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Nilius B, Szallasi A. Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine. Pharmacol Rev 2014; 66:676-814. [DOI: 10.1124/pr.113.008268] [Citation(s) in RCA: 348] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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302
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Kaneko Y, Szallasi A. Transient receptor potential (TRP) channels: a clinical perspective. Br J Pharmacol 2014; 171:2474-507. [PMID: 24102319 PMCID: PMC4008995 DOI: 10.1111/bph.12414] [Citation(s) in RCA: 283] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/28/2013] [Accepted: 08/31/2013] [Indexed: 12/14/2022] Open
Abstract
Transient receptor potential (TRP) channels are important mediators of sensory signals with marked effects on cellular functions and signalling pathways. Indeed, mutations in genes encoding TRP channels are the cause of several inherited diseases in humans (the so-called 'TRP channelopathies') that affect the cardiovascular, renal, skeletal and nervous systems. TRP channels are also promising targets for drug discovery. The initial focus of research was on TRP channels that are expressed on nociceptive neurons. Indeed, a number of potent, small-molecule TRPV1, TRPV3 and TRPA1 antagonists have already entered clinical trials as novel analgesic agents. There has been a recent upsurge in the amount of work that expands TRP channel drug discovery efforts into new disease areas such as asthma, cancer, anxiety, cardiac hypertrophy, as well as obesity and metabolic disorders. A better understanding of TRP channel functions in health and disease should lead to the discovery of first-in-class drugs for these intractable diseases. With this review, we hope to capture the current state of this rapidly expanding and changing field.
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Affiliation(s)
- Yosuke Kaneko
- Discovery Research Alliance, Ono Pharmaceutical Co. LtdOsaka, Japan
| | - Arpad Szallasi
- Department of Pathology and Laboratory Medicine, Monmouth Medical CenterLong Branch, NJ, USA
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303
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Soya M, Sato M, Sobhan U, Tsumura M, Ichinohe T, Tazaki M, Shibukawa Y. Plasma membrane stretch activates transient receptor potential vanilloid and ankyrin channels in Merkel cells from hamster buccal mucosa. Cell Calcium 2014; 55:208-18. [PMID: 24642224 DOI: 10.1016/j.ceca.2014.02.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 02/05/2014] [Accepted: 02/20/2014] [Indexed: 01/03/2023]
Abstract
Merkel cells (MCs) have been proposed to form a part of the MC-neurite complex with sensory neurons. Many transient receptor potential (TRP) channels have been identified in mammals; however, the activation properties of these channels in oral mucosal MCs remain to be clarified. We investigated the biophysical and pharmacological properties of TRP vanilloid (TRPV)-1, TRPV2, TRPV4, TRP ankyrin (TRPA)-1, and TRP melastatin (TRPM)-8 channels, which are sensitive to osmotic and mechanical stimuli by measurement of intracellular free Ca(2+) concentration ([Ca(2+)]i) using fura-2. We also analyzed their localization patterns through immunofluorescence. MCs showed immunoreaction for TRPV1, TRPV2, TRPV4, TRPA1, and TRPM8 channels. In the presence of extracellular Ca(2+), the hypotonic test solution evoked Ca(2+) influx. The [Ca(2+)]i increases were inhibited by TRPV1, TRPV2, TRPV4, or TRPA1 channel antagonists, but not by the TRPM8 channel antagonist. Application of TRPV1, TRPV2, TRPV4, TRPA1, or TRPM8 channel selective agonists elicited transient increases in [Ca(2+)]i only in the presence of extracellular Ca(2+). The results indicate that membrane stretching in MCs activates TRPV1, TRPV2, TRPV4, and TRPA1 channels, that it may be involved in synaptic transmission to sensory neurons, and that MCs could contribute to the mechanosensory transduction sequence.
