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 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 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 PIP2 Activates TRPV5 and Releases Its Inhibition by Intracellular Mg2+

2005 ◽  
Vol 126 (5) ◽  
pp. 439-451 ◽  
Author(s):  
Jason Lee ◽  
Seung-Kuy Cha ◽  
Tie-Jun Sun ◽  
Chou-Long Huang
Keyword(s):  
Phospholipase C ◽  
Conformational Change ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Receptor Activation ◽  
Selectivity Filter ◽  
Induced Voltage ◽  
Voltage Dependent ◽  
Transient Receptor

The transient receptor potential type V5 channel (TRPV5) is a Ca2+-selective TRP channel important for epithelial Ca2+ transport. Intracellular Mg2+ causes a fast voltage-dependent block of the TRPV5 channel by binding to the selectivity filter. Here, we report that intracellular Mg2+ binding to the selectivity filter of TRPV5 also causes a slower reversible conformational change leading to channel closure. We further report that PIP2 activates TRPV5. Activation of TRPV5 by PIP2 is independent of Mg2+. Yet, PIP2 decreases sensitivity of the channel to the Mg2+-induced slow inhibition. Mutation of aspartate-542, a critical Mg2+-binding site in the selectivity filter, abolishes Mg2+-induced slow inhibition. PIP2 has no effects on Mg2+-induced voltage-dependent block. Thus, PIP2 prevents the Mg2+-induced conformational change without affecting Mg2+ binding to the selectivity filter. Hydrolysis of PIP2 via receptor activation of phospholipase C sensitizes TRPV5 to the Mg2+-induced slow inhibition. These results provide a novel mechanism for regulation of TRP channels by phospholipase C–activating hormones via alteration of the sensitivity to intracellular Mg2+.

scholarly journals Expression profile of the transient receptor potential (TRP) family in neutrophil granulocytes: evidence for currents through long TRP channel 2 induced by ADP-ribose and NAD

2003 ◽  
Vol 371 (3) ◽  
pp. 1045-1053 ◽  
Author(s):  
Inka HEINER ◽  
Jörg EISFELD ◽  
Christian R. HALASZOVICH ◽  
Edith WEHAGE ◽  
Eberhard JÜNGLING ◽  
...  
Keyword(s):  
Transient Receptor Potential ◽  
Trp Channels ◽  
Single Channel ◽  
Gradient Centrifugation ◽  
Receptor Potential ◽  
Vanilloid Receptor ◽  
Trp Channel ◽  
Human Neutrophils ◽  
Neutrophil Granulocytes ◽  
Transient Receptor

An early key event in the activation of neutrophil granulocytes is Ca2+ influx. Members of the transient receptor potential (TRP) channel family may be held responsible for this. The aim of the present study is to analyse the expression pattern of TRP mRNA and identify characteristic currents unambiguously attributable to particular TRP channels. mRNA was extracted from human neutrophils, isolated by gradient centrifugation and also by magnetically labelled CD15 antibodies. The presence of mRNA was demonstrated using reverse transcriptase–PCR in neutrophils (controlled to be CD5-negative) as well as in human leukaemic cell line 60 (HL-60) cells, for the following TRP species: the long TRPC2 (LTRPC2), the vanilloid receptor 1, the vanilloid receptor-like protein 1 and epithelial Ca2+ channels 1 and 2. TRPC6 was specific for neutrophils, whereas only in HL-60 cells were TRPC1, TRPC2, TRPC3, melastatin 1 and melastatin-related 1 found. Patch-clamp measurements in neutrophils revealed non-selective cation currents evoked by intracellular ADP-ribose and by NAD+. Both these modes of activation have been found to be characteristic of LTRPC2. Furthermore, single-channel activity was resolved in neutrophils and it was indistinguishable from that in LTRPC2-transfected HEK-293 cells. The results provide evidence that LTRPC2 in neutrophil granulocytes forms an entry pathway for Na+ and Ca2+, which is regulated by ADP-ribose and the redox state.

