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Güiza J, Solís F, Valenzuela B, Arancibia D, Zamorano P, González J, Saavedra J, Neely A, Salgado M, Martínez AD, Sáez JC, Vega JL. Unnexin is a protein subunit of a large-pore channel expressed by unicellular organisms. Proc Natl Acad Sci U S A 2023; 120:e2307898120. [PMID: 37487087 PMCID: PMC10400985 DOI: 10.1073/pnas.2307898120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 06/23/2023] [Indexed: 07/26/2023] Open
Abstract
Cells of vertebrate and invertebrate organisms express proteins specialized in membrane channel-based cell-cell communication that are absent in unicellular organisms. We recently described the prediction of some members of the large-pore channel family in kinetoplastids, consisting of proteins called unnexins, which share several structural features with innexin and pannexin proteins. Here, we demonstrated that the unnexin1 protein (Unx1) is delivered to the cell membrane, displaying a topology consisting of four transmembrane domains with C and N termini on the cytoplasmic side and form large-pore channels that are permeable to small molecules. Low extracellular Ca2+/Mg2+ levels or extracellular alkalinization, but not mechanical stretching, increases channel activity. The Unx1 channel mediates the influx of Ca2+ and does not form intercellular dye coupling between HeLa Unx1 transfected cells. Unx1 channel function was further evidenced by its ability to mediate ionic currents when expressed in Xenopus oocytes. Downregulation of Unx1 mRNA with morpholine contains Trypanosoma cruzi invasion. Phylogenetic analysis revealed the presence of Unx1 homologs in other protozoan parasites, suggesting a conserved function for these channel parasites in other protists. Our data demonstrate that Unx1 forms large-pore membrane channels, which may serve as a diffusional pathway for ions and small molecules that are likely to be metabolic substrates or waste products, and signaling autocrine and paracrine molecules that could be involved in cell invasion. As morpholinos-induced downregulation of Unx1 reduces the infectivity of trypomastigotes, the Unx1 channels might be an attractive target for developing trypanocide drugs.
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Affiliation(s)
- Juan Güiza
- Laboratory of Gap Junction Proteins and Parasitic Diseases (GaPaL), Instituto Antofagasta, Universidad de Antofagasta, Antofagasta1240000, Chile
| | - Francisco Solís
- Laboratorio de Microorganismos Extremófilos, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta1240000, Chile
| | - Bernardita Valenzuela
- Laboratorio de Microorganismos Extremófilos, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta1240000, Chile
| | - Duxan Arancibia
- Laboratorio de Microorganismos Extremófilos, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta1240000, Chile
| | - Pedro Zamorano
- Laboratorio de Microorganismos Extremófilos, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta1240000, Chile
| | - Jorge González
- Departamento de Tecnología Médica, Unidad de Parasitología Molecular, Facultad Ciencias de la Salud, Universidad de Antofagasta, Antofagasta1240000, Chile
| | - Jonathan Saavedra
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso2381850, Chile
| | - Alan Neely
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso2381850, Chile
| | - Magdiel Salgado
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso2381850, Chile
| | - Agustín D. Martínez
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso2381850, Chile
| | - Juan C. Sáez
- Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso2381850, Chile
| | - José L. Vega
- Laboratory of Gap Junction Proteins and Parasitic Diseases (GaPaL), Instituto Antofagasta, Universidad de Antofagasta, Antofagasta1240000, Chile
- Departamento Biomédico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta1240000, Chile
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Polydnavirus Innexins Disrupt Host Cellular Encapsulation and Larval Maturation. Viruses 2021; 13:v13081621. [PMID: 34452485 PMCID: PMC8402728 DOI: 10.3390/v13081621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/09/2021] [Accepted: 08/13/2021] [Indexed: 11/17/2022] Open
Abstract
Polydnaviruses are dsDNA viruses associated with endoparasitoid wasps. Delivery of the virus during parasitization of a caterpillar and subsequent virus gene expression is required for production of an amenable environment for parasitoid offspring development. Consequently, understanding of Polydnavirus gene function provides insight into mechanisms of host susceptibility and parasitoid wasp host range. Polydnavirus genes predominantly are arranged in multimember gene families, one of which is the vinnexins, which are virus homologues of insect gap junction genes, the innexins. Previous studies of Campoletis sonorensis Ichnovirus Vinnexins using various heterologous systems have suggested the four encoded members may provide different functionality in the infected caterpillar host. Here, we expressed two of the members, vnxG and vnxQ2, using recombinant baculoviruses in susceptible host, the caterpillar Heliothis virescens. Following intrahemocoelic injections, we observed that >90% of hemocytes (blood cells) were infected, producing recombinant protein. Larvae infected with a vinnexin-recombinant baculovirus exhibited significantly reduced molting rates relative to larvae infected with a control recombinant baculovirus and mock-infected larvae. Similarly, larvae infected with vinnexin-recombinant baculoviruses were less likely to survive relative to controls and showed reduced ability to encapsulate chromatography beads in an immune assay. In most assays, the VnxG protein was associated with more severe pathology than VnxQ2. Our findings support a role for Vinnexins in CsIV and more broadly Ichnovirus pathology in infected lepidopteran hosts, particularly in disrupting multicellular developmental and immune physiology.
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Chen CX, He HJ, Cai QC, Zhang W, Kou TC, Zhang XW, You S, Chen YB, Liu T, Xiao W, Zhu QS, Luo KJ. Bracovirus-mediated innexin hemichannel closure in cell disassembly. iScience 2021; 24:102281. [PMID: 33817584 PMCID: PMC8008186 DOI: 10.1016/j.isci.2021.102281] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 02/19/2021] [Accepted: 03/03/2021] [Indexed: 01/10/2023] Open
Abstract
Cell-cell communication is necessary for cellular immune response. Hemichannel closure disrupts communication between intracellular and extracellular environments during polydnavirus-induced immunosuppression in invertebrates. However, the effects of hemichannel closure on cellular immune response are unclear. Here, we examined apoptotic body formation triggered by hemichannel closure in hemocytes of Spodoptera litura infected with bracovirus from the parasitic wasp, Microplitis bicoloratus. We showed that Microplitis bicoloratus bracovirus (MbBV) induced apoptotic cell disassembly, accompanied by hemichannel closure. Hemocyte apoptotic body formation was caused by the dysregulation of the innexins (Inxs), Inx1, Inx2, Inx3, and Inx4, during the MbBV-mediated inhibition of pI3K/AKT signaling and activation of caspase-3, which cleaved gap junction Inx proteins. Our results showed that hemichannel opening or closure in response to various stimuli, which induces the modulation of Inx levels, could inhibit or activate apoptotic body formation, respectively. Therefore, the "hemichannel open and close" model may regulate the cellular immune response.
