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Wolfgang Liedtke - One of the best experts on this subject based on the ideXlab platform.
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analysis of TRPV channel activation by stimulation of fceri and mrgpr receptors in mouse peritoneal mast cells
PLOS ONE, 2017Co-Authors: Alejandra Solislopez, Wolfgang Liedtke, Ulrich Kriebs, Alexander Marx, Stefanie Mannebach, M. J. Caterina, Marc Freichel, Volodymyr TsvilovskyyAbstract:The activation of mast cells (MC) is part of the innate and adaptive immune responses and depends on Ca2+ entry across the plasma membrane, leading to the release of preformed inflammatory mediators by degranulation or by de novo synthesis. The calcium conducting channels of the TRPV family, known by their thermo and osmotic sensitivity, have been proposed to be involved in the MC activation in murine, rat, and human mast cell models. So far, immortalized mast cell lines and nonspecific TRPV blockers have been employed to characterize the role of TRPV channels in MC. The aim of this work was to elucidate the physiological role of TRPV channels by using primary peritoneal mast cells (PMCs), a model of connective tissue type mast cells. Our RT-PCR and NanoString analysis identified the expression of TRPV1, TRPV2, and TRPV4 channels in PMCs. For determination of the functional role of the expressed TRPV channels we performed measurements of intracellular free Ca2+ concentrations and beta-hexosaminidase release in PMCs obtained from wild type and mice deficient for corresponding TRPV1, TRPV2 and TRPV4 in response to various receptor-mediated and physical stimuli. Furthermore, substances known as activators of corresponding TRPV-channels were also tested using these assays. Our results demonstrate that TRPV1, TRPV2, and TRPV4 do not participate in activation pathways triggered by activation of the high-affinity receptors for IgE (FceRI), Mrgprb2 receptor, or Endothelin-1 receptor nor by heat or osmotic stimulation in mouse PMCs.
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Analysis of TRPV channel activation by stimulation of FCεRI and MRGPR receptors in mouse peritoneal mast cells
PloS one, 2017Co-Authors: Alejandra Solis-lopez, Wolfgang Liedtke, Ulrich Kriebs, Alexander Marx, Stefanie Mannebach, M. J. Caterina, Marc Freichel, Volodymyr TsvilovskyyAbstract:The activation of mast cells (MC) is part of the innate and adaptive immune responses and depends on Ca2+ entry across the plasma membrane, leading to the release of preformed inflammatory mediators by degranulation or by de novo synthesis. The calcium conducting channels of the TRPV family, known by their thermo and osmotic sensitivity, have been proposed to be involved in the MC activation in murine, rat, and human mast cell models. So far, immortalized mast cell lines and nonspecific TRPV blockers have been employed to characterize the role of TRPV channels in MC. The aim of this work was to elucidate the physiological role of TRPV channels by using primary peritoneal mast cells (PMCs), a model of connective tissue type mast cells. Our RT-PCR and NanoString analysis identified the expression of TRPV1, TRPV2, and TRPV4 channels in PMCs. For determination of the functional role of the expressed TRPV channels we performed measurements of intracellular free Ca2+ concentrations and beta-hexosaminidase release in PMCs obtained from wild type and mice deficient for corresponding TRPV1, TRPV2 and TRPV4 in response to various receptor-mediated and physical stimuli. Furthermore, substances known as activators of corresponding TRPV-channels were also tested using these assays. Our results demonstrate that TRPV1, TRPV2, and TRPV4 do not participate in activation pathways triggered by activation of the high-affinity receptors for IgE (FceRI), Mrgprb2 receptor, or Endothelin-1 receptor nor by heat or osmotic stimulation in mouse PMCs.
