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Huffer K, Oskoui EV, Swartz KJ. Conservation of the cooling agent binding pocket within the TRPM subfamily. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.20.595003. [PMID: 38826484 PMCID: PMC11142142 DOI: 10.1101/2024.05.20.595003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Transient Receptor Potential (TRP) channels are a large and diverse family of tetrameric cation selective channels that are activated by many different types of stimuli, including noxious heat or cold, organic ligands such as vanilloids or cooling agents, or intracellular Ca2+. Structures available for all subtypes of TRP channels reveal that the transmembrane domains are closely related despite their unique sensitivity to activating stimuli. Here we use computational and electrophysiological approaches to explore the conservation of the cooling agent binding pocket identified within the S1-S4 domain of the Melastatin subfamily member TRPM8, the mammalian sensor of noxious cold, with other TRPM channel subtypes. We find that a subset of TRPM channels, including TRPM2, TRPM4 and TRPM5, contain well-conserved cooling agent binding pockets. We then show how the cooling agent icilin modulates activation of TRPM4 to intracellular Ca2+, enhancing the sensitivity of the channel to Ca2+ and diminishing outward-rectification to promote opening at negative voltages. Mutations known to promote or diminish activation of TRPM8 by icilin similarly alter activation of TRPM4 by the cooling agent, suggesting that icilin binds to the cooling agent binding pocket to promote opening of the channel. These findings demonstrate that TRPM4 and TRPM8 channels share related cooling agent binding pockets that are allosterically coupled to opening of the pore.
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Affiliation(s)
- Kate Huffer
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | | | - Kenton J. Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
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2
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Holderby KG, Kozak JA. Use of tetraethylammonium (TEA) and Tris loading for blocking TRPM7 channels in intact cells. Front Pharmacol 2024; 15:1341799. [PMID: 38659572 PMCID: PMC11039802 DOI: 10.3389/fphar.2024.1341799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 03/26/2024] [Indexed: 04/26/2024] Open
Abstract
Tetraethylammonium (TEA), a quaternary ammonium compound, is a well-known blocker of potassium channels belonging to various subfamilies, such as KV1-3, KCa1, 2 and prokaryotic KcsA. In many cases, TEA acts from the extracellular side by open pore blockade. TEA can also block transient receptor potential (TRP) cation channels, such as TRPM7, in a voltage-dependent manner. In human T lymphocytes, intracellular (cytosolic) TEA and its analog TMA (tetramethylammonium) inhibit TRPM7 channel currents in the outward but not inward direction. By contrast, intracellular Mg2+, protons and polyamines inhibit both outward and inward current components equally. Likewise, the majority of available pharmacological tools inhibit TRPM7 channels in a voltage-independent manner. Since TRPM7 is a steeply outwardly rectifying conductance, voltage-dependent blockers can be useful for studying the cellular functions of this channel. TRPM7 protein is endogenously expressed in diverse cell lines, including HEK, HeLa, CHO, RBL and Jurkat. Using patch-clamp electrophysiology, we found that incubating HEK293 and Jurkat T cells overnight in the presence of 20 mM TEA-Cl, resulted in the nearly complete blockade of whole-cell TRPM7 outward current, measured at break-in. By contrast, the inward current was unchanged in TEA-loaded cells. The blockade was fully reversible after washout of intracellular solution in whole-cell but not in perforated-patch recording configurations. Overnight incubation with 20 mM TMA-Cl resulted in a more modest blockade of the outward TRPM7 current. Internal 129 mM TMA and TEA eliminated most of the outward current. TEA uptake in transfected HEK293 cells led to blockade of recombinant murine TRPM7 and the Mg2+ and pH insensitive Ser1107Arg variant. Unexpectedly, Tris-HCl, a widely used pH buffer, could similarly be loaded into Jurkat and HEK cells, and preferentially blocked outward TRPM7 currents. 20 mM and 129 mM Tris in the internal solution blocked TRPM7 current in outward but not inward direction. Voltage-dependent channel blockade by TEA, TMA and Tris loading will be useful for studying the properties and functions of TRPM7-mediated ion transport in intact cells.
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Affiliation(s)
- Katherine G. Holderby
- Undergraduate Program in Physiology and Neuroscience, Dayton, OH, United States
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, United States
| | - J. Ashot Kozak
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, United States
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3
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Okada Y, Numata T, Sabirov RZ, Kashio M, Merzlyak PG, Sato-Numata K. Cell death induction and protection by activation of ubiquitously expressed anion/cation channels. Part 3: the roles and properties of TRPM2 and TRPM7. Front Cell Dev Biol 2023; 11:1246955. [PMID: 37842082 PMCID: PMC10576435 DOI: 10.3389/fcell.2023.1246955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 09/15/2023] [Indexed: 10/17/2023] Open
Abstract
Cell volume regulation (CVR) is a prerequisite for animal cells to survive and fulfill their functions. CVR dysfunction is essentially involved in the induction of cell death. In fact, sustained normotonic cell swelling and shrinkage are associated with necrosis and apoptosis, and thus called the necrotic volume increase (NVI) and the apoptotic volume decrease (AVD), respectively. Since a number of ubiquitously expressed ion channels are involved in the CVR processes, these volume-regulatory ion channels are also implicated in the NVI and AVD events. In Part 1 and Part 2 of this series of review articles, we described the roles of swelling-activated anion channels called VSOR or VRAC and acid-activated anion channels called ASOR or PAC in CVR and cell death processes. Here, Part 3 focuses on therein roles of Ca2+-permeable non-selective TRPM2 and TRPM7 cation channels activated by stress. First, we summarize their phenotypic properties and molecular structure. Second, we describe their roles in CVR. Since cell death induction is tightly coupled to dysfunction of CVR, third, we focus on their participation in the induction of or protection against cell death under oxidative, acidotoxic, excitotoxic, and ischemic conditions. In this regard, we pay attention to the sensitivity of TRPM2 and TRPM7 to a variety of stress as well as to their capability to physicall and functionally interact with other volume-related channels and membrane enzymes. Also, we summarize a large number of reports hitherto published in which TRPM2 and TRPM7 channels are shown to be involved in cell death associated with a variety of diseases or disorders, in some cases as double-edged swords. Lastly, we attempt to describe how TRPM2 and TRPM7 are organized in the ionic mechanisms leading to cell death induction and protection.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences (NIPS), Okazaki, Japan
- Department of Integrative Physiology, Graduate School of Medicine, AkitaUniversity, Akita, Japan
- Department of Physiology, School of Medicine, Aichi Medical Uniersity, Nagakute, Japan
- Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Cardiovascular Research Institute, Yokohama City University, Yokohama, Japan
| | - Tomohiro Numata
- Department of Integrative Physiology, Graduate School of Medicine, AkitaUniversity, Akita, Japan
| | - Ravshan Z. Sabirov
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Makiko Kashio
- National Institute for Physiological Sciences (NIPS), Okazaki, Japan
- Department of Physiology, School of Medicine, Aichi Medical Uniersity, Nagakute, Japan
| | - Peter G. Merzlyak
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Kaori Sato-Numata
- Department of Integrative Physiology, Graduate School of Medicine, AkitaUniversity, Akita, Japan
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4
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Zhang YY, Li XS, Ren KD, Peng J, Luo XJ. Restoration of metal homeostasis: a potential strategy against neurodegenerative diseases. Ageing Res Rev 2023; 87:101931. [PMID: 37031723 DOI: 10.1016/j.arr.2023.101931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/04/2023] [Accepted: 04/06/2023] [Indexed: 04/11/2023]
Abstract
Metal homeostasis is critical to normal neurophysiological activity. Metal ions are involved in the development, metabolism, redox and neurotransmitter transmission of the central nervous system (CNS). Thus, disturbance of homeostasis (such as metal deficiency or excess) can result in serious consequences, including neurooxidative stress, excitotoxicity, neuroinflammation, and nerve cell death. The uptake, transport and metabolism of metal ions are highly regulated by ion channels. There is growing evidence that metal ion disorders and/or the dysfunction of ion channels contribute to the progression of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). Therefore, metal homeostasis-related signaling pathways are emerging as promising therapeutic targets for diverse neurological diseases. This review summarizes recent advances in the studies regarding the physiological and pathophysiological functions of metal ions and their channels, as well as their role in neurodegenerative diseases. In addition, currently available metal ion modulators and in vivo quantitative metal ion imaging methods are also discussed. Current work provides certain recommendations based on literatures and in-depth reflections to improve neurodegenerative diseases. Future studies should turn to crosstalk and interactions between different metal ions and their channels. Concomitant pharmacological interventions for two or more metal signaling pathways may offer clinical advantages in treating the neurodegenerative diseases.
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Affiliation(s)
- Yi-Yue Zhang
- Department of Pharmacology, Xiangya School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Xi-Sheng Li
- Department of Laboratory Medicine, The Third Xiangya Hospital of Central South University, Changsha 410013,China
| | - Kai-Di Ren
- Department of Pharmacy, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Jun Peng
- Department of Pharmacology, Xiangya School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, Xiangya School of Pharmaceutical Sciences, Central South University, Changsha 410078, China.
| | - Xiu-Ju Luo
- Department of Laboratory Medicine, The Third Xiangya Hospital of Central South University, Changsha 410013,China.
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5
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Cheng XY, Li SF, Chen Y, Zhao YJ, Hu W, Lu C, Zhou RP. Transient receptor potential melastatin 7 and their modulators. Eur J Pharmacol 2022; 931:175180. [DOI: 10.1016/j.ejphar.2022.175180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 07/20/2022] [Accepted: 08/01/2022] [Indexed: 11/03/2022]
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Schmidt E, Narangoda C, Nörenberg W, Egawa M, Rössig A, Leonhardt M, Schaefer M, Zierler S, Kurnikova MG, Gudermann T, Chubanov V. Structural mechanism of TRPM7 channel regulation by intracellular magnesium. Cell Mol Life Sci 2022; 79:225. [PMID: 35389104 PMCID: PMC8989868 DOI: 10.1007/s00018-022-04192-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 01/26/2022] [Accepted: 02/02/2022] [Indexed: 01/03/2023]
Abstract
Zn2+, Mg2+ and Ca2+ are essential divalent cations implicated in many metabolic processes and signalling pathways. An emerging new paradigm is that the organismal balance of these cations predominantly depends on a common gatekeeper, the channel-kinase TRPM7. Despite extensive electrophysiological studies and recent cryo-EM analysis, an open question is how the channel activity of TRPM7 is activated. Here, we performed site-directed mutagenesis of mouse TRPM7 in conjunction with patch-clamp assessment of whole-cell and single-channel activity and molecular dynamics (MD) simulations to show that the side chains of conserved N1097 form an inter-subunit Mg2+ regulatory site located in the lower channel gate of TRPM7. Our results suggest that intracellular Mg2+ binds to this site and stabilizes the TRPM7 channel in the closed state, whereas the removal of Mg2+ favours the opening of TRPM7. Hence, our study identifies the structural underpinnings through which the TRPM7 channel is controlled by cytosolic Mg2+, representing a new structure–function relationship not yet explored among TRPM channels.