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Affiliation(s)
- Chang-Xu Chen
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
- Biocontrol Engineering Research Centre of Crop Disease & Pest in Yunnan Province, Kunming 650500, P. R. China
| | - Hao-Juan He
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
- Biocontrol Engineering Research Centre of Crop Disease & Pest in Yunnan Province, Kunming 650500, P. R. China
| | - Qiu-Chen Cai
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
- Biocontrol Engineering Research Centre of Crop Disease & Pest in Yunnan Province, Kunming 650500, P. R. China
| | - Wei Zhang
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
- Biocontrol Engineering Research Centre of Crop Disease & Pest in Yunnan Province, Kunming 650500, P. R. China
| | - Tian-Chao Kou
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
| | - Xue-Wen Zhang
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
| | - Shan You
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
| | - Ya-Bin Chen
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
| | - Tian Liu
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
- Biocontrol Engineering Research Centre of Crop Disease & Pest in Yunnan Province, Kunming 650500, P. R. China
| | - Wei Xiao
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
| | - Qi-Shun Zhu
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
| | - Kai-Jun Luo
- School of Life Sciences, Yunnan University, Kunming 650500, P.R. China
- Key Laboratory of the University in Yunnan Province for International Cooperation in Intercellular Communications and Regulations, Yunnan University, Kunming 650500, P.R. China
- Biocontrol Engineering Research Centre of Crop Disease & Pest in Yunnan Province, Kunming 650500, P. R. China
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Hasegawa DK, Zhang P, Turnbull MW. Intracellular dynamics of polydnavirus innexin homologues. INSECT MOLECULAR BIOLOGY 2020; 29:477-489. [PMID: 32683761 DOI: 10.1111/imb.12657] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 04/30/2020] [Accepted: 06/29/2020] [Indexed: 06/11/2023]
Abstract
Polydnaviruses associated with ichneumonid parasitoid wasps (Ichnoviruses) encode large numbers of genes, often in multigene families. The Ichnovirus Vinnexin gene family, which is expressed in parasitized lepidopteran larvae, encodes homologues of Innexins, the structural components of insect gap junctions. Here, we have examined intracellular behaviours of the Campoletis sonorensis Ichnovirus (CsIV) Vinnexins, alone and in combination with a host Innexin orthologue, Innexin2 (Inx2). QRT-PCR verified that transcription of CsIV vinnexins occurs contemporaneously with inx2, implying co-occurrence of Vinnexin and Inx2 proteins. Confocal microscopy demonstrated that epitope-tagged VinnexinG (VnxG) and VinnexinQ2 (VnxQ2) exhibit similar subcellular localization as Spodoptera frugiperda Inx2 (Sf-Inx2). Surface biotinylation assays verified that all three proteins localize to the cell surface, and cytochalasin B and nocodazole that they rely on actin and microtubule cytoskeletal networks for localization. Immunomicroscopy following co-transfection of constructs indicates extensive co-localization of Vinnexins with each other and Sf-Inx2, and live-cell imaging of mCherry-labelled Inx2 supports that Vinnexins may affect Sf-Inx2 distribution in a Vinnexin-specific fashion. Our findings support that the Vinnexins may disrupt host cell physiology in a protein-specific manner through altering gap junctional intercellular channel communication, as well as indirectly by affecting multicellular junction characteristics.
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Affiliation(s)
- D K Hasegawa
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
- USDA-ARS, Crop Improvement and Protection Research Unit, Salinas, CA, USA
| | - P Zhang
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, USA
| | - M W Turnbull
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, USA
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Yoshimura R, Suetsugu T, Kawahara A, Nakata K, Shikata M, Tanaka S, Ono T, Fushiki D, Endo Y. Formation of functional innexin hemichannels, as well as gap junctional channels, in an insect cell line, NIAs-AeAl-2, derived from Asian tiger mosquito Aedes albopictus (Diptera: Culicidae): A partial but significant contribution of innexin 2. JOURNAL OF INSECT PHYSIOLOGY 2020; 124:104060. [PMID: 32446763 DOI: 10.1016/j.jinsphys.2020.104060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Revised: 05/18/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
In vertebrates, gap junctions and hemichannels consisting of connexins are important cell surface structures for communication with neighboring cells and for the regulation of various cell functions. To date, various gap-junction-related proteins have been found, including innexins in invertebrates and pannexins in vertebrates. Significant contributions of gap junctions by innexins and (hemi-)channels by pannexins to numerous functions have been reported. Verification of the presence and functional significance of innexin hemichannels, however, remains a gap in our knowledge in innexin physiology. In this study, we revealed the localization of an innexin protein (innexin 2) on the cell surface in mosquito tissues and cultured cells. Furthermore, we demonstrated the presence of functional hemichannels, as well as gap junctions, in mosquito cells using dye transfer assays. The inward uptake of fluorescent dye was inhibited by anti-innexin 2 antibody. These results suggest that innexin hemichannels are formed to function in cultured mosquito cells, in at least a partially innexin 2-dependent manner. Although only a few studies on insect hemichannels have been published, innexin-based hemichannels, as well as innexin gap junctions, could also significantly contribute to insect intercellular signal transduction.
