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Yin Y, Wei L, Caseley EA, Lopez‐Charcas O, Wei Y, Li D, Muench SP, Roger S, Wang L, Jiang L. Leveraging the ATP-P2X7 receptor signalling axis to alleviate traumatic CNS damage and related complications. Med Res Rev 2023; 43:1346-1373. [PMID: 36924449 PMCID: PMC10947395 DOI: 10.1002/med.21952] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 11/11/2022] [Accepted: 02/28/2023] [Indexed: 03/18/2023]
Abstract
The P2X7 receptor is an exceptional member of the P2X purinergic receptor family, with its activation requiring high concentrations of extracellular adenosine 5'-triphosphate (ATP) that are often associated with tissue damage and inflammation. In the central nervous system (CNS), it is highly expressed in glial cells, particularly in microglia. In this review, we discuss the role and mechanisms of the P2X7 receptor in mediating neuroinflammation and other pathogenic events in a variety of traumatic CNS damage conditions, which lead to loss of neurological and cognitive functions. We raise the perspective on the steady progress in developing CNS-penetrant P2X7 receptor-specific antagonists that leverage the ATP-P2X7 receptor signaling axis as a potential therapeutic strategy to alleviate traumatic CNS damage and related complications.
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Affiliation(s)
- Yaling Yin
- Sino‐UK Joint Laboratory of Brain Function and Injury of Henan Province, Department of Physiology and PathophysiologyXinxiang Medical UniversityXinxiangChina
| | - Linyu Wei
- Sino‐UK Joint Laboratory of Brain Function and Injury of Henan Province, Department of Physiology and PathophysiologyXinxiang Medical UniversityXinxiangChina
| | - Emily A. Caseley
- Faculty of Biological Sciences, School of Biomedical SciencesUniversity of LeedsLeedsUK
| | - Osbaldo Lopez‐Charcas
- EA4245, Transplantation, Immunology and Inflammation, Faculty of MedicineUniversity of ToursToursFrance
| | - Yingjuan Wei
- Sino‐UK Joint Laboratory of Brain Function and Injury of Henan Province, Department of Physiology and PathophysiologyXinxiang Medical UniversityXinxiangChina
| | - Dongliang Li
- Sino‐UK Joint Laboratory of Brain Function and Injury of Henan Province, Department of Physiology and PathophysiologyXinxiang Medical UniversityXinxiangChina
- Sanquan College of Xinxiang Medical UniversityXinxiangChina
| | - Steve P. Muench
- Faculty of Biological Sciences, School of Biomedical SciencesUniversity of LeedsLeedsUK
| | - Sebastian Roger
- EA4245, Transplantation, Immunology and Inflammation, Faculty of MedicineUniversity of ToursToursFrance
| | - Lu Wang
- Sino‐UK Joint Laboratory of Brain Function and Injury of Henan Province, Department of Physiology and PathophysiologyXinxiang Medical UniversityXinxiangChina
| | - Lin‐Hua Jiang
- Sino‐UK Joint Laboratory of Brain Function and Injury of Henan Province, Department of Physiology and PathophysiologyXinxiang Medical UniversityXinxiangChina
- Faculty of Biological Sciences, School of Biomedical SciencesUniversity of LeedsLeedsUK
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Yue WWS, Yuan L, Braz JM, Basbaum AI, Julius D. TRPV1 drugs alter core body temperature via central projections of primary afferent sensory neurons. eLife 2022; 11:e80139. [PMID: 35968676 PMCID: PMC9377796 DOI: 10.7554/elife.80139] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 08/04/2022] [Indexed: 11/29/2022] Open
Abstract
TRPV1, a capsaicin- and heat-activated ion channel, is expressed by peripheral nociceptors and has been implicated in various inflammatory and neuropathic pain conditions. Although pharmacological modulation of TRPV1 has attracted therapeutic interest, many TRPV1 agonists and antagonists produce thermomodulatory side effects in animal models and human clinical trials, limiting their utility. These on-target effects may result from the perturbation of TRPV1 receptors on nociceptors, which transduce signals to central thermoregulatory circuits and release proinflammatory factors from their peripheral terminals, most notably the potent vasodilative neuropeptide, calcitonin gene-related peptide (CGRP). Alternatively, these body temperature effects may originate from the modulation of TRPV1 on vascular smooth muscle cells (vSMCs), where channel activation promotes arteriole constriction. Here, we ask which of these pathways is most responsible for the body temperature perturbations elicited by TRPV1 drugs in vivo. We address this question by selectively eliminating TRPV1 expression in sensory neurons or vSMCs and show that only the former abrogates agonist-induced hypothermia and antagonist-induced hyperthermia. Furthermore, lesioning the central projections of TRPV1-positive sensory nerve fibers also abrogates drug-mediated thermomodulation, whereas eliminating CGRP has no effect. Thus, TRPV1 drugs alter core body temperature by modulating sensory input to the central nervous system, rather than through peripheral actions on the vasculature. These findings suggest how mechanistically distinct TRPV1 antagonists may diminish inflammatory pain without affecting core body temperature.
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Affiliation(s)
- Wendy Wing Sze Yue
- Department of Physiology, University of CaliforniaSan FranciscoUnited States
| | - Lin Yuan
- Department of Physiology, University of CaliforniaSan FranciscoUnited States
| | - Joao M Braz
- Department of Anatomy, University of CaliforniaSan FranciscoUnited States
| | - Allan I Basbaum
- Department of Anatomy, University of CaliforniaSan FranciscoUnited States
| | - David Julius
- Department of Physiology, University of CaliforniaSan FranciscoUnited States
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3
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Inferiority complex: why do sensory ion channels multimerize? Biochem Soc Trans 2022; 50:213-222. [PMID: 35166323 PMCID: PMC9022975 DOI: 10.1042/bst20211002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 11/17/2022]
Abstract
Peripheral somatosensory nerves are equipped with versatile molecular sensors which respond to acute changes in the physical environment. Most of these sensors are ion channels that, when activated, depolarize the sensory nerve terminal causing it to generate action potentials, which is the first step in generation of most somatic sensations, including pain. The activation and inactivation of sensory ion channels is tightly regulated and modulated by a variety of mechanisms. Amongst such mechanisms is the regulation of sensory ion channel activity via direct molecular interactions with other proteins in multi-protein complexes at the plasma membrane of sensory nerve terminals. In this brief review, we will consider several examples of such complexes formed around a prototypic sensory receptor, transient receptor potential vanilloid type 1 (TRPV1). We will also discuss some inherent conceptual difficulties arising from the multitude of reported complexes.
