From the Institut für Physiologie, Universität Regensburg, Universitätsstraβe 31, D-93053 Regensburg, Germany
| | - Melanie Spitzner
- From the Institut für Physiologie, Universität Regensburg, Universitätsstraβe 31, D-93053 Regensburg, Germany
| | - Rainer Schreiber
- From the Institut für Physiologie, Universität Regensburg, Universitätsstraβe 31, D-93053 Regensburg, Germany
| | - Karl Kunzelmann
- From the Institut für Physiologie, Universität Regensburg, Universitätsstraβe 31, D-93053 Regensburg, Germany
- To whom correspondence should be addressed. Tel.: 49-954-4302; Fax: 49-941-4315; E-mail:
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25
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Shears SB. Can intervention in inositol phosphate signalling pathways improve therapy for cystic fibrosis? Expert Opin Ther Targets 2006; 9:1307-17. [PMID: 16300477 DOI: 10.1517/14728222.9.6.1307] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Airway epithelial cells from cystic fibrosis (CF) individuals cannot secrete adequate Cl- through cystic fibrosis transmembrane regulator, and their Na+ channel (ENaC) activity is increased so that excessive Na+ and water is absorbed from the lumen. These aberrant transport activities can, at least partly, be compensated by pharmacologically increasing the activities of Ca2+-activated Cl- channels (CaCCs). The therapeutic value of this approach is currently being examined in clinical trials of candidate CF drugs such as INS-37217 (Inspire Pharmaceuticals) and Moli1901 (Lantibio, Inc.). This review argues that these drug development programmes will be helped if one can fully understand how the CaCCs are inhibited by inositol 3,4,5,6-tetrakisphosphate (Ins(3,4,5,6)P4), so that there can be pharmacological intervention in this process. Furthermore, genes that encode enzymes controlling Ins(3,4,5,6)P4 metabolism should be viewed as impacting upon CaCC activity; this, in turn, may influence the severity of the CF condition. Expression profiling of genes that regulate inositol phosphate metabolism may also illuminate variability in patient response to treatment regimens that target CaCCs. Compounds have been developed that can activate CaCCs by antagonising their inhibition by Ins(3,4,5,6)P4. One member of this drug family (INO-4995; Inologic) was recently shown to inhibit ENaC, thereby reducing fluid absorbtion by airway epithelial cells.
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Affiliation(s)
- Stephen B Shears
- Inositol Phosphate Signaling Group, NIEHS/NIH/DHHS, Research Triangle Park, NC 27709, USA.
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26
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Piljić A, Schultz C. Annexin A4 self-association modulates general membrane protein mobility in living cells. Mol Biol Cell 2006; 17:3318-28. [PMID: 16687573 PMCID: PMC1483058 DOI: 10.1091/mbc.e06-01-0041] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Annexins are Ca2+-regulated phospholipid-binding proteins whose function is only partially understood. Annexin A4 is a member of this family that is believed to be involved in exocytosis and regulation of epithelial Cl- secretion. In this work, fluorescent protein fusions of annexin A4 were used to investigate Ca2+-induced annexin A4 translocation and self-association on membrane surfaces in living cells. We designed a novel, genetically encoded, FRET sensor (CYNEX4) that allowed for easy quantification of translocation and self-association. Mobility of annexin A4 on membrane surfaces was investigated by FRAP. The experiments revealed the immobile nature of annexin A4 aggregates on membrane surfaces, which in turn strongly reduced the mobility of transmembrane and plasma membrane associated proteins. Our work provides mechanistic insight into how annexin A4 may regulate plasma membrane protein function.
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Affiliation(s)
- Alen Piljić
- Gene Expression Programme, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Carsten Schultz
- Gene Expression Programme, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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27
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Yang L, Reece J, Gabriel SE, Shears SB. Apical localization of ITPK1 enhances its ability to be a modifier gene product in a murine tracheal cell model of cystic fibrosis. J Cell Sci 2006; 119:1320-8. [PMID: 16537650 DOI: 10.1242/jcs.02836] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
A new aspect of research into the pathogenesis of cystic fibrosis (CF) is a genetics-based search for ;modifier genes' that may affect the severity of CF lung disease. Using an alternative, cell biological approach, we show that ITPK1 should be considered a modifier gene. ITPK1 synthesizes an intracellular signal, inositol (3,4,5,6)-tetrakisphosphate [Ins(3,4,5,6)P4]. A bio-activatable, cell-permeable analogue of Ins(3,4,5,6)P4 inhibited Ca2+-dependent secretion of Cl- from polarized monolayers of immortalized mouse tracheal epithelial cells (MTEs). Analysis by high-pressure liquid chromatography showed endogenous Ins(3,4,5,6)P4 levels in CF MTEs were approximately 60% below those in wild-type MTEs (P<0.03). This adaptation, which improves purinergic activation of Ca2+-dependent Cl- secretion in CF MTEs, was exceptionally specific; there was no effect upon the cellular levels of all the other inositol phosphate signals. Real-time PCR provided the explanation: the level of ITPK1 expression in wild-type MTEs was twice as high as that in CF MTEs (P<0.002). The biological impact of this differential gene expression is amplified by ITPK1 being concentrated at the apical membrane of MTEs, which we discovered following confocal immunofluorescence microscopy. Compartmentalization of Ins(3,4,5,6)P4 synthesis adjacent to its site of action will enhance its regulatory capacity.
