1
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Makarenkova HP, Shah SB, Shestopalov VI. The two faces of pannexins: new roles in inflammation and repair. J Inflamm Res 2018; 11:273-288. [PMID: 29950881 PMCID: PMC6016592 DOI: 10.2147/jir.s128401] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Pannexins belong to a family of ATP-release channels expressed in almost all cell types. An increasing body of literature on pannexins suggests that these channels play dual and sometimes contradictory roles, contributing to normal cell function, as well as to the pathological progression of disease. In this review, we summarize our understanding of pannexin "protective" and "harmful" functions in inflammation, regeneration and mechanical signaling. We also suggest a possible basis for pannexin's dual roles, related to extracellular ATP and K+ levels and the activation of various types of P2 receptors that are associated with pannexin. Finally, we speculate upon therapeutic strategies related to pannexin using eyes, lacrimal glands, and peripheral nerves as examples of interesting therapeutic targets.
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Affiliation(s)
| | - Sameer B Shah
- Departments of Orthopaedic Surgery and Bioengineering, University of California.,Research Division, Veterans Affairs San Diego Healthcare System, San Diego, CA
| | - Valery I Shestopalov
- Bascom Eye Institute, Department of Ophthalmology, University of Miami, Miami, FL, USA.,Vavilov Institute for General Genetics, Russian Academy of Sciences.,Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
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2
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Whyte-Fagundes P, Kurtenbach S, Zoidl C, Shestopalov VI, Carlen PL, Zoidl G. A Potential Compensatory Role of Panx3 in the VNO of a Panx1 Knock Out Mouse Model. Front Mol Neurosci 2018; 11:135. [PMID: 29780304 PMCID: PMC5946002 DOI: 10.3389/fnmol.2018.00135] [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: 01/13/2018] [Accepted: 04/03/2018] [Indexed: 12/30/2022] Open
Abstract
Pannexins (Panx) are integral membrane proteins, with Panx1 being the best-characterized member of the protein family. Panx1 is implicated in sensory processing, and knockout (KO) animal models have become the primary tool to investigate the role(s) of Panx1 in sensory systems. Extending previous work from our group on primary olfaction, the expression patterns of Panxs in the vomeronasal organ (VNO), an auxiliary olfactory sense organ with a role in reproduction and social behavior, were compared. Using qRT-PCR and Immunohistochemistry (IHC), we confirmed the loss of Panx1, found similar Panx2 expression levels in both models, and a significant upregulation of Panx3 in mice with a global ablation of Panx1. Specifically, Panx3 showed upregulated expression in nerve fibers of the non-sensory epithelial layer in juvenile and adult KO mice and in the sensory layer of adults, which overlaps with Panx1 expression areas in WT populations. Since both social behavior and evoked ATP release in the VNO was not compromised in KO animals, we hypothesized that Panx3 could compensate for the loss of Panx1. This led us to compare Panx1 and Panx3 channels in vitro, demonstrating similar dye uptake and ATP release properties. Outcomes of this study strongly suggest that Panx3 may functionally compensate for the loss of Panx1 in the VNO of the olfactory system, ensuring sustained chemosensory processing. This finding extends previous reports on the upregulation of Panx3 in arterial walls and the skin of Panx1 KO mice, suggesting that roles of Panx1 warrant uncharacterized safeguarding mechanisms involving Panx3.
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Affiliation(s)
- Paige Whyte-Fagundes
- Department of Biology, York University, Toronto, ON, Canada.,Krembil Research Institute, University Health Network, Toronto, ON, Canada
| | - Stefan Kurtenbach
- Department of Biology, York University, Toronto, ON, Canada.,Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
| | | | - Valery I Shestopalov
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Peter L Carlen
- Krembil Research Institute, University Health Network, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Georg Zoidl
- Department of Biology, York University, Toronto, ON, Canada.,Krembil Research Institute, University Health Network, Toronto, ON, Canada.,Department of Psychology, York University, Toronto, ON, Canada
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3
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Ni M, He JG, Zhou HY, Lu XJ, Hu YL, Mao L, Wang F, Chen JG, Hu ZL. Pannexin-1 channel dysfunction in the medial prefrontal cortex mediates depressive-like behaviors induced by chronic social defeat stress and administration of mefloquine in mice. Neuropharmacology 2017; 137:256-267. [PMID: 29221793 DOI: 10.1016/j.neuropharm.2017.12.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/27/2017] [Accepted: 12/03/2017] [Indexed: 12/12/2022]
Abstract
Mefloquine (MFQ) is widely used for the treatment of malaria clinically. Apart from antimalarial effect, psychiatric side effects such as depression and anxiety of MFQ have been reported. Interestingly, MFQ is also known as a broad-spectrum pannexin-1 (Panx1) inhibitor. Panx1 is a new gap junction channel in the brain which mediates efflux of adenosine triphosphate (ATP). Although exogenous ATP has been known to produce a potential antidepressant-like effect, little is known about the role of Panx1 in pathophysiology of depression, especially the depression induced by administration of MFQ. Here, we used the chronic social defeat stress (CSDS) model and found a decrease in the expression and function of Panx1 in the medial prefrontal cortex (mPFC) of susceptible mice. Furthermore, pharmacological blockade of Panx1 in the mPFC with carbenoxolone (CBX) (100 mM) or 10Panx (100 μM) was sufficient to induce depressive-like behaviors and increase vulnerability to stress in mice, which were prevented by preconditioning with ATP (25 μM). Finally, systemic and intral-mPFC injection of MFQ both inhibited the activity of Panx1 and induced depressive-like and anxiety behaviors in mice with sub-threshold social defeat stress. Indeed, the behavioral abnormalities induced by MFQ were prevented by preconditioning with ATP in the mPFC. In conclusion, our study demonstrates a role of the Panx1 channel in chronic stress and MFQ-induced depressive-like and anxiety behaviors, which may provide a novel molecular mechanism for psychiatric side effects of MFQ.
