101
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Szöllősi AG, Oláh A, Tóth IB, Papp F, Czifra G, Panyi G, Bíró T. Transient receptor potential vanilloid-2 mediates the effects of transient heat shock on endocytosis of human monocyte-derived dendritic cells. FEBS Lett 2013; 587:1440-5. [PMID: 23542034 DOI: 10.1016/j.febslet.2013.03.027] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 03/20/2013] [Accepted: 03/20/2013] [Indexed: 01/20/2023]
Abstract
Our goal was to investigate the effect of heat shock on human monocyte-derived dendritic cells (DCs) and to dissect the role of thermosensitive transient receptor potential (TRP) channels in the process. We provide evidence that a short heat shock challenge (43 °C) decreased the endocytotic activity of the DCs and that this effect could be alleviated by the RNAi-mediated knockdown of TRPV2 but, importantly, not by the pharmacological (antagonists) or molecular (RNAi) suppression of TRPV1 and TRPV4 activities/levels. Likewise, the heat shock-induced robust membrane currents were selectively and markedly inhibited by TRPV2 "silencing" whereas modulation of TRPV1 and TRPV4 activities, again, had no effect. These intriguing data introduce TRPV2-coupled signaling as a key player in mediating the cellular actions of heat shock on DCs.
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Affiliation(s)
- Attila Gábor Szöllősi
- 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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102
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Kaßmann M, Harteneck C, Zhu Z, Nürnberg B, Tepel M, Gollasch M. Transient receptor potential vanilloid 1 (TRPV1), TRPV4, and the kidney. Acta Physiol (Oxf) 2013; 207:546-64. [PMID: 23253200 DOI: 10.1111/apha.12051] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 11/15/2012] [Accepted: 12/11/2012] [Indexed: 12/13/2022]
Abstract
Recent preclinical data indicate that activators of transient receptor potential channels of the vanilloid receptor subtype 1 (TRPV1) may improve the outcome of ischaemic acute kidney injury (AKI). The underlying mechanisms are unclear, but may involve TRPV1 channels in dorsal root ganglion neurones that innervate the kidney. Recent data identified TRPV4, together with TRPV1, to serve as major calcium influx channels in endothelial cells. In these cells, gating of individual TRPV4 channels within a four-channel cluster provides elementary calcium influx (calcium sparklets) to open calcium-activated potassium channels and promote vasodilation. The TRPV receptors can also form heteromers that exhibit unique conductance and gating properties, further increasing their spatio-functional diversity. This review summarizes data on electrophysiological properties of TRPV1/4 and their modulation by endogenous channel agonists such as 20-HETE, phospholipase C and phosphatidylinositide 3-kinase (PI3 kinase). We review important roles of TRPV1 and TRPV4 in kidney physiology and renal ischaemia reperfusion injury; further studies are warranted to address renoprotective mechanism of vanilloid receptors in ischaemic AKI including the role of the capsaicin receptor TRPV1 in primary sensory nerves and/or endothelium. Particular attention should be paid to understand the kidneys' ability to respond to ischaemic stimuli after catheter-based renal denervation therapy in man, whereas the discovery of novel pharmacological TRPV modulators may be a successful strategy for better treatment of acute or chronic kidney failure.
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Affiliation(s)
- M. Kaßmann
- Charité University Medicine, Section Nephrology/Intensive Care, Campus Virchow, and Experimental and Clinical Research Center (ECRC); Berlin; Germany
| | - C. Harteneck
- Institut für Experimentelle & Klinische Pharmakologie & Toxikologie and Interfaculty Center of Pharmacogenomics and Pharmaceutical Research (ICePhA); Eberhard-Karls-Universität; Tübingen; Germany
| | - Z. Zhu
- Department of Hypertension and Endocrinology, Center for Hypertension and Metabolic Diseases; Daping Hospital, Third Military Medical University, Chongqing Institute of Hypertension; Chongqing; China
| | - B. Nürnberg
- Institut für Experimentelle & Klinische Pharmakologie & Toxikologie and Interfaculty Center of Pharmacogenomics and Pharmaceutical Research (ICePhA); Eberhard-Karls-Universität; Tübingen; Germany
| | - M. Tepel
- Department of Nephrology, and University of Southern Denmark, Institute of Molecular Medicine, Cardiovascular and Renal Research, Institute of Clinical Research; Odense University Hospital; Odense; Denmark
| | - M. Gollasch
- Charité University Medicine, Section Nephrology/Intensive Care, Campus Virchow, and Experimental and Clinical Research Center (ECRC); Berlin; Germany
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103
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Wang S, Makhina EN, Masia R, Hyrc KL, Formanack ML, Nichols CG. Domain organization of the ATP-sensitive potassium channel complex examined by fluorescence resonance energy transfer. J Biol Chem 2012; 288:4378-88. [PMID: 23223337 DOI: 10.1074/jbc.m112.388629] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
K(ATP) channels link cell metabolism to excitability in many cells. They are formed as tetramers of Kir6.2 subunits, each associated with a SUR1 subunit. We used mutant GFP-based FRET to assess domain organization in channel complexes. Full-length Kir6.2 subunits were linked to YFP or cyan fluorescent protein (CFP) at N or C termini, and all such constructs, including double-tagged YFP-Kir6.2-CFP (Y6.2C), formed functional K(ATP) channels. In intact COSm6 cells, background emission of YFP excited by 430-nm light was ∼6%, but the Y6.2C construct expressed alone exhibited an apparent FRET efficiency of ∼25%, confirmed by trypsin digestion, with or without SUR1 co-expression. Similar FRET efficiency was detected in mixtures of CFP- and YFP-tagged full-length Kir6.2 subunits and transmembrane domain only constructs, when tagged at the C termini but not at the N termini. The FRET-reported Kir6.2 tetramer domain organization was qualitatively consistent with Kir channel crystal structures: C termini and M2 domains are centrally located relative to N termini and M1 domains, respectively. Additional FRET analyses were performed on cells in which tagged full-length Kir6.2 and tagged SUR1 constructs were co-expressed. These analyses further revealed that 1) NBD1 of SUR1 is closer to the C terminus of Kir6.2 than to the N terminus; 2) the Kir6.2 cytoplasmic domain is not essential for complexation with SUR1; and 3) the N-terminal half of SUR1 can complex with itself in the absence of either the C-terminal half or Kir6.2.
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Affiliation(s)
- Shizhen Wang
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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104
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Schindl R, Fritsch R, Jardin I, Frischauf I, Kahr H, Muik M, Riedl MC, Groschner K, Romanin C. Canonical transient receptor potential (TRPC) 1 acts as a negative regulator for vanilloid TRPV6-mediated Ca2+ influx. J Biol Chem 2012; 287:35612-35620. [PMID: 22932896 PMCID: PMC3471760 DOI: 10.1074/jbc.m112.400952] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
TRP proteins mostly assemble to homomeric channels but can also heteromerize, preferentially within their subfamilies. The TRPC1 protein is the most versatile member and forms various TRPC channel combinations but also unique channels with the distantly related TRPP2 and TRPV4. We show here a novel cross-family interaction between TRPC1 and TRPV6, a Ca2+ selective member of the vanilloid TRP subfamily. TRPV6 exhibited substantial co-localization and in vivo interaction with TRPC1 in HEK293 cells, however, no interaction was observed with TRPC3, TRPC4, or TRPC5. Ca2+ and Na+ currents of TRPV6-overexpressing HEK293 cells are significantly reduced by co-expression of TRPC1, correlating with a dramatically suppressed plasma membrane targeting of TRPV6. In line with their intracellular retention, remaining currents of TRPC1 and TRPV6 co-expression resemble in current-voltage relationship that of TRPV6. Studying the N-terminal ankyrin like repeat domain, structurally similar in the two proteins, we have found that these cytosolic segments were sufficient to mediate a direct heteromeric interaction. Moreover, the inhibitory role of TRPC1 on TRPV6 influx was also maintained by expression of only its N-terminal ankyrin-like repeat domain. Our experiments provide evidence for a functional interaction of TRPC1 with TRPV6 that negatively regulates Ca2+ influx in HEK293 cells.
