101
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Mongin AA. Volume-regulated anion channel--a frenemy within the brain. Pflugers Arch 2015; 468:421-41. [PMID: 26620797 DOI: 10.1007/s00424-015-1765-6] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/16/2015] [Accepted: 11/20/2015] [Indexed: 10/22/2022]
Abstract
The volume-regulated anion channel (VRAC) is a ubiquitously expressed yet highly enigmatic member of the superfamily of chloride/anion channels. It is activated by cellular swelling and mediates regulatory cell volume decrease in a majority of vertebrate cells, including those in the central nervous system (CNS). In the brain, besides its crucial role in cellular volume regulation, VRAC is thought to play a part in cell proliferation, apoptosis, migration, and release of physiologically active molecules. Although these roles are not exclusive to the CNS, the relative significance of VRAC in the brain is amplified by several unique aspects of its physiology. One important example is the contribution of VRAC to the release of the excitatory amino acid neurotransmitters glutamate and aspartate. This latter process is thought to have impact on both normal brain functioning (such as astrocyte-neuron signaling) and neuropathology (via promoting the excitotoxic death of neuronal cells in stroke and traumatic brain injury). In spite of much work in the field, the molecular nature of VRAC remained unknown until less than 2 years ago. Two pioneer publications identified VRAC as the heterohexamer formed by the leucine-rich repeat-containing 8 (LRRC8) proteins. These findings galvanized the field and are likely to result in dramatic revisions to our understanding of the place and role of VRAC in the brain, as well as other organs and tissues. The present review briefly recapitulates critical findings in the CNS and focuses on anticipated impact on the LRRC8 discovery on further progress in neuroscience research.
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Affiliation(s)
- Alexander A Mongin
- Center for Neuropharmacology and Neuroscience, Albany Medical College, 47 New Scotland Ave., Albany, NY, 12208, USA.
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102
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Hoffmann EK, Sørensen BH, Sauter DPR, Lambert IH. Role of volume-regulated and calcium-activated anion channels in cell volume homeostasis, cancer and drug resistance. Channels (Austin) 2015; 9:380-96. [PMID: 26569161 DOI: 10.1080/19336950.2015.1089007] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Volume-regulated channels for anions (VRAC) / organic osmolytes (VSOAC) play essential roles in cell volume regulation and other cellular functions, e.g. proliferation, cell migration and apoptosis. LRRC8A, which belongs to the leucine rich-repeat containing protein family, was recently shown to be an essential component of both VRAC and VSOAC. Reduced VRAC and VSOAC activities are seen in drug resistant cancer cells. ANO1 is a calcium-activated chloride channel expressed on the plasma membrane of e.g., secretory epithelia. ANO1 is amplified and highly expressed in a large number of carcinomas. The gene, encoding for ANO1, maps to a region on chromosome 11 (11q13) that is frequently amplified in cancer cells. Knockdown of ANO1 impairs cell proliferation and cell migration in several cancer cells. Below we summarize the basic biophysical properties of VRAC, VSOAC and ANO1 and their most important cellular functions as well as their role in cancer and drug resistance.
