1
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Cryo-EM structure of human heptameric pannexin 2 channel. Nat Commun 2023; 14:1118. [PMID: 36869038 PMCID: PMC9984531 DOI: 10.1038/s41467-023-36861-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Accepted: 02/19/2023] [Indexed: 03/05/2023] Open
Abstract
Pannexin 2 (Panx2) is a large-pore ATP-permeable channel with critical roles in various physiological processes, such as the inflammatory response, energy production and apoptosis. Its dysfunction is related to numerous pathological conditions including ischemic brain injury, glioma and glioblastoma multiforme. However, the working mechanism of Panx2 remains unclear. Here, we present the cryo-electron microscopy structure of human Panx2 at a resolution of 3.4 Å. Panx2 structure assembles as a heptamer, forming an exceptionally wide channel pore across the transmembrane and intracellular domains, which is compatible with ATP permeation. Comparing Panx2 with Panx1 structures in different states reveals that the Panx2 structure corresponds to an open channel state. A ring of seven arginine residues located at the extracellular entrance forms the narrowest site of the channel, which serves as the critical molecular filter controlling the permeation of substrate molecules. This is further verified by molecular dynamics simulations and ATP release assays. Our studies reveal the architecture of the Panx2 channel and provide insights into the molecular mechanism of its channel gating.
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2
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Alvarez CL, Chêne A, Semblat JP, Gamain B, Lapouméroulie C, Fader CM, Hattab C, Sévigny J, Denis MFL, Lauri N, Ostuni MA, Schwarzbaum PJ. Homeostasis of extracellular ATP in uninfected RBCs from a Plasmodium falciparum culture and derived microparticles. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183980. [PMID: 35654147 DOI: 10.1016/j.bbamem.2022.183980] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 05/11/2022] [Accepted: 05/26/2022] [Indexed: 12/20/2022]
Abstract
Plasmodium falciparum, a dangerous parasitic agent causing malaria, invades human red blood cells (RBCs), causing hemolysis and microvascular obstruction. These and other pathological processes of malaria patients are due to metabolic and structural changes occurring in uninfected RBCs. In addition, infection activates the production of microparticles (MPs). ATP and byproducts are important extracellular ligands modulating purinergic signaling within the intravascular space. Here, we analyzed the contribution of uninfected RBCs and MPs to the regulation of extracellular ATP (eATP) of RBCs, which depends on the balance between ATP release by specific transporters and eATP hydrolysis by ectonucleotidases. RBCs were cultured with P. falciparum for 24-48 h prior to experiments, from which uninfected RBCs and MPs were purified. On-line luminometry was used to quantify the kinetics of ATP release. Luminometry, colorimetry and radioactive methods were used to assess the rate of eATP hydrolysis by ectonucleotidases. Rates of ATP release and eATP hydrolysis were also evaluated in MPs. Uninfected RBCs challenged by different stimuli displayed a strong and transient activation of ATP release, together with an elevated rate of eATP hydrolysis. MPs contained ATP in their lumen, which was released upon vesicle rupture, and were able to hydrolyze eATP. Results suggest that uninfected RBCs and MPs can act as important determinants of eATP regulation of RBCs during malaria. The comparison of eATP homeostasis in infected RBCs, ui-RBCs, and MPs allowed us to speculate on the impact of P. falciparum infection on intravascular purinergic signaling and the control of the vascular caliber by RBCs.
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Affiliation(s)
- Cora L Alvarez
- Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini", Universidad de Buenos Aires (UBA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Farmacia y Bioquímica, Junín 956, C1113AAD Buenos Aires, Argentina; Universidad de Buenos Aires (UBA), Facultad de Ciencias Exactas y Naturales, Departamento de Biodiversidad y Biología Experimental, Intendente Güiraldes 2160, Ciudad Universitaria, C1428EGA Buenos Aires, Argentina
| | - Arnaud Chêne
- Université Paris Cité and Université des Antilles, INSERM, BIGR, F-75015 Paris, France
| | - Jean-Philippe Semblat
- Université Paris Cité and Université des Antilles, INSERM, BIGR, F-75015 Paris, France
| | - Benoît Gamain
- Université Paris Cité and Université des Antilles, INSERM, BIGR, F-75015 Paris, France
| | | | - Claudio M Fader
- Laboratorio de Fisiología y Fisiopatología del Glóbulo Rojo. Instituto de Histología y Embriología (IHEM), Universidad Nacional de Cuyo, CONICET, Mendoza, Argentina; Facultad de Odontología, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Claude Hattab
- Université Paris Cité and Université des Antilles, INSERM, BIGR, F-75015 Paris, France
| | - Jean Sévigny
- Centre de Recherche du CHU de Québec-Université Laval, Québec, QC, Canada; Département de Microbiologie-Infectiologie et d'Immunologie, Faculté de Médecine, Université Laval, Québec, QC, Canada
| | - María Florencia Leal Denis
- Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini", Universidad de Buenos Aires (UBA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Farmacia y Bioquímica, Junín 956, C1113AAD Buenos Aires, Argentina; Universidad de Buenos Aires (UBA), Facultad de Farmacia y Bioquímica, Departamento de Ciencias Químicas, Cátedra de Química Analítica, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Natalia Lauri
- Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini", Universidad de Buenos Aires (UBA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Farmacia y Bioquímica, Junín 956, C1113AAD Buenos Aires, Argentina; Universidad de Buenos Aires (UBA), Facultad de Farmacia y Bioquímica, Departamento de Ciencias Químicas, Cátedra de Química Analítica, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Mariano A Ostuni
- Université Paris Cité and Université des Antilles, INSERM, BIGR, F-75015 Paris, France
| | - Pablo J Schwarzbaum
- Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini", Universidad de Buenos Aires (UBA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Farmacia y Bioquímica, Junín 956, C1113AAD Buenos Aires, Argentina; Universidad de Buenos Aires (UBA), Facultad de Farmacia y Bioquímica, Departamento de Ciencias Químicas, Cátedra de Química Analítica, Junín 956, C1113AAD Buenos Aires, Argentina.
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3
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Rougé S, Genetet S, Leal Denis MF, Dussiot M, Schwarzbaum PJ, Ostuni MA, Mouro-Chanteloup I. Mechanosensitive Pannexin 1 Activity Is Modulated by Stomatin in Human Red Blood Cells. Int J Mol Sci 2022; 23:ijms23169401. [PMID: 36012667 PMCID: PMC9409209 DOI: 10.3390/ijms23169401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/11/2022] [Accepted: 08/18/2022] [Indexed: 11/16/2022] Open
Abstract
Pannexin 1 (PANX1) was proposed to drive ATP release from red blood cells (RBCs) in response to stress conditions. Stomatin, a membrane protein regulating mechanosensitive channels, has been proposed to modulate PANX1 activity in non-erythroid cells. To determine whether stomatin modulates PANX1 activity in an erythroid context, we have (i) assessed the in situ stomatin-PANX1 interaction in RBCs, (ii) measured PANX1-stimulated activity in RBCs expressing stomatin or from OverHydrated Hereditary Stomatocytosis (OHSt) patients lacking stomatin, and in erythroid K562 cells invalidated for stomatin. Proximity Ligation Assay coupled with flow imaging shows 27.09% and 6.13% positive events in control and OHSt RBCs, respectively. The uptake of dyes 5(6)-Carboxyfluorescein (CF) and TO-PRO-3 was used to evaluate PANX1 activity. RBC permeability for CF is 34% and 11.8% in control and OHSt RBCs, respectively. PANX1 permeability for TO-PRO-3 is 35.72% and 18.42% in K562 stom+ and stom− clones, respectively. These results suggest an interaction between PANX1 and stomatin in human RBCs and show a significant defect in PANX1 activity in the absence of stomatin. Based on these results, we propose that stomatin plays a major role in opening the PANX1 pore by being involved in a caspase-independent lifting of autoinhibition.
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Affiliation(s)
- Sarah Rougé
- Université Paris Cité and Université des Antilles, INSERM U1134, BIGR, F-75014 Paris, France
| | - Sandrine Genetet
- Université Paris Cité and Université des Antilles, INSERM U1134, BIGR, F-75014 Paris, France
| | - Maria Florencia Leal Denis
- Instituto de Química y Fisico-Química Biológicas “Prof. Alejandro C. Paladini”, UBA, CONICET, Facultad de Farmacia y Bioquímica, 1113 Buenos Aires, Argentina
| | - Michael Dussiot
- Université Paris Cité, INSERM U1163, IMAGINE, F-75015 Paris, France
| | - Pablo Julio Schwarzbaum
- Instituto de Química y Fisico-Química Biológicas “Prof. Alejandro C. Paladini”, UBA, CONICET, Facultad de Farmacia y Bioquímica, 1113 Buenos Aires, Argentina
| | - Mariano Anibal Ostuni
- Université Paris Cité and Université des Antilles, INSERM U1134, BIGR, F-75014 Paris, France
| | - Isabelle Mouro-Chanteloup
- Université Paris Cité and Université des Antilles, INSERM U1134, BIGR, F-75014 Paris, France
- Correspondence:
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Crocetti L, Guerrini G, Giovannoni MP, Melani F, Lamanna S, Di Cesare Mannelli L, Lucarini E, Ghelardini C, Wang J, Dahl G. New Panx-1 Blockers: Synthesis, Biological Evaluation and Molecular Dynamic Studies. Int J Mol Sci 2022; 23:4827. [PMID: 35563213 PMCID: PMC9103715 DOI: 10.3390/ijms23094827] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 04/22/2022] [Accepted: 04/26/2022] [Indexed: 12/25/2022] Open
Abstract
The channel protein Panx-1 is involved in some pathologies, such as epilepsy, ischemic stroke, cancer and Parkinson's disease, as well as in neuropathic pain. These observations make Panx-1 an interesting biological target. We previously published some potent indole derivatives as Panx-1 blockers, and as continuation of the research in this field we report here the studies on additional chemical scaffolds, naphthalene and pyrazole, appropriately substituted with those functions that gave the best results as in our indole series (sulphonamide functions and one/two carboxylic groups) and in Panx-1 blockers reported in the literature (sulphonic acid). Compounds 4 and 13, the latter being an analogue of the drug Probenecid, are the most potent Panx-1 blockers obtained in this study, with I = 97% and I = 93.7% at 50 µM, respectively. Both compounds, tested in a mouse model of oxaliplatin-induced neuropathic pain, showed a similar anti-hypersensitivity profile and are able to significantly increase the mouse pain threshold 45 min after the injection of the doses of 1 nmol and 3 nmol. Finally, the molecular dynamic studies and the PCA analysis have made it possible to identify a discriminating factor able to separate active compounds from inactive ones.