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Affiliation(s)
- Rainer Schindl
- Institute for Biophysics, University of Linz, A-4020 Linz, Austria.
| | - Reinhard Fritsch
- Institute for Biophysics, University of Linz, A-4020 Linz, Austria
| | - Isaac Jardin
- Department of Physiology, University of Extremadura, 10003 Caceres, Spain
| | - Irene Frischauf
- Institute for Biophysics, University of Linz, A-4020 Linz, Austria
| | - Heike Kahr
- School of Engineering/Enviromental/Sciences, University of Applied Sciences Upper Austria, A-4600 Wels, Austria
| | - Martin Muik
- Institute for Biophysics, University of Linz, A-4020 Linz, Austria
| | | | - Klaus Groschner
- Institute of Pharmacology and Toxicology, University of Graz, A-8010 Graz, Austria
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105
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Ho TC, Horn NA, Huynh T, Kelava L, Lansman JB. Evidence TRPV4 contributes to mechanosensitive ion channels in mouse skeletal muscle fibers. Channels (Austin) 2012; 6:246-54. [PMID: 22785252 DOI: 10.4161/chan.20719] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We recorded the activity of single mechanosensitive (MS) ion channels from membrane patches on single muscle fibers isolated from mice. We investigated the actions of various TRP (transient receptor potential) channel blockers on MS channel activity. 2-aminoethoxydiphenyl borate (2-APB) neither inhibited nor facilitated single channel activity at submillimolar concentrations. The absence of an effect of 2-APB indicates MS channels are not composed purely of TRPC or TRPV1, 2 or 3 proteins. Exposing patches to 1-oleolyl-2-acetyl-sn-glycerol (OAG), a potent activator of TRPC channels, also had no effect on MS channel activity. In addition, flufenamic acid and spermidine had no effect on the activity of single MS channels. By contrast, SKF-96365 and ruthenium red blocked single-channel currents at micromolar concentrations. SKF-96365 produced a rapid block of the open channel current. The blocking rate depended linearly on blocker concentration, while the unblocking rate was independent of concentration, consistent with a simple model of open channel block. A fit to the concentration-dependence of block gave k(on) = 13 x 10 ( 6) M (-1) s (-1) and k(off) = 1609 sec (-1) with K(D) = ~124 µM. Block by ruthenium red was complex, involving both reduction of the amplitude of the single-channel current and increased occupancy of subconductance levels. The reduction in current amplitude with increasing concentration of ruthenium red gave a K(D) = ~49 µM. The high sensitivity of MS channels to block by ruthenium red suggests MS channels in skeletal muscle contain TRPV subunits. Recordings from skeletal muscle isolated from TRPV4 knockout mice failed to show MS channel activity, consistent with a contribution of TRPV4. In addition, exposure to hypo-osmotic solutions increases opening of MS channels in muscle. Our results provide evidence TRPV4 contributes to MS channels in skeletal muscle.
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Affiliation(s)
- Tiffany C Ho
- Department of Cellular and Molecular Pharmacology, School of Medicine, University of California, San Francisco, San Francisco, CA, USA
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106
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Freichel M, Almering J, Tsvilovskyy V. The Role of TRP Proteins in Mast Cells. Front Immunol 2012; 3:150. [PMID: 22701456 PMCID: PMC3372879 DOI: 10.3389/fimmu.2012.00150] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 05/22/2012] [Indexed: 01/16/2023] Open
Abstract
Transient receptor potential (TRP) proteins form cation channels that are regulated through strikingly diverse mechanisms including multiple cell surface receptors, changes in temperature, in pH and osmolarity, in cytosolic free Ca(2+) concentration ([Ca(2+)](i)), and by phosphoinositides which makes them polymodal sensors for fine tuning of many cellular and systemic processes in the body. The 28 TRP proteins identified in mammals are classified into six subfamilies: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. When activated, they contribute to cell depolarization and Ca(2+) entry. In mast cells, the increase of [Ca(2+)](i) is fundamental for their biological activity, and several entry pathways for Ca(2+) and other cations were described including Ca(2+) release activated Ca(2+) (CRAC) channels. Like in other non-excitable cells, TRP channels could directly contribute to Ca(2+) influx via the plasma membrane as constituents of Ca(2+) conducting channel complexes or indirectly by shifting the membrane potential and regulation of the driving force for Ca(2+) entry through independent Ca(2+) entry channels. Here, we summarize the current knowledge about the expression of individual Trp genes with the majority of the 28 members being yet identified in different mast cell models, and we highlight mechanisms how they can regulate mast cell functions. Since specific agonists or blockers are still lacking for most members of the TRP family, studies to unravel their function and activation mode still rely on experiments using genetic approaches and transgenic animals. RNAi approaches suggest a functional role for TRPC1, TRPC5, and TRPM7 in mast cell derived cell lines or primary mast cells, and studies using Trp gene knock-out mice reveal a critical role for TRPM4 in mast cell activation and for mast cell mediated cutaneous anaphylaxis, whereas a direct role of cold- and menthol-activated TRPM8 channels seems to be unlikely for the development of cold urticaria at least in mice.
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Affiliation(s)
- Marc Freichel
- Pharmakologisches Institut, Universität HeidelbergHeidelberg, Germany
| | - Julia Almering
- Pharmakologisches Institut, Universität HeidelbergHeidelberg, Germany
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107
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Cao X, Yang F, Zheng J, Wang K. Intracellular proton-mediated activation of TRPV3 channels accounts for the exfoliation effect of α-hydroxyl acids on keratinocytes. J Biol Chem 2012; 287:25905-16. [PMID: 22679014 DOI: 10.1074/jbc.m112.364869] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α-Hydroxyl acids (AHAs) from natural sources act as proton donors and topical compounds that penetrate skin and are well known in the cosmetic industry for their use in chemical peels and improvement of the skin. However, little is known about how AHAs cause exfoliation to expose fresh skin cells. Here we report that the transient receptor potential vanilloid 3 (TRPV3) channel in keratinocytes is potently activated by intracellular acidification induced by glycolic acid. Patch clamp recordings and cell death assay of both human keratinocyte HaCaT cells and TRPV3-expressing HEK-293 cells confirmed that intracellular acidification led to direct activation of TRPV3 and promoted cell death. Site-directed mutagenesis revealed that an N-terminal histidine residue, His-426, known to be involved in 2-aminoethyl diphenylborinate-mediated TRPV3 activation, is critical for sensing intracellular proton levels. Taken together, our findings suggest that intracellular protons can strongly activate TRPV3, and TRPV3-mediated proton sensing and cell death in keratinocytes may serve as a molecular basis for the cosmetic use of AHAs and their therapeutic potential in acidic pH-related skin disorders.
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Affiliation(s)
- Xu Cao
- Department of Neurobiology, Neuroscience Research Institute, Peking University Health Science Center, China
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108
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Cui Y, Yang F, Cao X, Yarov-Yarovoy V, Wang K, Zheng J. Selective disruption of high sensitivity heat activation but not capsaicin activation of TRPV1 channels by pore turret mutations. ACTA ACUST UNITED AC 2012; 139:273-83. [PMID: 22412190 PMCID: PMC3315147 DOI: 10.1085/jgp.201110724] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The capsaicin receptor transient receptor potential vanilloid (TRPV)1 is a highly heat-sensitive ion channel. Although chemical activation and heat activation of TRPV1 elicit similar pungent, painful sensation, the molecular mechanism underlying synergistic activation remains mysterious. In particular, where the temperature sensor is located and whether heat and capsaicin share a common activation pathway are debated. To address these fundamental issues, we searched for channel mutations that selectively affected one form of activation. We found that deletion of the first 10 amino acids of the pore turret significantly reduced the heat response amplitude and shifted the heat activation threshold, whereas capsaicin activation remained unchanged. Removing larger portions of the turret disrupted channel function. Introducing an artificial sequence to replace the deleted region restored sensitive capsaicin activation in these nonfunctional channels. The heat activation, however, remained significantly impaired, with the current exhibiting diminishing heat sensitivity to a level indistinguishable from that of a voltage-gated potassium channel, Kv7.4. Our results demonstrate that heat and capsaicin activation of TRPV1 are structurally and mechanistically distinct processes, and the pore turret is an indispensible channel structure involved in the heat activation process but is not part of the capsaicin activation pathway. Synergistic effect of heat and capsaicin on TRPV1 activation may originate from convergence of the two pathways on a common activation gate.
