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Oheim M, van 't Hoff M, Feltz A, Zamaleeva A, Mallet JM, Collot M. New red-fluorescent calcium indicators for optogenetics, photoactivation and multi-color imaging. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:2284-306. [PMID: 24681159 DOI: 10.1016/j.bbamcr.2014.03.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 03/09/2014] [Indexed: 01/15/2023]
Abstract
Most chemical and, with only a few exceptions, all genetically encoded fluorimetric calcium (Ca(2+)) indicators (GECIs) emit green fluorescence. Many of these probes are compatible with red-emitting cell- or organelle markers. But the bulk of available fluorescent-protein constructs and transgenic animals incorporate green or yellow fluorescent protein (GFP and YFP respectively). This is, in part, not only heritage from the tendency to aggregate of early-generation red-emitting FPs, and due to their complicated photochemistry, but also resulting from the compatibility of green-fluorescent probes with standard instrumentation readily available in most laboratories and core imaging facilities. Photochemical constraints like limited water solubility and low quantum yield have contributed to the relative paucity of red-emitting Ca(2+) probes compared to their green counterparts, too. The increasing use of GFP and GFP-based functional reporters, together with recent developments in optogenetics, photostimulation and super-resolution microscopies, has intensified the quest for red-emitting Ca(2+) probes. In response to this demand more red-emitting chemical and FP-based Ca(2+)-sensitive indicators have been developed since 2009 than in the thirty years before. In this topical review, we survey the physicochemical properties of these red-emitting Ca(2+) probes and discuss their utility for biological Ca(2+) imaging. Using the spectral separability index Xijk (Oheim M., 2010. Methods in Molecular Biology 591: 3-16) we evaluate their performance for multi-color excitation/emission experiments, involving the identification of morphological landmarks with GFP/YFP and detecting Ca(2+)-dependent fluorescence in the red spectral band. We also establish a catalog of criteria for evaluating Ca(2+) indicators that ideally should be made available for each probe. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Martin Oheim
- CNRS, UMR 8154, Paris F-75006, France; INSERM, U603, Paris F-75006, France; University Paris Descartes, PRES Sorbonne Paris Cité, Laboratory of Neurophysiology and New Microscopies, 45 rue des Saints Pères, Paris F-75006, France.
| | - Marcel van 't Hoff
- CNRS, UMR 8154, Paris F-75006, France; INSERM, U603, Paris F-75006, France; University Paris Descartes, PRES Sorbonne Paris Cité, Laboratory of Neurophysiology and New Microscopies, 45 rue des Saints Pères, Paris F-75006, France; University of Florence, LENS - European Laboratory for Non-linear Spectroscopy, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
| | - Anne Feltz
- Ecole Normale Supérieure, Institut de Biologie de l'ENS (IBENS), Paris F-75005, France; INSERM U1024, Paris F-75005, France; CNRS UMR 8197, Paris F-75005, France
| | - Alsu Zamaleeva
- Ecole Normale Supérieure, Institut de Biologie de l'ENS (IBENS), Paris F-75005, France; INSERM U1024, Paris F-75005, France; CNRS UMR 8197, Paris F-75005, France
| | - Jean-Maurice Mallet
- UPMC Université́ Paris 06, Ecole Normale Supérieure (ENS), 24 rue Lhomond, Paris F-75005, France; CNRS UMR 7203, Paris F-75005, France
| | - Mayeul Collot
- UPMC Université́ Paris 06, Ecole Normale Supérieure (ENS), 24 rue Lhomond, Paris F-75005, France; CNRS UMR 7203, Paris F-75005, France
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202
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Sangaletti R, Dahl G, Bianchi L. Mechanosensitive unpaired innexin channels in C. elegans touch neurons. Am J Physiol Cell Physiol 2014; 307:C966-77. [PMID: 25252948 DOI: 10.1152/ajpcell.00246.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Invertebrate innexin proteins share sequence homology with vertebrate pannexins and general membrane topology with both pannexins and connexins. While connexins form gap junctions that mediate intercellular communication, pannexins are thought to function exclusively as plasma membrane channels permeable to both ions and small molecules. Undoubtedly, certain innexins function as gap junction proteins. However, due to sequence similarity to pannexins, it was postulated that innexins also function as plasma membrane channels. Indeed, some of the leech innexins were found to mediate ATP release as unpaired membrane channels with shared pharmacology to pannexin channels. We show here that Caenorhabditis elegans touch-sensing neurons express a mechanically gated innexin channel with a conductance of ∼1 nS and voltage-dependent and K(+)-selective subconductance state. We also show that C. elegans touch neurons take up ethidium bromide through a mechanism that is activated and blocked by innexin activating stimuli and inhibitors, respectively. Finally, we present evidence that touch neurons' innexins are required for cell death induced by chemical ischemia. Our work demonstrates that innexins function as plasma membrane channels in native C. elegans neurons, where they may play a role in pathological cell death.
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Affiliation(s)
- Rachele Sangaletti
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
| | - Laura Bianchi
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
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203
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Abstract
In less than a decade, a small family of channel-forming glycoproteins, named pannexins, have captured the interest of many biologists, in large part due to their association with common diseases, ranging from cancers to neuropathies to infectious diseases. Although the pannexin family consists of only three members (Panx1, Panx2 and Panx3), one or more of these pannexins are expressed in virtually every mammalian organ, implicating their potential role in a diverse array of pathophysiologies. Panx1 is the most extensively studied, but features of this pannexin must be cautiously extrapolated to the other pannexins, as for example we now know that Panx2, unlike Panx1, exhibits unique properties such as a tendency to be retained within intracellular compartments. In the present review, we assess the biochemical and channel features of pannexins focusing on the literature which links these unique molecules to over a dozen diseases and syndromes. Although no germ-line mutations in genes encoding pannexins have been linked to any diseases, many cases have shown that high pannexin expression is associated with disease onset and/or progression. Disease may also occur, however, when pannexins are underexpressed, highlighting that pannexin expression must be exquisitely regulated. Finally, we discuss some of the most pressing questions and controversies in the pannexin field as the community seeks to uncover the full biological relevance of pannexins in healthy organs and during disease.
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204
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Langlois S, Xiang X, Young K, Cowan BJ, Penuela S, Cowan KN. Pannexin 1 and pannexin 3 channels regulate skeletal muscle myoblast proliferation and differentiation. J Biol Chem 2014; 289:30717-30731. [PMID: 25239622 PMCID: PMC4215249 DOI: 10.1074/jbc.m114.572131] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Pannexins constitute a family of three glycoproteins (Panx1, -2, and -3) forming single membrane channels. Recent work demonstrated that Panx1 is expressed in skeletal muscle and involved in the potentiation of contraction. However, Panxs functions in skeletal muscle cell differentiation, and proliferation had yet to be assessed. We show here that Panx1 and Panx3, but not Panx2, are present in human and rodent skeletal muscle, and their various species are differentially expressed in fetal versus adult human skeletal muscle tissue. Panx1 levels were very low in undifferentiated human primary skeletal muscle cells and myoblasts (HSMM) but increased drastically during differentiation and became the main Panx expressed in differentiated cells. Using HSMM, we found that Panx1 expression promotes this process, whereas it was impaired in the presence of probenecid or carbenoxolone. As for Panx3, its lower molecular weight species were prominent in adult skeletal muscle but very low in the fetal tissue and in undifferentiated skeletal muscle cells and myoblasts. Its overexpression (∼43-kDa species) induced HSMM differentiation and also inhibited their proliferation. On the other hand, a ∼70-kDa immunoreactive species of Panx3, likely glycosylated, sialylated, and phosphorylated, was highly expressed in proliferative myoblasts but strikingly down-regulated during their differentiation. Reduction of its endogenous expression using two Panx3 shRNAs significantly inhibited HSMM proliferation without triggering their differentiation. In summary, our results demonstrate that Panx1 and Panx3 are co-expressed in human skeletal muscle myoblasts and play a pivotal role in dictating the proliferation and differentiation status of these cells.
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Affiliation(s)
- Stéphanie Langlois
- Department of Surgery, Division of Paediatric Surgery, University of Ottawa, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada,; Apoptosis Research Center, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada
| | - Xiao Xiang
- Apoptosis Research Center, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada,; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada
| | - Kelsey Young
- Apoptosis Research Center, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada
| | - Bryce J Cowan
- Department of Dermatology and Skin Science, University of British Columbia, Vancouver, British Columbia V5Z 4E8, Canada, and
| | - Silvia Penuela
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Kyle N Cowan
- Department of Surgery, Division of Paediatric Surgery, University of Ottawa, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada,; Apoptosis Research Center, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada,; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8L1, Canada,.
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205
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Kurtenbach S, Kurtenbach S, Zoidl G. Emerging functions of pannexin 1 in the eye. Front Cell Neurosci 2014; 8:263. [PMID: 25309318 PMCID: PMC4163987 DOI: 10.3389/fncel.2014.00263] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 08/14/2014] [Indexed: 01/23/2023] Open
Abstract
Pannexin 1 (Panx1) is a high-conductance, voltage-gated channel protein found in vertebrates. Panx1 is widely expressed in many organs and tissues, including sensory systems. In the eye, Panx1 is expressed in major divisions including the retina, lens and cornea. Panx1 is found in different neuronal and non-neuronal cell types. The channel is mechanosensitive and responds to changes in extracellular ATP, intracellular calcium, pH, or ROS/nitric oxide. Since Panx1 channels operate at the crossroad of major signaling pathways, physiological functions in important autocrine and paracrine feedback signaling mechanisms were hypothesized. This review starts with describing in depth the initial Panx1 expression and localization studies fostering functional studies that uncovered distinct roles in processing visual information in subsets of neurons in the rodent and fish retina. Panx1 is expressed along the entire anatomical axis from optical nerve to retina and cornea in glia, epithelial and endothelial cells as well as in neurons. The expression and diverse localizations throughout the eye points towards versatile functions of Panx1 in neuronal and non-neuronal cells, implicating Panx1 in the crosstalk between immune and neural cells, pressure related pathological conditions like glaucoma, wound repair or neuronal cell death caused by ischemia. Summarizing the literature on Panx1 in the eye highlights the diversity of emerging Panx1 channel functions in health and disease.
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Affiliation(s)
- Sarah Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Stefan Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Georg Zoidl
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada ; Department of Biology, Faculty of Science, York University Toronto, ON, Canada
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206
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Momboisse F, Olivares MJ, Báez-Matus X, Guerra MJ, Flores-Muñoz C, Sáez JC, Martínez AD, Cárdenas AM. Pannexin 1 channels: new actors in the regulation of catecholamine release from adrenal chromaffin cells. Front Cell Neurosci 2014; 8:270. [PMID: 25237296 PMCID: PMC4154466 DOI: 10.3389/fncel.2014.00270] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 08/20/2014] [Indexed: 11/13/2022] Open
Abstract
Chromaffin cells of the adrenal gland medulla synthesize and store hormones and peptides, which are released into the blood circulation in response to stress. Among them, adrenaline is critical for the fight-or-flight response. This neurosecretory process is highly regulated and depends on cytosolic [Ca2+]. By forming channels at the plasma membrane, pannexin-1 (Panx1) is a protein involved in many physiological and pathological processes amplifying ATP release and/or Ca2+ signals. Here, we show that Panx1 is expressed in the adrenal gland where it plays a role by regulating the release of catecholamines. In fact, inhibitors of Panx1 channels, such as carbenoxolone (Cbx) and probenecid, reduced the secretory activity induced with the nicotinic agonist 1,1-dimethyl-4-phenyl-piperazinium (DMPP, 50 μM) in whole adrenal glands. A similar inhibitory effect was observed in single chromaffin cells using Cbx or 10Panx1 peptide, another Panx1 channel inhibitors. Given that the secretory response depends on cytosolic [Ca2+] and Panx1 channels are permeable to Ca2+, we studied the possible implication of Panx1 channels in the Ca2+ signaling occurring during the secretory process. In support of this possibility, Panx1 channel inhibitors significantly reduced the Ca2+ signals evoked by DMPP in single chromaffin cells. However, the Ca2+ signals induced by caffeine in the absence of extracellular Ca2+ was not affected by Panx1 channel inhibitors, suggesting that this mechanism does not involve Ca2+ release from the endoplasmic reticulum. Conversely, Panx1 inhibitors significantly blocked the DMPP-induce dye uptake, supporting the idea that Panx1 forms functional channels at the plasma membrane. These findings indicate that Panx1 channels participate in the control the Ca2+ signal that triggers the secretory response of adrenal chromaffin cells. This mechanism could have physiological implications during the response to stress.