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Affiliation(s)
- Letizia Crocetti
- NEUROFARBA, Pharmaceutical and Nutraceutical Section, University of Florence, Via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy; (L.C.); (G.G.); (F.M.); (S.L.)
| | - Gabriella Guerrini
- NEUROFARBA, Pharmaceutical and Nutraceutical Section, University of Florence, Via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy; (L.C.); (G.G.); (F.M.); (S.L.)
| | - Maria Paola Giovannoni
- NEUROFARBA, Pharmaceutical and Nutraceutical Section, University of Florence, Via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy; (L.C.); (G.G.); (F.M.); (S.L.)
| | - Fabrizio Melani
- NEUROFARBA, Pharmaceutical and Nutraceutical Section, University of Florence, Via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy; (L.C.); (G.G.); (F.M.); (S.L.)
| | - Silvia Lamanna
- NEUROFARBA, Pharmaceutical and Nutraceutical Section, University of Florence, Via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy; (L.C.); (G.G.); (F.M.); (S.L.)
| | - Lorenzo Di Cesare Mannelli
- NEUROFARBA, Pharmacology and Toxicology Section, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (L.D.C.M.); (E.L.); (C.G.)
| | - Elena Lucarini
- NEUROFARBA, Pharmacology and Toxicology Section, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (L.D.C.M.); (E.L.); (C.G.)
| | - Carla Ghelardini
- NEUROFARBA, Pharmacology and Toxicology Section, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (L.D.C.M.); (E.L.); (C.G.)
| | - Junjie Wang
- Department of Physiology and Biophysics, University of Miami School of Medicine, 1600 N.W. 10th Avenue, Miami, FL 33136, USA; (J.W.); (G.D.)
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami School of Medicine, 1600 N.W. 10th Avenue, Miami, FL 33136, USA; (J.W.); (G.D.)
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Dossi E, Rouach N. Pannexin 1 channels and ATP release in epilepsy: two sides of the same coin : The contribution of pannexin-1, connexins, and CALHM ATP-release channels to purinergic signaling. Purinergic Signal 2021; 17:533-548. [PMID: 34495463 DOI: 10.1007/s11302-021-09818-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/08/2021] [Indexed: 11/29/2022] Open
Abstract
Purinergic signaling mediated by ATP and its metabolites contributes to various brain physiological processes as well as to several pathological conditions, including neurodegenerative and neurological disorders, such as epilepsy. Among the different ATP release pathways, pannexin 1 channels represent one of the major conduits being primarily activated in pathological contexts. Investigations on in vitro and in vivo models of epileptiform activity and seizures in mice and human tissues revealed pannexin 1 involvement in aberrant network activity and epilepsy, and highlighted that pannexin 1 exerts a complex role. Pannexin 1 can indeed either sustain seizures through release of ATP that can directly activate purinergic receptors, or tune down epileptic activity via ATP-derived adenosine that decreases neuronal excitability. Interestingly, in-depth analysis of the literature unveils that this dichotomy is only apparent, as it depends on the model of seizure induction and the type of evoked epileptiform activity, two factors that can differentially activate pannexin 1 channels and trigger distinct intracellular signaling cascades. Here, we review the general properties and ATP permeability of pannexin 1 channels, and discuss their impact on acute epileptiform activity and chronic epilepsy according to the regime of activity and disease state. These data pave the way for the development of new antiepileptic strategies selectively targeting pannexin 1 channels in a context-dependent manner.
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Affiliation(s)
- Elena Dossi
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé Et de la Recherche Médicale U1050, Collège de France, Labex Memolife, Université PSL, Paris, France.
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé Et de la Recherche Médicale U1050, Collège de France, Labex Memolife, Université PSL, Paris, France.
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6
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Purohit R, Bera AK. Pannexin 1 plays a pro-survival role by attenuating P2X7 receptor-mediated Ca 2+ influx. Cell Calcium 2021; 99:102458. [PMID: 34479067 DOI: 10.1016/j.ceca.2021.102458] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 07/27/2021] [Accepted: 08/16/2021] [Indexed: 10/20/2022]
Abstract
Extracellular ATP works as an autocrine and/or paracrine signaling molecule by activating plasma membrane-localized purinergic receptors. Stimulation of purinergic P2X7 receptor (P2X7R) increases cytosolic Ca2+ ([Ca2+]c), which in turn activates Pannexin 1 (Panx1) channel. In earlier studies, Panx1 and P2X7R have been shown to interact physically. Also, both the channels have been implicated in similar pathophysiological processes. In this study, we investigated the effect of Panx1 on P2X7R-mediated Ca2+influx. Panx1 attenuated P2X7R-mediated [Ca2+]c rise in CHO-K1 and HEK-293 cells. [Ca2+]c rise was higher in Panx1 knockdown astrocytes. The inhibitory effect was unaffected in the presence of Panx1 blocker, carbenoxolone. The region between 350th and 386th amino acid residues in the carboxyl terminus (CT) of Panx1 was found to be crucial for inhibiting P2X7R. Like full-length Panx1, the CT (350th to 426th amino acids) alone was able to attenuate the [Ca2+]c rise. Further, CT prevented cell death caused by P2X7R overactivation. Based on our results, we propose a novel pro-survival role of Panx1 exerted by modulating P2X7R.
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Affiliation(s)
- Rutambhara Purohit
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600 036, India
| | - Amal Kanti Bera
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600 036, India.
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Mim C, Perkins G, Dahl G. Structure versus function: Are new conformations of pannexin 1 yet to be resolved? J Gen Physiol 2021; 153:211971. [PMID: 33835130 PMCID: PMC8042604 DOI: 10.1085/jgp.202012754] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Pannexin 1 (Panx1) plays a decisive role in multiple physiological and pathological settings, including oxygen delivery to tissues, mucociliary clearance in airways, sepsis, neuropathic pain, and epilepsy. It is widely accepted that Panx1 exerts its role in the context of purinergic signaling by providing a transmembrane pathway for ATP. However, under certain conditions, Panx1 can also act as a highly selective membrane channel for chloride ions without ATP permeability. A recent flurry of publications has provided structural information about the Panx1 channel. However, while these structures are consistent with a chloride selective channel, none show a conformation with strong support for the ATP release function of Panx1. In this Viewpoint, we critically assess the existing evidence for the function and structure of the Panx1 channel and conclude that the structure corresponding to the ATP permeation pathway is yet to be determined. We also list a set of additional topics needing attention and propose ways to attain the large-pore, ATP-permeable conformation of the Panx1 channel.
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Affiliation(s)
- Carsten Mim
- Department of Biomedical Engineering and Health Systems Royal Institute of Technology, Huddinge, Sweden
| | - Guy Perkins
- National Center for Microscopy and Imaging Research, University of California, San Diego School of Medicine, La Jolla, CA
| | - Gerhard Dahl
- Department of Physiology, University of Miami School of Medicine, Miami, FL
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8
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Deng Z, He Z, Maksaev G, Bitter RM, Rau M, Fitzpatrick JAJ, Yuan P. Cryo-EM structures of the ATP release channel pannexin 1. Nat Struct Mol Biol 2020; 27:373-381. [PMID: 32231289 DOI: 10.1038/s41594-020-0401-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 02/25/2020] [Indexed: 12/15/2022]
Abstract
The plasma membrane adenosine triphosphate (ATP) release channel pannexin 1 (PANX1) has been implicated in many physiological and pathophysiological processes associated with purinergic signaling, including cancer progression, apoptotic cell clearance, inflammation, blood pressure regulation, oocyte development, epilepsy and neuropathic pain. Here we present near-atomic-resolution structures of human and frog PANX1 determined by cryo-electron microscopy that revealed a heptameric channel architecture. Compatible with ATP permeation, the transmembrane pore and cytoplasmic vestibule were exceptionally wide. An extracellular tryptophan ring located at the outer pore created a constriction site, potentially functioning as a molecular sieve that restricts the size of permeable substrates. The amino and carboxyl termini, not resolved in the density map, appeared to be structurally dynamic and might contribute to narrowing of the pore during channel gating. In combination with functional characterization, this work elucidates the previously unknown architecture of pannexin channels and establishes a foundation for understanding their unique channel properties.
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Affiliation(s)
- Zengqin Deng
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
| | - Zhihui He
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
| | - Grigory Maksaev
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
| | - Ryan M Bitter
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA
| | - Michael Rau
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, MO, USA
| | - James A J Fitzpatrick
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA.,Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, MO, USA.,Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, USA.,Department of Biomedical Engineering, Washington University in Saint Louis, St. Louis, MO, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA. .,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO, USA.
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9
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Lagos-Cabré R, Burgos-Bravo F, Avalos AM, Leyton L. Connexins in Astrocyte Migration. Front Pharmacol 2020; 10:1546. [PMID: 32009957 PMCID: PMC6974553 DOI: 10.3389/fphar.2019.01546] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 11/29/2019] [Indexed: 12/18/2022] Open
Abstract
Astrocytes have long been considered the supportive cells of the central nervous system, but during the last decades, they have gained much more attention because of their active participation in the modulation of neuronal function. For example, after brain damage, astrocytes become reactive and undergo characteristic morphological and molecular changes, such as hypertrophy and increase in the expression of glial fibrillary acidic protein (GFAP), in a process known as astrogliosis. After severe damage, astrocytes migrate to the lesion site and proliferate, which leads to the formation of a glial scar. At this scar-forming stage, astrocytes secrete many factors, such as extracellular matrix proteins, cytokines, growth factors and chondroitin sulfate proteoglycans, stop migrating, and the process is irreversible. Although reactive gliosis is a normal physiological response that can protect brain cells from further damage, it also has detrimental effects on neuronal survival, by creating a hostile and non-permissive environment for axonal repair. The transformation of astrocytes from reactive to scar-forming astrocytes highlights migration as a relevant regulator of glial scar formation, and further emphasizes the importance of efficient communication between astrocytes in order to orchestrate cell migration. The coordination between astrocytes occurs mainly through Connexin (Cx) channels, in the form of direct cell-cell contact (gap junctions, GJs) or contact between the extracellular matrix and the astrocytes (hemichannels, HCs). Reactive astrocytes increase the expression levels of several proteins involved in astrocyte migration, such as αvβ3 Integrin, Syndecan-4 proteoglycan, the purinergic receptor P2X7, Pannexin1, and Cx43 HCs. Evidence has indicated that Cx43 HCs play a role in regulating astrocyte migration through the release of small molecules to the extracellular space, which then activate receptors in the same or adjacent cells to continue the signaling cascades required for astrocyte migration. In this review, we describe the communication of astrocytes through Cxs, the role of Cxs in inflammation and astrocyte migration, and discuss the molecular mechanisms that regulate Cx43 HCs, which may provide a therapeutic window of opportunity to control astrogliosis and the progression of neurodegenerative diseases.