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Affiliation(s)
- Yuanyuan Cui
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA 95616, USA
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109
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Berg KA, Patwardhan AM, Akopian AN. Receptor and channel heteromers as pain targets. Pharmaceuticals (Basel) 2012; 5:249-78. [PMID: 24281378 PMCID: PMC3763638 DOI: 10.3390/ph5030249] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 02/04/2012] [Accepted: 02/15/2012] [Indexed: 12/20/2022] Open
Abstract
Recent discoveries indicate that many G-protein coupled receptors (GPCRs) and channels involved in pain modulation are able to form receptor heteromers. Receptor and channel heteromers often display distinct signaling characteristics, pharmacological properties and physiological function in comparison to monomer/homomer receptor or ion channel counterparts. It may be possible to capitalize on such unique properties to augment therapeutic efficacy while minimizing side effects. For example, drugs specifically targeting heteromers may have greater tissue specificity and analgesic efficacy. This review will focus on current progress in our understanding of roles of heteromeric GPCRs and channels in pain pathways as well as strategies for controlling pain pathways via targeting heteromeric receptors and channels. This approach may be instrumental in the discovery of novel classes of drugs and expand our repertoire of targets for pain pharmacotherapy.
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Affiliation(s)
- Kelly A. Berg
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; (K.A.B.)
| | - Amol M. Patwardhan
- Department of Anesthesiology, Arizona Health Sciences Center, Tucson, AZ 85724, USA; (A.M.P.)
| | - Armen N. Akopian
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; (K.A.B.)
- Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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110
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Storti B, Bizzarri R, Cardarelli F, Beltram F. Intact microtubules preserve transient receptor potential vanilloid 1 (TRPV1) functionality through receptor binding. J Biol Chem 2012; 287:7803-11. [PMID: 22262838 DOI: 10.1074/jbc.m111.332296] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transient receptor potential cation channel subfamily V member 1 (TRPV1) is a protein currently under scrutiny as a pharmacological target for pain management therapies. Recently, the role of TRPV1-microtubule interaction in transducing nociception stimuli to cells by cytoskeletal rearrangement was proposed. In this work, we investigate TRPV1-microtubule interaction in living cells under the resting or activated state of TRPV1, as well as in presence of structurally intact or depolymerized cytoskeletal microtubules. We combined a toolbox of high resolution/high sensitivity fluorescence imaging techniques (such as FRET, correlation spectroscopy, and fluorescence anisotropy) to monitor TRPV1 aggregation status, membrane mobility, and interaction with microtubules. We found that TRPV1 is a dimeric membrane protein characterized by two populations with different diffusion properties in basal condition. After stimulation with resiniferatoxin, TRPV1 dimers tetramerize. The tetramers and the slower population of TRPV1 dimers bind dynamically to intact microtubules but not to tubulin dimers. Upon microtubule disassembly, the interaction with TRPV1 is lost thereby inducing receptor self-aggregation with partial loss of functionality. Intact microtubules play an essential role in maintaining TRPV1 functionality toward activation stimuli. This previously undisclosed property mirrors the recently reported role of TRPV1 in modulating microtubule assembly/disassembly and suggests the participation of these two players in a feedback cycle linking nociception and cytoskeletal remodeling.
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Affiliation(s)
- Barbara Storti
- National Enterprise for nanoScience and nanoTechnology (NEST), Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, 56127 Pisa, Italy.
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111
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Structural rearrangements underlying ligand-gating in Kir channels. Nat Commun 2012; 3:617. [PMID: 22233627 PMCID: PMC4277880 DOI: 10.1038/ncomms1625] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 11/29/2011] [Indexed: 11/17/2022] Open
Abstract
Inward rectifier potassium (Kir) channels are physiologically regulated by a wide range of ligands that all act on a common gate, although structural details of gating are unclear. Here we show, using small molecule fluorescent probes attached to introduced cysteines, the molecular motions associated with gating of KirBac1.1 channels. The accessibility of the probes indicates a major barrier to fluorophore entry to the inner cavity. Changes in FRET between fluorophores attached to KirBac1.1 tetramers show that PIP2-induced closure involves tilting and rotational motions of secondary structural elements of the cytoplasmic domain that couple ligand binding to a narrowing of the cytoplasmic vestibule. The observed ligand-dependent conformational changes in KirBac1.1 provide a general model for ligand-induced Kir channel gating at the molecular level.
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112
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Carreño O, Corominas R, Fernández-Morales J, Camiña M, Sobrido MJ, Fernández-Fernández JM, Pozo-Rosich P, Cormand B, Macaya A. SNP variants within the vanilloid TRPV1 and TRPV3 receptor genes are associated with migraine in the Spanish population. Am J Med Genet B Neuropsychiatr Genet 2012; 159B:94-103. [PMID: 22162417 DOI: 10.1002/ajmg.b.32007] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 11/14/2011] [Indexed: 01/07/2023]
Abstract
The transient receptor potential (TRP) superfamily of non-selective cationic channels are involved in several processes plausibly relevant to migraine pathophysiology, including multimodal sensory and pain perception, central and peripheral sensitization, and regulation of calcium homeostasis. With the aim of identifying single nucleotide polymorphisms (SNPs) in TRP genes that may confer increased genetic susceptibility to migraine, we carried out a case-control genetic association study with replication, including a total of 1,040 cases and 1,037 controls. We genotyped 149 SNPs covering 14 TRP genes with known brain expression. The two-stage study comprised samples of 555 and 485 Spanish, Caucasian patients, selected according to the ICHD-II criteria for the diagnosis of migraine without aura (MO) or migraine with aura (MA). In the discovery sample, 19 SNPs in ten TRP genes showed nominal association (P < 0.05) with MO, MA, or overall migraine. In the replication sample, nominal association was confirmed for TRPV3 rs7217270 in MA and TRPV1 rs222741 in the overall migraine group. Risk haplotypes were identified for seven of the genes showing nominal association in the discovery set, but none of them was replicated. The present findings suggest that members of the vanilloid TRPV subfamily of receptors contribute to the genetic susceptibility to migraine in the Spanish population.
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Affiliation(s)
- Oriel Carreño
- Facultat de Biologia, Departament de Genètica, Universitat de Barcelona, Barcelona, Spain
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113
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Cheng W, Yang F, Liu S, Colton CK, Wang C, Cui Y, Cao X, Zhu MX, Sun C, Wang K, Zheng J. Heteromeric heat-sensitive transient receptor potential channels exhibit distinct temperature and chemical response. J Biol Chem 2011; 287:7279-88. [PMID: 22184123 DOI: 10.1074/jbc.m111.305045] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPV1 and TRPV3 are two heat-sensitive ion channels activated at distinct temperature ranges perceived by human as hot and warm, respectively. Compounds eliciting human sensations of heat or warmth can also potently activate these channels. In rodents, TRPV3 is expressed predominantly in skin keratinocytes, whereas in humans TRPV1 and TRPV3 are co-expressed in sensory neurons of dorsal root ganglia and trigeminal ganglion and are known to form heteromeric channels with distinct single channel conductances as well as sensitivities to TRPV1 activator capsaicin and inhibitor capsazepine. However, how heteromeric TRPV1/TRPV3 channels respond to heat and other stimuli remains unknown. In this study, we examined the behavior of heteromeric TRPV1/TRPV3 channels activated by heat, capsaicin, and voltage. Our results demonstrate that the heteromeric channels exhibit distinct temperature sensitivity, activation threshold, and heat-induced sensitization. Changes in gating properties apparently originate from interactions between TRPV1 and TRPV3 subunits. Our results suggest that heteromeric TRPV1/TRPV3 channels are unique heat sensors that may contribute to the fine-tuning of sensitivity to sensory inputs.
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Affiliation(s)
- Wei Cheng
- Laboratory of Biomedical Optics, College of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116023, China
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114
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Pask GM, Jones PL, Rützler M, Rinker DC, Zwiebel LJ. Heteromeric Anopheline odorant receptors exhibit distinct channel properties. PLoS One 2011; 6:e28774. [PMID: 22174894 PMCID: PMC3235152 DOI: 10.1371/journal.pone.0028774] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 11/15/2011] [Indexed: 11/30/2022] Open
Abstract
Background Insect odorant receptors (ORs) function as odorant-gated ion channels consisting of a conventional, odorant-binding OR and the Orco coreceptor. While Orco can function as a homomeric ion channel, the role(s) of the conventional OR in heteromeric OR complexes has largely focused only on odorant recognition. Results To investigate other roles of odorant-binding ORs, we have employed patch clamp electrophysiology to investigate the properties of the channel pore of several OR complexes formed by a range of different odorant-specific Anopheles gambiae ORs (AgOrs) each paired with AgOrco. These studies reveal significant differences in cation permeability and ruthenium red susceptibility among different AgOr complexes. Conclusions With observable differences in channel function, the data support a model in which the odorant-binding OR also affects the channel pore. The variable effect contributed by the conventional OR on the conductive properties of odorant-gated sensory channels adds additional complexity to insect olfactory signaling, with differences in odor coding beginning with ORs on the periphery of the olfactory system.
