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Shimizu T, Yanase N, Fujii T, Sakakibara H, Sakai H. Regulation of TRPV1 channel activities by intracellular ATP in the absence of capsaicin. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183782. [PMID: 34555418 DOI: 10.1016/j.bbamem.2021.183782] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 09/10/2021] [Accepted: 09/15/2021] [Indexed: 06/13/2023]
Abstract
Transient receptor potential vanilloid 1 (TRPV1) is a voltage-dependent non-selective cation channel activated by capsaicin, the main pungent ingredient of chili peppers, and noxious heat. Although TRPV1 channels produce outwardly rectifying currents even in the absence of capsaicin, little is known about the regulation mechanism of the TRPV1 currents. In the present study, we found that intracellular ATP regulates the basal activities of TRPV1 channels in a concentration-dependent manner. The ATP-dependent regulation of TRPV1 channels was mediated by phosphoinositides. Moreover, an increase in intracellular ATP concentration negatively shifted voltage-dependent activation of TRPV1 channels. These results suggest that the ATP-dependent production of phosphoinositides regulates the voltage-dependent gating of the basal TRPV1 channel activities in the absence of capsaicin.
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Affiliation(s)
- Takahiro Shimizu
- Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan.
| | - Nobuhiro Yanase
- Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
| | - Takuto Fujii
- Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
| | - Haruka Sakakibara
- Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
| | - Hideki Sakai
- Department of Pharmaceutical Physiology, Faculty of Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
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2
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Liu Y, Yang H, Fu Y, Pan Z, Qiu F, Xu Y, Yang X, Chen Q, Ma D, Liu Z. TRPV1 Antagonist Prevents Neonatal Sevoflurane-Induced Synaptic Abnormality and Cognitive Impairment in Mice Through Regulating the Src/Cofilin Signaling Pathway. Front Cell Dev Biol 2021; 9:684516. [PMID: 34307363 PMCID: PMC8293754 DOI: 10.3389/fcell.2021.684516] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/14/2021] [Indexed: 11/13/2022] Open
Abstract
Long-term neurodevelopmental disorders following neonatal anesthesia have been reported both in young animals and in children. The activation of transient receptor potential vanilloid 1 (TRPV1) channels in hippocampus adversely affects neurodevelopment. The current study explored the underlying mechanism of TRPV1 channels on long-lasting cognitive dysfunction induced by anesthetic exposure to the developing brain. we demonstrated that TRPV1 expression was increased after sevoflurane exposure both in vitro and in vivo. Sevoflurane exposure to hippocampal neurons decreased the synaptic density and the surface GluA1 expression, as well as increased co-localization of internalized AMPAR in early and recycling endosomes. Sevoflurane exposure to newborn mice impaired learning and memory in adulthood, and reduced AMPAR subunit GluA1, 2 and 3 expressions in the crude synaptosomal fractions from mouse hippocampus. The inhibition of TRPV1 reversed the phenotypic changes induced by sevoflurane. Moreover, sevoflurane exposure increased Src phosphorylation at tyrosine 416 site thereby reducing cofilin phosphorylation. TRPV1 blockade reversed these suppressive effects of sevoflurane. Our data suggested that TRPV1 antagonist may protect against synaptic damage and cognitive dysfunction induced by sevoflurane exposure during the brain developing stage.
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Affiliation(s)
- Yuqiang Liu
- Department of Anesthesiology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Han Yang
- Department of Anesthesiology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Yifei Fu
- Department of Anesthesiology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Zhenglong Pan
- Department of Anesthesiology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Fang Qiu
- Department of Anesthesiology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Yanwen Xu
- Shenzhen Key Laboratory of Neurosurgery, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
| | - Xinping Yang
- Department of Anesthesiology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Qian Chen
- Division of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, London, United Kingdom
| | - Daqing Ma
- Division of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, London, United Kingdom
| | - Zhiheng Liu
- Department of Anesthesiology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
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Ca 2+ Regulation of TRP Ion Channels. Int J Mol Sci 2018; 19:ijms19041256. [PMID: 29690581 PMCID: PMC5979445 DOI: 10.3390/ijms19041256] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 04/16/2018] [Accepted: 04/17/2018] [Indexed: 12/20/2022] Open
Abstract
Ca2+ signaling influences nearly every aspect of cellular life. Transient receptor potential (TRP) ion channels have emerged as cellular sensors for thermal, chemical and mechanical stimuli and are major contributors to Ca2+ signaling, playing an important role in diverse physiological and pathological processes. Notably, TRP ion channels are also one of the major downstream targets of Ca2+ signaling initiated either from TRP channels themselves or from various other sources, such as G-protein coupled receptors, giving rise to feedback regulation. TRP channels therefore function like integrators of Ca2+ signaling. A growing body of research has demonstrated different modes of Ca2+-dependent regulation of TRP ion channels and the underlying mechanisms. However, the precise actions of Ca2+ in the modulation of TRP ion channels remain elusive. Advances in Ca2+ regulation of TRP channels are critical to our understanding of the diversified functions of TRP channels and complex Ca2+ signaling.
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Zhuang J, Zhao L, Zang N, Xu F. Prenatal nicotinic exposure augments cardiorespiratory responses to activation of bronchopulmonary C-fibers. Am J Physiol Lung Cell Mol Physiol 2015; 308:L922-30. [PMID: 25747962 PMCID: PMC4421788 DOI: 10.1152/ajplung.00241.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 03/01/2015] [Indexed: 12/26/2022] Open
Abstract
Rat pups prenatally exposed to nicotine (PNE) present apneic (lethal ventilatory arrest) responses during severe hypoxia. To clarify whether these responses are of central origin, we tested PNE effects on ventilation and diaphragm electromyography (EMGdi) during hypoxia in conscious rat pups. PNE produced apnea (lethal ventilatory arrest) identical to EMGdi silencing during hypoxia, indicating a central origin of this apneic response. We further asked whether PNE would sensitize bronchopulmonary C-fibers (PCFs), a key player in generating central apnea, with increase of the density and transient receptor potential cation channel subfamily V member 1 (TRPV1) expression of C-fibers/neurons in the nodose/jugular (N/J) ganglia and neurotrophic factors in the airways and lungs. We compared 1) ventilatory and pulmonary C-neural responses to right atrial bolus injection of capsaicin (CAP, 0.5 μg/kg), 2) bronchial substance P-immunoreactive (SP-IR) fiber density, 3) gene and protein expressions of TRPV1 in the ganglia, and 4) nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) protein in bronchoalveolar lavage fluid (BALF) and TrkA and TrkB genes in the ganglia between control and PNE pups. PNE markedly strengthened the PCF-mediated apneic response to CAP via increasing pulmonary C-neural sensitivity. PNE also enhanced bronchial SP-IR fiber density and N/J ganglia neural TRPV1 expression associated with increased gene expression of TrkA in the N/G ganglia and decreased NGF and BDNF in BALF. Our results suggest that PNE enhances PCF sensitivity likely through increasing PCF density and TRPV1 expression via upregulation of neural TrkA and downregulation of pulmonary BDNF, which may contribute to the PNE-promoted central apnea (lethal ventilatory arrest) during hypoxia.
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Affiliation(s)
- Jianguo Zhuang
- Pathophysiology Program, Lovelace Respiratory Research Institute, Albuquerque, New Mexico
| | - Lei Zhao
- Pathophysiology Program, Lovelace Respiratory Research Institute, Albuquerque, New Mexico
| | - Na Zang
- Pathophysiology Program, Lovelace Respiratory Research Institute, Albuquerque, New Mexico
| | - Fadi Xu
- Pathophysiology Program, Lovelace Respiratory Research Institute, Albuquerque, New Mexico
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Trkulja CL, Jansson ET, Jardemark K, Orwar O. Probing structure and function of ion channels using limited proteolysis and microfluidics. J Am Chem Soc 2014; 136:14875-82. [PMID: 25254316 DOI: 10.1021/ja507285w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Even though gain, loss, or modulation of ion channel function is implicated in many diseases, both rare and common, the development of new pharmaceuticals targeting this class has been disappointing, where it has been a major problem to obtain correlated structural and functional information. Here, we present a microfluidic method in which the ion channel TRPV1, contained in proteoliposomes or in excised patches, was exposed to limited trypsin proteolysis. Cleaved-off peptides were identified by MS, and electrophysiological properties were recorded by patch clamp. Thus, the structure-function relationship was evaluated by correlating changes in function with removal of structural elements. Using this approach, we pinpointed regions of TRPV1 that affect channel properties upon their removal, causing changes in current amplitude, single-channel conductance, and EC50 value toward its agonist, capsaicin. We have provided a fast "shotgun" method for chemical truncation of a membrane protein, which allows for functional assessments of various peptide regions.
