1
|
Shapovalov G, Gordienko D, Prevarskaya N. Store operated calcium channels in cancer progression. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 363:123-168. [PMID: 34392928 DOI: 10.1016/bs.ircmb.2021.02.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In recent decades cancer emerged as one of the leading causes of death in the developed countries, with some types of cancer contributing to the top 10 causes of death on the list of the World Health Organization. Carcinogenesis, a malignant transformation causing formation of tumors in normal tissues, is associated with changes in the cell cycle caused by suppression of signaling pathways leading to cell death and facilitation of those enhancing proliferation. Further progression of cancer, during which benign tumors acquire more aggressive phenotypes, is characterized by metastatic dissemination through the body driven by augmented motility and invasiveness of cancer cells. All these processes are associated with alterations in calcium homeostasis in cancer cells, which promote their proliferation, motility and invasion, and dissuade cell death or cell cycle arrest. Remodeling of store-operated calcium entry (SOCE), one of the major pathways regulating intracellular Ca2+ concentration ([Ca2+]i), manifests a key event in many of these processes. This review systematizes current knowledge on the mechanisms recruiting SOCE-related proteins in carcinogenesis and cancer progression.
Collapse
Affiliation(s)
- George Shapovalov
- Laboratory of Cell Physiology, INSERM U1003, Laboratory of Excellence Ion Channels Science and Therapeutics, Department of Biology, Faculty of Science and Technologiesa, University of Lille, Villeneuve d'Ascq, France.
| | - Dmitri Gordienko
- Laboratory of Cell Physiology, INSERM U1003, Laboratory of Excellence Ion Channels Science and Therapeutics, Department of Biology, Faculty of Science and Technologiesa, University of Lille, Villeneuve d'Ascq, France
| | - Natalia Prevarskaya
- Laboratory of Cell Physiology, INSERM U1003, Laboratory of Excellence Ion Channels Science and Therapeutics, Department of Biology, Faculty of Science and Technologiesa, University of Lille, Villeneuve d'Ascq, France
| |
Collapse
|
2
|
Carvacho I, Piesche M, Maier TJ, Machaca K. Ion Channel Function During Oocyte Maturation and Fertilization. Front Cell Dev Biol 2018; 6:63. [PMID: 29998105 PMCID: PMC6028574 DOI: 10.3389/fcell.2018.00063] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 06/04/2018] [Indexed: 12/20/2022] Open
Abstract
The proper maturation of both male and female gametes is essential for supporting fertilization and the early embryonic divisions. In the ovary, immature fully-grown oocytes that are arrested in prophase I of meiosis I are not able to support fertilization. Acquiring fertilization competence requires resumption of meiosis which encompasses the remodeling of multiple signaling pathways and the reorganization of cellular organelles. Collectively, this differentiation endows the egg with the ability to activate at fertilization and to promote the egg-to-embryo transition. Oocyte maturation is associated with changes in the electrical properties of the plasma membrane and alterations in the function and distribution of ion channels. Therefore, variations on the pattern of expression, distribution, and function of ion channels and transporters during oocyte maturation are fundamental to reproductive success. Ion channels and transporters are important in regulating membrane potential, but also in the case of calcium (Ca2+), they play a critical role in modulating intracellular signaling pathways. In the context of fertilization, Ca2+ has been shown to be the universal activator of development at fertilization, playing a central role in early events associated with egg activation and the egg-to-embryo transition. These early events include the block of polyspermy, the completion of meiosis and the transition to the embryonic mitotic divisions. In this review, we discuss the role of ion channels during oocyte maturation, fertilization and early embryonic development. We will describe how ion channel studies in Xenopus oocytes, an extensively studied model of oocyte maturation, translate into a greater understanding of the role of ion channels in mammalian oocyte physiology.
Collapse
Affiliation(s)
- Ingrid Carvacho
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile
| | - Matthias Piesche
- Biomedical Research Laboratories, Medicine Faculty, Universidad Católica del Maule, Talca, Chile
| | - Thorsten J. Maier
- Department of Anesthesiology, Intensive Care Medicine and Pain Therapy, Goethe-University Hospital, Frankfurt, Germany
| | - Khaled Machaca
- Department of Physiology and Biophysics, Weill Cornell-Medicine-Qatar, Education City, Qatar Foundation, Doha, Qatar
| |
Collapse
|
3
|
Plattner H, Verkhratsky A. Inseparable tandem: evolution chooses ATP and Ca2+ to control life, death and cellular signalling. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0419. [PMID: 27377729 DOI: 10.1098/rstb.2015.0419] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2016] [Indexed: 01/01/2023] Open
Abstract
From the very dawn of biological evolution, ATP was selected as a multipurpose energy-storing molecule. Metabolism of ATP required intracellular free Ca(2+) to be set at exceedingly low concentrations, which in turn provided the background for the role of Ca(2+) as a universal signalling molecule. The early-eukaryote life forms also evolved functional compartmentalization and vesicle trafficking, which used Ca(2+) as a universal signalling ion; similarly, Ca(2+) is needed for regulation of ciliary and flagellar beat, amoeboid movement, intracellular transport, as well as of numerous metabolic processes. Thus, during evolution, exploitation of atmospheric oxygen and increasingly efficient ATP production via oxidative phosphorylation by bacterial endosymbionts were a first step for the emergence of complex eukaryotic cells. Simultaneously, Ca(2+) started to be exploited for short-range signalling, despite restrictions by the preset phosphate-based energy metabolism, when both phosphates and Ca(2+) interfere with each other because of the low solubility of calcium phosphates. The need to keep cytosolic Ca(2+) low forced cells to restrict Ca(2+) signals in space and time and to develop energetically favourable Ca(2+) signalling and Ca(2+) microdomains. These steps in tandem dominated further evolution. The ATP molecule (often released by Ca(2+)-regulated exocytosis) rapidly grew to be the universal chemical messenger for intercellular communication; ATP effects are mediated by an extended family of purinoceptors often linked to Ca(2+) signalling. Similar to atmospheric oxygen, Ca(2+) must have been reverted from a deleterious agent to a most useful (intra- and extracellular) signalling molecule. Invention of intracellular trafficking further increased the role for Ca(2+) homeostasis that became critical for regulation of cell survival and cell death. Several mutually interdependent effects of Ca(2+) and ATP have been exploited in evolution, thus turning an originally unholy alliance into a fascinating success story.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.
Collapse
Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Alexei Verkhratsky
- Faculty of Biological Sciences, University of Manchester, Manchester M13 9PT, UK Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain Department of Neurosciences, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain University of Nizhny Novgorod, Nizhny Novgorod 603022, Russia
| |
Collapse
|
4
|
Abstract
Ca2+ entry into the cell via store-operated Ca2+ release-activated Ca2+ (CRAC) channels triggers diverse signaling cascades that affect cellular processes like cell growth, gene regulation, secretion, and cell death. These store-operated Ca2+ channels open after depletion of intracellular Ca2+ stores, and their main features are fully reconstituted by the two molecular key players: the stromal interaction molecule (STIM) and Orai. STIM represents an endoplasmic reticulum-located Ca2+ sensor, while Orai forms a highly Ca2+-selective ion channel in the plasma membrane. Functional as well as mutagenesis studies together with structural insights about STIM and Orai proteins provide a molecular picture of the interplay of these two key players in the CRAC signaling cascade. This review focuses on the main experimental advances in the understanding of the STIM1-Orai choreography, thereby establishing a portrait of key mechanistic steps in the CRAC channel signaling cascade. The focus is on the activation of the STIM proteins, the subsequent coupling of STIM1 to Orai1, and the consequent structural rearrangements that gate the Orai channels into the open state to allow Ca2+ permeation into the cell.
Collapse
Affiliation(s)
- Isabella Derler
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria; and
| | - Isaac Jardin
- Department of Physiology, University of Extremadura, Cáceres, Spain
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Linz, Austria; and
| |
Collapse
|
5
|
Derler I, Jardin I, Stathopulos PB, Muik M, Fahrner M, Zayats V, Pandey SK, Poteser M, Lackner B, Absolonova M, Schindl R, Groschner K, Ettrich R, Ikura M, Romanin C. Cholesterol modulates Orai1 channel function. Sci Signal 2016; 9:ra10. [PMID: 26814231 DOI: 10.1126/scisignal.aad7808] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
STIM1 (stromal interaction molecule 1) and Orai proteins are the essential components of Ca(2+) release-activated Ca(2+) (CRAC) channels. We focused on the role of cholesterol in the regulation of STIM1-mediated Orai1 currents. Chemically induced cholesterol depletion enhanced store-operated Ca(2+) entry (SOCE) and Orai1 currents. Furthermore, cholesterol depletion in mucosal-type mast cells augmented endogenous CRAC currents, which were associated with increased degranulation, a process that requires calcium influx. Single point mutations in the Orai1 amino terminus that would be expected to abolish cholesterol binding enhanced SOCE to a similar extent as did cholesterol depletion. The increase in Orai1 activity in cells expressing these cholesterol-binding-deficient mutants occurred without affecting the amount in the plasma membrane or the coupling of STIM1 to Orai1. We detected cholesterol binding to an Orai1 amino-terminal fragment in vitro and to full-length Orai1 in cells. Thus, our data showed that Orai1 senses the amount of cholesterol in the plasma membrane and that the interaction of Orai1 with cholesterol inhibits its activity, thereby limiting SOCE.
Collapse
Affiliation(s)
- Isabella Derler
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria.
| | - Isaac Jardin
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Martin Muik
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Marc Fahrner
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Vasilina Zayats
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, CZ-373 33 Nové Hrady, Czech Republic
| | - Saurabh K Pandey
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, CZ-373 33 Nové Hrady, Czech Republic
| | - Michael Poteser
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Barbara Lackner
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Marketa Absolonova
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Rainer Schindl
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria
| | - Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Harrachgasse 21/4, 8010 Graz, Austria
| | - Rüdiger Ettrich
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, CZ-373 33 Nové Hrady, Czech Republic
| | - Mitsu Ikura
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Christoph Romanin
- Institute of Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz, Austria.
| |
Collapse
|
6
|
Singaravelu K, Nelson C, Bakowski D, de Brito OM, Ng SW, Di Capite J, Powell T, Scorrano L, Parekh AB. Mitofusin 2 regulates STIM1 migration from the Ca2+ store to the plasma membrane in cells with depolarized mitochondria. J Biol Chem 2011; 286:12189-201. [PMID: 21220420 DOI: 10.1074/jbc.m110.174029] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Store-operated Ca2+ channels in the plasma membrane (PM) are activated by the depletion of Ca2+ from the endoplasmic reticulum (ER) and constitute a widespread and highly conserved Ca2+ influx pathway. After store emptying, the ER Ca2+ sensor STIM1 forms multimers, which then migrate to ER-PM junctions where they activate the Ca2+ release-activated Ca2+ channel Orai1. Movement of an intracellular protein to such specialized sites where it gates an ion channel is without precedence, but the fundamental question of how STIM1 migrates remains unresolved. Here, we show that trafficking of STIM1 to ER-PM junctions and subsequent Ca2+ release-activated Ca2+ channel activity is impaired following mitochondrial depolarization. We identify the dynamin-related mitochondrial protein mitofusin 2, mutations of which causes the inherited neurodegenerative disease Charcot-Marie-Tooth IIa in humans, as an important component of this mechanism. Our results reveal a molecular mechanism whereby a mitochondrial fusion protein regulates protein trafficking across the endoplasmic reticulum and reveals a homeostatic mechanism whereby mitochondrial depolarization can inhibit store-operated Ca2+ entry, thereby reducing cellular Ca2+ overload.