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Affiliation(s)
- Else K Hoffmann
- a Department of Biology ; Section for Cell Biology and Physiology; University of Copenhagen ; Copenhagen , Denmark
| | - Belinda H Sørensen
- a Department of Biology ; Section for Cell Biology and Physiology; University of Copenhagen ; Copenhagen , Denmark
| | - Daniel P R Sauter
- a Department of Biology ; Section for Cell Biology and Physiology; University of Copenhagen ; Copenhagen , Denmark
| | - Ian H Lambert
- a Department of Biology ; Section for Cell Biology and Physiology; University of Copenhagen ; Copenhagen , Denmark
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103
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Affiliation(s)
- Thomas Voets
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium
| | - Bernd Nilius
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium
| | - Rudi Vennekens
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, University of Leuven, Leuven, Belgium
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104
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Planells-Cases R, Lutter D, Guyader C, Gerhards NM, Ullrich F, Elger DA, Kucukosmanoglu A, Xu G, Voss FK, Reincke SM, Stauber T, Blomen VA, Vis DJ, Wessels LF, Brummelkamp TR, Borst P, Rottenberg S, Jentsch TJ. Subunit composition of VRAC channels determines substrate specificity and cellular resistance to Pt-based anti-cancer drugs. EMBO J 2015; 34:2993-3008. [PMID: 26530471 PMCID: PMC4687416 DOI: 10.15252/embj.201592409] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 10/05/2015] [Indexed: 11/25/2022] Open
Abstract
Although platinum‐based drugs are widely used chemotherapeutics for cancer treatment, the determinants of tumor cell responsiveness remain poorly understood. We show that the loss of subunits LRRC8A and LRRC8D of the heteromeric LRRC8 volume‐regulated anion channels (VRACs) increased resistance to clinically relevant cisplatin/carboplatin concentrations. Under isotonic conditions, about 50% of cisplatin uptake depended on LRRC8A and LRRC8D, but neither on LRRC8C nor on LRRC8E. Cell swelling strongly enhanced LRRC8‐dependent cisplatin uptake, bolstering the notion that cisplatin enters cells through VRAC. LRRC8A disruption also suppressed drug‐induced apoptosis independently from drug uptake, possibly by impairing VRAC‐dependent apoptotic cell volume decrease. Hence, by mediating cisplatin uptake and facilitating apoptosis, VRAC plays a dual role in the cellular drug response. Incorporation of the LRRC8D subunit into VRAC substantially increased its permeability for cisplatin and the cellular osmolyte taurine, indicating that LRRC8 proteins form the channel pore. Our work suggests that LRRC8D‐containing VRACs are crucial for cell volume regulation by an important organic osmolyte and may influence cisplatin/carboplatin responsiveness of tumors.
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Affiliation(s)
- Rosa Planells-Cases
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Darius Lutter
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Charlotte Guyader
- Division of Molecular Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Nora M Gerhards
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Florian Ullrich
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Deborah A Elger
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Asli Kucukosmanoglu
- Division of Molecular Pathology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Guotai Xu
- Division of Molecular Pathology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Felizia K Voss
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - S Momsen Reincke
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | - Vincent A Blomen
- Division of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Daniel J Vis
- Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Lodewyk F Wessels
- Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Thijn R Brummelkamp
- Division of Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Piet Borst
- Division of Molecular Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Sven Rottenberg
- Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland Division of Molecular Pathology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
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105
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Bolte P, Herrling R, Dorgau B, Schultz K, Feigenspan A, Weiler R, Dedek K, Janssen-Bienhold U. Expression and Localization of Connexins in the Outer Retina of the Mouse. J Mol Neurosci 2015; 58:178-92. [PMID: 26453550 DOI: 10.1007/s12031-015-0654-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 09/08/2015] [Indexed: 01/30/2023]
Abstract
The identification of the proteins that make up the gap junction channels between rods and cones is of crucial importance to understand the functional role of photoreceptor coupling within the retinal network. In vertebrates, connexin proteins constitute the structural components of gap junction channels. Connexin36 is known to be expressed in cones whereas extensive investigations have failed to identify the corresponding connexin expressed in rods. Using immunoelectron microscopy, we demonstrate that connexin36 (Cx36) is present in gap junctions of cone but not rod photoreceptors in the mouse retina. To identify the rod connexin, we used nested reverse transcriptase polymerase chain reaction and tested retina and photoreceptor samples for messenger RNA (mRNA) expression of all known connexin genes. In addition to connexin36, we detected transcripts for connexin32, connexin43, connexin45, connexin50, and connexin57 in photoreceptor samples. Immunohistochemistry showed that connexin43, connexin45, connexin50, and connexin57 proteins are expressed in the outer plexiform layer. However, none of these connexins was detected at gap junctions between rods and cones as a counterpart of connexin36. Therefore, the sought-after rod protein must be either an unknown connexin sequence, a connexin36 splice product not detected by our antibodies, or a protein from a further gap junction protein family.