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Affiliation(s)
- Ming Ni
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jin-Gang He
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Hai-Yun Zhou
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Xiao-Jia Lu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yuan-Lang Hu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Li Mao
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Fang Wang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Collaborative-Innovation Center for Brain Science, Wuhan, 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, 430030, China
| | - Jian-Guo Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Collaborative-Innovation Center for Brain Science, Wuhan, 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, 430030, China
| | - Zhuang-Li Hu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Collaborative-Innovation Center for Brain Science, Wuhan, 430030, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, Wuhan, 430030, China.
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4
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Zorzi V, Paciello F, Ziraldo G, Peres C, Mazzarda F, Nardin C, Pasquini M, Chiani F, Raspa M, Scavizzi F, Carrer A, Crispino G, Ciubotaru CD, Monyer H, Fetoni AR, M Salvatore A, Mammano F. Mouse Panx1 Is Dispensable for Hearing Acquisition and Auditory Function. Front Mol Neurosci 2017; 10:379. [PMID: 29234270 PMCID: PMC5712377 DOI: 10.3389/fnmol.2017.00379] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 10/30/2017] [Indexed: 11/13/2022] Open
Abstract
Panx1 forms plasma membrane channels in brain and several other organs, including the inner ear. Biophysical properties, activation mechanisms and modulators of Panx1 channels have been characterized in detail, however the impact of Panx1 on auditory function is unclear due to conflicts in published results. To address this issue, hearing performance and cochlear function of the Panx1−/− mouse strain, the first with a reported global ablation of Panx1, were scrutinized. Male and female homozygous (Panx1−/−), hemizygous (Panx1+/−) and their wild type (WT) siblings (Panx1+/+) were used for this study. Successful ablation of Panx1 was confirmed by RT-PCR and Western immunoblotting in the cochlea and brain of Panx1−/− mice. Furthermore, a previously validated Panx1-selective antibody revealed strong immunoreactivity in WT but not in Panx1−/− cochleae. Hearing sensitivity, outer hair cell-based “cochlear amplifier” and cochlear nerve function, analyzed by auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recordings, were normal in Panx1+/− and Panx1−/− mice. In addition, we determined that global deletion of Panx1 impacts neither on connexin expression, nor on gap-junction coupling in the developing organ of Corti. Finally, spontaneous intercellular Ca2+ signal (ICS) activity in organotypic cochlear cultures, which is key to postnatal development of the organ of Corti and essential for hearing acquisition, was not affected by Panx1 ablation. Therefore, our results provide strong evidence that, in mice, Panx1 is dispensable for hearing acquisition and auditory function.