scholarly journals A Transient Receptor Potential Ion Channel in Chlamydomonas Shares Key Features with Sensory Transduction-Associated TRP Channels in Mammals

2015 ◽  
Vol 27 (1) ◽  
pp. 177-188 ◽  
Author(s):  
Luis Arias-Darraz ◽  
Deny Cabezas ◽  
Charlotte K. Colenso ◽  
Melissa Alegría-Arcos ◽  
Felipe Bravo-Moraga ◽  
...  
Keyword(s):  
Ion Channel ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Sensory Transduction ◽  
Key Features ◽  
Transient Receptor

scholarly journals Transient receptor potential ion channel function in sensory transduction and cellular signaling cascades underlying visceral hypersensitivity

2017 ◽  
Vol 312 (6) ◽  
pp. G635-G648 ◽  
Author(s):  
Dafne Balemans ◽  
Guy E. Boeckxstaens ◽  
Karel Talavera ◽  
Mira M. Wouters
Keyword(s):  
Signaling Pathways ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Visceral Hypersensitivity ◽  
Sensory Transduction ◽  
Trp Channel ◽  
Visceral Afferents ◽  
Altered Expression ◽  
Transient Receptor

Visceral hypersensitivity is an important mechanism underlying increased abdominal pain perception in functional gastrointestinal disorders including functional dyspepsia, irritable bowel syndrome, and inflammatory bowel disease in remission. Although the exact pathophysiological mechanisms are poorly understood, recent studies described upregulation and altered functions of nociceptors and their signaling pathways in aberrant visceral nociception, in particular the transient receptor potential (TRP) channel family. A variety of TRP channels are present in the gastrointestinal tract (TRPV1, TRPV3, TRPV4, TRPA1, TRPM2, TRPM5, and TRPM8), and modulation of their function by increased activation or sensitization (decreased activation threshold) or altered expression in visceral afferents have been reported in visceral hypersensitivity. TRP channels directly detect or transduce osmotic, mechanical, thermal, and chemosensory stimuli. In addition, pro-inflammatory mediators released in tissue damage or inflammation can activate receptors of the G protein-coupled receptor superfamily leading to TRP channel sensitization and activation, which amplify pain and neurogenic inflammation. In this review, we highlight the present knowledge on the functional roles of neuronal TRP channels in visceral hypersensitivity and discuss the signaling pathways that underlie TRP channel modulation. We propose that a better understanding of TRP channels and their modulators may facilitate the development of more selective and effective therapies to treat visceral hypersensitivity.

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 Expression of Transient Receptor Potential Ankyrin 1 and Transient Receptor Potential Vanilloid 1 in the Gut of the Peri-Weaning Pig Is Strongly Dependent on Age and Intestinal Site

Animals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2417
Author(s):  
Elout Van Liefferinge ◽  
Noémie Van Noten ◽  
Jeroen Degroote ◽  
Gunther Vrolix ◽  
Mario Van Poucke ◽  
...  
Keyword(s):  
Small Intestine ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
The Body ◽  
Enteroendocrine Cells ◽  
Sensory Transduction ◽  
Transient Receptor Potential Vanilloid ◽  
Distal Small Intestine ◽  
Transient Receptor

Transient receptor potential (TRP) channels contribute to sensory transduction in the body, agonized by a variety of stimuli, such as phytochemicals, and they are predominantly distributed in afferent neurons. Evidence indicates their expression in non-neuronal cells, demonstrating their ability to modulate gastrointestinal function. Targeting TRP channels could potentially be used to regulate gastrointestinal secretion and motility, yet their expression in the pig is unknown. This study investigated TRPA1 and TRPV1 expression in different gut locations of piglets of varying age. Colocalization with enteroendocrine cells was established by immunohistochemistry. Both channels were expressed in the gut mucosa. TRPV1 mRNA abundance increased gradually in the stomach and small intestine with age, most notably in the distal small intestine. In contrast, TRPA1 exhibited sustained expression across ages and locations, with the exception of higher expression in the pylorus at weaning. Immunohistochemistry confirmed the endocrine nature of both channels, showing the highest frequency of colocalization in enteroendocrine cells for TRPA1. Specific co-localization on GLP-1 immunoreactive cells indicated their possible role in GLP-1 release and the concomitant intestinal feedback mechanism. Our results indicate that TRPA1 and TRPV1 could play a role in gut enteroendocrine activity. Moreover, age and location in the gut significantly affected gene expression.