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Affiliation(s)
- Ling Yang
- Inositol Signaling Section, and N.I.E.H.S. / N.I.H. / D.H.S.S., Research Triangle Park, NC 27709, USA
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28
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Abstract
Calcium-activated chloride channels (CaCCs) play important roles in cellular physiology, including epithelial secretion of electrolytes and water, sensory transduction, regulation of neuronal and cardiac excitability, and regulation of vascular tone. This review discusses the physiological roles of these channels, their mechanisms of regulation and activation, and the mechanisms of anion selectivity and conduction. Despite the fact that CaCCs are so broadly expressed in cells and play such important functions, understanding these channels has been limited by the absence of specific blockers and the fact that the molecular identities of CaCCs remains in question. Recent status of the pharmacology and molecular identification of CaCCs is evaluated.
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Affiliation(s)
- Criss Hartzell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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29
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Abstract
In many species the pancreatic duct epithelium secretes HCO3- ions at a concentration of around 140 mM by a mechanism that is only partially understood. We know that HCO3- uptake at the basolateral membrane is achieved by Na+-HCO3- cotransport and also by a H+-ATPase and Na+/H+ exchanger operating together with carbonic anhydrase. At the apical membrane, the secretion of moderate concentrations of HCO3- can be explained by the parallel activity of a Cl-/HCO3- exchanger and a Cl- conductance, either the cystic fibrosis transmembrane conductance regulator (CFTR) or a Ca2+-activated Cl- channel (CaCC). However, the sustained secretion of HCO3- into a HCO- -rich luminal fluid cannot be explained by conventional Cl-/HCO3- exchange. HCO3- efflux across the apical membrane is an electrogenic process that is facilitated by the depletion of intracellular Cl-, but it remains to be seen whether it is mediated predominantly by CFTR or by an electrogenic SLC26 anion exchanger.
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Affiliation(s)
- Martin C Steward
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
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30
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Moody M, Pennington C, Schultz C, Caldwell R, Dinkel C, Rossi MW, McNamara S, Widdicombe J, Gabriel S, Traynor-Kaplan AE. Inositol polyphosphate derivative inhibits Na+ transport and improves fluid dynamics in cystic fibrosis airway epithelia. Am J Physiol Cell Physiol 2005; 289:C512-20. [PMID: 15857902 PMCID: PMC1800890 DOI: 10.1152/ajpcell.00591.2004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Amiloride-sensitive, epithelial Na(+) channel (ENaC)-mediated, active absorption of Na(+) is elevated in the airway epithelium of cystic fibrosis (CF) patients, resulting in excess fluid removal from the airway lumen. This excess fluid/volume absorption corresponds to CF transmembrane regulator-linked defects in ENaC regulation, resulting in the reduced mucociliary clearance found in CF airways. Herein we show that INO-4995, a synthetic analog of the intracellular signaling molecule, D-myo-inositol 3,4,5,6-tetrakisphosphate, inhibits Na(+) and fluid absorption across CF airway epithelia, thus alleviating this critical pathology. This conclusion was based on electrophysiological studies, fluid absorption, and (22)Na(+) flux measurements in CF airway epithelia, contrasted with normal epithelia, and on electrophysiological studies in Madin-Darby canine kidney cells and 3T3 cells overexpressing ENaC. The effects of INO-4995 were long-lasting, dose-dependent, and more pronounced in epithelia from CF patients vs. controls. These findings support preclinical development of INO-4995 for CF treatment and demonstrate for the first time the therapeutic potential of inositol polyphosphate derivatives.