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Affiliation(s)
- Ryoichi Yoshimura
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan.
| | - Taeko Suetsugu
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan; Laboratory for Cell Asymmetry, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-Minamimachi, Chuo-Ku, Kobe, Hyogo 650-0047, Japan
| | - Ai Kawahara
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan
| | - Kana Nakata
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan
| | - Masato Shikata
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan
| | - Souma Tanaka
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan
| | - Tsutomu Ono
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan
| | - Daisuke Fushiki
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan
| | - Yasuhisa Endo
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Kyoto 606-8585, Japan
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Raad H, Robichon A. The pleiotropic effects of Innexin genes expressed in Drosophila glia encompass wing chemosensory sensilla. J Neurosci Res 2019; 97:1319-1330. [PMID: 31257643 DOI: 10.1002/jnr.24485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/05/2019] [Accepted: 06/07/2019] [Indexed: 11/07/2022]
Abstract
The neuroanatomy of Drosophila wing chemosensilla and the analysis of their sensory organ precursor cell lineage have demonstrated that they are surprisingly related to taste perception. The microarchitecture of wing bristles limits the use of electrophysiology methods to investigate wing chemosensory mechanisms. However, by monitoring the fluorescence of the complex calcium/GCaMP, calcium flux triggered upon tastant stimulation was observed within sensilla aligned along the wing anterior nerve. This string of fluorescent puncta was impaired in wings of Innexin 2 (Inx2) mutant flies; although it is unclear whether the Innexin proteins act at the level of the wing imaginal disc, adult wing and/or at both levels. Glial cells known to shelter Innexin(s) expression have no documented role in adult chemosensory sensilla. Our data suggest that Innexin(s) are likely required for the maturation of functional wing chemosensilla in adulthood. The unexpected presence of most Innexin transcripts in adult wing RNAseq data set argues for the expression of Innexin proteins in the larval imaginal wing disc that are continued in wing chemosensilla at adulthood. OPEN PRACTICES: This article has earned an Open Data badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available as supporting materials and includes the electronic lab notebook. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.
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Affiliation(s)
- Hussein Raad
- INRA, CNRS, Université Côte d'Azur, Institut Sophia Agrobiotech, Sophia Antipolis, France.,Lebanese International University, Mazraa, Lebanon
| | - Alain Robichon
- INRA, CNRS, Université Côte d'Azur, Institut Sophia Agrobiotech, Sophia Antipolis, France
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Güiza J, Barría I, Sáez JC, Vega JL. Innexins: Expression, Regulation, and Functions. Front Physiol 2018; 9:1414. [PMID: 30364195 PMCID: PMC6193117 DOI: 10.3389/fphys.2018.01414] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/18/2018] [Indexed: 01/02/2023] Open
Abstract
The innexin (Inx) proteins form gap junction channels and non-junctional channels (named hemichannels) in invertebrates. These channels participate in cellular communication playing a relevant role in several physiological processes. Pioneer studies conducted mainly in worms and flies have shown that innexins participate in embryo development and behavior. However, recent studies have elucidated new functions of innexins in Arthropoda, Nematoda, Annelida, and Cnidaria, such as immune response, and apoptosis. This review describes emerging data of possible new roles of innexins and summarizes the data available to date.
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Affiliation(s)
- Juan Güiza
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Iván Barría
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile.,Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - José L Vega
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
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Zhang P, Turnbull MW. Virus innexin expression in insect cells disrupts cell membrane potential and pH. J Gen Virol 2018; 99:1444-1452. [PMID: 30091698 DOI: 10.1099/jgv.0.001132] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Certain parasitoid wasps are associated with Polydnaviruses, symbiotic viruses that encode virulence factors which are essential to successful parasitization by the wasp of a caterpillar host. Members of one group of Polydnaviruses, the Ichnoviruses, encode a multi-gene family known as Vinnexins. Vinnexins are homologues of insect gap junction genes, and form functional gap junctions that may affect host cell physiology. However, the role of Vinnexins in host pathology and the mechanism by which these affect their caterpillar host are largely unknown. In this article, we generated recombinant baculoviruses to express vinnexins in Spodoptera frugiperda (Sf9) cells. To measure cell physiological changes caused by Vinnexins, cells were probed with a membrane potential-sensitive probe, DiBac4(3), and a pH indicator, carboxyfluorescein diacetate (CFDA). In addition, we utilized carbenoxolone and ouabain, respectively, to probe the role of gap junctions and hemi-channels, and Na+/K+-ATPase in establishing membrane potential in studied cells. Our results indicate that Vinnexins induce cell membrane depolarization and cytoplasmic alkalization to a degree specific to each tested Vinnexin, and that neither Vinnexin hemi-channels nor Na+/K+-ATPase appear to underlie these effects directly. These results hint that members of the Vinnexin protein family may affect host bio-electrical phenomena to disrupt host cell physiology, and that the individual proteins of the family may differentially affect host physiology.
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Affiliation(s)
- Peng Zhang
- 1Department of Plant and Environmental Science, Clemson University, Clemson, SC, USA
| | - Matthew W Turnbull
- 1Department of Plant and Environmental Science, Clemson University, Clemson, SC, USA
- 2Department of Biological Sciences, Clemson University, Clemson, SC, USA
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Kolosov D, Piermarini PM, O'Donnell MJ. Malpighian tubules of Trichoplusia ni: recycling ions via gap junctions and switching between secretion and reabsorption of Na+ and K+ in the distal ileac plexus. J Exp Biol 2018; 221:jeb.172296. [DOI: 10.1242/jeb.172296] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/10/2018] [Indexed: 12/12/2022]
Abstract
The functional kidney in insects consists of the Malpighian tubules and hindgut. Malpighian tubules secrete ions and fluid aiding in hydromineral homeostasis, acid-base balance, and metabolic waste excretion. In many insects, including lepidopterans, the Malpighian tubule epithelium consists of principal cells (PCs) and secondary cells (SCs). The SCs in the Malpighian tubules of larvae of the lepidopteran Trichoplusia ni have been shown to reabsorb K+, transporting it in a direction opposite to that in the neighbouring PCs that secrete K+. One of the mechanisms that could enable such an arrangement is a gap junction (GJ)-based coupling of the two cell types. In the current study, we have immunolocalised GJ protein Innexin-2 to the PC-PC and SC-PC cell-cell borders. We have demonstrated that GJs in the SC-containing region of the Malpighian tubules enable Na+ and K+ reabsorption by the SCs. We also demonstrated that in ion-loaded animals PCs switch from Na+/K+ secretion to reabsorption, resulting in an ion-transporting phenotype similar to that of tubules with pharmacologically blocked GJs. Concomitantly, mRNA abundance encoding GJ proteins was downregulated. Finally, we observed that such PC-based reabsorption was only present in the distal ileac plexus connected to the rectal complex. We propose that this plasticity in the PC function in the distal ileac plexus is likely to be aimed at providing ion supply for the SC function in this segment of the tubule.