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Affiliation(s)
- Raúl Lagos-Cabré
- Cellular Communication Laboratory, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Advanced Center for Chronic Diseases (ACCDiS), Center for Studies on Exercise, Metabolism and Cancer (CEMC), Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM), Universidad de Chile, Santiago, Chile
| | - Francesca Burgos-Bravo
- Cellular Communication Laboratory, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Advanced Center for Chronic Diseases (ACCDiS), Center for Studies on Exercise, Metabolism and Cancer (CEMC), Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM), Universidad de Chile, Santiago, Chile
| | - Ana María Avalos
- Facultad de Ciencias de la Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Santiago, Chile
| | - Lisette Leyton
- Cellular Communication Laboratory, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Advanced Center for Chronic Diseases (ACCDiS), Center for Studies on Exercise, Metabolism and Cancer (CEMC), Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM), Universidad de Chile, Santiago, Chile
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10
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Nielsen BS, Toft-Bertelsen TL, Lolansen SD, Anderson CL, Nielsen MS, Thompson RJ, MacAulay N. Pannexin 1 activation and inhibition is permeant-selective. J Physiol 2020; 598:361-379. [PMID: 31698505 DOI: 10.1113/jp278759] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 11/05/2019] [Indexed: 01/14/2023] Open
Abstract
KEY POINTS The large-pore channel pannexin 1 (Panx1) is expressed in many cell types and can open upon different, yet not fully established, stimuli. Panx1 permeability is often inferred from channel permeability to fluorescent dyes, but it is currently unknown whether dye permeability translates to permeability to other molecules. Cell shrinkage and C-terminal cleavage led to a Panx1 open-state with increased permeability to atomic ions (current), but did not alter ethidium uptake. Panx1 inhibitors affected Panx1-mediated ion conduction differently from ethidium permeability, and inhibitor efficiency towards a given molecule therefore cannot be extrapolated to its effects on the permeability of another. We conclude that ethidium permeability does not reflect equal permeation of other molecules and thus is no measure of general Panx1 activity. ABSTRACT Pannexin 1 (Panx1) is a large-pore membrane channel connecting the extracellular milieu with the cell interior. While several activation regimes activate Panx1 in a variety of cell types, the selective permeability of an open Panx1 channel remains unresolved: does a given activation paradigm increase Panx1's permeability towards all permeants equally and does fluorescent dye flux serve as a proxy for biological permeation through an open channel? To explore permeant-selectivity of Panx1 activation and inhibition, we employed Panx1-expressing Xenopus laevis oocytes and HEK293T cells. We report that different mechanisms of activation of Panx1 differentially affected ethidium and atomic ion permeation. Most notably, C-terminal truncation or cell shrinkage elevated Panx1-mediated ion conductance, but had no effect on ethidium permeability. In contrast, extracellular pH changes predominantly affected ethidium permeability but not ionic conductance. High [K+ ]o did not increase the flux of either of the two permeants. Once open, Panx1 demonstrated preference for anionic permeants, such as Cl- , lactate and glutamate, while not supporting osmotic water flow. Panx1 inhibitors displayed enhanced potency towards Panx1-mediated currents compared to that of ethidium uptake. We conclude that activation or inhibition of Panx1 display permeant-selectivity and that permeation of ethidium does not necessarily reflect an equal permeation of smaller biological molecules and atomic ions.
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Affiliation(s)
- Brian Skriver Nielsen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Trine Lisberg Toft-Bertelsen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sara Diana Lolansen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Connor L Anderson
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Morten Schak Nielsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Roger J Thompson
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Nanna MacAulay
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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11
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Leal Denis MF, Lefevre SD, Alvarez CL, Lauri N, Enrique N, Rinaldi DE, Gonzalez-Lebrero R, Vecchio LE, Espelt MV, Stringa P, Muñoz-Garay C, Milesi V, Ostuni MA, Herlax V, Schwarzbaum PJ. Regulation of extracellular ATP of human erythrocytes treated with α-hemolysin. Effects of cell volume, morphology, rheology and hemolysis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:896-915. [PMID: 30726708 DOI: 10.1016/j.bbamcr.2019.01.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 01/10/2019] [Accepted: 01/30/2019] [Indexed: 12/17/2022]
Abstract
Alpha-hemolysin (HlyA) of uropathogenic strains of Escherichia coli irreversibly binds to human erythrocytes (RBCs) and triggers activation of ATP release and metabolic changes ultimately leading to hemolysis. We studied the regulation of extracellular ATP (ATPe) of RBCs exposed to HlyA. Luminometry was used to assess ATP release and ATPe hydrolysis, whereas changes in cell volume and morphology were determined by electrical impedance, ektacytometry and aggregometry. Exposure of RBCs to HlyA induced a strong increase of [ATPe] (3-36-fold) and hemolysis (1-44-fold), partially compensated by [ATPe] hydrolysis by ectoATPases and intracellular ATPases released by dead cells. Carbenoxolone, a pannexin 1 inhibitor, partially inhibited ATP release (43-67%). The un-acylated toxin ProHlyA and the deletion analog HlyA∆914-936 were unable to induce ATP release or hemolysis. For HlyA treated RBCs, a data driven mathematical model showed that simultaneous lytic and non-lytic release mainly governed ATPe kinetics, while ATPe hydrolysis became important after prolonged toxin exposure. HlyA induced a 1.5-fold swelling, while blocking this swelling reduced ATP release by 77%. Blocking ATPe activation of purinergic P2X receptors reduced swelling by 60-80%. HlyA-RBCs showed an acute 1.3-2.2-fold increase of Ca2+i, increased crenation and externalization of phosphatidylserine. Perfusion of HlyA-RBCs through adhesion platforms showed strong adhesion to activated HMEC cells, followed by rapid detachment. HlyA exposed RBCs exhibited increased sphericity under osmotic stress, reduced elongation under shear stress, and very low aggregation in viscous media. Overall results showed that HlyA-RBCs displayed activated ATP release, high but weak adhesivity, low deformability and aggregability and high sphericity.
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Affiliation(s)
- M F Leal Denis
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Junín 956 Buenos Aires, Argentina.; Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Analítica, Cátedra de Química Química Analítica y Fisicoquímica, Junín 956 Buenos Aires, Argentina
| | - S D Lefevre
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015 Paris, France.; Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015 Paris, France
| | - C L Alvarez
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Junín 956 Buenos Aires, Argentina.; Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Biodiversidad y Biología Experimental, Intendente Güiraldes 2160 Buenos Aires, Argentina
| | - N Lauri
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Junín 956 Buenos Aires, Argentina.; Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica. Cátedra de Química Biológica Superior, Junín 956 Buenos Aires, Argentina
| | - N Enrique
- Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), Facultad de Ciencias Exactas, Calle 47 y 115 La Plata, Argentina.; Universidad Nacional de la Plata, Facultad de Ciencias Exactas, Departamento de Ciencias Biológicas, Cátedra de Fisiología, Calle 47, Casco Urbano, La Plata, Argentina
| | - D E Rinaldi
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Junín 956 Buenos Aires, Argentina.; Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Cátedra de Química Biológica, Junín 956 Buenos Aires, Argentina
| | - R Gonzalez-Lebrero
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Junín 956 Buenos Aires, Argentina.; Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Cátedra de Química Biológica, Junín 956 Buenos Aires, Argentina
| | - L E Vecchio
- Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), Facultad de Ciencias Exactas, Calle 47 y 115 La Plata, Argentina.; Universidad Nacional de la Plata, Facultad de Ciencias Exactas, Departamento de Ciencias Biológicas, Cátedra de Fisiología, Calle 47, Casco Urbano, La Plata, Argentina
| | - M V Espelt
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Junín 956 Buenos Aires, Argentina.; Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica. Cátedra de Química Biológica Superior, Junín 956 Buenos Aires, Argentina
| | - P Stringa
- Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), Facultad de Ciencias Exactas, Calle 47 y 115 La Plata, Argentina.; Universidad Favaloro, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Medicina Traslacional, Trasplante y Bioingeniería (IMETTyB), Av. Entre Ríos 495, Buenos Aires, Argentina.; Universidad Nacional de La Plata, Laboratorio de Trasplante de Órganos y Tejidos, Facultad de Ciencias, Calle 60 y 120, La Plata, Argentina
| | - C Muñoz-Garay
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México (UNAM), Av. Universidad s/n, Cuernavaca, Mexico
| | - V Milesi
- Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), Facultad de Ciencias Exactas, Calle 47 y 115 La Plata, Argentina.; Universidad Nacional de la Plata, Facultad de Ciencias Exactas, Departamento de Ciencias Biológicas, Cátedra de Fisiología, Calle 47, Casco Urbano, La Plata, Argentina
| | - M A Ostuni
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015 Paris, France.; Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015 Paris, France
| | - V Herlax
- Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP) "Prof. Dr. Rodolfo R. Brenner", Facultad de Ciencias Médicas, Av. 60 y Av. 120, La Plata, Argentina.; Universidad Nacional de La Plata, Facultad de Ciencias Médicas, Av. 60 y Av. 120, La Plata, Argentina
| | - P J Schwarzbaum
- Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Junín 956 Buenos Aires, Argentina.; Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica. Cátedra de Química Biológica Superior, Junín 956 Buenos Aires, Argentina..
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12
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Molecular Identities and ATP Release Activities of Two Types of Volume-Regulatory Anion Channels, VSOR and Maxi-Cl. CURRENT TOPICS IN MEMBRANES 2018; 81:125-176. [PMID: 30243431 DOI: 10.1016/bs.ctm.2018.07.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
An elaborate volume regulation system based on interplay of ion channels and transporters was evolved to cope with constant osmotic challenges caused by intensive metabolism, transport and other physiological/pathophysiological events. In animal cells, two types of anion channels are directly activated by cell swelling and involved in the regulatory volume decrease (RVD): volume-sensitive outwardly rectifying anion channel (VSOR), also called volume-regulated anion channel (VRAC), and Maxi-Cl which is the most major type of maxi-anion channel (MAC). These two channels have very different biophysical profiles and exhibit opposite dependence on intracellular ATP. After several decades of verifying many false-positive candidates for VSOR and Maxi-Cl, LRRC8 family proteins emerged as major VSOR components, and SLCO2A1 protein as a core of Maxi-Cl. Still, neither of these proteins alone can fully reproduce the native channel phenotypes suggesting existence of missing components. Although both VSOR and Maxi-Cl have pores wide enough to accommodate bulky ATP4- and MgATP2- anions, evidence accumulated hitherto, based on pharmacological and gene silencing experiments, suggests that Maxi-Cl, but not VSOR, serves as one of the major pathways for the release of ATP from swollen and ischemic/hypoxic cells. Relations of VSOR and Maxi-Cl with diseases and their selective pharmacology are the topics promoted by recent advance in molecular identification of the two volume-activated, volume-regulatory anion channels.
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13
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Marginedas-Freixa I, Alvarez CL, Moras M, Leal Denis MF, Hattab C, Halle F, Bihel F, Mouro-Chanteloup I, Lefevre SD, Le Van Kim C, Schwarzbaum PJ, Ostuni MA. Human erythrocytes release ATP by a novel pathway involving VDAC oligomerization independent of pannexin-1. Sci Rep 2018; 8:11384. [PMID: 30061676 PMCID: PMC6065367 DOI: 10.1038/s41598-018-29885-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 07/20/2018] [Indexed: 12/14/2022] Open
Abstract
We previously demonstrated that the translocase protein TSPO2 together with the voltage-dependent anion channel (VDAC) and adenine nucleotide transporter (ANT) were involved in a membrane transport complex in human red blood cells (RBCs). Because VDAC was proposed as a channel mediating ATP release in RBCs, we used TSPO ligands together with VDAC and ANT inhibitors to test this hypothesis. ATP release was activated by TSPO ligands, and blocked by inhibitors of VDAC and ANT, while it was insensitive to pannexin-1 blockers. TSPO ligand increased extracellular ATP (ATPe) concentration by 24–59% over the basal values, displaying an acute increase in [ATPe] to a maximal value, which remained constant thereafter. ATPe kinetics were compatible with VDAC mediating a fast but transient ATP efflux. ATP release was strongly inhibited by PKC and PKA inhibitors as well as by depleting intracellular cAMP or extracellular Ca2+, suggesting a mechanism involving protein kinases. TSPO ligands favoured VDAC polymerization yielding significantly higher densities of oligomeric bands than in unstimulated cells. Polymerization was partially inhibited by decreasing Ca2+ and cAMP contents. The present results show that TSPO ligands induce polymerization of VDAC, coupled to activation of ATP release by a supramolecular complex involving VDAC, TSPO2 and ANT.