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Affiliation(s)
- Fanny Momboisse
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - María José Olivares
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Ximena Báez-Matus
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - María José Guerra
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Carolina Flores-Muñoz
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Juan C Sáez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile ; Departamento de Fisiología, Pontifícia Universidad Católica de Chile Santiago, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Ana M Cárdenas
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
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207
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Takada H, Furuya K, Sokabe M. Mechanosensitive ATP release from hemichannels and Ca²⁺ influx through TRPC6 accelerate wound closure in keratinocytes. J Cell Sci 2014; 127:4159-71. [PMID: 25097230 DOI: 10.1242/jcs.147314] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cutaneous wound healing is accelerated by exogenous mechanical forces and is impaired in TRPC6-knockout mice. Therefore, we designed experiments to determine how mechanical force and TRPC6 channels contribute to wound healing using HaCaT keratinocytes. HaCaT cells were pretreated with hyperforin, a major component of a traditional herbal medicine for wound healing and also a TRPC6 activator, and cultured in an elastic chamber. At 3 h after scratching the confluent cell layer, the ATP release and intracellular Ca(2+) increases in response to stretching (20%) were live-imaged. ATP release was observed only in cells at the frontier facing the scar. The diffusion of released ATP caused intercellular Ca(2+) waves that propagated towards the rear cells in a P2Y-receptor-dependent manner. The Ca(2+) response and wound healing were inhibited by ATP diphosphohydrolase apyrase, the P2Y antagonist suramin, the hemichannel blocker CBX and the TRPC6 inhibitor diC8-PIP2. Finally, the hemichannel-permeable dye calcein was taken up only by ATP-releasing cells. These results suggest that stretch-accelerated wound closure is due to the ATP release through mechanosensitive hemichannels from the foremost cells and the subsequent Ca(2+) waves mediated by P2Y and TRPC6 activation.
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Affiliation(s)
- Hiroya Takada
- Department of Physiology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan
| | - Kishio Furuya
- Department of Physiology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan
| | - Masahiro Sokabe
- Department of Physiology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, 65 Tsurumai, Nagoya, 466-8550, Japan
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208
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Bravo D, Ibarra P, Retamal J, Pelissier T, Laurido C, Hernandez A, Constandil L. Pannexin 1: a novel participant in neuropathic pain signaling in the rat spinal cord. Pain 2014; 155:2108-15. [PMID: 25102401 DOI: 10.1016/j.pain.2014.07.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 06/30/2014] [Accepted: 07/29/2014] [Indexed: 01/28/2023]
Abstract
Pannexin 1 (panx1) is a large-pore membrane channel expressed in many tissues of mammals, including neurons and glial cells. Panx1 channels are highly permeable to calcium and adenosine triphosphatase (ATP); on the other hand, they can be opened by ATP and glutamate, two crucial molecules for acute and chronic pain signaling in the spinal cord dorsal horn, thus suggesting that panx1 could be a key component for the generation of central sensitization during persistent pain. In this study, we examined the effect of three panx1 blockers, namely, 10panx peptide, carbenoxolone, and probenecid, on C-reflex wind-up activity and mechanical nociceptive behavior in a spared nerve injury neuropathic rat model involving sural nerve transection. In addition, the expression of panx1 protein in the dorsal horn of the ipsilateral lumbar spinal cord was measured in sural nerve-transected and sham-operated control rats. Sural nerve transection resulted in a lower threshold for C-reflex activation by electric stimulation of the injured hindpaw, together with persistent mechanical hypersensitivity to pressure stimuli applied to the paw. Intrathecal administration of the panx1 blockers significantly depressed the spinal C-reflex wind-up activity in both neuropathic and sham control rats, and decreased mechanical hyperalgesia in neuropathic rats without affecting the nociceptive threshold in sham animals. Western blotting showed that panx1 was similarly expressed in the dorsal horn of lumbar spinal cord from neuropathic and sham rats. The present results constitute the first evidence that panx1 channels play a significant role in the mechanisms underlying central sensitization in neuropathic pain.
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Affiliation(s)
- David Bravo
- Laboratory of Neurobiology, Department of Biology, Faculty of Chemistry and Biology, University of Santiago of Chile, Santiago, Chile
| | - Paula Ibarra
- Laboratory of Neurobiology, Department of Biology, Faculty of Chemistry and Biology, University of Santiago of Chile, Santiago, Chile
| | - Jeffri Retamal
- Laboratory of Neurobiology, Department of Biology, Faculty of Chemistry and Biology, University of Santiago of Chile, Santiago, Chile
| | - Teresa Pelissier
- Program of Molecular and Clinical Pharmacology, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Claudio Laurido
- Laboratory of Neurobiology, Department of Biology, Faculty of Chemistry and Biology, University of Santiago of Chile, Santiago, Chile
| | - Alejandro Hernandez
- Laboratory of Neurobiology, Department of Biology, Faculty of Chemistry and Biology, University of Santiago of Chile, Santiago, Chile
| | - Luis Constandil
- Laboratory of Neurobiology, Department of Biology, Faculty of Chemistry and Biology, University of Santiago of Chile, Santiago, Chile.
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209
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Wang J, Ambrosi C, Qiu F, Jackson DG, Sosinsky G, Dahl G. The membrane protein Pannexin1 forms two open-channel conformations depending on the mode of activation. Sci Signal 2014; 7:ra69. [PMID: 25056878 DOI: 10.1126/scisignal.2005431] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Pannexin1 (Panx1) participates in several signaling events that involve adenosine triphosphate (ATP) release, including the innate immune response, ciliary beat in airway epithelia, and oxygen supply in the vasculature. The view that Panx1 forms a large ATP release channel has been challenged by the association of a low-conductance, small anion-selective channel with the presence of Panx1. We showed that Panx1 membrane channels can function in two distinct modes with different conductances and permeabilities when heterologously expressed in Xenopus oocytes. When stimulated by potassium ions (K(+)), Panx1 formed a high-conductance channel of ~500 pS that was permeable to ATP. Various physiological stimuli can induce this ATP-permeable conformation of the channel in several cell types. In contrast, the channel had a low conductance (~50 pS) with no detectable ATP permeability when activated by voltage in the absence of K(+). The two channel states were associated with different reactivities of the terminal cysteine of Panx1 to thiol reagents, suggesting different conformations. Single-particle electron microscopic analysis revealed that K(+) stimulated the formation of channels with a larger pore diameter than those formed in the absence of K(+). These data suggest that different stimuli lead to distinct channel structures with distinct biophysical properties.
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Affiliation(s)
- Junjie Wang
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA
| | - Cinzia Ambrosi
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA 92093-06083, USA
| | - Feng Qiu
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA
| | - David G Jackson
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA
| | - Gina Sosinsky
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA 92093-06083, USA. Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093-06083, USA
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA.
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210
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Onami K, Kimura Y, Ito Y, Yamauchi T, Yamasaki K, Aiba S. Nonmetal Haptens Induce ATP Release from Keratinocytes through Opening of Pannexin Hemichannels by Reactive Oxygen Species. J Invest Dermatol 2014; 134:1951-1960. [DOI: 10.1038/jid.2014.93] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 01/30/2014] [Accepted: 02/03/2014] [Indexed: 01/21/2023]
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211
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Taylor KA, Wright JR, Vial C, Evans RJ, Mahaut-Smith MP. Amplification of human platelet activation by surface pannexin-1 channels. J Thromb Haemost 2014; 12:987-98. [PMID: 24655807 PMCID: PMC4238786 DOI: 10.1111/jth.12566] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 03/04/2014] [Indexed: 02/03/2023]
Abstract
BACKGROUND Pannexin-1 (Panx1) forms an anion-selective channel with a permeability up to ~1 kDa and represents a non-lytic, non-vesicular ATP release pathway in erythrocytes, leukocytes and neurons. Related connexin gap junction proteins have been reported in platelets; however, the expression and function of the pannexins remain unknown. OBJECTIVE To determine the expression and function of pannexins in human plate-lets, using molecular, cellular and functional techniques. METHODS Panx1 expression in human platelets was det-ermined using qPCR and antibody-based techniques. Contributions of Panx1 to agonist-evoked efflux of cytoplasmic calcein, Ca(2+) influx, ATP release and aggregation were assessed in washed platelets under conditions where the P2X1 receptor response was preserved (0.32 U mL(-1) apyrase). Thrombus formation in whole blood was assessed in vitro using a shear chamber assay. Two structurally unrelated and widely used Panx1 inhibitors, probenecid and carbenoxolone, were used throughout this study, at concentrations that do not affect connexin channels. RESULTS PANX1, but not PANX2 or PANX3, mRNA was detected in human platelets. Furthermore, Panx1 protein is glycosylated and present on the plasma membrane of platelets, and displays weak physical association with P2X1 receptors. Panx1 inhibition blocked thrombin-evoked efflux of calcein, and reduced Ca(2+) influx, ATP release, platelet aggregation and thrombus formation under arterial shear rates in vitro. The Panx1-dependent contribution was not additive to that of P2X1 receptors. CONCLUSIONS Panx1 is expressed on human platelets and amplifies Ca(2+) influx, ATP release and aggregation through the secondary activation of P2X1 receptors. We propose that Panx1 represents a novel target for the management of arterial thrombosis.
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Affiliation(s)
- K A Taylor
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, UK
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212
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Alvarez CL, Schachter J, de Sá Pinheiro AA, Silva LDS, Verstraeten SV, Persechini PM, Schwarzbaum PJ. Regulation of extracellular ATP in human erythrocytes infected with Plasmodium falciparum. PLoS One 2014; 9:e96216. [PMID: 24858837 PMCID: PMC4032238 DOI: 10.1371/journal.pone.0096216] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 04/03/2014] [Indexed: 11/18/2022] Open
Abstract
In human erythrocytes (h-RBCs) various stimuli induce increases in [cAMP] that trigger ATP release. The resulting pattern of extracellular ATP accumulation (ATPe kinetics) depends on both ATP release and ATPe degradation by ectoATPase activity. In this study we evaluated ATPe kinetics from primary cultures of h-RBCs infected with P. falciparum at various stages of infection (ring, trophozoite and schizont stages). A "3V" mixture containing isoproterenol (β-adrenergic agonist), forskolin (adenylate kinase activator) and papaverine (phosphodiesterase inhibitor) was used to induce cAMP-dependent ATP release. ATPe kinetics of r-RBCs (ring-infected RBCs), t-RBCs (trophozoite-infected RBCs) and s-RBCs (schizont-infected RBCs) showed [ATPe] to peak acutely to a maximum value followed by a slower time dependent decrease. In all intraerythrocytic stages, values of ΔATP1 (difference between [ATPe] measured 1 min post-stimulus and basal [ATPe]) increased nonlinearly with parasitemia (from 2 to 12.5%). Under 3V exposure, t-RBCs at parasitemia 94% (t94-RBCs) showed 3.8-fold higher ΔATP1 values than in h-RBCs, indicative of upregulated ATP release. Pre-exposure to either 100 µM carbenoxolone, 100 nM mefloquine or 100 µM NPPB reduced ΔATP1 to 83-87% for h-RBCs and 63-74% for t94-RBCs. EctoATPase activity, assayed at both low nM concentrations (300-900 nM) and 500 µM exogenous ATPe concentrations increased approx. 400-fold in t94-RBCs, as compared to h-RBCs, while intracellular ATP concentrations of t94-RBCs were 65% that of h-RBCs. In t94-RBCs, production of nitric oxide (NO) was approx. 7-fold higher than in h-RBCs, and was partially inhibited by L-NAME pre-treatment. In media with L-NAME, ΔATP1 values were 2.7-times higher in h-RBCs and 4.2-times higher in t94-RBCs, than without L-NAME. Results suggest that P. falciparum infection of h-RBCs strongly activates ATP release via Pannexin 1 in these cells. Several processes partially counteracted ATPe accumulation: an upregulated ATPe degradation, an enhanced NO production, and a decreased intracellular ATP concentration.