Collapse
Affiliation(s)
- Karthika Singaravelu
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Stiber JA, Rosenberg PB. The role of store-operated calcium influx in skeletal muscle signaling. Cell Calcium 2010; 49:341-9. [PMID: 21176846 DOI: 10.1016/j.ceca.2010.11.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 11/29/2010] [Indexed: 11/29/2022]
Abstract
In cardiac and skeletal muscle Ca(2+) release from intracellular stores triggers actomyosin cross-bridge formation and the generation of contractile force. In the face of large fluctuations of intracellular calcium ([Ca(2+)](i)) that occur with contractile activity, myocytes are able to sense and respond to changes in workload and patterns of activation through calcium signaling pathways which modulate gene expression and cellular metabolism. Store-operated calcium influx has emerged as a mechanism by which calcium signaling pathways are activated in order to respond to the changing demands of the myocyte. Abnormalities of store-operated calcium influx may contribute to maladaptive muscle remodeling in multiple disease states. The importance of store-operated calcium influx in muscle is confirmed in mice lacking STIM1 which die perinatally and in patients with mutations on STIM1 or Orai1 who exhibit a myopathy exhibited by hypotonia. In this review, we consider the role of store-operated Ca(2+) entry into skeletal muscle as a critical mediator of Ca(2+) dependent gene expression and how alterations in Ca(2+) influx may influence muscle development and disease.
Collapse
Affiliation(s)
- Jonathan A Stiber
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States
| | | |
Collapse
|
8
|
Disli OM, Ozdemir E, Berkan O, Bagcivan I, Durmus N, Parlak A. Rho-kinase inhibitors Y-27632 and fasudil prevent agonist-induced vasospasm in human radial artery. Can J Physiol Pharmacol 2010; 87:595-601. [PMID: 19767883 DOI: 10.1139/y09-043] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Radial artery (RA) vasospasm remains a potential cause of early graft failure after coronary artery bypass graft surgery, despite pretreatment with alpha-adrenergic or calcium channel blockers. Our aim was to investigate the mechanism of the vasorelaxant effects of Rho-kinase inhibitors (Y-27632 and fasudil) on the human RA. Segments were obtained from 30 patients undergoing coronary artery bypass graft and were divided into 3-4 mm vascular rings. The rings were stimulated with 10(-5) mol/L phenylephrine (PE) by using the isolated tissue bath technique and were relaxed with 10(-6) mol/L acetylcholine. Relaxation responses were recorded for Y-27632 (10(-9)-10(-4) mol/L), fasudil (10(-9)-10(-4) mol/L), and sodium nitroprusside (SNP) (10(-9)-10(-5) mol/L). Y-27632 and fasudil relaxation responses were repeated in either N(G)-nitro-L-arginine (L-NNA), which is a specific endothelial nitric oxide synthase inhibitor, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), which is a guanylate cyclase inhibitor. SNP relaxation responses were repeated in 10(-8) mol/L Y-27632 and 10(-8) mol/L fasudil. Y-27632 and fasudil caused concentration-dependent vasorelaxation in RA rings precontracted with PE, and maximal relaxation (100%) was recorded at the highest concentration used (10(-4) mol/L). The vasorelaxant effects of Y-27632 and fasudil were significantly reduced in the presence of L-NNA and ODQ, and the pD2 values of Y-27632 and fasudil were not changed. The vasorelaxant effects of SNP were significantly increased in the presence of Y-27632 and fasudil, and the pD(2) values of SNP were not changed. These findings indicate that Y-27632 and fasudil caused concentration-dependent vasorelaxation in the RA rings. Because this effect was decreased in a dose-dependent manner by L-NNA and ODQ, the relaxant effects of Y-27632 and fasudil could be due to stimulation by nitric oxide that is being released. Rho-kinase inhibitors may have an important role in preventing vasospasm in arterial grafts used for coronary artery surgery.
Collapse
Affiliation(s)
- Olcay Murat Disli
- Department of Cardiovascular Surgery, Cumhuriyet University School of Medicine, Sivas 58140, Turkey.
| | | | | | | | | | | |
Collapse
|
9
|
Abstract
The Ca2+release-activated Ca2+ (CRAC) channel is a highly Ca2+-selective store-operated channel expressed in T cells, mast cells, and various other tissues. CRAC channels regulate critical cellular processes such as gene expression, motility, and the secretion of inflammatory mediators. The identification of Orai1, a key subunit of the CRAC channel pore, and STIM1, the endoplasmic reticulum (ER) Ca2+ sensor, have provided the tools to illuminate the mechanisms of regulation and the pore properties of CRAC channels. Recent evidence indicates that the activation of CRAC channels by store depletion involves a coordinated series of steps, which include the redistributions of STIM1 and Orai1, direct physical interactions between these proteins, and conformational changes in Orai1, culminating in channel activation. Additional studies have revealed that the high Ca2+ selectivity of CRAC channels arises from the presence of an intrapore Ca2+ binding site, the properties of which are finely honed to occlude the permeation of the much more prevalent Na+. Structure-function studies have led to the identification of the potential pore-binding sites for Ca2+, providing a firm framework for understanding the mechanisms of selectivity and gating of the CRAC channel. This review summarizes recent progress in understanding the mechanisms of CRAC channel activation, pore properties, and modulation.
Collapse
Affiliation(s)
- Murali Prakriya
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University School of Medicine, Chicago, IL 60611, USA.
| |
Collapse
|
10
|
Sours-Brothers S, Ding M, Graham S, Ma R. Interaction between TRPC1/TRPC4 assembly and STIM1 contributes to store-operated Ca2+ entry in mesangial cells. Exp Biol Med (Maywood) 2009; 234:673-82. [PMID: 19307462 DOI: 10.3181/0809-rm-279] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Although Orai1 protein was recently identified as the component of CRAC channels in hematopoietic cells, store-operated channels (SOC) in other cell types may have a different molecular entity. Also, the activation mechanism of SOC remains unclear, in general. In the present study, we tested the hypothesis that TRPC1 and TRPC4 proteins were functional subunits of SOC in glomerular mesangial cells (MCs) and that STIM1 was required for the channel activation through interaction with the TRPC proteins. In cultured human MCs, cell-attached patch clamp and fura-2 fluorescence measurements showed that single knockdown of either TRPC1 or TRPC4 significantly attenuated thapsigargin-induced membrane currents and Ca2+ entry as well as Ang II-induced channel activity. Double knockdown of both TRPCs resulted in a comparable inhibition on store-operated Ca2+ entry with single knockdown of either TRPC. Consistent with our previous report, co-immunoprecipitation showed a physical interaction between TRPC1 and TRPC4. Furthermore, we found that knockdown of STIM1 using RNAi significantly reduced the thapsigargin-stimulated membrane currents. Co-immunoprecipitation showed that STIM1 interacted with TRPC4, but not TRPC1. In addition, simultaneous inhibition of STIM1 and TRPC1 resulted in a comparable effect on SOC with single inhibition of either one of them. Taken together, we conclude that in glomerular mesangial cells, the TRPC1/TRPC4 complexes constitute the functional subunits of SOC and that the interaction between STIM1 and TRPC4 may be the mechanism for the activation of the channels.
Collapse
Affiliation(s)
- Sherry Sours-Brothers
- Department of Integrative Physiology, University of North Texas Health Science Center, RES-302G, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
| | | | | | | |
Collapse
|
11
|
Yamashita M, Navarro-Borelly L, McNally BA, Prakriya M. Orai1 mutations alter ion permeation and Ca2+-dependent fast inactivation of CRAC channels: evidence for coupling of permeation and gating. ACTA ACUST UNITED AC 2008; 130:525-40. [PMID: 17968026 PMCID: PMC2151669 DOI: 10.1085/jgp.200709872] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ca(2+) entry through store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels is an essential trigger for lymphocyte activation and proliferation. The recent identification of Orai1 as a key CRAC channel pore subunit paves the way for understanding the molecular basis of Ca(2+) selectivity, ion permeation, and regulation of CRAC channels. Previous Orai1 mutagenesis studies have indicated that a set of conserved acidic amino acids in trans membrane domains I and III and in the I-II loop (E106, E190, D110, D112, D114) are essential for the CRAC channel's high Ca(2+) selectivity. To further dissect the contribution of Orai1 domains important for ion permeation and channel gating, we examined the role of these conserved acidic residues on pore geometry, properties of Ca(2+) block, and channel regulation by Ca(2+). We find that alteration of the acidic residues lowers Ca(2+) selectivity and results in striking increases in Cs(+) permeation. This is likely the result of enlargement of the unusually narrow pore of the CRAC channel, thus relieving steric hindrance for Cs(+) permeation. Ca(2+) binding to the selectivity filter appears to be primarily affected by changes in the apparent on-rate, consistent with a rate-limiting barrier for Ca(2+) binding. Unexpectedly, the mutations diminish Ca(2+)-mediated fast inactivation, a key mode of CRAC channel regulation. The decrease in fast inactivation in the mutant channels correlates with the decrease in Ca(2+) selectivity, increase in Cs(+) permeability, and enlargement of the pore. We propose that the structural elements involved in ion permeation overlap with those involved in the gating of CRAC channels.
Collapse
Affiliation(s)
- Megumi Yamashita
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | | | | | | |
Collapse
|
12
|
Chang WC, Di Capite J, Nelson C, Parekh AB. All-or-none activation of CRAC channels by agonist elicits graded responses in populations of mast cells. THE JOURNAL OF IMMUNOLOGY 2007; 179:5255-63. [PMID: 17911611 DOI: 10.4049/jimmunol.179.8.5255] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In nonexcitable cells, receptor stimulation evokes Ca(2+) release from the endoplasmic reticulum stores followed by Ca(2+) influx through store-operated Ca(2+) channels in the plasma membrane. In mast cells, store-operated entry is mediated via Ca(2+) release-activated Ca(2+) (CRAC) channels. In this study, we find that stimulation of muscarinic receptors in cultured mast cells results in Ca(2+)-dependent activation of protein kinase Calpha and the mitogen activated protein kinases ERK1/2 and this is required for the subsequent stimulation of the enzymes Ca(2+)-dependent phospholipase A(2) and 5-lipoxygenase, generating the intracellular messenger arachidonic acid and the proinflammatory intercellular messenger leukotriene C(4). In cell population studies, ERK activation, arachidonic acid release, and leukotriene C(4) secretion were all graded with stimulus intensity. However, at a single cell level, Ca(2+) influx was related to agonist concentration in an essentially all-or-none manner. This paradox of all-or-none CRAC channel activation in single cells with graded responses in cell populations was resolved by the finding that increasing agonist concentration recruited more mast cells but each cell responded by generating all-or-none Ca(2+) influx. These findings were extended to acutely isolated rat peritoneal mast cells where muscarinic or P2Y receptor stimulation evoked all-or-none activation of Ca(2+)entry but graded responses in cell populations. Our results identify a novel way for grading responses to agonists in immune cells and highlight the importance of CRAC channels as a key pharmacological target to control mast cell activation.