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Shah S, Carver CM, Mullen P, Milne S, Lukacs V, Shapiro MS, Gamper N. Local Ca 2+ signals couple activation of TRPV1 and ANO1 sensory ion channels. Sci Signal 2020; 13:13/629/eaaw7963. [PMID: 32345727 DOI: 10.1126/scisignal.aaw7963] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
ANO1 (TMEM16A) is a Ca2+-activated Cl- channel (CaCC) expressed in peripheral somatosensory neurons that are activated by painful (noxious) stimuli. These neurons also express the Ca2+-permeable channel and noxious heat sensor TRPV1, which can activate ANO1. Here, we revealed an intricate mechanism of TRPV1-ANO1 channel coupling in rat dorsal root ganglion (DRG) neurons. Simultaneous optical monitoring of CaCC activity and Ca2+ dynamics revealed that the TRPV1 ligand capsaicin activated CaCCs. However, depletion of endoplasmic reticulum (ER) Ca2+ stores reduced capsaicin-induced Ca2+ increases and CaCC activation, suggesting that ER Ca2+ release contributed to TRPV1-induced CaCC activation. ER store depletion by plasma membrane-localized TRPV1 channels was demonstrated with an ER-localized Ca2+ sensor in neurons exposed to a cell-impermeable TRPV1 ligand. Proximity ligation assays established that ANO1, TRPV1, and the IP3 receptor IP3R1 were often found in close proximity to each other. Stochastic optical reconstruction microscopy (STORM) confirmed the close association between all three channels in DRG neurons. Together, our data reveal the existence of ANO1-containing multichannel nanodomains in DRG neurons and suggest that coupling between TRPV1 and ANO1 requires ER Ca2+ release, which may be necessary to enhance ANO1 activation.
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Affiliation(s)
- Shihab Shah
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Chase M Carver
- Department of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Pierce Mullen
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Stephen Milne
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Viktor Lukacs
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Mark S Shapiro
- Department of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Nikita Gamper
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK. .,Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, People's Republic of China
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5
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Pham TH, Jin SW, Lee GH, Park JS, Kim JY, Thai TN, Han EH, Jeong HG. Sesamin Induces Endothelial Nitric Oxide Synthase Activation via Transient Receptor Potential Vanilloid Type 1. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:3474-3484. [PMID: 32077699 DOI: 10.1021/acs.jafc.9b07909] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Sesamin, the most abundant lignan in sesame seed oil, has many biological activities. However, the underlying molecular mechanisms behind the regulatory effects of sesamin on endothelial nitric oxide synthase (eNOS) activity and nitric oxide (NO) generation in endothelial cells (ECs) remain unclear. Sesamin induced the intracellular level of NO and eNOS phosphorylation in ECs in a concentration- and time-dependent manner. Additionally, sesamin induced levels of intracellular calcium, leading to the phosphorylation of calmodulin-dependent protein kinase II (CaMKII) at Thr286, calcium/calmodulin-dependent protein kinase kinase beta (CaMKKβ) at Ser511, protein kinase A (PKA) at Thr197, Akt at Ser473, and AMP-activated protein kinase (AMPK) at Thr172. In particular, blocking of the transient receptor potential vanilloid type 1 (TRPV1) channel by capsazepine (TRPV1 antagonist), as well as TRPV1 knockdown via TRPV1 silencing RNA, abrogated sesamin-induced PKA, Akt, AMPK, CaMKII, CaMKKβ, and eNOS phosphorylation and NO level in ECs. Furthermore, sesamin inhibited TNF-α-induced NF-κB translocation, intercellular adhesion molecule-1 expression, and monocyte adhesion. Sesamin triggered eNOS activity and NO production via activation of TRPV1-calcium signaling, which involved the phosphorylation of PKA, CaMKII, CaMKKβ, Akt, and AMPK. Sesamin may be useful for treating or preventing the endothelial dysfunction correlated with cardiovascular diseases.
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Affiliation(s)
- Thi Hoa Pham
- College of Pharmacy, Chungnam National University, Daejeon 34134, Republic of Korea
- Molecular Microbiology Lab, Institute of Biotechnology, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam
| | - Sun Woo Jin
- College of Pharmacy, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Gi Ho Lee
- College of Pharmacy, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Jin Song Park
- College of Pharmacy, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Ji Yeon Kim
- College of Pharmacy, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Tuyet Ngan Thai
- College of Pharmacy, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Eun Hee Han
- Drug & Disease Target Research Team, Division of Bioconvergence Analysis, Korea Basic Science Institute (KBSI), Cheongju 28119, Republic of Korea
| | - Hye Gwang Jeong
- College of Pharmacy, Chungnam National University, Daejeon 34134, Republic of Korea
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6
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Maksoud MJE, Tellios V, An D, Xiang Y, Lu W. Nitric oxide upregulates microglia phagocytosis and increases transient receptor potential vanilloid type 2 channel expression on the plasma membrane. Glia 2019; 67:2294-2311. [DOI: 10.1002/glia.23685] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 07/02/2019] [Accepted: 07/06/2019] [Indexed: 12/21/2022]
Affiliation(s)
- Matthew J. E. Maksoud
- Graduate Program of Neuroscience The University of Western Ontario London Canada
- Department of Molecular Medicine Robarts Research Institute, The University of Western Ontario London Canada
| | - Vasiliki Tellios
- Graduate Program of Neuroscience The University of Western Ontario London Canada
- Department of Molecular Medicine Robarts Research Institute, The University of Western Ontario London Canada
| | - Dong An
- Department of Molecular Medicine Robarts Research Institute, The University of Western Ontario London Canada
| | - Yun‐Yan Xiang
- Department of Molecular Medicine Robarts Research Institute, The University of Western Ontario London Canada
| | - Wei‐Yang Lu
- Graduate Program of Neuroscience The University of Western Ontario London Canada
- Department of Molecular Medicine Robarts Research Institute, The University of Western Ontario London Canada