scholarly journals Store-operated Ca2+ entry: a key component of the insulin secretion machinery

2016 ◽  
Vol 57 (3) ◽  
pp. F35-F39 ◽  
Author(s):  
Jessica Sabourin ◽  
Florent Allagnat
Keyword(s):  
Insulin Secretion ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Leading Role ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Transient Receptor ◽  
Insulin Exocytosis

Normal plasma glucose level is ensured by the action of insulin, the major hypoglycemic hormone. Therefore, it is not surprising that insulin release from pancreatic β-cells of the islets of Langerhans is controlled by an array of balanced mechanisms in which glucose plays the leading role. Glucose triggers insulin secretion through the well-described pathway of ATP-driven closure of ATP-sensitive potassium channels (KATP), depolarization of the plasma membrane, and opening of the voltage-dependent Ca2+ channels (VDCC). The subsequent rapid rise in cytoplasmic free Ca2+ concentration triggers insulin exocytosis. However, despite more than 40 years of investigation, certain aspects of the intracellular Ca2+ responses to glucose and secretagogues remain unexplained, suggesting the involvement of additional Ca2+ channels. Here, we discuss the emerging role of store-operated Ca2+ channels carried by Orai1 and transient receptor potential canonical 1 (TRPC1) proteins and regulated by the stromal interaction molecule 1 (STIM1) in the control of glucose-induced insulin secretion. The role of other voltage-independent cation channels formed by other members of the TRP channels family is also addressed.

scholarly journals The Transmembrane Segment S6 Determines Cation versus Anion Selectivity of TRPM2 and TRPM8

2007 ◽  
Vol 282 (38) ◽  
pp. 27598-27609 ◽  
Author(s):  
Frank J. P. Kühn ◽  
Gabriel Knop ◽  
Andreas Lückhoff
Keyword(s):  
Transient Receptor Potential ◽  
Trp Channels ◽  
Reversal Potential ◽  
Receptor Potential ◽  
Cold Temperatures ◽  
Transmembrane Segments ◽  
Anion Selectivity ◽  
Voltage Dependent ◽  
Ion Substitution ◽  
Transient Receptor

TRPM2 and TRPM8, closely related members of the transient receptor potential (TRP) family, are cation channels activated by quite different mechanisms. Their transmembrane segments S5 and S6 are highly conserved. To identify common structures in S5 and S6 that govern interaction with the pore, we created a chimera in which the S5-pore-S6 region of TRPM8 was inserted into TRPM2, along with a lysine at each transition site. Currents through this chimera were induced by ADP-ribose (ADPR) in cooperation with Ca2+. In contrast to wild-type TRPM2 channels, currents through the chimera were carried by Cl-, as demonstrated in ion substitution experiments using the cation N-methyl-d-glucamine (NMDG) and the anion glutamate. Extracellular NMDG had no effects. The substitution of either intracellular or extracellular Cl- with glutamate shifted the reversal potential, decreased the current amplitude and induced a voltage-dependent block relieved by depolarization. The lysine in S6 was responsible for the anion selectivity; insertion of a lysine into corresponding sites within S6 of either TRPM2 or TRPM8 created anion channels that were activated by ADPR (TRPM2 I1045K) or by cold temperatures (TRPM8 V976K). The positive charge of the lysine was decisive for the glutamate block because the mutant TRPM2 I1045H displayed cation currents that were blocked at acidic but not alkaline intracellular pH values. We conclude that the distal part of S6 is crucial for the discrimination of charge. Because of the high homology of S6 in the whole TRP family, this new role of S6 may apply to further TRP channels.

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