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Affiliation(s)
- Carolina L Trkulja
- Department of Chemical and Biological Engineering, Chalmers University of Technology , SE-412 96 Göteborg, Sweden
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Wilhelmsen K, Khakpour S, Tran A, Sheehan K, Schumacher M, Xu F, Hellman J. The endocannabinoid/endovanilloid N-arachidonoyl dopamine (NADA) and synthetic cannabinoid WIN55,212-2 abate the inflammatory activation of human endothelial cells. J Biol Chem 2014; 289:13079-100. [PMID: 24644287 DOI: 10.1074/jbc.m113.536953] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Although cannabinoids, such as Δ(9)-tetrahydrocannabinol, have been studied extensively for their psychoactive effects, it has become apparent that certain cannabinoids possess immunomodulatory activity. Endothelial cells (ECs) are centrally involved in the pathogenesis of organ injury in acute inflammatory disorders, such as sepsis, because they express cytokines and chemokines, which facilitate the trafficking of leukocytes to organs, and they modulate vascular barrier function. In this study, we find that primary human ECs from multiple organs express the cannabinoid receptors CB1R, GPR18, and GPR55, as well as the ion channel transient receptor potential cation channel vanilloid type 1. In contrast to leukocytes, CB2R is only minimally expressed in some EC populations. Furthermore, we show that ECs express all of the known endocannabinoid (eCB) metabolic enzymes. Examining a panel of cannabinoids, we demonstrate that the synthetic cannabinoid WIN55,212-2 and the eCB N-arachidonoyl dopamine (NADA), but neither anandamide nor 2-arachidonoylglycerol, reduce EC inflammatory responses induced by bacterial lipopeptide, LPS, and TNFα. We find that endothelial CB1R/CB2R are necessary for the effects of NADA, but not those of WIN55,212-2. Furthermore, transient receptor potential cation channel vanilloid type 1 appears to counter the anti-inflammatory properties of WIN55,212-2 and NADA, but conversely, in the absence of these cannabinoids, its inhibition exacerbates the inflammatory response in ECs activated with LPS. These data indicate that the eCB system can modulate inflammatory activation of the endothelium and may have important implications for a variety of acute inflammatory disorders that are characterized by EC activation.
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Nagy I, Friston D, Valente JS, Torres Perez JV, Andreou AP. Pharmacology of the capsaicin receptor, transient receptor potential vanilloid type-1 ion channel. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 2014; 68:39-76. [PMID: 24941664 DOI: 10.1007/978-3-0348-0828-6_2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The capsaicin receptor, transient receptor potential vanilloid type 1 ion channel (TRPV1), has been identified as a polymodal transducer molecule on a sub-set of primary sensory neurons which responds to various stimuli including noxious heat (> -42 degrees C), protons and vanilloids such as capsaicin, the hot ingredient of chilli peppers. Subsequently, TRPV1 has been found indispensable for the development of burning pain and reflex hyperactivity associated with inflammation of peripheral tissues and viscera, respectively. Therefore, TRPV1 is regarded as a major target for the development of novel agents for the control of pain and visceral hyperreflexia in inflammatory conditions. Initial efforts to introduce agents acting on TRPV1 into clinics have been hampered by unexpected side-effects due to wider than expected expression in various tissues, as well as by the complex pharmacology, of TRPV1. However, it is believed that better understanding of the pharmacological properties of TRPV1 and specific targeting of tissues may eventually lead to the development of clinically useful agents. In order to assist better understanding of TRPV1 pharmacology, here we are giving a comprehensive account on the activation and inactivation mechanisms and the structure-function relationship of TRPV1.
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Abstract
Nociception is the process whereby primary afferent nerve fibers of the somatosensory system detect noxious stimuli. Pungent irritants from pepper, mint, and mustard plants have served as powerful pharmacological tools for identifying molecules and mechanisms underlying this initial step of pain sensation. These natural products have revealed three members of the transient receptor potential (TRP) ion channel family--TRPV1, TRPM8, and TRPA1--as molecular detectors of thermal and chemical stimuli that activate sensory neurons to produce acute or persistent pain. Analysis of TRP channel function and expression has validated the existence of nociceptors as a specialized group of somatosensory neurons devoted to the detection of noxious stimuli. These studies are also providing insight into the coding logic of nociception and how specification of nociceptor subtypes underlies behavioral discrimination of noxious thermal, chemical, and mechanical stimuli. Biophysical and pharmacological characterization of these channels has provided the intellectual and technical foundation for developing new classes of analgesic drugs.
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Affiliation(s)
- David Julius
- Department of Physiology, University of California, San Francisco, California 94158;
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9
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Lukacs V, Rives JM, Sun X, Zakharian E, Rohacs T. Promiscuous activation of transient receptor potential vanilloid 1 (TRPV1) channels by negatively charged intracellular lipids: the key role of endogenous phosphoinositides in maintaining channel activity. J Biol Chem 2013; 288:35003-13. [PMID: 24158445 PMCID: PMC3853253 DOI: 10.1074/jbc.m113.520288] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 10/18/2013] [Indexed: 11/06/2022] Open
Abstract
The regulation of the heat- and capsaicin-activated transient receptor potential vanilloid 1 (TRPV1) channels by phosphoinositides is controversial. Data in cellular systems support the dependence of TRPV1 activity on phosphoinositides. The purified TRPV1, however, was recently shown to be fully functional in artificial liposomes in the absence of phosphoinositides. Here, we show that several other negatively charged phospholipids, including phosphatidylglycerol, can also support TRPV1 activity in excised patches at high concentrations. When we incorporated TRPV1 into planar lipid bilayers consisting of neutral lipids, capsaicin-induced activity depended on phosphatidylinositol 4,5-bisphosphate. We also found that TRPV1 activity in excised patches ran down and that MgATP reactivated the channel. Inhibition of phosphatidylinositol 4-kinases or enzymatic removal of phosphatidylinositol abolished this effect of MgATP, suggesting that it activated TRPV1 by generating endogenous phosphoinositides. We conclude that endogenous phosphoinositides are positive cofactors for TRPV1 activity. Our data highlight the importance of specificity in lipid regulation of ion channels and may reconcile discordant data obtained in various experimental settings.
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Affiliation(s)
- Viktor Lukacs
- From the Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, New Jersey 07103 and
| | - Jan-Michael Rives
- From the Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, New Jersey 07103 and
| | - Xiaohui Sun
- Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine, Peoria, Illinois 61605
| | - Eleonora Zakharian
- Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine, Peoria, Illinois 61605
| | - Tibor Rohacs
- From the Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, New Jersey 07103 and
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10
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Winter Z, Buhala A, Ötvös F, Jósvay K, Vizler C, Dombi G, Szakonyi G, Oláh Z. Functionally important amino acid residues in the transient receptor potential vanilloid 1 (TRPV1) ion channel--an overview of the current mutational data. Mol Pain 2013; 9:30. [PMID: 23800232 PMCID: PMC3707783 DOI: 10.1186/1744-8069-9-30] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 06/17/2013] [Indexed: 12/30/2022] Open
Abstract
This review aims to create an overview of the currently available results of site-directed mutagenesis studies on transient receptor potential vanilloid type 1 (TRPV1) receptor. Systematization of the vast number of data on the functionally important amino acid mutations of TRPV1 may provide a clearer picture of this field, and may promote a better understanding of the relationship between the structure and function of TRPV1. The review summarizes information on 112 unique mutated sites along the TRPV1, exchanged to multiple different residues in many cases. These mutations influence the effect or binding of different agonists, antagonists, and channel blockers, alter the responsiveness to heat, acid, and voltage dependence, affect the channel pore characteristics, and influence the regulation of the receptor function by phosphorylation, glycosylation, calmodulin, PIP2, ATP, and lipid binding. The main goal of this paper is to publish the above mentioned data in a form that facilitates in silico molecular modelling of the receptor by promoting easier establishment of boundary conditions. The better understanding of the structure-function relationship of TRPV1 may promote discovery of new, promising, more effective and safe drugs for treatment of neurogenic inflammation and pain-related diseases and may offer new opportunities for therapeutic interventions.
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Affiliation(s)
- Zoltán Winter
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary.
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11
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Tsuji F, Aono H. Role of transient receptor potential vanilloid 1 in inflammation and autoimmune diseases. Pharmaceuticals (Basel) 2012; 5:837-52. [PMID: 24280677 PMCID: PMC3763671 DOI: 10.3390/ph5080837] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 08/02/2012] [Accepted: 08/15/2012] [Indexed: 12/21/2022] Open
Abstract
Transient receptor potential vanilloid 1 (TRPV1), a non-selective cation channel, is a receptor activated by high temperatures and chemical agonists such as the vanilloids and protons. Because of these properties, TRPV1 has emerged as a polymodal nocisensor of nociceptive afferent neurons. TRPV1 is thought to be a central transducer of hyperalgesia and a prime target for controlling pain pharmacologically because it is a point where many proalgesic pathways converge and it is upregulated and sensitized by inflammation and injury. However, whether TRPV1 agonists promote or inhibit inflammation remains unclear. We recently demonstrated that SA13353 (1-[2-(1-adamantyl)ethyl]-1-pentyl-3-[3-(4-pyridyl)propyl]urea), a novel TRPV1 agonist, inhibits tumor necrosis factor-a production by the activation of capsaicin-sensitive afferent neurons and reduces the severity of symptoms in kidney injury, lung inflammation, arthritis, and encephalomyelitis. These results suggest that TRPV1 agonists may act as anti-inflammatories in certain inflammatory and autoimmune conditions in vivo. Given the potential deleterious effects of inhibiting the population of channels with a protective function, caution should be taken in the use of potent TRPV1 antagonists as a general strategy to treat inflammation. Further studies are required to clarify the role of TRPV1 and neuropeptides, which are released because of TRPV1 activation in inflammation and autoimmune diseases.