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Affiliation(s)
- Irene Marginedas-Freixa
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015, Paris, France.,Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015, Paris, France
| | - Cora Lilia Alvarez
- Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini", UBA, CONICET, Facultad de Farmacia y Bioquímica, Junín 956, Buenos Aires, Argentina.,Universidad de Buenos Aires. Facultad Ciencias Exactas y Naturales, Departamento de Biodiversidad y Biología Experimental, Buenos Aires, Argentina
| | - Martina Moras
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015, Paris, France.,Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015, Paris, France
| | - María Florencia Leal Denis
- Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini", UBA, CONICET, Facultad de Farmacia y Bioquímica, Junín 956, Buenos Aires, Argentina.,Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Analítica y Fisicoquímica, Cátedra de Química Analítica, Buenos Aires, Argentina
| | - Claude Hattab
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015, Paris, France.,Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015, Paris, France
| | - François Halle
- UMR7200, Laboratoire d'Innovation Thérapeutique, Faculty of Pharmacy, University of Strasbourg, CNRS, 67400, Illkirch Graffenstaden, France
| | - Frédéric Bihel
- UMR7200, Laboratoire d'Innovation Thérapeutique, Faculty of Pharmacy, University of Strasbourg, CNRS, 67400, Illkirch Graffenstaden, France
| | - Isabelle Mouro-Chanteloup
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015, Paris, France.,Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015, Paris, France
| | - Sophie Denise Lefevre
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015, Paris, France.,Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015, Paris, France
| | - Caroline Le Van Kim
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015, Paris, France.,Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015, Paris, France
| | - Pablo Julio Schwarzbaum
- Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini", UBA, CONICET, Facultad de Farmacia y Bioquímica, Junín 956, Buenos Aires, Argentina.,Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica. Cátedra de Química Biológica Superior, Buenos Aires, Argentina
| | - Mariano Anibal Ostuni
- UMR-S1134, Integrated Biology of Red Blood Cells, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Université de la Réunion, Université des Antilles, F-75015, Paris, France. .,Institut National de la Transfusion Sanguine, Laboratoire d'Excellence GR-Ex, F-75015, Paris, France.
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14
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Wang J, Jackson DG, Dahl G. Cationic control of Panx1 channel function. Am J Physiol Cell Physiol 2018; 315:C279-C289. [PMID: 29719168 DOI: 10.1152/ajpcell.00303.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The sequence and predicted membrane topology of pannexin1 (Panx1) places it in the family of gap junction proteins. However, rather than forming gap junction channels, Panx1 forms channels in the nonjunctional membrane. Panx1 operates in two distinct open states, depending on the mode of stimulation. The exclusively voltage-gated channel has a small conductance (<100 pS) and is highly selective for the flux of chloride ions. The Panx1 channel activated by various physiological stimuli or by increased concentrations of extracellular potassium ions has a large conductance (~500 pS, however, with multiple, long-lasting subconductance states) and is nonselectively permeable to small molecules, including ATP. To test whether the two open conformations also differ pharmacologically, the effects of di-and trivalent cations on the two Panx1 channel conformations were investigated. The rationale for this venture was that, under certain experimental conditions, ATP release from cells can be inhibited by multivalent cations, yet the literature indicates that the ATP release channel Panx1 is not affected by these ions. Consistent with previous reports, the Panx1 channel was not activated by removal of extracellular Ca2+ and the currents through the voltage-activated channel were not altered by Ca2+, Zn2+, Ba2+, or Gd3+. In contrast, the Panx1 channel activated to the large channel conformation by extracellular K+, osmotic stress, or low oxygen was inhibited by the multivalent cations in a dose-dependent way. Thus, monovalent cations activated the Panx1 channel from the closed state to the "large" conformation, while di- and trivalent cations exclusively inhibited this large channel conformation.
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Affiliation(s)
- Junjie Wang
- Department of Physiology and Biophysics, University of Miami School of Medicine , Miami, Florida
| | - David George Jackson
- Department of Physiology and Biophysics, University of Miami School of Medicine , Miami, Florida
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami School of Medicine , Miami, Florida
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15
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Dinarelli S, Longo G, Dietler G, Francioso A, Mosca L, Pannitteri G, Boumis G, Bellelli A, Girasole M. Erythrocyte's aging in microgravity highlights how environmental stimuli shape metabolism and morphology. Sci Rep 2018; 8:5277. [PMID: 29588453 PMCID: PMC5869709 DOI: 10.1038/s41598-018-22870-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 01/25/2018] [Indexed: 12/15/2022] Open
Abstract
The determination of the function of cells in zero-gravity conditions is a subject of interest in many different research fields. Due to their metabolic unicity, the characterization of the behaviour of erythrocytes maintained in prolonged microgravity conditions is of particular importance. Here, we used a 3D-clinostat to assess the microgravity-induced modifications of the structure and function of these cells, by investigating how they translate these peculiar mechanical stimuli into modifications, with potential clinical interest, of the biochemical pathways and the aging processes. We compared the erythrocyte's structural parameters and selected metabolic indicators that are characteristic of the aging in microgravity and standard static incubation conditions. The results suggest that, at first, human erythrocytes react to external stimuli by adapting their metabolic patterns and the rate of consumption of the cell resources. On longer timeframes, the cells translate even small differences in the environment mechanical solicitations into structural and morphologic features, leading to distinctive morphological patterns of aging.
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Affiliation(s)
- S Dinarelli
- Istituto di Struttura della Materia - CNR, Via fosso del cavaliere 100, 00133, Roma, Italy
| | - G Longo
- Istituto di Struttura della Materia - CNR, Via fosso del cavaliere 100, 00133, Roma, Italy.,LPMV-IPhys-EPFL, Route de la Sorge, Lausanne, Switzerland
| | - G Dietler
- LPMV-IPhys-EPFL, Route de la Sorge, Lausanne, Switzerland
| | - A Francioso
- Dipartimento di Scienze Biochimiche "A. Rossi-Fanelli" Universita "Sapienza", Piazzale A. Moro 5, 00185, Roma, Italy
| | - L Mosca
- Dipartimento di Scienze Biochimiche "A. Rossi-Fanelli" Universita "Sapienza", Piazzale A. Moro 5, 00185, Roma, Italy
| | - G Pannitteri
- Dipartimento di Scienze cardiovascolari, respiratorie, nefrologiche, anestesiologiche e geriatriche Università "Sapienza", Piazzale A. Moro 5, 00185, Roma, Italy
| | - G Boumis
- Dipartimento di Scienze Biochimiche "A. Rossi-Fanelli" Universita "Sapienza", Piazzale A. Moro 5, 00185, Roma, Italy
| | - A Bellelli
- Dipartimento di Scienze Biochimiche "A. Rossi-Fanelli" Universita "Sapienza", Piazzale A. Moro 5, 00185, Roma, Italy
| | - M Girasole
- Istituto di Struttura della Materia - CNR, Via fosso del cavaliere 100, 00133, Roma, Italy.
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16
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Garg C, Seo JH, Ramachandran J, Loh JM, Calderon F, Contreras JE. Trovafloxacin attenuates neuroinflammation and improves outcome after traumatic brain injury in mice. J Neuroinflammation 2018; 15:42. [PMID: 29439712 PMCID: PMC5812039 DOI: 10.1186/s12974-018-1069-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 01/17/2018] [Indexed: 12/20/2022] Open
Abstract
Background Trovafloxacin is a broad-spectrum antibiotic, recently identified as an inhibitor of pannexin-1 (Panx1) channels. Panx1 channels are important conduits for the adenosine triphosphate (ATP) release from live and dying cells that enhances the inflammatory response of immune cells. Elevated extracellular levels ATP released upon injury activate purinergic pathways in inflammatory cells that promote migration, proliferation, phagocytosis, and apoptotic signals. Here, we tested whether trovafloxacin administration attenuates the neuroinflammatory response and improves outcomes after brain trauma. Methods The murine controlled cortical impact (CCI) model was used to determine whether in vivo delivery of trovafloxacin has anti-inflammatory and neuroprotective actions after brain trauma. Locomotor deficit was assessed using the rotarod test. Levels of tissue damage markers and inflammation were measured using western blot, qPCR, and immunofluorescence. In vitro assays were used to evaluate whether trovafloxacin blocks ATP release and cell migration in a chemotactic-stimulated microglia cell line. Results Trovafloxacin treatment of CCI-injured mice significantly reduced tissue damage markers and improved locomotor deficits. In addition, trovafloxacin treatment significantly reduced mRNA levels of several pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α), which correlates with an overall reduction in the accumulation of inflammatory cell types (neutrophils, microglia/macrophages, and astroglia) at the injury zone. To determine whether trovafloxacin exerted these effects by direct action on immune cells, we evaluated its effect on ATP release and cell migration using a chemotactic-stimulated microglial cell line. We found that trovafloxacin significantly inhibited both ATP release and migration of these cells. Conclusion Our results show that trovafloxacin administration has pronounced anti-inflammatory and neuroprotective effects following brain injury. These findings lay the foundation for future studies to directly test a role for Panx1 channels in pathological inflammation following brain trauma. Electronic supplementary material The online version of this article (10.1186/s12974-018-1069-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Charu Garg
- Department of Pharmacology, Physiology and Neurosciences, New Jersey Medical School, Rutgers University, 185 South Orange Ave, Newark, NJ, 07103, USA
| | - Joon Ho Seo
- Department of Pharmacology, Physiology and Neurosciences, New Jersey Medical School, Rutgers University, 185 South Orange Ave, Newark, NJ, 07103, USA
| | - Jayalakshmi Ramachandran
- Department of Pharmacology, Physiology and Neurosciences, New Jersey Medical School, Rutgers University, 185 South Orange Ave, Newark, NJ, 07103, USA
| | - Ji Meng Loh
- Department of Mathematical Sciences, New Jersey Institute of Technology, University Heights, Newark, NJ, 07102, USA
| | - Frances Calderon
- Department of Pharmacology, Physiology and Neurosciences, New Jersey Medical School, Rutgers University, 185 South Orange Ave, Newark, NJ, 07103, USA.
| | - Jorge E Contreras
- Department of Pharmacology, Physiology and Neurosciences, New Jersey Medical School, Rutgers University, 185 South Orange Ave, Newark, NJ, 07103, USA.