- Department of Physiology and Pharmacology The University of Western Ontario London Canada
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7
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Fenwick AJ, Fowler DK, Wu SW, Shaffer FJ, Lindberg JEM, Kinch DC, Peters JH. Direct Anandamide Activation of TRPV1 Produces Divergent Calcium and Current Responses. Front Mol Neurosci 2017; 10:200. [PMID: 28680392 PMCID: PMC5478686 DOI: 10.3389/fnmol.2017.00200] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 06/07/2017] [Indexed: 01/22/2023] Open
Abstract
In the brainstem nucleus of the solitary tract (NTS), primary vagal afferent neurons express the transient receptor potential vanilloid subfamily member 1 (TRPV1) at their central terminals where it contributes to quantal forms of glutamate release. The endogenous membrane lipid anandamide (AEA) is a putative TRPV1 agonist in the brain, yet the extent to which AEA activation of TRPV1 has a neurophysiological consequence is not well established. We investigated the ability of AEA to activate TRPV1 in vagal afferent neurons in comparison to capsaicin (CAP). Using ratiometric calcium imaging and whole-cell patch clamp recordings we confirmed that AEA excitatory activity requires TRPV1, binds competitively at the CAP binding site, and has low relative affinity. While AEA-induced increases in peak cytosolic calcium were similar to CAP, AEA-induced membrane currents were significantly smaller. Removal of bath calcium increased the AEA current with no change in peak CAP currents revealing a calcium sensitive difference in specific ligand activation of TRPV1. Both CAP- and AEA-activated TRPV1 currents maintained identical reversal potentials, arguing against a major difference in ion selectivity to resolve the AEA differences in signaling. In contrast with CAP, AEA did not alter spontaneous glutamate release at NTS synapses. We conclude: (1) AEA activation of TRPV1 is markedly different from CAP and produces different magnitudes of calcium influx from whole-cell current; and (2) exogenous AEA does not alter spontaneous glutamate release onto NTS neurons. As such, AEA may convey modulatory changes to calcium-dependent processes, but does not directly facilitate glutamate release.
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Affiliation(s)
- Axel J Fenwick
- Department of Integrative Physiology and Neuroscience, Washington State UniversityPullman, WA, United States
| | - Daniel K Fowler
- Department of Integrative Physiology and Neuroscience, Washington State UniversityPullman, WA, United States
| | - Shaw-Wen Wu
- Department of Integrative Physiology and Neuroscience, Washington State UniversityPullman, WA, United States
| | - Forrest J Shaffer
- Department of Integrative Physiology and Neuroscience, Washington State UniversityPullman, WA, United States
| | - Jonathan E M Lindberg
- Department of Integrative Physiology and Neuroscience, Washington State UniversityPullman, WA, United States
| | - Dallas C Kinch
- Department of Integrative Physiology and Neuroscience, Washington State UniversityPullman, WA, United States
| | - James H Peters
- Department of Integrative Physiology and Neuroscience, Washington State UniversityPullman, WA, United States
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8
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Wei L, Caseley E, Li D, Jiang LH. ATP-induced P2X Receptor-Dependent Large Pore Formation: How Much Do We Know? Front Pharmacol 2016; 7:5. [PMID: 26858647 PMCID: PMC4732382 DOI: 10.3389/fphar.2016.00005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/11/2016] [Indexed: 01/05/2023] Open
Affiliation(s)
- Linyu Wei
- Department of Physiology and Neurobiology, Xinxiang Medical UniversityXinxiang, China; Faculty of Biological Sciences, School of Biomedical Sciences, University of LeedsLeeds, UK
| | - Emily Caseley
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds Leeds, UK
| | - Dongliang Li
- Department of Physiology and Neurobiology, Xinxiang Medical University Xinxiang, China
| | - Lin-Hua Jiang
- Department of Physiology and Neurobiology, Xinxiang Medical UniversityXinxiang, China; Faculty of Biological Sciences, School of Biomedical Sciences, University of LeedsLeeds, UK
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Samways DSK, Tomkiewicz E, Langevin OM, Bukhari M. Measurement of relative Ca²⁺ permeability during sustained activation of TRPV1 receptors. Pflugers Arch 2015; 468:201-11. [PMID: 26490461 DOI: 10.1007/s00424-015-1741-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 09/28/2015] [Accepted: 09/30/2015] [Indexed: 12/14/2022]
Abstract
Some cation permeable ligand-gated ion channels, including the capsaicin-sensitive TRPV1, have been reported to exhibit a time-dependent increase in permeability to large inorganic cations during sustained activation, a phenomenon termed "pore dilation." TRPV1 conducts substantial Ca(2+) entry, and it has been suggested that this channel undergoes a time-dependent change in Ca(2+) permeability relative to Na(+) (P Ca/P Na) that parallels pore dilation. However, our experiments employing whole cell patch clamp photometry and single channel recordings to directly measure relative Ca(2+) current in TRPV1 expressing HEK293 cells show that relative Ca(2+) influx remains constant for the duration of capsaicin-evoked channel activation. Further, we present evidence from patch clamp photometry experiments suggesting that sustained activation of Ca(2+) permeable ion channels in the voltage-clamp configuration leads to rapid saturation of the pipette Ca(2+) chelator, and that subsequent observed shifts in the current reversal potentials in the presence of extracellular Ca(2+) are likely due to intracellular accumulation of this ion and a movement of the Ca(2+) equilibrium potential (E Ca) towards zero. Finally, using an adapted reversal potential-based protocol in which cells are only exposed to Ca(2+) after sustained capsaicin exposure in the absence of added extracellular Ca(2+), we demonstrate that the calculated P Ca/P Na is unaffected by duration of TRPV1 activation. In conclusion, we find no evidence in support of a time-dependent change in P Ca/P Na for TRPV1. Our data further urges caution in estimating relative Ca(2+) permeability using reversal potentials, as there is a limited time window in which the cytosolic Ca(2+) chelator included in the patch pipette can prevent localised elevations in cytosolic free Ca(2+) and thus allow for an accurate estimate of this important channel permeability parameter.