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Affiliation(s)
- Petra Bolte
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Animal Navigation, University of Oldenburg, 26111, Oldenburg, Germany
| | - Regina Herrling
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany
| | - Birthe Dorgau
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK
| | - Konrad Schultz
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany
| | - Andreas Feigenspan
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Animal Physiology, FAU Erlangen-Nuremberg, 91058, Erlangen, Germany
| | - Reto Weiler
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany
| | - Karin Dedek
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany. .,Research Center Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany.
| | - Ulrike Janssen-Bienhold
- Neurobiology Group, Department for Neuroscience, School of Medicine and Health Sciences, University of Oldenburg, 26111, Oldenburg, Germany. .,Research Center Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany.
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106
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TMEM16, LRRC8A, bestrophin: chloride channels controlled by Ca2+ and cell volume. Trends Biochem Sci 2015; 40:535-43. [DOI: 10.1016/j.tibs.2015.07.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 07/10/2015] [Accepted: 07/10/2015] [Indexed: 01/13/2023]
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107
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Pedersen SF, Klausen TK, Nilius B. The identification of a volume-regulated anion channel: an amazing Odyssey. Acta Physiol (Oxf) 2015; 213:868-81. [PMID: 25565132 DOI: 10.1111/apha.12450] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 12/05/2014] [Accepted: 01/05/2015] [Indexed: 01/03/2023]
Abstract
The volume-regulated anion channel (VRAC) plays a pivotal role in cell volume regulation in essentially all cell types studied. Additionally, VRAC appears to contribute importantly to a wide range of other cellular functions and pathological events, including cell motility, cell proliferation, apoptosis and excitotoxic glutamate release in stroke. Although biophysically, pharmacologically and functionally thoroughly described, VRAC has until very recently remained a genetic orphan. The search for the molecular identity of VRAC has been long and has yielded multiple potential candidates, all of which eventually turned out to have properties not fully compatible with those of VRAC. Recently, two groups have independently identified the protein leucine-rich repeats containing 8A (LRRC8A), belonging to family of proteins (LRRC8A-E) distantly related to pannexins, as the likely pore-forming subunit of VRAC. In this brief review, we summarize the history of the discovery of VRAC, outline its basic biophysical and pharmacological properties, link these to several cellular functions in which VRAC appears to play important roles, and sketch the amazing search for the molecular identity of this channel. Finally, we describe properties of the LRRC8 proteins, highlight some features of the LRRC8A knockout mouse and discuss the impact of the discovery of LRRC8 as VRAC on future research.
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Affiliation(s)
- S. F. Pedersen
- Section for Cell and Developmental Biology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
| | - T. K. Klausen
- Section for Cell and Developmental Biology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
| | - B. Nilius
- Laboratory of Ion Channel Research; Department of Cellular and Molecular Medicine; KU Leuven, Campus Gasthuisberg; Leuven Belgium
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108
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Baranova A. LRRC8s revisited: and now they SWELL! (Retrospective on DOI 10.1002/bies.201100173). Bioessays 2014; 36:1017-8. [PMID: 25257378 DOI: 10.1002/bies.201400159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Ancha Baranova
- School of Systems Biology, George Mason University, Fairfax, VA, USA; Research Centre for Medical Genetics, Moscow, Russia
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109
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Sørensen BH, Thorsteinsdottir UA, Lambert IH. Acquired cisplatin resistance in human ovarian A2780 cancer cells correlates with shift in taurine homeostasis and ability to volume regulate. Am J Physiol Cell Physiol 2014; 307:C1071-80. [PMID: 25252947 DOI: 10.1152/ajpcell.00274.2014] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cisplatin resistance is a major challenge in the treatment of cancer and develops through reduced drug accumulation and an increased ability to avoid drug-induced cell damage, cell shrinkage, and hence initiation of apoptosis. Uptake and release of the semiessential amino acid taurine contribute to cell volume homeostasis, and taurine has been reported to have antiapoptotic effects. Here we find that volume-sensitive taurine release in cisplatin-sensitive [wild-type (WT)] human ovarian cancer A2780 cells is reduced in the presence of the phospholipase A2 inhibitor bromenol lactone, the 5-lipoxygenase (5-LO) inhibitor ETH 615-139, and the cysteine leukotriene receptor 1 (CysLT1) antagonist zafirlukast and impaired by the anion channel blocker DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonate). Comparing WT and cisplatin-resistant (RES) A2780 cells we also find that evasion of cisplatin-induced cell death in RES A2780 cells correlates with an increased accumulation of taurine, due to an increased taurine uptake and a concomitant impairment of the volume-sensitive taurine release pathway, as well an inability to reduce cell volume after osmotic cell swelling. Downregulation of volume-sensitive taurine release in RES A2780 cells correlates with reduced expression of the leucine-rich repeat-containing protein 8A (LRRC8A). Furthermore, acute (18 h) exposure to cisplatin (5-10 μM) increases taurine release and LRRC8A expression in WT A2780 cells whereas cisplatin has no effect on LRRC8A expression in RES A2780 cells. It is suggested that shift in LRRC8A activity can be used as biomarker for apoptotic progress and acquirement of drug resistance.