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TRPV Ion Channels and Sensory Transduction of Osmotic and Mechanical Stimuli in Mammals
Sensing with Ion Channels, 2008Co-Authors: Wolfgang LiedtkeAbstract:In signal transduction in metazoan cells, ion channels of the transient receptor potential (TRP) family have been identified as responding to diverse external and inter- nal stimuli, amongst them osmotic stimuli. This chapter will highlight findings on the TRP vanilloid (TRPV) subfamily - both vertebrate and invertebrate members. Of the six mammalian TRPV channels, TRPV1, 2 and 4 have been demonstrated to function in transduction of osmotic stimuli. TRPV channels have been found to function in cellular as well as systemic osmotic homeostasis in vertebrates. Invertebrate TRPV channels - five in Caenorhabditis elegans and two in Drosophila - have been shown to play a role in mechanosensation such as hearing and proprioception in Drosophila and nose touch in C. elegans, and in the response to osmotic stimuli in C. elegans. In a striking example of evolutionary conservation of function, mammalian TRPV4 has been found to rescue osmo- and mechano-sensory deficits of the TRPV mutant strain osm-9 in C. elegans, despite the fact that the respective proteins share not more than 26% orthology.
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Molecular Mechanisms of TRPV4‐Mediated Neural Signaling
Annals of the New York Academy of Sciences, 2008Co-Authors: Wolfgang LiedtkeAbstract:In signal transduction of metazoan cells, ion channels of the family of transient receptor potential (TRP) have been identified to respond to diverse external and internal stimuli, among them osmotic stimuli. This review highlights a specific member of the TRPV subfamily, the TRPV4 channel, initially named vanilloid-receptor related osmotically activated channel (VR-OAC) or OTRPC4. In a striking example of evolutionary conservation of function, mammalian TRPV4 has been found to rescue osmo- and mechanosensory deficits of the TRPV mutant strain osm-9 in Caenorhabditis elegans. This is an astounding finding given the
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Role of TRPV ion channels in sensory transduction of osmotic stimuli in mammals.
Experimental physiology, 2007Co-Authors: Wolfgang LiedtkeAbstract:In signal transduction of metazoan cells, ion channels of the family of transient receptor potential (TRP) have been identified to respond to diverse external and internal stimuli, amongst them osmotic stimuli. This report highlights findings pertaining to the TRPV subfamily, focusing on mammalian members. Of the six mammalian TRPV channels, TRPV1, 2 and 4 were demonstrated to function in transduction of osmotic stimuli. TRPV channels have been found to function in cellular as well as systemic osmotic homeostasis. In a striking example of evolutionary conservation of function, mammalian TRPV4 has been found to rescue osmosensory deficits of the TRPV mutant strain osm-9 in Caenorhabditis elegans, despite not more than 26% orthology of the respective proteins.
Rachelle Gaudet - One of the best experts on this subject based on the ideXlab platform.
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Structural Comparison of Ankyrin Repeat Domain of TRPV Channels
Biophysical Journal, 2011Co-Authors: Hitoshi Inada, Rachelle GaudetAbstract:Transient receptor potential (TRP) channels are tetrameric cation channels involved with sensing of various stimuli from internal and external environments. Six TRPV proteins, TRPV1-6, constitute the vanilloid subfamily of the TRP channel superfamily. TRPV proteins contain six transmembrane segments flanked by two cytoplasmic domains; a large N-terminal domain containing ankyrin repeats and a short C-terminal domain. The N-terminal ankyrin repeat domain (ARD) binds to small molecules and proteins. For example, ATP and calmodulin (CaM) can bind to the ARD and regulate the channel activity of TRPV1, TRPV3 and TRPV4 but not TRPV2, TRPV5, and TRPV6. To date, several structures of TRPV-ARDs have been reported. TRP-ARD structure contains six ankyrin repeats (ANK1 - ANK6) joined with loops (Fingers 1 - 5). To obtain insight into regulatory mechanisms mediated by ATP and CaM binding, structures of the TRPV-ARDs are compared. Structures available include published and unpublished structures of ARDs in the absence or presence of regulatory ligands, as well as structures of ARDs that do not bind these regulatory ligands. Structural comparison showed that Finger 3 in ARD has a large variation in TRPV-ARD structures. Finger 3 is twisted and shrunken in the ATP-bound form of TRPV4-ARD, while it is extended in ATP-free forms of TRPV4-ARD. Finger 3 structures of ATP-bound ARDs (TRPV1 and TRPV4) are similar to those of ARDs that do not bind ATP (TRPV2 and TRPV6). Conserved aromatic residues on Finger 2 might contribute to ATP binding. Interestingly, most mutations causing human genetic diseases in human TRPV4-ARD are located away from ATP binding site, suggesting that additional regulatory interactions and mechanisms exist.