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Affiliation(s)
- Cora Lilia Alvarez
- Instituto de Química y Fisicoquímica Biológicas (Facultad de Farmacia y Bioquímica), Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal de Rio de Janeiro, Rio de Janeiro, Brasil
- INPeTAm Instituto Nacional de Ciência e Tecnologia em Pesquisa Translacional em Saúde e Ambiente na Reigião Amazônica, Rio de Janeiro, Brasil
| | - Julieta Schachter
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal de Rio de Janeiro, Rio de Janeiro, Brasil
- INPeTAm Instituto Nacional de Ciência e Tecnologia em Pesquisa Translacional em Saúde e Ambiente na Reigião Amazônica, Rio de Janeiro, Brasil
| | - Ana Acacia de Sá Pinheiro
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal de Rio de Janeiro, Rio de Janeiro, Brasil
| | - Leandro de Souza Silva
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal de Rio de Janeiro, Rio de Janeiro, Brasil
| | - Sandra Viviana Verstraeten
- Instituto de Química y Fisicoquímica Biológicas (Facultad de Farmacia y Bioquímica), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Pedro Muanis Persechini
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal de Rio de Janeiro, Rio de Janeiro, Brasil
- INPeTAm Instituto Nacional de Ciência e Tecnologia em Pesquisa Translacional em Saúde e Ambiente na Reigião Amazônica, Rio de Janeiro, Brasil
| | - Pablo Julio Schwarzbaum
- Instituto de Química y Fisicoquímica Biológicas (Facultad de Farmacia y Bioquímica), Universidad de Buenos Aires, Buenos Aires, Argentina
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213
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Vroman R, Klaassen LJ, Howlett MH, Cenedese V, Klooster J, Sjoerdsma T, Kamermans M. Extracellular ATP hydrolysis inhibits synaptic transmission by increasing ph buffering in the synaptic cleft. PLoS Biol 2014; 12:e1001864. [PMID: 24844296 PMCID: PMC4028192 DOI: 10.1371/journal.pbio.1001864] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 04/10/2014] [Indexed: 11/18/2022] Open
Abstract
A slow mechanism of retinal synaptic inhibition involves hydrolysis of ATP released from pannexin 1 channels (from the tips of horizontal cell dendrites); the resulting protons and phosphates acidify the synaptic cleft, which inhibits neurotransmitter release. Neuronal computations strongly depend on inhibitory interactions. One such example occurs at the first retinal synapse, where horizontal cells inhibit photoreceptors. This interaction generates the center/surround organization of bipolar cell receptive fields and is crucial for contrast enhancement. Despite its essential role in vision, the underlying synaptic mechanism has puzzled the neuroscience community for decades. Two competing hypotheses are currently considered: an ephaptic and a proton-mediated mechanism. Here we show that horizontal cells feed back to photoreceptors via an unexpected synthesis of the two. The first one is a very fast ephaptic mechanism that has no synaptic delay, making it one of the fastest inhibitory synapses known. The second one is a relatively slow (τ≈200 ms), highly intriguing mechanism. It depends on ATP release via Pannexin 1 channels located on horizontal cell dendrites invaginating the cone synaptic terminal. The ecto-ATPase NTPDase1 hydrolyses extracellular ATP to AMP, phosphate groups, and protons. The phosphate groups and protons form a pH buffer with a pKa of 7.2, which keeps the pH in the synaptic cleft relatively acidic. This inhibits the cone Ca2+ channels and consequently reduces the glutamate release by the cones. When horizontal cells hyperpolarize, the pannexin 1 channels decrease their conductance, the ATP release decreases, and the formation of the pH buffer reduces. The resulting alkalization in the synaptic cleft consequently increases cone glutamate release. Surprisingly, the hydrolysis of ATP instead of ATP itself mediates the synaptic modulation. Our results not only solve longstanding issues regarding horizontal cell to photoreceptor feedback, they also demonstrate a new form of synaptic modulation. Because pannexin 1 channels and ecto-ATPases are strongly expressed in the nervous system and pannexin 1 function is implicated in synaptic plasticity, we anticipate that this novel form of synaptic modulation may be a widespread phenomenon. At the first retinal synapse, specific cells—horizontal cells (HCs)—inhibit photoreceptors and help to organize the receptive fields of another retinal cell type, bipolar cells. This synaptic interaction is crucial for visual contrast enhancement. Here we show that horizontal cells feed back to photoreceptors via a very fast ephaptic mechanism and a relatively slow mechanism. The slow mechanism requires ATP release via Pannexin 1 (Panx1) channels that are located on HC dendrites near the site where photoreceptors release the neurotransmitter glutamate to HCs and bipolar cells. The released ATP is hydrolyzed to produce AMP, phosphate groups, and protons; these phosphates and protons form a pH buffer, which acidifies the synaptic cleft. This slow acidification inhibits presynaptic calcium channels and consequently reduces the neurotransmitter release of photoreceptors. This demonstrates a new way in which ATP release can be involved in synaptic modulation. Surprisingly, the action of ATP is not purinergic but is mediated via changes in the pH buffer capacity in the synaptic cleft. Given the broad expression of Panx1 channels in the nervous system and the suggestion that Panx1 function underlies stabilization of synaptic plasticity and is needed for learning, we anticipate that this mechanism will be more widespread than just occurring at the first retinal synapse.
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Affiliation(s)
- Rozan Vroman
- Netherlands Institute for Neuroscience, Amsterdam, the Netherlands
| | - Lauw J. Klaassen
- Netherlands Institute for Neuroscience, Amsterdam, the Netherlands
| | | | | | - Jan Klooster
- Netherlands Institute for Neuroscience, Amsterdam, the Netherlands
| | | | - Maarten Kamermans
- Netherlands Institute for Neuroscience, Amsterdam, the Netherlands
- * E-mail:
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214
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Sondersorg AC, Busse D, Kyereme J, Rothermel M, Neufang G, Gisselmann G, Hatt H, Conrad H. Chemosensory information processing between keratinocytes and trigeminal neurons. J Biol Chem 2014; 289:17529-40. [PMID: 24790106 DOI: 10.1074/jbc.m113.499699] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Trigeminal fibers terminate within the facial mucosa and skin and transmit tactile, proprioceptive, chemical, and nociceptive sensations. Trigeminal sensations can arise from the direct stimulation of intraepithelial free nerve endings or indirectly through information transmission from adjacent cells at the peripheral innervation area. For mechanical and thermal cues, communication processes between skin cells and somatosensory neurons have already been suggested. High concentrations of most odors typically provoke trigeminal sensations in vivo but surprisingly fail to activate trigeminal neuron monocultures. This fact favors the hypothesis that epithelial cells may participate in chemodetection and subsequently transmit signals to neighboring trigeminal fibers. Keratinocytes, the major cell type of the epidermis, express various receptors that enable reactions to multiple environmental stimuli. Here, using a co-culture approach, we show for the first time that exposure to the odorant chemicals induces a chemical communication between human HaCaT keratinocytes and mouse trigeminal neurons. Moreover, a supernatant analysis of stimulated keratinocytes and subsequent blocking experiments with pyrodoxalphosphate-6-azophenyl-2',4'-disulfonate revealed that ATP serves as the mediating transmitter molecule released from skin cells after odor stimulation. We show that the ATP release resulting from Javanol® stimulation of keratinocytes was mediated by pannexins. Consequently, keratinocytes act as chemosensors linking the environment and the trigeminal system via ATP signaling.
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Affiliation(s)
- Anna Christina Sondersorg
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Daniela Busse
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Jessica Kyereme
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Markus Rothermel
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Gitta Neufang
- Dermatological Skin Care, Beiersdorf AG, D-20245 Hamburg, Germany
| | - Günter Gisselmann
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Hanns Hatt
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Heike Conrad
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
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215
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Mizoguchi K, Kanno H, Ikarashi Y, Kase Y. Specific binding and characteristics of 18β-glycyrrhetinic acid in rat brain. PLoS One 2014; 9:e95760. [PMID: 24752617 PMCID: PMC3994142 DOI: 10.1371/journal.pone.0095760] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 03/28/2014] [Indexed: 01/01/2023] Open
Abstract
18β-Glycyrrhetinic acid (GA) is the aglycone of glycyrrhizin that is a component of Glycyrrhiza, and has several pharmacological actions in the central nervous system. Recently, GA has been demonstrated to reach the brain by crossing the blood-brain barrier in rats after oral administration of a Glycyrrhiza-containing traditional Japanese medicine, yokukansan. These findings suggest that there are specific binding sites for GA in the brain. Here we show evidence that [3H]GA binds specifically to several brain areas by quantitative autoradiography; the density was higher in the hippocampus, moderate in the caudate putamen, nucleus accumbens, amygdala, olfactory bulb, cerebral cortex, thalamus, and mid brain, and lower in the brain stem and cerebellum. Several kinds of steroids, gap junction-blocking reagents, glutamate transporter-recognized compounds, and glutamate receptor agonists did not inhibit the [3H]GA binding. Microautoradiography showed that the [3H]GA signals in the hippocampus were distributed in small non-neuronal cells similar to astrocytes. Immunohistochemical analysis revealed that immunoreactivity of 11β-hydroxysteroid dehydrogenase type-1 (11β-HSD1), a defined molecule recognized by GA, was detected mainly in neurons, moderately in astrocytes, and very slightly in microglial cells, of the hippocampus. These results demonstrate that specific binding sites for GA exist in rat brain tissue, and suggest that the pharmacological actions of GA may be related to 11β-HSD1 in astrocytes. This finding provides important information to understand the pharmacology of GA in the brain.
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Affiliation(s)
- Kazushige Mizoguchi
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., Yoshiwara, Ami-machi, Inashiki-gun, Ibaraki, Japan
| | - Hitomi Kanno
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., Yoshiwara, Ami-machi, Inashiki-gun, Ibaraki, Japan
| | - Yasushi Ikarashi
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., Yoshiwara, Ami-machi, Inashiki-gun, Ibaraki, Japan
| | - Yoshio Kase
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., Yoshiwara, Ami-machi, Inashiki-gun, Ibaraki, Japan
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216
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Jackson DG, Wang J, Keane RW, Scemes E, Dahl G. ATP and potassium ions: a deadly combination for astrocytes. Sci Rep 2014; 4:4576. [PMID: 24694658 PMCID: PMC3974143 DOI: 10.1038/srep04576] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 03/18/2014] [Indexed: 11/09/2022] Open
Abstract
The ATP release channel Pannexin1 (Panx1) is self-regulated, i.e. the permeant ATP inhibits the channel from the extracellular space. The affinity of the ATP binding site is lower than that of the purinergic P2X7 receptor allowing a transient activation of Panx1 by ATP through P2X7R. Here we show that the inhibition of Panx1 by ATP is abrogated by increased extracellular potassium ion concentration ([K(+)]o) in a dose-dependent manner. Since increased [K(+)]o is also a stimulus for Panx1 channels, it can be expected that a combination of ATP and increased [K(+)]o would be deadly for cells. Indeed, astrocytes did not survive exposure to these combined stimuli. The death mechanism, although involving P2X7R, does not appear to strictly follow a pyroptotic pathway. Instead, caspase-3 was activated, a process inhibited by Panx1 inhibitors. These data suggest that Panx1 plays an early role in the cell death signaling pathway involving ATP and K(+) ions. Additionally, Panx1 may play a second role once cells are committed to apoptosis, since Panx1 is also a substrate of caspase-3.
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Affiliation(s)
- David G Jackson
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33136
| | - Junjie Wang
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33136
| | - Robert W Keane
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33136
| | - Eliana Scemes
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, 10461
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33136
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217
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Bhaskaracharya A, Dao-Ung P, Jalilian I, Spildrejorde M, Skarratt KK, Fuller SJ, Sluyter R, Stokes L. Probenecid blocks human P2X7 receptor-induced dye uptake via a pannexin-1 independent mechanism. PLoS One 2014; 9:e93058. [PMID: 24671093 PMCID: PMC3966854 DOI: 10.1371/journal.pone.0093058] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 02/28/2014] [Indexed: 11/18/2022] Open
Abstract
P2X7 is a ligand-gated ion channel which is activated by ATP and displays secondary permeability characteristics. The mechanism of development of the secondary permeability pathway is currently unclear, although a role for the hemichannel protein pannexin-1 has been suggested. In this study we investigated the role of pannexin-1 in P2X7-induced dye uptake and ATP-induced IL-1β secretion from human monocytes. We found no pharmacological evidence for involvement of pannexin-1 in P2X7-mediated dye uptake in transfected HEK-293 cells with no inhibition seen for carbenoxolone and the pannexin-1 mimetic inhibitory peptide, 10Panx1. However, we found that probenecid inhibited P2X7-induced cationic and anionic dye uptake in stably transfected human P2X7 HEK-293 cells. An IC50 value of 203 μM was calculated for blockade of ATP-induced responses at human P2X7. Probenecid also reduced dye uptake and IL-1β secretion from human CD14+ monocytes whereas carbenoxolone and 10Panx1 showed no inhibitory effect. Patch clamp and calcium indicator experiments revealed that probenecid directly blocks the human P2X7 receptor.