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17
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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18
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 895] [Impact Index Per Article: 149.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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19
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Grygorczyk R, Orlov SN. Effects of Hypoxia on Erythrocyte Membrane Properties-Implications for Intravascular Hemolysis and Purinergic Control of Blood Flow. Front Physiol 2017; 8:1110. [PMID: 29312010 PMCID: PMC5744585 DOI: 10.3389/fphys.2017.01110] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 12/14/2017] [Indexed: 01/08/2023] Open
Abstract
Intravascular hemolysis occurs in hereditary, acquired, and iatrogenic hemolytic conditions but it could be also a normal physiological process contributing to intercellular signaling. New evidence suggests that intravascular hemolysis and the associated release of adenosine triphosphate (ATP) may be an important mechanism for in vivo local purinergic signaling and blood flow regulation during exercise and hypoxia. However, the mechanisms that modulate hypoxia-induced RBC membrane fragility remain unclear. Here, we provide an overview of the role of RBC ATP release in the regulation of vascular tone and prevailing assumptions on the putative release mechanisms. We show importance of intravascular hemolysis as a source of ATP for local purinergic regulation of blood flow and discuss processes that regulate membrane propensity to rupture under stress and hypoxia.
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Affiliation(s)
| | - Sergei N. Orlov
- Biology, M. V. Lomonosov Moscow State University, Moscow, Russia
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20
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Chiu YH, Schappe MS, Desai BN, Bayliss DA. Revisiting multimodal activation and channel properties of Pannexin 1. J Gen Physiol 2017; 150:19-39. [PMID: 29233884 PMCID: PMC5749114 DOI: 10.1085/jgp.201711888] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Accepted: 11/09/2017] [Indexed: 12/23/2022] Open
Abstract
Pannexin 1 (Panx1) forms plasma membrane ion channels that are widely expressed throughout the body. Panx1 activation results in the release of nucleotides such as adenosine triphosphate and uridine triphosphate. Thus, these channels have been implicated in diverse physiological and pathological functions associated with purinergic signaling, such as apoptotic cell clearance, blood pressure regulation, neuropathic pain, and excitotoxicity. In light of this, substantial attention has been directed to understanding the mechanisms that regulate Panx1 channel expression and activation. Here we review accumulated evidence for the various activation mechanisms described for Panx1 channels and, where possible, the unitary channel properties associated with those forms of activation. We also emphasize current limitations in studying Panx1 channel function and propose potential directions to clarify the exciting and expanding roles of Panx1 channels.
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Affiliation(s)
- Yu-Hsin Chiu
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA
| | - Michael S Schappe
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA
| | - Bimal N Desai
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA
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21
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Keller AS, Diederich L, Panknin C, DeLalio LJ, Drake JC, Sherman R, Jackson EK, Yan Z, Kelm M, Cortese-Krott MM, Isakson BE. Possible roles for ATP release from RBCs exclude the cAMP-mediated Panx1 pathway. Am J Physiol Cell Physiol 2017; 313:C593-C603. [PMID: 28855161 DOI: 10.1152/ajpcell.00178.2017] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 08/23/2017] [Accepted: 08/23/2017] [Indexed: 01/21/2023]
Abstract
Red blood cell (RBC)-derived adenosine triphosphate (ATP) has been proposed as an integral component in the regulation of oxygen supply to skeletal muscle. In ex vivo settings RBCs have been shown to release ATP in response to a number of stimuli, including stimulation of adrenergic receptors. Further evidence suggested that ATP release from RBCs was dependent on activation of adenylate cyclase (AC)/cyclic adenosine monophosphate (cAMP)-dependent pathways and involved the pannexin 1 (Panx1) channel. Here we show that RBCs express Panx1 and confirm its absence in Panx1 knockout (-/-) RBCs. However, Panx1-/- mice lack any decrease in exercise performance, challenging the assumptions that Panx1 plays an essential role in increased blood perfusion to exercising skeletal muscle and therefore in ATP release from RBCs. We therefore tested the role of Panx1 in ATP release from RBCs ex vivo in RBC suspensions. We found that stimulation with hypotonic potassium gluconate buffer resulted in a significant increase in ATP in the supernatant, but this was highly correlated with RBC lysis. Next, we treated RBCs with a stable cAMP analog, which did not induce ATP release from wild-type or Panx1-/- mice. Similarly, multiple pharmacological treatments activating AC in RBCs increased intracellular cAMP levels (as measured via mass spectrometry) but did not induce ATP release. The data presented here question the importance of Panx1 for exercise performance and dispute the general assumption that ATP release from RBCs via Panx1 is regulated via cAMP.
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Affiliation(s)
- Alexander S Keller
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia.,Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Lukas Diederich
- Cardiovascular Research Laboratory, Division of Cardiology, Pneumology, and Vascular Medicine, Medical Faculty, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
| | - Christina Panknin
- Cardiovascular Research Laboratory, Division of Cardiology, Pneumology, and Vascular Medicine, Medical Faculty, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
| | - Leon J DeLalio
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia.,Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Joshua C Drake
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Robyn Sherman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Edwin Kerry Jackson
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Zhen Yan
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia.,Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Malte Kelm
- Cardiovascular Research Laboratory, Division of Cardiology, Pneumology, and Vascular Medicine, Medical Faculty, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
| | - Miriam M Cortese-Krott
- Cardiovascular Research Laboratory, Division of Cardiology, Pneumology, and Vascular Medicine, Medical Faculty, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany;
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia.,Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, Virginia
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22
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Begandt D, Good ME, Keller AS, DeLalio LJ, Rowley C, Isakson BE, Figueroa XF. Pannexin channel and connexin hemichannel expression in vascular function and inflammation. BMC Cell Biol 2017; 18:2. [PMID: 28124621 PMCID: PMC5267334 DOI: 10.1186/s12860-016-0119-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Control of blood flow distribution and tissue homeostasis depend on the tight regulation of and coordination between the microvascular network and circulating blood cells. Channels formed by connexins or pannexins that connect the intra- and extracellular compartments allow the release of paracrine signals, such as ATP and prostaglandins, and thus play a central role in achieving fine regulation and coordination of vascular function. This review focuses on vascular connexin hemichannels and pannexin channels. We review their expression pattern within the arterial and venous system with a special emphasis on how post-translational modifications by phosphorylation and S-nitrosylation of these channels modulate their function and contribute to vascular homeostasis. Furthermore, we highlight the contribution of these channels in smooth muscle cells and endothelial cells in the regulation of vasomotor tone as well as how these channels in endothelial cells regulate inflammatory responses such as during ischemic and hypoxic conditions. In addition, this review will touch on recent evidence implicating a role for these proteins in regulating red blood cell and platelet function.
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Affiliation(s)
- Daniela Begandt
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Miranda E Good
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Alex S Keller
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Leon J DeLalio
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Carol Rowley
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Brant E Isakson
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.,Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Xavier F Figueroa
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
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23
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Leal Denis MF, Alvarez HA, Lauri N, Alvarez CL, Chara O, Schwarzbaum PJ. Dynamic Regulation of Cell Volume and Extracellular ATP of Human Erythrocytes. PLoS One 2016; 11:e0158305. [PMID: 27355484 PMCID: PMC4927150 DOI: 10.1371/journal.pone.0158305] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Accepted: 06/13/2016] [Indexed: 11/18/2022] Open
Abstract
Introduction The peptide mastoparan 7 (MST7) triggered in human erythrocytes (rbcs) the release of ATP and swelling. Since swelling is a well-known inducer of ATP release, and extracellular (ATPe), interacting with P (purinergic) receptors, can affect cell volume (Vr), we explored the dynamic regulation between Vr and ATPe. Methods and Treatments We made a quantitative assessment of MST7-dependent kinetics of Vr and of [ATPe], both in the absence and presence of blockers of ATP efflux, swelling and P receptors. Results In rbcs 10 μM MST7 promoted acute, strongly correlated changes in [ATPe] and Vr. Whereas MST7 induced increases of 10% in Vr and 190 nM in [ATPe], blocking swelling in a hyperosmotic medium + MST7 reduced [ATPe] by 40%. Pre-incubation of rbcs with 10 μM of either carbenoxolone or probenecid, two inhibitors of the ATP conduit pannexin 1, reduced [ATPe] by 40–50% and swelling by 40–60%, while in the presence of 80 U/mL apyrase, an ATPe scavenger, cell swelling was prevented. While exposure to 10 μM NF110, a blocker of ATP-P2X receptors mediating sodium influx, reduced [ATPe] by 48%, and swelling by 80%, incubation of cells in sodium free medium reduced swelling by 92%. Analysis and Discussion Results were analyzed by means of a mathematical model where ATPe kinetics and Vr kinetics were mutually regulated. Model dependent fit to experimental data showed that, upon MST7 exposure, ATP efflux required a fast 1960-fold increase of ATP permeability, mediated by two kinetically different conduits, both of which were activated by swelling and inactivated by time. Both experimental and theoretical results suggest that, following MST7 exposure, ATP is released via two conduits, one of which is mediated by pannexin 1. The accumulated ATPe activates P2X receptors, followed by sodium influx, resulting in cell swelling, which in turn further activates ATP release. Thus swelling and P2X receptors constitute essential components of a positive feedback loop underlying ATP-induced ATP release of rbcs.
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Affiliation(s)
- M. Florencia Leal Denis
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
| | - H. Ariel Alvarez
- Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), CONICET, Universidad Nacional de La Plata (UNLP), La Plata, Argentina
| | - Natalia Lauri
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
| | - Cora L. Alvarez
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
| | - Osvaldo Chara
- Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), CONICET, Universidad Nacional de La Plata (UNLP), La Plata, Argentina
- Center for Information Services and High Performance Computing (ZIH), Technische Universität Dresden (TUD), Dresden, Germany
| | - Pablo J. Schwarzbaum
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
- * E-mail:
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24
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Dahl G. ATP release through pannexon channels. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2014.0191. [PMID: 26009770 DOI: 10.1098/rstb.2014.0191] [Citation(s) in RCA: 170] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Extracellular adenosine triphosphate (ATP) serves as a signal for diverse physiological functions, including spread of calcium waves between astrocytes, control of vascular oxygen supply and control of ciliary beat in the airways. ATP can be released from cells by various mechanisms. This review focuses on channel-mediated ATP release and its main enabler, Pannexin1 (Panx1). Six subunits of Panx1 form a plasma membrane channel termed 'pannexon'. Depending on the mode of stimulation, the pannexon has large conductance (500 pS) and unselective permeability to molecules less than 1.5 kD or is a small (50 pS), chloride-selective channel. Most physiological and pathological stimuli induce the large channel conformation, whereas the small conformation so far has only been observed with exclusive voltage activation of the channel. The interaction between pannexons and ATP is intimate. The pannexon is not only the conduit for ATP, permitting ATP efflux from cells down its concentration gradient, but the pannexon is also modulated by ATP. The channel can be activated by ATP through both ionotropic P2X as well as metabotropic P2Y purinergic receptors. In the absence of a control mechanism, this positive feedback loop would lead to cell death owing to the linkage of purinergic receptors with apoptotic processes. A control mechanism preventing excessive activation of the purinergic receptors is provided by ATP binding (with low affinity) to the Panx1 protein and gating the channel shut.