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Affiliation(s)
- Manabu Soya
- Department of Dental Anesthesiology, Tokyo Dental College, Chiba 261-8502, Japan
| | - Masaki Sato
- Department of Physiology, Tokyo Dental College, Tokyo 101-0061, Japan
| | - Ubaidus Sobhan
- Department of Physiology, Tokyo Dental College, Tokyo 101-0061, Japan
| | - Maki Tsumura
- Department of Physiology, Tokyo Dental College, Tokyo 101-0061, Japan
| | - Tatsuya Ichinohe
- Department of Dental Anesthesiology, Tokyo Dental College, Chiba 261-8502, Japan
| | - Masakazu Tazaki
- Department of Physiology, Tokyo Dental College, Tokyo 101-0061, Japan
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304
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Wang X, Piccolo CW, Cohen BM, Buttner EA. Transient receptor potential melastatin (TRPM) channels mediate clozapine-induced phenotypes in Caenorhabditis elegans. J Neurogenet 2014; 28:86-97. [PMID: 24564792 DOI: 10.3109/01677063.2013.879717] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The molecular mechanisms of action of antipsychotic drugs (APDs) are not fully understood. Here, we characterize phenotypes of missense and knockout mutations in the Caenorhabditis elegans transient receptor potential melastatin (TRPM) channel ortholog gtl-2, a candidate APD target identified in a genome-wide RNAi (RNA interference) screen for Suppressors of Clozapine-induced Larval Arrest (scla genes). We then employ the developmental phenotypes of gtl-2(lf) mutants to validate our previous gtl-2(RNAi) result. GTL-2 acts in the excretory canal cell to regulate Mg(2+) homeostasis. Using exc (excretory canal abnormal) gene mutants, we demonstrate that excretory canal cell function is necessary for clozapine-induced developmental delay and lethality. Moreover, cell-specific promoter-driven expression studies reveal that GTL-2 function in the excretory canal cell is important for its role in the SCLA phenotype. We then investigate the mechanism by which GTL-2 function in the excretory canal cell impacts clozapine-induced phenotypes. gtl-2(lf) mutations cause hypermagnesemia, and we show that exposure of the wild-type strain to high Mg(2+) phenocopies gtl-2(lf) with respect to suppression of clozapine-induced developmental delay and lethality. Our results suggest that GTL-2 TRPM channel function in the excretory canal cell is important for clozapine's developmental effects. TRP channels are expressed in mammalian brain and are implicated in the pathogenesis of mental illnesses but have not been previously implicated in APD action.
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Affiliation(s)
- Xin Wang
- Department of Psychiatry, Harvard Medical School , Boston, Massachusetts , USA
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305
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Abstract
The Drosophila "transient receptor potential" channel is the prototypical TRP channel, belonging to and defining the TRPC subfamily. Together with a second TRPC channel, trp-like (TRPL), TRP mediates the transducer current in the fly's photoreceptors. TRP and TRPL are also implicated in olfaction and Malpighian tubule function. In photoreceptors, TRP and TRPL are localised in the ~30,000 packed microvilli that form the photosensitive "rhabdomere"-a light-guiding rod, housing rhodopsin and the rest of the phototransduction machinery. TRP (but not TRPL) is assembled into multimolecular signalling complexes by a PDZ-domain scaffolding protein (INAD). TRPL (but not TRP) undergoes light-regulated translocation between cell body and rhabdomere. TRP and TRPL are also found in photoreceptor synapses where they may play a role in synaptic transmission. Like other TRPC channels, TRP and TRPL are activated by a G protein-coupled phospholipase C (PLCβ4) cascade. Although still debated, recent evidence indicates the channels can be activated by a combination of PIP2 depletion and protons released by the PLC reaction. PIP2 depletion may act mechanically as membrane area is reduced by cleavage of PIP2's bulky inositol headgroup. TRP, which dominates the light-sensitive current, is Ca(2+) selective (P Ca:P Cs >50:1), whilst TRPL has a modest Ca(2+) permeability (P Ca:P Cs ~5:1). Ca(2+) influx via the channels has profound positive and negative feedback roles, required for the rapid response kinetics, with Ca(2+) rapidly facilitating TRP (but not TRPL) and also inhibiting both channels. In trp mutants, stimulation by light results in rapid depletion of microvillar PIP2 due to lack of Ca(2+) influx required to inhibit PLC. This accounts for the "transient receptor potential" phenotype that gives the family its name and, over a period of days, leads to light-dependent retinal degeneration. Gain-of-function trp mutants with uncontrolled Ca(2+) influx also undergo retinal degeneration due to Ca(2+) cytotoxicity. In vertebrate retina, mice knockout studies suggest that TRPC6 and TRPC7 mediate a PLCβ4-activated transducer current in intrinsically photosensitive retinal ganglion cells, expressing melanopsin. TRPA1 has been implicated as a "photo-sensing" TRP channel in human melanocytes and light-sensitive neurons in the body wall of Drosophila.