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Affiliation(s)
| | | | | | - Ray Caldwell
- University of North Carolina, Chapel Hill, North Carolina
| | - Carlo Dinkel
- European Molecular Biology Laboratory, Heidelberg, Germany
| | | | | | | | - Sherif Gabriel
- University of North Carolina, Chapel Hill, North Carolina
| | - Alexis E. Traynor-Kaplan
- Inologic Inc., Seattle, Washington
- Address for reprint requests and other correspondence: A. Traynor-Kaplan, Inologic Inc., 101 Elliot Ave. West, Suite 100, Seattle, WA 98119 (e-mail: )
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31
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Shears SB, Yang L, Qian X. Cell signaling by a physiologically reversible inositol phosphate kinase/phosphatase. ACTA ACUST UNITED AC 2005; 44:265-77. [PMID: 15581495 DOI: 10.1016/j.advenzreg.2004.02.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Stephen B Shears
- Laboratory of Signal Transduction, Inositol Signaling Section, National Institute of Environmental Health Sciences, NIH/DHHS, Research Triangle Park, NC 27709, USA.
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Torres JJ, Cornelisse LN, Harks EGA, Van Meerwijk WPM, Theuvenet APR, Ypey DL. Modeling action potential generation and propagation in NRK fibroblasts. Am J Physiol Cell Physiol 2004; 287:C851-65. [PMID: 15140749 DOI: 10.1152/ajpcell.00220.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Normal rat kidney (NRK) fibroblasts change their excitability properties through the various stages of cell proliferation. The present mathematical model has been developed to explain excitability of quiescent (serum deprived) NRK cells. It includes as cell membrane components, on the basis of patch-clamp experiments, an inwardly rectifying potassium conductance ( GKir), an L-type calcium conductance ( GCaL), a leak conductance ( Gleak), an intracellular calcium-activated chloride conductance [ GCl(Ca)], and a gap junctional conductance ( Ggj), coupling neighboring cells in a hexagonal pattern. This membrane model has been extended with simple intracellular calcium dynamics resulting from calcium entry via GCaLchannels, intracellular buffering, and calcium extrusion. It reproduces excitability of single NRK cells and cell clusters and intercellular action potential (AP) propagation in NRK cell monolayers. Excitation can be evoked by electrical stimulation, external potassium-induced depolarization, or hormone-induced intracellular calcium release. Analysis shows the roles of the various ion channels in the ultralong (∼30 s) NRK cell AP and reveals the particular role of intracellular calcium dynamics in this AP. We support our earlier conclusion (De Roos A, Willems PH, van Zoelen EJ, and Theuvenet AP. Am J Physiol Cell Physiol 273: C1900–C1907, 1997) that AP generation and propagation may act as a rapid mechanism for the propagation of intracellular calcium waves, thus contributing to fast intercellular calcium signaling. The present model serves as a starting point to further analyze excitability changes during contact inhibition and cell transformation.
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Affiliation(s)
- J J Torres
- Institute "Carlos I" for Theoretical and Computational Physics, University of Granada, Spain
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Olson JE, Li GZ, Wang L, Lu L. Volume-regulated anion conductance in cultured rat cerebral astrocytes requires calmodulin activity. Glia 2004; 46:391-401. [PMID: 15095369 DOI: 10.1002/glia.20014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We examined the calmodulin dependence of anion channel activation during hypo-osmotic swelling in rat cerebral astrocytes. Control cells bathed in iso-osmotic (290 mOsm) phosphate-buffered saline (PBS) and recorded using a patch electrode containing 140 mM KCl increased membrane conductance threefold over basal levels after 12 min in hypo-osmotic (200 mOsm) PBS. Cells injected with monoclonal anticalmodulin antibody demonstrated no increase in membrane conductance during a subsequent exposure to hypo-osmotic PBS. In contrast, cells iontophoretically injected with monoclonal antiglial fibrillary acidic protein antibody or with anticalmodulin antibody absorbed with an excess of free calmodulin demonstrated an increase in conductance during hypo-osmotic exposure similar to that of control cells. Conductance in iso-osmotic conditions was unchanged by antibody injection. Similar results were obtained when using patch electrode and bath solutions containing chloride as the only cell permeant ion, indicating a calmodulin-dependent anion current is activated with this degree of hypo-osmotic treatment. Western blots confirmed the specificity of the anticalmodulin and antiglial fibrillary acidic protein antibodies used in this study for proteins of 17 and 51 kD, respectively. In addition, in vitro studies demonstrated inhibition of the calmodulin-dependent activation of phosphodiesterase by the anticalmodulin antibody. Thus, binding of this antibody to calmodulin causes functional inhibition of calmodulin activity. No change in the intensity or cellular distribution of calmodulin immunostaining was observed during 30 min of hypo-osmotic exposure. However, increased immunostaining for activated calmodulin kinase IIalpha was observed after 10 min of hypo-osmotic exposure, suggesting initiation of calmodulin-dependent processes by cell swelling. The data indicate calmodulin activity is critical for activation of volume-regulated anion channels in rat cerebral astrocytes.