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Affiliation(s)
- Belinda Halling Sørensen
- Department of Biology, Section of Cellular and Developmental Biology, The August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - Unnur Arna Thorsteinsdottir
- Department of Biology, Section of Cellular and Developmental Biology, The August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - Ian Henry Lambert
- Department of Biology, Section of Cellular and Developmental Biology, The August Krogh Building, University of Copenhagen, Copenhagen, Denmark
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110
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Kurtenbach S, Whyte-Fagundes P, Gelis L, Kurtenbach S, Brazil E, Zoidl C, Hatt H, Shestopalov VI, Zoidl G. Investigation of olfactory function in a Panx1 knock out mouse model. Front Cell Neurosci 2014; 8:266. [PMID: 25309319 PMCID: PMC4162419 DOI: 10.3389/fncel.2014.00266] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 08/18/2014] [Indexed: 01/01/2023] Open
Abstract
Pannexin 1 (Panx1), the most extensively investigated member of a channel-forming protein family, is able to form pores conducting molecules up to 1.5 kDa, like ATP, upon activation. In the olfactory epithelium (OE), ATP modulates olfactory responsiveness and plays a role in proliferation and differentiation of olfactory sensory neurons (OSNs). This process continuously takes place in the OE, as neurons are replaced throughout the whole lifespan. The recent discovery of Panx1 expression in the OE raises the question whether Panx1 mediates ATP release responsible for modulating chemosensory function. In this study, we analyzed pannexin expression in the OE and a possible role of Panx1 in olfactory function using a Panx1−/− mouse line with a global ablation of Panx1. This mouse model has been previously used to investigate Panx1 functions in the retina and adult hippocampus. Here, qPCR, in-situ hybridization, and immunohistochemistry (IHC) demonstrated that Panx1 is expressed in axon bundles deriving from sensory neurons of the OE. The localization, distribution, and expression of major olfactory signal transduction proteins were not significantly altered in Panx1−/− mice. Further, functional analysis of Panx1−/− animals does not reveal any major impairment in odor perception, indicated by electroolfactogram (EOG) measurements and behavioral testing. However, ATP release evoked by potassium gluconate application was reduced in Panx1−/− mice. This result is consistent with previous reports on ATP release in isolated erythrocytes and spinal or lumbar cord preparations from Panx1−/− mice, suggesting that Panx1 is one of several alternative pathways to release ATP in the olfactory system.
