1
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Kostritskaia Y, Klüssendorf M, Pan YE, Hassani Nia F, Kostova S, Stauber T. Physiological Functions of the Volume-Regulated Anion Channel VRAC/LRRC8 and the Proton-Activated Chloride Channel ASOR/TMEM206. Handb Exp Pharmacol 2024; 283:181-218. [PMID: 37468723 DOI: 10.1007/164_2023_673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Volume-regulated anion channels (VRACs) and the acid-sensitive outwardly rectifying anion channel (ASOR) mediate flux of chloride and small organic anions. Although known for a long time, they were only recently identified at the molecular level. VRACs are heteromers consisting of LRRC8 proteins A to E. Combining the essential LRRC8A with different LRRC8 paralogues changes key properties of VRAC such as conductance or substrate selectivity, which is how VRACs are involved in multiple physiological functions including regulatory volume decrease, cell proliferation and migration, cell death, purinergic signalling, fat and glucose metabolism, insulin signalling, and spermiogenesis. VRACs are also involved in pathological conditions, such as the neurotoxic release of glutamate and aspartate. Certain VRACs are also permeable to larger, organic anions, including antibiotics and anti-cancer drugs, making them an interesting therapeutic target. ASOR, also named proton-activated chloride channel (PAC), is formed by TMEM206 homotrimers on the plasma membrane and on endosomal compartments where it mediates chloride flux in response to extracytosolic acidification and plays a role in the shrinking and maturation of macropinosomes. ASOR has been shown to underlie neuronal swelling which causes cell death after stroke as well as promoting the metastasis of certain cancers, making them intriguing therapeutic targets as well.
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Affiliation(s)
- Yulia Kostritskaia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Malte Klüssendorf
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Yingzhou Edward Pan
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Fatemeh Hassani Nia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Simona Kostova
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Tobias Stauber
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany.
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2
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Bakowski D, Murray F, Parekh AB. Store-Operated Ca 2+ Channels: Mechanism, Function, Pharmacology, and Therapeutic Targets. Annu Rev Pharmacol Toxicol 2020; 61:629-654. [PMID: 32966177 DOI: 10.1146/annurev-pharmtox-031620-105135] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Calcium (Ca2+) release-activated Ca2+ (CRAC) channels are a major route for Ca2+ entry in eukaryotic cells. These channels are store operated, opening when the endoplasmic reticulum (ER) is depleted of Ca2+, and are composed of the ER Ca2+ sensor protein STIM and the pore-forming plasma membrane subunit Orai. Recent years have heralded major strides in our understanding of the structure, gating, and function of the channels. Loss-of-function and gain-of-function mutants combined with RNAi knockdown strategies have revealed important roles for the channel in numerous human diseases, making the channel a clinically relevant target. Drugs targeting the channels generally lack specificity or exhibit poor efficacy in animal models. However, the landscape is changing, and CRAC channel blockers are now entering clinical trials. Here, we describe the key molecular and biological features of CRAC channels, consider various diseases associated with aberrant channel activity, and discuss targeting of the channels from a therapeutic perspective.
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Affiliation(s)
| | - Fraser Murray
- Pandeia Therapeutics, Oxford OX4 4GP, United Kingdom
| | - Anant B Parekh
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford OX1 3PT, United Kingdom; , .,Current affiliation: National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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3
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Trothe J, Ritzmann D, Lang V, Scholz P, Pul Ü, Kaufmann R, Buerger C, Ertongur-Fauth T. Hypotonic stress response of human keratinocytes involves LRRC8A as component of volume-regulated anion channels. Exp Dermatol 2019; 27:1352-1360. [PMID: 30252954 DOI: 10.1111/exd.13789] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 09/16/2018] [Indexed: 01/02/2023]
Abstract
The barrier function of the human epidermis is constantly challenged by environmental osmotic fluctuations. Hypotonic stress triggers cell swelling, which is counteracted by a compensatory mechanism called regulatory volume decrease (RVD) involving volume-regulated anion channels (VRACs). Recently, it was discovered that VRACs are composed of LRRC8 heteromers and that LRRC8A functions as the essential VRAC subunit in various mammalian cell types; however, the molecular identity of VRACs in the human epidermis remains to be determined. Here, we investigated the expression of LRRC8A and its role in hypotonic stress response of human keratinocytes. Immunohistological staining showed that LRRC8A is preferentially localized in basal and suprabasal epidermal layers. RNA sequencing revealed that LRRC8A is the most abundant subunit within the LRRC8 gene family in HaCaT cells as well as in primary normal human epidermal keratinocytes (NHEKs). To determine the contribution of LRRC8A to hypotonic stress response, we generated HaCaT- and NHEK-LRRC8A knockout cells by using CRISPR-Cas9. I- influx assays using halide-sensitive YFP showed that LRRC8A is crucially important for mediating VRAC activity in HaCaTs and NHEKs. Moreover, cell volume measurements using calcein-AM dye further revealed that LRRC8A also substantially contributes to RVD. In summary, our study provides new insights into hypotonic stress response and suggests an important role of LRRC8A as VRAC component in human keratinocytes.
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Affiliation(s)
| | | | - Victoria Lang
- Department of Dermatology, Venerology and Allergology, Clinic of the Goethe-University, Frankfurt am Main, Germany
| | | | | | - Roland Kaufmann
- Department of Dermatology, Venerology and Allergology, Clinic of the Goethe-University, Frankfurt am Main, Germany
| | - Claudia Buerger
- Department of Dermatology, Venerology and Allergology, Clinic of the Goethe-University, Frankfurt am Main, Germany
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4
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Chen L, König B, Liu T, Pervaiz S, Razzaque YS, Stauber T. More than just a pressure relief valve: physiological roles of volume-regulated LRRC8 anion channels. Biol Chem 2019; 400:1481-1496. [DOI: 10.1515/hsz-2019-0189] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 04/27/2019] [Indexed: 12/29/2022]
Abstract
Abstract
The volume-regulated anion channel (VRAC) is a key player in the volume regulation of vertebrate cells. This ubiquitously expressed channel opens upon osmotic cell swelling and potentially other cues and releases chloride and organic osmolytes, which contributes to regulatory volume decrease (RVD). A plethora of studies have proposed a wide range of physiological roles for VRAC beyond volume regulation including cell proliferation, differentiation and migration, apoptosis, intercellular communication by direct release of signaling molecules and by supporting the exocytosis of insulin. VRAC was additionally implicated in pathological states such as cancer therapy resistance and excitotoxicity under ischemic conditions. Following extensive investigations, 5 years ago leucine-rich repeat-containing family 8 (LRRC8) heteromers containing LRRC8A were identified as the pore-forming components of VRAC. Since then, molecular biological approaches have allowed further insight into the biophysical properties and structure of VRAC. Heterologous expression, siRNA-mediated downregulation and genome editing in cells, as well as the use of animal models have enabled the assessment of the proposed physiological roles, together with the identification of new functions including spermatogenesis and the uptake of antibiotics and platinum-based cancer drugs. This review discusses the recent molecular biological insights into the physiology of VRAC in relation to its previously proposed roles.
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Affiliation(s)
- Lingye Chen
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Benjamin König
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Tianbao Liu
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Sumaira Pervaiz
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Yasmin S. Razzaque
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Tobias Stauber
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
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5
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Liu Y, Zhang H, Men H, Du Y, Xiao Z, Zhang F, Huang D, Du X, Gamper N, Zhang H. Volume-regulated Cl - current: contributions of distinct Cl - channels and localized Ca 2+ signals. Am J Physiol Cell Physiol 2019; 317:C466-C480. [PMID: 31242393 DOI: 10.1152/ajpcell.00507.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The swelling-activated chloride current (ICl,swell) is induced when a cell swells and plays a central role in maintaining cell volume in response to osmotic stress. The major contributor of ICl,swell is the volume-regulated anion channel (VRAC). Leucine-rich repeat containing 8A (LRRC8A; SWELL1) was recently identified as an essential component of VRAC, but the mechanisms of VRAC activation are still largely unknown; moreover, other Cl- channels, such as anoctamin 1 (ANO1), were also suggested to contribute to ICl,swell. In this present study, we investigated the roles of LRRC8A and ANO1 in activation of ICl,swell; we also explored the role of intracellular Ca2+ in ICl,swell activation. We used a CRISPR/Cas9 gene editing approach, electrophysiology, live fluorescent imaging, selective pharmacology, and other approaches to show that both LRRC8A and ANO1 can be activated by cell swelling in HEK293 cells. Yet, both channels contribute biophysically and pharmacologically distinct components to ICl,swell, with LRRC8A being the major component. Cell swelling induced oscillatory Ca2+ transients, and these Ca2+ signals were required to activate both the LRRC8A- and ANO1-dependent components of ICl,swell. Both ICl,swell components required localized rather than global Ca2+ for activation. Interestingly, while intracellular Ca2+ was necessary and sufficient to activate ANO1, it was necessary but not sufficient to activate LRRC8A-mediated currents. Finally, Ca2+ transients linked to the ICl,swell activation were mediated by the G protein-coupled receptor-independent PLC isoforms.