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Affiliation(s)
- James E Olson
- Department of Emergency Medicine, Wright State University School of Medicine, Cox Institute, Kettering, Ohio 45429, USA.
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Zonia L, Munnik T. Osmotically induced cell swelling versus cell shrinking elicits specific changes in phospholipid signals in tobacco pollen tubes. PLANT PHYSIOLOGY 2004; 134:813-23. [PMID: 14739344 PMCID: PMC344556 DOI: 10.1104/pp.103.029454] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2003] [Revised: 08/21/2003] [Accepted: 11/15/2003] [Indexed: 05/18/2023]
Abstract
Pollen tube cell volume changes rapidly in response to perturbation of the extracellular osmotic potential. This report shows that specific phospholipid signals are differentially stimulated or attenuated during osmotic perturbations. Hypo-osmotic stress induces rapid increases in phosphatidic acid (PA). This response occurs starting at the addition of 25% (v/v) water to the pollen tube cultures and peaks at 100% (v/v) water. Increased levels of PA were detected within 30 s and reached maximum by 15 to 30 min after treatment. The pollen tube apical region undergoes a 46% increase in cell volume after addition of 100% water (v/v), and there is an average 7-fold increase in PA. This PA increase appears to be generated by phospholipase D because concurrent transphosphatidylation of n-butanol results in an average 8-fold increase in phosphatidylbutanol. Hypo-osmotic stress also induces an average 2-fold decrease in phosphatidylinositol phosphate; however, there are no detectable changes in the levels of phosphatidylinositol bisphosphates. In contrast, salt-induced hyperosmotic stress from 50 to 400 mm NaCl inhibits phospholipase D activity, reduces the levels of PA, and induces increases in the levels of phosphatidylinositol bisphosphate isomers. The pollen tube apical region undergoes a 41% decrease in cell volume at 400 mm NaCl, and there is an average 2-fold increase in phosphatidylinositol 3,5-bisphosphate and 1.4-fold increase in phosphatidylinositol 4,5-bisphosphate. The phosphatidylinositol 3,5-bisphosphate increase is detected within 30 s and reaches maximum by 15 to 30 min after treatment. In summary, these results demonstrate that hypo-osmotic versus hyperosmotic perturbation and the resultant cell swelling or shrinking differentially activate specific phospholipid signaling pathways in tobacco (Nicotiana tabacum) pollen tubes.
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Affiliation(s)
- Laura Zonia
- Institute of Experimental Botany, Na Pernikarce 15, 160 00 Prague 6, Czech Republic.
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35
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Robinson NC, Huang P, Kaetzel MA, Lamb FS, Nelson DJ. Identification of an N-terminal amino acid of the CLC-3 chloride channel critical in phosphorylation-dependent activation of a CaMKII-activated chloride current. J Physiol 2004; 556:353-68. [PMID: 14754994 PMCID: PMC1664934 DOI: 10.1113/jphysiol.2003.058032] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
CLC-3, a member of the CLC family of chloride channels, mediates function in many cell types in the body. The multifunctional calcium-calmodulin-dependent protein kinase II (CaMKII) has been shown to activate recombinant CLC-3 stably expressed in tsA cells, a human embryonic kidney cell line derivative, and natively expressed channel protein in a human colonic tumour cell line T84. We examined the CaMKII-dependent regulation of CLC-3 in a smooth muscle cell model as well as in the human colonic tumour cell line, HT29, using whole-cell voltage clamp. In CLC-3-expressing cells, we observed the activation of a Cl(-) conductance following intracellular introduction of the isolated autonomous CaMKII into the voltage-clamped cell via the patch pipette. The CaMKII-dependent Cl(-) conductance was not observed following exposure of the cells to 1 microm autocamtide inhibitory peptide (AIP), a selective inhibitor of CaMKII. Arterial smooth muscle cells express a robust CaMKII-activated Cl(-) conductance; however, CLC-3(-/-) cells did not. The N-terminus of CLC-3, which contains a CaMKII consensus sequence, was phosphorylated by CaMKII in vitro, and mutation of the serine at position 109 (S109A) abolished the CaMKII-dependent Cl(-) conductance, indicating that this residue is important in the gating of CLC-3 at the plasma membrane.