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Affiliation(s)
- Gregory M. Pask
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Patrick L. Jones
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Michael Rützler
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
- The Water and Salt Research Center, Institute of Anatomy, University of Aarhus, Aarhus C, Denmark
| | - David C. Rinker
- Center for Human Genetics Research, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Laurence J. Zwiebel
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Pharmacology, Centers for Molecular Neuroscience and Human Genetics Research, Institutes of Chemical Biology and Global Health and Program in Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- * E-mail:
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115
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Abstract
Transient receptor potential channels, of the vanilloid subtype (TRPV), act as sensory mediators, being activated by endogenous ligands, heat, mechanical and osmotic stress. Within the vasculature, TRPV channels are expressed in smooth muscle cells, endothelial cells, as well as in peri-vascular nerves. Their varied distribution and polymodal activation properties make them ideally suited to a role in modulating vascular function, perceiving and responding to local environmental changes. In endothelial cells, TRPV1 is activated by endocannabinoids, TRPV3 by dietary agonists and TRPV4 by shear stress, epoxyeicosatrienoic acids (EETs) and downstream of Gq-coupled receptor activation. Upon activation, these channels contribute to vasodilation via nitric oxide, prostacyclin and intermediate/small conductance potassium channel-dependent pathways. In smooth muscle, TRPV4 is activated by endothelial-derived EETs, leading to large conductance potassium channel activation and smooth muscle hyperpolarization. Conversely, smooth muscle TRPV2 channels contribute to global calcium entry and may aid constriction. TRPV1 and TRPV4 are expressed in sensory nerves and can cause vasodilation through calcitonin gene-related peptide and substance P release as well as mediating vascular function via the baroreceptor reflex (TRPV1) or via increasing sympathetic outflow during osmotic stress (TRPV4). Thus, TRPV channels play important roles in the regulation of normal and pathological cellular function in the vasculature.
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Affiliation(s)
- R L Baylie
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, USA.
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116
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Shuart NG, Haitin Y, Camp SS, Black KD, Zagotta WN. Molecular mechanism for 3:1 subunit stoichiometry of rod cyclic nucleotide-gated ion channels. Nat Commun 2011; 2:457. [PMID: 21878911 PMCID: PMC3265371 DOI: 10.1038/ncomms1466] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 08/01/2011] [Indexed: 11/20/2022] Open
Abstract
Molecular determinants of ion channel tetramerization are well characterized, but those involved in heteromeric channel assembly are less clearly understood. The heteromeric composition of native channels is often precisely controlled. Cyclic nucleotide-gated (CNG) channels from rod photoreceptors exhibit a 3:1 stoichiometry of CNGA1 and CNGB1 subunits that tunes the channels for their specialized role in phototransduction. Here we show, using electrophysiology, fluorescence, biochemistry, and X-ray crystallography, that the mechanism for this controlled assembly is the formation of a parallel 3-helix coiled-coil domain of the carboxy-terminal leucine zipper region of CNGA1 subunits, constraining the channel to contain three CNGA1 subunits, followed by preferential incorporation of a single CNGB1 subunit. Deletion of the carboxy-terminal leucine zipper domain relaxed the constraint and permitted multiple CNGB1 subunits in the channel. The X-ray crystal structures of the parallel 3-helix coiled-coil domains of CNGA1 and CNGA3 subunits were similar, suggesting that a similar mechanism controls the stoichiometry of cone CNG channels. The assembly mechanisms of heteromeric ion channels are poorly understood. Using a range of techniques, Shuartet al.determine the mechanism by which rod photoreceptor cyclic nucleotide-gated channels assume a 3:1 stoichiometry of CNGA1 and CNGB1 subunits.![]()
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Affiliation(s)
- Noah G Shuart
- Howard Hughes Medical Institute and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, USA
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117
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Movement of hClC-1 C-termini during common gating and limits on their cytoplasmic location. Biochem J 2011; 436:415-28. [DOI: 10.1042/bj20102153] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Functionally, the dimeric human skeletal muscle chloride channel hClC-1 is characterized by two distinctive gating processes, fast (protopore) gating and slow (common) gating. Of these, common gating is poorly understood, but extensive conformational rearrangement is suspected. To examine this possibility, we used FRET (fluorescence resonance energy transfer) and assessed the effects of manipulating the common-gating process. Closure of the common gate was accompanied by a separation of the C-termini, whereas, with opening, the C-termini approached each other more closely. These movements were considerably smaller than those seen in ClC-0. To estimate the C-terminus depth within the cytoplasm we constructed a pair of split hClC-1 fragments tagged extracellularly and intracellularly respectively. These not only combined appropriately to rescue channel function, but we detected positive FRET between them. This restricts the C-termini of hClC-1 to a position close to its membrane-resident domain. From mutants in which fast or common gating were affected, FRET revealed a close linkage between the two gating processes with the carboxyl group of Glu232 apparently acting as the final effector for both.
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118
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Zhang F, Liu S, Yang F, Zheng J, Wang K. Identification of a tetrameric assembly domain in the C terminus of heat-activated TRPV1 channels. J Biol Chem 2011; 286:15308-16. [PMID: 21357419 DOI: 10.1074/jbc.m111.223941] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transient receptor potential (TRP) channels as cellular sensors are thought to function as tetramers. Yet, the molecular determinants governing channel multimerization remain largely elusive. Here we report the identification of a segment comprising 21 amino acids (residues 752-772 of mouse TRPV1) after the known TRP-like domain in the channel C terminus that functions as a tetrameric assembly domain (TAD). Purified recombinant C-terminal proteins of TRPV1-4, but not the N terminus, mediated the protein-protein interaction in an in vitro pulldown assay. Western blot analysis combined with electrophysiology and calcium imaging demonstrated that TAD exerted a robust dominant-negative effect on wild-type TRPV1. When fused with the membrane-tethered peptide Gap43, the TAD blocked the formation of stable homomultimers. Calcium imaging and current recordings showed that deletion of the TAD in a poreless TRPV1 mutant subunit suppressed its dominant-negative phenotype, confirming the involvement of the TAD in assembly of functional channels. Our findings suggest that the C-terminal TAD in TRPV1 channels functions as a domain that is conserved among TRPV1-4 and mediates a direct subunit-subunit interaction for tetrameric assembly.
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Affiliation(s)
- Feng Zhang
- Department of Neurobiology, Neuroscience Research Institute, Peking University Health Science Center, Beijing 100191, China
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119
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Jin M, Wu Z, Chen L, Jaimes J, Collins D, Walters ET, O'Neil RG. Determinants of TRPV4 activity following selective activation by small molecule agonist GSK1016790A. PLoS One 2011; 6:e16713. [PMID: 21339821 PMCID: PMC3038856 DOI: 10.1371/journal.pone.0016713] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Accepted: 01/11/2011] [Indexed: 11/19/2022] Open
Abstract
TRPV4 (Transient Receptor Potential Vanilloid 4) channels are activated by a wide range of stimuli, including hypotonic stress, non-noxious heat and mechanical stress and some small molecule agonists (e.g. phorbol ester 4α-PDD). GSK1016790A (GSK101) is a recently discovered specific small molecule agonist of TRPV4. Its effects on physical determinants of TRPV4 activity were evaluated in HeLa cells transiently transfected with TRPV4 (HeLa-TRPV4). GSK101 (10 nM) causes a TRPV4 specific Ca(2+) influx in HeLa-TRPV4 cells, but not in control transfected cells, which can be inhibited by ruthenium red and Ca(2+)-free medium more significantly at the early stage of the activation rather than the late stage, reflecting apparent partial desensitization. Western blot analysis showed that GSK101 activation did not induce an increase in TRPV4 expression at the plasma membrane, but caused an immediate and sustained downregulation of TRPV4 on the plasma membrane in HeLa-TRPV4 cells. Patch clamp analysis also revealed an early partial desensitization of the channel which was Ca(2+)-independent. FRET analysis of TRPV4 subunit assembly demonstrated that the GSK101-induced TRPV4 channel activation/desensitization was not due to alterations in homotetrameric channel formation on the plasma membrane. It is concluded that GSK101 specifically activates TRPV4 channels, leading to a rapid partial desensitization and downregulation of the channel expression on the plasma membrane. TRPV4 subunit assembly appears to occur during trafficking from the ER/Golgi to the plasma membrane and is not altered by agonist stimulation.
