scholarly journals Transient Receptor Potential Melastatin 8 Channel Inhibition Potentiates the Hypothermic Response to Transient Receptor Potential Vanilloid 1 Activation in the Conscious Mouse

2014 ◽  
Vol 42 (5) ◽  
pp. e355-e363 ◽  
Author(s):  
Viktor V. Feketa ◽  
Yi Zhang ◽  
Zhijuan Cao ◽  
Adithya Balasubramanian ◽  
Christopher M. Flores ◽  
...  
Keyword(s):  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Transient Receptor Potential Vanilloid ◽  
Transient Receptor Potential Melastatin ◽  
Channel Inhibition ◽  
Hypothermic Response ◽  
Transient Receptor

scholarly journals TRPM4 is required for calcium oscillations downstream from the stretch-activated TRPV4 channel

2021 ◽  
Author(s):  
Oleg Yarishkin ◽  
Tam T. Phuong ◽  
Felix Vazquez-Chona ◽  
Jacques A Bertrand ◽  
Sarah Redmon ◽  
...  
Keyword(s):  
Calcium Signaling ◽  
Molecular Mechanisms ◽  
Transient Receptor Potential ◽  
Membrane Surface ◽  
Receptor Potential ◽  
Calcium Oscillations ◽  
Transient Receptor Potential Vanilloid ◽  
Transient Receptor Potential Melastatin ◽  
Transient Receptor ◽  
Insight Into

Transduction of mechanical information is influenced by physical, chemical and thermal cues but the molecular mechanisms through which transducer activation shapes temporal signaling remain underexplored. In the present study, electrophysiology, histochemistry and functional imaging were combined with gene silencing and heterologous expression to gain insight into calcium signaling downstream from TRPV4 (Transient Receptor Potential Vanilloid 4), a stretch-activated nonselective cation channel. We show that trabecular meshwork (TM) cells, which employ mechanotransduction to actively regulate intraocular pressure, respond to the TRPV4 agonist GSK1016790A with fluctuations in intracellular Ca2+ concentration ([Ca2+]i) and an increase in [Na+]i. [Ca2+]i oscillations coincided with a monovalent cation current that was suppressed by BAPTA, Ruthenium Red and 9-phenanthrol, an inhibitor of TRPM4 (Transient Receptor Potential Melastatin 4) channels. Accordingly, TM cells expressed TRPM4 mRNA, protein at the expected 130-150 kDa and showed punctate TRPM4 immunoreactivity at the membrane surface. Genetic silencing of TRPM4 antagonized TRPV4-evoked oscillatory signaling whereas TRPV4 and TRPM4 co-expression in HEK-293 cells reconstituted the oscillations. Membrane potential recordings indicated that TRPM4-dependent oscillations required release of Ca2+ from internal stores. 9-phenanthrol did not affect the outflow facility in mouse eyes. Collectively, our results show that TRPV4 activity initiates dynamic calcium signaling in TM cells by stimulating TRPM4 channels and intracellular Ca2+ release. These findings provide insight into the complexity of membrane-cytosolic interactions during TRPV4 signaling and may foster strategies to promote homeostatic regulation and counter pathological remodeling within the conventional outflow pathway of the mammalian eye.

Heartburn Sensation in Non-Erosive Reflux Disease: Pattern of Superficial Sensory Nerves Expressing TRPV1 and Epithelial Cells Expressing ASIC3 Receptors

2021 ◽  
Author(s):  
Ahsen Ustaoglu ◽  
Akinari Sawada ◽  
Chung Lee ◽  
Wei-Yi Lei ◽  
Chien-Lin Chen ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Reflux Disease ◽  
Transient Receptor Potential ◽  
Sensory Nerve ◽  
Receptor Potential ◽  
Sensory Nerves ◽  
Transient Receptor Potential Vanilloid ◽  
Esophageal Mucosa ◽  
Transient Receptor Potential Melastatin ◽  
Transient Receptor