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differential regulation of TRPV1 TRPV3 and TRPV4 sensitivity through a conserved binding site on the ankyrin repeat domain
Journal of Biological Chemistry, 2010Co-Authors: Christopher B Phelps, Ruiqi Rachel Wang, Shelly Seungah Choo, Rachelle GaudetAbstract:Transient receptor potential vanilloid (TRPV) channels, which include the thermosensitive TRPV1–V4, have large cytoplasmic regions flanking the transmembrane domain, including an N-terminal ankyrin repeat domain. We show that a multiligand binding site for ATP and calmodulin previously identified in the TRPV1 ankyrin repeat domain is conserved in TRPV3 and TRPV4, but not TRPV2. Accordingly, TRPV2 is insensitive to intracellular ATP, while, as previously observed with TRPV1, a sensitizing effect of ATP on TRPV4 required an intact binding site. In contrast, ATP reduced TRPV3 sensitivity and potentiation by repeated agonist stimulations. Thus, ATP and calmodulin, acting through this conserved binding site, are key players in generating the different sensitivity and adaptation profiles of TRPV1, TRPV3, and TRPV4. Our results suggest that competing interactions of ATP and calmodulin influence channel sensitivity to fluctuations in calcium concentration and perhaps even metabolic state. Different feedback mechanisms likely arose because of the different physiological stimuli or temperature thresholds of these channels.
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structural analyses of the ankyrin repeat domain of TRPV6 and related TRPV ion channels
Biochemistry, 2008Co-Authors: Christopher B Phelps, Ruiqi Rachel Wang, Robert J. Huang, Polina V Lishko, Rachelle GaudetAbstract:Transient Receptor Potential (TRP) proteins are cation channels composed of a transmembrane domain flanked by large N- and C-terminal cytoplasmic domains. All members of the vanilloid family of TRP channels (TRPV) possess an N-terminal ankyrin repeat domain (ARD). The ARD of mammalian TRPV6, an important regulator of calcium uptake and homeostasis, is essential for channel assembly and regulation. The 1.7 A crystal structure of the TRPV6-ARD reveals conserved structural elements unique to the ARDs of TRPV proteins. First, a large twist between the fourth and fifth repeats is induced by residues conserved in all TRPV ARDs. Second, the third finger loop is the most variable region in sequence, length and conformation. In TRPV6, a number of putative regulatory phosphorylation sites map to the base of this third finger. Size exclusion chromatography and crystal packing indicate that the TRPV6-ARD does not assemble as a tetramer and is monomeric in solution. Adenosine triphosphate-agarose and calmodulin-agarose pull-down assays show that the TRPV6-ARD does not interact with either ligand, indicating a different functional role for the TRPV6-ARD than in the paralogous thermosensitive TRPV1 channel. Similar biochemical findings are also presented for the highly homologous mammalian TRPV5-ARD. The implications of the structural and biochemical data on the role of the ankyrin repeats in different TRPV channels are discussed. The Transient Receptor Potential (TRP) proteins are a superfamily of cation channels with diverse functions. All TRP channels share a similar six-transmembrane-segment iontransport domain flanked by intracellular N- and C-terminal domains, and are expected to function as tetramers. TRP channels are divided into seven subfamilies based on sequence similarity in their cytosolic domains, (TRPA – ANKTM1, TRPC – canonical, TRPM – melastatin, TRPN – NOMP-C, TRPV – vanilloid receptor, and the more distantly related
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structural analyses of the ankyrin repeat domain of TRPV6 and related TRPV ion channels