Collapse
Affiliation(s)
- Wei-Chiao Chang
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | | | | | | |
Collapse
|
13
|
Alapati VR, McKenzie C, Blair A, Kenny D, MacDonald A, Shaw AM. Mechanisms of U46619- and 5-HT-induced contraction of bovine pulmonary arteries: role of chloride ions. Br J Pharmacol 2007; 151:1224-34. [PMID: 17592513 PMCID: PMC2189823 DOI: 10.1038/sj.bjp.0707338] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Thromboxane A(2) and 5-hydroxytryptamine (5-HT) are implicated in pulmonary hypertension. The involvement of chloride, voltage-operated calcium channels (VOCCs), store-operated calcium channels (SOCCs) and the Rho kinase in the contractile response of bovine pulmonary arteries (BPA) to the thromboxane A(2) mimetic U46619 and 5-HT was investigated. EXPERIMENTAL APPROACH Endothelium-intact ring segments of BPA were mounted in Krebs/Henseleit buffer (37 degrees C) under a tension of 2g and gassed with 95%O(2)/5%CO(2). KEY RESULTS Depletion or removal of extracellular chloride, inhibition of chloride and SOCC, Na:K:2Cl, Cl/HCO(3), Rho kinase inhibited contractions to U46619. Combining Rho kinase inhibition and chloride channel blockade (with NPPB) almost abolished the contractions to U46619. In contrast 5-HT-induced contraction was inhibited by verapamil and mibefradil. Depletion of stored calcium with caffeine almost abolished the response to U46619 but not 5-HT. The contraction by the sarco(endo)plasmic reticulum Ca(2+)-ATPase inhibitor CPA was abolished by SOCC and chloride channel blockade (with NPPB) and by chloride depletion. CONCLUSIONS AND IMPLICATIONS This study suggests that the contractile response of BPA to U46619 involves Rho kinase together with a chloride-sensitive mechanism, which does not involve VOCC but may have a role in calcium release and calcium entry via SOCC. In contrast contraction of the BPA by 5-HT appears to involve verapamil- and mibefradil-sensitive VOCC. This study may indicate that the use of calcium channel blockers in the management of pulmonary hypertension may not always be effective and that Rho kinase and chloride channels may be targets for the development of new therapies.
Collapse
Affiliation(s)
- V R Alapati
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University Glasgow, UK
| | - C McKenzie
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University Glasgow, UK
| | - A Blair
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University Glasgow, UK
| | - D Kenny
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University Glasgow, UK
| | - A MacDonald
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University Glasgow, UK
| | - A M Shaw
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University Glasgow, UK
- Author for correspondence:
| |
Collapse
|
14
|
Chung SC, Limnander A, Kurosaki T, Weiss A, Korenbrot JI. Coupling Ca2+ store release to Icrac channel activation in B lymphocytes requires the activity of Lyn and Syk kinases. ACTA ACUST UNITED AC 2007; 177:317-28. [PMID: 17452533 PMCID: PMC2064139 DOI: 10.1083/jcb.200702050] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Activation of the B cell receptor complex in B lymphocytes causes Ca2+ release from intracellular stores, which, in turn, activates ion channels known as Icrac. We investigated the mechanisms that link Ca2+ store release to channel gating in DT40 B lymphocyte cell lines genetically manipulated to suppress the expression of several tyrosine kinases: Btk, Lyn, Syk, and the Blnk adaptor molecule. The simultaneous but not the independent suppression of Lyn and Syk expression prevents the activation of Icrac without interfering with thapsigargin-sensitive Ca2+ store release. Icrac activation by Ca2+ is reversed in mutant cells by the homologous expression of the missing kinases. Pharmacological inhibition of kinase activity by LavendustinA and PP2 cause the same functional deficit as the genetic suppression of enzyme expression. Biochemical assays demonstrate that kinase activity is required as a tonic signal: targets must be phosphorylated to link Ca2+ store release to Icrac gating. The action of kinases on Icrac activation does not arise from control of the expression level of the stromal interaction molecule 1 and Orai1 proteins.
Collapse
Affiliation(s)
- S Clare Chung
- Department of Physiology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | | | | | | | | |
Collapse
|
15
|
Zhou H, Iwasaki H, Nakamura T, Nakamura K, Maruyama T, Hamano SI, Ozaki S, Mizutani A, Mikoshiba K. 2-Aminoethyl diphenylborinate analogues: Selective inhibition for store-operated Ca2+ entry. Biochem Biophys Res Commun 2007; 352:277-82. [PMID: 17140548 DOI: 10.1016/j.bbrc.2006.10.174] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2006] [Accepted: 10/25/2006] [Indexed: 11/28/2022]
Abstract
Capacitative calcium entry (CCE), the mechanism that replenishes the internal Ca2+ stores with Ca2+ from the extracellular milieu in response to depletion of the store, is mediated by Ca2+ channels in the plasma membrane generally referred to as store-operated channels (SOCs). However, the roles of SOCs in the more physiological context have been fully elucidated. 2-Aminoethyl diphenylborinate (2-APB) strongly inhibits SOCs, as well as inositol-1,4,5 trisphosphate (IP3) receptors. In the present study, we screened a library of 166 2-APB analogues for effects on CCE and IP3-induced Ca2+ release in order to discover specific SOC inhibitors, and found that some blocked both store-operated and receptor-operated Ca2+ influx more strongly and selectively than 2-APB. Indeed, these new compounds ceased the prolonged intracellular Ca2+ oscillations induced by a low concentration of ATP in CHO-K1 cells. These novel SOC inhibitors will be valuable pharmacological and biochemical tools for elucidating the physiological roles.
Collapse
Affiliation(s)
- Hong Zhou
- The Division of Molecular Neurobiology, Institute of Medical Sciences, University of Tokyo, 4-6-1 Shirokanedai, Tokyo 108-8639, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Xu SZ, Boulay G, Flemming R, Beech DJ. E3-targeted anti-TRPC5 antibody inhibits store-operated calcium entry in freshly isolated pial arterioles. Am J Physiol Heart Circ Physiol 2006; 291:H2653-9. [PMID: 16861696 DOI: 10.1152/ajpheart.00495.2006] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Smooth muscle cells in arterioles have pivotal roles in the determination of blood pressure and distribution of local blood flow. The cells exhibit calcium entry in response to passive store depletion, but the mechanisms and relevance of this phenomenon are poorly understood. Previously, a role for canonical transient receptor potential 1 (TRPC1) was indicated, but heterologous expression studies showed TRPC1 to have poor function in isolation, suggesting a requirement for additional proteins. Here we test the hypothesis that TRPC5 is such an additional protein, because TRPC5 forms heteromultimeric channels with TRPC1, and RNA encoding TRPC5 is present in arterioles. Recordings were from arteriolar fragments freshly isolated from rabbit pial membrane. Ionic current in response to store depletion has properties like that of the TRPC1/TRPC5 heteromultimer, and so the effect of the E3-targeted, externally acting, anti-TRPC5 blocking antibody (T5E3) was explored. T5E3 suppressed calcium entry in store-depleted arterioles but had no effect in the absence of store depletion. T5E3 preadsorbed to its antigenic peptide did not inhibit calcium entry. TRPC6 is commonly detected in smooth muscle and is present in the arterioles, but T5E3 had no effect on TRPC6. The data suggest that calcium entry occurring in response to passive store depletion in smooth muscle cells of arterioles involves TRPC5 as well as TRPC1.
Collapse
Affiliation(s)
- Shang-Zhong Xu
- Institute of Membrane and Systems Biology, University of Leeds, Leeds, LS2 9JT, UK
| | | | | | | |
Collapse
|
17
|
Prakriya M, Lewis RS. Regulation of CRAC channel activity by recruitment of silent channels to a high open-probability gating mode. ACTA ACUST UNITED AC 2006; 128:373-86. [PMID: 16940559 PMCID: PMC2151560 DOI: 10.1085/jgp.200609588] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
CRAC (calcium release-activated Ca2+) channels attain an extremely high selectivity for Ca2+ from the blockade of monovalent cation permeation by Ca2+ within the pore. In this study we have exploited the blockade by Ca2+ to examine the size of the CRAC channel pore, its unitary conductance for monovalent cations, and channel gating properties. The permeation of a series of methylammonium compounds under divalent cation-free conditions indicates a minimum pore diameter of 3.9 Å. Extracellular Ca2+ blocks monovalent flux in a manner consistent with a single intrapore site having an effective Ki of 20 μM at −110 mV. Block increases with hyperpolarization, but declines below −100 mV, most likely due to permeation of Ca2+. Analysis of monovalent current noise induced by increasing levels of block by extracellular Ca2+ indicates an open probability (Po) of ∼0.8. By extrapolating the variance/mean current ratio to the condition of full blockade (Po = 0), we estimate a unitary conductance of ∼0.7 pS for Na+, or three to fourfold higher than previous estimates. Removal of extracellular Ca2+ causes the monovalent current to decline over tens of seconds, a process termed depotentiation. The declining current appears to result from a reduction in the number of active channels without a change in their high open probability. Similarly, low concentrations of 2-APB that enhance ICRAC increase the number of active channels while open probability remains constant. We conclude that the slow regulation of whole-cell CRAC current by store depletion, extracellular Ca2+, and 2-APB involves the stepwise recruitment of silent channels to a high open-probability gating mode.
Collapse
Affiliation(s)
- Murali Prakriya
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | | |
Collapse
|
18
|
Plattner H, Hentschel J. Sub-second cellular dynamics: time-resolved electron microscopy and functional correlation. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 255:133-76. [PMID: 17178466 DOI: 10.1016/s0074-7696(06)55003-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Subcellular processes, from molecular events to organellar responses and cell movement, cover a broad scale in time and space. Clearly the extremes, such as ion channel activation are accessible only by electrophysiology, whereas numerous routine methods exist for relatively slow processes. However, many other processes, from a millisecond time scale on, can be "caught" only by methods providing appropriate time resolution. Fast freezing (cryofixation) is the method of choice in that case. In combination with follow-up methodologies appropriate for electron microscopic (EM) analysis, with all its variations, such technologies can also provide high spatial resolution. Such analyses may include, for example, freeze-fracturing for analyzing restructuring of membrane components, scanning EM and other standard EM techniques, as well as analytical EM analyses. The latter encompass energy-dispersive x-ray microanalysis and electron spectroscopic imaging, all applicable, for instance, to the second messenger, calcium. Most importantly, when conducted in parallel, such analyses can provide a structural background to the functional analyses, such as cyclic nucleotide formation or protein de- or rephosphorylation during cell stimulation. In sum, we discuss many examples of how it is practically possible to achieve strict function-structure correlations in the sub-second time range. We complement this review by discussing alternative methods currently available to analyze fast cellular phenomena occurring in the sub-second time range.
Collapse
Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | | |
Collapse
|
19
|
Dangel GR, Lang F, Lepple-Wienhues A. Effect of sphingosine on Ca2+ entry and mitochondrial potential of Jurkat T cells--interaction with Bcl2. Cell Physiol Biochem 2005; 16:9-14. [PMID: 16121028 DOI: 10.1159/000087726] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2005] [Indexed: 01/15/2023] Open
Abstract
Triggers of Jurkat T cell apoptosis include sphingosine and ceramide. Sphingosine and ceramide further inhibit capacitative Ca2+ entry (ICRAC), an effect leading to inactivation but not death of Jurkat T cells. Mitochondria are key organelles in the machinery leading to apoptosis and on the other hand have been shown to participate in the regulation of Ca2+ entry. The present experiments were performed to explore whether treatment of Jurkat T cells with sphingosine leads to apoptosis and reduced Ca2+ entry and whether those effects are sensitive to expression of the antiapoptotic protein Bcl2, localized in the outer mitochondrial membrane. Exposure of Jurkat T cells to 10 microM spingosine was according to DiOC6 fluorescence followed by mitochondrial depolarization and according to Fura-red/Fluo-3 fluorescence followed by decreased capacitative Ca2+ entry. Mitochondrial depolarization was significantly delayed in cells overexpressing wild type Bcl2 or Bcl2 targeted to the mitochondrial membrane, whereas no significant influence on mitochondrial depolarization was observed in cells expressing Bcl2 lacking the membrane targeting motif or Bcl2 targeted to the endoplasmatic reticulum. In contrast to mitochondrial potential, the blunting of capacitative Ca2+ entry following sphingosine treatment was not sensitive to mitochondrial Bcl2 expression. In conclusion sphingosine exposure leads to both, mitochondrial depolarization and inhibition of capacitative Ca2+ entry. Mitochondrial Bcl2 reverses the effect on mitochondria but not on Ca2+ entry and thus leads to dissociation of those two sequelae of sphingosine treatment.