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Affiliation(s)
- Veronica Zorzi
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,School of Medicine, Institute of Otolaryngology, Catholic University, Rome, Italy
| | - Fabiola Paciello
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Gaia Ziraldo
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,School of Medicine, Institute of Otolaryngology, Catholic University, Rome, Italy
| | - Chiara Peres
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Flavia Mazzarda
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Science, Roma Tre University, Rome, Italy
| | - Chiara Nardin
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Science, Roma Tre University, Rome, Italy
| | - Miriam Pasquini
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, Italy
| | - Francesco Chiani
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Marcello Raspa
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | | | - Andrea Carrer
- Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy
| | - Giulia Crispino
- Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy
| | | | - Hannah Monyer
- Department of Clinical Neurobiology, Deutches Krebforschungzentrum, University of Heidelberg, Heidelberg, Germany
| | - Anna R Fetoni
- School of Medicine, Institute of Otolaryngology, Catholic University, Rome, Italy
| | - Anna M Salvatore
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Fabio Mammano
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy.,Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
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5
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Whyte-Fagundes P, Siu R, Brown C, Zoidl G. Pannexins in vision, hearing, olfaction and taste. Neurosci Lett 2017; 695:32-39. [PMID: 28495272 DOI: 10.1016/j.neulet.2017.05.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 04/06/2017] [Accepted: 05/05/2017] [Indexed: 12/25/2022]
Abstract
In mammals, the pannexin gene family consists of three members (Panx1, 2, 3), which represent a class of integral membrane channel proteins sharing some structural features with chordate gap junction proteins, the connexins. Since their discovery in the early 21st century, pannexin expression has been detected throughout the vertebrate body including eye, ear, nose and tongue, making the investigation of the roles of this new class of channel protein in health and disease very appealing. The localization in sensory organs, coupled with unique channel properties and associations with major signaling pathways make Panx1, and its relative's, significant contributors for fundamental functions in sensory perception. Until recently, cell-based studies were at the forefront of pannexin research. Lately, the availability of mice with genetic ablation of pannexins opened new avenues for testing pannexin functions and behavioural phenotyping. Although we are only at the beginning of understanding the roles of pannexins in health and disease, this review summarizes recent advances in elucidating the various emerging roles pannexins play in sensory systems, with an emphasis on unresolved conflicts.
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Affiliation(s)
- Paige Whyte-Fagundes
- Graduate Program In Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Ryan Siu
- Graduate Program In Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Cherie Brown
- Graduate Program In Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Georg Zoidl
- Department of Biology, Faculty of Science, York University, Toronto, ON, Canada; Center for Vision Research, York University, Toronto, ON, Canada.
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6
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Xu J, Chen L, Li L. Pannexin hemichannels: A novel promising therapy target for oxidative stress related diseases. J Cell Physiol 2017; 233:2075-2090. [PMID: 28295275 DOI: 10.1002/jcp.25906] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 03/09/2017] [Indexed: 12/16/2022]
Abstract
Pannexins, which contain three subtypes: pannexin-1, -2, and -3, are vertebrate glycoproteins that form non-junctional plasma membrane intracellular hemichannels via oligomerization. Oxidative stress refers to an imbalance of the generation and elimination of reactive oxygen species (ROS). Studies have shown that elevated ROS levels are pivotal in the development of a variety of diseases. Recent studies indicate that the occurrence of these oxidative stress related diseases is associated with pannexin hemichannels. It is also reported that pannexins regulate the production of ROS which in turn may increase the opening of pannexin hemichannels. In this paper, we review recent researches about the important role of pannexin hemichannels in oxidative stress related diseases. Thus, pannexin hemichannels, novel therapeutic targets, hold promise in managing oxidative stress related diseases such as the tumor, inflammatory bowel diseases (IBD), pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), cardiovascular disease, insulin resistance (IR), and neural degeneration diseases.
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Affiliation(s)
- Jin Xu
- Learning Key Laboratory for Pharmacoproteomics, Institute of Pharmacy and Pharmacology, University of South China, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, P. R. China
| | - Linxi Chen
- Learning Key Laboratory for Pharmacoproteomics, Institute of Pharmacy and Pharmacology, University of South China, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, P. R. China
| | - Lanfang Li
- Learning Key Laboratory for Pharmacoproteomics, Institute of Pharmacy and Pharmacology, University of South China, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, P. R. China
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7
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Diezmos EF, Sandow SL, Perera DS, King DW, Bertrand PP, Liu L. Pannexin-2 is expressed in the human colon with extensive localization in the enteric nervous system. Neurogastroenterol Motil 2015; 27:672-83. [PMID: 25773474 DOI: 10.1111/nmo.12541] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 02/16/2015] [Indexed: 02/08/2023]
Abstract
BACKGROUND Pannexin-2 (Panx2) is a member of the novel group of membrane spanning protein channels present in the central nervous system. Limited studies have examined Panx2 in the intestine, where it may have important physiological roles. The present study characterized Panx2 expression and localization in the human colon in health and disease states. METHODS Immunofluorescence determined Panx2 localization and co-localization, and quantitative real-time PCR and Western blot determined gene and protein expression in ulcerative colitis (UC), Crohn's disease (CD), and control human colon. KEY RESULTS Panx2 was widely expressed in myenteric and submucosal ganglia, particularly in the cytoplasm of neurons. Panx2 was also expressed on smooth muscle of the muscularis and blood vessels, some non-lymphoid leukocytes, mast cells, and mucosal epithelial cells. Co-localization of Panx2 occurred with β-tubulin, neuronal nitric oxide synthase, substance P, vesicular acetylcholine transporter, and calcitonin gene-related peptide, indicating widespread Panx2 expression in extrinsic and intrinsic neurons. Molecular studies revealed a 3.4-fold higher level of Panx2 mRNA in ascending compared to sigmoid muscularis (p < 0.05), despite similar protein levels. Similarly, UC muscularis showed a 35-fold up-regulation in Panx2 mRNA, but not in protein (p < 0.05). CONCLUSIONS & INFERENCES Here, we demonstrated the dense expression of Panx2 in the enteric nervous system and the co-localization of Panx2 with a spectrum of neuronal markers, indicating that Panx2 may be involved in mediating neurotransmission in the colon. The substantial increase in Panx2 mRNA in UC muscle but not protein suggests that the Panx2 translation process may be disrupted in UC.