Biochemistry, 2008Co-Authors: Christopher B Phelps, Ruiqi Rachel Wang, Robert J. Huang, Polina V Lishko, Rachelle GaudetAbstract:Transient receptor potential (TRP) proteins are cation channels composed of a transmembrane domain flanked by large N- and C-terminal cytoplasmic domains. All members of the vanilloid family of TRP channels (TRPV) possess an N-terminal ankyrin repeat domain (ARD). The ARD of mammalian TRPV6, an important regulator of calcium uptake and homeostasis, is essential for channel assembly and regulation. The 1.7 A crystal structure of the TRPV6-ARD reveals conserved structural elements unique to the ARDs of TRPV proteins. First, a large twist between the fourth and fifth repeats is induced by residues conserved in all TRPV ARDs. Second, the third finger loop is the most variable region in sequence, length and conformation. In TRPV6, a number of putative regulatory phosphorylation sites map to the base of this third finger. Size exclusion chromatography and crystal packing indicate that the TRPV6-ARD does not assemble as a tetramer and is monomeric in solution. Adenosine triphosphate-agarose and calmodulin-agarose pull-down assays show that the TRPV6-ARD does not interact with either ligand, indicating a different functional role for the TRPV6-ARD than in the paralogous thermosensitive TRPV1 channel. Similar biochemical findings are also presented for the highly homologous mammalian TRPV5-ARD. The implications of the structural and biochemical data on the role of the ankyrin repeats in different TRPV channels are discussed.
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structure of the n terminal ankyrin repeat domain of the TRPV2 ion channel
Journal of Biological Chemistry, 2006Co-Authors: Xiangshu Jin, Jason Touhey, Rachelle GaudetAbstract:The TRPV ion channels mediate responses to many sensory stimuli including heat, low pH, neuropeptides, and chemical ligands. All TRPV subfamily members contain an intracellular N-terminal ankyrin repeat domain (ARD), a prevalent protein interaction motif. The 1.6-A crystal structure of the TRPV2-ARD, with six ankyrin repeats, reveals several atypical structural features. Repeats one through three display unusually long and flexible fingers with a large number of exposed aromatic residues, whereas repeats five and six have unusually long outer helices. Furthermore, a large counterclockwise twist observed in the stacking of repeats four and five breaks the regularity of the domain, altering the shape of surfaces available for interactions with proteins or other cellular ligands. Both solution studies and crystal packing interactions indicate that the TRPV2-ARD does not form homo-oligomers, suggesting that the ARD of TRPV ion channels may be used for interactions with regulatory factors rather than in promoting tetrameric assembly of the ion channels.
Dietrich Busselberg - One of the best experts on this subject based on the ideXlab platform.
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modulation of intracellular calcium influences capsaicin induced currents of TRPV 1and voltage activated channel currents in nociceptive neurones
Journal of The Peripheral Nervous System, 2007Co-Authors: Tim Hagenacker, Dietrich BusselbergAbstract:Modulation of intracellular calcium ([Ca2+](i)) has a major impact on processing of nociceptive signals. While activation of the transient receptor potential vanilloid-1 (TRPV-1) receptor/channel complex increases [Ca2+](i) by Ca2+ entry from the extracellular space, as well as by Ca2+ release from intracellular stores, the Ca2+ entry through voltage-activated calcium channels (VACCs) is modulated simultaneously. To clarify the relations between [Ca2+](i) and the activation of TRPV-1 receptor and VACC currents [I(TRPV-1) and I(Ca(V))], we performed voltage clamp experiments using Ba2+ as well as Ca2+ as a charge carrier. The TRPV-1 receptor was activated by the application of 0.5 microM capsaicin, and the currents through TRPV-1 and VACC [I(TRPV-1) and I(Ca(V))] were measured either when Ca2+ release from intracellular stores was pharmacologically promoted or prevented. With Ba2+ as the divalent charge carrier, capsaicin (0.5 microM) reduced I(Ca(V)) (elicited by a depolarization to 0 mV) to 52.7 +/- 4.5% of baseline, and the elicited current through the TRPV-1 receptor/channel complex was 6.6 +/- 0.9% [relative to peak I(Ca(V))]. These currents were significantly different when Ca2+ was used as charge carrier: the I(Ca(V)) reductions were decreased to 17.8 +/- 5.9% of baseline, while the I(TRPV-1) was as high as 57.1 +/- 9.1% of I(Ca(V)). Increases of [Ca2+](i) by releasing Ca2+ from intracellular stores (using caffeine, 10 mM) before the application of capsaicin increased the I(TRPV-1) (14.1 +/- 7%), while the I(Ca(V)) was decreased to 51.6 +/- 4.9% compared with control. A preexperimental partial reduction of the Ca2+ release from the stores by dantrolene (5 microM) resulted in less pronounced effects [24.5 +/- 8.8%, relative to peak I(Ca(V))] for I(TRPV-1), and a reduction to 35.4 +/- 3% of baseline for I(Ca(V)) after capsaicin application.