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Affiliation(s)
- Min Jin
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, Texas, United States of America
| | - Zizhen Wu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, Texas, United States of America
| | - Ling Chen
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, Texas, United States of America
| | - Jose Jaimes
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, Texas, United States of America
| | - Diana Collins
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, Texas, United States of America
| | - Edgar T. Walters
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, Texas, United States of America
| | - Roger G. O'Neil
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center, Houston, Texas, United States of America
- * E-mail:
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120
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Transient receptor proteins illuminated: Current views on TRPs and disease. Vet J 2011; 187:153-64. [DOI: 10.1016/j.tvjl.2010.01.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 01/21/2010] [Accepted: 01/25/2010] [Indexed: 11/23/2022]
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121
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Abstract
Structural studies on TRP channels, while limited, are poised for a quickened pace and rapid expansion. As of yet, no high-resolution structure of a full length TRP channel exists, but low-resolution electron cryomicroscopy structures have been obtained for 4 TRP channels, and high-resolution NMR and X-ray crystal structures have been obtained for the cytoplasmic domains, including an atypical protein kinase domain, ankyrin repeats, coiled coil domains and a Ca(2+)-binding domain, of 6 TRP channels. These structures enhance our understanding of TRP channel assembly and regulation. Continued technical advances in structural approaches promise a bright outlook for TRP channel structural biology.
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122
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Sudbury JR, Ciura S, Sharif-Naeini R, Bourque CW. Osmotic and thermal control of magnocellular neurosecretory neurons - role of an N-terminal variant of trpv1. Eur J Neurosci 2010; 32:2022-30. [DOI: 10.1111/j.1460-9568.2010.07512.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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123
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FRET analysis of protein tyrosine kinase c-Src activation mediated via aryl hydrocarbon receptor. Biochim Biophys Acta Gen Subj 2010; 1810:427-31. [PMID: 21145940 DOI: 10.1016/j.bbagen.2010.11.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2010] [Revised: 11/04/2010] [Accepted: 11/25/2010] [Indexed: 01/25/2023]
Abstract
BACKGROUND Activation of the protein tyrosine kinase c-Src (c-Src kinase) induced by the exposure to the environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been shown in various cell types. Most previous works used Western blot analysis to detect the phosphorylation on the Tyr416 residue, which activates c-Src kinase. METHODS Here we compared the results of c-Src tyrosine phosphorylation via aryl hydrocarbon receptor (AhR)-dependent mechanisms from Western blot analysis with fluorescent resonance energy transfer (FRET) assay detecting c-Src activation after treatment with TCDD to activate AhR in two different human cell types. RESULTS Western blot analyses show time-dependent phosphorylation of c-Src by TCDD in HepG2 and MCF-10A cells. Data from FRET assay visualized and quantified the activation of c-Src kinase induced by TCDD in living cells of both cell types. The FRET efficiency decreased by 20%, 5 min after TCDD treatment and continued decreasing until the end of the experiment, 25 min after TCDD treatment. PP2, a c-Src specific inhibitor, suppressed both TCDD- and epidermal growth factor- (EGF) induced c-Src activation. In contrast, the AhR antagonist 3'-methoxy-4'nitroflavone (MNF) blocked only TCDD- but not EGF-induced activation of c-Src. CONCLUSIONS The current study shows that the early activation of c-Src via EGF and AhR signaling pathways can be visualized in living cells using the FRET assay which is in line with Western blot analysis. GENERAL SIGNIFICANCE The FRET assay provides a useful tool to visualize and quantify c-Src kinase activation via AhR in living cells.
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124
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Tulu Buber M, Cerne R, Cortés RY, Bryant RW, Paul Lee S. Overexpression of Human Transient Receptor Potential M5 Upregulates Endogenous Human Transient Receptor Potential A1 in a Stable HEK Cell Line. Assay Drug Dev Technol 2010; 8:695-702. [DOI: 10.1089/adt.2010.0316] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- M. Tulu Buber
- Discovery Research, Redpoint Bio Corporation, Ewing, New Jersey
| | - Rok Cerne
- Discovery Research, Redpoint Bio Corporation, Ewing, New Jersey
| | - Rosa Y. Cortés
- Discovery Research, Redpoint Bio Corporation, Ewing, New Jersey
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125
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Heteromerization of TRP channel subunits: extending functional diversity. Protein Cell 2010; 1:802-10. [PMID: 21203922 DOI: 10.1007/s13238-010-0108-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 09/01/2010] [Indexed: 01/03/2023] Open
Abstract
Transient receptor potential (TRP) channels are widely found throughout the animal kingdom. By serving as cellular sensors for a wide spectrum of physical and chemical stimuli, they play crucial physiological roles ranging from sensory transduction to cell cycle modulation. TRP channels are tetrameric protein complexes. While most TRP subunits can form functional homomeric channels, heteromerization of TRP channel subunits of either the same subfamily or different subfamilies has been widely observed. Heteromeric TRP channels exhibit many novel properties compared to their homomeric counterparts, indicating that co-assembly of TRP channel subunits has an important contribution to the diversity of TRP channel functions.
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126
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Abbruzzetti S, Bizzarri R, Luin S, Nifosì R, Storti B, Viappiani C, Beltram F. Photoswitching of E222Q GFP mutants: "concerted" mechanism of chromophore isomerization and protonation. Photochem Photobiol Sci 2010; 9:1307-19. [PMID: 20859582 DOI: 10.1039/c0pp00189a] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photochromic (i.e. reversibly photoswitchable) fluorescent proteins increasingly find applications as biomarkers for advanced bioimaging applications. From a mechanistic point of view, photochromicity usually stems from the reversible cis-trans photoisomerization of the chromophore. We demonstrated experimentally that cis-trans photoisomerization constitutes a very efficient deactivation pathway of isolated chromophores upon visible light excitation. Nonetheless, this intrinsic property is seldom displayed by chromophores in the folded protein structure. We found that the E222Q amino acid replacement restores efficient photochromicity in otherwise poorly switchable green fluorescent protein variants of different optical properties. Glutamic acid 222 is known to play a pivotal role in the inner proton wires that involve the GFP chromophore and the surrounding residues. Hence its substitution with an isosteric but non-ionizable residue presumably leads to a extensive rewiring of proton pathways around the chromophore, which has a deep effect also on the photochromic properties. In this work, we review and discuss the main photophysical properties of photochromic E222Q GFP mutants. Additionally we show, by means of flash-photolysis experiments, that chromophore cis to trans photoswitching involves a molecular mechanism where stereochemical isomerization and chromophore protonation occur in a coordinated way. Such a "concerted" mechanism is, in our opinion, at the basis of efficient photochromic behavior and might be activated by the E222Q mutation.
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Affiliation(s)
- Stefania Abbruzzetti
- Dipartimento di Fisica, Università di Parma, viale G. P. Usberti 7A, 43100, Parma, Italy
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127
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Thermosensitive TRP channel pore turret is part of the temperature activation pathway. Proc Natl Acad Sci U S A 2010; 107:7083-8. [PMID: 20351268 DOI: 10.1073/pnas.1000357107] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Temperature sensing is crucial for homeotherms, including human beings, to maintain a stable body core temperature and respond to the ambient environment. A group of exquisitely temperature-sensitive transient receptor potential channels, termed thermoTRPs, serve as cellular temperature sensors. How thermoTRPs convert thermal energy (heat) into protein conformational changes leading to channel opening remains unknown. Here we demonstrate that the pathway for temperature-dependent activation is distinct from those for ligand- and voltage-dependent activation and involves the pore turret. We found that mutant channels with an artificial pore turret sequence lose temperature sensitivity but maintain normal ligand responses. Using site-directed fluorescence recordings we observed that temperature change induces a significant rearrangement of TRPV1 pore turret that is coupled to channel opening. This movement is specifically associated to temperature-dependent activation and is not observed during ligand- and voltage-dependent channel activation. These observations suggest that the turret is part of the temperature-sensing apparatus in thermoTRP channels, and its conformational change may give rise to the large entropy that defines high temperature sensitivity.