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Affiliation(s)
- N C Robinson
- Department of Neurobiology, Pharmacology, and Physiology, The University of Chicago, 947 East 58(th) Street, AB-500 MC-0926, Chicago, IL 60637, USA
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Shears SB. How versatile are inositol phosphate kinases? Biochem J 2004; 377:265-80. [PMID: 14567754 PMCID: PMC1223885 DOI: 10.1042/bj20031428] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Revised: 10/14/2003] [Accepted: 10/20/2003] [Indexed: 01/31/2023]
Abstract
This review assesses the extent and the significance of catalytic versatility shown by several inositol phosphate kinases: the inositol phosphate multikinase, the reversible Ins(1,3,4) P (3)/Ins(3,4,5,6) P (4) kinase, and the kinases that synthesize diphosphoinositol polyphosphates. Particular emphasis is placed upon data that are relevant to the situation in vivo. It will be shown that catalytic promiscuity towards different inositol phosphates is not typically an evolutionary compromise, but instead is sometimes exploited to facilitate tight regulation of physiological processes. This multifunctionality can add to the complexity with which inositol signalling pathways interact. This review also assesses some proposed additional functions for the catalytic domains, including transcriptional regulation, protein kinase activity and control by molecular 'switching', all in the context of growing interest in 'moonlighting' (gene-sharing) proteins.
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Affiliation(s)
- Stephen B Shears
- Inositol Signaling Section, Laboratory of Signal Transduction, NIEHS/NIH/DHSS Research Triangle Park, NC 27709, USA.
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Saito S, Shimazawa R, Shirai R. Diastereoselective Synthesis of D- and L-myo-Inositol 3,4,5,6-Tetrakisphosphates from D-Glucose via Dihydroxylation of (+)-Conduritol B Derivatives. Chem Pharm Bull (Tokyo) 2004; 52:727-32. [PMID: 15187396 DOI: 10.1248/cpb.52.727] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Syntheses of D- and L-myo-inositol 3,4,5,6-tetrakisphosphates were achieved via diastereoselective 1,2-addition of vinylcopper reagent with the chiral aldehyde prepared from 1,2,5,6-diisopropylidene-D-glucose, ring-closing metathesis of 1,7-diene with Grubbs catalyst followed by catalytic OsO(4) dihydroxylation of (+)-conduritol B derivatives.
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Affiliation(s)
- Shintaro Saito
- Research and Education Center for Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0101, Japan
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Boese SH, Aziz O, Simmons NL, Gray MA. Kinetics and regulation of a Ca2+-activated Cl- conductance in mouse renal inner medullary collecting duct cells. Am J Physiol Renal Physiol 2003; 286:F682-92. [PMID: 14678946 DOI: 10.1152/ajprenal.00123.2003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Using the whole cell patch-clamp technique, a Ca2+-activated Cl- conductance (CaCC) was transiently activated by extracellular ATP (100 microM) in primary cultures of mouse inner medullary collecting duct (IMCD) cells and in the mouse IMCD-K2 cell line. ATP also transiently increased intracellular Ca2+ concentration ([Ca2+]i) from 100 nM to peak values of approximately 750 nM in mIMCD-K2 cells, with a time course similar to the ATP-induced activation and decay of the CaCC. Removal of extracellular Ca2+ had no major effect on the peak Cl- conductance or the increase in [Ca2+]i induced by ATP, suggesting that Ca2+ released from intracellular stores directly activates the CaCC. In mIMCD-K2 cells, a rectifying time- and voltage-dependent current was observed when [Ca2+]i was fixed via the patch pipette to between 100 and 500 nM. Maximal activation occurred at approximately 1 microM [Ca2+]i, with currents losing any kinetics and displaying a linear current-voltage relationship. From Ca2+-dose-response curves, an EC50 value of approximately 650 nM at -80 mV was obtained, suggesting that under physiological conditions the CaCC would be near fully activated by mucosal nucleotides. Noise analysis of whole cell currents in mIMCD-K2 cells suggests a single-channel conductance of 6-8 pS and a density of approximately 5,000 channels/cell. In conclusion, the CaCC in mouse IMCD cells is a low-conductance, nucleotide-sensitive Cl- channel, whose activity is tightly coupled to changes in [Ca2+]i over the normal physiological range.