Collapse
|
20
|
Zhang SL, Yu Y, Roos J, Kozak JA, Deerinck TJ, Ellisman MH, Stauderman KA, Cahalan MD. STIM1 is a Ca2+ sensor that activates CRAC channels and migrates from the Ca2+ store to the plasma membrane. Nature 2005; 437:902-5. [PMID: 16208375 PMCID: PMC1618826 DOI: 10.1038/nature04147] [Citation(s) in RCA: 1106] [Impact Index Per Article: 58.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2005] [Accepted: 08/22/2005] [Indexed: 01/09/2023]
Abstract
As the sole Ca2+ entry mechanism in a variety of non-excitable cells, store-operated calcium (SOC) influx is important in Ca2+ signalling and many other cellular processes. A calcium-release-activated calcium (CRAC) channel in T lymphocytes is the best-characterized SOC influx channel and is essential to the immune response, sustained activity of CRAC channels being required for gene expression and proliferation. The molecular identity and the gating mechanism of SOC and CRAC channels have remained elusive. Previously we identified Stim and the mammalian homologue STIM1 as essential components of CRAC channel activation in Drosophila S2 cells and human T lymphocytes. Here we show that the expression of EF-hand mutants of Stim or STIM1 activates CRAC channels constitutively without changing Ca2+ store content. By immunofluorescence, EM localization and surface biotinylation we show that STIM1 migrates from endoplasmic-reticulum-like sites to the plasma membrane upon depletion of the Ca2+ store. We propose that STIM1 functions as the missing link between Ca2+ store depletion and SOC influx, serving as a Ca2+ sensor that translocates upon store depletion to the plasma membrane to activate CRAC channels.
Collapse
Affiliation(s)
- Shenyuan L. Zhang
- Department of Physiology and Biophysics and Center for Immunology, University of California, Irvine, California 92697, USA
| | - Ying Yu
- Department of Physiology and Biophysics and Center for Immunology, University of California, Irvine, California 92697, USA
| | - Jack Roos
- TorreyPines Therapeutics, Inc., La Jolla, California 92037, USA
| | - J. Ashot Kozak
- Department of Physiology and Biophysics and Center for Immunology, University of California, Irvine, California 92697, USA
| | - Thomas J. Deerinck
- National Center for Microscopy and Imaging Research, Center for Research in Biological Structure and the Department of Neurosciences, University of California, San Diego, La Jolla, California 92093, USA
| | - Mark H. Ellisman
- National Center for Microscopy and Imaging Research, Center for Research in Biological Structure and the Department of Neurosciences, University of California, San Diego, La Jolla, California 92093, USA
| | | | - Michael D. Cahalan
- Department of Physiology and Biophysics and Center for Immunology, University of California, Irvine, California 92697, USA
- Corresponding author: Michael D. Cahalan telephone: (949) 824-7776 fax: (949) 824-3143
| |
Collapse
|
21
|
Pores-Fernando AT, Bauer RA, Wurth GA, Zweifach A. Exocytic responses of single leukaemic human cytotoxic T lymphocytes stimulated by agents that bypass the T cell receptor. J Physiol 2005; 567:891-903. [PMID: 16020463 PMCID: PMC1474224 DOI: 10.1113/jphysiol.2005.089565] [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: 11/08/2022] Open
Abstract
Cytotoxic T lymphocytes kill targets via secretion of lytic agents including perforin and granzymes. Recently, new methods have been developed to monitor cytotoxic T lymphocyte degranulation. These include detecting the appearance of lysosome-associated membrane protein on the cell's surface, and monitoring decreases in cellular perforin content. We have combined these methods with microscopy and flow cytometry to provide the first analysis of how single cytotoxic T cells degranulate. We used TALL-104 human leukaemic cytotoxic T cells as a model system, and stimulated them with thapsigargin and PMA, soluble agents that mimic the two major signalling pathways activated by T cell receptor cross-linking. Our results indicate that essentially every TALL-104 cell responds to maximal stimulation by releasing about half of its lytic granule complement. This reflects complete release of the contents of half the cell's granules, rather than partial release of the contents of all of the granules. Sub-maximal stimulation reduces both the fraction of cells that respond and the magnitude of single cell responses. We find that individual cells respond to maximal stimulation with a variable latency, and provide evidence that, once it starts, degranulation is a slow process taking tens of minutes.
Collapse
Affiliation(s)
- Arun T Pores-Fernando
- Department of Physiology and Biophysics, University of Colorado Health Sciences Center, Aurora, 80045, USA
| | | | | | | |
Collapse
|
22
|
Zufall F, Ukhanov K, Lucas P, Liman ER, Leinders-Zufall T. Neurobiology of TRPC2: from gene to behavior. Pflugers Arch 2005; 451:61-71. [PMID: 15971083 DOI: 10.1007/s00424-005-1432-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Accepted: 04/01/2005] [Indexed: 11/25/2022]
Abstract
The mammalian vomeronasal organ (VNO), a part of the accessory olfactory system, plays an essential role in the sensing of pheromonal signals. The VNO has emerged as an excellent model to investigate the functional role of transient receptor potential (TRP) channels in intact neurons and intact physiological systems. TRPC2, a member of the (canonical) TRPC subfamily, is highly localized to the dendritic tip of vomeronasal sensory neurons. Phenotypic analysis of mice exhibiting a targeted deletion in the TRPC2 gene has established that TRPC2 occupies a fundamental role in the transduction machinery underlying the detection of pheromone signals by the VNO. TRPC2-deficient mice exhibit striking behavioral defects in the regulation of sexual and social behaviors. A previously unknown Ca(2+)-permeable, diacylglycerol (DAG)-activated cation channel found at the dendritic tip of vomeronasal neurons is severely defective in TRPC2 mutants, providing the first clear example for the existence of native DAG-gated cation channels in the mammalian nervous system. The experimental strategy employed in the mouse VNO now serves as a powerful model for examining the native functions of other TRP genes.
Collapse
Affiliation(s)
- Frank Zufall
- Department of Anatomy and Neurobiology and Program in Neuroscience, University of Maryland School of Medicine, 20 Penn Street, Baltimore, MD 21201-1509, USA.
| | | | | | | | | |
Collapse
|
23
|
Wilson SM, Mason HS, Ng LC, Montague S, Johnston L, Nicholson N, Mansfield S, Hume JR. Role of basal extracellular Ca2+ entry during 5-HT-induced vasoconstriction of canine pulmonary arteries. Br J Pharmacol 2005; 144:252-64. [PMID: 15655514 PMCID: PMC1575999 DOI: 10.1038/sj.bjp.0706077] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
1. Measurements of artery contraction, cytosolic [Ca(2+)], and Ca(2+) permeability were made to examine contractile and cytosolic [Ca(2+)] responses of canine pulmonary arteries and isolated cells to 5-hydroxytryptamine (5-HT), and to determine the roles of intracellular Ca(2+) release and extracellular Ca(2+) entry in 5-HT responses. 2. The EC(50) for 5-HT-mediated contractions and cytosolic [Ca(2+)] increases was approximately 10(-7) M and responses were inhibited by ketanserin, a 5-HT(2A)-receptor antagonist. 3. 5-HT induced cytosolic [Ca(2+)] increases were blocked by 20 microM Xestospongin-C and by 2-APB (IC(50)=32 microM inhibitors of InsP(3) receptor activation. 4. 5-HT-mediated contractions were reliant on release of InsP(3) but not ryanodine-sensitive Ca(2+) stores. 5. 5-HT-mediated contractions and cytosolic [Ca(2+)] increases were partially inhibited by 10 microM nisoldipine, a voltage-dependent Ca(2+) channel blocker. 6. Extracellular Ca(2+) removal reduced 5-HT-mediated contractions further than nisoldipine and ablated cytosolic [Ca(2+)] increases and [Ca(2+)] oscillations. Similar to Ca(2+) removal, Ni(2+) reduced cytosolic [Ca(2+)] and [Ca(2+)] oscillations. 7. Mn(2+) quench of fura-2 and voltage-clamp experiments showed that 5-HT failed to activate any significant voltage-independent Ca(2+) entry pathways, including store-operated and receptor-activated nonselective cation channels. Ni(2+) but not nisoldipine or Gd(3+) blocked basal Mn(2+) entry. 8. Voltage-clamp experiments showed that simultaneous depletion of both InsP(3) and ryanodine-sensitive intracellular Ca(2+) stores activates a current with linear voltage dependence and a reversal potential consistent with it being a nonselective cation channel. 5-HT did not activate this current. 9. Basal Ca(2+) entry, rather than CCE, is important to maintain 5-HT-induced cytosolic [Ca(2+)] responses and contraction in canine pulmonary artery.
Collapse
Affiliation(s)
- Sean M Wilson
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
| | - Helen S Mason
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
| | - Lih C Ng
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
| | - Stephen Montague
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
| | - Louise Johnston
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
| | - Neil Nicholson
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
| | - Sarah Mansfield
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
| | - Joseph R Hume
- Department of Pharmacology, University of Nevada School of Medicine, Reno, MS 318, NV 89557, U.S.A
- Author for correspondence:
| |
Collapse
|
24
|
Klepeis VE, Weinger I, Kaczmarek E, Trinkaus-Randall V. P2Y receptors play a critical role in epithelial cell communication and migration. J Cell Biochem 2005; 93:1115-33. [PMID: 15449317 DOI: 10.1002/jcb.20258] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cellular injury induces a complex series of events that involves Ca2+ signaling, cell communication, and migration. One of the first responses following mechanical injury is the propagation of a Ca2+ wave (Klepeis et al. [2001] J Cell Sci 114(Pt 23):4185-4195). The wave is generated by the extracellular release of ATP, which also induces phosphorylation of ERK (Yang et al. [2004] J Cell Biochem 91(5):938-950). ATP and other nucleotides, which bind to and activate specific purinergic receptors were used to mimic injury. Our goal was to determine which of the P2Y purinergic receptors are expressed and stimulated in corneal epithelial cells and which signaling pathways are activated leading to changes in cell migration, an event critical for wound closure. In this study, we demonstrated that the P2Y1, P2Y2, P2Y4, P2Y6, and P2Y11 receptors were present in corneal epithelial cells. A potency profile was determined by Ca2+ imaging for nucleotide agonists as follows: ATP > or = UTP > ADP > or = UDP. In contrast, negligible responses were seen for beta,gamma-meATP, a general P2X receptor agonist and adenosine, a P1 receptor agonist. Homologous desensitization of the Ca2+ response was observed for the four nucleotides. However, P2Y receptor internalization and degradation was not detected following stimulation with ATP, which is in contrast to EGFR internalization observed in response to EGF. ATP induced cell migration was comparable to that of EGF and was maximal at 1 microM. Cells exposed to ATP, UTP, ADP, and UDP demonstrated a rapid twofold increase in phosphorylation of paxillin at Y31 and Y118, however, there was no activation elicited by beta,gamma-meATP or adenosine. Additional studies demonstrated that wound closure was inhibited by reactive blue 2. These results indicate that P2Y receptors play a critical role in the injury repair process.