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Affiliation(s)
- Archana Bhaskaracharya
- Sydney Medical School Nepean, University of Sydney, Nepean Hospital, Penrith, New South Wales, Australia
| | - Phuong Dao-Ung
- Sydney Medical School Nepean, University of Sydney, Nepean Hospital, Penrith, New South Wales, Australia
| | - Iman Jalilian
- School of Biological Sciences, Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Mari Spildrejorde
- School of Biological Sciences, Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Kristen K. Skarratt
- Sydney Medical School Nepean, University of Sydney, Nepean Hospital, Penrith, New South Wales, Australia
| | - Stephen J. Fuller
- Sydney Medical School Nepean, University of Sydney, Nepean Hospital, Penrith, New South Wales, Australia
| | - Ronald Sluyter
- School of Biological Sciences, Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
| | - Leanne Stokes
- Sydney Medical School Nepean, University of Sydney, Nepean Hospital, Penrith, New South Wales, Australia
- Health Innovations Research Institute, School of Medical Sciences, RMIT University, Bundoora, Melbourne, Victoria, Australia
- * E-mail:
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218
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Billaud M, Lohman AW, Johnstone SR, Biwer LA, Mutchler S, Isakson BE. Regulation of cellular communication by signaling microdomains in the blood vessel wall. Pharmacol Rev 2014; 66:513-69. [PMID: 24671377 DOI: 10.1124/pr.112.007351] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
It has become increasingly clear that the accumulation of proteins in specific regions of the plasma membrane can facilitate cellular communication. These regions, termed signaling microdomains, are found throughout the blood vessel wall where cellular communication, both within and between cell types, must be tightly regulated to maintain proper vascular function. We will define a cellular signaling microdomain and apply this definition to the plethora of means by which cellular communication has been hypothesized to occur in the blood vessel wall. To that end, we make a case for three broad areas of cellular communication where signaling microdomains could play an important role: 1) paracrine release of free radicals and gaseous molecules such as nitric oxide and reactive oxygen species; 2) role of ion channels including gap junctions and potassium channels, especially those associated with the endothelium-derived hyperpolarization mediated signaling, and lastly, 3) mechanism of exocytosis that has considerable oversight by signaling microdomains, especially those associated with the release of von Willebrand factor. When summed, we believe that it is clear that the organization and regulation of signaling microdomains is an essential component to vessel wall function.
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Affiliation(s)
- Marie Billaud
- Dept. of Molecular Physiology and Biophysics, University of Virginia School of Medicine, PO Box 801394, Charlottesville, VA 22902.
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219
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Innexin and pannexin channels and their signaling. FEBS Lett 2014; 588:1396-402. [PMID: 24632288 DOI: 10.1016/j.febslet.2014.03.007] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 03/06/2014] [Indexed: 01/24/2023]
Abstract
Innexins are bifunctional membrane proteins in invertebrates, forming gap junctions as well as non-junctional membrane channels (innexons). Their vertebrate analogues, the pannexins, have not only lost the ability to form gap junctions but are also prevented from it by glycosylation. Pannexins appear to form only non-junctional membrane channels (pannexons). The membrane channels formed by pannexins and innexins are similar in their biophysical and pharmacological properties. Innexons and pannexons are permeable to ATP, are present in glial cells, and are involved in activation of microglia by calcium waves in glia. Directional movement and accumulation of microglia following nerve injury, which has been studied in the leech which has unusually large glial cells, involves at least 3 signals: ATP is the "go" signal, NO is the "where" signal and arachidonic acid is a "stop" signal.
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220
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Bou Saab J, Losa D, Chanson M, Ruez R. Connexins in respiratory and gastrointestinal mucosal immunity. FEBS Lett 2014; 588:1288-96. [PMID: 24631537 DOI: 10.1016/j.febslet.2014.02.059] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 02/27/2014] [Accepted: 02/27/2014] [Indexed: 12/18/2022]
Abstract
The mucosal lining forms the physical and chemical barrier that protects against pathogens and hostile particles and harbors its own population of bacteria, fungi and archea, known as the microbiota. The immune system controls tolerance of this population of microorganisms that have proven to be beneficial for its host. Keeping its physical integrity and a correct balance with the microbiota, the mucosa preserves its homeostasis and its protective function and maintains host's health. However, in some conditions, pathogens may succeed in breaching mucosal homeostasis and successfully infecting the host. In this review we will discuss the role the mucosa plays in the defense against bacterial pathogens by considering the gap junction protein connexins. We will detail their implication in mucosal homeostasis and upon infection with bacteria in the respiratory and the gastrointestinal tracts.
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Affiliation(s)
- Joanna Bou Saab
- Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Davide Losa
- Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Marc Chanson
- Geneva University Hospitals and University of Geneva, Geneva, Switzerland.
| | - Richard Ruez
- Geneva University Hospitals and University of Geneva, Geneva, Switzerland
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221
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Unexpected link between an antibiotic, pannexin channels and apoptosis. Nature 2014; 507:329-34. [PMID: 24646995 PMCID: PMC4078991 DOI: 10.1038/nature13147] [Citation(s) in RCA: 192] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Accepted: 02/12/2014] [Indexed: 12/17/2022]
Abstract
Plasma membrane pannexin 1 channels (PANX1) release nucleotide find-me
signals from apoptotic cells to attract phagocytes. In a small molecule screen,
we discovered the quinolone antibiotic trovafloxacin as a novel PANX1 inhibitor.
Although quinolones are widely used to treat bacterial infections, some
quinolones have unexplained side effects, including deaths among children. PANX1
is a direct target of trovafloxacin at drug concentrations seen in human plasma,
and its inhibition led to dysregulated fragmentation of apoptotic cells. Genetic
loss of PANX1 phenocopied trovafloxacin effects, revealing a non-redundant role
for pannexin channels in regulating cellular disassembly during apoptosis.
Increase in drug-resistant bacteria worldwide and the dearth of new antibiotics
is a major human health challenge. Comparing different quinolone antibiotics
suggests that certain structural features may contribute to PANX1 blockade.
These data identify a novel linkage between an antibiotic, pannexin channels,
and cellular integrity, and suggest that re-engineering certain quinolones might
help develop newer antibacterials.
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222
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Shoji KF, Sáez PJ, Harcha PA, Aguila HL, Sáez JC. Pannexin1 channels act downstream of P2X 7 receptors in ATP-induced murine T-cell death. Channels (Austin) 2014; 8:142-56. [PMID: 24590064 DOI: 10.4161/chan.28122] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Death of murine T cells induced by extracellular ATP is mainly triggered by activation of purinergic P2X 7 receptors (P2X 7Rs). However, a link between P2X 7Rs and pannexin1 (Panx1) channels, which are non-selective, has been recently demonstrated in other cell types. In this work, we characterized the expression and cellular distribution of pannexin family members (Panxs 1, 2 and 3) in isolated T cells. Panx1 was the main pannexin family member clearly detected in both helper (CD4+) and cytotoxic (CD8+) T cells, whereas low levels of Panx2 were found in both T-cell subsets. Using pharmacological and genetic approaches, Panx1 channels were found to mediate most ATP-induced ethidium uptake since this was drastically reduced by Panx1 channel blockers (10Panx1, Probenecid and low carbenoxolone concentration) and absent in T cells derived from Panx1-/- mice. Moreover, electrophysiological measurements in wild-type CD4+ cells treated with ATP unitary current events and pharmacological sensitivity compatible with Panx1 channels were found. In addition, ATP release from T cells treated with 4Br-A23187, a calcium ionophore, was completely blocked with inhibitors of both connexin hemichannels and Panx1 channels. Panx1 channel blockers drastically reduced the ATP-induced T-cell mortality, indicating that Panx1 channels mediate the ATP-induced T-cell death. However, mortality was not reduced in T cells of Panx1-/- mice, in which levels of P2X 7Rs and ATP-induced intracellular free Ca2+ responses were enhanced suggesting that P2X 7Rs take over Panx1 channels lose-function in mediating the onset of cell death induced by extracellular ATP.
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Affiliation(s)
- Kenji F Shoji
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile
| | - Pablo J Sáez
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile
| | - Paloma A Harcha
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile
| | - Hector L Aguila
- Department of Immunology; University of Connecticut Health Center; Farmington, CT USA
| | - Juan C Sáez
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile; Instituto Milenio; Centro Interdisciplinario de Neurociencias de Valparaíso; Valparaíso, Chile
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223
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Makarenkova HP, Shestopalov VI. The role of pannexin hemichannels in inflammation and regeneration. Front Physiol 2014; 5:63. [PMID: 24616702 PMCID: PMC3933922 DOI: 10.3389/fphys.2014.00063] [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: 11/11/2013] [Accepted: 02/02/2014] [Indexed: 12/19/2022] Open
Abstract
Tissue injury involves coordinated systemic responses including inflammatory response, targeted cell migration, cell-cell communication, stem cell activation and proliferation, and tissue inflammation and regeneration. The inflammatory response is an important prerequisite for regeneration. Multiple studies suggest that extensive cell-cell communication during tissue regeneration is coordinated by purinergic signaling via extracellular adenosine triphosphate (ATP). Most recent data indicates that ATP release for such communication is mediated by hemichannels formed by connexins and pannexins. The Pannexin family consists of three vertebrate proteins (Panx 1, 2, and 3) that have low sequence homology with other gap junction proteins and were shown to form predominantly non-junctional plasma membrane hemichannels. Pannexin-1 (Panx1) channels function as an integral component of the P2X/P2Y purinergic signaling pathway and is arguably the major contributor to pathophysiological ATP release. Panx1 is expressed in many tissues, with highest levels detected in developing brain, retina and skeletal muscles. Panx1 channel expression and activity is reported to increase significantly following injury/inflammation and during regeneration and differentiation. Recent studies also report that pharmacological blockade of the Panx1 channel or genetic ablation of the Panx1 gene cause significant disruption of progenitor cell migration, proliferation, and tissue regeneration. These findings suggest that pannexins play important roles in activation of both post-injury inflammatory response and the subsequent process of tissue regeneration. Due to wide expression in multiple tissues and involvement in diverse signaling pathways, pannexins and connexins are currently being considered as therapeutic targets for traumatic brain or spinal cord injuries, ischemic stroke and cancer. The precise role of pannexins and connexins in the balance between tissue inflammation and regeneration needs to be further understood.
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Affiliation(s)
- Helen P Makarenkova
- Department of Cell and Molecular Biology, The Scripps Research Institute La Jolla, CA, USA
| | - Valery I Shestopalov
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine Miami, FL, USA ; Department of Cell Biology and Anatomy, Vavilov Institute for General Genetics Moscow, Russia
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Sarrouilhe D, Dejean C, Mesnil M. Involvement of gap junction channels in the pathophysiology of migraine with aura. Front Physiol 2014; 5:78. [PMID: 24611055 PMCID: PMC3933780 DOI: 10.3389/fphys.2014.00078] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 02/07/2014] [Indexed: 12/28/2022] Open
Abstract
Migraine is a common, recurrent, and disabling primary headache disorder with a genetic component which affects up to 20% of the population. One third of all patients with migraine experiences aura, a focal neurological disturbance that manifests itself as visual, sensitive or motor symptoms preceding the headache. In the pathophysiology of migraine with aura, activation of the trigeminovascular system from the meningeal vessels mediates migraine pain via the brainstem and projections ascend to the thalamus and cortex. Cortical spreading depression (CSD) was proposed to trigger migraine aura and to activate perivascular trigeminal nerves in the cortex. Quinine, quinidine and the derivative mefloquine are able to inhibit CSD suggesting an involvement of neuronal connexin36 channels in CSD propagation. More recently, CSD was shown to induce headache by activating the trigeminovascular system through the opening of stressed neuronal Pannexin1 channels. A novel benzopyran compound, tonabersat, was selected for clinical trial on the basis of its inhibitory activity on CSD and neurogenic inflammation in animal models of migraine. Interestingly, in the time course of animal model trials, tonabersat was shown to inhibit trigeminal ganglion (TGG) neuronal-glial cell gap junctions, suggesting that this compound could prevent peripheral sensitization within the ganglion. Three clinical trials aimed at investigating the effectiveness of tonabersat as a preventive drug were negative, and conflicting results were obtained in other trials concerning its ability to relieve attacks. In contrast, in another clinical trial, tonabersat showed a preventive effect on attacks of migraine with aura but had no efficacy on non-aura attacks. Gap junction channels seem to be involved in several ways in the pathophysiology of migraine with aura and emerge as a new promising putative target in treatment of this disorder.
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Affiliation(s)
- Denis Sarrouilhe
- Laboratoire de Physiologie Humaine, Faculté de Médecine et Pharmacie, Université de Poitiers Poitiers, France
| | - Catherine Dejean
- Service Pharmacie, Centre Hospitalier Henri Laborit Poitiers, France
| | - Marc Mesnil
- Faculté des Sciences Fondamentales et Appliquées, STIM, ERL 7368-CNRS, Université de Poitiers Poitiers, France
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Abstract
The pannexins (Panxs) are a family of chordate proteins homologous to the invertebrate gap junction forming proteins named innexins. Three distinct Panx paralogs (Panx1, Panx2, and Panx3) are shared among the major vertebrate phyla, but they appear to have suppressed (or even lost) their ability to directly couple adjacent cells. Connecting the intracellular and extracellular compartments is now widely accepted as Panx's primary function, facilitating the passive movement of ions and small molecules along electrochemical gradients. The tissue distribution of the Panxs ranges from pervasive to very restricted, depending on the paralog, and are often cell type-specific and/or developmentally regulated within any given tissue. In recent years, Panxs have been implicated in an assortment of physiological and pathophysiological processes, particularly with respect to ATP signaling and inflammation, and they are now considered to be a major player in extracellular purinergic communication. The following is a comprehensive review of the Panx literature, exploring the historical events leading up to their discovery, outlining our current understanding of their biochemistry, and describing the importance of these proteins in health and disease.