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Affiliation(s)
- Damien S K Samways
- Department of Biology, Clarkson University, 177 Science Center, 8 Clarkson Ave., P.O. Box 5805, Potsdam, NY, 13699-5805, USA.
| | - Evan Tomkiewicz
- Department of Biology, Clarkson University, 177 Science Center, 8 Clarkson Ave., P.O. Box 5805, Potsdam, NY, 13699-5805, USA
| | - Olivia M Langevin
- Department of Biology, Clarkson University, 177 Science Center, 8 Clarkson Ave., P.O. Box 5805, Potsdam, NY, 13699-5805, USA
| | - Maurish Bukhari
- Department of Biology, Clarkson University, 177 Science Center, 8 Clarkson Ave., P.O. Box 5805, Potsdam, NY, 13699-5805, USA
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Rohacs T. Phosphoinositide regulation of TRPV1 revisited. Pflugers Arch 2015; 467:1851-69. [PMID: 25754030 PMCID: PMC4537841 DOI: 10.1007/s00424-015-1695-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 02/12/2015] [Accepted: 02/16/2015] [Indexed: 01/22/2023]
Abstract
The heat- and capsaicin-sensitive transient receptor potential vanilloid 1 ion channel (TRPV1) is regulated by plasma membrane phosphoinositides. The effects of these lipids on this channel have been controversial. Recent articles re-ignited the debate and also offered resolution to place some of the data in a coherent picture. This review summarizes the literature on this topic and provides a detailed and critical discussion on the experimental evidence for the various effects of phosphatidylinositol 4,5-bisphosphayte [PI(4,5)P2 or PIP2] on TRPV1. We conclude that PI(4,5)P2 and potentially its precursor PI(4)P are positive cofactors for TRPV1, acting via direct interaction with the channel, and their depletion by Ca(2+)-induced activation of phospholipase Cδ isoforms (PLCδ) limits channel activity during capsaicin-induced desensitization. Other negatively charged lipids at higher concentrations can also support channel activity, which may explain some controversies in the literature. PI(4,5)P2 also partially inhibits channel activity in some experimental settings, and relief from this inhibition upon PLCβ activation may contribute to sensitization. The negative effect of PI(4,5)P2 is more controversial and its mechanism is less well understood. Other TRP channels from the TRPV and TRPC families may also undergo similar dual regulation by phosphoinositides, thus the complexity of TRPV1 regulation is not unique to this channel.
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Affiliation(s)
- Tibor Rohacs
- Department of Pharmacology and Physiology Rutgers, New Jersey Medical School, 185 South Orange Ave, Newark, NJ, USA,
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Marcoline FV, Bethel N, Guerriero CJ, Brodsky JL, Grabe M. Membrane Protein Properties Revealed through Data-Rich Electrostatics Calculations. Structure 2015; 23:1526-1537. [PMID: 26118532 DOI: 10.1016/j.str.2015.05.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 04/09/2015] [Accepted: 05/02/2015] [Indexed: 01/29/2023]
Abstract
The electrostatic properties of membrane proteins often reveal many of their key biophysical characteristics, such as ion channel selectivity and the stability of charged membrane-spanning segments. The Poisson-Boltzmann (PB) equation is the gold standard for calculating protein electrostatics, and the software APBSmem enables the solution of the PB equation in the presence of a membrane. Here, we describe significant advances to APBSmem, including full automation of system setup, per-residue energy decomposition, incorporation of PDB2PQR, calculation of membrane-induced pKa shifts, calculation of non-polar energies, and command-line scripting for large-scale calculations. We highlight these new features with calculations carried out on a number of membrane proteins, including the recently solved structure of the ion channel TRPV1 and a large survey of 1,614 membrane proteins of known structure. This survey provides a comprehensive list of residues with large electrostatic penalties for being embedded in the membrane, potentially revealing interesting functional information.
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Affiliation(s)
- Frank V Marcoline
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA
| | - Neville Bethel
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA; Integrative Program in Quantitative Biology, University of California, San Francisco, CA 94158, USA
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Michael Grabe
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.
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12
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Borbiro I, Badheka D, Rohacs T. Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides. Sci Signal 2015; 8:ra15. [PMID: 25670203 DOI: 10.1126/scisignal.2005667] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Capsaicin is an activator of the heat-sensitive TRPV1 (transient receptor potential vanilloid 1) ion channels and has been used as a local analgesic. We found that activation of TRPV1 channels with capsaicin either in dorsal root ganglion neurons or in a heterologous expression system inhibited the mechanosensitive Piezo1 and Piezo2 channels by depleting phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its precursor phosphatidylinositol 4-phosphate [PI(4)P] from the plasma membrane through Ca(2+)-induced phospholipase Cδ (PLCδ) activation. Experiments with chemically inducible phosphoinositide phosphatases and receptor-induced activation of PLCβ indicated that inhibition of Piezo channels required depletion of both PI(4)P and PI(4,5)P2. The mechanically activated current amplitudes decreased substantially in the excised inside-out configuration, where the membrane patch containing Piezo1 channels is removed from the cell. PI(4,5)P2 and PI(4)P applied to these excised patches inhibited this decrease. Thus, we concluded that Piezo channel activity requires the presence of phosphoinositides, and the combined depletion of PI(4,5)P2 and PI(4)P reduces channel activity. In addition to revealing a role for distinct membrane lipids in mechanosensitive ion channel regulation, these data suggest that inhibition of Piezo2 channels may contribute to the analgesic effect of capsaicin.
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Affiliation(s)
- Istvan Borbiro
- Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Doreen Badheka
- Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Tibor Rohacs
- Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, NJ 07103, USA.