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Affiliation(s)
- Eva Schmidt
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Chamali Narangoda
- Chemistry Department, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Wolfgang Nörenberg
- Rudolf-Boehm Institute of Pharmacology and Toxicology, Leipzig University, Leipzig, Germany
| | - Miyuki Egawa
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Anna Rössig
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Marion Leonhardt
- Rudolf-Boehm Institute of Pharmacology and Toxicology, Leipzig University, Leipzig, Germany
| | - Michael Schaefer
- Rudolf-Boehm Institute of Pharmacology and Toxicology, Leipzig University, Leipzig, Germany
| | - Susanna Zierler
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany.,Institute of Pharmacology, Johannes Kepler University Linz, Linz, Austria
| | - Maria G Kurnikova
- Chemistry Department, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Thomas Gudermann
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany. .,Comprehensive Pneumology Center, a member of the German Center for Lung Research (DZL), Munich, Germany.
| | - Vladimir Chubanov
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany.
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7
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TRPM7 Ion Channel: Oncogenic Roles and Therapeutic Potential in Breast Cancer. Cancers (Basel) 2021; 13:cancers13246322. [PMID: 34944940 PMCID: PMC8699295 DOI: 10.3390/cancers13246322] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 12/20/2022] Open
Abstract
Simple Summary Breast cancer is the most frequently diagnosed malignant tumor and the second leading cause of cancer death in women worldwide. The risk of developing breast cancer is 12.8%, i.e., 1 in 8 people, and a woman’s risk of dying is approximately 1 in 39. Calcium signals play an important role in various cancers and transport calcium ions may have altered expression in breast cancer, such as the TRPM7 calcium permeant ion channel, where overexpression may be associated with a poor prognosis. This review focuses on the TRPM7 channel, and the oncogenic roles studied so far in breast cancer. The TRPM7 ion channel is suggested as a potential and prospective target in the diagnosis and treatment of breast cancer. Abstract The transient receptor potential melastatin-subfamily member 7 (TRPM7) is a divalent cations permeant channel but also has intrinsic serine/threonine kinase activity. It is ubiquitously expressed in normal tissues and studies have indicated that it participates in important physiological and pharmacological processes through its channel-kinase activity, such as calcium/magnesium homeostasis, phosphorylation of proteins involved in embryogenesis or the cellular process. Accumulating evidence has shown that TRPM7 is overexpressed in human pathologies including breast cancer. Breast cancer is the second leading cause of cancer death in women with an incidence rate increase of around 0.5% per year since 2004. The overexpression of TRPM7 may be associated with a poor prognosis in breast cancer patients, so more efforts are needed to research a new therapeutic target. TRPM7 regulates the levels of Ca2+, which can alter the signaling pathways involved in survival, cell cycle progression, proliferation, growth, migration, invasion, epithelial-mesenchymal transition and thus determines cell behavior, promoting tumor development. This work provides a complete overview of the TRPM7 ion channel and its main involvements in breast cancer. Special consideration is given to the modulation of the channel as a potential target in breast cancer treatment by inhibition of proliferation, migration and invasion. Taken together, these data suggest the potential exploitation of TRPM7 channel-kinase as a therapeutic target and a diagnostic biomarker.
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Chokshi R, Bennett O, Zhelay T, Kozak JA. NSAIDs Naproxen, Ibuprofen, Salicylate, and Aspirin Inhibit TRPM7 Channels by Cytosolic Acidification. Front Physiol 2021; 12:727549. [PMID: 34733174 PMCID: PMC8558630 DOI: 10.3389/fphys.2021.727549] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 09/10/2021] [Indexed: 01/23/2023] Open
Abstract
Non-steroidal anti-inflammatory drugs (NSAIDs) are used for relieving pain and inflammation accompanying numerous disease states. The primary therapeutic mechanism of these widely used drugs is the inhibition of cyclooxygenase 1 and 2 (COX1, 2) enzymes that catalyze the conversion of arachidonic acid into prostaglandins. At higher doses, NSAIDs are used for prevention of certain types of cancer and as experimental treatments for Alzheimer’s disease. In the immune system, various NSAIDs have been reported to influence neutrophil function and lymphocyte proliferation, and affect ion channels and cellular calcium homeostasis. Transient receptor potential melastatin 7 (TRPM7) cation channels are highly expressed in T lymphocytes and are inhibited by Mg2+, acidic pH, and polyamines. Here, we report a novel effect of naproxen, ibuprofen, salicylate, and acetylsalicylate on TRPM7. At concentrations of 3–30mM, they reversibly inhibited TRPM7 channel currents. By measuring intracellular pH with the ratiometric indicator BCECF, we found that at 300μM to 30mM, these NSAIDs reversibly acidified the cytoplasm in a concentration-dependent manner, and propose that TRPM7 channel inhibition is a consequence of cytosolic acidification, rather than direct. NSAID inhibition of TRPM7 channels was slow, voltage-independent, and displayed use-dependence, increasing in potency upon repeated drug applications. The extent of channel inhibition by salicylate strongly depended on cellular PI(4,5)P2 levels, as revealed when this phospholipid was depleted with voltage-sensitive lipid phosphatase (VSP). Salicylate inhibited heterologously expressed wildtype TRPM7 channels but not the S1107R variant, which is insensitive to cytosolic pH, Mg2+, and PI(4,5)P2 depletion. NSAID-induced acidification was also observed in Schneider 2 cells from Drosophila, an organism that lacks orthologous COX genes, suggesting that this effect is unrelated to COX enzyme activity. A 24-h exposure to 300μM–10mM naproxen resulted in a concentration-dependent reduction in cell viability. In addition to TRPM7, the described NSAID effect would be expected to apply to other ion channels and transporters sensitive to intracellular pH.
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Affiliation(s)
- Rikki Chokshi
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine, College of Science and Mathematics, Wright State University, Dayton, OH, United States
| | - Orville Bennett
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine, College of Science and Mathematics, Wright State University, Dayton, OH, United States
| | - Tetyana Zhelay
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine, College of Science and Mathematics, Wright State University, Dayton, OH, United States
| | - J Ashot Kozak
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine, College of Science and Mathematics, Wright State University, Dayton, OH, United States
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9
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Beesetty P, Rockwood J, Kaitsuka T, Zhelay T, Hourani S, Matsushita M, Kozak JA. Phagocytic activity of splenic macrophages is enhanced and accompanied by cytosolic alkalinization in TRPM7 kinase-dead mice. FEBS J 2021; 288:3585-3601. [PMID: 33354894 DOI: 10.1111/febs.15683] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 10/29/2020] [Accepted: 12/21/2020] [Indexed: 12/31/2022]
Abstract
Transient receptor potential melastatin 7 (TRPM7) is a unique protein functioning as a cation channel as well as a serine/threonine kinase and is highly expressed in immune cells such as lymphocytes and macrophages. TRPM7 kinase-dead (KD) mouse model has been used to investigate the role of this protein in immune cells; these animals display moderate splenomegaly and ectopic hemopoiesis. The basal TRPM7 current magnitudes in peritoneal macrophages isolated from KD mice were higher; however, the maximum currents, achieved after cytoplasmic Mg2+ washout, were not different. In the present study, we investigated the consequences of TRPM7 kinase inactivation in splenic and peritoneal macrophages. We measured the basal phagocytic activity of splenic macrophages using fluorescent latex beads, pHrodo zymosan bioparticles, and opsonized red blood cells. KD macrophages phagocytized more efficiently and had slightly higher baseline calcium levels compared to WT cells. We found no obvious differences in store-operated Ca2+ entry between WT and KD macrophages. By contrast, the resting cytosolic pH in KD macrophages was significantly more alkaline than in WT. Pharmacological blockade of sodium hydrogen exchanger 1 (NHE1) reversed the cytosolic alkalinization and reduced phagocytosis in KD macrophages. Basal TRPM7 channel activity in KD macrophages was also reduced after NHE1 blockade. Cytosolic Mg2+ sensitivity of TRPM7 channels measured in peritoneal macrophages was similar in WT and KD mice. The higher basal TRPM7 channel activity in KD macrophages is likely due to alkalinization. Our results identify a novel role for TRPM7 kinase as a suppressor of basal phagocytosis and a regulator of cellular pH.
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Affiliation(s)
- Pavani Beesetty
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, USA
| | - Jananie Rockwood
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, USA
| | - Taku Kaitsuka
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Japan
| | - Tetyana Zhelay
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, USA
| | - Siham Hourani
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, USA
| | - Masayuki Matsushita
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan
| | - J Ashot Kozak
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, USA
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10
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Mendu SK, Stremska ME, Schappe MS, Moser EK, Krupa JK, Rogers JS, Stipes EJ, Parker CA, Braciale TJ, Perry JSA, Desai BN. Targeting the ion channel TRPM7 promotes the thymic development of regulatory T cells by promoting IL-2 signaling. Sci Signal 2020; 13:eabb0619. [PMID: 33293462 PMCID: PMC7884026 DOI: 10.1126/scisignal.abb0619] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The thymic development of regulatory T (Treg) cells, crucial suppressors of the responses of effector T (Teff) cells, is governed by the transcription factor FOXP3. Despite the clinical importance of Treg cells, there is a dearth of druggable molecular targets capable of increasing their numbers in vivo. We found that inhibiting the function of the TRPM7 chanzyme (ion channel and enzyme) potentiated the thymic development of Treg cells in mice and led to a substantially higher frequency of functional Treg cells in the periphery. In addition, TRPM7-deficient mice were resistant to T cell-driven hepatitis. Deletion of Trpm7 and inhibition of TRPM7 channel activity by the FDA-approved drug FTY720 increased the sensitivity of T cells to the cytokine interleukin-2 (IL-2) through a positive feed-forward loop involving increased expression of the IL-2 receptor α-subunit and activation of the transcriptional regulator STAT5. Enhanced IL-2 signaling increased the expression of Foxp3 in thymocytes and promoted thymic Treg (tTreg) cell development. Thus, these data indicate that inhibiting TRPM7 activity increases Treg cell numbers, suggesting that it may be a therapeutic target to promote immune tolerance.