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Affiliation(s)
- Stephen R Bond
- Genome Technology Branch, Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health Bethesda, MD, USA ; Department of Cellular and Physiological Science, Life Sciences Institute, University of British Columbia Vancouver, BC, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Science, Life Sciences Institute, University of British Columbia Vancouver, BC, Canada
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226
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Lohman AW, Isakson BE. Differentiating connexin hemichannels and pannexin channels in cellular ATP release. FEBS Lett 2014; 588:1379-88. [PMID: 24548565 DOI: 10.1016/j.febslet.2014.02.004] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2014] [Revised: 02/06/2014] [Accepted: 02/06/2014] [Indexed: 12/22/2022]
Abstract
Adenosine triphosphate (ATP) plays a fundamental role in cellular communication, with its extracellular accumulation triggering purinergic signaling cascades in a diversity of cell types. While the roles for purinergic signaling in health and disease have been well established, identification and differentiation of the specific mechanisms controlling cellular ATP release is less well understood. Multiple mechanisms have been proposed to regulate ATP release with connexin (Cx) hemichannels and pannexin (Panx) channels receiving major focus. However, segregating the specific roles of Panxs and Cxs in ATP release in a plethora of physiological and pathological contexts has remained enigmatic. This multifaceted problem has arisen from the selectivity of pharmacological inhibitors for Panxs and Cxs, methodological differences in assessing Panx and Cx function and the potential compensation by other isoforms in gene silencing and genetic knockout models. Consequently, there remains a void in the current understanding of specific contributions of Panxs and Cxs in releasing ATP during homeostasis and disease. Differentiating the distinct signaling pathways that regulate these two channels will advance our current knowledge of cellular communication and aid in the development of novel rationally-designed drugs for modulation of Panx and Cx activity, respectively.
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Affiliation(s)
- Alexander W Lohman
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA 22098, United States; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States
| | - Brant E Isakson
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA 22098, United States; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States.
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227
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Panx1 regulates cellular properties of keratinocytes and dermal fibroblasts in skin development and wound healing. J Invest Dermatol 2014; 134:2026-2035. [PMID: 24522432 DOI: 10.1038/jid.2014.86] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 01/08/2014] [Accepted: 02/02/2014] [Indexed: 12/15/2022]
Abstract
Pannexin1 (Panx1), a channel-forming glycoprotein is expressed in neonatal but not in aged mouse skin. Histological staining of Panx1 knockout (KO) mouse skin revealed a reduction in epidermal and dermal thickness and an increase in hypodermal adipose tissue. Following dorsal skin punch biopsies, mutant mice exhibited a significant delay in wound healing. Scratch wound and proliferation assays revealed that cultured keratinocytes from KO mice were more migratory, whereas dermal fibroblasts were more proliferative compared with controls. In addition, collagen gels populated with fibroblasts from KO mice exhibited significantly reduced contraction, comparable to WT fibroblasts treated with the Panx1 blocker, probenecid. KO fibroblasts did not increase α-smooth muscle actin expression in response to TGF-β, as is the case for differentiating WT myofibroblasts during wound contraction. We conclude that Panx1 controls cellular properties of keratinocytes and dermal fibroblasts during early stages of skin development and modulates wound repair upon injury.
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228
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Shestopalov VI, Slepak VZ. Molecular pathways of pannexin1-mediated neurotoxicity. Front Physiol 2014; 5:23. [PMID: 24575045 PMCID: PMC3920106 DOI: 10.3389/fphys.2014.00023] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 01/10/2014] [Indexed: 01/09/2023] Open
Abstract
Pannexin1 (Panx1) forms non-selective membrane channels, structurally similar to gap junction hemichannels, and are permeable to ions, nucleotides, and other small molecules below 900 Da. Panx1 activity has been implicated in paracrine signaling and inflammasome regulation. Recent studies in different animal models showed that overactivation of Panx1 correlates with a selective demise of several types of neurons, including retinal ganglion cells, brain pyramidal, and enteric neurons. The list of Panx1 activators includes extracellular ATP, glutamate, high K(+), Zn(2+), fibroblast growth factors (FGFs),pro-inflammatory cytokines, and elevation of intracellular Ca(2+). Most of these molecules are released following mechanical, ischemic, or inflammatory injury of the CNS, and rapidly activate the Panx1 channel. Prolonged opening of Panx1 channel induced by these "danger signals" triggers a cascade of neurotoxic events capable of killing cells. The most vulnerable cell type are neurons that express high levels of Panx1. Experimental evidence suggests that Panx1 channels mediate at least two distinct neurotoxic processes: increased permeability of the plasma membrane and activation of the inflammasome in neurons and glia. Importantly, both pharmacological and genetic inactivation of Panx1 suppresses both these processes, providing a marked protection in several disease and injury models. These findings indicate that external danger signals generated after diverse types of injuries converge to activate Panx1. In this review we discuss molecular mechanisms associated with Panx1 toxicity and the crosstalk between different pathways.
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Affiliation(s)
- Valery I Shestopalov
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine Miami, FL, USA ; Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine Miami, FL, USA ; Vavilov Institute of General Genetics, Moscow, Russian Federation, University of Miami Miller School of Medicine Miami, FL, USA
| | - Vladlen Z Slepak
- Department of Molecular Pharmacology, University of Miami Miller School of Medicine Miami, FL, USA ; Neuroscience Program, University of Miami Miller School of Medicine Miami, FL, USA
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229
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Patel D, Zhang X, Veenstra RD. Connexin hemichannel and pannexin channel electrophysiology: how do they differ? FEBS Lett 2014; 588:1372-8. [PMID: 24434538 DOI: 10.1016/j.febslet.2013.12.023] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 12/20/2013] [Accepted: 12/30/2013] [Indexed: 12/21/2022]
Abstract
Connexin hemichannels are postulated to form a cell permeabilization pore for the uptake of fluorescent dyes and release of cellular ATP. Connexin hemichannel activity is enhanced by low external [Ca(2+)]o, membrane depolarization, metabolic inhibition, and some disease-causing gain-of-function connexin mutations. This paper briefly reviews the electrophysiological channel conductance, permeability, and pharmacology properties of connexin hemichannels, pannexin 1 channels, and purinergic P2X7 receptor channels as studied in exogenous expression systems including Xenopus oocytes and mammalian cell lines such as HEK293 cells. Overlapping pharmacological inhibitory and channel conductance and permeability profiles makes distinguishing between these channel types sometimes difficult. Selective pharmacology for Cx43 hemichannels (Gap19 peptide), probenecid or FD&C Blue #1 (Brilliant Blue FCF, BB FCF) for Panx1, and A740003, A438079, or oxidized ATP (oATP) for P2X7 channels may be the best way to distinguish between these three cell permeabilizing channel types. Endogenous connexin, pannexin, and P2X7 expression should be considered when performing exogenous cellular expression channel studies. Cell pair electrophysiological assays permit the relative assessment of the connexin hemichannel/gap junction channel ratio not often considered when performing isolated cell hemichannel studies.
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Affiliation(s)
- Dakshesh Patel
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Xian Zhang
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Richard D Veenstra
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States.
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230
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Penuela S, Lohman AW, Lai W, Gyenis L, Litchfield DW, Isakson BE, Laird DW. Diverse post-translational modifications of the pannexin family of channel-forming proteins. Channels (Austin) 2014; 8:124-30. [PMID: 24418849 DOI: 10.4161/chan.27422] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The pannexin family of channel-forming proteins is composed of 3 distinct but related members called Panx1, Panx2, and Panx3. Pannexins have been implicated in many physiological processes as well as pathological conditions, primarily through their function as ATP release channels. However, it is currently unclear if all pannexins are subject to similar or different post-translational modifications as most studies have focused primarily on Panx1. Using in vitro biochemical assays performed on ectopically expressed pannexins in HEK-293T cells, we confirmed that all 3 pannexins are N-glycosylated to different degrees, but they are not modified by sialylation or O-linked glycosylation in a manner that changes their apparent molecular weight. Using cell-free caspase assays, we also discovered that similar to Panx1, the C-terminus of Panx2 is a substrate for caspase cleavage. Panx3, on the other hand, is not subject to caspase digestion but an in vitro biotin switch assay revealed that it was S-nitrosylated by nitric oxide donors. Taken together, our findings uncover novel and diverse pannexin post-translational modifications suggesting that they may be differentially regulated for distinct or overlapping cellular and physiological functions.
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Affiliation(s)
- Silvia Penuela
- Department of Anatomy and Cell Biology; University of Western Ontario; London, ON Canada
| | - Alexander W Lohman
- Robert M Berne Cardiovascular Research Center; Department of Molecular Physiology and Biological Physics; University of Virginia; Charlottesville, VA USA
| | - Wesley Lai
- Department of Anatomy and Cell Biology; University of Western Ontario; London, ON Canada; Department of Molecular Genetics; University of Toronto; The Hospital for Sick Children; Toronto, ON Canada
| | - Laszlo Gyenis
- Department of Biochemistry; University of Western Ontario; London, ON Canada
| | - David W Litchfield
- Department of Biochemistry; University of Western Ontario; London, ON Canada
| | - Brant E Isakson
- Robert M Berne Cardiovascular Research Center; Department of Molecular Physiology and Biological Physics; University of Virginia; Charlottesville, VA USA
| | - Dale W Laird
- Department of Anatomy and Cell Biology; University of Western Ontario; London, ON Canada
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231
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Li KY, Qiu Y, Jiang Y, Luo CH, Lin XP, Wang J, Yang N. Effect of probenecid on pharmacokinetics and tolerability of olmesartan in healthy chinese volunteers. Curr Ther Res Clin Exp 2014; 76:7-10. [PMID: 25067982 PMCID: PMC3994918 DOI: 10.1016/j.curtheres.2013.11.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/17/2013] [Indexed: 10/25/2022] Open
Abstract
BACKGROUND Olmesartan is an angiotensin II receptor antagonist and is effective and well tolerated in the treatment of arterial hypertension. Probenecid is a well-established hypouricemic agent for the treatment of hyperuricemia and gout. OBJECTIVE The goal of this study was to examine the impact of coadministration of probenecid on the pharmacokinetic parameters and tolerability of olmesartan in healthy volunteers. METHODS In a randomized, open-label, 2-way crossover study, 12 volunteers received 2 oral treatments (olmesartan alone or olmesartan plus probenecid) separated by 4 days. Blood samples were obtained for a 48-hour pharmacokinetic evaluation after drug administration. Tolerability was assessed by monitoring vital signs and laboratory tests before and after administration of the study drug. RESULTS Pharmacokinetic parameters were evaluated in 6 male and 6 female healthy volunteers (mean age, 22 [range, 20-25] years]; weight, 56.0 [range, 51.0-60.0] kg). Probenecid coadministration increased olmesartan Css-av, AUC0→∞, and AUC0-48 by 40%, 50%, and 50%, respectively (P = 0.018, 0.000, 0.000, respectively), but there was no statistical significance for Tmax, t1/2, Css-max, and Css-min between olmesartan plus probenecid and olmesartan alone (P = 0.697, 0.053, 0.521, and 0.734, respectively). No serious adverse event (AE) was reported during the study. The proportion of volunteers with AEs in the olmesartan plus probenecid period (5 of 12 [42%]) was higher than that in the olmesartan-alone period (1 of 12 [8%]). All of the AEs during the olmesartan plus probenecid period were abnormal routine urine test results. The AE in olmesartan-alone period was dizziness. All AEs were classified as mild and considered to be at least possibly related to treatment. All volunteers recovered from the AEs by 2 weeks after the end of the study. CONCLUSIONS Probenecid increases the exposure speed of olmesartan by increasing the AUC0-48, AUC0→∞, and Css-av. The combined treatment of olmesartan medoxomil with probenecid may increase the occurrence of genitourinary side effects. ClinicalTrials.gov identifier: NCT01907373.