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Affiliation(s)
- Dennis Kolosov
- McMaster University, Department of Biology, Hamilton, ON, Canada
| | - Peter M. Piermarini
- The Ohio State University, Ohio Agricultural Research and Development Center, Department of Entomology, Wooster, OH, USA
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Hall DH. Gap junctions in C. elegans: Their roles in behavior and development. Dev Neurobiol 2017; 77:587-596. [PMID: 27294317 PMCID: PMC5412865 DOI: 10.1002/dneu.22408] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/08/2016] [Accepted: 06/08/2016] [Indexed: 01/07/2023]
Abstract
The nematode Caenorhabditis elegans utilizes gap junctions in different fashions in virtually all of its cells. This model animal has a surprisingly large number of innexin genes within its genome, and many nematode cell types can express multiple innexins at once, leading to the formation of diverse junction types and enough redundancy to limit the effect of single gene knockdowns on animal development or behavioral phenotypes. Here, we review the general properties of these junctions, their expression patterns, and their known roles in tissue development and in the animal's connectome. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 587-596, 2017.
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Affiliation(s)
- David H Hall
- Department of Neuroscience, Center for C. elegans Anatomy, Albert Einstein College of Medicine, Bronx, New York, 10461
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Hasegawa DK, Erickson SL, Hersh BM, Turnbull MW. Virus Innexins induce alterations in insect cell and tissue function. JOURNAL OF INSECT PHYSIOLOGY 2017; 98:173-181. [PMID: 28077262 DOI: 10.1016/j.jinsphys.2017.01.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 10/10/2016] [Accepted: 01/06/2017] [Indexed: 06/06/2023]
Abstract
Polydnaviruses are dsDNA viruses that induce immune and developmental alterations in their caterpillar hosts. Characterization of polydnavirus gene families and family members is necessary to understand mechanisms of pathology and evolution of these viruses, and may aid to elucidate the role of host homologues if present. For example, the polydnavirus vinnexin gene family encodes homologues of insect gap junction genes (innexins) that are expressed in host immune cells (hemocytes). While the roles of Innexin proteins and gap junctions in insect immunity are largely unclear, we previously demonstrated that Vinnexins form functional gap junctions and alter the junctional characteristics of a host Innexin when co-expressed in paired Xenopus oocytes. Here, we test the effect of ectopic vinnexin expression on host cell physiology using both a lepidopteran cell culture model and a dipteran whole organism model. Vinnexin expression in the cell culture system resulted in gene-specific alterations in cell morphology and a slight, but non-statistically significant, reduction in gap junction activity as measured by dye transfer, while ectopic expression of a lepidopteran innexin2 gene led to morphological alterations and increase in gap junction activity. Global ectopic expression in the model dipteran, Drosophila melanogaster, of one vinnexin (vinnexinG) or D. melanogaster innexin2 (Dm-inx2) resulted in embryonic lethality, while expression of the other vinnexin genes had no effect. Furthermore, ectopic expression of vinnexinG, but not other vinnexin genes or Dm-inx2, in D. melanogaster larval gut resulted in developmental arrest in the pupal stage. These data indicate the vinnexins likely have gene-specific roles in host manipulation. They also support the use of Drosophila in further analysis of the role of Vinnexins and other polydnavirus genes in modifying host physiological processes. Finally, our findings suggest the vinnexin genes may be useful to perturb and characterize the physiological functions of insect Innexins.
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Affiliation(s)
- Daniel K Hasegawa
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
| | | | - Bradley M Hersh
- Department of Biology, Allegheny College, Meadville, PA 16335, USA.
| | - Matthew W Turnbull
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA; Department of Plant and Environmental Sciences, Clemson University, Clemson, SC 29634, USA.
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12
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Lautemann J, Bohrmann J. Relating proton pumps with gap junctions: colocalization of ductin, the channel-forming subunit c of V-ATPase, with subunit a and with innexins 2 and 3 during Drosophila oogenesis. BMC DEVELOPMENTAL BIOLOGY 2016; 16:24. [PMID: 27412523 PMCID: PMC4944501 DOI: 10.1186/s12861-016-0124-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Accepted: 06/29/2016] [Indexed: 01/21/2023]
Abstract
BACKGROUND Ion-transport mechanisms and gap junctions are known to cooperate in creating bioelectric phenomena, like pH gradients, voltage gradients and ion fluxes within single cells, tissues, organs, and whole organisms. Such phenomena have been shown to play regulatory roles in a variety of developmental and regenerative processes. Using Drosophila oogenesis as a model system, we aim at characterizing in detail the mechanisms underlying bioelectric phenomena in order to reveal their regulatory functions. We, therefore, investigated the stage-specific distribution patterns of V-ATPase components in relation to gap-junction proteins. RESULTS We analysed the localization of the V-ATPase components ductin (subunit c) and subunit a, and the gap-junction components innexins 2 and 3, especially in polar cells, border cells, stalk cells and centripetally migrating cells. These types of follicle cells had previously been shown to exhibit characteristic patterns of membrane channels as well as membrane potential and intracellular pH. Stage-specifically, ductin and subunit a were found either colocalized or separately enriched in different regions of soma and germ-line cells. While ductin was often more prominent in plasma membranes, subunit a was more prominent in cytoplasmic and nuclear vesicles. Particularly, ductin was enriched in polar cells, stalk cells, and nurse-cell membranes, whereas subunit a was enriched in the cytoplasm of border cells, columnar follicle cells and germ-line cells. Comparably, ductin and both innexins 2 and 3 were either colocalized or separately enriched in different cellular regions. While ductin often showed a continuous membrane distribution, the distribution of both innexins was mostly punctate. Particularly, ductin was enriched in polar cells and stalk cells, whereas innexin 2 was enriched in the oolemma, and innexin 3 in centripetally migrating follicle cells. In lateral follicle-cell membranes, the three proteins were found colocalized as well as separately concentrated in presumed gap-junction plaques. CONCLUSIONS Our results support the notion of a large variety of gap junctions existing in the Drosophila ovary. Moreover, since ductin is the channel-forming part of a proton pump and, like the innexins, is able to form junctional as well as non-junctional membrane channels, a plethora of cellular functions could be realized by using these proteins. The distribution and activity patterns of such membrane channels are expected to contribute to developmentally important bioelectric signals.