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Affiliation(s)
- Gerhard Dahl
- School of Medicine, University of Miami, 1600 NW 10th Avenue, Miami, FL 33136, USA
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25
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Burnstock G. Blood cells: an historical account of the roles of purinergic signalling. Purinergic Signal 2015; 11:411-34. [PMID: 26260710 PMCID: PMC4648797 DOI: 10.1007/s11302-015-9462-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 07/23/2015] [Indexed: 12/17/2022] Open
Abstract
The involvement of purinergic signalling in the physiology of erythrocytes, platelets and leukocytes was recognised early. The release of ATP and the expression of purinoceptors and ectonucleotidases on erythrocytes in health and disease are reviewed. The release of ATP and ADP from platelets and the expression and roles of P1, P2Y(1), P2Y(12) and P2X1 receptors on platelets are described. P2Y(1) and P2X(1) receptors mediate changes in platelet shape, while P2Y(12) receptors mediate platelet aggregation. The changes in the role of purinergic signalling in a variety of disease conditions are considered. The successful use of P2Y(12) receptor antagonists, such as clopidogrel and ticagrelor, for the treatment of thrombosis, myocardial infarction and stroke is discussed.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK.
- Department of Pharmacology and Therapeutics, The University of Melbourne, Melbourne, Australia.
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26
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Abstract
Piezo proteins (Piezo1 and Piezo2) are recently identified mechanically activated cation channels in eukaryotic cells and associated with physiological responses to touch, pressure, and stretch. In particular, human RBCs express Piezo1 on their membranes, and mutations of Piezo1 have been linked to hereditary xerocytosis. To date, however, physiological functions of Piezo1 on normal RBCs remain poorly understood. Here, we show that Piezo1 regulates mechanotransductive release of ATP from human RBCs by controlling the shear-induced calcium (Ca(2+)) influx. We find that, in human RBCs treated with Piezo1 inhibitors or having mutant Piezo1 channels, the amounts of shear-induced ATP release and Ca(2+) influx decrease significantly. Remarkably, a critical extracellular Ca(2+) concentration is required to trigger significant ATP release, but membrane-associated ATP pools in RBCs also contribute to the release of ATP. Our results show how Piezo1 channels are likely to function in normal RBCs and suggest a previously unidentified mechanotransductive pathway in ATP release. Thus, we anticipate that the study will impact broadly on the research of red cells, cellular mechanosensing, and clinical studies related to red cell disorders and vascular disease.
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27
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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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28
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Kurtenbach S, Whyte-Fagundes P, Gelis L, Kurtenbach S, Brazil E, Zoidl C, Hatt H, Shestopalov VI, Zoidl G. Investigation of olfactory function in a Panx1 knock out mouse model. Front Cell Neurosci 2014; 8:266. [PMID: 25309319 PMCID: PMC4162419 DOI: 10.3389/fncel.2014.00266] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 08/18/2014] [Indexed: 01/01/2023] Open
Abstract
Pannexin 1 (Panx1), the most extensively investigated member of a channel-forming protein family, is able to form pores conducting molecules up to 1.5 kDa, like ATP, upon activation. In the olfactory epithelium (OE), ATP modulates olfactory responsiveness and plays a role in proliferation and differentiation of olfactory sensory neurons (OSNs). This process continuously takes place in the OE, as neurons are replaced throughout the whole lifespan. The recent discovery of Panx1 expression in the OE raises the question whether Panx1 mediates ATP release responsible for modulating chemosensory function. In this study, we analyzed pannexin expression in the OE and a possible role of Panx1 in olfactory function using a Panx1−/− mouse line with a global ablation of Panx1. This mouse model has been previously used to investigate Panx1 functions in the retina and adult hippocampus. Here, qPCR, in-situ hybridization, and immunohistochemistry (IHC) demonstrated that Panx1 is expressed in axon bundles deriving from sensory neurons of the OE. The localization, distribution, and expression of major olfactory signal transduction proteins were not significantly altered in Panx1−/− mice. Further, functional analysis of Panx1−/− animals does not reveal any major impairment in odor perception, indicated by electroolfactogram (EOG) measurements and behavioral testing. However, ATP release evoked by potassium gluconate application was reduced in Panx1−/− mice. This result is consistent with previous reports on ATP release in isolated erythrocytes and spinal or lumbar cord preparations from Panx1−/− mice, suggesting that Panx1 is one of several alternative pathways to release ATP in the olfactory system.
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Affiliation(s)
- Stefan Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Paige Whyte-Fagundes
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Lian Gelis
- Department of Cell Physiology, Ruhr University Bochum Bochum, Germany
| | - Sarah Kurtenbach
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Emerson Brazil
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Christiane Zoidl
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
| | - Hanns Hatt
- Department of Cell Physiology, Ruhr University Bochum Bochum, Germany
| | - Valery I Shestopalov
- Department of Ophthalmology, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami Miami, FL, USA ; Vavilov Institute of General Genetics, Russian Academy of Sciences Moscow, Russia
| | - Georg Zoidl
- Department of Psychology, Faculty of Health, York University Toronto, ON, Canada
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29
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Richards JP, Yosten GLC, Kolar GR, Jones CW, Stephenson AH, Ellsworth ML, Sprague RS. Low O2-induced ATP release from erythrocytes of humans with type 2 diabetes is restored by physiological ratios of C-peptide and insulin. Am J Physiol Regul Integr Comp Physiol 2014; 307:R862-8. [PMID: 25080497 DOI: 10.1152/ajpregu.00206.2014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
ATP release from erythrocytes in response to reduced oxygen (O2) tension stimulates local vasodilation, enabling these cells to direct perfusion to areas in skeletal muscle in need of O2. Erythrocytes of humans with type 2 diabetes do not release ATP in response to low O2. Both C-peptide and insulin individually inhibit low O2-induced ATP release from healthy human erythrocytes, yet when coadministered at physiological concentrations and ratios, no inhibition is seen. Here, we determined: that 1) erythrocytes of healthy humans and humans with type 2 diabetes possess a C-peptide receptor (GPR146), 2) the combination of C-peptide and insulin at physiological ratios rescues low O2-induced ATP release from erythrocytes of humans with type 2 diabetes, 3) residual C-peptide levels reported in humans with type 2 diabetes are not adequate to rescue low O2-induced ATP release in the presence of 1 nM insulin, and 4) the effects of C-peptide and insulin are neither altered by increased glucose levels nor explained by changes in erythrocyte deformability. These results suggest that the addition of C-peptide to the treatment regimen for type 2 diabetes could have beneficial effects on tissue oxygenation, which would help to ameliorate the concomitant peripheral vascular disease.
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Affiliation(s)
- Jennifer P Richards
- Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, Missouri
| | - Gina L C Yosten
- Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, Missouri
| | - Grant R Kolar
- Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, Missouri
| | - Cory W Jones
- Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, Missouri
| | - Alan H Stephenson
- Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, Missouri
| | - Mary L Ellsworth
- Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, Missouri
| | - Randy S Sprague
- Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, Missouri
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30
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da Silva-Souza HA, de Lira MN, Patel NK, Spray DC, Persechini PM, Scemes E. Inhibitors of the 5-lipoxygenase pathway activate pannexin1 channels in macrophages via the thromboxane receptor. Am J Physiol Cell Physiol 2014; 307:C571-9. [PMID: 25080488 DOI: 10.1152/ajpcell.00087.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A multitude of environmental signaling molecules influence monocyte and macrophage innate and adaptive immune responses, including ATP and prostanoids. Interestingly, purinergic (P2) and eicosanoid receptor signaling interact such that the activation of P2 receptors leads to prostanoid production, which can then interfere with P2Y-mediated macrophage migration. Recent studies suggest that blockade of 5-lipoxygenase (5-LOX) in macrophages can activate a permeation pathway involved in the influx of dye and the release of ATP. Here, we provide evidence that pannexin1 (Panx1) is a component of this pathway and present the intracellular signaling molecules linking the thromboxane (TP) receptor to Panx1-mediated dye influx and ATP release. Using pharmacological tools and transgenic mice deficient in Panx1, we show that two 5-LOX pathway inhibitors induce ATP release and influx of dye in a Panx1-dependent manner. Electrophysiological recordings performed in wild-type and Panx1-deficient macrophages confirmed that these 5-LOX pathway inhibitors activate currents characteristic of Panx1 channels. We found that the mechanism by which Panx1 channels are activated under this condition involves activation of the TP receptor that is mediated by the cAMP/PKA pathway. This is to our knowledge the first evidence for the involvement of Panx1 in the TP receptor signaling pathway. Future studies aimed to clarify the contribution of this TP-Panx1 signaling network to macrophage immune responses are likely to be important for targeting inflammatory and autoimmune diseases.
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Affiliation(s)
- Hercules A da Silva-Souza
- Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia de Pesquisa Translacional em Saúde e Ambiente da Região Amazônica-INPeTAm, Rio de Janeiro, Brazil; and Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Maria Nathália de Lira
- Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Naman K Patel
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - David C Spray
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
| | - Pedro Muanis Persechini
- Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia de Pesquisa Translacional em Saúde e Ambiente da Região Amazônica-INPeTAm, Rio de Janeiro, Brazil; and
| | - Eliana Scemes
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
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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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Dourado M, Wong E, Hackos DH. Pannexin-1 is blocked by its C-terminus through a delocalized non-specific interaction surface. PLoS One 2014; 9:e99596. [PMID: 24911976 PMCID: PMC4049774 DOI: 10.1371/journal.pone.0099596] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/02/2014] [Indexed: 11/18/2022] Open
Abstract
The Pannexin-1 (Panx1) channel is known to become activated under a variety of physiological conditions resulting in the release of medium-sized molecules such as ATP and amino acids from the cell. The detailed molecular mechanism of activation of the channel resulting in the opening of the Pannexin pore is poorly understood. The best-studied gating mechanism is caspase-3/7-mediated cleavage and truncation of the c-terminus. In the absence of caspase-cleavage, the c-terminal peptide maintains the channel in the closed state, possibly by directly plugging the pore from the intracellular side. We sought to understand in detail the part of the c-terminus necessary for this interaction by alanine-scanning and truncation mutagenesis of the c-terminal gating peptide. These experiments demonstrate that no single amino acid side-chain is necessary for this interaction. In fact, replacing blocks of 10–12 amino acids in different parts of the c-terminal peptide with alanines fails to disrupt the ability of the c-terminus to keep the channel closed. Surprisingly, even replacing the entire c-terminal gating peptide with a scrambled peptide of the same length maintains the interaction in some cases. Further analysis revealed that the interaction surface, while delocalized, is located within the amino-terminal two-thirds of the c-terminal peptide. Such a delocalized and potentially low-affinity interaction surface is allowed due to the high effective concentration of the c-terminal peptide near the inner vestibule of the pore and likely explains why this region is poorly conserved between species. This type of weak interaction with a tethered gating peptide may be required to maintain high-sensitivity to caspase-dependent activation.