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Affiliation(s)
- Kun-Yan Li
- Center of New Drug Clinical Trial, Hunan Provincial Tumor Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, China
| | - Yu Qiu
- Center of New Drug Clinical Trial, Hunan Provincial Tumor Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, China
| | - Yun Jiang
- Center of New Drug Clinical Trial, Hunan Provincial Tumor Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, China
| | - Chen-Hui Luo
- Center of New Drug Clinical Trial, Hunan Provincial Tumor Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, China
| | - Xiao-Ping Lin
- Center of New Drug Clinical Trial, Hunan Provincial Tumor Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, China
| | - Jing Wang
- Center of New Drug Clinical Trial, Hunan Provincial Tumor Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, China
| | - Nong Yang
- Center of New Drug Clinical Trial, Hunan Provincial Tumor Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, China
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232
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Kringelbach TM, Aslan D, Novak I, Schwarz P, Jørgensen NR. UTP-induced ATP release is a fine-tuned signalling pathway in osteocytes. Purinergic Signal 2013; 10:337-47. [PMID: 24374572 PMCID: PMC4040174 DOI: 10.1007/s11302-013-9404-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 12/10/2013] [Indexed: 11/30/2022] Open
Abstract
Osteocytes reside as a cellular network throughout the mineralised matrix of bone and are considered the primary mechanosensors of this tissue. They sense mechanical stimulation such as fluid flow and are able to regulate osteoblast and osteoclast functions on the bone surface. Previously, we found that ATP is released load-dependently from osteocytes from the onset of mechanical stimulation. Therefore, the aim of the present study was to investigate whether and how ATP release can be evoked in osteocytes via purinergic receptor activation. ATP release was quantified by real-time determination using the luciferin-luciferase assay and the release pathway was investigated using pharmacological inhibition. The P2Y receptor profile was analysed using gene expression analysis by reverse transcription polymerase chain reaction, while functional testing was performed using measurements of intracellular calcium responses to P2 receptor agonists. These investigations demonstrated that MLO-Y4 osteocytes express functional P2Y(2), P2Y(4), P2Y(12) and P2Y(13) receptors in addition to the previously reported P2X receptors. Further, we found that osteocytes respond to nucleotides such as ATP, UTP and ADP by increasing the intracellular calcium concentration and that they release ATP dose-dependently upon stimulation with 1-10 μM UTP. In addition to this, osteocytes release large amounts of ATP upon cell rupture, which might also be a source for other nucleotides, such as UTP. These findings indicate that mechanically induced ATP signals may be propagated by P2 receptor activation and further ATP release in the osteocyte network and implicate purinergic signalling as a central signalling pathway in osteocyte mechanotransduction.
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Affiliation(s)
- Tina M. Kringelbach
- />Research Center of Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark
- />Research Center of Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark
- />The Osteoporosis and Bone Metabolic Unit, Department of Endocrinology, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
- />The Osteoporosis and Bone Metabolic Unit, Department of Clinical Biochemistry, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
| | - Derya Aslan
- />Research Center of Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark
- />Research Center of Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark
| | - Ivana Novak
- />Department of Biology, University of Copenhagen, Copenhagen Ø, Denmark
| | - Peter Schwarz
- />Research Center of Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark
- />Research Center of Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark
- />Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark
| | - Niklas R. Jørgensen
- />Research Center of Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark
- />Research Center of Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark
- />The Osteoporosis and Bone Metabolic Unit, Department of Endocrinology, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
- />The Osteoporosis and Bone Metabolic Unit, Department of Clinical Biochemistry, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
- />Research Center of Ageing and Osteoporosis, Department of Diagnostics, Glostrup Hospital, Ndr. Ringvej 57, 2600 Glostrup, Denmark
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Xiong XX, Gu LJ, Shen J, Kang XH, Zheng YY, Yue SB, Zhu SM. Probenecid protects against transient focal cerebral ischemic injury by inhibiting HMGB1 release and attenuating AQP4 expression in mice. Neurochem Res 2013; 39:216-24. [PMID: 24317635 DOI: 10.1007/s11064-013-1212-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 10/31/2013] [Accepted: 11/25/2013] [Indexed: 12/11/2022]
Abstract
Stroke results in inflammation, brain edema, and neuronal death. However, effective neuroprotectants are not available. Recent studies have shown that high mobility group box-1 (HMGB1), a proinflammatory cytokine, contributes to ischemic brain injury. Aquaporin 4 (AQP4), a water channel protein, is considered to play a pivotal role in ischemia-induced brain edema. More recently, studies have shown that pannexin 1 channels are involved in cerebral ischemic injury and the cellular inflammatory response. Here, we examined whether the pannexin 1 channel inhibitor probenecid could reduce focal ischemic brain injury by inhibiting cerebral inflammation and edema. Transient focal ischemia was induced in C57BL/6J mice by middle cerebral artery occlusion (MCAO) for 1 h. Infarct volume, neurological score and cerebral water content were evaluated 48 h after MCAO. Immunostaining, western blot analysis and ELISA were used to assess the effects of probenecid on the cellular inflammatory response, HMGB1 release and AQP4 expression. Administration of probenecid reduced infarct size, decreased cerebral water content, inhibited neuronal death, and reduced inflammation in the brain 48 h after stroke. In addition, HMGB1 release from neurons was significantly diminished and serum HMGB1 levels were substantially reduced following probenecid treatment. Moreover, AQP4 protein expression was downregulated in the cortical penumbra following post-stroke treatment with probenecid. These results suggest that probenecid, a powerful pannexin 1 channel inhibitor, protects against ischemic brain injury by inhibiting cerebral inflammation and edema.
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Affiliation(s)
- Xiao-Xing Xiong
- Department of Anesthesia, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
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Boyce AKJ, Prager RT, Wicki-Stordeur LE, Swayne LA. Pore positioning: current concepts in Pannexin channel trafficking. Channels (Austin) 2013; 8:110-7. [PMID: 24300303 DOI: 10.4161/chan.27287] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Pannexins (Panxs) are a multifaceted family of ion and metabolite channels that play key roles in a number of physiological and pathophysiological settings. These single membrane large-pore channels exhibit a variety of tissue, cell type, and subcellular distributions. The lifecycles of Panxs are complex, yet must be understood to accurately target these proteins for future therapeutic use. Here we review the basics of Panx function and localization, and then analyze the recent advances in knowledge regarding Panx trafficking. We examine several intrinsic features of Panxs including specific post-translational modifications, the divergent C-termini, and oligomerization, all of which contribute to Panx anterograde transport pathways. Further, we examine the potential influence of extrinsic factors, such as protein-protein interactions, on Panx trafficking. Finally, we highlight what is currently known with respect to Panx internalization and retrograde transport, and present new data illustrating Panx1 internalization following an activating stimulus.
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Affiliation(s)
- Andrew K J Boyce
- Division of Medical Sciences; Island Medical Program; University of Victoria; Victoria, British Columbia, Canada
| | - Ross T Prager
- Division of Medical Sciences; Island Medical Program; University of Victoria; Victoria, British Columbia, Canada
| | - Leigh E Wicki-Stordeur
- Division of Medical Sciences; Island Medical Program; University of Victoria; Victoria, British Columbia, Canada
| | - Leigh Anne Swayne
- Division of Medical Sciences; Island Medical Program; University of Victoria; Victoria, British Columbia, Canada; Department of Biology; University of Victoria; Victoria, British Columbia, Canada; Department of Biochemistry and Microbiology; University of Victoria; Victoria, British Columbia, Canada; Department of Cellular and Physiological Sciences; University of British Columbia; Vancouver, British Columbia, Canada
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235
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Thiede BR, Corwin JT. Permeation of fluorophore-conjugated phalloidin into live hair cells of the inner ear is modulated by P2Y receptors. J Assoc Res Otolaryngol 2013; 15:13-30. [PMID: 24263968 DOI: 10.1007/s10162-013-0425-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 10/23/2013] [Indexed: 12/18/2022] Open
Abstract
Phalloidin, a toxin isolated from the death cap mushroom, Amanita phalloides, binds to filamentous actin with high affinity, and this has made fluorophore-conjugated phalloidin a useful tool in cellular imaging. Hepatocytes take up phalloidin via the liver-specific organic anion transporting polypeptide 1b2, but phalloidin does not permeate most living cells. Rapid entry of styryl dyes into live hair cells has been used to evaluate function, but the usefulness of those fluorescence dyes is limited by broad and fixed absorption spectra. Since phalloidin can be conjugated to fluorophores with various spectra, we investigated whether it would permeate living hair cells. When we incubated mouse utricles in 66 nM phalloidin-CF488A and followed that by washes in phalloidin-free medium, we observed that it entered a subset of hair cells and labeled entire hair bundles fluorescently after 20 min. Incubations of 90 min labeled nearly all the hair bundles. When phalloidin-treated utricles were cultured for 24 h after washout, the label disappeared from the hair cells and progressively but heterogeneously labeled filamentous actin in the supporting cells. We investigated how phalloidin may enter hair cells and found that P2 receptor antagonists, pyridoxalphosphate-6-azophenyl-2', 4'-disulfonic acid and suramin, blocked phalloidin entry, while the P2Y receptor ligands, uridine-5'-diphosphate and uridine-5'-triphosphaste, stimulated uptake. Consistent with that, the P2Y6 receptor antagonist, MRS 2578, decreased phalloidin uptake. The results show that phalloidin permeates live hair cells through a pathway that requires metabotropic P2Y receptor signaling and suggest that phalloidin can be transferred from hair cells to supporting cells in culture.
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Affiliation(s)
- Benjamin R Thiede
- Department of Neuroscience, University of Virginia School of Medicine, 409 Lane Rd, PO Box 801392, Charlottesville, VA, 22908, USA
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Orellana JA, Sáez JC, Bennett MVL, Berman JW, Morgello S, Eugenin EA. HIV increases the release of dickkopf-1 protein from human astrocytes by a Cx43 hemichannel-dependent mechanism. J Neurochem 2013; 128:752-63. [PMID: 24134157 DOI: 10.1111/jnc.12492] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 09/27/2013] [Accepted: 10/11/2013] [Indexed: 11/26/2022]
Abstract
Human immunodeficiency virus-1 (HIV) is a public health issue and a major complication of the disease is NeuroAIDS. In vivo, microglia/macrophages are the main cells infected. However, a low but significant number of HIV-infected astrocytes has also been detected, but their role in the pathogenesis of NeuroAIDS is not well understood. Our previous data indicate that gap junction channels amplify toxicity from few HIV-infected into uninfected astrocytes. Now, we demonstrated that HIV infection of astrocytes results in the opening of connexin43 hemichannels (HCs). HIV-induced opening of connexin43 HCs resulted in dysregulated secretion of dickkopf-1 protein (DKK1, a soluble wnt pathway inhibitor). Treatment of mixed cultures of neurons and astrocytes with DKK1, in the absence of HIV infection, resulted in the collapse of neuronal processes. HIV infection of mixed cultures of human neurons and astrocytes also resulted in the collapse of neuronal processes through a DKK1-dependent mechanism. In addition, dysregulated DKK1 expression in astrocytes was observed in human brain tissue sections of individuals with HIV encephalitis as compared to tissue sections from uninfected individuals. Thus, we demonstrated that HIV infection of astrocytes induces dysregulation of DKK1 by a HC-dependent mechanism that contributes to the brain pathogenesis observed in HIV-infected individuals. Our studies demonstrated that HIV infection of astrocytes, despite minimal replication and a low number of infected cells, induces dysregulation of DKK1 secretion by a Cx43 hemichannel (HC)-dependent mechanism. Enhanced DKK1 secretion in response to HIV infection of glial cells compromised formation and stability of neuronal processes, similar to the synaptic compromise observed in HIV-infected individuals. In addition, analysis of human brain tissue sections obtained from encephalitic individuals also shows enhanced expression of DKK1 in astrocytes. Our data provide a novel mechanism by which HIV infection of glial cells participate in the pathogenesis of brain dysfunction observed in HIV-infected individuals. LRP5 = Low-density lipoprotein receptor-related protein 5.