Collapse
Affiliation(s)
- Veronica E Klepeis
- Department of Pathology, Boston University School of Medicine, Boston, MA, 02118
| | | | | | | |
Collapse
|
25
|
Abstract
In electrically nonexcitable cells, Ca2+influx is essential for regulating a host of kinetically distinct processes involving exocytosis, enzyme control, gene regulation, cell growth and proliferation, and apoptosis. The major Ca2+entry pathway in these cells is the store-operated one, in which the emptying of intracellular Ca2+stores activates Ca2+influx (store-operated Ca2+entry, or capacitative Ca2+entry). Several biophysically distinct store-operated currents have been reported, but the best characterized is the Ca2+release-activated Ca2+current, ICRAC. Although it was initially considered to function only in nonexcitable cells, growing evidence now points towards a central role for ICRAC-like currents in excitable cells too. In spite of intense research, the signal that relays the store Ca2+content to CRAC channels in the plasma membrane, as well as the molecular identity of the Ca2+sensor within the stores, remains elusive. Resolution of these issues would be greatly helped by the identification of the CRAC channel gene. In some systems, evidence suggests that store-operated channels might be related to TRP homologs, although no consensus has yet been reached. Better understood are mechanisms that inactivate store-operated entry and hence control the overall duration of Ca2+entry. Recent work has revealed a central role for mitochondria in the regulation of ICRAC, and this is particularly prominent under physiological conditions. ICRACtherefore represents a dynamic interplay between endoplasmic reticulum, mitochondria, and plasma membrane. In this review, we describe the key electrophysiological features of ICRACand other store-operated Ca2+currents and how they are regulated, and we consider recent advances that have shed insight into the molecular mechanisms involved in this ubiquitous and vital Ca2+entry pathway.
Collapse
Affiliation(s)
- Anant B Parekh
- Department of Physiology, University of Oxford, United Kingdom.
| | | |
Collapse
|
26
|
Brünig I, Kaech S, Brinkhaus H, Oertner TG, Matus A. Influx of extracellular calcium regulates actin-dependent morphological plasticity in dendritic spines. Neuropharmacology 2005; 47:669-76. [PMID: 15458838 DOI: 10.1016/j.neuropharm.2004.07.038] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Revised: 07/27/2004] [Accepted: 07/27/2004] [Indexed: 10/26/2022]
Abstract
Dendritic spines contain a specialized cytoskeleton composed of dynamic actin filaments capable of producing rapid changes in their motility and morphology. Transient changes in Ca2+ levels in the spine cytoplasm have been associated with the modulation of these effects in a variety of ways. To characterize the contribution of Ca2+ fluxes originating through different pathways to these phenomena, we used time-lapse imaging of cultured hippocampal neurons expressing GFP-actin to follow the influence of postsynaptic neurotransmitter receptors, voltage-activated Ca2+ channels and release from internal Ca2+ stores on spine actin dynamics. Stimulation of AMPA receptors produced a rapid blockade of actin-dependent spine motility that was immediately reversible when AMPA was removed. Stimulation of NMDA receptors also blocked spine motility but in this case suppression of actin dynamics was delayed by up to 30 min depending on NMDA concentration and motility was never seen to recover when NMDA was removed. These effects could be mimicked by depolarizing neurons under appropriate circumstances demonstrating the involvement of voltage-activated Ca2+ channels in AMPA receptor-mediated effects and the receptor associated Ca2+ channel in the effects of NMDA. Caffeine, an agent that releases Ca2+ from internal stores, had no immediate effect on spine actin, a result compatible with the lack of caffeine-releasable Ca2+ in cultured hippocampal neurons under resting conditions. Blocking internal store function by thapsigargin led to a delayed suppression of spine actin dynamics that was dependent on extracellular Ca2+. Together these results indicate the common involvement of changes in Ca2+ levels in modulating actin-dependent effects on dendritic spine motility and morphology through several modes of electrophysiological activation.
Collapse
Affiliation(s)
- Ina Brünig
- Friedrich Miescher Institute, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | | | | | | | | |
Collapse
|
27
|
Moreau B, Straube S, Fisher RJ, Putney JW, Parekh AB. Ca2+-calmodulin-dependent facilitation and Ca2+ inactivation of Ca2+ release-activated Ca2+ channels. J Biol Chem 2004; 280:8776-83. [PMID: 15611075 DOI: 10.1074/jbc.m409619200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In non-excitable cells, one major route for Ca2+ influx is through store-operated Ca2+ channels in the plasma membrane. These channels are activated by the emptying of intracellular Ca2+ stores, and in some cell types store-operated influx occurs through Ca2+ release-activated Ca2+ (CRAC) channels. Here, we report that intracellular Ca2+ modulates CRAC channel activity through both positive and negative feedback steps in RBL-1 cells. Under conditions in which cytoplasmic Ca2+ concentration can fluctuate freely, we find that store-operated Ca2+ entry is impaired either following overexpression of a dominant negative calmodulin mutant or following whole-cell dialysis with a calmodulin inhibitory peptide. The peptide had no inhibitory effect when intracellular Ca2+ was buffered strongly at low levels. Hence, Ca2+-calmodulin is not required for the activation of CRAC channels per se but is an important regulator under physiological conditions. We also find that the plasma membrane Ca2+ATPase is the dominant Ca2+ efflux pathway in these cells. Although the activity of the Ca2+ pump is regulated by calmodulin, the store-operated Ca2+ entry is more sensitive to inhibition by the calmodulin mutant than by Ca2+ extrusion. Hence, these two plasmalemmal Ca2+ transport systems may differ in their sensitivities to endogenous calmodulin. Following the activation of Ca2+ entry, the rise in intracellular Ca2+ subsequently feeds back to further inhibit Ca2+ influx. This slow inactivation can be activated by a relatively brief Ca2+ influx (30-60 s); it reverses slowly and is not altered by overexpression of the calmodulin mutant. Hence, the same messenger, intracellular Ca2+, can both facilitate and inactivate Ca2+ entry through store-operated CRAC channels and through different mechanisms.
Collapse
Affiliation(s)
- Ben Moreau
- Laboratory of Cellular and Molecular Signalling, Department of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, United Kingdom
| | | | | | | | | |
Collapse
|
28
|
Beech DJ, Muraki K, Flemming R. Non-selective cationic channels of smooth muscle and the mammalian homologues of Drosophila TRP. J Physiol 2004; 559:685-706. [PMID: 15272031 PMCID: PMC1665181 DOI: 10.1113/jphysiol.2004.068734] [Citation(s) in RCA: 196] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Accepted: 07/20/2004] [Indexed: 12/25/2022] Open
Abstract
Throughout the body there are smooth muscle cells controlling a myriad of tubes and reservoirs. The cells show enormous diversity and complexity compounded by a plasticity that is critical in physiology and disease. Over the past quarter of a century we have seen that smooth muscle cells contain--as part of a gamut of ion-handling mechanisms--a family of cationic channels with significant permeability to calcium, potassium and sodium. Several of these channels are sensors of calcium store depletion, G-protein-coupled receptor activation, membrane stretch, intracellular Ca2+, pH, phospholipid signals and other factors. Progress in understanding the channels has, however, been hampered by a paucity of specific pharmacological agents and difficulty in identifying the underlying genes. In this review we summarize current knowledge of these smooth muscle cationic channels and evaluate the hypothesis that the underlying genes are homologues of Drosophila TRP (transient receptor potential). Direct evidence exists for roles of TRPC1, TRPC4/5, TRPC6, TRPV2, TRPP1 and TRPP2, and more are likely to be added soon. Some of these TRP proteins respond to a multiplicity of activation signals--promiscuity of gating that could enable a variety of context-dependent functions. We would seem to be witnessing the first phase of the molecular delineation of these cationic channels, something that should prove a leap forward for strategies aimed at developing new selective pharmacological agents and understanding the activation mechanisms and functions of these channels in physiological systems.
Collapse
Affiliation(s)
- D J Beech
- School of Biomedical Sciences, University of Leeds, LS2 9JT, UK.
| | | | | |
Collapse
|
29
|
Zeng F, Xu SZ, Jackson PK, McHugh D, Kumar B, Fountain SJ, Beech DJ. Human TRPC5 channel activated by a multiplicity of signals in a single cell. J Physiol 2004; 559:739-50. [PMID: 15254149 PMCID: PMC1665180 DOI: 10.1113/jphysiol.2004.065391] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Here we explore the activation mechanisms of human TRPC5, a putative cationic channel that was cloned from a region of the X chromosome associated with mental retardation. No basal activity was evident but activity was induced by carbachol stimulation of muscarinic receptors independently of Ca2+ release. This is 'receptor activation', as described for mouse TRPC5. In addition, and in the absence of receptor stimulation, extracellular gadolinium (0.1 mm) activated TRPC5, an effect that was mimicked by 5-20 mm extracellular Ca2+ with intracellular Ca2+ buffered. We refer to this as 'external ionic activation'. TRPC5 was also activated by modest elevation of [Ca2+]i in the absence of GTP--'calcium activation'. A putative fourth activation mechanism is a signal from depleted intracellular Ca2+ stores. Consistent with this idea, human TRPC5 was activated by a standard store-depletion/Ca2+ re-entry protocol, an effect that was difficult to explain by calcium activation. Multiplicity of TRPC5 activation was demonstrated in single cells and thus not dependent on heterogeneity of expression levels or cellular context. Therefore, human TRPC5 is activated by a range of stimuli, avoiding dependence on a single critical activator as in many other ion channels. One of these stimuli would seem to be a change in Ca2+ handling by the endoplasmic reticulum.
Collapse
Affiliation(s)
- Fanning Zeng
- School of Biomedical Sciences, University of Leeds, LS2 9JT, UK
| | | | | | | | | | | | | |
Collapse
|
30
|
Kahr H, Schindl R, Fritsch R, Heinze B, Hofbauer M, Hack ME, Mörtelmaier MA, Groschner K, Peng JB, Takanaga H, Hediger MA, Romanin C. CaT1 knock-down strategies fail to affect CRAC channels in mucosal-type mast cells. J Physiol 2004; 557:121-32. [PMID: 15020691 PMCID: PMC1665038 DOI: 10.1113/jphysiol.2004.062653] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CaT1, the calcium transport protein 1 encoded by TRPV6, is able to generate a Ca(2+) conductance similar but not identical to the classical CRAC current in mucosal-type mast cells. Here we show that CaT1-derived Ca(2+) entry into HEK293 cells is effectively inhibited either by expression of various dominant negative N-terminal fragments of CaT1 (N(334)-CaT1, N(198)-CaT1 and N(154)-CaT1) or by antisense suppression. By contrast, the endogenous CRAC current of the mast cells was unaffected by CaT1 antisense and siRNA knockdown but markedly suppressed by two (N(334)-CaT1, N(198)-CaT1) of the dominant negative N-CaT1 fragments. Inhibition of CRAC current was not an unspecific, toxic effect, as inward rectifier K(+) and MagNuM currents of the mast cells were not significantly affected by these N-CaT1 fragments. The shortest N(154)-CaT1 fragment inhibited CaT1-derived currents in mast cells, but failed to inhibit CRAC currents. Thus, the structural requirements of rCaT N-terminal fragments for inhibition of rCaT1 and CRAC channels are different. These results together with the lack of CaT1 antisense and siRNA effects on currents render it unlikely that CaT1 is a component of native CRAC channels in mast cells. The data further demonstrate a novel strategy for CRAC current inhibition by an N-terminal structure of CaT1.