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Mohammadi-Farani A, Ghazi-Khansari M, Sahebgharani M. Glucose concentration in culture medium affects mRNA expression of TRPV1 and CB1 receptors and changes capsaicin toxicity in PC12 cells. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2014; 17:673-378. [PMID: 25691944 PMCID: PMC4322151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 02/17/2014] [Indexed: 11/29/2022]
Abstract
OBJECTIVE S Hyperglycemia is widely recognized as the underlying cause for some debilitating conditions in diabetic patients. The role of cannabinoid CB1 and vanilloid TRPV1 receptors and their endogenous agonists, endovanilloids, in diabetic neuropathy is shown in many studies. Here we have used PC12 cell line to investigate the possible influence of glucose concentration in culture medium on cytoprotective or toxic effects of a CB1 [WIN55 212-2 (WIN)], or TRPV1 [Capsaicin (CAS)] agonist. MATERIALS AND METHODS Cell viability was tested using the MTT assay. We have also measured TRPV1 and CB1 transcripts by real time reverse transcription-polymerase chain reaction while cells were grown in low (5.5 mM) and high (50 mM) glucose concentrations. RESULTS Real time PCR results indicated that high glucose medium increased (P<0.01) TRPV1 mRNA and decreased (P <0.001) that of CB1. Cell culture tests show that hyperglycemic cells are more vulnerable (Dose × Medium, F (3,63)=41.5, P<0.001) to the toxic effects of capsaicin compared to those grown in low glucose medium. CONCLUSION These findings propose that hyperglycemic conditions may result in neuronal cell death because of inducing a counterbalance between cytotoxic TRPV1 and cytoprotective CB1 receptors.
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Affiliation(s)
- Ahmad Mohammadi-Farani
- Novel Drug Delivery Research Center, Faculty of Pharmacy, Kermanshah University of Medical Sciences, Kermanshah, Iran,Corresponding author: Ahmad Mohammadi-Farani. Faculty of Pharmacy, Parastar Boulevard, Daneshgah St, Kermanshah, Iran. ;
| | - Mahmoud Ghazi-Khansari
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mousa Sahebgharani
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
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Nilius B, Szallasi A. Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine. Pharmacol Rev 2014; 66:676-814. [DOI: 10.1124/pr.113.008268] [Citation(s) in RCA: 348] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Samways DSK, Li Z, Egan TM. Principles and properties of ion flow in P2X receptors. Front Cell Neurosci 2014; 8:6. [PMID: 24550775 PMCID: PMC3914235 DOI: 10.3389/fncel.2014.00006] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 01/06/2014] [Indexed: 12/25/2022] Open
Abstract
P2X receptors are a family of trimeric ion channels that are gated by extracellular adenosine 5′-triphosphate (ATP). These receptors have long been a subject of intense research interest by virtue of their vital role in mediating the rapid and direct effects of extracellular ATP on membrane potential and cytosolic Ca2+ concentration, which in turn underpin the ability of ATP to regulate a diverse range of clinically significant physiological functions, including those associated with the cardiovascular, sensory, and immune systems. An important aspect of an ion channel's function is, of course, the means by which it transports ions across the biological membrane. A concerted effort by investigators over the last two decades has culminated in significant advances in our understanding of how P2X receptors conduct the inward flux of Na+ and Ca2+ in response to binding by ATP. However, this work has relied heavily on results from current recordings of P2X receptors altered by site-directed mutagenesis. In the absence of a 3-dimensional channel structure, this prior work provided only a vague and indirect appreciation of the relationship between structure, ion selectivity and flux. The recent publication of the crystal structures for both the closed and open channel conformations of the zebrafish P2X4 receptor has thus proved a significant boon, and has provided an important opportunity to overview the amassed functional data in the context of a working 3-dimensional model of a P2X receptor. In this paper, we will attempt to reconcile the existing functional data regarding ion permeation through P2X receptors with the available crystal structure data, highlighting areas of concordance and discordance as appropriate.
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Affiliation(s)
| | - Zhiyuan Li
- Guangzhou Institute of Biomedicine and Health, University of Chinese Academy of Sciences Guangzhou, China
| | - Terrance M Egan
- Department of Pharmacological and Physiological Science, The Center for Excellence in Neuroscience, Saint Louis University School of Medicine St. Louis, MO, USA
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Abstract
Like most other members of the TRP family, the Trpm3 gene encodes proteins that form cation-permeable ion channels on the plasma membrane. However, TRPM3 proteins have several unique features that set them apart from the other members of this diverse family. The Trpm3 gene encodes for a surprisingly large number of isoforms generated mainly by alternative splicing. Only for two of the (at least) eight sites at which sequence diversity is generated the functional consequences have been elucidated, one leading to nonfunctional channels, the other one profoundly affecting the ionic selectivity. In the Trpm3 gene an intronic microRNA (miR-204) is co-transcribed with Trpm3. By regulating the expression of a multitude of genes, miR-204 increases the functional complexity of the Trpm3 locus. Over the past years, important progress has been made in discovering pharmacological tools to manipulate TRPM3 channel activity. These substances have facilitated the identification of endogenously expressed functional TRPM3 channels in nociceptive neurons, pancreatic beta cells, and vascular smooth muscle cells, among others. TRPM3 channels, which themselves are temperature sensitive, thus have been implicated in sensing noxious heat, in modulating insulin release, and in secretion of inflammatory cytokines. However, in many tissues where TRPM3 proteins are known to be expressed, no functional role has been identified for these channels so far. Because of the availability of adequate pharmacological and genetic tools, it is expected that future investigations on TRPM3 channels will unravel important new aspects and functions of these channels.
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Affiliation(s)
- Johannes Oberwinkler
- Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, 35037, Marburg, Germany,
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Szolcsányi J, Pintér E. Transient receptor potential vanilloid 1 as a therapeutic target in analgesia. Expert Opin Ther Targets 2013; 17:641-57. [PMID: 23421411 DOI: 10.1517/14728222.2013.772580] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION The selective excitatory action of capsaicin followed by long-term chemoanalgesia due to an action on the 'capsaicin receptor' of C-polymodal nociceptors, cloned 15 years ago, opened up fascinating perspectives for a class of nociceptor blocking analgesics. AREAS COVERED The TRPV1/capsaicin receptor is an integrative, chemoceptive, noxious heat-gated cation channel also gated by several endogenous ligands and sensitized by phosphorylation through intracellular cascades triggered from receptors of bradykinin, prostanoids, NGF and interactions with TRPA1. In this review, types of sensory receptors and unique mechanisms for blocking nociceptor action, e.g., 'pore dilation' intracellular acidosis and the long-term function-related mitochondrial swelling at the nerve terminals and sensory neurons are summarized. In humans the 8% capsaicin dermal patch is already in usage for nondiabetic neuropathic pain and two topical preparations of civamide have also been approved recently for cluster headache and osteoarthritis. Evidence for epidermal nerve terminal loss in humans after topical applications and misleading results on sensory neuron death evoked by TRPV1 agonism in animals are discussed. EXPERT OPINION The unique 'multisteric' gating of TRPV1 channel which is opened and modulated in various conformational changes to natural stimuli differs from the operation of canonical ligand-gated channels and makes it suitable to initiate development of second generation of TRPV1 antagonists without on-target side effects of hyperthermia and risk of burn injury.