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Affiliation(s)
- Yani Liu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China.,Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, China
| | - Huiran Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China.,Department of Pulmonary Medicine, the Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Hongchao Men
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Yuwei Du
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Ziqian Xiao
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Fan Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Dongyang Huang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China.,School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
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6
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König B, Hao Y, Schwartz S, Plested AJ, Stauber T. A FRET sensor of C-terminal movement reveals VRAC activation by plasma membrane DAG signaling rather than ionic strength. eLife 2019; 8:45421. [PMID: 31210638 PMCID: PMC6597245 DOI: 10.7554/elife.45421] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 06/14/2019] [Indexed: 12/13/2022] Open
Abstract
Volume-regulated anion channels (VRACs) are central to cell volume regulation. Recently identified as hetero-hexamers formed by LRRC8 proteins, their activation mechanism remains elusive. Here, we measured Förster resonance energy transfer (FRET) between fluorescent proteins fused to the C-termini of LRRC8 subunits. Inter-subunit FRET from LRRC8 complexes tracked VRAC activation. With patch-clamp fluorometry, we confirmed that the cytoplasmic domains rearrange during VRAC opening. With these FRET reporters, we determined VRAC activation, non-invasively, in live cells and their subcompartments. Reduced intracellular ionic strength did not directly activate VRACs, and VRACs were not activated on endomembranes. Instead, pharmacological manipulation of diacylglycerol (DAG), and protein kinase D (PKD) activity, activated or inhibited plasma membrane-localized VRACs. Finally, we resolved previous contradictory reports concerning VRAC activation, using FRET to detect robust activation by PMA that was absent during whole-cell patch clamp. Overall, non-invasive VRAC measurement by FRET is an essential tool for unraveling its activation mechanism.
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Affiliation(s)
- Benjamin König
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Yuchen Hao
- Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,NeuroCure, Charité Universitätsmedizin, Berlin, Germany
| | - Sophia Schwartz
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Andrew Jr Plested
- Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,NeuroCure, Charité Universitätsmedizin, Berlin, Germany
| | - Tobias Stauber
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
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7
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Kunzelmann K, Ousingsawat J, Benedetto R, Cabrita I, Schreiber R. Contribution of Anoctamins to Cell Survival and Cell Death. Cancers (Basel) 2019; 11:E382. [PMID: 30893776 PMCID: PMC6468699 DOI: 10.3390/cancers11030382] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 03/13/2019] [Accepted: 03/16/2019] [Indexed: 02/07/2023] Open
Abstract
Before anoctamins (TMEM16 proteins) were identified as a family of Ca2+-activated chloride channels and phospholipid scramblases, the founding member anoctamin 1 (ANO1, TMEM16A) was known as DOG1, a marker protein for gastrointestinal stromal tumors (GIST). Meanwhile, ANO1 has been examined in more detail, and the role of ANO1 in cell proliferation and the development of different types of malignomas is now well established. While ANO5, ANO7, and ANO9 may also be relevant for growth of cancers, evidence has been provided for a role of ANO6 (TMEM16F) in regulated cell death. The cellular mechanisms by which anoctamins control cell proliferation and cell death, respectively, are just emerging; however, the pronounced effects of anoctamins on intracellular Ca2+ levels are likely to play a significant role. Recent results suggest that some anoctamins control membrane exocytosis by setting Ca2+i levels near the plasma membrane, and/or by controlling the intracellular Cl- concentration. Exocytosis and increased membrane trafficking induced by ANO1 and ANO6 may enhance membrane expression of other chloride channels, such as CFTR and volume activated chloride channels (VRAC). Notably, ANO6-induced phospholipid scrambling with exposure of phosphatidylserine is pivotal for the sheddase function of disintegrin and metalloproteinase (ADAM). This may support cell death and tumorigenic activity of IL-6 by inducing IL-6 trans-signaling. The reported anticancer effects of the anthelminthic drug niclosamide are probably related to the potent inhibitory effect on ANO1, apart from inducing cell cycle arrest through the Let-7d/CDC34 axis. On the contrary, pronounced activation of ANO6 due to a large increase in intracellular calcium, activation of phospholipase A2 or lipid peroxidation, can lead to ferroptotic death of cancer cells. It therefore appears reasonable to search for both inhibitors and potent activators of TMEM16 in order to interfere with cancer growth and metastasis.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
| | - Jiraporn Ousingsawat
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
| | - Roberta Benedetto
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
| | - Ines Cabrita
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
| | - Rainer Schreiber
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
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8
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Chen J, Dou Y, Zheng X, Leng T, Lu X, Ouyang Y, Sun H, Xing F, Mai J, Gu J, Lu B, Yan G, Lin J, Zhu W. TRPM7 channel inhibition mediates midazolam-induced proliferation loss in human malignant glioma. Tumour Biol 2016; 37:14721-14731. [PMID: 27629139 DOI: 10.1007/s13277-016-5317-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 09/05/2016] [Indexed: 01/09/2023] Open
Abstract
The melastatin-like transient receptor potential 7 (TRPM7) has been implicated in proliferation or apoptosis of some cancers, indicating the potential of TRPM7 as an anti-anaplastic target. Here, we identified the characteristic TRPM7 channel currents in human malignant glioma MGR2 cells, which could be blocked by a pharmacologic inhibitor Gd3+. We mined the clinical sample data from Oncomine Database and found that human malignant glioma tissues expressed higher TRPM7 mRNA than normal brain ones. Importantly, we identified a widely used clinical anesthetic midazolam as a TRPM7 inhibitor. Midazolam treatment for seconds suppressed the TRPM7 currents and calcium influx, and treatment for 48 h inhibited the TRPM7 expression. The inhibitory effect on TRPM7 accounts for the proliferation loss and G0/G1 phase cell cycle arrest induced by midazolam. Our data demonstrates that midazolam represses proliferation of human malignant glioma cells through inhibiting TRPM7 currents, which may be further potentiated by suppressing the expression of TRPM7. Our result indicates midazolam as a pharmacologic lead compound with brain-blood barrier permeability for targeting TRPM7 in the glioma.
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Affiliation(s)
- Jingkao Chen
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, 510006, People's Republic of China
| | - Yunling Dou
- Department of Anesthesiology, Department of Pathology and Department of Cardiology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510080, People's Republic of China
| | - Xiaoke Zheng
- Department of Anesthesiology, Department of Pathology and Department of Cardiology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510080, People's Republic of China
| | - Tiandong Leng
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA, 30329, USA
| | - Xiaofang Lu
- Department of Anesthesiology, Department of Pathology and Department of Cardiology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510080, People's Republic of China
| | - Ying Ouyang
- Department of Pediatrics, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, 510120, People's Republic of China
| | - Huawei Sun
- Department of Anesthesiology, Department of Pathology and Department of Cardiology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510080, People's Republic of China
| | - Fan Xing
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Jialuo Mai
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Jiayu Gu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Bingzheng Lu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Guangmei Yan
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center and Collaborative Innovation Center for Cancer Medicine, Guangzhou, People's Republic of China
| | - Jun Lin
- Department of Anesthesiology, Stony Brook University Health Science Center, Stony Brook, NY, 11794-8480, USA.
| | - Wenbo Zhu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China. .,South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center and Collaborative Innovation Center for Cancer Medicine, Guangzhou, People's Republic of China.