Collapse
Affiliation(s)
- Heike Kahr
- Institute for Biophysics, University of Linz, A-4040 Linz, Austria
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Lucas P, Ukhanov K, Leinders-Zufall T, Zufall F. A diacylglycerol-gated cation channel in vomeronasal neuron dendrites is impaired in TRPC2 mutant mice: mechanism of pheromone transduction. Neuron 2004; 40:551-61. [PMID: 14642279 DOI: 10.1016/s0896-6273(03)00675-5] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Vomeronasal sensory neurons play a crucial role in detecting pheromones, but the chemoelectrical transduction mechanism remains unclear and controversial. A major barrier to the resolution of this question has been the lack of an activation mechanism of a key transduction component, the TRPC2 channel. We have identified a Ca(2+)-permeable cation channel in vomeronasal neuron dendrites that is gated by the lipid messenger diacylglycerol (DAG), independently of Ca(2+) or protein kinase C. We demonstrate that ablation of the TRPC2 gene causes a severe deficit in the DAG-gated channel, indicating that TRPC2 encodes a principal subunit of this channel and that the primary electrical response to pheromones depends on DAG but not Ins(1,4,5)P(3), Ca(2+) stores, or arachidonic acid. Thus, a previously unanticipated mechanism involving direct channel opening by DAG underlies the transduction of sensory cues in the accessory olfactory system.
Collapse
Affiliation(s)
- Philippe Lucas
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | | | | | | |
Collapse
|
32
|
Store-operated calcium channels: properties, functions and the search for a molecular mechanism. MOLECULAR INSIGHTS INTO ION CHANNEL BIOLOGY IN HEALTH AND DISEASE 2004. [DOI: 10.1016/s1569-2558(03)32006-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
33
|
Clapham DE, Montell C, Schultz G, Julius D. International Union of Pharmacology. XLIII. Compendium of Voltage-Gated Ion Channels: Transient Receptor Potential Channels. Pharmacol Rev 2003; 55:591-6. [PMID: 14657417 DOI: 10.1124/pr.55.4.6] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The transient receptor potential (TRP) proteins are six transmembrane-containing subunits that combine to form cation-selective ion channels. TRP channels are present in yeast, Drosophila, Caenorhabditis elegans, and mammals. They are widely distributed and sense local changes in stimuli ranging from light to temperature and osmolarity. Mammals contain at least 22 distinct genes encoding these ion channels. This summary article presents an overview of the molecular relationships among the TRP channels and a standard nomenclature for them, which is derived from the IUPHAR Compendium of Voltage-Gated Ion Channels. The complete Compendium, including data tables for each member of the TRP channel family, can be found at http://www.iuphar-db.org/iuphar-ic/.
Collapse
Affiliation(s)
- David E Clapham
- Howard Hughes Medical Institute, Children's Hospital, 1309 Enders Building, 320 Longwood Ave., Boston, MA 02115, USA.
| | | | | | | |
Collapse
|
34
|
Baryshnikov SG, Rogachevskaja OA, Kolesnikov SS. Calcium signaling mediated by P2Y receptors in mouse taste cells. J Neurophysiol 2003; 90:3283-94. [PMID: 12878712 DOI: 10.1152/jn.00312.2003] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Evidence implicates a number of neuroactive substances and their receptors in mediating complex cell-to-cell communications in the taste bud. Recently, we found that ATP, a ubiquitous neurotransmitter/neuromodulator, mobilizes intracellular Ca2+ in taste cells by activating P2Y receptors. Here, P2Y receptor-cellular response coupling was characterized in detail using single cell ratio photometry and the inhibitory analysis. The sequence of underlying events was shown to include ATP-dependent activation of PLC, IP3 production, and IP3 receptor-mediated Ca2+ release followed by Ca2+ influx. Data obtained favor SOC channels rather than receptor-operated channels as a pathway for Ca2+ influx that accompanies Ca2+ release. Intracellular Ca2+ mobilized by ATP is apparently extruded by the plasma membrane Ca2+-ATPase, while a contribution of the Na+/Ca2+ exchange and other mechanisms of Ca2+ clearance is negligible. Cyclic AMP-dependent phosphorylation is likely to control a gain of the phosphoinositide cascade involved in ATP transduction. ATP-responsive taste cells are abundant in circumvallate, foliate, and fungiform papillae. Taken together, our observations point to a putative role for ATP as a neurotransmitter operative in the taste bud.
Collapse
Affiliation(s)
- Sergey G Baryshnikov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | | | | |
Collapse
|
35
|
Jiang X, Newell EW, Schlichter LC. Regulation of a TRPM7-like current in rat brain microglia. J Biol Chem 2003; 278:42867-76. [PMID: 12904301 DOI: 10.1074/jbc.m304487200] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Non-excitable cells use Ca2+ influx for essential functions but usually lack voltage-gated Ca2+ channels. The main routes of Ca2+ entry appear to be store-operated channels or Ca2+-permeable non-selective cation channels, of which the magnesium-inhibited cation (or magnesium-nucleotide-regulated metal cation) current has received considerable recent attention. This current appears to be produced by one of the recently cloned transient receptor potential (TRP) channels, TRPM7. In this study of rat microglia, we identified TRPM7 transcripts and a prevalent current with the hallmark biophysical and pharmacological features of TRPM7. This is the first identification of a TRPM7-like current in the brain. There is little known about how members of the TRPM sub-family normally become activated. Using whole-cell patch clamp recordings from rat microglia, we found that the TRPM7-like current activates spontaneously after break-in and that the current and its activation are inhibited by elevated intracellular Mg2+ but not affected by cell swelling or a wide range of intracellular Ca2+ concentrations. The TRPM7-like current in microglia appears to depend on tyrosine phosphorylation. It was inhibited by several tyrosine kinase inhibitors, including a peptide (Src 40-58) that was shown previously to inhibit Src actions, but not by inactive drugs or peptide analogues. The current did not depend on the cell activation state; i.e. it was the same in microglia recently removed from the brain or when cultured under a wide range of conditions that favor the resting or activated state. Because TRPM7 channels are permeable to Ca2+, this current may be important for microglia functions that depend on elevations in intracellular Ca2+.
Collapse
Affiliation(s)
- Xinpo Jiang
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, 399 Bathurst Street, Toronto, Ontario M5T 2S8, Canada
| | | | | |
Collapse
|
36
|
Li H, Ayer LM, Lytton J, Deans JP. Store-operated cation entry mediated by CD20 in membrane rafts. J Biol Chem 2003; 278:42427-34. [PMID: 12920111 DOI: 10.1074/jbc.m308802200] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
B cell activation requires sustained elevation of cytoplasmic free calcium, achieved by influx through store-operated calcium (SOC) channels. The molecular identity of these channels is not known. Ectopic expression of the raft-associated tetraspan protein CD20 in Chinese hamster ovary cells introduced a novel SOC entry pathway that was permeable to strontium as well as to calcium. The activity of this SOC pathway was abolished by deletion of a cytoplasmic sequence in CD20 essential for its efficient raft localization. Strontium-permeable SOC channels were detected in B cells, and B cell receptor-stimulated influx was significantly reduced by downregulation of CD20 expression using short interfering RNA and also by cholesterol depletion. This is the first evidence that raft-associated CD20 constitutes a component of a SOC entry pathway activated by the B cell receptor.
Collapse
Affiliation(s)
- Haidong Li
- Immunology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary Health Sciences Center, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
| | | | | | | |
Collapse
|
37
|
Machaca K. Ca2+-calmodulin-dependent protein kinase II potentiates store-operated Ca2+ current. J Biol Chem 2003; 278:33730-7. [PMID: 12821654 PMCID: PMC1282465 DOI: 10.1074/jbc.m305023200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A rise in intracellular Ca2+ (Ca2+i) mediates various cellular functions ranging from fertilization to gene expression. A ubiquitous Ca2+ influx pathway that contributes significantly to the generation of Ca2+i signals, especially in non-excitable cells, is store-operated Ca2+ entry (SOCE). Consequently, the modulation of SOCE current affects Ca2+i dynamics and thus the ensuing cellular response. Therefore, it is important to define the mechanisms that regulate SOCE. Here we show that a rise in Ca2+i potentiates SOCE. This potentiation is mediated by Ca2+-calmodulin-dependent protein kinase II (CaMKII), because inhibition of endogenous CaMKII activity abrogates Ca2+i-mediated SOCE potentiation and expression of constitutively active CaMKII potentiates SOCE current independently of Ca2+i. Moreover, we present evidence that CaMKII potentiates SOCE by altering SOCE channel gating. The regulation of SOCE by CaMKII defines a novel modulatory mechanism of SOCE with important physiological consequences.
Collapse
Affiliation(s)
- Khaled Machaca
- Department of Physiology & Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
| |
Collapse
|
38
|
Basora N, Boulay G, Bilodeau L, Rousseau E, Payet MD. 20-hydroxyeicosatetraenoic acid (20-HETE) activates mouse TRPC6 channels expressed in HEK293 cells. J Biol Chem 2003; 278:31709-16. [PMID: 12794071 DOI: 10.1074/jbc.m304437200] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the present study, we show that the eicosanoid compound, 20-hydroxyeicosatetraenoic acid (20-HETE), an important arachidonic acid metabolite, activates mouse TRPC6 in a stable, overexpressing HEK293 cell line, Hek-t6.11. Application of 20-HETE rapidly induced an inward, non-selective current in whole-cell recordings, which was inhibited by N-methyl-d-glucamine, 1.8 mm Ca2+, and 100 microM Gd3+ but remained unaffected by flufenamate and indomethacin. The current-voltage relationship obtained at low concentrations of 20-HETE (1-10 microM) demonstrated slight inward rectification, whereas the highest concentration of 20-HETE tested (30 microM) showed outward rectification, as shown previously for these channels using 100 microM 1-oleoyl-2-acetyl-sn-glycerol. Dose-response curves indicate that 20-HETE activated TRPC6 channels with an EC50 = 0.8 microM. Single channel analysis using inside-out patches revealed that 20-HETE increased open probability of mouse TRPC6 channels approximately 3-fold, and this was in a membrane-delimited fashion. Interestingly, 20-HETE did not provoke changes in intracellular Ca2+ concentrations. Thus, we have identified an arachidonic acid metabolite, 20-HETE, as a novel activator for a TRP family member, TRPC6.
Collapse
Affiliation(s)
- Nuria Basora
- Department of Physiology and Biophysics, Faculty of Medicine, University of Sherbrooke, Québec J1H 5N4, Canada.
| | | | | | | | | |
Collapse
|
39
|
Flemming R, Xu SZ, Beech DJ. Pharmacological profile of store-operated channels in cerebral arteriolar smooth muscle cells. Br J Pharmacol 2003; 139:955-65. [PMID: 12839869 PMCID: PMC1573921 DOI: 10.1038/sj.bjp.0705327] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. In this study, we determined a pharmacological profile of store-operated channels (SOCs) in smooth muscle cells of rabbit pial arterioles. Ca(2+)-indicator dyes, fura-PE3 or fluo-4, were used to track [Ca(2+)](i) and 10 micro M methoxyverapamil (D600) was present in all experiments on SOCs to prevent voltage-dependent Ca(2+) entry. Store depletion was induced using thapsigargin or cyclopiazonic acid. 2. SOC-mediated Ca(2+) entry was inhibited concentration dependently by Gd(3+) (IC(50) 101 nM). It was also inhibited by 10 micro M La(3+) (70% inhibition, N=5), 100 micro M Ni(2+) (57% inhibition, N=5), 75 micro M 2-aminoethoxydiphenylborate (66% inhibition, N=4), 100 micro M capsaicin (12% inhibition, N=3) or preincubation with 10 micro M wortmannin (76% inhibition, N=4). It was completely resistant to 1 micro M nifedipine (N=5), 10 micro M SKF96365 (N=6), 10 micro M LOE908 (N=14), 10-100 micro M ruthenium red (N=1+2), 100 micro M sulindac (N=4), 0.5 mM streptomycin (N=3) or 1 : 10,000 dilution Grammostolla spatulata venom (N=4). 3. RT-PCR experiments on isolated arteriolar fragments showed expression of mRNA species for TRPC1, 3, 4, 5 and 6. 4. The pharmacological profile of SOC-mediated Ca(2+) entry in arterioles supports the hypothesis that these SOCs are distinct from tonically active background channels and several store-operated and other nonselective cation channels described in other cells. Similarities with the pharmacology of TRPC1 support the hypothesis that TRPC1 is a subunit of the arteriolar smooth muscle SOC.