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Affiliation(s)
- Fumio Tsuji
- Research and Development Center, Santen Pharmaceutical Co., Ltd., 8916-16 Takayama-cho, Ikoma, Nara 630-0101, Japan.
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12
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Premkumar LS, Abooj M. TRP channels and analgesia. Life Sci 2012; 92:415-24. [PMID: 22910182 DOI: 10.1016/j.lfs.2012.08.010] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 07/25/2012] [Accepted: 08/02/2012] [Indexed: 01/07/2023]
Abstract
Since cloning and characterizing the first nociceptive ion channel Transient Receptor Potential (TRP) Vanilloid 1 (TRPV1), other TRP channels involved in nociception have been cloned and characterized, which include TRP Vanilloid 2 (TRPV2), TRP Vanilloid 3 (TRPV3), TRP Vanilloid 4 (TRPV4), TRP Ankyrin 1 (TRPA1) and TRP Melastatin 8 (TRPM8), more recently TRP Canonical 1, 5, 6 (TRPC1, 5, 6), TRP Melastatin 2 (TRPM2) and TRP Melastatin 3 (TRPM3). These channels are predominantly expressed in C and Aδ nociceptors and transmit noxious thermal, mechanical and chemical sensitivities. TRP channels are modulated by pro-inflammatory mediators, neuropeptides and cytokines. Significant advances have been made targeting these receptors either by antagonists or agonists to treat painful conditions. In this review, we will discuss TRP channels as targets for next generation analgesics and the side effects that may ensue as a result of blocking/activating these receptors, because they are also involved in physiological functions such as release of vasoactive neuropeptides and regulation of vascular tone, maintenance of the body temperature, gastrointestinal motility, urinary bladder control, etc.
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Affiliation(s)
- Louis S Premkumar
- Department of Pharmacology, Southern Illinois University School of Medicine Springfield, IL 62702, USA.
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13
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Kukday SS, Manandhar SP, Ludley MC, Burriss ME, Alper BJ, Schmidt WK. Cell-permeable, small-molecule activators of the insulin-degrading enzyme. ACTA ACUST UNITED AC 2012; 17:1348-61. [PMID: 22740246 DOI: 10.1177/1087057112451921] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The insulin-degrading enzyme (IDE) cleaves numerous small peptides, including biologically active hormones and disease-related peptides. The propensity of IDE to degrade neurotoxic Aβ peptides marks IDE as a potential therapeutic target for Alzheimer disease. Using a synthetic reporter based on the yeast a-factor mating pheromone precursor, which is cleaved by multiple IDE orthologs, we identified seven small molecules that stimulate rat IDE activity in vitro. Half-maximal activation of IDE by the compounds is observed in vitro in the range of 43 to 198 µM. All compounds decrease the K(m) of IDE. Four compounds activate IDE in the presence of the competing substrate insulin, which disproportionately inhibits IDE activity. Two compounds stimulate rat IDE activity in a cell-based assay, indicating that they are cell permeable. The compounds demonstrate specificity for rat IDE since they do not enhance the activities of IDE orthologs, including human IDE, and they appear specific for a-factor-based reporters since they do not enhance rat IDE-mediated cleavage of Aβ-based reporters. Our results suggest that IDE activators function in the context of specific enzyme-substrate pairs, indicating that the choice of substrate must be considered in addition to target validation in IDE activator screens.
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14
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Aguado-Llera D, Bacarizo J, Gregorio-Teruel L, Taberner FJ, Cámara-Artigas A, Neira JL. Biophysical characterization of the isolated C-terminal region of the transient receptor potential vanilloid 1. FEBS Lett 2012; 586:1154-9. [DOI: 10.1016/j.febslet.2012.03.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 03/14/2012] [Accepted: 03/14/2012] [Indexed: 11/28/2022]
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15
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Chung S, Kim YH, Koh JY, Nam TS, Ahn DS. Intracellular acidification evoked by moderate extracellular acidosis attenuates transient receptor potential V1 (TRPV1) channel activity in rat dorsal root ganglion neurons. Exp Physiol 2011; 96:1270-81. [PMID: 21930676 DOI: 10.1113/expphysiol.2011.059444] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Transient receptor potential V1 (TRPV1) has been suggested to play an important role in detecting decreases in extracellular pH (pH(o)). Results from recent in vivo studies, however, have suggested that TRPV1 channels play less of a role in sensing a moderately acidic pH(o) (6.0 < pH < 7.0) than predicted from the in vitro experiments. A clear explanation for this discrepancy between the in vitro and in vivo data has not yet been provided. We report here that intracellular acidification induced by a moderately low pH(o) (6.4) almost completely inhibited the effect of extracellular acidosis on TRPV1 activity. In our experiments, sodium acetate (20 mm), which was used to induce intracellular acidosis, attenuated the capsaicin-evoked TRPV1 current (I(CAP)) in a reversible manner in whole-cell patch-clamp mode and shifted the concentration-response curve to the right. Likewise, the concentration-response curve was significantly shifted to the right by lowering the pH of the pipette solution from 7.2 to 6.5. In addition, application of an acidic bath solution (pH 6.4) to the intracellular side also significantly suppressed I(CAP) in inside-out patch mode. In cell-attached patch mode, the single-channel activity of i(CAP) was significantly attenuated by intracellular acidosis that was induced by a decrease in pH(o) (6.4). These results suggested that intracellular acidification induced by a low pH(o) inhibited TRPV1 activity. When studied in perforated patch mode or by acidifying the intracellular pipette solution, potentiation or activation of TRPV1 by extracellular acidosis (pH 6.4) at 37 °C was almost completely inhibited. Likewise, enhancement of neuronal excitability by a moderately acidic pH(o) (6.4) at a physiological temperature (37 °C) was attenuated by lowering the pH of the pipette solution to 6.5 or using perforated patch mode. Taken together, these results suggest that extracellular acidosis of moderate intensity may not significantly modulate TRPV1 activity in physiological conditions at which intracellular pH can be readily affected by pH(o), and this phenomenon is due to attenuation of TRPV1 channel activity by low-pH(o)-induced intracellular acidification.
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Affiliation(s)
- Seungsoo Chung
- Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seodaemun-gu, Seoul 120-752, Republic of Korea
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16
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Wang S, Chuang HH. C-terminal dimerization activates the nociceptive transduction channel transient receptor potential vanilloid 1. J Biol Chem 2011; 286:40601-7. [PMID: 21926175 DOI: 10.1074/jbc.m111.256669] [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
Covalent modification of the specific cysteine residue(s) by oxidative stress robustly potentiates transient receptor potential vanilloid 1 (TRPV1) and sensitizes nociception. Here we provide biochemical evidence of dimerization of TRPV1 subunits upon exposure to phenylarsine oxide and hydrogen peroxide (H(2)O(2)), two chemical surrogates of oxidative stress. A disulfide bond formed between apposing cysteines ligates two C termini, serving as the structural basis of channel sensitization by oxidative covalent C-terminal modification. Systematic cysteine scanning of the C terminus of a cysteineless TRPV1 channel revealed a critical region within which any cysteine introduced phenylarsine oxide activation to mutant TRPV1. Oxidative sensitization persisted even when this region is substituted with a random peptide linker containing a single cysteine. So did insertion of this region to TRPV3, a homolog lacking the corresponding region and resistant to oxidative challenge. These results suggest that the non-conserved linker in the TRPV1 C terminus senses environmental oxidative stress and adjusts channel activity during cumulative oxidative damage by lowering the activation threshold of gating elements shared by TRPV channels.
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Affiliation(s)
- Shu Wang
- Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853, USA
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17
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Zakharian E, Cao C, Rohacs T. Intracellular ATP supports TRPV6 activity via lipid kinases and the generation of PtdIns(4,5) P₂. FASEB J 2011; 25:3915-28. [PMID: 21810903 DOI: 10.1096/fj.11-184630] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Transient receptor potential vanilloid 6 (TRPV6) channels play an important role in Ca(2+) absorption in the intestines. Both phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] and cytoplasmic ATP have been proposed to be important for maintaining TRPV6 activity. To evaluate whether PtdIns(4,5)P(2) and ATP affect channel activity directly or indirectly, we have used a dual approach, examining channel activity in excised patches and planar lipid bilayers. In excised inside-out patch-clamp measurements, ATP reactivated the human TRPV6 channels after current rundown only in the presence of Mg(2+). The effect of MgATP was inhibited by 3 structurally different compounds that inhibit type III phosphatidylinositol 4-kinases (PI4Ks). PtdIns(4,5)P(2) also activated TRPV6 in excised patches, while its precursor PtdIns(4)P had only minimal effect. These data demonstrate that MgATP provides substrate for lipid kinases, allowing the resynthesis of PtdIns(4,5)P(2). To determine whether PtdIns(4,5)P(2) is a direct activator of TRPV6, we purified and reconstituted the channel protein in planar lipid bilayers. The reconstituted channel showed high activity in the presence of PtdIns(4,5)P(2), while PtdIns(4)P induced only minimal activity. Our data establish PtdIns(4,5)P(2) as a direct activator of TRPV6 and demonstrate that intracellular ATP regulates the channel indirectly as a substrate for type III PI4Ks.
