201
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Affiliation(s)
- Michael X Zhu
- Department of Neuroscience and Center for Molecular Neurobiology, Ohio State University, Columbus, OH 43210, USA.
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202
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203
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A role of the transient receptor potential domain of vanilloid receptor I in channel gating. J Neurosci 2007; 27:11641-50. [PMID: 17959807 DOI: 10.1523/jneurosci.2457-07.2007] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Transient receptor potential vanilloid receptor subtype 1 (TRPV1) is an ionotropic receptor activated by temperature and chemical stimuli. The C-terminal region that is adjacent to the channel gate, recognized as the TRP domain, is a molecular determinant of receptor assembly. However, the role of this intracellular domain in channel function remains elusive. Here, we show that replacement of the TRP domain of TRPV1 with the cognate region of TRPV channels (TRPV2-TRPV6) did not affect receptor assembly and trafficking to the cell surface, although those receptors containing the TRP domain of the distantly related TRPV5 and TRPV6 did not display ion channel activity. Notably, functional chimeras exhibited an impaired sensitivity to the activating stimuli, consistent with a significant contribution of this protein domain to channel function. At variance with TRPV1, voltage-dependent gating of chimeric channels could not be detected in the absence of capsaicin and/or heat. Biophysical analysis of functional chimeras revealed that the TRP domain appears to act as a molecular determinant of the activation energy of channel gating. Together, these findings uncover a role of the TRP domain in intersubunit interactions near the channel gate that contribute to the coupling of stimulus sensing to channel opening.
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204
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Abstract
Many plant and animal toxins cause aversive behaviors in animals due to their pungent or unpleasant taste or because they cause other unpleasant senstations like pain. This article reviews the current state of knowledge of toxins that act at the TRPV1 ion channel, which is expressed in primary sensory neurons, is activated by multiple painful stimuli and is thought to be a key pain sensor and integrator. The recent finding that painful peptide "vanillotoxin" components of tarantula toxin activate the TRPV1 ion channel to cause pain led us to survey what is known about toxins that act at this receptor. Toxins from plants, spiders and jellyfish are considered. Where possible, structural information about sites of interaction is considered in relation to toxin-binding sites on the Kv ion channel, for which more structural information exists. We discuss a developing model where toxin agonists such as resiniferatoxin and vanillotoxins are proposed to interact with a region of TRPV1 that is homologous to the "voltage sensor" in the Kv1.2 ion channel, to open the channel and activate primary sensory nerves, causing pain.
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205
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Abstract
TRPV1 and TRPM8 are sensory nerve ion channels activated by heating and cooling, respectively. A variety of physical and chemical stimuli activate these receptors in a synergistic manner but the underlying mechanisms are unclear. Both channels are voltage sensitive, and temperature and ligands modulate this voltage dependence. Thus, a voltage-sensing mechanism has become an attractive model to explain the generalized gating of these and other thermo-sensitive TRP channels. We show here using whole-cell and single channel measurements that voltage produces only a partial activation of TRPV1 and TRPM8. At room temperature (20-25 degrees C) membrane depolarization evokes responses that saturate at approximately 50-60% of the maximum open probability. Furthermore, high concentrations of capsaicin (10 microm), resiniferatoxin (5 microm) and menthol (6 mm) reveal voltage-independent gating. Similarly, other modes of TRPV1 regulation including heat, protein kinase C-dependent phosphorylation, and protons enhance both the efficacy and sensitivity of voltage activation. In contrast, the TRPV1 antagonist capsazepine produces the opposite effects. These data can be explained by an allosteric model in which voltage, temperature, agonists and inverse agonists are independently coupled, either positively or negatively, to channel gating. Thus, voltage acts separately but in concert with other stimuli to regulate channel activation, and, therefore, a voltage-sensitive mechanism is unlikely to represent a final, gating mechanism for these channels.
