scholarly journals The Na+/Ca2+ Exchanger Inhibitor, KB-R7943, Blocks a Nonselective Cation Channel Implicated in Chemosensory Transduction

2009 ◽  
Vol 101 (3) ◽  
pp. 1151-1159 ◽  
Author(s):  
A. Pezier ◽  
Y. V. Bobkov ◽  
B. W. Ache
Keyword(s):  
Transient Receptor Potential ◽  
Single Channel ◽  
Receptor Potential ◽  
Trpc Channels ◽  
Dependent Manner ◽  
Open Probability ◽  
Olfactory Transduction ◽  
Voltage Dependent ◽  
Chemosensory Transduction ◽  
Transient Receptor

The mechanism(s) of olfactory transduction in invertebrates remains to be fully understood. In lobster olfactory receptor neurons (ORNs), a nonselective sodium-gated cation (SGC) channel, a presumptive transient receptor potential (TRP)C channel homolog, plays a crucial role in olfactory transduction, at least in part by amplifying the primary transduction current. To better determine the functional role of the channel, it is important to selectively block the channel independently of other elements of the transduction cascade, causing us to search for specific pharmacological blockers of the SGC channel. Given evidence that the Na+/Ca2+ exchange inhibitor, KB-R7943, blocks mammalian TRPC channels, we studied this probe as a potential blocker of the lobster SGC channel. KB-R7943 reversibly blocked the SGC current in both inside- and outside-out patch recordings in a dose- and voltage-dependent manner. KB-R7943 decreased the channel open probability without changing single channel amplitude. KB-R7943 also reversibly and in a dose-dependent manner inhibited both the odorant-evoked discharge of lobster ORNs and the odorant-evoked whole cell current. Our findings strongly imply that KB-R7943 potently blocks the lobster SGC channel and likely does so directly and not through its ability to block the Na+/Ca2+ exchanger.

scholarly journals Potentiation of TRPC5 by Protons

2007 ◽  
Vol 282 (46) ◽  
pp. 33868-33878 ◽  
Author(s):  
Marcus Semtner ◽  
Michael Schaefer ◽  
Olaf Pinkenburg ◽  
Tim D. Plant
Keyword(s):  
Phospholipase C ◽  
Transient Receptor Potential ◽  
Single Channel ◽  
Receptor Potential ◽  
High Sensitivity ◽  
Transient Receptor Potential Channel ◽  
Extracellular Ph ◽  
Dependent Manner ◽  
Open Probability ◽  
Transient Receptor

Mammalian members of the classical transient receptor potential channel subfamily (TRPC) are Ca2+-permeable cation channels involved in receptor-mediated increases in intracellular Ca2+. TRPC4 and TRPC5 form a group within the TRPC subfamily and are activated in a phospholipase C-dependent manner by an unidentified messenger. Unlike most other Ca2+-permeable channels, TRPC4 and -5 are potentiated by micromolar concentrations of La3+ and Gd3+. This effect results from an action of the cations at two glutamate residues accessible from the extracellular solution. Here, we show that TRPC4 and -5 respond to changes in extracellular pH. Lowering the pH increased both G protein-activated and spontaneous TRPC5 currents. Both effects were already observed with small reductions in pH (from 7.4 to 7.0) and increased up to pH 6.5. TRPC4 was also potentiated by decreases in pH, whereas TRPC6 was only inhibited, with a pIC50 of 5.7. Mutation of the glutamate residues responsible for lanthanoid sensitivity of TRPC5 (E543Q and E595Q) modified the potentiation of TRPC5 by acid. Further evidence for a similarity in the actions of lanthanoids and H+ on TRPC5 is the reduction in single channel conductance and dramatic increase in channel open probability in the presence of either H+ or Gd3+ that leads to larger integral currents. In conclusion, the high sensitivity of TRPC5 to H+ indicates that, in addition to regulation by phospholipase C and other factors, the channel may act as a sensor of pH that links decreases in extracellular pH to Ca2+ entry and depolarization.