The underlying causes of heartburn, characteristic symptom of gastro-esophageal reflux disease(GERD), remain incompletely understood. Superficial afferent innervation of the esophageal mucosa in nonerosive reflux disease(NERD) may drive nociceptive reflux perception, but its acid-sensing role has not yet been established. Transient receptor potential vanilloid subfamily member-1(TRPV1), transient receptor potential Melastatin 8(TRPM8), and acid sensing ion channel 3(ASIC3) are regulators of sensory nerve activity and could be important reflux-sensing receptors within the esophageal mucosa. We characterised TRPV1, TRPM8, and ASIC3 expression in esophageal mucosa of GERD patients. We studied 10 NERD, 10 erosive reflux disease(ERD), 7 functional heartburn(FH), and 8 Barrett's esophagus(BE) patients. Biopsies obtained from the distal esophageal mucosa were co-stained with TRPV1, TRPM8, or ASIC3, and CGRP, CD45, or E-cadherin. RNA expression of TRPV1, TRPM8, and ASIC3 was assessed using qPCR. NERD patients had significantly increased expression of TRPV1 on superficial sensory nerves compared to ERD (p=0.028) or BE (p=0.017). Deep intrapapillary nerve endings did not express TRPV1 in all phenotypes studied. ASIC3 was exclusively expressed on epithelial cells most significantly in NERD and ERD patients (p=<0.0001). TRPM8 was expressed on submucosal CD45+ leukocytes. Superficial localisation of TRPV1-immunoreactive nerves in NERD, and increased ASIC3 co-expression on epithelial cells in NERD and ERD suggests a mechanism for heartburn sensation. Esophageal epithelial cells may play a sensory role in acid reflux perception and act interdependently with TRPV1-expressing mucosal nerves to augment hypersensitivity in NERD patients, raising the enticing possibility of topical antagonists for these ion channels as a therapeutic option.

scholarly journals Gαq sensitizes TRPM8 to inhibition by PI(4,5)P2 depletion upon receptor activation

2018 ◽  
Author(s):  
Luyu Liu ◽  
Yevgen Yudin ◽  
Chifei Kang ◽  
Natalia Shirokova ◽  
Tibor Rohacs
Keyword(s):  
Plasma Membrane ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Receptor Activation ◽  
Gpcr Activation ◽  
Transient Receptor Potential Melastatin ◽  
Channel Inhibition ◽  
Direct Binding ◽  
Mouse Dorsal Root Ganglion ◽  
Transient Receptor

ABSTRACTActivation of G-protein coupled receptors (GPCRs) was proposed to inhibit the cold and menthol sensitive Transient Receptor Potential Melastatin 8 (TRPM8) channels via direct binding of Gαq to the channel. It is well documented that TRPM8 requires the plasma membrane phospholipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2 or PIP2] for activity. It was claimed however that a decrease in cellular levels of this lipid does not contribute to channel inhibition upon receptor activation. Here we show that supplementing the whole cell patch pipette with PI(4,5)P2 reduced inhibition of TRPM8 by activation of Gαq-coupled receptors in mouse dorsal root ganglion (DRG) neurons. Activation of the same receptors induced Phospholipase C (PLC) activation and decreased plasma membrane PI(4,5)P2 levels in these neurons. PI(4,5)P2 also reduced inhibition of TRPM8 by activation of heterologously expressed Gαq-coupled muscarinic M1 receptors. Co-expression of a constitutively active Gαq protein that does not couple to PLC inhibited TRPM8 activity, and in cells expressing this protein decreasing PI(4,5)P2 levels using a voltage sensitive 5’-phosphatase induced a stronger inhibition of TRPM8 activity than in control cells. Our data indicate that PI(4,5)P2 depletion plays an important role in TRPM8 inhibition upon GPCR activation, and Gαq inhibits the channel by reducing its apparent affinity for PI(4,5)P2 and thus sensitizes the channel to inhibition by decreasing PI(4,5)P2 levels.

Quaternary Lidocaine Derivative QX-314 Activates and Permeates Human TRPV1 and TRPA1 to Produce Inhibition of Sodium Channels and Cytotoxicity

2016 ◽  
Vol 124 (5) ◽  
pp. 1153-1165 ◽  
Author(s):  
Thomas Stueber ◽  
Mirjam J. Eberhardt ◽  
Christoph Hadamitzky ◽  
Annette Jangra ◽  
Stefan Schenk ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Transient Receptor Potential ◽  
Sodium Current ◽  
Receptor Potential ◽  
Transient Receptor Potential Vanilloid ◽  
Viable Cells ◽  
Channel Inhibition ◽  
Transient Receptor ◽  
Human Isoforms