Collapse
Affiliation(s)
- R Flemming
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT
| | - S Z Xu
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT
| | - D J Beech
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT
- Author for correspondence:
| |
Collapse
|
40
|
Abstract
The Ca2+ release-activated Ca2+ (CRAC) channel is a highly Ca2+-selective store-operated channel that is expressed in T lymphocytes, mast cells, and other hematopoietic cells. In T cells, CRAC channels are essential for generating the prolonged intracellular Ca2+ ([Ca2+](i)) elevation required for the expression of T-cell activation genes. Here we review recent work addressing CRAC channel regulation, pore properties, and the search for CRAC channel genes. Of the current models for CRAC current (I(CRAC)) activation, several new studies argue against a conformational coupling mechanism in which IP(3) receptors communicate store depletion to CRAC channels through direct physical interaction. The study of CRAC channels has been complicated by the fact that they lose activity in the absence of extracellular Ca2+. Attempts to maintain current size by removing intracellular Mg2+ have been found to unmask Mg2+-inhibited cation (MIC/MagNuM/TRPM7) channels, which have been mistaken in several studies for the CRAC channel. Recent studies under conditions that prevent MIC activation reveal that CRAC channels use high-affinity binding of Ca2+ in the pore to achieve high Ca2+ selectivity but have a surprisingly low conductance for both Ca2+ (approximately 10fS) and Na+ (approximately 0.2pS). Pore properties provide a unique fingerprint that provides a stringent test for potential CRAC channel genes and suggest models for the ion selectivity mechanism.
Collapse
Affiliation(s)
- Murali Prakriya
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Beckman Center B-111A, Stanford, CA 94305, USA
| | | |
Collapse
|
41
|
Liu X, Singh BB, Ambudkar IS. TRPC1 is required for functional store-operated Ca2+ channels. Role of acidic amino acid residues in the S5-S6 region. J Biol Chem 2003; 278:11337-43. [PMID: 12536150 DOI: 10.1074/jbc.m213271200] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The exact role of TRPC1 in store-operated calcium influx channel (SOCC) function is not known. We have examined the effect of overexpression of full-length TRPC1, depletion of endogenous TRPC1, and expression of TRPC1 in which the proposed pore region (S5-S6, amino acids (aa) 557-620) was deleted or modified by site-directed mutagenesis on thapsigargin- and carbachol-stimulated SOCC activity in HSG cells. TRPC1 overexpression induced channel activity that was indistinguishable from the endogenous SOCC activity. Transfection with antisense hTRPC1 decreased SOCC activity although characteristics of SOCC-mediated current, I(SOC), were not altered. Expression of TRPC1 Delta 567-793, but not TRPC1 Delta 664-793, induced a similar decrease in SOCC activity. Furthermore, TRPC1 Delta 567-793 was co-immunoprecipitated with endogenous TRPC1. Simultaneous substitutions of seven acidic aa in the S5-S6 region (Asp --> Asn and Glu --> Gln) decreased SOCC-mediated Ca(2+), but not Na(+), current and induced a left shift in E(rev). Similar effects were induced by E576K or D581K, but not D581N or E615K, substitution. Furthermore, expressed TRPC1 proteins interacted with each other. Together, these data demonstrate that TRPC1 is required for generation of functional SOCC in HSG cells. We suggest that TRPC1 monomers co-assemble to form SOCC and that specific acidic aa residues in the proposed pore region of TRPC1 contribute to Ca(2+) influx.
Collapse
Affiliation(s)
- Xibao Liu
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | |
Collapse
|
42
|
Mignen O, Thompson JL, Shuttleworth TJ. Ca2+ selectivity and fatty acid specificity of the noncapacitative, arachidonate-regulated Ca2+ (ARC) channels. J Biol Chem 2003; 278:10174-81. [PMID: 12522216 DOI: 10.1074/jbc.m212536200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The arachidonate-regulated, Ca(2+)-selective ARC channels represent a novel receptor-activated pathway for the entry of Ca(2+) in nonexcitable cells that is entirely separate from the widely studied store-operated, Ca(2+) release-activated Ca(2+) channels. Activation of ARC channels occurs specifically at the low agonist concentrations typically associated with oscillatory Ca(2+) signals and appears to provide the predominant mode of Ca(2+) entry under these conditions (Mignen, O., Thompson, J. L., and Shuttleworth, T. J. (2001) J. Biol. Chem. 276, 35676-35683). In this study we demonstrate that ARC channels are present in a variety of different cell types including both cell lines and primary cells. Examination of their pharmacology revealed that currents through these channels are significantly inhibited by low concentrations (< 5 microm) of Gd(3+), are unaffected by 100 microm 2-aminoethyoxydiphenyl borane, and are not activated by the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (100 microm). Their selectivity for Ca(2+) was assessed by determining the EC(50) for external Ca(2+) block of the monovalent currents observed in the absence of external divalent cations. The value obtained (150 nm) indicates that the Ca(2+) selectivity of ARC channels is extremely high. Examination of the ability of various fatty acids, including arachidonic acid, to activate the ARC channels demonstrated that activation does not reflect any nonspecific membrane fluidity or detergent effects, shows a high degree of specificity for arachidonic acid over other fatty acids (especially monounsaturated and saturated fatty acids), and is independent of any arachidonic acid metabolite. Moreover, studies using the charged analogue arachidonyl coenzyme A demonstrate that activation of the ARC channels reflects an action of the fatty acid specifically at the internal face of the plasma membrane. Whether this involves a direct action of arachidonic acid on the channel protein itself or an action on some intermediary molecule is, at present, unclear.
Collapse
Affiliation(s)
- Olivier Mignen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, New York 14642, USA
| | | | | |
Collapse
|
43
|
Parekh AB. Store-operated Ca2+ entry: dynamic interplay between endoplasmic reticulum, mitochondria and plasma membrane. J Physiol 2003; 547:333-48. [PMID: 12576497 PMCID: PMC2342659 DOI: 10.1113/jphysiol.2002.034140] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In eukaryotic cells, hormones and neurotransmitters that engage the phosphoinositide pathway evoke a biphasic increase in intracellular free Ca2+ concentration: an initial transient release of Ca2+ from intracellular stores is followed by a sustained phase of Ca2+ influx. This influx is generally store-dependent and is required for controlling a host of Ca2+-dependent processes ranging from exocytosis to cell growth and proliferation. In many cell types, store-operated Ca2+ entry is manifest as a non-voltage-gated Ca2+ current called ICRAC (Ca2+ release-activated Ca2+ current). Just how store emptying activates CRAC channels remains unclear, and some of our recent experiments that address this issue will be described. No less important from a physiological perspective is the weak Ca2+ buffer paradox: whereas macroscopic (whole cell) ICRAC can be measured routinely in the presence of strong intracellular Ca2+ buffer, the current is generally not detectable under physiological conditions of weak buffering following store emptying with the second messenger InsP3. In this review, I describe some of our experiments aimed at understanding just why InsP3 is ineffective under these conditions and which lead us to conclude that respiring mitochondria are essential for the activation of ICRAC in weak intracellular Ca2+ buffer. Mitochondrial Ca2+ uptake also increases the dynamic range over which InsP3 functions as the second messenger that controls Ca2+ influx. Finally, we find that Ca2+-dependent slow inactivation of Ca2+ influx, a widespread but poorly understood phenomenon that helps shape the profile of an intracellular Ca2+ signal, is regulated by mitochondrial Ca2+ buffering. Thus, by enabling macroscopic store-operated Ca2+ current to activate and then by controlling its extent and duration, mitochondria play a crucial role in all stages of store-operated Ca2+ influx. Store-operated Ca2+ entry reflects therefore a dynamic interplay between endoplasmic reticulum, mitochondria and plasma membrane.
Collapse
Affiliation(s)
- Anant B Parekh
- Department of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
| |
Collapse
|
44
|
Wilson SM, Mason HS, Smith GD, Nicholson N, Johnston L, Janiak R, Hume JR. Comparative capacitative calcium entry mechanisms in canine pulmonary and renal arterial smooth muscle cells. J Physiol 2002; 543:917-31. [PMID: 12231648 PMCID: PMC2290529 DOI: 10.1113/jphysiol.2002.021998] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Experiments were performed to determine whether capacitative Ca(2+) entry (CCE) can be activated in canine pulmonary and renal arterial smooth muscle cells (ASMCs) and whether activation of CCE parallels the different functional structure of the sarcoplasmic reticulum (SR) in these two cell types. The cytosolic [Ca(2+)] was measured by imaging fura-2-loaded individual cells. Increases in the cytosolic [Ca(2+)] due to store depletion in pulmonary ASMCs required simultaneous depletion of both the inositol 1,4,5-trisphosphate (InsP(3))- and ryanodine (RY)-sensitive SR Ca(2+) stores. In contrast, the cytosolic [Ca(2+)] rises in renal ASMCs occurred when the SR stores were depleted through either the InsP(3) or RY pathways. The increase in the cytosolic [Ca(2+)] due to store depletion in both pulmonary and renal ASMCs was present in cells that were voltage clamped and was abolished when cells were perfused with a Ca(2+)-free bathing solution. Rapid quenching of the fura-2 signal by 100 microM Mn(2+) following SR store depletion indicated that extracellular Ca(2+) entry increased in both cell types and also verified that activation of CCE in pulmonary ASMCs required the simultaneous depletion of the InsP(3)- and RY-sensitive SR Ca(2+) stores, while CCE could be activated in renal ASMCs by the depletion of either of the InsP(3)- or RY-sensitive SR stores. Store depletion Ca(2+) entry in both pulmonary and renal ASMCs was strongly inhibited by Ni(2+) (0.1-10 mM), slightly inhibited by Cd(2+) (200-500 microM), but was not significantly affected by the voltage-gated Ca(2+) channel (VGCC) blocker nisoldipine (10 microM). The non-selective cation channel blocker Gd(3+) (100 microM) inhibited a portion of the Ca(2+) entry in 6 of 18 renal but not pulmonary ASMCs. These results provide evidence that SR Ca(2+) store depletion activates CCE in parallel with the organization of intracellular Ca(2+) stores in canine pulmonary and renal ASMCs.