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306
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Zygmunt PM, Ermund A, Movahed P, Andersson DA, Simonsen C, Jönsson BAG, Blomgren A, Birnir B, Bevan S, Eschalier A, Mallet C, Gomis A, Högestätt ED. Monoacylglycerols activate TRPV1--a link between phospholipase C and TRPV1. PLoS One 2013; 8:e81618. [PMID: 24312564 PMCID: PMC3847081 DOI: 10.1371/journal.pone.0081618] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 10/25/2013] [Indexed: 01/17/2023] Open
Abstract
Phospholipase C-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate generates diacylglycerol, inositol 1,4,5-trisphosphate and protons, all of which can regulate TRPV1 activity via different mechanisms. Here we explored the possibility that the diacylglycerol metabolites 2-arachidonoylglycerol and 1-arachidonoylglycerol, and not metabolites of these monoacylglycerols, activate TRPV1 and contribute to this signaling cascade. 2-Arachidonoylglycerol and 1-arachidonoylglycerol activated native TRPV1 on vascular sensory nerve fibers and heterologously expressed TRPV1 in whole cells and inside-out membrane patches. The monoacylglycerol lipase inhibitors methylarachidonoyl-fluorophosphonate and JZL184 prevented the metabolism of deuterium-labeled 2-arachidonoylglycerol and deuterium-labeled 1-arachidonoylglycerol in arterial homogenates, and enhanced TRPV1-mediated vasodilator responses to both monoacylglycerols. In mesenteric arteries from TRPV1 knock-out mice, vasodilator responses to 2-arachidonoylglycerol were minor. Bradykinin and adenosine triphosphate, ligands of phospholipase C-coupled membrane receptors, increased the content of 2-arachidonoylglycerol in dorsal root ganglia. In HEK293 cells expressing the phospholipase C-coupled histamine H1 receptor, exposure to histamine stimulated the formation of 2-AG, and this effect was augmented in the presence of JZL184. These effects were prevented by the diacylglycerol lipase inhibitor tetrahydrolipstatin. Histamine induced large whole cell currents in HEK293 cells co-expressing TRPV1 and the histamine H1 receptor, and the TRPV1 antagonist capsazepine abolished these currents. JZL184 increased the histamine-induced currents and tetrahydrolipstatin prevented this effect. The calcineurin inhibitor ciclosporin and the endogenous "entourage" compound palmitoylethanolamide potentiated the vasodilator response to 2-arachidonoylglycerol, disclosing TRPV1 activation of this monoacylglycerol at nanomolar concentrations. Furthermore, intracerebroventricular injection of JZL184 produced TRPV1-dependent antinociception in the mouse formalin test. Our results show that intact 2-arachidonoylglycerol and 1-arachidonoylglycerol are endogenous TRPV1 activators, contributing to phospholipase C-dependent TRPV1 channel activation and TRPV1-mediated antinociceptive signaling in the brain.