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9
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Benedetto R, Sirianant L, Pankonien I, Wanitchakool P, Ousingsawat J, Cabrita I, Schreiber R, Amaral M, Kunzelmann K. Relationship between TMEM16A/anoctamin 1 and LRRC8A. Pflugers Arch 2016; 468:1751-63. [PMID: 27514381 DOI: 10.1007/s00424-016-1862-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 07/23/2016] [Accepted: 07/26/2016] [Indexed: 10/21/2022]
Abstract
TMEM16A/anoctamin 1/ANO1 and VRAC/LRRC8 are independent chloride channels activated either by increase in intracellular Ca(2+) or cell swelling, respectively. In previous studies, we observed overlapping properties for both types of channels. (i) TMEM16A/ANO1 and LRRC8 are inhibited by identical compounds, (ii) the volume-regulated anion channel VRAC requires compartmentalized Ca(2+) increase to be fully activated, (iii) anoctamins are activated by cell swelling, (iv) both channels have a role for apoptotic cell death, (v) both channels are possibly located in lipid rafts/caveolae like structures, and (vi) VRAC and anoctamin 1 currents are not additive when each are fully activated. In the present study, we demonstrate in different cell types that loss of LRRC8A expression not only inhibited VRAC, but also attenuated Ca(2+) activated Cl(-) currents. Moreover, expression of LRRC8A enhanced Ca(2+) activated Cl(-) currents, and both LRRC8A and ANO1 could be coimmunoprecipitated. We found that LRRC8A becomes accessible to biotinylation upon exposure to hypotonic bath solution, while membrane capacitance was not enhanced. When intracellular Ca(2+) was increased in ANO1-expressing cells, the membrane capacitance was enhanced and increased binding of FM4-64 to the membrane was observed. As this was not seen in cells lacking ANO1 expression, a role of ANO1 for exocytosis was suggested. We propose that ANO1 and LRRC8A are activated in parallel. Thus, ionomycin or purinergic stimulation will not only activate ANO1 but also LRRC8 currents. Cell swelling will not only activate LRRC8/VRAC, but also stimulate ANO1 currents by enhancing compartmentalized Ca(2+) increase and/or through swelling induced autocrine release of ATP.
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Affiliation(s)
- Roberta Benedetto
- Physiological Institute, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany
| | - Lalida Sirianant
- Physiological Institute, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany
| | - Ines Pankonien
- Faculty of Sciences, Biosystems & Integrative Sciences Institute, University of Lisboa, Lisbon, Portugal
| | - Podchanart Wanitchakool
- Physiological Institute, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany
| | - Jiraporn Ousingsawat
- Physiological Institute, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany
| | - Ines Cabrita
- Physiological Institute, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany
| | - Rainer Schreiber
- Physiological Institute, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany
| | - Margarida Amaral
- Faculty of Sciences, Biosystems & Integrative Sciences Institute, University of Lisboa, Lisbon, Portugal
| | - Karl Kunzelmann
- Physiological Institute, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany.
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10
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Yin MZ, Park SW, Kang TW, Kim KS, Yoo HY, Lee J, Hah JH, Sung MH, Kim SJ. Activation of K(+) channel by 1-EBIO rescues the head and neck squamous cell carcinoma cells from Ca(2+) ionophore-induced cell death. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2015; 20:25-33. [PMID: 26807020 PMCID: PMC4722188 DOI: 10.4196/kjpp.2016.20.1.25] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 08/14/2015] [Accepted: 08/14/2015] [Indexed: 12/11/2022]
Abstract
Ion channels in carcinoma and their roles in cell proliferation are drawing attention. Intracellular Ca2+ ([Ca2+]i)-dependent signaling affects the fate of cancer cells. Here we investigate the role of Ca2+-activated K+ channel (SK4) in head and neck squamous cell carcinoma cells (HNSCCs) of different cell lines; SNU-1076, OSC-19 and HN5. Treatment with 1 µM ionomycin induced cell death in all the three cell lines. Whole-cell patch clamp study suggested common expressions of Ca2+-activated Cl- channels (Ano-1) and Ca2+-activated nonselective cation channels (CAN). 1-EBIO, an activator of SK4, induced outward K+ current (ISK4) in SNU-1076 and OSC-19. In HN5, ISK4 was not observed or negligible. The 1-EBIO-induced current was abolished by TRAM-34, a selective SK4 blocker. Interestingly, the ionomycin-induced cell death was effectively prevented by 1-EBIO in SNU-1076 and OSC-19, and the rescue effect was annihilated by combined TRAM-34. Consistent with the lower level of ISK4, the rescue by 1-EBIO was least effective in HN5. The results newly demonstrate the role of SK4 in the fate of HNSCCs under the Ca2+ overloaded condition. Pharmacological modulation of SK4 might provide an intriguing novel tool for the anti-cancer strategy in HNSCC.
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Affiliation(s)
- Ming Zhe Yin
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea.; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea.; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Seok-Woo Park
- Department of Otolaryngology, Seoul National University Hospital, Seoul 03080, Korea.; Cancer Research Institute, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Tae Wook Kang
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Kyung Soo Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea.; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea.; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Hae Young Yoo
- Chung-Ang University Red Cross College of Nursing, Seoul 06974, Korea
| | - Junho Lee
- Department of Otolaryngology, Seoul National University Hospital, Seoul 03080, Korea
| | - J Hun Hah
- Department of Otolaryngology, Seoul National University Hospital, Seoul 03080, Korea.; Cancer Research Institute, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Myung Hun Sung
- Department of Otolaryngology, Seoul National University Hospital, Seoul 03080, Korea.; Cancer Research Institute, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea.; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea.; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 03080, Korea
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11
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Cellular volume regulation by anoctamin 6: Ca²⁺, phospholipase A2 and osmosensing. Pflugers Arch 2015; 468:335-49. [PMID: 26438191 DOI: 10.1007/s00424-015-1739-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 08/30/2015] [Accepted: 09/29/2015] [Indexed: 02/08/2023]
Abstract
During cell swelling, Cl(-) channels are activated to lower intracellular Cl(-) concentrations and to reduce cell volume, a process termed regulatory volume decrease (RVD). We show that anoctamin 6 (ANO6; TMEM16F) produces volume-regulated anion currents and controls cell volume in four unrelated cell types. Volume regulation is compromised in freshly isolated intestinal epithelial cells from Ano6-/- mice and also in lymphocytes from a patient lacking expression of ANO6. Ca(2+) influx is activated and thus ANO6 is stimulated during cell swelling by local Ca(2+) increase probably in functional nanodomains near the plasma membrane. This leads to stimulation of phospholipase A2 (PLA2) and generation of plasma membrane lysophospholipids, which activates ANO6. Direct application of lysophospholipids also activates an anion current that is inhibited by typical ANO6 blocker. An increase in intracellular Ca(2+) supports activation of ANO6, but is not required when PLA2 is fully activated, while re-addition of arachidonic acid completely blocked ANO6. Moreover, ANO6 is activated by low intracellular Cl(-) concentrations and may therefore operate as a cellular osmosensor. High intracellular Cl(-) concentration inhibits ANO6 and activation by PLA2. Taken together, ANO6 supports volume regulation and volume activation of anion currents by action as a Cl(-) channel or by scrambling membrane phospholipids. Thereby, it may support the function of LRRC8 proteins.
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12
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Sirianant L, Ousingsawat J, Tian Y, Schreiber R, Kunzelmann K. TMC8 (EVER2) attenuates intracellular signaling by Zn2+ and Ca2+ and suppresses activation of Cl- currents. Cell Signal 2014; 26:2826-33. [PMID: 25220380 DOI: 10.1016/j.cellsig.2014.09.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/01/2014] [Accepted: 09/02/2014] [Indexed: 11/25/2022]
Abstract
Eight paralogue members form the family of transmembrane channel-like (TMC) proteins that share considerable sequence homology to anoctamin 1 (Ano1, TMEM16A). Ano1 is a Ca(2+) activated Cl(-) channel that is related to head and neck cancer, often caused by human papilloma virus (HPV) infection. Mutations in TMC 6 and 8 (EVER1, EVER2) cause epidermodysplasia verruciformis. This rare skin disease is characterized by abnormal susceptibility to HPV infection and cancer. We found that in contrast to Ano1 the common paralogues TMC4-TMC8 did not produce Ca(2+) activated Cl(-) currents when expressed in HEK293 cells. On the contrary, TMC8 was found to be localized in the endoplasmic reticulum (ER), where it inhibited receptor mediated Ca(2+) release, activation of Ano1 and volume regulated LRRC8-related Cl(-) currents. Zn(2+) is co-released from the ER together with Ca(2+) and thereby further augments Ca(2+) store release. Because TMC8 is required to lower cytosolic Zn(2+) concentrations by the Zn(2+) transporter ZnT-1, we hypothesize that HPV infections and cancer caused by mutations in TMC8 are related to upregulated Zn(2+)/Ca(2+) signaling and activation of Ano1.