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Affiliation(s)
- Suresh K Mendu
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Marta E Stremska
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, VA 22908, USA
| | - Michael S Schappe
- Howard Hughes Medical Institute, Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | | | - Julia K Krupa
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Jason S Rogers
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Eric J Stipes
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Clare A Parker
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Thomas J Braciale
- Carter Immunology Center, University of Virginia, Charlottesville, VA 22908, USA
| | - Justin S A Perry
- Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
- Louis V. Gerstner Jr. Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
- Department of Immunology and Microbial Pathogenesis, Weill Cornell Medical College, New York, NY 10065, USA
| | - Bimal N Desai
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
- Carter Immunology Center, University of Virginia, Charlottesville, VA 22908, USA
- Robert M. Berne Cardiovascular Research Center, Charlottesville, VA 22908, USA
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11
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Mellott A, Rockwood J, Zhelay T, Luu CT, Kaitsuka T, Kozak JA. TRPM7 channel activity in Jurkat T lymphocytes during magnesium depletion and loading: implications for divalent metal entry and cytotoxicity. Pflugers Arch 2020; 472:1589-1606. [PMID: 32964285 DOI: 10.1007/s00424-020-02457-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/26/2020] [Accepted: 08/28/2020] [Indexed: 12/14/2022]
Abstract
TRPM7 is a cation channel-protein kinase highly expressed in T lymphocytes and other immune cells. It has been proposed to constitute a cellular entry pathway for Mg2+ and divalent metal cations such as Ca2+, Zn2+, Cd2+, Mn2+, and Ni2+. TRPM7 channels are inhibited by cytosolic Mg2+, rendering them largely inactive in intact cells. The dependence of channel activity on extracellular Mg2+ is less well studied. Here, we measured native TRPM7 channel activity in Jurkat T cells maintained in external Mg2+ concentrations varying between 400 nM and 1.4 mM for 1-3 days, obtaining an IC50 value of 54 μM. Maintaining the cells in 400 nM or 8 μM [Mg2+]o resulted in almost complete activation of TRPM7 in intact cells, due to cytosolic Mg2+ depletion. A total of 1.4 mM [Mg2+]o was sufficient to fully eliminate the basal current. Submillimolar concentrations of amiloride prevented cellular Mg2+ depletion but not loading. We investigated whether the cytotoxicity of TRPM7 permeant metal ions Ni2+, Zn2+, Cd2+, Co2+, Mn2+, Sr2+, and Ba2+ requires TRPM7 channel activity. Mg2+ loading modestly reduced cytotoxicity of Zn2+, Co2+, Ni2+, and Mn2+ but not of Cd2+. Channel blocker NS8593 reduced Co2+ and Mn2+ but not Cd2+ or Zn2+ cytotoxicity and interfered with Mg2+ loading as evaluated by TRPM7 channel basal activity. Ba2+ and Sr2+ were neither detectably toxic nor permeant through the plasma membrane. These results indicate that in Jurkat T cells, entry of toxic divalent metal cations primarily occurs through pathways distinct from TRPM7. By contrast, we found evidence that Mg2+ entry requires TRPM7 channels.
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Affiliation(s)
- Alayna Mellott
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, 45435, USA
| | - Jananie Rockwood
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, 45435, USA
| | - Tetyana Zhelay
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, 45435, USA
| | - Charles Tuan Luu
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, 45435, USA
| | - Taku Kaitsuka
- School of Pharmacy in Fukuoka, International University of Health and Welfare, Enokizu 137-1, Okawa, Fukuoka, Japan
| | - J Ashot Kozak
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, OH, 45435, USA.
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12
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TRPM7 mediates kidney injury, endothelial hyperpermeability and mortality during endotoxemia. J Transl Med 2020; 100:234-249. [PMID: 31444399 DOI: 10.1038/s41374-019-0304-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 06/24/2019] [Accepted: 07/19/2019] [Indexed: 12/17/2022] Open
Abstract
Sepsis is the main cause of mortality in patients admitted to intensive care units. During sepsis, endothelial permeability is severely augmented, contributing to renal dysfunction and patient mortality. Ca2+ influx and the subsequent increase in intracellular [Ca2+]i in endothelial cells (ECs) are key steps in the establishment of endothelial hyperpermeability. Transient receptor potential melastatin 7 (TRPM7) ion channels are permeable to Ca2+ and are expressed in a broad range of cell types and tissues, including ECs and kidneys. However, the role of TRPM7 on endothelial hyperpermeability during sepsis has remained elusive. Therefore, we investigated the participation of TRPM7 in renal vascular hyperpermeability, renal dysfunction, and enhanced mortality induced by endotoxemia. Our results showed that endotoxin increases endothelial hyperpermeability and Ca2+ overload through the TLR4/NOX-2/ROS/NF-κB pathway. Moreover, endotoxin exposure was shown to downregulate the expression of VE-cadherin, compromising monolayer integrity and enhancing vascular hyperpermeability. Notably, endotoxin-induced endothelial hyperpermeability was substantially inhibited by pharmacological inhibition and specific suppression of TRPM7 expression. The endotoxin was shown to upregulate the expression of TRPM7 via the TLR4/NOX-2/ROS/NF-κB pathway and induce a TRPM7-dependent EC Ca2+ overload. Remarkably, in vivo experiments performed in endotoxemic animals showed that pharmacological inhibition and specific suppression of TRPM7 expression inhibits renal vascular hyperpermeability, prevents kidney dysfunction, and improves survival in endotoxemic animals. Therefore, our results showed that TRPM7 mediates endotoxemia-induced endothelial hyperpermeability, renal dysfunction, and enhanced mortality, revealing a novel molecular target for treating renal vascular hyperpermeability and kidney dysfunction during endotoxemia, sepsis, and other inflammatory diseases.
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Zhelay T, Wieczerzak KB, Beesetty P, Alter GM, Matsushita M, Kozak JA. Depletion of plasma membrane-associated phosphoinositides mimics inhibition of TRPM7 channels by cytosolic Mg 2+, spermine, and pH. J Biol Chem 2018; 293:18151-18167. [PMID: 30305398 PMCID: PMC6254349 DOI: 10.1074/jbc.ra118.004066] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 10/04/2018] [Indexed: 12/20/2022] Open
Abstract
Transient receptor potential cation channel subfamily M member 7 (TRPM7) is an ion channel/protein kinase belonging to the TRP melastatin and eEF2 kinase families. Under physiological conditions, most native TRPM7 channels are inhibited by cytoplasmic Mg2+, protons, and polyamines. Currents through these channels (ITRPM7) are robustly potentiated when the cell interior is exchanged with low Mg2+-containing buffers. ITRPM7 is also potentiated by phosphatidyl inositol bisphosphate (PI(4,5)P2) and suppressed by its hydrolysis. Here we characterized internal Mg2+- and pH-mediated inhibition of TRPM7 channels in HEK293 cells overexpressing WT voltage-sensing phospholipid phosphatase (VSP) or its catalytically inactive variant VSP-C363S. VSP-mediated depletion of membrane phosphoinositides significantly increased channel sensitivity to Mg2+ and pH. Proton concentrations that were too low to inhibit ITRPM7 when the VSP-C363S variant was expressed (pH 8.2) became inhibitory in WT VSP-expressing cells. At pH 6.5, protons inhibited ITRPM7 both in WT and VSP C363S-expressing cells but with a faster time course in the WT VSP-expressing cells. Inhibition by 150 μm Mg2+ was also significantly faster in the WT VSP-expressing cells. Cellular PI(4,5)P2 depletion increased the sensitivity of TRPM7 channels to the inhibitor 2-aminoethyl diphenyl borinate, which acidifies the cytosol. Single substitutions at Ser-1107 of TRPM7, reducing its sensitivity to Mg2+, also decreased its inhibition by spermine and acidic pH. Furthermore, these channel variants were markedly less sensitive to VSP-mediated PI(4,5)P2 depletion than the WT. We conclude that the internal Mg2+-, polyamine-, and pH-mediated inhibition of TRPM7 channels is not direct but, rather, reflects electrostatic screening and resultant disruption of PI(4,5)P2-channel interactions.
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Affiliation(s)
- Tetyana Zhelay
- From the Departments of Neuroscience, Cell Biology, and Physiology and
| | | | - Pavani Beesetty
- From the Departments of Neuroscience, Cell Biology, and Physiology and
| | - Gerald M Alter
- Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio 45435 and
| | - Masayuki Matsushita
- the Department of Molecular and Cellular Physiology, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan
| | - J Ashot Kozak
- From the Departments of Neuroscience, Cell Biology, and Physiology and.
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14
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Sun Y, Schaar A, Sukumaran P, Dhasarathy A, Singh BB. TGFβ-induced epithelial-to-mesenchymal transition in prostate cancer cells is mediated via TRPM7 expression. Mol Carcinog 2018; 57:752-761. [PMID: 29500887 PMCID: PMC5947546 DOI: 10.1002/mc.22797] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 02/22/2018] [Accepted: 02/28/2018] [Indexed: 12/13/2022]
Abstract
Growth factors, such as the transforming growth factor beta (TGFβ), play an important role in promoting metastasis of prostate cancer, thus understanding how TGFβ could induce prostate cancer cell migration may enable us to develop targeted strategies for treatment of advanced metastatic prostate cancer. To more clearly define the mechanism(s) involved in prostate cancer cell migration, we undertook a series of studies utilizing non‐malignant prostate epithelial cells RWPE1 and prostate cancer DU145 and PC3 cells. Our studies show that increased cell migration was observed in prostate cancer cells, which was mediated through epithelial‐to‐mesenchymal transition (EMT). Importantly, addition of Mg2+, but not Ca2+, increased cell migration. Furthermore, TRPM7 expression, which functions as an Mg2+ influx channel, was also increased in prostate cancer cells. Inhibition of TRPM7 currents by 2‐APB, significantly blocked cell migration in both DU145 and PC3 cells. Addition of growth factor TGFβ showed a further increase in cell migration, which was again blocked by the addition of 2‐APB. Importantly, TGFβ addition also significantly increased TRPM7 expression and function, and silencing of TRPM7 negated TGFβ‐induced cell migration along with a decrease in EMT markers showing loss of cell adhesion. Furthermore, resveratrol, which decreases prostate cancer cell migration, inhibited TRPM7 expression and function including TGFβ‐induced cell migration and activation of TRPM7 function. Together, these results suggest that Mg2+ influx via TRPM7 promotes cell migration by inducing EMT in prostate cancer cells and resveratrol negatively modulates TRPM7 function thereby inhibiting prostate cancer metastasis.
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Affiliation(s)
- Yuyang Sun
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota
| | - Anne Schaar
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota
| | - Pramod Sukumaran
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota
| | - Archana Dhasarathy
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota
| | - Brij B Singh
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota
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15
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Inactivation of TRPM7 kinase in mice results in enlarged spleens, reduced T-cell proliferation and diminished store-operated calcium entry. Sci Rep 2018; 8:3023. [PMID: 29445164 PMCID: PMC5813043 DOI: 10.1038/s41598-018-21004-w] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 01/29/2018] [Indexed: 12/20/2022] Open
Abstract
T lymphocytes enlarge (blast) and proliferate in response to antigens in a multistep program that involves obligatory cytosolic calcium elevations. Store-operated calcium entry (SOCE) pathway is the primary source of Ca2+ in these cells. Here, we describe a novel modulator of blastogenesis, proliferation and SOCE: the TRPM7 channel kinase. TRPM7 kinase-dead (KD) K1646R knock-in mice exhibited splenomegaly and impaired blastogenic responses elicited by PMA/ionomycin or anti-CD3/CD28 antibodies. Splenic T-cell proliferation in vitro was weaker in the mutant compared to wildtype littermates. TRPM7 current magnitudes in WT and KD mouse T cells were, however, similar. We tested the dependence of T-cell proliferation on external Ca2+ and Mg2+ concentrations. At a fixed [Mg2+o] of ~0.4 mM, Ca2+o stimulated proliferation with a steep concentration dependence and vice versa, at a fixed [Ca2+o] of ~0.4 mM, Mg2+o positively regulated proliferation but with a shallower dependence. Proliferation was significantly lower in KD mouse than in wildtype at all Ca2+ and Mg2+ concentrations. Ca2+ elevations elicited by anti-CD3 antibody were diminished in KD mutant T cells and SOCE measured in activated KD splenocytes was reduced. These results demonstrate that a functional TRPM7 kinase supports robust SOCE, blastogenesis and proliferation, whereas its inactivation suppresses these cellular events.