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128
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Abstract
Although a unifying characteristic common to all transient receptor potential (TRP) channel functions remains elusive, they could be described as tetramers formed by subunits with six transmembrane domains and containing cation-selective pores, which in several cases show high calcium permeability. TRP channels constitute a large superfamily of ion channels, and can be grouped into seven subfamilies based on their amino acid sequence homology: the canonical or classic TRPs, the vanilloid receptor TRPs, the melastatin or long TRPs, ankyrin (whose only member is the transmembrane protein 1 [TRPA1]), TRPN after the nonmechanoreceptor potential C (nonpC), and the more distant cousins, the polycystins and mucolipins. Because of their role as cellular sensors, polymodal activation and gating properties, many TRP channels are activated by a variety of different stimuli and function as signal integrators. Thus, how TRP channels function and how function relates to given structural determinants contained in the channel-forming protein has attracted the attention of biophysicists as well as molecular and cell biologists. The main purpose of this review is to summarize our present knowledge on the structure of channels of the TRP ion channel family. In the absence of crystal structure information for a complete TRP channel, we will describe important protein domains present in TRP channels, structure-function mutagenesis studies, the few crystal structures available for some TRP channel modules, and the recent determination of some TRP channel structures using electron microscopy.
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129
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Samie MA, Grimm C, Evans JA, Curcio-Morelli C, Heller S, Slaugenhaupt SA, Cuajungco MP. The tissue-specific expression of TRPML2 (MCOLN-2) gene is influenced by the presence of TRPML1. Pflugers Arch 2010; 459:79-91. [PMID: 19763610 DOI: 10.1007/s00424-009-0716-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 08/12/2009] [Accepted: 08/14/2009] [Indexed: 11/29/2022]
Abstract
Mucolipidosis type IV is a lysosomal storage disorder caused by the loss or dysfunction of the mucolipin-1 (TRPML1) protein. It has been suggested that TRPML2 could genetically compensate (i.e., become upregulated) for the loss of TRPML1. We thus investigated this possibility by first studying the expression pattern of mouse TRPML2 and its basic channel properties using the varitint-waddler (Va) model. Here, we confirmed the presence of long variant TRPML2 (TRPML2lv) and short variant (TRPML2sv) isoforms. We showed for the first time that, heterologously expressed, TRPML2lv-Va is an active, inwardly rectifying channel. Secondly, we quantitatively measured TRPML2 and TRPML3 mRNA expressions in TRPML1-/- null and wild-type (Wt) mice. In wild-type mice, the TRPML2lv transcripts were very low while TRPML2sv and TRPML3 transcripts have predominant expressions in lymphoid and kidney organs. Significant reductions of TRPML2sv, but not TRPML2lv or TRPML3 transcripts, were observed in lymphoid and kidney organs of TRPML1-/- mice. RNA interference of endogenous human TRPML1 in HEK-293 cells produced a comparable decrease of human TRPML2 transcript levels that can be restored by overexpression of human TRPML1. Conversely, significant upregulation of TRPML2sv transcripts was observed when primary mouse lymphoid cells were treated with nicotinic acid adenine dinucleotide phosphate, or N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinoline sulfonamide, both known activators of TRPML1. In conclusion, our results indicate that TRPML2 is unlikely to compensate for the loss of TRPML1 in lymphoid or kidney organs and that TRPML1 appears to play a novel role in the tissue-specific transcriptional regulation of TRPML2.
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Affiliation(s)
- Mohammad A Samie
- Department of Biological Science, and Center for Applied, Biotechnology Studies, California State University Fullerton, 800 N State College Blvd, Fullerton, CA 92831, USA
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130
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Chang Y, Schlenstedt G, Flockerzi V, Beck A. Properties of the intracellular transient receptor potential (TRP) channel in yeast, Yvc1. FEBS Lett 2009; 584:2028-32. [DOI: 10.1016/j.febslet.2009.12.035] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 12/18/2009] [Indexed: 10/20/2022]
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131
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Vilceanu D, Honore P, Hogan QH, Stucky CL. Spinal nerve ligation in mouse upregulates TRPV1 heat function in injured IB4-positive nociceptors. THE JOURNAL OF PAIN 2009; 11:588-99. [PMID: 20015699 DOI: 10.1016/j.jpain.2009.09.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Revised: 09/23/2009] [Accepted: 09/29/2009] [Indexed: 01/14/2023]
Abstract
UNLABELLED Peripheral nerve injury leads to neuropathic pain, but the underlying mechanisms are not clear. The TRPV1 channel expressed by nociceptors is one receptor for noxious heat and inflammatory molecules. Lumbar 4 (L4) spinal nerve ligation (SNL) in mice induced persistent heat hyperalgesia 4 to 10 days after injury. The heat hypersensitivity was completely reversed by the TRPV1 antagonist A-425619. Furthermore, DRG neurons were isolated from the injured L4 ganglia or adjacent L3 ganglia 4 to 10 days after L4 SNL. Whole-cell patch-clamp recordings were performed and heat stimuli (22 degrees C to 50 degrees C/3 s) were applied to the soma. Neurons were classified by soma size and isolectin-B4 (IB4) binding. Among directly injured L4 neurons, SNL increased the percentage of small-diameter IB4-positive neurons that were heat-sensitive from 13% (naive controls) to 56% and conversely decreased the proportion of small IB4-negative neurons that were heat-sensitive from 66% (naive controls) to 34%. There was no change in IB4 binding in neurons from the injured ganglia. Surprisingly, in neurons from the adjacent L3 ganglia, SNL had no effect on the heat responsiveness of either IB4-positive or negative small neurons. Also, SNL had no effect on heat responses in medium-large-diameter neurons from either the injured or adjacent ganglia. PERSPECTIVE TRPV1 function is upregulated in IB4-positive sensory neurons, and TRPV1 is responsible for the behavioral heat hypersensitivity in the spinal nerve ligation model. Because IB4-positive neurons may contribute to the emotional perception of pain, TRPV1 antagonists, targeting both sensory and affective pain components, could have broad analgesic effects.
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Affiliation(s)
- Daniel Vilceanu
- Department of Cell Biology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226-0509, USA
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132
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Zeevi DA, Frumkin A, Offen-Glasner V, Kogot-Levin A, Bach G. A potentially dynamic lysosomal role for the endogenous TRPML proteins. J Pathol 2009; 219:153-62. [PMID: 19557826 DOI: 10.1002/path.2587] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 05/28/2009] [Indexed: 11/10/2022]
Abstract
Lysosomal storage disorders (LSDs) constitute a diverse group of inherited diseases that result from lysosomal storage of compounds occurring in direct consequence to deficiencies of proteins implicated in proper lysosomal function. Pathology in the LSD mucolipidosis type IV (MLIV), is characterized by lysosomal storage of lipids together with water-soluble materials in cells from every tissue and organ of affected patients. Mutations in the mucolipin 1 (TRPML1) protein cause MLIV and TRPML1 has also been shown to interact with two of its paralogous proteins, mucolipin 2 (TRPML2) and mucolipin 3 (TRPML3), in heterologous expression systems. Heterogeneous lysosomal storage is readily identified in electron micrographs of MLIV patient cells, suggesting that proper TRPML1 function is essential for the maintenance of lysosomal integrity. In order to investigate whether TRPML2 and TRPML3 also play a role in the maintenance of lysosomal integrity, we conducted gene-specific knockdown assays against these protein targets. Ultrastructural analysis revealed lysosomal inclusions in both TRPML2 and TRPML3 knockdown cells, suggestive of a common mechanism for these proteins, in parallel with TRPML1, in the regulation of lysosomal integrity. However, co-immunoprecipitation assays revealed that physical interactions between each of the endogenous TRPML proteins are quite limited. In addition, we found that all three endogenous proteins only partially co-localize with each other in lysosomal as well as extra-lysosomal compartments. This suggests that native TRPML2 and TRPML3 might participate with native TRPML1 in a dynamic form of lysosomal regulation. Given that depletion of TRPML2/3 led to lysosomal storage typical to an LSD, we propose that depletion of these proteins might also underlie novel LSD pathologies not described hitherto.