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Affiliation(s)
- Peter M. Zygmunt
- Department of Laboratory Medicine, Lund University, Lund, Sweden
- Lund University Pain Research Centre, Lund University, Lund, Sweden
- * E-mail: (PMZ); (EDH)
| | - Anna Ermund
- Department of Laboratory Medicine, Lund University, Lund, Sweden
| | - Pouya Movahed
- Department of Laboratory Medicine, Lund University, Lund, Sweden
| | - David A. Andersson
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | | | - Bo A. G. Jönsson
- Department of Laboratory Medicine, Lund University, Lund, Sweden
| | - Anders Blomgren
- Department of Laboratory Medicine, Lund University, Lund, Sweden
| | - Bryndis Birnir
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Stuart Bevan
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Alain Eschalier
- Clermont Université, Université d'Auvergne, Pharmacologie Fondamentale et Clinique de la Douleur, Laboratoire de Pharmacologie, Facultés de Médecine/Pharmacie, Clermont-Ferrand, France
- Inserm, U1107 Neuro-Dol, Clermont-Ferrand, France
- CHU Clermont-Ferrand, Service de Pharmacologie, Hôpital G. Montpied, Clermont-Ferrand, France
| | - Christophe Mallet
- Clermont Université, Université d'Auvergne, Pharmacologie Fondamentale et Clinique de la Douleur, Laboratoire de Pharmacologie, Facultés de Médecine/Pharmacie, Clermont-Ferrand, France
- Inserm, U1107 Neuro-Dol, Clermont-Ferrand, France
| | - Ana Gomis
- Instituto de Neurociencias, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Spain
| | - Edward D. Högestätt
- Department of Laboratory Medicine, Lund University, Lund, Sweden
- Lund University Pain Research Centre, Lund University, Lund, Sweden
- * E-mail: (PMZ); (EDH)
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307
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Von Niederhäusern V, Kastenhuber E, Stäuble A, Gesemann M, Neuhauss SCF. Phylogeny and expression of canonical transient receptor potential (TRPC) genes in developing zebrafish. Dev Dyn 2013; 242:1427-41. [PMID: 24038627 DOI: 10.1002/dvdy.24041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/29/2013] [Accepted: 08/14/2013] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Canonical transient receptor potential (TRPC) channels are nonselective, calcium-permeable cation channels that are expressed in a great variety of organisms, tissues, and cell types. TRPC channels are known to be involved in the transduction of polymodal sensory input. Additionally, they are implicated in a variety of developmental processes. Distinct gating mechanisms have been elucidated so far, but their exact functional role in vertebrate organisms still needs to be resolved. RESULTS We now used the teleost Danio rerio to perform a comprehensive expression analysis of the trpc gene subfamily. Based on the sequence homology to the seven described mammalian TRPC channels, we identified 12 trpc genes in the zebrafish genome. All but trpc1 and trpc3 are represented by two paralogs. We further describe the specific expression patterns of trpc transcripts in whole-mounts during the first 5 days of development. CONCLUSIONS Consistent with their proposed role in sensory transduction zebrafish trpcs are predominantly expressed in neural structures such as the olfactory, visual, mechanosensitive, and motor systems. Intriguingly, zebrafish paralogs show mainly nonoverlapping expression patterns, suggesting that duplicated genes have either split their functions or have adapted new ones.
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Affiliation(s)
- Valentin Von Niederhäusern
- University of Zurich, Institute of Molecular Life Sciences, Neuroscience Center Zurich and Center for Integrative Human Physiology, Zurich, Switzerland
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308
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Nilius B, Bíró T. TRPV3: a ‘more than skinny’ channel. Exp Dermatol 2013; 22:447-52. [DOI: 10.1111/exd.12163] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2013] [Indexed: 02/02/2023]
Affiliation(s)
- Bernd Nilius
- Department of Cellular and Molecular Medicine; Laboratory Ion Channel Research; KU Leuven; Leuven Belgium
| | - Tamás Bíró
- DE-MTA “Lendület” Cellular Physiology Research Group; Department of Physiology; University of Debrecen; Medical and Health Science Center; Research Center for Molecular Medicine; Debrecen Hungary
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309
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Hypotonic-induced Stretching of Plasma Membrane Activates Transient Receptor Potential Vanilloid Channels and Sodium–Calcium Exchangers in Mouse Odontoblasts. J Endod 2013; 39:779-87. [DOI: 10.1016/j.joen.2013.01.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 01/29/2013] [Accepted: 01/30/2013] [Indexed: 11/22/2022]
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310
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311