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Affiliation(s)
- S H Boese
- School of Cell and Molecular Bioscience, Univ. Medical School, Newcastle Upon Tyne, NE2 4HH, UK
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Hidaka K, Kanematsu T, Caffrey JJ, Takeuchi H, Shears SB, Hirata M. The importance to chondrocyte differentiation of changes in expression of the multiple inositol polyphosphate phosphatase. Exp Cell Res 2003; 290:254-64. [PMID: 14567985 DOI: 10.1016/s0014-4827(03)00337-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It is important to both physiological and pathological osteogenesis to understand the significance of changes in gene expression in growth-plate chondrocytes that transit between the proliferative and hypertrophic states. MINPP is one such gene of interest. The Minpp protein dephosphorylates highly phosphorylated inositol signaling molecules InsP(5) and InsP(6). We show here that the ATDC5 chondrocyte progenitor cell line can recapitulate developmentally specific changes in MINPP expression previously only seen in longitudinal bone growth plates-both an initial 2-3-fold increase and a subsequent decrease back to initial levels during transition to hypertrophy. The increase in MINPP expression was accompanied by a 40% decrease in InsP(6) levels in ATDC5 cells. However, InsP(5) levels were not modified. Furthermore, throughout the hypertrophic phase, during which MINPP expression decreased, there were no alterations in InsP(5) and InsP(6) levels. We also created an ATDC5 line that stably overexpressed Minpp at 2-fold higher levels than in wild-type cells. This had no significant effect upon cellular levels of InsP(5) and InsP(6). Thus, substantial changes in MINPP expression can occur without a net effect upon InsP(5) and InsP(6) turnover in vivo. On the other hand, Minpp-overexpressing cells showed impaired chondrogenesis. We noted that the expression of alkaline phosphatase activity was inversely correlated with the expression of MINPP. The ATDC5 cells that overexpress Minpp failed to show an insulin-dependent increase in alkaline phosphatase levels, which presumably affects phosphate balance [J. Biol. Chem. 276 (2001) 33995], and may be the reason cellular differentiation was impaired. In any case, we conclude that Minpp is important to chondrocyte differentiation, but in a manner that is, surprisingly, independent of inositol polyphosphate turnover.
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Affiliation(s)
- Kiyoshi Hidaka
- Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
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40
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Rudolf MT, Dinkel C, Traynor-Kaplan AE, Schultz C. Antagonists of myo-inositol 3,4,5,6-tetrakisphosphate allow repeated epithelial chloride secretion. Bioorg Med Chem 2003; 11:3315-29. [PMID: 12837542 DOI: 10.1016/s0968-0896(03)00188-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cystic fibrosis (CF) patients suffer from a defect in hydration of mucosal membranes due to mutations in the cystic fibrosis transmembrane regulator (CFTR), an apical chloride channel in mucosal epithelia. Disease expression in CF knockout mice is organ specific, varying with the level of expression of calcium activated Cl(-) channels (CLCA). Therefore, restoring transepithelial Cl(-) secretion by augmenting alternate Cl(-) channels, such as CLCA, could be beneficial. However, CLCA-mediated Cl(-) secretion is transient, due in part to the inhibitory effects of myo-inositol 3,4,5,6-tetrakisphosphate [Ins(3,4,5,6)P(4)]. This suggests that antagonists of Ins(3,4,5,6)P(4) could be useful in treatment of CF. We have, therefore, synthesized a series of membrane-permeant Ins(3,4,5,6)P(4) derivatives, carrying alkyl substituents on the hydroxyl groups and screened them for effects on Cl(-) secretion in a human colonic epithelial cell line, T(84). While membrane-permeant Ins(3,4,5,6)P(4) derivatives had no direct effects on carbachol-stimulated Cl(-) secretion, Ins(3,4,5,6)P(4) derivatives, but not enantiomeric Ins(1,4,5,6)P(4) derivatives, reversed the inhibitory effect of Ins(3,4,5,6)P(4) on subsequent thapsigargin activation of Cl(-) secretion. The extent of the antagonistic effect of the Ins(3,4,5,6)P(4) derivatives varied with the position of the alkyl substituents. Derivatives with a cyclohexylidene ketal or a butyl-chain at the 1-position reversed the Ins(3,4,5,6)P(4)-mediated inhibition of Cl(-) secretion by up to 96 and 85%, respectively, whereas butylation of the 1- and 2-position generated a reversal effect of only 65%. Derivatives carrying the butyl chain only at the 2-position showed no antagonistic effect. These data: (1) Support the hypothesis that Ins(3,4,5,6)P(4) stereospecifically inhibits Ca(2+) activated Cl(-) secretion and that Ins(3,4,5,6)P(4) mediates most, if not all of the cholinergic-mediated inhibition of chloride secretion in T(84) cells; (2) Demonstrate Ins(3,4,5,6)P(4)-mediated inhibition can be completely reversed with rationally designed membrane-permeant Ins(3,4,5,6)P(4) antagonists; (3) Demonstrate that a SAR for membrane-permeant Ins(3,4,5,6) P(4) antagonists can be generated and screened in a physiologically relevant cell-based assay; (4) Indicate that Ins(3,4,5,6)P(4) derivatives could serve as a starting point for the development of therapeutics to treat cystic fibrosis.