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Affiliation(s)
- Stefan Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Paige Whyte-Fagundes
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Lian Gelis
- Department of Cell Physiology, Ruhr University Bochum Bochum, Germany
| | - Sarah Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Emerson Brazil
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Christiane Zoidl
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Hanns Hatt
- Department of Cell Physiology, Ruhr University Bochum Bochum, Germany
| | - Valery I Shestopalov
- Department of Ophthalmology, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami Miami, FL, USA ; Vavilov Institute of General Genetics, Russian Academy of Sciences Moscow, Russia
| | - Georg Zoidl
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
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111
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Akita T, Okada Y. Characteristics and roles of the volume-sensitive outwardly rectifying (VSOR) anion channel in the central nervous system. Neuroscience 2014; 275:211-31. [DOI: 10.1016/j.neuroscience.2014.06.015] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/06/2014] [Accepted: 06/07/2014] [Indexed: 01/05/2023]
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112
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Primary vitamin D receptor target genes as biomarkers for the vitamin D3 status in the hematopoietic system. J Nutr Biochem 2014; 25:875-84. [DOI: 10.1016/j.jnutbio.2014.04.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 03/10/2014] [Accepted: 04/02/2014] [Indexed: 12/16/2022]
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113
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Qiu Z, Dubin AE, Mathur J, Tu B, Reddy K, Miraglia LJ, Reinhardt J, Orth AP, Patapoutian A. SWELL1, a plasma membrane protein, is an essential component of volume-regulated anion channel. Cell 2014; 157:447-458. [PMID: 24725410 DOI: 10.1016/j.cell.2014.03.024] [Citation(s) in RCA: 416] [Impact Index Per Article: 41.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 02/24/2014] [Accepted: 03/18/2014] [Indexed: 12/23/2022]
Abstract
Maintenance of a constant cell volume in response to extracellular or intracellular osmotic changes is critical for cellular homeostasis. Activation of a ubiquitous volume-regulated anion channel (VRAC) plays a key role in this process; however, its molecular identity in vertebrates remains unknown. Here, we used a cell-based fluorescence assay and performed a genome-wide RNAi screen to find components of VRAC. We identified SWELL1 (LRRC8A), a member of a four-transmembrane protein family with unknown function, as essential for hypotonicity-induced iodide influx. SWELL1 is localized to the plasma membrane, and its knockdown dramatically reduces endogenous VRAC currents and regulatory cell volume decrease in various cell types. Furthermore, point mutations in SWELL1 cause a significant change in VRAC anion selectivity, demonstrating that SWELL1 is an essential VRAC component. These findings enable further molecular characterization of the VRAC channel complex and genetic studies for understanding the function of VRAC in normal physiology and disease.
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Affiliation(s)
- Zhaozhu Qiu
- Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121, USA; Department of Molecular and Cellular Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Adrienne E Dubin
- Department of Molecular and Cellular Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jayanti Mathur
- Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121, USA
| | - Buu Tu
- Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121, USA
| | - Kritika Reddy
- Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121, USA
| | - Loren J Miraglia
- Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121, USA
| | - Jürgen Reinhardt
- Novartis Institutes for Biomedical Research, Basel 4056, Switzerland
| | - Anthony P Orth
- Genomics Institute of the Novartis Research Foundation, San Diego, CA 92121, USA
| | - Ardem Patapoutian
- Department of Molecular and Cellular Neuroscience, Howard Hughes Medical Institute, The Scripps Research Institute, La Jolla, CA 92037, USA.
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114
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Beckel JM, Argall AJ, Lim JC, Xia J, Lu W, Coffey EE, Macarak EJ, Shahidullah M, Delamere NA, Zode GS, Sheffield VC, Shestopalov VI, Laties AM, Mitchell CH. Mechanosensitive release of adenosine 5'-triphosphate through pannexin channels and mechanosensitive upregulation of pannexin channels in optic nerve head astrocytes: a mechanism for purinergic involvement in chronic strain. Glia 2014; 62:1486-501. [PMID: 24839011 DOI: 10.1002/glia.22695] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 05/01/2014] [Accepted: 05/02/2014] [Indexed: 12/21/2022]
Abstract
As adenosine 5'-triphosphate (ATP) released from astrocytes can modulate many neural signaling systems, the triggers and pathways for this ATP release are important. Here, the ability of mechanical strain to trigger ATP release through pannexin channels and the effects of sustained strain on pannexin expression were examined in rat optic nerve head astrocytes. Astrocytes released ATP when subjected to 5% of equibiaxial strain or to hypotonic swelling. Although astrocytes expressed mRNA for pannexins 1-3, connexin 43, and VNUT, pharmacological analysis suggested a predominant role for pannexins in mechanosensitive ATP release, with Rho kinase contribution. Astrocytes from panx1(-/-) mice had reduced baseline and stimulated levels of extracellular ATP, confirming the role for pannexins. Swelling astrocytes triggered a regulatory volume decrease that was inhibited by apyrase or probenecid. The swelling-induced rise in calcium was inhibited by P2X7 receptor antagonists A438079 and AZ10606120, in addition to apyrase and carbenoxolone. Extended stretch of astrocytes in vitro upregulated expression of panx1 and panx2 mRNA. A similar upregulation was observed in vivo in optic nerve head tissue from the Tg-MYOC(Y437H) mouse model of chronic glaucoma; genes for panx1, panx2, and panx3 were increased, whereas immunohistochemistry confirmed increased expression of pannexin 1 protein. In summary, astrocytes released ATP in response to mechanical strain, with pannexin 1 the predominant efflux pathway. Sustained strain upregulated pannexins in vitro and in vivo. Together, these findings provide a mechanism by which extracellular ATP remains elevated under chronic mechanical strain, as found in the optic nerve head of patients with glaucoma.