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Affiliation(s)
- Eleonora Zakharian
- University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103, USA
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18
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Székely JI, Pataki A. Recent findings on the pathogenesis of bronchial asthma. Part I. Asthma as a neurohumoral disorder, a pathological vago-vagal axon reflex. ACTA ACUST UNITED AC 2009; 96:1-17. [PMID: 19264038 DOI: 10.1556/aphysiol.96.2009.1.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The novel data on the pathogenesis of asthma are summarized in this three-part review. Its immunological background is well established but it is more than an immunological disorder. Multiple lines indicate that both peripheral and central neural mechanisms are also involved in the pathogenesis of asthma. In the present first part of the review asthma is described as vago-vagal axon reflex brought about by multiple positive feed-back mechanisms, receptor upregulation, wind-up, phenotypic switch and formation of a pathological conditioned reflex. In the coming second part the main dispositional (mostly hormonal) and external contributing factors are reviewed, while the third part deals with the role of inheritance, i.e., with gene alleles leading to enhanced production of mediators of asthma.
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Affiliation(s)
- J I Székely
- Department of Human Physiology, Medical School, Semmelweis University, Ulloi út 78/a, H-1085 Budapest, Hungary.
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19
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Molecular modeling of the full-length human TRPV1 channel in closed and desensitized states. J Membr Biol 2008; 223:161-72. [PMID: 18791833 DOI: 10.1007/s00232-008-9123-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Accepted: 08/07/2008] [Indexed: 10/21/2022]
Abstract
The transient receptor potential vanilloid subtype 1 (TRPV1) is a member of the TRP family gated by vanilloids, heat, and protons. Structurally, TRPV1 subunits have a modular architecture underlying different functionalities, namely stimuli recognition, channel gating, ion selectivity, subunit oligomerization, and regulation by intracellular signaling molecules. Considering modular organization and recent structural information in the ion channel field, we have modeled a full-length TRPV1 by assembly of its major modules: the cytosolic N-terminal, C-terminal, and membrane-spanning region. For N-terminal, we used the ankyrin repeat structure fused with the N-end segment. The membrane domain was modeled with the structure of the eukaryotic, voltage-gated Kv1.2 K+ channel. The C-terminus was cast using the coordinates of HCN channels. The extensive structure-function data available for TRPV1 was used to validate the models in terms of the location of molecular determinants of function in the structure. Additionally, the current information allowed the modeling of the vanilloid receptor in the closed and desensitized states. The closed state shows the N-terminal module highly exposed and accessible to adenosine triphosphate and the C-terminal accessible to phosphoinositides. In contrast, the desensitized state depicts the N-terminal and C-terminal modules close together, compatible with an interaction mediated by Ca2+ -calmodulin complex. These models identify potential previously unrecognized intra- and interdomain interactions that may play an important functional role. Although the molecular models should be taken with caution, they provide a helpful tool that yields testable hypothesis that further our understanding on ion channels work in terms of underlying protein structure.
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20
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Rohacs T, Thyagarajan B, Lukacs V. Phospholipase C mediated modulation of TRPV1 channels. Mol Neurobiol 2008; 37:153-63. [PMID: 18528787 DOI: 10.1007/s12035-008-8027-y] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Accepted: 05/13/2008] [Indexed: 12/31/2022]
Abstract
The transient receptor potential vanilloid type 1 (TRPV1) channels are involved in both thermosensation and nociception. They are activated by heat, protons, and capsaicin and modulated by a plethora of other agents. This review will focus on the consequences of phospholipase C (PLC) activation, with special emphasis on the effects of phosphatidylinositol 4,5-bisphosphate (PIP2) on these channels. Two opposing effects of PIP2 have been reported on TRPV1. PIP2 has been proposed to inhibit TRPV1, and relief from this inhibition was suggested to be involved in sensitization of these channels by pro-inflammatory agents. In excised patches, however, PIP2 was shown to activate TRPV1. Calcium flowing through TRPV1 activates PLC and the resulting depletion of PIP2 was proposed to play a role in capsaicin-induced desensitization of these channels. We will describe the data indicating involvement of PLC and PIP2 in sensitization and desensitization of TRPV1 and will also discuss other pathways potentially contributing to these two phenomena. We attempt to resolve the seemingly contradictory data by proposing that PIP2 can both activate and inhibit TRPV1 depending on the experimental conditions, more specifically on the level of stimulation of these channels. Finally, we also discuss data in the literature indicating that other TRP channels, TRPA1 and some members of the TRPC subfamily, may also be under a similar dual control by PIP2.
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Affiliation(s)
- Tibor Rohacs
- Department of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, Newark, NJ, USA.
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21
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Pabbidi RM, Yu SQ, Peng S, Khardori R, Pauza ME, Premkumar LS. Influence of TRPV1 on diabetes-induced alterations in thermal pain sensitivity. Mol Pain 2008; 4:9. [PMID: 18312687 PMCID: PMC2275252 DOI: 10.1186/1744-8069-4-9] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Accepted: 03/01/2008] [Indexed: 12/24/2022] Open
Abstract
A common complication associated with diabetes is painful or painless diabetic peripheral neuropathy (DPN). The mechanisms and determinants responsible for these peripheral neuropathies are poorly understood. Using both streptozotocin (STZ)-induced and transgene-mediated murine models of type 1 diabetes (T1D), we demonstrate that Transient Receptor Potential Vanilloid 1 (TRPV1) expression varies with the neuropathic phenotype. We have found that both STZ- and transgene-mediated T1D are associated with two distinct phases of thermal pain sensitivity that parallel changes in TRPV1 as determined by paw withdrawal latency (PWL). An early phase of hyperalgesia and a late phase of hypoalgesia are evident. TRPV1-mediated whole cell currents are larger and smaller in dorsal root ganglion (DRG) neurons collected from hyperalgesic and hypoalgesic mice. Resiniferatoxin (RTX) binding, a measure of TRPV1 expression is increased and decreased in DRG and paw skin of hyperalgesic and hypoalgesic mice, respectively. Immunohistochemical labeling of spinal cord lamina I and II, dorsal root ganglion (DRG), and paw skin from hyperalgesic and hypoalgesic mice reveal increased and decreased TRPV1 expression, respectively. A role for TRPV1 in thermal DPN is further suggested by the failure of STZ treatment to influence thermal nociception in TRPV1 deficient mice. These findings demonstrate that altered TRPV1 expression and function contribute to diabetes-induced changes in thermal perception.
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Affiliation(s)
- Reddy M Pabbidi
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
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22
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Gharat L, Szallasi A. Medicinal chemistry of the vanilloid (Capsaicin) TRPV1 receptor: current knowledge and future perspectives. Drug Dev Res 2008. [DOI: 10.1002/ddr.20218] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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23
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Abstract
Many plant and animal toxins cause aversive behaviors in animals due to their pungent or unpleasant taste or because they cause other unpleasant senstations like pain. This article reviews the current state of knowledge of toxins that act at the TRPV1 ion channel, which is expressed in primary sensory neurons, is activated by multiple painful stimuli and is thought to be a key pain sensor and integrator. The recent finding that painful peptide "vanillotoxin" components of tarantula toxin activate the TRPV1 ion channel to cause pain led us to survey what is known about toxins that act at this receptor. Toxins from plants, spiders and jellyfish are considered. Where possible, structural information about sites of interaction is considered in relation to toxin-binding sites on the Kv ion channel, for which more structural information exists. We discuss a developing model where toxin agonists such as resiniferatoxin and vanillotoxins are proposed to interact with a region of TRPV1 that is homologous to the "voltage sensor" in the Kv1.2 ion channel, to open the channel and activate primary sensory nerves, causing pain.
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24
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Lishko PV, Procko E, Jin X, Phelps CB, Gaudet R. The ankyrin repeats of TRPV1 bind multiple ligands and modulate channel sensitivity. Neuron 2007; 54:905-18. [PMID: 17582331 DOI: 10.1016/j.neuron.2007.05.027] [Citation(s) in RCA: 311] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Revised: 05/08/2007] [Accepted: 05/30/2007] [Indexed: 10/23/2022]
Abstract
TRPV1 plays a key role in nociception, as it is activated by heat, low pH, and ligands such as capsaicin, leading to a burning pain sensation. We describe the structure of the cytosolic ankyrin repeat domain (ARD) of TRPV1 and identify a multiligand-binding site important in regulating channel sensitivity within the TRPV1-ARD. The structure reveals a binding site that accommodates triphosphate nucleotides such as ATP, and biochemical studies demonstrate that calmodulin binds the same site. Electrophysiology experiments show that either ATP or PIP2 prevent desensitization to repeated applications of capsaicin, i.e., tachyphylaxis, while calmodulin plays an opposing role and is necessary for tachyphylaxis. Mutations in the TRPV1-ARD binding site eliminate tachyphylaxis. We present a model for the calcium-dependent regulation of TRPV1 via competitive interactions of ATP and calmodulin at the TRPV1-ARD-binding site and discuss its relationship to the C-terminal region previously implicated in interactions with PIP2 and calmodulin.