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Verkhratsky A, Reyes RC, Parpura V. TRP channels coordinate ion signalling in astroglia. Rev Physiol Biochem Pharmacol 2013; 166:1-22. [PMID: 23784619 DOI: 10.1007/112_2013_15] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Astroglial excitability is based on highly spatio-temporally coordinated fluctuations of intracellular ion concentrations, among which changes in Ca(2+) and Na(+) take the leading role. Intracellular signals mediated by Ca(2+) and Na(+) target numerous molecular cascades that control gene expression, energy production and numerous homeostatic functions of astrocytes. Initiation of Ca(2+) and Na(+) signals relies upon plasmalemmal and intracellular channels that allow fluxes of respective ions down their concentration gradients. Astrocytes express several types of TRP channels of which TRPA1 channels are linked to regulation of functional expression of GABA transporters, whereas TRPV4 channels are activated following osmotic challenges and are up-regulated in ischaemic conditions. Astrocytes also ubiquitously express several isoforms of TRPC channels of which heteromers assembled from TRPC1, 4 and/or 5 subunits that likely act as stretch-activated channels and are linked to store-operated Ca(2+) entry. The TRPC channels mediate large Na(+) fluxes that are associated with the endoplasmic reticulum Ca(2+) signalling machinery and hence coordinate Na(+) and Ca(2+) signalling in astroglia.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK,
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312
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Sakai T, Sato S, Ishimoto H, Kitamoto T. Significance of the centrally expressed TRP channel painless in Drosophila courtship memory. Learn Mem 2012; 20:34-40. [PMID: 23247253 DOI: 10.1101/lm.029041.112] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Considerable evidence has demonstrated that transient receptor potential (TRP) channels play vital roles in sensory neurons, mediating responses to various environmental stimuli. In contrast, relatively little is known about how TRP channels exert their effects in the central nervous system to control complex behaviors. This is also true for the Drosophila TRP channel encoded by painless (pain). The Pain TRP channel is expressed in a subset of sensory neurons and involved in behavioral responses to thermal, chemical, and mechanical stimuli. Its physiological roles in brain neurons, however, remain largely elusive. Using multiple mutant alleles and tranformants for pain, here we demonstrate that the brain-expressed Pain TRP channel is required for long-term memory (LTM), but not for short-lasting memory, induced by courtship conditioning in adult males. The courtship LTM phenotype in pain mutants was rescued by expressing wild-type pain temporarily, prior to conditioning, in adult flies. In addition, targeted expression of painRNAi in either the mushroom bodies (MBs) or insulin-producing cells (IPCs) resulted in defective courtship LTM. These results indicate that the Pain TRP channels in the MBs and IPCs control neuronal plasticity that is required for the formation of a certain type of long-lasting associative memory in Drosophila.
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Affiliation(s)
- Takaomi Sakai
- Department of Biological Sciences, Tokyo Metropolitan University, Hachi-oji 192-0397, Tokyo, Japan
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313
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O'Tousa JE, Wu CF. Bill Pak's vision: the neurogenetics of phototransduction. J Neurogenet 2012; 26:103-5. [PMID: 22794102 DOI: 10.3109/01677063.2012.694933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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314
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Gailly P. TRP channels in normal and dystrophic skeletal muscle. Curr Opin Pharmacol 2012; 12:326-34. [PMID: 22349418 DOI: 10.1016/j.coph.2012.01.018] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 01/31/2012] [Accepted: 01/31/2012] [Indexed: 01/29/2023]
Abstract
TRP proteins constitute non-selective cation-permeable ion channels, most of which are permeable to Ca²⁺. In skeletal muscle, several isoforms of the TRPC (Canonical), TRPV (Vanilloid) and TRPM (Melastatin) subfamilies are expressed. In particular, TRPC1, C3 and C6, TRPV2 and V4, TRPM4 and TRPM7 have been consistently found in cultured myoblasts or in adult muscles. These channels seem to directly or indirectly respond to membrane stretch or to Ca²⁺ stores depletion; some isoforms might also constitute unregulated Ca²⁺ leak channels. Their function is largely unknown. TRPC1 and C3 have been involved in muscle development, in particular in myoblasts migration and differentiation. TRPC1 and V4 might allow a basal influx of Ca²⁺ at rest. Their lack has consequences on muscle fatigue. TRPV2 seems to be stretch-sensitive. It localizes mainly in intracellular pools at rest, and translocates to the plasma membrane upon IGF-1 stimulation. TRP channels seem to be involved in the pathophysiology of muscle disorders. In particular in Duchenne muscular dystrophy, the lack of the cytoskeletal protein dystrophin induces a disregulation of several ion channels leading to an abnormal influx of Ca²⁺. We discuss here, the possible involvement of TRP channels in this abnormal influx of Ca²⁺.