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16
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Oh HG, Chung S. Activation of transient receptor potential melastatin 7 (TRPM7) channel increases basal autophagy and reduces amyloid β-peptide. Biochem Biophys Res Commun 2017; 493:494-499. [PMID: 28870815 DOI: 10.1016/j.bbrc.2017.08.163] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 08/31/2017] [Indexed: 11/24/2022]
Abstract
Cerebral accumulation of amyloid β-peptide (Aβ), which is produced from amyloid precursor protein (APP), is the primary cause of Alzheimer's disease (AD). Autophagy recycles cellular components and digests intracellular components including Aβ. The Ca2+- and Mg2+-permeable transient receptor potential melastatin 7 (TRPM7) channel underlies the constitutive Ca2+ influx in some cells. Since we already reported that TRPM7 channel-mediated Ca2+ influx regulates basal autophagy, we hypothesize that the activation of TRPM7 channel could increase basal autophagy and consequently decrease Aβ. In this study, we showed that naltriben (NTB), a specific TRPM7 channel activator, induced Ca2+ influx and activated autophagic signaling in neuroblastoma SH-SY5Y cells. NTB also promoted co-localization of LC3 and APP, and reduced Aβ. Furthermore, we found that an early-onset familial AD-associated presenilin1 ΔE9 (PS1 ΔE9) mutant cells had attenuated basal autophagy. NTB was able to recover autophagy and decrease Aβ in PS1 ΔE9 cells. Our results show that the activating TRPM7 channel may prevent AD-related Aβ neuropathology via modulating Ca2+-regulated basal autophagy.
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Affiliation(s)
- Hyun Geun Oh
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 440-746, South Korea
| | - Sungkwon Chung
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 440-746, South Korea.
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17
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Taruno A, Marunaka Y. Hypotonicity activates a voltage-dependent membrane conductance in N2a neuroblastoma cells. Biochem Biophys Res Commun 2017; 484:331-335. [PMID: 28130109 DOI: 10.1016/j.bbrc.2017.01.118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 01/22/2017] [Indexed: 01/26/2023]
Abstract
To maintain cellular and bodily homeostasis, cells respond to extracellular stimuli including osmotic stress by activating various ion channels, which have been implicated in many physiological and pathophysiological conditions. However, cellular osmosensory mechanisms remain elusive. Here, we report a novel voltage-dependent current in N2a cells activated by exposure to hypotonic stress. After a hypotonic challenge, N2a cells sequentially develop two distinct currents. The volume-regulated anion channel (VRAC) current emerges first and, after a delay, activation of a previously uncharacterized strongly outwardly rectifying current follows. The latter, delayed current (Id) is insensitive to NPPB, a nonspecific blocker of Cl- channels, and intracellular Mg2+, which inhibits VRAC and swelling-activated TRPM3 and TRPM7 channels. Replacement of extracellular Na+ with NMDG+ reduces inward tail currents, suggesting that Id is mediated by cations. Finally, Id shows voltage-dependent activation with slow activation kinetics and half-maximal activation at +76 mV. These pharmacological and biophysical characteristics of Id are distinct from those of known osmotic cell swelling-activated ion channels. In conclusion, our data identify and characterize a novel osmotically-activated, voltage-dependent ion channel in N2a cells.
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Affiliation(s)
- Akiyuki Taruno
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto 602-8566, Japan.
| | - Yoshinori Marunaka
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto 602-8566, Japan; Department of Bio-Ionomics, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto 602-8566, Japan.
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18
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Abstract
Calcium (Ca2+) and magnesium (Mg2+) ions have been shown to play an important role in regulating various neuronal functions. In the present review we focus on the emerging role of transient potential melastatin-7 (TRPM7) channel in not only regulating Ca2+ and Mg2+ homeostasis necessary for biological functions, but also how alterations in TRPM7 function/expression could induce neurodegeneration. Although eight TRPM channels have been identified, the channel properties, mode of activation, and physiological responses of various TRPM channels are quite distinct. Among the known 8 TRPM channels only TRPM6 and TRPM7 channels are highly permeable to both Ca2+ and Mg2+; however here we will only focus on TRPM7 as unlike TRPM6, TRPM7 channels are abundantly expressed in neuronal cells. Importantly, the discrepancy in TRPM7 channel function and expression leads to various neuronal diseases such as Alzheimer disease (AD) and Parkinson disease (PD). Further, it is emerging as a key factor in anoxic neuronal death and in other neurodegenerative disorders. Thus, by understanding the precise involvement of the TRPM7 channels in different neurodegenerative diseases and by understanding the factors that regulate TRPM7 channels, we could uncover new strategies in the future that could evolve as new drug therapeutic targets for effective treatment of these neurodegenerative diseases.
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Affiliation(s)
- Yuyang Sun
- a Department of Basic Science ; School of Medicine and Health Sciences, University of North Dakota ; Grand Forks , ND USA
| | - Pramod Sukumaran
- a Department of Basic Science ; School of Medicine and Health Sciences, University of North Dakota ; Grand Forks , ND USA
| | - Anne Schaar
- a Department of Basic Science ; School of Medicine and Health Sciences, University of North Dakota ; Grand Forks , ND USA
| | - Brij B Singh
- a Department of Basic Science ; School of Medicine and Health Sciences, University of North Dakota ; Grand Forks , ND USA
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19
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Oh HG, Chun YS, Park CS, Kim TW, Park MK, Chung S. Regulation of basal autophagy by transient receptor potential melastatin 7 (TRPM7) channel. Biochem Biophys Res Commun 2015; 463:7-12. [DOI: 10.1016/j.bbrc.2015.05.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 05/04/2015] [Indexed: 10/23/2022]
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20
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Abstract
PURPOSE OF REVIEW The tight control of blood magnesium (Mg) levels is of central importance for numerous physiological processes. A persistent low Mg status (hypomagnesemia) is associated with severe health risks and is involved in the pathogenesis of type 2 diabetes mellitus, osteoporosis, asthma, and heart and vascular diseases. The current view has expanded significantly as a result of the identification of novel genes and regulatory pathways involved in hypomagnesemic disorders. This review aims to give an up-to-date overview of transient receptor potential melastatin 6 (TRPM6) regulation and its role in the maintenance of Mg homeostasis. RECENT FINDINGS The epithelial Mg channel TRPM6 is considered to be the Mg entry pathway in the distal convoluted tubule of the kidney, where it functions as gatekeeper for controlling the body's Mg balance. Various factors and hormones contribute not only to the function, but also to the dysregulation of TRPM6, which has a substantial impact on renal Mg handling. Recent genetic and molecular studies have further elucidated the signaling processes of epithelial Mg transport, including their effect on the expression and function of TRPM6. SUMMARY Knowledge of TRPM6 functioning is of vital importance to decipher its role in Mg handling and will, in particular, provide a molecular basis for achieving a better understanding of Mg mal(re)absorption and hence systemic Mg balance.
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Visser D, Middelbeek J, van Leeuwen FN, Jalink K. Function and regulation of the channel-kinase TRPM7 in health and disease. Eur J Cell Biol 2014; 93:455-65. [DOI: 10.1016/j.ejcb.2014.07.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 06/24/2014] [Accepted: 07/01/2014] [Indexed: 11/30/2022] Open
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22
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Leng TD, Lin J, Sun HW, Zeng Z, O'Bryant Z, Inoue K, Xiong ZG. Local anesthetic lidocaine inhibits TRPM7 current and TRPM7-mediated zinc toxicity. CNS Neurosci Ther 2014; 21:32-9. [PMID: 25169754 DOI: 10.1111/cns.12318] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Revised: 07/30/2014] [Accepted: 07/31/2014] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Previous study demonstrated that overstimulation of TRPM7 substantially contributes to zinc-mediated neuronal toxicity. Inhibition of TRPM7 activity and TRPM7-mediated intracellular Zn(2+) accumulation may represent a promising strategy in the treatment of stroke. AIMS To investigate whether local anesthetics lidocaine could inhibit TRPM7 channel and TRPM7-mediated zinc toxicity. METHODS Whole-cell patch-clamp technique was used to investigate the effect of local anesthetics on TRPM7 currents in cultured mouse cortical neurons and TRPM7-overexpressed HEK293 cells. Fluorescent Zn(2+) imaging technique was used to study the effect of lidocaine on TRPM7-mediated intracellular Zn(2+) accumulation. TRPM7-mediated zinc toxicity in neurons was used to evaluate the neuroprotective effect of lidocaine. RESULTS (1) Lidocaine dose dependently inhibits TRPM7-like currents, with an IC50 of 11.55 and 11.06 mM in cultured mouse cortical neurons and TRPM7-overexpressed HEK293 cells, respectively; (2) Lidocaine inhibits TRPM7 currents in a use/frequency-dependent manner; (3) Lidocaine inhibits TRPM7-mediated intracellular Zn(2+) accumulation in both cortical neurons and TRPM7-overexpressed HEK293 cells; (4) TRPM7-mediated Zn(2+) toxicity is ameliorated by lidocaine in cortical neurons; (5) QX-314 has a similar inhibitory effect as lidocaine on TRPM7 currents when applied extracellularly; (6) Procaine also shows potent inhibitory effect on the TRPM7 currents in cortical neurons. CONCLUSION Our data provide the first evidence that local anesthetic lidocaine inhibits TRPM7 channel and TRPM7-mediated zinc toxicity.
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Affiliation(s)
- Tian-Dong Leng
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA, USA
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23
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Abstract
SIGNIFICANCE Environmental and endogenous reactive species such as reactive oxygen species (ROS), reactive nitrogen species (RNS), and other electrophiles are not only known to exert toxic effects on organisms, but are also emerging as molecules that mediate cell signaling responses. However, the mechanisms underlying this cellular redox signaling by reactive species remains largely uncharacterized. RECENT ADVANCES Ca2+-permeable cation channels encoded by the transient receptor potential (trp) gene superfamily are characterized by a wide variety of activation triggers that act from outside and inside the cell. Recent studies have revealed that multiple TRP channels sense reactive species and induce diverse physiological and pathological responses, such as cell death, chemokine production, and pain transduction. TRP channels sense reactive species either indirectly through second messengers or directly via oxidative modification of cysteine residues. In this review, we describe the activation mechanisms and biological roles of redox-sensitive TRP channels, including TRPM2, TRPM7, TRPC5, TRPV1, and TRPA1. CRITICAL ISSUES The sensitivity of TRP channels to reactive species in vitro has been well characterized using molecular and pharmacological approaches. However, the precise activation mechanism(s) and in vivo function(s) of ROS/RNS-sensitive TRP channels remain elusive. FUTURE DIRECTIONS Redox sensitivity of TRP channels has been shown to mediate previously unexplained biological phenomena and is involved in various pathologies. Understanding the physiological significance and activation mechanisms of TRP channel regulation by reactive species may lead to TRP channels becoming viable pharmacological targets, and modulators of these channels may offer therapeutic options for previously untreatable diseases.