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Affiliation(s)
- Marco T Rudolf
- Institut für Organische Chemie, Universität Bremen, UFT, 28359 Bremen, Germany
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41
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Affiliation(s)
- Brian Q Phillippy
- United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA 70124, USA
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Zonia L, Feijó JA. State and spectral properties of chloride oscillations in pollen. Biophys J 2003; 84:1387-98. [PMID: 12547818 PMCID: PMC1302714 DOI: 10.1016/s0006-3495(03)74953-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2002] [Accepted: 09/27/2002] [Indexed: 12/15/2022] Open
Abstract
Pollen tube growth is a dynamic system expressing a number of oscillating circuits. Our recent work identified a new circuit, oscillatory efflux of Cl(-) anion from the pollen tube apex. Cl(-) efflux is the first ion signal found to be coupled in phase with growth oscillations. Functional analyses indicate an active role for Cl(-) flux in pollen tube growth. In this report the dynamical properties of Cl(-) efflux are examined. Phase space analysis demonstrates that the system trajectory converges on a limit cycle. Fourier analysis reveals that two harmonic frequencies characterize normal growth. Cl(-) efflux is inhibited by the channel blocker DIDS, is stimulated by hypoosmotic treatment, and is antagonized by the signal encoded in inositol 3,4,5,6-tetrakisphosphate. These perturbations induce transitions of the limit cycle to new metastable states or cause system collapse to a static attractor centered near the origin. These perturbations also transform the spectral profile, inducing subharmonic frequencies, transitions to period doubling and tripling, superharmonic resonance, and chaos. These results indicate that Cl(-) signals in pollen tubes display features that are characteristic of active oscillators that carry frequency-encoded information. A reaction network of the Cl(-) oscillator coupled to two nonlinear feedback circuits that may drive pollen tube growth oscillations is considered.
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Affiliation(s)
- Laura Zonia
- Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Na Pernikarce 15, 160 00 Prague 6, Czech Republic.
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43
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Abstract
AIM This review describes molecular and functional properties of the following Cl- channels: the ClC family of voltage-dependent Cl- channels, the cAMP-activated transmembrane conductance regulator (CFTR), Ca2+ activated Cl- channels (CaCC) and volume-regulated anion channels (VRAC). If structural data are available, their relationship with the function of Cl- channels will be discussed. We also describe shortly some recently discovered channels, including high conductance Cl- channels and the family of bestrophins. We illustrate the growing physiological importance of these channels in the plasma membrane and in intracellular membranes, including their involvement in transepithelial transport, pH regulation of intracellular organelles, regulation of excitability and volume regulation. Finally, we discuss the role of Cl- channels in various diseases and describe the pathological phenotypes observed in knockout mice models.
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Affiliation(s)
- B Nilius
- KU Leuven, Laboratorium voor Fysiologie, Campus Gasthuisberg, Leuven, Belgium
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Renström E, Ivarsson R, Shears SB. Inositol 3,4,5,6-tetrakisphosphate inhibits insulin granule acidification and fusogenic potential. J Biol Chem 2002; 277:26717-20. [PMID: 12055181 DOI: 10.1074/jbc.c200314200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ClC Cl(-) channels in endosomes, synaptosomes, lysosomes, and beta-cell insulin granules provide charge neutralization support for the functionally indispensable acidification of the luminal interior by electrogenic H(+)-ATPases (Jentsch, T. J., Stein, V., Weinreich, F., and Zdebik, A. A. (2002) Physiol. Rev. 82, 503-568). Regulation of ClC activity is, therefore, of widespread biological significance (Forgac, M. (1999) J. Biol. Chem. 274, 12951-12954). We now ascribe just such a regulatory function to the increases in cellular levels of inositol 3,4,5,6-tetrakisphosphate (Ins(3,4,5,6)P(4)) that inevitably accompany activation of the ubiquitous Ins(1,4,5)P(3) signaling pathway. We used confocal imaging to record insulin granule acidification in single mouse pancreatic beta-cells. Granule acidification was reduced by perfusion of single cells with 10 microm Ins(3,4,5,6)P(4) (the concentration following receptor activation), whereas at 1 microm ("resting" levels), Ins(3,4,5,6)P(4) was ineffective. This response to Ins(3,4,5,6)P(4) was not mimicked by 100 microm Ins(1,4,5,6)P(4) or by 100 microm Ins(1,3,4,5,6)P(5). Ins(3,4,5,6)P(4) did not affect granular H(+)-ATPase activity or H(+) leak, indicating that Ins(3,4,5,6)P(4) instead inhibited charge neutralization by ClC. The Ins(3,4,5,6)P(4)-mediated inhibition of vesicle acidification reduced exocytic release of insulin as determined by whole-cell capacitance recordings. This may impinge upon type 2 diabetes etiology. Regulatory control over vesicle acidification by this negative signaling pathway in other cell types should be considered.