scholarly journals Structure of the human TRPM4 ion channel in a lipid nanodisc

Science ◽  
2017 ◽  
Vol 359 (6372) ◽  
pp. 228-232 ◽  
Author(s):  
Henriette E. Autzen ◽  
Alexander G. Myasnikov ◽  
Melody G. Campbell ◽  
Daniel Asarnow ◽  
David Julius ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Calcium Binding ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Dependent Manner ◽  
Calcium Binding Site ◽  
Voltage Dependent ◽  
Transient Receptor ◽  
Lipid Nanodiscs

Transient receptor potential (TRP) melastatin 4 (TRPM4) is a widely expressed cation channel associated with a variety of cardiovascular disorders. TRPM4 is activated by increased intracellular calcium in a voltage-dependent manner but, unlike many other TRP channels, is permeable to monovalent cations only. Here we present two structures of full-length human TRPM4 embedded in lipid nanodiscs at ~3-angstrom resolution, as determined by single-particle cryo–electron microscopy. These structures, with and without calcium bound, reveal a general architecture for this major subfamily of TRP channels and a well-defined calcium-binding site within the intracellular side of the S1-S4 domain. The structures correspond to two distinct closed states. Calcium binding induces conformational changes that likely prime the channel for voltage-dependent opening.

scholarly journals TLR4 activation of TRPC6-dependent calcium signaling mediates endotoxin-induced lung vascular permeability and inflammation

2012 ◽  
Vol 209 (11) ◽  
pp. 1953-1968 ◽  
Author(s):  
Mohammad Tauseef ◽  
Nebojsa Knezevic ◽  
Koteswara R. Chava ◽  
Monica Smith ◽  
Sukriti Sukriti ◽  
...  
Keyword(s):  
Vascular Permeability ◽  
Transient Receptor Potential ◽  
Endothelial Permeability ◽  
Receptor Potential ◽  
Trpc Channels ◽  
Dependent Manner ◽  
Barrier Dysfunction ◽  
Barrier Disruption ◽  
Transient Receptor ◽  
Lung Vascular Permeability

Lung vascular endothelial barrier disruption and the accompanying inflammation are primary pathogenic features of acute lung injury (ALI); however, the basis for the development of both remains unclear. Studies have shown that activation of transient receptor potential canonical (TRPC) channels induces Ca2+ entry, which is essential for increased endothelial permeability. Here, we addressed the role of Toll-like receptor 4 (TLR4) intersection with TRPC6-dependent Ca2+ signaling in endothelial cells (ECs) in mediating lung vascular leakage and inflammation. We find that the endotoxin (lipopolysaccharide; LPS) induces Ca2+ entry in ECs in a TLR4-dependent manner. Moreover, deletion of TRPC6 renders mice resistant to endotoxin-induced barrier dysfunction and inflammation, and protects against sepsis-induced lethality. TRPC6 induces Ca2+ entry in ECs, which is secondary to the generation of diacylglycerol (DAG) induced by LPS. Ca2+ entry mediated by TRPC6, in turn, activates the nonmuscle myosin light chain kinase (MYLK), which not only increases lung vascular permeability but also serves as a scaffold to promote the interaction of myeloid differentiation factor 88 and IL-1R–associated kinase 4, which are required for NF-κB activation and lung inflammation. Our findings suggest that TRPC6-dependent Ca2+ entry into ECs, secondary to TLR4-induced DAG generation, participates in mediating both lung vascular barrier disruption and inflammation induced by endotoxin.