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Modulation of intracellular calcium influences capsaicin‐induced currents of TRPV‐1and voltage‐activated channel currents in nociceptive neurones
Journal of the peripheral nervous system : JPNS, 2007Co-Authors: Tim Hagenacker, Dietrich BusselbergAbstract:Modulation of intracellular calcium ([Ca2+](i)) has a major impact on processing of nociceptive signals. While activation of the transient receptor potential vanilloid-1 (TRPV-1) receptor/channel complex increases [Ca2+](i) by Ca2+ entry from the extracellular space, as well as by Ca2+ release from intracellular stores, the Ca2+ entry through voltage-activated calcium channels (VACCs) is modulated simultaneously. To clarify the relations between [Ca2+](i) and the activation of TRPV-1 receptor and VACC currents [I(TRPV-1) and I(Ca(V))], we performed voltage clamp experiments using Ba2+ as well as Ca2+ as a charge carrier. The TRPV-1 receptor was activated by the application of 0.5 microM capsaicin, and the currents through TRPV-1 and VACC [I(TRPV-1) and I(Ca(V))] were measured either when Ca2+ release from intracellular stores was pharmacologically promoted or prevented. With Ba2+ as the divalent charge carrier, capsaicin (0.5 microM) reduced I(Ca(V)) (elicited by a depolarization to 0 mV) to 52.7 +/- 4.5% of baseline, and the elicited current through the TRPV-1 receptor/channel complex was 6.6 +/- 0.9% [relative to peak I(Ca(V))]. These currents were significantly different when Ca2+ was used as charge carrier: the I(Ca(V)) reductions were decreased to 17.8 +/- 5.9% of baseline, while the I(TRPV-1) was as high as 57.1 +/- 9.1% of I(Ca(V)). Increases of [Ca2+](i) by releasing Ca2+ from intracellular stores (using caffeine, 10 mM) before the application of capsaicin increased the I(TRPV-1) (14.1 +/- 7%), while the I(Ca(V)) was decreased to 51.6 +/- 4.9% compared with control. A preexperimental partial reduction of the Ca2+ release from the stores by dantrolene (5 microM) resulted in less pronounced effects [24.5 +/- 8.8%, relative to peak I(Ca(V))] for I(TRPV-1), and a reduction to 35.4 +/- 3% of baseline for I(Ca(V)) after capsaicin application.
Katsuhiro Hirakawa - One of the best experts on this subject based on the ideXlab platform.
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expression of transient receptor potential vanilloid TRPV families 1 2 3 and 4 in the mouse olfactory epithelium
Rhinology, 2009Co-Authors: Mohamed Khalifa Ahmed, Takuya Ishibashi, Masaya Takumida, Takao Hamamoto, Katsuhiro HirakawaAbstract:Abstract We investigated the expression of transient receptor potential vanilloid (TRPV)-1-4 in the mouse olfactory epithelium (OE) in comparison to its expression in respiratory epithelium. CBA/J mice were used. The localization of TRPV-1, -2, -3 and -4 in the nasal mucosa was investigated using immunohistochemistry and a double staining study for TRPV-1 and -2 and SP was also carried out. TRPV-1-4, were expressed variably in the OE with a diffuse pattern in lamina propria, and were expressed in respiratory epithelium with strong positive expression in glandular cells of lamina propria. The double-staining study revealed coexpression of TRPV-1 and -2 and substance P (SP) in the trigeminal nerve fibers of the OE. Coexpression of TRPV-1 and SP was marked around the blood vessels and seromucinous gland of respiratory epithelium while TRPV-2 showed no co-localization. TRPV-1-4 were found to be localized in the mouse OE and respiratory epithelium. Our results suggest that TRPVs may play multiple roles in the OE, contributing to olfactory adaptation, olfactory/trigeminal interactions in nasal chemoreception and OE homeostasis; they may also be involved in olfactory transduction as well as olfactory dysfunction secondary to sinonasal inflammatory disease. TRPVs in respiratory mucosa may play a significant role in nasal nociception, ciliary movement and the regulation of mucous secretion.