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Affiliation(s)
- David A Zeevi
- Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem, Israel
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133
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Yu Y, Ulbrich MH, Li MH, Buraei Z, Chen XZ, Ong ACM, Tong L, Isacoff EY, Yang J. Structural and molecular basis of the assembly of the TRPP2/PKD1 complex. Proc Natl Acad Sci U S A 2009; 106:11558-63. [PMID: 19556541 PMCID: PMC2710685 DOI: 10.1073/pnas.0903684106] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Indexed: 01/20/2023] Open
Abstract
Mutations in PKD1 and TRPP2 account for nearly all cases of autosomal dominant polycystic kidney disease (ADPKD). These 2 proteins form a receptor/ion channel complex on the cell surface. Using a combination of biochemistry, crystallography, and a single-molecule method to determine the subunit composition of proteins in the plasma membrane of live cells, we find that this complex contains 3 TRPP2 and 1 PKD1. A newly identified coiled-coil domain in the C terminus of TRPP2 is critical for the formation of this complex. This coiled-coil domain forms a homotrimer, in both solution and crystal structure, and binds to a single coiled-coil domain in the C terminus of PKD1. Mutations that disrupt the TRPP2 coiled-coil domain trimer abolish the assembly of both the full-length TRPP2 trimer and the TRPP2/PKD1 complex and diminish the surface expression of both proteins. These results have significant implications for the assembly, regulation, and function of the TRPP2/PKD1 complex and the pathogenic mechanism of some ADPKD-producing mutations.
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Affiliation(s)
- Yong Yu
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Maximilian H. Ulbrich
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Ming-Hui Li
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Xing-Zhen Chen
- Membrane Protein Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada T6G 2H7; and
| | - Albert C. M. Ong
- Kidney Genetics Group, Academic Unit of Nephrology, Sheffield Kidney Institute, University of Sheffield Medical School, Sheffield S10 2RX, United Kingdom
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Ehud Y. Isacoff
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- Material Science and Physical Bioscience Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, NY 10027
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134
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PSD-95 regulates D1 dopamine receptor resensitization, but not receptor-mediated Gs-protein activation. Cell Res 2009; 19:612-24. [PMID: 19274064 DOI: 10.1038/cr.2009.30] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The present study aims to define the role of postsynaptic density (PSD)-95 in the regulation of dopamine (DA) receptor function. We found that PSD-95 physically associates with either D(1) or D(2) DA receptors in co-transfected HEK-293 cells. Stimulation of DA receptors altered the association between D(1) receptor and PSD-95 in a time-dependent manner. Functional assays indicated that PSD-95 co-expression did not affect D(1) receptor-stimulated cAMP production, Gs-protein activation or receptor desensitization. However, PSD-95 accelerated the recovery of internalized membrane receptors by promoting receptor recycling, thus resulting in enhanced resensitization of internalized D(1) receptors. Our results provide a novel mechanism for regulating DA receptor recycling that may play an important role in postsynaptic DA functional modulation and synaptic neuroplasticity.
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135
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Qu Z, Cheng W, Cui Y, Cui Y, Zheng J. Human disease-causing mutations disrupt an N-C-terminal interaction and channel function of bestrophin 1. J Biol Chem 2009; 284:16473-16481. [PMID: 19372599 PMCID: PMC2713530 DOI: 10.1074/jbc.m109.002246] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 04/01/2009] [Indexed: 11/06/2022] Open
Abstract
Mutations in the human bestrophin 1 (hBest1) chloride channel cause Best vitelliform macular dystrophy. Although mutations in its transmembrane domains were found to alter biophysical properties of the channel, the mechanism for disease-causing mutations in its N and C termini remains elusive. We hypothesized that these mutations lead to channel dysfunction through disruption of an N-C-terminal interaction. Here, we present data demonstrating that hBest1 N and C termini indeed interact both in vivo and in vitro. In addition, using a spectrum-based fluorescence resonance energy transfer method, we showed that functional hBest1 channels in the plasma membrane were multimers. Disease-causing mutations in the N terminus (R19C, R25C, and K30C) and the C terminus (G299E, D301N, and D312N) caused channel dysfunction and disruption of the N-C interaction. Consistent with the functional and biochemical results, mutants D301N and D312N clearly reduced fluorescence resonance energy transfer signal, indicating that the N-C interaction was indeed perturbed. These results suggest that hBest1 functions as a multimer in the plasma membrane, and disruption of the N-C interaction by mutations leads to hBest1 channel dysfunction.
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Affiliation(s)
- Zhiqiang Qu
- From the Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322; Department of Physiology, Qingdao University School of Medicine, Qingdao, Shandong 266071, China.
| | - Wei Cheng
- Department of Physiology and Membrane Biology, University of California, School of Medicine, Davis, California 95616
| | - Yuanyuan Cui
- From the Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Yuanyuan Cui
- Department of Physiology and Membrane Biology, University of California, School of Medicine, Davis, California 95616
| | - Jie Zheng
- Department of Physiology and Membrane Biology, University of California, School of Medicine, Davis, California 95616
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136
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Jara-Oseguera A, Llorente I, Rosenbaum T, Islas LD. Properties of the inner pore region of TRPV1 channels revealed by block with quaternary ammoniums. ACTA ACUST UNITED AC 2009; 132:547-62. [PMID: 18955595 PMCID: PMC2571972 DOI: 10.1085/jgp.200810051] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The transient receptor potential vanilloid 1 (TRPV1) nonselective cationic channel is a polymodal receptor that activates in response to a wide variety of stimuli. To date, little structural information about this channel is available. Here, we used quaternary ammonium ions (QAs) of different sizes in an effort to gain some insight into the nature and dimensions of the pore of TRPV1. We found that all four QAs used, tetraethylammonium (TEA), tetrapropylammonium (TPrA), tetrabutylammonium, and tetrapentylammonium, block the TRPV1 channel from the intracellular face of the channel in a voltage-dependent manner, and that block by these molecules occurs with different kinetics, with the bigger molecules becoming slower blockers. We also found that TPrA and the larger QAs can only block the channel in the open state, and that they interfere with the channel's activation gate upon closing, which is observed as a slowing of tail current kinetics. TEA does not interfere with the activation gate, indicating that this molecule can reside in its blocking site even when the channel is closed. The dependence of the rate constants on the size of the blocker suggests a size of around 10 A for the inner pore of TRPV1 channels.
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Affiliation(s)
- Andrés Jara-Oseguera
- Departamento de Fisiología, Facultad de Medicina, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, D.F., 04510, México
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137
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Broad LM, Mogg AJ, Beattie RE, Ogden AM, Blanco MJ, Bleakman D. TRP channels as emerging targets for pain therapeutics. Expert Opin Ther Targets 2008; 13:69-81. [DOI: 10.1517/14728220802616620] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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138
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Liang S, Yang F, Zhou C, Wang Y, Li S, Sun CK, Puglisi JL, Bers D, Sun C, Zheng J. Temperature-dependent activation of neurons by continuous near-infrared laser. Cell Biochem Biophys 2008; 53:33-42. [PMID: 19034696 DOI: 10.1007/s12013-008-9035-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2008] [Indexed: 01/28/2023]
Abstract
Optical control of neuronal activity has a number of advantages over electrical methods and can be conveniently applied to intact individual neurons in vivo. In this study, we demonstrated an experimental approach in which a focused continuous near-infrared (CNI) laser beam was used to activate single rat hippocampal neurons by transiently elevating the local temperature. Reversible changes in the amplitude and kinetics of neuronal voltage-gated Na and K channel currents were recorded following irradiation with a single-mode 980 nm CNI-laser. Using single-channel recordings under controlled temperatures as a means of calibration, it was estimated that temperature at the neuron rose by 14 degrees C in 500 ms. Computer simulation confirmed that small temperature changes of about 5 degrees C were sufficient to produce significant changes in neuronal excitability. The method should be broadly applicable to studies of neuronal activity under physiological conditions, in particular studies of temperature-sensing neurons expressing thermoTRP channels.
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Affiliation(s)
- Shanshan Liang
- Lab of Biomedical Optics, College of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116023, People's Republic of China
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139
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MacGlashan D. IgE receptor and signal transduction in mast cells and basophils. Curr Opin Immunol 2008; 20:717-23. [PMID: 18822373 DOI: 10.1016/j.coi.2008.08.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 08/27/2008] [Accepted: 08/28/2008] [Indexed: 12/11/2022]
Abstract
There are many aspects of mast cell and basophil biology that are being explored today. Notably, there is a wide variety of studies of the roles these two cell types play in the development of a multitude of diseases and the role they play in the general immune response. But the original reasons for studying these two cells types--because they are considered crucial to immediate hypersensitivity reactions--remain a driving force for research. These two cell types express the complete high affinity IgE receptor and aggregation of this receptor results in the secretion of multiple potent mediators that cause many of the signs and symptoms of an allergic reaction. Understanding more about the biology of the receptor and the signaling that it initiates remains important to the development of new therapeutic approaches to inhibit this reaction.
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Affiliation(s)
- Donald MacGlashan
- Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, United States.