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Affiliation(s)
- José A Matta
- Department of Pharmacology, Georgetown University, MedDent SW401, 3900 Reservoir Rd Washington, DC 20007, USA
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206
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Karashima Y, Damann N, Prenen J, Talavera K, Segal A, Voets T, Nilius B. Bimodal action of menthol on the transient receptor potential channel TRPA1. J Neurosci 2007; 27:9874-84. [PMID: 17855602 PMCID: PMC6672629 DOI: 10.1523/jneurosci.2221-07.2007] [Citation(s) in RCA: 388] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
TRPA1 is a calcium-permeable nonselective cation transient receptor potential (TRP) channel that functions as an excitatory ionotropic receptor in nociceptive neurons. TRPA1 is robustly activated by pungent substances in mustard oil, cinnamon, and garlic and mediates the inflammatory actions of environmental irritants and proalgesic agents. Here, we demonstrate a bimodal sensitivity of TRPA1 to menthol, a widely used cooling agent and known activator of the related cold receptor TRPM8. In whole-cell and single-channel recordings of heterologously expressed TRPA1, submicromolar to low-micromolar concentrations of menthol cause channel activation, whereas higher concentrations lead to a reversible channel block. In addition, we provide evidence for TRPA1-mediated menthol responses in mustard oil-sensitive trigeminal ganglion neurons. Our data indicate that TRPA1 is a highly sensitive menthol receptor that very likely contributes to the diverse psychophysical sensations after topical application of menthol to the skin or mucous membranes of the oral and nasal cavities.
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Affiliation(s)
- Yuji Karashima
- Laboratorium voor Fysiologie, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
| | - Nils Damann
- Laboratorium voor Fysiologie, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
| | - Jean Prenen
- Laboratorium voor Fysiologie, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
| | - Karel Talavera
- Laboratorium voor Fysiologie, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
| | - Andrei Segal
- Laboratorium voor Fysiologie, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
| | - Thomas Voets
- Laboratorium voor Fysiologie, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
| | - Bernd Nilius
- Laboratorium voor Fysiologie, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
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207
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Phelps CB, Gaudet R. The role of the N terminus and transmembrane domain of TRPM8 in channel localization and tetramerization. J Biol Chem 2007; 282:36474-80. [PMID: 17908685 DOI: 10.1074/jbc.m707205200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transient receptor potential (TRP) channels are a family of cation channels involved in diverse cellular functions. They are composed of a transmembrane domain of six putative transmembrane segments flanked by large N- and C-terminal cytoplasmic domains. The melastatin subfamily (TRPM) channels have N-terminal domains of approximately 700 amino acids with four regions of shared homology and C-terminal domains containing the conserved TRP domain followed by a coiled-coil region. Here we investigated the effects of N- and C-terminal deletions on the cold and menthol receptor, TRPM8, expressed heterologously in Sf21 insect cells. Patch-clamp electrophysiology was used to study channel activity and revealed that only deletion of the first 39 amino acids was tolerated by the channel. Further N-terminal truncation or any C-terminal deletions prevented proper TRPM8 function. Confocal microscopy with immunofluorescence revealed that amino acids 40-86 are required for localization to the plasma membrane. Furthermore, analysis of deletion mutant oligomerization shows that the transmembrane domain is sufficient for TPRM8 assembly into tetramers. TRPM8 channels with C-terminal deletions tetramerize and localize properly but are inactive, indicating that although not essential for tetramerization and localization, the C terminus is critical for proper function of the channel sensor and/or gate.
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Affiliation(s)
- Christopher B Phelps
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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208
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Bandell M, Macpherson LJ, Patapoutian A. From chills to chilis: mechanisms for thermosensation and chemesthesis via thermoTRPs. Curr Opin Neurobiol 2007; 17:490-7. [PMID: 17706410 PMCID: PMC2080617 DOI: 10.1016/j.conb.2007.07.014] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Accepted: 07/19/2007] [Indexed: 11/30/2022]
Abstract
Six highly temperature-sensitive ion channels of the transient receptor potential (TRP) family have been implicated to mediate temperature sensation. These channels, expressed in sensory neurons innervating the skin or the skin itself, are active at specific temperatures ranging from noxious cold to burning heat. In addition to temperature sensation thermoTRPs are the receptors of a growing number of environmental chemicals (chemesthesis). Recent studies have provided some striking new insights into the molecular mechanism of thermal and chemical activation of these biological thermometers.