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Affiliation(s)
- Philippe Gailly
- Laboratory of Cell Physiology, Institute of Neuroscience, Université catholique de Louvain, 55 av. Hippocrate, B1.55.12, 1200 Brussels, Belgium.
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315
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Suzuki E, Masai I, Inoue H. Phosphoinositide Metabolism inDrosophilaPhototransduction: A Coffee Break Discussion Leads to 30 Years of History. J Neurogenet 2012; 26:34-42. [DOI: 10.3109/01677063.2011.647144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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316
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Lev S, Katz B, Tzarfaty V, Minke B. Signal-dependent hydrolysis of phosphatidylinositol 4,5-bisphosphate without activation of phospholipase C: implications on gating of Drosophila TRPL (transient receptor potential-like) channel. J Biol Chem 2012; 287:1436-47. [PMID: 22065576 PMCID: PMC3256851 DOI: 10.1074/jbc.m111.266585] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 10/23/2011] [Indexed: 11/06/2022] Open
Abstract
In Drosophila, a phospholipase C (PLC)-mediated signaling cascade, couples photo-excitation of rhodopsin to the opening of the transient receptor potential (TRP) and TRP-like (TRPL) channels. A lipid product of PLC, diacylglycerol (DAG), and its metabolites, polyunsaturated fatty acids (PUFAs) may function as second messengers of channel activation. However, how can one separate between the increase in putative second messengers, change in pH, and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) depletion when exploring the TRPL gating mechanism? To answer this question we co-expressed the TRPL channels together with the muscarinic (M1) receptor, enabling the openings of TRPL channels via G-protein activation of PLC. To dissect PLC activation of TRPL into its molecular components, we used a powerful method that reduced plasma membrane-associated PI(4,5)P(2) in HEK cells within seconds without activating PLC. Upon the addition of a dimerizing drug, PI(4,5)P(2) was selectively hydrolyzed in the cell membrane without producing DAG, inositol trisphosphate, or calcium signals. We show that PI(4,5)P(2) is not an inhibitor of TRPL channel activation. PI(4,5)P(2) hydrolysis combined with either acidification or application of DAG analogs failed to activate the channels, whereas PUFA did activate the channels. Moreover, a reduction in PI(4,5)P(2) levels or inhibition of DAG lipase during PLC activity suppressed the PLC-activated TRPL current. This suggests that PI(4,5)P(2) is a crucial substrate for PLC-mediated activation of the channels, whereas PUFA may function as the channel activator. Together, this study defines a narrow range of possible mechanisms for TRPL gating.
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Affiliation(s)
- Shaya Lev
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Institute of Medical Research Israel-Canada, The Edmond and Lily Safra Center for Brain Sciences, Faculty of Medicine of the Hebrew University, Jerusalem 91120, Israel
| | - Ben Katz
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Institute of Medical Research Israel-Canada, The Edmond and Lily Safra Center for Brain Sciences, Faculty of Medicine of the Hebrew University, Jerusalem 91120, Israel
| | - Vered Tzarfaty
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Institute of Medical Research Israel-Canada, The Edmond and Lily Safra Center for Brain Sciences, Faculty of Medicine of the Hebrew University, Jerusalem 91120, Israel
| | - Baruch Minke
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Institute of Medical Research Israel-Canada, The Edmond and Lily Safra Center for Brain Sciences, Faculty of Medicine of the Hebrew University, Jerusalem 91120, Israel
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317
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Chorna T, Hasan G. The genetics of calcium signaling in Drosophila melanogaster. Biochim Biophys Acta Gen Subj 2011; 1820:1269-82. [PMID: 22100727 DOI: 10.1016/j.bbagen.2011.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 10/31/2011] [Accepted: 11/02/2011] [Indexed: 01/13/2023]
Abstract
BACKGROUND Genetic screens for behavioral and physiological defects in Drosophila melanogaster, helped identify several components of calcium signaling of which some, like the Trps, were novel. For genes initially identified in vertebrates, reverse genetic methods have allowed functional studies at the cellular and systemic levels. SCOPE OF REVIEW The aim of this review is to explain how various genetic methods available in Drosophila have been used to place different arms of Ca2+ signaling in the context of organismal development, physiology and behavior. MAJOR CONCLUSION Mutants generated in genes encoding a range of Ca2+ transport systems, binding proteins and enzymes affect multiple aspects of neuronal and muscle physiology. Some also affect the maintenance of ionic balance and excretion from malpighian tubules and innate immune responses in macrophages. Aspects of neuronal physiology affected include synaptic growth and plasticity, sensory transduction, flight circuit development and function. Genetic interaction screens have shown that mechanisms of maintaining Ca2+ homeostasis in Drosophila are cell specific and require a synergistic interplay between different intracellular and plasma membrane Ca2+ signaling molecules. GENERAL SIGNIFICANCE Insights gained through genetic studies of conserved Ca2+ signaling pathways have helped understand multiple aspects of fly physiology. The similarities between mutant phenotypes of Ca2+ signaling genes in Drosophila with certain human disease conditions, especially where homologous genes are causative factors, are likely to aid in the discovery of underlying disease mechanisms and help develop novel therapeutic strategies. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling.