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Affiliation(s)
- Polina V Lishko
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA
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25
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Grycova L, Lansky Z, Friedlova E, Vlachova V, Kubala M, Obsilova V, Obsil T, Teisinger J. ATP binding site on the C-terminus of the vanilloid receptor. Arch Biochem Biophys 2007; 465:389-98. [PMID: 17706589 DOI: 10.1016/j.abb.2007.06.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 06/29/2007] [Accepted: 06/30/2007] [Indexed: 10/23/2022]
Abstract
Transient receptor potential channel vanilloid receptor subunit 1 (TRPV1) is a thermosensitive cation channel activated by noxious heat as well as a wide range of chemical stimuli. Although ATP by itself does not directly activate TRPV1, it was shown that intracellular ATP increases its activity by directly interacting with the Walker A motif residing on the C-terminus of TRPV1. In order to identify the amino acid residues that are essential for the binding of ATP to the TRPV1 channel, we performed the following point mutations of the Walker A motif: P732A, D733A, G734A, K735A, D736A, and D737A. Employing bulk fluorescence measurements, namely a TNP-ATP competition assay and FITC labelling and quenching experiments, we identified the key role of the K735 residue in the binding of the nucleotide. Experimental data was interpreted according to our molecular modelling simulations.
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Affiliation(s)
- Lenka Grycova
- Institute of Physiology, Academy of Sciences of the Czech Republic, Vídenská 1083, 14220 Prague, Czech Republic
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26
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Lyall V, Phan THT, Mummalaneni S, Mansouri M, Heck GL, Kobal G, DeSimone JA. Effect of nicotine on chorda tympani responses to salty and sour stimuli. J Neurophysiol 2007; 98:1662-74. [PMID: 17615133 DOI: 10.1152/jn.00366.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The effect of nicotine on the benzamil (Bz)-insensitive (transient receptor potential vanilloid-1 variant cation channel, TRPV1t) and the Bz-sensitive (epithelial Na(+) channel, ENaC) salt taste receptors and sour taste was investigated by monitoring intracellular Na(+) and H(+) activity (pH(i)) in polarized fungiform taste receptor cells (TRCs) and the chorda tympani (CT) nerve responses to NaCl, KCl, and HCl. CT responses in Sprague-Dawley rats and both wildtype and TRPV1 knockout (KO) mice were recorded in the presence and absence of agonists [resiniferatoxin (RTX) and elevated temperature] and an antagonist (SB-366791) of TRPV1t, the ENaC blocker (Bz), and varying apical pH (pH(o)). At concentrations <0.015 M, nicotine enhanced and at >0.015 M, it inhibited CT responses to KCl and NaCl. Nicotine produced maximum enhancement in the Bz-insensitive NaCl CT response at pH(o) between 6 and 7. RTX and elevated temperature increased the sensitivity of the CT response to nicotine in salt-containing media, and SB-366791 inhibited these effects. TRPV1 KO mice demonstrated no Bz-insensitive CT response to NaCl and no sensitivity to nicotine, RTX, and elevated temperature. We conclude that nicotine modulates salt responses by direct interaction with TRPV1t. At pH(o) >8, the apical membrane permeability of nicotine was increased significantly, resulting in increase in TRC pH(i) and volume, activation of ENaC, and enhancement of the Bz-sensitive NaCl CT response. At pH(o) >8, nicotine also inhibited the phasic component of the HCl CT response. We conclude that the effects of nicotine on ENaC and the phasic HCl CT response arise from increases in TRC pH(i) and volume.
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Affiliation(s)
- Vijay Lyall
- Department of Physiology, Virginia Commonwealth University, Sanger Hall 3010, 1101 E. Marshall St., Richmond, VA 23298-0551, USA.
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27
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Abstract
The capsaicin receptor, TRPV1, contributes to thermal and chemical sensitivity of primary afferent neurons of the pain pathway, but many aspects of its regulation remain elusive. In this issue of Neuron, Lishko et al. describe a high-resolution structure of a TRPV1 domain, providing insight into the molecular basis of channel modulation while revealing new functions for a widely expressed protein interaction fold.
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Affiliation(s)
- Benjamin R Myers
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94143, USA.
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28
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Wynn G, Burnstock G. Adenosine 5'-triphosphate and its relationship with other mediators that activate pelvic nerve afferent neurons in the rat colorectum. Purinergic Signal 2006; 2:517-26. [PMID: 18404489 PMCID: PMC2104004 DOI: 10.1007/s11302-005-5305-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Revised: 11/17/2005] [Accepted: 11/18/2005] [Indexed: 11/26/2022] Open
Abstract
Evidence of a role for purinergic signalling in visceral afferents involving P2X2, P2X3 and P2Y1 receptors exists, which appears to be important during inflammation. This study aimed to evaluate the degree of interaction between adenosine 5′-triphosphate (ATP) and other mediators that activate sensory nerves in the colorectum. Recordings from pelvic nerve afferents were made during application of agents to the in-vitro colorectal preparation. Analysis allowed calculation of single unit activity. When applied individually, bradykinin (78%) and 5-hydoxytryptamine (77%) activated the greatest number of neurons, followed by substance P, protons, ATP and capsaicin. Prostaglandin E2 stimulated the least number (54%) and had a longer latency. Seventy-seven percent of all units studied either responded to both ATP and capsaicin or to neither, giving the greatest degree of activity correlation. Five percent of units were activated by all seven agents and no units were activated by a single agent alone. 5-hydroxytryptamine, capsaicin and protons, when co-applied with ATP, increased pelvic nerve activity to a greater degree than the sum of the individual responses. It is concluded that ATP activates pelvic nerve afferents and acts synergistically with protons, capsaicin and 5-hydroxytryptamine. The pattern of neuronal activation suggests that visceral afferents are polymodal but the receptor expression on their terminals is variable.
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Affiliation(s)
- Gregory Wynn
- Autonomic Neuroscience Centre, Royal Free and University College School of Medicine, Rowland Hill Street, London, NW3 2PF UK
| | - Geoffrey Burnstock
- Autonomic Neuroscience Centre, Royal Free and University College School of Medicine, Rowland Hill Street, London, NW3 2PF UK
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29
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Barsanti C, Pellegrini M, Pellegrino M. Regulation of the mechanosensitive cation channels by ATP and cAMP in leech neurons. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:666-72. [PMID: 16725106 DOI: 10.1016/j.bbamem.2006.03.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Revised: 03/08/2006] [Accepted: 03/13/2006] [Indexed: 10/24/2022]
Abstract
Single-channel recordings were used to study the modulation of stretch-activated channels (SACs) by intracellular adenosine nucleotides in identified leech neurons. These channels exhibited two activity modes, spike-like (SL) and multiconductance (MC), displaying different polymodal activation. In the absence of mechanical stimulation, internal perfusion of excised patches with ATP induced robust and reversible activation of the MC but not of the SL mode. The ATP effect on channel activity was dose-dependent within a range of 1 microM-1 mM and was induced at different values of intracellular pH and Ca2+. The non-hydrolyzable ATP analog AMP-PNP, ATP without Mg2+ or ADP also effectively enhanced MC activity. Adenosine mimicked the effect of its nucleotides. At negative membrane potentials, both ATP and adenosine activated the channel. Moreover, ATP but not adenosine induced a flickering block. Addition of cAMP during maximal ATP activation completely and reversibly inhibited the channel, with activation and deactivation times of minutes. However, cAMP alone only induced a weak and rapid channel activation, without inhibitory effects. The expression of these channels in the growth cones of leech neurons, their permeability to Ca2+ and their sensitivity to intracellular cAMP are consistent with a role in the Ca2+ oscillations associated with cell growth.
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Affiliation(s)
- Cristina Barsanti
- Dipartimento di Fisiologia e Biochimica G. Moruzzi, Università di Pisa, Via S. Zeno 31, 56127, Pisa, Italy
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30
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Nagy I, Sántha P, Jancsó G, Urbán L. The role of the vanilloid (capsaicin) receptor (TRPV1) in physiology and pathology. Eur J Pharmacol 2005; 500:351-69. [PMID: 15464045 DOI: 10.1016/j.ejphar.2004.07.037] [Citation(s) in RCA: 198] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2004] [Indexed: 02/06/2023]
Abstract
The cloning of the vanilloid receptor 1 opened a floodgate for discoveries regarding the function of this complex molecule. It has been found that, in addition to heat, protons and vanilloids, this receptor also responds to various endogenous ligands. Furthermore, it has been also emerged that, through associations with other molecules, the vanilloid receptor 1 plays an important role in the integration of various stimuli and modulation of cellular excitability. Although, originally, the vanilloid receptor 1 was associated with nociceptive primary afferent fibres, it has been gradually revealed that it is broadly expressed in the brain, epidermis and visceral cells. The expression pattern of the vanilloid receptor 1 indicates that it could be involved in various physiological functions and in the pathomechanisms of diverse diseases. Here, we summarise the molecular, pharmacological and physiological characteristics, and putative functions, of the vanilloid receptor 1, and discuss the therapeutic potential of this molecule.
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Affiliation(s)
- István Nagy
- Department of Anaesthetics and Intensive Care, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, United Kingdom.