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Affiliation(s)
- Jonathan M Beckel
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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115
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Lee CC, Freinkman E, Sabatini DM, Ploegh HL. The protein synthesis inhibitor blasticidin s enters mammalian cells via leucine-rich repeat-containing protein 8D. J Biol Chem 2014; 289:17124-31. [PMID: 24782309 DOI: 10.1074/jbc.m114.571257] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Leucine-rich repeat-containing 8 (LRRC8) proteins have been identified as putative receptors involved in lymphocyte development and adipocyte differentiation. They remain poorly characterized, and no specific function has been assigned to them. There is no consensus on how this family of proteins might function because homology searches suggest that members of the LRRC8 family act not as plasma membrane receptors, but rather as channels that mediate cell-cell signaling. Here we provide experimental evidence that supports a role for LRRC8s in the transport of small molecules. We show that LRRC8D is a mammalian protein required for the import of the antibiotic blasticidin S. We characterize localization and topology of LRRC8A and LRRC8D and demonstrate that LRRC8D interacts with LRRC8A, LRRC8B, and LRRC8C. Given the suggested involvement in solute transport, our results support a model in which LRRC8s form one or more complexes that may mediate cell-cell communication by transporting small solutes.
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Affiliation(s)
- Clarissa C Lee
- From the Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Elizaveta Freinkman
- From the Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
| | - David M Sabatini
- From the Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, the David H. Koch Institute for Integrative Cancer Research at Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, the Broad Institute, Cambridge, Massachusetts 02142, and the Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Hidde L Ploegh
- From the Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
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116
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Kumar L, Chou J, Yee CSK, Borzutzky A, Vollmann EH, von Andrian UH, Park SY, Hollander G, Manis JP, Poliani PL, Geha RS. Leucine-rich repeat containing 8A (LRRC8A) is essential for T lymphocyte development and function. ACTA ACUST UNITED AC 2014; 211:929-42. [PMID: 24752297 PMCID: PMC4010910 DOI: 10.1084/jem.20131379] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Lrrc8a is a ubiquitously expressed gene that encodes a leucine-rich repeat (LRR)-containing protein detected at higher levels on the surface of thymocytes than on other immune cells. We generated Lrrc8a(-/-) mice to investigate the role of LRRC8A in lymphocyte development and function. Lrrc8a(-/-) mice had increased prenatal and postnatal mortality, growth retardation, and multiple tissue abnormalities. Lrrc8a(-/-) mice displayed a modest block in B cell development but intact intrinsic B cell function. In contrast, both Lrrc8a(-/-) mice and Lrrc8a(-/-)→Rag2(-/-) bone marrow chimeras exhibited a severe cell-intrinsic block in early thymic development, with decreased proliferation and increased apoptosis of thymocytes, and impaired peripheral T cell function. Thymic epithelial cells expressed an LRRC8A ligand that was critical for double-negative to double-positive thymocyte differentiation and survival in vitro. LRRC8A constitutively associated with the GRB2-GAB2 complex and lymphocyte-specific protein tyrosine kinase (LCK) in thymocytes. LRRC8A ligation activated AKT via the LCK-ZAP-70-GAB2-PI3K pathway, and AKT phosphorylation was markedly reduced in the thymus of Lrrc8a(-/-) mice. These findings reveal an essential role for LRRC8A in T cell development, survival, and function.