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Affiliation(s)
- Daisuke Kozai
- 1 Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University , Kyoto, Japan
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Endotoxin-induced vascular endothelial cell migration is dependent on TLR4/NF-κB pathway, NAD(P)H oxidase activation, and transient receptor potential melastatin 7 calcium channel activity. Int J Biochem Cell Biol 2014; 55:11-23. [PMID: 25130439 DOI: 10.1016/j.biocel.2014.08.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 07/16/2014] [Accepted: 08/04/2014] [Indexed: 12/22/2022]
Abstract
Endothelial dysfunction is decisive and leads to the development of several inflammatory diseases. Endotoxemia-derived sepsis syndrome exhibits a broad inflammation-induced endothelial dysfunction. We reported previously that the endotoxin, lipopolysaccharide (LPS), induces the conversion of endothelial cells (ECs) into activated fibroblasts, showing a myofibroblast-like protein expression profile. Enhanced migration is a hallmark of myofibroblast function. However, the mechanism involved in LPS-induced EC migration is no totally understood. Some studies have shown that the transient receptor potential melastatin 7 (TRPM7) ion channel is involved in fibroblast and tumor cell migration through the regulation of calcium influx. Furthermore, LPS modulates TRPM7 expression. However, whether TRPM7 is involved in LPS-induced EC migration remains unknown. Here, we study the participation of LPS as an inducer of EC migration and study the mechanism underlying evaluating the participation of the TRPM7 ion channel. Our results demonstrate that LPS induced EC migration in a dose-dependent manner. Furthermore, this migratory process was mediated by the TLR-4/NF-κB pathway and the generation of ROS through the PKC-activated NAD(P)H oxidase. In addition, LPS increased the intracellular calcium level and the number of focal adhesion kinase (FAK)-positive focal adhesions in EC. Finally, we demonstrate that using TRPM7 blockers or suppressing TRPM7 expression through siRNA successfully inhibits the calcium influx and the LPS-induced EC migration. These results point out TRPM7 as a new target in the drug design for several inflammatory diseases that impair vascular endothelium function.
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Permeation, regulation and control of expression of TRP channels by trace metal ions. Pflugers Arch 2014; 467:1143-64. [PMID: 25106481 PMCID: PMC4435931 DOI: 10.1007/s00424-014-1590-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 07/10/2014] [Accepted: 07/13/2014] [Indexed: 01/26/2023]
Abstract
Transient receptor potential (TRP) channels form a diverse family of cation channels comprising 28 members in mammals. Although some TRP proteins can only be found on intracellular membranes, most of the TRP protein isoforms reach the plasma membrane where they form ion channels and control a wide number of biological processes. There, their involvement in the transport of cations such as calcium and sodium has been well documented. However, a growing number of studies have started to expand our understanding of these proteins by showing that they also transport other biologically relevant metal ions like zinc, magnesium, manganese and cobalt. In addition to this newly recognized property, the activity and expression of TRP channels can be regulated by metal ions like magnesium, gadolinium, lanthanum or cisplatin. The aim of this review is to highlight the complex relationship between metal ions and TRP channels.
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26
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Zhou W, Guo S, Xiong Z, Liu M. Oncogenic role and therapeutic target of transient receptor potential melastatin 7 channel in malignancy. Expert Opin Ther Targets 2014; 18:1177-96. [DOI: 10.1517/14728222.2014.940894] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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27
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Inoue H, Murayama T, Tashiro M, Sakurai T, Konishi M. Mg(2+)- and ATP-dependent inhibition of transient receptor potential melastatin 7 by oxidative stress. Free Radic Biol Med 2014; 72:257-66. [PMID: 24747489 DOI: 10.1016/j.freeradbiomed.2014.04.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 04/09/2014] [Accepted: 04/10/2014] [Indexed: 11/25/2022]
Abstract
Transient receptor potential melastatin 7 (TRPM7) is a Ca(2+)- and Mg(2+)-permeable nonselective cation channel that contains a unique carboxyl-terminal serine/threonine protein kinase domain. It has been reported that reactive oxygen species associated with hypoxia or ischemia activate TRPM7 current and then induce Ca(2+) overload resulting in neuronal cell death in the brain. In this study, we aimed to investigate the molecular mechanisms of TRPM7 regulation by hydrogen peroxide (H2O2) using murine TRPM7 expressed in HEK293 cells. Using the whole-cell patch-clamp technique, it was revealed that the TRPM7 current was inhibited, not activated, by the application of H2O2 to the extracellular solution. This inhibition was not reversed after washout or treatment with dithiothreitol, suggesting irreversible oxidation of TRPM7 or its regulatory factors by H2O2 under whole-cell recording. Application of an electrophile, N-methylmaleimide (NMM), which covalently modifies cysteine residues in proteins, also inhibited TRPM7 current irreversibly. The effects of H2O2 and NMM were dependent on free [Mg(2+)]i; the inhibition was stronger when cells were perfused with higher free [Mg(2+)]i solutions via pipette. In addition, TRPM7 current was not inhibited by H2O2 when millimolar ATP was included in the intracellular solution, even in the presence of substantial free [Mg(2+)]i, which is sufficient for TRPM7 inhibition by H2O2 in the absence of ATP. Moreover, a kinase-deficient mutant of TRPM7 (K1645R) was similarly inhibited by H2O2 just like the wild-type TRPM7 in a [Mg(2+)]i- and [ATP]i-dependent manner, indicating no involvement of the kinase activity of TRPM7. Thus, these data suggest that oxidative stress inhibits TRPM7 current under pathological conditions that accompany intracellular ATP depletion and free [Mg(2+)]i elevation.
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Affiliation(s)
- Hana Inoue
- Department of Physiology, Tokyo Medical University, 160-8402 Tokyo, Japan.
| | - Takashi Murayama
- Cellular and Molecular Pharmacology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Michiko Tashiro
- Department of Physiology, Tokyo Medical University, 160-8402 Tokyo, Japan
| | - Takashi Sakurai
- Cellular and Molecular Pharmacology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Masato Konishi
- Department of Physiology, Tokyo Medical University, 160-8402 Tokyo, Japan
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Echeverría C, Montorfano I, Hermosilla T, Armisén R, Velásquez LA, Cabello-Verrugio C, Varela D, Simon F. Endotoxin induces fibrosis in vascular endothelial cells through a mechanism dependent on transient receptor protein melastatin 7 activity. PLoS One 2014; 9:e94146. [PMID: 24710004 PMCID: PMC3978016 DOI: 10.1371/journal.pone.0094146] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 03/14/2014] [Indexed: 02/06/2023] Open
Abstract
The pathogenesis of systemic inflammatory diseases, including endotoxemia-derived sepsis syndrome, is characterized by endothelial dysfunction. It has been demonstrated that the endotoxin lipopolysaccharide (LPS) induces the conversion of endothelial cells (ECs) into activated fibroblasts through endothelial-to-mesenchymal transition mechanism. Fibrogenesis is highly dependent on intracellular Ca2+ concentration increases through the participation of calcium channels. However, the specific molecular identity of the calcium channel that mediates the Ca2+ influx during endotoxin-induced endothelial fibrosis is still unknown. Transient receptor potential melastatin 7 (TRPM7) is a calcium channel that is expressed in many cell types, including ECs. TRPM7 is involved in a number of crucial processes such as the conversion of fibroblasts into activated fibroblasts, or myofibroblasts, being responsible for the development of several characteristics of them. However, the role of the TRPM7 ion channel in endotoxin-induced endothelial fibrosis is unknown. Thus, our aim was to study whether the TRPM7 calcium channel participates in endotoxin-induced endothelial fibrosis. Using primary cultures of ECs, we demonstrated that TRPM7 is a crucial protein involved in endotoxin-induced endothelial fibrosis. Suppression of TRPM7 expression protected ECs from the fibrogenic process stimulated by endotoxin. Downregulation of TRPM7 prevented the endotoxin-induced endothelial markers decrease and fibrotic genes increase in ECs. In addition, TRPM7 downregulation abolished the endotoxin-induced increase in ECM proteins in ECs. Furthermore, we showed that intracellular Ca2+ levels were greatly increased upon LPS challenge in a mechanism dependent on TRPM7 expression. These results demonstrate that TRPM7 is a key protein involved in the mechanism underlying endotoxin-induced endothelial fibrosis.
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Affiliation(s)
- Cesar Echeverría
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
| | - Ignacio Montorfano
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
| | - Tamara Hermosilla
- Centro de Estudios Moleculares de la Celula, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Ricardo Armisén
- Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Centro de Investigacion y Tratamiento del Cancer, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Luis A. Velásquez
- Center for Integrative Medicine and Innovative Science (CIMIS), Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
- Centro para el Desarrollo de la Nanociencia y Nanotecnología, Universidad de Santiago de Chile, Santiago, Chile
| | - Claudio Cabello-Verrugio
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
| | - Diego Varela
- Centro de Estudios Moleculares de la Celula, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Instituto de Ciencias Biomedicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Felipe Simon
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
- * E-mail:
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Proton-sensitive cation channels and ion exchangers in ischemic brain injury: new therapeutic targets for stroke? Prog Neurobiol 2014; 115:189-209. [PMID: 24467911 DOI: 10.1016/j.pneurobio.2013.12.008] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 11/28/2013] [Accepted: 12/24/2013] [Indexed: 12/13/2022]
Abstract
Ischemic brain injury results from complicated cellular mechanisms. The present therapy for acute ischemic stroke is limited to thrombolysis with the recombinant tissue plasminogen activator (rtPA) and mechanical recanalization. Therefore, a better understanding of ischemic brain injury is needed for the development of more effective therapies. Disruption of ionic homeostasis plays an important role in cell death following cerebral ischemia. Glutamate receptor-mediated ionic imbalance and neurotoxicity have been well established in cerebral ischemia after stroke. However, non-NMDA receptor-dependent mechanisms, involving acid-sensing ion channel 1a (ASIC1a), transient receptor potential melastatin 7 (TRPM7), and Na(+)/H(+) exchanger isoform 1 (NHE1), have recently emerged as important players in the dysregulation of ionic homeostasis in the CNS under ischemic conditions. These H(+)-sensitive channels and/or exchangers are expressed in the majority of cell types of the neurovascular unit. Sustained activation of these proteins causes excessive influx of cations, such as Ca(2+), Na(+), and Zn(2+), and leads to ischemic reperfusion brain injury. In this review, we summarize recent pre-clinical experimental research findings on how these channels/exchangers are regulated in both in vitro and in vivo models of cerebral ischemia. The blockade or transgenic knockdown of these proteins was shown to be neuroprotective in these ischemia models. Taken together, these non-NMDA receptor-dependent mechanisms may serve as novel therapeutic targets for stroke intervention.
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Abstract
The channel kinases TRPM6 and TRPM7 are fusion proteins with an ion transport domain and an enzymatically active kinase domain. TRPM7 has been found in every mammalian tissue investigated to date. The two-in-one protein structure, the ubiquitous expression profile, and the protein's unique biophysical characteristics that enable divalent ion transport involve TRPM7 in a plethora of (patho)physiological processes. With its prominent role in cellular and systemic magnesium homeostasis, TRPM7 emerges as a key player in embryonic development, global ischemia, cardiovascular disease, and cancer.