Magnesium-dependent block of the light-activated and trp-dependent conductance in Drosophila photoreceptors

1995 ◽  
Vol 74 (6) ◽  
pp. 2590-2599 ◽  
Author(s):  
R. C. Hardie ◽  
M. H. Mojet
Keyword(s):  
Transient Receptor Potential ◽  
Single Channel ◽  
Noise Analysis ◽  
Physiological Role ◽  
Receptor Potential ◽  
Cell Voltage ◽  
Resting Potential ◽  
Fold Reduction ◽  
Voltage Dependent ◽  
Transient Receptor

1. The effect of Mg2+ on the light-sensitive conductance in Drosophila photoreceptors was examined with the use of whole cell voltage-clamp recordings from dissociated ommatidia. In wild type (WT) photoreceptors, at resting potential (-70 mV). Mgo2+ reduces response amplitude by up to approximately 4-fold in the presence of normal (1.5 mM) Cao2+ and by up to 20-fold in the absence of Cao2+. The Mg2+ concentration required for 50% maximum block (K1/2) was approximately 1 mM with 1.5 mM Cao2+ and approximately 280 microM in Ca(2+)-free Ringer. 2. The Mg2+ block was largely relieved in photoreceptors of the transient receptor potential mutant (trp): the maximum block being only approximately twofold with a K1/2 of approximately 4 mM in both Ca(2+)-free and 1.5 mM Cao2+. 3. The Mg2+ block in WT, but not in trp, was strongly voltage dependent, being relieved by both hyperpolarization and depolarization. The Mg2+ block in WT also resulted in slower response kinetics because of the associated decrease in Ca2+ influx. 4. Noise analysis indicates that, with normal Ca(zero)2+, the Mg2+ block in WT is associated with a approximately 10-fold reduction in effective single-channel conductance al resting potential. 5. The results support the hypothesis that the trp gene encodes a subunit of a light-sensitive channel, which is required for sensitivity to block by Mg2+. The concentration and voltage dependence of the Mg2+ block suggest it plays an important physiological role in determining the gain, kinetics, and signal-to-noise of transduction.

scholarly journals Transient Receptor Potential Canonical (TRPC) Channels: Then and Now

Cells ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1983
Author(s):  
Xingjuan Chen ◽  
Gagandeep Sooch ◽  
Isaac S. Demaree ◽  
Fletcher A. White ◽  
Alexander G. Obukhov
Keyword(s):  
Molecular Mechanisms ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Hereditary Diseases ◽  
Trpc Channels ◽  
Dependent Manner ◽  
Transient Receptor Potential Canonical ◽  
Cell Functions ◽  
Transient Receptor

Twenty-five years ago, the first mammalian Transient Receptor Potential Canonical (TRPC) channel was cloned, opening the vast horizon of the TRPC field. Today, we know that there are seven TRPC channels (TRPC1–7). TRPCs exhibit the highest protein sequence similarity to the Drosophila melanogaster TRP channels. Similar to Drosophila TRPs, TRPCs are localized to the plasma membrane and are activated in a G-protein-coupled receptor-phospholipase C-dependent manner. TRPCs may also be stimulated in a store-operated manner, via receptor tyrosine kinases, or by lysophospholipids, hypoosmotic solutions, and mechanical stimuli. Activated TRPCs allow the influx of Ca2+ and monovalent alkali cations into the cytosol of cells, leading to cell depolarization and rising intracellular Ca2+ concentration. TRPCs are involved in the continually growing number of cell functions. Furthermore, mutations in the TRPC6 gene are associated with hereditary diseases, such as focal segmental glomerulosclerosis. The most important recent breakthrough in TRPC research was the solving of cryo-EM structures of TRPC3, TRPC4, TRPC5, and TRPC6. These structural data shed light on the molecular mechanisms underlying TRPCs’ functional properties and propelled the development of new modulators of the channels. This review provides a historical overview of the major advances in the TRPC field focusing on the role of gene knockouts and pharmacological tools.