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Affiliation(s)
- János Szolcsányi
- University of Pécs Medical School, Department of Pharmacology and Pharmacotherapy , H-7624 Pécs, Szigeti u. 12 , Hungary.
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Duan L, Yan Y, Sun Y, Zhao B, Hu W, Li G. Contribution of TRPV1 and multidrug resistance proteins in the permeation of capsaicin across different intestinal regions. Int J Pharm 2013; 445:134-40. [PMID: 23402980 DOI: 10.1016/j.ijpharm.2013.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 01/17/2013] [Accepted: 02/03/2013] [Indexed: 10/27/2022]
Abstract
OBJECTIVE The aim of the study was to observe the characteristic of permeation of capsaicin across jejunum, ileum and colon in the rat, and to investigate the role of transient receptor potential cation channel (TRPV1). The interaction of capsaicin with P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) was also investigated. METHOD The transport of capsaicin across three intestinal segments in rats was investigated using Ussing-chamber System. RESULTS The permeability of capsaicin across the colonic ileac or jejunal membrane was significantly different in M-S direction (11.679 ± 2.001, 5.336 ± 1.248, 1.395 ± 0.673, ×10(-6)cm/s). TRPV1 non-competitive antagonist ruthenium red significantly decreased the permeability of capsaicin in M-S direction across colonic membrane. The permeability of capsaicin could also be inhibited unconventionally by the BCRP inhibitor novobiocin in M-S direction across colon. However, either the P-gp inhibitor verapamil or the MRP2 inhibitor probenecid did not affect the transport of capsaicin in all three segments. CONCLUSION We firstly proved that the permeability of capsaicin across colon was significantly higher than that across jejunum or ileum. Furthermore, TRPV1 might mediate the transport of capsaicin across the intestinal membrane. Therefore, the colon-specific highest permeation of capsaicin could be the consequence of the colon-specific distribution of TRPV1. For another, there may be another transport pathway mediating the permeation of capsaicin in M-S direction, which could be inhibited by novobiocin.
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Affiliation(s)
- Lian Duan
- Department of Pharmacy, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China
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Yu H, Li Q, Zhou X, Kolosov VP, Perelman JM. Transient receptor potential vanilloid 1 receptors mediate acid-induced mucin secretion via Ca2+ influx in human airway epithelial cells. J Biochem Mol Toxicol 2012; 26:179-86. [PMID: 22566028 DOI: 10.1002/jbt.20413] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 08/09/2011] [Accepted: 08/20/2011] [Indexed: 12/20/2022]
Abstract
Mucin hypersecretion is a key pathological feature of inflammatory respiratory diseases. Previous studies have reported that acids (gastroesophageal reflux or environmental exposure) induce many respiratory symptoms and are implicated in the pathophysiology of obstructive airway diseases. To understand these mechanisms, we measured acid-induced mucin secretion in human bronchial epithelial cells. In the present study, acid induced inward currents of transient receptor potential vanilloid (TRPV)1 and mucin 5AC (MUC5AC) secretion dose dependently, which were inhibited by TRPV1 antagonist capsazepine in a concentration-dependent manner. TRPV1 agonist capsaicin mediated a concentration-dependent increase in TRPV1 inward currents and MUC5AC secretion. Furthermore, capsaicin enhanced acid-induced TRPV1 inward currents and MUC5AC secretion. Acid-induced Ca(2+) influx was prevented by capsazepine dose dependently and enhanced by capsaicin. Pretreatment only with capsaicin also increased the Ca(2+) concentration in a concentration-dependent manner. These data suggest that pharmacological inhibition of calcium-permeable TRPV1 receptors could be used to prevent acid-induced mucin secretion, thereby providing a potential mechanism to reduce their toxicity.
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Affiliation(s)
- Hongmei Yu
- Division of Respiratory Medicine, Second Affiliated Hospital, Chongqing Medical University, Chongqing 400010, People's Republic of China
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Ho KW, Ward NJ, Calkins DJ. TRPV1: a stress response protein in the central nervous system. AMERICAN JOURNAL OF NEURODEGENERATIVE DISEASE 2012; 1:1-14. [PMID: 22737633 PMCID: PMC3560445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 04/21/2012] [Indexed: 06/01/2023]
Abstract
The transient receptor potential (TRP) family comprises a diverse group of cation channels that regulate a variety of intracellular signaling pathways. The TRPV1 (vanilloid 1) channel is best known for its role in nociception and sensory transmission. First studied in the dorsal root ganglia as the receptor for capsaicin, TRPV1 is now recognized to have a broader distribution and function within the central nervous system (CNS). Because it can be activated by a range of potentially noxious stimuli, TRPV1's polymodal nature and ability to interact with other receptor pathways make it a candidate for a stress response protein. As a result, TRPV1 is emerging as a key mediator of CNS function through modulation of both glial and neuronal activity. Growing evidence has suggested that TRPV1 can mediate a variety of pathways from glial reactivity and cytokine release to synaptic transmission and plasticity. This review highlights the increasing importance of TRPV1 as a regulator of CNS function in response to stress.
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Affiliation(s)
- Karen W Ho
- The Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN 37205, USA
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Samways DSK, Khakh BS, Egan TM. Allosteric modulation of Ca2+ flux in ligand-gated cation channel (P2X4) by actions on lateral portals. J Biol Chem 2012; 287:7594-602. [PMID: 22219189 PMCID: PMC3293559 DOI: 10.1074/jbc.m111.322461] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 01/03/2012] [Indexed: 12/27/2022] Open
Abstract
Human P2X receptors are a family of seven ATP-gated ion channels that transport Na(+), K(+), and Ca(2+) across cell surface membranes. The P2X4 receptor is unique among family members in its sensitivity to the macrocyclic lactone, ivermectin, which allosterically modulates both ion conduction and channel gating. In this paper we show that removing the fixed negative charge of a single acidic amino acid (Glu(51)) in the lateral entrance to the transmembrane pore markedly attenuates the effect of ivermectin on Ca(2+) current and channel gating. Ca(2+) entry through P2X4 receptors is known to trigger downstream signaling pathways in microglia. Our experiments show that the lateral portals could present a novel target for drugs in the treatment of microglia-associated disease including neuropathic pain.