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Affiliation(s)
- Lalida Sirianant
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
| | - Jiraporn Ousingsawat
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
| | - Yuemin Tian
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
| | - Rainer Schreiber
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
| | - Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
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13
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Stott JB, deCourcey F, Ennis M, Zholos AV. Functional and pharmacological characterization of volume-regulated anion channels in human normal and cystic fibrosis bronchial and nasal epithelial cells. Eur J Pharmacol 2014; 740:183-91. [PMID: 25034811 DOI: 10.1016/j.ejphar.2014.07.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 06/17/2014] [Accepted: 07/03/2014] [Indexed: 12/11/2022]
Abstract
Volume-regulated anion channels (VRACs) are widely present in various cell types and have important functions ranging from regulatory volume decrease to control of cell proliferation and apoptosis. Here we aimed to compare the biophysical features and pharmacological profiles of VRAC currents in healthy and cystic fibrosis (CF) respiratory epithelial cells in order to characterize these currents both functionally and pharmacologically. Whole-cell electrophysiology was used to characterize the VRAC current in normal (16HBE14o-; HBE) and CF cell lines (CFBE14o-; CFBE), as well as in native human nasal epithelial cells. Application of hypotonic solution produced current responses of similar sizes in both HBE and CFBE cells. Biophysical properties of VRACs, such as instantaneous activation and deactivation upon voltage step, some inactivation at potentials positive to 40 mV and outwardly-rectifying I-V curves, were indistinguishable in both cell types. Extensive pharmacological analysis of the currents revealed a similar pharmacological profile in response to three blockers--NPPB, DCPIB and DIDS. Native primary human nasal epithelial cells from both healthy and CF volunteers also showed typical VRAC responses of comparable sizes. VRACs in these cells were more sensitive to external solution hypotonicity compared to HBE and CFBE cells. In all cell types studied robust VRAC currents could be induced at constant cell volume by G-protein activation with GTPγS infusion. This study provides the first extensive comparative functional and pharmacological analysis of VRAC currents in normal and CF airway epithelial cells and shows that VRACs are unimpaired molecularly or functionally in CF.
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Affiliation(s)
- Jennifer B Stott
- Centre for Infection and Immunity, Health Sciences Building, Queen׳s University Belfast, Belfast BT9 7AE, UK; Centre for Experimental Medicine, ICS-A, Queen׳s University Belfast, Belfast BT12 6BA, UK
| | - Francine deCourcey
- Centre for Infection and Immunity, Health Sciences Building, Queen׳s University Belfast, Belfast BT9 7AE, UK
| | - Madeleine Ennis
- Centre for Infection and Immunity, Health Sciences Building, Queen׳s University Belfast, Belfast BT9 7AE, UK
| | - Alexander V Zholos
- Institute of Biology, Taras Shevchenko Kiev National University, 2 Academician Glushkov Avenue, Kiev 01601, Ukraine.
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14
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Abstract
Vertebrates can sense and avoid noxious heat that evokes pain. Many thermoTRP channels are associated with temperature sensation. TRPV1 is a representative ion channel that is activated by noxious heat. Anoctamin 1 (ANO1) is a Cl- channel activated by calcium that is highly expressed in small sensory neurons, colocalized with markers for nociceptors, and most surprisingly, activated by noxious heat over 44oC. Although ANO1 is a Cl- channel, opening of this channel leads to depolarization of sensory neurons, suggesting a role in nociception. Indeed, the functional deletion of ANO1 in sensory neurons triggers the reduction in thermal pain sensation. Thus, it seems clear that ANO1 is a heat sensor in a nociceptive pathway. Since ANO1 modulators are developed for the purpose of treating chronic diseases such as cystic fibrosis, this finding is likely to predict unwanted effects and provide a guide for better developmental strategy
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Affiliation(s)
- Hawon Cho
- Sensory Research Center, CRI, College of Pharmacy, Seoul National University
| | - Uhtaek Oh
- Sensory Research Center, CRI, College of Pharmacy, Seoul National University, ; Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 151-742, Republic of Korea
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15
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Saul S, Stanisz H, Backes CS, Schwarz EC, Hoth M. How ORAI and TRP channels interfere with each other: interaction models and examples from the immune system and the skin. Eur J Pharmacol 2013; 739:49-59. [PMID: 24291108 DOI: 10.1016/j.ejphar.2013.10.071] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 10/08/2013] [Accepted: 10/17/2013] [Indexed: 11/16/2022]
Abstract
Four types of Ca(2+) selective ion channels are known, ten voltage gated Ca(2+) (CaV) channels, four CatSper channels, three store operated CRAC channels (ORAI channels) and at least two members of the TRPV subfamily (TRPV5, TRPV6). Some of the other TRP channels also show some Ca(2+) selectivity like certain splice variants of TRPM3. In addition to Ca(2+) selective channels, various cation channels play an important role for Ca(2+) entry and furthermore, they may also regulate Ca(2+) entry through other channels by modulating the membrane potential or other means as outlined in this review. Of the different types of cation channels, TRP channels form one of the most prominent families of non-selective cation channels with functional relevance in electrically non-excitable and electrically excitable cell types. Among these, the seven channels of the TRPC subfamily are rather non-selective with very modest Ca(2+) selectivity, whereas in the other subfamilies, cation selectivity ranges from monovalent selectivity (i.e. TRPM4, TRPM5) to divalent selectivity (i.e. TRPM6, TRPM7) or Ca(2+) selectivity (i.e. TRPV5, TRPV6). Rather than discussing the heavily reviewed individual functions of ORAI or TRP channels, we summarize data and present models how TRP and ORAI may functionally interact to guide cellular functions. We focus on T lymphocytes representing a more ORAI-dominated tissue and skin as model system in which both ORAI and TRP channel have been reported to control relevant functions. We present several interaction models how ORAI and TRP may interfere with each other's function.
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Affiliation(s)
- Stephanie Saul
- Department of Biophysics, School of Medicine, Saarland University, Homburg, Germany
| | - Hedwig Stanisz
- Department of Dermatology, School of Medicine, Saarland University, Homburg, Germany
| | - Christian S Backes
- Department of Biophysics, School of Medicine, Saarland University, Homburg, Germany
| | - Eva C Schwarz
- Department of Biophysics, School of Medicine, Saarland University, Homburg, Germany
| | - Markus Hoth
- Department of Biophysics, School of Medicine, Saarland University, Homburg, Germany.
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16
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Catacuzzeno L, Michelucci A, Sforna L, Aiello F, Sciaccaluga M, Fioretti B, Castigli E, Franciolini F. Identification of key signaling molecules involved in the activation of the swelling-activated chloride current in human glioblastoma cells. J Membr Biol 2013; 247:45-55. [PMID: 24240542 DOI: 10.1007/s00232-013-9609-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 10/14/2013] [Indexed: 12/17/2022]
Abstract
The swelling-activated chloride current (I Cl,Vol) is abundantly expressed in glioblastoma (GBM) cells, where it controls cell volume and invasive migration. The transduction pathway mediating I Cl,Vol activation in GBM cells is, however, poorly understood. By means of pharmacological and electrophysiological approaches, on GL-15 human GBM cells we found that I Cl,Vol activation by hypotonic swelling required the activity of a U73122-sensitive phospholipase C (PLC). I Cl,Vol activation could also be induced by the membrane-permeable diacylglycerol (DAG) analog OAG. In contrast, neither calcium (Ca(2+)) chelation by BAPTA-AM nor changes in PKC activity were able to affect I Cl,Vol activation by hypotonic swelling. We further found that R59022, an inhibitor of diacylglycerol kinase (DGK), reverted I Cl,Vol activation, suggesting the involvement of phosphatidic acid. In addition, I Cl,Vol activation required the activity of a EHT1864-sensitive Rac1 small GTPase and the resulting actin polymerization, as I Cl,Vol activation was prevented by cytochalasin B. We finally show that I Cl,Vol can be activated by the promigratory fetal calf serum in a PLC- and DGK-dependent manner. This observation is potentially relevant because blood serum can likely come in contact with glioblastoma cells in vivo as a result of the tumor-related partial breakdown of the blood-brain barrier. Given the relevance of I Cl,Vol in GBM cell volume regulation and invasiveness, the several key signaling molecules found in this study to be involved in the activation of the I Cl,Vol may represent potential therapeutic targets against this lethal cancer.