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Affiliation(s)
- Lalit Kumar
- Division of Immunology and 2 Joint Program in Transfusion Medicine, Division of Laboratory Medicine, Boston Children's Hospital; and 3 Department of Pediatrics, 4 Department of Microbiology and Immunobiology, and 5 Department of Pathology, Harvard Medical School, Boston, MA 02115
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117
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Voss FK, Ullrich F, Münch J, Lazarow K, Lutter D, Mah N, Andrade-Navarro MA, von Kries JP, Stauber T, Jentsch TJ. Identification of LRRC8 heteromers as an essential component of the volume-regulated anion channel VRAC. Science 2014; 344:634-8. [PMID: 24790029 DOI: 10.1126/science.1252826] [Citation(s) in RCA: 428] [Impact Index Per Article: 42.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Regulation of cell volume is critical for many cellular and organismal functions, yet the molecular identity of a key player, the volume-regulated anion channel VRAC, has remained unknown. A genome-wide small interfering RNA screen in mammalian cells identified LRRC8A as a VRAC component. LRRC8A formed heteromers with other LRRC8 multispan membrane proteins. Genomic disruption of LRRC8A ablated VRAC currents. Cells with disruption of all five LRRC8 genes required LRRC8A cotransfection with other LRRC8 isoforms to reconstitute VRAC currents. The isoform combination determined VRAC inactivation kinetics. Taurine flux and regulatory volume decrease also depended on LRRC8 proteins. Our work shows that VRAC defines a class of anion channels, suggests that VRAC is identical to the volume-sensitive organic osmolyte/anion channel VSOAC, and explains the heterogeneity of native VRAC currents.
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Affiliation(s)
- Felizia K Voss
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin
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118
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Kurtenbach S, Kurtenbach S, Zoidl G. Gap junction modulation and its implications for heart function. Front Physiol 2014; 5:82. [PMID: 24578694 PMCID: PMC3936571 DOI: 10.3389/fphys.2014.00082] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 02/10/2014] [Indexed: 01/04/2023] Open
Abstract
Gap junction communication (GJC) mediated by connexins is critical for heart function. To gain insight into the causal relationship of molecular mechanisms of disease pathology, it is important to understand which mechanisms contribute to impairment of gap junctional communication. Here, we present an update on the known modulators of connexins, including various interaction partners, kinases, and signaling cascades. This gap junction network (GJN) can serve as a blueprint for data mining approaches exploring the growing number of publicly available data sets from experimental and clinical studies.
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Affiliation(s)
- Stefan Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Sarah Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Georg Zoidl
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada ; Department of Biology, Faculty of Science, York University Toronto, ON, Canada ; Center for Vision Research, York University Toronto, ON, Canada
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119
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Abstract
The pannexins (Panxs) are a family of chordate proteins homologous to the invertebrate gap junction forming proteins named innexins. Three distinct Panx paralogs (Panx1, Panx2, and Panx3) are shared among the major vertebrate phyla, but they appear to have suppressed (or even lost) their ability to directly couple adjacent cells. Connecting the intracellular and extracellular compartments is now widely accepted as Panx's primary function, facilitating the passive movement of ions and small molecules along electrochemical gradients. The tissue distribution of the Panxs ranges from pervasive to very restricted, depending on the paralog, and are often cell type-specific and/or developmentally regulated within any given tissue. In recent years, Panxs have been implicated in an assortment of physiological and pathophysiological processes, particularly with respect to ATP signaling and inflammation, and they are now considered to be a major player in extracellular purinergic communication. The following is a comprehensive review of the Panx literature, exploring the historical events leading up to their discovery, outlining our current understanding of their biochemistry, and describing the importance of these proteins in health and disease.
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Affiliation(s)
- Stephen R Bond
- Genome Technology Branch, Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health Bethesda, MD, USA ; Department of Cellular and Physiological Science, Life Sciences Institute, University of British Columbia Vancouver, BC, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Science, Life Sciences Institute, University of British Columbia Vancouver, BC, Canada
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120
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A reporter screen in a human haploid cell line identifies CYLD as a constitutive inhibitor of NF-κB. PLoS One 2013; 8:e70339. [PMID: 23861985 PMCID: PMC3704534 DOI: 10.1371/journal.pone.0070339] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 06/21/2013] [Indexed: 11/23/2022] Open
Abstract
The development of forward genetic screens in human haploid cells has the potential to transform our understanding of the genetic basis of cellular processes unique to man. So far, this approach has been limited mostly to the identification of genes that mediate cell death in response to a lethal agent, likely due to the ease with which this phenotype can be observed. Here, we perform the first reporter screen in the near-haploid KBM7 cell line to identify constitutive inhibitors of NF-κB. CYLD was the only currently known negative regulator of NF-κB to be identified, thus uniquely distinguishing this gene. Also identified were three genes with no previous known connection to NF-κB. Our results demonstrate that reporter screens in haploid human cells can be applied to investigate the many complex signaling pathways that converge upon transcription factors.