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Affiliation(s)
- E F Diezmos
- School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
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8
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Le Vasseur M, Lelowski J, Bechberger JF, Sin WC, Naus CC. Pannexin 2 protein expression is not restricted to the CNS. Front Cell Neurosci 2014; 8:392. [PMID: 25505382 PMCID: PMC4243559 DOI: 10.3389/fncel.2014.00392] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 11/03/2014] [Indexed: 11/27/2022] Open
Abstract
Pannexins (Panx) are proteins homologous to the invertebrate gap junction proteins called innexins (Inx) and are traditionally described as transmembrane channels connecting the intracellular and extracellular compartments. Three distinct Panx paralogs (Panx1, Panx2 and Panx3) have been identified in vertebrates but previous reports on Panx expression and functionality focused primarily on Panx1 and Panx3 proteins. Several gene expression studies reported that Panx2 transcript is largely restricted to the central nervous system (CNS) hence suggesting that Panx2 might serve an important role in the CNS. However, the lack of suitable antibodies prevented the creation of a comprehensive map of Panx2 protein expression and Panx2 protein localization profile is currently mostly inferred from the distribution of its transcript. In this study, we characterized novel commercial monoclonal antibodies and surveyed Panx2 expression and distribution at the mRNA and protein level by real-time qPCR, Western blotting and immunofluorescence. Panx2 protein levels were readily detected in every tissue examined, even when transcriptional analysis predicted very low Panx2 protein expression. Furthermore, our results indicate that Panx2 transcriptional activity is a poor predictor of Panx2 protein abundance and does not correlate with Panx2 protein levels. Despite showing disproportionately high transcript levels, the CNS expressed less Panx2 protein than any other tissues analyzed. Additionally, we showed that Panx2 protein does not localize at the plasma membrane like other gap junction proteins but remains confined within cytoplasmic compartments. Overall, our results demonstrate that the endogenous expression of Panx2 protein is not restricted to the CNS and is more ubiquitous than initially predicted.
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Affiliation(s)
- Maxence Le Vasseur
- Department of Cellular and Physiological Sciences, The Life Science Institute, University of British Columbia Vancouver, BC, Canada
| | - Jonathan Lelowski
- Department of Cellular and Physiological Sciences, The Life Science Institute, University of British Columbia Vancouver, BC, Canada
| | - John F Bechberger
- Department of Cellular and Physiological Sciences, The Life Science Institute, University of British Columbia Vancouver, BC, Canada
| | - Wun-Chey Sin
- Department of Cellular and Physiological Sciences, The Life Science Institute, University of British Columbia Vancouver, BC, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Sciences, The Life Science Institute, University of British Columbia Vancouver, BC, Canada
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9
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Abstract
In less than a decade, a small family of channel-forming glycoproteins, named pannexins, have captured the interest of many biologists, in large part due to their association with common diseases, ranging from cancers to neuropathies to infectious diseases. Although the pannexin family consists of only three members (Panx1, Panx2 and Panx3), one or more of these pannexins are expressed in virtually every mammalian organ, implicating their potential role in a diverse array of pathophysiologies. Panx1 is the most extensively studied, but features of this pannexin must be cautiously extrapolated to the other pannexins, as for example we now know that Panx2, unlike Panx1, exhibits unique properties such as a tendency to be retained within intracellular compartments. In the present review, we assess the biochemical and channel features of pannexins focusing on the literature which links these unique molecules to over a dozen diseases and syndromes. Although no germ-line mutations in genes encoding pannexins have been linked to any diseases, many cases have shown that high pannexin expression is associated with disease onset and/or progression. Disease may also occur, however, when pannexins are underexpressed, highlighting that pannexin expression must be exquisitely regulated. Finally, we discuss some of the most pressing questions and controversies in the pannexin field as the community seeks to uncover the full biological relevance of pannexins in healthy organs and during disease.
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10
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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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11
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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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12
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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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