Unitary Recordings of TRP and TRPL Channels From Isolated Drosophila Retinal Photoreceptor Rhabdomeres: Activation by Light and Lipids

2009 ◽  
Vol 101 (5) ◽  
pp. 2372-2379 ◽  
Author(s):  
Ricardo Delgado ◽  
Juan Bacigalupo
Keyword(s):  
Fatty Acids ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Single Channel ◽  
Receptor Potential ◽  
Sensory Transduction ◽  
Retinal Photoreceptor ◽  
Dependent Activity ◽  
Voltage Dependent ◽  
Transient Receptor

Transient receptor potential (TRP) channels play key roles in sensory transduction. The TRP family founding members, the Drosophila light-dependent channels, were previously studied under voltage clamp, but had not been characterized in intact rhabdomeres at single-channel level. We report patch-clamp recordings from intact isolated photoreceptors of wt and mutant flies lacking TRP ( trp 343), TRPL ( trpl 302), or both channels ( trp 313 ; trpl 302). Unitary currents were activated by light in rhabdomere-attached patches. In excised rhabdomeral patches, the channels were directly activated by molecules implicated in phototransduction, such as diacylglycerol and polyunsaturated fatty acids. Currents recorded from trpl photoreceptors are blocked by external Ca2+, Mg2+ (1 mM), and La3+ (20 μM), whereas those from trp photoreceptors are not. Rhabdomeric patches lacked voltage-dependent activity. Patches from trp;trpl mutants were devoid of channels. These characteristics match the macroscopic conductances, suggesting that the unitary currents from Drosophila trpl and trp photoreceptors correspond to TRP and TRPL.

scholarly journals Transient Receptor Potential Cation Channels and Calcium Dyshomeostasis in a Mouse Model Relevant to Malignant Hyperthermia

2020 ◽  
Vol 133 (2) ◽  
pp. 364-376 ◽  
Author(s):  
Jose Rafael Lopez ◽  
Vikas Kaura ◽  
Phillip Hopkins ◽  
Xiaochen Liu ◽  
Arkady Uryach ◽  
...  
Keyword(s):  
Mouse Model ◽  
Malignant Hyperthermia ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Muscle Cells ◽  
Cation Channels ◽  
Trpc Channels ◽  
Dependent Manner ◽  
Wild Type ◽  
Transient Receptor

Background Until recently, the mechanism for the malignant hyperthermia crisis has been attributed solely to sustained massive Ca2+ release from the sarcoplasmic reticulum on exposure to triggering agents. This study tested the hypothesis that transient receptor potential cation (TRPC) channels are important contributors to the Ca2+ dyshomeostasis in a mouse model relevant to malignant hyperthermia. Methods This study examined the mechanisms responsible for Ca2+ dyshomeostasis in RYR1-p.G2435R mouse muscles and muscle cells using calcium and sodium ion selective microelectrodes, manganese quench of Fura2 fluorescence, and Western blots. Results RYR1-p.G2435R mouse muscle cells have chronically elevated intracellular resting calcium and sodium and rate of manganese quench (homozygous greater than heterozygous) compared with wild-type muscles. After exposure to 1-oleoyl-2-acetyl-sn-glycerol, a TRPC3/6 activator, increases in intracellular resting calcium/sodium were significantly greater in RYR1-p.G2435R muscles (from 153 ± 11 nM/10 ± 0.5 mM to 304 ± 45 nM/14.2 ± 0.7 mM in heterozygotes P < 0.001] and from 251 ± 25 nM/13.9 ± 0.5 mM to 534 ± 64 nM/20.9 ± 1.5 mM in homozygotes [P < 0.001] compared with 123 ± 3 nM/8 ± 0.1 mM to 196 ± 27 nM/9.4 ± 0.7 mM in wild type). These increases were inhibited both by simply removing extracellular Ca2+ and by exposure to either a nonspecific (gadolinium) or a newly available, more specific pharmacologic agent (SAR7334) to block TRPC6- and TRPC3-mediated cation influx into cells. Furthermore, local pretreatment with SAR7334 partially decreased the elevation of intracellular resting calcium that is seen in RYR1-p.G2435R muscles during exposure to halothane. Western blot analysis showed that expression of TRPC3 and TRPC6 were significantly increased in RYR1-p.G2435R muscles in a gene–dose–dependent manner, supporting their being a primary molecular basis for increased sarcolemmal cation influx. Conclusions Muscle cells in knock-in mice expressing the RYR1-p.G2435R mutation are hypersensitive to TRPC3/6 activators. This hypersensitivity can be negated with pharmacologic agents that block TRPC3/6 activity. This reinforces the working hypothesis that transient receptor potential cation channels play a critical role in causing intracellular calcium and sodium overload in malignant hyperthermia–susceptible muscle, both at rest and during the malignant hyperthermia crisis. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

scholarly journals The native TRPP2-dependent channel of murine renal primary cilia