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31
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Holzer P. TRPV1 and the gut: from a tasty receptor for a painful vanilloid to a key player in hyperalgesia. Eur J Pharmacol 2004; 500:231-41. [PMID: 15464036 DOI: 10.1016/j.ejphar.2004.07.028] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2004] [Indexed: 12/26/2022]
Abstract
Capsaicin, the pungent ingredient in red pepper, has been used since ancient times as a spice, despite the burning sensation associated with its intake. More than 50 years ago, Nikolaus Jancso discovered that capsaicin can selectively stimulate nociceptive primary afferent neurons. The ensuing research established that the neuropharmacological properties of capsaicin are due to its activation of the transient receptor potential ion channel of the vanilloid type 1 (TRPV1). Expressed by primary afferent neurons innervating the gut and other organs, TRPV1 is gated not only by vanilloids such as capsaicin, but also by noxious heat, acidosis and intracellular lipid mediators such as anandamide and lipoxygenase products. Importantly, TRPV1 can be sensitized by acidosis and activation of various pro-algesic pathways. Upregulation of TRPV1 in inflammatory bowel disease and the beneficial effect of TRPV1 downregulation in functional dyspepsia and irritable bladder make this polymodal nociceptor an attractive target of novel therapies for chronic abdominal pain.
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Affiliation(s)
- Peter Holzer
- Department of Experimental and Clinical Pharmacology, Medical University of Graz, Universitätsplatz 4, A-8010 Graz, Austria.
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33
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Liu B, Ma W, Ryu S, Qin F. Inhibitory modulation of distal C-terminal on protein kinase C-dependent phospho-regulation of rat TRPV1 receptors. J Physiol 2004; 560:627-38. [PMID: 15375192 PMCID: PMC1665281 DOI: 10.1113/jphysiol.2004.069054] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The vanilloid receptor TRPV1, previously known as VR1, has been implicated in pain sensation under both physiological and pathological conditions. The channel is highly expressed in sensory ganglion neurones and is activated by a range of noxious stimuli including irritant chemicals, acids and heat. In order to understand the structural basis underlying this polymodal activation and the regulation by intracellular signalling pathways, we have investigated the functional roles of the cytoplasmic C-terminal of rat TRPV1. A mutant with the maximal truncation of the distal C-terminal encompassing the last 88 residues was constructed. Of interest, this mutant exhibited a Ca(2+)-dependent functional loss; it was irresponsive to capsaicin in the presence of extracellular Ca(2+), but fully functional otherwise. Further studies of this construct revealed that extracellular Ca(2+) alone could activate the channel, and that the activation required protein kinase C (PKC) phosphorylation at S502, an event that was up-regulated by external Ca(2+) entry. We compared the truncation mutant with wild-type TRPV1 and demonstrated that it had a significantly increased sensitivity to PKC phosphorylation. These results suggest the distal C-terminal of TRPV1 can inhibit phosphorylation-induced potentiation of the wild-type channel. They also call into question some established functions of the distal C-terminal of TRPV1, including its roles in agonist binding and functional desensitization. We suggest that the functional loss of the truncation mutant, in the presence of extracellular Ca(2+), was not due to disruption of agonist binding or gating, but rather to desensitization promoted by unstimulated extracellular Ca(2+) entry.
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Affiliation(s)
- Beiying Liu
- Department of Physiology and Biophysical Sciences, State University of New York at Buffalo, NY 14214, USA
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34
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Abstract
Temperature affects functions of all ion channels, but few of them can be gated directly. The vanilloid receptor VR1 provides one exception. As a pain receptor, it is activated by heat >42 degrees C in addition to other noxious stimuli, e.g. acids and vanilloids. Although it is understood how ligand- and voltage-gated channels might detect their stimuli, little is known on how heat could be sensed and activate a channel. In this study, we characterized the heat-induced single-channel activity of VR1, in an attempt to localize the temperature-dependent components involved in the activation of the channel. At <42 degrees C, openings were few and brief. Raising the ambient temperature rapidly increased the frequency of openings. Despite the large temperature coefficient of the apparent activity (Q(10) approximately 27), the unitary current, the open dwell-times, and the intraburst closures were all only weakly temperature dependent (Q(10) < 2). Instead, heat had a localized effect on the reduction of long closures between bursts (Q(10) approximately 7) and the elongation of burst durations (Q(10) approximately 32). Both membrane lipids and solution ionic strength affected the temperature threshold of the activation, but neither diminished the response. The thermodynamic basis of heat activation is discussed, to elucidate what makes a thermal-sensitive channel unique.
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Affiliation(s)
- Beiying Liu
- Department of Physiology and Biophysical Sciences, State University of New York at Buffalo, Buffalo, New York 14214, USA
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35
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Ai T, Bompadre SG, Wang X, Hu S, Li M, Hwang TC. Capsaicin potentiates wild-type and mutant cystic fibrosis transmembrane conductance regulator chloride-channel currents. Mol Pharmacol 2004; 65:1415-26. [PMID: 15155835 DOI: 10.1124/mol.65.6.1415] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To examine the effects of capsaicin on cystic fibrosis transmembrane conductance regulator (CFTR), we recorded wild-type and mutant CFTR chloride-channel currents using patch-clamp methods. The effects of capsaicin were compared with those of genistein, a well-characterized CFTR activator. In whole-cell experiments, capsaicin potentiates cAMP-stimulated wild-type CFTR currents expressed in NIH 3T3 cells or Chinese hamster ovary cells in a dose-dependent manner with a maximal response approximately 60% of that with genistein and an apparent Kd of 48.4 +/- 6.8 microM. In cell-attached recordings, capsaicin alone fails to activate CFTR in cells that show negligible basal CFTR activity, indicating that capsaicin does not stimulate the cAMP cascade. The magnitude of potentiation with capsaicin depends on the channel activity before drug application; the lower the prestimulated Po, the higher the potentiation. Single-channel kinetic analysis shows that capsaicin potentiates CFTR by increasing the opening rate and decreasing the closing rate of the channel. Capsaicin may act as a partial agonist of genistein because the maximally enhanced wild-type CFTR currents with genistein are partially inhibited by capsaicin. Capsaicin increases DeltaR-CFTR, a protein kinase A (PKA)-independent, constitutively active channel, in cell-attached patches. In excised inside-out patches, capsaicin potentiates the PKA-phosphorylated, ATP-dependent CFTR activity. Both capsaicin and genistein potentiate the cAMP-stimulated G551D-CFTR, DeltaF508-CFTR, and 8SA mutant channel currents. The binding site for capsaicin is probably located at the cytoplasmic domain of CFTR, because pipette application of capsaicin fails to potentiate CFTR activity. In conclusion, capsaicin is a partial agonist of genistein in activation of the CFTR chloride channel. Both compounds affect ATP-dependent gating of CFTR.
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Affiliation(s)
- Tomohiko Ai
- Department of Medical Pharmacology and Physiology, Dalton Cardiovascular Research Center, University of Missouri-Columbia School of Medicine, Columbia, Missouri 65211, USA
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36
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Premkumar LS, Qi ZH, Van Buren J, Raisinghani M. Enhancement of potency and efficacy of NADA by PKC-mediated phosphorylation of vanilloid receptor. J Neurophysiol 2004; 91:1442-9. [PMID: 14973326 DOI: 10.1152/jn.00745.2003] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The search for an endogenous ligand for the vanilloid receptor (VR or TRPV1) has led to the identification of N-arachidonyl dopamine (NADA). This study investigates the role of protein kinase C (PKC)-mediated phosphorylation on NADA-induced membrane currents in Xenopus oocytes heterologously expressing TRPV1 and in dorsal root ganglion (DRG) neurons. In basal state, current induced by 10 microM NADA is 5-10% of the current induced by 1 microM capsaicin or protons at pH 5. However, PKC activator, phorbol 12,13-dibutyrate (PDBu) strongly potentiated ( approximately 15-fold) the NADA-induced current. Repeated application of NADA at short intervals potentiated its own response approximately fivefold in a PKC-dependent manner. PKC inhibitor, bisindolylmaleimide (BIM, 500 nM), a mutant TRPV1 (S800A/S502A), and maximal activation of PKC abolished the potentiation induced by repeated application of NADA. As a further confirmation that NADA could stimulate PKC, pretreatment with NADA potentiated the response of protons at pH 5 (approximately 20 fold), which was dramatically reduced in the mutant TRPV1. In DRG neurons, capsaicin (100 nM) induced a approximately 15 mV depolarization and initiated a train of action potentials compared with 1 microM NADA that produced a approximately 5 mV response. Pretreatment with PDBu induced significantly larger depolarization and potentiated NADA-induced current. Furthermore, exposure of NADA to the intracellular surface of the membrane-induced larger currents suggesting inaccessibility to the intracellular binding site might contribute to its weaker action. These results indicate that NADA is a potent agonist of VR when the receptor is in the PKC-mediated phosphorylation state.
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Affiliation(s)
- Louis S Premkumar
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois 62702, USA.