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Affiliation(s)
- Andrea Fleig
- Center for Biomedical Research at The Queen's Medical Center, Honolulu, HI, USA,
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31
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Abstract
The physiological and clinical relevance of Mg(2+) has evolved over the last decades. The molecular identification of multiple Mg(2+) transporters (Acdp2, MagT1, Mrs2, Paracellin-1, SLC41A1, SLC41A2, TRPM6 and TRPM7) and their biophysical characterization in recent years has improved our understanding of Mg(2+) homeostasis regulation and has provided a basis for investigating the role of Mg(2+) in the immune system. Deletions and mutations of Mg(2+) transporters produce severe phenotypes with more systemic symptoms than those seen with Ca(2+) channel deletions, which tend to be more specific and less profound. Deficiency of the Mg(2+) permeable ion channels TRPM6 or TRPM7 in mice is lethal at embryonic day 12.5 or at day 6.5, respectively, and, even more surprisingly, chicken DT40 B cells lacking TRPM7 die after 24-48 h. Recent progress made in Mg(2+) research has helped to define underlying mechanisms of two hereditary diseases, human Hypomagnesemia (TRPM6 deletion) and X-chromosomal immunodeficiency (MagT1 deletion), and has revealed a potential new role for Mg(2+) as a second messenger. Future elucidation of human Mg(2+) transporters (Mrs2, SLC41A1, SLC41A2, TRPM7) expressed in immunocytes, beyond MagT1 and TRPM6, will widen our knowledge about the potential role of Mg(2+) in the activation of the immune response.
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Simon F, Varela D, Cabello-Verrugio C. Oxidative stress-modulated TRPM ion channels in cell dysfunction and pathological conditions in humans. Cell Signal 2013; 25:1614-24. [PMID: 23602937 DOI: 10.1016/j.cellsig.2013.03.023] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 03/25/2013] [Accepted: 03/28/2013] [Indexed: 10/27/2022]
Abstract
The transient receptor potential melastatin (TRPM) protein family is an extensive group of ion channels expressed in several types of mammalian cells. Many studies have shown that these channels are crucial for performing several physiological functions. Additionally, a large body of evidence indicates that these channels are also involved in numerous human diseases, known as channelopathies. A characteristic event frequently observed during pathological states is the raising in intracellular oxidative agents over reducing molecules, shifting the redox balance and inducing oxidative stress. In particular, three members of the TRPM subfamily, TRPM2, TRPM4 and TRPM7, share the remarkable feature that their activities are modulated by oxidative stress. Because of the increase in oxidative stress, these TRPM channels function aberrantly, promoting the onset and development of diseases. Increases, absences, or modifications in the function of these redox-modulated TRPM channels are associated with cell dysfunction and human pathologies. Therefore, the effect of oxidative stress on ion channels becomes an essential part of the pathogenic mechanism. Thus, oxidative stress-modulated ion channels are more susceptible to generating pathological states than oxidant-independent channels. This review examines the most relevant findings regarding the participation of the oxidative stress-modulated TRPM ion channels, TRPM2, TRPM4, and TRPM7, in human diseases. In addition, the potential roles of these channels as therapeutic tools and targets for drug design are discussed.
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Affiliation(s)
- Felipe Simon
- Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, 8370146, Santiago, Chile.
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Chubanov V, Mederos y Schnitzler M, Meißner M, Schäfer S, Abstiens K, Hofmann T, Gudermann T. Natural and synthetic modulators of SK (K(ca)2) potassium channels inhibit magnesium-dependent activity of the kinase-coupled cation channel TRPM7. Br J Pharmacol 2012; 166:1357-76. [PMID: 22242975 DOI: 10.1111/j.1476-5381.2012.01855.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Transient receptor potential cation channel subfamily M member 7 (TRPM7) is a bifunctional protein comprising a TRP ion channel segment linked to an α-type protein kinase domain. TRPM7 is essential for proliferation and cell growth. Up-regulation of TRPM7 function is involved in anoxic neuronal death, cardiac fibrosis and tumour cell proliferation. The goal of this work was to identify non-toxic inhibitors of the TRPM7 channel and to assess the effect of blocking endogenous TRPM7 currents on the phenotype of living cells. EXPERIMENTAL APPROACH We developed an aequorin bioluminescence-based assay of TRPM7 channel activity and performed a hypothesis-driven screen for inhibitors of the channel. The candidates identified were further assessed electrophysiologically and in cell biological experiments. KEY RESULTS TRPM7 currents were inhibited by modulators of small conductance Ca²⁺ -activated K⁺ channels (K(Ca)2.1-2.3; SK) channels, including the antimalarial plant alkaloid quinine, CyPPA, dequalinium, NS8593, SKA31 and UCL 1684. The most potent compound NS8593 (IC₅₀ 1.6 µM) specifically targeted TRPM7 as compared with other TRP channels, interfered with Mg²⁺ -dependent regulation of TRPM7 channel and inhibited the motility of cultured cells. NS8593 exhibited full and reversible block of native TRPM7-like currents in HEK 293 cells, freshly isolated smooth muscle cells, primary podocytes and ventricular myocytes. CONCLUSIONS AND IMPLICATIONS This study reveals a tight overlap in the pharmacological profiles of TRPM7 and K(Ca)2.1-2.3 channels. NS8593 acts as a negative gating modulator of TRPM7 and is well-suited to study functional features and cellular roles of endogenous TRPM7.
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Affiliation(s)
- V Chubanov
- Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany.
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Harada M, Luo X, Qi XY, Tadevosyan A, Maguy A, Ordog B, Ledoux J, Kato T, Naud P, Voigt N, Shi Y, Kamiya K, Murohara T, Kodama I, Tardif JC, Schotten U, Van Wagoner DR, Dobrev D, Nattel S. Transient receptor potential canonical-3 channel-dependent fibroblast regulation in atrial fibrillation. Circulation 2012; 126:2051-64. [PMID: 22992321 DOI: 10.1161/circulationaha.112.121830] [Citation(s) in RCA: 199] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
BACKGROUND Fibroblast proliferation and differentiation are central in atrial fibrillation (AF)-promoting remodeling. Here, we investigated fibroblast regulation by Ca(2+)-permeable transient receptor potential canonical-3 (TRPC3) channels. METHODS AND RESULTS Freshly isolated rat cardiac fibroblasts abundantly expressed TRPC3 and had appreciable nonselective cation currents (I(NSC)) sensitive to a selective TPRC3 channel blocker, pyrazole-3 (3 μmol/L). Pyrazole-3 suppressed angiotensin II-induced Ca(2+) influx, proliferation, and α-smooth muscle actin protein expression in fibroblasts. Ca(2+) removal and TRPC3 blockade suppressed extracellular signal-regulated kinase phosphorylation, and extracellular signal-regulated kinase phosphorylation inhibition reduced fibroblast proliferation. TRPC3 expression was upregulated in atria from AF patients, goats with electrically maintained AF, and dogs with tachypacing-induced heart failure. TRPC3 knockdown (based on short hairpin RNA [shRNA]) decreased canine atrial fibroblast proliferation. In left atrial fibroblasts freshly isolated from dogs kept in AF for 1 week by atrial tachypacing, TRPC3 protein expression, currents, extracellular signal-regulated kinase phosphorylation, and extracellular matrix gene expression were all significantly increased. In cultured left atrial fibroblasts from AF dogs, proliferation rates, α-smooth muscle actin expression, and extracellular signal-regulated kinase phosphorylation were increased and were suppressed by pyrazole-3. MicroRNA-26 was downregulated in canine AF atria; experimental microRNA-26 knockdown reproduced AF-induced TRPC3 upregulation and fibroblast activation. MicroRNA-26 has NFAT (nuclear factor of activated T cells) binding sites in the 5' promoter region. NFAT activation increased in AF fibroblasts, and NFAT negatively regulated microRNA-26 transcription. In vivo pyrazole-3 administration suppressed AF while decreasing fibroblast proliferation and extracellular matrix gene expression. CONCLUSIONS TRPC3 channels regulate cardiac fibroblast proliferation and differentiation, likely by controlling the Ca(2+) influx that activates extracellular signal-regulated kinase signaling. AF increases TRPC3 channel expression by causing NFAT-mediated downregulation of microRNA-26 and causes TRPC3-dependent enhancement of fibroblast proliferation and differentiation. In vivo, TRPC3 blockade prevents AF substrate development in a dog model of electrically maintained AF. TRPC3 likely plays an important role in AF by promoting fibroblast pathophysiology and is a novel potential therapeutic target.
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Affiliation(s)
- Masahide Harada
- Department of Medicine and Research Center, Montreal Heart Institute and Universite´ de Montre´al, Montreal, Quebec, Canada
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Desai BN, Krapivinsky G, Navarro B, Krapivinsky L, Carter BC, Febvay S, Delling M, Penumaka A, Ramsey IS, Manasian Y, Clapham DE. Cleavage of TRPM7 releases the kinase domain from the ion channel and regulates its participation in Fas-induced apoptosis. Dev Cell 2012; 22:1149-62. [PMID: 22698280 PMCID: PMC3397829 DOI: 10.1016/j.devcel.2012.04.006] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 03/13/2012] [Accepted: 04/11/2012] [Indexed: 10/28/2022]
Abstract
Transient receptor potential melastatin-like 7 (TRPM7) is a channel protein that also contains a regulatory serine-threonine kinase domain. Here, we find that Trpm7-/- T cells are deficient in Fas-receptor-induced apoptosis and that TRPM7 channel activity participates in the apoptotic process and is regulated by caspase-dependent cleavage. This function of TRPM7 is dependent on its function as a channel, but not as a kinase. TRPM7 is cleaved by caspases at D1510, disassociating the carboxy-terminal kinase domain from the pore without disrupting the phosphotransferase activity of the released kinase but substantially increasing TRPM7 ion channel activity. Furthermore, we show that TRPM7 regulates endocytic compartmentalization of the Fas receptor after receptor stimulation, an important process for apoptotic signaling through Fas receptors. These findings raise the possibility that other members of the TRP channel superfamily are also regulated by caspase-mediated cleavage, with wide-ranging implications for cell death and differentiation.
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Affiliation(s)
- Bimal N Desai
- Department of Cardiology, Howard Hughes Medical Institute, Manton Center for Orphan Disease, Children's Hospital Boston, and Department of Neurobiology, Harvard Medical School, Enders Building 1309, 320 Longwood Avenue, Boston, MA 02115, USA
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Calcium homeostasis modulator 1 (CALHM1) is the pore-forming subunit of an ion channel that mediates extracellular Ca2+ regulation of neuronal excitability. Proc Natl Acad Sci U S A 2012; 109:E1963-71. [PMID: 22711817 DOI: 10.1073/pnas.1204023109] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extracellular Ca(2+) (Ca(2+)(o)) plays important roles in physiology. Changes of Ca(2+)(o) concentration ([Ca(2+)](o)) have been observed to modulate neuronal excitability in various physiological and pathophysiological settings, but the mechanisms by which neurons detect [Ca(2+)](o) are not fully understood. Calcium homeostasis modulator 1 (CALHM1) expression was shown to induce cation currents in cells and elevate cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) in response to removal of Ca(2+)(o) and its subsequent addback. However, it is unknown whether CALHM1 is a pore-forming ion channel or modulates endogenous ion channels. Here we identify CALHM1 as the pore-forming subunit of a plasma membrane Ca(2+)-permeable ion channel with distinct ion permeability properties and unique coupled allosteric gating regulation by voltage and [Ca(2+)](o). Furthermore, we show that CALHM1 is expressed in mouse cortical neurons that respond to reducing [Ca(2+)](o) with enhanced conductance and action potential firing and strongly elevated [Ca(2+)](i) upon Ca(2+)(o) removal and its addback. In contrast, these responses are strongly muted in neurons from mice with CALHM1 genetically deleted. These results demonstrate that CALHM1 is an evolutionarily conserved ion channel family that detects membrane voltage and extracellular Ca(2+) levels and plays a role in cortical neuronal excitability and Ca(2+) homeostasis, particularly in response to lowering [Ca(2+)](o) and its restoration to normal levels.