2017 ◽  
Vol 312 (1) ◽  
pp. F96-F108 ◽  
Author(s):  
Steven J. Kleene ◽  
Nancy K. Kleene
Keyword(s):  
Primary Cilium ◽  
Primary Cilia ◽  
Transient Receptor Potential ◽  
Single Channel ◽  
Receptor Potential ◽  
Open Probability ◽  
Electrophysiological Properties ◽  
Murine Cell Line ◽  
Autosomal Dominant Polycystic Kidney ◽  
Transient Receptor

Autosomal dominant polycystic kidney disease (ADPKD) is the most common life-threatening monogenic renal disease. ADPKD results from mutations in either of two proteins: polycystin-1 (also known as PC1 or PKD1) or transient receptor potential cation channel, subfamily P, member 2 (TRPP2, also known as polycystin-2, PC2, or PKD2). Each of these proteins is expressed in the primary cilium that extends from many renal epithelial cells. Existing evidence suggests that the cilium can promote renal cystogenesis, while PC1 and TRPP2 counter this cystogenic effect. To better understand the function of TRPP2, we investigated its electrophysiological properties in the native ciliary membrane. We recorded directly from the cilia of mIMCD-3 cells, a murine cell line of renal epithelial origin. In one-third of cilia examined, a large-conductance channel was observed. The channel was not permeable to Cl¯ but conducted cations with permeability ratios PK: PCa: PNa of 1:0.55:0.14. The single-channel conductance ranged from 97 pS in typical physiological solutions to 189 pS in symmetrical 145 mM KCl. Open probability of the channel was very sensitive to membrane depolarization or increasing cytoplasmic free Ca2+ in the low micromolar range, with the open probability increasing in either case. Knocking out TRPP2 by CRISPR/Cas9 genome editing eliminated the channel current, establishing it as TRPP2 dependent. Possible mechanisms for activating the TRPP2-dependent channel in the renal primary cilium are discussed.

scholarly journals Therapeutic inhibition of keratinocyte TRPV3 sensory channel by local anesthetic dyclonine

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Qiang Liu ◽  
Jin Wang ◽  
Xin Wei ◽  
Juan Hu ◽  
Conghui Ping ◽  
...  
Keyword(s):  
Transient Receptor Potential ◽  
Single Channel ◽  
Receptor Potential ◽  
Epidermal Keratinocytes ◽  
Transient Receptor Potential Vanilloid ◽  
Growth Disorders ◽  
Open Probability ◽  
Gain Of Function ◽  
Sensory Channel

The multimodal sensory channel transient receptor potential vanilloid-3 (TRPV3) is expressed in epidermal keratinocytes and implicated in chronic pruritus, allergy, and inflammation-related skin disorders. Gain-of-function mutations of TRPV3 cause hair growth disorders in mice and Olmsted Syndrome in human. We here report that mouse and human TRPV3 channel is targeted by the clinical medication dyclonine that exerts a potent inhibitory effect. Accordingly, dyclonine rescued cell death caused by gain-of-function TRPV3 mutations and suppressed pruritus symptoms in vivo in mouse model. At the single-channel level, dyclonine inhibited TRPV3 open probability but not the unitary conductance. By molecular simulations and mutagenesis, we further uncovered key residues in TRPV3 pore region that could toggle the inhibitory efficiency of dyclonine. The functional and mechanistic insights obtained on dyclonine-TRPV3 interaction will help to conceive updated therapeutics for skin inflammation.

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