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changes in transient receptor potential vanilloid TRPV 1 2 3 and 4 expression in mouse inner ear following gentamicin challenge
Acta Oto-laryngologica, 2009Co-Authors: Takuya Ishibashi, Masaya Takumida, Nana Akagi, Katsuhiro Hirakawa, Matti AnnikoAbstract:Conclusion. It is suggested that transient receptor potential vanilloid (TRPV)-1 and -2 may be of pathological significance for sensory cells and ganglions, while TRPV-3 and -4 may play an important part in neuroprotection of the inner ear. Objective. Changes in the expression of TRPV-1, -2, -3, and -4 in gentamicin (GM)-treated mouse inner ear were studied. Materials and methods. CBA/J mice were used in this study. The localization of TRPV-1, -2, -3, and -4 in the inner ear of both untreated and GM-treated CBA/J animals (intratympanic injection of 5 mg GM) was investigated by immunohistochemistry. Results. TRPV-1, -2, and -3 were co-expressed in the inner ear sensory and ganglion cells, while TRPV-4 was also expressed in the stria vascularis and vestibular dark cells. Following GM treatment, the intensity of immunofluorescent reaction to TRPV-1 and TRPV-2 increased, while that to TRPV-3 and TRPV-4 decreased.
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expression of transient receptor potential vanilloid TRPV 1 2 3 and 4 in mouse inner ear
Acta Oto-laryngologica, 2008Co-Authors: Takuya Ishibashi, Masaya Takumida, Nana Akagi, Katsuhiro Hirakawa, Matti AnnikoAbstract:Conclusion. It is suggested that transient receptor potential vanilloids (TRPVs) may play a functional role in cell physiology and TRPV-4 and -2 may play an important part in fluid homeostasis in the inner ear. Objective. Expression of TRPV-1, -2, -3, and -4 in the normal mouse inner ear was studied. Materials and methods. CBA/J mice were used in this study. The localization of TRPV-1, -2, -3, and -4 in the inner ear, i.e. cochlea, vestibular end organs, and endolymphatic sac, was investigated by immunohistochemistry. Results. TRPV-1, -2, and -3 were co-expressed in hair cells and supporting cells of the organ of Corti, in spiral ganglion cells, sensory cells in vestibular end organs, vestibular ganglion cells, and sensory nerve fibers. TRPV-2 was also detected in the stria vascularis, dark cells, and endolymphatic sac. TRPV-4 was expressed in hair cells and supporting cells of the organ of Corti, in marginal cells of the stria vascularis, spiral ganglion cells, vestibular sensory cells, vestibular dark c...
Tim Hagenacker - One of the best experts on this subject based on the ideXlab platform.