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Affiliation(s)
- Juan Andres Orellana
- Public Health Research Institute (PHRI), Rutgers New Jersey Medical School, Rutgers The State University of New Jersey, Newark, New Jersey, USA
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Meigh L, Greenhalgh SA, Rodgers TL, Cann MJ, Roper DI, Dale N. CO₂directly modulates connexin 26 by formation of carbamate bridges between subunits. eLife 2013; 2:e01213. [PMID: 24220509 PMCID: PMC3821526 DOI: 10.7554/elife.01213] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Homeostatic regulation of the partial pressure of CO2 (PCO2) is vital for life. Sensing of pH has been proposed as a sufficient proxy for determination of PCO2 and direct CO2-sensing largely discounted. Here we show that connexin 26 (Cx26) hemichannels, causally linked to respiratory chemosensitivity, are directly modulated by CO2. A ‘carbamylation motif’, present in CO2-sensitive connexins (Cx26, Cx30, Cx32) but absent from a CO2-insensitive connexin (Cx31), comprises Lys125 and four further amino acids that orient Lys125 towards Arg104 of the adjacent subunit of the connexin hexamer. Introducing the carbamylation motif into Cx31 created a mutant hemichannel (mCx31) that was opened by increases in PCO2. Mutation of the carbamylation motif in Cx26 and mCx31 destroyed CO2 sensitivity. Course-grained computational modelling of Cx26 demonstrated that the proposed carbamate bridge between Lys125 and Arg104 biases the hemichannel to the open state. Carbamylation of Cx26 introduces a new transduction principle for physiological sensing of CO2. DOI:http://dx.doi.org/10.7554/eLife.01213.001 A number of gaseous molecules, including nitric oxide and carbon monoxide, play important roles in many cellular processes by acting as signalling molecules. Surprisingly, however, it has long been assumed that carbon dioxide – a gaseous molecule that is produced during cellular metabolism – is not a signalling molecule. Controlling the concentration of carbon dioxide (CO2) in a biological system is essential to sustain life, and it was thought that the body used pH – which is the concentration of hydrogen ions – as a proxy for the level of CO2. The concentration of CO2 is related to pH because CO2 reacts with water to form carbonic acid, which quickly breaks down to form hydrogen ions and bicarbonate ions. This close relationship has led many researchers to equate pH-sensing with CO2-sensing, and to suggest that a physiological receptor for CO2 does not exist. Recent research into structures called connexin hemichannels has challenged this view. Researchers found that when pH levels were held constant, increasing the level of CO2 caused the structures to open up, suggesting that CO2 could be directly detected by the hemichannels. Each hemichannel contains six connexin subunits, but the details of how the CO2 molecules interact with the individual connexin subunits to open up the hemichannels remained mysterious. Now Meigh et al. show that CO2 molecules bind to a specific amino acid (lysine) at a particular place (residue 125) in one of the connexin subunits to form a carbamate group. This group then interacts with the amino acid (arginine) at residue 104 in a neighbouring connexin subunit to form a carbamate bridge between the two subunits. This leads to structural changes that cause the gap junction hemichannels to open and release signals that can activate other cells. Since connexin hemichannels are found throughout the human body, these results suggest that CO2 might act as a signalling molecule in processes as diverse as the control of blood flow, breathing, hearing and reproduction. DOI:http://dx.doi.org/10.7554/eLife.01213.002
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Affiliation(s)
- Louise Meigh
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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Orellana JA, Montero TD, von Bernhardi R. Astrocytes inhibit nitric oxide-dependent Ca(2+) dynamics in activated microglia: involvement of ATP released via pannexin 1 channels. Glia 2013; 61:2023-37. [PMID: 24123492 DOI: 10.1002/glia.22573] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 08/13/2013] [Accepted: 08/19/2013] [Indexed: 01/22/2023]
Abstract
Under inflammatory conditions, microglia exhibit increased levels of free intracellular Ca(2+) and produce high amounts of nitric oxide (NO). However, whether NO, Ca(2+) dynamics, and gliotransmitter release are reciprocally modulated is not fully understood. More importantly, the effect of astrocytes in the potentiation or suppression of such signaling is unknown. Our aim was to address if astrocytes could regulate NO-dependent Ca(2+) dynamics and ATP release in LPS-stimulated microglia. Griess assays and Fura-2AM time-lapse fluorescence images of microglia revealed that LPS produced an increased basal [Ca(2+) ]i that depended on the sequential activation of iNOS, COXs, and EP1 receptor. TGFβ1 released by astrocytes inhibited the abovementioned responses and also abolished LPS-induced ATP release by microglia. Luciferin/luciferase assays and dye uptake experiments showed that release of ATP from LPS-stimulated microglia occurred via pannexin 1 (Panx1) channels, but not connexin 43 hemichannels. Moreover, in LPS-stimulated microglia, exogenous ATP triggered activation of purinergic P2Y1 receptors resulting in Ca(2+) release from intracellular stores. Interestingly, TGFβ1 released by astrocytes inhibited ATP-induced Ca(2+) response in LPS-stimulated microglia to that observed in control microglia. Finally, COX/EP1 receptor signaling and activation of P2 receptors via ATP released through Panx1 channels were critical for the increased NO production in LPS-stimulated microglia. Thus, Ca(2+) dynamics depended on the inflammatory profile of microglia and could be modulated by astrocytes. The understanding of mechanisms underlying glial cell regulatory crosstalk could contribute to the development of new treatments to reduce inflammatory cytotoxicity in several brain pathologies.
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Affiliation(s)
- Juan A Orellana
- Departamento de Neurología; Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
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Bjaelde RG, Arnadottir SS, Overgaard MT, Leipziger J, Praetorius HA. Renal epithelial cells can release ATP by vesicular fusion. Front Physiol 2013; 4:238. [PMID: 24065923 PMCID: PMC3776935 DOI: 10.3389/fphys.2013.00238] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 08/13/2013] [Indexed: 11/22/2022] Open
Abstract
Renal epithelial cells have the ability to release nucleotides as paracrine factors. In the intercalated cells of the collecting duct, ATP is released by connexin30 (cx30), which is selectively expressed in this cell type. However, ATP is released by virtually all renal epithelia and the aim of the present study was to identify possible alternative nucleotide release pathways in a renal epithelial cell model. We used MDCK (type1) cells to screen for various potential ATP release pathways. In these cells, inhibition of the vesicular H+-ATPases (bafilomycin) reduced both the spontaneous and hypotonically (80%)-induced nucleotide release. Interference with vesicular fusion using N-ethylamide markedly reduced the spontaneous nucleotide release, as did interference with trafficking from the endoplasmic reticulum to the Golgi apparatus (brefeldin A1) and vesicular transport (nocodazole). These findings were substantiated using a siRNA directed against SNAP-23, which significantly reduced spontaneous ATP release. Inhibition of pannexin and connexins did not affect the spontaneous ATP release in this cell type, which consists of ~90% principal cells. TIRF-microscopy of either fluorescently-labeled ATP (MANT-ATP) or quinacrine-loaded vesicles, revealed that spontaneous release of single vesicles could be promoted by either hypoosmolality (50%) or ionomycin. This vesicular release decreased the overall cellular fluorescence by 5.8 and 7.6% respectively. In summary, this study supports the notion that spontaneous and induced ATP release can occur via exocytosis in renal epithelial cells.
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Affiliation(s)
- Randi G Bjaelde
- Department of Biomedicine, Aarhus University Aarhus, Denmark
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Richter K, Kiefer KP, Grzesik BA, Clauss WG, Fronius M. Hydrostatic pressure activates ATP-sensitive K+ channels in lung epithelium by ATP release through pannexin and connexin hemichannels. FASEB J 2013; 28:45-55. [PMID: 24048216 DOI: 10.1096/fj.13-229252] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Lungs of air-breathing vertebrates are constantly exposed to mechanical forces and therefore are suitable for investigation of mechanotransduction processes in nonexcitable cells and tissues. Freshly dissected Xenopus laevis lungs were used for transepithelial short-circuit current (ISC) recordings and were exposed to increased hydrostatic pressure (HP; 5 cm fluid column, modified Ussing chamber). I(SC) values obtained under HP (I(5cm)) were normalized to values before HP (I(0cm)) application (I(5cm)/I(0cm)). Under control conditions, HP decreased I(SC) (I(5cm)/I(0cm)=0.84; n=68; P<0.0001). This effect was reversible and repeatable ≥30 times. Preincubation with ATP-sensitive K(+) channel (K(ATP)) inhibitors (HMR1098 and glibenclamide) prevented the decrease in I(SC) (I(5cm)/I(0cm): HMR1098=1.19, P<0.0001; glibenclamide=1.11, P<0.0001). Similar effects were observed with hemichannel inhibitors (I(5cm)/I(0cm): meclofenamic acid=1.09, P<0.0001; probenecid=1.0, P<0.0001). The HP effect was accompanied by release of ATP (P<0.05), determined by luciferin-luciferase luminescence in perfusion solution from the luminal side of an Ussing chamber. ATP release was abrogated by both meclofenamic acid and probenecid. RT-PCR experiments revealed the expression of pannexin and connexin hemichannels and KATP subunit transcripts in X. laevis lung. These data show an activation of KATP in pulmonary epithelial cells in response to HP that is induced by ATP release through mechanosensitive pannexin and connexin hemichannels. These findings represent a novel mechanism of mechanotransduction in nonexcitable cells.
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Affiliation(s)
- Katrin Richter
- 2Institute of Animal Physiology, Justus Liebig University, Giessen, Heinrich Buff Ring 26, D-35392 Giessen, Germany.
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Taruno A, Matsumoto I, Ma Z, Marambaud P, Foskett JK. How do taste cells lacking synapses mediate neurotransmission? CALHM1, a voltage-gated ATP channel. Bioessays 2013; 35:1111-8. [PMID: 24105910 DOI: 10.1002/bies.201300077] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
CALHM1 was recently demonstrated to be a voltage-gated ATP-permeable ion channel and to serve as a bona fide conduit for ATP release from sweet-, umami-, and bitter-sensing type II taste cells. Calhm1 is expressed in taste buds exclusively in type II cells and its product has structural and functional similarities with connexins and pannexins, two families of channel protein candidates for ATP release by type II cells. Calhm1 knockout in mice leads to loss of perception of sweet, umami, and bitter compounds and to impaired gustatory nerve responses to these tastants. These new studies validate the concept of ATP as the primary neurotransmitter from type II cells to gustatory neurons. Furthermore, they identify voltage-gated ATP release through CALHM1 as an essential molecular mechanism of ATP release in taste buds. We discuss these new findings, as well as unresolved issues in peripheral taste signaling that we hope will stimulate future research.
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Affiliation(s)
- Akiyuki Taruno
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
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242
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Wicki-Stordeur LE, Swayne LA. Panx1 regulates neural stem and progenitor cell behaviours associated with cytoskeletal dynamics and interacts with multiple cytoskeletal elements. Cell Commun Signal 2013; 11:62. [PMID: 23964896 PMCID: PMC3765679 DOI: 10.1186/1478-811x-11-62] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 08/19/2013] [Indexed: 11/25/2022] Open
Abstract
Background Pannexins (Panxs) are relatively newly discovered large-pore ion and metabolite permeable channels. Although no proteomics-based interactome has yet been published, Panx1 has been demonstrated to interact with actin in an ectopic expression system. This interaction affects both Panx1 plasma membrane stability as well as cytoskeletal remodelling. The current study builds on our recent discovery of Panx1 expression in ventricular zone (VZ) neural stem and progenitor cells (NSC/NPCs), and on the demonstrated interaction of Panx1 with the cytoskeleton. Findings Here we demonstrate that Panx1 also plays roles in two additional cell behaviours associated with neurogenesis, including cell migration and neurite extension. Furthermore, we confirm an endogenous interaction between actin and Panx1, and identify a new interaction with actin-related protein 3, an actin cytoskeleton-modulating protein. Conclusions This study further establishes the importance of Panx1 in the cell biology of NSC/NPCs and strengthens and expands our knowledge of Panx1 interactions with the cytoskeleton.
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Affiliation(s)
- Leigh E Wicki-Stordeur
- Division of Medical Sciences, Island Medical Program, University of Victoria, Victoria, British Columbia, Canada
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Pinheiro AR, Paramos-de-Carvalho D, Certal M, Costa MA, Costa C, Magalhães-Cardoso MT, Ferreirinha F, Sévigny J, Correia-de-Sá P. Histamine induces ATP release from human subcutaneous fibroblasts, via pannexin-1 hemichannels, leading to Ca2+ mobilization and cell proliferation. J Biol Chem 2013; 288:27571-27583. [PMID: 23918924 DOI: 10.1074/jbc.m113.460865] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Changes in the regulation of connective tissue ATP-mediated mechano-transduction and remodeling may be an important link to the pathogenesis of chronic pain. It has been demonstrated that mast cell-derived histamine plays an important role in painful fibrotic diseases. Here we analyzed the involvement of ATP in the response of human subcutaneous fibroblasts to histamine. Acute histamine application caused a rise in intracellular Ca(2+) ([Ca(2+)]i) and ATP release from human subcutaneous fibroblasts via H1 receptor activation. Histamine-induced [Ca(2+)]i rise was partially attenuated by apyrase, an enzyme that inactivates extracellular ATP, and by blocking P2 purinoceptors with pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) tetrasodium salt and reactive blue 2. [Ca(2+)]i accumulation caused by histamine was also reduced upon blocking pannexin-1 hemichannels with (10)Panx, probenecid, or carbenoxolone but not when connexin hemichannels were inhibited with mefloquine or 2-octanol. Brefeldin A, an inhibitor of vesicular exocytosis, also did not block histamine-induced [Ca(2+)]i mobilization. Prolonged exposure of human subcutaneous fibroblast cultures to histamine favored cell growth and type I collagen synthesis via the activation of H1 receptor. This effect was mimicked by ATP and its metabolite, ADP, whereas the selective P2Y1 receptor antagonist, MRS2179, partially attenuated histamine-induced cell growth and type I collagen production. Expression of pannexin-1 and ADP-sensitive P2Y1 receptor on human subcutaneous fibroblasts was confirmed by immunofluorescence confocal microscopy and Western blot analysis. In conclusion, histamine induces ATP release from human subcutaneous fibroblasts, via pannexin-1 hemichannels, leading to [Ca(2+)]i mobilization and cell growth through the cooperation of H1 and P2 (probably P2Y1) receptors.