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Affiliation(s)
- Michael Bandell
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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209
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Kühn FJP, Knop G, Lückhoff A. The transmembrane segment S6 determines cation versus anion selectivity of TRPM2 and TRPM8. J Biol Chem 2007; 282:27598-609. [PMID: 17604279 DOI: 10.1074/jbc.m702247200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPM2 and TRPM8, closely related members of the transient receptor potential (TRP) family, are cation channels activated by quite different mechanisms. Their transmembrane segments S5 and S6 are highly conserved. To identify common structures in S5 and S6 that govern interaction with the pore, we created a chimera in which the S5-pore-S6 region of TRPM8 was inserted into TRPM2, along with a lysine at each transition site. Currents through this chimera were induced by ADP-ribose (ADPR) in cooperation with Ca(2+). In contrast to wild-type TRPM2 channels, currents through the chimera were carried by Cl(-), as demonstrated in ion substitution experiments using the cation N-methyl-D-glucamine (NMDG) and the anion glutamate. Extracellular NMDG had no effects. The substitution of either intracellular or extracellular Cl(-) with glutamate shifted the reversal potential, decreased the current amplitude and induced a voltage-dependent block relieved by depolarization. The lysine in S6 was responsible for the anion selectivity; insertion of a lysine into corresponding sites within S6 of either TRPM2 or TRPM8 created anion channels that were activated by ADPR (TRPM2 I1045K) or by cold temperatures (TRPM8 V976K). The positive charge of the lysine was decisive for the glutamate block because the mutant TRPM2 I1045H displayed cation currents that were blocked at acidic but not alkaline intracellular pH values. We conclude that the distal part of S6 is crucial for the discrimination of charge. Because of the high homology of S6 in the whole TRP family, this new role of S6 may apply to further TRP channels.
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Affiliation(s)
- Frank J P Kühn
- Institute of Physiology, Medical Faculty, RWTH Aachen, D-52057 Aachen, Germany.
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210
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Brauchi S, Orta G, Mascayano C, Salazar M, Raddatz N, Urbina H, Rosenmann E, Gonzalez-Nilo F, Latorre R. Dissection of the components for PIP2 activation and thermosensation in TRP channels. Proc Natl Acad Sci U S A 2007; 104:10246-51. [PMID: 17548815 PMCID: PMC1891241 DOI: 10.1073/pnas.0703420104] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Indexed: 01/01/2023] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP2) plays a central role in the activation of several transient receptor potential (TRP) channels. The role of PIP2 on temperature gating of thermoTRP channels has not been explored in detail, and the process of temperature activation is largely unexplained. In this work, we have exchanged different segments of the C-terminal region between cold-sensitive (TRPM8) and heat-sensitive (TRPV1) channels, trying to understand the role of the segment in PIP2 and temperature activation. A chimera in which the proximal part of the C-terminal of TRPV1 replaces an equivalent section of TRPM8 C-terminal is activated by PIP2 and confers the phenotype of heat activation. PIP2, but not temperature sensitivity, disappears when positively charged residues contained in the exchanged region are neutralized. Shortening the exchanged segment to a length of 11 aa produces voltage-dependent and temperature-insensitive channels. Our findings suggest the existence of different activation domains for temperature, PIP2, and voltage. We provide an interpretation for channel-PIP2 interaction using a full-atom molecular model of TRPV1 and PIP2 docking analysis.