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modulation of intracellular calcium influences capsaicin induced currents of TRPV 1and voltage activated channel currents in nociceptive neurones
Journal of The Peripheral Nervous System, 2007Co-Authors: Tim Hagenacker, Dietrich BusselbergAbstract:Modulation of intracellular calcium ([Ca2+](i)) has a major impact on processing of nociceptive signals. While activation of the transient receptor potential vanilloid-1 (TRPV-1) receptor/channel complex increases [Ca2+](i) by Ca2+ entry from the extracellular space, as well as by Ca2+ release from intracellular stores, the Ca2+ entry through voltage-activated calcium channels (VACCs) is modulated simultaneously. To clarify the relations between [Ca2+](i) and the activation of TRPV-1 receptor and VACC currents [I(TRPV-1) and I(Ca(V))], we performed voltage clamp experiments using Ba2+ as well as Ca2+ as a charge carrier. The TRPV-1 receptor was activated by the application of 0.5 microM capsaicin, and the currents through TRPV-1 and VACC [I(TRPV-1) and I(Ca(V))] were measured either when Ca2+ release from intracellular stores was pharmacologically promoted or prevented. With Ba2+ as the divalent charge carrier, capsaicin (0.5 microM) reduced I(Ca(V)) (elicited by a depolarization to 0 mV) to 52.7 +/- 4.5% of baseline, and the elicited current through the TRPV-1 receptor/channel complex was 6.6 +/- 0.9% [relative to peak I(Ca(V))]. These currents were significantly different when Ca2+ was used as charge carrier: the I(Ca(V)) reductions were decreased to 17.8 +/- 5.9% of baseline, while the I(TRPV-1) was as high as 57.1 +/- 9.1% of I(Ca(V)). Increases of [Ca2+](i) by releasing Ca2+ from intracellular stores (using caffeine, 10 mM) before the application of capsaicin increased the I(TRPV-1) (14.1 +/- 7%), while the I(Ca(V)) was decreased to 51.6 +/- 4.9% compared with control. A preexperimental partial reduction of the Ca2+ release from the stores by dantrolene (5 microM) resulted in less pronounced effects [24.5 +/- 8.8%, relative to peak I(Ca(V))] for I(TRPV-1), and a reduction to 35.4 +/- 3% of baseline for I(Ca(V)) after capsaicin application.
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Modulation of intracellular calcium influences capsaicin‐induced currents of TRPV‐1and voltage‐activated channel currents in nociceptive neurones
Journal of the peripheral nervous system : JPNS, 2007Co-Authors: Tim Hagenacker, Dietrich BusselbergAbstract:Modulation of intracellular calcium ([Ca2+](i)) has a major impact on processing of nociceptive signals. While activation of the transient receptor potential vanilloid-1 (TRPV-1) receptor/channel complex increases [Ca2+](i) by Ca2+ entry from the extracellular space, as well as by Ca2+ release from intracellular stores, the Ca2+ entry through voltage-activated calcium channels (VACCs) is modulated simultaneously. To clarify the relations between [Ca2+](i) and the activation of TRPV-1 receptor and VACC currents [I(TRPV-1) and I(Ca(V))], we performed voltage clamp experiments using Ba2+ as well as Ca2+ as a charge carrier. The TRPV-1 receptor was activated by the application of 0.5 microM capsaicin, and the currents through TRPV-1 and VACC [I(TRPV-1) and I(Ca(V))] were measured either when Ca2+ release from intracellular stores was pharmacologically promoted or prevented. With Ba2+ as the divalent charge carrier, capsaicin (0.5 microM) reduced I(Ca(V)) (elicited by a depolarization to 0 mV) to 52.7 +/- 4.5% of baseline, and the elicited current through the TRPV-1 receptor/channel complex was 6.6 +/- 0.9% [relative to peak I(Ca(V))]. These currents were significantly different when Ca2+ was used as charge carrier: the I(Ca(V)) reductions were decreased to 17.8 +/- 5.9% of baseline, while the I(TRPV-1) was as high as 57.1 +/- 9.1% of I(Ca(V)). Increases of [Ca2+](i) by releasing Ca2+ from intracellular stores (using caffeine, 10 mM) before the application of capsaicin increased the I(TRPV-1) (14.1 +/- 7%), while the I(Ca(V)) was decreased to 51.6 +/- 4.9% compared with control. A preexperimental partial reduction of the Ca2+ release from the stores by dantrolene (5 microM) resulted in less pronounced effects [24.5 +/- 8.8%, relative to peak I(Ca(V))] for I(TRPV-1), and a reduction to 35.4 +/- 3% of baseline for I(Ca(V)) after capsaicin application.