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Affiliation(s)
- Luigi Catacuzzeno
- Dipartimento di Biologia Cellulare e Ambientale, Universita' di Perugia, Via Pascoli 1, 06123, Perugia, Italy,
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17
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Hollenhorst MI, Lips KS, Wolff M, Wess J, Gerbig S, Takats Z, Kummer W, Fronius M. Luminal cholinergic signalling in airway lining fluid: a novel mechanism for activating chloride secretion via Ca²⁺-dependent Cl⁻ and K⁺ channels. Br J Pharmacol 2012; 166:1388-402. [PMID: 22300281 DOI: 10.1111/j.1476-5381.2012.01883.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Recent studies detected the expression of proteins involved in cholinergic metabolism in airway epithelial cells, although the function of this non-neuronal cholinergic system is not known in detail. Thus, this study focused on the effect of luminal ACh as a regulator of transepithelial ion transport in epithelial cells. EXPERIMENTAL APPROACH RT-PCR experiments were performed using mouse tracheal epithelial cells for ChAT and organic cation transporter (OCT) transcripts. Components of tracheal airway lining fluid were analysed with desorption electrospray ionization (DESI) MS. Effects of nicotine on mouse tracheal epithelial ion transport were examined with Ussing-chamber experiments. KEY RESULTS Transcripts encoding ChAT and OCT1-3 were detected in mouse tracheal epithelial cells. The DESI experiments identified ACh in the airway lining fluid. Luminal ACh induced an immediate, dose-dependent increase in the transepithelial ion current (EC₅₀: 23.3 µM), characterized by a transient peak and sustained plateau current. This response was not affected by the Na⁺-channel inhibitor amiloride. The Cl⁻-channel inhibitor niflumic acid or the K⁺-channel blocker Ba²⁺ attenuated the ACh effect. The calcium ionophore A23187 mimicked the ACh effect. Luminal nicotine or muscarine increased the ion current. Experiments with receptor gene-deficient animals revealed the participation of muscarinic receptor subtypes M₁ and M₃. CONCLUSIONS AND IMPLICATIONS The presence of luminal ACh and activation of transepithelial ion currents by luminal ACh receptors identifies a novel non-neuronal cholinergic pathway in the airway lining fluid. This pathway could represent a novel drug target in the airways.
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Affiliation(s)
- Monika I Hollenhorst
- Institute of Animal Physiology, Justus-Liebig-University Giessen, Giessen, Germany
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18
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Opening of chloride channels by 1α,25-dihydroxyvitamin D3 contributes to photoprotection against UVR-induced thymine dimers in keratinocytes. J Invest Dermatol 2012; 133:776-782. [PMID: 23014341 DOI: 10.1038/jid.2012.343] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
UVR produces vitamin D in skin, which is hydroxylated locally to 1α,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)). 1,25(OH)(2)D(3) protects skin cells against UVR-induced DNA damage, including thymine dimers, but the mechanism is unknown. As DNA repair is inhibited by nitric oxide (NO) products but facilitated by p53, we examined whether 1,25(OH)(2)D(3) altered the expression of nitrotyrosine, a product of NO, or p53 after UVR in human keratinocytes. 1,25(OH)(2)D(3) and the nongenomic agonist 1α,25-dihydroxylumisterol(3) reduced nitrotyrosine 16 hours after UVR, detected by a sensitive whole-cell ELISA. p53 was enhanced after UVR, and this was further augmented in the presence of 1,25(OH)(2)D(3). DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid), a chloride channel blocker previously shown to prevent 1,25(OH)(2)D(3)-induced chloride currents in osteoblasts, had no effect on thymine dimers on its own but prevented the 1,25(OH)(2)D(3)-induced protection against thymine dimers. Independent treatment with DIDS, at concentrations that had no effect on thymine dimers, blocked UVR-induced upregulation of p53. In contrast, reduction of nitrotyrosine remained in keratinocytes treated with 1,25(OH)(2)D(3) and DIDS at concentrations shown to block decreases in post-UVR thymine dimers. These results suggest that 1,25(OH)(2)D(3)-induced chloride currents help protect from UVR-induced thymine dimers, but further increases in p53 or reductions of nitrotyrosine by 1,25(OH)(2)D(3) are unlikely to contribute substantially to this protection.
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19
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Raoux M, Azorin N, Colomban C, Rivoire S, Merrot T, Delmas P, Crest M. Chemicals inducing acute irritant contact dermatitis mobilize intracellular calcium in human keratinocytes. Toxicol In Vitro 2012; 27:402-8. [PMID: 22906572 DOI: 10.1016/j.tiv.2012.08.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 04/16/2012] [Accepted: 08/02/2012] [Indexed: 01/30/2023]
Abstract
Intracellular Ca(2+) increase is a common feature of multiple cellular pathways associated with receptor and channel activation, mediator secretion and gene regulation. We investigated the possibility of using this Ca(2+) signal as a biomarker for a reaction to chemical irritants of normal human keratinocytes (NHK) in submerged primary cell culture. We tested 14 referenced chemical compounds classified as strong (seven), weak (four) or non- (three) irritants in acute irritant contact dermatitis. We found that the strong irritant compounds tested at 20-40 mM induced an intracellular Ca(2+) increase measurable by spectrofluorimetry in an automated test. Weak and non-irritant compounds however did not increase intracellular Ca(2+) concentration. We further investigated the mechanisms by which the amine heptylamine, classified as a R34 corrosive compound, increases intracellular Ca(2+). Heptylamine (20mM) induced an ATP release that persisted in the absence of intra- and extra-cellular Ca(2+). In addition, we found that this ATP activates NHK purinergic receptors that subsequently cause the increase in intracellular Ca(2+) from sarcoplasmic reticular stores. We conclude that measuring the intracellular Ca(2+) concentration in NHK is a suitable and easy way of determining any potential reaction to soluble chemical compounds.
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Affiliation(s)
- Matthieu Raoux
- Université de la Méditerranée, Centre National de la Recherche Scientifique UMR 6231, Marseille, France
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20
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The calcium-activated chloride channel anoctamin 1 acts as a heat sensor in nociceptive neurons. Nat Neurosci 2012; 15:1015-21. [PMID: 22634729 DOI: 10.1038/nn.3111] [Citation(s) in RCA: 272] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 04/19/2012] [Indexed: 12/18/2022]
Abstract
Nociceptors are a subset of small primary afferent neurons that respond to noxious chemical, thermal and mechanical stimuli. Ion channels in nociceptors respond differently to noxious stimuli and generate electrical signals in different ways. Anoctamin 1 (ANO1 also known as TMEM16A) is a Ca(2+)-activated chloride channel that is essential for numerous physiological functions. We found that ANO1 was activated by temperatures over 44 °C with steep heat sensitivity. ANO1 was expressed in small sensory neurons and was highly colocalized with nociceptor markers, which suggests that it may be involved in nociception. Application of heat ramps to dorsal root ganglion (DRG) neurons elicited robust ANO1-dependent depolarization. Furthermore, knockdown or deletion of ANO1 in DRG neurons substantially reduced nociceptive behavior in thermal pain models. These results indicate that ANO1 is a heat sensor that detects nociceptive thermal stimuli in sensory neurons and possibly mediates nociception.