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Affiliation(s)
- Sebastian Brauchi
- *Laboratory of Biophysics and Molecular Physiology, Centro de Estudios Cientificos, Valdivia 509-9100, Chile
| | - Gerardo Orta
- *Laboratory of Biophysics and Molecular Physiology, Centro de Estudios Cientificos, Valdivia 509-9100, Chile
| | - Carolina Mascayano
- Centro de Bioinformatica y Simulacion Molecular Simulation Center, Universidad de Talca, Talca 346-0000, Chile
| | - Marcelo Salazar
- *Laboratory of Biophysics and Molecular Physiology, Centro de Estudios Cientificos, Valdivia 509-9100, Chile
| | - Natalia Raddatz
- *Laboratory of Biophysics and Molecular Physiology, Centro de Estudios Cientificos, Valdivia 509-9100, Chile
| | - Hector Urbina
- Centro de Bioinformatica y Simulacion Molecular Simulation Center, Universidad de Talca, Talca 346-0000, Chile
| | - Eduardo Rosenmann
- *Laboratory of Biophysics and Molecular Physiology, Centro de Estudios Cientificos, Valdivia 509-9100, Chile
| | - Fernando Gonzalez-Nilo
- Centro de Bioinformatica y Simulacion Molecular Simulation Center, Universidad de Talca, Talca 346-0000, Chile
| | - Ramon Latorre
- *Laboratory of Biophysics and Molecular Physiology, Centro de Estudios Cientificos, Valdivia 509-9100, Chile
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211
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Abstract
The TRP superfamily of cation channels encompasses 28 mammalian members related to the product of the Drosophila trp (transient receptor potential) gene. TRP channels have a widespread distribution in many cell types and organs and gate in response to a broad variety of physical and chemical stimuli; as such, they can be considered as ubiquitous cellular sensors. Several recent studies reported modulation of different TRP channels by phosphoinositides, in particular by phosphatidylinositol 4,5-bisphosphate (PIP(2)). In most cases, PIP(2) promotes TRP channel activation. Here we provide a brief overview of current insights and controversies about the mechanisms and structural determinants of PIP(2)-TRP channel interactions, and zoom in on the regulation of the Ca(2+)- and voltage-gated TRPM4 by phosphoinositides.
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Affiliation(s)
- Thomas Voets
- Laboratory of Ion Channel Research, Division of Physiology, Department of Molecular Cell Biology, KU Leuven, Onderwijs & Navorsing 1, Herestraat 49 bus 802, 3000 Leuven, Belgium.
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212
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Vriens J, Owsianik G, Janssens A, Voets T, Nilius B. Determinants of 4 alpha-phorbol sensitivity in transmembrane domains 3 and 4 of the cation channel TRPV4. J Biol Chem 2007; 282:12796-803. [PMID: 17341586 DOI: 10.1074/jbc.m610485200] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPV4, a Ca(2+)-permeable member of the vanilloid subgroup of the transient receptor potential (TRP) channels, is activated by cell swelling and moderate heat (>27 degrees C) as well as by diverse chemical compounds including synthetic 4 alpha-phorbol esters, the plant extract bisandrographolide A, and endogenous epoxyeicosatrienoic acids (EETs; 5,6-EET and 8,9-EET). Previous work identified a tyrosine residue located in the first half of putative transmembrane segment 3 (TM3) as a crucial determinant for the activation of TRPV4 by its most specific agonist 4 alpha-phorbol 12,13-didecanoate (4 alpha-PDD), suggesting that 4 alpha-PDD interacts with the channel through its transmembrane segments. To obtain insight in the 4 alpha-PDD-binding site and in the mechanism of ligand-dependent TRPV4 activation, we investigated the consequences of specific point mutations in TM4 on the sensitivity of the channel to different chemical and physical stimuli. Mutations of two hydrophobic residues in the central part of TM4 (Leu(584) and Trp(586)) caused a severe reduction of the sensitivity of the channel to 4 alpha-PDD, bisandrographolide A, and heat, whereas responses to cell swelling, arachidonic acid, and 5,6-EET remained unaffected. In contrast, mutations of two residues in the C-terminal part of TM4 (Tyr(591) and Arg(594)) affected channel activation of TRPV4 by all stimuli, suggesting an involvement in channel gating rather than in interaction with agonists. Based on a comparison of the responses of WT and mutant TRPV4 to 4 alpha-PDD and different 4 alpha-phorbol esters, we conclude that the length of the fatty acid moiety determines the ligand binding affinity and propose a model for the interaction between 4 alpha-phorbol esters and the TM3/4 region of TRPV4.
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Affiliation(s)
- Joris Vriens
- Department of Physiology, Campus Gasthuisberg, KU Leuven, B-3000 Leuven, Belgium.
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