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Affiliation(s)
- Erik Renström
- Department of Physiological Sciences, Lund University, BMC F11 SE-221 84 Lund, Sweden.
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Abstract
Ins(3,4,5,6)P(4) is an inhibitor of Ca(2+)-activated Cl(-) channels, but further understanding has been hindered by ignorance of how it is made in cells. It now transpires that one protein with ATP-dependent kinase and phosphatase activities interconverts Ins(3,4,5,6)P(4) and Ins(1,3,4,5,6)P(5), as well as several other inositol polyphosphates.
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Affiliation(s)
- Robert H Michell
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK.
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46
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Jentsch TJ, Stein V, Weinreich F, Zdebik AA. Molecular structure and physiological function of chloride channels. Physiol Rev 2002; 82:503-68. [PMID: 11917096 DOI: 10.1152/physrev.00029.2001] [Citation(s) in RCA: 934] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cl- channels reside both in the plasma membrane and in intracellular organelles. Their functions range from ion homeostasis to cell volume regulation, transepithelial transport, and regulation of electrical excitability. Their physiological roles are impressively illustrated by various inherited diseases and knock-out mouse models. Thus the loss of distinct Cl- channels leads to an impairment of transepithelial transport in cystic fibrosis and Bartter's syndrome, to increased muscle excitability in myotonia congenita, to reduced endosomal acidification and impaired endocytosis in Dent's disease, and to impaired extracellular acidification by osteoclasts and osteopetrosis. The disruption of several Cl- channels in mice results in blindness. Several classes of Cl- channels have not yet been identified at the molecular level. Three molecularly distinct Cl- channel families (CLC, CFTR, and ligand-gated GABA and glycine receptors) are well established. Mutagenesis and functional studies have yielded considerable insights into their structure and function. Recently, the detailed structure of bacterial CLC proteins was determined by X-ray analysis of three-dimensional crystals. Nonetheless, they are less well understood than cation channels and show remarkably different biophysical and structural properties. Other gene families (CLIC or CLCA) were also reported to encode Cl- channels but are less well characterized. This review focuses on molecularly identified Cl- channels and their physiological roles.
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Affiliation(s)
- Thomas J Jentsch
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany.
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47
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Ho MWY, Yang X, Carew MA, Zhang T, Hua L, Kwon YU, Chung SK, Adelt S, Vogel G, Riley AM, Potter BVL, Shears SB. Regulation of Ins(3,4,5,6)P(4) signaling by a reversible kinase/phosphatase. Curr Biol 2002; 12:477-82. [PMID: 11909533 DOI: 10.1016/s0960-9822(02)00713-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regulation of Cl(-) channel conductance by Ins(3,4,5,6)P(4) provides receptor-dependent control over salt and fluid secretion, cell volume homeostasis, and electrical excitability of neurones and smooth muscle. Ignorance of how Ins(3,4,5,6)P(4) is synthesized has long hindered our understanding of this signaling pathway. We now show Ins(3,4,5,6)P(4) synthesis by Ins(1,3,4,5,6)P(5) 1-phosphatase activity by an enzyme previously characterized as an Ins(3,4,5,6)P(4) 1-kinase. Rationalization of these phenomena with a ligand binding model unveils Ins(1,3,4)P(3) as not simply an alternative kinase substrate, but also an activator of Ins(1,3,4,5,6)P(5) 1-phosphatase. Stable overexpression of the enzyme in epithelial monolayers verifies its physiological role in elevating Ins(3,4,5,6)P(4) levels and inhibiting secretion. It is exceptional for a single enzyme to catalyze two opposing signaling reactions (1-kinase/1-phosphatase) under physiological conditions. Reciprocal coordination of these opposing reactions offers an alternative to general doctrine that intracellular signals are regulated by integrating multiple, distinct phosphatases and kinases.
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Affiliation(s)
- Melisa W Y Ho
- Inositide Signaling Group, Laboratory of Signal Transduction and National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
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Ho MW, Shears SB. Regulation of calcium-activated chloride channels by inositol 3,4,5,6 tetrakisphosphate. CURRENT TOPICS IN MEMBRANES 2002. [DOI: 10.1016/s1063-5823(02)53041-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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49
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Properties and role of calcium-activated chloride channels in pancreatic duct cells. CURRENT TOPICS IN MEMBRANES 2002. [DOI: 10.1016/s1063-5823(02)53036-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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The endogenous calcium-activated Cl channel in Xenopus oocytes: A physiologically and biophysically rich model system. CURRENT TOPICS IN MEMBRANES 2002. [DOI: 10.1016/s1063-5823(02)53026-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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