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Affiliation(s)
- Damien S. K. Samways
- From the Department of Pharmacological and Physiological Science and The Center for Excellence in Neuroscience, Saint Louis University School of Medicine, St. Louis, Missouri, 63130 and
| | - Baljit S. Khakh
- the Departments of Physiology and Neurobiology, UCLA, David Geffen School of Medicine, Los Angeles, California 90095
| | - Terrance M. Egan
- From the Department of Pharmacological and Physiological Science and The Center for Excellence in Neuroscience, Saint Louis University School of Medicine, St. Louis, Missouri, 63130 and
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Samways DSK, Egan TM. Calcium-dependent decrease in the single-channel conductance of TRPV1. Pflugers Arch 2011; 462:681-91. [PMID: 21892726 DOI: 10.1007/s00424-011-1013-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 08/08/2011] [Accepted: 08/09/2011] [Indexed: 11/30/2022]
Abstract
TRPV1 is a Ca(2+) permeable cation channel gated by multiple stimuli including noxious heat, capsaicin, protons, and extracellular cations. In this paper, we show that Ca(2+) causes a concentration and voltage-dependent decrease in the capsaicin-gated TRPV1 single-channel conductance. This Ca(2+)-dependent effect on conductance was strongest at membrane potentials between -60 and +20 mV, but was diminished at more hyperpolarised potentials. Using simultaneous recordings of membrane current and fura-2 fluorescence to measure the fractional Ca(2+) current of whole-cell currents evoked through wild-type and mutant TRPV1, we investigated a possible link between the mechanisms underlying Ca(2+) permeation and the Ca(2+)-dependent effect on conductance. Surprisingly, we found no evidence of a structural correlation, and observed that the substitution of amino acids known to regulate Ca(2+) permeability had little effect on the ability for Ca(2+) to decrease TRPV1 conductance. However, we did observe that the Ca(2+)-dependent effect on conductance was not diminished by negative hyperpolarisation for a mutant receptor with severely impaired Ca(2+) permeability, TRPV1-D646N/E648Q/E651Q. This would be consistent with the idea that Ca(2+) reduces conductance by interacting with an intra-pore binding site, and that negative hyperpolarization reduces occupancy of this site by speeding the exit of Ca(2+) into the cell. Taken together, our data show that in addition to directly and indirectly regulating channel gating, Ca(2+) also directly reduces the conductance of TRPV1. Surprisingly, the mechanism underlying this Ca(2+)-dependent effect on conductance is largely independent of mechanisms governing Ca(2+) permeability.
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Affiliation(s)
- Damien S K Samways
- Department of Pharmacological and Physiological Science,Center for Excellence in Neuroscience, Saint Louis University School of Medicine, 1402 S. Grand Boulevard, St. Louis, MO, USA.
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Activity-dependent targeting of TRPV1 with a pore-permeating capsaicin analog. Proc Natl Acad Sci U S A 2011; 108:8497-502. [PMID: 21536874 DOI: 10.1073/pnas.1018550108] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The capsaicin receptor TRPV1 is the principal transduction channel for nociception. Excessive TRPV1 activation causes pathological pain. Ideal pain mangement requires selective inhibition of hyperactive pain-sensing neurons, but sparing normal nociception. We sought to determine whether it is possible to use activity-dependent TRPV1 agonists to identify nerves with excessive TRPV1 activity, as well as exploit the TRPV1 pore to deliver charged anesthetics for neuronal silencing. We synthesized a series of permanently charged capsaicinoids and found that one, cap-ET, efficaciously evoked TRPV1-dependent entry of Ca(2+) or the large cationic dye YO-PRO-1 comparably to capsaicin, but far smaller electrical currents. Cap-ET-induced YO-PRO-1 transport required permeation of both the agonist and the dye through the TRPV1 pore and could be enhanced by kinase activation or oxidative covalent modification. Moreover, cap-ET reduced capsaicin-induced currents by a voltage-dependent block of the pore. A low dose of cap-ET elicited entry of permanently charged Na(+) channel blockers to effectively suppress Na(+) currents in sensory neurons presensitized with oxidative chemicals. These results implicate therapeutic potential of these unique TRPV1 agonists exhibiting activity-dependent ion transport but of minimal pain-producing risks.
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Karashima Y, Prenen J, Talavera K, Janssens A, Voets T, Nilius B. Agonist-induced changes in Ca(2+) permeation through the nociceptor cation channel TRPA1. Biophys J 2010; 98:773-83. [PMID: 20197030 DOI: 10.1016/j.bpj.2009.11.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 10/16/2009] [Accepted: 11/05/2009] [Indexed: 12/19/2022] Open
Abstract
The Ca(2+)-permeable cation channel TRPA1 acts as an ionotropic receptor for various pungent compounds and as a noxious cold sensor in sensory neurons. It is unclear what proportion of the TRPA1-mediated current is carried by Ca(2+) ions and how the permeation pathway changes during stimulation. Here, based on the relative permeability of the nonstimulated channel to cations of different size, we estimated a pore diameter of approximately 11 A. Combined patch-clamp and Fura-2 fluorescence recordings revealed that with 2 mM extracellular Ca(2+), and at a membrane potential of -80 mV, approximately 17% of the inward TRPA1 current is carried by Ca(2+). Stimulation with mustard oil evoked an apparent dilatation of the pore of 3 A and an increase in divalent cation selectivity and fractional Ca(2+) current. Mutations in the putative pore that reduced the divalent permeability and fractional Ca(2+) current also prevented mustard-oil-induced increases in Ca(2+) permeation. It is interesting that fractional Ca(2+) currents for wild-type and mutant TRPA1 were consistently higher than values predicted based on biionic reversal potentials using the Goldman-Hodgkin-Katz equation, suggesting that binding of Ca(2+) in the pore hinders monovalent cation permeation. We conclude that the pore of TRPA1 is dynamic and supports a surprisingly large Ca(2+) influx.