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Affiliation(s)
- Julia Lautemann
- Institut für Biologie II, RWTH Aachen University, Abt. Zoologie und Humanbiologie, Worringerweg 3, 52056, Aachen, Germany
| | - Johannes Bohrmann
- Institut für Biologie II, RWTH Aachen University, Abt. Zoologie und Humanbiologie, Worringerweg 3, 52056, Aachen, Germany.
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13
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Chen YB, Xiao W, Li M, Zhang Y, Yang Y, Hu JS, Luo KJ. N-TERMINALLY ELONGATED SpliInx2 AND SpliInx3 REDUCE BACULOVIRUS-TRIGGERED APOPTOSIS VIA HEMICHANNEL CLOSURE. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2016; 92:24-37. [PMID: 27030553 DOI: 10.1002/arch.21328] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 02/16/2016] [Accepted: 02/17/2016] [Indexed: 06/05/2023]
Abstract
The hemichannel and gap junction channel are major portals for the release of factors responsible for the effects of apoptotic cells on the spread of apoptosis to neighboring cells and apoptotic corpse clearance, typically by phagocytes. The N-terminal cytoplasmic domain in the connexins, gap junction proteins in vertebrate, has been implicated in regulating channel closure. However, little is known about how the hemichannel close responds to apoptotic signaling transduction leading to the reduction of neighboring cellular apoptosis in an invertebrate. An insect Bac-to-Bac expression system, pFastBac(TM) HT A, allows us to construct an N-terminally elongated SpliInx2 (Nte-Inx2) and SpliInx3 (Nte-Inx3). Here, we demonstrated that recombinant baculovirus Bac-Nte-Inx2 (reBac-Net-Inx2) and Bac-Nte-Inx3 (reBac-Nte-Inx3) closed the endogenous hemichannel on the Sf9 cell surface. Importantly, primary baculovirus infections significantly caused early apoptosis, and this apoptosis was reduced by hemichannel-closed Sf9 cells at 24-h post-infection (PI). Although N-terminal-elongated residue led to the increase in the phosphorylated sites in both Nte-Inx2 and Nte-Inx3 and an additional transmembrane domain in Nte-Inx3, both the proteins localized on the cell surface, suggesting Nte-Inxs proteins could mediate hemichannel closure. Further supporting evidence showed that hemichannel closure was dependent on N-Inxs expressed by baculovirus polyhedrin promoter, which began to express at 18-24 h PI. These results identify an unconventional function of N-terminal-elongated innexins that could act as a plug to manipulate hemichannel closure and provide a mechanism connecting the effect of hemichannel closure directly to apoptotic signaling transduction from intracellular to extracellular compartment.
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Affiliation(s)
- Ya-Bin Chen
- School of Life Sciences, Yunnan University, Kunming, P. R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Wei Xiao
- School of Life Sciences, Yunnan University, Kunming, P. R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Ming Li
- School of Life Sciences, Yunnan University, Kunming, P. R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Yan Zhang
- School of Life Sciences, Yunnan University, Kunming, P. R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Yang Yang
- School of Life Sciences, Yunnan University, Kunming, P. R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Jian-Sheng Hu
- School of Life Sciences, Yunnan University, Kunming, P. R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Kai-Jun Luo
- School of Life Sciences, Yunnan University, Kunming, P. R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
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Wang SP, Chen FY, Dong LX, Zhang YQ, Chen HY, Qiao K, Wang KJ. A novel innexin2 forming membrane hemichannel exhibits immune responses and cell apoptosis in Scylla paramamosain. FISH & SHELLFISH IMMUNOLOGY 2015; 47:485-499. [PMID: 26384843 DOI: 10.1016/j.fsi.2015.09.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 09/06/2015] [Accepted: 09/14/2015] [Indexed: 06/05/2023]
Abstract
Innexins are a class of transmembrane proteins that are important for embryonic development, morphogenesis and electrical synapse formation. In the present study, a novel innexin2 gene from Scylla paramamosain was named Sp-inx2 and characterized. The complete cDNA and genomic DNA sequences of Sp-inx2 were revealed. Sp-inx2 mRNA transcripts were distributed in various tissues of S. paramamosain and were most abundant in the hemocytes. The Sp-inx2 was significantly upregulated in hemocyte, gill and hepatopancreas tissues with the challenge of either Vibrio alginolyticus, Vibrio parahaemolyticus or lipopolysaccharides (LPSs) when analyzed at 3 and 6 h using quantitative real-time PCR, suggesting that it could activate an immune response against the challenge of LPSs or Vibrio species. Using the chemical inhibitors carbenoxolone and probenecid, the absorption of the fluorescent dye Lucifer yellow decreased in the primary cultured hemocytes of crabs, thus confirming that hemichannels composed of Sp-inx2 existed in the crab hemocytes. With LPS stimulation, the level of mRNA transcripts and protein expression of Sp-inx2 in the same cultured hemocytes gradually increased from 6 to 48 h, while the activity of hemichannels was down-regulated at 6 and 12 h, demonstrating that LPSs could modulate the absorption activity of hemichannels in addition to its upregulation of Sp-inx2 gene expression. Furthermore, the dye uptake rate in HeLa cells in which Sp-inx2 was ectopically expressed increased dramatically but the increase was significantly down-regulated with the addition of 50 μg mL(-1) LPS, suggesting that the LPS stimulation could effectively reduce the activity of hemichannels. Interestingly, with the ectopic expression of Sp-inx2 in HeLa and EPC cells, apoptosis spontaneously occurred in both cultured cell lines when detected using TUNEL assay. In summary, a new Sp-inx2 gene was first characterized in a marine animal S. paramamosain and it had a function associated with immune response and cell apoptosis.