Collapse
Affiliation(s)
- Sean M Wilson
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | | | | | | | | | | | | |
Collapse
|
45
|
Affiliation(s)
- David E Clapham
- Howard Hughes Medical Institute Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| |
Collapse
|
46
|
Schindl R, Kahr H, Graz I, Groschner K, Romanin C. Store depletion-activated CaT1 currents in rat basophilic leukemia mast cells are inhibited by 2-aminoethoxydiphenyl borate. Evidence for a regulatory component that controls activation of both CaT1 and CRAC (Ca(2+) release-activated Ca(2+) channel) channels. J Biol Chem 2002; 277:26950-8. [PMID: 12011062 DOI: 10.1074/jbc.m203700200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The intestinal Ca(2+) transport protein CaT1 encoded by TRPV6 has been reported (Yue, L., Peng, J. B., Hediger, M. A., and Clapham, D. E. (2001) Nature 410, 705-709) to be all or a part of the Ca(2+) release-activated Ca(2+) channel (CRAC). The major characteristic of CRAC is its activation following store depletion. We expressed CaT1 in HEK293 cells and rat basophilic leukemia (RBL) mast cells and measured whole-cell currents by the patch clamp technique. In HEK293 cells, the expression of CaT1 consistently yielded a constitutively active current, the size of which was strongly dependent on the holding potential and duration of voltage ramps. In CaT1-expressing RBL cells, the current was either activated by store depletion or was constitutively active at a higher current density. CaT1 currents could be clearly distinguished from endogenous CRAC by their typical current-voltage relationship in divalent free solution. 2-aminoethoxydiphenyl borate (2-APB), which is considered a blocker of CRAC, was tested for its inhibitory effect on both cell types expressing CaT1. Endogenous CRAC as well as store-dependent CaT1-derived currents of RBL cells were largely blocked by 75 microm 2-APB, whereas constitutively active CaT1 currents in both RBL and HEK293 cells were slightly potentiated. These results indicate that despite the difference in the permeation properties of CRAC and CaT1 channels, the latter are similarly able to form store depletion-activated conductances in RBL mast cells that are inhibited by 2-APB.
Collapse
Affiliation(s)
- Rainer Schindl
- Institute for Biophysics, University of Linz, A-4040 Linz, Austria
| | | | | | | | | |
Collapse
|
47
|
Oka T, Sato K, Hori M, Ozaki H, Karaki H. FcepsilonRI cross-linking-induced actin assembly mediates calcium signalling in RBL-2H3 mast cells. Br J Pharmacol 2002; 136:837-46. [PMID: 12110608 PMCID: PMC1573417 DOI: 10.1038/sj.bjp.0704788] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
1. To determine the role of actin assembly in the Ca(2+) signalling of mast cells activated by cross-linking of FcepsilonRI, we examined the effects of cytochalasin D, an inhibitor of actin polymerization. 2. In the RBL-2H3 cells, F-actin content was increased by sensitization with anti-dinitrophenol (DNP) IgE. In these cells, cytochalasin D induced oscillatory increases in cytosolic Ca(2+) ([Ca(2+)](i)); these increase were inhibited by jasplakinolide, a stabilizer of actin filaments. 3. In the IgE-sensitized RBL-2H3 cells, DNP-human serum albumin (DNP-HSA) augmented actin assembly. DNP-HSA also increased the production of IP(3), [Ca(2+)](i) and degranulation. Cytochalasin D enhanced all of these DNP-HSA-induced effects. 4. In a Ca(2+)-free solution, DNP-HSA induced a transient increase in [Ca(2+)](i), and this increase was accelerated by cytochalasin D. After cessation of the DNP-HSA-induced Ca(2+) release, the re-addition of Ca(2+) induced a sustained increase in [Ca(2+)](i) through capacitative Ca(2+) entry (CCE), and this increase was enhanced by cytochalasin D. 5 The effect of cytochalasin D in enhancing the CCE activity was prevented by xestospongin C. 6. In contrast, neither the Ca(2+) release nor the CCE activation that was induced by thapsigargin was affected by cytochalasin D. 7. These results suggest that actin de-polymerization stimulates the FcepsilonRI-mediated signalling to augment the release of Ca(2+) from the endoplasmic reticulum in RBL-2H3 cells.
Collapse
Affiliation(s)
- Tatsuya Oka
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Koichi Sato
- Department of Radio Isotope Center, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Masatoshi Hori
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Hiroshi Ozaki
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
- Author for correspondence:
| | - Hideaki Karaki
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
| |
Collapse
|
48
|
Prakriya M, Lewis RS. Separation and characterization of currents through store-operated CRAC channels and Mg2+-inhibited cation (MIC) channels. J Gen Physiol 2002; 119:487-507. [PMID: 11981025 PMCID: PMC2233817 DOI: 10.1085/jgp.20028551] [Citation(s) in RCA: 240] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although store-operated calcium release-activated Ca(2+) (CRAC) channels are highly Ca(2+)-selective under physiological ionic conditions, removal of extracellular divalent cations makes them freely permeable to monovalent cations. Several past studies have concluded that under these conditions CRAC channels conduct Na(+) and Cs(+) with a unitary conductance of approximately 40 pS, and that intracellular Mg(2+) modulates their activity and selectivity. These results have important implications for understanding ion permeation through CRAC channels and for screening potential CRAC channel genes. We find that the observed 40-pS channels are not CRAC channels, but are instead Mg(2+)-inhibited cation (MIC) channels that open as Mg(2+) is washed out of the cytosol. MIC channels differ from CRAC channels in several critical respects. Store depletion does not activate MIC channels, nor does store refilling deactivate them. Unlike CRAC channels, MIC channels are not blocked by SKF 96365, are not potentiated by low doses of 2-APB, and are less sensitive to block by high doses of the drug. By applying 8-10 mM intracellular Mg(2+) to inhibit MIC channels, we examined monovalent permeation through CRAC channels in isolation. A rapid switch from 20 mM Ca(2+) to divalent-free extracellular solution evokes Na(+) current through open CRAC channels (Na(+)-I(CRAC)) that is initially eightfold larger than the preceding Ca(2+) current and declines by approximately 80% over 20 s. Unlike MIC channels, CRAC channels are largely impermeable to Cs(+) (P(Cs)/P(Na) = 0.13 vs. 1.2 for MIC). Neither the decline in Na(+)-I(CRAC) nor its low Cs(+) permeability are affected by intracellular Mg(2+) (90 microM to 10 mM). Single openings of monovalent CRAC channels were not detectable in whole-cell recordings, but a unitary conductance of 0.2 pS was estimated from noise analysis. This new information about the selectivity, conductance, and regulation of CRAC channels forces a revision of the biophysical fingerprint of CRAC channels, and reveals intriguing similarities and differences in permeation mechanisms of voltage-gated and store-operated Ca(2+) channels.
Collapse
Affiliation(s)
- Murali Prakriya
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | | |
Collapse
|
49
|
Singh BB, Liu X, Tang J, Zhu MX, Ambudkar IS. Calmodulin regulates Ca(2+)-dependent feedback inhibition of store-operated Ca(2+) influx by interaction with a site in the C terminus of TrpC1. Mol Cell 2002; 9:739-50. [PMID: 11983166 DOI: 10.1016/s1097-2765(02)00506-3] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The mechanism involved in [Ca(2+)](i)-dependent feedback inhibition of store-operated Ca(2+) entry (SOCE) is not yet known. Expression of Ca(2+)-insensitive calmodulin (Mut-CaM) but not wild-type CaM increased SOCE and decreased its Ca(2+)-dependent inactivation. Expression of TrpC1 lacking C terminus aa 664-793 (TrpC1DeltaC) also attenuated Ca(2+)-dependent inactivation of SOCE. CaM interacted with endogenous and expressed TrpC1 and with GST-TrpC1 C terminus but not with TrpC1DeltaC. Two CaM binding domains, aa 715-749 and aa 758-793, were identified. Expression of TrpC1Delta758-793 but not TrpC1Delta715-749 mimicked the effects of TrpC1DeltaC and Mut-CaM on SOCE. These data demonstrate that CaM mediates Ca(2+)-dependent feedback inhibition of SOCE via binding to a domain in the C terminus of TrpC1. These findings reveal an integral role for TrpC1 in the regulation of SOCE.
Collapse
Affiliation(s)
- Brij B Singh
- Secretory Physiology Section, Gene Therapy and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | | | |
Collapse
|
50
|
Oka T, Sato K, Hori M, Ozaki H, Karaki H. Xestospongin C, a novel blocker of IP3 receptor, attenuates the increase in cytosolic calcium level and degranulation that is induced by antigen in RBL-2H3 mast cells. Br J Pharmacol 2002; 135:1959-66. [PMID: 11959799 PMCID: PMC1573325 DOI: 10.1038/sj.bjp.0704662] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. We evaluated the role of the cross-linking of Fc epsilon RI-mediated inositol 1,4,5-triphosphate (IP(3)) in the increase in cytosolic Ca(2+) level ([Ca(2+)](i)) using xestospongin C, a selective membrane permeable blocker of IP(3) receptor, in RBL-2H3 mast cells. 2. In the cells sensitized with anti-dinitrophenol (DNP) IgE, DNP-human serum albumin (DNP-HSA) and thapsigargin induced degranulation of beta-hexosaminidase and a sustained increase in [Ca(2+)](i). Xestospongin C (3 - 10 microM) inhibited both of these changes that were induced by DNP-HSA without changing those induced by thapsigargin. 3. In the absence of external Ca(2+), DNP-HSA induced a transient increase in [Ca(2+)](i). Xestospongin C (3 - 10 microM) inhibited this increase in [Ca(2+)](i). 4. In the cells permeabilized with beta-escin, the application of IP(3) decreased Ca(2+) in the endoplasmic reticulum (ER) as evaluated by mag-fura-2. Xestospongin C (3 - 10 microM) inhibited the effect of IP(3). 5. After the depletion of Ca(2+) stores due to stimulation with DNP-HSA or thapsigargin, the addition of Ca(2+) induced capacitative calcium entry (CCE). Xestospongin C (3 - 10 microM) inhibited the DNP-HSA-induced CCE, whereas it did not affect the thapsigargin-induced CCE. 6. These results suggest that Fc epsilon RI-mediated generation of IP(3) contributes to Ca(2+) release not only in the initial phase but also in the sustained phase of the increase in [Ca(2+)](i), resulting in prolonged Ca(2+) depletion in the ER. The ER Ca(2+) depletion may subsequently activate CCE to achieve a continuous [Ca(2+)](i) increase, which is necessary for degranulation in the RBL-2H3 mast cells. Xestospongin C may inhibit Ca(2+) release and consequently may attenuate degranulation.
Collapse
MESH Headings
- Animals
- Calcium/metabolism
- Calcium Channels/metabolism
- Cell Degranulation/drug effects
- Cell Membrane Permeability/drug effects
- Cytosol/drug effects
- Cytosol/enzymology
- Cytosol/metabolism
- Dinitrophenols/antagonists & inhibitors
- Dinitrophenols/pharmacology
- Endoplasmic Reticulum/drug effects
- Endoplasmic Reticulum/metabolism
- Escin/pharmacology
- Haptens/pharmacology
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate/pharmacology
- Inositol 1,4,5-Trisphosphate Receptors
- Macrocyclic Compounds
- Mast Cells/drug effects
- Mast Cells/enzymology
- Mast Cells/metabolism
- Oxazoles/pharmacology
- Rats
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Receptors, Cytoplasmic and Nuclear/metabolism
- Serum Albumin/antagonists & inhibitors
- Serum Albumin/pharmacology
- Tumor Cells, Cultured/drug effects
- Tumor Cells, Cultured/enzymology
- Tumor Cells, Cultured/metabolism
- beta-N-Acetylhexosaminidases/antagonists & inhibitors
- beta-N-Acetylhexosaminidases/metabolism
Collapse
Affiliation(s)
- Tatsuya Oka
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Koichi Sato
- Radio Isotope Center, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Masatoshi Hori
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Hiroshi Ozaki
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-Ku, Tokyo 113-8657, Japan
- Author for correspondence:
| | - Hideaki Karaki
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-Ku, Tokyo 113-8657, Japan
| |
Collapse
|