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Gwanyanya A, Macianskiene R, Mubagwa K. Insights into the effects of diclofenac and other non-steroidal anti-inflammatory agents on ion channels. ACTA ACUST UNITED AC 2012; 64:1359-75. [PMID: 22943167 DOI: 10.1111/j.2042-7158.2012.01479.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES Diclofenac and other non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of inflammation and pain. Most effects of NSAIDs are attributed to the inhibition of cyclooxygenases (COX). However, many NSAIDs may have other effects not related to COX, including the modulation of various ion channels. The clinical implications of the effects on channels are not fully understood. This review outlines the effects of NSAIDs, with special attention to diclofenac, on ion channels and highlights the possible underlying mechanisms. KEY FINDINGS NSAIDs have effects on channels such as inhibition, activation or changes in expression patterns. The channels affected include voltage-gated Na(+) , Ca(2+) , or K(+) channels, ligand-gated K(+) channels, transient receptor potential and other cation channels as well as chloride channels in several types of cells. The mechanisms of drug actions not related to COX inhibition may involve drug-channel interactions, interference with the generation of second messengers, changes in channel expression, or synergistic/antagonist interactions with other channel modulators. SUMMARY The effects on ion channels may account for novel therapeutic actions of NSAIDs or for adverse effects. Among the NSAIDs, diclofenac may serve as a template for developing new channel modulators and as a tool for investigating the actions of other drugs.
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Affiliation(s)
- Asfree Gwanyanya
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Bahia PK, Bennett ES, Taylor-Clark TE. Reductions in external divalent cations evoke novel voltage-gated currents in sensory neurons. PLoS One 2012; 7:e31585. [PMID: 22328938 PMCID: PMC3273472 DOI: 10.1371/journal.pone.0031585] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 01/09/2012] [Indexed: 12/31/2022] Open
Abstract
It has long been recognized that divalent cations modulate cell excitability. Sensory nerve excitability is of critical importance to peripheral diseases associated with pain, sensory dysfunction and evoked reflexes. Thus we have studied the role these cations play on dissociated sensory nerve activity. Withdrawal of both Mg2+ and Ca2+ from external solutions activates over 90% of dissociated mouse sensory neurons. Imaging studies demonstrate a Na+ influx that then causes depolarization-mediated activation of voltage-gated Ca2+ channels (CaV), which allows Ca2+ influx upon divalent re-introduction. Inhibition of CaV (ω-conotoxin, nifedipine) or NaV (tetrodotoxin, lidocaine) fails to reduce the Na+ influx. The Ca2+ influx is inhibited by CaV inhibitors but not by TRPM7 inhibition (spermine) or store-operated channel inhibition (SKF96365). Withdrawal of either Mg2+ or Ca2+ alone fails to evoke cation influxes in vagal sensory neurons. In electrophysiological studies of dissociated mouse vagal sensory neurons, withdrawal of both Mg2+ and Ca2+ from external solutions evokes a large slowly-inactivating voltage-gated current (IDF) that cannot be accounted for by an increased negative surface potential. Withdrawal of Ca2+ alone fails to evoke IDF. Evidence suggests IDF is a non-selective cation current. The IDF is not reduced by inhibition of NaV (lidocaine, riluzole), CaV (cilnidipine, nifedipine), KV (tetraethylammonium, 4-aminopyridine) or TRPM7 channels (spermine). In summary, sensory neurons express a novel voltage-gated cation channel that is inhibited by external Ca2+ (IC50∼0.5 µM) or Mg2+ (IC50∼3 µM). Activation of this putative channel evokes substantial cation fluxes in sensory neurons.
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Affiliation(s)
- Parmvir K. Bahia
- Department of Molecular Pharmacology and Physiology, College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Eric S. Bennett
- Department of Molecular Pharmacology and Physiology, College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Thomas E. Taylor-Clark
- Department of Molecular Pharmacology and Physiology, College of Medicine, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
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Chokshi R, Matsushita M, Kozak JA. Detailed examination of Mg2+ and pH sensitivity of human TRPM7 channels. Am J Physiol Cell Physiol 2012; 302:C1004-11. [PMID: 22301056 DOI: 10.1152/ajpcell.00422.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
TRPM7 channel kinase is a protein highly expressed in cells of hematopoietic lineage, such as lymphocytes. Studies performed in native and heterologous expression systems have shown that TRPM7 forms nonselective cation channels functional in the plasma membrane and activated on depletion of cellular Mg(2+). In addition to internal Mg(2+), cytosolic pH and the phospholipid phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)] are potent physiological regulators of this channel: protons inhibit, while PI(4,5)P(2) is required for TRPM7 channel activity. These channels are also inhibited from inside by other metal cations and polyamines. While the regulation of TRPM7 channels by internal metal ions, acidic pH, and PI(4,5)P(2) is voltage independent, extracellular metal cations and polyamines block voltage dependently at micromolar concentrations and appear to occupy a distinct blocking site. In the present study we investigated intracellular Mg(2+) and pH dependence of native TRPM7 currents using whole cell patch-clamp electrophysiology in human Jurkat T lymphocytes and HEK293 cells. Our main findings are 1) Mg(2+) inhibition involves not one but two separate sites of high (∼10 μM) and low (∼165 μM) affinity; and 2) while sharing certain characteristics with Mg(2+) inhibition, protons most likely inhibit through one inhibitory site, corresponding to the low-affinity Mg(2+) site, with an estimated IC(50) of pH 6.3. Additionally, we present data on amplitude distribution of preactivated TRPM7 currents in Jurkat T lymphocytes in the absence of prior Mg(2+) or proton depletion.
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Mason MJ, Schaffner C, Floto RA, Teo QA. Constitutive expression of a Mg2+-inhibited K+ current and a TRPM7-like current in human erythroleukemia cells. Am J Physiol Cell Physiol 2011; 302:C853-67. [PMID: 22135214 DOI: 10.1152/ajpcell.00071.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Whole cell patch-clamp experiments were undertaken to define the basal K(+) conductance(s) in human erythroleukemia cells and its contribution to the setting of resting membrane potential. Experiments revealed a non-voltage-activated, noninactivating K(+) current. The magnitude of the current recorded under whole cell conditions was inhibited by an increase in free intracellular Mg(2+) concentration. Activation or inactivation of the Mg(2+)-inhibited K(+) current (MIP) was paralleled by activation or inactivation of a Mg(2+)-inhibited TRPM7-like current displaying characteristics indistinguishable from those reported for molecularly identified TRPM7 current. The MIP and TRPM7 currents were inhibited by 5-lipoxygenase inhibitors. However, inhibition of the MIP current was temporally distinct from inhibition of TRPM7 current, allowing for isolation of the MIP current. Isolation of the MIP conductance revealed a current reversing near the K(+) equilibrium potential, indicative of a highly K(+)-selective conductance. Consistent with this finding, coactivation of the nonselective cation current TRPM7 and the MIP current following dialysis with nominally Mg(2+)-free pipette solution resulted in hyperpolarized whole cell reversal potentials, consistent with an important role for the MIP current in the setting of a negative resting membrane potential. The MIP and TRPM7-like conductances were constitutively expressed under in vivo conditions of intracellular Mg(2+), as judged by their initial detection and subsequent inactivation following dialysis with a pipette solution containing 5 mM free Mg(2+). The MIP current was blocked in a voltage-dependent fashion by extracellular Cs(+) and, to a lesser degree, by Ba(2+) and was blocked by extracellular La(3+) and 2-aminoethoxydiphenyl borate. MIP currents were unaffected by blockers of ATP-sensitive K(+) channels, human ether-à-go-go-related gene current, and intermediate-conductance Ca(2+)-activated K(+) channels. In addition, the MIP current displayed characteristics distinct from conventional inwardly rectifying K(+) channels. A similar current was detected in the leukemic cell line CHRF-288-11, consistent with this current being more generally expressed in cells of leukemic origin.
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Affiliation(s)
- Michael J Mason
- Department of Physiology, Development, and Neuroscience, University of Cambridge, UK.
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Runnels LW. TRPM6 and TRPM7: A Mul-TRP-PLIK-cation of channel functions. Curr Pharm Biotechnol 2011; 12:42-53. [PMID: 20932259 DOI: 10.2174/138920111793937880] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 05/07/2010] [Indexed: 12/31/2022]
Abstract
Unique among ion channels, TRPM6 and TRPM7 garnered much interest upon their discovery as the first ion channels to possess their own kinase domain. Soon after their identification, the two proteins were quickly linked to the regulation of magnesium homeostasis. However, study of their physiological functions in mouse and zebrafish have revealed expanding roles for these channel-kinases that include skeletogenesis and melanopore formation, thymopoiesis, cell adhesion, and neural fold closure during early development. In addition, mutations in the TRPM6 gene constitute the underlying genetic defect in hypomagnesemia with secondary hypocalcemia, a rare autosomal-recessive disease characterized by low serum magnesium accompanied by hypocalcemia. Depletion of TRPM7 expression in brain, on the other hand, proved successful in mitigating much of the cellular devastation that accompanies oxygen-glucose deprivation during ischemia. The aim of this review is to summarize the data emerging from molecular genetic, biochemical, electrophysiological, and pharmacological studies of these unique channel-kinases.
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Affiliation(s)
- Loren W Runnels
- Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
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Bae CYJ, Sun HS. TRPM7 in cerebral ischemia and potential target for drug development in stroke. Acta Pharmacol Sin 2011; 32:725-33. [PMID: 21552293 DOI: 10.1038/aps.2011.60] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Searching for effective pharmacological agents for stroke treatment has largely been unsuccessful. Despite initial excitement, antagonists for glutamate receptors, the most studied receptor channels in ischemic stroke, have shown insufficient neuroprotective effects in clinical trials. Outside the traditional glutamate-mediated excitotoxicity, recent evidence suggests few non-glutamate mechanisms, which may also cause ionic imbalance and cell death in cerebral ischemia. Transient receptor potential melastatin 7 (TRPM7) is a Ca(2+) permeable, non-selective cation channel that has recently gained attention as a potential cation influx pathway involved in ischemic events. Compelling new evidence from an in vivo study demonstrated that suppression of TRPM7 channels in adult rat brain in vivo using virally mediated gene silencing approach reduced delayed neuronal cell death and preserved neuronal functions in global cerebral ischemia. In this review, we will discuss the current understanding of the role of TRPM7 channels in physiology and pathophysiology as well as its therapeutic potential in stroke.