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Affiliation(s)
- Shu-Ping Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Fang-Yi Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen University, Xiamen, Fujian, PR China; Fujian Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen, Fujian, PR China
| | - Li-Xia Dong
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Ya-Qun Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Hui-Yun Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen University, Xiamen, Fujian, PR China; Fujian Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen, Fujian, PR China
| | - Kun Qiao
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Ke-Jian Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen University, Xiamen, Fujian, PR China; Fujian Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen, Fujian, PR China.
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15
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Calkins TL, Piermarini PM. Pharmacological and Genetic Evidence for Gap Junctions as Potential New Insecticide Targets in the Yellow Fever Mosquito, Aedes aegypti. PLoS One 2015; 10:e0137084. [PMID: 26325403 PMCID: PMC4556631 DOI: 10.1371/journal.pone.0137084] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 08/13/2015] [Indexed: 12/02/2022] Open
Abstract
The yellow fever mosquito Aedes aegypti is an important vector of viral diseases that impact global health. Insecticides are typically used to manage mosquito populations, but the evolution of insecticide resistance is limiting their effectiveness. Thus, identifying new molecular and physiological targets in mosquitoes is needed to facilitate insecticide discovery and development. Here we test the hypothesis that gap junctions are valid molecular and physiological targets for new insecticides. Gap junctions are intercellular channels that mediate direct communication between neighboring cells and consist of evolutionarily distinct proteins in vertebrate (connexins) and invertebrate (innexins) animals. We show that the injection of pharmacological inhibitors of gap junctions (i.e., carbenoxolone, meclofenamic acid, or mefloquine) into the hemolymph of adult female mosquitoes elicits dose-dependent toxic effects, with mefloquine showing the greatest potency. In contrast, when applied topically to the cuticle, carbenoxolone was the only inhibitor to exhibit full efficacy. In vivo urine excretion assays demonstrate that both carbenoxolone and mefloquine inhibit the diuretic output of adult female mosquitoes, suggesting inhibition of excretory functions as part of their mechanism of action. When added to the rearing water of 1st instar larvae, carbenoxolone and meclofenamic acid both elicit dose-dependent toxic effects, with meclofenamic acid showing the greatest potency. Injecting a double-stranded RNA cocktail against innexins into the hemolymph of adult female mosquitoes knock down whole-animal innexin mRNA expression and decreases survival of the mosquitoes. Taken together these data indicate that gap junctions may provide novel molecular and physiological targets for the development of insecticides.
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Affiliation(s)
- Travis L. Calkins
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, United States of America
| | - Peter M. Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, United States of America
- * E-mail:
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16
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Pang Z, Li M, Yu D, Yan Z, Liu X, Ji X, Yang Y, Hu J, Luo K. TWO INNEXINS OF Spodoptera litura INFLUENCES HEMICHANNEL AND GAP JUNCTION FUNCTIONS IN CELLULAR IMMUNE RESPONSES. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2015; 90:43-57. [PMID: 25939810 DOI: 10.1002/arch.21243] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Insect cellular immune responses include encapsulation, nodule formation, and phagocytosis. Hemichannels and gap junctions are involved in these cellular actions. Innexins (Inxs: analogous to the vertebrate connexins) form hemichannels and gap junctions, but the molecular mechanisms underlying their biology is still unclear. In this article, we reported a steady-state level of Inxs (SpliInxs) in hemocytes of Spodoptera litura, which formed nonfunctional hemichannels on the cell surface to maintain normal metabolism. We also reported that two innnexins (SpliInx2 and SpliInx3) were expressed significantly higher in hemocytes compared to other tissues, suggesting that they play important roles in hemocytes. Amino acid analysis found that two cysteine residues in two extracellular loops provided the capability for SpliInx2 and SpliInx3 hemichannels to dock into gap junctions. Western blotting demonstrated that both extracellular and intracellular loops of SpliInx3 and the extracellular loops of SpliInx2 might undergo posttranslational modification during the formation of a steady-state hemichannel. During hemichannel formation, SpliInx2 presented as one isoform, while SpliInx3 presented as three isoforms. These results provide fundamental knowledge for further study of how steady-state levels of SpliInxs are dynamically adjusted to perform cellular immune responses under immune challenge.