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Affiliation(s)
- Tetyana Chorna
- National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
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318
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Montell C. The history of TRP channels, a commentary and reflection. Pflugers Arch 2011; 461:499-506. [PMID: 21287198 DOI: 10.1007/s00424-010-0920-3] [Citation(s) in RCA: 322] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 12/23/2010] [Indexed: 11/30/2022]
Abstract
The transient receptor potential (TRP) family of cation channels has redefined our understanding of sensory physiology. In one animal or another, all senses depend on TRP channels. These include vision, taste, smell, hearing, and various forms of touch, including the ability to sense changes in temperature. The first trp gene was identified because it was disrupted in a Drosophila mutant with defective vision. However, there was no clue as to its biochemical function until the cloning, and analysis of the deduced amino acid sequence suggested that trp encoded a cation channel. This concept was further supported by subsequent electrophysiological studies, including alteration of its ion selectivity by an amino acid substitution within the pore loop. The study of TRP channels emerged as a field with the identification of mammalian homologs, some of which are direct sensors of environmental temperature. At least one TRP channel is activated downstream of a thermosensory signaling cascade, demonstrating that there exist two modes of activation, direct and indirect, through which TRP channels respond to changes in temperature. Mutations in many TRP channels result in disease, including a variety of sensory impairments.
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Affiliation(s)
- Craig Montell
- Department of Biological Chemistry, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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A brief history of trp: commentary and personal perspective. Pflugers Arch 2011; 461:493-8. [PMID: 21286746 DOI: 10.1007/s00424-011-0922-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 01/10/2011] [Indexed: 10/18/2022]
Abstract
The history of the discovery of the transient receptor potential (TRP) cation channel superfamily began in 1969 with Cosens and Manning's isolation of the Drosophila transient receptor potential mutant, in which the photoreceptor response decays during continuous illumination. Early studies from Minke found that the elementary light response was unaffected in trp mutants, and he attributed the defect to an intermediate stage of phototransduction. Montell and Rubin cloned the trp gene in 1989: they recognised it as a transmembrane protein, but also concluded that it did not encode the light-sensitive channels. In 1991, Minke and Selinger proposed that TRP represented a Ca2+ transporter required for refilling intracellular InsP3-sensitive Ca2+ stores, in turn required for activation of the light-sensitive channels. Also in 1991, after developing a photoreceptor patch clamp preparation, I showed that the light-sensitive channels themselves were highly permeable to Ca2+, questioning the need for such a dedicated Ca2+ transporter. In 1992, in collaboration with Minke, I resolved this paradox by showing there were two classes of light-sensitive channels, one highly Ca2+ permeable and eliminated in trp mutants. This represented the first and compelling evidence that TRP represented a light-sensitive channel and was supported by the cloning of the second light-sensitive channel, TRPL, by Kelly's lab. Three years later, in 1995, the labs of Montell and Birnbaumer independently cloned TRPC1, the first of 29 vertebrate TRP isoforms distributed amongst seven subfamilies.
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