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Liu L, Zhu W, Zhang ZS, Yang T, Grant A, Oxford G, Simon SA. Nicotine inhibits voltage-dependent sodium channels and sensitizes vanilloid receptors. J Neurophysiol 2003; 91:1482-91. [PMID: 14657192 DOI: 10.1152/jn.00922.2003] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Nicotine is an alkaloid that is used by large numbers of people. When taken into the body, it produces a myriad of physiological actions that occur primarily through the activation of neuronal nicotinic acetylcholine receptors (nAChRs). We have explored its ability to modulate TRPV1 receptors and voltage-gated sodium channels. The reason for investigating nicotine's effect on sodium channels is to obtain a better understanding of its anti-nociceptive properties. The reasons for investigating its effects on capsaicin-activated TRPV1 channels are to understand how it may modulate this channel that is involved in pain, inflammation, and gustatory physiology. Whole cell patch-clamp recordings from rat trigeminal ganglion (TG) nociceptors revealed that nicotine exhibited anesthetic properties by decreasing the number of evoked action potentials and by inhibiting tetrodotoxin-resistant sodium currents. This anesthetic property can be produced without the necessity of activating nAChRs. Nicotine also modulates TRPV1 receptors inducing a several-fold increase in capsaicin-activated currents in both TG neurons and in cells with heterologously expressed TRPV1 receptors. This sensitizing effect does not require the activation of nAChRs. Nicotine did not alter the threshold temperature (approximately 41 degrees C) of heat-activated currents in TG neurons that were attributed to arise from the activation of TRPV1 receptors. In this regard, its effect on TRPV1 receptors differs from those of ethanol that has been shown to increase the capsaicin-activated current but decrease the threshold temperature. These studies document several new effects of nicotine on channels involved in nociception and indicate how they may impact physiological processes involving pain and gustation.
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Affiliation(s)
- L Liu
- Department of Anesthesiology, Duke University, Durham 27710, USA
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Vlachová V, Teisinger J, Susánková K, Lyfenko A, Ettrich R, Vyklický L. Functional role of C-terminal cytoplasmic tail of rat vanilloid receptor 1. J Neurosci 2003; 23:1340-50. [PMID: 12598622 PMCID: PMC6742269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
The vanilloid receptor [transient receptor potential (TRP)V1, also known as VR1] is a member of the TRP channel family. These receptors share a significant sequence homology, a similar predicted structure with six transmembrane-spanning domains (S1-S6), a pore-forming region between S5 and S6, and the cytoplasmically oriented C- and N-terminal regions. Although structural/functional studies have identified some of the key amino acids influencing the gating of the TRPV1 ion channel, the possible contributions of terminal regions to vanilloid receptor function remain elusive. In the present study, C-terminal truncations of rat TRPV1 have been constructed to characterize the contribution of the cytoplasmic C-terminal region to TRPV1 function and to delineate the minimum amount of C tail necessary to form a functional channel. The truncation of 31 residues was sufficient to induce changes in functional properties of TRPV1 channel. More pronounced effects of C-terminal truncation were seen in mutants lacking the final 72 aa. These changes were characterized by a decline of capsaicin-, pH-, and heat-sensitivity; progressive reduction of the activation thermal threshold (from 41.5 to 28.6 degrees C); and slowing of the activation rate of heat-evoked membrane currents (Q10 from 25.6 to 4.7). The voltage-induced currents of the truncated mutants exhibited a slower onset, markedly reduced outward rectification, and significantly smaller peak tail current amplitudes. Truncation of the entire TRPV1 C-terminal domain (155 residues) resulted in a nonfunctional channel. These results indicate that the cytoplasmic COOH-terminal domain strongly influences the TRPV1 channel activity, and that the distal half of this structural domain confers specific thermal sensitivity.
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Affiliation(s)
- Viktorie Vlachová
- Institute of Physiology, Academy of Sciences, 142 20 Prague 4, Czech Republic.
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Premkumar LS, Agarwal S, Steffen D. Single-channel properties of native and cloned rat vanilloid receptors. J Physiol 2002; 545:107-17. [PMID: 12433953 PMCID: PMC2290669 DOI: 10.1113/jphysiol.2002.016352] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The responses of single-channel currents to capsaicin were recorded using the giga-seal patch-clamp technique in cell-attached and excised (inside-out/outside-out) patches from embryonic rat dorsal root ganglion (DRG) neurones in culture and in Xenopus oocytes heterologously expressing the rat vanilloid receptor (rVR1). Native and cloned vanilloid receptor (VR)-mediated currents exhibited outward rectification. In both the DRG neurones and oocytes expressing VR1, the chord conductances at -60 and +60 mV were approximately 50 and approximately 100 pS, respectively. At positive potentials, the channel exhibited a single conductance state. In contrast, at negative potentials, brief sojourns to subconductance states were apparent. The probability of the channel being open (P(o)) was dependent on the transmembrane voltage and the patch configuration (i.e. cell-attached vs. excised). In both DRG neurones and oocytes, the P(o) was greater at positive (+60 mV) than at negative (-60 mV) potentials. In cell-attached patches, the P(o) was approximately twofold higher, regardless of the applied potential. Most likely, the outward rectification observed in whole-cell currents is due to the voltage dependence of single-channel conductance and P(o). The open-time distributions of single-channel currents recorded from native and cloned VRs in the presence of low agonist concentrations (0.01-0.03 microM) were best fitted with three exponential components. The closed-time distributions were best fitted by five exponential components. At higher concentrations (0.5-1 microM), an additional component was required to fit the open-time distribution, and the number of exponential components needed to fit the closed-time distributions was reduced to two. The overall mean open time at +60 mV was approximately 4 ms, compared to approximately 1.2 ms at -60 mV. However, the overall mean closed time was not voltage dependent. There were no significant differences between the native and cloned receptors. A comparison of single-channel properties of native and heterologously expressed VR channels indicates that expression of the rVR1 subunit alone can account for the single-channel behaviour of the majority of the native VRs. These results suggest that either native VRs are made up of VR1 subunits, or the incorporation of subunits other than VR1 does not influence the functional properties. The responses of single-channel currents to capsaicin were recorded using the giga-seal patch-clamp technique in cell-attached and excised (inside-out/outside-out) patches from embryonic rat dorsal root ganglion (DRG) neurones in culture and in Xenopus oocytes heterologously expressing the rat vanilloid receptor (rVR1). Native and cloned vanilloid receptor (VR)-mediated currents exhibited outward rectification. In both the DRG neurones and oocytes expressing VR1, the chord conductances at -60 and +60 mV were approximately 50 and approximately 100 pS, respectively. At positive potentials, the channel exhibited a single conductance state. In contrast, at negative potentials, brief sojourns to subconductance states were apparent. The probability of the channel being open (P(o)) was dependent on the transmembrane voltage and the patch configuration (i.e. cell-attached vs. excised). In both DRG neurones and oocytes, the P(o) was greater at positive (+60 mV) than at negative (-60 mV) potentials. In cell-attached patches, the P(o) was approximately twofold higher, regardless of the applied potential. Most likely, the outward rectification observed in whole-cell currents is due to the voltage dependence of single-channel conductance and P(o). The open-time distributions of single-channel currents recorded from native and cloned VRs in the presence of low agonist concentrations (0.01-0.03 microM) were best fitted with three exponential components. The closed-time distributions were best fitted by five exponential components. At higher concentrations (0.5-1 microM), an additional component was required to fit the open-time distribution, and the number of exponential components needed to fit the closed-time distributions was reduced to two. The overall mean open time at +60 mV was approximately 4 ms, compared to approximately 1.2 ms at -60 mV. However, the overall mean closed time was not voltage dependent. There were no significant differences between the native and cloned receptors. A comparison of single-channel properties of native and heterologously expressed VR channels indicates that expression of the rVR1 subunit alone can account for the single-channel behaviour of the majority of the native VRs. These results suggest that either native VRs are made up of VR1 subunits, or the incorporation of subunits other than VR1 does not influence the functional properties.
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Affiliation(s)
- Louis S Premkumar
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
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Wang Y, Szabo T, Welter JD, Toth A, Tran R, Lee J, Kang SU, Suh YG, Blumberg PM, Lee J. High affinity antagonists of the vanilloid receptor. Mol Pharmacol 2002; 62:947-56. [PMID: 12237342 DOI: 10.1124/mol.62.4.947] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vanilloid receptor VR1 has attracted great interest as a sensory transducer for capsaicin, protons, and heat, and as a therapeutic target. Here we characterize two novel VR1 antagonists, KJM429 [N-(4-tert-butylbenzyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea] and JYL1421 [N-(4-tert-butylbenzyl)-N'-[3-fluoro-4-(methylsulfonylamino)benzyl]thiourea], with enhanced activity compared with capsazepine on rat VR1 expressed in Chinese hamster ovary (CHO) cells. JYL1421, the more potent of the two novel antagonists, inhibited [(3)H]resiniferatoxin binding to rVR1 with an affinity of 53.5 +/- 6.5 nM and antagonized capsaicin-induced calcium uptake with an EC(50) of 9.2 +/- 1.6 nM, reflecting 25- and 60-fold greater potencies than capsazepine. Both JYL1421 and KJM429 antagonized RTX as well as capsaicin and their mechanism was competitive. The responses to JYL1421 and KJM429 differed for calcium uptake by rVR1 induced by heat or pH. JYL1421 antagonized the response to both pH 6.0 and 5.5, whereas KJM429 antagonized at pH 6.0 but was an agonist at lower pH (<5.5). For heat, JYL1421 fully antagonized and KJM429 partially antagonized. Capsazepine showed only weak antagonism for both pH and heat. Responses of rVR1 to different activators could thus be differentially affected by different ligands. In cultured dorsal root ganglion neurons, JYL1421 and KJM429 likewise behaved as antagonists for capsaicin, confirming that the antagonism is not limited to heterologous expression systems. Finally, JYL1421 and KJM429 had little or no effect on ATP-induced calcium uptake in CHO cells lacking rVR1, unlike capsazepine. We conclude that JYL1421 is a competitive antagonist of rVR1, blocking response to all three of the agonists (capsaicin, heat, and protons) with enhanced potency relative to capsazepine.