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Affiliation(s)
- Zunyu Pang
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Ming Li
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Dongshuai Yu
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Zhang Yan
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Xinyi Liu
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Xinglai Ji
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Yang Yang
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Jiansheng Hu
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
| | - Kaijun Luo
- School of Life Sciences and Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R., China
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17
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Li M, Pang Z, Xiao W, Liu X, Zhang Y, Yu D, Yang M, Yang Y, Hu J, Luo K. A transcriptome analysis suggests apoptosis-related signaling pathways in hemocytes of Spodoptera litura after parasitization by Microplitis bicoloratus. PLoS One 2014; 9:e110967. [PMID: 25350281 PMCID: PMC4211697 DOI: 10.1371/journal.pone.0110967] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 09/19/2014] [Indexed: 01/01/2023] Open
Abstract
Microplitis bicoloratus parasitism induction of apoptotic DNA fragmentation of host Spodoptera litura hemocytes has been reported. However, how M. bicoloratus parasitism regulates the host signaling pathways to induce DNA fragmentation during apoptosis remains unclear. To address this question, we performed a new RNAseq-based comparative analysis of the hemocytes transcriptomes of non-parasitized and parasitized S. litura. We were able to assemble a total of more than 11.63 Gbp sequence, to yield 20,571 unigenes. At least six main protein families encoded by M. bicoloratus bracovirus are expressed in the parasitized host hemocytes: Ankyrin-repeat, Ben domain, C-type lectin, Egf-like and Mucin-like, protein tyrosine phosphatase. The analysis indicated that during DNA fragmentation and cell death, 299 genes were up-regulated and 2,441 genes were down-regulated. Data on five signaling pathways related with cell death, the gap junctions, Ca2+, PI3K/Akt, NF-κB, ATM/p53 revealed that CypD, which is involved in forming a Permeability Transition Pore Complex (PTPC) to alter mitochondrial membrane permeabilization (MMP), was dramatically up-regulated. The qRT-PCR also provided that the key genes for cell survival were down-regulated under M. bicoloratus parasitism, including those encoding Inx1, Inx2 and Inx3 of the gap junction signaling pathway, p110 subunit of the PI3K/Akt signaling pathway, and the p50 and p65 subunit of the NF-κB signaling pathway. These findings suggest that M. bicoloratus parasitism may regulate host mitochondria to trigger internucleosomal DNA fragmentation. This study will facilitate the identification of immunosuppression-related genes and also improves our understanding of molecular mechanisms underlying polydnavirus-parasitoid-host interaction.
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Affiliation(s)
- Ming Li
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Zunyu Pang
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Wei Xiao
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Xinyi Liu
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Yan Zhang
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Dongshuai Yu
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Minjun Yang
- Shanghai–Ministry of Science and Technology Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, P. R. China
| | - Yang Yang
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Jiansheng Hu
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
| | - Kaijun Luo
- School of Life Sciences, Yunnan University, Kunming, P. R. China; Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P. R. China
- * E-mail:
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18
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Sangaletti R, Dahl G, Bianchi L. Mechanosensitive unpaired innexin channels in C. elegans touch neurons. Am J Physiol Cell Physiol 2014; 307:C966-77. [PMID: 25252948 DOI: 10.1152/ajpcell.00246.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Invertebrate innexin proteins share sequence homology with vertebrate pannexins and general membrane topology with both pannexins and connexins. While connexins form gap junctions that mediate intercellular communication, pannexins are thought to function exclusively as plasma membrane channels permeable to both ions and small molecules. Undoubtedly, certain innexins function as gap junction proteins. However, due to sequence similarity to pannexins, it was postulated that innexins also function as plasma membrane channels. Indeed, some of the leech innexins were found to mediate ATP release as unpaired membrane channels with shared pharmacology to pannexin channels. We show here that Caenorhabditis elegans touch-sensing neurons express a mechanically gated innexin channel with a conductance of ∼1 nS and voltage-dependent and K(+)-selective subconductance state. We also show that C. elegans touch neurons take up ethidium bromide through a mechanism that is activated and blocked by innexin activating stimuli and inhibitors, respectively. Finally, we present evidence that touch neurons' innexins are required for cell death induced by chemical ischemia. Our work demonstrates that innexins function as plasma membrane channels in native C. elegans neurons, where they may play a role in pathological cell death.
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Affiliation(s)
- Rachele Sangaletti
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
| | - Gerhard Dahl
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
| | - Laura Bianchi
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida
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19
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Li MWM, Wang J, Zhao YO, Fikrig E. Innexin AGAP001476 is critical for mediating anti-Plasmodium responses in Anopheles mosquitoes. J Biol Chem 2014; 289:24885-97. [PMID: 25035430 DOI: 10.1074/jbc.m114.554519] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The Toll and IMD pathways are known to be induced upon Plasmodium berghei and Plasmodium falciparum infection, respectively. It is unclear how Plasmodium or other pathogens in the blood meal and their invasion of the midgut epithelium would trigger the innate immune responses in immune cells, in particular hemocytes. Gap junctions, which can mediate both cell-to-cell and cell-to-extracellular communication, may participate in this signal transduction. This study examined whether innexins, gap junction proteins in insects, are involved in anti-Plasmodium responses in Anopheles gambiae. Inhibitor studies using carbenoxolone indicated that blocking innexons resulted in an increase in Plasmodium oocyst number and infection prevalence. This was accompanied by a decline in TEP1 levels in carbenoxolone-treated mosquitoes. Innexin AGAP001476 mRNA levels in midguts were induced during Plasmodium infection and a knockdown of AGAP001476, but not AGAP006241, caused an induction in oocyst number. Silencing AGAP001476 caused a concurrent increase in vitellogenin levels, a TEP1 inhibitor, in addition to a reduced level of TEP1-LRIM1-APL1C complex in hemolymph. Both vitellogenin and TEP1 are regulated by Cactus under the Toll pathway. Simultaneous knockdown of cactus and AGAP001476 failed to reverse the near refractoriness induced by the knockdown of cactus, suggesting that the AGAP001476-mediated anti-Plasmodium response is Cactus-dependent. These data demonstrate a critical role for innexin AGAP001476 in mediating innate immune responses against Plasmodium through Toll pathway in mosquitoes.