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21
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Sun S, Titushkin I, Varner J, Cho M. Millimeter wave-induced modulation of calcium dynamics in an engineered skin co-culture model: role of secreted ATP on calcium spiking. JOURNAL OF RADIATION RESEARCH 2012; 53:159-167. [PMID: 22510588 DOI: 10.1269/jrr.11037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have previously designed and characterized a 94 GHz exposure system that allows real-time monitoring of subcellular interactions induced by millimeter wave (MMW) stimulation. For example, studies of the calcium dynamics in neuronal cells in response to 94 GHz irradiation suggested that MMW stimulation increased calcium spiking. In this study, we engineered a 3D co-culture model that represents the major constituents of skin. We used this experimental model along with the custom-designed MMW exposure system to investigate the effects of 94 GHz irradiation in the skin-like tissue construct. Unlike typical non-excitable cells, keratinocytes exhibited calcium spikes in their resting state. Exposure to a 94 GHz irradiation induced a statistically significant increase in the calcium spiking. When co-cultured with neuronal cells in the 3D co-culture skin model, changes in the calcium spiking in neuronal cells depended on the MMW input power. Further, the 94 GHz irradiation caused ATP secretion by keratincytes. ATP is a major factor that modulates the calcium spiking in neuronal cells. Surprisingly, while a 5-fold increase in the ATP secretion enhanced the calcium spiking in neuronal cells, a 10-fold increase significantly hindered the calcium dynamics. Computational simulation of ATP-induced calcium dynamics was in general agreement with the experimental findings, suggesting the involvement of the ATP-sensitive purinergic receptors. The engineered co-culture skin model offers a physiologically relevant environment in which the calcium dynamics is regulated both by the cell-MMW and cell-cell interactions.
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Affiliation(s)
- Shan Sun
- Department of Bioengineering, University of Illinois, Chicago, IL, USA
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22
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Catacuzzeno L, Aiello F, Fioretti B, Sforna L, Castigli E, Ruggieri P, Tata AM, Calogero A, Franciolini F. Serum-activated K and Cl currents underlay U87-MG glioblastoma cell migration. J Cell Physiol 2011; 226:1926-33. [PMID: 21506123 DOI: 10.1002/jcp.22523] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Glioblastoma cells in vivo are exposed to a variety of promigratory signals, including undefined serum components that infiltrate into high grade gliomas as result of blood-brain barrier breakdown. Glioblastoma cell migration has been further shown to depend heavily on ion channels activity. We have then investigated the modulatory effects of fetal calf serum (FCS) on ion channels, and their involvement in U87-MG cells migration. Using the perforated patch-clamp technique we have found that, in a subpopulation of cells (42%), FCS induced: (1) an oscillatory activity of TRAM-34 sensitive, intermediate-conductance calcium-activated K (IK(Ca) ) channels, mediated by calcium oscillations previously shown to be induced by FCS in this cell line; (2) a stable activation of a DIDS- and NPPB-sensitive Cl current displaying an outward rectifying instantaneous current-voltage relationship and a slow, voltage-dependent inactivation. By contrast, in another subpopulation of cells (32%) FCS induced a single, transient IK(Ca) current activation, always accompanied by a stable activation of the Cl current. The remaining cells did not respond to FCS. In order to understand whether the FCS-induced ion channel activities are instrumental to promoting cell migration, we tested the effects of TRAM-34 and DIDS on the FCS-induced U87-MG cell migration using transwell migration assays. We found that these inhibitors were able to markedly reduce U87-MG cell migration in the presence of FCS, and that their co-application resulted in an almost complete arrest of migration. It is concluded that the modulation of K and Cl ion fluxes is essential for the FCS-induced glioblastoma cell migration.
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Affiliation(s)
- Luigi Catacuzzeno
- Dipartimento di Biologia Cellulare e Ambientale, Universita' di Perugia, Perugia, Italy.
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23
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Azorin N, Raoux M, Rodat-Despoix L, Merrot T, Delmas P, Crest M. ATP signalling is crucial for the response of human keratinocytes to mechanical stimulation by hypo-osmotic shock. Exp Dermatol 2011; 20:401-7. [PMID: 21355886 DOI: 10.1111/j.1600-0625.2010.01219.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Touch is detected through receptors located in the skin and the activation of channels in sensory nerve fibres. Epidermal keratinocytes themselves, however, may sense mechanical stimulus and contribute to skin sensation. Here, we showed that the mechanical stimulation of human keratinocytes by hypo-osmotic shock releases adenosine triphosphate (ATP) and increases intracellular calcium. We demonstrated that the release of ATP was found to be calcium independent because emptying the intracellular calcium stores did not cause ATP release; ATP release was still observed in the absence of external calcium and it persisted on chelating cytosolic calcium. On the other hand, the released ATP activated purinergic receptors and mobilized intracellular calcium stores. The resulting depletion of stored calcium led to the activation of capacitative calcium entry. Increase in cytosolic calcium concentration was blocked by the purinergic receptor blocker suramin, phospholipase C inhibitor and apyrase, which hydrolyses ATP. Collectively, our data demonstrate that human keratinocytes are mechanically activated by hypo-osmotic shock, leading first to the release of ATP, which in turn stimulates purinergic receptors, resulting in the mobilization of intracellular calcium and capacitative calcium entry. These results emphasize the crucial role of ATP signalling in the transduction of mechanical stimuli in human keratinocytes.
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Affiliation(s)
- Nathalie Azorin
- Université de la Méditerranée, Centre National de la Recherche Scientifique (CNRS) UMR6231, Marseille, France
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24
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da Silva MB, Costa VMA, Pereira VRA, de Albertim GJB, de Melo EBB, Bezerra DP, da Silva RP, Rodrigues CG, Carneiro CMM, Yuldasheva LN, Krasilnikov OV. Ion channels in volume regulation of clonal kidney cells. Cell Prolif 2010; 43:529-41. [PMID: 21039991 DOI: 10.1111/j.1365-2184.2010.00702.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVES Clonal kidney cells (Vero cells) are extensively utilized in the manufacture of biological preparations for disease diagnostics and therapeutics and also in preparation of vaccines. In all cells, regulation of volume is an essential function coupled to a variety of physiological processes and is a topic of interest. The objective here was to investigate involvement of ion channels in the process of volume regulation of Vero cells. METHODS Involvement of ion channels in cell volume regulation was studied using video-microscopy and flow cytometry. Pharmacologically unaltered cells of different sizes, which are presumably at different phases of the cell cycle, were used. RESULTS Ion transport inhibitors altered all phases of regulatory volume decrease (RVD) of Vero cells, rate of initial cell swelling, V(max) and volume recovery. Effects were dependent on type of inhibitor and on cell size (cell cycle phase). Participation of aquaporins in RVD was suggested. Inhibitors decelerated growth, arresting Vero cells at the G(0) /G(1) phase boundary. Electrophysiological study confirmed presence of volume-activated Cl(-) channels and K(+) channels in plasmatic membranes of the cells. CONCLUSION Vero cells of all sizes maintained the ability to recover from osmotic swelling. Activity of ion channels was one of the key factors that controlled volume regulation and proliferation of the cells.
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Affiliation(s)
- M B da Silva
- Department of Biophysics and Radiobiology, Federal University of Pernambuco, Recife, PE, Brazil
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Chen JP, Luan Y, You CX, Chen XH, Luo RC, Li R. TRPM7 regulates the migration of human nasopharyngeal carcinoma cell by mediating Ca2+ influx. Cell Calcium 2010; 47:425-32. [DOI: 10.1016/j.ceca.2010.03.003] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 03/05/2010] [Accepted: 03/09/2010] [Indexed: 01/08/2023]
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Yang YD, Cho H, Koo JY, Tak MH, Cho Y, Shim WS, Park SP, Lee J, Lee B, Kim BM, Raouf R, Shin YK, Oh U. TMEM16A confers receptor-activated calcium-dependent chloride conductance. Nature 2008; 455:1210-5. [PMID: 18724360 DOI: 10.1038/nature07313] [Citation(s) in RCA: 1026] [Impact Index Per Article: 64.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 08/05/2008] [Indexed: 01/28/2023]
Abstract
Calcium (Ca(2+))-activated chloride channels are fundamental mediators in numerous physiological processes including transepithelial secretion, cardiac and neuronal excitation, sensory transduction, smooth muscle contraction and fertilization. Despite their physiological importance, their molecular identity has remained largely unknown. Here we show that transmembrane protein 16A (TMEM16A, which we also call anoctamin 1 (ANO1)) is a bona fide Ca(2+)-activated chloride channel that is activated by intracellular Ca(2+) and Ca(2+)-mobilizing stimuli. With eight putative transmembrane domains and no apparent similarity to previously characterized channels, ANO1 defines a new family of ionic channels. The biophysical properties as well as the pharmacological profile of ANO1 are in full agreement with native Ca(2+)-activated chloride currents. ANO1 is expressed in various secretory epithelia, the retina and sensory neurons. Furthermore, knockdown of mouse Ano1 markedly reduced native Ca(2+)-activated chloride currents as well as saliva production in mice. We conclude that ANO1 is a candidate Ca(2+)-activated chloride channel that mediates receptor-activated chloride currents in diverse physiological processes.