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Cheng H, Feng JM, Figueiredo ML, Zhang H, Nelson PL, Marigo V, Beck A. Transient receptor potential melastatin type 7 channel is critical for the survival of bone marrow derived mesenchymal stem cells. Stem Cells Dev 2011; 19:1393-403. [PMID: 19929312 DOI: 10.1089/scd.2009.0262] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The transient receptor potential melastatin type 7 channel (TRPM7) is a member of the TRP family of ion channels that is essential for cell proliferation and viability. Mesenchymal stem cells (MSCs) from bone marrow are a potential source for tissue repair due to their ability to differentiate into specialized cells. However, the role of TRPM7 in stem cells is unknown. In this study, we characterized TRPM7 in mouse MSCs using molecular biology, immunocytochemistry, and patch clamp. We also investigated TRPM7 function using a lentiviral vector and specific shRNA to knockdown gene expression. By RT-PCR and immunocytochemistry, we identified TRPM7, but not TRPM6, a close family member with similar function. Electrophysiological recordings during depletion of intracellular Mg(2+) or Mg(2+)-ATP resulted in the development of currents typical for the channel. Furthermore, 2-aminoethoxydiphenyl borate (1 pM-100 microM) inhibited TRPM7 in a concentration-dependent manner. The molecular suppression of TRPM7 significantly decreased MSC proliferation and viability as determined by MTT assay. In addition, TRPM7 gene expression was up-regulated during osteogenesis. These findings demonstrate that TRPM7 is required for MSC survival and perhaps involved in the differentiation process.
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Affiliation(s)
- Henrique Cheng
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
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TRPM7, the Mg2+ Inhibited Channel and Kinase. TRANSIENT RECEPTOR POTENTIAL CHANNELS 2011; 704:173-83. [DOI: 10.1007/978-94-007-0265-3_9] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Lee BC, Hong SE, Lim HH, Kim DH, Park CS. Alteration of the Transcriptional Profile of Human Embryonic Kidney Cells by Transient Overexpression of Mouse TRPM7 Channels. Cell Physiol Biochem 2011; 27:313-26. [DOI: 10.1159/000327958] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/09/2011] [Indexed: 11/19/2022] Open
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Lu B, Zhang Q, Wang H, Wang Y, Nakayama M, Ren D. Extracellular calcium controls background current and neuronal excitability via an UNC79-UNC80-NALCN cation channel complex. Neuron 2010; 68:488-99. [PMID: 21040849 DOI: 10.1016/j.neuron.2010.09.014] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2010] [Indexed: 01/17/2023]
Abstract
In contrast to its extensively studied intracellular roles, the molecular mechanisms by which extracellular Ca(2+) regulates the basal excitability of neurons are unclear. One mechanism is believed to be through Ca(2+)'s interaction with the negative charges on the cell membrane (the charge screening effect). Here we show that, in cultured hippocampal neurons, lowering [Ca(2+)](e) activates a NALCN channel-dependent Na(+)-leak current (I(L-Na)). The coupling between [Ca(2+)](e) and NALCN requires a Ca(2+)-sensing G protein-coupled receptor, an activation of G-proteins, an UNC80 protein that bridges NALCN to a large novel protein UNC79 in the same complex, and the last amino acid of NALCN's intracellular tail. In neurons from nalcn and unc79 knockout mice, I(L-Na) is insensitive to changes in [Ca(2+)](e), and reducing [Ca(2+)](e) fails to elicit the excitatory effects seen in the wild-type. Therefore, extracellular Ca(2+) influences neuronal excitability through the UNC79-UNC80-NALCN complex in a G protein-dependent fashion.
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Affiliation(s)
- Boxun Lu
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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Abstract
Many ion channels and transporters are involved in the filtration, secretion, and resorption of electrolytes by the kidney. In recent years, the superfamily of transient receptor potential (TRP) ion channels have received deserved attention because mutated TRP channels are linked to human kidney diseases. This review focuses on two TRP members--TRPC6 and TRPM6--and their functions in the kidney. Gain-of-function mutations in TRPC6 are the cause for progressive kidney failure with urinary protein loss such as FSGS. Thus, TRPC6 is an essential signaling component in a functional slit diaphragm formed by podocytes around the glomerular capillaries. Loss-of-function mutations in TRPM6 are a molecular cause of hypomagnesemia with secondary hypocalcemia, suggesting that TRPM6 is critically involved in transcellular Mg2+ transport in the kidney. Here, we highlight how recent studies analyzing function and expression of these channels in the kidney improve our mechanistic understanding of TRP channel function in general and pave the way to new, promising therapeutic strategies to target kidney diseases such as FSGS and hypomagnesemia with secondary hypocalcemia.
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Affiliation(s)
- Alexander Dietrich
- Institute of Pharmacology and Toxicology, School of Medicine, University of Marburg, Marburg, Germany
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Du J, Xie J, Zhang Z, Tsujikawa H, Fusco D, Silverman D, Liang B, Yue L. TRPM7-mediated Ca2+ signals confer fibrogenesis in human atrial fibrillation. Circ Res 2010; 106:992-1003. [PMID: 20075334 DOI: 10.1161/circresaha.109.206771] [Citation(s) in RCA: 251] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
RATIONALE Cardiac fibrosis contributes to pathogenesis of atrial fibrillation (AF), which is the most commonly sustained arrhythmia and a major cause of morbidity and mortality. Although it has been suggested that Ca(2+) signals are involved in fibrosis promotion, the molecular basis of Ca(2+) signaling mechanisms and how Ca(2+) signals contribute to fibrogenesis remain unknown. OBJECTIVE To determine the molecular mechanisms of Ca(2+)-permeable channel(s) in human atrial fibroblasts, and to investigate how Ca(2+) signals contribute to fibrogenesis in human AF. METHODS AND RESULTS We demonstrate that the transient receptor potential (TRP) melastatin related 7 (TRPM7) is the molecular basis of the major Ca(2+)-permeable channel in human atrial fibroblasts. Endogenous TRPM7 currents in atrial fibroblasts resemble the biophysical and pharmacological properties of heterologous expressed TRPM7. Knocking down TRPM7 by small hairpin RNA largely eliminates TRPM7 current and Ca(2+) influx in atrial fibroblasts. More importantly, atrial fibroblasts from AF patients show a striking upregulation of both TRPM7 currents and Ca(2+) influx and are more prone to myofibroblast differentiation, presumably attributable to the enhanced expression of TRPM7. TRPM7 small hairpin RNA markedly reduced basal AF fibroblast differentiation. Transforming growth factor (TGF)-beta1, the major stimulator of atrial fibrosis, requires TRPM7-mediated Ca(2+) signal for its effect on fibroblast proliferation and differentiation. Furthermore, TGF-beta1-induced differentiation of cultured human atrial fibroblasts is well correlated with an increase of TRPM7 expression induced by TGF-beta1. CONCLUSIONS Our results establish that TRPM7 is the major Ca(2+)-permeable channel in human atrial fibroblasts and likely plays an essential role in TGF-beta1-elicited fibrogenesis in human AF.
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Affiliation(s)
- Jianyang Du
- Department of Cell Biology/Cardiology, ARB EG024, MC-3946, University of Connecticut Health Center, 263 Farmington Ave, Farmington, CT 06030, USA
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Mishra R, Rao V, Ta R, Shobeiri N, Hill CE. Mg2+- and MgATP-inhibited and Ca2+/calmodulin-sensitive TRPM7-like current in hepatoma and hepatocytes. Am J Physiol Gastrointest Liver Physiol 2009; 297:G687-94. [PMID: 19661151 DOI: 10.1152/ajpgi.90683.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Although understood to be ubiquitously expressed, the functional identification and significance of Mg(2+)-inhibited, nonspecific cation currents has been established in only a few cell types. Here we identified an outwardly rectifying nonspecific cation current in quiescent rat hepatocytes and the proliferating and polarized rat hepatoma, WIF-B. Under whole cell recording conditions in which cells were bathed and dialyzed with Na-gluconate solutions, the latter Ca(2+) and Mg(2+) free, current reversed close to 0 mV, was time independent, and was greater than 10 times higher at +120 mV compared with -120 mV. Outward current at -120 mV developed slowly, from 17.7 +/- 10.3 pA/pF at patch rupture to 106.6 +/- 15.6 pA/pF at 12 min in WIF-B cells, and 4.9 +/- 2.7 to 20.6 +/- 5.6 pA/pF in rat hepatocytes. The nonspecific TRP channel inhibitor, 2-aminoethoxyphenylborate (2-APB), inhibited current (IC(50) = 72 +/- 13 microM) and caused apoptotic cell death in WIF-B cells. Rat hepatocyte survival was more resistant to 2-APB. Dialysis of WIF-B cells with physiological concentrations of Mg(2+) and Mg-ATP, but not ATP alone, inhibited current development, suggesting that Trpm7 rather than Trpm6 underlies this current. RT-PCR demonstrated that both Trpm6 and Trpm7 are expressed at similar levels in both cell types, suggesting that the functional differences noted are not transcript dependent. Intracellular Ca(2+) (IC(50) = 125 +/- 35 nM) also inhibited current development, and this could be partially relieved by the calmodulin and Ca(2+)/calmodulin-dependent kinase inhibitors W-7, staurosporine, KN-93, or calmodulin kinase II (CaMKII) inhibitory peptide. To summarize, our results show that in addition to their established Mg(2+) sensitivity, Trpm7-like channels are inhibited by cytosolic Ca(2+) in a CaMKII-dependent manner and may support hepatocellular survival during proliferation.
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Affiliation(s)
- Ravi Mishra
- Department of Biology and Medicine, Hotel Dieu Hospital and Queen's University, Kingston, Ontario, Canada
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Abstract
For more than 25 years, it has been widely appreciated that Ca2+ influx is essential to trigger T-lymphocyte activation. Patch clamp analysis, molecular identification, and functional studies using blockers and genetic manipulation have shown that a unique contingent of ion channels orchestrates the initiation, intensity, and duration of the Ca2+ signal. Five distinct types of ion channels--Kv1.3, KCa3.1, Orai1+ stromal interacting molecule 1 (STIM1) [Ca2+-release activating Ca2+ (CRAC) channel], TRPM7, and Cl(swell)--comprise a network that performs functions vital for ongoing cellular homeostasis and for T-cell activation, offering potential targets for immunomodulation. Most recently, the roles of STIM1 and Orai1 have been revealed in triggering and forming the CRAC channel following T-cell receptor engagement. Kv1.3, KCa3.1, STIM1, and Orai1 have been found to cluster at the immunological synapse following contact with an antigen-presenting cell; we discuss how channels at the synapse might function to modulate local signaling. Immuno-imaging approaches are beginning to shed light on ion channel function in vivo. Importantly, the expression pattern of Ca2+ and K+ channels and hence the functional network can adapt depending upon the state of differentiation and activation, and this allows for different stages of an immune response to be targeted specifically.
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Affiliation(s)
- Michael D Cahalan
- Department of Physiology and Biophysics, and the Institute for Immunology, University of California, Irvine, Irvine, CA 92697-4561, USA.
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