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Affiliation(s)
- Michelle Dourado
- Department of Neuroscience, Genentech, South San Francisco, California, United States of America
| | - Evera Wong
- Department of Neuroscience, Genentech, South San Francisco, California, United States of America
| | - David H Hackos
- Department of Neuroscience, Genentech, South San Francisco, California, United States of America
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Mairbäurl H, Ruppe FA, Bärtsch P. Role of hemolysis in red cell adenosine triphosphate release in simulated exercise conditions in vitro. Med Sci Sports Exerc 2014; 45:1941-7. [PMID: 23575515 DOI: 10.1249/mss.0b013e318296193a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Specific adenosine triphosphate (ATP) release from red blood cells has been discussed as a possible mediator controlling microcirculation in states of decreased tissue oxygen. Because intravascular hemolysis might also contribute to plasma ATP, we tested in vitro which portion of ATP release is due to hemolysis in typical exercise-induced strains to the red blood cells (shear stress, deoxygenation, and lactic acidosis). METHODS Human erythrocytes were suspended in dextran-containing media (hematocrit 10%) and were exposed to shear stress in a rotating Couette viscometer at 37°C. Desaturation (oxygen saturation of hemoglobin ∼20%) was achieved by tonometry with N2 before shear stress exposure. Cells not exposed to shear stress were used as controls. Na lactate (15 mM), lactic acid (15 mM, pH 7.0), and HCl (pH 7.0) were added to simulate exercise-induced lactic acidosis. After incubation, extracellular hemoglobin was measured to quantify hemolysis. ATP was measured with the luciferase assay. RESULTS Shear stress increased extracellular ATP in a stress-related and time-dependent manner. Hypoxia induced a ∼10-fold increase in extracellular ATP in nonsheared cells and shear stress-exposed cells. Lactic acid had no significant effect on ATP release and hemolysis. In normoxic cells, approximately 20%-50% of extracellular ATP was due to hemolysis. This proportion decreased to less than 10% in hypoxic cells. CONCLUSIONS Our results indicate that when exposing red blood cells to typical strains they encounter when passing through capillaries of exercising skeletal muscle, ATP release from red blood cells is caused mainly by deoxygenation and shear stress, whereas lactic acidosis had only a minor effect. Hemolysis effects were decreased when hemoglobin was deoxygenated. Together, by specific release and hemolysis, extracellular ATP reaches values that have been shown to cause local vasodilatation.
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Affiliation(s)
- Heimo Mairbäurl
- Medical Clinic VII, Sports Medicine, University of Heidelberg, Heidelberg, GERMANY
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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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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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Mairbäurl H. Red blood cells in sports: effects of exercise and training on oxygen supply by red blood cells. Front Physiol 2013; 4:332. [PMID: 24273518 PMCID: PMC3824146 DOI: 10.3389/fphys.2013.00332] [Citation(s) in RCA: 214] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 10/25/2013] [Indexed: 11/24/2022] Open
Abstract
During exercise the cardiovascular system has to warrant substrate supply to working muscle. The main function of red blood cells in exercise is the transport of O2 from the lungs to the tissues and the delivery of metabolically produced CO2 to the lungs for expiration. Hemoglobin also contributes to the blood's buffering capacity, and ATP and NO release from red blood cells contributes to vasodilation and improved blood flow to working muscle. These functions require adequate amounts of red blood cells in circulation. Trained athletes, particularly in endurance sports, have a decreased hematocrit, which is sometimes called “sports anemia.” This is not anemia in a clinical sense, because athletes have in fact an increased total mass of red blood cells and hemoglobin in circulation relative to sedentary individuals. The slight decrease in hematocrit by training is brought about by an increased plasma volume (PV). The mechanisms that increase total red blood cell mass by training are not understood fully. Despite stimulated erythropoiesis, exercise can decrease the red blood cell mass by intravascular hemolysis mainly of senescent red blood cells, which is caused by mechanical rupture when red blood cells pass through capillaries in contracting muscles, and by compression of red cells e.g., in foot soles during running or in hand palms in weightlifters. Together, these adjustments cause a decrease in the average age of the population of circulating red blood cells in trained athletes. These younger red cells are characterized by improved oxygen release and deformability, both of which also improve tissue oxygen supply during exercise.
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Affiliation(s)
- Heimo Mairbäurl
- Medical Clinic VII, Sports Medicine, University of Heidelberg Heidelberg, Germany
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Samuels SE, Lipitz JB, Wang J, Dahl G, Muller KJ. Arachidonic acid closes innexin/pannexin channels and thereby inhibits microglia cell movement to a nerve injury. Dev Neurobiol 2013; 73:621-31. [PMID: 23650255 DOI: 10.1002/dneu.22088] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 04/24/2013] [Accepted: 04/26/2013] [Indexed: 01/04/2023]
Abstract
Pannexons are membrane channels formed by pannexins and are permeable to ATP. They have been implicated in various physiological and pathophysiological processes. Innexins, the invertebrate homologues of the pannexins, form innexons. Nerve injury induces calcium waves in glial cells, releasing ATP through glial pannexon/innexon channels. The ATP then activates microglia. More slowly, injury releases arachidonic acid (ArA). The present experiments show that ArA itself reduced the macroscopic membrane currents of innexin- and of pannexin-injected oocytes; ArA also blocked K(+) -induced release of ATP. In leeches, whose large glial cells have been favorable for studying control of microglia migration, ArA blocked glial dye-release and, evidently, ATP-release. A physiological consequence in the leech was block of microglial migration to nerve injuries. Exogenous ATP (100 µM) reversed the effect, for ATP causes activation and movement of microglia after nerve injury, but nitric oxide directs microglia to the lesion. It was not excluded that metabolites of ArA may also inhibit the channels. But for all these effects, ArA and its non-metabolizable analog eicosatetraynoic acid (ETYA) were indistinguishable. Therefore, ArA itself is an endogenous regulator of pannexons and innexons. ArA thus blocks release of ATP from glia after nerve injury and thereby, at least in leeches, stops microglia at lesions.
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Affiliation(s)
- Stuart E Samuels
- Neuroscience Program, University of Miami, Miami, Florida, 33136, USA
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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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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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Hanstein R, Negoro H, Patel NK, Charollais A, Meda P, Spray DC, Suadicani SO, Scemes E. Promises and pitfalls of a Pannexin1 transgenic mouse line. Front Pharmacol 2013; 4:61. [PMID: 23675350 PMCID: PMC3648696 DOI: 10.3389/fphar.2013.00061] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 04/20/2013] [Indexed: 12/26/2022] Open
Abstract
Gene targeting strategies have become a powerful technology for elucidating mammalian gene function. The recently generated knockout (KO)-first strategy produces a KO at the RNA processing level and also allows for the generation of conditional KO alleles by combining FLP/FRT and Cre/loxP systems, thereby providing high flexibility in gene manipulation. However, this multipurpose KO-first cassette might produce hypomorphic rather than complete KOs if the RNA processing module is bypassed. Moreover, the generation of a conditional phenotype is also dependent on specific activity of Cre recombinase. Here, we report the use of an efficient molecular biological approach to test pannexin1 (Panx1) mRNA expression in global and conditional Panx1 KO mice derived from the KO-first mouse line, Panx1tm1a(KOMP)Wtsi. Using qRT-PCR, we demonstrate that tissues from wild-type (WT) mice show a range of Panx1 mRNA expression levels, with highest expression in trigeminal ganglia, bladder and spleen. Unexpectedly, we found that in mice homozygous for the KO-first allele, Panx1 mRNA expression is not abolished but reduced by 70% compared to that of WT tissues. Thus, Panx1 KO-first mice present a hypomorphic phenotype. Crosses of Panx1 KO-first with FLP deleter mice generated Panx1f/f mice. Further crosses of the latter mice with mGFAP-Cre or NFH-Cre mice were used to generate astrocyte- and neuron-specific Panx1 deletions, respectively. A high incidence of ectopic Cre expression was found in offspring of both types of conditional Panx1 KO mice. Our study demonstrates that Panx1 expression levels in the global and conditional Panx1 KO mice derived from KO-first mouse lines must be carefully characterized to ensure modulation of Panx1 gene expression. The precise quantitation of Panx1 expression and its relation to function is expected to provide a foundation for future efforts aimed at deciphering the role of Panx1 under physiological and pathological conditions.
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Affiliation(s)
- Regina Hanstein
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University New York, NY, USA
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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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Cone AC, Ambrosi C, Scemes E, Martone ME, Sosinsky GE. A comparative antibody analysis of pannexin1 expression in four rat brain regions reveals varying subcellular localizations. Front Pharmacol 2013; 4:6. [PMID: 23390418 PMCID: PMC3565217 DOI: 10.3389/fphar.2013.00006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 01/09/2013] [Indexed: 11/13/2022] Open
Abstract
Pannexin1 (Panx1) channels release cytosolic ATP in response to signaling pathways. Panx1 is highly expressed in the central nervous system. We used four antibodies with different Panx1 anti-peptide epitopes to analyze four regions of rat brain. These antibodies labeled the same bands in Western blots and had highly similar patterns of immunofluorescence in tissue culture cells expressing Panx1, but Western blots of brain lysates from Panx1 knockout and control mice showed different banding patterns. Localizations of Panx1 in brain slices were generated using automated wide field mosaic confocal microscopy for imaging large regions of interest while retaining maximum resolution for examining cell populations and compartments. We compared Panx1 expression over the cerebellum, hippocampus with adjacent cortex, thalamus, and olfactory bulb. While Panx1 localizes to the same neuronal cell types, subcellular localizations differ. Two antibodies with epitopes against the intracellular loop and one against the carboxy terminus preferentially labeled cell bodies, while an antibody raised against an N-terminal peptide highlighted neuronal processes more than cell bodies. These labeling patterns may be a reflection of different cellular and subcellular localizations of full-length and/or modified Panx1 channels where each antibody is highlighting unique or differentially accessible Panx1 populations. However, we cannot rule out that one or more of these antibodies have specificity issues. All data associated with experiments from these four antibodies are presented in a manner that allows them to be compared and our claims thoroughly evaluated, rather than eliminating results that were questionable. Each antibody is given a unique identifier through the NIF Antibody Registry that can be used to track usage of individual antibodies across papers and all image and metadata are made available in the public repository, the Cell Centered Database, for on-line viewing, and download.
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Affiliation(s)
- Angela C Cone
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA, USA
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Dahl G, Keane RW. Pannexin: from discovery to bedside in 11±4 years? Brain Res 2012; 1487:150-9. [PMID: 22771709 PMCID: PMC3590907 DOI: 10.1016/j.brainres.2012.04.058] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Revised: 03/29/2012] [Accepted: 04/11/2012] [Indexed: 12/22/2022]
Abstract
Pannexin1 (Panx1) originally was discovered as a gap junction related protein. However, rather than forming the cell-to-cell channels of gap junctions, Panx1 forms a mechanosensitive and highly ATP permeable channel in the cell membrane allowing the exchange of molecules between the cytoplasm and the extracellular space. The list of arguments for Panx1 representing the major ATP release channel includes: (1) Panx1 is expressed in (all?) cells releasing ATP in a non-vesicular fashion, such as erythrocytes; (2) in cells with polar release of ATP, Panx1 is expressed at the ATP release site, such as the apical membrane in airway epithelial cells; (3) the pharmacology of Panx1 channels matches that of ATP release; (4) mutation of Panx1 in strategic positions in the protein modifies ATP release; and (5) knockdown or knockout of Panx1 attenuates or abolishes ATP release. Panx1, in association with the purinergic receptor P2X7, is involved in the innate immune response and in apoptotic/pyroptotic cell death. Inflammatory processes are responsible for amplification of the primary lesion in CNS trauma and stroke. Panx1, as an early signal event and as a signal amplifier in these processes, is an obvious target for the prevention of secondary cell death due to inflammasome activity. Since Panx1 inhibitors such as probenecid are already clinically tested in different settings they should be considered for therapy in stroke and CNS trauma.