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Affiliation(s)
- Young Duk Yang
- Sensory Research Center, CRI, College of Pharmacy, Seoul National University, Seoul 151-742, Korea
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Volume-activated chloride channels in mice Leydig cells. Pflugers Arch 2008; 457:493-504. [PMID: 18574591 DOI: 10.1007/s00424-008-0525-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 04/08/2008] [Accepted: 04/22/2008] [Indexed: 10/21/2022]
Abstract
Production and secretion of testosterone in Leydig cells are mainly controlled by the luteinizing hormone (LH). Biochemical evidences suggest that the activity of Cl(-) ions can modulate the steroidogenic process, but the specific ion channels involved are not known. Here, we extend the characterization of Cl(-) channels in mice Leydig cells (50-60 days old) by describing volume-activated Cl(-) currents (I(Cl,swell)). The amplitude of I(Cl,swell) is dependent on the osmotic gradient across the cell membrane, with an apparent EC(50) of approximately 75 mOsm. These currents display the typical biophysical signature of volume-activated anion channels (VRAC): dependence on intracellular ATP, outward rectification, inactivation at positive potentials, and selectivity sequence (I(- )> Cl(- )> F(-)). Staurosporine (200 nM) did not block the activation of I(Cl,swell). The block induced by 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB; 128 microM), SITS (200 microM), ATP (500 microM), pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS; 100 miccroM), and Suramin (10 microM) were described by the permeant blocker model with apparent dissociation constant at 0 mV K(do) and fractional distance of the binding site (delta) of 334 microM and 47 %, 880 microM and 35 %, 2,100 microM and 49%, 188 microM and 27%, and 66.5 microM and 49%, respectively. These numbers were derived from the peak value of the currents. We conclude that I(Cl,swell) in Leydig cells are activated independently of purinergic stimulation, that Suramin and PPADS block these currents by a direct interaction with VRAC and that ATP is able to permeate this channel.
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Franco R, Panayiotidis MI, de la Paz LDO. Autocrine signaling involved in cell volume regulation: the role of released transmitters and plasma membrane receptors. J Cell Physiol 2008; 216:14-28. [PMID: 18300263 DOI: 10.1002/jcp.21406] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cell volume regulation is a basic homeostatic mechanism transcendental for the normal physiology and function of cells. It is mediated principally by the activation of osmolyte transport pathways that result in net changes in solute concentration that counteract cell volume challenges in its constancy. This process has been described to be regulated by a complex assortment of intracellular signal transduction cascades. Recently, several studies have demonstrated that alterations in cell volume induce the release of a wide variety of transmitters including hormones, ATP and neurotransmitters, which have been proposed to act as extracellular signals that regulate the activation of cell volume regulatory mechanisms. In addition, changes in cell volume have also been reported to activate plasma membrane receptors (including tyrosine kinase receptors, G-protein coupled receptors and integrins) that have been demonstrated to participate in the regulatory process of cell volume. In this review, we summarize recent studies about the role of changes in cell volume in the regulation of transmitter release as well as in the activation of plasma membrane receptors and their further implications in the regulation of the signaling machinery that regulates the activation of osmolyte flux pathways. We propose that the autocrine regulation of Ca2+-dependent and tyrosine phosphorylation-dependent signaling pathways by the activation of plasma membrane receptors and swelling-induced transmitter release is necessary for the activation/regulation of osmolyte efflux pathways and cell volume recovery. Furthermore, we emphasize the importance of studying these extrinsic signals because of their significance in the understanding of the physiology of cell volume regulation and its role in cell biology in vivo, where the constraint of the extracellular space might enhance the autocrine or even paracrine signaling induced by these released transmitters.
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Affiliation(s)
- Rodrigo Franco
- Laboratory of Cell Biology and Signal Transduction, Biomedical Research Unit, FES-Iztacala, UNAM, Mexico.
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Fernandes J, Lorenzo IM, Andrade YN, Garcia-Elias A, Serra SA, Fernández-Fernández JM, Valverde MA. IP3 sensitizes TRPV4 channel to the mechano- and osmotransducing messenger 5'-6'-epoxyeicosatrienoic acid. ACTA ACUST UNITED AC 2008; 181:143-55. [PMID: 18378772 PMCID: PMC2287294 DOI: 10.1083/jcb.200712058] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mechanical and osmotic sensitivity of the transient receptor potential vanilloid 4 (TRPV4) channel depends on phospholipase A2 (PLA2) activation and the subsequent production of the arachidonic acid metabolites, epoxyeicosatrienoic acid (EET). We show that both high viscous loading and hypotonicity stimuli in native ciliated epithelial cells use PLA2–EET as the primary pathway to activate TRPV4. Under conditions of low PLA2 activation, both also use extracellular ATP-mediated activation of phospholipase C (PLC)–inositol trisphosphate (IP3) signaling to support TRPV4 gating. IP3, without being an agonist itself, sensitizes TRPV4 to EET in epithelial ciliated cells and cells heterologously expressing TRPV4, an effect inhibited by the IP3 receptor antagonist xestospongin C. Coimmunoprecipitation assays indicated a physical interaction between TRPV4 and IP3 receptor 3. Collectively, our study suggests a functional coupling between plasma membrane TRPV4 channels and intracellular store Ca2+ channels required to initiate and maintain the oscillatory Ca2+ signal triggered by high viscosity and hypotonic stimuli that do not reach a threshold level of PLA2 activation.
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Affiliation(s)
- Jacqueline Fernandes
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
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Busetto S, Trevisan E, Decleva E, Dri P, Menegazzi R. Chloride movements in human neutrophils during phagocytosis: characterization and relationship to granule release. THE JOURNAL OF IMMUNOLOGY 2007; 179:4110-24. [PMID: 17785850 DOI: 10.4049/jimmunol.179.6.4110] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Chloride ion efflux is an early event occurring after exposure of human neutrophils to several soluble agonists. Under these circumstances, a rapid and reversible fall in the high basal intracellular chloride (Cl-i) levels is observed. This event is thought to play a crucial role in the modulation of several critical neutrophil responses including activation and up-regulation of adhesion molecules, cell attachment and spreading, cytoplasmic alkalinization, and activation of the respiratory burst. At present, however, no data are available on chloride ion movements during neutrophil phagocytosis. In this study, we provide evidence that phagocytosis of Candida albicans opsonized with either whole serum, complement-derived opsonins, or purified human IgG elicits an early and long-lasting Cl- efflux accompanied by a marked, irreversible loss of Cl-i. Simultaneous assessment of Cl- efflux and phagocytosis in cytochalasin D-treated neutrophils indicated that Cl- efflux occurs without particle ingestion. These results suggest that engagement of immune receptors is sufficient to promote chloride ion movements. Several structurally unrelated chloride channel blockers inhibited phagocytosis-induced Cl- efflux as well as the release of azurophilic-but not specific-granules. It implicates that different neutrophil secretory compartments display distinct sensitivity to Cl-i modifications. Intriguingly, inhibitors of Cl- exchange inhibited cytosolic Ca2+ elevation, whereas Cl- efflux was not impaired in Ca2+-depleted neutrophils. We also show that FcgammaR(s)- and CR3/CR1-mediated Cl- efflux appears to be dependent on protein tyrosine phosphorylation but independent of PI3K and phospholipase C activation.