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121
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Piepoli A, Palmieri O, Maglietta R, Panza A, Cattaneo E, Latiano A, Laczko E, Gentile A, Carella M, Mazzoccoli G, Ancona N, Marra G, Andriulli A. The expression of leucine-rich repeat gene family members in colorectal cancer. Exp Biol Med (Maywood) 2012; 237:1123-8. [PMID: 23045723 DOI: 10.1258/ebm.2012.012042] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
This study was conducted to evaluate the association of the leucine-rich repeat (LRR) gene family with colorectal cancer (CRC). The expression of members of the LRR gene family were analyzed in 17 CRC specimens and in 59 healthy colorectal tissues by using Human Exon1.0ST microarray, and in 25 CRC specimens and 32 healthy colorectal tissues by U133Plus2.0 microarray. An association was found for 25 genes belonging to the plant-specific (PS) class of LRR genes (P = 0.05 for Exon1.0 ST and P = 0.04 for U133Plus2.0). In both data-sets, in CRC, we found down-regulation of SHOC2 (P < 0.00003) and LRRC28 (P < 0.01) and up-regulation of LRSAM1 (P < 0.000001), while up-regulation of MFHAS1 (P = 0.0005) and down-regulation of WDFY3 (P = 0.026) were found only in the Exon1.0 ST data-set. The PS LLR gene class encodes proteins that activate immune cells and might play a key role in programmed cell death and autophagy. SHOC2 and LRRC28 genes involved in RAS-mediated signaling, which hinders nutrient deprivation-induced autophagy, might be a possible link between the negative control of autophagy and tumorigenesis.
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Affiliation(s)
- Ada Piepoli
- Laboratory and Division of Gastroenterology, IRCCS Casa Sollievo della Sofferenza Hospital, Viale Cappuccini n.1, San Giovanni Rotondo (FG), Italy.
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122
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Romanov RA, Bystrova MF, Rogachevskaya OA, Sadovnikov VB, Shestopalov VI, Kolesnikov SS. The ATP permeability of pannexin 1 channels in a heterologous system and in mammalian taste cells is dispensable. J Cell Sci 2012; 125:5514-23. [PMID: 22956545 DOI: 10.1242/jcs.111062] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Afferent output in type II taste cells is mediated by ATP liberated through ion channels. It is widely accepted that pannexin 1 (Panx1) channels are responsible for ATP release in diverse cell types, including taste cells. While biophysical evidence implicates slow deactivation of ion channels following ATP release in taste cells, recombinant Panx1 activates and deactivates rapidly. This inconsistency could indicate that the cellular context specifies Panx1 functioning. We cloned Panx1 from murine taste tissue, and heterologously expressed it in three different cell lines: HEK-293, CHO and neuroblastoma SK-N-SH cells. In all three cell lines, Panx1 transfection yielded outwardly rectifying anion channels that exhibited fast gating and negligible permeability to anions exceeding 250 Da. Despite expression of Panx1, the host cells did not liberate ATP upon stimulation, making it unclear whether Panx1 is involved in taste-related ATP secretion. This issue was addressed using mice with genetic ablation of the Panx1 gene. The ATP-biosensor assay revealed that, in taste cells devoid of Panx1, ATP secretion was robust and apparently unchanged compared with the control. Our data suggest that Panx1 alone forms a channel that has insufficient permeability to ATP. Perhaps, a distinct subunit and/or a regulatory circuit that is absent in taste cells is required to enable a high ATP-permeability mode of a native Panx1-based channel.
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Affiliation(s)
- Roman A Romanov
- Institute of Cell Biophysics, Russian Academy of Sciences, Institutional Street 3, Pushchino, Moscow Region, 142290, Russia
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Affiliation(s)
- Ancha Baranova
- School of Systems Biology, George Mason University, Fairfax, VA, USA.
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