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Affiliation(s)
- Yun Wang
- National Cancer Institute, Bethesda, Maryland 20892, USA
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41
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Jacobson KA, Jarvis MF, Williams M. Purine and pyrimidine (P2) receptors as drug targets. J Med Chem 2002; 45:4057-93. [PMID: 12213051 DOI: 10.1021/jm020046y] [Citation(s) in RCA: 229] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases/NIH, Bethesda, MD 20892, USA
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42
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Kovári Z, Flachner B, Náray-Szabó G, Vas M. Crystallographic and thiol-reactivity studies on the complex of pig muscle phosphoglycerate kinase with ATP analogues: correlation between nucleotide binding mode and helix flexibility. Biochemistry 2002; 41:8796-806. [PMID: 12102622 DOI: 10.1021/bi020210j] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Crystal structure of the ternary complex of pig muscle phosphoglycerate kinase (PGK) with the substrate 3-phosphoglycerate (3-PG) and the Mg(2+) complex of beta,gamma-methylene-adenosine-5'-triphosphate (AMP-PCP), a nonreactive analogue of the nucleotide substrate, MgATP, has been determined by X-ray diffraction at 2.5 A resolution. The overall structure of the protein exhibits an open conformation, similar to that of the previously determined ternary complex of the pig muscle enzyme with beta,gamma-imido-adenosine-5'-triphosphate (AMP-PNP) in place of AMP-PCP (May, Vas, Harlos, and Blake (1996) Proteins 24, 292-303). The orientation and details of interactions of the nucleotide phosphates, however, show marked differences. The beta-phosphate is linked to the conserved Asp 218, i.e., to the N-terminus of helix 8, through the Mg(2+) ion; the previously observed interactions of the metal complex of AMP-PNP or ADP with the conserved Asn 336 and the N-terminus of helix 13 are completely absent. These structural differences are maintained themselves in solution studies. Inhibition and binding experiments show a slightly weaker interaction of PGK with MgAMP-PCP than with MgAMP-PNP: at pH 7.5, the K(d) values are 1.07 +/- 0.18 and 0.41 +/- 0.08 mM, respectively. The difference is further enhanced by 3-PG: the K(d) values are 2.80 +/- 0.66 and 0.68 +/- 0.11 mM, respectively. Thus, the previously observed weakening effect of 3-PG on nucleotide binding (Merli, Szilágyi, Flachner, Rossi, and Vas (2002) Biochemistry 41, 111-119) is more pronounced with MgAMP-PCP. The discordance between substrate analogues also shows up in thiol reactivity studies. In their binary complexes, both ATP analogues protect the fast-reacting thiols of PGK in helix 13 against modification to similar extent. In their ternary complexes, however, which also contain bound 3-PG, the protective effect of MgAMP-PCP, but not of MgAMP-PNP, is largely abolished. This indicates a much smaller effect of MgAMP-PCP on the conformation of helix 13, which is in good correlation with its altered mode of phosphate binding and the ensuing increase in the flexibility of helix 13, as shown by elevated crystallographic B-factors. The possible existence of alternative site(s) for binding of the nucleotide phosphates may have functional relevance.
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Affiliation(s)
- Zoltán Kovári
- Eötvös Loránd University, Department of Theoretical Chemistry, H-1518, Budapest 112, P.O. Box 32, Hungary
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Sugiura T, Tominaga M, Katsuya H, Mizumura K. Bradykinin lowers the threshold temperature for heat activation of vanilloid receptor 1. J Neurophysiol 2002; 88:544-8. [PMID: 12091579 DOI: 10.1152/jn.2002.88.1.544] [Citation(s) in RCA: 236] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bradykinin (BK) is an inflammatory mediator that plays a pivotal role in pain and hyperalgesia to heat in inflamed tissues by exciting nociceptors and sensitizing them to heat through activation of protein kinase C (PKC). It has been suggested that the capsaicin receptor (VR1), a nociceptor-specific cation channel sensitive to noxious heat, protons, and capsaicin, is a channel that is modified by BK in these effects. In this study, we examined how BK modulates the activity of VR1. We measured VR1 currents using the patch-clamp technique in human embryonic kidney-derived (HEK293) cells expressing VR1 and B2 BK receptor. We found that BK lowered the threshold temperature for activation of VR1 currents in HEK cells down to well below the physiological body temperature in a concentration-dependent manner through PKC activation. We also demonstrated that in capsaicin-sensitive dorsal root ganglion (DRG) neurons the activation threshold of heat-induced current, which is considered to be VR-1 mediated, was lowered by BK and that this effect was also mediated by PKC. These data further support the supposition that modulation of VR1 is a mechanism for the BK-induced excitation of nociceptors and their sensitization to heat.
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Affiliation(s)
- Takeshi Sugiura
- Department of Anesthesiology and Resuscitology, Nagoya City University Medical School, Nagoya 467-0001, Japan
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Abstract
The cloned vanilloid (capsaicin) receptor subtype 1 (VR1) integrates multiple noxious stimuli on peripheral terminals of primary sensory neurons. The initial excitation of these neurons is followed by a lasting refractory state, traditionally termed desensitization, that has clear therapeutic potential. Capsaicin is used to relieve neuropathic pain, uremic pruritus, and bladder overactivity. The ultrapotent vanilloid resiniferatoxin, now in phase 2 clinical trials, has improved tolerability. A less recognized human exposure to high capsaicin concentrations may occur by pepper sprays used in law enforcement. Evidence is mounting that VR1 expression is not restricted to sensory neurons. From the olfactory bulb to the cerebellum, VR1-expressing neurons are present in a number of brain nuclei, where they might be activated by anandamide. VR1 presence also was demonstrated in nonneuronal tissues. These discoveries place VR1 in a much broader perspective than pain perception and enhance the potential for unforeseen side effects, especially following prolonged vanilloid therapy. The expression of VR1 is plastic and down-regulated during vanilloid therapy, which might have a pivotal role in desensitization. Good evidence suggests altered VR1 expression in various disease states. This recognition not only may provide novel insights into pathogenesis but also may prove useful in diagnosis.
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Affiliation(s)
- Arpad Szallasi
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Sanchez JF, Krause JE, Cortright DN. The distribution and regulation of vanilloid receptor VR1 and VR1 5' splice variant RNA expression in rat. Neuroscience 2002; 107:373-81. [PMID: 11718993 DOI: 10.1016/s0306-4522(01)00373-6] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The vanilloid (capsaicin) receptor, VR1, is expressed in dorsal root ganglion and mediates the sensory response to vanilloids and other noxious stimuli. There is evidence for VR1 expression in CNS regions as well, but its function in these tissues is unknown. The identification of a rat VR1 5' splice variant and the rat stretch inhibitable channel, which are also expressed in dorsal root ganglia and CNS, raises the possibility that these and/or other VR1 variants may regulate VR1 activity. We have used a quantitative ribonuclease protection assay to characterize the central and peripheral expression of VR1 and VR1 variant RNA in the rat. The data confirm that VR1 is widely expressed in CNS, with highest RNA levels found in cerebral cortex, hippocampus, and cerebellum. VR1 RNA expression in dorsal root ganglia is approximately 28 times greater than in any other tissue sample studied. VR1 5' splice variant RNA is expressed at levels 12 times lower than VR1 in dorsal root ganglia, but at similar levels to VR1 in all other tissues examined. A VR1-related RNA expressed at high levels in kidney was detected, and was distinct from VR1 or stretch inhibitable channel. Our results also show that peripheral inflammation does not change VR1 RNA levels in rat dorsal root ganglia. Systemic resiniferatoxin administration, however, decreases VR1 expression in dorsal root ganglia by 65-80%, an effect that persists for at least 2 months. This study demonstrates that VR1 is expressed at high levels in dorsal root ganglia relative to other tissues and that VR1 5' splice variant is expressed at low levels in dorsal root ganglia compared to VR1. VR1 gene expression in dorsal root ganglia is regulated in response to systemic resiniferatoxin but not peripheral inflammation.
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Affiliation(s)
- J F Sanchez
- Department of Biochemistry and Molecular Biology, Neurogen Corporation, 35 N.E. Industrial Road, Branford, CT 06405, USA
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Abstract
Anandamide was the first endogenous ligand of cannabinoid receptors to be discovered in 1992. Yet, this compound also efficiently activates receptors specific for capsaicin, known as vanilloid type 1 receptors (VR1). Whether anandamide is a physiological VR1 ligand is controversial. However, very recent reports demonstrate that activation of VR1 by anandamide can be significantly enhanced by various regulatory factors, suggesting that this compound might act as an "endovanilloid" under certain conditions.
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Affiliation(s)
- V Di Marzo
- Istituto per la Chimica di Molecole di Interesse Biologico, Consiglio Nazionale delle Ricerche, Viale Toiano 6, Arco Felice, 80072 Napoli, Italy.
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47
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Premkumar LS. Interaction between vanilloid receptors and purinergic metabotropic receptors: pain perception and beyond. Proc Natl Acad Sci U S A 2001; 98:6537-9. [PMID: 11390988 PMCID: PMC34386 DOI: 10.1073/pnas.121190798] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- L S Premkumar
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
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