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Affiliation(s)
- Sara Busetto
- Department of Physiology and Pathology, University of Trieste, Trieste, Italy
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31
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Varela D, Simon F, Olivero P, Armisén R, Leiva-Salcedo E, Jørgensen F, Sala F, Stutzin A. Activation of H 2O 2-Induced VSOR Cl - Currents in HTC Cells Require Phospholipase Cγ1 Phosphorylation and Ca 2+ Mobilisation. Cell Physiol Biochem 2007; 20:773-80. [DOI: 10.1159/000110437] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/09/2007] [Indexed: 11/19/2022] Open
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Jun DJ, Kim J, Jung SY, Song R, Noh JH, Park YS, Ryu SH, Kim JH, Kong YY, Chung JM, Kim KT. Extracellular ATP mediates necrotic cell swelling in SN4741 dopaminergic neurons through P2X7 receptors. J Biol Chem 2007; 282:37350-8. [PMID: 17962183 DOI: 10.1074/jbc.m707915200] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Extracellular ATP has recently been identified as an important regulator of cell death in response to pathological insults. When SN4741 cells, which are dopaminergic neurons derived from the substantia nigra of transgenic mouse embryos, are exposed to ATP, cell death occurs. This cell death is associated with prominent cell swelling, loss of ER integrity, the formation of many large cytoplasmic vacuoles, and subsequent cytolysis and DNA release. In addition, the cleavage of caspase-3, a hallmark of apoptosis, is induced by ATP treatment. However, caspase inhibitors do not overcome ATP-induced cell death, indicating that both necrosis and apoptosis are associated with ATP-induced cell death and suggesting that a necrotic event might override the apoptotic process. In this study we also found that P2X(7) receptors (P2X(7)Rs) are abundantly expressed in SN4741 cells, and both ATP-induced swelling and cell death are reversed by pretreatment with the P2X(7)Rs antagonist, KN62, or by knock-down of P2X(7)Rs with small interfering RNAs. Therefore, extracellular ATP release from injured tissues may act as an accelerating factor in necrotic SN4741 dopaminergic cell death via P2X(7)Rs.
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Affiliation(s)
- Dong-Jae Jun
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Nam-Gu, Pohang, Republic of Korea
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Raoux M, Colomban C, Delmas P, Crest M. The Amine-Containing Cutaneous Irritant Heptylamine Inhibits the Volume-Regulated Anion Channel and Mobilizes Intracellular Calcium in Normal Human Epidermal Keratinocytes. Mol Pharmacol 2007; 71:1685-94. [PMID: 17384225 DOI: 10.1124/mol.106.033324] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many amines are skin irritants and cause contact dermatitis. However, little is known about their mechanisms of action in keratinocytes except that they induce the release of the inflammatory mediators cytokines and ATP. Here, we tested whether volume-regulated anion channels (VRACs) in primary cultures of normal human epidermal keratinocytes are modulated by the referenced amine-containing cutaneous irritant heptylamine. Under isotonic conditions, we isolated the VRAC current (I(VRAC)) from other conductances using a high Ca(2+)-buffering internal solution. I(VRAC) ran up after patch rupturing and reached a plateau within 15 min. It was reversibly and dose-dependently inhibited by heptylamine with an IC(50) value of 260 microM. Cell-swelling caused by the application of a hypotonic solution increased 2.7-fold I(VRAC) and reduced the inhibition of VRAC by heptylamine with a dose-response curve shifted approximately 10-fold to the right. In addition, we showed, using cell-attached patch recordings, that adding heptylamine to the bath inhibited VRAC activity. This suggests that heptylamine diffuses into the membrane to inhibit VRAC. Finally, we demonstrated that heptylamine induced Ca(2+)-store depletion and that VRAC inhibition was not caused by the increase in cytosolic Ca(2+). Taken together, these results identify heptylamine as a blocker of VRAC and suggest that Ca(2+)-store depletion may be involved in mechanisms of irritant contact dermatitis caused by heptylamine.
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Affiliation(s)
- Matthieu Raoux
- Laboratoire de Neurophysiologie Cellulaire, CNRS UMR 6150, IFR Jean Roche, Faculté de Médecine, Université de la Méditerranée, Boulevard Pierre Dramard, 13916, Marseille Cedex 20, France
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Beck B, Zholos A, Sydorenko V, Roudbaraki M, Lehen'kyi V, Bordat P, Prevarskaya N, Skryma R. TRPC7 is a receptor-operated DAG-activated channel in human keratinocytes. J Invest Dermatol 2006; 126:1982-93. [PMID: 16741513 DOI: 10.1038/sj.jid.5700352] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Muscarinic and purinergic receptors expressed in keratinocytes are an important part of a functional system for cell growth. While several aspects of this process are clearly dependent on Ca(2+) homeostasis, less is known about the mechanisms controlling Ca(2+) entry during epidermal receptor stimulation. We used patch-clamp technique to study responses to carbachol (CCh) and adenosine triphosphate (ATP) in HaCaT human keratinocytes. Both agonists induced large currents mediated by cation-selective channels about three times more permeable to Ca(2+) than Na(+), suggesting that they play an important role in receptor-operated Ca(2+) entry. CCh- and ATP-induced currents were inhibited by 1-[6-([(17beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino)hexyl]-1H-pyrrole-2,5-dione, a phospholipase C (PLC) blocker. Investigation of the pathways downstream of PLC activation revealed that InsP(3) did not affect the agonist responses. In contrast, 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeable analog of 1,2-diacylglycerol (DAG), evoked a similar cation current. This action appears to be direct, since the effects of activators or inhibitors of protein kinase C were comparatively small. Finally, transient receptor potential canonical 7 (TRPC7) specific knockdown by antisense oligonucleotides led to a decrease in ATP- and CCh-induced calcium entry, as well as OAG-evoked current. We concluded that activation of both muscarinic and purinergic receptors via a common DAG-dependent link opens Ca(2+)-permeable TRPC7 channels.
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Affiliation(s)
- Benjamin Beck
- Laboratoire de Physiologie Cellulaire, inserm, U800, Equipe labellisée par la Ligue contre le cancer, Villeneuve d'Ascq, France
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Guan YY, Wang GL, Zhou JG. The ClC-3 Cl− channel in cell volume regulation, proliferation and apoptosis in vascular smooth muscle cells. Trends Pharmacol Sci 2006; 27:290-6. [PMID: 16697056 DOI: 10.1016/j.tips.2006.04.008] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 03/09/2006] [Accepted: 04/19/2006] [Indexed: 01/23/2023]
Abstract
The volume-regulated Cl(-) current (I(Cl.vol)) is responsible for the transmembrane Cl(-) transport that is involved in cell volume regulatory mechanisms. Although the regulation of cell volume is a fundamental function of healthy cells for maintaining constant size, the molecular genetic identification of I(Cl.vol) is still being debated. Recent studies in vascular smooth muscle support the idea that ClC-3, a member of the voltage-gated ClC Cl(-) channel family, is the molecular component involved in the activation or regulation of I(Cl.vol). Moreover, gene-targeting studies in vascular smooth muscle cells (VSMCs) and other cell types indicate emerging roles of ClC-3 in cell proliferation and apoptosis. These findings indicate that ClC-3 might be involved in modulating vascular remodeling in hypertension and arteriosclerosis.
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Affiliation(s)
- Yong-Yuan Guan
- Department of Pharmacology, Zhongshan Medical College, Sun Yat-sen University, 74 Zhongshan 2 Road, Guangzhou 510089, China.
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Abstract
Maturing spermatozoa passing through the epididymis experience increasing osmolality in the luminal environment and mature cells are stored in fluids hyper-osmotic to serum. When ejaculated into the female tract, they encounter a hypo-osmotic challenge which initiates the process of regulatory volume decrease (RVD). Defects in RVD result in hindrance of mucus penetration in man and failure of utero-tubal passage in mice. Epididymal sperm from the mouse and cynomolgus monkey and ejaculated sperm from man and monkey have been isolated and dispersed in media with osmolalities mimicking those of uterine fluid or cervical mucus. The effects of specific and broad-spectrum ion channel blockers indicate the involvement of separate K+ and Cl- channels as well as organic osmolytes in physiological sperm RVD, with mechanisms developed during epididymal maturation. Western blotting and immuno-cytochemistry identify and localise some of these channels which play a crucial role in fertilisation in vivo and could be targets for post-testicular contraception.
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Affiliation(s)
- C H Yeung
- Institute of Reproductive Medicine of the University, D-48129 Münster, Germany.
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