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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.
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Sandilos JK, Bayliss DA. Physiological mechanisms for the modulation of pannexin 1 channel activity. J Physiol 2012; 590:6257-66. [PMID: 23070703 DOI: 10.1113/jphysiol.2012.240911] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
It is widely recognized that ATP, along with other nucleotides, subserves important intercellular signalling processes. Among various nucleotide release mechanisms, the relatively recently identified pannexin 1 (Panx1) channel is gaining prominence by virtue of its ability to support nucleotide permeation and release in a variety of different tissues. Here, we review recent advances in our understanding of the factors that control Panx1 channel activity. By using electrophysiological and biochemical approaches, diverse mechanisms that dynamically regulate Panx1 channel function have been identified in various settings; these include, among others, activation by caspase-mediated channel cleavage in apoptotic immune cells, by G protein-coupled receptors in vascular smooth muscle, by low oxygen tension in erythrocytes and neurons, by high extracellular K(+) in various cell types and by stretch/strain in airway epithelia. Delineating the distinct mechanisms of Panx1 modulation that prevail in different physiological contexts provides the possibility that these channels, and ATP release, could ultimately be targeted in a context-dependent manner.
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Affiliation(s)
- Joanna K Sandilos
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA.
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Hanner F, Lam L, Nguyen MTX, Yu A, Peti-Peterdi J. Intrarenal localization of the plasma membrane ATP channel pannexin1. Am J Physiol Renal Physiol 2012; 303:F1454-9. [PMID: 22952282 DOI: 10.1152/ajprenal.00206.2011] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the renal tubules, ATP released from epithelial cells stimulates purinergic receptors, regulating salt and water reabsorption. However, the mechanisms by which ATP is released into the tubular lumen are multifaceted. Pannexin1 (Panx1) is a newly identified. ubiquitously expressed protein that forms connexin-like channels in the plasma membrane, which have been demonstrated to function as a mechanosensitive ATP conduit. Here, we report on the localization of Panx1 in the mouse kidney. Using immunofluorescence, strong Panx1 expression was observed in renal tubules, including proximal tubules, thin descending limbs, and collecting ducts, along their apical cell membranes. In the renal vasculature, Panx1 expression was localized to vascular smooth muscle cells in renal arteries, including the afferent and efferent arterioles. Additionally, we tested whether Panx1 channels expressed in renal epithelial cells facilitate luminal ATP release by measuring the ATP content of urine samples freshly collected from wild-type and Panx1(-/-) mice. Urinary ATP levels were reduced by 30% in Panx1(-/-) compared with wild-type mice. These results suggest that Panx1 channels in the kidney may regulate ATP release and via purinergic signaling may participate in the control of renal epithelial fluid and electrolyte transport and vascular functions.
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Affiliation(s)
- Fiona Hanner
- Department of Physiology and Biophysics, Univ. of Southern California, Los Angeles, CA 90033, USA
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46
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Islam MR, Uramoto H, Okada T, Sabirov RZ, Okada Y. Maxi-anion channel and pannexin 1 hemichannel constitute separate pathways for swelling-induced ATP release in murine L929 fibrosarcoma cells. Am J Physiol Cell Physiol 2012; 303:C924-35. [PMID: 22785119 DOI: 10.1152/ajpcell.00459.2011] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The maxi-anion channel plays a classically recognized role in controlling the membrane potential through the chloride conductance. It also has novel functions as a regulated pathway for the release of the anionic signaling molecules ATP and excitatory amino acids from cells subjected to osmotic perturbation, ischemia, or hypoxia. Because hemichannels formed by pannexins and connexins have been reported to mediate ATP release from a number of cell types, these hemichannels may represent the molecular correlate of the maxi-anion channel. Here, we found that L929 fibrosarcoma cells express functional maxi-anion channels which mediate a major portion of swelling-induced ATP release, and that ATP released via maxi-anion channels facilitates the regulatory volume decrease after osmotic swelling. Also, it was found that the cells express the mRNA for pannexin 1, pannexin 2, and connexin 43. Hypotonicity-induced ATP release was partially suppressed not only by known blockers of the maxi-anion channel but also by several blockers of pannexins including the pannexin 1-specific blocking peptide (10)Panx1 and small interfering (si)RNA against pannexin 1 but not pannexin 2. The inhibitory effects of maxi-anion channel blockers and pannexin 1 antagonists were additive. In contrast, maxi-anion channel activity was not affected by pannexin 1 antagonists and siRNAs against pannexins 1 and 2. Although a connexin 43-specific blocking peptide, Gap27, slightly suppressed hypotonicity-induced ATP release, maxi-anion channel activity was not affected by Gap27 or connexin 43-specific siRNA. Thus, it is concluded that the maxi-anion channel is a molecular entity distinct from pannexin 1, pannexin 2, and connexin 43, and that the maxi-anion channel and the hemichannels constitute separate pathways for swelling-induced ATP release in L929 cells.
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Affiliation(s)
- Md Rafiqul Islam
- Dept. of Cell Physiology, National Institute for Physiological Sciences, Myodaiji-cho, Okazaki 444-8585, Japan
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47
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Purinoceptor signaling in malaria-infected erythrocytes. Microbes Infect 2012; 14:779-86. [PMID: 22580091 DOI: 10.1016/j.micinf.2012.04.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Revised: 04/13/2012] [Accepted: 04/13/2012] [Indexed: 01/25/2023]
Abstract
Human erythrocytes are endowed with ATP release pathways and metabotropic and ionotropic purinoceptors. This review summarizes the pivotal function of purinergic signaling in erythrocyte control of vascular tone, in hemolytic septicemia, and in malaria. In malaria, the intraerythrocytic parasite exploits the purinergic signaling of its host to adapt the erythrocyte to its requirements.
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Lazarowski ER. Vesicular and conductive mechanisms of nucleotide release. Purinergic Signal 2012; 8:359-73. [PMID: 22528679 DOI: 10.1007/s11302-012-9304-9] [Citation(s) in RCA: 228] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 01/21/2012] [Indexed: 12/22/2022] Open
Abstract
Extracellular nucleotides and nucleosides promote a vast range of physiological responses, via activation of cell surface purinergic receptors. Virtually all tissues and cell types exhibit regulated release of ATP, which, in many cases, is accompanied by the release of uridine nucleotides. Given the relevance of extracellular nucleotide/nucleoside-evoked responses, understanding how ATP and other nucleotides are released from cells is an important physiological question. By facilitating the entry of cytosolic nucleotides into the secretory pathway, recently identified vesicular nucleotide and nucleotide-sugar transporters contribute to the exocytotic release of ATP and UDP-sugars not only from endocrine/exocrine tissues, but also from cell types in which secretory granules have not been biochemically characterized. In addition, plasma membrane connexin hemichannels, pannexin channels, and less-well molecularly defined ATP conducting anion channels have been shown to contribute to the release of ATP (and UTP) under a variety of conditions.
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Affiliation(s)
- Eduardo R Lazarowski
- School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7248, USA.
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Suadicani SO, Iglesias R, Wang J, Dahl G, Spray DC, Scemes E. ATP signaling is deficient in cultured Pannexin1-null mouse astrocytes. Glia 2012; 60:1106-16. [PMID: 22499153 DOI: 10.1002/glia.22338] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 03/16/2012] [Indexed: 11/11/2022]
Abstract
Pannexins (Panx1, 2, and 3) comprise a group of proteins expressed in vertebrates that share weak yet significant sequence homology with the invertebrate gap junction proteins, the innexins. In contrast to the other vertebrate gap junction protein family (connexin), pannexins do not form intercellular channels, but at least Panx1 forms nonjunctional plasma membrane channels. Panx1 is ubiquitously expressed and has been shown to form large conductance (500 pS) channels that are voltage dependent, mechanosensitive, and permeable to relatively large molecules such as ATP. Pharmacological and knockdown approaches have indicated that Panx1 is the molecular substrate for the so-called "hemichannel" originally attributed to connexin43 and that Panx1 is the pore-forming unit of the P2X(7) receptor. Here, we describe, for the first time, conductance and permeability properties of Panx1-null astrocytes. The electrophysiological and fluorescence imaging analyses performed on these cells fully support our previous pharmacological and Panx1 knockdown studies that showed profoundly lower dye uptake and ATP release than wild-type untreated astrocytes. As a consequence of decreased ATP paracrine signaling, intercellular calcium wave spread is altered in Panx1-null astrocytes. Moreover, we found that in astrocytes as in Panx1-expressing oocytes, elevated extracellular K(+) activates Panx1 channels independently of membrane potential. Thus, on the basis of our present findings and our previous report, we propose that Panx1 channels serve as K(+) sensors for changes in the extracellular milieu such as those occurring under pathological conditions.
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Affiliation(s)
- Sylvia O Suadicani
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Sridharan M, Bowles EA, Richards JP, Krantic M, Davis KL, Dietrich KA, Stephenson AH, Ellsworth ML, Sprague RS. Prostacyclin receptor-mediated ATP release from erythrocytes requires the voltage-dependent anion channel. Am J Physiol Heart Circ Physiol 2011; 302:H553-9. [PMID: 22159995 DOI: 10.1152/ajpheart.00998.2011] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Erythrocytes have been implicated as controllers of vascular caliber by virtue of their ability to release the vasodilator ATP in response to local physiological and pharmacological stimuli. The regulated release of ATP from erythrocytes requires activation of a signaling pathway involving G proteins (G(i) or G(s)), adenylyl cyclase, protein kinase A, and the cystic fibrosis transmembrane conductance regulator as well as a final conduit through which this highly charged anion exits the cell. Although pannexin 1 has been shown to be the final conduit for ATP release from human erythrocytes in response to reduced oxygen tension, it does not participate in transport of ATP following stimulation of the prostacyclin (IP) receptor in these cells, which suggests that an additional protein must be involved. Using antibodies directed against voltage-dependent anion channel (VDAC)1, we confirm that this protein is present in human erythrocyte membranes. To address the role of VDAC in ATP release, two structurally dissimilar VDAC inhibitors, Bcl-x(L) BH4(4-23) and TRO19622, were used. In response to the IP receptor agonists, iloprost and UT-15C, ATP release was inhibited by both VDAC inhibitors although neither iloprost-induced cAMP accumulation nor total intracellular ATP concentration were altered. Together, these findings support the hypothesis that VDAC is the ATP conduit in the IP receptor-mediated signaling pathway in human erythrocytes. In addition, neither the pannexin inhibitor carbenoxolone nor Bcl-x(L) BH4(4-23) attenuated ATP release in response to incubation of erythrocytes with the β-adrenergic receptor agonist isoproterenol, suggesting the presence of yet another channel for ATP release from human erythrocytes.
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Affiliation(s)
- Meera Sridharan
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, Saint Louis, Missouri, MO 63104, USA.
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