Abstract Background The relatively membrane-impermeable lidocaine derivative QX-314 has been reported to permeate the ion channels transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential cation channel, subfamily A, member 1 (TRPA1) to induce a selective inhibition of sensory neurons. This approach is effective in rodents, but it also seems to be associated with neurotoxicity. The authors examined whether the human isoforms of TRPV1 and TRPA1 allow intracellular entry of QX-314 to mediate sodium channel inhibition and cytotoxicity. Methods Human embryonic kidney 293 (HEK-293) cells expressing wild-type or mutant human (h) TRPV1 or TRPA1 constructs as well as the sodium channel Nav1.7 were investigated by means of patch clamp and ratiometric calcium imaging. Cytotoxicity was examined by flow cytometry. Results Activation of hTRPA1 by carvacrol and hTRPV1 by capsaicin produced a QX-314–independent reduction of sodium current amplitudes. However, permeation of QX-314 through hTRPV1 or hTRPA1 was evident by a concentration-dependent, use-dependent inhibition of Nav1.7 activated at 10 Hz. Five and 30 mM QX-314 activated hTRPV1 via mechanisms involving the intracellular vanilloid-binding domain and hTRPA1 via unknown mechanisms independent of intracellular cysteins. Expression of hTRPV1, but not hTRPA1, was associated with a QX-314–induced cytotoxicity (viable cells 48 ± 5% after 30 mM QX-314) that was ameliorated by the TRPV1 antagonist 4-(3-chloro-2-pyridinyl)-N-[4-(1,1-dimethylethyl)phenyl]-1-piperazinecarboxamide (viable cells 81 ± 5%). Conclusions The study data demonstrate that QX-314 directly activates and permeates the human isoforms of TRPV1 and TRPA1 to induce inhibition of sodium channels, but also a TRPV1-dependent cytotoxicity. These results warrant further validation of this approach in more intact preparations and may be valuable for the development of this concept into clinical practice.

scholarly journals Sensitivity of TRPM7 channels to Mg2+ characterized in cell-free patches of Jurkat T lymphocytes

2012 ◽  
Vol 302 (11) ◽  
pp. C1642-C1651 ◽  
Author(s):  
Rikki Chokshi ◽  
Masayuki Matsushita ◽  
J. Ashot Kozak
Keyword(s):  
Transient Receptor Potential ◽  
Single Channel ◽  
Receptor Potential ◽  
Whole Cell ◽  
Transient Receptor Potential Melastatin ◽  
Channel Inhibition ◽  
Gradual Development ◽  
Transient Receptor ◽  
Free Membrane ◽  
Inside Out

Transient receptor potential melastatin 7 (TRPM7) channels were originally identified electrophysiologically when depletion of cytosolic Mg2+ resulted in the gradual development of an outwardly rectifying cation current. Conversely, inclusion of millimolar Mg2+ in internal solutions prevented activation of these channels in whole cell patch clamp. We recently demonstrated that the Jurkat T-cell whole cell TRPM7 channels are inhibited by internal Mg2+ in a biphasic manner, displaying high [IC50(1) ≈ 10 μM] and low [IC50(2) ≈ 165 μM] affinity inhibitor sites. In that study, we had characterized the dependence of the maximum cell current density on intracellular Mg2+ concentration. To characterize Mg2+ inhibition in Jurkat T cells in more detail and compare it to whole cell results, we recorded single TRPM7 channels in cell-free membrane patches and investigated the dependence of their activity on Mg2+ added on the cytoplasmic side. We systematically varied free Mg2+ from 265 nM to 407 μM and evaluated the extent of channel inhibition in inside-out patch for 58 patches. We found that the TRPM7 channel shows two conductance levels of 39.0 pS (γ1) and 18.6 pS (γ2) and that both are reversibly inhibited by internal Mg2+. The 39.0-pS conductance is the dominant state of the channel, observed most frequently in this recording configuration. The dose-response relation in inside-out patches shows a steeper Mg2+ dependence than in whole cell, yielding IC50(1) of 25.1 μM and IC50(2) of 91.2 μM.. Single-channel analysis shows that the primary effect of Mg2+ in multichannel patches is a reversible reduction of the number of conducting channels (No). Additionally, at high Mg2+ concentrations, we observed a saturating 20% reduction in unitary conductance (γ1). Thus Mg2+ inhibition in whole cell can be explained by a drop in individual participating channels and a modest reduction in conductance. We also found that TRPM7 channels in some patches were not sensitive to this ion at submaximal Mg2+ concentrations. Interestingly, Mg2+ inhibition showed the property of use dependence: with repeated applications, Mg2+ effect became gradually more potent, which suggests that Mg2+ sensitivity of the channel is a dynamic characteristic that depends on other membrane factors.

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