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140
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Samways DSK, Khakh BS, Egan TM. Tunable calcium current through TRPV1 receptor channels. J Biol Chem 2008; 283:31274-8. [PMID: 18775990 DOI: 10.1074/jbc.c800131200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPV1 receptors are polymodal cation channels that open in response to diverse stimuli including noxious heat, capsaicin, and protons. Because Ca2+ is vital for TRPV1 signaling, we sought to precisely measure its contribution to TRPV1 responses and discovered that the Ca2+ current was tuned by the mode of activation. Using patch clamp photometry, we found that the fraction of the total current carried by Ca2+ (called the Pf%) was significantly smaller for TRPV1 currents evoked by protons than for those evoked by capsaicin. Using site-directed mutagenesis, we discovered that the smaller Pf% was due to protonation of three acidic amino acids (Asp646, Glu648, and Glu651) that are located in the mouth of the pore. Thus, in keeping with recent reports of time-dependent changes in the ionic permeability of some ligand-gated ion channels, we now show for the first time that the physiologically important Ca2+ current of the TRPV1 receptor is also dynamic and depends on the mode of activation. This current is significantly smaller when the receptor is activated by a change in pH, owing to atomic scale interactions of H+ and Ca2+ with the fixed negative charge of side chains in the pore.
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Affiliation(s)
- Damien S K Samways
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA.
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141
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Sharif-Naeini R, Ciura S, Bourque CW. TRPV1 gene required for thermosensory transduction and anticipatory secretion from vasopressin neurons during hyperthermia. Neuron 2008; 58:179-85. [PMID: 18439403 DOI: 10.1016/j.neuron.2008.02.013] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Revised: 12/22/2007] [Accepted: 02/13/2008] [Indexed: 11/27/2022]
Abstract
Increases in core body temperature promote thermoregulatory cooling by stimulating sweat production and preemptive renal water reabsorption through the release of vasopressin (VP, antidiuretic hormone). The mechanism by which the hypothalamus orchestrates this anticipatory VP release during hyperthermia is unknown but has been linked to a central thermosensory mechanism. Here, we report that thermal stimuli spanning core body temperatures activate a calcium-permeable, ruthenium red- and SB366791-sensitive nonselective cation conductance in hypothalamic VP neurons. This response is associated with a depolarizing receptor potential and an increase in action potential firing rate, indicating that these neurons are intrinsically thermosensitive. The thermosensitivity of VP neurons isolated from trpv1 knockout (Trpv1(-/-)) mice was significantly lower than that of wild-type counterparts. Moreover, Trpv1(-/-) mice showed an impaired VP response to hyperthermia in vivo. Channels encoded by the trpv1 gene thus confer thermosensitivity in central VP neurons and contribute to the thermal control of VP release in vivo.
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Affiliation(s)
- Reza Sharif-Naeini
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montreal, QC, Canada
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142
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Vetter I, Cheng W, Peiris M, Wyse BD, Roberts-Thomson SJ, Zheng J, Monteith GR, Cabot PJ. Rapid, opioid-sensitive mechanisms involved in transient receptor potential vanilloid 1 sensitization. J Biol Chem 2008; 283:19540-50. [PMID: 18482991 DOI: 10.1074/jbc.m707865200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
TRPV1 is a nociceptive, Ca2+-selective ion channel involved in the development of several painful conditions. Sensitization of TRPV1 responses by cAMP-dependent PKA crucially contributes to the development of inflammatory hyperalgesia. However, the pathways involved in potentiation of TRPV1 responses by cAMP-dependent PKA remain largely unknown. Using HEK cells stably expressing TRPV1 and the mu opioid receptor, we demonstrated that treatment with the adenylate cyclase activator forskolin significantly increased the multimeric TRPV1 species. Pretreatment with the mu opioid receptor agonist morphine reversed this increased TRPV1 multimerization. FRET analysis revealed that treatment with forskolin did not cause multimerization of pre-existing TRPV1 monomers on the plasma membrane and that intracellular pools of TRPV1 exist mostly as monomers in this model. This suggests that increased TRPV1 multimerization occurred from an intracellular store of inactive TRPV1 monomers. Treatment with forskolin also caused an increase in TRPV1 expression on the plasma membrane not resulting from increased TRPV1 expression, and this rapid TRPV1 translocation was inhibited by treatment with morphine. Thus, potentiation of TRPV1 responses by cAMP-dependent PKA involves plasma membrane insertion of functional TRPV1 multimers formed from an intracellular store of inactive TRPV1 monomers. This potentiation occurs rapidly and can be dynamically modulated by activation of the mu opioid receptor under conditions where cAMP levels are raised, such as with inflammation. Increased translocation and multimerization of TRPV1 channels provide a cellular mechanism for fine-tuning of nociceptive responses that allow for rapid modulation of TRPV1 responses independent of transcriptional changes.
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Affiliation(s)
- Irina Vetter
- School of Pharmacy, The University of Queensland, St Lucia, Queensland 4072, Australia
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143
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Sharif-Naeini R, Ciura S, Zhang Z, Bourque C. Contribution of TRPV channels to osmosensory transduction, thirst, and vasopressin release. Kidney Int 2008; 73:811-5. [DOI: 10.1038/sj.ki.5002788] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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144
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Fritzsch B, Beisel KW, Pauley S, Soukup G. Molecular evolution of the vertebrate mechanosensory cell and ear. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2008; 51:663-78. [PMID: 17891725 PMCID: PMC3918877 DOI: 10.1387/ijdb.072367bf] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The molecular basis of mechanosensation, mechanosensory cell development and mechanosensory organ development is reviewed with an emphasis on its evolution. In contrast to eye evolution and development, which apparently modified a genetic program through intercalation of genes between the master control genes on the top (Pax6, Eya1, Six1) of the hierarchy and the structural genes (rhodopsin) at the bottom, the as yet molecularly unknown mechanosensory channel precludes such a firm conclusion for mechanosensors. However, recent years have seen the identification of several structural genes which are involved in mechanosensory tethering and several transcription factors controlling mechanosensory cell and organ development; these warrant the interpretation of available data in very much the same fashion as for eye evolution: molecular homology combined with potential morphological parallelism. This assertion of molecular homology is strongly supported by recent findings of a highly conserved set of microRNAs that appear to be associated with mechanosensory cell development across phyla. The conservation of transcription factors and their regulators fits very well to the known or presumed mechanosensory specializations which can be mostly grouped as variations of a common cellular theme. Given the widespread distribution of the molecular ability to form mechanosensory cells, it comes as no surprise that structurally different mechanosensory organs evolved in different phyla, presenting a variation of a common theme specified by a conserved set of transcription factors in their cellular development. Within vertebrates and arthropods, some mechanosensory organs evolved into auditory organs, greatly increasing sensitivity to sound through modifications of accessory structures to direct sound to the specific sensory epithelia. However, while great attention has been paid to the evolution of these accessory structures in vertebrate fossils, comparatively less attention has been spent on the evolution of the inner ear and the central auditory system. Recent advances in our molecular understanding of ear and brain development provide novel avenues to this neglected aspect of auditory neurosensory evolution.
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Affiliation(s)
- Bernd Fritzsch
- Creighton University, Dept of Biomedical Sciences, Omaha, NE 68178, USA.
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145
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Gao Y, Liu SS, Qiu S, Cheng W, Zheng J, Luo JH. Fluorescence resonance energy transfer analysis of subunit assembly of the ASIC channel. Biochem Biophys Res Commun 2007; 359:143-50. [PMID: 17532298 PMCID: PMC2039887 DOI: 10.1016/j.bbrc.2007.05.077] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Accepted: 05/14/2007] [Indexed: 11/21/2022]
Abstract
Acid-sensing ion channels (ASICs) are believed to be homo- or heteromeric complexes, which have been verified by classical methods such as co-immunoprecipitation or electrophysiological assays. However, the exact subunit combinations of ASICs in living cells have not been established yet. Here, we apply assays based on fluorescence resonance energy transfer (FRET) between GFP color mutants CFP and YFP to investigate ASIC assembly directly in living cells. Homomerization as well as heteromerization of different combinations of ASIC subunits were found. In addition, our results suggest the formation of heteromeric 1a/2a channels of stoichiometry consisting of at least two 1a subunits and two 2a subunits. Similar stoichiometry was observed from heteromeric 1a/2b and 2a/2b channels. Our results imply that these heteromeric ASIC channels contain at least four subunits.
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Affiliation(s)
- Ying Gao
- Department of Neurobiology, Institute for Neuroscience, Zhejiang University School of Medicine, Hangzhou 310058, China
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