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Affiliation(s)
- Ana Rita Pinheiro
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB); Área Técnico-Científica de Fisioterapia, Escola Superior de Tecnologia da Saúde do Instituto Politécnico do Porto, 4400-330 Vila Nova de Gaia, Portugal
| | - Diogo Paramos-de-Carvalho
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB)
| | - Mariana Certal
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB)
| | - Maria Adelina Costa
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB); Departamento de Química, Instituto de Ciências Biomédicas Abel Salazar-Universidade do Porto (ICBAS-UP), 4050-313 Porto, Portugal
| | - Cristina Costa
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB)
| | | | - Fátima Ferreirinha
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB)
| | - Jean Sévigny
- Centre de Recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec, Québec, Québec G1V 4G2, Canada; Département de Microbiologie-Infectiologie et d'Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Paulo Correia-de-Sá
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB).
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Alvarez-Fischer D, Noelker C, Grünewald A, Vulinović F, Guerreiro S, Fuchs J, Lu L, Lombès A, Hirsch EC, Oertel WH, Michel PP, Hartmann A. Probenecid potentiates MPTP/MPP+toxicity by interference with cellular energy metabolism. J Neurochem 2013; 127:782-92. [DOI: 10.1111/jnc.12343] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 06/10/2013] [Accepted: 06/13/2013] [Indexed: 01/01/2023]
Affiliation(s)
- Daniel Alvarez-Fischer
- UPMC Univ Paris 06; UMR_S 975 - UMR 7725; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Inserm U 975; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- CNRS; UMR 7225; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Department of Neurology; Philipps-University Marburg; Marburg Germany. Institute of Neurogenetics; University of Lübeck; Lübeck Germany. Department of Psychiatry; University of Lübeck; Lübeck Germany
| | - Carmen Noelker
- UPMC Univ Paris 06; UMR_S 975 - UMR 7725; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Inserm U 975; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- CNRS; UMR 7225; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Department of Neurology; Philipps-University Marburg; Marburg Germany
| | - Anne Grünewald
- Institute of Neurogenetics; University of Lübeck; Lübeck Germany
| | - Franca Vulinović
- Institute of Neurogenetics; University of Lübeck; Lübeck Germany
| | - Serge Guerreiro
- UPMC Univ Paris 06; UMR_S 975 - UMR 7725; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Inserm U 975; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- CNRS; UMR 7225; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
| | - Julia Fuchs
- Collège de France; Center for Interdisciplinary Research in Biology (CIRB); CNRS UMR 7241/INSERM U1050; Paris France
| | - Lixia Lu
- UPMC Univ Paris 06; UMR_S 975 - UMR 7725; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Inserm U 975; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- CNRS; UMR 7225; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Department of Neurology; Philipps-University Marburg; Marburg Germany
| | - Anne Lombès
- Institut Cochin; INSERM UMRS 1016; CNRS UMR 8104; Université Paris Descartes; Paris France
| | - Etienne C. Hirsch
- UPMC Univ Paris 06; UMR_S 975 - UMR 7725; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Inserm U 975; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- CNRS; UMR 7225; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
| | | | - Patrick P. Michel
- UPMC Univ Paris 06; UMR_S 975 - UMR 7725; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Inserm U 975; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- CNRS; UMR 7225; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
| | - Andreas Hartmann
- UPMC Univ Paris 06; UMR_S 975 - UMR 7725; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Inserm U 975; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- CNRS; UMR 7225; Centre de Recherche en Neurosciences, ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- ICM; Therapeutique Experimentale de la Neurodegenerescence; Paris France
- Department of Neurology; Philipps-University Marburg; Marburg Germany. Département de Neurologie; Pôle des Maladies du Système Nerveux; Hôpital de la Pitié-Salpêtrière; Paris France
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Leal Denis MF, Incicco JJ, Espelt MV, Verstraeten SV, Pignataro OP, Lazarowski ER, Schwarzbaum PJ. Kinetics of extracellular ATP in mastoparan 7-activated human erythrocytes. Biochim Biophys Acta Gen Subj 2013; 1830:4692-707. [PMID: 23742824 DOI: 10.1016/j.bbagen.2013.05.033] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 04/24/2013] [Accepted: 05/20/2013] [Indexed: 01/26/2023]
Abstract
BACKGROUND The peptide mastoparan 7 (MST7) stimulated ATP release in human erythrocytes. We explored intra- and extracellular processes governing the time-dependent accumulation of extracellular ATP (i.e., ATPe kinetics). METHODS Human erythrocytes were treated with MST7 in the presence or absence of two blockers of pannexin 1. ATPe concentration was monitored by luciferin-luciferase based real-time luminometry. RESULTS Exposure of human erythrocytes to MST7 led to an acute increase in [ATPe], followed by a slower increase phase. ATPe kinetics reflected a strong activation of ATP efflux and a low rate of ATPe hydrolysis by ectoATPase activity. Enhancement of [ATPe] by MST7 required adhesion of erythrocytes to poly-D-lysin-coated coverslips, and correlated with a 31% increase of cAMP and 10% cell swelling. However, when MST7 was dissolved in a hyperosmotic medium to block cell swelling, ATPe accumulation was inhibited by 49%. Erythrocytes pre-exposure to 10μM of either carbenoxolone or probenecid, two blockers of pannexin 1, exhibited a partial reduction of ATP efflux. Erythrocytes from pannexin 1 knockout mice exhibited similar ATPe kinetics as those of wild type mice erythrocytes exposed to pannexin 1 blockers. CONCLUSIONS MST7 induced release of ATP required either cell adhesion or strong activation of cAMP synthesis. Part of this release required cell swelling. Kinetic analysis and a data driven model suggested that ATP efflux is mediated by two ATP conduits displaying different kinetics, with one conduit being fully blocked by pannexin 1 blockers. GENERAL SIGNIFICANCE Kinetic analysis of extracellular ATP accumulation from human erythrocytes and potential effects on microcirculation.
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246
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Diezmos EF, Sandow SL, Markus I, Shevy Perera D, Lubowski DZ, King DW, Bertrand PP, Liu L. Expression and localization of pannexin-1 hemichannels in human colon in health and disease. Neurogastroenterol Motil 2013; 25:e395-405. [PMID: 23594276 DOI: 10.1111/nmo.12130] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 03/16/2013] [Indexed: 12/13/2022]
Abstract
BACKGROUND Pannexin-1 (Panx1) proteins can function as channels for adenosine triphosphate (ATP) release, but there have been limited studies investigating their potential role in the human intestine. The aim of this study was to characterize Panx1 expression and distribution in the human colon and its potential involvement in inflammatory bowel diseases (IBD). METHODS Human colon segments were dissected into mucosa and muscularis layers, and evaluated for Panx1 expression by real-time PCR and Western blotting. Immunohistochemistry was conducted to localize the cellular distribution of Panx1 in intact tissues. KEY RESULTS In the colonic muscularis of ulcerative colitis (UC), Panx1 mRNA expression showed a 3.5-fold reduction compared with control (P = 0.0015), but no change was seen in UC mucosa. In contrast, down-regulation of Panx1 mRNA was observed in both muscularis and mucosa of Crohn's disease (CD), showing a 2.7- and 1.8-fold reduction, respectively (P < 0.05). There was reduced Panx1 protein expression in CD muscularis, but no change in CD mucosa, UC muscularis, or UC mucosa. Pannexin-1 immunoreactivity was mainly localized to enteric ganglia, blood vessel endothelium, erythrocytes, epithelial cells, and goblet cells. Inflammatory bowel disease samples showed a similar overall pattern of Panx1 staining, but in UC myenteric ganglia, there was a significant reduction in Panx1 immunoreactivity. Significant Panx1 positive leukocyte infiltrations were seen at the sites of inflammation. CONCLUSIONS & INFERENCES The presence of Panx1 in the colon and changes to its distribution in disease suggests that Panx1 channels may play an important role in mediating gut function and in IBD pathophysiology.
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Affiliation(s)
- E F Diezmos
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
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Assessing a potential role of host Pannexin 1 during Chlamydia trachomatis infection. PLoS One 2013; 8:e63732. [PMID: 23700432 PMCID: PMC3659042 DOI: 10.1371/journal.pone.0063732] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 04/04/2013] [Indexed: 01/08/2023] Open
Abstract
Pannexin 1 (Panx1) is a plasma membrane channel glycoprotein that plays a role in innate immune response through association with the inflammasome complex. Probenecid, a classic pharmacological agent for gout, has also been used historically in combination therapy with antibiotics to prevent cellular drug efflux and has been reported to inhibit Panx1. As the inflammasome has been implicated in the progression of Chlamydia infections, and with chlamydial infections at record levels in the US, we therefore investigated whether probenecid would have a direct effect on Chlamydia trachomatis development through inhibition of Panx1. We found chlamydial development to be inhibited in a dose-dependent, yet reversible manner in the presence of probenecid. Drug treatment induced an aberrant chlamydial morphology consistent with persistent bodies. Although Panx1 was shown to localize to the chlamydial inclusion, no difference was seen in chlamydial development during infection of cells derived from wild-type and Panx1 knockout mice. Therefore, probenecid may inhibit C. trachomatis growth by an as yet unresolved mechanism.
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248
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Di Virgilio F. The Therapeutic Potential of Modifying Inflammasomes and NOD-Like Receptors. Pharmacol Rev 2013; 65:872-905. [DOI: 10.1124/pr.112.006171] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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249
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Heinrich A, Andó RD, Túri G, Rózsa B, Sperlágh B. K+ depolarization evokes ATP, adenosine and glutamate release from glia in rat hippocampus: a microelectrode biosensor study. Br J Pharmacol 2013; 167:1003-20. [PMID: 22394324 DOI: 10.1111/j.1476-5381.2012.01932.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE This study was undertaken to characterize the ATP, adenosine and glutamate outflow evoked by depolarization with high K(+) concentrations, in slices of rat hippocampus. EXPERIMENTAL APPROACH We utilized the microelectrode biosensor technique and extracellular electrophysiological recording for the real-time monitoring of the efflux of ATP, adenosine and glutamate. KEY RESULTS ATP, adenosine and glutamate sensors exhibited transient and reversible current during depolarization with 25 mM K(+) , with distinct kinetics. The ecto-ATPase inhibitor ARL67156 enhanced the extracellular level of ATP and inhibited the prolonged adenosine efflux, suggesting that generation of adenosine may derive from the extracellular breakdown of ATP. Stimulation-evoked ATP, adenosine and glutamate efflux was inhibited by tetrodotoxin, while exposure to Ca(2+) -free medium abolished ATP and adenosine efflux from hippocampal slices. Extracellular elevation of ATP and adenosine were decreased in the presence of NMDA receptor antagonists, D-AP-5 and ifenprodil, whereas non-NMDA receptor blockade by CNQX inhibited glutamate but not ATP and adenosine efflux. The gliotoxin fluoroacetate and P2X7 receptor antagonists inhibited the K(+) -evoked ATP, adenosine and glutamate efflux, while carbenoxolone in low concentration and probenecid decreased only the adenosine efflux. CONCLUSIONS AND IMPLICATIONS Our results demonstrated activity-dependent gliotransmitter release in the hippocampus in response to ongoing neuronal activity. ATP and glutamate were released by P2X7 receptor activation into extracellular space. Although the increased extracellular levels of adenosine did derive from released ATP, adenosine might also be released directly via pannexin hemichannels.
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Affiliation(s)
- A Heinrich
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary Femtonics Ltd, Budapest, Hungary
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Dahl G, Qiu F, Wang J. The bizarre pharmacology of the ATP release channel pannexin1. Neuropharmacology 2013; 75:583-93. [PMID: 23499662 DOI: 10.1016/j.neuropharm.2013.02.019] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 02/08/2013] [Accepted: 02/26/2013] [Indexed: 12/29/2022]
Abstract
Pannexins were originally thought to represent a second and redundant family of gap junction proteins in addition to the well characterized connexins. However, it is now evident that pannexins function as unapposed membrane channels and the major role of Panx1 is that of an ATP release channel. Despite the contrasting functional roles, connexins, innexins and pannexins share pharmacological properties. Most gap junction blockers also attenuate the function of Panx1, including carbenoxolone, mefloquine and flufenamic acid. However, in contrast to connexin based gap junction channels, Panx1 channel activity can be attenuated by several groups of drugs hitherto considered very specific for other proteins. The drugs affecting Panx1 channels include several transport inhibitors, chloride channel blockers, mitochondrial inhibitors, P2X7 receptor ligands, inflammasome inhibitors and malaria drugs. These observations indicate that Panx1 may play an extended role in a wider spectrum of physiological functions. Alternatively, Panx1 may share structural domains with other proteins, not readily revealed by sequence alignments. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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Affiliation(s)
- Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami, School of Medicine, PO Box 016430, Miami, FL 33101, USA.
| | - Feng Qiu
- Department of Physiology and Biophysics, University of Miami, School of Medicine, PO Box 016430, Miami, FL 33101, USA
| | - Junjie Wang
- Department of Physiology and Biophysics, University of Miami, School of Medicine, PO Box 016430, Miami, FL 33101, USA
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