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Affiliation(s)
- Michelle W M Li
- From the Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520 and the Howard Hughes Medical Institute, Chevy Chase, Maryland 20815
| | - Jiuling Wang
- From the Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520 and
| | - Yang O Zhao
- From the Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520 and the Howard Hughes Medical Institute, Chevy Chase, Maryland 20815
| | - Erol Fikrig
- From the Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520 and the Howard Hughes Medical Institute, Chevy Chase, Maryland 20815
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20
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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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Hasegawa DK, Turnbull MW. Recent findings in evolution and function of insect innexins. FEBS Lett 2014; 588:1403-10. [DOI: 10.1016/j.febslet.2014.03.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/03/2014] [Accepted: 03/04/2014] [Indexed: 10/25/2022]
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Liu T, Li M, Zhang Y, Pang Z, Xiao W, Yang Y, Luo K. A role for Innexin2 and Innexin3 proteins from Spodoptera litura in apoptosis. PLoS One 2013; 8:e70456. [PMID: 23936205 PMCID: PMC3728205 DOI: 10.1371/journal.pone.0070456] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 06/18/2013] [Indexed: 12/31/2022] Open
Abstract
Gap junctions formed by two hemichannels from two neighboring cells are cell-to-cell communication channels; hemichannels are communication channels between intracellular and extracellular environments. Hemichannels are hexameric proteins formed by connexins, pannexins, innexins and vinnexins. Innexin-hemichannels (innexons) exist in the lepidopteran cell surface, but their component innexins and functions have not been reported. Recent studies by others have demonstrated that hemichannels, connexons and pannexons from vertebrates serve as regulators of apoptosis via inactivating the PI3K/Akt signaling pathway. Here, the apoptogenic properties of innexons are demonstrated using two innexin cDNAs, Spli-inx2 and Spli-inx3, which were isolated from hemocytes of lepidopteran Spodoptera litura. Alignment analysis revealed that these two genes belong to a conserved innexin family, as they contain the insect signature YYQWV motif at the beginning of the second transmembrane domain. Immunofluorescence showed that two fusion proteins, Inx2-V5 and Inx3-V5, were localized predominantly in the cell membrane, cytoplasm and also nuclei. Ectopic expression in Sf9 cells and over-expression of Inx2 and Inx3 in Spli221 cells promoted apoptosis. In the Spli221 cells, apoptotic cells presented remarkable membrane blebbing. This study also showed that Sf9 and Spli221 cells undergo low level apoptosis under normal culture conditions, but not Hi5 cells. In Hi5 stable cell lines, biotinylation was used to isolate surface proteins and confirm Inx2 and Inx3 localization in the cell membrane and also further data showed that Hi5 cells may activate the PI3K signaling pathway via phosphorylating molecular Akt downstream. This result suggests that innexon-promoted apoptosis may be involving the PI3K/Akt signaling pathway. These findings will facilitate further examinations of the apoptotic regulation by the PI3K/Akt signaling pathway and comparative studies of innexons, connexons, pannexons, and vinnexons.
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Affiliation(s)
- Tian Liu
- School of Life Sciences, Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, Yunnan, P. R. China
| | - Ming Li
- School of Life Sciences, Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, Yunnan, P. R. China
| | - Yan Zhang
- School of Life Sciences, Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, Yunnan, P. R. China
| | - Zunyu Pang
- School of Life Sciences, Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, Yunnan, P. R. China
| | - Wei Xiao
- School of Life Sciences, Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, Yunnan, P. R. China
| | - Yang Yang
- School of Life Sciences, Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, Yunnan, P. R. China
| | - Kaijun Luo
- School of Life Sciences, Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, Yunnan, P. R. China
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Yazdani N, Firme CP, Macagno ER, Baker MW. Expression of a dominant negative mutant innexin in identified neurons and glial cells reveals selective interactions among gap junctional proteins. Dev Neurobiol 2013; 73:571-86. [DOI: 10.1002/dneu.22082] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 02/25/2013] [Accepted: 02/26/2013] [Indexed: 11/12/2022]
Affiliation(s)
- Neema Yazdani
- Section of Cell and Developmental Biology; University of California; San Diego La Jolla; California; 92093
| | - Constantine P. Firme
- Section of Cell and Developmental Biology; University of California; San Diego La Jolla; California; 92093
| | - Eduardo R. Macagno
- Section of Cell and Developmental Biology; University of California; San Diego La Jolla; California; 92093
| | - Michael W. Baker
- Section of Cell and Developmental Biology; University of California; San Diego La Jolla; California; 92093
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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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Shelby KS, Popham HJR. RNA-Seq Study of Microbially Induced Hemocyte Transcripts from Larval Heliothis virescens (Lepidoptera: Noctuidae). INSECTS 2012; 3:743-62. [PMID: 26466627 PMCID: PMC4553588 DOI: 10.3390/insects3030743] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 07/13/2012] [Accepted: 08/02/2012] [Indexed: 01/19/2023]
Abstract
Larvae of the tobacco budworm are major polyphagous pests throughout the Americas. Development of effective microbial biopesticides for this and related noctuid pests has been stymied by the natural resistance mediated innate immune response. Hemocytes play an early and central role in activating and coordinating immune responses to entomopathogens. To approach this problem we completed RNA-seq expression profiling of hemocytes collected from larvae following an in vivo challenge with bacterial and fungal cell wall components to elicit an immune response. A de novo exome assembly was constructed by combination of sequence tags from all treatments. Sequence tags from each treatment were aligned separately with the assembly to measure expression. The resulting table of differential expression had >22,000 assemblies each with a distinct combination of annotation and expression. Within these assemblies >1,400 were upregulated and >1,500 downregulated by immune activation with bacteria or fungi. Orthologs to innate immune components of other insects were identified including pattern recognition, signal transduction pathways, antimicrobial peptides and enzymes, melanization and coagulation. Additionally orthologs of components regulating hemocytic functions such as autophagy, apoptosis, phagocytosis and nodulation were identified. Associated cellular oxidative defenses and detoxification responses were identified providing a comprehensive snapshot of the early response to elicitation.
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Affiliation(s)
- Kent S Shelby
- Biological Control of Insects Research Laboratory, USDA Agricultural Research Service, 1503 S. Providence Road, Columbia, MO 65203, USA.
| | - Holly J R Popham
- Biological Control of Insects Research Laboratory, USDA Agricultural Research Service, 1503 S. Providence Road, Columbia, MO 65203, USA.
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Bennett MVL. Not what you thought: how H+ ions combine with taurine or other aminosulfonates to close Cx26 channels. ACTA ACUST UNITED AC 2011; 138:377-80. [PMID: 21896917 PMCID: PMC3182444 DOI: 10.1085/jgp.201110711] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Michael V L Bennett
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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