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Affiliation(s)
- Yuji Karashima
- Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Belgium
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Kim HJ, Yamaguchi S, Li Q, So I, Muallem S. Properties of the TRPML3 channel pore and its stable expansion by the Varitint-Waddler-causing mutation. J Biol Chem 2010; 285:16513-20. [PMID: 20378547 DOI: 10.1074/jbc.m109.078204] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPML3 is a H(+)-regulated Ca(2+) channel that shuttles between intracellular compartments and the plasma membrane. The A419P mutation causes the varitint-waddler phenotype as a result of gain-of-function (GOF). The mechanism by which A419P leads to GOF is not known. Here, we show that the TRPML3 pore is dynamic when conducting Ca(2+) to change its conductance and permeability, which appears to be mediated by trapping Ca(2+) within the pore. The pore properties can be restored by strong depolarization or by conducting Na(+) through the pore. The A419P mutation results in expanded channel pore with altered permeability that limits modulation of the pore by Ca(2+). This effect is specific for the A419P mutation and is not reproduced by other GOF mutations, including A419G, H283A, and proline mutations in the fifth transmembrane domain. These findings describe a novel mode of a transient receptor potential channel behavior and suggest that pore expansion by the A419P mutation may contribute to the varitint-waddler phenotype.
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Affiliation(s)
- Hyun Jin Kim
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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Abstract
Although a unifying characteristic common to all transient receptor potential (TRP) channel functions remains elusive, they could be described as tetramers formed by subunits with six transmembrane domains and containing cation-selective pores, which in several cases show high calcium permeability. TRP channels constitute a large superfamily of ion channels, and can be grouped into seven subfamilies based on their amino acid sequence homology: the canonical or classic TRPs, the vanilloid receptor TRPs, the melastatin or long TRPs, ankyrin (whose only member is the transmembrane protein 1 [TRPA1]), TRPN after the nonmechanoreceptor potential C (nonpC), and the more distant cousins, the polycystins and mucolipins. Because of their role as cellular sensors, polymodal activation and gating properties, many TRP channels are activated by a variety of different stimuli and function as signal integrators. Thus, how TRP channels function and how function relates to given structural determinants contained in the channel-forming protein has attracted the attention of biophysicists as well as molecular and cell biologists. The main purpose of this review is to summarize our present knowledge on the structure of channels of the TRP ion channel family. In the absence of crystal structure information for a complete TRP channel, we will describe important protein domains present in TRP channels, structure-function mutagenesis studies, the few crystal structures available for some TRP channel modules, and the recent determination of some TRP channel structures using electron microscopy.
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Liu B, Yao J, Wang Y, Li H, Qin F. Proton inhibition of unitary currents of vanilloid receptors. ACTA ACUST UNITED AC 2009; 134:243-58. [PMID: 19720962 PMCID: PMC2737227 DOI: 10.1085/jgp.200910255] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Protons, which are released during inflammation and injury, regulate many receptors and ion channels involved in pain transduction, including capsaicin channels (transient receptor potential vanilloid receptors 1). Whereas extracellular acidification both sensitizes and directly activates the channel, it also causes concomitant reduction of the unitary current amplitudes. Here, we investigate the mechanisms and molecular basis of this inhibitory effect of protons on channel conductance. Single-channel recordings showed that the unitary current amplitudes decreased with extracellular pH in a dose-dependent manner, consistent with a model in which protons bind to a site within the channel with an apparent pKa of ∼6. The inhibition was voltage dependent, ∼65% at −60 mV and 37% at +60 mV when pH was reduced from 7.4 to 5.5. The unitary current amplitudes reached saturation at [K+] ≥ 1 M, and notably the maximum amplitudes did not converge with different pHs, inconsistent with a blockade model based on surface charge screening or competitive inhibition of permeating ions. Mutagenesis experiments uncovered two acidic residues critical for proton inhibition, one located at the pore entrance and the other on the pore helix. Based on homology to the KcsA structure, the two acidic residues, along with another basic residue also on the pore helix, could form a triad interacting with each other through extensive hydrogen bonds and electrostatic contacts, suggesting that protons may mediate the interactions between the selectivity filter and pore helix, thereby altering the local structure in the filter region and consequently the conductance of the channel.
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Affiliation(s)
- Beiying Liu
- Department of Physiology and Biophysical Sciences, State University of New York at Buffalo, Buffalo, NY 14214, USA
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Samways DSK, Harkins AB, Egan TM. Native and recombinant ASIC1a receptors conduct negligible Ca2+ entry. Cell Calcium 2009; 45:319-25. [PMID: 19185346 DOI: 10.1016/j.ceca.2008.12.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 11/21/2008] [Accepted: 12/04/2008] [Indexed: 12/15/2022]
Abstract
Acid Sensing Ion Channels (ASICs) are a family of proton-gated cation channels that play a role in the sensation of noxious stimuli. Of these, ASIC1a is the only family member that is reported to be permeable to Ca(2+), although the absolute magnitude of the Ca(2+) current is unclear. Here, we used patch-clamp photometry to determine the contribution of Ca(2+) to total current through native and recombinant ASIC1a receptors. We found that acidification of the extracellular medium evoked amiloride and psalmotoxin 1-sensitive currents in isolated chick dorsal root ganglion neurons and human embryonic kidney cells, but did not alter fura-2 fluorescence when the bath concentration of Ca(2+) was close to that found in normal physiological conditions. Further, activation of recombinant ASIC1a receptors also failed to produce measurable changes in fluorescence despite of the fact that the total cation current through the over-expressed receptor was ten-fold larger than that of the native channels. Finally, we imaged a field of intact DRG neurons loaded with the Ca(2+)-sensing dye Fluo-4, and found that acidification increased [Ca(2+)](i) in a small population of cells. Thus, although our whole-field imaging data agree with previous studies that activation of ASIC1a receptors can potentially cause elevations in intracellular free Ca(2+), our single cell data strongly challenges the view that Ca(2+) entry through the ASIC1a receptor itself contributes to this response.
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Affiliation(s)
- Damien S K Samways
- Department of Pharmacological and Physiological Science, and The Center for Excellence in Neuroscience, Saint Louis University School of Medicine, St Louis, MO 63104, USA.
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